Positive Electrode Active Material With Dual Particle Sizes for Li Battery
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high energy density, high operating voltage, and high conductivity, as well as maintaining low-temperature performance.
Innovation Solution
A positive electrode active material comprising first particles with a specific olivine-based lithium compound and second particles with a larger average particle diameter, mixed in a specific ratio, to enhance energy density and conductivity, while stabilizing the structure and improving low-temperature properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single particle size of positive electrode active material is used, then the manufacturing process is simple, but the energy density and conductivity are insufficient
Solution Approach 1:
The positive electrode active material is segmented into two distinct particle size ranges: first particles with 0.5-2.0 μm diameter and second particles with 2.0-5.0 μm diameter. This segmentation allows each particle size to contribute differently to performance - smaller particles provide higher surface area for reactions while larger particles maintain structural stability, thereby achieving high energy density without excessive manufacturing complexity
Solution Approach 2:
Different regions of the electrode are populated with different particle sizes to optimize local performance. The first particles (smaller) are distributed throughout to provide high reactivity zones, while second particles (larger) are present to provide structural backbone. This local quality differentiation enables the electrode to simultaneously achieve high conductivity in reactive zones and structural integrity overall
2Quantity of substance
If high operating voltage is pursued, then energy density improves, but conductivity and low-temperature performance deteriorate
Solution Approach 1:
The patent uses a composite material system combining two different lithium phosphate-based compounds with distinct particle sizes. The first particles (0.5-2.0 μm) of one compound provide high conductivity and low-temperature performance, while the second particles (2.0-5.0 μm) of another compound contribute to structural stability and high operating voltage capability. This composite approach allows the electrode to achieve high energy density through high voltage operation while maintaining reliability at low temperatures through the conductive network provided by the smaller particles
Data Source
AI summary
A positive electrode active material for a rechargeable lithium battery, a positive electrode including the positive electrode active material, and a rechargeable lithium battery including the positive electrode are disclosed. The positive electrode active material includes first particles comprising a compound of Lia1Fex1B1y1PO4-b1 and having a first average particle diameter, and second particles comprising a compound of Lia2Nix2COy2Mnz2Xc2O2-b2 and having a second average particle diameter that is greater than the first average particle diameter. The content (e.g., amount) of the first particles is greater than the content (e.g., amount) of the second particles in the positive electrode active material.