Glycolide additives enrich organic components in the solid electrolyte interphase enabling stable ultrathin lithium metal anodes

Stable lithium (Li) metal anodes are a foundation stone for practical Li metal batteries. An ultrathin Li metal anode (<50 μm) is the premise to realize high-energy-density Li metal batteries. However, the uneven Li plating/stripping induced by the unstable solid electrolyte interphase (SEI) leads to the rapid depletion of active Li and electrolyte, resulting in a poor cycle life of ultrathin Li metal anodes. Herein, an electrolyte additive, glycolide (GL), is proposed to prolong the cycle life of ultrathin Li metal anodes. GL additives decompose on the Li metal anode to enrich the organic components in the SEI. The uniformity of Li deposition is improved with the introduction of GL additives. Under practical conditions with an ultrathin Li metal anode (50 μm) and a high loading LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode (3.0 mA h cm-2), 175 cycles were achieved in Li|NCM523 cells with GL additives compared with 86 cycles without GL additives. This work further promotes the design of electrolyte additives for stabilizing ultrathin Li metal anodes.