High Lithium Storage Capacity Research Articles

Rational design of N-doped C-encapsulated flower-like nickel-based heterostructured microsphere anodes for high-capacity and stable lithium storage.

Designing a unique morphology and nanoarchitecture with a heterostructure is regarded as an efficient strategy to achieve lithium-ion batteries (LIBs) with high capacity and cycle life. Herein, N-doped C-encapsulated flower-like NiS/Ni3(BO3)2 heterostructures (NiS/Ni3(BO3)2/NC) with a core-shell morphology are successfully synthesized by a facile general method to improve the rate performance and prolong the cycle life of LIBs. The coated NC layer and core-shell structure with elasticity can relieve the volume expansion during the lithiation/delithiation process to strengthen the stability of the structure. Moreover, the NC layer and NiS/Ni3(BO3)2/NC heterostructure can enhance the electronic conductivity of the electrode and guarantee fast and unimpeded electron transfer channels, thereby improving the electrochemical reaction kinetics. Owing to the synergy of heterostructures and core-shell layer, the as-synthesized NiS/Ni3(BO3)2/NC anode acquires a specific charge capacity of 549 mA h g-1 at 0.2 A g-1 after 100 cycles; meanwhile, a reversible capacity of 322 mA h g-1 can be maintained even at 1 A g-1 after 500 cycles. This study develops a universal interface manipulation strategy for the synthesis of M3B2O6-based or/and other advanced transition metal compound anode materials for the practical applications of LIBs.

Electron transition enhanced in-situ co-reduction mechanism enabling high-capacity and stable lithium storage for MoO3-x anode

Transition metal oxides (TMOs) often achieve excellent performance through micro-scale regulation and structural evolution, especially as electrode materials for lithium-ion batteries (LIBs). Recently, in order to improve the inferior rate capability, sluggish reaction kinetics, and fast capacity decay of transition metal oxide MoO3 during a long-term charge/discharge process, a variety of composite materials and synthetic routes have been developed. However, the expensive multi-step synthesis, weak interaction between composites, and poor intrinsic conductivity of MoO3 severely hinder the large-scale commercial application of composites. Therefore, a simple, green and low-cost electron transition enhanced one-step co-reduction strategy is proposed to synthesize a novel MoO3-x nanoparticle/few-layer reduced graphene oxide (rGO) composite (denoted as MNR) with strong terminal-bonding (MoO2–O–C-rGO). The strategy ingeniously realizes the fabrication of oxygen vacancies (MoO3-x) and the in-situ reduction of graphene oxide (GO), as well as accomplish the dual regulation of scale and structure by forming a strong terminal-bonding effect. Significantly, the obtained MNR anode exhibits an ultrahigh discharge capacity (1415 mA h g−1 at 1.0 A g−1) and long cycle stability (94 % capacity retention after 700 cycles), which is superior to the previously reported MoO3-based composites. Moreover, the full battery coupled with LiFePO4 cathode also reveals a competitive energy density (369 Wh kg−1). The results suggest a novel approach for the fabrication and wide application of TMOs/rGO composites.

