Porous Negative Electrode Layer for Battery Micro-Short Suppression
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries experience chemically-occurring micro short circuits due to metal fragments being trapped during production, leading to metal ion deposition and growth, which causes electrical shorts.
Innovation Solution
The battery design incorporates a negative electrode active material layer with controlled voids, specifically an average equivalent circle diameter from 9.6 μm to 35.8 μm, an average circularity of 0.26 or more, and an area percentage from 3.1% to 30.9%, formed using void-forming aids like microcapsules to prevent metal deposition and reduce short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voids are formed in the negative electrode active material layer to prevent metal deposition growth, then reliability is improved, but device complexity increases due to controlled void formation requirements
Solution Approach 1:
The negative electrode active material layer is designed with controlled voids (porosity) having specific characteristics: average equivalent circle diameter of 9.6 μm to 35.8 μm, average circularity of 0.26 or more, and area percentage of 3.1% to 30.9%. These porous structures provide spaces where metal ions can be deposited without growing toward the positive electrode, thereby preventing micro short circuits while maintaining electrode integrity
Solution Approach 2:
The invention specifies precise parameter ranges for the voids to achieve the desired effect. By controlling the average equivalent circle diameter (9.6-35.8 μm), circularity (≥0.26), and area percentage (3.1-30.9%), the electrode structure is optimized to accommodate metal deposition in a controlled manner, preventing uncontrolled growth that would cause short circuits
2Manufacturing precision
If void-forming aids like microcapsules are used to create controlled voids, then manufacturing precision is improved, but device complexity increases due to additional materials and processes
Solution Approach 1:
Void-forming aids such as microcapsules are introduced as intermediary substances during electrode manufacturing. These aids create the desired void structures when they decompose or are removed, providing a controlled method to generate pores with specific size and distribution characteristics without directly forming the voids themselves
Solution Approach 2:
The void-forming aids are incorporated into the negative electrode active material layer during the manufacturing process before the electrode is finalized. This preliminary action ensures that the voids are formed in the correct positions and with the desired characteristics before the electrode is assembled into the battery, allowing for precise control of the final electrode structure
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
This configuration effectively decreases the occurrence of chemically-occurring micro short circuits by allowing metal deposition within the voids, thereby preventing growth towards the positive electrode, and also reduces the thickness increase of the negative electrode active material layer during charging.
Implementation Method 1
The metal ions migrate to the negative electrode. At the negative electrode, the metal ions are reduced to become solid, and then deposited.
Implementation Method 2
it may be because metal is deposited inside the voids and therefore tends not to grow toward the positive electrode
Data Source
AI summary
A non-aqueous electrolyte secondary battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte solution. At least part of the separator is interposed between the positive electrode and the negative electrode. The negative electrode includes a negative electrode substrate and a negative electrode active material layer. The negative electrode active material layer is placed on a surface of the negative electrode substrate. Voids are formed in the negative electrode active material layer. In a cross section parallel to a thickness direction of the negative electrode active material layer, the voids have an average equivalent circle diameter from 9.6 μm to 35.8 μm, an average circularity of 0.26 or more, and an area percentage from 3.1% to 30.9%.