Shijie Cheng

A high performance sulfur-doped disordered carbon anode for sodium ion batteries

Sulfur-doped disordered carbon is facilely synthesized and investigated as an anode for sodium ion batteries. Benefiting from the high sulfur doping (∼26.9 wt%), it demonstrates a high reversible capacity of 516 mA h g−1, excellent rate capability as well as superior cycling stability (271 mA h g−1 at 1 A g−1 after 1000 cycles).

Layered SnS2 cross-linked by carbon nanotubes as a high performance anode for sodium ion batteries

A SnS2@CNT nanocomposite as a high performance sodium-ion battery anode material is prepared via a facile sintering route. Benefiting from the high conductivity and strong mechanical properties of the CNTs, the SnS2@CNT with a unique nanostructure of 2D SnS2 sheets cross-linked by 1D CNTs, delivers a high reversible capacity of 758 mA h g−1 at 100 mA g−1 and an excellent cyclability with a capacity retention of 87% over 300 cycles. More impressively, over 445 mA h g−1 can be obtained at a high current density of 5 A g−1, demonstrating a superior rate capability.

Glycol Derived Carbon- TiO 2 as Low Cost and High Performance Anode Material for Sodium-Ion Batteries

Carbon coated TiO2 (TiO2@C) is fabricated by a convenient and green one-pot solvothermal method, in which ethylene glycol serve as both the reaction medium and carbon source without the addition of any other carbon additives. During the solvothermal process, ethylene glycol polymerize and coordinate with Ti4+ to form the polymeric ligand precursor, then the polymer brushes carbonize and convert to homogeneous carbon layer firmly anchored on the TiO2 nanoparticles (~1 nm thickness). The polymerization and carbonization process of the ethylene glycol is confirmed by FT-IR, Raman, TG and TEM characterizations. Benefiting from the well-dispersed nanoparticles and uniform carbon coating, the as-prepared TiO2@C demonstrate a high reversible capacity of 317 mAh g−1 (94.6% of theoretical value), remarkable rate capability of 125 mAh g−1 at 3.2 A g−1 and superior cycling stability over 500 cycles, possibly being one of the highest capacities reported for TiO2.

Molten salt electrochemical synthesis of sodium titanates as high performance anode materials for sodium ion batteries

Sodium ion batteries are attractive alternatives to lithium ion batteries for stationary energy storage technology, and titanates are considered as promising anode materials for sodium ion batteries. Herein, a series of sodium titanates were synthesized via a simple, fast and controllable electrochemical route from solid TiO2 in molten salts of NaF–NaCl–NaI. For the first time, the as-prepared Na0.23TiO2 and Na0.46TiO2 were utilized as anode materials for sodium ion batteries, with a sodium storage capacity of 185 mA h g−1 and 215 mA h g−1 after 200 cycles, respectively. High rate and long term tests indicated the excellent cycle performance due to the formation of a 3D porous electrode structure during the long term charge/discharge processes.

Na3V2(PO4)3/C synthesized by a facile solid-phase method assisted with agarose as a high-performance cathode for sodium-ion batteries

A type of Na3V2(PO4)3/C (NVP/C) cathode material for sodium ion batteries was synthesized via a facile solid-phase method. Agarose, a natural polysaccharide from seaweed that can form a 3D network structure through hydrogen bonds in polar solvents, was used as a carbon source and a medium to form NVP/C particles as nanograins with a thin layer of carbon coating in a 3D carbon network. As the cathode, the NVP/C material exhibited a reversible capacity of 116 mA h g−1 at 1C, which is very close to its theoretical capacity (117.6 mA h g−1), with a capacity retention of 97.3% after 500 cycles. At 20C, the NVP/C had a capacity of 100 mA h g−1 and still kept a relatively stable capacity of 78 mA h g−1 after being cycled 7000 times. Based on the excellent performance of the obtained cathode material, a sodium ion full cell was assembled with S-doped carbon as the anode, which delivered 110 mA h g−1 of discharge capacity at 200 mA h g−1 (calculated using NVP as the cathode) and displayed an average voltage of around 1.7 V. All of these results imply that the prepared NVP/C has potential for application in sodium ion batteries for large-scale energy storage.

