Positive Electrode Material Mixing for Dense Lithium Battery Cathodes
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Solution Overview
Problem
Existing lithium nickel cobalt metal oxide positive electrode materials face limitations in capacity, thermal stability, and swelling due to lithium by-products, and high packing density leads to degraded battery performance and life characteristics.
Innovation Solution
A method involving mixing two positive electrode active materials with different average particle diameters, pre-sintering, and optimizing the equivalence ratio of lithium compounds during preparation to enhance sintering uniformity and packing density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of nickel in lithium nickel cobalt metal oxide is increased to improve capacity, then reversible capacity increases, but lithium by-products (LiOH and Li2CO3) are generated on the surface causing swelling phenomenon
Solution Approach 1:
The patent removes the harmful lithium by-products (LiOH and Li2CO3) from the surface of the positive electrode active material through a washing process using water or dilute acid solution, thereby eliminating the cause of swelling while preserving the high-capacity nickel-rich material
Solution Approach 2:
The patent controls the oxidation state of nickel by adjusting the sintering atmosphere and temperature parameters, preventing nickel from remaining as Ni2+ which would otherwise generate lithium by-products, thus reducing swelling while maintaining high capacity
2Quantity of substance
If the positive electrode active material is rolled to increase packing density per unit volume, then energy density increases, but the positive electrode active material is damaged degrading battery life characteristics
Solution Approach 1:
The patent performs pre-sintering before the main sintering process to preliminarily form the crystal structure and strengthen the material, making it more resistant to damage during subsequent rolling and electrode fabrication processes
Solution Approach 2:
The patent creates a composite structure by combining the positive electrode active material with a coating layer that provides mechanical strength and protection, allowing the material to withstand rolling pressure while maintaining high packing density
3Quantity of substance
If LiCoO2 is used as positive electrode active material to achieve high operating voltage and excellent capacity characteristics, then battery performance is improved, but thermal stability deteriorates due to unstable crystal structure
Solution Approach 1:
The patent applies local substitution by replacing only a portion of the nickel atoms with cobalt and manganese atoms at specific lattice positions, thereby improving thermal stability in critical regions while preserving the high-capacity nickel-rich composition in other regions
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 improves capacity, resistance, and life characteristics of lithium secondary batteries by ensuring uniform sintering and increased packing density, minimizing lithium by-products, and reducing processing time and material damage.
Implementation Method 1
pre-sintering, and optimizing the equivalence ratio of lithium compounds during preparation to enhance sintering uniformity
Data Source
AI summary
A positive electrode material includes a first positive electrode active material and a second positive electrode active material. The first positive electrode active material has an average particle diameter (D50) of 10 μm to 30 μm and the second positive electrode active material has a smaller average particle diameter than the first positive electrode active material. An equivalent weight of lithium in the first positive electrode active material and an equivalent weight of lithium in the second positive electrode active material are different.