Antinomy (Sb) has received considerable attention as one of the most promising anode materials for sodium-ion batteries (SIBs) because of its high theoretical capacity and suitable working voltage. However, the large volume change of Sb during the alloying/dealloying process causes poor cycling stability and low rate capability, which hinder its practical application. Here, we substantially enhance the sodium storage performance of Sb by binding Sb nanoparticles in ionic liquid-derived nitrogen-enriched carbon (Sb@NC) via pyrolysis of an SbCl3/1-ethyl-3-methylimidazolium dicyanamide mixture. The Sb@NC composite exhibits a high reversible capacity of 440 mA h g−1 at a current density of 100 mA g−1, superior rate performance of 285 and 237 mA h g−1 at the high current densities of 2 and 5 A g−1, respectively, and greatly improved cycle life of 328 mA h g−1 at the current density of 100 A g−1 after 300 cycles in the half cell of SIBs. In the full cell, the energy density of Sb@NC//Na3V2(PO4)3/C is approximately 147 W h kg−1 at a power density of 50 W kg−1. Even at 2.37 kW kg−1, an energy density of around 65 W h kg−1 is still retained. The remarkably improved electrochemical performance could be assigned to the synergistic effect of nanoscale size, uniform distribution, and chemical coupling effect between Sb and ionic liquid-derived nitrogen-enriched carbon.

Rechargeable sodium-ion batteries have lately received considerable attention as an alternative to lithium-ion batteries because sodium resources are essentially inexhaustible and ubiquitous around the world. Despite recent reports on cathode materials for sodium-ion batteries have shown electrochemical activities close to their lithium-ion counterparts, the major scientific challenge for sodium-ion batteries is to exploit efficient anode materials. Herein, we demonstrate that a hybrid material composed of few-layer SnS2 nanosheets sandwiched between reduced graphene oxide (RGO) nanosheets exhibits a high specific capacity of 843 mAh g–1 (calculated based on the mass of SnS2 only) at a current density of 0.1 A g–1 and a 98% capacity retention after 100 cycles when evaluated between 0.01 and 2.5 V. Employing ex situ high-resolution transmission electron microscopy and selected area electron diffraction techniques, we illustrate the high specific capacity of our anode through a 3-fold mechanism of intercalation of sodium ions along the ab-plane of SnS2 nanosheets and the subsequent formation of Na2S2 and Na15Sn4 through conversion and alloy reactions. The existence of RGO nanosheets in the hybrid material functions as a flexible backbone and high-speed electronic pathways, guaranteeing that an appropriate resilient space buffers the anisotropic dilation of SnS2 nanosheets along the ab-plane and c-axis for stable cycling performance.

Sodium-ion batteries (SIBs) have received much attention for scalable electrical energy storage because of the abundance and wide availability of sodium resources. However, it is still unclear whether carbon anodes can realize large-scale commercial application in SIBs as in lithium-ion batteries. Recently, great attention has been devoted to hard carbon which has been treated as a promising choice. Herein, we observe that the turbostratic lattice of kelp-derived hard carbon (KHC) is repeatedly expandable and shrinkable upon cycling, where the interlayer distance varies between 3.9 and 4.3 Å. Such interlayer spacing dilation is highly reversible, giving rise to high rate capability (a stable capacity of 96 mA h g−1 at 1000 mA g−1) and excellent cycling performance (205 mA h g−1 after 300 cycles at 200 mA g−1). Furthermore, kelp-derived hard carbon exhibits a good specific capacity at potentials higher than 0.05 V, which make it an essentially dendrite-free anode for SIBs.

