Self-Assembled Conductive Metal-Oxide Nanofiber Interface for Stable Li-Metal Anode

Synergistic Promotion of Adsorption-Conversion for Lithium Polysulfides through Ion/Electron Coconductive Catalytic Triple-Phase Interface by the Geometric Torsion of Lithium Lanthanum Titanate Electrocatalyst

Rationally designing and constructing ionic/electronic coconductor electrocatalysts with adjustable active sites to enhance the redox kinetics of lithium-sulfur batteries (LSBs) in lean electrolyte conditions is a challenge. Herein, this study presents the promotion for lithium polysulfides (LiPSs) redox kinetics through the construction of ion/electron coconductive catalytic triple-phase interface using lithium lanthanum titanate/carbon (LLTO/C) nanofibers, which is due to manipulating the geometric torsion of BO6 octahedron in LLTO. Experiments and theoretical calculations demonstrate that geometric torsion changes the coordination environment of O-Ti-O in LLTO and causes oxygen vacancy and lattice distortion. This enhances the local electronic state density, ion migration rate, and high catalytic activity of LLTO, thereby resulting in a synergistic effect for good chemisorption and rapid catalytic conversion of LiPSs. Therefore, when the modified separator is used, LSBs with the electrocatalyst realize a high discharge capacity of 1024 mA h·g-1 at a high current rate of 2 C. Upon a high sulfur loading of 9 mg ·cm-2 and a lean electrolyte/sulfur ratio of 4 μL· mg-1, an acceptable areal capacity of 9.1 mA h· cm-2 is achieved. This work provides a new perspective for the rational design of ionic/electronic coconductor catalysts for LSBs.

Advances in Nanofibrous Materials for Stable Lithium-Metal Anodes

Lithium metal is regarded as the most potential anode material for improving the energy density of batteries due to its high specific capacity and low electrode potential. However, the practical application of lithium-metal anodes (LMAs) still faces severe challenges such as uncontrollable dendrites growth and large volume expansion. The development of functional nanomaterials has brought opportunities for the revival of LMAs. Among them, nanofibrous materials show great application potential for LMAs protection due to their distinct functional and structural features. Here, the latest research progress in nanofibrous materials for LMAs is systematically outlined. First, the problems existing in the practical application of LMAs are analyzed. Then, prospective strategies and recent research progress toward stable LMAs based on nanofibrous materials are summarized from the aspects of artificial protective layers, three-dimensional frameworks, separators, and solid-state electrolytes. Finally, the future development of nanofibrous materials for the protection of lithium-metal batteries is summarized and prospected. This review establishes a close connection between nanofibrous materials and LMA modification and provides insight for the development of high-safety lithium-metal batteries.

Multifunctional Protection Layers via a Self-Driven Chemical Reaction To Stabilize Lithium Metal Anodes

The Li metal anode is considered one of the most potential anodes due to its highest theoretical specific capacity and the lowest redox potential. However, the scalable preparation of safe Li anodes remains a challenge. In the present study, a LiF-rich protection layer has been developed using self-driven chemical reactions between the Li_3xLa_2/3-xTiO₃/polyvinylidene fluoride/dimethylacetamide (LLTO/PVDF/DMAc) solution and the Li metal. After coating the LLTO/PVDF/DMAc solution to Li foil, PVDF reacted with Li spontaneously to form LiF, and the accompanying Ti⁴⁺ ions (in LLTO) were reduced to Ti³⁺ to form a mixed ionic and electronic conductor Li_xLLTO. The protective layer can redistribute the Li-ion transport, regulate the even Li deposition, and inhibit the Li dendrite growth. When paired with LiFePO₄, NCM811, and S cathodes, the batteries have demonstrated excellent capacity retention and cycling stability. More importantly, a volumetric energy density of 478 Wh L^-1 and 78% capacity retention after 310 cycles have been achieved by using a S/Li_xLLTO-Li pouch cell. This work provides a feasible avenue to provide large-scale preparation of safe Li anodes for the next-generation pouch-type Li-S batteries as ideal power sources for flexible electronic devices.

