Importing Tin Nanoparticles into Biomass-Derived Silicon Oxycarbides with High-Rate Cycling Capability Based on Supercritical Fluid Technology

Silicon oxycarbides (SiOC) are regarded as potential anode materials for lithium-ion batteries, although inferior cycling stability and rate performance greatly limit their practical applications. Herein, amorphous SiOC is synthesized from Chlorella by means of a biotemplate method based on supercritical fluid technology. On this basis, tin particles with sizes of several nanometers are introduced into the SiOC matrix through the biosorption feature of Chlorella. As lithium-ion battery anodes, SiOC and Sn@SiOC can deliver reversible capacities of 440 and 502 mAh g⁻¹ after 300 cycles at 100 mA g⁻¹ with great cycling stability. Furthermore, as-synthesized Sn@SiOC presents an excellent high-rate cycling capability, which exhibits a reversible capacity of 209 mAh g⁻¹ after 800 cycles at 5000 mA g⁻¹; this is 1.6 times higher than that of SiOC. Such a novel approach has significance for the preparation of high-performance SiOC-based anodes.     

Biomimetic Straw-Like Bundle Cobalt-Doped Fe2O3 Electrodes towards Superior Lithium-Ion Storage

Biomimetic straw-like bundles of Co-doped Fe₂O₃ (SCF), with Co²⁺ incorporated into the lattice of α-Fe₂O₃, was fabricated through a cost-effective hydrothermal process and used as the anode material for lithium-ion batteries (LIBs). The SCF exhibited ultrahigh initial discharge specific capacity (1760.7 mA h⁻¹ g⁻¹ at 200 mA g⁻¹) and cycling stability (with the capacity retention of 1268.3 mA h⁻¹ g⁻¹ after 350 cycles at 200 mA g⁻¹). In addition, a superior rate capacity of 376.1 mA h⁻¹ g⁻¹ was obtained at a high current density of 4000 mA g⁻¹. The remarkable electrochemical lithium storage of SCF is attributed to the Co-doping, which increases the unit cell volume and affects the whole structure. It makes the Li⁺ insertion–extraction process more flexible. Meanwhile, the distinctive straw-like bundle structure can accelerate Li ion diffusion and alleviate the huge volume expansion upon cycling.     

Superior Lithium‐Ion Storage Properties of Si‐Based Composite Powders with Unique Si@Carbon@Void@Graphene Configuration

Composite powders of the configuration Si@carbon@void@graphene were prepared by a one‐step spray pyrolysis process, by adding polyvinylpyrrolidone (PVP) to a precursor solution containing graphene oxide (GO) sheets and silicon nanoparticles (NPs). Morphological analysis indicates that the individual Si NPs are coated with amorphous carbon and encapsulated in a micrometer‐sized graphene ball structure that offers a large amount of buffer space. The addition of PVP improves the stability of the colloidal spray solution containing the GO sheets and the Si NPs. Consequently, the prepared Si@C@void@graphene composite powders have a relatively more uniform morphology than the Si@void@graphene composite powders prepared from the spray solution without PVP. The first charge and discharge capacities of the Si@C@void@graphene electrode measured at 0.1 A g^?1 are as high as 3102 and 2215 mA h g^?1, respectively. With an increase in the current rate from 0.5 to 11 A g^?1, 46 % of the original capacity (i.e., 2134 mA h g^?1) is maintained. After 500 cycles at a high rate of 7 A g^?1, the Si@C@void@graphene electrode shows 84 % capacity retention and 99.8 % of the average Coulombic efficiency. The superior cycling and rate capabilities of the prepared Si@C@void@graphene electrode could be attributed to the uniform carbon coating of the Si NPs and the graphene ball structure, which facilitates efficient diffusion of Li ions and prevents the penetration of electrolyte into graphene ball during cycling.     

