Shengyang Dong

Biomass derived carbon for energy storage devices

Electrochemical energy storage devices are becoming increasingly more important for reducing fossil fuel energy consumption in transportation and for the widespread deployment of intermittent renewable energy. The applications of different energy storage devices in specific situations are all primarily reliant on the electrode materials, especially carbon materials. Biomass-derived carbon materials are receiving extensive attention as electrode materials for energy storage devices because of their tunable physical/chemical properties, environmental concern, and economic value. In this review, recent developments in the biomass-derived carbon materials and the properties controlling the mechanism behind their operation are presented and discussed. Moreover, progress on the applications of biomass-derived carbon materials as electrodes for energy storage devices is summarized, including electrochemical capacitors, lithium–sulfur batteries, lithium-ion batteries, and sodium-ion batteries. The effects of the pore structure, surface properties, and graphitic degree on the electrochemical performance are discussed in detail, which will guide further rational design of the biomass-derived carbon materials for energy storage devices.

Pseudocapacitive behaviours of Na2Ti3O7@CNT coaxial nanocables for high-performance sodium-ion capacitors

Hybrid sodium-ion capacitors (NICs) have tremendous potential in large-scale energy storage applications due to their low cost, long lifetime and high power. However, it remains a great challenge to find a desirable anode material with fast kinetics and superior cycle life. Here an applicable strategy to in situ grow Na2Ti3O7 on 1D CNTs as an anode material for sodium-ion capacitors is presented. Benefiting from the unique 1D nanostructure and the presence of pseudocapacitive charge storage mechanism, the Na2Ti3O7@CNT electrode exhibits excellent electrochemical performance with high rate capability and superb cycling stability. Moreover, a high performance hybrid NIC is also fabricated by using Na2Ti3O7@CNTs as an anode and activated carbon derived from the outer peanut shell as a cathode, which delivers high energy density (58.5 W h kg−1), high power density (3000 W kg−1), and long term cycle life (retaining ca. 75% of its original capacity at 0.4 A g−1 after 4000 cycles).

From biomolecule to Na3V2(PO4)3/nitrogen-decorated carbon hybrids: highly reversible cathodes for sodium-ion batteries

Sodium ion batteries (SIBs) working at room temperature offer promising opportunities for renewable energy storage applications because of the abundant supply and low cost of sodium, low capacity, inferior rate capability and limited cycle life remain a significant challenge in their electrochemical operations. Herein, we report the preparation of hierarchically Na3V2(PO4)3/nitrogen-decorated carbon hybrids via solvothermal reaction using biomolecule of adenosine 5′-triphosphate disodium salt (ATP), as a novel precursor and environmentally friendly multifunctional source, simultaneously including sodium, phosphorus, carbon, nitrogen. The results demonstrate that Na3V2(PO4)3 nanocrystals are encapsulated in interconnected carbon nanosheets with moderate nitrogen doping (2.88%) to form a bundle-like structure, where the carbon nanosheets not only serve as a highly conducting pathway facilitating electron and ion transport, but as a shielding matrix to accommodate volume changes upon electrochemical cycling; thus, improving stability and reversibility of the Na3V2(PO4)3 cathode. Thus, the obtained materials deliver a high reversible capacity of 110.9 mA h g−1 at a low current rate of 0.2 C, as well as outstanding rate performance, suggesting that the Na3V2(PO4)3/nitrogen-doped carbon hybrids are promising cathode materials to be used in high-performance sodium ion batteries.

Zinc cobalt sulfide nanosheets grown on nitrogen-doped graphene/carbon nanotube film as a high-performance electrode for supercapacitors

To improve the energy density of supercapacitors, a new type of electrode material with high electrochemical activity and favorable morphology is extremely desired. Ternary metal sulfides with higher electrochemical capacity and activity than mono-metal sulfides hold great promise in the field of energy storage devices. Herein, an advanced electrode composed of zinc cobalt sulfide nanosheets supported on sandwich-like nitrogen-doped graphene/carbon nanotubes (NGN/CNTs) film has been successfully fabricated through a two-step synthesis. Benefiting from the characteristic features and 3D electrode architectures, the Zn0.76Co0.24S electrode exhibits a high specific capacitance of 2484 F g−1 at 2 A g−1 and excellent cycling stability (almost no capacitance fading after 10000 cycles at 30 A g−1). This creative nanostructure design of ternary transition metal sulfides could provide a promising prospect for application in energy storage devices. Moreover, an asymmetric supercapacitor was also fabricated by using Zn0.76Co0.24S/NGN/CNTs film as the positive electrode and NGN/CNTs film as the negative electrode, exhibiting a high energy density of 50.2 W h kg−1 at 387.5 W kg−1 and superior cycling stability of 100% initial capacity retention over 2000 cycles. This creative nanostructure design could provide a promising new way to develop high-performance supercapacitors and shed new light on configuring carbon-based ternary transition metal sulfide electrode materials in energy storage and conversion devices.

