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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.

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]

Room-temperature sodium-ion batteries have attracted great attentions for large-scale energy storage applications in renewable energy. However, exploring suitable anode materials with high reversible capacity and cyclic stability is still a challenge. The VS4, with parallel quasi-1D chains structure of V4+(S22-)2, which provides large interchain distance of 5.83 Å and high capacity, has showed great potential for sodium storage. Here, the uniform cuboid-shaped VS4 nanoparticles are prepared as anode for sodium-ion batteries by the controllable of graphene oxide (GO)-template contents. It exhibits superb electrochemical performances of high-specific charge capacity (≈580 mAh·g-1 at 0.1 A·g-1), long-cycle-life (≈98% retain at 0.5 A·g-1 after 300 cycles), and high rates (up to 20 A·g-1). In addition, electrolytes are optimized to understand the sodium storage mechanism. It is thus demonstrated that the findings have great potentials for the applications in high-performance sodium-ion batteries. [ABSTRACT FROM AUTHOR]

As recently explored lithium-ion battery (LIB) anode materials, transition metal vanadates have attracted much attention due to their excellent electrochemical performance. In this work, we successfully synthesized solid Co3V2O8 microspheres (sCVO MSs) via a facile and controllable hydrothermal reaction, and the magical formation mechanism was also revealed by the different morphologies of sCVO MSs at different reaction times. When tested as LIB anode materials, sCVO MSs showed superior reversible capacities (∼780 mA h g−1 after 250 cycles at 1000 mA g−1 and as high as 550 mA h g−1 even after 400 cycles at 5000 mA g−1) and excellent rate performance (a capacity of ∼500 mA h g−1 at a current density of 2000 mA g−1). It is accordingly demonstrated that uniform sCVO MSs have great potential to be used as high-performance LIB anodes. [ABSTRACT FROM AUTHOR]

Transition metal vanadates have attracted much attention for high capacity anodes of lithium ion batteries (LIBs). However, they have obvious drawbacks (short cycle-lives and low rate performance) because of the intrinsically low electronic conductivity and serious volume variation during Li-ion desorption and insertion. In particular, pure Co3V2O8 micro-pencils (pCVO MPs) have a stable and regular crystal structure, large tap density and uniform grain size, but, unfortunately, they have not exhibited expected electrochemical performance. Herein, we report the successful preparation of reduced graphene oxide coated Co3V2O8 micro-pencils (rGO@CVO MPs) through a facile approach combining hydrothermal synthesis with thermal reduction. When tested as anodes for LIBs, rGO@CVO MPs exhibit superior electrochemical performance compared to that of pure Co3V2O8 micro-pencils (pCVO MPs). The anodes of rGO@CVO MPs show a high reversible capacity of 760 mA h g−1 over 200 cycles at 200 mA g−1, and 500 mA h g−1 can remain after 500 cycles at 1000 mA g−1, with an increase in 200 mA h g−1 in contrast to the pCVO MPs. It is consequently demonstrated that the composite material (rGO@CVO MPs) is a promising anode material for LIBs. [ABSTRACT FROM AUTHOR]

Si nanoparticle (Si-NP) composite anode with high rate and long cycle life is an attractive anode material for lithium-ion battery (LIB) in hybrid electric vehicle (HEV)/pure electric vehicle (PEV). In this work, a carbon nanotube (CNT)/reduced graphene oxide (rGO)/Si nanoparticle composite with alternated structure as Li-ion battery anode is prepared. In this structure, rGO completely wraps the entire Si/CNT networks by different layers and CNT networks provide fast electron transport pathways with reduced solid-state diffusion, so that the stable solid-electrolyte interphase layer can form on the whole surface of the matrix instead of on single Si nanoparticle, which ensure the high cycle stability to achieve the excellent cycle performance. As a result, the CNT/rGO/Si-NP anode exhibits high performances with long cycle life (≈455 mAh g−1 at 15 A g−1 after 2000 cycles), high specific charge capacity (≈2250 mAh g−1 at 0.2 A g−1, ≈650 mAh g−1 at 15 A g−1), and fast charge/discharge rates (up to 16 A g−1). This nanostructure anode with facile and low-cost synthesis method, as well as excellent electrochemical performances, makes it attractive for the long life cycles at high rate of the next generation LIB applications in HEV/PEV. [ABSTRACT FROM AUTHOR]