High Volumetric Energy Density of LiFePO4/KB Cathode Materials Based on Ketjen Black Additive

Abstract

AbstractHigh tap density and superior electronic conductivity of LiFePO4/KB was synthesized by a combination of wet ball‐milling, spray drying, and carbothermal reduction with Ketjen black (KB) as a carbon additive. KB is a conductive carbon black with the special chain‐like structure. When KB is used to coat on the surface of primary particles of LiFePO4, the chain‐like structure can form a developed 3D network structure between the primary particles of LiFePO4. This special structure can not only provide conductive channels for electrons but also cause the primary particles of LiFePO4 to aggregate tightly. Comparing to the conventional carbon coating materials (only glucose as the carbon source) with a low volumetric energy density of 452.5 Wh L−1 at 1 C rate, we simultaneously increased the electrical conductivity (7.8×10−2 S cm−1) and tap density (1.6 g cm−3) by adding KB, resulting in a higher volumetric energy density of 829.9 Wh L−1 at 1 C rate. When KB is added at 5 % of glucose mass, the LiFePO4/KB composite shows an excellent discharge capacity of 161.6 mAh g−1 at 0.2 C and the 97.7 % retention rate after 500 cycles at 5 C.