A Stable Fe3O4-Based Hybrid Anodes for High Performance Li-Ion Batteries

There is an increasing demand for high-performance Li-ion batteries especially due to environmental concerns. To meet the high-performance requirements of the Li-ion batteries, conversion-type anodes stand out with their capacities. The crystal structure of magnetite (Fe3O4) benefits from its empty interstitial sites which hinders volume changes during the insertion and extraction of lithium ions. Combined with its high theoretical lithium storage capacity and abundance, Fe3O4 has great potential as an alternative anode. Yet in its practical use, the material suffers from severe capacity degradation, mainly due to the formation of a passive metallic iron layer on the electrode [1]. Another suggested mechanism responsible for the deterioration of the performance is the formation of electrochemically inactive FeO-based side products upon delithiation process [2].In this study, we utilize reduced graphene oxide (rGO) as a substrate for the ultrafine Fe3O4 nanoparticles to form a two-dimensional hybrid material with improved characteristics. Under a mild hydrothermal condition, nanoparticles were deposited by a simple redox process in an interconnected porous network of graphene. Graphene aids in improving the Fe3O4 performance not only by reducing the charge transfer resistance, buffering the volume change induced stresses and facilitating the ion transport but also by forming an effective interface with the delocalized electrons of Fe3O4 to further result in the increase of battery capacitance by the interfacial conjugation mechanism, as confirmed by in-situ EIS measurements. The Fe3O4 particles have been effectively stabilized on the rGO surface, becoming less prone to agglomeration during cycling. Consequently, the deliverable specific capacity of the hybrid material was gradually improved upon extended cycling, reaching from 1500 mAh/g up to 2200 mAh/g at 0.5 A/g at the end of 100 cycles of operation. The increase of the specific capacity during the extended cycling was attributed to the chemical and structural changes of the electrode material evaluated by TEM and ex-situ EELS measurements. It was confirmed that the particle size is greatly reduced to 1-2 nm scale, improving the lithium-ion diffusion kinetics by the increased surface area and reversibility of the redox reaction upon graphene contribution. Moreover, the aged cells were observed to still deliver around 1100 mAh/g capacity upon more than 250 times cycling at 1 A/g, indicating the great potential of the ultrafine Fe3O4 decorated reduced graphene hybrids as superior performance Li-ion battery anode materials.

Novel Ultra-Stable 2D SbBi Alloy Structure with Precise Regulation Ratio Enables Long-Stable Potassium/Lithium-Ion Storage.

The inferior cycling stabilities or low capacities of 2D Sb or Bi limit their applications in high-capacity and long-stability potassium/lithium-ion batteries (PIBs/LIBs). Therefore, integrating the synergy of high-capacity Sb and high-stability Bi to fabricate 2D binary alloys is an intriguing and challenging endeavor. Herein, a series of novel 2D binary SbBi alloys with different atomic ratios are fabricated using a simple one-step co-replacement method. Among these fabricated alloys, the 2D-Sb0.6 Bi0.4 anode exhibits high-capacity and ultra-stable potassium and lithium storage performance. Particularly, the 2D-Sb0.6 Bi0.4 anode has a high-stability capacity of 381.1 mAh g-1 after 500 cycles at 0.2 A g-1 (≈87.8% retention) and an ultra-long-cycling stability of 1000 cycles (0.037% decay per cycle) at 1.0 A g-1 in PIBs. Besides, the superior lithium and potassium storage mechanism is revealed by kinetic analysis, in-situ/ex-situ characterization techniques, and theoretical calculations. This mainly originates from the ultra-stable structure and synergistic interaction within the 2D-binary alloy, which significantly alleviates the volume expansion, enhances K+ adsorption energy, and decreases the K+ diffusion energy barrier compared to individual 2D-Bi or 2D-Sb. This study verifies a new scalable design strategy for creating 2D binary (even ternary) alloys, offering valuable insights into their fundamental mechanisms in rechargeable batteries.

A feasible recycling route for spent graphite: Microwave-assisted puffing with Fe2O3 loading to construct high-performance anode for lithium-ion batteries

Nowadays, one of the important issues associating with the lithium-ion battery industry is to address the inefficient utilization of spent graphite from plenty of spent batteries. Conventional methods including discarding or burning will exacerbate the environmental risks, which calls for novel routes to optimize the recycling of spent graphite. This study proposes a novel recycling strategy for spent graphite to construct Fe2O3@microwave-puffed graphite (Fe2O3@MPG) composite anode for high-capacity lithium storage. By means of mild intercalation followed by microwave treatment, spent graphite is converted to puffed graphite which can be used as framework for loading Fe2O3 to form Fe2O3@MPG with sandwich structure. This sandwich structure can provide conductive networks and channels to enhance conductivity and Li ions transfer, as well as confine Fe2O3 in microwave-puffed graphite framework to ease the structural instability caused by the volume change of Fe2O3, thereby endowing the Fe2O3@MPG composite with superior rate performance, high capacity, and excellent structural stability. The Fe2O3@MPG electrode possesses a specific capacity of 1100 mAh g−1 at 200 mA g−1, exhibits excellent rate performance with a capacity of 632 mAh g−1 at 2000 mA g−1, and delivers an outstanding cycling performance for 500 cycles. This study not only provides an important method for the efficient recycling of spent graphite but develops a universal method for modifying transition metal oxides anode utilizing spent graphite, thereby promoting the closed-loop lifecycle of graphite and the resource sustainability in the LIBs industry.

