Anode with Flexion-Graded Layer for Fast Charge Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with rapid lithium ion entrance/exit at the anode, leading to extreme expansion and deformation, compromising battery performance and safety during quick charge-discharge.
Innovation Solution
An anode design featuring a current collector with an active material-containing layer comprising an outermost layer with a higher degree of flexion and a lower layer with a smaller degree of flexion, where the outermost layer suppresses rapid lithium ion intercalation and the lower layer acts as a buffer to absorb expansion, preventing deformation during charge-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the anode uses a conventional single-layer active material structure, then the battery can achieve high charge-discharge rates, but the anode undergoes rapid expansion and deformation due to fast lithium ion intercalation
Solution Approach 1:
The anode active material layer is divided into two distinct layers: a first layer with high degree of flexion and a second layer with low degree of flexion. This segmentation allows each layer to perform its specific function - the first layer suppresses rapid lithium ion entrance/exit while the second layer provides structural stability, resolving the contradiction between charge-discharge rate and structural stability.
Solution Approach 2:
Different regions of the anode are given different mechanical properties through the two-layer structure. The first layer has high degree of flexion to control lithium ion flux locally at the electrolyte interface, while the second layer has low degree of flexion to maintain overall structural integrity. This local differentiation of properties allows simultaneous achievement of fast charge-discharge and structural stability.
2Speed
If the anode active material particles expand rapidly during fast charge, then lithium ions intercalate quickly, but the anode deforms and safety is compromised
Solution Approach 1:
The first layer with high degree of flexion acts as a preliminary control mechanism that suppresses rapid lithium ion entrance into the anode active material particles. By controlling the lithium ion flux at the interface before it reaches the bulk active material, the system prevents the harmful rapid expansion and deformation that would compromise safety, while still allowing sufficient charge-discharge rates.
3Power
If the cathode experiences rapid lithium ion entrance/exit during fast charge-discharge, then high power output is achieved, but the cathode undergoes deformation and crystal structure distortion
Solution Approach 1:
The anode's two-layer structure segments the lithium ion transport pathway, creating a controlled interface that regulates lithium ion flux to the cathode. This segmentation prevents excessive rapid lithium ion exchange at the cathode, maintaining its structural integrity while still enabling high power output through optimized charge-discharge rates.
Data Source
AI summary
An anode is provided as one capable of suppressing rapid entrance/exit of lithium ions during quick charge-discharge and ensuring sufficient safety in use as an anode of a lithium-ion secondary battery. The anode is an anode for lithium-ion secondary battery having a current collector, and an active material-containing layer formed on the current collector, wherein 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 wherein a degree of flexion of the outermost layer is larger than a degree of flexion of the lower layer.