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CN-121573716-B - Preparation method of monocrystalline manganese sesquioxide, lithium manganate positive electrode material and lithium battery

CN121573716BCN 121573716 BCN121573716 BCN 121573716BCN-121573716-B

Abstract

The invention discloses a preparation method of monocrystalline manganese sesquioxide, a lithium manganate positive electrode material and a lithium battery, belonging to the technical field of lithium batteries, wherein the preparation method takes manganese sulfate as a manganese source, mn 2+ is restrained from being excessively oxidized by controlling the content of reducing substances through a reducing additive, mn 3+ is stabilized through a composite additive, and high-purity monocrystal manganese sesquioxide with regular hexahedral morphology is prepared through combination of solid content control, multi-stage pH value adjustment and aging processes. The lithium manganate anode material is prepared by calcining the single crystal manganese sesquioxide and lithium carbonate according to the mole ratio of Li/Mn of 0.55:1. The method has the advantages of mild process, low cost of raw materials, easy industrialized amplification, adaptation to the requirements of high-performance lithium batteries, and solves the problems of low purity, impurity morphology, high energy consumption and insufficient electrochemical performance of the traditional method.

Inventors

  • WANG TAO
  • ZHOU TONG
  • JIANG JIANBING
  • GAO XUGUANG
  • HUANG XIANGPING
  • TANG PEIYUAN
  • TAN SIRUI
  • MA BOKAI
  • YAN TAO

Assignees

  • 湘潭电化科技股份有限公司

Dates

Publication Date
20260508
Application Date
20260128

Claims (9)

  1. 1. A method for preparing monocrystalline manganese sesquioxide, comprising the following steps: S100, preparing a MnSO 4 solution, and adding a reducing additive to form a first mixed solution for inhibiting excessive oxidation of Mn 2+ to Mn 4+ , wherein the reducing additive comprises an aldehyde group-containing compound and sulfite, and provides a reducing substance, and the content of the reducing substance is 300-800 mug/ml; S200, adding a first complexing agent into the first mixed solution, regulating the first complexing agent to a first pH range, stirring the first mixed solution at a set temperature to enable Mn 2+ in the first mixed solution to generate Mn (OH) 2 ,Mn(OH) 2 , and partially converting the Mn 2 ,Mn(OH) 2 and oxygen into MnOOH to generate a second mixed solution with Mn 3+ crystal nucleus precursor, wherein the first pH range is 7.0-7.6, the set temperature is 25-65 ℃, the first complexing agent is one or more of ammonium sulfate, ammonia water, ethylenediamine, triethanolamine and nitrilotriacetic acid, and the addition content of the first complexing agent is 1-5 g/L; S300, adding a composite additive consisting of phosphoric acid and a second complexing agent into the second mixed solution, regulating the pH value to a second pH value range, enabling Mn 3+ dissociated from MnOOH and the composite additive to form a Mn-containing complex, preventing Mn 3+ from being differentiated into Mn 2+ and Mn 4+ , stirring and standing under the air condition, and dehydrating and converting the Mn OOH into pure-phase Mn 2 O 3 crystal nuclei in the process of slowly releasing Mn 3+ from the complex to obtain a third mixed solution containing Mn 2 O 3 crystal nuclei, wherein the second complexing agent is one or more of ethylenediamine tetraacetic acid second complexing agent, sodium citrate, cetyltrimethylammonium bromide or n-butyl alcohol, the addition content of the second complexing agent is 1-5 g/L, the mass ratio of phosphoric acid to the second complexing agent is 1:0.05-0.45, the second pH value range is 6.5-7.0, and the Mn-containing complex is [ Mn (PO 4 ) n ] 3- ; S400, adding the third mixed solution and a pH regulator in parallel, regulating the third mixed solution to a third pH range by taking air or oxygen as an oxidant, controlling the solid content during regulating the pH to inhibit secondary nucleation, and promoting the directional growth of Mn 2 O 3 crystal nuclei into monocrystalline particles to obtain a fourth mixed solution containing monocrystalline particles, wherein the solid particles in the solid content are Mn-containing solid particles, and the third pH range is 7.0-8.5; S500, adjusting the fourth mixed solution to a fourth pH range, aging to enable the morphology of the monocrystalline particles to be regular into a regular hexahedron, and carrying out solid-liquid separation and purification treatment to obtain the regular hexahedral monocrystalline manganese sesquioxide, wherein the fourth pH range is 6.8-7.8.
  2. 2. The method for preparing single crystal manganese sesquioxide according to claim 1, wherein in the step S100, the aldehyde group-containing compound is any one or more of glucose and maltose, the sulfite is any one or more of sodium sulfite and potassium sulfite, and the addition amount of the reducing additive is 0.01% -0.05% of the mass of the MnSO 4 solution.
  3. 3. The method for producing single crystal manganese sesquioxide according to claim 2, wherein in the step S100, the reducing substance includes a reducing group of an aldehyde group-containing compound and a reducing ion of sulfite.
  4. 4. The method for producing a single crystal manganese sesquioxide according to claim 1, wherein in the step S200, the stirring time is 0.1 to 1h.
  5. 5. The method for producing a single crystal manganese sesquioxide according to claim 1, wherein in the step S300, the stirring and the standing are performed under air conditions for 3 to 24 hours.
  6. 6. The method for preparing monocrystalline manganese sesquioxide according to claim 1, wherein in the step S400, the time of mixing the third mixed solution and the pH regulator is 3-20 h, the solid content in the mixing reaction is controlled to be 1-12%, the solid content is the ratio of the mass of solid particles containing Mn to the total mass of the mixed reaction system, the pH regulator is one or more selected from sodium hydroxide solution, ammonia water and potassium hydroxide solution, and the concentration of the sodium hydroxide solution is 1-5 mol/L.
  7. 7. The method for producing a single crystal manganese sesquioxide according to claim 1, wherein in the step S500, the aging time is 1 to 6 hours, and the obtained regular hexahedral single crystal manganese sesquioxide has a particle diameter D50 of 0.5 to 5 μm.
  8. 8. A lithium manganate cathode material, characterized in that raw materials of the lithium manganate cathode material comprise lithium carbonate and single crystal manganese sesquioxide prepared by the preparation method of the single crystal manganese sesquioxide according to any one of claims 1-7, and the single crystal manganese sesquioxide and the lithium carbonate are mixed according to a mole ratio of Li/Mn of 0.55:1.
  9. 9. A lithium battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode comprises the lithium manganate positive electrode material of claim 8.

