The present invention relates to a method of preparing a high hydrophobic silica aerogel having a low tap density and a hydrophobic silica aerogel prepared thereby. The method of preparing a hydrophobic silica aerogel according to the present invention may have good productivity and economic efficiency, because preparation time is reduced by simultaneously performing surface modification and solvent substitution in a single step, and may control a degree of hydrophobicity of the prepared silica aerogel by controlling a surface modification reaction by including a step of adding ammonium hydroxide. Thus, a hydrophobic silica aerogel having excellent physical properties, such as tap density and specific surface area, as well as high hydrophobicity obtained by controlling the degree of hydrophobicity may be prepared.

Provided are graphene nanosheets having a polyaromatic hydrocarbon concentration of less than about 0.7% by weight. Also provided are Graphene nanosheets having a polyaromatic hydrocarbon concentration of about 0.01% to about 0.5%.

The present invention belongs to the field of materials, and relates to an environment-friendly precursor, a cathode material for a lithium-ion battery, and preparation methods thereof. The method for preparing an environment-friendly precursor provided in the present invention includes: subjecting a metal and/or a metal oxide, an oxidant, water, and a complexing agent to a chemical corrosion crystallization reaction at an electrical conductivity equal to or greater than 200 uS/cm, a redox potential ORP value equal to or less than 100 my, and a complexing agent concentration of 3-50 g/L. The precursor prepared by using the method provided in the present invention has advantages that no waste water is produced during dissolution and crystallization, and that water is constantly consumed, so that the purpose of environmental friendliness can be achieved. Moreover, the first charge and discharge efficiency of a lithium-ion battery can be effectively improved by means of the precursor.

The invention relates to a process for preparing aluminates of the general formula (I)

A.sub.1B.sub.xAl.sub.12-xO.sub.19-y where A is at least one element from the group consisting of Sr, Ba and La, B is at least one element from the group consisting of Mn, Fe, Co, Ni, Rh, Cu and Zn, x=0.05-1.0, y is a value determined by the oxidation states of the other elements, which comprises the steps (i) provision of one or more solutions or suspensions comprising precursor compounds of the elements A and B and also a precursor compound of aluminum in a solvent, (ii) conversion of the solutions or suspensions or the solutions into an aerosol, (iii) introduction of the aerosol into a directly or indirectly heated pyrolysis zone, (iv) carrying out of the pyrolysis and (v) separation of the resulting particles comprising hexaaluminate of the general formula (I) from the pyrolysis gas.

The present invention relates to silicon-based powders and a method for producing the silicon-based powders. The method for producing the silicon-based powders includes a hydrolysis step of a silicon precursor having an alkoxy group, a condensation step and a drying step. By a specific weight ratio of water to the silicon precursor having the alkoxy group and a silicon precursor having a secondary amino group and an alkyl group, in the method for producing the silicon-based powders, the condensation step can be performed without organic solvents, and a modification on silicon-based gels can be performed to enhance a safety of processes and a hydrophobicity of the resulted silicon-based powders, and decrease a thermal conductivity and a bulk density of the resulted silicon-based powders.

A positive electrode active material for a lithium secondary battery, including secondary particles formed by aggregation of primary particles capable of being doped and undoped with lithium ions, said positive electrode active material having: an α-NaFeO.sub.2 type crystal structure represented by formula: Li[Li.sub.x(Ni.sub.aCo.sub.bMn.sub.cM.sub.d).sub.1-x]O.sub.2 (I), wherein 0≦x≦0.1, 0.7<a<1, 0<b<0.2, 0≦c<0.2, 0<d<0.1, a+b+c+d=1, and M is at least one metal element selected from the group consisting of Fe, Cr, Ti, Mg, Al, Zr, Ca, Sc, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In and Sn; and a crystallite size α/crystallite size β ratio (α/β) of 1.60 to 2.40, wherein the crystallite size α is within a peak region of 2θ=18.7±1° and the crystallite size β is within a peak region of 2θ=44.4±1°, each determined by a powder X-ray diffraction measurement using Cu-Kα radiation.

High specific capacity lithium rich lithium metal oxide materials are coated with inorganic compositions, such as metal fluorides, to improve the performance of the materials as a positive electrode active material. The resulting coated material can exhibit an increased specific capacity, and the material can also exhibit improved cycling. The materials can be formed while maintaining a desired relatively high average voltage such that the materials are suitable for the formation of commercial batteries. Suitable processes are described for the synthesis of the desired coated compositions that can be adapted for commercial production.

[Object] Provided is a means which is capable, with respect to a non-aqueous electrolyte secondary battery, of suppressing a decrease in capacity when the battery is used for a long period of time, and improving cycle characteristics. [Solving Means] Disclosed is a positive electrode active substance for a non-aqueous electrolyte secondary battery comprising a composite oxide containing lithium and nickel, in which the positive electrode active substance has a structure of secondary particles formed by aggregation of primary particles, the average particle diameter of the primary particles (D1) is 0.9 μm or less, and the ratio value (D2/D1)) of the average particle diameter of the secondary particles (D2) to the average particle diameter of the primary particles (D1) is 11 or more. [Representative Drawing] None

A positive active material for a rechargeable lithium battery includes a first positive active material including a secondary particle including at least two agglomerated primary particles, where at least one part of the primary particles has a radial arrangement structure, as well as a second positive active material having a monolith structure. The first and second positive active materials may both include nickel-based positive active materials. A method of preparing the positive active material, and a rechargeable lithium battery including a positive electrode including the positive active material are also provided.

Ternary precursor particles used for a lithium-ion battery, the ternary precursor particles having a Ni.sub.xCo.sub.yMn.sub.z(OH).sub.2, wherein, x+y+z=1, 0<x<1, 0<y<1, 0<z<1; each ternary precursor particle is a spheroidal structure, and comprises a shell, a transition layer and a particle core; the shell is a dense structure, the particle core is a porous structure, a density of the shell is greater than a density of the particle core, the transition layer surrounds the particle core and is sandwiched between the shell and the particle core; each ternary precursor particle is a mixture formed by mixing the nickel hydroxide, the cobalt hydroxide and the manganese hydroxide at the atomic level; a crystallinity of the shell is greater than a crystallinity of the transition layer, and the crystallinity of the transition layer is greater than a crystallinity of the particle core.