Modeling and simulation in rate performance of solid-state lithium-ion batteries at low temperatures

Solid-state lithium-ion batteries (SSBs) not only improve the energy density of batteries, but also solve the unavoidable battery safety problems of liquid electrolytes. However, the rate capability of SSBs cannot meet the needs of practical applications due to the defects of low ionic conductivity and slow reaction rate of solid-solid interface, which becomes one of the bottlenecks restricting its development. Moreover, SSBs usually suffer from capacity reduction and security problems under low temperatures. This paper established a two-dimensional model of SSBs based on a multi-physical field simulation software, and studied the rate performance of SSBs under low temperatures. The distribution of lithium ion concentration in both electrolyte and cathode, diffusion coefficient of lithium ion and high rate discharge behavior of SSBs at low temperature were discussed in details. The simulation results exhibit that the rate capability of SSBs at low temperature can be improved by appropriately reducing the thickness of solid-state electrolyte. When the electrolyte thickness is fixed as 0.6 μm, the discharge capacities decrease from 0.345 Ah m−2 to 0.343 Ah m−2 as the discharge rates increase from 3C to 8C, together with a high capacity retention ratio of 99.5 %. Besides, SSBs can still maintain a high and flat discharge platform even at the high rate of 8C. This study proposes a method to improve the rate performance of solid state battery at low working temperatures, which has a theoretical guiding significance and engineering value for the structure design of SSBs.