Assembly: A Key Enabler for the Construction of Superior Silicon-Based Anodes

Fluorine-ion-regulated yolk-shell carbon-silicon anode material for high performance lithium ion batteries

Silicon is considered as the next-generation anode material for lithium-ion batteries due to its high theoretical specific capacity and abundant crustal abundance. However, its poor electrical conductivity results in slow diffusion of lithium ions during battery operation. Simultaneously, the alloying process of silicon undergoes a 300 % volume change, leading to structural fractures in silicon during the cycling process. As a result, it loses contact with the current collector, continuously exposing active sites, and forming a sustained solid electrolyte interface (SEI) membrane. This paper presents the design of a fluorine-ion-regulated yolk-shell carbon-silicon anode material, highlighting the following advantages: (a) Alleviating volume changes through the design of a yolk-shell structure, thereby maintaining material structural integrity during cycling. (b) Carbon shell prevents silicon from coming into contact with the electrolyte, simultaneously improving silicon's electrical conductivity and increasing ion/electron conductivity. (c) Utilizing fluorine-ion interface modification to obtain an SEI membrane rich in fluorine components (such as LiF), thereby enhancing its long cycling performance. The F-Si@Void@C exhibits outstanding electrochemical performance, with a reversible capacity of 1166 mAh/g after 900 cycles at a current density of 0.5 A/g.

Designing a Se-intercalated MOF/MXene-derived nanoarchitecture for advancing the performance and durability of lithium-selenium batteries

Lithium-selenium batteries have emerged as a promising alternative to lithium-sulfur batteries due to their high electrical conductivity and comparable volume capacity. However, challenges such as the shuttle effect of polyselenides and high-volume fluctuations hinder their practical implementation. To address these issues, we propose synthesizing Fe-CNT/TiO2 catalyst through high-temperature sintering of an amalgamated nanoarchitecture of carbon nanotubes decorated metal-organic framework (MOF) and MXene, optimized for efficient selenium hosting, leveraging the distinctive physicochemical properties. The catalytic features inherent in the porous Se@Fe-CNT/TiO2 nanoarchitecture were instrumental in promoting efficient ion and electron transport, and lithium-polyselenide kinetics, while its inherent porosity could play a crucial role in inhibiting electrode stress during cycling. This nanoarchitecture exhibits remarkable battery performance, retaining 99.7% of theoretical capacity after 425 cycles at 0.5 C rate and demonstrating 95.8% capacity retention after 2000 cycles at 1 C rate, with ∼100% Coulombic efficiency. Additionally, the Se@Fe-CNT/TiO2 electrode exhibited an impressive recovery of 297.5 mAh/g (97.9%) capacity after undergoing 450 cycles at a charging rate of 10 C and a discharging rate of 1 C. This synergistic integration of MOF- and MXene-derived materials unveils new possibilities for high-performance and durable LSeBs, thus advancing electrochemical energy storage systems.

A graphene-like hollow sphere anode for lithium-ion batteries

We report a flash Joule heating method for the rapid preparation of graphene-like materials. The L-GHS exhibited a uniform diameter of 200 nm and an ideal specific surface area of 670 m2 g-1. Meanwhile, the specific capacity of L-GHS remained at 942 mA h g-1 after 600 cycles (1 A g-1), which shows excellent electrochemical performance.

The Promising Potential of Gallium Based Liquid Metals for Energy Storage

Energy storage devices play a crucial role in various applications, such as powering electronics, power backup for homes and businesses, and support for the integration of renewable energy sources into electrical grid applications. Electrode materials for energy storage devices are preferred to have a flexible nature, conductive, better capacity, and low-toxicity. Using Gallium based liquid metal alloys, such as Eutectic Gallium-Indium (EGaIn), Eutectic Gallium-Tin (EGaSn), and Eutectic Gallium-Indium-Tin (EGaInSn), as electrode materials play very important role in energy storage devices. These liquid metals have some interesting properties with a self-healing nature, high mechanical stability, compatibility with various materials, fluidity, low young's modulus, high electrical and thermal conductivity. Those properties have made it suitable to be used in various energy storage devices. In this mini review, we have concisely described the advantages and challenges of using liquid metal as electrode materials for various energy storage devices.

