Study on Prediction Model of Performance and Degradation of LFP/Graphite Lithium-ion Battery

Abstract

The initial degradation behavior of lithium-ion batteries is complicated, and it has been difficult to construct a model that sufficiently matches the capacity change in cycle life tests and calendar life tests under different conditions. In this study, we measured the performance and lifetime of LiFePO4/Graphite lithium-ion battery and analyzed their electrochemical and degradation characteristics. As a result, we predicted the mechanism as follows. There are two or more phases of side reactions, including reversible reaction that forms the SEI layer and the sequential reaction that produces the non-rechargeable substance. These reactions proceed simultaneously, and each reaction rate changes depending on the electrode potential. In addition, the SEI layer is formed by the former reversible reaction and prevents the diffusion of the deteriorated substance. This model is able to fit to the complicated degrading behavior of the lithium-ion battery.

Keywords

• degradation
• lfp cathode
• sei layer
• lithium-ion battery