Antimony is a promising high-capacity anode material in sodium-ion batteries, but it generally shows poor cycling stability because of its large volume changes during sodium ion insertion and extraction processes. To alleviate or even overcome this problem, we develop a hybrid carbon encapsulation strategy to improve the anode performance of antimony through the combination of antimony/nitrogen-doped carbon (Sb/N-carbon) hybrid nanostructures and the carbon nanotube (CNT) network. When evaluated as an anode material for sodium-ion batteries, the as-synthesized Sb/N-carbon + CNT composite exhibits superior cycling stability and rate performance in comparison with Sb/N-carbon or Sb/CNT composite. A high charge capacity of 543 mA h g–1 with initial charge capacity retention of 87.7% is achieved after 200 cycles at a current density of 0.1 A g–1. Even under 10 A g–1, a reversible capacity of 258 mA h g–1 can be retained. The excellent sodium storage properties can be attributed to the formation of Sb–N bonding between the antimony nanoparticle and the nitrogen-doped carbon shell in addition to the electronically conductive and flexible CNT network. The hybrid carbon encapsulation strategy is simple yet very effective, and it also provides new avenues for designing advanced anode materials for sodium-ion batteries.

Sodium-ion batteries have recently attracted considerable attention as a promising alternative to lithium-ion batteries owing to the natural abundance and low cost of sodium compared with lithium. Among all proposed anode materials for sodium-ion batteries, antimony is a desirable candidate due to its high theoretical capacity (660 mA h g–1). Herein, an antimony/multilayer graphene hybrid, in which antimony is homogeneously anchored on multilayer graphene, is produced by a confined vapor deposition method. The chemical bonding can realize robust and intimate contact between antimony and multilayer graphene, and the uniform distribution of antimony and the highly conductive and flexible multilayer graphene can not only improve sodium ion diffusion and electronic transport but also stabilize the solid electrolyte interphase upon the large volume changes of antimony during cycling. Consequently, the antimony/multilayer graphene hybrid shows a high reversible sodium storage capacity (452 mA h g–1 at a current density of 100 mA g–1), stable long-term cycling performance with 90% capacity retention after 200 cycles, and excellent rate capability (210 mA h g–1 under 5000 mA g–1). This facile synthesis approach and unique nanostructure can potentially be extended to other alloy materials for sodium-ion batteries.

Co3S4 porous nanosheets embedded in flexible graphene sheets have been synthesized through a simple freeze-drying and subsequent hydrazine treatment process. The robust structural stability of the as-prepared three-dimensional sandwich-like Co3S4–PNS/GS composite affords improved rate performance and cycling stability for both lithium and sodium storage.

Tungsten disulfide, which possesses a well-defined layered structure, has been intensively studied as an anode material for lithium ion batteries, but it usually suffers from poor cycling stability because of its large volume changes during lithium insertion and extraction processes. Herein, we develop a self-assembled double carbon coating to enhance the anode performance of WS2 via a self-assembly process between oleylamine-coated WS2 nanosheets and graphene oxide and subsequent pyrolysis treatment. When employed as an anode material for lithium ion batteries, the as-prepared WS2@C/reduced graphene oxide (WS2@C/RGO) composite exhibits excellent cycling stability and rate capability when compared to WS2@C nanosheets. A reversible capacity of 486 mA h g–1 and around 90% capacity retention were obtained after 200 cycles at a current density of 0.5 A g–1. Even under 10 A g–1, a high reversible capacity of 126 mA h g–1 can be retained. The good electrochemical performance could be attributed to the external electronically conductive and flexible RGO coating in addition to the surface carbon layer and the uniform distribution of WS2 nanosheets. The self-assembled dual carbon coating strategy is facile yet effective, and it may be applied to other high-capacity anode materials with huge volume changes and poor electrical conductivities.

Although lithium–selenium batteries have attracted significant attention for high-energy-density energy storage systems due to their high volumetric capacity, their implementation has been hampered by the dissolution of polyselenide intermediates into electrolyte. Herein, we report a novel selenium/microporous carbon nanofiber composite as a high-performance cathode for lithium–selenium batteries through binding selenium in microporous carbon nanofibers. Under vacuum and heat treatment, selenium particles are easily transformed into chainlike Sen molecules that chemically bond with the inner surfaces of microporous carbon nanofibers. This chemical bonding can not only promote robust and intimate contact between selenium and carbonaceous nanofiber matrix but also alleviate the active material dissolution during cycling. Moreover, selenium is homogeneously distributed in the micropores of the highly conductive carbonaceous nanofiber matrix, which is favorable for the fast diffusions of both lithium ions and electrons. As a result, a high reversible capacity of 581 mA h g–1 in the first cycle at 0.1 C and over 400 mA h g–1 after 2000 cycles at 1 C with excellent cyclability and high rate performance (over 420 mA h g–1 at 5 C, 3.39 A g–1) are achieved with the selenium/microporous carbon nanofibers composite as a cathode for lithium–selenium batteries, performing among the best of current selenium–carbon cathodes. This simple preparation method and strongly coupling hybrid nanostructure can be extended to other selenium-based alloy cathode materials for lithium–selenium batteries.

