Composite Li-Ion Cell Cathode Layout for Uniform Mixed-Material Coating
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Solution Overview
Problem
The integration of different types of positive electrode active materials in lithium-ion batteries is challenging due to differences in particle sizes and surface energies, leading to agglomeration and uneven coating surface densities, which affects energy density and cycle life.
Innovation Solution
A composite cell design is implemented, where multiple positive electrode sheets with specific capacity ratios, surface densities, and specific surface resistances are used. Each sheet contains a combination of high-energy density and low-energy density active materials, with controlled mass proportions and multi-layer coating structures to ensure uniform potential distribution and prevent 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 sheet is divided into multiple layers, with each layer containing a specific type of positive electrode active material. This segmentation prevents agglomeration by separating materials with different particle sizes and surface energies into distinct layers, while still achieving the goal of integrating different material types in the same electrode.
Solution Approach 2:
The patent creates a composite electrode structure by combining multiple types of positive electrode active materials (oxide-based and phosphate-based) in a multi-layer configuration. This composite approach allows each material to maintain its individual properties while benefiting from the synergistic effects of different materials with complementary advantages.
2Stability of the object's composition
If multi-layer coating method is used to avoid agglomeration, then slurry uniformity is improved, but coating surface density becomes uneven when proportions of different materials differ greatly
Solution Approach 1:
Different regions (layers) of the positive electrode sheet have different compositions and properties. Each layer is designed with specific material composition and coating surface density to optimize performance. This local quality approach allows the electrode to achieve uniform overall performance while accommodating different material proportions in specific layers.
3Quantity of substance
If oxide-based positive electrode active materials are used, then energy density is improved, but structural stability deteriorates
Solution Approach 1:
The patent combines oxide-based positive electrode active materials (high energy density) with phosphate-based materials (high structural stability) in a multi-layer configuration. This composite structure allows the electrode to achieve both high energy density from the oxide-based materials and long cycle life from the phosphate-based materials, resolving the contradiction between energy density and structural stability.
4Duration of action of stationary object
If phosphate-based positive electrode active materials are used, then cycle life is improved, but energy density deteriorates
Solution Approach 1:
The patent combines phosphate-based positive electrode active materials (long cycle life) with oxide-based materials (high energy density) in a multi-layer configuration. This composite structure allows the electrode to achieve both long cycle life from the phosphate-based materials and high energy density from the oxide-based materials, resolving the contradiction between cycle life and energy density.
Data Source
AI summary
A composite cell and a battery containing the composite cell are provided. The composite cell includes positive electrode sheets each satisfying 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, 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 of the first positive electrode sheet is 0.0001 to 0.1500 Ω/mm2·g.