CN-122025581-A - Composite lithium iron manganese phosphate positive electrode material and preparation method thereof

CN122025581ACN 122025581 ACN122025581 ACN 122025581ACN-122025581-A

Abstract

The invention discloses a composite lithium iron manganese phosphate anode material and a preparation method thereof, wherein the chemical formula of the composite lithium iron manganese phosphate anode material is LiMn x‑a Mg a Fe 1‑ x PO 4 , a = 0.01-0.03, x = 0.5-0.8, a carbon layer and a sulfonated manganese phthalocyanine layer are sequentially coated on the surface of lithium iron manganese phosphate from inside to outside. The positive electrode material provided by the invention not only can effectively inhibit manganese dissolution, and the manganese dissolution rate is lower than 30.9ppm, but also has obvious advantages in the aspects of compaction density, ion/electron conductivity, cycle life and the like.

Inventors

DU ZIJIAN
SHI YINGFEI
LI YUEWEI
SHI YI
LI KAILING
CHEN XIANGJUN
LI YULONG
SHI JUNFENG

Assignees

锂源(深圳)科学研究有限公司
锂源(天津)科技有限公司
常州锂源新能源科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (8)

1. A composite lithium iron manganese phosphate anode material is characterized in that the chemical formula is Wherein And the surface of the lithium iron manganese phosphate is sequentially coated with a carbon layer and a sulfonated manganese phthalocyanine layer from inside to outside.
2. A method for preparing the composite lithium iron manganese phosphate positive electrode material according to claim 1, which is characterized by comprising the following steps: (1) The lithium source, the manganese source, the iron source, the phosphorus source and the magnesium source are according to the chemical formula Calculating the addition amount, mixing with a carbon source and water, ball-milling to prepare slurry, spray-drying, granulating, calcining, and cooling to obtain carbon-coated lithium iron manganese phosphate particles; (2) And grinding and uniformly mixing carbon-coated lithium iron manganese phosphate particles, sulfonated manganese phthalocyanine and a dispersing agent, and performing spray drying granulation to obtain the lithium iron manganese phosphate anode material with the sulfonated manganese phthalocyanine and the carbon layer coated in sequence.
3. The method for preparing the composite lithium iron manganese phosphate positive electrode material according to claim 2, wherein the addition mass of the sulfonated manganese phthalocyanine accounts for 0.5-10% of the mass of the carbon-coated lithium iron manganese phosphate particles.
4. The method for preparing a composite lithium iron manganese phosphate positive electrode material according to claim 3, wherein the addition mass of the sulfonated manganese phthalocyanine accounts for 0.5-3% of the mass of the carbon-coated lithium iron manganese phosphate particles.
5. The method for preparing the composite lithium iron manganese phosphate cathode material according to claim 2, wherein the carbon source is added in an amount of 1-20% of the total mass of the lithium source, the manganese source, the iron source, the phosphorus source and the magnesium source, and is selected from one or more of glucose, sucrose, fructose, lactose, citric acid, starch, ethylene glycol, polyvinylpyrrolidone, methanol, ethanol, glycine, aspartic acid, tartaric acid, beta-cyclodextrin, graphene and carbon nanotubes.
6. The method of preparing a composite lithium manganese iron phosphate positive electrode material according to claim 2, wherein the lithium source is selected from one or more of lithium carbonate, lithium phosphate, lithium sulfate, lithium chloride, lithium hydroxide, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium nitrate, lithium oxalate or lithium acetate; the manganese source is selected from one or more of manganous oxide, manganese carbonate, manganese acetate, manganous oxide or manganese oxide; the iron source is selected from one or more of ferric phosphate, ferric oxide, ferric acetate, ferric sulfate or ferric nitrate; the phosphorus source is selected from one or more of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, lithium phosphate, ferric phosphate and manganese phosphate.
7. The method of preparing a composite lithium iron manganese phosphate cathode material according to claim 2, wherein the magnesium source is selected from one or more of magnesium oxide, magnesium nitrate, magnesium chloride, magnesium carbonate, magnesium sulfate, magnesium hydroxide, magnesium acetate, magnesium phosphate, magnesium sulfide.
8. The method for preparing a composite lithium iron manganese phosphate positive electrode material according to claim 2, wherein the dispersing agent is absolute ethyl alcohol, a PEG aqueous solution or a PVP aqueous solution.

