Two-dimensional transition-metal carbide materials (termed MXene) have attracted huge attention in the field of electrochemical energy storage due to their excellent electrical conductivity, high volumetric capacity, etc. Herein, with inspiration from the interesting structure of pillared interlayered clays, we attempt to fabricate pillared Ti3C2 MXene (CTAB–Sn(IV)@Ti3C2) via a facile liquid-phase cetyltrimethylammonium bromide (CTAB) prepillaring and Sn4+ pillaring method. The interlayer spacing of Ti3C2 MXene can be controlled according to the size of the intercalated prepillaring agent (cationic surfactant) and can reach 2.708 nm with 177% increase compared with the original spacing of 0.977 nm, which is currently the maximum value according to our knowledge. Because of the pillar effect, the assembled LIC exhibits a superior energy density of 239.50 Wh kg–1 based on the weight of CTAB–Sn(IV)@Ti3C2 even under higher power density of 10.8 kW kg–1. When CTAB–Sn(IV)@Ti3C2 anode couples with commercial AC cathode, LIC reveals higher energy density and power density compared with conventional MXene materials.Keywords: lithium-ion capacitors; MXene; nanocomposites; pillared structure; Ti3C2;

Lithium–sulfur (Li–S) battery is one of the most attractive candidates for the next-generation energy storage system. However, the intrinsic insulating nature of sulfur and the notorious polysulfide shuttle are the major obstacles, which hinder the commercial application of Li–S battery. Confining sulfur into conductive porous carbon matrices with designed polarized surfaces is regarded as a promising and effective strategy to overcome above issues. Herein, we propose to use microalgaes (Schizochytrium sp.) as low-cost, renewable carbon/nitrogen precursors and biological templates to synthesize N-doped porous carbon microspheres (NPCMs). These rational designed NPCMs can not only render the sulfur-loaded NPCMs (NPCSMs) composites with high electronic conductivity and sulfur content, but also greatly suppress the diffusion of polysulfides by strongly physical and chemical adsorptions. As a result, NPCSMs cathode demonstrates a superior reversible capacity (1030.7 mA h g–1) and remarkable capacity retention (91%) at 0.1 A g–1 after 100 cycles. Even at an extremely high current density of 5 A g–1, NPCSMs still can deliver a satisfactory discharge capacity of 692.3 mAh g–1. This work reveals a sustainable and effective biosynthetic strategy to fabricate N-doped porous carbon matrices for high performance sulfur cathode in Li–S battery, as well as offers a fascinating possibility to rationally design and synthesize novel carbon-based composites.Keywords: biotemplating method; lithium−sulfur batteries; microalgaes; nitrogen doping; porous carbon microspheres;

Considerable research efforts have been devoted to the lithium–sulfur battery due to its advantages such as high theoretical capacity, high energy density, and low cost. However, the shuttle effect and the irreversible deposition of Li2S result in severe capacity decay and low Coulombic efficiency. Herein, we discovered that the transition metal phosphides cannot only trap the soluble polysulfides but also effectively catalyze the decomposition of Li2S to improve the utilization of active materials. Compared with the cathodes without transition metal phosphides, the cathodes based on Ni2P, Co2P, and Fe2P all exhibit higher reversible capacity and improved cycling performance. The Ni2P-added electrode delivers capacities of 1165, 1024, 912, 870, and 812 mAh g–1 at 0.1, 0.2, 0.5, 1.0, and 2.0 C, respectively, and high capacity retention of 96% after 300 cycles at 0.2 C. Even with a high sulfur mass loading of 3.4 mg cm–2, the capacity retention remains 90.3% after 400 cycles at 0.5 C. Both density functional theory calculations and electrochemical tests reveal that the transition metal phosphides show higher adsorption energies and lower dissociation energies of Li2S than those of carbon materials.

