Analysis of the relationship between vertical imparity distribution of conductive additive and electrochemical behaviors in lithium ion batteries

Abstract

In this work, double layered LiFePO4 materials with different content of conductive carbon black are proposed for evaluating systematically the influence of imparity distribution of conductive additive on the electrochemical behaviors of cathode material for lithium ion batteries. Their polarization effects and electrochemical performances were investigated and compared in detail. It was found that there exists a simple empirical rule correlating the distribution of the conductive additive and the depolarization effect under the premise that the total content of the conductive additive is kept constant. The electrochemical performance of LiFePO4/C electrode tends to get better with increasing the conductive additive loading in the lower layer. This can be attributed to that the more conductive additive content in the lower layer could provide more available paths for electronic transmission, and markedly decrease the interfacial impedance between LiFePO4/C cathode material and current collector, thus improving the ability of collecting electron and maintaining a reliable electron transport system, especially under high current densities. This finding can enlighten us to design a more rational optimization of the electrode by controlling the distribution of conductive additive in the cathode material for high performance lithium ion batteries.