Thanks to abundant resource and rapid redox reaction kinetics, iodine is regarded as promising positive materials in the batteries. However, the shuttling effect due to the high solubility of iodine in the electrolyte makes the performance of battery poor. In this paper, polyethylene glycol (PEG400) and potassium iodide were added into zinc-ion aqueous electrolyte. PEG400 could complex with iodine to reduce the dissolution of iodine, therefore alleviating the formation of soluble triiodide (I₃^-) from iodine and iodide ions. Furthermore, this electrolyte was used in the battery with double carbon cloths as the current collectors, double separators and zinc anode. At the current density of 1 mA·cm^-2, the first discharge capacity reached 1.62 mAh·cm^-2, and the coulombic efficiency was around 93%. Iodine involved in the electrochemical redox reaction is calculated to account for 47.52% of the total mass of iodine in this electrolyte. At high current density of 7 mA·cm^-2, its coulombic efficiency still remained 98%, and the rate of capacity retention was 58.33% after 1,200 cycles.

The development of green and sustainable water-splitting hydrogen production technology is beneficial to reducing the over-reliance on fossil fuels and realizing the strategic goal of "carbon neutral". As one of the half reactions for water splitting, oxygen evolution reaction has suffered the problems of sluggish four-electron transfer process and relatively slow reaction kinetics. Therefore, exploring efficient and stable catalysts for oxygen evolution reaction is of critical importance for water-splitting technology. Metal alkoxides are a series of compounds formed by the coordination function of metal ions with alcohol molecules. Metal alkoxides possess the double advantages of organic materials and inorganic materials, which makes them reveal a promising application in the electrochemical field. In view of the poor activity and stability of the current oxygen evolution reaction electrocatalysts, this study has adopted the alkoxide-based self-template method to prepare the carbon-encapsulated NiFeV-based electrocatalysts through using the solid NiFeV-alkoxides as precursors. The organic components in solid metal alkoxides are employed to achieve the graphitized carbon encapsulation after the high-temperature calcination process, which is beneficial for improving the conductivity and corrosion resistance of catalysts. Through adjusting the V doping amounts and the calcination temperatures, the electronic structure of NiFe nanoparticles and carbon encapsulation were optimized, which are both key influence factors for oxygen evolution performances. As a result, the oxygen evolution catalysts with high activity and stability were obtained successfully in this work. The experimental results have shown that the NiFeV-based catalysts presented a uniform spherical structure with carbon encapsulation. The current density of 20 mA·cm^-2 could be obtained at the overpotential of only 381 mV as an electrocatalyst for oxygen evolution reaction in water electrolysis. After the continuous 10000 s durability test, the NiFeV-based catalyst exhibited slight reduction in current density but still maintained the catalytic activity almost similar to the initial one, revealing a good oxygen evolution stability. The excellent catalytic activity and stability of NiFeV-based catalysts are believed to be mainly attributed to the uniform spherical structure, the optimized regulation of V on the electronic structure and the protective effect of carbon encapsulation on metal particles. The V element in the catalysts exhibited the rich redox states of V³⁺, V⁴⁺ and V⁵⁺, which can effectively adjust the electronic structure of adjacent atoms and optimize the binding energy of oxygen reduction reaction intermediates, thus improving the electrocatalytic performance of catalysts. This work provides a useful guidance for improving the electrocatalytic performance of oxygen evolution catalysts through the V-doping and carbon encapsulation strategies.