Nitrogen-Linked Hexaazatrinaphthylene Polymer as Cathode Material in Lithium-Ion Battery

Nitrogen-linked hexaazatrinaphthylene polymer ( N²-HATN ) as organic cathode material with low HOMO–LOMO gap was synthesized and was observed to possess reversible high capacity and unexpected long-term cycling stability. The pre-treated N²-HATN and pRGO combination demonstrated good structure compatibility and the resultant cathode exhibited a constant increment of capacity during the redox cycles. The initial capacity at 0.05 A g⁻¹ was 406 mA h⁻¹ g⁻¹, and increased to 630 mA h⁻¹ g⁻¹ after 70 cycles. At 0.5 A g⁻¹ discharging rate, the capacity increased from an initial value of 186 mA h⁻¹ g⁻¹ to 588 mA h⁻¹ g⁻¹ after 1600 cycles. The pseudocapacitance-type behavior is postulated to be attributed to the structure compatibility between the active material and pRGO.     

Si-O-C骨架支撑型高循环性能锂离子电池硅基负极材料

通过经济有效的方法制备得到一种具有长循环寿命的高效稳定性硅/硅氧碳/无定形碳的复合负极材料结构. 在这种结构中,以具有稳定化学性能的硅氧碳结构作为骨架,来支撑和隔离硅纳米颗粒结构. 材料中包含的无定形碳组分可提高硅/硅氧碳结构的电导性能. 这种复合负极结构在0.3C电流充放电情况下,不仅能发挥出637.3 mAh·g^-1的比容量,而且在经过100 周的充放电循环后,其容量保持率也达到86%. 这种新型硅基负极材料的设计为其他功能材料的设计提供了一种潜在可能的方法.     

Structural Design and Synthesis of an SnO2@C@Co-NC Composite as a High-Performance Anode Material for Lithium-Ion Batteries

To overcome the drawbacks of the structural instability and poor conductivity of SnO₂-based anode materials, a hollow core–shell-structured SnO₂@C@Co-NC (NC=N-doped carbon) composite was designed and synthesized by employing the heteroatom-doping and multiconfinement strategies. This composite material showed a much-reduced resistance to charge transfer and excellent cycling performance compared to the bare SnO₂ nanoparticles and SnO₂@C composites. The doped heteroatoms and heterostructure boost the charge transfer, and the porous structure shortens the Li-ion diffusion pathway. Also, the volume expansion of SnO₂ NPs is accommodated by the hollow space and restricted by the multishell heteroatom-doped carbon framework. As a result, this structured anode material delivered a high initial capacity of 1559.1 mA h g⁻¹ at 50 mA g⁻¹ and an initial charge capacity of 627.2 mA h g⁻¹ at 500 mA g⁻¹. Moreover, the discharge capacity could be maintained at 410.8 mA h g⁻¹ after 500 cycles with an attenuation rate of only 0.069 % per cycle. This multiconfined SnO₂@C@Co-NC structure with superior energy density and durable lifespan is highly promising for the next-generation lithium-ion batteries.     

Facile Synthesis of Ultra-Small Few-Layer Nanostructured MoSe2 Embedded on N,P Co-Doped Bio-Carbon for High-Performance Half/Full Sodium-Ion and Potassium-Ion Batteries

Sodium/potassium-ion batteries (SIBs/PIBs) arouse intensive interest on account of the natural abundance of sodium/potassium resources, the competitive cost and appropriate redox potential. Nevertheless, the huge challenge for SIBs/PIBs lies in the scarcity of an anode material with high capacity and stable structure, which are capable of accommodating large-size ions during cycling. Furthermore, using sustainable natural biomass to fabricate electrodes for energy storage applications is a hot topic. Herein, an ultra-small few-layer nanostructured MoSe₂ embedded on N, P co-doped bio-carbon is reported, which is synthesized by using chlorella as the adsorbent and precursor. As a consequence, the MoSe₂/NP-C-2 composite represents exceedingly impressive electrochemical performance for both sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It displays a promising reversible capacity (523 mAh g⁻¹ at 100 mA g⁻¹ after 100 cycles) and impressive long-term cycling performance (192 mAh g⁻¹ at 5 A g⁻¹ even after 1000 cycles) in SIBs, which are some of the best properties of MoSe₂-based anode materials for SIBs to date. To further probe the great potential applications, full SIBs pairing the MoSe₂/NP-C-2 composite anode with a Na₃V₂(PO₄)₃ cathode also exhibits a satisfactory capacity of 215 mAh g⁻¹ at 500 mA g⁻¹ after 100 cycles. Moreover, it also delivers a decent reversible capacity of 131 mAh g⁻¹ at 1 A g⁻¹ even after 250 cycles for PIBs.     

