Revisiting the Role of Physical Confinement and Chemical Regulation of 3D Hosts for 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.

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.

Lithium Metal Anodes: Advancing our Mechanistic Understanding of Cycling Phenomena in Liquid and Solid Electrolytes

Lithium metal anodes have the potential to be a disruptive technology for next-generation batteries with high energy densities, but their electrochemical performance is limited by a lack of fundamental understanding into the mechanistic origins that underpin their poor reversibility, morphological evolution (including dendrite growth), and interfacial instability. The goal of this perspective is to summarize the current state-of-the-art understanding of these phenomena, and highlight knowledge gaps where additional research is needed. The various stages of cycling are described sequentially, including nucleation, growth, open-circuit rest periods, and electrodissolution (stripping). A direct comparison of lessons learned from liquid and solid-state electrolyte systems is made throughout the discussion, providing cross-cutting insights between these research communities. Major themes of the discussion include electro-chemo-mechanical coupling, insights from in situ/operando analysis, and the interplay between experimental observations and computational modeling. Finally, a series of fundamental research questions are proposed to identify critical knowledge gaps and inform future research directions.

From Liquid to Solid-State Lithium Metal Batteries: Fundamental Issues and Recent Developments

The widespread adoption of lithium-ion batteries has been driven by the proliferation of portable electronic devices and electric vehicles, which have increasingly stringent energy density requirements. Lithium metal batteries (LMBs), with their ultralow reduction potential and high theoretical capacity, are widely regarded as the most promising technical pathway for achieving high energy density batteries. In this review, we provide a comprehensive overview of fundamental issues related to high reactivity and migrated interfaces in LMBs. Furthermore, we propose improved strategies involving interface engineering, 3D current collector design, electrolyte optimization, separator modification, application of alloyed anodes, and external field regulation to address these challenges. The utilization of solid-state electrolytes can significantly enhance the safety of LMBs and represents the only viable approach for advancing them. This review also encompasses the variation in fundamental issues and design strategies for the transition from liquid to solid electrolytes. Particularly noteworthy is that the introduction of SSEs will exacerbate differences in electrochemical and mechanical properties at the interface, leading to increased interface inhomogeneity-a critical factor contributing to failure in all-solid-state lithium metal batteries. Based on recent research works, this perspective highlights the current status of research on developing high-performance LMBs.

Trend of Developing Aqueous Liquid and Gel Electrolytes for Sustainable, Safe, and High-Performance Li-Ion Batteries

Current lithium-ion batteries (LIBs) rely on organic liquid electrolytes that pose significant risks due to their flammability and toxicity. The potential for environmental pollution and explosions resulting from battery damage or fracture is a critical concern. Water-based (aqueous) electrolytes have been receiving attention as an alternative to organic electrolytes. However, a narrow electrochemical-stability window, water decomposition, and the consequent low battery operating voltage and energy density hinder the practical use of aqueous electrolytes. Therefore, developing novel aqueous electrolytes for sustainable, safe, high-performance LIBs remains challenging. This Review first commences by summarizing the roles and requirements of electrolytes-separators and then delineates the progression of aqueous electrolytes for LIBs, encompassing aqueous liquid and gel electrolyte development trends along with detailed principles of the electrolytes. These aqueous electrolytes are progressed based on strategies using superconcentrated salts, concentrated diluents, polymer additives, polymer networks, and artificial passivation layers, which are used for suppressing water decomposition and widening the electrochemical stability window of water of the electrolytes. In addition, this Review discusses potential strategies for the implementation of aqueous Li-metal batteries with improved electrolyte-electrode interfaces. A comprehensive understanding of each strategy in the aqueous system will assist in the design of an aqueous electrolyte and the development of sustainable and safe high-performance batteries.

