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The factors affecting the capacity degradation of lithium-ion batteries with LiCoO2 as the cathode material at high voltage are discussed, and then doping and surface coating strategies are proposed as corresponding solutions.

Currently, silicon is considered among the foremost promising anode materials, due to its high capacity, abundant reserves, environmental friendliness, and low working potential. However, the huge volume changes in silicon anode materials can pulverize the material particles and result in the shedding of active materials and the continual rupturing of the solid electrolyte interface film, leading to a short cycle life and rapid capacity decay. Therefore, the practical application of silicon anode materials is hindered. However, carbon recombination may remedy this defect. In silicon/carbon composite anode materials, silicon provides ultra-high capacity, and carbon is used as a buffer, to relieve the volume expansion of silicon; thus, increasing the use of silicon-based anode materials. To ensure the future utilization of silicon as an anode material in lithium-ion batteries, this review considers the dampening effect on the volume expansion of silicon particles by the formation of carbon layers, cavities, and chemical bonds. Silicon-carbon composites are classified herein as coated core-shell structure, hollow core-shell structure, porous structure, and embedded structure. The above structures can adequately accommodate the Si volume expansion, buffer the mechanical stress, and ameliorate the interface/surface stability, with the potential for performance enhancement. Finally, a perspective on future studies on Si−C anodes is suggested. In the future, the rational design of high-capacity Si−C anodes for better lithium-ion batteries will narrow the gap between theoretical research and practical applications.

With the explosive growth of energy storage devices, commonly used lithium-ion batteries can hardly match the increased demands of energy-density, lithium-sulfur batteries have been regarded as promising candidates due to their high energy-density (2600 Wh Kg−1) and low cost. However, lithium sulfur batteries still face many problems such as polysulfide shuttle effect originated from dissolution of lithium polysulfide, that leaded to the capacity fading of batteries and corrosion of lithium anodes, greatly limited their practical applications. To settle these problems, many remarkable developments have been made by the construction of separators with the dimension design of employing the materials related by metal-organic frameworks (MOFs), shedding a light on the improvement of lithium-sulfur batteries. Herein, this article aims to summarize recent developments in MOF-related separators of lithium-sulfur batteries in terms of the structural dimensions of MOF-related materials, including their architectural compositions in separators and facilitation mechanisms of battery performances. At last, an outlook section was provided to discuss remaining challenges of separators as well as potential research directions and possible prospects, to offer new thoughts for future studies of lithium-sulfur batteries.

Nickel-rich cathode has received much attention due to its high energy density, high capacity, low cost and environmental friendliness. The existence of intercrystalline microcracks in NCM seriously affects the structural stability and integrity of the battery crystal surface. Irreversible phase transitions result in changes in lattice parameters, the interface side reactions severely corrode the crystal surface, and secondary particle heterogeneity leads to uneven reactions. Common amorphous microcracks include single crystal, gradient doping, etc. This review first introduced the microcrack mechanism of NCM, and then summarized two solutions: single crystal and gradient doping. Finally, we presented new views and insights, and hope to give enlightenment on the subsequent inhibition of intercrystal microcrack, and construct the reasonable structure of NCM cathode.

Layered lithium nickel cobalt aluminum oxides cathode materials (α-NaFeO2 structure, Space group: R-3 m) are prepared using an unusual flocculation precipitation process. The synthesis strategy utilized the new aluminum precursor containing nickel, cobalt and aluminum hydroxides has a different mechanism from that for conventional coprecipitation process. As-prepared LiNi0.85Co0.17Al0.03O2 delivers a first cycle capacity of 164 mAh g−1 at 1C rate. The stored sample delivers a first cycle capacity of 146 mAh g−1 and the capacity retention rate of 93% in 40 cycles at 1C rate. Its stored cell exhibits a capacity of 99 mAh g−1 at 1C rate. The particle surface of the sample has a coating layer of Li3.62aLi4.31bNi0.172+Ni0.833+Co0.062+Al0.373+O0.98aO12.6b (with the structure of Li2CO3, LiAl5O8 and α-NaFeO2). The coating layer can prevent the reaction between the particles and moisture in the air or the particles and electrolytes in the cell at 55 °C. Therefore, LiNi0.85Co0.17Al0.03O2 exhibits excellent rate performance and stored one for its low polarization, high stability α-NaFeO2 structure and high stable coating layer. The exceptional overall performance of the as-synthesized LiNi0.85Co0.17Al0.03O2 presents itself a promising cathode material for next generation lithium-ion batteries.

Composite paper sheet containing titanium dioxide and diatomite (TiDI) was prepared via a papermaking technique. The composite sheet was applied to remove phenol from aqueous solution. The composite sheet with a 2:1 mass ratio of cellulosic-fiber to TiDI removed phenol more effectively under UV irradiation than the composite paper sheet that utilized titanium dioxide (TiO2) alone. Composite paper sheets that contained TiDI with a TiO2/diatomite mass ratio of 1:2 removed phenol most effectively. The results showed that the TiDI composite paper could serve as a functional material to photodegrade phenol from aqueous solution under UV irradiation effectively.

Separators with low ionic impedances and high thermal/electrochemical stability are desirable for high-performance Li-ion batteries. Herein, a composite layer consisting of AlPO4, poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and polymethyl methacrylate (PMMA) is coated on the polypropylene (PP) separator matrix. The coated PP exhibits an electrolyte uptake of 2.28%, leading to improved ionic conductivity and Li-ion diffusion coefficient. In addition, this separator has a wide electrochemical stability window, high peeling strength of 111.2 N m−1 and superior thermal stability at 170 °C. By applying this coated separator in the cell with LiNi0.5Co0.2Mn0.3O2 cathode, excellent cycling stability and rate performance can be also obtained. The improved electrochemical performances can be attributed to that AlPO4 in the coating layer exhibits high electrolyte uptake and firmly combines with the PP matrix.

The Fe doped TiO2 (FET) gels were synthesized by different ferric salts and analyzed by thermal gravimetric analyzer and X-ray diffraction. The TG curves show that the valence states of Fe had a great influence on the preparation of FET gels, Fe 3+ was easy to replace titanium atoms to form lattice and the anatase phase was effectively established when the calcination temperature over 400 ˚C.The XRD spectra indicates that the anatase phase constantly changed into the rutile phase when the calcination temperature over 600 ˚C and the nitrate is beneficial to the formation of mixed crystal.

Jingzheng,Weng , Feng Gao,Lihui,Chen, Renhui,Qiu b,* College of Material Engineering,Fujian Agriculture and Forestry University, Fuzhou, Fujian Province 350002, China College of Materials Science and Engineering ,Fujian Normal University ,Fuzhou, Fujian Province 350007,China 3 College of Transportation and Civil Engineering, Fujian Agriculture and Forestry University, Jinshan, Fuzhou, Fujian Province 350002, P. R. China jackyweng@vip.163.com, renhuiqiu@fafu.edu.cn * corresponding author

Fe doped TiO2 particles were synthesized by sol-gel method. This gel was dried at 70 ˚C during 2 hours and afterwards was calcined at 450 ˚C during 4 h. Under calcinations at 450 ˚C (4 h), catalyst particle with an average diameter around 59 nm and monophasic anatase structure were obtained. The 0.3wt% Fe/TiO2 catalyst behaved as efficient and stable catalyst for the photodegradation of phenol solution. At the experimental conditions of initial phenol solution at 10 mg/L, initial pH of the phenol solution at 6.0, UV lamp at 20 W, catalysts concentration at 0.5 g/L , the COD removal of 99 % could be achieved after 240 min of photodegradation reaction.