Layered Positive Electrode Structure for Stable Li-Ion Cycling
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in enhancing safety performance and cycle storage performance, particularly due to detachment of conductive agents during expansion cycles, which affects interface resistance and reduces cycle performance and high-temperature storage performance.
Innovation Solution
A positive electrode structure is introduced, comprising a positive current collector, a positive active material layer, a bonding layer, and a conductive layer with specific weight percentages of conductive agents and binders, along with a bonding layer having a higher binder content to enhance adhesion and a conductive layer with controlled thickness to maintain conductivity and prevent detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode structure is used, then the manufacturing process is simple, but the cycle performance and high-temperature storage performance are insufficient
Solution Approach 1:
The positive electrode is segmented into multiple functional layers: a positive active material layer containing lithium-containing positive active material, a bonding layer containing binder and conductive agent, and optionally a protective layer. This segmentation allows each layer to perform its specific function optimally, improving cycle performance and high-temperature storage performance while maintaining manufacturing feasibility.
Solution Approach 2:
The patent uses composite materials in the electrode structure, particularly in the bonding layer which combines binder and conductive agent, and in the positive active material layer which uses lithium-containing positive active material. These composite materials provide both mechanical integrity and electrical conductivity, resolving the contradiction between reliability and device complexity.
2Strength
If the electrode structure is optimized for adhesion, then detachment risk is reduced, but the conductivity may be compromised
Solution Approach 1:
The bonding layer is designed as a composite material containing both binder (for adhesion) and conductive agent (for conductivity). This composite structure allows the bonding layer to simultaneously provide strong adhesion between the positive active material layer and current collector while maintaining electrical conductivity, thus resolving the contradiction between strength and reliability.
3Use of energy by moving object
If high energy density is maintained, then the battery capacity is high, but the safety performance and stability deteriorate
Solution Approach 1:
The electrode is segmented into functional layers with the protective layer providing safety functions while the positive active material layer maintains high energy density. This segmentation allows the battery to achieve both high energy density and improved safety performance by isolating the high-energy materials from direct contact with electrolyte and other components.
Solution Approach 2:
The use of lithium-containing positive active material in combination with the bonding layer containing binder and conductive agent creates a composite structure that maintains high energy density while improving stability and safety performance through the synergistic effects of the different materials.
Data Source
AI summary
A positive electrode including a positive current collector, a positive active material layer, a bonding layer and a conductive layer. The bonding layer is disposed between the positive current collector and the positive active material layer. The conductive layer is disposed between the bonding layer and the positive active material layer. The conductive layer includes a conductive agent with a weight percent of 20 wt % to 95 wt % and a binder with a weight percent of 5 wt % to 80 wt %. This helps to improve the cycle performance and the high-temperature storage performance of the electrochemical device.