One-step synthesis of hollow structured Si/C composites based on expandable microspheres as anodes for lithium ion batteries

Si/C composites of carbon hollow structures loaded with Si nanoparticles (NPs) (Si/C-HSs) were prepared by one-step pyrolysis of a mixture of Si NPs and expandable microspheres (EMs). For the Si/C-HSs, hollow carbon shells with rough surfaces were formed by directly carbonizing the polymer shells of EMs, and the Si NPs fell into the void space or were loaded on the rough surfaces of the carbon shells. The EM-based carbon shells accommodated the volume expansion of the Si NPs and improved the electrical conductivity of the composites. As a result, the Si/C-HSs exhibited a high capacity (initial reversible capacity: 854.4 mAh g^− 1 at 300 mA g^− 1), stable cycling performance (capacity retention: 80% after 50 cycles), and excellent rate capability.     

Fe-Doped CoP Flower-Like Microstructure on Carbon Membrane as Integrated Electrode with Enhanced Sodium Ion Storage

Poor cyclability and rate performance always impede the development of transition metal phosphide-based anode materials. Many strategies have been used to address the above problems, such as the designing of hierarchical structures, combination with carbon materials, and doping with other metal elements. Considering those strategies, a flower-like Fe-doped CoP material is designed. The synthesis consists of microsheets grown on a carbon membrane (CM, leaves as precursor) through a hydrothermal method and in situ phosphorization. The Fe doping and carbon membrane synergistically induce the formation of a flower-like hierarchical microstructure during the crystal-growing process. The unique hierarchical microstructure increases the contact area between electrode and electrolyte, and accommodates the volume expansion during cycling. The hierarchical Fe-doped CoP grown directly on the carbon membrane increases the active sites for intercalation of sodium species and further promotes the internal electron conduction in the Fe-doped CoP/CM electrode. Thereby, the Fe-doped CoP/CM as the anode electrode for sodium ion batteries exhibits a high specific capacity of 515 mA h g⁻¹ at 100 mA g⁻¹ after 100 cycles. Even if the current density rises to 500 mA g⁻¹, the specific capacity is still maintained at 324 mA h g⁻¹ after 500 cycles, showing superior rate performances and cyclability.     

In-situ Grown SnO2 Nanospheres on Reduced GO Nanosheets as Advanced Anodes for Lithium-ion Batteries

Nanostructured tin dioxide (SnO₂) has emerged as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (1494 mA h g⁻¹) and excellent stability. Unfortunately, the rapid capacity fading and poor electrical conductivity of bulk SnO₂ material restrict its practical application. Here, SnO₂ nanospheres/reduced graphene oxide nanosheets (SRG) are fabricated through in-situ growth of carbon-coated SnO₂ using template-based approach. The nanosheet structure with the external layer of about several nanometers thickness can not only accommodate the volume change of Sn lattice during cycling but also enhance the electrical conductivity effectively. Benefited from such design, the SRG composites could deliver an initial discharge capacity of 1212.3 mA h g⁻¹ at 0.1 A g⁻¹, outstanding cycling performance of 1335.6 mA h g⁻¹ after 500 cycles at 1 A g⁻¹, and superior rate capability of 502.1 mA h g⁻¹ at 5 A g⁻¹ after 10 cycles. Finally, it is believed that this method could provide a versatile and effective process to prepare other metal-oxide/reduced graphene oxide (rGO) 2D nanocomposites.     

