In Situ Formed Tribofilms as Efficient Organic/Inorganic Hybrid Interlayers for Stabilizing Lithium Metal Anodes

Lithium metal based battery systems with ultra-high energy density beyond 500 W h kg-1

As industries and consumption patterns evolve, new electrical appliances are increasingly playing critical roles in national production, defense, and cognitive exploration. However, the slow development of energy storage devices with ultra-high energy density (beyond 500 W h kg-1) has impeded the promotion and widespread application of the next generation of intelligent, multi-scenario electrical equipment. Among the numerous ultra-high specific energy battery systems, lithium metal batteries (LMBs) hold significant potential for applications in advanced and sophisticated fields. This potential is primarily due to lithium metal's high specific capacity (3860 mA h g-1). However, LMBs face numerous challenges, including the growth of lithium dendrites, poor cycle stability, and safety concerns. In recent years, research on the mechanisms of Li metal-based battery systems, innovation in electrode materials, and optimization of device configurations have made significant progress. In this highlight, we provide a comprehensive overview of the storage mechanisms and the latest advancements in high-energy-density LMBs, represented by systems such as Li-Li1-xMO2, Li-S/Se, Li-gas (CO2/air/O2), Li-CFx, and all-solid-state LMBs. By integrating the current research findings, we highlight the opportunities and future research directions for high-energy-density LMBs, offering new guiding perspectives for their development under practical conditions.

In Situ-Constructed Multifunctional Composite Anode with Ultralong-Life Toward Advanced Lithium-Metal Batteries

Metallic lithium is the most competitive anode material for next-generation high-energy batteries. Nevertheless, the extensive volume expansion and uncontrolled Li dendrite growth of lithium metal not only cause potential safety hazards but also lead to low Coulombic efficiency and inferior cycling lifespan for Li metal batteries. Herein, a multifunctional dendrite-free composite anode (Li/SnS2) is proposed through an in situ melt-infusion strategy. In this configuration, the 3D cross-linked porous Li2S/Li22Sn5 framework facilitates the rapid penetration of electrolytes and accommodates the volume expansion during the repeated Li-plating process. Meanwhile, the lithiophilic Li2S phases with a low Li+ transport barrier ensure preferential Li deposition, effectively avoiding uneven electron distribution. Moreover, the Li22Sn5 electron conductors with appropriate Li+ bonding ability guarantee rapid charge transport and mass transfer. Most importantly, the steady multifunctional skeleton with sufficient inner interfaces (Li2S/Li22Sn5) in the whole electrode, not only realizes the redistribution of the localized free electron, contributing to the decomposition of Li clusters, but also induces a planar deposition model, thus restraining the generation of Li dendrites. Consequently, an unprecedented cyclability of over 6 500 h under an ultrahigh areal capacity of 10 mAh cm-2 and a current rate of 20 mA cm-2 is achieved for the prepared Li2S/Li22Sn5 composite anode. Moreover, the assembled Li/SnS2||LiFePO4 (LFP) pouch full-cells also demonstrate remarkable rate capability and a convincing cycling lifespan of more than 2 000 cycles at 2 C.

Boosting High-Voltage Practical Lithium Metal Batteries with Tailored Additives

The lithium (Li) metal anode is widely regarded as an ideal anode material for high-energy-density batteries. However, uncontrolled Li dendrite growth often leads to unfavorable interfaces and low Coulombic efficiency (CE), limiting its broader application. Herein, an ether-based electrolyte (termed FGN-182) is formulated, exhibiting ultra-stable Li metal anodes through the incorporation of LiFSI and LiNO3 as dual salts. The synergistic effect of the dual salts facilitates the formation of a highly robust SEI film with fast Li+ transport kinetics. Notably, Li||Cu half cells exhibit an average CE reaching up to 99.56%. In particular, pouch cells equipped with high-loading lithium cobalt oxide (LCO, 3 mAh cm-2) cathodes, ultrathin Li chips (25 μm), and lean electrolytes (5 g Ah-1) demonstrate outstanding cycling performance, retaining 80% capacity after 125 cycles. To address the gas issue in the cathode under high voltage, cathode additives 1,3,6-tricyanohexane is incorporated with FGN-182; the resulting high-voltage LCO||Li (4.4 V) pouch cells can cycle steadily over 93 cycles. This study demonstrates that, even with the use of ether-based electrolytes, it is possible to simultaneously achieve significant improvements in both high Li utilization and electrolyte tolerance to high voltage by exploring appropriate functional additives for both the cathode and anode.

