•Cox/Li3Ti4Co1−xCrO12 was prepared by solid-state method under reducing atmosphere.•The Co modified samples showed excellent electrochemical performance.•The enhanced performance can be explained by the improved conductivities.•Oxygen vacancies were generated during the calcination under reducing atmosphere.•Oxygen vacancies are responsible for the promoted conductivities.New anode materials (Cox/Li3Ti4Co1−xCrO12) had been successfully prepared via a high temperature solid-state method. Pure phase Co-Cr replaced solid solution (Li3Ti4CoCrO12) was obtained by calcinating the precursor under air atmosphere while the Co modified solid solutions (Cox/Li3Ti4Co1−xCrO12) were prepared under a reducing atmosphere. Various methods, such as XRD, SEM, EDX mapping, cyclic testing, EIS, CV, XPS and EPR were employed to characterize the powder samples and investigate their electrochemical behavior. SEM results showed spherical shape of the products with nano sized primary crystals. EDX mapping further confirmed the different existence of the Co element, uniform distribution of Co2+ ions within the spinel lattice and separated metallic Co on the particle surface. Cyclic tests revealed that the Co modified samples showed great promotion in their electrochemical performance. For the sample with x = 0.1, the best results with an initial capacity of 157.6 mA h/g and a capacity retention of 96.4% after 100 runs were observed. Such promotion can be explained by the improved electronic conductivity and enhanced Li+ diffusion coefficient confirmed by the EIS and CV simulation, which was caused by the oxygen vacancy produced during the calcination under the reducing atmosphere.

LiFe0.4Mn0.6−xCrxPO4/C (x ≤ 0.01) cathode materials with different Cr-doping were synthesized by a nano-milling assisted solid-state method. The experimental results demonstrated that Cr-doping can significantly improve the electrochemical performance of the target material. Among the samples synthesized, the LiFe0.4Mn0.595Cr0.005PO4/C (with 0.5 atm% of Cr) sample exhibited the highest specific capacity and the best rate performance. It delivered initial discharge capacities of 164.0, 156.2, 147.5 and 139.3 mA h g−1 at 0.1C, 0.5C, 2C and 5C, respectively. Moreover, it showed the best cycle stability with capacity retention of 99.2% after 50 cycles at 0.1C. Such enhancement can be ascribed to the improvements in not only the electronic conductivity, but also the Li ion diffusion coefficient. Powder conductivity tests revealed that the conductivity of the powder sample with 0.5% Cr doping presents the highest conductivity of 5.91 × 10−5 S cm−1, which is almost 5.3 times that of the pristine sample. Calculations of diffusion coefficients using the EIS data also suggested a highest Li ion diffusion coefficient of 4.36 × 10−10 cm2 s−1 for the sample with 0.5% Cr doping, which is almost 4.6 times that of the pristine sample. The synthesized LiFe0.4Mn0.595Cr0.005PO4/C with such excellent electrochemical performance showed great potential for application in high-power devices.

•We prepare 3D graphene/LiFePO4/graphene sandwich composite by a facile method.•The 3D CVD graphene acted as the high conductivity supporting framework.•LiFePO4 nanoparticles were anchored onto the 3D graphene framework covered by graphene sheets.•It shows 164 mAh g−1 at 0.2 C and of 95.7% capacity retention after 100 cycles.In this paper, we have successfully synthesized a three dimensional graphene/LiFePO4/graphene (3DG/LFP/G) sandwich composite by an in-situ hydrothermal method, in which chemical vapor deposited 3D graphene acts as the high conductivity supporting framework, while the LiFePO4 nanoparticles are anchored onto the 3D graphene framework covered by graphene sheets. XRD and SEM results confirmed the formation of the 3DG/LFP/G sandwich composite. Cyclic Voltammetry curve of the sandwich composite shows sharper redox peaks and reduced voltage separation when compared to the reference electrodes, suggesting high specific capacity and good rate performance. Further charge/discharge measurements presented high capacity of 164 mAh g−1 at 0.2 C and 124 mAh g−1 at 10 C (75.7% of its initial capacity) for the sandwich composite, with capacity retention of 95.7% after 100 cycles, implying potential application in lithium ion battery at high rates. The EIS investigation suggests that both the electronic conductivity and the Li ion diffusion are promoted by the underlined 3D graphene framework, which is regarded as the reason for the enhanced electrochemical performance.