Amidation-Dominated Re-Assembly Strategy for Single-Atom Design/Nano-Engineering: Constructing Ni/S/C Nanotubes with Fast and Stable K-Storage

An amidation-dominated re-assembly strategy is developed to prepare uniform single atom Ni/S/C nanotubes. In this re-assembly process, a single-atom design and nano-structured engineering are realized simultaneously. Both the NiO₅ single-atom active centers and nanotube framework endow the Ni/S/C ternary composite with accelerated reaction kinetics for potassium-ion storage. Theoretical calculations and electrochemical studies prove that the atomically dispersed Ni could enhance the convention kinetics and decrease the decomposition energy barrier of the chemically-absorbed small-molecule sulfur in Ni/S/C nanotubes, thus lowering the electrode reaction overpotential and resistance remarkably. The mechanically stable nanotube framework could well accommodate the volume variation during potassiation/depotassiation process. As a result, a high K-storage capacity of 608 mAh g⁻¹ at 100 mA g⁻¹ and stable cycling capacity of 330.6 mAh g⁻¹ at 1000 mA g⁻¹ after 500 cycles are achieved.     

Engineering Na−Mo−O/Graphene Oxide Composites with Enhanced Electrochemical Performance for Lithium Ion Batteries

Sodium molybdate (Na−Mo−O) wrapped by graphene oxide (GO) composites have been prepared via a simple in-situ precipitation method at room temperature. The composites are mainly constructed with one dimension (1D) ultra-long sodium molybdate nanorods, which are wrapped by the flexible GO. The introduction of GO is expected to not merely provide more active sites for lithium-ions storage, but also improve the charge transfer rate of the electrode. The testing electrochemical performances corroborated the standpoint: The Na−Mo−O/GO composites delivers specific capacities of 718 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹, and 570 mAh g⁻¹ after 500 cycles at a high rate of 500 mA g⁻¹; for comparison, the bare Na−Mo−O nanorod shows a severe capacity decay, which deliver only 332 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹. In view of the cost-efficient and less time-consuming in synthesis, and one-step preparation without further treatment, these Na−Mo−O nanorods/GO composites present potential and prospective anodes for LIBs.     

Electrostatic Interactions Leading to Hierarchical Interpenetrating Electroconductive Networks in Silicon Anodes for Fast Lithium Storage

Recently, the frequency of combining MXene, which has unique properties such as metal-level conductivity and large specific surface area, with silicon to achieve excellent electrochemical performance has increased considerably. There is no doubt that the introduction of MXene can improve the conductivity of silicon and the cycling stability of electrodes after elaborate structure design. However, most exhaustive contacts can only improve the electrode conductivity on the plane. Herein, a MXene@Si/CNTs (HIEN-MSC) composite with hierarchical interpenetrating electroconductive networks has been synthesized by electrostatic self-assembly. In this process, the CNTs are first combined with silicon nanoparticles and then assembled with MXene nanosheets. Inserting CNTs into silicon nanoparticles can not only reduce the latter‘s agglomeration, but also immobilizes them on the three-dimensional conductive framework composed of CNTs and MXene nanosheets. Therefore, the HIEN-MSC electrode shows superior rate performance (high reversible capacity of 280 mA h⁻¹ even tested at 10 A g⁻¹), cycling stability (stable reversible capacity of 547 mA h g⁻¹ after 200 cycles at 1 A g⁻¹) and applicability (a high reversible capacity of 101 mA h g⁻¹ after 50 cycles when assembled with NCM622 into a full cell). These results may provide new insights for other electrodes with excellent rate performance and long-cycle stability.     