Chemical Bonding and Activity of Atomically Dispersed Silicon in Two- and Three-Dimensional Materials.

On the basis of the especially tunable electronic property of Si, several kinds of nanomaterials with atomically dispersed Si were constructed and characterized by extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations. The new-type Si(X≡Y)n wide-bandgap semiconductors featuring through-space d-π* hyperconjugation exhibit unique properties in photoelectric conversion, photoconductivity, structural mechanics, etc. The SiC8 siligraphene with the planar tetracoordinate Si (ptSi) has a high lithium-storage capacity and comparably facile surface migration behaviors of both Li and Li+, making it a promising anode material for high-performance Li-ion batteries. The atomically dispersed Si sites of 2D monolayer materials, such as ptSi and three- and four-coordinated Si atoms, generally exhibit remarkable catalytic activity toward CO2 activation with different electron mechanisms, resulting in different scaling relations between the activity and the p-band center. The computational findings enrich the understanding of structural and chemical properties of silicon and open up avenues for developing Si-based functional materials.

Insight into the Li-Storage Property of Surface-Modified Ti2Nb10O29 Anode Material for High-Rate Application.

Ti-based anode materials are considered to be an alternative to graphite anodes to accomplish high-rate application requirements. Ti2Nb10O29 (TNO15) has attracted much attention due to its high lithium storage capacity through the utilization of multiple redox couples and a suitable operating voltage window of 1.0 to 2.0 V vs Li/Li+. However, poor intrinsic electronic conductivity has limited the futuristic applicability of this material to the battery anode. In this work, we report the modification of TNO15 by introducing oxygen vacancies and using few-layered carbon and copper coatings on the surface to improve its Li+ storage property. With the support of the galvanostatic intermittent titration technique (GITT), we found that the diffusion coefficient of carbon/copper coated TNO15 is 2 orders of magnitude higher than that of the uncoated sample. Here, highly conductive copper metal on the surface of the carbon-coated oxygen-vacancy-incorporated TNO15 increases the overall electronic and ionic conductivity. The prepared TNO15-800-C-Cu-700 half-cell shows a significant rate capability of 92% when there is a 10-fold increase in the current density. In addition, the interconnected TNO15 nanoparticles create a porous microsphere structure, which enables better Li-ion transportation during charge/discharge process, and experiences an enhancement after the carbon and copper coating on the surface of the primary TNO15 nanocrystallites.

Excellent lithium storage performance of bipyridinium-based polymerized ionic liquids as anode in lithium-ion batteries

For organic electrode materials, slow Li+ diffusion kinetics is a main obstacle to the realization of high lithium storage capacity through a super-lithiation reaction. Here, bipyridinium-based polymerized ionic liquids (PILs) have been synthesized by the ionothermal trimerization of 1,1-dicyanomethyl bipyridinium bromide ILs in molten ZnCl2 matrix, and are used as an anode material for the first time. In which, the ionic chains are beneficial for fast Li+ diffusion, as well as the p-π resonance structure between methylene and aromatic ring helps the electron conduction. Electrochemical analysis shows PILs-400 can deliver 1201.5 mAh g−1 at 0.1 A g−1 and almost no capacity loss with the capacity of 873.6 mAh g−1 over 500 cycles at 2 A g−1. Theoretical calculation reveals that all functional groups of triazine, methylene, and bipyridinium have taken part in the redox reaction, and this reaction is associated with a three-step insertion process of 19 Li+ for each repetitive unit in forming Li19C14N5, along with the reversible formation of N-Li and C-Li bonds.

