Regulate the Solvation Structure and Interface by Nitrate in Phosphate-Based Electrolytes for 4.5 V-Class Ni-Rich Batteries

Phosphate-based electrolyte propels the advanced battery system with high safety. Unfortunately, restricted by poor electrochemical stability, it is difficult to be compatible with advanced lithium metal anodes and Ni-rich cathodes. To alleviate these issues, the study has developed a phosphate-based localized high-concentration electrolyte with a nitrate-driven solvation structure, and the nitrate-derived N-rich inorganic interface shows excellent performance in stabilizing the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode interface and modulating the lithium deposition morphology on the anode. The results show that the Li|| NCM811 cell has exceptional long-cycle stability of >80% capacity retention after 800 cycles at 4.3 V, 1 C. A more prominent capacity retention rate of 93.3% after 200 cycles can be reached with the high voltage of 4.5 V. While being compatible with the phosphate-based electrolyte with good flame retardancy and the good electrochemical stability of Ni-rich lithium metal battery (LMBs) systems, the present work expands the construction of anion-rich solvation structures, which is expected to promote the development of the high-performance LMBs with safety.

Conductive polymer polyaniline covering promotes the electrochemical properties of a nickel-rich quaternary cathode LiNi0.88Co0.06Mn0.03Al0.03O2

Conductive polymer PANI coated Ni-rich quaternary cathode LiNi0.88Co0.06Mn0.03Al0.03O2 demonstrates superior cycling performance owing to the stable surface protective layer.

Challenges and Modification Strategies of Ni-Rich Cathode Materials Operating at High-Voltage

Ni-rich cathode materials have become promising candidates for lithium-based automotive batteries due to the obvious advantage of electrochemical performance. Increasing the operating voltage is an effective means to obtain a higher specific capacity, which also helps to achieve the goal of high energy density (capacity × voltage) of power lithium-ion batteries (LIBs). However, under high operating voltage, surface degradation will occur between Ni-rich cathode materials and the electrolytes, forming a solid interface film with high resistance, releasing O₂, CO₂ and other gases. Ni-rich cathode materials have serious cation mixing, resulting in an adverse phase transition. In addition, the high working voltage will cause microcracks, leading to contact failure and repeated surface reactions. In order to solve the above problems, researchers have proposed many modification methods to deal with the decline of electrochemical performance for Ni-rich cathode materials under high voltage such as element doping, surface coating, single-crystal fabrication, structural design and multifunctional electrolyte additives. This review mainly introduces the challenges and modification strategies for Ni-rich cathode materials under high voltage operation. The future application and development trend of Ni-rich cathode materials for high specific energy LIBs are projected.