Nanowire of WP as a High-Performance Anode Material for Sodium-Ion Batteries

The design and development of electrode materials with high specific capacity and long cycling life for sodium-ion batteries (SIBs) is still a critical challenge. In this communication, we report the development of tungsten phosphide (WP) nanowire on carbon cloth (WP/CC) as an anode for SIBs. The WP/CC exhibits superior sodium storage capability with 502 mA h g⁻¹ at 0.1 A g⁻¹. Moreover, this anode is capable of delivering a long lifespan at 2 A g⁻¹ with an excellent capacity retention of 99 % after 1000 cycles.     

High‐Loading Nano‐SnO2 Encapsulated in situ in Three‐Dimensional Rigid Porous Carbon for Superior Lithium‐Ion Batteries

Tin oxide nanoparticles (SnO₂ NPs) have been encapsulated in situ in a three‐dimensional ordered space structure. Within this composite, ordered mesoporous carbon (OMC) acts as a carbon framework showing a desirable ordered mesoporous structure with an average pore size (≈6 nm) and a high surface area (470.3 m² g^?1), and the SnO₂ NPs (≈10 nm) are highly loaded (up to 80 wt %) and homogeneously distributed within the OMC matrix. As an anode material for lithium‐ion batteries, a SnO₂@OMC composite material can deliver an initial charge capacity of 943 mAh g^?1 and retain 68.9 % of the initial capacity after 50 cycles at a current density of 50 mA g^?1, even exhibit a capacity of 503 mA h g^?1 after 100 cycles at 160 mA g^?1. In situ encapsulation of the SnO₂ NPs within an OMC framework contributes to a higher capacity and a better cycling stability and rate capability in comparison with bare OMC and OMC ex situ loaded with SnO₂ particles (SnO₂/OMC). The significantly improved electrochemical performance of the SnO₂@OMC composite can be attributed to the multifunctional OMC matrix, which can facilitate electrolyte infiltration, accelerate charge transfer, and lithium‐ion diffusion, and act as a favorable buffer to release reaction strains for lithiation/delithiation of the SnO₂ NPs.     

Solution Synthesis of Porous Silicon Particles as an Anode Material for Lithium Ion Batteries

Nanostructured silicon-based materials with porous structures have recently been found to be impressive anode materials with high capacity and cycling performance for lithium-ion batteries. However, the current methods of preparing porous silicon have generally been confronted with the requirement for multiple steps and complex synthesis. In the present study, porous silicon with high surface area was prepared by using a high yielding and simple reaction in which commercial magnesium powder readily reacts with HSiCl₃ with the help of an amine catalyst under mild conditions. The obtained porous silicon was coated with a nitrogen-doped carbon layer and used as the anode for lithium-ion batteries. The porous Si-carbon nanocomposites exhibited excellent cycling performance with a retained discharge capacity of 1300 mA h g⁻¹ after 200 cycles at 1 A g⁻¹ and a discharge capacity of 750 mA h g⁻¹ at a current density of 2 A g⁻¹ after 250 cycles. Remarkably, the Coulombic efficiency was maintained at nearly 100 % throughout the measurements.     

Highly Concentrated Electrolyte towards Enhanced Energy Density and Cycling Life of Dual-Ion Battery

Dual-ion batteries (DIBs) have attracted much attention owing to their low cost, high voltage, and environmental friendliness. As the source of active ions during the charging/discharging process, the electrolyte plays a critical role in the performance of DIBs, including capacity, energy density, and cycling life. However, most used electrolyte systems based on the LiPF₆ salt demonstrate unsatisfactory performance in DIBs. We have successfully developed a 7.5 mol kg⁻¹ lithium bis(fluorosulfonyl)imide (LiFSI) in a carbonate electrolyte system. Compared with diluted electrolytes, this highly concentrated electrolyte exhibits several advantages: 1) enhanced intercalation capacity and cycling stability of the graphite cathode, 2) optimized structural stability of the Al anode, and 3) significantly increased battery energy density. A proof-of-concept DIB based on this concentrated electrolyte exhibits a discharge capacity of 94.0 mAh g⁻¹ at 200 mA g⁻¹ and 96.8 % capacity retention after 500 cycles. By counting both the electrode materials and electrolyte, the energy density of this DIB reaches up to ≈180 Wh kg⁻¹, which is among the best performances of DIBs reported to date.     

