Approaching the downsizing limit of silicon for surface-controlled lithium storage

A Rapid, Scalable Laser-Scribing Process to Prepare Si/Graphene Composites for Lithium-Ion Batteries

Silicon has gained significant attention as a lithium-ion battery anode material due to its high theoretical capacity compared to conventional graphite. Unfortunately, silicon anodes suffer from poor cycling performance caused by their extreme volume change during lithiation and de-lithiation. Compositing silicon particles with 2D carbon materials, such as graphene, can help mitigate this problem. However, an unaddressed challenge remains: a simple, inexpensive synthesis of Si/graphene composites. Here, a one-step laser-scribing method is proposed as a straightforward, rapid (≈3 min), scalable, and less-energy-consuming (≈5 W for a few minutes under air) process to prepare Si/laser-scribed graphene (LSG) composites. In this research, two types of Si particles, Si nanoparticles (SiNPs) and Si microparticles (SiMPs), are used. The rate performance is improved after laser scribing: SiNP/LSG retains 827.6 mAh g-1 at 2.0 A gSi+C -1, while SiNP/GO (before laser scribing) retains only 463.8 mAh g-1. This can be attributed to the fast ion transport within the well-exfoliated 3D graphene network formed by laser scribing. The cyclability is also improved: SiNP/LSG retains 88.3% capacity after 100 cycles at 2.0 A gSi+C -1, while SiNP/GO retains only 57.0%. The same trend is found for SiMPs: the SiMP/LSG shows better rate and cycling performance than SiMP/GO composites.

Functional Alkali Metal-Based Ternary Chalcogenides: Design, Properties, and Opportunities

The search for novel materials has recently brought research attention to alkali metal-based chalcogenides (ABZ) as a new class of semiconducting inorganic materials. Various theoretical and computational studies have highlighted many compositions of this class as ideal functional materials for application in energy conversion and storage devices. This Perspective discusses the expansive compositional landscape of ABZ compositions that inherently gives a wide spectrum of properties with great potential for application. In the present paper, we examine the technique of synthesizing this particular class of materials and explore their potential for compositional engineering in order to manipulate key functional properties. This study presents the notable findings that have been documented thus far in addition to outlining the potential avenues for implementation and the associated challenges they present. By fulfilling the sustainability requirements of being relativity earth-abundant, environmentally benign, and biocompatible, we anticipate a promising future for alkali metal chalcogenides. Through this Perspective, we aim to inspire continued research on this emerging class of materials, thereby enabling forthcoming breakthroughs in the realms of photovoltaics, thermoelectrics, and energy storage.

A Brief Overview of Silicon Nanoparticles as Anode Material: A Transition from Lithium-Ion to Sodium-Ion Batteries

The successful utilization of silicon nanoparticles (Si-NPs) to enhance the performance of Li-ion batteries (LIBs) has demonstrated their potential as high-capacity anode materials for next-generation LIBs. Additionally, the availability and relatively low cost of sodium resources have a significant influence on developing Na-ion batteries (SIBs). Despite the unique properties of Si-NPs as SIBs anode material, limited study has been conducted on their application in these batteries. However, the knowledge gained from using Si-NPs in LIBs can be applied to develop Si-based anodes in SIBs by employing similar strategies to overcome their drawbacks. In this review, a brief history of Si-NPs' usage in LIBs is provided and discuss the strategies employed to overcome the challenges, aiming to inspire and offer valuable insights to guide future research endeavors.

A densely packed air-stable free-standing film with FeP nanoparticles@C@P-doped reduced graphene oxide for sodium-ion batteries

Developing a facile strategy which enhances the structural stability and air/moisture stability of transition metal phosphides for practical applications is important but challenging. Herein, we designed a densely packed free-standing film consisting of carbon-coated FeP nanoparticles anchored on P-doped graphene (FeP@C@PG film) through solventless thermal decomposition and the roll-press method. Phytic acid serves a multifunctional role as both a phosphorus source to prepare ultrafine FeP nanoparticles and a protective layer to improve air stability along with hydrophobic graphene and maximize the utilization of phosphide. This structure can enhance electron/ion transport kinetics, allowing for full utilization of active materials, and buffer large volume expansions while preventing pulverization/aggregation during cycling. Noticeably, the densely packed structure can greatly enhance oxidation resistance by effectively blocking the penetration of air/moisture. Therefore, the FeP@C@PG film delivers a stable reversible capacity of 536.6 mA h g-1 after 1000 cycles at 1 A g-1 with good capacity retention, an excellent rate capability of 440.7 mA h g-1 at 5 A g-1, and excellent oxidation stability at 80 °C in air. Furthermore, a pouch-type full-cell exhibits excellent rate/cycling performance and bendability. This study provides a new direction for the rational design and practical applications of advanced P-based materials used in alkali metal-ion batteries.

