Dual-Layer Positive Electrode Coating for Uniform Binder Distribution
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Solution Overview
Problem
Existing secondary batteries face issues with non-uniform binder distribution, high production costs due to expensive materials, and limited performance improvement from single-layer electrodes, particularly when using Ni-enriched lithium composite oxides as positive electrode materials.
Innovation Solution
A positive electrode with a dual-layer structure is proposed, where the lower layer includes a sacrificial positive electrode material like Li6CoO4 and a different composition of positive electrode active material, and the upper layer includes a conductive material and binder resin, ensuring uniform binder distribution and improved electroconductivity using single-walled carbon nanotubes (SWCNTs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li2NiO2 is used as a sacrificial positive electrode material to supplement irreversible capacity, then the battery capacity is improved, but the production cost increases due to high material cost
Solution Approach 1:
The patent uses LiCoO3 as a sacrificial positive electrode material that is deliberately designed to be consumed during initial charging cycles to supplement irreversible capacity. This material is sacrificed to enable the use of higher capacity materials like Li2NiO3 in the main electrode structure, ultimately reducing overall production costs while maintaining high battery capacity.
Solution Approach 2:
The patent changes the chemical composition parameters of the positive electrode material by using LiCoO3 with specific lithium content and oxidation states. By controlling the lithium content and oxidation state of Co in LiCoO3, the patent optimizes the sacrificial material's ability to supplement irreversible capacity while controlling material costs.
2Quantity of substance
If the loading amount of electrode active material is increased to improve energy density, then the battery capacity is improved, but the binder distribution becomes non-uniform causing increased resistance
Solution Approach 1:
The patent segments the positive electrode into multiple layers with different compositions. The lower layer contains LiCoO3 sacrificial material while the upper layer contains Li2NiO3 active material. This segmentation allows each layer to have optimized binder distribution and material loading, preventing the binder floating issue while maintaining high overall energy density.
Solution Approach 2:
The patent applies local quality by having different material compositions and binder distributions in different regions of the electrode. The lower layer has specific binder content optimized for LiCoO3, while the upper layer has binder content optimized for Li2NiO3, ensuring uniform binder distribution throughout the thick electrode structure.
3Device complexity
If a single-layer electrode structure is used to simplify manufacturing, then the device complexity is reduced, but the ability to localize electrode materials at specific portions is limited
Solution Approach 1:
The patent divides the positive electrode into multiple layers, each with specific functional materials. The lower layer contains LiCoO3 sacrificial material for supplementing irreversible capacity, while the upper layer contains Li2NiO3 for high capacity. This segmentation enables material localization while maintaining relatively simple manufacturing processes.
Solution Approach 2:
The patent transitions from a single-layer to a multi-layer electrode structure, adding the dimension of vertical layering. This allows different materials to be localized at different heights (lower layer vs. upper layer) while maintaining a planar electrode geometry that is compatible with existing manufacturing techniques.
Data Source
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AI summary
The present disclosure relates to a positive electrode for a secondary battery. According to the present disclosure, when manufacturing a positive electrode having the same thickness, it is possible to make the binder distribution uniform in the thickness direction of the electrode active material layer by using a dual layer coating process, and to provide an effect of improving binding force by allowing the binder resin of the lower layer portion of the positive electrode active material layer to be retained in the lower layer portion. In addition, it is possible to improve the electrochemical characteristics of a battery by using a different composition of positive electrode material in the upper layer portion and the lower layer portion of the positive electrode, particularly, by introducing a sacrificial positive electrode material merely to the lower layer portion.