CN-116969435-B - Preparation method of lithium iron manganese phosphate, positive electrode material and lithium ion battery

CN116969435BCN 116969435 BCN116969435 BCN 116969435BCN-116969435-B

Abstract

The application discloses a preparation method of lithium iron manganese phosphate, a positive electrode material and a lithium ion battery, and relates to the technical field of batteries. The method comprises the steps of using a manganese source and an iron source, obtaining ferromanganese oxide through solid-phase sintering, wherein at least one of the manganese source and the iron source is oxide, carrying out solid-phase mixing on the ferromanganese oxide, a lithium source and a phosphorus source, and carrying out solid-phase sintering at 350-900 ℃ to obtain lithium ferromanganese phosphate. The preparation method provided by the application can reduce the use of sulfate, thereby reducing the generation of toxic gas sulfur dioxide. And the method is favorable for synthesizing the high-purity high-tap-density lithium iron manganese phosphate material, reduces the process cost and improves the performance of the prepared lithium iron manganese phosphate material. The positive electrode material and the lithium ion battery provided by the application comprise the lithium iron manganese phosphate prepared by the preparation method.

Inventors

WANG ZHENGWEI
WANG YONGCHEN
LI NA
FENG XIAO
ZHU HUAJUN
YANG ZHE
LIU FUZHAO
CHEN MENGTING

Assignees

星恒电源股份有限公司
四川星恒青源新材料科技有限公司

Dates

Publication Date: 20260505
Application Date: 20230822

Claims (9)

1. The preparation method of the lithium iron manganese phosphate is characterized by comprising the following steps: Obtaining ferromanganese oxide by solid phase sintering by using a manganese source and an iron source, wherein at least one of the manganese source and the iron source is oxide; Solid-phase mixing the ferromanganese oxide with a lithium source and a phosphorus source, and performing solid-phase sintering at 350-900 ℃ to obtain lithium ferromanganese phosphate; a step of obtaining ferromanganese oxide by means of solid phase sintering using a manganese source and an iron source, comprising: Performing solid-phase sintering on the first mixture containing the manganese source and the iron source at 300-1200 ℃ to obtain a first ferromanganese oxide, wherein the first ferromanganese oxide is (Mn 0.8 Fe 0.1 ) 2 O 4 or Mn 0.6 Fe 0.2 O; Performing solid-phase sintering on the second mixture containing the manganese source and the iron source at 300-1200 ℃ to obtain a second ferromanganese oxide, wherein the second ferromanganese oxide is (Mn 0.1 Fe 0.5 ) 2 O 4 or Mn 0.3 Fe 0.4 O, and the median particle size of the second ferromanganese oxide is smaller than that of the first ferromanganese oxide; And carrying out solid phase mixing on the first ferromanganese oxide and the second ferromanganese oxide, and carrying out solid phase sintering at 300-1200 ℃ to obtain the ferromanganese oxide with rich manganese on the inner layer and rich iron on the outer layer.
2. The method for producing lithium manganese iron phosphate according to claim 1, wherein one or more of a carbon source, an M source, and an N source is further added in the step of solid-phase mixing the first manganese iron oxide and the second manganese iron oxide, and in the step of solid-phase mixing the manganese iron oxide with a lithium source and a phosphorus source; wherein the M source is a doped cation source and the N source is a doped anion source.
3. The method for preparing lithium iron manganese phosphate according to claim 2, wherein the carbon source is one or more of sucrose, glucose, fructose, citric acid, phenolic resin, polyvinyl alcohol, polyethylene glycol, starch, carbon black, acetylene black, graphite, graphene, and conductive carbon tube.
4. The method of claim 2, wherein the source of dopant cations comprises one or more of aluminum, magnesium, nickel, cobalt, titanium, copper, calcium, niobium, chromium, zinc, lanthanum, antimony, tellurium, strontium, tungsten, indium, yttrium, and the source of dopant anions comprises fluorine and/or sulfur.
5. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the manganese source is one or more of trimanganese tetraoxide, dimanganese trioxide, manganous oxide, manganese dioxide, monohydroxy manganese oxide MnO (OH), hydrated manganese dioxide MnO (OH) 2 , manganese hydroxide Mn (OH) 2 , manganese sulfate, manganese carbonate, manganese oxalate, and manganese acetate.
6. The method for preparing lithium iron manganese phosphate according to claim 1, wherein the iron source is one or more of ferroferric oxide, ferric oxide, ferrous oxide, basic ferric oxide FeO (OH), ferric hydroxide, ferrous sulfate, ferric carbonate, ferric oxalate, ferrous oxalate, ferric acetate, and ferric citrate.
7. The method for preparing lithium manganese iron phosphate according to claim 1, wherein the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium oxalate, lithium acetate, lithium sulfate, lithium nitrate, and lithium chloride; The phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium tripolyphosphate, phosphoric acid, calcium phosphate, ferric phosphate, lithium dihydrogen phosphate and manganese phosphate.
8. A positive electrode material comprising the lithium iron manganese phosphate produced by the production method according to any one of claims 1 to 7.
9. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, wherein the positive electrode sheet comprises the positive electrode material of claim 8.

