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Photocatalysis is a new type of renewable energy technology used in environmental treatment and hydrogen energy production. In this regard, a new class of photocatalysts, TiO2 aerogels, are attractive for having the chemical characteristics of TiO2 nanomaterials such as high catalytic activity, good stability, non-toxic, and non-polluting, and the structural characteristics of aerogels such as large specific surface area, high porosity, the 3-dimensional interconnected network structure composed of relatively uniform nanoparticles, and high light transmittance. Here we review the recent progress in TiO2 aerogels for photocatalysis, focusing on preparation techniques, the crystalline phases’ influence on photocatalytic properties, the modification of photocatalytic properties, and the analysis and discussion of future development. In particular, we first summarize various preparation techniques, including sol–gel method, nanoparticles self-assembly synthesis, and high-temperature aerosol technique, then detail the structure and composition of TiO2 crystalline phases that affect the photocatalytic properties. Subsequently, we discuss strategies to further enhance the photocatalytic properties of TiO2 aerogels by the composite of SiO2 aerogel semiconductors, the doping of metal dopants, and the doping or composite of non-metallic substances, and elaborate the modification mechanism and the modification effect achieved. Finally, combined with the research status of TiO2 aerogels and the development experience of other aerogels, we conduct a reasonable analysis and discussion on their further research directions and industrialization roads.

For lithium‐sulfur batteries (Li‐S batteries), a high‐content electrolyte typically can exacerbate the shuttle effect, while a lean electrolyte may lead to decreased Li‐ion conductivity and reduced catalytic conversion efficiency, so achieving an appropriate electrolyte‐to‐sulfur ratio (E/S ratio) is essential for improving the battery cycling efficiency. A quasi‐solid electrolyte (COF‐SH@PVDF‐HFP) with strong adsorption and high catalytic conversion was constructed for in situ covalent organic framework (COF) growth on highly polarized polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) fibers. COF‐SH@PVDF‐HFP enables efficient Li‐ion conductivity with low‐content liquid electrolyte and effectively suppresses the shuttle effect. The results based on in situ Fourier‐transform infrared, in situ Raman, UV–Vis, X‐ray photoelectron, and density functional theory calculations confirmed the high catalytic conversion of COF‐SH layer containing sulfhydryl and imine groups for the lithium polysulfides. Lithium plating/stripping tests based on Li/COF‐SH@PVDF‐HFP/Li show excellent lithium compatibility (5 mAh cm−2 for 1400 h). The assembled Li‐S battery exhibits excellent rate (2 C 688.7 mAh g−1) and cycle performance (at 2 C of 568.8 mAh g−1 with a capacity retention of 77.3% after 800 cycles). This is the first report to improve the cycling stability of quasi‐solid‐state Li‐S batteries by reducing both the E/S ratio and the designing strategy of sulfhydryl‐functionalized COF for quasi‐solid electrolytes. This process opens up the possibility of the high performance of solid‐state Li‐S batteries. [ABSTRACT FROM AUTHOR]

Lithium ion capacitors with liquid electrolyte are prone to leakage, combustion, explosion and other dangerous accidents. To solve these problems, the solid gel separator prepared by polyvinylidene fluoride - six fluoropropene (PVDF-HFP) is used in this work to improve the safety and stability of lithium ion supercapacitors. The PVDF-HFP based gel separator was used to replace the commercial separator and electrolyte in the lithium ion capacitor. The solid-state lithium ion supercapacitor was matched with porous carbon (PC) and hard carbon (HC). The maximum energy density of the device is 148.76 wh/kg, even at the power density of 33.6 kW/kg, which still retains 20.6 wh/kg. In addition, 83.3% capacity of solid-state lithium-ion supercapacitor is retained after 8000 times of charge and discharge. The requirements of high power energy density, high cycle stability and high safety are realized.

The NiCo2S4/C hybrid material was successfully prepared by a simple one-step hydrothermal method. Carbon composite increases the specific surface area of the material and provides more ion attachment points during the electrochemical process. Conducive to the ion transportation and transfer, the composition of carbon material greatly improves the conductivity of the hybrid material. Electric double-layer capacitor materials can accept transferred ions faster than pseudocapacitor materials, enable the hybrid materials better adapt to intensity current changes. Compared with a single carbon material or a pseudocapacitance material, it has a higher specific capacity. This discovery is of great significance to the research of pseudocapacitive materials and supercapacitors.