A Promising Approach towards the Commercialization of Lithium Sulfur Batteries: Prelithiated Graphene

AbstractLithium‐sulfur (Li‐S) batteries are a promising candidate technology for high‐energy rechargeable batteries due to their advantages of abundant materials and inherently high energy. However, the practical applications of Li‐S batteries are challenged by several obstacles, including the low sulfur utilization and poor lifespan, which are partly attributed to the shuttle of lithium polysulfides and lithium dendrite growth during cycling.[1] The shuttling of polysulfide ions between the electrodes in a Li‐S battery is a major technical issue triggering the self‐discharge and limiting the cycle life.[2] A stable lithium anode is essential for maintaining the good cycle stability of Li‐S batteries in practical applications.[3] To address these lithium related issues, various carbon materials, including graphite and graphene, have been investigated as suitable lithium hosts to use as anode materials for Li‐S batteries.[4] In this study, prelithiated graphite and graphene‐based anode materials are obtained by galvanostatic charging method to improve the performance of Li‐S batteries and compare the electrochemical properties especially in terms of capacity retention and rate capability. According to the results, graphene showed better performance due to its high lithium storage capacity and fast lithium‐ion diffusion rate. Inductively Coupled Plasma Emission Spectrometer (ICP‐OES) results showed that the Li+ content of the graphite, graphite/graphene, and graphene electrodes measured as 26.5, 33.2, and 45.6 wt%, respectively after the lithiation process. 1 Ah pouch cell was assembled with prelithiated graphene anode showing an energy density of about 400 Wh kg−1 in the first cycle and protected its specific capacity of 60 % after 100 cycles in a liquid‐based Li‐S battery system.

Design optimization of spinel-rocksalt intergrown high entropy oxide structure for enhanced electrochemical properties

The advantages of each phase can be utilized to prepare a dual-phase intergrown anode consisting of spinel (Fd-3m) and rocksalt (Fm-3m) phases through the solid-state method. This approach leverages the high redox activity and lithium storage capacity of the rocksalt phase, as well as the good kinetics and stability of the spinel structure. By adjusting the sintering temperature, the ratio of the spinel phase (S-HEO) to the rocksalt phase (R-HEO) in the novel intergrown high entropy oxide structure (d-HEO) can be modulated, allowing for control over its electrochemical properties. Through this, an optimized S-HEO/R-HEO ratio can be achieved, resulting in high capacity coupled with desired cyclic stability and rate performance. This work demonstrates an effective strategy for constructing spinel-rocksalt intergrown structures. Furthermore, optimizing the structural properties of the dual-phase may shed light on material design for electrochemical energy storage and new applications of advanced HEOs.

Investigation and Improvement of the Pressure Control in Si Anode Based Solid-State Batteries

Solid state batteries (SSBs) are promising next generation propulsion for electric vehicles due to their improved safety, high gravimetric and volumetric energy densities, and increased reliability. Silicon is one of the limited choices for the anode material for the SSBs due to its high applicable capacity, low operating potential and natural abundance. However, significant challenges remain for the commercialization of Si anode based SSBs, including the insufficient operational and calendar life, requirement of high stack pressure for operation, and inadequate fast charge capability.Almost each of the technical challenges associated with Si anode is entangled with the volume change of Si during charging and discharging. Si possesses high lithium storage capacity because it can form various LixSiy compounds upon lithiation. For example, when 3.75 moles of Li+ is added to 1 mole of Si, the compound Li15Si4 is formed, which gives a capacity of 3578 mAh/gSi. What accompanies this is a considerable volume expansion (e.g., 280% increase for Li15Si4), resulting from the reorganization of the compound crystals. Assuming an anode that initially composes of perfectly compacted Si particles, this volume expansion translates to a 56% increase in the thickness of the Si anode. In a practical SSB, the real thickness variation in the Si anode is expected to be smaller because of the architecture design of the anode. Nonetheless, this volume change in Si creates many problems, including the Si particle pulverization, delamination of electrode from the current collector and electrolyte separator, loss of electronic and ion conductions in the electrode, among others. To maintain the electric contact in Si anode based SSBs, high stack pressures, from several MPa to several tens of MPa, are normally applied.In this work, we carefully measure the real-time stack pressure in a specially designed setup. The stress-strain characteristics of Si anode based SSBs during operation, including the stack pressure spike and the degradation of the average stack pressure, is studied and correlated with the Si anode structure changes. Furthermore, different measures, including external and internal ones, are explored to improve the cell pressure control. The external measures include selecting an appropriate spring and using a mechanical buffer layer, while the internal measure refers to an elastic current collector design. As a result, a better SSB pressure control is obtained. More importantly, a reduction of the stack pressure significantly below 10 MPa without compromising the cell performance is achieved.