High ionic conductivity Li0.33La0.557TiO3nanofiber/polymer composite solid electrolyte for flexible transparent InZnO synaptic transistors

With the rapid development of wearable artificial intelligence devices, there is an increasing demand for flexible oxide neuromorphic transistors with the solid electrolytes. To achieve high-performance flexible synaptic transistors, the solid electrolytes should exhibit good mechanical bending characteristics and high ion conductivity. However, the polymer-based electrolytes with good mechanical bending characteristics show poor ion conductivity (10^-6-10^-7S cm^-1), which limits the performance of flexible synaptic transistors. Thus, it is urgent to improve the ion conductivity of the polymer-based electrolytes. In the work, a new strategy of electrospun Li_0.33La_0.557TiO₃nanofibers-enhanced ion transport pathway is proposed to simultaneously improve the mechanical bending and ion conductivity of polyethylene oxide/polyvinylpyrrolidone-based solid electrolytes. The flexible InZnO synaptic transistors with Li_0.33La_0.557TiO₃nanofibers-based solid electrolytes successfully simulated excitatory post-synaptic current, paired-pulse-facilitation, dynamic time filter, nonlinear summation, two-terminal input dynamic integration and logic function. This work is a useful attempt to develop high-performance synaptic transistors.

Solid-State Lithium Metal Batteries with Extended Cycling Enabled by Dynamic Adaptive Solid-State Interfaces

Improving the long-term cycling stability of solid-state lithium (Li)-metal batteries (SSBs) is a severe challenge because of the notorious solid-solid interfacial contact loss originating from the repeated expansion and contraction of the Li anodes. Here, it is reported that high-performance SSBs are enabled by constructing brick-and-mortar electrolytes that can dynamically adapt to the interface changes during cycling. An electrolyte film with a high mechanical strain (250%) is fabricated by filling viscoelastic (600% strain) and piezoelectric block-copolymer electrolytes (mortar) into a mixed conductor Li_0.33 La_0.56 TiO_3-x nanofiber film (brick). During Li-plating, the electrolytes can homogenize the interfacial electric field and generate piezoelectricity to promote uniform Li-deposition, while the mortar can adhere to the Li-anode without interfacial disintegration in the reversed Li-stripping. As a result, the electrolytes show excellent compatibility with the electrodes, leading to a long electrochemical cyclability at room temperature. The symmetrical Li//Li cells run stably for 1880 h without forming dendrites, and the LiFePO₄ /Li full batteries deliver high coulombic efficiency (>99.5%) and capacity retention (>85%) over 550 cycles. More practically, the pouch cells exhibit excellent flexibility and safety for potential practical applications.

Three-Dimensional (3D) Nanostructured Skeleton Substrate Composed of Hollow Carbon Fiber/Carbon Nanosheet/ZnO for Stable Lithium Anode

The practical applications of Li metal batteries (LMBs) have long been limited by the obstacles of low Coulombic efficiency (CE) and formation of dendrites on Li metal electrode. Herein, we demonstrated the synthesis of a novel three-dimensional (3D) nanostructured skeleton substrate composed of nitrogen-doped hollow carbon fiber/carbon nanosheets/ZnO (NHCF/CN/ZnO) using 2-methylimidazole (2-MIZ)-coated 3D cloth as a scaffold. The mechanism of formation of this novel hierarchical structure was investigated. The multilayered hierarchical structure and abundant lithiophilic nucleation sites of the substrate provide a stable environment for the deposition and stripping of lithium metal, thus preventing the generation of lithium dendrites. Consequently, the lithium anode based on the NHCF/CN/ZnO current collector demonstrated an excellent Coulombic efficiency of 96.47% after 400 cycles at 0.5 mA cm^-2. The prepared NHCF/CN/ZnO/Li electrode also showed outstanding cycling performance of over 800 h and an ultralow voltage hysteresis of less than 30 mV in a symmetric cell at 5 mA cm^-2 and 5 mAh cm^-2. Even at a high loading of the cathode with 10.4 mg cm^-2, the full cell of NHCF/CN/ZnO/Li anode with LiFePO₄ can also work very well. Our work offers a path toward the facial preparation of 3D hierarchical structure for high-performance lithium metal batteries.

