Development of High Performance Mn-based Spinels as Cathode Materials for Li-ion Batteries

Abstract

As potential cathode candidates for large-capacity lithium ion batteries, spinel lithium manganese oxides have many advantages such as high operating voltage, abundance, low manufacturing cost, low toxicity, and excellent voltage profile compared to commonly used cathode materials (such as layered LiCoO2). Also, manganese is inexpensive and environmentally friendly material. However, LiMn2O4 undergoes serious capacity fading at elevated temperature. In order to overcome the disadvantage, material scientists have been making great efforts for developing stable LiMn2O4 materials. As a result, following methods have been highlighted for industries because of their facile synthetic methods and low cost of production; 1) Partial cationic substitution of manganese with other metal elements, and 2) Surface coatings and particle size control. In the last two decades, the lifespan of Mn-based spinel cathode at elevated temperature has been improved by applying above methods. However, there are trade-offs among the battery performances. For example, more substituted metal (M) in LiMn2-xMxO4 leads to better cycleability at elevated temperatures. However, doping level is inversery proportional to the gravimetric capacity. In addition, coating layer can positively affect on the cycleability and safety, but may impede the Li-ion transfer, that results in low rate capability. In the same manner, the larger particle size gives rise to the better cycleability, but it returns the lower rate capability. The objective of my research projects is to develop high energy and high power cathode materials without sacrificing other important battery performances. The project can be divided into two parts: Part 1: Experimental Section 3.1-3.2 A Study on the improvement of the rate capability without sacrificing the volumetric energy density Part 2: Experimental Section 3.3-3.4 A Study on the improvement of the cycleability without sacrificing the energy density and rate capability