Rational Design of Silicon Nanodots/Carbon Anodes by Partial Oxidization Strategy with High-Performance Lithium-Ion Storage

Silicon (Si) is considered a promising anode material for rechargeable lithium-ion batteries (LIBs) due to its high theoretical capacity, low working potential, and safety features. However, the practical use of Si-based anodes is hampered by their huge volume expansion during the process of lithiation/delithiation, and they have relatively low intrinsic electronic conductivity, therefore seriously restricting their application in energy storage. Here, we propose a facile approach to directly transform siliceous biomass (bamboo leaves) into a porous carbon skeleton-wrapped Si nanodot architecture through a partial oxidization strategy and magnesium thermal reaction to obtain a high Si nanodot component composite (denoted as Si/C-O). With the synergistic effect of the porous carbon skeleton structure and uniformly dispersed Si nanodots, the Si/C-O composite anode with a stable structure that can avoid pulverization and accommodate volume expansion during cycling is fabricated. As expected, the biomass-converted Si/C-O anode not only presents a high Si component (59.7 wt %) by TGA but also exhibits an excellent capacity of 1013 mAh g^-1 at 0.5 A g^-1 and robust cycling stability with a capacity retention of 526 mAh g^-1 after 650 cycles. Moreover, the Si/C-O anode demonstrates considerable performance in practical LIBs when assembled with a commercial LiNi_0.8Co_0.1Mn_0.1O₂ cathode. This work provides an effective strategy and long-term insights into the utilization of porous Si-based materials converted by biomass to design and synthesize high-performance LIB materials.

Reinforced concrete inspired Si/rGO/cPAN hybrid electrode: highly improved lithium storage via Si electrode nanoarchitecture engineering

Electrode nanoarchitecture engineering is a transformative way to improve the structural stability and build robust transport charge pathways for high-capacity silicon in lithium ion batteries (LIBs). However, the violent expansion of silicon during the lithiation/delithiation process is the chief reason for its limited industrialization. Here, we fabricated an integrated electrode structure using polyacrylonitrile (PAN) and graphene oxide (GO) inspired by reinforced concrete. Based on low-temperature annealing, cyclized PAN was assembled on the surface of silicon nanoparticles and tightly combined with reduced graphene oxide (rGO), which could construct stable and efficient transport channels for electrons and lithium ions and address the issues of electrode structure and interface stability. The resultant Si/rGO/cPAN (RC-Si) as the LIB anode exhibits exceptional combined performances including extraordinary mechanical properties, excellent cycling stability (∼1150 mA h g^-1 at 2 A g^-1 over 500 cycles), superior rate capability (∼600 mA h g^-1 at 12 A g^-1), and high areal capacity (∼5.6 mA h cm^-2 at 0.5 mA cm^-2). The novel electrode design concept is promising to promote the practical application of silicon anodes and open a new avenue to develop other high-capacity anodes for high-performance batteries.

Mg2SiO4/Si-Coated Disproportionated SiO Composite Anodes with High Initial Coulombic Efficiency for Lithium Ion Batteries

Silicon monoxide (SiO) is considered as one of the most promising anode material candidates for next-generation high-energy-density lithium ion batteries (LIBs) due to its high specific capacity and relatively lower volume expansion than that of Si. However, a large number of irreversible products are formed during the first charging and discharging process, resulting in a low initial Coulombic efficiency (ICE) of SiO. Herein, we report an economical and convenient method to increase the ICE of SiO without sacrificing its specific capacity by a solid reaction between magnesium silicide (Mg₂Si) and micron-sized SiO. The reaction product (named MSO) exhibits a unique core-shell structure with uniformly distributed Mg₂SiO₄ and Si as the shell and disproportionated SiO as the core. MSO exhibits a superior ICE and a high reversible capacity of 81.7% and 1306.1 mAh g^-1, respectively, which can be further increased to 88.7% and 1446.4 mAh g^-1 after carbon coating, and improved cyclic stability compared to bare SiO. This work provides a simple yet effective strategy to address the low ICE issue of SiO anode materials to promote the practical application of SiO.