Silicon-based lithium-ion battery anodes have brought encouraging results to the current state-of-the-art battery technologies due to their high theoretical capacity, but their large-scale application has been hampered by a large volume change (>300%) of silicon upon lithium insertion and extraction, which leads to severe electrode pulverization and capacity degradation. Polymeric surfactants directing the combination of silicon nanoparticles and reduced graphene oxide have attracted great interest as promising choices for accommodating the huge volume variation of silicon. However, the influence of different polymeric surfactants on improving the electrochemical performance of silicon/reduced graphene oxide (Si/RGO) anodes remains unclear because of the different structural configurations of polymeric surfactants. Here, we systematically study the effect of different polymeric surfactants on enhancing the Si/RGO anode performance. Three of the most well-known polymeric surfactants, poly(sodium 4-styrenesulfonate) (PSS), poly(diallydimethylammonium chloride) (PDDA), and polyvinylpyrrolidone (PVP), were used to direct the combination of silicon nanoparticles and RGO through van der Waals interaction. The Si/RGO anodes made from these composites act as ideal models to investigate and compare how the van der Waals forces between polymeric surfactants and GO affect the final silicon anode performance from both experimental observations and theoretical simulations. We found that the capability of these three surfactants in enhancing long-term cycling stability and high-rate performance of the Si/RGO anodes decreased in the order of PVP > PDDA > PSS.

In contrast to the extensive investigation of the electrochemical performance of conventional carbon materials in sodium-ion batteries, there has been scarcely any study of sodium storage property of fluorine-doped carbon. Here we report for the first time the application of fluorine-doped carbon particles (F-CP) synthesized through pyrolysis of lotus petioles as anode materials for sodium-ion batteries. Electrochemical tests demonstrate that the F-CP electrode delivers an initial charge capacity of 230 mA h g–1 at a current density of 50 mA g–1 between 0.001 and 2.8 V, which greatly outperforms the corresponding value of 149 mA h g–1 for the counterpart banana peels-derived carbon (BPC). Even under 200 mA g–1, the F-CP electrode could still exhibit a charge capacity of 228 mA h g–1 with initial charge capacity retention of 99.1% after 200 cycles compared to the BPC electrode with 107 mA h g–1 and 71.8%. The F-doping and the large interlayer distance as well as the disorder structure contribute to a lowering of the sodium ion insertion–extraction barrier, thus promoting the Na+ diffusion and providing more active sites for Na+ storage. In specific, the F-CP electrode shows longer low-discharge-plateau and better kinetics than does the common carbon-based electrode. The unique electrochemical performance of F-CP enriches the existing knowledge of the carbon-based electrode materials and broadens avenues for rational design of anode materials in sodium-ion batteries.

A novel selenium–carbon composite has been fabricated by embedding selenium in metal–organic framework-derived microporous carbon polyhedra. Such interconnected microporous carbon polyhedra possess a large surface area and pore volume to effectively confine Se, and suppress the dissolution of polyselenides in the electrolyte. This selenium–carbon composite shows ultrastable cycling performance when used as a cathode material for lithium–selenium batteries.

