Positive Electrode Coating Balance for Low DCR Li-Ion Batteries
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Solution Overview
Problem
Existing lithium-ion batteries struggle to balance high energy density, power performance, and cycle-life performance, particularly in applications requiring continuous high power output like Electric Vertical Takeoff and Landing (EVTOL) equipment.
Innovation Solution
A positive electrode plate with a coating layer containing a monocrystalline and polycrystalline ternary material, where the mass ratio of the monocrystalline ternary material, the mass percentage of the conductive agent, and the areal-density of the coating layer satisfy the formula 0.39<106ab2/c2<2, ensuring optimal energy density, cycle-life performance, and power performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the coating layer uses only polycrystalline ternary material to increase areal-density for higher energy density, then the energy density improves, but the DCR (diffusion resistance) performance deteriorates due to longer lithium ion diffusion paths
Solution Approach 1:
The positive electrode active material is segmented into two distinct crystal structure types: monocrystalline ternary material (providing short diffusion paths for low DCR) and polycrystalline ternary material (providing high areal-density for high energy density). This segmentation allows each component to fulfill its specific function optimally while working together in the composite coating layer.
Solution Approach 2:
The patent employs a composite material system combining monocrystalline and polycrystalline ternary materials in specific proportions (where the mass ratio a of monocrystalline to total ternary material is 0.10≤a≤0.50). This composite structure synergistically integrates the advantages of both crystal types: the monocrystalline phase reduces diffusion resistance while the polycrystalline phase increases areal-density, achieving both high energy density and excellent DCR performance simultaneously.
2Quantity of substance
If the areal-density of the coating layer is increased to improve energy density, then the energy density improves, but the power performance deteriorates due to increased diffusion resistance
Solution Approach 1:
The coating layer is segmented into monocrystalline and polycrystalline ternary material phases, where the monocrystalline segments provide efficient lithium ion diffusion channels that maintain low DCR even at high areal-densities, thus preserving power performance while achieving high energy density.
Solution Approach 2:
The patent optimizes the mass ratio parameter a (monocrystalline ternary material content) within the range 0.10≤a≤0.50, and controls the areal-density c within 12≤c≤18 mg/cm2. By adjusting these parameters according to the formula 0.40≤106ab2/c2≤1.78, the battery achieves optimal balance between areal-density (energy density) and diffusion resistance (power performance).
3Reliability
If the mass ratio of monocrystalline ternary material is increased to improve DCR performance, then the DCR performance improves, but the areal-density decreases leading to lower energy density
Solution Approach 1:
The composite material system combines monocrystalline and polycrystalline ternary materials in optimized proportions. The monocrystalline phase (10-50 mass%) ensures excellent DCR performance with short diffusion paths, while the polycrystalline phase contributes to high areal-density. The synergistic composite structure achieves both low DCR and high energy density that neither material could achieve alone.
Solution Approach 2:
The patent precisely controls the mass ratio parameter a within 0.10≤a≤0.50 and integrates it with areal-density parameter c in the optimization formula 0.40≤106ab2/c2≤1.78. This parameter optimization ensures that increasing monocrystalline content for low DCR does not excessively reduce areal-density, maintaining high energy density while achieving excellent DCR performance.
4Power
If the content of conductive agent is increased to improve power performance, then the power performance improves, but the areal-density of active material decreases leading to lower energy density
Solution Approach 1:
The patent optimizes the mass percentage content parameter b of conductive agent within 0.025≤b≤0.040, integrating it with monocrystalline ratio a and areal-density c in the formula 0.40≤106ab2/c2≤1.78. This comprehensive parameter optimization ensures sufficient conductive agent for excellent power performance while minimizing its impact on areal-density, maintaining high energy density.
Data Source
AI summary
The present disclosure provides a positive electrode, including a positive electrode current collector and a coating layer coated on at least one surface of the positive electrode current collector perpendicular to a thickness direction. The coating layer includes a positive electrode active material and a conductive agent, and the positive electrode active material includes a monocrystalline ternary material and a polycrystalline ternary material. The coating layer satisfies Formula I: 0.39<106ab2/c2<2; where in Formula I, a is a mass ratio of the monocrystalline ternary material in the positive electrode active material, b is a mass percentage content of the conductive agent in the coating layer, and c is an areal-density of the coating layer in mg/cm2. In the present disclosure, when the positive electrode satisfies the Formula I, the lithium-ion battery prepared by the positive electrode could achieve an excellent DCR performance while ensuring energy density and cycle-life performance simultaneously.