The Study Of Capacity Fading In Lithium Ion Batteries

Lithium-ion battery mainly consists of positive electrode, negativeelectrode, separator and electrolyte. The capacity of lithium-ion batterydepends on the positive and negative electrode active material and the ratioof the mass. Lithium-ion battery cycle life affected by many factors, suchas the active material matching with the electrolyte, the active material andpreparation process, the electrode structural properties, the purity andcomposition of the electrolyte, the thermal stability and chemical stabilityof the separator.In order to study the mechanism of capacity fading and improve thecyclic life of lithium-ion batteries, the paper employed prismatic battery todetermine the properties of porous electrode by using mercury instrumentand electrochemical performance through CC-CV charging anddischarging and AC impedance.The results showed that the higher current rate, the faster capacityfading. Via mercury instrument, the porosity, pore area, pore size andtortuosity were detected during the cycles; porosity reflects the masstransference of Li+; pore area reflects electrochemical reaction area; poresize and tortuosity reflect diffusion path. The value of ohmic resistance,SEI resistance, charge transfer resistance and diffusion resistance increasedduring the cycles by AC impedance test.