Hard carbons have been extensively investigated as anode materials for sodium-ion batteries due to their disordered structure and large interlayer distance, which facilitates sodium-ion uptake and release. Herein, we report a graphene-templated carbon (GTC) hybrid via a facile two-step strategy involving a graphene oxide-directed self-assembly process and subsequent pyrolysis treatment. When evaluated as an anode material for sodium-ion batteries, the GTC electrode exhibits ultralong cycling stability and excellent rate capability. A reversible capacity of 205 mA h g–1 and more than 92% capacity retention were achieved after 2000 cycles at a current density of 200 mA g–1. Even at 10 A g–1 a high reversible capacity of 45 mA h g–1 can be obtained. The superior electrochemical performance is due to the strong coupling effect between graphitic nanocrystallites and the graphene template and the large interlayer distance of the graphitic nanocrystallites, both of which can not only effectively relieve the sodiation-induced stress and preserve the electrode integrity during cycling but also promote the electron and sodium-ion transport.

Antimony has attracted enormous attention as anode materials for sodium-ion batteries owing to its high theoretical gravimetric capacity (∼660 mA h g–1). Despite the outstanding gravimetric capacity advantage, antimony suffers from unsatisfactory electrochemical performance originating from its huge volume changes during repeated sodium insertion/extraction. Herein, we synthesize an SbOx/reduced graphene oxide (SbOx/RGO) composite through a wet-milling approach accompanied by redox reaction between Sb and GO. When used as an anode material for sodium-ion batteries, SbOx/RGO exhibits high rate capability and stable cycling performance. A reversible capacity of 352 mA h g–1 was obtained even at a current density of 5 A g–1. More than 95% capacity retention (409 mA h g–1) was achieved after 100 cycles at a current density of 1 A g–1. The excellent electrochemical performance is due to the Sb–O bonding between nanometer-sized SbOx particles surface and highly conductive RGO, which can not only effectively prevent SbOx nanoparticles from aggregation upon cycling but also promote the electrons and sodium ions transportation.

Ge nanoparticles/C composites are desirable electrode materials for high energy and power density lithium-ion batteries. However, the production of well-dispersed Ge nanoparticles in a carbon network remains a challenge because of rapid grain growth during high-temperature thermal reduction. Herein, we report a PVP-assisted hydrolysis approach for fabricating a Ge nanoparticles/reduced graphene oxide composite (denoted as Ge/RGO) made of ∼5 nm Ge nanoparticles that are uniformly distributed within a nitrogen-doped RGO carbon matrix. The Ge/RGO composite exhibits an initial discharge capacity of 1475 mA h g–1 and a reversible capacity of 700 mA h g–1 after 200 cycles at a current density of 0.5 A g–1. Moreover, Ge/RGO shows a capacity of 210 mA h g–1 even at a high current density of 10 A g–1. The excellent performance of the Ge/RGO composite is attributed to its unique nanostructure, including Ge nanoparticles, homogeneous particle distribution, and highly conductive RGO carbon matrix. These properties alleviate the pulverization problem, prevent Ge particle aggregation, and facilitate electron and lithium-ion transportation.

Tin possesses a high theoretical specific capacity as anode materials for Li-ion batteries, and considerable efforts have been contributed to mitigating the capacity fading along with its huge volume expansion during lithium insertion and extraction processes, mainly through nanostructured material design. Herein, we present Sn nanoparticles encapsulated in nitrogen-doped graphene sheets through heat-treatment of the SnO2 nanocrystals/nitrogen-doped graphene hybrid. The specific architecture of the as-prepared Sn@N-RGO involves three advantages, including a continuous graphene conducting network, coating Sn surface through Sn–N and Sn–O bonding generated between Sn nanoparticles and graphene, and porous and flexible structure for accommodating the large volume changes of Sn nanoparticles. As an anode material for lithium-ion batteries, the hybrid exhibits a reversible capacity of 481 mA h g–1 after 100 cycles under 0.1 A g–1 and a charge capacity as high as 307 mA h g–1 under 2 A g–1.

