Highly Lithiophilic Copper-Reinforced Scaffold Enables Stable Li Metal Anode

3D-hosted lithium metal anodes

Lithium metal anodes are an appealing choice for rechargeable batteries due to their exceptionally high theoretical capacity of about 3860 mA h g-1. However, the uneven plating/stripping of lithium metal anodes leads to serious dendrite growth and low coulombic efficiency, curtailing their practical applications. The 3D scaffold/host strategy emerges as a promising approach that concurrently mitigates volume changes and dendrite growth. This review provides an overview of the regulating mechanisms behind scaffold/host materials for dendrite-free applications, tracing their historical development and recent progress across five key stages: material texture selection, lithiophilic modification, structural design, multi-strategy integration, and practical implementation. Additionally, scaffold/host materials are categorized based on their material texture, with a thorough examination of their respective advantages and drawbacks. Furthermore, this tutorial outlines the obstacles and complexities associated with implementing scaffold/host strategies. Finally, the determining factors that affect the electrochemical performances of scaffold/host materials are discussed, along with possible design criteria and future development prospects. This tutorial aims to provide guidance for researchers on the design of advanced scaffold/host materials for advanced Li metal anodes for batteries.

In Situ Construction of Efficient Interface Layer with Lithiophilic Nanoseeds toward Dendrite-Free and Low N/P Ratio Li Metal Batteries

Li metal is considered as one of the most promising candidates for constructing advanced high-energy energy storage due to its ultrahigh theoretical capacity and lowest electrochemical potential. However, its practical commercialization is seriously hindered by the challenges of Li dendrite growth, low Coulombic efficiency, and huge volumetric variation. Herein, an efficient in situ generated Li₂ S-rich interface layer joint with preplanted Sb nano active sites in hosted Li metal anode is easily achieved with the nanosized Sb₂ S₃ decorated carbonaceous network. The yielded CC@Sb₂ S₃ @Li anode demonstrates uniform Li deposition, high Coulombic efficiency, and alleviated volumetric variation. Therefore, the Li symmetric cells show ultralong lifespan stable cycling over 3200 cycles with a very low voltage hysteresis (≈18 mV) at 5 mA cm^-2 . Impressively, the Li|LiFePO₄ full cell delivers an exceptionally prolonged cycling over 180 cycles with a superior capacity retention as high as ≈90% even under the harsh condition of an extremely low negative to positive capacity ratio of ≈0.44 with lean electrolyte (4.4 µL mAh^-1 ). Moreover, the Li|LiNi_0.5 Co_0.2 Mn_0.3 O₂ full cell also maintains an excellent cycling performance under the more realistic harsh conditions. This work provides a new avenue and significant step paving the Li metal toward the practical application.

Uniform Deposition of Li-Metal Anodes Guided by 3D Current Collectors with In Situ Modification of the Lithiophilic Matrix

The lithium (Li)-metal anode is deemed as the "holy gray" of the next-generation Li-metal system because of its high theoretical specific capacity, minimal energy density, and lowest standard electrode potential. Nevertheless, its commercial application has been limited by the large volume variation during charge and discharge, the unstable interface between the Li metal and electrolyte, and uneven deposition of Li. Herein, we present a 3D host (Cu) with lithiophilic matrix (CuO and SnO₂) in situ modification via a facile ammonia oxidation method to serve as a current collector for the Li-metal anode. The 3D Cu host embellished by CuO and SnO₂ is abbreviated as 3D CSCC. By increasing interfacial activity, lowering the nucleation barrier, and accommodating changes in volume of the Li metal, the 3D CSCC electrode effectively demonstrates a homogeneous and dendrite-free deposition morphology with an excellent cycling performance up to 3000 h at a 1.0 mA cm^-2 current density. Additionally, the full cells paired with Li@3D CSCC anodes and LiCoO₂ cathodes show good capacity retention performance at 0.2 C.

Dendrite-Free and Stable Lithium Metal Battery Achieved by a Model of Stepwise Lithium Deposition and Stripping

A facile method is adopted to obtain cucumber-like lithiophilic composite skeleton. Massive lithiophilic sites in cucumber-like lithiophilic composite skeleton can promote and guide uniform Li depositions. A unique model of stepwise Li deposition and stripping is determined. The uncontrolled formation of lithium (Li) dendrites and the unnecessary consumption of electrolyte during the Li plating/stripping process have been major obstacles in developing safe and stable Li metal batteries. Herein, we report a cucumber-like lithiophilic composite skeleton (CLCS) fabricated through a facile oxidation-immersion-reduction method. The stepwise Li deposition and stripping, determined using in situ Raman spectra during the galvanostatic Li charging/discharging process, promote the formation of a dendrite-free Li metal anode. Furthermore, numerous pyridinic N, pyrrolic N, and Cu_xN sites with excellent lithiophilicity work synergistically to distribute Li ions and suppress the formation of Li dendrites. Owing to these advantages, cells based on CLCS exhibit a high Coulombic efficiency of 97.3% for 700 cycles and an improved lifespan of 2000 h for symmetric cells. The full cells assembled with LiFePO₄ (LFP), SeS₂ cathodes and CLCS@Li anodes demonstrate high capacities of 110.1 mAh g^-1 after 600 cycles at 0.2 A g^-1 in CLCS@Li|LFP and 491.8 mAh g^-1 after 500 cycles at 1 A g^-1 in CLCS@Li|SeS₂. The unique design of CLCS may accelerate the application of Li metal anodes in commercial Li metal batteries.

Advanced Electrolyte Design for High-Energy-Density Li-Metal Batteries under Practical Conditions

Given the limitations inherent in current intercalation-based Li-ion batteries, much research attention has focused on potential successors to Li-ion batteries such as lithium-sulfur (Li-S) batteries and lithium-oxygen (Li-O₂ ) batteries. In order to realize the potential of these batteries, the use of metallic lithium as the anode is essential. However, there are severe safety hazards associated with the growth of Li dendrites, and the formation of "dead Li" during cycles leads to the inevitable loss of active Li, which in the end is undoubtedly detrimental to the actual energy density of Li-metal batteries. For Li-metal batteries under practical conditions, a low negative/positive ratio (N/P ratio), a electrolyte/cathode ratio (E/C ratio) along with a high-voltage cathode is prerequisite. In this Review, we summarize the development of new electrolyte systems for Li-metal batteries under practical conditions, revisit the design criteria of advanced electrolytes for practical Li-metal batteries and provide perspectives on future development of electrolytes for practical Li-metal batteries.