•Lithiophilic ZnO quantum dots decorated hierarchical porous carbon was prepared.•The stripping/plating behavior of Li within the ZnO@HPC scaffold was investigated.•Dendrite-free lithium metal anode was achieved within the ZnO@HPC matrix.•3D Li within ZnO@HPC delivers much better electrochemical performance.Lithium metal as an attractive anode material has been widely used in the advanced energy storage technology such as lithium-sulfur and lithium-air batteries. However, suffering from the uncontrollable deposition, growth of lithium dendrite and the serious volume change within cycling process, the commercial application of lithium anode is impeded by the safety hazards and limited span-life. Here, we demonstrate a kind of bamboo-derived 3D hierarchical porous carbon decorated by ZnO quantum dots which can serve as a lithiophilic scaffold for dendrite-free Li metal anode. This carbon scaffold is stable against the serious volumetric change during cycles. In addition, the 3D porous scaffold can reduce the effective local current density. Most importantly, the lithiophilic ZnO quantum dots within the carbon can be used to induce lithium deposition. Notably, lithium metal up to 131 mAh cm−2 can be confined within ZnO@HPC, achieving acceptable volume expansion, considerable reduction in overpotential and effective dendrite suppression. Thus, 3D Li within ZnO@HPC scaffold could exhibit better capability and much lower voltage hysteresis when compared with Li foil in cells paired with LiCoO2. The function of the ZnO decorated 3D hierarchical porous carbon scaffold might provide innovative insights into the design principles for metallic lithium anodes.A subtle 3D porous carbon with the uniformly anchored ZnO quantum dots as the inducing agent for lithium deposition has been designed as promising matrix for dendrite-free lithium metal anode.Download high-res image (355KB)Download full-size image

•Fe3O4/C nanoparticles were successfully synthesized via a facile micro-tube method.•Easily available, carbon-rich kapok fibres play a dual role as the carbon source and the biotemplate.•As-prepared Fe3O4/C electrode exhibits notable cycle potential for anode material for LIBs.Kapok fibres were used as micro-tube biotemplate and bio-carbon source to synthesise Fe3O4/C composites, which were then utilised as anode materials. Fe3O4 nanoparticles were grown uniformly onto the external surface and internal channel of kapok carbon fibres. The flexibility, high specific surface area and electronic conduction of kapok fibres can buffer the volume expansion as well as inhibit the aggregation of Fe3O4 nanoparticles. Thus, the electrical integrity and structural of the Fe3O4/C composites electrode during lithiation/delithiation processes. The Fe3O4/C composites electrode delivers a high reversible capacity of 596 mA h g−1 after 100 cycles and an ultra-high coulombic efficiency approaching 100%. The high electrochemical performance of the Fe3O4/C composites can be caused by the synergistic effect of the Fe3O4 nanoparticles and the structure of kapok carbon fibres.Download high-res image (161KB)Download full-size image

Lithium–sulfur (Li–S) batteries have been the apple of people's eye with their high energy density and high theoretical capacity. However, challenges arising from the nature of materials have plagued the commercialization of this technology, among which the notorious shuttle effect, serious volume expansion and insulating nature of sulfur and its low order reduced products are key problems. Constructing nanocomposites of sulfur with heteroatom-doped carbon nanostructures is an efficient and promising approach. However, there are limited reports on boron and oxygen dual doping treatment used in lithium–sulfur batteries, let alone explaining an in-depth mechanism. Herein, we prepared boron and oxygen dually doped multi-walled carbon nanotubes (BO-MWNTs) as the host material for sulfur. With the successful introduction of boron and oxygen, the electrical conductivity of the carbon material is obviously increased. Furthermore, the effect of doped heteroatoms on the carbon/sulfur (C/S) composites and its mechanistic understanding are explored and confirmed via both experiments and Density Functional Theory (DFT) calculations. It is found that B and O dual dopants can offer abundant adsorptive sites and lead to strong chemisorption between the carbon and the sulfides. This dual doping treatment leads to improved cycling stability and rate capability performance of the C/S cathode. Hence, the proposed innovative mechanistic understanding of boron and oxygen doping on carbon materials is hopeful to shed light on the designing principle for advanced C/S composites.