•An antimony−cyano-based ionic liquid-derived nitrogen-doped carbon (SbCNC) hybrid is achieved.•The SbCNC hybrid is synthesized by ball-milling and subsequent pyrolysis treatment.•High reversible sodium storage capacity of 475 mAh g−1 at 100 mA g−1.•Good cycling performance (150 cycles) and excellent rate capability are demonstrated.•XPS studies reveal the formation of SbNC bonds between Sb and CNC.Antimony has received a great deal of attention as a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity of 660 mAh g−1. However, this application is significantly hampered by inherent large volume change and sluggish kinetics. To address these issues, an antimony−cyano-based ionic liquid-derived nitrogen-doped carbon (SbCNC) hybrid is proposed and synthesized by ball-milling and subsequent pyrolysis treatment. As an anode material for SIBs, the as-synthesized SbCNC hybrid delivers reversible capacities of 475 mAh g−1 at a current density of 100 mA g−1 and 203 mAh g−1 at 5000 mA g−1, and a 92.4% capacity retention based on the first-cycle capacity after 150 cycles at 100 mA g−1. Using ex situ X-ray photoelectron spectroscopy and elemental mapping techniques, we attribute the good structural integrity to the formation of SbNC bonds between Sb and the cyano-based ionic liquid-derived N-doped carbon matrix. Moreover, the presence of N-doped carbon network in the hybrid material serves as a robust protective cover and an electrical highway, buffering the substantial volume expansion of Sb nanoparticles and ensuring the fast electron transport for stable cycling operation.

A novel selenium–carbon composite has been fabricated by embedding selenium in metal–organic framework-derived microporous carbon polyhedra. Such interconnected microporous carbon polyhedra possess a large surface area and pore volume to effectively confine Se, and suppress the dissolution of polyselenides in the electrolyte. This selenium–carbon composite shows ultrastable cycling performance when used as a cathode material for lithium–selenium batteries.

Sodium-ion batteries (SIBs) have received much attention for scalable electrical energy storage because of the abundance and wide availability of sodium resources. However, it is still unclear whether carbon anodes can realize large-scale commercial application in SIBs as in lithium-ion batteries. Recently, great attention has been devoted to hard carbon which has been treated as a promising choice. Herein, we observe that the turbostratic lattice of kelp-derived hard carbon (KHC) is repeatedly expandable and shrinkable upon cycling, where the interlayer distance varies between 3.9 and 4.3 Å. Such interlayer spacing dilation is highly reversible, giving rise to high rate capability (a stable capacity of 96 mA h g−1 at 1000 mA g−1) and excellent cycling performance (205 mA h g−1 after 300 cycles at 200 mA g−1). Furthermore, kelp-derived hard carbon exhibits a good specific capacity at potentials higher than 0.05 V, which make it an essentially dendrite-free anode for SIBs.

Antinomy (Sb) has received considerable attention as one of the most promising anode materials for sodium-ion batteries (SIBs) because of its high theoretical capacity and suitable working voltage. However, the large volume change of Sb during the alloying/dealloying process causes poor cycling stability and low rate capability, which hinder its practical application. Here, we substantially enhance the sodium storage performance of Sb by binding Sb nanoparticles in ionic liquid-derived nitrogen-enriched carbon (Sb@NC) via pyrolysis of an SbCl3/1-ethyl-3-methylimidazolium dicyanamide mixture. The Sb@NC composite exhibits a high reversible capacity of 440 mA h g−1 at a current density of 100 mA g−1, superior rate performance of 285 and 237 mA h g−1 at the high current densities of 2 and 5 A g−1, respectively, and greatly improved cycle life of 328 mA h g−1 at the current density of 100 A g−1 after 300 cycles in the half cell of SIBs. In the full cell, the energy density of Sb@NC//Na3V2(PO4)3/C is approximately 147 W h kg−1 at a power density of 50 W kg−1. Even at 2.37 kW kg−1, an energy density of around 65 W h kg−1 is still retained. The remarkably improved electrochemical performance could be assigned to the synergistic effect of nanoscale size, uniform distribution, and chemical coupling effect between Sb and ionic liquid-derived nitrogen-enriched carbon.

Co3S4 porous nanosheets embedded in flexible graphene sheets have been synthesized through a simple freeze-drying and subsequent hydrazine treatment process. The robust structural stability of the as-prepared three-dimensional sandwich-like Co3S4–PNS/GS composite affords improved rate performance and cycling stability for both lithium and sodium storage.