The present invention provides a method of preparing an MOF-coated monocrystal ternary positive electrode material. Firstly, a solution A of nickel, cobalt and manganese metal salts, an ammonia complexing agent solution and a caustic soda liquid are added to a reactor for reaction to obtain a precursor core; then, an organic carboxylate is dissolved in an amount of an organic solvent to obtain a solution B; the solution B and a manganese metal salt solution with a given concentration are added to the reactor and aged to obtain an MOF-coated core-shell structure precursor; the core-shell structure precursor is pre-sintered at a low temperature to obtain a nickel-cobalt-manganese oxide with monocrystal structure; the nickel-cobalt-manganese oxide with monocrystal structure is uniformly mixed with LiOH.Math.H.sub.2O in a mortar and then calcined at a high temperature to obtain an MOF-coated monocrystal ternary positive electrode material.

A positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charging and discharging as compared with those of a known positive electrode active material. In order to form the positive electrode active material having the pseudo-spinel crystal structure in the charged state, it is preferable that a halogen source such as a fluorine and a magnesium source be mixed with particles of a composite oxide containing lithium, a transition metal, and oxygen, which is synthesized in advance, and then the mixture be heated at an appropriate temperature for an appropriate time.

The present invention provides a method of preparing an MOF-coated monocrystal ternary positive electrode material. Firstly, a solution A of nickel, cobalt and manganese metal salts, an ammonia complexing agent solution and a caustic soda liquid are added to a reactor for reaction to obtain a precursor core; then, an organic carboxylate is dissolved in an amount of an organic solvent to obtain a solution B; the solution B and a manganese metal salt solution with a given concentration are added to the reactor and aged to obtain an MOF-coated core-shell structure precursor; the core-shell structure precursor is pre-sintered at a low temperature to obtain a nickel-cobalt-manganese oxide with monocrystal structure; the nickel-cobalt-manganese oxide with monocrystal structure is uniformly mixed with LiOH.H.sub.2O in a mortar and then calcined at a high temperature to obtain an MOF-coated monocrystal ternary positive electrode material.

Positive electrode active material particle powder includes: lithium manganese oxide particle powder having Li and Mn as main components and a cubic spinel structure with an Fd-3m space group. The lithium manganese oxide particle powder is composed of secondary particles, which are aggregates of primary particles, an average particle diameter (D50) of the secondary particles being from 4 μm to 20 μm, and at least 80% of the primary particles exposed on surfaces of the secondary particles each have a polyhedral shape having at least one (110) plane that is adjacent to two (111) planes.

A positive electrode active material for a secondary battery includes a lithium metal composite oxide having a crystal structure based on a rock salt structure belonging to a space group Fm-3m, wherein the lithium metal composite oxide includes Cu and a transition metal element M1 other than Li and Cu. The lithium metal composite oxide is preferably represented by a composition formula Li.sub.aMn.sub.bCu.sub.cA.sup.2.sub.dO.sub.2-eF.sub.e (where A.sup.2 is at least one element excluding Li, Mn, Cu, O, and F, and 0<a≤1.35, 0.4≤b≤0.9, 0<c≤0.2, 0≤d≤0.2, 0≤e≤0.66, 1.75≤a+b+c+d≤2 are satisfied).

Disclosed are a reaction tower, a production system, and a production method for producing potassium manganate. The reaction tower includes a reaction tower body and a bubble generator. The reaction tower body has a reaction chamber. The bubble generator includes an outer housing. The outer housing is disposed in the reaction chamber and has a gas flow channel therein. The outer housing is configured to direct an external reactant gas into the gas flow channel. The outer housing is provided with multiple first pores each having a diameter less than 10 mm, via which the gas flow channel communicates with the reaction chamber. The reaction tower is used in the production system. The reactant gas is introduced into the reaction chamber in the form of small bubbles by the action of the bubble generator, to increase the area of contact of the reactant gas with manganese ore powder and lye.

The present disclosure provides a production system and a production method of potassium manganate, belonging to the technical field of production of potassium manganate. The production system of potassium manganate comprises a hot air generating device, a production device and a circulating air pipeline. The hot air generating device is configured provide hot air in a manner of burning fuel gas. The production device is configured to absorb heat in the hot air generated by the hot air generating device. The circulating air pipeline is configured to introduce the hot air passing through the production device into the hot air generating device to adjust temperature of the hot air.

Disclosed are a reaction tower, a production system, and a production method for producing potassium manganate. The reaction tower includes a reaction tower body and a bubble generator. The reaction tower body has a reaction chamber. The bubble generator includes an outer housing. The outer housing is disposed in the reaction chamber and has a gas flow channel therein. The outer housing is configured to direct an external reactant gas into the gas flow channel. The outer housing is provided with multiple first pores each having a diameter less than 10 mm, via which the gas flow channel communicates with the reaction chamber. The reaction tower is used in the production system. The reactant gas is introduced into the reaction chamber in the form of small bubbles by the action of the bubble generator, to increase the area of contact of the reactant gas with manganese ore powder and lye.

Positive electrode active material particle powder includes: lithium manganese oxide particle powder having Li and Mn as main components and a cubic spinel structure with an Fd-3m space group. The lithium manganese oxide particle powder is composed of secondary particles, which are aggregates of primary particles, an average particle diameter (D50) of the secondary particles being from 4 m to 20 m, and at least 80% of the primary particles exposed on surfaces of the secondary particles each have a polyhedral shape having at least one plane that is adjacent to two planes.

A method for producing lithium manganese oxide that is a precursor of a lithium adsorbent under atmospheric pressure is provided. The method for producing a precursor of a lithium adsorbent comprises tire following steps (1) to (3): (1) A 1.sup.st mixing step of mixing a manganese salt and alkali hydroxide, so as to obtain a 1.sup.st slurry containing manganese hydroxide; (2) a 2.sup.nd mixing step of adding lithium hydroxide to the 1.sup.st slurry and then mixing the mixture to obtain a 2.sup.nd slurry; and (3) an oxidation step of adding an oxidizing agent to the 2.sup.nd slurry, so as to obtain a precursor of a lithium adsorbent.
The method for producing a precursor of a lithium adsorbent comprises these steps, so that a precursor of a lithium adsorbent can be produced under atmospheric pressure. Therefore, a precursor of a lithium adsorbent can be produced at a limited cost.