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Selenium–sulfur solid solutions show unique advantages beyond sulfur and selenium as cathode materials for lithium batteries. Herein, we propose a dual-confined SexSy-based cathode with a three-dimensional (3D) network structure where Se0.4S0.6 is first encapsulated in double-layered hollow carbon spheres (DLHCs) and embedded by 3D graphene-like material (3DG) shells. The dissolution of polysulfides/ polyselenides in the cathode is effectively inhibited through dual confinement from DLHCs and 3DG as well as chemical binding between sulfur and selenium. Benefiting from the indispensable advantages of Se0.4S0.6 and the uniquely designed host architecture, the 3DG-DLHC-Se0.4S0.6 cathode delivers a high reversible capacity of 627 mAh g−1 at 0.2 A g−1 after 200 cycles, good rate capability of 533 mAh g−1 at 2 A g−1, and outstanding long cycling stability over 500 cycles with Coulombic efficiency almost reaching 100%.

In this work, the V2O3 nanoparticles (NPs) with ultrathin carbon shells were synthesized by a facile solvothermal process. The V2O3 NPs were about 30 nm and contained a carbon shell of about 2 nm thick. The V2O3 NPs were homogeneously dispersed and loosely packed. When used as anode material, the V2O3 core-shell NPs showed a reversible capacity up to 525 mA h g−1 at 200 mA g−1 over 200 cycles with good cycle stability and rate capability. The excellent electrochemical performance promotes its practical application in lithium-ion batteries.

Polyvinyl alcohol grafted poly (acrylic acid) (PVA-g-PAA) is synthesized through graft polymerization of acrylic acid (AA) onto PVA backbone via a free radical reaction. PVA-g-PAA is used as a water-soluble binder for silicon (Si) anodes in lithium-ion batteries (LIBs). The enhanced adhesion strength, excellent flexibility and high electrolyte uptake after grafting reaction render PVA-g-PAA a robust binder for Si anodes. Compared to linear PVA, PAA and CMC, optimal Si-PVA-g-10PAA electrode exhibits better cycle stability, higher Coulombic efficiency and more excellent rate capability, possessing a high electrical conductivity, low SEI/charge transfer resistance and fast lithium-ion diffusion coefficient. PVA-g-PAA binder not only maintains the electrode's mechanical and electrical integrity, facilitates a favorable electrochemical kinetics, but also assists in forming a stable SEI layer on Si surface upon long-term cycling. Such a strategy sheds light on the design of novel polymer binders for practical applications of high-capacity active materials with great volume change.

A dual-confined nanostructured reactor, featured with the small-sized platinum nanoparticles embedded in dendritic mesoporous silica nanospheres with a hierarchical porous graphene-like carbon protection shell, is designed and synthesized as an efficient SeS2 host for high-performance lithium-selenium/sulfur batteries. The rationally designed host framework, which combines the merits of strong chemical interaction effect, abundant catalytic active sites, and excellent conducting network, can realize efficient anchoring and fast conversion of lithium polysulfides/polyselenides during the electrochemical processes. Thus, this SeS2-based cathode shows a high initial capacity of 1013 mAh g−1 at 0.2 A g−1 and an outstanding cycling stability, with a capacity of 426 mAh g−1 over 500 cycles at 2 A g−1, corresponding to a low capacity decay of 0.07% per cycle. This study demonstrates a novel and efficient approach to overcome the hurdles of current lithium-sulfur systems for stable rechargeable batteries.

A novel molybdenum disulfide/carbon (MoS2/C) nanocomposite is synthesized by a simple hydrothermal method using glucose as a carbon source and Pluronic F127 as promoting agent in presence of MoS2 nanoparticles and followed by carbonization. Pluronic F127 is used as an essential agent which inhibits the spontaneous formation of carbon microspheres during the hydrothermal reaction. The composite electrode exhibits excellent cycling stability and rate capability, delivering a reversible capacity of 882.6 mA h g−1 at a current density of 50 mA g−1 and a capacity retention of 82.8% after 100 cycles at a current density of 100 mA g−1. At a higher current density of 300/500 mA g−1, it still retains a capacity of 603.6/461.6 mA h g−1 respectively, as compared to 295.6/228.4 mA h g−1 for the pristine MoS2 electrode. The composite shows favorable electrochemical kinetics compared with pristine MoS2 due to the incorporation of homogenous conductive carbon layer and its nanostructured morphology.

