A novel single lithium-ion (Li-ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4-styrenesulfonyl)(trifluoromethyl(S-trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI⁻), and high-molecular-weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass-transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li-ion transference number (t_Li⁺=0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li-ion conductivity as high as 1.35×10⁻⁴ S cm⁻¹ at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries.

A novel single lithium-ion (Li-ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4-styrenesulfonyl)(trifluoromethyl(S-trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI⁻), and high-molecular-weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass-transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li-ion transference number (t_Li⁺=0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li-ion conductivity as high as 1.35×10⁻⁴ S cm⁻¹ at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries.

A new type of concentrated electrolyte composed of Li[(FSO₂)N(SO₂CF₃)] (LiFTFSI), Li[N(SO₂F)₂] (LiFSI), and ether solvents can improve the cycling stability of lithium (Li) metal and inhibit Li-metal dendritic growth. The high average coulombic efficiency of >95 % and excellent cycling performance of >250 cycles for the Li|copper cells have been achieved, even at a high current density of 3 mA cm⁻². Moreover, the Li|LiFePO₄ cell exhibits superior cycling stability with capacity retention of >92 % at 0.2 C for more than 200 cycles and excellent C-rate capability.

Batteries and supercapacitors are critical devices for electrical energy storage with wide applications from portable electronics to transportation and grid. However, rechargeable batteries are typically limited in power density, while supercapacitors suffer low energy density. Here, a novel symmetric Na-ion pseudocapacitor with a power density exceeding 5.4 kW kg⁻¹ at 11.7 A g⁻¹, a cycling life retention of 64.5% after 10 000 cycles at 1.17 A g⁻¹, and an energy density of 26 Wh kg⁻¹ at 0.585 A g⁻¹ is reported. Such a device operates on redox reactions occurring on both electrodes with an identical active material, viz., Na₃V₂(PO₄)₃ encapsulated inside nanoporous carbon. This device, in a full-cell scale utilizing highly reversible and high-rate Na-ion intercalational pseudocapacitance, can bridge the performance gap between batteries and supercapacitors. The characteristics of the device and the potentially low-cost production make it attractive for hybrid electric vehicles and low-maintenance energy storage systems.

The alkali-ion storage in spinel lithium titanate (Li₄Ti₅O₁₂) is comprehensively investigated in this work. In Li₄Ti₅O₁₂, Na storage is more dependent on the particle size compared to Li storage. Electrochemical results show a Na-storage capacity from 150 to 16 mAh g⁻¹, with increasing particle size from 50 to 500 nm, whereas the Li-storage capacity appears to be independent of particle size. The Na-storage rate capability in Li₄Ti₅O₁₂ is much worse than that of Li, probably because of the sluggish Na⁺ diffusion in Li₄Ti₅O₁₂. Ab initio molecular dynamics simulations also indicate that this can be attributed to the slow diffusion kinetics of Na⁺ in spinel Li₄Ti₅O₁₂.

Transition metal compounds based on conversion reactions are promising electrode materials for lithium-ion batteries due to their higher lithium storage capacity compared with currently available commercial battery electrodes. Most of the studies on these materials in the literature focus on transition metal oxides and fluorides, and not much work on transition metal sulphides has been reported, partially due to their relatively poor electrochemical performance. Here, synthesis and characterization of a series of solid solution Fe_xMn_1-xS (x = 0.2, 0.5, 0.8) monosulphide compounds is reported. Interestingly, hexagonal FeS and cubic MnS can form a solid solution of Fe_xMn_1-xS (x < 0.57). It is demonstrated that the lithium storage voltage can be tuned by changing the Fe concentration in the Fe_xMn_1-xS matrix; meanwhile, the discharge-charge coulombic efficiency and cycle stability of Fe_xMn_1-xS are greatly enhanced in comparison with that of pure MnS. A half cell using Fe_0.5Mn_0.5S as electrode material achieves a high first cycle coulombic efficiency of 78.0% and a high reversible capacity of ca. 477 mAh g⁻¹ after 35 cycles, while for pure MnS the first cycle coulombic efficiency is only 45.9% and the capacity rapidly fades to ≈200 mAh g⁻¹ after 15 cycles. Although the solid solution state of Fe_0.5Mn_0.5S cannot be retained during conversion reaction as indicated by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM), the initial discharge “polarization”, which has been considered as one of the major hurdles for conversion reaction, can be significantly reduced by this type of material design. In addition, the size and distribution of the nucleated nanophases might also be altered by the initial solid solution state of Fe_0.5Mn_0.5S, contributing to the improved electrochemical performance reported here.

