Enhanced Cycling Performance by Transition Metal Substitution on Li2CuO2 Cathode Additive for Advanced Lithium-Ion Battery

Abstract

Lithium-Ion batteries (LIBs) have made remarkable progress in the last decade and have been employed so far as the most popular power source for electric vehicles (EVs). However, the energy density issue still remains a drawback for LIBs on long-range driving of EVs for the reason of significant irreversible Li+ loss in the initial charging process of LIBs, induced by a spontaneous formation of solid electrolyte interphase (SEI) on the anode surface. Therefore, strategic studies are required to maximize the energy density of LIBs as compensation of the initial loss of Li+ during cell operation. The utilization of a Li-excess cathode additive in commercial cathodes is an ideal approach to minimize the loss of energy density of LIBs. Recently, Li2CuO2 has been proposed as a potential cathode additive with many advantages over other candidates, including the following: (i) high charge capacity (~ 490 mAh g-1), (ii) comparable operating voltage window (2.5 ~ 4.3 V vs. Li/Li+) to commercial cathode materials, and (iii) abundance of copper (Cu) on the earth. But, its practical use is still restricted by the structural instability and spontaneous oxygen (O2) evolution (> 3.8 V vs. Li/Li+), which results in loss of reversibility during subsequent cycling. It is thus crucial to reinforce the structure of Li2CuO2 to make it more reliable as a cathode additive for charge compensation. In a pursuit of improving the structural stability of Li2CuO2, herein, we demonstrate structural modification via co-substitution by heteroatoms, such as nickel (Ni) and manganese (Mn), for improving the structural stability and electrochemical performance of Li2CuO2. Such an approach effectively enhances the reversibility of Li2CuO2 by suppressing continuous structural degradation and O2 gas evolution during cycling. Our findings provide new conceptual pathways for developing advanced cathode additives for high-energy LIBs.