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Using low cost, environment-friendly, and sustainable biomass is a unique approach to the preparation carbon-based composites for lithium ion batteries. In our research, hollow, derived microtubes (HMD) were fabricated from graphene/loofah sponge. Each microtube was wrapped with graphene, resulting in conductivity improvement, and facilitated easily controlled growth of ultra-thin MoS2 nanosheets. The method employed a simple process of soaking the HMD in graphene oxide (GO) dispersion liquid, and subsequent carbonization and activation of the HMD/rGO. When ultrathin MoS2 nanosheets were vertically and uniformly grown on the surface of the HMD/rGO, via the hydrothermal method, the HMD/rGO/MoS2 composite was obtained, and exhibited reversible lithium storage capacity of 838.2 mAh g−1 at a current density of 0.2 A g−1 after 200 cycles. This excellent electrochemical performance could be due to the high conductivity of HMD/rGO, a synergistic effect between HMD/rGO and MoS2 nanosheets, a reasonable structural design, and the high theoretical specific capacity of MoS2. Such a structure not only provides a novel, high-quality carbon template/matrix from cheap loofah sponge, but also provides a new way to design sustainable electrodes for electrochemical energy storage, and makes economical, multifunctional, carbon-based hybrids available for other applications.

The rational design of the nano structure is crucial for overcoming the inherent defect and engineering high performance of Li2MnSiO4 cathode material. In the present study, uniform coaxial carbon nanotube CNT@Li2MnSiO4@C has been designed and synthesized by an efficient step-by-step strategy and applied as high-performance cathode for lithium ion battery. It is demonstrated that the product has a uniform coaxial structure, the thickness of Li2MnSiO4 shell and outermost carbon layer is about 20 nm and 4.5 nm, respectively. This properly design can effectively improve the electric conductivity, shorten the Li ion diffusion length, relax volume change upon charge/discharge and relieve the manganese dissolution. Benefit from its unique structural features, the CNT@Li2MnSiO4@C electrode material overcomes the intrinsic disadvantage of Li2MnSiO4 of poor electronic/ionic conductivity and fast capacity fading rate, and hence exhibiting promising improvement on reversible capacity and cycling properties.

Manganese dioxide (MnO2) is an ideal electrode material for supercapacitors due to its low cost and large theoretical specific capacity. We reported the hydrothermal synthesis MnO2 nanostructures with different morphologies through the variation of hydrothermal temperature and dwell time. It was found that cauliflower-like δ-MnO2 particles are prepared at a lower temperature while the needle-like α-MnO2 nanorods are formed at a higher temperature. The morphologies of MnO2 were also affected by the hydrothermal dwell time. The needle-like α-MnO2 nanorods have the higher specific surface (114 m2 g−1) than that of the cauliflower-like δ-MnO2 particles. Electrochemical properties were evaluated using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The hierarchical multidimensional MnO2 architecture nanostructured surface with particles and nanorods, shows a maximum specific capacity (311.52 F g-1 at 0.3 A g−1). These results provided a generic guideline in developing different nanostructured electrode materials for electrochemical energy storage.

Development of carbon electrodes with high volumetric electrochemical performance is challenging for high-performance energy storage devices. In this work, we demonstrate a novel sucrose-derived porous carbon monolith (NPC-m) constructed by holey carbon nanosheets for super-high volumetric energy storages. NPC-m, derived from sucrose via a facile yet scalable and economic “bottom-up” synthesis route, exhibits a high specific surface area of 1376 m2 g−1, a narrow hole size distribution, and a high N content (∼6.65 at. %). Most importantly, a self-stacking density as high as 1.26 g cm−3 can be achieved via simple drying processes. The electrodes based on NPC-m in carbon electrodes deliver super-high volumetric capacities of 1385 mAh cm−3 (0.1 A g−1) for Li-ion batteries and 380 F cm−3 (0.5 A g−1) for supercapcacitors, highlighting their great potentials for high-performance energy storages.

We have successfully prepared three dimensional carbon nanotube foams (CNTF) by a simple environmental-friendly method. However, the as-grown CNTF shows a high electrical conductivity but a reduced specific surface area which limits its application as electrode materials in energy storage devices. In this work, the as-grown CNTF has been activated by using certain concentration of KOH aqueous solution. The results indicate that activation can enlarge the specific surface area by producing new pores with sizes from micropore to macropore, but give no important change in shape and size of the CNTF. We take the activated CNTFs as electrodes for supercapacitors and lithium-ion batteries respectively, and find that activation can clearly enhance the specific capacities and rate properties due to the enhanced specific surface area and hierarchical porous structures. The activated three dimensional CNTF materials can also be used as supporters for other active materials indicating a potential application prospects.

Sn has attracted tremendous attentions in sodium ion batteries (SIBs) for its high theoretical capacity, low cost and high electronic conductivity. However, one of the critical problems to hinder the widely practical application of SIBs is the fast capacity decay during repeated charge/discharge cycles owing to the vast volume expansion and aggregation of Sn nanoparticles. Herein, the spatially confined strategy is introduced to synthesize Sn/C@TiO2/TiN composite to address the above issues. The dual space-confined layers of carbonaceous microspheres and TiO2 could effectively buffer the volume expansion of Sn nanoparticles. Moreover, the dual conductive matrix of the inner carbon and outer TiN are favorable to enhance the electrode conductivity and accelerate Na+ and electrons transfer. In addition, the first-principles simulation is further employed to investigate the electrochemical dynamics (structural deformation) of the electrode. As a result, Sn/C@TiO2/TiN electrode exhibits a long cycle life stability (retains a capacity of 201.2 mAh/g after 500 cycles at 0.5 A/g). This spatially confined strategy might exert a profound impact on designing desirable electrode materials with long cycle life and fast redox kinetics in SIBs.

