Cathode active material, cathode, secondary battery and manufacturing methods for the same
An object of the present invention is to provide a cathode active material which contains small-particle sized and low-crystalline lithium transition metal silicate and which undergoes charge-discharge reaction at room temperature. The cathode active material for a non-aqueous electrolyte secondary battery is characterized by containing a lithium transition metal silicate and exhibits diffraction peaks having half widths of 0.175 to 0.6°, the peaks observed through powder X-ray diffractometry within a 2θ range of 5 to 50°.
1. A method for producing a lithium transition metal silicate cathode active material, characterized in that the method comprises:
supplying a lithium source, a transition metal source, a silicon source, and pure water to a reactor;
treating the mixture at 150 to 400° C. in the sealed pressure reactor, to thereby synthesize a cathode active material;
heating the cathode active material at 300 to 900° C. for 0.5 to 10 hours, to thereby produce an aggregated active material; and
pulverizing the aggregated active material, to thereby produce a lithium transition metal silicate cathode active material,
wherein the lithium transition metal silicate cathode active material exhibits diffraction peaks having half widths of 0.175 to 0.6°, the peaks being observed through powder X-ray diffractometry within a 2Θ range of 5 to 50°, or has a crystallite size of 5 to 50 nm, the crystallite size being determined through powder X-ray diffractometry within a 2θ range of 5 to 50°.
2. The method according to claim 1 , the method further comprising:
supplying a lithium source, a transition metal source, a silicon source, and pure water into flame in a reactor, to thereby synthesize an active material precursor;
heating the active material precursor at 300 to 900° C. for 0.5 to 10 hours, to thereby produce an aggregated active material; and
pulverizing the aggregated active material.
3. The method according to claim 2 , wherein the flame is an oxygen-hydrogen flame, and the reactor is filled with an inert gas.
4. The method according to claim 2 , wherein the flame is an oxygen-containing hydrocarbon flame, and the reactor is filled with an inert gas.
5. The method according to claim 2 , wherein the lithium source, the transition metal source, and the silicon source supplied into the flame is a chloride, and the source of the flame contains at least hydrogen gas and oxygen gas.
6. The method according to claim 2 , wherein the lithium source, the transition metal source, and the silicon source are supplied into the flame in the gas form, or in the liquid or solution form which has been caused to pass through a vaporizer before the supply.
7. A cathode active material production method according to claim 1 , wherein heating is performed in the presence of an additional carbon source in the production of the aggregated active material.
8. A cathode active material production method according to claim 1 , wherein the aggregated active material is porous and has a pore size, as observed on the surface thereof, of 0.01 to 0.6 μm.
9. A method for producing a cathode for a non-aqueous electrolyte secondary battery, characterized in that the method comprises applying, onto a collector, a slurry containing a cathode active material which has been produced through a cathode active material production method as recited in claim 1 .
10. A non-aqueous electrolyte secondary battery cathode production method according to claim 9 , wherein the slurry contains secondary particles formed through granulation of the cathode active material and having a particle size of 0.5 to 20 μm.