Recently, great attention has been paid to all-solid-state lithium–sulfur (Li–S) batteries for their high energy density and security. But large-scale application of this technology is hindered by the poor ionic conductivity of solid-state electrolytes and high interfacial resistance at ambient temperature. In addition, seeking an appropriate carbon matrix for solid-state Li–S batteries is challenging. Herein, with the purpose of addressing these problems, N-doped carbon nanosheets (N-CNs) as a matrix for optimizing a sulfur cathode was successfully prepared. Furthermore, we fabricated innovative poly(ethylene oxide) (PEO)-based solid-state polymer electrolytes (SSPEs) containing ionic liquid grafted oxide nanoparticles (IL@NPs), which showed high ionic conductivity at low temperatures. Additionally, the differences among IL@NPs based on ZrO2, TiO2, and SiO2 are compared. The electrolyte with IL@ZrO2 showed the highest ionic conductivity of 4.95 × 10−4, 2.32 × 10−4 S cm−1 at 50 and 37 °C, respectively. With advanced and innovative designs in both cathode and electrolyte, our solid-state Li–S battery exhibits improved electrochemical performance. The battery with SSPEs based on IL@ZrO2 delivered a high specific capacity of 986, 600 mA h g−1 at 50 and 37 °C, respectively. It's believed that this strategy, using IL@NPs added SSPEs and the N-CNs/S cathode, may shed light on prospective applications with all-solid-state Li–S batteries.

A quasi-hexagonal prism-shaped carbon nitride (H-C3N4) was synthesized from urea-derived C3N4 (U-C3N4) using an alkaline hydrothermal process. U-C3N4 decomposition followed by hydrogen bond rearrangement of hydrolyzed products leads to the formation of a quasi-hexagonal prism-shaped structure. The H-C3N4 catalysts displayed superior activity in the photoreduction of CO2 with H2O compared to U-C3N4. The enhanced photocatalytic activities can be attributed to the promotion of incompletely coordinated nitrogen atom formation in the C3N4 molecules.

Pyrite FeS2 decorated sulfur-doped carbon (FeS2@S-C) fibers have been successfully synthesized by a facile bio-templating method and applied as the anode material for lithium ion batteries (LIBs). Cotton was used as both the carbon source and the template. SEM and TEM results showed that the FeS2 nanoparticles fabricated using 0.2 M FeSO4 were uniformly embedded in or attached on the surface of the carbon fibers. FeS2@S-C synthesized with 0.2 M FeSO4 showed the best cycle stability and rate capability, which retained a high reversible specific capacity of 689 mAh g−1 after 100 cycles. The specific capacities are about 1200, 900, 700, 550 and 400 mAh g−1 after every 10 cycles at 0.1, 0.2, 0.5, 1 and 2 A g−1. The excellent electrochemical performance can be ascribed to the highly conductive sulfur-doped carbon and the homogeneous distribution of FeS2 nanoparticles. It is believed that the S-doped carbon matrix acts as an effective buffer layer helping relieve the volume strain as well as a hinder preventing FeS2 from aggregating during cycling, which ensure the high electrochemical performance. This kind of low-cost anode with high specific capacity and improved cycling stability show potential application for high capacity lithium-ion batteries.

Silicon oxycarbide (Si–O–C) materials with high specific capacity are considered as a promising anodic material alternative to commercial graphite for advanced Li-ion batteries. However, the rapid capacity fading and poor rate performance are the main obstacles for practical application and still remain a large challenge. In this work, microalgae (Nannochloropsis) served as a biological template and carbon source to synthesize Si–O–C microspheres with the assistance of supercritical CO2 fluid. Compared to conventional artificial templates, microalgae is abundant, renewable and available, and can be regarded as a promising biological template. Meanwhile, supercritical CO2 fluid with high penetration, high diffusivity and high dissolving capacity can serve as a superior solvent to guarantee the efficient mass transfer and uniform dispersion of precursors. As anodic materials for Li-ion batteries, Si–O–C microspheres exhibit a high reversible specific capacity of 450 mA h g−1 at a current density of 0.1 A g−1 over 200 cycles, excellent rate cycling stability and high coulombic efficiency (100%). The discovery of this novel strategy to fabricate Si–O–C materials presents possibilities for energy storage applications.

