Ni/Mn and Al Dual Concentration-Gradients To Mitigate Voltage Decay and Capacity Fading of Li-Rich Layered Cathodes

Abstract

Li-rich layered oxides (LLOs) suffer from severe voltage decay and capacity fading which have hindered their practical application for years. Herein, Co-free LLO microspheres with Ni/Mn and Al dual concentration-gradients are constructed to mitigate the above obstacles. One concentration-gradient is an electrochemical active gradient (Ni/Mn), and the other is an electrochemical inert gradient (Al). XPS and soft and hard XAS after different cycles prove that the combination of dual concentration-gradients effectively mitigates interfacial reactions, structural evolution, and the generation of lower-valence Mn3+/Mn4+ or Mn2+/Mn3+ redox couples during cycling. As a result, the voltage fading rate of LLO cathode with dual concentration-gradients after 100 cycles is as small as 0.97 mV/cycle at 100 mA g–1. Furthermore, its capacity retention ratio is also as large as 84.1% after 400 cycles at 300 mA g–1. The combination of dual concentration-gradients in this work provides a way to develop advanced LLO cathodes for practical application in the near future.