Gradient Active Material Loading in Jelly-Roll Electrodes
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Solution Overview
Problem
The nonuniform distribution of active material layers in jelly-roll type electrode assemblies leads to uneven electrochemical reactions, electrolyte consumption, and increased pressure, resulting in reduced battery capacity and service life due to jelly-roll twist and wrinkles.
Innovation Solution
A jelly-roll structure is developed where the inner active material layer has a lower loading amount than the outer layer, with the loading amount gradually increasing from the central region to the outermost region, ensuring uniform electrolyte consumption and preventing material lumping and density increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the active material loading amount is uniform across the entire electrode sheet, then the manufacturing process is simple, but the nonuniform distribution of active material layers leads to uneven electrochemical reactions and jelly-roll twist
Solution Approach 1:
The patent applies local quality by varying the active material loading amount across different regions of the electrode sheet. Specifically, the loading amount is set to be smaller at the inner surface (radius R1) and larger at the outer surface (radius R2), creating a radial gradient distribution. This local variation compensates for the nonuniform stress distribution during winding, preventing jelly-roll twist while maintaining manufacturing feasibility through controlled deposition processes.
Solution Approach 2:
The patent implements parameter changes by modifying the active material loading amount as a function of radial position. The loading amount transitions from a smaller value at the inner radius to a larger value at the outer radius, creating a continuous gradient. This parameter variation optimizes the electrochemical reaction uniformity and prevents structural deformation during battery operation.
2Strength
If the active material loading amount is increased at the inner surface to compensate for pressure, then the density increases and material lumps, but the electrochemical reaction becomes more active and electrolyte consumption increases
Solution Approach 1:
The patent applies local quality by setting different active material loading amounts at different radial positions. The inner surface (smaller radius) has a smaller loading amount to prevent excessive density and material lumping, while the outer surface has a larger loading amount to maintain electrochemical activity. This localized optimization ensures uniform electrolyte consumption across the electrode structure.
Solution Approach 2:
The patent applies preliminary anti-action by pre-compensating for the pressure-induced density increase and material lumping at the inner surface through controlled reduction of active material loading. This preventive measure counteracts the harmful effects of compression during winding, maintaining material integrity and uniform electrochemical performance.
3Ease of manufacture
If the loading amount of inner active material layer is set to 0.6-0.8 ratio of outer layer, then winding is easy and wrinkles are prevented, but the capacity ratio becomes unbalanced and service life decreases
Solution Approach 1:
The patent implements parameter changes by establishing a radial gradient in active material loading amount, where the loading increases from the inner surface to the outer surface. This gradient distribution optimizes both winding performance and long-term battery service life by balancing the electrochemical reaction uniformity across different regions, preventing capacity degradation over time.
Solution Approach 2:
The patent applies dynamics by creating a dynamic loading distribution that adapts to the radial position. Rather than a fixed uniform loading, the active material amount varies continuously from inner to outer regions, optimizing the balance between manufacturing ease and operational durability throughout the battery's service life.
Data Source
Figure 1
Figure 2~3
AI summary
Disclosed herein is a jelly-roll type electrode assembly ("jelly-roll") of a cathode/separator/anode structure, wherein the jelly-roll is constructed in a structure in which each electrode has active material layers formed on opposite major surfaces of a sheet-type current collector, the loading amount of an active material for the inner active material layer, constituting the inner surface of each sheet when each sheet is wound, is less than that of an active material for the outer active material layer, constituting the outer surface of each sheet when each sheet is wound, and the loading amount of the active material for the inner active material layer gradually increases from the central region of each wound sheet to the outermost region of each wound sheet.