Water-Processable and Multiscale-Designed Vanadium Oxide Cathodes with Predominant Zn2+ Intercalation Pseudocapacitance toward High Gravimetric/Areal/Volumetric Capacity

Layered vanadium oxides have great potential as cathode materials for recently surged aqueous zinc-ion batteries (AZIBs). However, achieving high energy/power densities simultaneously is challenging, and side reactions related to more frequently than disclosed Zn²⁺ /proton co-insertion mechanism aggravate stability concerns. Herein, an engineered binder-free cathode configuration based on water-processable and high packing-density sheet-shaped composites of carbon nanotubes network, surface poly(3,4-ethylenedioxythiophene) (PEDOT) bridging coating, and ultrasmall PEDOT-intercalated V₂ O₅ nanoflakes is developed, and therein, large pseudocapacitance via predominant (≈91%) Zn²⁺ intercalation is revealed. Besides competitive gravimetric/areal capacity, the binder-free cathodes exhibit high volumetric capacity of 1106.1 mAh cm^-3 and high-rate capability of 180.0 mA g^-1 at 30 A g^-1 as well as long-cycling stability. Such combined level of performance and unwanted reaction mechanism are attributed to the contained multiscale material/electrode design formula from crystal structure modification to 3D architecture construction of whole electrode, which endows the binder-free cathodes with abundant accessible sites for Zn²⁺ storage, but the least hydroxyl terminated surface for H⁺ insertion, as well as highly conductive network for electron transfer and fast Zn²⁺ diffusion kinetics throughout the electrode. Combined with scalable fabrication protocols, this study opens up great opportunities for high-performance vanadium oxide cathodes practically applicable to AZIBs.

AENET-LAMMPS and AENET-TINKER: Interfaces for accurate and efficient molecular dynamics simulations with machine learning potentials

Machine-learning potentials (MLPs) trained on data from quantum-mechanics based first-principles methods can approach the accuracy of the reference method at a fraction of the computational cost. To facilitate efficient MLP-based molecular dynamics and Monte Carlo simulations, an integration of the MLPs with sampling software is needed. Here, we develop two interfaces that link the atomic energy network (ænet) MLP package with the popular sampling packages TINKER and LAMMPS. The three packages, ænet, TINKER, and LAMMPS, are free and open-source software that enable, in combination, accurate simulations of large and complex systems with low computational cost that scales linearly with the number of atoms. Scaling tests show that the parallel efficiency of the ænet-TINKER interface is nearly optimal but is limited to shared-memory systems. The ænet-LAMMPS interface achieves excellent parallel efficiency on highly parallel distributed-memory systems and benefits from the highly optimized neighbor list implemented in LAMMPS. We demonstrate the utility of the two MLP interfaces for two relevant example applications: the investigation of diffusion phenomena in liquid water and the equilibration of nanostructured amorphous battery materials.

Lithium-Ion Capacitors: A Review of Design and Active Materials

Lithium-ion capacitors (LICs) have gained significant attention in recent years for their increased energy density without altering their power density. LICs achieve higher capacitance than traditional supercapacitors due to their hybrid battery electrode and subsequent higher voltage. This is due to the asymmetric action of LICs, which serves as an enhancer of traditional supercapacitors. This culminates in the potential for pollution-free, long-lasting, and efficient energy-storing that is required to realise a renewable energy future. This review article offers an analysis of recent progress in the production of LIC electrode active materials, requirements and performance. In-situ hybridisation and ex-situ recombination of composite materials comprising a wide variety of active constituents is also addressed. The possible challenges and opportunities for future research based on LICs in energy applications are also discussed.

Reversible Silicon Anodes with Long Cycles by Multifunctional Volumetric Buffer Layers

Establishing a stable, stress-relieving configuration is imperative to achieve a reversible silicon anode for high energy density lithium-ion batteries. Herein, we propose a silicon composite anode (denoted as T-Si@C), which integrates free space and mixed carbon shells doped with rigid TiO₂/Ti₅Si₃ nanoparticles. In this configuration, the free space accommodates the silicon volume fluctuation during battery operation. The carbon shells with embedded TiO₂/Ti₅Si₃ nanoparticles maintain the structural stability of the anode while accelerating the lithium-ion diffusion kinetics and mitigating interfacial side reactions. Based on these advantages, T-Si@C anodes demonstrate an outstanding lithium storage performance with impressive long-term cycling reversibility and good rate capability. Additionally, T-Si@C//LiFePO₄ full cells show superior electrochemical reversibility. This work highlights the importance of rational structural manipulation of silicon anodes and affords fresh insights into achieving advanced silicon anodes with long life.

A three-dimensional bi-conductive Si-based anode for high-performance lithium ion batteries

A high-coulombic-efficiency Si-based anode material is designed and synthesized.

