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Owing to the worldwide abundance and low-cost of Na, room-temperature Na-ion batteries are emerging as attractive energy storage systems for large- scale grids. Increasing the Na content in cathode materials is one of the effective ways to achieve high energy density. Prussian blue and its analogues （PBAs） are promising Na-rich cathode materials since they can theoretically store two Na＋ ions per formula unit. However, increasing the Na content in PBAs cathode materials remains a major challenge. Here we show that sodium iron hexacyanoferrate with high Na content can be obtained by simply controlling the reducing agent and reaction atmosphere during synthesis. The Na content can reach as high as 1.63 per formula, which is the highest value for sodium iron hexacyanoferrate. This Na-rich sodium iron hexacyanoferrate demonstrates a high specific capacity of 150 mAh·g^-1 and remarkable cycling performance with 90% capacity retention after 200 cycles. Furthermore, the Na intercalation/ de-intercalation mechanism has been systematically studied by in situ Raman spectroscopy, X-ray diffraction and X-ray absorption spectroscopy analysis for the first time. The Na-rich sodium iron hexacyanoferrate can function as a plenteous Na reservoir and has great potential as a cathode material for practical Na-ion batteries.

An aerosol spray pyrolysis technique is used to synthesize a spherical nano-Sb@C composite. Instrumental analyses reveal that the micro-nanostructured composite with an optimized Sb content of 68.8 wt% is composed of ultra-small Sb nanoparticles （10 nm） uniformly embedded within a spherical porous C matrix （denoted as 10-Sb@C）. The content and size of Sb can be controlled by altering the concentration of the precursor. As an anode material of sodium-ion batteries, 10-Sb@C provides a discharge capacity of 435 mAh.g^-1 in the second cycle and 385 mAh.g^-1 （a capacity retention of 88.5%） after 500 cycles at 100 mAh.g^-1. In particular, the electrode exhibits an excellent rate capability （355, 324, and 270 mAh.g^-1 at 1,000, 2,000, and 4,000 mAh.g^-1, respectively）. Such a high-rate performance for the Sb-C anode has rarely been reported. The remarkable electrochemical behavior of 10-Sb@C is attributed to the synergetic effects of ultra-small Sb nanoparticles with an uniform distribution and a porous C framework, which can effectively alleviate the stress associated with a large volume change and suppress the agglomeration of the pulverized nanoparticles during prolonged charge-discharge cycling.

Lithium iron phosphate （LiFePO4） is a potential high efficiency cathode material for lithium ion batteries, but the low electronic conductivity and single diffusion channel for lithium ions require good particle size and shape control during the synthesis of this material. In this paper, six LiFePO4 nanocrystals with different size and shape have been successfully synthesized in ethylene glycol. The addition sequence Fe-PO4-Li helps to form LiFePO4 nanocrystals with mostly {010} faces exposed, and increasing the amount of LiOH leads to a decrease in particle size. The electrochemical performance of the six distinct LiFePO4 particles show that the most promising LiFePO4 nanocrystals either have predominant {010} face exposure or high specific area, with little iron（II） oxidation.

A high voltage layered Li1.2Ni0.16Co0.08Mn0.56O2 cathode material with a hollow spherical structure has been synthesized by molten-salt method in a NaCI flux. Characterization by X-ray diffraction and scanning electron microscopy confirmed its structure and proved that the as-prepared powder is constituted of small, homogenously sized hollow spheres （1-1.5 μm）. The material exhibited enhanced rate capability and high first cycle efficiency due to the good dispersion of secondary particles. Galvanostatic cycling at different temperatures （20, 40, and 60 ℃） and a current rate of 2 C （500 mA.g-1） showed no significant capacity fade.

Li-rich cathode materials have been considered as promising candidates for high-energy lithium ion batteries （LIBs）. In this study, we report a new series of Li-rich materials （Li[Li1/B-2x/BMn2/3-x/3Nix]O2 （0.09 ≤x≤ 0.2）） doped with small amounts of Ni as cathode materials in LIBs, which exhibited unusual phenomenon of capacity increase up to tens of cycles due to the continuous activation of the Li2MnO3 phase. Both experimental and computational results indicate that unlike commonly studied Ni-doped Li-rich cathode materials, smaller amounts of Ni doping can promote the stepwise Li2MnO3 activation to obtain increased specific capacity and better cycling capability. In contrast, excessive Ni will over-activate the Li2MnO3 and result in a large capacity loss in the first cycle. The Lil.25Mn0.625Ni0.12sO2 material with an optimized content of Ni delivered a superior high capacity of -280 mAh.g-1 and good cycling stability at room temperature.

