Layered Li-rich Oxide Cathode Microparticle 0.4Li2MnO3∙0.6Li(Mn0.43Ni0.36Co0.21)O2 Decorated with Nano Grains and its Electroochemical Performance

Abstract

The development of alternative energy sources has become the primary strategy to overcome unstable crude-oil prices and the issues associated with climate change. Seasonal variations in alternative energy sources have prompted the need for an energy storage system. Reduction of carbon dioxide is also a key strategy for solving the problem of climate change. Carbon dioxide produced by transportation constitutes almost one-third of total carbon dioxide production. Replacing gasoline-based transportation with electric vehicles represents a promising solution to reduce carbon dioxide emissions. Among the various types of batteries, lithium secondary batteries are considered the most attractive option because of their light weight and high power density. However, the current technical specifications are not quite satisfactory for full scale commercialization of electric vehicles (EVs) and hybrid electric vehicles (HEVs). Increasing driving range and reducing the cost of batteries remain key issues that need to be addressed. Nano-composite layered compounds of xLi2MnO3·(1-x) LiMO2 (M = Ni, Co, Mn) were recently shown to exhibit high capacities in the high voltage region of –4.6 V and have lower cost and better safety compared to LiCoO2, which is used in commercial lithium-ion batteries. However, the layered xLi2MnO3·(1-x) LiMO2 shows low rate capability due to low electronic conductivity, which is caused by the insulating Li[Li1/3Mn2/3]O2 component. Therefore, the low rate capability of these batteries needs to be addressed for use in EVs and HEVs, which require fast charge/discharge reactions. Various methods have been developed to improve the rate capability of layered xLi2MnO3·(1-x) LiMO2 composite particles, such as doping with another transition metal, surface modification, and coating. However, attempts to control the morphology and particles size has not been reported due to limitations in the preparation methods. The cathode particles are normally prepared by a solid-state reaction or liquid phase methods and these methods require a high calcination temperature and long calcination time to obtain desirable composite phase. These calcination conditions result in aggregation and growth of primary particles, which degrades the diffusion of lithium ions between the electrode and electrolyte. Spray pyrolysis has recently been used for the preparation of multicomponent ceramic particles due to its several advantages, such as being a simple system, ease of controlling particle size and preparing spherical particles of multi-components and formation of a pure well-crystallized phase at low calcination temperature. Thus, in this study, we prepared spherical 0.4Li2MnO3∙0.6Li(Mn0.43Ni0.36Co0.21)O2 microparticles decorated with nano-grains via spray pyolysis and the structural and electrochemical performance of the prepared particles were investigated.