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A high-performance Si@SiO2@C anode material for Li-ion batteries was obtained by a novel synthetic strategy based on a mechanical milling and molten salt coactivated magnesiothermic reduction at a low temperature of 200 °C, only using rice husk as the Si and C sources. The anode material obtained presented an electrochemically favorable architecture, in which crystalline Si particles with a size of ~15 nm were uniformly embedded in the amorphous carbon and SiO2 matrix. The amount of the Si, SiO2 and C components in the anode material was determined to be about 17.2, 24.5 and 58.3 wt%, respectively. Electrochemical analyses demonstrated that the Si@SiO2@C anode material showed excellent electrochemical performance, delivering a reversible capacity of 1277.3 mAh g−1 at a current density of 0.1 A g−1, still possessing a high capacity of 910.2 mAh g−1 when increasing current density to 5 A g−1. After cycled for 200 cycles at 1.0 A g−1, the anode still preserved a reversible capacity of 973.1 mAh g−1, showing a capacity retention of 93.1% and a Coulumbic efficiency higher than 99.7%. Importantly, the synthetic strategy is not only more facile and cost effective, but also more environmentally friendly, compared with those recently reported. Thus it is promising to be applied for large-scale transformation of rice husk to high-performance Si@C-based anode materials for Li-ion batteries.

Ultrathin Ni Co Al layered double hydroxide (LDH) sheets directly grew on reduced graphene oxide (RGO) nanosheets by a facile hydrothermal route in a mixed solvent of water and ethylene glycol, yielding the RGO/Ni 0.75−x Co x Al 0.25 -LDH (x = 0, 0.05, 0.15) composites. Structural analyses revealed that the resulting composites presented a unique morphology of crumpled silk veil waves, in which the ultrathin Ni 0.75−x Co x Al 0.25 -LDH sheets, composed of 2–3 host layers, were entangled with the rippled RGO nanosheets. Electrochemical analyses demonstrated that the RGO/Ni 0.70 Co 0.05 Al 0.25 -LDH composite showed superior supercapacitive performance, as compared with the pure Ni 0.70 Co 0.05 Al 0.25 -LDH and the RGO/Ni 0.75−x Co x Al 0.25 -LDH (x = 0, 0.15) composites. It exhibited not only ultrahigh cycling stability and good rate capability, but also considerably high specific capacitance. It possessed a high specific capacitance of 1544 F g −1 at current densities of 1 A g −1 , still delivering a high capacitance of 1081 F g −1 at an increased current density of 40 A g −1 . After cycled at 10 A g −1 for 2000 cycles, it retained a capacitance of 1343 F g −1 without capacitance decay observed. The superb supercapacitive performance along with the facile synthesis method adopted suggested that the RGO/Ni 0.70 Co 0.05 Al 0.25 -LDH composite was promising for supercapacitor applications.

A nano-sized Si anode material was synthesized by a novel and highly efficient route of ball-milling assisted low-temperature aluminothermic reduction at 150–180 °C in a eutectic NaCl/KCl/AlCl3 mixture, using white carbon black and coarse-grained Al powder as the starting materials. After extending the duration of ball-milling assisted aluminothermic reduction to 10 h, the obtained Si yield reached as high as 94%. The synthesized nano-Si mainly consisted of irregular porous agglomerates constructed by ultrafine primary particles with a particle size less than 50 nm. The nano-Si anode showed a superior electrochemical performance. Its maximum discharge and charge capacities at a current density of 0.05 A g−1 were 3075 and 2597 mAh g−1, respectively, leading to a high initial Coulumbic efficiency of 84.5%. The nano-Si anode exhibited reversible capacities of 2458 mAh g−1 at 0.2 A g−1, and of 1169 mAh g−1 at a high current density of 5 A g−1. After cycling at 1 A g−1 for 400 cycles, it still delivered a high reversible capacity of 804 mAh g−1. The synthetic strategy, which is not only facile and highly efficient, but also low-cost and environmentally benign, is thus promising to be applied for mass production of nano-Si anode materials for next-generation Li-ion batteries.