Two-dimensional transition metal carbide materials called MXenes show potential application for energy storage due to their remarkable electrical conductivity and low Li+ diffusion barrier. However, the lower capacity of MXene anodes limits their further application in lithium-ion batteries. Herein, with inspiration from the unique metal ion uptake behavior of highly conductive Ti3C2 MXene, we overcome this impediment by fabricating Sn4+ ion decorated Ti3C2 nanocomposites (PVP-Sn(IV)@Ti3C2) via a facile polyvinylpyrrolidone (PVP)-assisted liquid-phase immersion process. An amorphous Sn(IV) nanocomplex, about 6–7 nm in lateral size, has been homogeneously anchored on the surface of alk-Ti3C2 matrix by ion-exchange and electrostatic interactions. In addition, XRD and TEM results demonstrate the successful insertion of Sn4+ into the interlamination of an alkalization-intercalated Ti3C2 (alk-Ti3C2) matrix. Due to the possible “pillar effect” of Sn between layers of alk-Ti3C2 and the synergistic effect between the alk-Ti3C2 matrix and Sn, the nanocomposites exhibit a superior reversible volumetric capacity of 1375 mAh cm–3 (635 mAh g–1) at 216.5 mA cm–3 (100 mA g–1), which is significantly higher than that of a graphite electrode (550 mAh cm–3), and show excellent cycling stability after 50 cycles. Even at a high current density of 6495 mA cm–3 (3 A g–1), these nanocomposites retain a stable specific capacity of 504.5 mAh cm–3 (233 mAh g–1). These results demonstrate that PVP-Sn(IV)@Ti3C2 nanocomposites offer fascinating potential for high-performance lithium-ion batteries.Keywords: lithium-ion battery; MXene; nanocomposites; Ti3C2;

The further development of electrode materials with high capacity and excellent rate capability presents a great challenge for advanced lithium-ion batteries. Herein, we demonstrate a battery-capacitive synchronous lithium storage mechanism based on a scrupulous design of TiC/NiO core/shell nanoarchitecture, in which the TiC nanowire core exhibits a typical double-layer capacitive behavior, and the NiO nanosheet shell acts as active materials for Li+ storage. The as-constructed TiC/NiO (32 wt % NiO) core/shell nanoarchitecture offers high overall capacity and excellent cycling ability, retaining above 507.5 mAh g–1 throughout 60 cycles at a current density of 200 mA g–1 (much higher than theoretical value of the TiC/NiO composite). Most importantly, the high rate capability is far superior to that of NiO or other metal oxide electrode materials, owing to its double-layer capacitive characteristics of TiC nanowire and intrinsic high electrical conductivity for facile electron transport during Li+ storage process. Our work offers a promising approach via a rational hybridization of two electrochemical energy storage materials for harvesting high capacity and good rate performance.Keywords: core/shell nanoarchitecture; lithium storage mechanism; lithium-ion batteries; metal oxides; titanium carbide;

Hollow α-Fe2O3 microcubes were fabricated by a facile hydrothermal method in an ethanol–water co-solvent system. The as-synthesized microcubes have a uniform size with an edge length of about 1.5 μm. Time and solvent proportion dependent experiments reveal that the ethanol adsorption and surface-protected etching mechanisms play key roles in the formation hollow cubic structures. Compared with their solid counterparts, hollow α-Fe2O3 microcubes show an enhanced electrochemical performance in terms of long-term cycling (458 mA h g−1 at a current density of 100 mA g−1 after 100 cycles) and high rate capability (859, 855, 688 and 460 mA h g−1 at current densities of 100, 200, 500 and 1000 mA g−1, respectively). These remarkable electrochemical properties can be attributed to the unique hollow microstructure, which could retain structural stability, relieve stress and increase reaction areas.

