1. Integration of laser structuring into the electrode manufacturing process chain for lithium-ion batteries 

Lucas Hille*, Marc P. Noecker, Byeongwang Ko, Johannes Kriegler, Josef Keilhofer, Sandro Stock, Michael F. Zaeh

Technical University of Munich, TUM School of Engineering and Design, Department of Mechanical Engineering, Institute for Machine Tools and Industrial Management, Boltzmannstr. 15, 85748, Garching, Gemany 

 Despite the electrochemical benefits of laser electrode structuring, the process is not yet implemented in state-of-the-art industrial battery production due to limited knowledge regarding its implementation into the manufacturing process chain. In this study, three integration positions for laser structuring into the electrode manufacturing process chain were investigated with respect to different product properties.  The obtained electrodes were analyzed regarding geometrical, mechanical and electrochemical characteristics. Electrodes were structured either after coating, after drying or after calendering using pulsed laser radiation. Laser structuring before drying was found to offer advantages such as no deterioration of the mechanical electrode properties, a low number of residual particles on the electrode surfaces and nearly no increase in the electrode thicknesses. Yet, the poor structure geometries, the high fraction of clogged pores and the comparatively low electrochemical performance improvements diminish the attractiveness of laser structuring before drying. Although laser structuring after calendering yielded the highest process stability and the most desirable structure geometries, a nearly equal electrochemical performance was observed for structuring of dry electrodes before and after calendering. 

2. An Improved High-rate Discharging Performance of “Unbalanced” LiFePO4 Cathodes with Different LiFePO4 Loadings by a Grid-patterned Micrometer Size-holed Electrode Structuring

Takashi TSUDA,a Yuta ISHIHARA,a Tatsuya WATANABE,a Nobuo ANDO,b Takao GUNJI,a Naohiko SOMA,c Susumu NAKAMURA,d Narumi HAYASHI,e Takeo OHSAKA,b and Futoshi MATSUMOTO,a

a, Department of Materials and Life Chemistry, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, Kanagawa 221-     8686, Japan                                                                                                                                                                                                b, Research Institute for Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, Kanagawa 221-8686,            Japan                                                                                                                                                                                                          c, Wired Co., Ltd., 1628 Hitotsuyashiki shinden, Sanjo, Niigata 959-1152, Japan                                                                                          d, Department of Electrical and Electronic Systems Engineering, National Institute of Technology, Nagaoka College, 888 Nishikatakai,        Nagaoka, Niigata 940-8532, Japan                                                                                                                                                               e, Industrial Research Institute of Niigata Prefecture, 1-11-1 Abuminishi, Chuo-ku, Niigata 950-0915, Japan 

 In this study, we aim at clarifying the effect of a grid-patterned micrometer-sized cathode holing on the high-rate discharging performance of the LFP/LFP cathodes which are composed of LFP layer/Al current collector/LFP layer and have different LFP loading amounts (i.e., different capacities) on both sides of an Al current collector and thus will be called “unbalanced” LFP/LFP cathodes. we have fabricated parallel-connected batteries which are composed of two different (or same) LFP/LFP loading cathodes (i.e., unbalanced (or balanced) LFP/LFP cathodes) and two Li metal anodes and examined their high-rate discharging performance. The degradation of charging/discharging capacities in the rate-performance test of lithium iron phosphate (LFP) cathodes with different loading amounts of an active material on both sides of a current collector (i.e., “unbalanced” LFP/LFP cathodes) in a laminated cell (typically composed of anode/separator/unbalanced cathodes/separator/ anode) was not observed actually at low C-rates (e.g., 0.1 C). However, the rate-performance data obtained at high C-rates (e.g., >5 C) indicated that the imbalance of the loading amounts of an active cathode material on both sides of an Al current collector causes a significant capacity degradation. We have found that it is possible to prevent the capacity degradation observed at high C-rates by holing the unbalanced LFP/LFP cathodes in a micrometer-sized grid-patterned way (the percentages of the holed area are typically several %) using a pico-second pulsed laser. Forming micrometer-sized grid-patterned holes in the LFP/LFP cathodes leads to an improved capacity and high-rate performance of their charging/discharging processes.

3. Laser structuring of graphite anodes and NMC cathodes – Proportionate influence on electrode characteristics and cell performance 

Lucas Hille∗ , Lingji Xu, Josef Keilhofer, Sandro Stock, Johannes Kriegler, Michael F. Zaeh 

Institute for Machine Tools and Industrial Management, Technical University of Munich, Boltzmannstr. 15, 85748, Garching, Germany 

 In this study, The impact on the performance of coin cells comprising anodes and cathodes in pristine and structured conditions, respectively, was investigated in a discharge rate test. Coin cells featuring the laser-structured electrodes showed a superior rate capability in discharge tests in comparison to their unstructured counterparts.The effect was particularly pronounced for cells with structured anodes at currents between 1 C and 3 C. Characteristic features in the incremental capacities indicated cell polarization and diffusion inhibition as the rate-limiting mechanisms at high discharge rates and revealed differences in the dominating deintercalation stages between the cell configurations. Fitting an equivalent circuit model to the impedance spectra of symmetric cells showed a reduction of the ionic resistances by approx. Electrode structuring offers a great potential to overcome rate limitations and improve the cell performance, particularly when applied on the anode side. Differences in terms of cell performance between cells comprising structured anodes and pristine cathodes vs. structured anodes and cathodes were limited to very high currents (5 C).  A similar behavior was observed for the MacMullin numbers and effective tortuosities of the electrodes. In conclusion, laser structuring offers a particular potential to overcome the diffusion-limiting characteristics of the graphite anodes. The insights into the proportionate impact of anode or cathode structuring are of high value for the design and manufacturing of future lithium-ionbatteries.