Sulfide and Oxide Inorganic Solid Electrolytes for All-Solid-State Li Batteries: A Review

Energy storage materials are finding increasing applications in our daily lives, for devices such as mobile phones and electric vehicles. Current commercial batteries use flammable liquid electrolytes, which are unsafe, toxic, and environmentally unfriendly with low chemical stability. Recently, solid electrolytes have been extensively studied as alternative electrolytes to address these shortcomings. Herein, we report the early history, synthesis and characterization, mechanical properties, and Li+ ion transport mechanisms of inorganic sulfide and oxide electrolytes. Furthermore, we highlight the importance of the fabrication technology and experimental conditions, such as the effects of pressure and operating parameters, on the electrochemical performance of all-solid-state Li batteries. In particular, we emphasize promising electrolyte systems based on sulfides and argyrodites, such as LiPS5Cl and β-Li3PS4, oxide electrolytes, bare and doped Li7La3Zr2O12 garnet, NASICON-type structures, and perovskite electrolyte materials. Moreover, we discuss the present and future challenges that all-solid-state batteries face for large-scale industrial applications.

Polymer Template Synthesis of Flexible SiO2 Nanofibers to Upgrade Composite Electrolytes

Flexible oxide ceramic films offer prospects for revolutionizing diverse fields such as energy and electronics, but their fabrication methods are typically elaborate and cannot be expanded. Here, we report a scalable strategy to fabricate flexible and robust SiO₂ nanofiber films with controllable morphology using a sol-gel electrospinning method followed by low-temperature calcination. When applied to composite polymer electrolytes (CPEs) for solid-state batteries by filling polyethylene oxide into porous ceramic films, SiO₂ nanofibers with large surface areas (51 m²·g^-1) demonstrate strong Lewis interfacial interactions and isotropic ionic transfer channels that mitigate polymer crystallinity and Li⁺-concentration polarization, imparting high conductivity (1.3 × 10^-4 S·cm^-1 at 30 °C) and structural stability to the electrolytes. As a result, all-solid-state LiFePO₄||Li shows great rate capability and long cycling stability with high discharge capacities of 159 and 132 mA·h·g^-1 at 0.5C under 60 and 45 °C, respectively, demonstrating broad commercial prospects for the scale production of efficient solid electrolytes.

Stable Lithium Metal Anode Enabled by a Lithiophilic and Electron/Ion Conductive Framework

Li metal anode has been considered as the ideal anode for next-generation batteries due to its ultrahigh capacity and lowest electrochemical potential. However, its practical application is still impeded by low Coulombic efficiency, huge volume change, and safety hazards arising from Li dendrite growth. In this work, a three-dimensional (3D) structured highly stable Li metal anode is designed and easily preapred. Benefiting from the in situ reaction between Li metal and AlN, highly Li⁺ conductive Li₃N and lithiophilic LiAl alloy have been simultaneously formed and homogeneously distributed in the framework, in which Li metal is finely dispersed and embedded. The outstanding electron/ion mixed conductivity of Li₃N/LiAl and 3D composite structure with enhanced interfacial area significantly improve the electrode kinetics and suppress the volume change on cycling, while a lithiophilic effect of LiAl alloy and uniform distribution of Li ion flux inside the electrode avoid dendritic Li deposition. As a result, the proposed Li metal electrode exhibits exceptional electrochemical reversibility in both carbonate and ether-based electrolytes. Paired with LiFePO₄ and sulfurized polyacrylonitrile (S@pPAN) cathodes, the full cells deliver highly stable and long-term cycling performance. Therefore, the proposed strategy to fabricate Li metal anodes could promote the practical application of Li metal batteries.