Positive electrode active material for lithium battery
With the object of providing a positive electrode active material for lithium battery that can increase the filling density, can increase the output characteristics, and furthermore, with a small voltage decrease during conservation at high temperature in a charged state, a positive electrode active material for lithium battery is proposed, containing a spinel type (Fd3-m) lithium transition metal oxide represented by general formula Li 1+x M 2−x O 4−δ (where M represents a transition metal including Mn, Al and Mg, x represents 0.01 to 0.08 and 0≦δ) and a boron compound, the inter-the atomic distance Li—O of the spinel type lithium transition metal oxide being 1.971 Å to 2.006 Å, and the amount of magnetic substance measured for the positive electrode active material for lithium battery being 600 ppb or less.
1. A positive electrode active material for lithium battery, containing a spinel type Fd3-m lithium transition metal oxide represented by general formula Li 1+x M 2−x O 4−δ wherein M consists of Mn, Al and Mg, x represents 0.01 to 0.08 and 0≦δ, and a boron compound,
the spinel type Fd3-m lithium transition metal oxide having an inter-atomic distance Li—O of 1.978 Å to 2.006 Å as measured by the Rietveld method using the fundamental method, and the amount of magnetic deposit measured for the positive electrode active material for lithium battery being 600 ppb or less when measured by a measurement method comprising:
in a 500 cc lidded resinous container, 500 cc of ion-exchanged water and one cylindrical stirring bar-type magnet covered with tetrafluoroethylene wherein the magnet has a range of magnetic force within 100 mT to 150 mT when the magnetic force is measured using TESLA METER Model TM-601 by KANETEC are added to 100 g of positive electrode active substance material in powder form, which is placed on a ball mill rotating stage, and rotating to produce a slurry;
next, the magnet is taken out, immersed in ion-exchanged water and the excess powder attached to the magnet is eliminated with an ultrasound cleaner;
next, the magnet is taken out, immersed in aqua regia, heated at 80° C. for 30 minutes in aqua regia to dissolve magnetic deposits, and aqua regia in which magnetic deposit has dissolved is analyzed for the amounts of iron, nickel, chromium and zinc with ICP Atomic Emission Spectrometer, and, with the total amounts thereof as the amount of magnetic deposit, the amount of magnetic deposit per weight of positive electrode active substance material is calculated.
2. The positive electrode active material for lithium battery according to the claim 1 , wherein the spinel type lithium transition metal oxide is represented by the general formula Li(Li x Mg y Al z Mn 2−x−y−z ) O 4−δ wherein 0.01≦x≦0.08, 0.02≦y≦0.07, 0.06≦z≦0.14 and 0≦δ.
3. The positive electrode active material for lithium battery according to the claim 1 , wherein the crystallite size of the spinel type lithium transition metal oxide is 500 nm to 2000 nm.
4. The positive electrode active material for lithium battery according to claim 2 , wherein the crystallite size of the spinel type lithium transition metal oxide is 500 nm to 2000 nm.
5. A lithium battery for an electric vehicle or for a hybrid electric vehicle provided with the positive electrode active material for lithium battery according to claim 1 as a positive electrode active substance.