•Boron carbide nanoflakes were successfully synthesized via a bamboo-based carbon thermal reduction method.•A fluoride-assisted VLS nucleation and VS growth mechanism were proposed.•We studied the resistivity of boron carbide nanoflakes via in situ TEM techniques for the first time.Boron carbide nanoflakes have been successfully synthesized by a facile and cost-effective bamboo-based carbon thermal reduction method. The majority of the boron carbide products exhibited a flake-like morphology with lateral dimensions of 0.5–50 μm in width and more than 50 μm in length, while the thickness was less than 150 nm. The structural, morphological, and elemental analyses demonstrated that these nanoflakes grew via the fluoride-assisted vapor–liquid–solid combined with vapor–solid growth mechanism. The corresponding growth model was proposed. In addition, the electrical property of individual boron carbide nanoflake was investigated by an in situ two point method inside a transmission electron microscope. The resistivity of boron carbide nanoflakes was measured to be 0.14 MΩ cm.Graphical abstractB4C nanoflakes were synthesized via a facile and cost-effective bamboo-based carbon thermal reduction method.

Hollow porous micro/nanostructures with high surface area and shell permeability have attracted tremendous attention. Particularly, the synthesis and structural tailoring of diverse hollow porous materials is regarded as a crucial step toward the realization of high-performance electrode materials, which has several advantages including a large contact area with electrolyte, a superior structural stability, and a short transport path for Li+ ions. Meanwhile, owing to the inexpensive, abundant, environmentally benign, and renewable biological resources provided by nature, great efforts have been devoted to understand and practice the biotemplating technology, which has been considered as an effective strategy to achieve morphology-controllable materials with structural specialty, complexity, and related unique properties. Herein, we are inspired by the natural microalgae with its special features (easy availability, biological activity, and carbon sources) to develop a green and facile biotemplating method to fabricate monodisperse MnO/C microspheres for lithium-ion batteries. Due to the unique hollow porous structure in which MnO nanoparticles were tightly embedded into a porous carbon matrix and form a penetrative shell, MnO/C microspheres exhibited high reversible specific capacity of 700 mAh g–1 at 0.1 A g–1, excellent cycling stability with 94% capacity retention, and enhanced rate performance of 230 mAh g–1 at 3 A g–1. This green, sustainable, and economical strategy will extend the scope of biotemplating synthesis for exploring other functional materials in various structure-dependent applications such as catalysis, gas sensing, and energy storage.Keywords: biotemplate; hollow; lithium-ion batteries; microalgae; MnO/C; porous structure

NbC nanowires (NWs) have been successfully synthesized by a bamboo-based carbon-thermal method and used as potential platinum catalyst support for direct methanol fuel cells (DMFCs). The NbC NWs show a highly oriented growth behavior, high electrical conductivity, and outstanding oxidation resistance. Well-deposited platinum (Pt) nanoparticles with the average size of about 6 nm were highly dispersed on the surface of the NbC NWs via sodium borohydride reduction method. Compared with conventional Pt/C (Vulcan XC-72) catalyst, the Pt/NbC NWs catalyst presented a distinctly enhanced methanol oxidation reaction (MOR) by a negative shift in the onset potential and an increase of the peak current density. Meanwhile, the Pt/NbC NW catalyst showed excellent electrochemical stability, which could be attributed to little change of electrochemical surface area during methanol oxidation. On the basis of these intrinsic properties and one-dimensional nanoarchitecture, the NbC NWs will be attractive as a promising catalyst support in DMFCs.

