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Potassium-ion batteries (KIBs) are considered to be promising energy-storage-systems in the post-Li-ion batteries. Conversion and alloy reaction anode materials draw much attention owing to high theoretical capacities. However, their inherent volume expansions always block the K-ion diffusion or interrupt electron transfer to a degree, resulting in degraded performances at high rates. It is supposed that the rate capability of the anode would be improved when the avenues for ion/electron are kept expedite simultaneously. Herein, SnS2 and carbon hybrid submicro-fibers with optimized channels were prepared as integrated KIBs electrodes to clarify the effect of the bi-continuous avenues on the rate capability. In this configuration, SnS2 nanosheets are confined by carbon and further crosslinked into 3D network. The 3D carbon submicro-fibers are adopted as a network for electron transfer, while the channels play the role of ion diffusion avenues. Owing to the stable and expedite bi-continuous electron/ion avenues, the rate capability of the SnS2@C–1V1 SMF electrode (137.5 mAh g−1 at 2.0 A g−1) is improved when compared to the counterparts (3.6 mAh g−1 and 94.5 mAh g−1 at the same condition). This work will offer an important reference for the optimization design and construction of KIBs anode materials with high rate capability.

To enhance the electronic conductivity of TiO 2 , carbon-coating has been used as a simple and effective method for improving the electrochemical performances of TiO 2 in sodium ion batteries. In this work, considering the internal connection between TiO 2 and the coated carbon-layer, we synthesized carbon-coated TiO 2 composites (TiO 2 /C) via hydrothermal method and subsequent calcination, assisted with different types of surfactant as carbon sources. Due to strong electrostatic attraction, cationic surfactant CTAB (cetyltrimethyl ammonium bromide) generates a uniformly-coated carbon layer onto TiO 2 surface, which enables good electronic conductivity and fast kinetics of the product. Therefore, TiO 2 /C assisted with CTAB as carbon source (TiO 2 /C-C) shows optimal sodium storage performance with excellent specific capacity (303 mA h g −1 at 0.1 C) and satisfying cycling stability, offering promising anode for constructing high capacity sodium ion batteries.

LiBH4@xZZCO composites are successfully synthesized by confining LiBH4 in hierarchical porous ZnO/ZnCo2O4 (ZZCO) nanoparticles via a chemical impregnation method, and the effect of ZZCO on the dehydrogenation performance is systematically investigated. It is found that dehydrogenation properties of LiBH4 are significantly improved, especially for the LiBH4@2ZZCO composite. The onset desorption temperature of LiBH4@2ZZCO is decreased to 169 °C, and the majority of hydrogen release occurs at 275 °C, much lower than raw LiBH4. In addition, 8.7 wt% H2 could be released below 500 °C. Moreover, the apparent activation energy (Ea) has been reduced from 146 kJ/mol (pure LiBH4) to 120.22 kJ/mol. The improved dehydrogenation properties are attributed to the synergistic effect of nanoconfinement and destabilization of ZZCO nanoparticles.

In this paper, we report the synthesis of graphene-like MoS2/graphene hybrid by a facile lithium-assisted sonication method and its cathode application for rechargeable Mg batteries. Instrumental analyses elucidate that the composite displays a three-dimensional (3D) porous architecture constructed by exfoliated single or few MoS2 layers, and some graphene is intercalated in the MoS2 gallery with an enlarged interlayer spacing from 0.62 to 0.98 nm. The obtained MoS2/graphene hybrid exhibits high electrochemical performance with a remarkable capacity (115.9 mA h g−1) and good cyclic stability (82.5 mA h g−1 after 50 cycles). This is owing to the synergistic effect between the graphene-like MoS2 and the highly conductive graphene, which can effectively facilitate the Mg2+ ions diffusion and electrons transfer, provide abundant active sites for Mg2+ intercalation, and prevent structural collapse upon prolonged cycling.

We report on the preparation of the three dimensional (3D) network structure CuO by rapid and facile engraving method and their application as high rate anode for sodium ion battery. The CuO is rapidly synthesized by in-situ etched and oxidated the specified Cu foils within 15 min. It shows the 3D network architecture with flower-like nanosheets connected by nanowires, which provides the porous structure, short ion diffusion pathway and collaborative electronic transmission. Furthermore, the etched CuO can be directly used as anode for sodium ion battery without polymer additions or conductive agents. The electrodes exhibit excellent electrochemical performance with a high capacity of 680 mAh·g −1 at 50 mA g −1 and a reversible capacity of 280 mAh·g −1 at 1000 mA g −1 . In addition, the electrochemical reaction and detail charge/discharge process are carefully explored to discover the conversion reaction routes and the recession reason. Thus, the 3D network structure CuO might open an insight for transition-metal oxides as energy storage materials.

