Positive electrode active material for nonaqueous electrolyte secondary batteries, and production method thereof

Patent metadata

Field	Value
Publication number	US-2018047977-A1
Application number	US-201615555597-A
Country	US
Kind code	A1
Filing date	Mar 1, 2016
Priority date	Mar 3, 2015
Publication date	Feb 15, 2018
Grant date	—

Abstract

A method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries, includes: a mixing step of adding a W compound powder having a solubility A adjusted to 2.0 g/L or less to a Li-metal composite oxide powder and stirring in water washing of the composite oxide powder, the solubility A being determined by stirring the W compound in water having a pH of 12.5 at 25° C. for 20 minutes, the composite oxide powder being represented by the formula: Li c Ni 1-x-y Co x M y O 2 and composed of primary and secondary particles, followed by solid-liquid separation, to thereby obtain a tungsten-containing mixture with the tungsten compound dispersed in the composite oxide powder; and a heat-treating step of heat-treating the mixture to uniformly disperse W on the surface of primary particles and thereby form a compound containing W and Li from the W and Li in the mixture, on the surface of primary particles.

First claim

1 . A method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries, comprising:
a mixing step of adding a tungsten compound powder having a solubility A adjusted to 2.0 g/L or less to a lithium-metal composite oxide powder and stirring them in water washing of the lithium-metal composite oxide powder, the solubility A being determined by stirring the tungsten compound in water having a pH of 12.5 at 25° C. for 20 minutes, the lithium-metal composite oxide powder being represented by a general formula: Li c Ni 1-x-y Co x M y O2 (where 0≦x≦0.35, 0≦y≦0.35, and 0.97≦c≦1.25 are satisfied, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) and being composed of primary particles and secondary particles formed by aggregation of the primary particles, followed by solid-liquid separation, to thereby obtain a tungsten-containing mixture with the tungsten compound dispersed in the lithium-metal composite oxide powder; and a heat-treating step of heat-treating the tungsten-containing mixture obtained in the mixing step to uniformly disperse tungsten on a surface of the primary particles of the lithium-metal composite oxide powder, and thereafter form a compound containing tungsten and lithium from the tungsten dispersed uniformly on the surface of the primary particles and lithium in the tungsten-containing mixture, on the surface of the primary particles of the lithium-metal composite oxide powder.

2 . The method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the tungsten compound added in the mixing step is lithium tungstate.

3 . The method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the heat treatment in the heat-treating step is performed at a temperature of 100 to 600° C. in an oxygen atmosphere or in a vacuum atmosphere.

4 . The method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 , wherein an amount of tungsten contained in the tungsten-containing mixture is 0.05 to 3.0 at % with respect to the total number of atoms of Ni, Co and M contained in the lithium-metal composite oxide powder mixed.

5 . The method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 , wherein the tungsten compound added in the mixing step comprises 80% or more of (Li 2 WO 4 )7(H 2 O) 4 .

6 . The method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 2 , wherein the lithium tungstate is obtained by a reaction of lithium hydroxide and a tungsten compound.

7 . The method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 , wherein a temperature in the water washing in the mixing step is 40° C. or less.

8 . A positive electrode active material for nonaqueous electrolyte secondary batteries, comprising a lithium-metal composite oxide represented by a general formula (1): Li a Ni 1-x-y Co x M y W z O 2+α (where 0≦x≦0.35, 0≦y≦0.35, 0.0005≦z≦0.030, 0.97≦a≦1.25, 0≦α≦0.20, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) and composed of primary particles and secondary particles formed by aggregation of the primary particles,
wherein a compound containing lithium and tungsten is formed on a surface of the primary particles of the lithium-metal composite oxide, and when voids between the primary particles at any 20 or more points are EDX analyzed in transmission-type electron microscope observation of a cross section of the secondary particles, tungsten is detected at 50% or more of the number of the voids analyzed.

9 . The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 8 , wherein the compound containing lithium and tungsten is present on the surface of the primary particles of the lithium-metal composite oxide as coating thin film having a film thickness of 1 to 100 nm.

10 . The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 8 , wherein the compound containing lithium and tungsten is present on the surface of the primary particles of the lithium-metal composite oxide in both forms of thin film having a film thickness of 1 to 100 nm and fine particles having a particle size of 1 to 200 nm.

11 . The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 8 , wherein an amount of tungsten contained in the compound containing lithium and tungsten is 0.08 to 3.0 at % in terms of the number of W atoms with respect to the total number of atoms of Ni, Co and M contained in the lithium-metal composite oxide.

12 . The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 8 , wherein the lithium-metal composite oxide is represented by a general formula (2): Li b Ni 1-x-y Co x M y O 2 (where 0≦x≦0.35, 0≦y≦0.35, and 0.95≦b≦1.20 are satisfied, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al).

Assignees

• Sumitomo Metal Mining Co

Inventors

• Furuichi Yuki
• Komukai Tetsufumi

Classifications

• C01G53/42 Primary

  containing alkali metals, e.g. LiNiO2 · CPC title

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• C01P2002/54

  one element only · CPC title

• H01M4/36 Primary

  Selection of substances as active materials, active masses, active liquids · CPC title

• H01M4/62

  Selection of inactive substances as ingredients for active masses, e.g. binders, fillers · CPC title