4. High-capacity, low-tortuosity LiFePO4-Based composite cathode enabled by self-supporting structure combined with laser drilling technology 

Shaoping Wu, Hongpeng Zheng, Xinyue Wang, Nan Zhang, Weizheng Cheng, Benwei Fu, Haochang Chen, Hezhou Liu, Huanan Duan * 

State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China 

 Because of their high energy densities, high working voltages, and relatively light weights, lithium-ion batteries (LIBs) have grown into the dominating power source for consumer electronics and electrical vehicles over the last few decades.  A thick electrode with high areal capacity is a promising way to improve the energy density of batteries, but the development of a thick electrode is limited by poor mechanical stability and sluggish ion and electron transport. Here, we design a self-supporting cathode that consists of cellulose nanofibers, multi-walled carbon nanotubes, and lithium iron phosphate (LFP), and introduce a uniform microchannel structure to the cathode by laser drilling technology. The cellulose nanofibers and multi-walled carbon nanotubes construct a conductive network. The microchannel structure enables outstanding ion and electron transport and significantly improves the rate capability of the electrode. Meanwhile, the local heat by the laser produces an amorphous carbon layer on the inner surface of the microchannel, which helps form a stable cathode-electrolyte interface and enhances the capacity retention of the thick electrode. Notably, the drilled thick cathode with an LFP load of 40 mg cm− 2 and an areal capacity of 5.33 mAh cm− 2 exhibits substantially improved cycling stability at 0.5C than the undrilled samples. This work demonstrates a promising design concept for thick electrodes to high-performance energy storage devices. 

5.Wettability in electrodes and its impact on the performance of lithium-ion batteries

Dong Hyup Jeon

Department of Mechanical System Engineering, Dongguk University-Gyeongju, Gyeongju 38066, Republic of Korea

 Wettability by the electrolyte is claimed to be one of the challenges in the development of high-performance lithium-ion batteries. Non-uniform wetting leads to inhomogeneous distribution of current density and unstable formation of solid electrolyte interface film. Incomplete wetting influences the cell performance and causes the formation of lithium plating in the anode, which leads to safety issue. Research has pointed out that insufficient wetting could be found in the electrode, and the wetting characteristics would be different in each electrode. Here we use lattice Boltzmann simulation to show the electrolyte distribution and understand the wetting characteristics in the cathode and anode. We develop a multiphase lattice Boltzmann model with the reconstruction of electrode microstructure using a stochastic generation method. We use a porous electrode model to identify the effect of wettability on the cell performance and to elucidate the dependence of capacity on the wettability. Our results would lead to more reliable lithium-ion battery designs, and establish a framework to inspect the wettability inside electrodes. 

6.Laser ablation for structuring Li-ion electrodes for fast charging and its impact on material properties, rate capability, Li plating, and wetting

Nathan Dunlap a, Dana B. Sulas-Kern a, Peter J. Weddle a, Francois Usseglio-Viretta a, Patrick Walker a, Paul Todd a, David Boone b, Andrew M. Colclasure a, Kandler Smith a, Bertrand J. Tremolet de Villers a, Donal P. Finegan a

a, National Renewable Energy Laboratory (NREL), 15013 Denver West Parkway, Golden, CO 80401, United States of America

b, Clarios, 5757 North Green Bay Avenue, Florist Tower, Milwaukee, WI 53209, United States of America

 Laser ablation is a scalable technique for decreasing the effective tortuosity of electrodes by selectively removing material with high precision. Applied to thick electrode coatings, this work focuses on understanding the impact of laser ablation on electrode material properties at the beginning of life and synergistic impacts of ablated channels on cell performance throughout their cycle life. Post laser ablation, local changes in chemistry, crystallography, and morphology of the laser-impacted electrode regions are investigated. It is shown that femtosecond pulsed laser ablation can achieve high-rate material removal with minor material damage locally at the interface of the impacted zones. The capacity achieved during a 6C (10 min) constant-current constant-voltage charge to 4.2 V improved from 1 mAh cm−2 for the non-ablated electrodes to almost 2 mAh cm−2 for the ablated electrodes. This benefit is attributed to a synergistic effect of enhanced wetting and decreased electrode tortuosity. The benefit was maintained for over 120 cycles, and upon disassembly decreased Li-plating on the graphite anode was observed. Finally, multi-physics modeling in conjunction with wetting analyses showed that laser ablating either one of the electrodes led to substantial improvements in wetting and rate capability, indicating that substantial performance benefits can be achieved by ablating only the graphite anode as apposed to both electrodes.

7.Microstructure and defect engineering of graphite anodes by pulsed laser annealing for enhanced performance of lithium – ion batteries 

Nayna Khosla A, Jagdish Narayan A, Roger Narayan A,B, Xiao-Guang Sun C, Mariappan Parans Paranthaman C

A, Department of Materials Science and Engineering, Centennial Campus, North Carolina State University, Raleigh, NC, 27695-7907, United States

B, Joint Department of Biomedical Engineering, Centennial Campus, North Carolina State University and UNC Chapel Hill, Raleigh, NC, 27695, United States

C, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6100, United States

 Nanosecond pulsed laser annealing significantly improves cyclability and current carrying capacity of lithium-ion batteries (LIBs). This improvement is achieved by engineering of microstructure and defect contents present in graphite in a controlled way by using pulsed laser annealing (PLA) to increase the number density of Li+ ion trapping sites. The PLA treatment causes the following changes: (1) creates surface steps and grooves between the grains to improve Li+ ion charging and intercalation rates; (2) removes inactive polyvinylidene difluoride (PVDF) binder from the top of graphite grains and between the grains which otherwise tends to block the Li+ migration; and (3) produces carbon vacancies in (0001) planes which can provide Li+ charging sites. From X-ray diffraction data, we find upshift in diffraction peak or reduction in planar spacing, from which vacancy concentration was estimated to be about 1.0%, which is higher than the thermodynamic equilibrium concentration of vacancies. The laser treatment creates single and multiple C vacancies which provide sites for Li+ ions, and it also produces steps and grooves for Li+ ions to enter the intercalating sites. It is envisaged that the formation of these sites enhances Li+ ion absorption during charge and discharge cycles. The current capacity increases from an average 360 mAh/g to 430 mAh/g, and C–V shows significant reduction in SEI layer formation after the laser treatment. If the vacancy concentration is too high and charge-discharge cycles are long, then trapping of electrons by Li+ may occur, which can lead to Li0 formation and Li plating causing reduction in current capacity.