One-Step Low-Temperature Molten Salt Synthesis of Two-Dimensional Si@SiOx@C Hybrids for High-Performance Lithium-Ion Batteries

Various strategies have been developed to mitigate the huge volume expansion of a silicon-based anode during the process of (de)lithiation and accelerate the transport rate of the ions/electrons for lithium-ion batteries (LIBs). Here, we report a one-step synthetic route through a low-temperature eutectic molten salt (LiCl-KCl, 352 °C) to fabricate two-dimensional (2D) silicon-carbon hybrids (Si@SiO_x@MpC), in which the silicon nanoparticles (SiNPs) with an ultrathin SiO_x layer are fully encapsulated by graphene-like carbon nanosheets derived from a low-cost mesophase pitch. The combination of an amorphous graphene-like carbon conductive matrix and a SiO_x protective layer strongly promotes the electrical conductivity, structure stability, and reaction kinetics of the SiNPs. Consequently, the optimized Si@SiO_x@MpC-2 anode delivers large reversible capacity (1239 mAh g^-1 at 1.0 A g^-1), superior rate performance (762 mAh g^-1 at 8 A g^-1), and long cycle life over 600 cycles (degradation rate of only 0.063% every cycle). When coupled with a homemade nano-LiFePO₄ cathode in a full cell, it exhibits a promising energy density of 193.5 Wh kg^-1 and decent cycling stability for 200 cycles at 1C. The methodology driven by salt melt synthesis paves a low-cost way toward simple fabrication and manipulation of silicon-carbon materials in liquid media.

Stable high-capacity and high-rate silicon-based lithium battery anodes upon two-dimensional covalent encapsulation

Silicon is a promising anode material for lithium-ion and post lithium-ion batteries but suffers from a large volume change upon lithiation and delithiation. The resulting instabilities of bulk and interfacial structures severely hamper performance and obstruct practical use. Stability improvements have been achieved, although at the expense of rate capability. Herein, a protocol is developed which we describe as two-dimensional covalent encapsulation. Two-dimensional, covalently bound silicon-carbon hybrids serve as proof-of-concept of a new material design. Their high reversibility, capacity and rate capability furnish a remarkable level of integrated performances when referred to weight, volume and area. Different from existing strategies, the two-dimensional covalent binding creates a robust and efficient contact between the silicon and electrically conductive media, enabling stable and fast electron, as well as ion, transport from and to silicon. As evidenced by interfacial morphology and chemical composition, this design profoundly changes the interface between silicon and the electrolyte, securing the as-created contact to persist upon cycling. Combined with a simple, facile and scalable manufacturing process, this study opens a new avenue to stabilize silicon without sacrificing other device parameters. The results hold great promise for both further rational improvement and mass production of advanced energy storage materials.

Stabilizing silicon without sacrificing other device parameters is essential for practical use in lithium and post lithium battery anodes. Here, the authors show the skin-like two-dimensional covalent encapsulation furnishing a remarkable level of integrated lithium storage performances of silicon.

Graphene Oxide-Polypyrrole Coating for Functional Ceramics

Ceramic substrates were metallized with a Ni-Mo-P electroless coating and further modified with a polypyrrole (PPy) coating by the electrodeposition method. The properties of the polypyrrole coating were studied with the addition of a graphene oxide (GO) nanomaterial prior to the electrodeposition and its reduction degree. Fourier Transform Infrared Spectroscopy, Field-Emission Scanning Electron Microscopy, Raman spectroscopy and cyclic voltammetry were employed to characterize the properties of the coatings. The results indicated the successful synthesis of conductive electrodes by the proposed approach. The electrodeposition of PPy and its charge storage properties are improved by chemically reduced GO. The surface capacitive contribution to the total stored charge was found to be dominant and increased 2–3 fold with the reduction of GO. The chemically reduced GO-modified PPy exhibits the highest capacitance of 660 F g⁻¹ at 2 mV s⁻¹, and shows a good cyclability of 94% after 500 charge/discharge cycles. The enclosed results indicate the use of an NiMoP electroless coating, and modification with a carbon nanomaterial and conducting polymer is a viable approach for achieving functional ceramics.

