Effects of Copper Doping in High-Rate, Lithium Manganese-Rich Layered Oxide Cathodes for Lithium-Ion Batteries

Lithium manganese-rich layered oxides are promising cathode materials for lithium-ion batteries due to their high discharge capacity, but they suffer from capacity fading and poor rate performance. Herein we report on the physicochemical and electrochemical properties of Li1.15Mn0.7Ni0.2Co0.1O2 synthesized via a sol gel method, and study the effect of copper doping on the resulting materials. Electrochemical testing at 1 C revealed 1 % Cu doping enhanced capacity retention (from 58 % to 78 %) but also decreased capacity, while in contrast 10 % Cu doping increased capacity by 21 %. Thorough characterization (including x-ray diffraction, scanning electron microscopy, inductively coupled plasma-optical emission spectroscopy, and electrochemical analyses such as voltage vs. capacity and dQ/dV plots) was employed to understand these results, which may be attributed to the competition of two different phenomena depending on the copper content. Consequently, this work highlights the importance of targeting bespoke stoichiometries depending on the desired electrochemical characteristics - an important point for the future design of materials for fast charging and high power applications.