We have successfully fabricated 3D carbon nanotube foams macrostructure by direct conversing CO2. Taking these carbon nanotube foams as substrates, large scale mace-like carbon nanotube foams/Co(OH)2 ordered arrays have been fabricated by a simple hydrothermal method. Electrochemical analysis indicates that the carbon nanotube foams hybrid architectures exhibit good energy-storage performance with high specific capacity of 614.3C g−1 at 0.5 A g−1 and 444.5C g−1 at 10 A g−1 calculated based on active materials with a voltage window of 0.45 V. Besides, the electrodes also illustrate excellent long cycle life along with 96.8% specific capacity retained after 3000 cycle tests. An asymmetric supercapacitor was also assembled using carbon nanotube foams/Co(OH)2 as positive electrode and bare carbon nanotube foams as negative electrode. The highest power density and energy density of the asymmetric cell is 7.2 kW kg−1 and 13.0 Wh kg−1, respectively. Moreover, this environmental friendly template-directed CVD technique is adaptable and multitalented, and can be a general strategy for preparing a kind of three-dimensional macroscopic structures with excellent properties and novel applications.

Carbon nanotube (CNT) is an ideal electrode material for supercapacitors due to its low electronic and ionic charge-transfer resistances. Here we reported the direct synthesis 3D carbon nanotube foam (CNTF) macrostructure by conversing CO2 through template-directed chemical vapour deposition. Using this unique network structure and outstanding electrical and mechanical properties of the CNTF, as an example, we demonstrate the excellent electrochemical properties of Ni(OH)2/CNTF composite. Based on the total mass of the electrode, as high as specific capacitances of 259 and 131 F g−1 are obtained at current densities of 0.5 and 10 A g−1 respectively. Meanwhile, the electrode also exhibits excellent long cycle life along with 94.0% specific capacitance retained after 2000 cycle tests. Moreover, this template-directed CVD technique is versatile and scalable, and can be a general strategy for fabricating a broad class of three-dimensional macroscopic structures of determined shapes with excellent properties and new uses.

Ultrathin Co3O4 nanosheets with a mesoporous structure and a large surface area are hydrothermally grown on a three dimensional nickel foam. The ultrathin mesoporous Co3O4 nanosheets are grown on Ni foam with robust adhesion, which endows fast ion and electron transport, large electroactive surface area, and excellent structural stability. Such unique nanoarchitecture exhibits remarkable electrochemical performance with high capacitance and desirable cycle life. When evaluate as an electrode material for supercapacitors, the Co3O4 nanosheets electrode is able to deliver high specific capacitance of 2194 F g−1 at a current density of 1 A g−1 in 1 M KOH aqueous solution. The electrode also exhibits excellent cycling stability by retaining 93.1% of the maximum capacitance after 5000 charge-discharge cycles. The fabrication strategy presented here is facile, cost-effective, and can offer a way for energy storage device applications.

Hierarchical mesoporous conch-like Co 3 O 4 nanostructure arrays with the thickness of a few nanometers supported on Ni foam substrate have been fabricated by a hydrothermal approach together with a post-annealing treatment. The highly ordered three-dimensional (3D) nanostructure offers numerous advantages duo to the desired properties of macroporosity, including enhanced mass transport for the electrolyte flow, thereby reducing the device resistance and faster the reaction kinetics. Such unique nanoarchitecture exhibits remarkable electrochemical performance with high capacitance and desirable cycle life. When evaluate as an electrode material for supercapacitors, the Co 3 O 4 nanostructure arrays (NCAs) electrode is able to deliver high areal capacitance of 4.11 F cm −2 at a current density of 5 mA cm −2 in 2 M NaOH aqueous solution. The electrode also exhibits excellent cycling stability by retaining 93% of the maximum capacitance after 5000 charge-discharge cycles. The fabrication strategy presented here is facile, cost-effective, and can offer a new pathway for large-scale energy storage device applications.

A modified hydrothermal method was developed to synthesize tin oxide doped with highly dispersed silicon oxide. The microstructure, morphology and electrochemical performance of the mixtures were analyzed by X-ray diffraction (XRD), infra-red (IR), scanning electron microscopy (SEM) and electrochemical methods. The average size of the particles is about 30 nm. Silicon oxide as matrix should be able to support the anode changes accompanied by the formation of lithium–tin alloys, thus an improvement of the cycleability of the Li-ion battery would be expected. The electrochemical results showed that addition of silicon oxide reduces the irreversible capacity during the first discharge/charge cycle. The material delivers a charge capacity of more than 750 mAh g−1. The capacity loss per-cycle is about 0.9% after cycling 20 times. The electrochemical performance indicates that silicon oxide is an appropriate matrix and these composites are good anode candidates for application in lithium-ion batteries.