Positive Electrode Insulating Layer for N/P Ratio Control
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in consistently maintaining the N/P ratio of the positive and negative electrodes, leading to issues such as dendrite formation and reduced safety, especially when the N/P ratio falls below 1, and conventional methods to control the ratio increase processing costs and complicate electrode stacking.
Innovation Solution
A positive electrode for lithium secondary batteries is designed with an insulating layer on the current collector, featuring a discontinuous structure that is completely covered by the active material layer, with specific thickness and length ratios, and optionally includes an auxiliary insulating layer on the sliding portion to control the N/P ratio and prevent lithium precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the coating width of the negative electrode composite layer is made wider than the positive electrode composite layer to prevent N/P ratio reversal, then the N/P ratio can be controlled, but the amount of slurry increases processing cost and the tab portion narrows causing interference problems
Solution Approach 1:
The negative electrode composite layer is segmented into different width sections: a first section with a first width and a second section with a second width that is smaller than the first width. This segmentation allows the N/P ratio to be controlled in different regions, preventing reversal while avoiding excessive slurry usage and tab interference.
Solution Approach 2:
Different sections of the negative electrode composite layer have different widths tailored to local requirements. The first section has a wider width to ensure adequate N/P ratio control, while the second section has a narrower width to reduce slurry usage and prevent tab interference, optimizing both N/P ratio control and manufacturing ease locally.
2Manufacturing precision
If the negative electrode composite layer is made wider to prevent N/P ratio reversal, then the N/P ratio can be controlled, but the tab portion narrows making it difficult to control electrode position during stacking
Solution Approach 1:
The negative electrode composite layer is divided into sections with different widths, allowing the tab portion to maintain adequate width for position control during stacking while other sections provide sufficient coverage for N/P ratio control.
Solution Approach 2:
The width of the negative electrode composite layer is optimized locally: wider in regions where N/P ratio control is critical, and narrower in regions where tab access and position control are priorities, achieving both objectives without compromise.
3Productivity
If conventional coating methods are used, then productivity is improved through slitting, but the N/P ratio reversal phenomenon frequently occurs
Solution Approach 1:
The negative electrode composite layer is segmented into sections with different widths, allowing the electrode to be slit into multiple pieces while maintaining appropriate N/P ratio in each section, thus enabling both high productivity through slitting and consistent N/P ratio control.
Data Source
AI summary
A positive electrode for a lithium secondary battery includes an insulating layer and a positive electrode active material layer sequentially stacked on a positive electrode current collector in which the insulating layer is completely covered on the inside of the edge of the positive electrode active material layer. The positive electrode has the advantage of being applicable to various lithium secondary battery models because it is easy to control the N/P ratio during assembly with the negative electrode. An electrode manufacturing method of the same is also provided.