Gao Ruimin, Zhan Minzhi, Li Tingcan, Xiong Pei, Zhang Qian, Chen Zhefeng, Wang Jike, Ai Xinping, Pan Feng, Suo Liumin, Qian Jiangfeng
Hubei Key Laboratory of Electrochemical Power Sources, College of Chemistry and, Molecular Sciences, Wuhan University, Wuhan, Hubei, 430072, China.
School of Advanced Materials, Peking University, Shenzhen Graduate School, Shenzhen, 518055, China.
Adv Sci (Weinh). 2025 May;12(19):e2503558. doi: 10.1002/advs.202503558. Epub 2025 Mar 20.
Anode-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 Li NiCoMnO (Li NCM523) cathode as an internal Li reservoir to compensate for lithium loss during extended cycling. A rigorous investigation of the deep discharge behavior of the Li NCM523 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 LiO 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 LiNCM523 releases an additional charge capacity of ≈160 mAh g during the first charge. Consequently, the AFLMBs (LiNCM523||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.
无阳极锂金属电池（AFLMBs）具有显著提高能量密度的潜力。然而，由于寄生反应不可避免地导致锂损失，其实际应用受到循环寿命缩短的限制。本研究通过引入过锂化的Li NiCoMnO（Li NCM523）阴极作为内部锂库来补偿长时间循环过程中的锂损失，从而应对这一挑战。对Li NCM523阴极深度放电行为的严格研究揭示了在x = 0.7时的一个关键过锂化阈值。在这个阈值下，过量的锂离子通过从LiO八面体转变为两个四面体位置而安全地容纳在晶体结构中。超过这个阈值（x≥0.7），由于过渡金属（TM）离子的不可逆还原，阴极的结构稳定性会显著受损。最佳的富锂LiNCM523在首次充电过程中释放出约160 mAh g的额外充电容量。因此，AFLMBs（LiNCM523||Cu）在0.5 C下循环100次后容量保持率达到93.3%，在1 C下循环200次后容量保持率达到78.5%。这些发现建立了一种设计优质过锂化过渡金属氧化物阴极材料的研究范式，并强调了锂库在延长AFLMBs循环寿命中的关键作用。