N-doped carbon encapsulated CoMoO4 nanorods as long-cycle life anode for sodium-ion batteries

Volume expansion and poor conductivity result in poor cyclability and low rate capability, which are the major challenges of transition-metal oxide as anode materials for sodium-ion batteries (SIBs). Herein, N-doped carbon encapsulated CoMoO₄ (CoMoO₄@NC) nanorods are developed as excellent anode materials for SIBs with long-cycle life. The N-doped carbon shells serve as buffer to accommodate severe volume changes during sodiation/desodiation, and at the same time improve electronic conductivity and activate surface sites of CoMoO₄. The optimized composite presents rapid reaction kinetics and excellent cycle stability. Even at a high current density of 1 A g^-1, it still shows long-cycle life and maintains specific capacity of 190 mAh g^-1 after 3200 cycles. Furthermore, CoMoO₄@NC anode is applied to match with Na₃V₂(PO₄)₃ cathode to assemble full-cells, in which it accomplishes reversible capacity of 152 mAh g^-1 after 100 cycles, with capacity retention of 75% at a current density of 1 A g^-1, highlighting the practical application for SIBs.

Si/a-C Nanocomposites with a Multiple Buffer Structure via One-Step Magnetron Sputtering for Ultrahigh-Stability Lithium-Ion Battery Anodes

Large volume expansion and serious pulverization of silicon are two major challenges for Si-based anode batteries. Herein, a high-mass-load (3.0 g cm^-3) silicon-doped amorphous carbon (Si/a-C) nanocomposite with a hierarchical buffer structure is prepared by one-step magnetron sputtering. The uniform mixing of silicon and carbon is realized on the several-nanometer scale by cosputter deposition of silicon and carbon. The boundary of the primary particles, made up of nanocarbon and nanosilicon, and the boundary of the secondary particles aggregated by the primary particles can provide accommodation space for the volume expansion of silicon and effectively buffer the volume expansion of silicon. Meanwhile, the continuous and uniformly distributed amorphous carbon enhances the conductivity of the Si/a-C nanocomposites. Typically, the 20% Si/a-C cell shows a superior initial discharge capacity of 845.3 mAh g^-1 and achieves excellent cycle performance of up to 1000 cycles (609.4 mAh g^-1) at the current density of 1 A g^-1. Furthermore, the 20% Si/a-C cell exhibits a high capacity of 602.8 mAh g^-1 with the stable discharge/charge rate performance in several extreme conditions (-40-70 °C). In view of the validity and mass productivity of the magnetron sputtering, a potential route for the industrial preparation of the Si/a-C anode nanocomposites is therefore highlighted by this study.

A hierarchical layering design for stable, self-restrained and high volumetric binder-free lithium storage

A hierarchical layering strategy is developed for silicon anodes. The resultant parallelly oriented graphene-sandwiched layered silicon/graphene hybrid microparticles exhibit stable cycling with high volumetric capacity when being charged and discharged at high rates and commercial loading levels, attributable to the designed architecture.

Flexible Graphene-Wrapped Carbon Nanotube/Graphene@MnO2 3D Multilevel Porous Film for High-Performance Lithium-Ion Batteries

The ingenious design of a freestanding flexible electrode brings the possibility for power sources in emerging wearable electronic devices. Here, reduced graphene oxide (rGO) wraps carbon nanotubes (CNTs) and rGO tightly surrounded by MnO₂ nanosheets, forming a 3D multilevel porous conductive structure via vacuum freeze-drying. The sandwich-like architecture possesses multiple functions as a flexible anode for lithium-ion batteries. Micrometer-sized pores among the continuously waved rGO layers could extraordinarily improve ion diffusion. Nano-sized pores among the MnO₂ nanosheets and CNT/rGO@MnO₂ particles could provide vast accessible active sites and alleviate volume change. The tight connection between MnO₂ and carbon skeleton could facilitate electron transportation and enhance structural stability. Due to the special structure, the rGO-wrapped CNT/rGO@MnO₂ porous film as an anode shows a high capacity, excellent rate performance, and superior cycling stability (1344.2 mAh g^-1 over 630 cycles at 2 A g^-1 , 608.5 mAh g^-1 over 1000 cycles at 7.5 A g^-1 ). Furthermore, the evolutions of microstructure and chemical valence occurring inside the electrode after cycling are investigated to illuminate the structural superiority for energy storage. The excellent electrochemical performance of this freestanding flexible electrode makes it an attractive candidate for practical application in flexible energy storage.

Graphene hybridization for energy storage applications

Graphene hybridization principles and strategies for various energy storage applications are reviewed from the view point of material structure design, bulk electrode construction, and material/electrode collaborative engineering.

