Positive Electrode Lithium Carbonate Control for Battery Swelling
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries face issues with gas generation at high temperatures, leading to swelling, which is not adequately suppressed by reducing lithium carbonate content, and increasing production costs with phosphoric acid treatments, while high lithium carbonate levels exacerbate swelling.
Innovation Solution
A non-aqueous electrolyte secondary battery with a positive electrode containing lithium carbonate and lithium hydrogencarbonate in a controlled amount (500 ppm to 3000 ppm) and a weight loss of 70% or less from 25°C to 300°C, achieved through heating the positive electrode at 250°C to 300°C, to reduce gas generation and maintain cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the amount of lithium carbonate is reduced to suppress gas generation, then battery swelling is reduced, but cycle characteristics are degraded
Solution Approach 1:
The patent applies parameter changes by precisely controlling the amount of lithium carbonate within a specific range (500-3000 ppm) and controlling the weight loss percentage (70% or less) to simultaneously achieve gas suppression and maintain cycle characteristics. This quantitative parameter optimization resolves the contradiction between reducing harmful gas generation and preserving reliable cycle performance.
Solution Approach 2:
The patent employs partial action by not completely eliminating lithium carbonate but rather maintaining an optimal amount that is sufficient to prevent cycle degradation while being limited enough to suppress gas generation. This partial presence of lithium carbonate at controlled levels resolves the contradiction between complete gas suppression and cycle characteristic maintenance.
2Reliability
If the amount of lithium carbonate is increased to improve safety valve operation, then overcharge safety is enhanced, but battery swelling increases
Solution Approach 1:
The patent resolves this contradiction by optimizing the lithium carbonate parameter to a specific range (500-3000 ppm) that is sufficient to ensure safety valve operation during overcharge but limited enough to prevent excessive gas generation and battery swelling. This precise parameter control allows simultaneous achievement of safety and swelling suppression.
Solution Approach 2:
The patent applies partial action by maintaining lithium carbonate at an optimal level rather than maximizing it, achieving just enough presence to ensure safety valve functionality while avoiding excess that would cause swelling. This balanced approach resolves the contradiction between safety enhancement and swelling control.
3Object-affected harmful factors
If phosphoric acid treatment is applied to reduce gas generation, then gas generation is suppressed, but production cost increases
Solution Approach 1:
The patent extracts and eliminates the need for complex phosphoric acid treatment processes by instead controlling the lithium carbonate content through simpler manufacturing methods. This removes the costly treatment step while still achieving gas generation suppression through optimized lithium carbonate levels, resolving the contradiction between gas suppression and manufacturing ease.
Solution Approach 2:
The patent replaces expensive phosphoric acid treatment with a more economical approach of controlling lithium carbonate content during manufacturing. This cost-effective method achieves the same gas suppression effect without requiring additional costly processing steps, resolving the contradiction between gas generation control and production cost.
4Quantity of substance
If the density of active material is increased to meet high energy density demand, then energy density is improved, but space for gas entry is reduced causing noticeable swelling
Solution Approach 1:
The patent resolves this contradiction by optimizing the lithium carbonate parameter within a specific range (500-3000 ppm) that suppresses gas generation at the active material surface. This parameter control prevents gas accumulation even in high-density configurations with limited space, allowing high energy density to be achieved without noticeable swelling.
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
The solution effectively suppresses gas generation and maintains high cycle characteristics, ensuring the battery's capacity retention and reduced swelling even after repetitive charge and discharge.
Implementation Method 1
heating the positive electrode at a temperature of 250° C. or more and 300° C. or less
Data Source
AI summary
Disclosed is a non-aqueous electrolyte secondary battery including a positive electrode including a lithium-containing transition metal composite oxide as a positive electrode active material, a negative electrode including a negative electrode active material, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. The positive electrode contains lithium carbonate and lithium hydrogencarbonate in a total amount of 500 ppm or more and 3000 ppm or less, and exhibits a weight loss by temperature increase from 25° C. to 300° C. at 5° C./min of 70% or less of the total amount and of 1500 ppm or less. The non-aqueous electrolyte includes a non-aqueous solvent and a lithium salt. The non-aqueous solvent may contain a cyclic carbonate and a chain carbonate.