Poly(vinylidene fluoride)-based hybrid gel polymer electrolytes for additive-free lithium sulfur batteries

The permeation of dissolved lithium polysulfides across the porous polyolefin-based commercial separator is a major hindrance for using lithium sulfur batteries (LSBs). In this work, the poly(vinylidene fluoride) (PVDF)-based gel polymer electrolyte (GPE) with a compact morphology to block polysulfide penetration is prepared using a simple solution-casting method, and the strategy of incorporating poly(ethylene oxide) and nano zirconium dioxide is applied to guarantee electrolyte uptake and Li+ mobility. Superior to the commercial separator with liquid electrolyte, the LSB assembled with additive-free GPE exhibits a high initial capacity of 1429 mA h g−1, coulombic efficiency of 96% at 0.2C and improved rate performance. After 500 cycles at 1C, the LSB could still deliver a capacity of 847.2 mA h g−1, with a low fading rate of 0.05%. The LSB with high sulfur loading (5.2 mg cm−2) could attain a high areal capacity of 4.6 mA h cm−2. Results of scanning electron microscopy suggest that such a hybrid GPE could effectively protect the lithium anode from polysulfide corrosion. Therefore, this novel membrane of hybrid PVDF-based GPE provides a simple and effective method to establish high-performance LSBs.

A two-dimensional hybrid of SbOx nanoplates encapsulated by carbon flakes as a high performance sodium storage anode

Metallic Sb has been extensively researched as a Na storage anode due to its high capacity and low cost, but it suffers from poor cycling stability stemming from its huge volume change (∼390%) during cycling. Herein, a unique two-dimensional hybrid structure of SbOx nanoplates encapsulated by carbon flakes (SbOx@CF) was fabricated by templating with soluble NaCl. Benefiting from its two-dimensional structure providing rapid Na+ ion uptake and removal and uniform coating endowing a stable buffer layer, the hybrid presents a high reversible capacity (451 mA h g−1) and excellent rate capability (114 mA h g−1 at 4 A g−1), as well as stable cycling (442 mA h g−1 after 100 cycles with 98% capacity retention). This work opens up a facile, controllable, economical and extendable approach to prepare advanced two-dimensional metal oxides for batteries and supercapacitors.

Nickel sulfide nanospheres anchored on reduced graphene oxide in situ doped with sulfur as a high performance anode for sodium-ion batteries

NiSx–rGOS is prepared via a facile and cost effective hydrothermal process, with the structure of ultrafine NiSx nanospheres uniformly wrapped in the in situ S-doped rGO matrix. The uniform nanostructural NiSx and high conductivity of S-doped rGO (rGOS) can effectively increase the ionic and electronic conductivity of the NiSx–rGOS composite, thus resulting in high capacity utilization of the active materials. Moreover, the buffering layer provided by the rGOS matrix can accommodate the volume change of the NiSx and protect the nanoparticles from aggregation during the repeated cycling process. The as-prepared NiSx–rGOS composite demonstrates a high reversible capacity of 516 mA h g−1 at 0.2 A g−1 with a capacity retention of 96.8% over 100 cycles and a remarkable rate performance of 414 mA h g−1 at 4 A g−1, possibly exhibiting the best electrochemical performances of nickel sulfide for sodium-ion batteries.

Facile synthesis of an Fe3O4/FeO/Fe/C composite as a high-performance anode for lithium-ion batteries

Fe3O4/FeO/Fe nanoparticles coated with amorphous carbon are prepared via a facile and scalable in situ-reduction solid synthesis route as high-performance anode material for lithium ion batteries (LIBs). The amorphous carbon coating is produced by carbonization of glucose in the precursor, leading to partial reduction of Fe3+ in situ and a tight intermolecular contact between Fe3O4/FeO/Fe nanoparticles and the carbon layer. The formation of Fe in the composite dramatically increases the conductivity of the electrode, making a significant contribution to the enhancement of electrochemical performance. When used as anode materials in lithium ion batteries, the as-prepared Fe3O4/FeO/Fe/C composite shows super high rate capability (685, 545, and 407 mA h g−1 at 2, 5, and 10C, respectively, 1C = 1 A g−1) and excellent cycling performance (900 mA h g−1 after 500 cycles at 1C).

A polyimide–MWCNTs composite as high performance anode for aqueous Na-ion batteries

A polyimide–MWCNT composite (PNP@CNT) synthesized from 1,4,5,8-naphthalenetetracarboxylic-dianhydride (NTCDA) and phenylene diamine (PDA) was investigated as a novel anode for aqueous Na-ion batteries. This composite demonstrates a high reversible capacity of 149 mA h g−1 at quite a low potential of −0.65 V (vs. SCE), superior rate capability and long-term cycling stability. The feasibility of PNP@CNTs in aqueous Na-ion full batteries is also confirmed in conjunction with the Na0.44MnO2 cathode, possibly serving as a high performance aqueous Na host anode for large-scale electric energy storage applications.