Endothermic Dehydrogenation-Driven Preventive Magnesiation of Sio by Magnesium Hydride for High-Performance Sio-Based Lithium Storage Materials

Silicon monoxide (SiO)-based materials have gained much attention as high-capacity lithium storage materials because of their superior cycle performance. However, low initial Coulombic efficiency (ICE) of SiO derived from the irreversible electrochemical reaction of the amorphous SiO2 phase in SiO makes wide use of the SiO-based anode materials in lithium-ion batteries challenging. Magnesiation of SiO is one of the promising solutions to improve ICE of SiO-based anode materials. Here, we propose an endothermic dehydrogenation-driven magnesiation of SiO by employing MgH2 to improve both ICE and cycle performance. The resulting Si/Mg2SiO4 nanocomposite material showed much-improved ICE of 89.5% and long-term cycle performance for over 300 cycles compared to the homologue prepared by the magnesiation of SiO using Mg and pristine SiO. High-resolution transmission electron microscopy with thermogravimetry−differential scanning calorimetry revealed that the endothermic dehydrogenation of MgH2 mitigates the rapid temperature rise during magnesiation of SiO, thereby inhibiting the increase of Si domain size in the resulting Si/Mg2SiO4 nanocomposite. Detailed material characterization and electrochemical analysis of Si/Mg2SiO4 nanocomposite materials will be discussed in this presentation.

3D spatially-confined magnetic anodes towards advanced lithium ion batteries

Magnetic transition-metal oxides show great prospect as alternatives to prevail anodic carbonaceous substances for lithium ion battery in virtue of their splendid theoretical capacity. However, in addition to their intrinsic poor electronic conductivity, the severe agglomeration of the forming magnetic metal nanoparticles during discharging will deteriorate their actual electrochemical performance in a strong magnetic field environment. Here, we demonstrate a 3D spatially-confining magnetic anode to settle all these dilemmas, in which conversion-type magnetic Fe3O4 nanoparticles with a thin carbon encapsulation layer are anchoring onto 3D nickel nanotube arrays skeleton (Ni/Fe3O4@C NTAs). The carbon shell spatially confines the agglomeration of Fe nanoparticles and maintains the exceptional integrity of structure. The Ni/Fe3O4@C NTAs anode exhibits high-capacity lithium storage (∼1286 mAh g−1 at 0.1 C) and superior rate/cycle capability (retaining ∼97 % of initial reversible value at 1 C after long-term 1000 cycles).

