Composite Cell Cathode Layout for Uniform Potential Distribution
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Solution Overview
Problem
Existing lithium-ion battery technologies face challenges in integrating different types of positive electrode active materials effectively, leading to issues such as agglomeration, uneven energy distribution, and impedance problems due to differences in particle sizes and surface energies.
Innovation Solution
A composite cell design is introduced, featuring multiple positive electrode sheets with specific capacity ratios, surface densities, and resistance levels. The sheets include a first positive electrode sheet with a ternary active material and a second sheet with materials like lithium iron phosphate, optimized to achieve uniform potential distribution and alleviate lithium deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If different types of positive electrode active materials are mixed in a blending manner and coated directly on current collector, then the coating process is simple, but agglomeration occurs due to differences in particle sizes and surface energies
Solution Approach 1:
The positive electrode sheets are divided into multiple types (first, second, third, fourth positive electrode sheets) with different active material compositions and capacity densities. This segmentation allows each sheet type to have optimized properties, avoiding agglomeration issues while maintaining manufacturing feasibility through standardized production of each sheet type.
Solution Approach 2:
Different regions of the battery pack are assigned different types of positive electrode sheets based on local requirements. For example, the first and second positive electrode sheets with higher capacity densities can be placed in regions where energy density is prioritized, while the third and fourth sheets with lower capacity densities and better stability are placed in regions prioritizing cycle life and safety.
2Use of energy by moving object
If oxide-based positive electrode active materials are used, then energy density is high, but structural stability is poor
Solution Approach 1:
The battery pack uses a composite structure combining different types of positive electrode sheets with different material characteristics. The oxide-based sheets (first and second) provide high energy density, while the phosphate-based sheets (third and fourth) provide structural stability and long cycle life. This composite approach allows the system to achieve both high energy density and structural stability simultaneously.
3Duration of action of stationary object
If phosphate-based positive electrode active materials are used, then cycle life is long and safety is improved, but energy density is low
Solution Approach 1:
The battery pack combines phosphate-based positive electrode sheets (third and fourth) with oxide-based sheets (first and second) in a composite structure. The phosphate-based sheets contribute long cycle life and safety, while the oxide-based sheets contribute high energy density. This composite material strategy allows the system to achieve both long cycle life and high energy density.
Solution Approach 2:
Phosphate-based positive electrode sheets are strategically placed in regions where cycle life and safety are prioritized, while oxide-based sheets are placed in regions where energy density is the primary concern. This local optimization allows the overall system to achieve both long cycle life and high energy density.
4Stability of the object's composition
If multi-layer coating method is used to avoid agglomeration, then slurry uniformity is improved, but coating surface density of material with smaller proportion becomes too small for process realization
Solution Approach 1:
Instead of using multi-layer coating to achieve uniformity, the invention segments the battery pack into multiple types of positive electrode sheets, each with optimized composition and capacity density. This allows each sheet type to be manufactured with appropriate coating density, avoiding the coating precision issues that would arise from trying to coat low-proportion materials in small amounts.
Data Source
Figure 1
Figure 2~3
AI summary
A composite cell (1) and a battery containing the composite cell are provided. The composite cell includes positive electrode sheets. Each positive electrode sheet satisfies a condition that a ratio of its capacity per unit area to a capacity per unit area of any other positive electrode sheet is 0.9 to 1.1. The positive electrode sheets include first positive electrode sheets (1-4), and positive electrode active materials contained in the first positive electrode sheet include a first positive electrode active material and a second positive electrode active material. An energy density of the first positive electrode active material is greater than that of the second positive electrode active material. On each of the first positive electrode sheets, 10%≤m1m0≤ 50%, an average single-side surface density of the positive active coating layer is 50 to 650 g/m2, and a specific surface resistance is 0.0001 to 0.1500 Ω/mm2·g.