Separator Coating with Core-Shell Binder for Battery Rate Performance
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Solution Overview
Problem
The existing polymer binders in separators for electrochemical devices, such as lithium-ion batteries, face challenges with poor electrolyte wetting and transport due to their weak polar nature, leading to issues like lithium precipitation and reduced cycle performance, which are not effectively addressed by increasing crosslinking or adjusting formation process conditions.
Innovation Solution
A separator with a porous substrate coated with a first polymer binder and inorganic particles, forming a core-shell structured coating that enhances electrolyte transport and bonding, while maintaining mechanical integrity, thereby improving the rate and cycle performance of electrochemical devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the degree of crosslinking of the polymer binder is increased to reduce the degree of swelling, then the swelling is reduced, but the rigidity of the particles increases which results in a decrease in bonding force
Solution Approach 1:
The patent uses a composite binder system combining a first polymer binder (acrylic acid or acrylate polymer) and a second polymer binder (carboxymethyl cellulose or starch derivative) in specific ratios. This composite approach allows the first binder to provide structural stability with controlled swelling while the second binder maintains flexibility and bonding force, resolving the contradiction between reducing swelling and maintaining bonding strength.
Solution Approach 2:
The patent optimizes the molecular weight, composition ratio, and crosslinking degree of the polymer binders as key parameters. By carefully controlling the crosslinking degree to be within a specific range and adjusting the ratio of first to second binder (1:9 to 4:6), the patent achieves optimal balance between swelling control and bonding force without excessive rigidity.
2Ease of manufacture
If the formation process conditions are adjusted (reducing temperature, pressure, and time), then the processing is simplified, but the interface adhesive force between the separator and the electrode plate is reduced
Solution Approach 1:
The patent optimizes the formation process parameters including temperature (100-150°C), pressure (0.1-10 MPa), and time (1-24 hours) within specific ranges. The optimized binder composition enables effective bonding within this moderate parameter range, achieving good interface adhesion without requiring extreme conditions that would complicate manufacturing.
Solution Approach 2:
The dual-polymer binder system provides synergistic effects where the first binder offers thermal stability and the second binder enhances interfacial adhesion. This composite structure enables effective bonding at moderate formation process conditions, resolving the contradiction between ease of manufacture and bonding strength.
3Shape
If the polymer binder is pressed and adhered to form a film after swelling, then the film formation is achieved, but the rate performance and cycle performance are affected and lithium precipitation occurs
Solution Approach 1:
The patent controls the swelling degree of the polymer binder within a specific range (30-70%) through optimized crosslinking and composition. This controlled swelling allows sufficient film formation while preventing excessive compression that would cause lithium precipitation and performance degradation. The specific molecular weight range (10,000-1,000,000) also contributes to optimal film properties.
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
The use of inorganic particles in the coating improves the bonding force and electrolyte transport, leading to enhanced rate and cycle performance of electrochemical devices by preventing film formation during the formation process and ensuring consistent particle distribution, thus addressing the limitations of traditional polymer binders.
Implementation Method 1
a polymer binder of a separator is pressed and adhered to form a film after swelling in an electrolyte
Implementation Method 2
a binder coating including inorganic particles is formed on a porous substrate of a separator, which prevents the binder from being pressed and adhered to form a film
Implementation Method 3
the first polymer binder includes core-shell structured particles
Data Source
AI summary
A separator includes a porous substrate and a first coating located on at least one surface of the porous substrate. The first coating includes a first polymer binder and first inorganic particles, and the first polymer binder comprising core-shell structured particles. 0.3×Dv50 of the first polymer binder≤Dv50 of the first inorganic particles≤0.7×Dv50 of the first polymer binder. Dv50 represents a particle size which reaches 50% of a cumulative volume from a side of small particle size in a granularity distribution on a volume basis The first inorganic particles are used in the first coating, ensuring that the first polymer binder has a bonding function, electrolyte transport is promoted, and the rate performance of the electrochemical device is improved.