Facile synthesis and electrochemical performance of lithium-rich layered oxides with stable hierarchical structure through HEPES-assisted co-precipitation method

Abstract

Lithium-rich layered oxide (LLO) electrode material is now actively developed as a promising cathode for next-generation lithium-ion batteries due to its high specific capacity. The electrochemical property of the LLO material is mainly regulated by preparation conditions. Here, we report a facile 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) assisted co-precipitation method to prepare Li1.2Mn0.54Co0.13Ni0.13O2. The HEPES buffer solution with strong pH buffering capacity not only can keep the pH of the reaction solution stable, but also acts a complexing agent to promote the uniform distribution of elements and in control of the nucleation and growth rate of crystals during the co-precipitation process. The dispersant role of HEPES helps to prepare regular LLO microspheres with unique hierarchical structure, which endows sufficient contact of the particles with electrolyte, shortens Li+ diffusion path and provides high structural stability. The electrode demonstrates superior electrochemical performance and excellent cycling stability at different discharge currents. High discharge capacities of 147.2 and 100.0 mAh g−1 could be achieved after 200 cycles at high current densities of 5 C and 10 C, respectively. The paper provides a novel strategy of the controllable route for high energy storage materials and reveals the correlation between the cation distribution and the electrochemical performance stability of the materials.