8.High-rate and excellent-cycle performance Li4Ti5O12 electrodes with 3D porous copper foils as current collectors fabricated using a femtosecond laser processing strategy 

Quansheng Li a b, Xuesong Mei a b c, Xiaofei Sun a b c, Yanbin Han a b, Bin Liu a b c, Zikang Wang a b, Anastase Ndahimana a b, Jianlei Cui a b c, Wenjun Wang a b c

a, State key laboratory for manufacturing system engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China

b, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China

c, Shaanxi Key Laboratory of Intelligent Robots, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China

 Owing to their excellent structural superiorities of large storage space, high specific surface area and reduced volume expansion during battery charge and discharge cycles, 3D porous current collectors have received much concern in the anode of lithium-ion batteries. However, reasonable designing and efficient manufacturing of 3D porous copper foils as current collectors (PCFCCs) remain a great challenge due to the small thickness, soft texture, and variability of copper foils. These material characteristics make it hard to manufacture 3D micro-structure on copper foils and impede the practical application of lithium-ion batteries in more fields. Herein, an efficient and effective strategy is reported to enhance the electrochemical performance of Li4Ti5O12 (LTO) electrodes via rationally designing and manufacturing 3D porous copper foils as current collectors. As a result, the 3D PCFCCs based LTO electrode displays low electrode polarization, excellent-cycle performance and ultra-high rate capacity. Moreover, the structures of various 3D PCFCCs are systematically studied for the first time, the design of 3D PCFCCs is optimized, and the mechanism of improving battery performance is explored. In addition, the proper micro-nano-pore-structures can facilitate electrolyte penetration and the solvated Li+ transport, and the excellent Li+ transmission ability of 3D PCFCCs is verified by simulation.

9.Electro-plating and stripping behavior on lithium metal electrode with ordered three-dimensional structure 

Quan Li a b, Baogang Quan a, Wenjun Li a, Jiaze Lu a b, Jieyun Zheng a, Xiqian Yu a, Junjie Li a, Hong Li a

a, Institute of Physics, Chinese Academy of Science, Beijing 100190, China

b, University of Chinese Academy of Sciences, Beijing 100049, China

 The growth of lithium dendrite is one of the major problems that need to be solved before the application of metallic lithium anode to commercial rechargeable lithium batteries. The three-dimensional host framework with well-defined architecture acting as current collector has been proved to be able to regulate the lithium plating/stripping behavior and thus to suppress the dendrite growth. In this work, a surface-patterned lithium electrode (spLi) with hexagonal arrays of micro-sized holes has been successfully fabricated by micro-fabrication methods. By employing scanning electron microscope (SEM) and optical microscope, the lithium plating/stripping behavior on spLi was directly visualized. The electrochemical performances of the spLi electrode were evaluated in Li symmetric cell and Li|LiCoO2 half-cell using carbonate ester and ether based electrolyte. It is found that the geometry of the hole has a strong influence on the lithium plating/stripping behavior, and the deposited lithium perfers to fill in the micro-sized holes due to the favorable kinetics. The hole structure preserves throughout battery cycling with no obvious dendrite growth and surface roughness after multiple plating/stripping cycles. These phenomena can well explain the excellent electrochemical performances of the surface-patterned lithium electrode (spLi) compared with bare lithium electrode. This research also demonstrates that lithium metal can serve as stable framework to host lithium plating/stripping, nevertheless, efforts are still needed to further optimize the architecture to achieve more evenly lithium plating/stripping.

10.Processing of lithium metal for the production of post-lithium-ion batteries using a pulsed nanosecond fiber laser 

Johannes Kriegler *, Tran Manh Duy Nguyen, Lazar Tomcic, Lucas Hille, Sophie Grabmann, Elena Irene Jaimez-Farnham, Michael F. Zaeh

Technical University of Munich (TUM); TUM School of Engineering and Design; Department of Mechanical Engineering, Institute for Machine Tools and Industrial Management (iwb); Boltzmannstrasse 15, 85748 Garching, Germany

 Lithium metal is a favored anode material in various post-lithium-ion battery types. Developing processing routines for lithium anodes is necessary to pave the way for large-format lithium metal batteries. Laser cutting is a feasible production process to create the required electrode contours. In the scope of this work, model calculations were used to derive implications of the cell design on the relevant range of lithium layer thicknesses. Furthermore, nanosecond-pulsed laser cutting was evaluated for separating 50 μm-thick lithium foils. Cause-effect relationships between process parameters and quality criteria were analyzed through empirical investigations. The ablation thresholds for various pulse durations were determined experimentally. Different process regimes were identified using scanning electron microscopy with explosive boiling at high fluences as the most efficient ablation mechanism enabling cutting speeds of up to 6.6 m s−1. The influence of the peak pulse fluence, the pulse frequency, the pulse duration, and the pulse overlap on the formation of melt superelevations at the cut edge was studied using laser scanning microscopy. The presented results contribute to a better understanding of the nanosecond-pulsed laser process and provide a basis for developing tailored process strategies for laser cutting of lithium metal within industrial-scale battery production.