A Co–Ni doped LiMn 2 O 4 spinel cathode material with a nominal stoichiometry of LiMn 1.95 Co 0.025 Ni 0.025 O 4 was synthesized by a sol–gel mediated solid-state route at a low temperature of 650 °C, using a highly dispersed ultra-fine Mn 3 O 4 as the Mn source. Also, a pelletizing process was adopted to optimize its morphology. It was revealed that the Co–Ni doped LiMn 2 O 4 obtained consisted of porous nanoparticles-constructed LiMn 1.95 Co 0.025 Ni 0.025 O 4 granules with a size of 30–50 μm, which combined the favorable characteristics of both nano-sized and bulk materials, i.e. considerably large specific surface area and high tap density. The cathode material exhibited excellent electrochemical performance. Notably, its rate capability was extraordinarily high, which was superior to that of pristine or doped LiMn 2 O 4 materials ever reported. It showed a discharge capacity of 119 mA h g −1 at a current rate of 0.2 C (1 C = 148 mA g −1 ), and retained a capacity of 111 mA h g −1 at 10 C, presenting a 93% capacity retention. After 200 cycles at 1 C and 25 °C, it delivered a capacity of 112 mA h g −1 , retaining 97% of its initial capacity. After 100 cycles at 1 C and 55 °C, it showed a capacity of 110 mA h g −1 , preserving 96% of its initial capacity. The excellent electrochemical performance together with the facile synthesis process allowed the synthesized LiMn 1.95 Co 0.025 Ni 0.025 O 4 to be a promising cathode material for high-power Li-ion batteries.

A shell/core Co-incorporated LiMn 2 O 4 cathode material was synthesized by a facile modified sol–gel process, using highly dispersed Mn 3 O 4 nanoparticles as the Mn source. Structural characterization revealed that the shell layer, which was 5–10 nm thick, and composed of spinel LiMn 1.83 Co 0.17 O 4 , grew homogeneously on the spinel LiMn 2 O 4 core with a size of ~50 nm. Electrochemical results showed that electrochemical performance of the shell/core cathode material compared favorably with that of the Co-doped LiMn 2 O 4 counterparts. Also its rate capability and cycling performance were apparently superior to those of pristine LiMn 2 O 4 synthesized under the same conditions. The shell/core cathode material exhibited a discharge capacity of 127 mAh g −1 at a current rate of 0.5 C (where 1 C=148 mA g −1 ), and retained a capacity of 103 mAh g −1 at 10 C, showing 81% capacity retention. After 200 cycles at 1 C and 25 °C, it delivered a capacity of 123 mAh g −1 , retaining 98% of its initial capacity. After 100 cycles at 1 C and 55 °C, it showed a capacity of 118 mAh g −1 , preserving 94% of its initial capacity. Its excellent electrochemical performance along with the facile synthesis process allowed the shell/core cathode material to serve as a promising cathode for high-performance Li-ion batteries.

A reduced graphene oxide/Ni(OH)2 composite with excellent supercapacitive performance was synthesized by a facile hydrothermal route without organic solvents or templates used. XRD and SEM results reveal that the nickel hydroxide, which crystallizes into hexagonal β-Ni(OH)2 nanoflakes with a diameter less than 200 nm and a thickness of about 10 nm, is well combined with the reduced graphene oxide sheets. Electrochemical performance of the synthesized composite as an electrode material was investigated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements. Its specific capacitance is determined to be 1672 F/g at a scan rate of 2 mV/s, and 696 F/g at a high scan rate of 50 mV/s. After 2000 cycles at a current density of 10 A/g, the composite exhibits a specific capacitance of 969 F/g, retaining about 86% of its initial capacitance. The composite delivers a high energy density of 83.6 W·h/kg at a power density of 1.0 kW/kg. The excellent supercapacitive performance along with the easy synthesis method allows the synthesized composite to be promising for supercapacitor applications.

Porous nanoparticles-constructed granule LiMn2O4 spinel was achieved by a solid-state reaction at a relatively low temperature of 600 °C, using a highly reactive Mn3O4 as manganese source, prepared by a precipitation-oxidation process. The granule LiMn2O4, well-crystallized with negligible oxygen deficiency, combines the advantages of nano-structured and bulk materials, exhibiting excellent electrochemical performance and a high tap density of 2.05 g cm−3. Importantly, its cycling performance, especially at elevated temperatures, compares favorably with that of the doped or surface-coated LiMn2O4 materials reported. Also, it shows superior rate capability and cycling performance to the dispersive nanoparticle LiMn2O4 synthesized under the same conditions. The granule LiMn2O4 exhibits a discharge capacity of 121 mAh g−1 at a current rate of 1 C (where 1 C = 148 mA g−1), and retains a capacity of 103 mAh g−1 at 15 C, showing 85% capacity retention. After 200 cycles at 1 C and 25 °C, it delivers a capacity of 119 mAh g−1, retaining 98% of its initial capacity. After 100 cycles at 1 C and 55 °C, it shows a capacity of 114 mAh g−1, preserving 95% of its initial capacity. Due to its excellent electrochemical performance and facile synthesis process adopted, the granule LiMn2O4 can serve as a promising cathode for high-performance Li-ion batteries.