First-principles study on the adsorption and lithium storage capacities of Hf3C2 and Hf3C2T2(T = O, F, S) MXenes

Based on the theoretical framework of the first principle, the adsorption and theoretical lithium storage capacities of Hf3C2 and surface functionalized Hf3C2T2(T = O, F, S) MXenes were studied. The structural stability of the system and the influence of electrical properties on energy storage properties are analyzed when different functional groups are located in different positions. The formation energy results suggest that the three functional Hf3C2T2(T = O, F, S) structures are energetically stable, and the CCP site is the most stable among the possible sites of HCP, TOP and CCP. By calculating the energy bands and density of states, it is proved that F-functionalized Hf3C2F2 is not conducive to adsorption. During the adsorption process, the lithium intercalation process is carried out in the way of surface adsorption of atoms, in which the HCP site of bare Hf3C2 and the CCP site of functionalized Hf3C2T2 are the most favorable adsorption sites. The storage capacities of bare Hf3C2, Hf3C2O2, and Hf3C2S2 are 287.51 mAhg−1, 271.95 mAhg−1 and 258.00 mAhg−1, respectively. The Hf3C2O2 has a higher lithium storage capacity than Hf3C2S2, so both oxygen functionalized Hf3C2O2 and bare Hf3C2 are promising battery materials.

ZIF-8 derived ZnFe2O4 nanoparticles as a high-performance anode material for lithium-ion batteries

ZnFe2O4 nanoparticles and ZnO/ZnFe2O4 composites were prepared by simple calcination of Fe2O3/ZIF-8. The bimetallic ZnFe2O4 not only inherit the high lithium storage capacity of Fe2O3, but also exhibit higher conductivity than that of single Fe or Zn oxides. The effect of Fe2O3 content in the raw materials on the structure and electrochemical performance of the product was discussed. Appropriate amount of Fe2O3 helps to obtain ZnFe2O4 nanoparticles with small size and porous structure, which can shorten the diffusion path of lithium ions, increase the contact area between the electrode material and electrolyte, thus improving the performance of the material. After 200 cycles at a current density of 300 mA g−1, the specific capacity can reach 1223.2 mAh/g. When the current density is increased to 2 A/g, the discharge specific capacity is retained at 809.4 mAh/g after 500 cycles.

Hierarchical-Structured Fe2O3 Anode with Exposed (001) Facet for Enhanced Lithium Storage Performance.

The hierarchical structure is an ideal nanostructure for conversion-type anodes with drastic volume expansion. Here, we demonstrate a tin-doping strategy for constructing Fe2O3 brushes, in which nanowires with exposed (001) facets are stacked into the hierarchical structure. Thanks to the tin-doping, the conductivity of the Sn-doped Fe2O3 has been improved greatly. Moreover, the volume changes of the Sn-doped Fe2O3 anodes can be limited to ~4% vertical expansion and ~13% horizontal expansion, thus resulting in high-rate performance and long-life stability due to the exposed (001) facet and the unique hierarchical structure. As a result, it delivers a high reversible lithium storage capacity of 580 mAh/g at a current density of 0.2C (0.2 A/g), and excellent rate performance of above 400 mAh/g even at a high current density of 2C (2 A/g) over 500 cycles, which is much higher than most of the reported transition metal oxide anodes. This doping strategy and the unique hierarchical structures bring inspiration for nanostructure design of functional materials in energy storage.

Advantages of Structure and Electrochemical Properties of Graphene Prepared from Tectonically Deformed Coal.

Asa low-cost carbon-rich resource, coal has been widely used to prepare excellent electrochemical energy-storage carbon materials such as graphene. However, the different structures of carbon source will affect the performance of carbon materials. To explore the feasibility of preparing high-performance graphene from the carbon source affected by tectonic stress in coal, in this paper, series products of coal-based graphene are prepared by tectonically deformed coal (TDC) and normal structural coal (NSC). The structural parameters are characterized by HRTEM, XRD, Raman, and low-temperature CO2 and N2 adsorption, and the electrochemical performance of coal-based graphene lithium battery is tested by galvanostatic charge-discharge and cyclic voltammetry. The results show that tectonic stress makes the proportion of the medium-long aromatic fringes, preferred orientation degree (POD), and multilayer stacking in TDC aromatic fringes slightly higher than those in NSC. At the same temperature, the relatively large microcrystalline size, the high order degree, and more pore structures make the local molecular oriented (LMO) domain vertical height (d) and graphitization degree (G) of the coal-based graphite microcrystalline structure prepared by TDC better than those of NSC, which indicates that the carbon source in TDC contains more graphitizable carbon structures. This makes the graphene prepared by TDC not only possess perfectly ordered crystal planes but also relatively abundant nanochannels. High lithium-storage capacity and low charge-transfer resistance make the electrochemical performance of graphene prepared by TDC as an anode electrode material for lithium-ion batteries superior to that by NSC.