Na₃V₂(PO₄)₃ is one of the most important cathode materials for sodium-ion batteries, delivering about two Na extraction/insertion from/into the unit structure. To understand the mechanism of sodium storage, a detailed structure of rhombohedral Na₃V₂(PO₄)₃ and its sodium extracted phase of NaV₂(PO₄)₃ are investigated at the atomic scale using a variety of advanced techniques. It is found that two different Na sites (6b, M1 and 18e, M2) with different coordination environments co-exist in Na₃V₂(PO₄)₃, whereas only one Na site (6b, M1) exists in NaV₂(PO₄)₃. When Na is extracted from Na₃V₂(PO₄)₃ to form NaV₂(PO₄)₃, Na⁺ occupying the M2 site (CN = 8) is extracted and the rest of the Na remains at M1 site (CN = 6). In addition, the Na atoms are not randomly distributed, possibly with an ordered arrangement in M2 sites locally for Na₃V₂(PO₄)₃. Na⁺ ions at the M1 sites in Na₃V₂(PO₄)₃ tend to remain immobilized, suggesting a direct M2-to-M2 conduction pathway. Only Na occupying the M2 sites can be extracted, suggesting about two Na atoms able to be extracted from the Na₃V₂(PO₄)₃ structure.

Layered sodium titanium oxide, Na₂Ti₃O₇, is synthesized by a solid-state reaction method as a potential anode for sodium-ion batteries. Through optimization of the electrolyte and binder, the microsized Na₂Ti₃O₇ electrode delivers a reversible capacity of 188 mA h g⁻¹ in 1 M NaFSI/PC electrolyte at a current rate of 0.1C in a voltage range of 0.0–3.0 V, with sodium alginate as binder. The average Na storage voltage plateau is found at ca. 0.3 V vs. Na⁺/Na, in good agreement with a first-principles prediction of 0.35 V. The Na storage properties in Na₂Ti₃O₇ are investigated from thermodynamic and kinetic aspects. By reducing particle size, the nanosized Na₂Ti₃O₇ exhibits much higher capacity, but still with unsatisfied cyclic properties. The solid-state interphase layer on Na₂Ti₃O₇ electrode is analyzed. A zero-current overpotential related to thermodynamic factors is observed for both nano- and microsized Na₂Ti₃O₇. The electronic structure, Na⁺ ion transport and conductivity are investigated by the combination of first-principles calculation and electrochemical characterizations. On the basis of the vacancy-hopping mechanism, a quasi-3D energy favorable trajectory is proposed for Na₂Ti₃O₇. The Na⁺ ions diffuse between the TiO₆ octahedron layers with pretty low activation energy of 0.186 eV.

Highly ordered mesoporous crystalline MoSe₂ is synthesized using mesoporous silica SBA-15 as a hard template via a nanocasting strategy. Selenium powder and phosphomolybdic acid (H₃PMo₁₂O₄₀) are used as Se and Mo sources, respectively. The obtained products have a highly ordered hexagonal mesostructure and a rod-like particle morphology, analogous to the mother template SBA-15. The UV-vis-NIR spectrum of the material shows a strong light absorption throughout the entire visible wavelength region. The direct bandgap is estimated to be 1.37 eV. The high surface area MoSe₂ mesostructure shows remarkable photocatalytic activity for the degradation of rhodamine B, a model organic dye, in aqueous solution under visible light irradiation. In addition, the synthesized mesoporous MoSe₂ possess a reversible lithium storage capacity of 630 mAh g⁻¹ for at least 35 cycles without any notable decrease. The rate performance of mesoporous MoSe₂ is much better than that of analogously synthesized mesoporous MoS₂, making it a promising anode for the lithium ion battery.

A uniform and thin amorphous layer of a CN compound was coated on porous Li₄Ti₅O₁₂ by pyrolysis of urea on its surface at a rather low temperature of 400 °C in an Ar atmosphere. Such a CN coating layer greatly improved the electrochemical performance of Li₄Ti₅O₁₂. After coating, Li₄Ti₅O₁₂ showed good rate and excellent cycling performance. Reversible capacities for the coated sample of 134 and 105 mAh g⁻¹ were obtained at current rates of 5C and 10C, respectively, in the voltage range of 1–2.2 V, which is approximately two and five times higher than those of pristine Li₄Ti₅O₁₂ at the same current rates. Excellent capacity retention of 95.8 % was achieved for the coated sample after 2000 cycles in a half cell at a 2C rate.

An approach to synthesize monodisperse nanospheres with nanoporous structure through a solvent extraction route using an acid–base-coupled extractant has been developed. The nanospheres form through self-assembly and templating by reverse micelles in the organic solvent extraction systems. More importantly, the used extractant in this route can be recycled. The power of this approach is demonstrated by the synthesis of monodisperse iron phosphate nanospheres, exhibiting promising applications in energy storage. The synthetic parameters have been optimized. Based on this, a possible formation mechanism is also proposed. The synthetic procedure is relatively simple and could be extended to synthesize other water-insoluble inorganic metal salts.

Graphene–carbon nanotube nanocomposites that contain multitubular co-axial and hollow cavity microstructures are prepared. Nanometer-scale graphene sheets are anchored with oxalic acid and consequently linked to each other via oxalyl bonding, thereby self-assembling into numerous outer tubes with distinct borders and a homogeneous thickness along the innermost pristine tube, which acts as a template. The resulting interstitial inclusion of oxalic acid into the graphene stacking modifies both the surface and the bulk properties of the newly formed tubes. It is observed that the unique microstructure of the modified graphene–carbon nanotube nanocomposite significantly facilitates the insertion and extraction of lithium, demonstrating superior electrochemical performance as anodes for lithium-based batteries. This facile chemical approach provides a new graphene architecture, showing superior stability, for use as anode material in lithium ion batteries.