Oxygen vacancy-induced spinel phase and Li3PO4 Coating Enabling performance promotion of Li1.2Mn0.54Ni0.13Co0.13O2 Cathodes

Li-rich Mn-based layered oxides (LRMOs) with high specific capacity and elevated working voltage, are regarded as promising candidates for next-generation lithium-ion batteries (LIBs). Nevertheless, LRMOs still face serious challenges, e.g., voltage decay, subpar rate performance, and subpar cycling performance. These issues significantly limit their electrochemical performance and practical application. Currently, a lot of endeavors are being dedicated to handling the above problems. Herein, we propose a simple dual-interface modification method, which involves treating the surface of the Li-rich Mn-based layered oxides with a specific concentration of NH 4 H 2 PO 4 solution to produce Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 @spinel@Li 3 PO 4 . The findings indicate that the surface coating layer of Li 3 PO 4 not only functions to safeguard the material against electrolyte corrosion but also facilitates an enhanced diffusion rate of Li + to a certain degree. Furthermore, oxygen vacancies are created on the surface as a result of the reduction of NH3 produced by the breakdown of NH 4 H 2 PO 4 . This phenomenon subsequently facilitates the dissolution of transition metal (TM) ions to form a local spinel layer. The spinel layer can reduce phase distortion, create a 3D diffusion path for Li + transmission, inhibit oxygen over-oxidation, and enhance dynamic stability. Therefore, the LRMO treated with NH₄H₂PO₄ delivers an exceptionally high first-discharge capacity of 301.59 mAh g⁻¹ and an initial Coulombic efficiency of 93.13 %, compared with 278.47 mAh g⁻¹ and 80.68 % for pristine LRMO. After 100 cycles at 1 C, the treated material retains 90.47 % of initial capacity, whereas the untreated counterpart retains only 73.62 %. The material also shows minimal voltage decay, measured at only 3.025 mV per cycle, and possesses favorable rate capability, achieving up to 157.88 mAh g⁻¹ at a rate of 5C. Clearly, this dual-interface modification approach provides crucial technical insights that are vital for the advancement and high-performance industrialization LRMO.