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

The practical application of Li metal anodes (LMAs) is limited by uncontrolled dendrite growth and side reactions. Herein, we propose a new friction-induced strategy to produce high-performance thin Li anode (Li@CFO). By virtue of the in situ friction reaction between fluoropolymer grease and Li strips during rolling, a robust organic/inorganic hybrid interlayer (lithiophilic LiF/LiC6 framework hybridized -CF2-O-CF2- chains) was formed atop Li metal. The derived interface contributes to reversible Li plating/stripping behaviors by mitigating side reactions and decreasing the solvation degree at the interface. The Li@CFO||Li@CFO symmetrical cell exhibits a remarkable lifespan for 5,600 h (1.0 mA cm-2 and 1.0 mAh cm-2) and 1,350 cycles even at a harsh condition (18.0 mA cm-2 and 3.0 mAh cm-2). When paired with high-loading LiFePO4 cathodes, the full cell lasts over 450 cycles at 1C with a high-capacity retention of 99.9%. This work provides a new friction-induced strategy for producing high-performance thin LMAs.

Modulating Ionic Transport and Interface Chemistry via Surface-Modified Silica Carrier in Nano Colloid Electrolyte for Stable Cycling of Li-Metal Batteries

Tailoring the Li+ microenvironment is crucial for achieving fast ionic transfer and a mechanically reinforced solid-electrolyte interphase (SEI), which administers the stable cycling of Li-metal batteries (LMBs). Apart from traditional salt/solvent compositional tuning, this study presents the simultaneous modulation of Li+ transport and SEI chemistry using a citric acid (CA)-modified silica-based colloidal electrolyte (C-SCE). CA-tethered silica (CA-SiO2 ) can render more active sites for attracting complex anions, leading to further dissociation of Li+ from the anions, resulting in a high Li+ transference number (≈0.75). Intermolecular hydrogen bonds between solvent molecules and CA-SiO2 and their migration also act as nano-carrier for delivering additives and anions toward the Li surface, reinforcing the SEI via the co-implantation of SiO2 and fluorinated components. Notably, C-SCE demonstrated Li dendrite suppression and improved cycling stability of LMBs compared with the CA-free SiO2 colloidal electrolyte, hinting that the surface properties of the nanoparticles have a huge impact on the dendrite-inhibiting role of nano colloidal electrolytes.

F-Doped Carbon Nanoparticles-Based Nucleation Assistance for Fast and Uniform Three-Dimensional Zn Deposition

Aqueous Zn metal-based batteries have considerable potential as energy storage system; however, their application is extremely limited by dendrite development and poor reversibility. In this study, to overcome both challenges, F-doped carbon nanoparticles (FCNPs) are uniformly constructed on substrates (Ti, Zn, Cu, and steel) by a plasma-assisted surface modification, which endows reversible and uniform deposition of Zn metal. FCNPs with high surface charge density act as nucleation assistors and form numerous homogenous Zn nucleation sites toward Zn 3D growth, which improves Zn plating kinetic and results in uniform Zn deposition. Furthermore, the ZnF₂  solid electrolyte interface generated during cycling contributes to rapid mass transfer and enhances Zn reversibility, but also suppresses the side reaction. Accordingly, the half-cell of P-Ti coupled with Zn exhibits an average Coulombic efficiency of 99.47% with 500 cycles. The symmetric cell of the P-Zn anode presents a lifespan of over 1500 h at the current density of 5 mA cm^-2 . Notably, the cell works for 100 h at 50 mA cm^-2 . It is believed that this ingenious surface modification broadens revolutionary methods for uniform metallic deposition, as well as the dendrite-free rechargeable batteries system.