Preparation of ZnCo2O4 nanoflowers on a 3D carbon nanotube/nitrogen-doped graphene film and its electrochemical capacitance

Homogeneous ZnCo2O4 nanoflowers have been synthesized on a 3D layered structure of carbon nanotubes/nitrogen-doped graphene (NGN/CNTs) film by a hydrothermal process and subsequent calcination method. The ZnCo2O4 nanoflowers have an average diameter of 4 μm, and are composed of petals less than 100 nanometers. The as-synthesized ZnCo2O4/NGN/CNT film can be directly used as a flexible electrode with a high specific capacitance of 1802 F g−1 at 1 A g−1 and excellent cycling stability (almost 0% fade after 4000 sustaining charge/discharge at 10 A g−1). These results suggest that the obtained electrode has a promising application prospect in flexible energy conversion/storage devices. In addition, a binder-free asymmetric supercapacitor has been synthesized with the ZnCo2O4/NGN/CNT film as the positive electrode and the NGN/CNT film as the negative electrode. This demonstrates superior energy density (≈37.19 W h kg−1 at 750 W kg−1) and power density (≈14.992 kW kg−1 at 14.16 W h kg−1).

Porous NiCo2O4 nanotubes as a noble-metal-free effective bifunctional catalyst for rechargeable Li–O2 batteries

Porous NiCo2O4 nanotubes have been successfully synthesized using a facile and cost-effective electrospinning method and used as a noble-metal-free catalyst for rechargeable Li–O2 batteries. The as-synthesized NiCo2O4 nanotubes possess hollow cavities and porous walls, and were found to significantly improve the electrochemical performance of Li–O2 batteries, by endowing them with a high initial discharge capacity, reduced overpotential as well as good rate capability. Excellent cycling stability over 110 cycles with a highly discharged voltage platform of 2.4 V at 200 mA gc−1 was achieved. By means of FESEM, XRD, Raman spectroscopy and GITT analysis, toroidal-shaped Li2O2 particles were identified as the dominant discharge product and it was revealed that the Li2O2 can be completely decomposed during the charging process, indicating its superior reversibility as an effective bifunctional catalyst for Li–O2 batteries. All the results indicated that the porous NiCo2O4 nanotubes expressed intriguing properties and great potential applications as a noble-metal-free effective bifunctional catalyst for rechargeable Li–O2 batteries.

Self-supported electrodes of Na2Ti3O7 nanoribbon array/graphene foam and graphene foam for quasi-solid-state Na-ion capacitors

There is an urgent need but it is still a huge challenge to integrate high energy and power density with high safety in a single energy storage device. Addressing this issue largely depends on design of new energy storage systems with novel electrode architectures. Herein, a novel electrochemical energy storage device called a quasi-solid-state Na-ion capacitor (QSS-NIC) is designed based on a 3D self-supported Na2Ti3O7 nanoribbon array/graphene foam (NTO/GF) anode and graphene foam (GF) cathode, and a Na-ion conducting gel polymer as the electrolyte and separator, without any binders, conducting additives or metal current collectors. Benefiting from the unique 3D self-supported cathode and anode, the GF//NTO/GF configuration achieves a high energy density of 70.6 W h kg−1 and high power density of 4000 W kg−1 on the basis of the mass of both electrodes, and a prominent cycling stability over 5000 cycles (capacitance retention ∼73.2%). This work successfully demonstrates a proof of concept of QSS-NIC as a high performance energy storage device based on two self-supported electrodes, which could provide a feasible approach to bridge the performance gap between capacitors and Na-ion batteries.

Nb2O5 nanoparticles encapsulated in ordered mesoporous carbon matrix as advanced anode materials for Li ion capacitors

Lithium ion capacitors (LICs), which have high energy density and power density and benefit from the combination of the merits of batteries and supercapacitors, have been attracted tremendous attention. The sluggish faradaic battery anode is a big challenge for the development of high-performance LICs. In this study, an Nb2O5/ordered mesoporous carbon (CMK-3) nanocomposite has been synthesized via the nanocasting technology using CMK-3 as the hard template and NbCl5 as the precursor. The Nb2O5/CMK-3 electrode exhibits significantly enhanced electrochemical performance in terms of specific capacity, rate capability and cyclic stability when compared with bulk Nb2O5. Furthermore, a high performance LIC composed of the Nb2O5/CMK-3 nanocomposite as the anode and activated carbon derived from peanut shell as the cathode was constructed, which exhibits a high energy density of 43.9 W h kg−1 (at a power density of 87.5 W kg−1) and high power density of 8750 W kg−1 (at an energy density of 24.4 W h kg−1). Such outstanding performance mainly stems from the synergic effects between the mesoporous carbon matrices and the well-dispersed active material nanoparticles, which increase electronic conductivity and the reactivity of Nb2O5.