Conventional SiO2 aerogels composed of 0-dimensional nanoparticles do not have large-scale compression, tensile, and shear deformation capabilities, and the poor mechanical properties hinder their further development and application. We report a scalable strategy to construct the nanoporous network of a SiO2 aerogel by alternately linking octa-(aminophenyl)-T8-POSS and hexaphthalic acid. The resulting SiO2 aerogel exhibits high strengths (compression, tensile and shear strengths are 26.4, 9.16, and 8.31 MPa, respectively), excellent deformabilities (fracture compression, tensile, and shear strains are 82.63%, 57.81% and 108.02%, respectively), flexbile processability and good structural stability (only 1.7% plastic deformation occurs after 100 load–unload cycles at a large compression strain of 70%). Also, the mesoporous interconnected nanoskeleton with high porosity and the composition of fully hydrophobic groups also give the aerogel low thermal conductivities (0.02854 W/(m K) at 25 °C and 0.04638 W/(m K) at 300 °C) and superhydrophobic properties (hydrophobic angle 160° and saturated mass moisture absorption rate about 0.375%). The combination of these excellent properties ensures that the aerogel can be used as an efficient thermal insulation material for extreme environments, such as those where comprehensive mechanical and hydrophobic properties are strictly required. [ABSTRACT FROM AUTHOR]

Transparent conductive oxide (TCO) film acts as the window layer and carrier transport layer of silicon heterojunction (SHJ) solar cells. The optoelectrical and contact properties of TCO films, as well as the sputtering damage, limit the further efficiency improvement. Herein, the microstructure, morphology, and optoelectrical properties of sputtering‐prepared zinc‐doped indium oxide (IZO) are analyzed. The substrate temperature has a significant impact on the film growth and the cell performance. The IZO film is amorphous when substrate temperature is below 200 °C, while it seems the emergence of nanocrystals with the increased temperature, resulting in the highest conductivity (3070 S cm−1) and carrier mobility (47.9 cm2 V−1 s−1). In addition, the low carrier concentration and surface potential of IZO promote less optical parasitic absorption and higher work function. The IZO films are applied as the contact layer of SHJ solar cells. An impressive efficiency of 24.02% on an M2‐sized wafer is achieved, indicating great potential for the mass production application after careful optimization. [ABSTRACT FROM AUTHOR]

Spinel Li4Mn5O12 was successfully prepared by the wet chemical method to modify the surface of Li1.2Ni0.2Mn0.6O2. The results showed that an ultrathin spinel Li4Mn5O12 surface-modified layer with a thickness of approximately 10 nm was successfully constructed on the raw material surface, and that the cationic order was improved. In addition, the lithium ion diffusion coefficients (DLi+) of the raw materials and the modified materials were calculated using the EIS test and impedance fitting. The results indicated that the ultrathin Li4Mn5O12 surface modification shell can increase the lithium ion diffusion rate of the material and improve the rate capability of the material. So, the surface modification layer of spinel Li4Mn5O12 can reduce the oxygen loss of the first cycle and improve the cationic order of the material. Therefore, the first coulombic efficiency of Li4Mn5O12/Li1.2Ni0.2Mn0.6O2 material at the current density of 12.5 mA·g−1 reaches 80.46%, and the capacity retention rate reaches 91.74% after 50 cycles, which are 3.36% and 21.23% higher than those of the raw materials, respectively. It showed better electrochemical reversibility and cyclic stability. This study provides a straightforward and convenient modification method for improving the stability of cobalt-free lithium-rich manganese cathode materials and has a favorable application prospect. [ABSTRACT FROM AUTHOR]

Lithium–sulfur batteries are deemed as optimal energy devices for the next generation of high‐energy‐density energy storage. However, several problems such as low energy density and short cycle life hinder their application in industry. Here, MoS2–MoN heterostructure nanosheets grown on carbon nanotube arrays as free‐standing cathodes are reported. In this heterostructure, MoN works as a promoter to provide coupled electrons to accelerate the redox reaction of polysulfides while the MoS2, with a two‐dimensional layered structure, provides smooth Li+ diffusion pathways. Through their respective advantages, both MoN and MoS2 could mutually boost the process of "adsorption‐diffusion‐conversion" of polysulfides, which have a synergy enhancement effect to restrain the lithium polysulfides from shuttling. The designed cathodes show excellent long‐term cycling performances of 1000 cycles at 1C with a low decay rate of 0.039% per cycle and a high rate capability up to 6C. A high initial areal capacity of 13.3 mAh cm−2 is also achieved under a low electrolyte volume/sulfur loading (E/S) ratio of 6.3 mL g−1. This strategy of promoting polysulfide conversion by heterostructure MoS2–MoN as presented in this work can provide a more structured design strategy for future advanced Li–S energy storage systems. [ABSTRACT FROM AUTHOR]