Lithium-Ion Positive Electrode Boundary Coating for Swelling Control
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Solution Overview
Problem
The application of an insulating material as a thin film is difficult due to the gap between coating equipment and the work, leading to increased thickness, cost, and cracking risks in lithium ion secondary batteries with high energy density.
Innovation Solution
A positive electrode for lithium ion secondary batteries is designed with a first mixture layer containing a positive electrode active material and a second mixture layer with conductive particles, where the second mixture layer is partially covered by the first and positioned at the boundary between formed and non-formed areas, allowing for continuous or intermittent application to form a thin film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional positive electrode is used, then the battery can operate, but the battery swells due to electrolyte decomposition and gas generation at the electrode surface
Solution Approach 1:
A porous coating layer is introduced as an intermediary between the positive electrode and the electrolyte. This coating layer mediates the interaction by allowing lithium ion transport while preventing direct contact between the electrolyte and electrode surface, thereby suppressing electrolyte decomposition and gas generation that cause battery swelling.
Solution Approach 2:
The coating layer is designed with a porous structure having specific pore size distribution. The porous structure allows lithium ions to diffuse through while providing a large surface area for stable solid electrolyte interface formation, preventing electrolyte decomposition and subsequent battery swelling without blocking ion transport.
2Reliability
If the electrode surface is treated to prevent electrolyte decomposition, then battery stability improves, but internal stress increases causing coating peeling
Solution Approach 1:
The coating layer is designed with locally optimized properties: the inner region near the electrode surface has composition and pore structure optimized for strong adhesion and stress relief, while the outer region is optimized for lithium ion transport and electrolyte decomposition prevention. This local quality variation allows simultaneous achievement of coating stability and adhesion.
Solution Approach 2:
The coating layer composition and pore size are carefully controlled within specific ranges to balance adhesion and stress resistance. By optimizing parameters such as coating thickness, porosity, and chemical composition, the layer achieves sufficient adhesion strength while maintaining the ability to suppress electrolyte decomposition and prevent peeling.
3Object-generated harmful factors
If a coating layer is added to suppress electrolyte decomposition, then harmful gas generation decreases, but manufacturing complexity increases
Solution Approach 1:
The coating layer is formed through a self-service process where the electrode itself serves as the substrate for coating formation. The coating is deposited directly onto the electrode surface using existing electrode materials as precursors, eliminating the need for separate coating application equipment and simplifying the manufacturing process while still achieving the function of suppressing electrolyte decomposition.
Solution Approach 2:
The coating layer is formed as a composite structure incorporating multiple functional components in a single layer. This composite approach integrates adhesion promotion, stress relief, and electrolyte decomposition suppression functions into one unified coating, reducing the need for multiple separate layers and simplifying the overall electrode structure and manufacturing process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces manufacturing costs and enhances performance by enabling a thin film application, suppressing electrical contact, and preventing cracking, while maintaining high energy density.
Implementation Method 1
stabilizing a solid electrolyte interface by use of a porous coating layer having pores with a specific size distribution
Implementation Method 2
the porous coating layer having pores with a specific size distribution, thereby stable solid electrolyte interface formation is promoted
Implementation Method 3
supply of lithium ions to the positive electrode is continuous
Data Source
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AI summary
Provided is a positive electrode for a lithium ion secondary battery including a metal foil (9) (current collector), a first mixture layer (11) which is provided on one surface of the metal foil (9) and contains a positive electrode active material, and a second mixture layer (12) which is partially covered by the first mixture layer (11) and includes, as a main component, particles different from the active material, in which the second mixture layer (12) is provided on one end (11a) side of the first mixture layer (11) in a boundary portion between a formed area of the first mixture layer (11) and a non-formed area of the first mixture layer (11), one end (12a) of the second mixture layer (12) is positioned between the one surface of the metal foil (9) and a lower surface of the first mixture layer (11) in the formed area of the first mixture layer (11), and the other end (12b) is positioned in the non-formed area, and the first mixture layer (11) and the second mixture layer (12) contain a dispersed conductive substance.