![]() This preferential adsorption of additives increases the local overpotential and decreases the deposition rate at the tips, leading to more uniform distribution of electric current. Commonly, appropriate amounts of stable complex ions are formed by coordination of the leveling additives to metal species, which can be preferentially adsorbed on the protruding regions of the cathode surface that have thinner diffusion layer and stronger electrical field. The leveling abilities of additives used in these electrolyte solutions are closely related to their influences on cathodic polarization. Therefore, approaches relying only on a mechanically strong SEI film do not involve a fundamental change to the dendrite formation mechanism and may fail to offer longer-lasting protection to the Li metal.Īlthough the development of effective electrolytes for stable SEI films and Li deposition is still in its infant stage, leveling additives have been widely used in traditional metal electroplating such as Cu, , Ni, , Zn, , Mn, and Ag, to improve the quality of coatings. Moreover, once the uneven Li deposition occurs, the SEI layer will be easily broken by localized stresses, which aggravates the inhomogeneous current density distribution and ultimately leads to dendritic growth. However, the thickness and composition of these in-situ formed SEIs are nonuniform upon repeated cycling, especially under high current density, thereby causing an unstable electrode interface. It has been reported that LiF-rich SEI with high uniformity and stability can be in-situ formed by introducing fluorine-containing co-solvents or additives such as LiF, , fluoroethylene carbonate (FEC), ,, , lithium difluoro(oxalate)borate (LiDFOB), and LiPF 6. Among these strategies, electrolyte engineering offers a convenient route to suppress Li dendrite growth, because it is compatible with the existing battery manufacturing process. Tremendous efforts have been devoted to constructing stable SEI films, including electrolyte engineering, ,, ,, ,, artificial protective layers, ,, ,, ,, , solid-state electrolytes, and separators. ![]() Furthermore, induced by locally enhanced electric field at the tip of the protrusions, Li deposition will preferentially occur on existing dendrites, and hence leading to a self-amplification effect of dendrite growth. Typically, during Li plating a higher deposition rate may occur at parts of the SEI that have a lower interface impedance due to their smaller thickness or more ion-conductive composition. The fragility and heterogeneity of the solid electrolyte interphase (SEI) were identified as the root cause of inhomogeneous current density distribution and Li dendrite growth. However, the unstable interface between Li metal and electrolyte gives rises to inhomogeneous lithium deposition and uncontrollable dendrite formation, as well as low Coulombic efficiency and poor cycle performance,. When paired with a conversion-type cathode such as sulfur or oxygen, ,, , a high-energy full battery can be obtained. Li metal is one of the highest-performing next-generation anodes due to its lowest electrode potential and high theoretical specific capacity. This self-leveling electrolyte approach opens up new perspective on the mechanistic and methodological aspects for designing safer lithium metal batteries. Moreover, a Li metal full-cell with high-loading LiFePO 4 cathode (12.5 mg cm −2) retains 98% capacity after 100 cycles at 0.5 C. Dense and dendrite-free Li deposition, as well as enhanced interfacial stability is achieved in such electrolyte, rendering a significantly improved Coulombic efficiency (97.24%) in Li||Cu cells and a superior cycling stability in Li||Li cells. Based on this principle, a self-leveling electrolyte comprising fluoroethylene carbonate (FEC) solvent and 12-Crown-4 additive is developed. ![]() The Li +–additive complexes with low electron-accepting ability are preferentially adsorbed on the initial protuberant tips of Li metal surface, which can effectively regulate the local polarization resistance and improve the current distribution uniformity. Herein, we propose a facile and feasible strategy of introducing 12-Crown-4 ether as a leveling additive into the electrolyte to inherently eliminate the self-amplification behavior of dendrite growth. ![]() However, the extremely unstable interfaces between lithium anode and electrolyte induce uncontrollable dendrite formation and low Coulombic efficiency, retarding its practical applications in Li metal batteries (LMB). Lithium (Li) metal is considered an ideal anode material for future high-energy rechargeable batteries. ![]()
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