Constructing atomically dispersed Snδ+ sites in porous carbon nanosheets to boost lithium-/sodium-storage capability

Nanoscale carbon-supported single atomic metal active centers (Mδ+) have recently caught much attention as a high-efficient catalyst in energy-conversion/-storage fields. Further works extended to employ these materials as the lithium-/sodium-storage anode. Inspired by the progresses, porous carbon nanosheets with abundant Snδ+ sites (Sn-PCNS) are prepared by easy-controllable template-directed method and post carbonization process in this work. Here, atomically dispersed Snδ+ is stabilized mainly by O/N moieties in carbon framework, which can enhance the electron transfer and Li+-/Na+-diffusion kinetics, thus benefiting the Li+-/Na+-storage capabilities. As a result, the Sn-PCNS electrode can deliver a high lithium-storage capacity of 428 mA h g−1 at 10 A g−1 and show a long-term cycling performance for sodium storage at high rate (∼ 120 mA h g−1 at 5 A g−1 after 1000 cycles). This work not only provides a strategy for the preparation of new sheet-like carbon-based nanomaterials, but also offer an opportunity to promote the application of carbon-supported single atomic metal active centers in energy conversion and storage.

Enhanced Lithium Storage Performance in Si/MXene Porous Composites

As a potential negative electrode material for lithium-ion batteries (LIBs), silicon has a relatively high specific lithium storage capacity. However, the large volume change during the cycle may result in the isolation with the current collector and therefore the rapid capacity decay during cycling. The poor electric conductivity of the silicon limits the high-power density application in LIBs. To meet the above challenges, a stable Si/Ti3C2Tx composite material was designed. Si nanoparticles are bonded with -NH2 group so that the silicon surface has a positive charge, which can then be electrostatic self-assembly with negatively charged MXene nanosheets in a facile freeze-drying method. Silicon nanoparticles were anchored on the surface or inside the interspace of the MXene nanosheets, which could improve the conductivity of the composites. The composite material (NH2-Si/MXene) presented a stable and porous structure with extra room for silicon expansion and plentiful channels for carrier transportation. Benefiting from the improved structural stability and enhanced charge storage dynamics, the discharge capacity of NH2-Si/MXene is 1203.3 mAh g−1 after 100 cycles at 200 mA g−1. These results provide new insights for the application of silicon-based negative electrode materials in high-energy-density LIBs.

Core-shell structured Si@Cu nanoparticles segregated in graphene-carbon nanotube networks enable high reversible capacity and rate capability of anode for lithium-ion batteries

The volume expansion of Si electrodes and the poor conductivity of Si as well as the repeated rupture of solid electrolyte interface (SEI) lead to the rapid capacity decay of Si-based anode Li-ion batteries. The rational design of anode materials for the above problems is considered an effective solution. In this work, core-shell structured Si@Cu nanoparticles segregated in graphene-carbon nanotube networks (Si@Cu/CNT/rGO) is constructed by one-step hybrid and reduction self-assembly strategy. First, metallic copper was coated on silicon nanoparticles to improve the reaction kinetics of the cell during operation. The flexible reduced graphene oxide and rigid carbon nanotube are designed as a network structure for increasing the electrical conductivity and mechanical strength of the electrode material. This design not only provides sufficient buffering space for the volume change during cell operation, but also improves the electron migration effect of the composite Si@Cu/CNT/rGO. Thanks to this design, the composite electrode maintains a high lithium storage capacity of 1915.5 mAh/g (130 cycles) and 1486.7 mAh/g (200 cycles) after charging and discharging at 100 mA g−1 and 1000 mA g−1, respectively.