With upswing to fuel reserve concerns, the development of sustainable, clean, and safe energy-storage technologies is of much importance. [1] Thus, rechargeable lithiumion batteries have become a promising research topic. [2] Nowadays, the layered nickel-rich LiNi 1-x-y Co x Mn y O 2 (NMC) cathodes are the most promising options for lithium-ion batteries due to their high capacity, excellent electrochemical performance, and low cost. [3] However, to achieve the large-scale commercial application of nickel-rich NMC cathodes, several key challenges such as poor electrochemical stability and low thermal stability have to be solved. [4] One of the most concerning issues is surface structural degradation closely related to electrochemical and thermal stability. [4] Generally, the surface structure degradation of cathode materials is attributed to side reactions between the electrolyte and electrode. Due to the attack of residual water in the battery system, the electrolytes containing LiPF 6 will decompose to produce hydrogen fluoride (HF) [5] that will cause the excessive dissolution of the transition metal ion, which is harmful to the interface phase structure and particle integrity of cathode particles. [5,6] In addition, the nickel-rich NMC cathode can easily react with water and then form a thick uncontrollable cathode-electrolyte interface (CEI) layer on its surface during storage and recycling. [7] It has a negative impact on the efficient and uniform transport of lithium ions, which can cause polarization of the cathode, giving rise to stress concentration, cracks, and fragmentation, ultimately affecting the structural and electrochemical stability. [8] Moreover, it is worth noting that this problem becomes worse with high Ni content, high temperature, and a high cutoff voltage (>4.4 V versus Li þ /Li). For example, Jung et al. studied and compared the formation of surface contaminations on NMC811 and NMC111. [9] They found that NMC811 developed a surface layer of up to %10 nm thickness (nickel carbonate and minor nickel hydroxide) after ambient storage for 1 year, whereas no significant changes were observed on the NMC111 surface. [9] Qian et al found that the adsorption energy is À0.98, À0.37, and À0.54 eV for Ni─O, Co─O, and Mn─O bonds, respectively.