In this work, hierarchically porous NiO/C microspheres were successfully synthesized via a facile biotemplating method using natural porous lotus pollen grains as both the carbon source and the template. The as-prepared hierarchically porous NiO/C microspheres exhibited a large specific surface area and multiple pore size distribution, which could effectively increase the electrochemical reaction area and allow better penetration of the electrolyte. The Raman results also confirmed that the pollen grains have been well carbonized, which could provide good electronic conductivity. The specific capacities of the porous NiO/C microspheres after every 10 cycles at 0.1, 0.5, 1, and 3 A g−1 are about 698, 608, 454 and 352 mAh g−1. As an anode material in a Li ion half-cell, these unique hybrid hierarchically porous NiO/C microspheres exhibited fascinating electrochemical performance.

A visible-light photocatalytic, mesoporous, hierarchical spirulina/TiO2 composite with dye-sensitized surface was fabricated through a one-step hydrothermal process. The microstructure, mesoporous characteristics, surface morphology, as well as the visible-light photocatalytic activities are studied. The spirulina/TiO2 had an anatase phase and an enhanced harvesting of visible light. It was found that the spirulina/TiO2 composite exhibited higher specific surface area with narrow distributed mesopores. The photocatalytic activity of spirulina/TiO2 was evaluated by decolorizing methyl orange aqueous solutions under visible light irradiation. As a bio-template, spirulina prevents TiO2 from further aggregating and provides photosynthesis pigments as in situ dye-sensitizing source. The enlarged specific surface area and dye-sensitized surface improved the visible-light photocatalytic activity of spirulina/TiO2.

Unique amorphous FePO4 with particle size ranging from 20 to 80 nm has been successfully synthesized by a new cost-effective electrochemical method. This FePO4 possesses a mesoporous structure with specific surface area of 65.2 m2 g−1 and dominant pore diameter of 23.6 nm. The basic formation mechanism has been discussed. These amorphous mesoporous FePO4 nanoparticles can be used as precursors to prepare LiFePO4/C nanocrystals with porous structure. The obtained LiFePO4/C cathode materials exhibit excellent cycling performances. At a 0.5 C rate, the discharge capability is above 140.0 mA h g−1 and the capacity retention rate is higher than 98% after 50 cycles. The microstructural and electrochemical analyses reveal that these amorphous mesoporous FePO4 nanoparticles are the perfect precursors to prepare LiFePO4/C composite. Furthermore, this facile, cost-effective and green electrochemical strategy can be easily scaled up for commercialization, and also could open avenues towards synthesizing other mesoporous phosphate materials.Graphical abstractThe schematic diagram of formation mechanism for mesoporous FePO4 nanoparticles.Highlights► We synthesize amorphous mesoporous FePO4 via a new electrochemical method. ► The specific surface area is 65.2 m2 g−1, the dominant pore diameter is 23.6 nm. ► The LiFePO4/C prepared from FePO4 exhibits excellent electrochemical performance.

Here, we report a new biotemplating method to synthesize hierarchical LiFePO4/C microstructures using native spirulina as both the carbon source and the template. Owing to its unique hierarchical microstructure, spirulina-templated LiFePO4/C exhibits remarkable electrochemical performance as cathode materials for lithium ion batteries. This facile strategy may open avenues towards replicating specific biological structures for phosphate materials in other potential applications.

Self-assembled mesoporous LiFePO4 (LFP) with hierarchical spindle-like architectures has been successfully synthesized via the hydrothermal method. Time dependent X-ray diffraction, scanning electron microscopy, and cross section high resolution transmission electron microscopy are used to investigate the detailed growth mechanism of these unique architectures. Reaction time and pH value play multifold roles in controlling the microstructures of LFP. The LFP particles are uniform mesoporous spindles, which are comprised of numerous single-crystal LFP nanocrystals. As the cathode material for lithium batteries, LFP exhibits high initial discharge capacity (163 mAh g−1, 0.1 C), excellent high-rate discharge capability (111 mAh g−1, 5 C), and cycling stability. These enhanced electrochemical properties can be attributed to this unique microstructure, which will remain structural stability for long-term cycling. Furthermore, nanosizing of LFP nanocrystals can increase the electrochemical reaction surface, enhance the electronic conductivity, and promote lithium ion diffusion.Graphical abstractHighlights► A growth model of hierarchical spindle-like LiFePO4 has been proposed. ► The mesoporous structure remains the structural stability for long-term cycling. ► Nanocrystals achieve higher surface area and shorter Li+ diffusion length.