High voltage LiNi0.5Mn1.5O4 cathode material was prepared by two steps solid-state method with additive PEG dispersant. XRD, SEM, XPS and electrochemical tests have been carried out, and the results show that the PEG can promote the pyrolysis of MnO2 and limit the impurities formation. The secondary particle can also be effectively restrained in the pre-calcination of MnO2 and NiO, and the effect can be last to the final product. The capacity from Mn3+/Mn4+ couple was reduced and the whole capacity can reach 140.7 mAh g−1 with the retention rate of 81.33% after 100 cycles at 0.2C. Meanwhile, the product has better rate performance and surface stability than those prepared by traditional two-step solid-state method.

Xanthan Gum (XG) is systematically investigated and employed as water soluble binder for LiFePO4 (LFP) cathode in Li-ion batteries. XG binder exhibits good thermal stability and processes abundant functional groups such as carboxyl and hydroxyl, displaying a better adhesion strength of 0.085 N cm−1 than sodium carboxymethyl cellulose (CMC, 0.050 N cm−1), but inferior to polyvinylidene difluoride (PVDF, 0.170 N cm−1). The Rheology test reveals that the viscosity of LFP slurry prepared with XG binder is higher than that of PVDF, resulting in a better dispersion of LFP and carbon black particles. The electrochemical performances of LFP-XG electrode are investigated and compared with those of aqueous CMC and conventional PVDF binder. LFP-XG displays better cycle stability and rate performance than PVDF, comparable to CMC, which retains 55.3% capacity of C/5 at 5 C as compared to PVDF (34.8%) and CMC (57.8%). Cyclic voltammetry (CV) shows that LFP-XG has smaller redox polarization and faster lithium diffusion rate than PVDF while electrochemical impedance spectroscopy (EIS) measurement at specified intervals reveals its more favorable electrochemical kinetics than that with PVDF, similar to CMC, thus better rate capability. Scanning electron microscopy (SEM) displays that LFP-XG has a more homogenous distribution of LFP and conductive carbon black particles with XG before cycling and better maintains its structure integrity after 100 cycles than that of PVDF. Furthermore, LFP-XG is observed to process a high ionic conductivity supported by dQ/dV profiles.

Silicon oxycarbonitride (SiOCN) composites with different carbon contents were synthesized by pyrolysis of precursors generated from aldimine condensation of 3-aminopropyltriethoxysilane (APTES) with different aldehydes and simultaneous hydrolysis of APTES. Both SiOCN-1 and SiOCN-5 composites, derived from formaldehyde and glutaraldehyde respectively, display similar bulky structure composed by aggregated nanospheres with a diameter of 70–100 nm. SiOCN-5 has a higher carbon content of 30.4% than 15.9% for SiOCN-1, while a lower specific surface area of 38.2 m2 g−1 than 76.0 m2 g−1 for SiOCN-1. SiOCN/S cathodes with sulfur loading of 1.2–1.5 mg cm−2 were fabricated using SiOCN as sulfur host on different current collector of aluminum foil (AL) or carbon paper (CP). When using aluminum foil as current collector, SiOCN-5/S-AL cathode exhibits better electrochemical performance than SiOCN-1/S-AL, primarily due to the higher electrical conductivity of SiOCN-5 comparing with SiOCN-1. When using porous carbon paper as current collector, SiOCN-5/S-CP cathode shows the best cycling performance with a discharge capacity of 648.9 mA h g−1 at 0.2C after 100 cycles. Even at a high rate of 1C, SiOCN-5/S-CP also exhibits an excellent cycling stability, delivering a reversible discharge capacity of 374.5 mA h g−1 after 500 cycles with a capacity retention of 73.0%.

Nanostructured sulfur cathode with a multiple core-shelled structure, featured with the spherical double-layered hollow carbon/sulfur composite (DLHC/S) coated with a conductive layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), is designed and synthesized for lithium-sulfur batteries. Transmission electron microscope images of DLHC/S single nanoparticle show that the sulfur aggregates predominantly in the interior space between the two carbon shells by using a vacuum infiltration process. The electric conductivity of DLHC/S@PEDOT:PSS increases over 5 times as comparing to DLHC/S without PEDOT:PSS coating. The composite cathode exhibits a high reversible capacity of 1089 mAh g−1 at 0.2C and superior rate capacity of 510 mAh g−1 even at 4 C, and also remarkable cycling stability with a capacity decay of 0.097% per cycle after 500 cycles at 1 C. The excellent electrochemical performances for DLHC/S@PEDOT:PSS cathode are primarily attributed to the engineering of the unique multiple core-shell structure of DLHC/S@PEDOT:PSS, which inhibits the sulfur dissolution into the electrolyte and the polysulfide shuttle effect, together with the conductivity enhancement due to PEDOT:PSS coating.