Heat-Treatment-Assisted Molten-Salt Strategy to Enhance Electrochemical Performances of Li-Rich Assembled Microspheres by Tailoring Their Surface Features

Constructing Li-rich Mn-based layered oxide (LMRO) assembled microspheres with fast kinetics and a stable surface will significantly improve discharge capacity and cyclic stability. In this work, a heat-treatment-assisted (HA) molten-salt (MS) strategy has been designed to prepare LMRO assembled microspheres HA-MS-LMRO (LMRO with heat-treatment-assisted molten-salt process). Electrochemical measurements demonstrate that HA-MS-LMRO possesses superior performance as a cathode for lithium-ion batteries. It delivers an initial discharge capacity of 181 mA h g⁻¹ at 200 mA g⁻¹, which is much higher than that of the LMRO (145 mA h g⁻¹). After 100 cycles, the capacity retention ratio for HA-MS-LMRO is 74.69 %, which is far larger than that of LMRO (23.06 %). Detailed analysis of the structure, valence state, and electrochemical impedance spectra shows that the heat-treatment-assisted molten-salt process plays an important role in the excellent performance of HA-MS-LMRO. The HA process enables the transition-metal ions in the synthesized samples to have stable surface valence states, which is conducive to maintaining structural stability and improving cycling performance. The following MS process facilitates the movement of lithium salt into the interior of the assembled microsphere precursors to prohibit the formation of lithium-containing amorphous compounds on the surface during the lithiation process, thus enhancing the Li-ion kinetics and increasing the initial discharge capacity. The current work provides guidance to promote the electrochemical performances of assembled microsphere cathode materials.     

3D Starfish-Like FeOF on Graphene Sheets: Engineered Synthesis and Lithium Storage Performance

To address the problems associated with poor conductivity and large volume variation in practical applications as a conversion cathode, engineering of hierarchical nanostructured FeOF coupled with conductive decoration is highly desired, yet rarely reported. Herein, 3D starfish-like FeOF on reduced graphene oxide sheets (FeOF/rGO) is successfully prepared, for the first time, through a combination of solvothermal reaction, self-assembly, and thermal reduction. Integrating the structural features of the 3D hierarchical nanostructure, which favorably shorten the path for electron/ion transport and alleviate volumetric changes, with those of graphene wrapping, which can further enhance the electrical conductivity and maintain the structural stability of the electrode, the as-prepared FeOF/rGO composite exhibits a superior lithium-storage performance, including a high reversible capacity (424.5 mA h⁻¹ g⁻¹ at 50 mA g⁻¹), excellent stability (0.016 % capacity decay per cycle during 180 cycles), and remarkable rate capability (275.8 mA h⁻¹ g⁻¹ at 2000 mA g⁻¹).     

Graphene/Amorphous Carbon Restriction Structure for Stable and Long-Lifespan Antimony Anode in Potassium-Ion Batteries

Sb-based materials have attracted much attention owing to their ability to undergo a multi-electron alloy reaction with K⁺. However, there are still the serious problems of volume change and aggregation of particles, which lead to rapid capacity fading and a limited lifespan. In this work, a graphene/amorphous carbon restriction structure is proposed, in which the amorphous carbon layer on the surface of Sb nanoparticles can protect the particles from pulverization, and the graphene can buffer the volume change of the material. In addition, the conductive network formed by the dual carbon structure effectively improves the rate performance of the material. Thus, the material delivers a high capacity of 550 mA h g⁻¹ at 100 mA g⁻¹, a rate capability of 370 mA h g⁻¹ at 2000 mA g⁻¹, and a long lifespan of 350 cycles without significant capacity fading. The dual carbon strategy proposed offers a reference for the design of high-performance anode materials.