High-Voltage Layered Ternary Oxide Cathode Materials: Failure Mechanisms and Modification Methods^†

Due to the large reversible capacity, high operating voltage and low cost, layered ternary oxide cathode materials LiNi_xCo_yAl_1−x−yO₂ (NCA) and LiNi_xCo_yMn_1−x−yO₂ (NCM) are considered as the most potential candidate materials for lithium-ion batteries (LIBs) used in (hybrid) electric vehicles (EVs). However, next-generation long-range EVs require a high specific capacity (around 203 mAh·g^–1 at 3.7V) at the cathode active material level, which is not provided with current commercially layered ternary oxide cathodes. Increasing the operating voltage is an effective method to improve the specific capacity of the cathode and the energy density of the battery, but the high operating voltage also causes a lot of problems, such as cation mixing and phase transformation, electrolyte decomposition, transition metal dissolution and microcracks. So far, researchers have carried out a lot of works to solve these issues. Surface coating, element doping and the design of electrolytes have been proved to be effective solutions. In this review, the failure mechanisms and modification methods of high-voltage layered ternary oxide cathode materials are summarized, which could provide valuable information to the research of high-voltage layered ternary oxide cathode materials in basic science and industrial production.