Red afterglow phosphors, Sr2SnO4:Sm3+ co-activated with alkali ions (K+, Na+) were prepared via solid-state reaction. The phase identification and photoluminescence were characterized and analyzed by X-ray diffraction (XRD), photoluminescence spectroscope, afterglow measurement and thermal luminescence spectroscope. XRD results confirmed an orthorhombic structure for all the samples prepared in the experiment, showing the doping ions had negligible influence on the crystal structure. The photoluminescent spectra of the Sm-doped phosphors revealed a group of reddish orange emission lines originating from 4G5/2 → 6HJ transition of Sm3+. The optimal doping concentration of Sm3+ was determined as 1 mol% and concentration quenching was observed afterwards. For the alkaline ion co-doped samples, Na+ and K+ ions were found profitable to improve both the photoluminescence and the afterglow behavior. Thermal simulated luminescence study indicated that the persistent afterglow of Sr2SnO4:Sm3+ phosphor and alkali ions (K+, Na+) co-doped Sm3+:Sr2SnO4 phosphors were generated by the recombination of the electrons released from the electron traps with the holes in the valence band. The co-doping of alkaline ions (K+, Na+) increased not only the initial trap concentration, but also increased the depth of electron traps, which can be regarded as the main reasons for the enhanced afterglow. Based on such results, possible mechanisms for the afterglow of Sr2SnO4:Sm3+ and alkaline ions (K+, Na+) co-doped phosphors were proposed.

A green emitting long afterglow phosphor Li2SrSiO4:Tb3+ was obtained via a conventional high temperature solid-state reaction in air atmosphere. X-ray diffraction (XRD), photoluminescence spectroscope (PLS), long afterglow spectroscope (LAS) and thermal luminescence spectroscope (TLS) were performed to characterize the physical properties of the phosphors. Typical 5D4-7Fj transitions of Tb3+ ions were detected by PL spectra, corresponding to CIE chromaticity coordinates of x=0.3161, y=0.5472. An optimal concentration of Tb3+ in the substrate was determined to be 1%. The Li2SrSiO4:Tb3+ phosphors showed a typical afterglow behavior when the UV source was switched off. A typical triple exponential decay behavior was confirmed after fitting the experimental data. Thermal simulated luminescence study further indicated that the afterglow behavior of Li2SrSiO4:Tb3+ phosphors was generated by the recombination of electrons with the holes resulted from the doping of rare-earth ions (Tb3+) in Li2SrSiO4 host. The long afterglow luminescence mechanism of Li2SrSiO4:Tb3+ is illustrated and discussed in details on the basis of the experimental results.

•Bluish Li4Ti5O12 with Ti3+ ions and oxygen vacancies was prepared by solid-state method under reducing atmosphere.•The XPS and EPR results confirmed the coexistence of Ti3+ ions and oxygen vacancies.•Both the electric conductivity and the Li ion diffusion coefficient were significantly enhanced.•The bluish O-LTO presented excellent specific capacity and rate performance.Bluish Li4Ti5O12 anode powder containing oxygen vacancies (O-LTO) was synthesized by solid state reaction under reductive atmosphere with 5 vol% H2/Ar, while white Li4Ti5O12 powder (reference Li4Ti5O12, R-LTO) was obtained in air in the experiment. XRD results revealed spinel structure for both anode materials and further Rietveld refinements of the patterns implied the formation of a non-stoichiometric compound, rather than the pristine Li4Ti5O12 phase, after calcinating in reductive atmosphere. SEM observation revealed spherical secondary particles for both powders composed of fine primary grains with size of submicron. The observed color difference between the O-LTO (bluish) and R-LTO (white), as revealed by DR UV–Vis investigation, could be ascribed to the formation of Ti3+ ions in the reductive atmosphere. XPS and EPR results confirmed the coexistence of Ti3+ ions and oxygen vacancies. The existence of oxygen vacancies resulted in significant increase in both Li ion diffusion coefficient and electric conductivity of the anode material, as proved by the CV tests and impedance measurements. The O-LTO sample showed advantages over the R-LTO sample, with a high specific capacity of 182.6 mAh/g at 0.2 C and a stable capacity retention of 98.7% after 100 cycles. Excellent rate performance was also observed for the O-LTO anode material. The specific capacities at 1C, 5C and 20C after 100 runs were recorded as 169 mAh/g, 153 mAh/g and 139 mAh/g for the O-LTO samples. All the results obtained in the experiment suggested high potential of the bluish O-LTO for the application as anode material for secondary Li ion batteries at high rates.