11.Nanosecond laser lithography enables concave-convex zinc metal battery anodes with ultrahigh areal capacity 

Zechuan Huang a, Haoyang Li b, Zhen Yang b, Haozhi Wang a, Jingnan Ding a, Luyao Xu c, Yanling Tian d, David Mitlin e, Jia Ding a, Wenbin Hu a

a, Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China

b, School of Mechanical Engineering, Tianjin University, Tianjin 300072, China

c, Shenzhen Zhongwu Technology Co., Ltd., Shenzhen 518052, China

d, School of Engineering, University of Warwick, Coventry CV4 7AL, UK

e, Materials Science Program & Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712-1591, USA

 Laser processing is employed to fabricated zinc-ion battery (ZIB) anodes with state-of-the-art electrochemical performance from commercial zinc foils. Lasers are widely utilized for industrial surface finishing but have received minimal attention for zinc surface modification. Laser lithography patterned zinc foils “LLP@ZF” are hydrophilic, with an electrolyte contact angle of 0°. This is due to the concave-convex surface geometry that enhances wetting (periodic crests, ridges and valleys, roughness 16.5 times planar). During electrodeposition LLP@ZF's surface geometry generates a periodic electric field and associated current density distribution that suppresses tip growth (per continuum simulations). Per Density Functional Theory (DFT) its surface oxide is zincophilic, resulting in low nucleation barriers during plating (e.g. 3.8 mV at 1 mA cm−2). A combination of these attributes leads to stable dendrite-free plating/stripping behavior and low overpotentials at fast charge (e.g. 48.2 mV at 8 mA cm−2 in symmetric cell). Cycling is possible at an unprecedented areal capacity of 50 mA h cm−2, with 400 h stability at 1 mA cm−2. Moreover, exceptional aqueous zinc battery (AZB) performance is achieved, with MnO2-based cathode loading 10 mg cm−2 and corresponding anode capacity 7.6 mA h cm−2. A broad comparison with literature indicates that LLP@ZF symmetric cell and full battery performance are among most favorable.

12.Nanosecond laser lithography enables concave-convex zinc metal battery anodes with ultrahigh areal capacity 

 Yijing Zheng 1,*ORCID,Lisa Pfäffl 1,Hans Jürgen Seifert 1 andWilhelm Pfleging 1,2

1, Institute for Applied Materials—Applied Materials Physics (IAM—AWP), Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany

2, Karlsruhe Nano Micro Facility (KNMF), H.-von-Helmholtz-Pl. 1, 76344 Eggenstein-Leopoldshafen, Germany

 For the development of thick film graphite electrodes, a 3D battery concept is applied, which significantly improves lithium-ion diffusion kinetics, high-rate capability, and cell lifetime and reduces mechanical tensions. Our current research indicates that 3D architectures of anode materials can prevent cells from capacity fading at high C-rates and improve cell lifespan. For the further research and development of 3D battery concepts, it is important to scientifically understand the influence of laser-generated 3D anode architectures on lithium distribution during charging and discharging at elevated C-rates. Laser-induced breakdown spectroscopy (LIBS) is applied post-mortem for quantitatively studying the lithium concentration profiles within the entire structured and unstructured graphite electrodes. Space-resolved LIBS measurements revealed that less lithium-ion content could be detected in structured electrodes at delithiated state in comparison to unstructured electrodes. This result indicates that 3D architectures established on anode electrodes can accelerate the lithium-ion extraction process and reduce the formation of inactive materials during electrochemical cycling. Furthermore, LIBS measurements showed that at high C-rates, lithium-ion concentration is increased along the contour of laser-generated structures indicating enhanced lithium-ion diffusion kinetics for 3D anode materials. This result is correlated with significantly increased capacity retention. Moreover, the lithium-ion distribution profiles provide meaningful information about optimizing the electrode architecture with respect to film thickness, pitch distance, and battery usage scenario.

13.Directing lateral growth of lithium dendrites in micro-compartmented anode arrays for safe lithium metal batteries

 Peichao Zou, Yang Wang, Sum-Wai Chiang, Xuanyu Wang, Feiyu Kang & Cheng Yang

Division of Energy and Environment, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China

School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China

 Uncontrolled growth of lithium dendrites during cycling has remained a challenging issue for lithium metal batteries. Thus far, various approaches have been proposed to delay or suppress dendrite growth, yet little attention has been paid to the solutions that can make batteries keep working when lithium dendrites are already extensively present. Here we develop an industry-adoptable technology to laterally direct the growth of lithium dendrites, where all dendrites are retained inside the compartmented copper current collector in a given limited cycling capacity. This featured electrode layout renders superior cycling stability (e.g., smoothly running for over 150 cycles at 0.5 mA cm−2). Numerical simulations indicate that reduced dendritic stress and damage to the separator are achieved when the battery is abusively running over the ceiling capacity to generate protrusions. This study may contribute to a deeper comprehension of metal dendrites and provide a significant step towards ultimate safe batteries.

14.Laser texturing of Li-ion battery electrode current collectors for improved active layer interface adhesion

 Luca Romoli (2), Adrian H.A. Lutey, Gianmarco Lazzini

Department of Engineering and Architecture, University of Parma, Parma 43124, Italy

 Nanosecond laser processing (NLP) is performed on aluminium and copper Li-ion battery (LIB) current collectors to improve the interface adhesion with active materials. The developed area ratio, Sdr, void volume, Vv, and maximum crater depth, h, are introduced to quantify the effectiveness and feasibility of NLP over a range of process parameters. By limiting the crater depth to half the foil thickness, increases in surface area of 20% and 13% are achieved on aluminium and copper foils of thickness 30 µm and 10 µm with a fluence of 24.8 J/cm2 and 49.5 J/cm2, respectively. The adhesion ratio of intact active material following peel-off tests on complete electrodes with textured current collectors is approximately 30% higher than with untreated current collectors.