High Lithium Storage Capacity and Long Cycling Life Fe3S4 Anodes with Reversible Solid Electrolyte Interface Films and Sandwiched Reduced Graphene Oxide Shells

Increasing demands for lithium-ion batteries (LIBs) with high energy density and high power density require highly reversible electrochemical reactions to enhance the cyclability and capacities of electrodes. As the reversible formation/decomposition of the solid electrolyte interface (SEI) film during the lithiation/delithiation process of Fe₃S₄ could bring about a higher capacity than its theoretical value, in the present work, synthesized Fe₃S₄ nanoparticles are sandwich-wrapped with reduced graphene oxide (RGO) to fabricate highly reversible and long cycling life anode materials for high-performance LIBs. The micron-sized long slit between sandwiched RGO sheets effectively prevents the aggregation of intermediate phases during the discharge/charge process and thus increases cycling capacity because of the reversible formation/decomposition of the SEI film driven by Fe nanoparticles. Furthermore, the RGO sheets interconnect with each other by a face-to-face mode to construct a more efficiently conductive network, and the maximum interfacial oxygen bridge bonds benefit the fast electron hopping from RGO to Fe₃S₄, improving the depth of the electrochemical reactions and facilitating the highly reversible lithiation/delithiation of Fe₃S₄. Thus, the resultant Fe₃S₄/RGO hybrid shows a highly reversible charge capacity of 1324 mA h g^-1 over 275 cycles at a current density of 100 mA g^-1, even retains 480 mA h g^-1 over 500 cycles at 1000 mA g^-1, which are much higher than reported values.

Room-Temperature Solution Synthesis of Mesoporous Silicon for Lithium Ion Battery Anodes

As an important optoelectronic and energy-storage material, porous silicon (PSi) has attracted great interest in various fields. The preparation of PSi, however, usually suffers from low yields and/or complicated syntheses. Herein, we report a facile solution method to prepare PSi with controllable high specific surface area. Commercial Zintl compound Mg₂Si readily reacts with HSiCl₃ in the presence of amines at room temperature to produce amorphous PSi in high yields, where in situ formed salt byproducts serve as templates to generate uniform mesopores of ca. 3.8 nm in diameter. After crystallization treatment at 700 °C in flow Ar gas for 40 min, the obtained crystalline PSi coated with carbon layers shows excellent electrochemical performance when served as lithium ion battery anodes. The reversible specific capacity is about 2250 mA h g^-1 at 0.1 A g^-1 and the capacity retention is maintained at 90% after cycling at high current density of 2 A g^-1 for 320 times. This simple, facile preparation method is very promising and paves the way for massive production of porous Si as high-performance anodes in Li-ion battery industry or for other applications, such as drug delivery systems and catalysis.

Two-Dimensional Porous Sandwich-Like C/Si-Graphene-Si/C Nanosheets for Superior Lithium Storage

A novel two-dimensional porous sandwich-like Si/carbon nanosheet is designed and successfully fabricated as an anode for superior lithium storage, where a porous Si nanofilm grows on the two sides of reduced graphene oxide (rGO) and is then coated with a carbon layer (denoted as C/Si-rGO-Si/C). The coexistence of micropores and mesopores in C/Si-rGO-Si/C nanosheets offers a rapid Li⁺ diffusion rate, and the porous Si provides a short pathway for electric transportation. Meanwhile, the coated carbon layer not only can promote to form a stable SEI layer, but also can improve the electric conductivity of nanoscale Si coupled with rGO. Thus, the unique nanostructures offer the resultant C/Si-rGO-Si/C electrode with high reversible capacity (1187 mA h g^-1 after 200 cycles at 0.2 A g^-1), excellent cycle stability (894 mA h g^-1 after 1000 cycles at 1 A g^-1), and high rate capability (694 mA h g^-1 at 5 A g^-1, 447 mA h g^-1 at 10 A g^-1).

Dual-phase spinel Li4Ti5O12/anatase TiO2 nanosheet anchored 3D reduced graphene oxide aerogel scaffolds as self-supporting electrodes for high-performance Na- and Li-ion batteries

Self-supporting LTO-AT/RGO composite as anode materiel was prepared via a facile hetero-assembly, freeze-drying, mechanical compression and annealing. They exhibit excellent electrochemical capability when used for LIBs and SIBs.

