The present invention relates to a method of producing a sodium iron(II)-hexacyanoferrate(II) (Na.sub.2-xFe[Fe(CN).sub.6].mH.sub.2O), where x is <0.4) material commonly referred to as Prussian White. The method comprises the steps of acid decomposition of Na.sub.4Fe(CN).sub.6.10H.sub.2O to a powder of Na.sub.2-xFe[Fe(CN).sub.6].mH.sub.2O, drying and enriching the sodium content in the Na.sub.2-xFe[Fe(CN).sub.6].mH.sub.2O powder by mixing the powder with a saturated or supersaturated solution of a reducing agent containing sodium in dry solvent under an inert gas. The steps of acid decomposition and enriching the sodium content are performed under non-hydrothermal conditions.

The present invention discloses a method of preparing an electrode material for lithium-ion batteries comprising the steps of preparing a mixture of precursors taken in predefined stoichiometric ratios for synthesis of lithium iron phosphate (LiFePO4), adding niobium pentoxide as a precursor for doping of niobium at Li+ site of LiFePO.sub.4 for synthesis of niobium doped LiFePO.sub.4 and ball milling operation provides nano sized powder particles. Now, a precursor of carbon is added to said mixture of precursors for synthesizing and obtaining carbon coated niobium doped LiFePO.sub.4 nano sized powder particles. Pellets of required size are prepared and sintered. The obtained pellets are structurally characterized.

An object is to reduce variation in shape of crystals that are to be formed. Solutions containing respective raw materials are made in an environment where an oxygen concentration is lower than that in air, the solutions containing the respective raw materials are mixed in an environment where an oxygen concentration is lower than that in air to form a mixture solution, and with use of the mixture solution, a composite oxide is formed by a hydrothermal method.

A composite containing phosphorus, lithium, iron, sulfur, and carbon as constituent elements wherein lithium sulfide (Li.sub.2S) is present in an amount of 90 mol % or more, and wherein the crystallite size calculated from the half-width of a diffraction peak based on the (111) plane of Li.sub.2S as determined by X-ray powder diffraction measurement is 80 nm or less. The composite exhibits a high capacity (in particular, a high discharge capacity) useful as an electrode active material for a lithium-ion secondary battery (in particular, a cathode active material for a lithium-ion secondary battery), without the need for stepwise pre-cycling treatment.

Precursor compounds of sodium alloy(s), for use as negative electrode active material in a sodium-ion battery, as well as to a negative electrode have the precursor compound of sodium alloy(s), as well as a sodium-ion battery having a negative electrode of this kind.

A lithium-ion battery anode layer, comprising an anode active material embedded in pores of a solid graphene foam composed of multiple pores and pore walls, wherein (a) the pore walls contain a pristine graphene or a non-pristine graphene material; (b) the anode active material contains particles of a niobium-containing composite metal oxide and is in an amount from 0.5% to 99% by weight based on the total weight of the graphene foam and the anode active material combined, and (c) the multiple pores are lodged with particles of the anode active material. Preferably, the solid graphene foam has a density from 0.01 to 1.7 g/cm.sup.3, a specific surface area from 50 to 2,000 m.sup.2/g, a thermal conductivity of at least 100 W/mK per unit of specific gravity, and/or an electrical conductivity no less than 1,000 S/cm per unit of specific gravity.

A graphene-enabled hybrid particulate for use as a lithium-ion battery anode active material, wherein the hybrid particulate is formed of a single or a plurality of graphene sheets and a single or a plurality of fine primary particles of a niobium-containing composite metal oxide, having a size from 1 nm to 10 m, and the graphene sheets and the primary particles are mutually bonded or agglomerated into the hybrid particulate containing an exterior graphene sheet or multiple exterior graphene sheets embracing the primary particles, and wherein the hybrid particulate has an electrical conductivity no less than 10.sup.4 S/cm and said graphene is in an amount of from 0.01% to 30% by weight based on the total weight of graphene and the niobium-containing composite metal oxide combined.

Disclosed herein are doped perovskite oxides. The doped perovskite oxides may be used as a cathode material in an electrochemical cell to electrochemically generate ammonia from N.sub.2. The doped perovskite oxides may be combined with nitride compounds, for instance iron nitride, to further increase the efficiency of the ammonia production.

A positive electrode includes a positive electrode active material layer, and the positive electrode active material layer includes a first lithium iron phosphate and a second lithium iron phosphate as a positive electrode active material, the first lithium iron phosphate has an average particle diameter D.sub.50 grater than that of the second lithium iron phosphate and at least one facet, and when the cross section of the positive electrode is observed with a scanning electron microscope (SEM), the cross section of the first lithium iron phosphate has at least one side having a length of 2 ?m or more.

The present application provides an iron-manganese-based positive electrode material, and a preparation method therefor and the use thereof. The preparation method comprises the steps of: S1, subjecting an inorganic compound of lithium and a Fe.sub.xMn.sub.y(OH).sub.2 precursor to oxidation sintering to obtain an intermediate product, wherein 0<x<1.0, 0<y<1.0, and x+y=1, and the ratio of the molar amount of Li in the inorganic compound of lithium to the total molar amount of Fe and Mn in the F.sub.xMn.sub.y(OH).sub.2 precursor is (0.1-0.5):1; and S2, subjecting the intermediate product to a second sintering under nitrogen or first inert gas atmosphere conditions to obtain the iron-manganese-based positive electrode material. The iron-manganese-based positive electrode material obtained by the preparation method of the present application has a relatively low content of a lithium element and a more stable structure, such that the intercalation and deintercalation process of lithium ions between the positive electrode and the electrolyte will not affect the original structure of the iron-manganese-based positive electrode material, and the cycling stability of the lithium-ion battery is further ensured.