A hybrid Carbon–Li1.3Al0.3Ti1.7(PO4)3 conductive coating for high current rate LiFePO4 cathode material

Abstract

A stable and conductive interface is essential in improving the performance of cathode materials in Li-ion batteries by reducing interfacial resistances and balancing the charge transfer, especially at high current rates. In this study, we design a hybrid conductive coating layer consisting of carbon (C) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte on olivine LiFePO4 (LFP) cathode material (LFP@C_LATP) to utilize the advantage of each coating component. Carbon is generally required to improve conductivity and protect LFP particles from undesirable side reactions at the electrode/electrolyte interface. At the same time, LATP is electrochemically active and exhibits superior Li-ion conductivity to LFP. Notably, our experimental results reveal that the coating layer can provide a buffer zone on the LFP particle surface to regulate Li-ion insertion/extraction, extend voltage plateaus, and contribute an extra capacity to the cathode material. The electrochemical performances of LFP@C_LATP, therefore, are significantly improved. As a result, the LFP@C_LATP cathode can deliver a discharge capacity of 164.5 mAh g−1 at 0.1 C. Particularly, it can be electrochemically active at an extremely high current rate, up to 60.0 C, after consecutively cycling for a number of cycles. This hybrid coating strategy is promising for developing high energy, high rate, and fast charge cathode materials.