Positive Electrode Material Coating for Uniform Lithium Phosphate Cathodes
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving high energy density, cycling performance, and safety performance due to non-uniform element distribution and material instability in positive electrode materials.
Innovation Solution
A method for preparing a positive electrode material involving mixing a precursor material, a lithium source, and an optional phosphorus source, followed by sintering, to create a pre-product with uniform element distribution and a dense coating layer, using a compound Mn x Fe y M (1-x-y) HPO 4 ·nH 2 O, where M includes transition metal elements, and applying a carbon coating to enhance stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional preparation methods are used for positive electrode materials, then the manufacturing process is simpler, but the element distribution is non-uniform and material stability is poor
Solution Approach 1:
The preparation process is divided into multiple stages: first forming a precursor material with controlled particle size (3-100 μm), then sintering to form the core, and finally coating the core to form the positive electrode material. This segmentation allows each stage to be optimized independently, achieving uniform element distribution and stable composition while maintaining manageable process complexity.
Solution Approach 2:
The precursor material is prepared in advance with specific particle size and composition characteristics before the main sintering process. This preliminary action ensures uniform element distribution in the precursor, which translates to uniform distribution in the final product, improving material stability without requiring complex in-situ control during sintering.
2Reliability
If the coating layer density is increased to reduce micropores, then the compacted density and electronic conductivity improve, but the specific surface area increases which may affect processability
Solution Approach 1:
The particle size of the precursor material is controlled within the range of 3-100 μm, and the compacted density is controlled at 1.35-2.5 g/cm³ at 30 MPa. These parameter optimizations allow the coating layer to achieve high density and good electronic conductivity while maintaining appropriate specific surface area for processability.
3Productivity
If the precursor material particle size is reduced to improve mixing and suspension, then the washing and filtration efficiency improves, but the compacted density may decrease
Solution Approach 1:
The precursor material particle size is optimized to 3-100 μm, which is small enough to facilitate washing, filtration, suspension, and mixing operations, yet large enough to maintain good compacted density (1.35-2.5 g/cm³ at 30 MPa) in the final product. This parameter optimization resolves the contradiction between processing efficiency and compacted density.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method results in a positive electrode material with improved specific capacity, cycling performance, and reduced powder resistivity, enhancing the battery's overall efficiency and processability.
Implementation Method 1
through sintering, volatile substances are evaporated, resulting in a dense pre-product
Implementation Method 2
a coating layer is prepared on the pre-product, which is conducive to increasing the density of the coating layer, reducing micropores on the coating layer
Data Source
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AI summary
A method for preparing a positive electrode material, a positive electrode material, a positive electrode plate, a battery, and an electric apparatus are disclosed. The method includes: mixing a precursor material, a lithium source, and an optional phosphorus source, and sintering to obtain a pre-product, where the precursor material includes a compound MnxFeyM(1-x-y)HPO4·nH2O, 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9, 0≤n≤6, and M includes one or more of transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, and Group IVA metal elements; and mixing the pre-product, a carbon source, and a solvent, drying, and sintering to obtain a positive electrode material. The positive electrode material of this application exhibits uniform element distribution, good material stability, high compacted density, low powder resistivity, and good electronic conductivity, thereby improving the specific capacity and cycling performance of a battery.