Stress‐Regulation Design of Lithium Alloy Electrode toward Stable Battery Cycling

Metallic tin (Sn) foil is a promising candidate anode for lithium‐ion batteries (LIBs) due to its metallurgical processability and high capacity. However, it suffers low initial Coulombic efficiency and inferior cycling stability due to its uneven alloying/dealloying reactions, large volume change and stress, and fast electrode structural degradation. Herein, we report an undulating LiSn electrode fabricated by a scalable two‐step procedure involving mechanical lithography and chemical prelithiation of Sn foil. With the combination of experimental measurements and chemo‐mechanical simulations, it was revealed the obtained undulating LiSn/Sn electrode could ensure better mechanical stability due to the pre‐swelling state from Sn to Li x Sn and undulating structure of lithography in comparison with plane Sn, homogenize the electrochemical alloying/dealloying reactions due to the activated surface materials, and compensate Li loss during cycling due to the introduction of excess Li from Li x Sn, thus enabling enhanced electrochemical performance. Symmetric cells consisting of undulating LiSn/Sn electrode with an active thickness of ∼5 um displayed stable cycling over 1000 h at 1 mA cm ‐2 and 1 mAh cm ‐2 with a low average overpotential of <15 mV. When paired with commercial LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathode with high mass loading of 15.8 mg cm ‐2 , the full cell demonstrated a high capacity of 2.4 mAh cm ‐2 and outstanding cycling stability with 84.9% capacity retention at 0.5 C after 100 cycles. This work presents an advanced LiSn electrode with stress‐regulation design toward high‐performance LIBs, and sheds light on the rational electrode design and processing of other high‐capacity lithium alloy anodes.