Negative Electrode Density Gradient for Battery Storage Capacity
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries, particularly lithium-ion batteries, experience capacity loss during storage due to charge carriers moving from face-to-face regions to non-face-to-face regions in the negative electrode active material layer, leading to local overcharge and metal ion dissolution, which reduces discharge capacity, especially under elevated temperatures.
Innovation Solution
The battery design incorporates a negative electrode active material layer with a face-to-face region and a non-face-to-face region, where the non-face-to-face region has a higher density to hinder charge carrier movement, preventing local overcharge and capacity loss. This is achieved by forming a high density part on the periphery and extra portions of the negative electrode sheet, which reduces charge carrier movement and metal ion precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the density of negative electrode active material layer is reduced to increase output power, then charge carriers can move more freely and release ability increases, but charge carriers move to non-face-to-face region during storage causing local overcharge and capacity loss
Solution Approach 1:
The patent applies local quality by creating a high density part specifically in the non-face-to-face region of the negative electrode active material layer, while maintaining lower density in the face-to-face region. This localized density modification prevents charge carrier migration to the non-face-to-face region during storage, thereby preventing local overcharge and capacity loss, while still maintaining high output power through the lower density face-to-face region.
2Temperature
If storage is performed at elevated temperature, then charge carriers move more freely in negative electrode active material layer, but storage-caused decrease in discharge capacity occurs more likely
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming a high density part in the non-face-to-face region before storage occurs. This pre-established high density structure creates a barrier that prevents charge carriers from migrating to the non-face-to-face region even when elevated temperatures increase charge carrier mobility during storage, thereby preventing local overcharge and capacity degradation.
3Quantity of substance
If charge carriers move to non-face-to-face region, then local overcharge occurs causing dissolution of metal species from positive electrode active material, but this reduces available charge carriers for charging and discharging
Solution Approach 1:
The patent applies parameter changes by modifying the density parameter of the negative electrode active material layer in the non-face-to-face region. By increasing the density in this specific region, the patent changes the physical structure to prevent charge carrier migration, thereby preventing local overcharge, metal ion dissolution from the positive electrode, and precipitation in the non-face-to-face region, maintaining the quantity of available charge carriers.
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 design effectively reduces storage-caused capacity loss while maintaining high output power by controlling the density of the negative electrode active material layer, preventing charge carrier movement and metal ion precipitation, thus enhancing the battery's performance and longevity.
Implementation Method 1
the non-face-to-face region NNF comprises a high density part NHD having a higher density than the face-to-face region NF
Data Source
AI summary
The present invention provides a non-aqueous electrolyte secondary battery that comprises a positive electrode sheet comprising a positive electrode active material layer, and a negative electrode sheet comprising a negative electrode active material layer. The positive electrode sheet and the negative electrode sheet are arranged such that the positive electrode active material layer and the negative electrode active material layer face each other. The negative electrode active material layer comprises a face-to-face region NF that faces the positive electrode active material layer and a non-face-to-face region NNF that does not face the positive electrode active material layer. The non-face-to-face region NNF includes a high density part NHD having a density higher than that of the region face-to-face NF.