Thermal Gradients with Sintered Solid State Electrolytes in Lithium-Ion Batteries

Abstract

The electrolyte is one of the three essential constituents of a Lithium-Ion battery (LiB) inaddition to the anode and cathode. During increasingly high power and high current charging anddischarging, the requirement for the electrolyte becomes more strict. Solid State Electrolyte (SSE) seesits niche for high power applications due to its ability to suppress concentration polarization andotherwise stable properties also related to safety. During high power and high current cycling, heatmanagement becomes more important and thermal conductivity measurements are needed. In thiswork, thermal conductivity was measured for three types of solid state electrolytes: Li7La3Zr2O12(LLZO), Li1.5Al0.5Ge1.5(PO4)3(LAGP), and Li1.3Al0.3Ti1.7(PO4)3(LATP) at different compactionpressures. LAGP and LATP were measured after sintering, and LLZO was measured before andafter sintering the sample material. Thermal conductivity for the sintered electrolytes was measuredto 0.470±0.009 WK−1m−1, 0.5±0.2 WK−1m−1and 0.49±0.02 WK−1m−1for LLZO, LAGP, andLATP respectively. Before sintering, LLZO showed a thermal conductivity of 0.22±0.02 WK−1m−1.An analytical temperature distribution model for a battery stack of 24 cells shows temperaturedifferences between battery center and edge of 1–2 K for standard liquid electrolytes and 7–9 K forsolid state electrolytes, both at the same C-rate of four.