Zn-enriched cathode layer interface via atomic surface reduction of LiNi_0.5Mn_1.5O₄: Computational and experimental insights

Despite having the ability to deliver 650 W h kg⁻¹ in addition to the impressive rate capability, superior thermal stability, and facilitated electronic and ionic lithium conduction, LiNi_0.5Mn_1.5O₄ (LNMO) is far from commercial applications. LNMO suffers from irreversible electrolytic degradation on its surface under high voltage operations leading to capacity fading and poor battery life. Therefore, this work aims to improve the stability and electrochemical behavior of LNMO by creating a Zn-enriched cathode layer interface via eccentric and facile diethyl zinc-assisted atomic surface reduction (Zn-ASR). In-depth surface characterization tools and computational calculations demonstrates a conformal 7-8 nm thin Zn-O and C-O enriched layer encapsulating the cathode particles resulting from Zn-ASR. The intensive comparative electrochemical and spectroscopic analysis, indicates superior electrochemical performance of the surface-reduced LNMO w.r.t rate capability (14% higher at 4C), cycling stability, and capacity retention (87% retention). A decrease in gaseous evolution on the surface-treated sample arising from the electrolyte degradation further explains the improvement in the stability and electrochemical behavior of Zn-ASR LNMO. This work proves that electrode material can be substantially improved and incentivized by the chemo-mechanical benefits of rationally designed surface layers.