Self-Assembly of Silicon Nanotubes Driven by a Biphasic Transition from the Natural Mineral Montmorillonite in Molten Salt Electrolysis

Silicon nanotubes (SNTs) have been considered as promising anode materials for lithium-ion batteries (LIBs). However, the reported strategies for preparing SNTs generally have special requirements for either expensive templates or complex catalysts. It is necessary to explore a cost-effective and efficient approach for the preparation of high-performance SNTs. In this work, a biphasic transformation strategy involving "solid-state reduction" and "dissolution-deposition" in molten salts is developed to prepare SNTs using montmorillonite as a precursor. The rod-like intermediate of silicon-aluminum-calcium is initially reduced in solid state, which then triggers the continuous dissolution and deposition of calcium silicate in the inner space of the intermediate to form a hollow structure during the subsequent reduction process. The transition from solid to liquid is crucial for improving the kinetics of deoxygenation and induces the self-assembly of SNTs during electrolysis. When the obtained SNTs is used as anode materials for LIBs, they exhibit a high capacity of 2791 mAh g-1 at 0.2 A g-1 , excellent rate capability of 1427 mA h g-1 at 2 A g-1 , and stable cycling performance with a capacity of 2045 mAh g-1 after 200 cycles at 0.5 A g-1 . This work provides a self-assembling, controllable, and cost-effective approach for fabricating SNTs.

Enabling Uniform and Stable Lithium-Ion Diffusion at the Ultrathin Artificial Solid-Electrolyte Interface in Siloxene Anodes

Constructing a stable and robust solid electrolyte interphase (SEI) has a decisive influence on the charge/discharge kinetics of lithium-ion batteries (LIBs), especially for silicon-based anodes which generate repeated destruction and regeneration of unstable SEI films. Herein, a facile way is proposed to fabricate an artificial SEI layer composed of lithiophilic chitosan on the surface of two-dimensional siloxene, which has aroused wide attention as an advanced anode for LIBs due to its special characteristics. The optimized chitosan-modified siloxene anode exhibits an excellent reversible cyclic stability of about 672.6 mAh g-1 at a current density of 1000 mA g-1 after 200 cycles and 139.9 mAh g-1 at 6000 mA g-1 for 1200 cycles. Further investigation shows that a stable and LiF-rich SEI film is formed and can effectively adhere to the surface during cycling, redistribute lithium-ion flux, and enable a relatively homogenous lithium-ion diffusion. This work provides constructive guidance for interface engineering strategy of nano-structured silicon anodes.

Rational Design of Ion-Conductive Layer on Si Anode Enables Superior-Stable Lithium-Ion Batteries

Silicon (Si) is considered a promising commercial material for the next-generation of high-energy density lithium-ion battery (LIB) due to its high theoretical capacity. However, the severe volume changes and the poor conductivity hinder the practical application of Si anode. Herein, a novel core-shell heterostructure, Si as the core and V3 O4 @C as the shell (Si@V3 O4 @C), is proposed by a facile solvothermal reaction. Theoretical simulations have shown that the in-situ-formed V3 O4 layer facilitates the rapid Li+ diffusion and lowers the energy barrier of Li transport from the carbon shell to the inner core. The 3D network structure constructed by amorphous carbon can effectively improve electronic conductivity and structural stability. Benefiting from the rationally designed structure, the optimized Si@V3 O4 @C electrode exhibits an excellent cycling stability of 1061.1 mAh g-1 at 0.5 A g-1 over 700 cycles (capacity retention of 70.0%) with an average Coulombic efficiency of 99.3%. In addition, the Si@V3 O4 @C||LiFePO4 full cell shows a superior capacity retention of 78.7% after 130 cycles at 0.5 C. This study opens a novel way for designing high-performance silicon anode for advanced LIBs.