We report on the strategy of Cu doping inducing the nanosize effect of CoO and their application as anode for lithium ion batteries. With an increase of Cu-doped amount, the structures and morphologies of CoO have special changes. The 0.05 mol Cu-doped CoO shows straw-like bundle structure assembled by nanorods, and the nanorods consist of ultra small nanoparticles (about 6–8 nm). Meanwhile, it shows an excellent rates performance and cycle life. The capacity of 800 mA h g−1 is obtained at 0.5 C after 80 cycles. The highest discharge capacity is 580 mA h g−1 at 10 C and the discharge capacities are relatively stable for 1000 cycles as an anode for Li-ion battery. Therefore, the controllable Cu-doped CoO composite could be deemed to be a potential candidate as an anode material.

In this work, 3D hierarchical flower-like MoS 2 spheres are successfully fabricated via a hydrothermal method followed by a heat treatment. The obtained product is composed of few-layered MoS 2 nanosheets with enlarged interlayer distance (ca. 0.66 nm) of the (002) plane. Meanwhile, the hydrogen storage properties of the as-prepared MoS 2 ball milled with LiBH 4 are systematically investigated. The results of temperature programmed desorption (TPD) and isothermal measurement suggest that the LiBH 4 –MoS 2 (as-prepared) mixture exhibits favorable dehydrogenation properties in both lowering the hydrogen release temperature and improving kinetics of hydrogen release rate. LiBH 4 –MoS 2 (as-prepared) sample (the preparation mass ratio is 1:1) starts to release hydrogen at 171 °C, and roughly 5.6 wt% hydrogen is released within 1 h when isothermally heated to 320 °C, which presents superior dehydrogenation performance compared to that of the bulk LiBH 4 . The excellent dehydrogenation performance of the LiBH 4 –MoS 2 (as-prepared) mixture may be attributed to the high active site density and enlarged interlayer distance of the MoS 2 nanosheets, 3D architectures and hierarchical structures.

A facile two-step annealing process is applied to synthesize nanocage Co3O4, using cobalt-based metal-organic framework as precursor and template. The as-obtained nanocages are composed of numerous Co3O4 nanoparticles. N2 adsorption–desorption isotherms show that the as-obtained Co3O4 has a porous structure with a favorable surface area of 110.6 m2 g−1. Electrochemical tests show that nanocage Co3O4 is a potential candidate as anode for lithium-ion batteries. A reversible specific capacity of 810 mAh g−1 was obtained after 100 cycles at a high specific current of 500 mA g−1. The material also displays good rate capability, with a reversible capacity of 1069, 1063, 850, and 720 mAh g−1 at specific current of 100, 200, 800, and 1000 mA g−1, respectively. The good electrochemical performance of nanocage Co3O4 can be attributed to its unique hierarchical hollow structure, which is maintained during electrochemical cycling.

Fabricating electrode with hierarchical heterostructure is an effective method to incorporate the merits of different active materials into an electrode with desired electrochemical performance. However, heterostructure electrodes constructed layer by layer may increase the ion diffusion distances inadvertently when used for alkali metal ion batteries, though the synergistic effects of the components are exhibited. In this work, Co3O4 nanocrystallines (about 5 nm) anchor on ultrathin MnO2 nanosheets, which assemble hierarchical heterostructure hollow spheres (named as MnO2/Co3O4). When used as LIBs anode, the different dimensions of the components in MnO2/Co3O4 make them accessible for the electrolyte synchronously, without enlarging the ion diffusion distance. Moreover, the unique hierarchical hollow structure mitigates the internal mechanical stress brought by the volume variations upon cycling, preventing the electrode collapse. Therefore, the as-prepared MnO2/Co3O4 electrode not only delivers a high reversible capacity of 1209.0 mAh g−1 at 0.4 A g −1 over 300 cycles, but also exhibits long cyclic stability (a capacity of 581.8 mAh g−1 at 2.0 A g−1 after 1100 cycles). This work could provide new insight into heterostructure materials for batteries.