5L-Scale Magnesio-Milling Reduction of Nanostructured SiO2 for High Capacity Silicon Anodes in Lithium-Ion Batteries

Nanostructured silicon (Si) is useful in many applications and has typically been synthesized by bottom-up colloid-based solution processes or top-down gas phase reactions at high temperatures. These methods, however, suffer from toxic precursors, low yields, and impractical processing conditions (i.e., high pressure). The magnesiothermic reduction of silicon oxide (SiO₂) has also been introduced as an alternative method. Here, we demonstrate the reduction of SiO₂ by a simple milling process using a lab-scale planetary-ball mill and industry-scale attrition-mill. Moreover, an ignition point where the reduction begins was consistently observed for the milling processes, which could be used to accurately monitor and control the reaction. The complete conversion of rice husk SiO₂ to high purity Si was demonstrated, taking advantage of the rice husk's uniform nanoporosity and global availability, using a 5L-scale attrition-mill. The resulting porous Si showed excellent performance as a Li-ion battery anode, retaining 82.8% of the initial capacity of 1466 mAh g^-1 after 200 cycles.

Grape-Like Fe3O4 Agglomerates Grown on Graphene Nanosheets for Ultrafast and Stable Lithium Storage

An in situ simple and effective synthesis method is effectively exploited to construct MOF-derived grape-like architecture anchoring on nitrogen-doped graphene, in which ultrafine Fe3O4 nanoparticles are uniformly dispersed (Fe3O4@C/NG). In this hybrid hierarchical structure, new synergistic features are accessed. The graphene oxide plane with functional groups is expected to alleviate the aggregation problem in the MOFs' growth. Moreover, the morphology and size of iron-based MOFs and carbon content are conveniently controlled by controlling the solution concentration of precursor. Through making use of in situ carbonization of the organic ligands in MOFs, Fe3O4 subunits are effectively protected by 3D interconnected conductive carbon at microscale. Consequently, when applied as anode materials, even as high as 10 A g(-1) after 1000 cycles, Fe3O4@C/NG still maintains as high as 458 mA h g(-1).

Facial Synthesis of Three-Dimensional Cross-Linked Cage for High-Performance Lithium Storage

Silicon/C composite is a promising anode material for high-energy Li-ion batteries. However, synthesizing high-performance Si-based materials at large scale and low cost remains a huge challenge. Here, we for the first time report the preparation of an interconnected three-dimensional (3D) porous Si-hybrid architecture by using a spray drying method. In this unique structure, the highly robust C-CNT-RGO cages not only can improve the conductivity of the electrode and buffer the volume expansion but also suppress the Si nanoparticles aggregation. As a result, the 3D Si@po-C/CNT/RGO electrode achieves long-life cycling stability at high rates (a reversible capacity of 854.9 mA h g(-1) at 2 A g(-1) after 500 cycles and capacity decay less than 0.013% per cycle) and good rate capability (1454.7, 1198.8, 949.2, 597.8, and 150 mA h g(-1) at current densities of 1, 2, 4, 10, and 20 A g(-1), respectively). Moreover, this novel electrode could deliver high reversible capacities and long-life stabilities even with high mass loading density (764.9 mA h g(-1) at 1.0 mg cm(-2) after 500 cycles and 472.2 mA h g(-1) at 1.5 mg cm(-2) after 400 cycles, respectively). This cheap and scalable strategy can be extended to fabricate other materials with large volume expansion (Sn, Ge, transition-metal oxides) and 3D porous carbon for other potential applications.

Controlled Prelithiation of Silicon Monoxide for High Performance Lithium-Ion Rechargeable Full Cells

Despite the recent considerable progress, the reversibility and cycle life of silicon anodes in lithium-ion batteries are yet to be improved further to meet the commercial standards. The current major industry, instead, adopts silicon monoxide (SiOx, x ≈ 1), as this phase can accommodate the volume change of embedded Si nanodomains via the silicon oxide matrix. However, the poor Coulombic efficiencies (CEs) in the early period of cycling limit the content of SiOx, usually below 10 wt % in a composite electrode with graphite. Here, we introduce a scalable but delicate prelithiation scheme based on electrical shorting with lithium metal foil. The accurate shorting time and voltage monitoring allow a fine-tuning on the degree of prelithiation without lithium plating, to a level that the CEs in the first three cycles reach 94.9%, 95.7%, and 97.2%. The excellent reversibility enables robust full-cell operations in pairing with an emerging nickel-rich layered cathode, Li[Ni0.8Co0.15Al0.05]O2, even at a commercial level of initial areal capacity of 2.4 mAh cm(-2), leading to a full cell energy density 1.5-times as high as that of graphite-LiCoO2 counterpart in terms of the active material weight.

Capacity-increasing robust porous SiO2/Si/graphene/C microspheres as an anode for Li-ion batteries

We unprecedentedly studied the synergetic effects between SiO₂ and Si as an anode for lithium-ion batteries, and the prepared composite exerts an increasing capacity.