Adjusting Ion Diffusion Kinetics of Li Deposition Enabled by an Elastic Porous Melamine Sponge Host for Stable Lithium Metal Anodes

Lithium (Li) dendritic growth and huge volume expansion seriously hamper Li-metal anode development. Herein, we design a lightweight 3D Li-ion-affinity host enabled by silver (Ag) nanoparticles fully decorating a porous melamine sponge (Ag@PMS) for dendrite-free and high-areal-capacity Li anodes. The compact Ag nanoparticles provide abundant preferred nucleation sites and give the host strong conductivity. Moreover, the high specific surface area and polar groups of the elastic, porous melamine sponge enhance the Li-ion diffusion kinetics, prompting homogeneity of Li deposition and stripping. As expected, the integrated 3D Ag@PMS-Li anode delivered a remarkable electrochemical performance, with a Coulombic efficiency (CE) of 97.14% after 450 cycles at 1 mA cm-2. The symmetric cell showed an ultralong lifespan of 3400 h at 1 mA cm-2 for 1 mAh cm-2. This study provides a facile and cost-effective strategy to design an advanced 3D framework for the preparation of a stable dendrite-free Li metal anode.

Bimetallic MOFs-Derived NiFe2O4/Fe2O3 Enabled Dendrite-free Lithium Metal Anodes with Ultra-High Area Capacity Based on An Intermittent Lithium Deposition Model

In practical operating conditions, the lithium deposition behavior is often influenced by multiple coupled factors and there is also a lack of comprehensive and long-term validation for dendrite suppression strategies. Our group previously proposed an intermittent lithiophilic model for high-performance three-dimensional (3D) composite lithium metal anode (LMA), however, the electrodeposition behavior was not discussed. To verify this model, this paper presents a modified 3D carbon cloth (CC) backbone by incorporating NiFe2O4/Fe2O3 (NFFO) nanoparticles derived from bimetallic NiFe-MOFs. Enhanced Li adsorption capacity and lithiophilic modulation were achieved by bimetallic MOFs-derivatives which prompted faster and more homogeneous Li deposition. The intermittent model was further verified in conjunction with the density functional theory (DFT) calculations and electrodeposition behaviors. As a result, the obtained Li-CC@NFFO||Li-CC@NFFO symmetric batteries exhibit prolonged lifespan and low hysteresis voltage even under ultra-high current and capacity conditions (5 mA cm-2, 10 mAh cm-2), what's more, the full battery coupled with a high mass loading (9 mg cm-2) of LiFePO4 cathode can be cycled at a high rate of 5 C, the capacity retention is up to 95.2 % before 700 cycles. This work is of great significance to understand the evolution of lithium dendrites on the 3D intermittent lithiophilic frameworks.

Homogeneously Planar-Exposure LiB Fiber Skeleton Toward Long-Lifespan Practical Li Metal Pouch Cells

LiB alloy is promising lithium (Li) metal anode material because the continuous internal LiB fiber skeleton can effectively suppress Li dendrites and structural pulverization. However, the unvalued surface states limit the practical application of LiB alloy anodes. Herein, the study examined the influence of the different exposure manners of the internal LiB fiber skeleton owing to the various surface states of the LiB alloy anode on electrochemical performance and targetedly proposed a scalable friction coating strategy to construct a lithiated fumed silica (LFS) functional layer with abundant electrochemically active sites on the surface of the LiB alloy anode. The LFS significantly suppresses the inhomogeneous interfacial electrochemical behavior of the LiB alloy anode and enables the exposure of the internal LiB fiber skeleton in a homogeneously planar manner (LFS-LiB). Thus, a 0.5 Ah LFS-LiB||LiCoO2 (LCO) pouch cell exhibits a discharge capacity retention rate of 80% after 388 cycles. Moreover, a 6.15 Ah LFS-LiB||S pouch cell with 409.3 Wh kg-1 exhibits a discharge capacity retention rate of 80% after 30 cycles. In conclusion, the study findings provide a new research perspective for Li alloy anodes.

Artificial LiF-Rich Interface Enabled by In situ Electrochemical Fluorination for Stable Lithium-Metal Batteries

Lithium (Li)-metal batteries are promising next-generation energy storage systems. One drawback of uncontrollable electrolyte degradation is the ability to form a fragile and nonuniform solid electrolyte interface (SEI). In this study, we propose the use of a fluorinated carbon nanotube (CNT) macrofilm (CMF) on Li metal as a hybrid anode, which can regulate the redox state at the anode/electrolyte interface. Due to the favorable reaction energy between the plated Li and fluorinated CNTs, the metal can be fluorinated directly to a LiF-rich SEI during the charging process, leading to a high Young's modulus (~2.0 GPa) and fast ionic transfer (~2.59×10-7  S cm-1 ). The obtained SEI can guide the homogeneous plating/stripping of Li during electrochemical processes while suppressing dendrite growth. In particular, the hybrid of endowed full cells with substantially enhanced cyclability allows for high capacity retention (~99.3 %) and remarkable rate capacity. This work can extend fluorination technology into a platform to control artificial SEI formation in Li-metal batteries, increasing the stability and long-term performance of the resulting material.