Li3V2−xNbx(PO4)3/C cathode materials were synthesized by a sol–gel method. X-ray diffraction patterns demonstrated that the appropriate addition of Nb did not destroy the lattice structure of Li3V2(PO4)3, and enlarged the unit cell volume, which could provide more space for lithium intercalation/de-intercalation. Transmission electron microscopy and energy dispersive X-ray spectroscopy analysis illustrated that Nb could not only be doped into the crystal lattice, but also form an amorphous (Nb, C, V, P and O) layer around the particles. As the cathode materials of Li-ion batteries, Li3V2−xNbx(PO4)3/C (x ≤ 0.15) exhibited higher discharge capacity and better cycle stability than the pure one. At a discharge rate of 0.5C, the initial discharge capacity of Li3V1.85Nb0.15(PO4)3/C was 162.4 mAh/g. The low charge-transfer resistances and large lithium ion diffusion coefficients confirmed that Li3V2−xNbx(PO4)3/C samples possessed better electronic conductivity and lithium ion mobility. These improved electrochemical performances can be attributed to the appropriate amount of Nb doping in Li3V2(PO4)3 system by enhancing structural stability and electrical conductivity.

LiFePO4/C composite cathode materials with carbon nano-interconnect structures were synthesized by one-step solid state reaction using low-cost asphalt as both carbon source and reducing agent. Based on the thermogravimetry, differential scanning calorimetry, transmission electron microscopy and high-resolution transmission electron microscopy, a growth model was proposed to illustrate the formation of the carbon nano-interconnect between the LiFePO4 grains. The LiFePO4/C composite shows enhanced discharge capacity (150 mAh g−1) with excellent capacity retention compared with the bare LiFePO4 (41 mAh g−1) due to the electronically conductive nanoscale networking provided by the asphalt-based carbon. The results prove that the asphalt is a perfect carbon source and reduction agent for cost-effective production of high performance LiFePO4/C composite.

Spherical LiFePO4/C powders were synthesized by the conventional solid-state reaction method via Ni doping. Low-cost asphalt was used as both the reduction agent and the carbon source. An Ni-doped spherical LiFePO4/C composite exhibited better electrochemical performances compared to an un-doped one. It presented an initial discharge capacity of 161 mAhg−1 at 0.1 C rate (the theoretical capacity of LiFePO4 with 5 wt% carbon is about 161 mAhg−1). After 50 cycles at 0.5 C rate, its capacity remained 137 mAhg−1 (100% of the initial capacity) compared to 115 mAhg−1 (92% of the initial capacity) for an un-doped one. The electrochemical impedance spectroscopy analysis and cyclic voltammograms results revealed that Ni doping could decrease the resistance of LiFePO4/C composite electrode drastically and improve its reversibility.

Lithium–sulfur (Li–S) batteries have been the apple of people's eye with their high energy density and high theoretical capacity. However, challenges arising from the nature of materials have plagued the commercialization of this technology, among which the notorious shuttle effect, serious volume expansion and insulating nature of sulfur and its low order reduced products are key problems. Constructing nanocomposites of sulfur with heteroatom-doped carbon nanostructures is an efficient and promising approach. However, there are limited reports on boron and oxygen dual doping treatment used in lithium–sulfur batteries, let alone explaining an in-depth mechanism. Herein, we prepared boron and oxygen dually doped multi-walled carbon nanotubes (BO-MWNTs) as the host material for sulfur. With the successful introduction of boron and oxygen, the electrical conductivity of the carbon material is obviously increased. Furthermore, the effect of doped heteroatoms on the carbon/sulfur (C/S) composites and its mechanistic understanding are explored and confirmed via both experiments and Density Functional Theory (DFT) calculations. It is found that B and O dual dopants can offer abundant adsorptive sites and lead to strong chemisorption between the carbon and the sulfides. This dual doping treatment leads to improved cycling stability and rate capability performance of the C/S cathode. Hence, the proposed innovative mechanistic understanding of boron and oxygen doping on carbon materials is hopeful to shed light on the designing principle for advanced C/S composites.