15.Nanosecond pulsed laser texturing of Li-ion battery electrode current collectors: Electrochemical characterization of cathode half-cells 

 Elisa Ravesio a, Adrian H.A. Lutey b, Daniele Versaci a, Luca Romoli c, Silvia Bodoardo a

a, Politecnico di Torino, Department of Applied Science and Technology, Electrochemistry Group, Corso Duca degli Abruzzi, 24, 10129 Turin, Italy

b, Università degli Studi di Parma, Dipartimento di Ingegneria e Architettura, Parco Area delle Scienze, 181/A, 43124 Parma, Italy

c, Università di Pisa, Dipartimento di Ingegneria Civile e Industriale, Largo Lucio Lazzarino, 56122 Pisa, Italy

 Lithium-ion batteries (LIBs) have emerged as the primary energy storage solution for numerous portable electronic devices, electric vehicles, and renewable energy systems. However, enhancing the performance and longevity of LIBs is of paramount importance to meet the increasing demand for efficient and sustainable energy storage solutions. To improve the performance of current LIBs, one of the most interesting aspects is to study and optimize the so-called inactive materials which constitute the battery. Within this context, the present work focuses on laser texturing of aluminium current collectors (CCs) to improve the electrochemical performance of lithium iron phosphate-based cathodes. Two different nanosecond laser treatments were used to increase the wettability of metallic CCs and improve adhesion between this element and the other components of the electrode. Both laser treatments enhanced adhesion between the active material and CC, exhibiting good electrochemical performance at high C-rates compared to cells with untextured CCs, as well as good rate capability. Interestingly, one of the two pattern geometries exhibited significant cycling stability, with a capacity retention of >86% after 500 cycles.

16.A two-step nanosecond laser surface texturing process with smooth surface finish

 Yibo Gao, Benxin Wu, Yun Zhou, Sha Tao

Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616, United States

 Surface texturing (for example, producing micro dimples on the surface) of mechanical parts has a great potential to improve the surface tribological properties. Surface texturing through nanosecond laser ablation has many associated advantages and hence has drawn lots of attentions. However, the produced micro dimple bottom (if through laser spot scanning) is often very rough, which may harm the surface tribological properties. In this paper, a two-step laser surface texturing process is proposed and studied, where a relatively high-fluence laser ablation step (which is to create dimples) is followed by a low-fluence laser-induced melting, melted material flow and re-solidification step (which is to smooth the ablated dimple bottom surface). The study shows that the two-step laser surface texturing process can produce dimples with very smooth bottom surfaces. The effects of laser pulse duration and scan speed in Step 2 on the dimple bottom surface morphology and roughness have also been investigated, and some very interesting physical phenomena have been found, which have been rarely reported before in literature. Some hypothesized explanations are given for the observed effects, which require future work to completely understand their underlying mechanisms.

17.Modification of aluminum current collectors with laser-scribed graphene for enhancing the performance of lithium ion batteries

Er-Chieh Cho a, Cai-Wan Chang-Jian b, Yen-Ju Wu c, Szu-Han Chao d, Jen-Hsien Huang e, Kuen-Chan Lee f, Huei Chu Weng g, Shih-Chieh Hsu d h

a, Department of Clinical Pharmacy, School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wuxing Street, Taipei City, 110, Taiwan

b, Department of Mechanical and Automation Engineering, I-Shou University, No.1, Sec. 1, Syuecheng Rd., Dashu District, Kaohsiung City, 84001, Taiwan

c, International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan

d, Department of Chemical and Materials Engineering, Tamkang University, No. 151, Yingzhuan Road, Tamsui District, New Taipei City, 25137, Taiwan

e, Department of Green Material Technology, Green Technology Research Institute, CPC Corporation, No.2, Zuonan Rd., Nanzi District, Kaohsiung City, 81126, Taiwan

f, Department of Science Education, National Taipei University of Education, No.134, Sec. 2, Heping E. Rd., Da-an District, Taipei City, 106, Taiwan

g, Department of Mechanical Engineering, Chung Yuan Christian University, No. 200, Chungpei Road, Chungli District, Taoyuan City, 32023, Taiwan

h, Water Treatment Science and Technology Research Center, Tamkang University, No. 151, Yingzhuan Road, Tamsui District, New Taipei City, 25137, Taiwan

 In this study, the graphene-modified Al foils are prepared to assemble lithium ion batteries (LIBs) through a three-step approach comprising: (1) deposition of the polyamic acid (PAA) on the Al substrate; (2) curing the PAA to form the polyimide (PI)-coated Al foils; (3) converting the PI into porous graphene by CO2 laser irradiation. With integration of the PI derived graphene (PDG) in the LIBs, the inserted PDG layer can enhance the adhesion and interface resistance between the active layer and Al electrode. The LiNi0.5Mn1.5O4 (LNMO)//Li4Ti5O12 (LTO) full cells with PDG layer are also fabricated to evaluate the effect of the modified layer on the cell performance. Compared to the pristine Al electrode, the modified current collector can improve the rate performance and reduce the temperature rise during the charge/discharge process leading to better cycling stability.

