Jelly-Roll Anode Graphite Composition for Winding Adhesion
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Solution Overview
Problem
Conventional jelly-roll type electrode assemblies face issues with anode mixture detachment during winding, leading to performance deterioration in secondary batteries, particularly due to uneven stress distribution and the use of active materials with the same composition on both sides of the current collector.
Innovation Solution
The electrode assembly features an anode mixture with a different composition on both sides of the current collector, where the inward side has a higher proportion of artificial graphite for improved adhesion and the outward side has more natural graphite to enhance adhesive strength and prevent detachment, along with specific surface area and tap density optimization for better performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same composition of active material is coated on both sides of the anode current collector, then the manufacturing process is simple, but the anode mixture detaches from the back side during winding
Solution Approach 1:
The patent applies different active material compositions to different locations (sides) of the anode current collector. The front side uses a first composition while the back side uses a second composition, allowing each side to be optimized for its specific functional requirements and stress conditions during winding.
Solution Approach 2:
The patent introduces asymmetric composition design where the anode active materials on the front and back sides have different compositions. This asymmetric approach addresses the asymmetric stress distribution during winding, preventing detachment on the back side while maintaining overall battery performance.
2Reliability
If natural graphite is used on the outward side to enhance adhesive strength, then detachment is prevented, but the output characteristics may be reduced
Solution Approach 1:
The patent optimizes adhesion locally on the back side by using natural graphite, while preserving power characteristics on the front side through appropriate composition selection. This localized optimization allows each side to fulfill its primary function without compromising the other.
Solution Approach 2:
The patent employs composite active material compositions on each side, combining different types of graphite (natural and artificial) in specific ratios. This composite approach allows balancing adhesion requirements with power characteristics by leveraging the complementary properties of different materials.
Data Source
AI summary
The present disclosure relates to a jelly-roll type electrode assembly in which a long sheet-type cathode and a long sheet-type anode are wound in a state where a separator is interposed between the cathode and the anode, wherein the anode is configured such that an anode mixture is formed on both sides of an anode current collector, and the anode current collector is configured such that when winding to form an electrode assembly, if a side that winds inward is referred to a first side and a side that winds outward is referred to a second side, an active material of a first anode mixture coated on the first side contains 70 wt % or more artificial graphite as an active material based on the total weight of the active material, and an active material of a second anode mixture coated on the second side contains 70 wt % or more natural graphite as an active material based on the total weight of the active material.