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The effects of calcination temperature on the physical and electrochemical performance of the Na 4 MnV(PO 4) 3 /C composites, which are prepared by a sol-gel method combined with the subsequent calcination in inert atmosphere, are reported in this work. The Na 4 MnV(PO 4) 3 /C composites are investigated by x-ray diffraction (XRD), N 2 adsorption/desorption isothermal, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and electrochemical measurements. The specific surface area, disorder of carbon, diffusion coefficients of Na+ (D Na) and electrochemical performance of Na 4 MnV(PO 4) 3 /C composites are greatly influenced by the calcination temperature. The surface area and disorder of carbon of Na 4 MnV(PO 4) 3 /C substantially decrease with the calcination temperature increasing. While the D Na and electrochemical performance of Na 4 MnV(PO 4) 3 /C composites improve with the calcination temperature from 650 to 750 °C and then degrade with the calcination temperatures from 750 to 850 °C. The results reveal that the optimal calcination temperature for the Na 4 MnV(PO 4) 3 /C composites is 750 °C and the corresponding Na 4 MnV(PO 4) 3 /C composite possesses the highest capacity and the best rate capability and cyclability amongst all these Na 4 MnV(PO 4) 3 /C composites in this work. • Na 4 MnV(PO 4) 3 /C (NMVP/C) was prepared by sol-gel route plus calcination in N 2 stream. • Calcination temperature impacts on physical and electrochemical properties of NMVP/C. • The optimal calcination temperature is 750 °C in the range of 650–850 °C. • The optimal NMVP/C has higher capacity and better rate capability and cyclability. • The optimal NMVP/C has discharge capacity of 108 mAh/g (0.2C) and 81.3 mAh/g (20C). [ABSTRACT FROM AUTHOR]

Sn4+ doped V 2 O 5 (Sn 0.1 V 2 O 5) sample was synthesized by a sol-gel method and post annealing at 400 °C for 1 h in air. The microstructure of the as-prepared the Sn 0.1 V 2 O 5 was analyzed by XRD, XPS, and SEM. The lithium storage performance of the Sn 0.1 V 2 O 5 was characterized by CV, EIS, and charge/discharge tests in the voltage window of 1.5–4.0 V (vs. Li/Li+). The results demonstrated that Sn doping can refine the grain size of V 2 O 5 , increase V4+ concentration in Sn 0.1 V 2 O 5 , and favor the formation of two-dimensional sheet-like morphology. Compared to undoped V 2 O 5 , the Sn 0.1 V 2 O 5 exhibited significantly enhanced lithium storage performance in the voltage window of 1.5–4.0 V (vs. Li/Li+). For example, after 100 cycles at 200 mA g−1, the Sn 0.1 V 2 O 5 retained a specific discharge capacity of 135 mAh g−1, much higher than that (91 mAh g−1) of the pure V 2 O 5. In addition, Sn 0.1 V 2 O 5 exhibited a higher initial coulombic efficiency (98.16%) than the undoped V 2 O 5 (91.05%). The improved lithium storage performance can be attributed to the increased lithium ion diffusion coefficient, enhanced electrochemical reaction reversibility, and decreased electrochemical reaction resistance upon Sn4+ doping. • Sn4+ doped V 2 O 5 is prepared by sol-gel method and post annealing treatment. • Sn4+ doping significantly enhances the lithium storage performance of V 2 O 5. • Sn4+ doping increases Li+ diffusivity and decreases charge-transfer resistance of V 2 O 5. • Sn4+ doping increases the initial coulombic efficiency of V 2 O 5. [ABSTRACT FROM AUTHOR]

FeMnO 3 (FMO) has received increasing interest as anode material for Li-ion batteries owning to its high theoretical capacity and abundant sources. However, the low electrical conductivity and sluggish kinetics seriously impede its practical application. Herein, nitrogen-doped FeMnO 3 (FMO-N) is prepared by a chemical co-precipitation method and post calcination. Compare to pure FMO, the FMO-N exhibits higher capacity (808 mA h g−1 at 500 mA g−1 after 200 cycles), better rate performance (374 mA h g−1 at 5000 mA g−1), and much enhanced kinetics. Considering the features of low cost and outstanding Li ion storage performance, this FMO-N could be a promising anode material for Li-ion batteries. • N doped FeMnO 3 has been prepared with ammonium bicarbonate as N source. • The N doped FeMnO 3 delivers a capacity of 807.7 mA h g−1 at 0.5 A g−1 after 200 cycles. • The N doped FeMnO 3 gives a capacity of 373.6 mA h g-1 at 5 A g−1. • The reaction kinetics and pseudocapacitive behavior are reinforced by N doping. [ABSTRACT FROM AUTHOR]