Mesoporous zinc cobaltite (ZnCo 2 O 4 ) microspheres have been successfully prepared by a facile solvothermal method followed by an annealing process. The as-prepared ZnCo 2 O 4 displays uniform sphere-like morphology composed of interconnected ZnCo 2 O 4 nanoparticles. The Brunauer–Emmett–Teller (BET) surface area of mesoporous ZnCo 2 O 4 microspheres is about 51.4 m 2 g −1 with dominant pore diameter of 7.5 nm. The novel ZnCo 2 O 4 material exhibits high specific capacitance of 953.2 F g −1 and 768.5 F g −1 at discharge current densities of 4 A g −1 and 30 A g −1 , respectively. The energy density can be estimated to be 26.68 Wh kg −1 at a power density of 8 kW kg −1 . The specific capacitance retention is 97.8% after 3000 cycles, suggesting its excellent cycling stability. The superior electrochemical performance is mainly attributed to the uniformity of the surface structure and the porosity of the microspheres, which benefit electrons and ions transportation, provide large electrode-electrolyte contact area, and meanwhile reduce volume change during the charge–discharge process. This method of constructing porous microspheres is very effective, yet simple, and it could be applied in other high-performance metal oxide electrode materials for electrochemical capacitors, as well as in Li-ion batteries.

Small amount of reduce graphene oxide (rGO) nanosheets modified Li 4 Ti 5 O 12 nanoparticles composite has been synthesized by a facile and environmental in-situ hydrothermal reaction with subsequent annealing. The small amount of rGO (only 1.2 wt. %) greatly improves the whole morphology and electrochemical performance of composite. The nanoparticles uniformly grow on the rGO nanosheets effective suppressing the agglomeration and enhancing the specific surface area. Meanwhile, the special discharge capacity is 187 mAh g −1 at 1 C and the high rates discharge capacity is 128 mAh g −1 at 80 C (discharge-charge time only 33s). In particular, the cells remain in good work condition after 2000 cycles at 80 C, which credibly evidence the excellent electrochemical performance as an anode for high-power LIBs.

One-dimensional porous Co 3 O 4 nanowires with different length have been successfully synthesized by thermal decomposition of Co-NA polymer precursors at various hydrothermal reaction times. The positive effects of longer nanowires and larger surface area on electrochemical performance of Co 3 O 4 samples were investigated systematically. All the as-prepared Co 3 O 4 samples display excellent discharge capacities and cycle stability on account of large surface area and porous structure, indicating great potential application of porous Co 3 O 4 nanowires for alkaline rechargeable batteries. The Co 3 O 4 -24 h sample with the longest length shows the most outstanding electrochemical performance, and displays the maximum discharge capacity of 450.1 mAh g −1 with the capacity retention of 90.4% after 100 cycles at a current density of 100 mA g −1 . Electrochemical reactions between Co and Co(OH) 2 occurring on the Co 3 O 4 electrodes are investigated by XRD, cyclic voltammetry (CV) and charge–discharge measurements.

A potential negative electrode material Co3O4@rGO is synthesized via a facile reflux condensation route. The electrochemical performances of Co3O4@rGO composite for alkaline rechargeable Ni/Co batteries have been systemically investigated for the first time. The reduced-graphene can remarkably enhance the electrochemical activity of Co3O4 materials, leading to a notable improvement of discharge capacity, cycle stability and rate capability. Interestingly, the maximum discharge capacity of Co3O4@rGO-20 (additive amount of GO is 20 mg) electrode can reach 511.4 mAh g−1 with the capacity retention of 89.1% after 100 cycles at a discharge current of 100 mA g−1. A properly electrochemical reaction mechanism of Co3O4@rGO electrode is also constructed in detail.

Using a green and effective method based on the solid state reaction between FePO4·2H2O and KBH4, high pure Fe2P nanoparticles are successfully prepared. The mass ratio of FePO4·2H2O to KBH4 has a decisive influence on the composition of the products. Moreover, Fe2P nanoparticles exhibit considerably high discharge capacities and excellent rate capability as the anode materials for nickel-based rechargeable batteries. The reversible discharge capacities are 413 and 343 mAh g−1 at currents of 100 and 500 mA g−1, respectively. It is expected that Fe2P nanoparticles have potential applications in nickel-based rechargeable batteries.

A simple solvent method is proposed for the recovery of waste LixCoO2 from lithium-ion batteries, which employs inexpensive DMF to remove the binder of PVDF. This method is convenient to manipulate and low-cost to apply. Electrochemical investigations indicate that recovered LixCoO2 materials with a small amount of S-doping exhibit excellent properties as negative materials for alkaline rechargeable Ni/Co batteries. At the discharge current density of 100 mA g−1, the LixCoO2 + 1% S electrode displays the max discharge capacity of 357 mAh g−1 and outstanding capacity retention rate of 85.5% after 100 cycles. It could overcome not only the sophisticated, energy-intensive shortcomings of conventional recycling methods, but also the high-cost restriction on alkaline rechargeable Ni/Co batteries.