18.Characterization of ultrafast-laser ablation of micro-structures in Li-ion battery anode and cathode materials: Morphology, rate, and efficiency

Ryan J. Tancin, Dana B. Sulas-Kern, François L.E. Usseglio-Viretta, Donal P. Finegan, Bertrand J. Tremolet de Villers

National Renewable Energy Laboratory (NREL), 15013 Denver West Parkway, Golden, CO 80401, United States of America

 Characterization of the rate and quality of ultrafast-laser ablation of Li-ion battery (LIB) electrode materials is presented for a collection of common and next-generation electrodes. Laser ablated micro-structures on the surface of LIB electrodes have been shown to provide dramatic enhancement of high-rate capability and electrode wetting. However, industrial adoption is hampered by a lack of data enabling informed choice of laser parameters and predicting process throughput. This work bridges this gap by providing characterization of the ablation process at more laser parameters (laser fluence and number of pulses used) than are currently available in the literature. Further, we expand on previous graphite and lithium iron phosphate (LFP) ablation work by extending ablation characterization to new LIB materials, providing high data resolution and adopting new characterization metrics which are relevant for industrial application of this technology. Ablated pores are characterized by their ablated depth, volume, and how the depth and volume ablation rate changes as a function of pore depth. Finally, we provide a detailed characterization of the morphology of laser ablated micro-structures which informs how material and laser parameters affect the quality of laser-processed electrodes.

19.Surface Reconditioning of Lithium Metal Electrodes by Laser Treatment for the Industrial Production of Enhanced Lithium Metal Batteries

Johannes Kriegler, Heiko Ballmes, Serge Dib, Ali Gökhan Demir, Lucas Hille, Yunhao Liang, Lovis Wach, Steffen Weinmann, Josef Keilhofer, Kun Joong Kim, Jennifer L. M. Rupp, Michael F. Zaeh

Schaeffler Technologies AG & Co. KG91074 Herzogenaurach, Germany

Department of Mechanical EngineeringPolitecnico di MilanoVia La Masa 1, Milan 20158, Italy

 Incorporating lithium metal anodes in next-generation batteries promises enhanced energy densities. However, lithium's reactivity results in the formation of a native surface film, affecting battery performance. Therefore, precisely controlling the chemical and morphological surface condition of lithium metal anodes is imperative for producing high-performance lithium metal batteries. This study demonstrates the efficacy of laser treatment for removing superficial contaminants from lithium metal substrates. To this end, picosecond-pulsed laser radiation is proposed for modifying the surface of lithium metal substrates. Scanning electron microscopy (SEM) revealed that different laser process regimes can be exploited to achieve a wide spectrum of surface morphologies. Energy-dispersive X-ray spectroscopy (EDX) confirmed substantial reductions of ≈80% in oxidic and carbonaceous surface species. The contamination layer removal translated into interfacial resistance reductions of 35% and 44% when testing laser-cleaned lithium metal anodes in symmetric all-solid-state batteries (ASSBs) with lithium phosphorus sulfur chloride (LPSCl) and lithium lanthanum zirconium oxide (LLZO) solid electrolytes, respectively. Finally, a framework for integrating laser cleaning into industrial battery production is suggested, evidencing the industrial feasibility of the approach. In summary, this work advances the understanding of lithium metal surface treatments and serves as proof of principle for its industrial applicability.

20.Laser-Induced Silicon Oxide for Anode-Free Lithium Metal Batteries

Weiyin Chen, Rodrigo V. Salvatierra, Muqing Ren, Jinhang Chen, Michael G. Stanford, James M. Tour

Schaeffler Technologies AG & Co. KG91074 Herzogenaurach, Germany

Chemistry DepartmentRice University6100 Main ST MS 60, Houston, TX 77005, USA

Department of Materials Science and NanoEngineeringSmalley-Curl Institute and The NanoCarbon CenterRice University6100 Main ST MS 222, Houston, TX 77005, USA

 The development of a rechargeable Li metal anode (LMA) is an important milestone for improved battery technology. Practical issues hindering LMAs are the formation of Li dendrites and inactive Li during plating and stripping processes, which can cause short circuits, thermal runaway, and low coulombic efficiency (CE). Here, the use of a laser-induced silicon oxide (LI-SiOx) layer derived from a commercial adhesive tape to improve the reversibility of Li metal batteries (LMBs) is studied. The silicone-based adhesive of the tape is converted by a commercial infrared laser into a homogeneous porous SiOx layer deposited directly over the current collector. The coating results in superior performance by suppressing the formation of Li dendrites and inactive Li and presenting higher average CE of 99.3% (2.0 mAh cm−2 at 2.0 mA cm−2) compared to bare electrodes. The thickness and morphology of the deposited Li is investigated, revealing a different mechanism of Li deposition on coated electrodes. The laser coating affords a method that is fast and avoids the use of toxic organic solvents and extensive drying times. The improved performance with the SiOx coating is demonstrated in LMB with a zero-excess (“anode-free”) configuration where a 100% improved performance is verified.

21.Emerging strategies for steering orientational deposition toward high-performance Zn metal anodes

Yuhan Zou a, Xianzhong Yang a, Lin Shen a, Yiwen Su a, Ziyan Chen a, Xiang Gao ab, Jiang Zhou ORCID logo*c and Jingyu Sun

a College of Energy, Soochow Institute for Energy and Materials Innovations, Key Laboratory for Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Soochow University, Suzhou 215006, P. R. China. E-mail: sunjy86@suda.edu.cn

b Beijing Graphene Institute, Beijing 100095, P. R. China

c School of Materials Science and Engineering, Key Laboratory of Electronic Packaging and Advanced Functional Materials of Hunan Province, Central South University, Changsha 410083, P. R. China

 Recent years have witnessed the renaissance of aqueous Zn-ion batteries (AZIBs). Nevertheless, the current development of high-performance AZIBs is confronted by the rapid capacity decay and irreversible cycling of Zn anodes, the culprit of which is unremitted dendritic growth. Harnessing the preferential deposition of Zn is an effective manoeuvre in the sense of alleviating problematic dendrite issues. Meanwhile, numerous studies have revealed that the crystallographic orientations of as-deposited Zn are close related to battery performance. Nonetheless, there is a lack of comprehensive overview to shed light on the formation rules and underlying mechanisms relating to induced orientation. In this review, we summarize the emerging design strategies of steering Zn orientational deposition and elaborate on the mechanistic insights toward the realization of highly reversible Zn anodes. The existing challenges and future outlooks in this realm are proposed at the end of the review to envisage the commercialization of AZIBs.

