Nanodiamond-modified separators and optimized graphene anodes for highly enhanced performance of lithium-ion batteries

Abstract

As one of the core components in lithium-ion batteries (LIBs), upgraded separators are of great demand to further improve the performance of LIBs. This work designed two types of polypropylene (PP) separators modified by nanodiamonds (NDs) and NDs/ZnCO3 (named DPP and DZPP separators, respectively) used to enhance the performance of LIBs. LIBs with the modified separators possess excellent cycling stabilities and high specific capacities at various current densities (739 mA h g−1 for DPP-LIBs and 910 mA h g−1 for DZPP-LIBs after 1000 cycling processes at a rate of 2 C), which are significantly superior as compared to LIBs with traditional PP separators (460 mA h g−1). NDs are favorable for building novel buffer layers on the modified separators during the cycling processes, resulting in uniform depositions of lithium-containing compounds. Furthermore, NDs migrate to graphite anodes and enhance the specific area of the anodes through forming few-layered graphene. The in-situ lithiation of ZnCO3 creates an additional Li2CO3 layer on the DZPP separators, which serves as a buffer layer to redistribute Li-ions during the cycling processes of DZPP-LIBs. It is demonstrated that the deposition of NDs and/or NDs/ZnCO3 on PP separators provides a feasible, low-cost, and highly efficient method to improve the performance of LIBs.