Sodium/potassium ion batteries (SIBs and PIBs) have attracted extensive attention because of the low cost and comparable energy density with lithium-ion batteries. However, their application is still impeded by the inherent sluggish kinetics of suitable anode materials. Herein, graphene-supported NiS 2 nanocrystals with a strong chemical Ni-O interaction (denoted as c-NiS 2 /rGO) are fabricated and adopted as a universal anode material for both SIBs and PIBs. It is found that the Ni-O interaction can chemically bridge NiS 2 with graphene networks, favoring the thermo-dynamical stabilization of NiS 2 /rGO heterostructure and dynamically accelerated ion/electron transport as revealed by a Density Functional Theory (DFT) simulation. Electrochemical investigations on SIB and PIB reveal a high cycle stability. Specifically, the c-NiS 2 /rGO shows a reversible capacity of 580.6 mAh g−1 at 5 A g−1 and 215.8 mAh g−1 at 2 A g−1 in SIB and PIB, respectively. This work shed lights on manipulation of nickel-sulfide/rGO based materials through interfacial engineering for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Mixed transition metal oxides have attracted much attention as anode materials for lithium-ion batteries because of their high theoretical capacity, low cost, and rich redox reaction. In this work, coralline-like FeMnO 3 anode materials are synthesized by a facile co-precipitation method and subsequent sintering in air. The influences of sintering temperature on the microstructure and electrochemical performance of the samples are investigated. The results demonstrated that with the increase of sintering temperature, the phase structure of the products changes from FeMnO 3 /Fe 2 O 3 /Mn 3 O 4 composites at 600 °C to pure phase FeMnO 3 at 1000 °C, accompanied with the size of the primary particle increasing from tens of nanometers to hundreds of nanometers. Discharge/charge performance tests indicated that the sample sintered at 600 °C presents the biggest fluctuation of capacity during cycling, while the sample sintered at 1000 °C gives a rather flat capacity during cycling; moreover, the pure phase FeMnO 3 at 1000 °C possesses the best rate capability among the three samples. For example, the pure phase FeMnO 3 sintered at 1000 °C delivers a specific capacity of 585 mA h g−1 after 290 cycles at the current of 1000 mA g−1; even at the high current density of 5 A g−1, the capacity still retained at 397 mA h g−1. Charge storage mechanism analysis revealed that the pure phase FeMnO 3 sintered at 1000 °C shows obvious pseudocapacitive behavior during the discharge/charge process, which partly account for its superior cycling performance and high-rate capability. • Coralline-like FeMnO 3 are synthesized by a facile co-precipitation method. • The coralline-like FeMnO 3 showed superior lithium storage performance. • The coralline-like FeMnO 3 showed significant pseudocapacitive behavior. • The FeMnO 3 exhibited a lithium diffusion coefficient of 2.42 × 10−15 cm2 s−1. [ABSTRACT FROM AUTHOR]

LiNi 0.6 Mn 0.2 Co 0.2 O 2 is considered as a promising Ni-rich layered cathode material of lithium-ion batteries due to low cost and high capacity. However, it is generally prepared by complicated precursor methods. In this work, LiNi 0.6 Mn 0.2 Co 0.2 O 2 is synthesized by a solid-state method with manganese acetate as manganese source and an effective mixing way. The as-prepared samples are characterized by XRD, FESEM, XPS and electrochemical techniques. The results show that the synthesized LiNi 0.6 Mn 0.2 Co 0.2 O 2 cathode materials have an α-NaFeO 2 type structure with insignificant cation mixing, octahedral single crystal and quasi sphere morphology, smaller particle size and good dispersion, so that it displays an initial discharge capacity of 163.6 mAh g−1 with a coulombic efficiency of 85.6% at 0.1C, a capacity retention of 99.1% after 100 cycles at 0.5C and an excellent rate performance, and also an initial discharge capacity of 177.3 mAh g−1 with capacity retention of 94.6% after 155 cycles at 55 °C. • Octahedral single crystal and quasi sphere of LiNi 0.6 Mn 0.2 Co 0.2 O 2 is synthesized by solid-state reaction. • LiNi 0.6 Mn 0.2 Co 0.2 O 2 has high crystallinity layered structure and insignificant cation mixing. • LiNi 0.6 Mn 0.2 Co 0.2 O 2 shows excellent coulombic efficiency, cycle stability and rate performance. [ABSTRACT FROM AUTHOR]

LiNi 0.8 Co 0.1 Mn 0.1 O 2 (LNCM811) is a promising cathode material for lithium ion batteries. However, it is difficult to commercialize on a large scale because of its unstable structure and fast capacity attenuation. To solve above problems, in this paper, the Na-doped LNCM811 material (LNCM811-Na) has been synthesized via hydrothermal method and high temperature solid phase method, and then it is coated with SiO 2 (LNCM811-Na@SiO 2) on the basis of Na doping. The structure, composition, morphology, and microstructure of LNCM811-Na@SiO 2 are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The results show that the specific capacity of the LNCM811–0.1Na@SiO 2 (3%) sample reaches 209 mAh g−1 at 0.5C (the LNCM811–0.1Na is 195 mAh g−1 and the LNCM811 is 178 mAh g−1). When the rate is increased to 10C, the specific capacity of the LNCM811–0.1Na@SiO 2 (3%) sample still reaches 115 mAh g−1 (the LNCM811–0.1Na is 95 mAh g−1 and the LNCM811 is 72 mAh g−1). The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) prove that Na doping and SiO 2 coating can effectively reduce the polarization and the charge transfer impedance, further promote the improvement of electrochemical performance. Thus, the LNCM811–0.1Na@SiO 2 (3%) sample is a very promising material in power batteries. • The LiNi 0.8 Co 0.1 Mn 0.1 O 2 composite was prepared by hydrothermal technology and high temperature solid phase method. • The LiNi 0.8 Co 0.1 Mn 0.1 O 2 composite was achieved by synergistic modification with sodium ion doping and silica coating. • Its cycle performance and rate performance were superior to the single sodium ion doped or silica coated samples. [ABSTRACT FROM AUTHOR]