Modification of NMC811 with titanium for enhanced cycling and high-voltage stability

Abstract

LiNi1-x-yMnxCoyO2 (NMC) with a nickel content of ≥80% is currently considered one of the most promising lithium-ion battery cathode materials for applications that require both a high energy density and reasonable costs. However, its widespread use has so far been limited by its inherently lower structural stability and higher surface reactivity compared to NMC materials with a lower nickel content. Here, we explore wet-chemical titanium-based bulk and surface modifications to improve the cycling and high-voltage stability of NMC811. We find that both doping and coating with titanium improve cycling stability. For example, the capacity retention of graphite/NMC811 full cells cycled for 200 cycles between 2.8 and 4.4 V at C/3 improves from 86.1% for the pristine NMC811 to 89.4% and 91.5% for the doped and coated samples, respectively. Combining doping and coating in a two-step process results in a material with the most balanced properties in terms of capacity, cycling stability, rate performance, and high-voltage stability.