Scalable Synthesis of a Porous Micro Si/Si-Ti Alloy Anode for Lithium-Ion Battery from Recovery of Titanium-Blast Furnace Slag

The extensive utilization of Si-anode-based lithium-ion batteries faces obstacles due to their substantial volume expansion, limited intrinsic conductivity, and low initial Coulombic efficiency (ICE). In this study, we present a straightforward, cost-effective, yet scalable method for producing a porous micro Si/Si-Ti alloy anode. This method utilizes titanium-blast furnace slag (TBFS) as a raw material and combines aluminothermic reduction with acid etching. By adjusting the Al:TBFS ratio, the specific surface area of the material can be facilely tailored, ranging from 25.89 to 43.23 m2 g-1, enhancing the ICE from 78.2 to 85.5%. The incorporation of the Si-Ti alloy skeleton and porous structure contributes to the enhanced cyclic stability (capacity retention from 50.7 to 96.9%) and conductivity (Rct from 107.7 to 76.6 Ω). The Si/Si-Ti anode exhibits excellent electrochemical performance, including delivering a specific capacity of 1161 mAh g-1 at 200 mA g-1 after 200 cycles and 1112 mAh g-1 at 500 mA g-1 after 100 cycles, with an improved ICE of 81.2%. This study introduces a successful methodology for designing novel Si anodes from recycling waste materials, providing valuable insights for future advancements in this area.

Electrolyte-assisted low-voltage decomposition of Li2C2O4 for efficient cathode pre-lithiation in lithium-ion batteries

Lithium oxalate (Li2C2O4) is an attractive cathode pre-lithiation additive for lithium-ion batteries (LIBs), but its application is hindered by its high decomposition potential (>4.7 V). Due to the liquid-solid synergistic effect of the NaNO2 additive and the LiNi0.83Co0.07Mn0.1O2 (NCM) cathode material, the decomposition efficiency of micro-Li2C2O4 reaches 100% at a low charge cutoff voltage of 4.3 V. Our work boosts the widespread practical application of Li2C2O4 by a simple and promising electrolyte-assisted cathode pre-lithiation strategy.

Unleashing the Potential of High-Capacity Anodes through an Interfacial Prelithiation Strategy

The scalable development of an environmentally adaptive and homogeneous Li+ supplementary route remains a formidable challenge for the existing prelithiation technologies, restricting the full potential of high-capacity anodes. In this study, we present a moisture-tolerant interfacial prelithiation approach through casting a hydrophobic poly(vinylidene-co-hexafluoropropylene) membrane blended with a deep-lithiated alloy (Li22Si5@C/PVDF-HFP) onto Si based anodes. This strategy could not only extend to various high-capacity anode systems (SiOx@C, hard carbon) but also align with industrial roll-to-roll assembly processes. By carefully adjusting the thickness of the prelithiation layer, the densely packed Si@C electrode (4.5 mAh cm-2) exhibits significantly improved initial Coulombic efficiency until a close-to-unit value, as well as extreme moisture tolerance (60% relative humidity). Furthermore, it achieves more than 10-fold enhancement of ionic conductivity across the electrode. As pairing the prelithiated Si@C anode with the LiNi0.8Co0.1Mn0.1O2 cathode, the 2 Ah pouch-format prototype balances an energy density of ∼371 Wh kg-1 and an extreme power output of 2450 W kg-1 as well as 83.8% capacity retention for 1000 cycles. The combined operando phase tracking and spatial arrangement analysis of the intermediate alloy elucidate that the enhanced Li utilization derives from the gradient stress dissipation model upon a spontaneous Li+ redistribution process.

