Recycling spent ternary cathodes into multi-heterogeneous Ni4N/Co5.47N/MnO composite catalysts enable efficient oxygen evolution reaction

Abstract

Fabricating efficient electrocatalysts for water splitting through recycling ternary (LiNi_1-x-yMn_xCo_yO₂) cathodes of spent lithium-ion batteries (LIBs) is promising and sustainable, however, the relative reasonable phase composition and microstructure still need be explored. Herein, a composite material composed of multi-heterogeneous Ni₄N/Co_5.47N/MnO nanoparticles coupled with porous carbon fibers was fabricated through a direct carbothermal reduction process of waste LiNi_0.5Mn_0.2Co_0.3O₂ (NCM523) cathodes material dispersed into nitrogenous spinning precursor. Interestingly, this optimized material obtained at 800 °C (NCM523@CF-800) possesses abundant Ni₄N/Co_5.47N/MnO multi-heterostructure, endowing it with multifaceted advantages as electrocatalysts for oxygen evolution reaction (OER). Specifically, the unique structural features of multi-heterostructure promote the transfer of electrons/charges on the interface, and highly enhance the reaction kinetics. Additionally, during OER process, because of the protection of carbon matrix, Ni₄N/Co_5.47N/MnO has the mere surface reconstruction and forms the real active oxygen-containing species especial NiOOH. And the maintained core of Ni₄N/Co_5.47N/MnO provides high conductivity for the formed active oxygen-containing species. As a result, the optimized NCM523@CF-800 employed as OER electrocatalyst in water electrolysis only require 271 mV to deliver a current density of 10 mA cm⁻² in 1 M KOH. Meanwhile, an excellent stability of 140 h can be achieved under high current density of about 160 mA cm⁻². This work may pave the way for the rapid and efficient recycling and utilization of spent battery electrode materials.