High‐Speed Lithium‐Ion Transfer inside Mesoporous Core–Shell LiFePO 4 /Carbon‐Sphere Cathodes

A thin layer of LiFePO 4 was coated onto a mesoporous carbon sphere to obtain a mesoporous core–shell LiFePO 4 /carbon sphere (LFP/MCS) composite, for which the thickness of the nanoscale LiFePO 4 thin shell was approximately 30–50 nm. Meanwhile, pristine LFP and MCS mixed with LFP samples (MCS‐m‐LFP) were prepared for comparison. The significantly larger surface area of LFP/MCS (43–151 m 2  g −1 ) compared with pristine LFP (12 m 2  g −1 ) is derived from the mesoporous carbon framework and thin nanoscale LFP shell. The large surface area of LFP/MCS provides greater surface content between the LiFePO 4 shell and electrolytes, which results in a high charge–discharge rate. Also, this remarkably thin LiFePO 4 cathode shell shortens the diffusion length of lithium ions thereby achieving a high charge–discharge rate for electrode materials. Consequently, under all charge–discharge rates (0.1–20  C ), the specific capacities of LFP/MCS are higher than those of both the pristine LFP and MCS‐m‐LFP. More specifically, at 10  C , LFP/MCS exhibited the excellent rate performance of 82 mAh g −1 , compared to 25 and 41 mAh g −1 for LFP and MCS‐m‐LFP, respectively. Furthermore, the discharge capacity for LFP/MCS at the high discharge rate of 20  C remains stable whereas that for LFP does not. This demonstrates the efficient transport capability of Li ions into the nanoscale LFP shell in the core–shell structure of LFP/MCS, which is essential for the improvement of the electrochemical performance.