Mechano-Electrochemically Promoting Lithium Atom Diffusion and Relieving Accumulative Stress for Deep-Cycling Lithium Metal Anodes.

Lithium metal batteries (LMBs) can double the energy density of lithium ion batteries. However, the notorious lithium dendrite growth and large volume change are not well addressed, especially under deep-cycling. Here, w e build an in-situ mechanical-electrochemical coupling system and find that tensile stress can induce smooth lithium deposition. Density functional theory (DFT) calculation and finite element method (FEM) simulation confirm the lithium atom diffusion energy barrier can be reduced when the lithium foils are under tensile strain. W e then incorporate tensile stress into lithium metal anodes by designing an adhesive copolymer layer attached to lithium in which the copolymer thinning can yield a tensile stress to the lithium foil. W e further prepared elastic lithium metal anode (ELMA) via introducing a 3D elastic conductive polyurethane (CPU) host for the copolymer-lithium bilayer to release accumulated internal stresses and resist volume variation. The ELMA can withstand hundreds of repeated compression-release cycles under 10% strain. LMBs paired with the ELMA and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode can operate beyond 250 cycles with 80% capacity retention under practical condition of 4 mAh cm -2 cathode capacity, 2.86 g Ah -1 electrolyte-to-capacity ratio (E/C) and 1.8 negative-to-cathode capacity ratio (N/P), 5 times of the life time using lithium foils. This article is protected by copyright. All rights reserved.