Xin Qian

Our group is particularly interested in the coupling between thermal generation and transport in electrochemistry systems. These couplings could be essential for the performance, safety, and stability of batteries or supercapacitors. The thermo-electrochemistry could also be important in developing clean and sustainable energy conversion materials and devices harvesting low-grade heat, such as ionic thermoelectrics and thermally regenerable batteries. We are combining molecular-level to device-scale modeling, spectroscopic measurements, and electrochemical characterizations to understand the transport and conversion of energy by ions. 

Atomistic modeling like molecular dynamics (MD) is a powerful tool for modeling thermal transport without ignoring the detailed atomic structures. However, MD suffers from the limited accuracy of potential fields. I developed potential fields from first-principles data for complex materials systems which are challenging to model using perturbation theory of phonon picture, including hybrid organic-inorganic materials, disordered oxides for thermal barrier coatings, material phases with dynamical instability. 

Characterizing thermal conductivity is a longstanding challenge in consensed matter physics and material science. Pump-probe thermoreflectance uses ultrafast lasers to create thermal excitation and monitor the thermal transport dynamics from a dozen of picoseconds to several nanoseconds. It primarily measures the through-plane thermal conductivity.  I focused on developing methods to characterize the entire anisotropic tensor of thermal conductivity using varied spot size, beam offset and transducerless approaches.