NaFeTiO4 nanorods of high yields （with diameters in the range of 30-50 nm and lengths of up to 1-5 μm） were synthesized by a facile sol-gel method and were utilized as an anode material for sodium-ion batteries for the first time. The obtained NaFeTiO4 nanorods exhibit a high initial discharge capacity of 294 mA·h·g^-1 at 0.2 C （1 C = 177 mA·g^-1）, and remain at 115 mA·h·g^-1 after 50 cycles. Furthermore, multi-walled carbon nanotubes （MWCNTs） were mechanically milled with the pristine material to obtain NaFeTiO4/MWCNTs. The NaFeTiO4/MWCNTs electrode exhibits a significantly improved electrochemical performance with a stable discharge capacity of 150 mA·h·g^-1 at 0.2 C after 50 cycles, and remains at 125 mA·h·g^-1 at 0.5 C after 420 cycles. The NaFeTiO4/MWCNTs//Na3V2（PO4）3/C full cell was assembled for the first time; it displays a discharge capacity of 70 mA·h·g^-1 after 50 cycles at 0.05 C, indicating its excellent performances. X-ray photoelectron spectroscopy, ex situ X-ray diffraction, and Raman measurements were performed to investigate the initial electrochemical mechanisms of the obtained NaFeTiO4/MWCNTs.

The main drawbacks of vanadium oxide as a cathode material are its low conductivity, low practical capacity and poor cycling stability. Adding Cr can improve its conductivity and a metastable amorphous state may provide higher capacity and stability. In this work, metastable amorphous Cr-V-O nano- particles have been successfully prepared through a facile co-precipitation reaction followed by annealing treatment. As a cathode material for lithium batteries, the metastable amorphous Cr-V-O nanoparticles exhibit high capacity （260 mAh/g at 100 mA/g between 1.5-4 V）, low capacity loss （more than 80% was retained after 200 cycles at 100 mA/g） and high rate capability （up to 3 A/g）.

The preparation of Li4SiO4-coated LiNi0.5Mn1.5O4 materials by sintering the SiO2-coated nickel-manganese oxides with lithium salts using abundant and low-cost sodium silicate as the silicon source was reported. The samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that a uniform and complete SiO2 coating layer could be obtained at a suitable pH value of 10, which transformed to a good LiaSiO4 coating layer afterwards. When used as the cathode materials for lithium-ion batteries, the Li4SiO4-coated LiNi0.5Mn1.5O4 samples deliver a better electrochemical performance in terms of the discharge capacity, rate capability, and cycling stability than that of the pristine material. It can still deliver 111.1 mAh/g at 20 C after 300 cycles, with a retention ratio of 93.1% of the stable capacity, which is far beyond that of the pristine material （101.3 mAh/g, 85.6%）.

As part of an effort to build a prototype flow battery system using a nano-suspension containing β-Ni（OH）2 nanoparticles as the cathode material, nano-sized β-Ni（OH）2 particles with well-controlled particle size and morphology were synthesized via the one-step precipitation of a NiCl2 precursor. The composition and morphology of the nanoparticles were characterized by scanning electronic microscopy （SEM） and X-ray diffraction （XRD）. The XRD patterns confirmed that β-Ni（OH）2 was successfully synthesized, while SEM results showed that the particle sizes range from 70 to 150 nm. To ensure that Ni（OH）2 could be employed in the nano-suspension flow battery, the electrochemical performance of the synthesized 13-Ni（OH）2 was initially tested in pouch cells through charge/discharge cycling. The phase transformations occurring during charge/discharge were investigated using in-situ X-ray absorption spectroscopy to obtain the shift in the oxidation state of Ni （X-ray adsorption near edge structure, XANES） and the distances between Ni and surrounding atoms in charged and discharged states （extended X-ray absorption fine structure, EXAFS）. XANES results indicated that the electrode in the discharged state was a mixture of phases because the edge position did not shift back completely. XAFS results further proved that the discharge capacity was provided by β-NiOOH and the ratio between β-Ni（OH）2 and γ-NiOOH in the electrode in the discharged state was 71：29. Preliminary nano-suspension tests in a lab-scale cell were conducted to understand the behavior of the nano-suspension during charge/discharge cycling and to optimize the operating conditions.

Carbon-coated LiFePO_4 hollow nanofibers as cathode materials for Li-ion batteries were obtained by coaxial electrospinning. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area analysis, galvanostatic charge–discharge, and electrochemical impedance spectroscopy（EIS） were employed to investigate the crystalline structure, morphology, and electrochemical performance of the as-prepared hollow nanofibers. The results indicate that the carbon-coated LiFePO_4 hollow nanofibers have good long-term cycling performance and good rate capability： at a current density of 0.2C（1.0C = 170 mA ·g^-1） in the voltage range of 2.5–4.2 V, the cathode materials achieve an initial discharge specific capacity of 153.16 mA h·g^-1 with a first charge–discharge coulombic efficiency of more than 97%, as well as a high capacity retention of 99% after 10 cycles; moreover, the materials can retain a specific capacity of 135.68 mA h·g^-1, even at 2C.