Description

Preparation method of monocrystalline manganese sesquioxide, lithium manganate positive electrode material and lithium battery Technical Field The invention relates to the technical field of lithium batteries, in particular to a preparation method of monocrystalline manganese sesquioxide, a lithium manganate positive electrode material and a lithium battery. Background Manganese oxide is known as an important transition metal oxide in terms of its multivalent nature, environmental friendliness and cost effectiveness, and with the rapid development of new energy technologies, particularly the rise of positive electrode materials for lithium ion batteries and sodium ion batteries, the demand for battery-grade manganese oxide has increased dramatically. However, the traditional preparation method has the problems of low purity, high energy consumption, uncontrollable morphology and the like, and needs to be improved urgently. Currently, the preparation methods of manganese sesquioxide in the market are mainly divided into three types: Firstly, a hydrolysis oxidation method is to prepare spherical or spheroidal manganese sesquioxide by taking electrolytic manganese metal as a raw material, carrying out hydrolysis oxidation through acid catalysis suspension, controlling oxidation-reduction potential and pH value, and finally washing and drying. However, the method needs to accurately control the addition of an oxidant (such as hydrogen peroxide and sodium hypochlorite) and an alkaline solution, has sensitive process parameters, and has high-purity electrolytic manganese metal (more than or equal to 99 percent) as a raw material and higher cost. And secondly, a high-temperature roasting method is adopted, and the divalent manganese salt is directly calcined at about 600 ℃ to prepare the manganese sesquioxide, but the energy consumption is high, the manganese sesquioxide is easy to sinter, the particle size of the product is uneven, and the morphology is uncontrollable. And thirdly, a solvothermal method, which uses soluble manganese salt (such as manganese nitrate) and copper salt as raw materials, and regulates crystal face growth in an alcohol solvent through hydrothermal reaction to generate the manganese sesquioxide with high catalytic activity. However, the method needs to introduce copper salt and other auxiliary agents, has higher cost and high precision requirement of synthesis conditions, is not suitable for process amplification, is difficult to recover solvent (such as sec-butyl alcohol), and has high environmental protection pressure. In addition, in lithium ion batteries, single crystal manganese sesquioxide has a shorter lithium ion diffusion path and higher structural stability than polycrystalline manganese sesquioxide. The monocrystal characteristic can inhibit volume expansion in the charge and discharge process, the cycle life is prolonged, and meanwhile, the nanoscale size and the larger specific surface area (40-50 m < 2 >/g) increase the density of active sites, so that the energy density and the rate capability of the battery are improved. The manganese sesquioxide with a single crystal structure has higher mechanical strength and thermal stability. Therefore, a preparation method of monocrystalline manganese sesquioxide with low synthesis cost and mild reaction conditions is needed. Disclosure of Invention The invention provides a preparation method of monocrystal manganese sesquioxide, a lithium manganate positive electrode material and a lithium battery, and aims to solve the technical problem of how to provide a preparation method of monocrystal manganese sesquioxide which is low in synthesis cost, mild in reaction condition, capable of preparing high purity and controllable in regular hexahedron morphology, and capable of meeting the requirements of the fields of lithium batteries and the like on high-quality monocrystal manganese sesquioxide. The preparation method of the monocrystalline manganese sesquioxide provided by the invention comprises the following steps: S100, preparing a MnSO 4 solution, and adding a reducing additive to form a first mixed solution for inhibiting excessive oxidation of Mn 2+ to Mn 4+; S200, adding a first complexing agent into the first mixed solution, adjusting the first complexing agent to a first pH range, and stirring the first mixed solution at a set temperature to enable Mn 2+ in the first mixed solution to generate Mn (OH) 2,Mn(OH)2, and enabling a reaction part of the Mn (OH) 2,Mn(OH)2 and oxygen to be converted into MnOOH so as to generate a second mixed solution with Mn 2+ crystal nucleus precursors; S300, adding a composite additive consisting of phosphoric acid and a second complexing agent into the second mixed solution, regulating the pH value to a second pH value range, and enabling Mn 3+ dissociated from MnOOH and the composite additive to form a Mn-containing complex to prevent Mn 3+ from being differentiated into Mn 2+ and Mn 4+; S400, ad