Demystifying the Salt‑Induced Li Loss:A Universal Procedure for the Electrolyte Design of Lithium‑Metal Batteries

Lithium(Li)metal electrodes show significantly different reversibility in the electrolytes with different salts.However,the understanding on how the salts impact on the Li loss remains unclear.Herein,using the electrolytes with different salts(e.g.,lithium hexafluorophosphate(LiPF_(6)),lithium difluoro(oxalato)borate(LiDFOB),and lithium bis(fluorosulfonyl)amide(LiFSI))as examples,we decouple the irreversible Li loss(SEI Li^(+)and“dead”Li)during cycling.It is found that the accumulation of both SEI Li^(+)and“dead”Li may be responsible to the irreversible Li loss for the Li metal in the electrolyte with LiPF_(6)salt.While for the electrolytes with LiDFOB and LiFSI salts,the accumulation of“dead”Li predominates the Li loss.We also demonstrate that lithium nitrate and fluoroethylene carbonate additives could,respectively,function as the“dead”Li and SEI Li^(+)inhibitors.Inspired by the above understandings,we propose a universal procedure for the electrolyte design of Li metal batteries(LMBs):(i)decouple and find the main reason for the irreversible Li loss;(ii)add the corresponding electrolyte additive.With such a Li-loss-targeted strategy,the Li reversibility was significantly enhanced in the electrolytes with 1,2-dimethoxyethane,triethyl phosphate,and tetrahydrofuran solvents.Our strategy may broaden the scope of electrolyte design toward practical LMBs.

A Stretchable Ionic Conductive Elastomer for High-Areal-Capacity Lithium-Metal Batteries

Developing high-areal-capacity and dendrite-free lithium(Li)anodes is of significant importance for the practical applications of the Li-metal secondary batteries.Herein,an effective strategy to stabilize the high-arealcapacity Li electrodeposition by modifying the Li metal with a stretchable ionic conductive elastomer(ICE)is demonstrated.The ICE layer prepared via an instant photocuring process shows a promising Li^(+)-ion conductivity at room temperature.When being used in Li-metal batteries,the thin ICE coating(~0.27μm)acts as both a stretchable constraint to minimize the Li loss and a protective layer to facilitate the uniform flux of Li ions.With this ICE-modifying strategy,the reversibility and cyclability of the Li anodes under high-areal-capacity condition in carbonate electrolyte are significantly improved,leading to a stable Li stripping/plating for 500 h at an ultrahigh areal capacity of 20 mAh cm^(-2)in commercial carbonate electrolyte.When coupled with industry-level thick LiFePO;electrodes(20.0 mg cm^(-2)),the cells with ICE-Li anodes show significantly enhanced rate and cycling capability.