Anode Layer Flexion Gradient for Lithium-Ion Battery Safety
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Solution Overview
Problem
Conventional methods for increasing the capacity of lithium-ion secondary battery electrodes by adjusting press pressure lead to surface crushing of active materials, causing dendrite formation and potential short circuits, compromising safety and performance.
Innovation Solution
An anode design featuring an active material-containing layer with a lower layer of higher flexion for increased capacity and an outermost layer of lower flexion to maintain electrolyte flow paths, preventing lithium ion accumulation and dendrite generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If press pressure is increased to increase electrode packing density and capacity, then electric capacity is improved, but active material on the surface is crushed and flow paths are closed causing dendrite formation and safety issues
Solution Approach 1:
The active material-containing layer is divided into two distinct layers: a lower layer with higher degree of flexion (2.5-4.0) for high capacity and an outermost layer with lower degree of flexion (1.3-2.0) for safety. This segmentation allows each layer to perform its specific function without compromising the other, resolving the contradiction between capacity and safety
Solution Approach 2:
Different regions of the electrode are given different properties: the lower layer has high degree of flexion to maximize lithium ion accommodation and capacity, while the outermost layer has low degree of flexion to maintain open flow paths and prevent dendrites. This local differentiation resolves the contradiction by optimizing each region for its specific purpose
2Quantity of substance
If press pressure is increased to increase electrode packing density, then capacity per volume is improved, but flow paths of electrolyte solution are closed
Solution Approach 1:
The electrode is segmented into two layers with different packing densities and flow path characteristics. The lower layer provides high density for capacity, while the outermost layer maintains open flow paths for electrolyte circulation, ensuring both high capacity and excellent high-rate discharge performance
Solution Approach 2:
The solution addresses the two-dimensional conflict between density and flow paths by introducing a vertical dimension with layered structure. Each layer operates at different density levels, allowing the electrode to achieve high overall capacity while maintaining surface flow paths for rapid ion transport
3Quantity of substance
If press pressure is increased to increase electrode density, then electric capacity is improved, but dendrite generation is promoted
Solution Approach 1:
The electrode structure is segmented into a high-density lower layer for capacity and a low-density outermost layer that prevents dendrite formation. This segmentation isolates the capacity-optimizing function from the safety-protecting function, allowing high capacity without dendrite generation
Solution Approach 2:
The invention converts the potential harm of high press pressure (which causes surface crushing and dendrites) into a benefit by applying it selectively to the lower layer only. The outermost layer is protected from excessive pressure, transforming what would be a harmful uniform compression into a beneficial selective compression that enhances capacity while preventing dendrites
Data Source
AI summary
An anode for lithium-ion secondary battery is provided as one capable of ensuring sufficient safety (suppression of dendrites) while achieving a higher capacity (higher density of the electrode), and permitting formation of a lithium-ion secondary battery with excellent high-rate discharge performance. An anode for lithium-ion secondary battery has a current collector, and an active material-containing layer formed on the current collector, the active material-containing layer is comprised of an outermost layer disposed on the farthest side from the current collector, and a lower layer composed of at least one layer disposed between the outermost layer and the current collector, and a degree of flexion of the outermost layer is smaller than that of the lower layer.