A self-assembly strategy for fabricating highly stable silicon/reduced graphene oxide anodes for lithium-ion batteries

High initial coulombic efficiency and improved cyclic stability were obtained by introducting CATB into GO and Si NPs.

Silicon nanoparticles grown on a reduced graphene oxide surface as high-performance anode materials for lithium-ion batteries

Silicon nanoparticles covalently attached on reduced graphene oxide exhibited good electrochemical performance as an anode in lithium-ion cells.

Dynamic Cross-Linking of Polymeric Binders Based on Host-Guest Interactions for Silicon Anodes in Lithium Ion Batteries

We report supramolecular cross-linking of polymer binders via dynamic host-guest interactions between hyperbranched β-cyclodextrin polymer and a dendritic gallic acid cross-linker incorporating six adamantane units for high-capacity silicon anodes. Calorimetric analysis in the solution phase indicates that the given host-guest complexation is a highly spontaneous and enthalpically driven process. These findings are further verified by carrying out gelation experiments in both aqueous and organic media. The dynamic cross-linking process enables intimate silicon-binder interaction, structural stability of electrode film, and controlled electrode-electrolyte interface, yielding enhanced cycling performance. Control experiments using both α, γ-CDp with different cavity sizes and a guest molecule incorporating a single adamantane unit verified that the enhanced cycle life originates from the host-guest interaction between β-cyclodextrin and adamantane. The impact of the dynamic cross-linking is maximized at an optimal stoichiometry between the two components. Importantly, the present investigation proves that the molecular-level tuning of the host-guest interactions can be translated directly to the cycling performance of silicon anodes.

High-Performance Silicon Battery Anodes Enabled by Engineering Graphene Assemblies

We propose a novel material/electrode design formula and develop an engineered self-supporting electrode configuration, namely, silicon nanoparticle impregnated assemblies of templated carbon-bridged oriented graphene. We have demonstrated their use as binder-free lithium-ion battery anodes with exceptional lithium storage performances, simultaneously attaining high gravimetric capacity (1390 mAh g(-1) at 2 A g(-1) with respect to the total electrode weight), high volumetric capacity (1807 mAh cm(-3) that is more than three times that of graphite anodes), remarkable rate capability (900 mAh g(-1) at 8 A g(-1)), excellent cyclic stability (0.025% decay per cycle over 200 cycles), and competing areal capacity (as high as 4 and 6 mAh cm(-2) at 15 and 3 mA cm(-2), respectively). Such combined level of performance is attributed to the templated carbon bridged oriented graphene assemblies involved. This engineered graphene bulk assemblies not only create a robust bicontinuous network for rapid transport of both electrons and lithium ions throughout the electrode even at high material mass loading but also allow achieving a substantially high material tap density (1.3 g cm(-3)). Coupled with a simple and flexible fabrication protocol as well as practically scalable raw materials (e.g., silicon nanoparticles and graphene oxide), the material/electrode design developed would propagate new and viable battery material/electrode design principles and opportunities for energy storage systems with high-energy and high-power characteristics.

General Strategy for Fabricating Sandwich-like Graphene-Based Hybrid Films for Highly Reversible Lithium Storage

We report a general strategy for the fabrication of freestanding sandwich-like graphene-based hybrid films by electrostatic adsorption and following reduction reaction. We demonstrate that by rational control of pH value in precursors, graphene oxide (GO) sheets can form three-dimensional (3D) sandwich frameworks with nanoparticles decorated between the layers of graphene. In our proof-of-concept study, we prepared the graphene/Si/graphene (G@Si@G) sandwich-like films. When used as negative electrode materials for lithium-ion batteries, it exhibits superior lithium-ion storage performance (∼1800 mA h g(-1) after 40 cycles at 100 mA g(-1)). Importantly, with this simple and general method, we also successfully synthesized graphene/Fe2O3/graphene and graphene/TiO2/graphene hybrid films, showing improved electrochemical performance. The good electrochemical property results from the enhanced electron transport rate, and the 3D flexible matrix to buffer volume changes during cycling. In addition, the porous sandwich structure consisting of plate-like graphene with high surface area provides effective electrolyte infiltration and promotes diffusion rate of Li(+), leading to an improved rate capability.

Mitigating mechanical failure of crystalline silicon electrodes for lithium batteries by morphological design

A novel strategy is developed to mitigate lithiation-induced fracture in crystalline Si anodes by deliberately designing anisometric anode morphologies to counteract the anisotropy in the crystalline/amorphous interface velocity.