Emerging Multiscale Porous Anodes toward Fast Charging Lithium-Ion Batteries

With the accelerated penetration of the global electric vehicle market, the demand for fast charging lithium-ion batteries (LIBs) that enable improvement of user driving efficiency and user experience is becoming increasingly significant. Robust ion/electron transport paths throughout the electrode have played a pivotal role in the progress of fast charging LIBs. Yet traditional graphite anodes lack fast ion transport channels, which suffer extremely elevated overpotential at ultrafast power outputs, resulting in lithium dendrite growth, capacity decay, and safety issues. In recent years, emergent multiscale porous anodes dedicated to building efficient ion transport channels on multiple scales offer opportunities for fast charging anodes. This review survey covers the recent advances of the emerging multiscale porous anodes for fast charging LIBs. It starts by clarifying how pore parameters such as porosity, tortuosity, and gradient affect the fast charging ability from an electrochemical kinetic perspective. We then present an overview of efforts to implement multiscale porous anodes at both material and electrode levels in diverse types of anode materials. Moreover, we critically evaluate the essential merits and limitations of several quintessential fast charging porous anodes from a practical viewpoint. Finally, we highlight the challenges and future prospects of multiscale porous fast charging anode design associated with materials and electrodes as well as crucial issues faced by the battery and management level.

Tight Binding and Dual Encapsulation Enabled Stable Thick Silicon/Carbon Anode with Ultrahigh Volumetric Capacity for Lithium Storage

Silicon (Si) is regarded as one of the most promising anode materials for high-performance lithium-ion batteries (LIBs). However, how to mitigate its poor intrinsic conductivity and the lithiation/delithiation-induced large volume change and thus structural degradation of Si electrodes without compromising their energy density is critical for the practical application of Si in LIBs. Herein, an integration strategy is proposed for preparing a compact micron-sized Si@G/CNF@NC composite with a tight binding and dual-encapsulated architecture that can endow it with superior electrical conductivity and deformation resistance, contributing to excellent cycling stability and good rate performance in thick electrode. At an ultrahigh mass loading of 10.8 mg cm-2 , the Si@G/CNF@NC electrode also presents a large initial areal capacity of 16.7 mA h cm-2 (volumetric capacity of 2197.7 mA h cm-3 ). When paired with LiNi0.95 Co0.02 Mn0.03 O2 , the pouch-type full battery displays a highly competitive gravimetric (volumetric) energy density of ≈459.1 Wh kg-1 (≈1235.4 Wh L-1 ).

Interphasial Pre-lithiation and Reinforcement of Micro-Si Anode through Fluorine-free Electrolytes

Micro-sized silicon (mSi) anodes offer advantages in cost and tap density over nanosized counterparts. However, its practical application still suffers from poor cyclability and low initial and later-cycle coulombic efficiency (CE), caused by the unstable solid electrolyte interphase (SEI) and irreversible lithiation of the surface oxide layer. Herein, a bifunctional fluorine (F)-free electrolyte was designed for the mSi anode to stabilize the interphase and improve the CE. A combined analysis revealed that this electrolyte can chemically pre-lithiate the native oxide layer by the reductive LiBH4 , and relieve SEI formation and accumulation to preserve the internal conductive network. The significance of this F-free electrolyte brings unprecedented F-free interphase that also enables the high-performance mSi electrode (80 wt % mSi), including high specific capacity of 2900 mAh/g, high initial CE of 94.7 % and excellent cyclability capacity retention of 94.3 % after 100 cycles at 0.2 C. This work confirms the feasibility of F-free interphase, thus opening up a new avenue toward cost-advantaged and environmentally friendly electrolytes for more emerging battery systems.