Description

Composite lithium iron manganese phosphate positive electrode material and preparation method thereof Technical Field The invention belongs to the field of preparation of lithium iron manganese phosphate anode materials, and particularly relates to a composite lithium iron manganese phosphate anode material and a preparation method thereof. Background As a new generation of green high-energy battery, the performance of the positive electrode material of the lithium ion battery is important. Among the numerous positive electrode materials, lithium iron phosphate (LiFePO 4, LFP) is widely used for its excellent safety, cycle life and cost advantages. And by introducing manganese element, the LMFP can raise the working voltage platform to about 4.1V while maintaining the safety and stability of LFP, thereby remarkably improving the energy density of the material. However, the LMFP materials, especially those with high manganese content, still have problems of low conductivity, manganese dissolution, etc., and the following new schemes are often adopted in the existing foundation to solve the problems, but the new schemes still have drawbacks, for example: (1) Carbon coating, namely, by coating a layer of amorphous carbon on the surface of LMFP particles, a conductive network can be constructed, and the electronic conductivity of the material is remarkably improved. However, the conventional carbon coating is generally hydrophobic and chemically inert, and although solving the electron conduction problem, the conventional carbon coating has no promoting effect on lithium ion transmission at the interface and may even form a hindrance, and more importantly, the carbon coating has limited effect on inhibiting manganese dissolution, so that the problem of long-term cycle stability of the LMFP cannot be fundamentally solved. (2) The ion doping is to stabilize the crystal structure, enlarge the diffusion channel of lithium ion or improve the intrinsic conductivity by introducing metal or nonmetal ions such as magnesium, zinc, fluorine and the like into LMFP crystal lattice, and the method can improve the performance to a certain extent, but has complex process and generally limited improvement effect, and is difficult to solve multiple problems such as electron, ion conduction, interface stability and the like at the same time. (3) The method can effectively improve the multiplying power performance, but the nano material has higher surface energy, so that the agglomeration of particles and the reduction of compaction density are easy to cause, and side reactions are possibly aggravated to negatively influence the problem of manganese dissolution. In addition, there have been studies on attempts to surface-modify electrode materials using organic molecules or polymers in order to improve interface properties. For example, surfactants are used to improve dispersibility or provide lithium-philic sites, but these small molecules are prone to fall off or break down during electrode preparation or cycling, and are not stable enough. In summary, the modification of lithium iron manganese phosphate in the prior art is mostly focused on the improvement of single performance, and lacks a technical scheme capable of synchronously and synergistically solving three core problems of electron conduction, ion conduction and interfacial chemical stability. Disclosure of Invention The invention aims to provide a composite lithium iron manganese phosphate positive electrode material and a preparation method thereof, so as to effectively and synchronously solve the technical problems of compact density, poor electronic conductivity, slow ion diffusion and serious manganese dissolution of the lithium iron manganese phosphate positive electrode material. The technical proposal is that the chemical formula of the composite lithium iron manganese phosphate anode material is as followsWhereinAnd the surface of the lithium iron manganese phosphate is sequentially coated with a carbon layer and a sulfonated manganese phthalocyanine layer from inside to outside. Further, the particle size of the composite lithium iron manganese phosphate positive electrode material is 50-400nm. The method for preparing the composite lithium iron manganese phosphate anode material comprises the following steps: (1) The lithium source, the manganese source, the iron source, the phosphorus source and the magnesium source are according to the chemical formula Calculating the addition amount, mixing with a carbon source and water, ball-milling to prepare slurry, spray-drying, granulating, calcining, and cooling to obtain carbon-coated lithium iron manganese phosphate particles; (2) And grinding and uniformly mixing carbon-coated lithium iron manganese phosphate particles, sulfonated manganese phthalocyanine and a dispersing agent, and performing spray drying granulation to obtain the lithium iron manganese phosphate anode material with the sulfonated manganese pht