Electrochemical and Thermal Behavior of Modified Li and Mn‐Rich Cathode Materials in Battery Prototypes: Impact of Pentasodium Aluminate Coating and Comprehensive Understanding of Its Evolution upon Cycling through Solid‐State Nuclear Magnetic Resonance Analysis

Abstract

In continuation of the work on the stabilization of the electrochemical performance of Li and Mn‐rich LixNiyCozMnwO2 (HE‐NCM, x > 1, w > 0.5, x + y + z + w = 2) cathode materials via atomic layer deposition (ALD) surface coatings, herein, the active role of aluminum oxides‐based coatings, during prolonged cycling in battery prototypes with graphite anodes, is discussed. Notable progress in electrochemical cycling and rate performance of Na‐aluminate‐coated Li1.142Mn0.513Ni0.230Co0.115O2 cathode material is established. These coated electrodes delivered a stable discharge capacity of 145 mAh g−1 (66% retention), compared to only 118 mAh g−1 (55% retention) for the uncoated sample at a 1.0 C rate after 400 cycles. Steady average discharge potential, lower voltage hysteresis, and stable energy density profiles are the noteworthy achievements for the coated material during cycling. Significant improvement in the coated material's thermal stability compared with the uncoated one has also been confirmed. The present study also enlightens about the Na‐aluminate coating's orientation and distribution on HE‐NCM material's surface. 23Na and 27Al solid‐state nuclear magnetic resonance (NMR) studies reveal the Na‐aluminate coating's crystalline constituent's disappearance upon cycling. The partial dissolution of Na5AlO4 coating, followed by forming a secondary disordered edge‐site phase that remains even after long‐term cycling, is disclosed.

Keywords

• atomic layer deposition
• Li and Mn‐rich NCM cathodes
• Li‐ion batteries
• Na‐aluminate coatings
• solid‐state nuclear magnetic resonance
• thermochemical behaviors