Heterogeneous Li-alloy interphase enabling Li compensation during cycling for high energy density batteries

Alloying elemental foil (e.g., Sn, Al, In, etc) anodes shows great promise for high-energy-density lithium (Li)-ion batteries due to their attractive capacities, low cost, and easy processability. The abundant Li loss, uneven electrochemical reactions, and continuous side reactions on cycling cause poor electrochemical performance. Herein, using Sn foil as a model system, we constructed a conformal heterogeneous Li-alloy interface alloying elemental foil (defined as “Sn/Li-LA”) with slightly higher delithiation potential than Li-Sn alloy. It could separate the electrolyte and active Li-Sn to suppress the side reactions between them, and meanwhile function as Li+ conductive layer to homogenize electrochemical reactions. Specially, an overpotential triggered Li compensation by Li-LA could extend the cycle life of batteries. As a result, the initial Coulombic efficiency of the Sn/Li-LA increased from 45.9% to 107.4%, and the average Coulombic efficiency increased from 98.6% to 99.5% for 350 cycles compared with the pristine Sn foil at 1 mA cm–2 and 1 mAh cm–2 in half cells, respectively. Full cells paired with LiNi0.6Co0.2Mn0.2O (∼15.3 mg cm–2) delivered high reversible capacities (∼180 mAh g–1, ∼2.8 mAh cm–2) with stable cycling for 230 cycles in sharp contrast to the pristine Sn anode (∼90 mAh g–1, 1.4 mAh cm–2). In situ construction of Li-LA interface with donable active Li provides an effective approach to address the Li loss and extend the lifespan of high-capacity anode for advanced Li-based batteries.