Precise Chemical Lithiation: A Pathway to Superior Li-Enriched Li<sub>1+<i>x</i></sub>NCM523 Cathodes for Long Life Anode-Free Li Metal Batteries
Tingcan Li, Ruimin Gao, Xuanze Wang, Mingyu Zhang, Mingyuan Jiang, Juzheng Zhang, Ran Tan, Jike Wang, Xinping Ai, Pei Xiong, Liumin Suo, Jiangfeng Qian
Abstract
Developing lithium-enriched cathodes, such as Li 1+ x NCM523 ( x ≥ 0), offers a promising approach to boost the cycling life of anode-free lithium metal batteries (AFLMBs). However, the traditional electrochemical prelithiation method is confined to laboratory studies, while conventional chemical prelithiation using highly reductive reagents like biphenyllithium (0.25 V vs Li + /Li) often causes severe surficial excessive-lithiation and structural degradation, compromising battery performance. Herein, we propose a precise chemical lithiation strategy using 9-fluorenone lithium (FL-2Li) as an optimal lithiation reagent to achieve controllable and uniform lithium insertion in Li 1+ x NCM523 cathodes. The redox potential of FL-2Li reagent (1.32 V vs Li + /Li) is strategically matched─slightly below the lithiation potential of Li 1.7 NCM523 (1.50 V) to allow tolerable overlithiation, yet above that of Li 2.0 NCM523 (1.0 V) to avoid excessive-lithiation, and significantly higher than Li 4.0 NCM523 (Li 2 O/TM, 0.75 V) to prevent irreversible structural collapse. This design yields a superior Li 1.7 NCM523 cathode with a homogeneous bulk-lithiated structure, thereby eliminating the core–shell effects typically observed with conventional reagents. Consequently, the chemically prelithiated Li 1.7 NCM523 exhibits superior electrochemical performance, achieving 86.16% capacity retention after 100 cycles at 1C in Cu||Li 1.7 NCM523 anode-free cells. Our findings established a versatile framework for the rational selection of lithiation reagents, providing critical theoretical insights and practical guidance for designing high-performance, scalable lithium-enriched cathodes, which may potentially advance battery technology for electric vehicles and energy storage systems.