A microwave‐based one‐pot process for homogeneous surface coating: improved electrochemical performance of Li(Ni1/3Mn1/3Co1/3)O2 with a nano‐scaled ZnO:Al layer

Abstract

Abstract In this article, a versatile process based on microwave‐assisted sol–gel synthesis is introduced in order to apply a surface coating on cathode material for lithium‐ion batteries. Here, a nano‐scaled ZnO:Al (AZO) layer is coated homogeneously onto Li(Ni1/3Mn1/3Co1/3)O2 (NMC111) powder at temperatures below 210°C within a few minutes. In contrast to other wet‐chemical coating techniques, the method described here is conducted in a one‐pot reaction and does not require a post‐annealing step at elevated temperatures. Investigations via high resolution transmission electron microscopy (HR‐TEM), scanning transmission electron microscopy (STEM) and inductively‐coupled plasma optical emission spectroscopy (ICP‐OES) promote a thorough understanding of coating microstructure and quality in dependence of reaction temperature, duration and precursor concentration. The AZO protective coating on NMC111 significantly reduces capacity fading during cycling in the voltage range of 3.0‐4.5 V. Furthermore, applying optimal quantities of the coating agent on NMC111 lead to enhanced specific capacities compared to the uncoated material.

Keywords

• cathode materials
• lithium‐ion batteries
• microwave synthesis
• sol–gel method
• ultrathin coating