A reduced graphene oxide/β-Ni(OH) 2 composite with excellent supercapacitive performance was prepared by a facile chemical precipitation. Reduced graphene oxide was ultrasonically dispersed in a Ni(NO 3 ) 2 solution, forming a suspension. Then let the prepared suspension stand for 0.5 h and 24 h, respectively, followed by stirring and adding NaOH solution into it for obtaining two types of composites. It was found that the standing time notably affected morphology and supercapacitive performance of the resulting composites. The composite derived from the 24 h-standing suspension presented an ideal morphology with nano-sized β-Ni(OH) 2 particles homogeneously growing on the reduced graphene oxide sheets. The composite exhibited ultra-large specific capacitance, high rate capability and good cycling stability in 6 mol L −1 KOH electrolyte. Its maximum specific capacitance was 2134 F g −1 at a scan rate of 2 mV s −1 , and a large specific capacitance of 882 F g −1 was still preserved at a high scan rate of 70 mV s −1 . After 2000 cycles at a current density of 10 A g −1 , the composite delivered a specific capacitance of 1141 F g −1 , retaining about 81% of its initial capacitance. The high performance and the simple synthesis route allowed the obtained composite to be promising for supercapacitor applications.

Ultra-fine Mn–Ni–Cu oxides (MNCO) are obtained by calcining a solid-state coordination derived oxalate Mn 0.68 Ni 0.22 Cu 0.10 C 2 O 4 · n H 2 O at 250–450 °C. The obtained MNCO present micron-sized agglomerates composed of primary particles with a size of ∼200 nm. The 250 °C- and 350 °C-obtained MNCO are poorly crystallized with a structure of α-MnO 2 , while the 450 °C-obtained MNCO contain multiphase oxides with structures of α-MnO 2 , γ-MnO 2 and Mn 2 O 3 . Electrochemical properties are investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy in 6 mol L −1 KOH electrolyte. The MNCO electrodes exhibit good supercapacitive performance, superior to that of powder-based MnO 2 electrodes. At a scan rate of 2 mV s −1 , the 250 °C-, 350 °C-, and 450 °C-obtained MNCO electrodes deliver capacitance values of 490, 293 and 205 F g −1 , respectively. At a current density of 1000 mA g −1 , the 250 °C-, 350 °C-, and 450 °C-obtained MNCO symmetrical capacitors exhibit capacitance values of 368, 286, and 135 F g −1 , respectively, retaining about 75, 81 and 87% of their initial capacitance values after 500 cycles, respectively.

Mesoporous Mn–Ni oxides with the chemical compositions of Mn1-x Ni x O δ (x = 0, 0.2, and 0.4) were prepared by a solid-state reaction route, using manganese sulfate, nickel chloride, and potassium hydroxide as starting materials. The obtained Mn–Ni oxides, mainly consisting of the phases of α- and γ-MnO2, presented irregular mesoporous agglomerates built from ultra-fine particles. Specific surface area of Mn1–x Ni x O δ was 42.8, 59.6, and 84.5 m2 g−1 for x = 0, 0.2, and 0.4, respectively. Electrochemical properties were investigated by cyclic voltammetry and galvanostatic charge/discharge in 6 mol L−1 KOH electrolyte. Specific capacitances of Mn1-x Ni x O δ were 343, 528, and 411 F g−1 at a scan rate of 2 mV s−1 for x = 0, 0.2, and 0.4, respectively, and decreased to 157, 183, and 130 F g−1 with increasing scan rate to 100 mV s−1, respectively. After 500 cycles at a current density of 1.24 A g−1, the symmetrical Mn1–x Ni x O δ capacitors delivered specific capacitances of 160, 250, and 132 F g−1 for x = 0, 0.2, and 0.4, respectively, retaining about 82%, 89%, and 75% of their respective initial capacitances. The Mn0.8Ni0.2O δ material showed better supercapacitive performance, which was promising for supercapacitor applications.

