Affiliation:
1. State Key Laboratory of Silicon Materials and School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, P. R. China
2. Department of Materials Science, Fudan University, Shanghai 200433, P. R. China
3. Institute of Science and Technology for New Energy, Xi’an Technological University, Xi’an 710021, P. R. China
Abstract
Li-rich Mn-based layered oxide (LMLO) cathode materials have high-capacity and high-energy density, which are highly potential for next generation Li-ion batteries; however, their disadvantages of low initial coulombic efficiency, poor cyclic stability, large voltage fading during cycling and poor rate capability hinder their practical applications. In this work, a novel surface modification strategy to improve the electrochemical properties of LMLO cathodes is developed, where a highly reductive compound of LiBH4 is adopted as an additive to a conventional electrolyte. Examined by a conventional LMLO material of Li[Formula: see text]Ni[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2- (L[Formula: see text]M[Formula: see text]LO), the cyclic stability and rate capability of the cathode are significantly improved when 0.3 wt.% LiBH4 is added. The cathode has an initial reversible discharge capacity of 280 mAh g[Formula: see text] at 20 mA g[Formula: see text], showing the capacity retention of 94.3% after 100 cycles. A capacity of 193 mAh g[Formula: see text] maintains after 300 cycles at 200 mA g[Formula: see text], corresponding to the capacity retention of 86.2%, and the capacity reaches as high as 138 mAh g[Formula: see text] at 2000 mA g[Formula: see text]. It is found that partial transition metals (TMs) at the surface of the L[Formula: see text]M[Formula: see text]LO particles are reduced by LiBH4 during the initial several cycles of activation, resulting in an in situ formation of a stable and lithium-diffusion feasible spinel structure surface coating in thickness of several nanometers with atomic match to the bulk particle. The surface coating not only retards the dissolution of the TMs from L[Formula: see text]M[Formula: see text]LO to the electrolyte, stabilizing the crystal structure during cycling, but also facilitates the lithium diffusion. As a result, the cyclic stability and rate capability of the cathode are evidently improved. The method is facile, scalable, and low cost, which has potential for commercial utilization.
Publisher
World Scientific Pub Co Pte Lt
Subject
General Materials Science