A novel composite of magnetite (Fe 3 O 4 ) nanoparticles (NPs) grown on reduced graphene oxide (rGO) has been synthesized by a facile hydrothermal technique without any surfactants or templates. In this method, the growth of Fe 3 O 4 NPs and the reduction of graphene oxide (GO) are completed in one single step. Moreover, we have prepared Fe 3 O 4 microcubes and Fe 3 O 4 /carbon nanotubes (CNTs) composite under the same condition. The electrochemical properties of the as-prepared samples are investigated as advanced electrode materials for supercapacitors. It is found that the Fe 3 O 4 /rGO nanocomposite displays much higher specific capacitances and better cycle stability than those of pure Fe 3 O 4 and Fe 3 O 4 /CNTs composite. Specifically, it exhibits a high specific discharge capacitance of 220.1 F g −1 at 0.5 A g −1 and remains stable after 3000 charge/discharge cycles. The improvement of the electrochemical performances of Fe 3 O 4 /rGO may be attributed to the chemical interaction between rGO and Fe 3 O 4 , lower agglomeration and smaller particle size of Fe 3 O 4 .

Three-dimensional SnS2 hierarchitectures have been fabricated via a facile solvothermal method. A possible growth mechanism has been propounded based on the time-dependent experiments. As anode material for lithium-ion batteries, the SnS2 hierarchitectures display long-term cycle stability and excellent high-rate performance. A high specific capacity of 549.5 mA h g−1 is achieved at a current density of 100 mA g−1 after 100 discharge/charge cycles. The superior electrochemical performances of SnS2 as lithium-ion batteries anode material can be attributed to the synergistic effect of the specific porous structure and the thin nanosheets.

Co/CMK-3 composites are synthesized via a facile hydrothermal route. The electrochemical performances of Co/CMK-3 composite as the negative electrode material for alkaline rechargeable Ni/Co batteries have been systemically investigated. Electrochemical measurements show that the CMK-3 can remarkably enhance the electrochemical activity of Co, leading to a notable improvement of the discharge capacity, cycle stability and rate capability. Interestingly, the discharge capacity of Co/CMK-3 (25 mg CMK-3) electrode can reach 519.3 mAh g −1 and retains about 365.8 mAh g −1 after 100 cycles at discharge current of 100 mA g −1 . The electrochemical reaction mechanism of Co/CMK-3 composite electrode can be attributed to the electrochemical redox reaction between Co and Co(OH) 2 .

Metastable vanadium dioxide/carbon (VO 2 (B)/C) nanobelts have been successfully synthesized via a facile surfactant-free hydrothermal method using V 2 O 5 and sucrose as reactants. The VO 2 (B)/C with carbon content of 0.96 wt.% shows well-distributed nanobelt morphology with an average width of 120–200 nm, thickness of 40–60 nm and length of 1–3 μm. The nanobelts exhibit preferable electrochemical performances with high initial discharge capacity, good cycling stability and excellent high-rate performance. The initial discharge capacity can reach 218.6 mAh g −1 , and maintain 152.6 mAh g −1 after 100 cycles at 50 mA g −1 . When the current density increases to 1000 mA g −1 , the discharge capacity is still as high as 138.2 mAh g −1 . VO 2 (B)/C nanobelts would be a promising cathode material for lithium ion batteries.

Many inactive materials have been found to be helpful for improving the electrochemical performance of Co electrode in alkaline rechargeable batteries, including B, P, Si, S, Si3N4, and BN. In this paper we find for the first time that selenium has a similar effect with them. Selenium incorporation is realized through a liquid-reduction method. The obtained Co–Se sample is investigated as the negative electrode material of alkaline rechargeable battery. Experimental results demonstrate that the Co–Se sample electrode shows excellent electrochemical reversibility and considerably high charge–discharge capacity, showing a great potential to enhance the electrochemical performance of Co-based alkaline rechargeable batteries. The electrochemical reaction mechanism and function mechanism of Se are also investigated.