Recently, great attention has been paid to all-solid-state lithium–sulfur (Li–S) batteries for their high energy density and security. But large-scale application of this technology is hindered by the poor ionic conductivity of solid-state electrolytes and high interfacial resistance at ambient temperature. In addition, seeking an appropriate carbon matrix for solid-state Li–S batteries is challenging. Herein, with the purpose of addressing these problems, N-doped carbon nanosheets (N-CNs) as a matrix for optimizing a sulfur cathode was successfully prepared. Furthermore, we fabricated innovative poly(ethylene oxide) (PEO)-based solid-state polymer electrolytes (SSPEs) containing ionic liquid grafted oxide nanoparticles (IL@NPs), which showed high ionic conductivity at low temperatures. Additionally, the differences among IL@NPs based on ZrO2, TiO2, and SiO2 are compared. The electrolyte with IL@ZrO2 showed the highest ionic conductivity of 4.95 × 10−4, 2.32 × 10−4 S cm−1 at 50 and 37 °C, respectively. With advanced and innovative designs in both cathode and electrolyte, our solid-state Li–S battery exhibits improved electrochemical performance. The battery with SSPEs based on IL@ZrO2 delivered a high specific capacity of 986, 600 mA h g−1 at 50 and 37 °C, respectively. It's believed that this strategy, using IL@NPs added SSPEs and the N-CNs/S cathode, may shed light on prospective applications with all-solid-state Li–S batteries.

Here, we report a new biotemplating method to synthesize hierarchical LiFePO4/C microstructures using native spirulina as both the carbon source and the template. Owing to its unique hierarchical microstructure, spirulina-templated LiFePO4/C exhibits remarkable electrochemical performance as cathode materials for lithium ion batteries. This facile strategy may open avenues towards replicating specific biological structures for phosphate materials in other potential applications.

In this work, hierarchically porous NiO/C microspheres were successfully synthesized via a facile biotemplating method using natural porous lotus pollen grains as both the carbon source and the template. The as-prepared hierarchically porous NiO/C microspheres exhibited a large specific surface area and multiple pore size distribution, which could effectively increase the electrochemical reaction area and allow better penetration of the electrolyte. The Raman results also confirmed that the pollen grains have been well carbonized, which could provide good electronic conductivity. The specific capacities of the porous NiO/C microspheres after every 10 cycles at 0.1, 0.5, 1, and 3 A g−1 are about 698, 608, 454 and 352 mAh g−1. As an anode material in a Li ion half-cell, these unique hybrid hierarchically porous NiO/C microspheres exhibited fascinating electrochemical performance.

Hollow α-Fe2O3 microcubes were fabricated by a facile hydrothermal method in an ethanol–water co-solvent system. The as-synthesized microcubes have a uniform size with an edge length of about 1.5 μm. Time and solvent proportion dependent experiments reveal that the ethanol adsorption and surface-protected etching mechanisms play key roles in the formation hollow cubic structures. Compared with their solid counterparts, hollow α-Fe2O3 microcubes show an enhanced electrochemical performance in terms of long-term cycling (458 mA h g−1 at a current density of 100 mA g−1 after 100 cycles) and high rate capability (859, 855, 688 and 460 mA h g−1 at current densities of 100, 200, 500 and 1000 mA g−1, respectively). These remarkable electrochemical properties can be attributed to the unique hollow microstructure, which could retain structural stability, relieve stress and increase reaction areas.