22.Ultrafast laser one-step construction of 3D micro-/nanostructures achieving high-performance zinc metal anodes

Yanan Liu, Ye Ding, Zeping Liu, Xingchen Li, Sichao Tian, Lishuang Fan, Jichang Xie, Liangliang Xu, Jinwoo Lee, Jian Li & Lijun Yang

Zhengzhou Research Institute, Harbin Institute of Technology, Zhengzhou 450000, P. R. China 2 Suzhou Research Institute, Harbin Institute of Technology, Suzhou 215104, P. R. China 3 School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, P. R. China 4 Defense Innovation Institute, Chinese Academy of Military Science, Beijing 100071, P. R. China

 Aqueous zinc-ion batteries (AZIBs) are promising for energy storage due to their safety, environmental friendliness, and high capacity. However, challenges with zinc anodes, such as dendrite growth and poor cycling stability, hinder their performance. This study introduces a one-step ultrafast laser processing technique (ULPT) to create precise 3D micro-/nanostructures on Zn anodes, improving Zn plating/stripping behavior and cycling stability. The method simplifies the manufacturing process and enhances the practicality of AZIBs. As a result, the presence of three-dimensional micro-/nanostructures on the zinc metal delivers stable zinc plating/stripping beyond 2500 h (2 mA cm-2/1 mAh cm-2) in symmetric cells, a high Coulombic efficiency (99.71%) in half cells, and moreover an improved capacity retention (71.8%) is also observed in full cells. Equally intriguingly, the pouch cell with three-dimensional micro-/nanostructures can operate across various bending states without severely compromising performance. This work provides an effective strategy to construct ultrafine and high-precision three-dimensional micro-/nanostructures achieving high-performance zinc metal anodes and is expected to be of immediate benefit to other metal-based electrodes.

23.Investigation of micro/nano formation mechanism of porous graphene induced by CO2 laser processing on polyimide film

Shigen Bai a,*, Yong Tang b, Lihui Lin b, Luoyuan Ruan a, Ruixuan Song a, Huanjian Chen a,Yu Du a, Hongyu Lin a, Yufeng Shan a, Yanru Tang a 

a Research Center for Sensing Materials and Devices, Intelligent Perception Institute, Zhejiang Lab, Hangzhou 311100, China 

b School of Mechanical & Automotive Engineering, South China University of Technology, Guangzhou 510641, China 

 Laser-induced graphene (LIG) prepared from polyimide (PI) films via a facile CO2 laser-writing technique, has garnered considerable application prospects in micro-supercapacitors, intelligent sensors, and flexible electronics. To achieve the controllable fabrication of LIG, it is essential to understand the micro/nano formation mechanism of LIG. Herein, we explored the micromorphology evolution law, Raman characteristics, primary elements content distribution, and main electron peaks variation of LIG. The experimental results reveal that i) the irradiation region presents a typical crater-like structure accompanied by abundant three-dimensional networks; ii) the low laser power of 3.89 W (9.9 %) is conducive to the formation of high-quality LIG with a small ID/ IG; iii) the excessive laser power over 4.15 W (>10 %) provokes element recombination between unstable carbon bonds (C–/C=) and oxygen in the air to reduce the relative carbon content; iv) too high temperature destroys the stability of the graphene structure, resulting in cracks, holes, and defects. Based on the abovementioned findings, we concluded the thermal decomposition process of PI and the local reaction mechanism of LIG. Finally, we realized the controllable fabrication of high-performance LIG with an ultra-small ID/IG (0.3), an extremely high carbon content (94.49 %), and the prominent wetting affinity along with permeability for a water-based electrolyte. 

24.Laser-induced Graphene Derived 3D Porous Structure for Stable Aqueous Zinc-ion Batteries

Chengjuan Yang; Yuchun Tong; Hui Xiao; Faze Chen; Zhen Yang

Key Laboratory of Mechanism Theory and Equipment Design of Ministry of Education, Tianjin, China

 Aqueous Zn-based batteries have the advantages of low cost, large capacity, high power, environmental safety, and high energy density. Therefore, aqueous zinc-ion batteries have a wide application prospect in energy-storage devices. However, the growth of Zn dendrites become the most troublesome problem affecting the lifetime of Zn batteries, which inhibits the further development of Zn-based batteries. A simple method is reported to regulate the nucleation of zinc by laser-induced graphene, so that the formation of zinc dendrites can be inhibited. In this work, a 3D composite structure containing laser-induced graphene (LIG) and polyimide (PI) was constructed on the zinc surface by processing PI films with laser. The 3D structure formed by laser treatment has a large specific surface area and abundant micropores, which can cause uniform distribution of zinc ions. More importantly, the large number of defects in LIG significantly reduced the nucleation overpotential of Zn, and mitigates Zn dendritic growth.

