Authors: Ruimin Gao, Minzhi Zhan, Tingcan Li, Pei Xiong, Qian Zhang, Zhefeng Chen, Jike Wang, Xinping Ai, Feng Pan, Liumin Suo, Jiangfeng Qian
Published: 2025-03-23
Source: Full article
AbstractAnode‐free lithium metal batteries (AFLMBs) offer the potential for significantly enhanced energy densities. However, their practical application is limited by a shortened cycling life due to inevitable Li loss from parasitic reactions. This study addresses this challenge by incorporating an over‐lithiated Li1+xNi0.5Co0.2Mn0.3O2 (Li1+xNCM523) cathode as an internal Li reservoir to compensate for lithium loss during extended cycling. A rigorous investigation of the deep discharge behavior of the Li1+xNCM523 cathode reveals a critical over‐lithiation threshold at x = 0.7. At this threshold, excess Li+ ions are safely accommodated within the crystal structure by a transformation from the LiO4 octahedron to two tetrahedral sites. Beyond this threshold (x ≥ 0.7), the structural stability of the cathode is significantly compromised due to the irreversible reduction of transition metal (TM) ions. The optimal Li‐rich Li1.7NCM523 releases an additional charge capacity of ≈160 mAh g−1 during the first charge. Consequently, the AFLMBs (Li1.7NCM523||Cu) achieve outstanding capacity retention of 93.3% after 100 cycles at 0.5 C and 78.5% after 200 cycles at 1 C. The findings establish a research paradigm for designing superior over‐lithiated transition metal oxide cathode materials and underscore the critical role of the lithium reservoir in extending the cycle life of AFLMBs.