Li₃VO₄, as a promising anode material for lithium ion batteries, has been widely studied because of its low and safe voltage, and large capacity. However, its poor electronic conductivity impedes the practical application of Li₃VO₄ particularly at high rates. In this paper, carbon confined Li₃VO₄ nano materials (Li₃VO₄/C) were synthesized by hydrothermal and solid-phase method, and for comparison, the Li₃VO₄ (N) nano materials without carbon confinement and Li₃VO₄ (B) materials were also synthesized by pure solid-phase method. The composition, structure, morphology and specific surface area of the three samples were studied by XRD, Raman, TEM and N₂ adsorption-desorption tests. It was found that the grain size of Li₃VO₄ in Li₃VO₄/C was the smallest, which is 51 nm, the grain size of Li₃VO₄ in Li₃VO₄ (N) was the second (93 nm), and the grain size of Li₃VO₄ prepared by pure solid-phase method was the largest (113 nm). The thickness of carbon confinement layer in Li₃VO₄/C was 2-4 nm, which was uniformly coated on the surface of Li₃VO₄. And the specific surface area and pore size distribution of the three samples were measured by BET and BJH methods. It was found that the samples prepared by hydrothermal and solid-phase method had mesoporous structure, and the Li₃VO₄ prepared by a simple solid-phase method had the least porous structure. The BET specific surface area and the pore volume of the carbon confinement sample were larger than those of the sample without carbon confinement layer (30.49 m²·g^-1 vs. 26.42 m²·g^-1 and 0.12 cm³·g^-1 vs. 0.05 cm³·g^-1), which is in agreement with the smaller grains of Li₃VO₄/C by XRD analysis, indicating that the carbon layer limits the growth of Li₃VO₄ grains, so as to increase the contact area between active material and electrolyte when the sample is used as the anode material of lithium ion battery. The charge-discharge performances of the synthesized samples as anodes of lithium ion battery were studied. It was found that the Li₃VO₄/C electrode displayed faster lithium ion storage performance than Li₃VO₄ (N) and Li₃VO₄ (B) electrodes. At the rates of 0.1 C, 0.5 C, 1 C, 5 C, 10 C and 20 C, the discharge capacities of Li₃VO₄/C were 435, 428, 401, 356, 302 and 280 mAh·g^-1, respectively. In particular, after 50 cycles at 5 C, Li₃VO₄/C still maintained 92.3% of the initial capacity, which fully reflects the characteristics of larger capacity, higher rate capability and better stability of Li₃VO₄/C electrode. By analyzing the relationship between morphology and electrochemical properties, it is considered that the carbon confinement layer reduces the ohmic polarization of Li₃VO₄ in the processes of charge and discharge, the large specific surface area improves the penetration efficiency of electrolyte, and the small particle size shortens the diffusion path of lithium ions. At the same time, the synthesis method in this work presents a universal strategy for the preparation of other transition metal oxide salts with porous structure and small particle.

The growing demands for electric vehicles and consumer electronics，as well as the expanding renewable energy storage market，have promoted extensive research on energy storage technologies with low cost，high energy density and safety. Lithium (Li) metal and solid-state electrolytes are considered as important components for next-generation batteries because of their great potential for improvements in energy density and safety performance. Inorganic garnet-type solid electrolytes with high Li-ion conductivity (about 10^-3 S·cm^-1) and high shear modulus (55 GPa) are considered to be ideal solid-state electrolytes，however，the issue of Li dendrite growth still obstructs their practical application. Herein，a simple and efficient strategy was developed to suppress the Li dendrite formation in the garnet solid electrolytes. A composite modification layer made of 2 nm LiF and 2 nm Sn thin layers was prepared on the surface of the Li_6.5La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) solid electrolyte by the high vacuum evaporation. The composite modification layer combined the advantages of LiF and Sn，which effectively improves the interfacial contact between the Li metal and LLZTO electrolyte，and promotes the uniform Li plating/stripping. The LiF-Sn composite modification layer was deposited on the surface of garnet electrolyte to increase the interfacial wettability between the garnet electrolyte and Li metal，which blocks the injection of electrons into the bulk phase of garnet. The LiF-Sn modification layer effectively enhanced the interfacial contact and inhibited the growth of lithium dendrites. Benefiting from the LiF-Sn interfacial modification，the cross-sectional SEM image shows the intimate contact between the LLZTO-LiF-Sn and the Li metal without any voids. In addition，the interfacial impedance of Li/garnet electrolyte interface decreased from 969 Ω·cm² to 3.5 Ω·cm². Meanwhile, the critical current density of the Li symmetric cell increased to 1.3 mA·cm^-2, and the Li symmetric cell could be cycled stably for 200 h at a current density of 0.4 mA·cm^-2. After disassembling the short-circuited Li/LLZTO/Li cell and reacting the Li metal with alcohol solution，it was found that Li dendrites had grown into the LLZTO pellet. However，the surface of the LiF-Sn-protected LLZTO remained smooth without dark spots from dendrites. The excellent electrochemical performance clearly shows that the LiF-Sn composite modification can effectively inhibit the formation of Li dendrite inside the garnet SSE, proving that this interfacial engineering provides a practical solution for addressing the key challenge of Li/LLZTO interface. At the same time，high vacuum evaporation is a matured industrial technology with large-scale application prospects and can be widely used to solve solid-state interface problems.