Description

Preparation method of lithium iron manganese phosphate, positive electrode material and lithium ion battery Technical Field The application relates to the technical field of batteries, in particular to a preparation method of lithium manganese iron phosphate, a positive electrode material and a lithium ion battery. Background The current synthesis methods of lithium iron manganese phosphate are mainly divided into a solid phase method and a coprecipitation method. The coprecipitation method adopts manganese source, iron source and complexing agent to coprecipitate to generate precursor, and the precursor reacts with phosphorus source and lithium source in solid phase or liquid phase to generate lithium manganese iron phosphate, such as Chinese patent No. CN105047922A. The traditional solid phase method adopts manganese source, iron source, phosphorus source and lithium source sintering, the process is simplest, but the performance of the synthesized material is worst, so the main stream is a coprecipitation method. It can be seen that, no matter LiMn xFe1-xPO4 is lithium iron phosphate when x=0 or lithium iron manganese phosphate when x is not equal to 0, the material synthesis is divided into a solid phase method and a liquid phase method, the traditional solid phase method has simple process but the synthesized material has the worst performance, the liquid phase method has good performance but the equipment corrosion prevention requirement causes high cost and has larger pressure on environmental protection. A brand new solid phase process is designed to synthesize the LiMn xFe1-xPO4 material, so that the performance of the material is improved, and the material has the characteristic of low cost. However, the method has the problems that the sulfate of manganese and iron is used as a manganese source and an iron source, so that toxic gas sulfur dioxide generated by the synthesis reaction needs to be treated, and the composite manganese iron lithium oxide has high hardness, is difficult to ball mill and is unfavorable for generating high-purity manganese iron lithium phosphate. The two sulfates have different thermal decomposition temperatures, so that the two sulfates are easy to agglomerate when the ferromanganese oxide is generated, the ball milling difficulty is increased, and the pure-phase ferromanganese oxide is not easy to generate. In addition, the synthesis reaction time in the related technology is longer, the reaction temperature is higher, meanwhile, the purity of ferromanganese oxide synthesized by the reaction of manganese salt and ferric salt is smaller, and the impurity phase byproducts such as iron oxide, manganese oxide and the like are also generated. In view of this, the present application has been made. Disclosure of Invention The application aims to provide a preparation method of lithium iron manganese phosphate, which can reduce the emission of toxic gas sulfur dioxide, improve the material performance and reduce the process cost. The application also aims to provide a positive electrode material and a lithium ion battery. The application is realized in the following way: in a first aspect, the present application provides a method for preparing lithium iron manganese phosphate, comprising: Obtaining ferromanganese oxide by solid phase sintering by using a manganese source and an iron source, wherein at least one of the manganese source and the iron source is oxide; and (3) carrying out solid phase mixing on the ferromanganese oxide and a lithium source and carrying out solid phase sintering at 350-900 ℃ to obtain the lithium ferromanganese phosphate. In an alternative embodiment, the step of obtaining ferromanganese oxide by means of solid phase sintering using a manganese source and an iron source comprises: Solid phase sintering is carried out on the first mixture containing the manganese source and the iron source at 300-1200 ℃ to obtain a first ferromanganese oxide (Mn aFe1-a)mOn; Solid phase sintering the second mixture containing the manganese source and the iron source at 300-1200 ℃ to obtain a second ferromanganese oxide (Mn bFe1-b)mOn, wherein the median particle size of the second ferromanganese oxide (Mn bFe1-b)mOn is smaller than that of the first ferromanganese oxide (Mn aFe1-a)mOn, 0< b < a <1; And (3) carrying out solid-phase mixing on the first ferromanganese oxide (Mn aFe1-a)mOn and the second ferromanganese oxide (Mn bFe1-b)mOn), and carrying out solid-phase sintering at 300-1200 ℃ to obtain the ferromanganese oxide with rich manganese in the inner layer and rich iron in the outer layer. In an alternative embodiment, one or more of a carbon source, an M source, and an N source is further added in the step of solid-phase mixing the first ferromanganese oxide (Mn aFe1-a)mOn and the second ferromanganese oxide (Mn bFe1-b)mOn, and the step of solid-phase mixing the ferromanganese oxide with the lithium source and the phosphorus source; Wherein the M source is a do