Hongsen Li

Biomass-derived porous carbon materials with sulfur and nitrogen dual-doping for energy storage

Nowadays, energy shortage is a serious socioeconomic problem. The recovery of biomass can make a very significant contribution in alleviating the burden on already-strained energy resources. Broad beans, which are abundant in amino acids and vitamins, are extensively cultivated worldwide. However, a large quantity of by-product, broad bean shells, remains unused and pollutes the environment from the incinerating and/or uncontrolled decomposition that results. In this paper, we report the synthesis of sulfur and nitrogen dual-doping porous carbon materials, for use as the electrode materials of energy storage devices, produced by carbonizing the shells of broad beans by a chemical activation. The specific capacitance of the as-prepared porous carbon material is as high as 202 F g−1, with a superior cycling performance for electric double layer capacitors at a current density of 0.5 A g−1. Furthermore, it also shows a stable performance for lithium ion batteries and sodium ion batteries, which suggests that it has a promising potential for wide applications in the field of energy storage devices.

General Strategy for Designing Core–Shell Nanostructured Materials for High-Power Lithium Ion Batteries

Because of its extreme safety and outstanding cycle life, Li(4)Ti(5)O(12) has been regarded as one of the most promising anode materials for next-generation high-power lithium-ion batteries. Nevertheless, Li(4)Ti(5)O(12) suffers from poor electronic conductivity. Here, we develop a novel strategy for the fabrication of Li(4)Ti(5)O(12)/carbon core-shell electrodes using metal oxyacetyl acetonate as titania and single-source carbon. Importantly, this novel approach is simple and general, with which we have successfully produce nanosized particles of an olivine-type LiMPO(4) (M = Fe, Mn, and Co) core with a uniform carbon shell, one of the leading cathode materials for lithium-ion batteries. Metal acetylacetonates first decompose with carbon coating the particles, which is followed by a solid state reaction in the limited reaction area inside the carbon shell to produce the LTO/C (LMPO(4)/C) core-shell nanostructure. The optimum design of the core-shell nanostructures permits fast kinetics for both transported Li(+) ions and electrons, enabling high-power performance.

Facile synthesis of N-doped carbon-coated Li4Ti5O12 microspheres using polydopamine as a carbon source for high rate lithium ion batteries

Nitrogen-doped (N-doped) carbon-coated Li4Ti5O12 microspheres are synthesized by a solution method combined with heat treatment, in which polydopamine-coated TiO2 is first prepared and subsequently transformed in situ into N-doped carbon-coated Li4Ti5O12 microspheres. Importantly, neither templates nor rigorous reaction conditions are needed in this process that makes it simple, effective and general. The thickness of the resulting N-doped carbon coating layer can be tailored by controlling the coating time of dopamine. The optimum designed N-doped carbon-coated Li4Ti5O12 microspheres with a continuous and high electronically conducting network demonstrated superior rate performance (123 mA h g−1 at 30 C) and excellent capacity retention (136.5 mA h g−1 after 200 cycles at 10 C) when used as anode material, indicating their promising application in high-rate lithium ion batteries.

Novel template-free solvothermal synthesis of mesoporous Li4Ti5O12-C microspheres for high power lithium ion batteries

A novel approach has been developed to synthesize mesoporous Li4Ti5O12-C microspheres under solvothermal conditions by a one-pot hydrolysis of TBT, chemical lithiation of TiO2 and carbonization of furfural, yielding a high-performance composite anode material for high energy/power density lithium ion batteries.

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).

Mesoporous NaTi2(PO4)3/CMK-3 nanohybrid as anode for long-life Na-ion batteries

In this work, a solvothermal strategy combined with following calcination was developed to synthesize a mesoporous NaTi2(PO4)3/CMK-3 (NTP/C) nanohybrid as a high-performance anode for next-generation Na-ion batteries (NIBs). Physicochemical characterizations demonstrated that NASICON-type structured NaTi2(PO4)3 (NTP) nanoparticles (NPs) with high crystallinity were homogeneously embedded in the mesoporous CMK-3 matrix. The mesoporous NTP/C nanohybrid as the anode for NIBs exhibited excellent electrochemical performance with high charge–discharge capability, good rate performance and long cycle life in non-aqueous electrolytes. The nanohybrid electrode delivered large specific capacities of 101, 76, 58, 39 mA h g−1 at 0.2, 0.5, 1.0 and 2.0 C, respectively, and retained it as high as 62.9 mA h g−1 even after 1000 cycles at 0.5 C. Compared to the pure NTP electrode, the mesoporous NTP/C hybrid anode with unique “meso–nano” architecture exhibited better Na-storage ability and indicated its promising application for rechargeable NIBs.

Three-dimensionally ordered porous TiNb2O7 nanotubes: a superior anode material for next generation hybrid supercapacitors

Hybrid supercapacitors are a very appealing power source with high energy density and power density because they employ both the merits of lithium ion batteries and supercapacitors. To balance such hybrid systems, the rate of the redox component must be substantially comparative to the levels of the double layer process. As far as the insertion-host material TiNb2O7 is concerned, we have used facile step electrode design consisting of the physically assisted template infusion of Ti–Nb sol into the pores of AAO followed by in situ conversion into porous TiNb2O7 nanotubes within the AAO walls under calcination, and finally making those templates dissolve away. Using such an electrode as the battery type anode and a graphene grass electrode as the capacitor type cathode, we successfully constructed a novel hybrid supercapacitor. Within a voltage range of 0–3 V, a high energy density of ∼74 W h kg−1 is achieved and it could remain as much as ∼34.5 W h kg−1 at a power of 7500 W kg−1. The present research sheds new light on the development of energy storage devices with both high energy density and high power density.

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.

Stabilized titanium nitride nanowire supported silicon core–shell nanorods as high capacity lithium-ion anodes

In this work, TiN NW supported silicon nanorods (TiN@Si NRs) are produced via direct radio frequency (RF) magnetron sputtering of Si deposition onto the surface of TiN NWs. Due to its superior mechanical stability and electrical conductivity, TiN provides more stable support and better conductive pathways for Si when compared with TiO2. The unique core–shell TiN@Si NR structure has enough void space to accommodate the large volume changes of Si during charge/discharge cycling. The novel 3D architecture electrode demonstrates exceptional electrochemical performances with ultrahigh specific capacity. Comparing with TiO2@Si NRs, TiN@Si NR electrodes exhibit improved cycling performances, which can still retain a capacity of 3258.8 mA h g−1 after 200 cycles at 1 A g−1. It should be noted that the TiN@Si NRs show an excellent rate performance even at a high current density (2256.6 mA h g−1 is realized at 10 A g−1). These results endow the electrodes with high power and long cycling stability.

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.