Nanocomposite Current Collectors for Anode-Free All-Solid-State Lithium Batteries

Abstract

The anode-free solid-state lithium battery (AFSSLB) is a type of lithium battery that utilizes an initial charging process to generate lithium metal as the anode. With a 1 : 1 anode-to-cathode capacity ratio, it enables any lithiated cathode system to achieve a maximal energy density. Furthermore, the incorporation of inorganic solid electrolytes in the AFSSLB greatly enhances its intrinsic safety. However, the AFSSLB faces challenges related to interfacial issues between the electrolyte and collector. During the cycling process, uneven lithium-ion flux can result in contact loss and dendrite growth, ultimately leading to rapid battery failure. Addressing these interfacial problems is crucial for the successful implementation and performance of AFSSLBs. The absence of initial lithium metal material prevents the battery system from accommodating additional lithium through a modified anode. Instead, it relies on high Coulomb efficiency during cycling. Consequently, ensuring continuous and uniform contact at the anode interface is crucial for maintaining the reversibility of lithium deposition. Herein, a nanocomposite current collector is introduced to enhance the interface between the collector and electrolyte in AFSSLB. In this approach, silver nanoparticles are dispersed within the carbon materials to construct a composite current collector. The incorporation of the silver-carbon nanocomposite layer results in a low interfacial impedance of 10 Ω∙cm⁻², indicating that the electrolyte-collector interface maintains contact throughout the charging and discharging processes. The focused ion beam (FIB) technology and electron microscopy were employed to analyze the battery cross sections, revealing that lithium metal could be deposited in a thickness of more than 25 μm without short-circuiting using this silver-carbon nanocomposite current collector. The solid-state batteries equipped with nanocomposite current collectors exhibited an enhanced dissolution of silver in the lithium metal, leading to the formation of abundant lithiophilic sites. The nanocomposites facilitate the rapid transfer of Li atoms within the anodes, thus achieving uniform lithium metal deposition. Theoretical analysis using the nucleation equation demonstrates that using nano-silver as a current collector can reduce the nucleation work required for deposition by at least four orders of magnitude. The smaller nucleation force contributes to the uniform and stable deposition of lithium metal during continuous cycling. The solid-state batteries demonstrated improved interfacial contact, resulting in the uniform and stable lithium metal deposition of over 7.0 mAh∙cm⁻² for more than 200 cycles at 0.25 mA∙cm⁻². The cycling performances of all-solidstate batteries can be significantly improved through the design of nanocomposite collectors. This presents an effective strategy for advancing the practical implementation of all-solid-state lithium metal batteries, particularly those utilizing an anode-free configuration.

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