High-valence Ni3+ construction and stability by electrochemical de-lithiation boosting oxygen evolution†

Abstract

The development of inexpensive and efficient oxygen evolution reaction (OER) catalysts is crucial for the large-scale application of water splitting to produce green hydrogen. Different from traditional preparation methods, in this study, the electronic structure of ternary NCM (LiNi_0.94Co_0.05Mn_0.01O₂) was directly reconstructed from the cathode of spent lithium-ion batteries through electrochemical de-lithiation technology to obtain efficient OER catalysts. The optimized NCM94-1V-90 min exhibits a low overpotential of 270 mV at 10 mA cm⁻² along with excellent stability for a 300 h durability test. The high OER performance is attributed to the electronic structure reconstruction and microstructure transformation during electrochemical de-lithiation, which generates a large number of high-valence Ni³⁺ and O vacancies as well as structural fragmentation, respectively, supplying more active sites and enhancing electronic conductivity, also confirmed by the density functional theory (DFT) theoretical calculation. The strategy of electrochemical de-lithiation technology to improve the OER electrocatalytic performance not only can recycle the cathode materials of lithium-ion batteries, but can also be extended to other electrode materials of spent batteries.