Building Better Li Metal Anodes in Liquid Electrolyte: Challenges and Progress

Abstract

Li metal has been widely recognized as a promising anode candidate for highenergy-density batteries. However, the inherent limitations of Li metal, that is, the low Coulombic efficiency and dendrite issues, make it still far from practical applications. In short, the low Coulombic efficiency shortens the cycle life of Li metal batteries, while the dendrite issue raises safety concerns. Thanks to the great efforts of the research community, prolific fundamental understanding as well as approaches for mitigating Li metal anode safety have been extensively explored. In this Review, Li electrochemical deposition behaviors have been systematically summarized, and recent progress in electrode design and electrolyte system optimization is reviewed. Finally, we discuss the future directions, opportunities, and challenges of Li metal anodes.

Air Stability and Interfacial Compatibility of Sulfide Solid Electrolytes for Solid‐State Lithium Batteries: Advances and Perspectives

“…Among the anodes, lithium is considered an ideal anode for high‐energy‐density solid‐state batteries due to its extremely high theoretical specific capacity, low potential and low density [44,45] . Theoretically, if the lithium anodes are matched with the SSEs, it is expected to greatly improve the energy density [46] and the safety of lithium batteries [47,48] . However, the instability of the interface between SSE and lithium anodes seriously limits the applications of lithium anodes.…”

“…[44,45] Theoretically, if the lithium anodes are matched with the SSEs, it is expected to greatly improve the energy density [46] and the safety of lithium batteries. [47,48] However, the instability of the interface between SSE and lithium anodes seriously limits the applications of lithium anodes.…”

Polymer Zwitterion-Based Artificial Interphase Layers for Stable Lithium Metal Anodes

“…The rapid growth of electric vehicles, smart electrical grids, and consumer electronics promotes the development of advanced energy-storage systems with high energy density. − Owing to its high specific capacity (3860 mA h g –1 ) and the lowest electrochemical reduction potential (−3.04 V vs the standard hydrogen electrode), the Li metal anode (LMA) is considered as the ideal anode material for high-energy batteries. , However, the commercial application of the LMA has been hindered by several intractable issues. , First of all, a thermodynamically unstable LMA can react with an organic electrolyte to generate a fragile solid electrolyte interphase (SEI) layer. , The subsequent destruction and reconstruction of the formed SEI layer during the plating process could cause low Coulombic efficiency (CE), high interfacial impedance, and depletion of both the electrolyte and active Li. , Furthermore, the breakage of the SEI layer could induce an inhomogeneous Li + ion diffusion, resulting in the initial Li nucleation and the follow-up growth of lithium dendrite. , Second, uncontrollable dendrite growth could pierce the polymer-based separator, resulting in a short circuit and a disastrous fire. − Last but not least, the large volume change accompanied by the host-free Li deposition leads to the collapse of dendrites and the formation of “dead Li”. , As a result, the LMA suffers from a short life span and potential safety hazards.…”

Enhancing the Cycling Stability for Lithium-Metal Batteries by Localized High-Concentration Electrolytes with 2-Fluoropyridine Additive

“…To solve the problem of TEP decomposition, Zhen et al proposed a high-concentration electrolyte (HCE, >3 M) based on the theory that the solvent and anion tend to form a contact-ion pair (CIP) with Li + by changing the molar ratio of Li-salt and solvent. , Unlike the solvent-separated ion pair (SSIP) in the low-concentration electrolytes, the active solvent molecules in HCE almost disappeared and the solvent had less contact with Li-metal, which can relieve the solvolysis to enhance the interface stability and widen the voltage range. , Although the coulombic efficiency is increased in HCE, it cannot be ignored that HCE is also restricted by its high cost, high viscosity, low ionic conductivity, and insufficient interface infiltration …”

“…3,29 Although the coulombic efficiency is increased in HCE, it cannot be ignored that HCE is also restricted by its high cost, high viscosity, low ionic conductivity, and insufficient interface infiltration. 30 Moreover, to maintain the solvation structure and reduce the viscosity of HCE, a diluent with a wider voltage window is employed to form a localized high-concentration electrolyte (LHCE) that can also keep the salt−solvent CIP structure. 12,31 By virtue of low viscosity, low polarity, and low dielectric constant, fluoroethers are widely used as a diluents, such as hydrofluoroether (HFE), 32 1,1,2,2-tetrafluoroethyl 2,2,3,3tetrafluoropropyl ether (TTE), 33 and bis(2,2,2-triflfluoroethyl) ether (BTFE).…”