Layered RbxLi(1−x)Ni0.8Co0.1Mn0.1O2 (x = 0, 0.005, 0.01, 0.02) materials were synthesized with different Rb concentrations using a solid state reaction method. All the materials were calcined at 800 °C for 12 h in a flowing oxygen atmosphere using NiO, CoO, MnO2, Rb2CO3 and LiOH·H2O as the raw materials. The influences of the amount of Rb+ ions in the cathodes on the electrochemical performance were investigated in detail. It was found from the results that the electrochemical performances of Rb doped materials were greatly improved. Among them the Rb0.5% sample presented the best performance; it delivered an initial discharging capacity of 188.9 mA h g−1 at 0.5C, improved by 13.52% when compared with that of a sample without Rb. A capacity retention of 88.9% after 100 cycles and an excellent high-rate performance of 152.3 mA h g−1 at 5C rate were also recorded for the same sample. The Li+ ion diffusion coefficient calculated from EIS turned out a value of 1.14 × 10−10 cm2 s−1, which is 3.42 times that of the non-doped sample. Both the enhanced performance and the accelerated Li+ ion diffusion could be explained by the changes in crystal structures. XRD whole pattern refinement revealed that the Rb+ ions were incorporated into the lattice by replacing the original Li+ ions, which resulted in reduced ionic mixing and the expansion in the c axis that led to the enhanced electrochemical performance. As a whole, incorporation of Rb in LiNi0.8Co0.1Mn0.1O2 by this approach showed great potential to serve as a promising cathode material for future applications.

Electric vehicles and high-power electrical appliances demand batteries of a high rate discharge performance, but it is still a challenge due to large electric resistance for very fast charge transport. In this paper, a nano-LiFePO4/graphene (G/LiFePO4) composite is synthesized by one-pot in situ hydrothermal method. The LiFePO4 nanoparticles are wrapped by graphene sheets on a three-dimensional (3D) free-standing graphene foam obtained from the self-assembling of graphene oxide, which is used as a highly conductive current collector. The as-prepared G/LiFePO4 composite has a 3D conductive network and can be directly used for the cathode without any conductive carbon black, binder or aluminum current collector. The electrochemical measurements show it has excellent rate performance, the 10C-rate specific discharge capacity is 115 mA h g−1. The overall electrochemical performance from this 3D self-assembly free-standing structure is superior in the similar reported system.

•LiFePO4 microplates grown in (010) and (001) lattice planes were prepared by a controllable method.•Two growth mechanisms based on nucleation and recrystallization process were proposed.•(010) microplates have a higher diffusion coefficient than the (001) ones.•(010) microplates exhibit high specific capacity, showing great potential for application in LIBs.Two different LiFePO4 microplates grown in parallel with (010) and (001) lattice planes were obtained using a controllable hydrothermal process. The as-synthesized materials were characterized physically and electrochemically. XRD, SEM and HRTEM investigations confirmed the preferred growth and two corresponding growth mechanisms based on nucleation and recrystallization process were proposed. The calculation of Li ion diffusion coefficient along [001] and [010] directions using CV and EIS results revealed that (010) microplates have a higher diffusion coefficient than the (001) ones, implying a good electrochemical performance for (010) microplates over the (001) ones. Capacity tests confirmed the above assumption. Both the two cathode materials showed high specific capacities, and the (010) microplates exhibit a value around 158 mAh g−1 at a rate of 0.5C, showing a great advantage of (010) microplates for future application in LIBs for EV application.

•A mesoporous silica membrane was fabricated on a macroporous alumina support.•A heat-sealing treatment procedure is introduced.•Air-cushion can prevent the infiltration of the precursor solution into pores.We report a unique technique for fabricating a uniform and crack-free surfactant-templated silica membrane on a porous alumina support. The porous alumina support was first subjected to a heat-sealing treatment, and then a mesoporous silica membrane derived from a surfactant template was deposited thereon by sol–gel processing. The surface topography of the silica membrane has been characterized. With the aid of the sealing procedure, an air-cushion was formed to provide sufficient additional supporting force to support the precursor film and prevent permeation of the precursor into the pores. The sol–gel deposition on the porous alumina support formed a uniform, crack-free silica membrane.