Influence of bridge structure manipulation on the electrochemical performance of π-conjugated molecule-bridged silicon quantum dot nanocomposite anode materials for lithium-ion batteries

To assess the influence of bridge structure manipulation on the electrochemical performance of π-conjugated molecule-bridged silicon quantum dot (Si QD) nanocomposite (SQNC) anode materials, we prepared two types of SQNCs by Sonogashira cross-coupling and hydrosilylation reactions; one is SQNC-VPEPV, wherein the Si QDs are covalently bonded by vinylene (V)-phenylene (P)-ethynylene (E)-phenylene-vinylene, and the other is SQNC-VPV. By comparing the electrochemical performances of the SQNCs, including that of the previously reported SQNC-VPEPEPV, we found that the SQNC with the highest specific capacity varied depending on the applied current density; SQNC-VPEPV (1420 mA h g^-1) > SQNC-VPV (779 mA h g^-1) > SQNC-VPEPEPV(465 mA h g^-1) at 800 mA g^-1, and SQNC-VPV (529 mA h g^-1) > SQNC-VPEPEPV (53 mA h g^-1) > SQNC-VPEPV (7 mA h g^-1) at 2000 mA g^-1. To understand this result, we performed EIS and GITT measurements of the SQNCs. In the course of investigating the lithium-ion diffusion coefficient, charge/discharge kinetics, and electrochemical performance of the SQNC anode materials, we found that electronic conductivity is a key parameter for determining the electrochemical performance of the SQNC. Two probable causes for the unique behavior of the electrochemical performances of the SQNCs are anticipated: (i) the SQNC with predominant electronic conductivity is varied depending on the current density applied during the cell operation, and (ii) the degree of surface oxidation of the Si QDs in the SQNCs varies depending on the structures of the surface organic molecules of the Si QDs and the bridging molecules of the SQNCs. Therefore, differences in the amount of oxides (SiO₂)/suboxides (SiO_x) on the surface of Si QDs lead to significant differences in conductivity and electrochemical performance between the SQNCs.

New Chemical Synthesis Strategy To Construct a Silicon/Carbon Nanotubes/Carbon-Integrated Composite with Outstanding Lithium Storage Capability

The Si/C anode is one of the most promising candidate materials for the next-generation lithium-ion batteries (LIBs). Herein, a silicon/carbon nanotubes/carbon (Si/CNTs/C) composite is in situ synthesized by a one-step reaction of magnesium silicide, calcium carbonate, and ferrocene. Transmission electron microscopy reveals that the growth of CNTs is attributed to the catalysis of iron atoms derived from the decomposition of ferrocene. In comparison to a Si/C composite, the cycle stability of the Si/CNTs/C composite can obviously be improved as an anode for LIBs. The enhanced performance is mainly attributed to the following factors: (i) the perfect combination of Si nanoparticles and in situ grown CNTs achieves high mechanical integrity and good electrical contact; (ii) Si nanoparticles are entangled in the CNT cage, effectively reducing the volume expansion upon cycling; and (iii) in situ grown CNTs can improve the conductivity of composites and provide lithium ion transport channels. Moreover, the full cell constructed by a LiFePO₄ cathode and Si/CNTs/C anode exhibits excellent cycling stability (137 mAh g^-1 after 300 cycles at 0.5 C with a capacity retention rate of 91.2%). This work provides a new way for the synthesis of a Si/C anode for high-performance LIBs.

Moiré Superlattice Structure in Two-Dimensional Catalysts: Synthesis, Property and Activity

Two-dimensional (2D) layered materials have been widely used as catalysts due to their high specific surface area, large fraction of uncoordinated surface atoms, and high charge carrier mobility. Moiré superlattice emerges in 2D layered materials with twist angle or lattice mismatch. By manipulating the moiré superlattice structure, 2D layered materials present modulated electronic band structure, topological edge states, and unconventional superconductivity which are tightly associated with the performance of catalysts. Hence, engineering moiré superlattice structures are proposed to be an important technology in modifying 2D layered materials for improved catalytic properties. However, currently, the investigation of moiré superlattice structure in a catalytic application is still in its infancy. This perspective starts with the discussion of structural features and fabrication strategy of 2D materials with moiré superlattice structure. Afterward, the catalytic applications, including electrocatalytic and photocatalytic applications, are summarized. In particular, the promotion mechanism of the catalytic performance caused by the moiré superlattice structure is proposed. Finally, the perspective is concluded by outlining the remaining challenges and possible solutions for the future development of 2D materials with moiré superlattice structure towards the catalytic applications.