An ultra-fine MnO 2 powder was synthesized by a novel route of solid-state coordination reaction. The structure and morphology were characterized by X-ray diffraction, scanning electron microscope and infrared spectroscopy. The MnO 2 powder with a primary particle size of ∼200 nm was composed of α-MnO 2 and γ-MnO 2 . Electrochemical properties of the MnO 2 electrode were examined by cyclic voltammetry, and galvanostatic charge/discharge and electrochemical impedance spectroscopy measurements in 6 mol L −1 KOH electrolyte. The MnO 2 electrode exhibited good supercapacitive performance. Specific capacitance values of 337 and 197 F g −1 were obtained for the MnO 2 electrode at scan rates of 2 and 50 mV s −1 , respectively. The MnO 2 electrode subjected to 500 cycles at a current density of 800 mA g −1 delivered a specific capacitance of 228 F g −1 , retaining 75% of its initial specific capacitance.

Co 0.30 Ni 0.66 Mn 2.04 O 4 negative temperature coefficient ceramics were derived from mixed oxalate Co 0.30 Ni 0.66 Mn 2.04 (C 2 O 4 ) 3 · n H 2 O. The mixed oxalate was synthesized by milling a mixture of cobalt acetate, nickel acetate, manganese acetate, and oxalic acid at room temperature. An ultra-fine Co 0.30 Ni 0.66 Mn 2.04 O 4 powder was obtained by calcining the mixed oxalate in air at 800 °C for 3 h. The oxide powder compact was sintered at a relatively low temperature of 1100 °C for 5 h, achieving a relative density of ∼98%. The specific resistivity ρ 25 °C and the thermal constant B 25/85 °C were 765.2 Ω cm and 3604 K, respectively. The resistance drift after aging at 150 °C for 500 h was 1.5%.

Cu 0.3 Ni 0.66 Mn 2.04 O 4 negative temperature coefficient (NTC) ceramic was prepared using mixed oxalate-derived oxide powder. The mixed oxalate was synthesized by milling a mixture of copper acetate, nickel acetate, manganese acetate and oxalic acid at room temperature. The spinel-structured oxide powder was obtained by calcining the mixed oxalate in air at 800 °C for 2 h. The oxide powder compact was sintered at a relatively low temperature of 1100 °C for 2.5 h, attaining a relative density of ∼98%. The sintered ceramic had a specific resistivity ρ 25 °C of 63.3 Ω cm and the thermal constant B 25/50 of 2740 K, and exhibited much reduced shift in electrical resistivity of ∼5% after annealing at 150 °C for 500 h in air. The difference in the electrical property of the as-prepared ceramic is attributed to the fine-grained microstructure and the lower sintering temperature used in the present study.

Effect of thermal history and chemical composition on aging of Ni x Mn3 − x O4 + δ (0.56 ≤ x ≤ 1.0) ceramics was investigated. It was found that all the Ni x Mn3 − x O4 + δ ceramic samples metallized by co-firing at 1050°C showed significant electrical stability with an aging coefficient less than 1.0%, while aging of those metallized by annealing at 850°C was increasingly serious with a rise in Ni content x, the aging coefficient ranging from 0.2% to 3.8%. However, the ceramic samples with Ni content x ≤ 0.70, whether metallized by co-firing or by annealing, exhibited extraordinarily high electrical stability with an aging coefficient less than 0.5%. The composition dependence of aging of the ceramic samples was explained qualitatively, based on the electrical conduction mechanism of small polaron hopping and on the aging mechanism of the cationic vacancy-assisted migration of cations to their thermodynamically preferable sites under thermal stress.

In this paper, the dense FexCu0.10Ni0.66Mn2.24−xO4 (0 ≤ x ≤ 0.90) ceramics with accurate stoichiometry are prepared by the route of solid-state coordination reaction. The effect of Fe addition on the electrical properties of the ceramics has been investigated by powder X-ray diffraction (XRD), electrical measurement and thermogravimetric analysis. With Fe content x increasing from 0 to 0.45, the resistivity remains almost unchanged, whereas the thermal constant B decreases drastically. With a further increase in x from 0.45 to 0.90, both the resistivity and the thermal constant B increase. With a rise in x from 0 to 0.9, the aging coefficient drops from 19.9 to 0.6%. The remarkable improvement of the electrical stability can be attributed to the mechanism that substitution of Fe3+ for Mn2+ and Mn3+ restrains the formation of cation vacancies in spinel lattice, thus the modification of cation distribution and the consequent aging under thermal stress is greatly alleviated.