A Highly-Lithiophilic Mn3O4/ZnO-Modified Carbon Nanotube Film for Dendrite-Free Lithium Metal Anodes

Lithium metal anode is deemed as a potential candidate for high energy density batteries, which has attracted increasing attention. Unfortunately, Li metal anode suffers from issues such as dendrite grown and volume expansion during cycling, which hinders its commercialization. Herein, we designed a porous and flexible self-supporting film comprising of single-walled carbon nanotube (SWCNT) modified with a highly-lithiophilic heterostructure (Mn₃O₄/ZnO@SWCNT) as the host material for Li metal anodes. The p-n-type heterojunction constructed by Mn₃O₄ and ZnO generates a built-in electric field that facilitates electron transfer and Li⁺ migration. Additionally, the lithiophilic Mn₃O₄/ZnO particles serve as the pre-implanted nucleation sites, dramatically reducing the lithium nucleation barrier due to their strong binding energy with lithium atoms. Moreover, the interwoven SWCNT conductive network effectively lowers the local current density and alleviates the tremendous volume expansion during cycling. Thanks to the aforementioned synergy, the symmetric cell composed of Mn₃O₄/ZnO@SWCNT-Li can stably maintain a low potential for more than 2500 h at 1 mA cm^-2 and 1 mAh cm^-2. Furthermore, the Li-S full battery composed of Mn₃O₄/ZnO@SWCNT-Li also shows excellent cycle stability. These results demonstrate that Mn₃O₄/ZnO@SWCNT has great potential as a dendrite-free Li metal host material.

Tailoring Practically Accessible Polymer/Inorganic Composite Electrolytes for All-Solid-State Lithium Metal Batteries: A Review

Highlights

The current issues and recent advances in polymer/inorganic composite electrolytes are reviewed. The molecular interaction between different components in the composite environment is highlighted for designing high-performance polymer/inorganic composite electrolytes. Inorganic filler properties that affect polymer/inorganic composite electrolyte performance are pointed out. Future research directions for polymer/inorganic composite electrolytes compatible with high-voltage lithium metal batteries are outlined.

Abstract

Solid-state electrolytes (SSEs) are widely considered the essential components for upcoming rechargeable lithium-ion batteries owing to the potential for great safety and energy density. Among them, polymer solid-state electrolytes (PSEs) are competitive candidates for replacing commercial liquid electrolytes due to their flexibility, shape versatility and easy machinability. Despite the rapid development of PSEs, their practical application still faces obstacles including poor ionic conductivity, narrow electrochemical stable window and inferior mechanical strength. Polymer/inorganic composite electrolytes (PIEs) formed by adding ceramic fillers in PSEs merge the benefits of PSEs and inorganic solid-state electrolytes (ISEs), exhibiting appreciable comprehensive properties due to the abundant interfaces with unique characteristics. Some PIEs are highly compatible with high-voltage cathode and lithium metal anode, which offer desirable access to obtaining lithium metal batteries with high energy density. This review elucidates the current issues and recent advances in PIEs. The performance of PIEs was remarkably influenced by the characteristics of the fillers including type, content, morphology, arrangement and surface groups. We focus on the molecular interaction between different components in the composite environment for designing high-performance PIEs. Finally, the obstacles and opportunities for creating high-performance PIEs are outlined. This review aims to provide some theoretical guidance and direction for the development of PIEs.

An Amorphous Anode for Proton Battery

Developing advanced electrode materials is crucial for improving the electrochemical performances of proton batteries. Currently, the anodes are primarily crystalline materials which suffer from inferior cyclic stability and high electrode potential. Herein, we propose amorphous electrode materials for proton batteries by using a general ion-exchange protocol to introduce multivalent metal cations for activating the host material. Taking Al3+ as an example, theoretical and experimental analysis demonstrates electrostatic interaction between metal cations and lattice oxygen, which is the primary barrier for direct introduction of the multivalent cations, is effectively weakened through ion exchange between Al3+ and pre-intercalated K+. The as-prepared Al-MoOx anode therefore delivered a remarkable capacity and outstanding cycling stability that outperforms most of the state-of-the-art counterparts. The assembled full cell also achieved a high voltage of 1.37 V. This work opens up new opportunities for developing high-performance electrodes of proton batteries by introducing amorphous materials.