A potential negative electrode material (mesoporous nano-Co 3 O 4 ) is synthesized via a simple thermal decomposition of precursor Co(OH) 2 hexagonal nanosheets in the air. The structure and morphology of the samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that the nano-Co 3 O 4 is present in mesoporous hexagonal nanoparticles. The average size of holes is about 5–15 nm. The electrochemical performances of mesoporous nano-Co 3 O 4 as the active starting negative electrode material for alkaline secondary battery are investigated by galvanostatic charge–discharge and cyclic voltammetry (CV) technique. The results demonstrate that the prepared mesoporous nano-Co 3 O 4 electrode displays excellent electrochemical performance. The discharge capacity of the mesoporous nano-Co 3 O 4 electrode can reach 436.5 mAh g −1 and retain about 351.5 mAh g −1 after 100 cycles at discharge current of 100 mA g −1 . A properly electrochemical reaction mechanism of mesoporous nano-Co 3 O 4 electrode is also constructed in detail.

A series of cobalt-carbon nanotube (CNT) composites is synthesized by direct ball-milling of Co and CNT powders with different Co/CNT weight ratios. The microstructure, morphology and chemical state of the ball-milled Co-CNT composites are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It is found that metallic Co nanoparticles of 50–100 nm in size are highly dispersed on the inactive CNT matrix after ball-milling. The electrochemical performance of Co-CNT composites as negative electrode material of alkaline rechargeable batteries is investigated by galvanostatic charge–discharge, linear polarization and cyclic voltammetry (CV) techniques. The results show that the Co-CNT composite (weight ratio 5/1, BM 10 h) displays the optimized electrochemical performance, including discharge capacity and cycle stability. The reversible faradaic reaction between Co and Co(OH)2 is dominant for ball-milled Co-CNT composites.

Carbon coated LiFePO4/C cathode material is synthesized with a novel sol–gel method, using cheap FePO4·2H2O as both iron and phosphorus sources and oxalic acid (H2C2O4·2H2O) as both complexant and reductant. In H2C2O4 solution, FePO4·2H2O is very simple to form transparent sols without controlling the pH value. Pure submicrometer structured LiFePO4 crystal is obtained with a particle size ranging from 100 to 500 nm, which is also uniformly coated with a carbon layer, about 2.6 nm in thickness. The as-synthesized LiFePO4/C sample exhibits high initial discharge capacity 160.5 mAh g−1 at 0.1 C rate, with a capacity retention of 98.7% after 50th cycle. The material also shows good high-rate discharge performances, about 106 mAh g−1 at 10 C rate. The improved electrochemical properties of as-synthesized LiFePO4/C are ascribed to its submicrometer scale particles and low electrochemical impedance. The sol–gel method may be of great interest in the practical application of LiFePO4/C cathode material.

Two kinds of different Co–S microspheres with novel structure are synthesized by liquid phase chemical method (hydrothermal method and solvothermal method), and their formation mechanisms are also constructed. The electrochemical properties as negative electrode for alkaline secondary batteries are first performed using LAND battery test instrument. Co–S nest-like spheres electrode displays high reversible discharge capacity of 250 mAh g−1 and excellent cycle stability at current density 200 mA g−1. The discharge curve and CV curve confirm that the reaction occurring on Co–S alloy electrode is a reversible redox reaction of Co. The higher specific surface areas of Co–S nest-like spheres may be responsible for the higher discharge capacity.

S-Co(OH) 2 composite is prepared via a facile co-precipitation method and investigated as negative electrode of Ni/Co battery. The addition of amorphous S improves the electrochemical properties of Co(OH) 2 electrode. The discharge capacity of S-Co(OH) 2 electrode can reach 413.2 mAh g −1 and still keep about 340 mAh g −1 after 300 cycles, which is much higher than that of S-free Co(OH) 2 electrode. Amorphous S in S-Co(OH) 2 electrode shows two functions during the charge–discharge process. One is that the addition of amorphous S with high specific surface area improves the dispersion of Co(OH) 2 platelets. The other is that the dissolution of amorphous S in electrode brings the new interspaces among the Co(OH) 2 platelets, these two factors largely increase the interspaces among Co(OH) 2 platelets. More interspaces are correlated to larger contact area with alkaline solution, which is in favor of the surface electrochemical redox. Thus, the capacity utilization of Co(OH) 2 is enhanced.

Vanadium oxide nanotubes were obtained as the main product in a sol–gel reaction followed by hydrothermal treatment from V2O5 precursors and octadecylamine. The tubes consist of concentric shells of highly crystalline vanadium oxide separated by alternation organic amine layers. The vanadium oxide nanotubes are redox-active and can electrochemically insert magnesium reversibly. The electrochemical insertion magnesium properties of vanadium oxide nanotubes were studied by electrochemical impedance (EIS) and cyclic voltammogram.