Molecular template derived ultrathin N-doped carbon layer on cobalt selenide nanobelts for durable and rapid sodium storage

Sodium-ion batteries(SIBs)are an attractive battery system because of similar characteristics to lithium-ion batteries(LIBs)and large Na element abundance.Nevertheless,exploring stable,high-capacity and high-rate anode materials for SIBs is still challenging now.Herein,diethylenetriamine(DETA)molecular template derived ultrathin N-doped carbon(NC)layer decorated CoSe_(2)nanobelts(CoSe_(2)/NC)are prepared by solvothermal reaction followed by calcination process.The CoSe_(2)/NC exhibits large potential as an anode for SIBs.Experiments and theoretical calculations reveal that the in situ formed conductive ultrathin NC layer can not only relieve the volume change of CoSe_(2)but also accelerate electron and ion transport.In addition,the nanobelt structure of CoSe_(2)/NC with abundant exposed active sites can obviously accelerate the electrochemical kinetics.Under the synergistic effect of special nanobelt structure and NC layer,the rate as well as cycling performances of CoSe_(2)/NC are obviously improved.A superior capacity retention of 94.8%is achieved at 2 A·g^(-1)after 2000 cycles.When using Na3V2(PO4)3 cathodes,the pouch full batteries can work steadily at 0.5 C,verifying the application ability.CoSe_(2)/NC anodes also exhibit impressive performances in LIBs and potassium-ion batteries(PIBs).

Preparation and electrochemical characterization of ultrathin WO3-x/C nanosheets as anode materials in lithium ion batteries

Ultrathin two-dimensional （2D） nanomaterials offer unique advantages compared to their counterparts in other dimensionalities. O-vacancies in such materials allow rapid electron diffusion. Carbon doping often improves the electric conductivity. Considering these merits, the WO3-x/C ultrathin 2D nanomaterial is expected to exhibit excellent electrochemical performance in Li-ion batteries. Here, ultrathin WO3-xC nanosheets were prepared via an acid-assisted one-pot process. The as-prepared WO3-x/C ultrathin nanosheets showed good electrochemical performance, with an initial discharge capacity of 1,866 mA·h·g^-1 at a current density of 200 mA·g^-1 After 100 cycles, the discharge and charge capacities were 662 and 661 mA·h·g^-1, respectively. The reversible capacity of the WO3-x/C ultrathin nanosheets exceeded those of WO3 and WOg-x nanosheets. The electrochemical testing results demonstrated that WO3-x/C ultrathin nanosheets are promising alternative anode materials for Li-ion batteries.

Bipolar electrode architecture enables high-energy aqueous rechargeable sodium ion battery

Aqueous rechargeable sodium ion batteries(ARSIBs),with intrinsic safety,low cost,and greenness,are attracting more and more attentions for large scale energy storage application.However,the low energy density hampers their practical application.Here,a battery architecture designed by bipolar electrode with graphite/amorphous carbon film as current collector shows high energy density and excellent rate-capability.The bipolar electrode architecture is designed to not only improve energy density of practical battery by minimizing inactive ingredient,such as tabs and cases,but also guarantee high rate-capability through a short electron transport distance in the through-plane direction instead of in-plane direction for traditional cell architecture.As a proof of concept,a prototype pouch cell of 8 V based on six Na_(2)MnFe(CN)_(6)||NaTi_(2)(PO_(4))_(3)bipolar electrodes stacking using a“water-in-polymer”gel electrolyte is demonstrated to cycle up to 4,000 times,with a high energy density of 86 Wh·kg^(−1)based on total mass of both cathode and anode.This result opens a new avenue to develop advance high-energy ARSIBs for grid-scale energy storage applications.