25.Three-dimensionalization via control of laser-structuring parameters for high energy and high power lithium-ion battery under various operating conditions

Junsu Park a, Hyeongi Song b, Inseok Jang c, Jaepil Lee c, Jeongwook Um c,Seong-guk Bae c, Jihun Kim b, Sungho Jeong c, Hyeong-Jin Kim b

a Ground Technology Research Institute, Agency for Defense Development, P.O. Box 35, Yuseong-gu, Daejeon 34186, Republic of Korea

b Graduate School of Energy Convergence, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea

c School of Mechanical Engineering, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea

 Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery (LIB) electrodes. In this work, the effects of laser structuring parameters (groove pitch and depth) on the fundamental characteristics of LIB electrode, such as interfacial area, internal resistances, material loss and electrochemical performance, are investigated. LiNi0.5Co0.2Mn0.3O2 cathodes were structured by a femtosecond laser by varying groove depth and pitch, which resulted in a material loss of 5%–14% and an increase of 140%–260% in the interfacial area between electrode surface and electrolyte. It is shown that the importance of groove depth and pitch on the electrochemical performance (specific capacity and areal discharge capacity) of laser-structured electrode varies with current rates. Groove pitch is more important at low current rate but groove depth is at high current rate. From the mapping of lithium concentration within the electrodes of varying groove depth and pitch by laser-induced breakdown spectroscopy, it is verified that the groove functions as a diffusion path for lithium ions. The ionic, electronic, and charge transfer resistances measured with symmetric and half cells showed that these internal resistances are differently affected by laser structuring parameters and the changes in porosity, ionic diffusion and electronic pathways. It is demonstrated that the laser structuring parameters for maximum electrode performance and minimum capacity loss should be determined in consideration of the main operating conditions of LIBs.

26.Ultrafast laser texturing to improve wettability of polyimide (Kapton) films

L. Orazi a,b , R. Pelaccia a,* , V. Siciliani a , K. Oubellaouch a , M. Mazzonetto a , B. Reggiani a,c

a Department of Sciences and Methods for Engineering, University of Modena and Reggio Emilia, Italy b EN&TECH, University of Modena and Reggio Emilia, Italy c INTERMECH, University of Modena and Reggio Emilia, Italy 

 The versatile properties of the polyimide Kapton, including the good mechanical strength, excellent insulation, great thermal stability (up to 450 °C), high chemical resistance, good dielectric property and high gas permeability. Aim of this study is investigating the possibility of increasing the wettability of polyimide Kapton thin films by laser texturing. The laser textured surfaces were characterized through the water contact angle measurement and the surface tension evaluation; morphological and topological analyses were performed by scanning electron microscopy and atomic force microscope, respectively. As main outcome, it was found that laser texturing increases the wettability with respect to the untreated material with a decrease of contact angle of more than 20 %. In addition, the ultrashort pulse laser induced, on the material, LIPSS structures oriented in the direction of the polarization plane.

27.Laser structuring of graphite anodes and NMC cathodes – Proportionate influence on electrode characteristics and cell performance

Lucas Hille, Lingji Xu, Josef Keilhofer, Sandro Stock, Johannes Kriegler, Michael F. Zaeh

Institute for Machine Tools and Industrial Management, Technical University of Munich, Boltzmannstr. 15, 85748, Garching, Germany

 For this study, microscopic diffusion channels were introduced into graphite anodes and NMC622 cathodes through short-pulsed laser radiation. Lithium-ion batteries (LIBs) are the dominating electrochemical energy storage solution for most consumer electronics and electric vehicles (EVs) today. The impact on the performance of coin cells comprising anodes and cathodes in pristine and structured conditions, respectively, was investigated in a discharge rate test. At high rates (1 C – 3 C), particularly cells with laser-structured anodes showed a significant increase in capacity retention of up to 10 % in comparison to cells with pristine anodes. Characteristic features in the incremental capacities indicated cell polarization and diffusion inhibition as the rate-limiting mechanisms at high discharge rates and revealed differences in the dominating deintercalation stages between the cell configurations. Fitting an equivalent circuit model to the impedance spectra of symmetric cells showed a reduction of the ionic resistances by approx. 45 % for the anodes and approx. 21 % for the cathodes through laser structuring. A similar behavior was observed for the MacMullin numbers and effective tortuosities of the electrodes. In conclusion, laser structuring offers a particular potential to overcome the diffusion-limiting characteristics of the graphite anodes. The insights into the proportionate impact of anode or cathode structuring are of high value for the design and manufacturing of future lithium-ion batteries.

28.Laser-induced transient conversion of rhodochrosite/polyimide into multifunctional MnO2/graphene electrodes for energy storage applications

Jun Cao a, Chunjie Yan a, Zefan Chai a, Zhigang Wang a, Minghe Du a, Gen Li a, Huanwen Wang a , Heng Deng a b

a Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China

b Shenzhen Research Institute, China University of Geosciences, Shenzhen 518000, China

 Rhodochrosite, one of the largest mineral sources of manganese with the chemical composition MnCO3, is commonly served as a low-cost naturally abundant manganese precursor for various industries such as steel, agriculture, and alloy fields. Laser-induced graphene (LIG) has been extensively investigated for electrochemical energy storage due to its easy synthesis and highly conductive nature. However, the limited charge accumulation in LIG usually leads to significantly low energy densities. In this work, we report a novel strategy to directly transform natural rhodochrosite into ultrafine manganese dioxide (MnO2) nanoparticles (NPs) in the polyimide (PI) substrate for high-performance micro-supercapacitors (MSCs) and lithium-ion batteries (LIBs) through a scalable and cost-effective laser processing method. Specifically, laser treatment on rhodochrosite/polyimide precursors induces the thermal explosion, which splits rhodochrosite (10 μm) into MnO2 NPs (12–16 nm) on the carbon matrix of LIG due to the sputtering effect. Benefiting from largely exposed active sites from the ultrafine MnO2 and the synergetic effect from highly conductive LIG, the MnO2/LIG MSCs show a high specific capacitance of 544.0 F g−1 (154.3 mF cm−2; 14.16 F cm−3) at 3 A/g and 82.1% capacitance retention after 10,000 cycles at 5A/g, in contrast to pure LIG (<100 F g−1). Moreover, the MnO2/LIG-based LIBs show the highest reversible discharge capacity of ∼1097 mAh g−1 at 0.2 A/g and ∼ 866.4 mAh g−1 at 1.0 A/g. This study opens a new route for synthesizing novel LIG-based composites from natural minerals.