Nonaqueous Battery SEI Coating via Carbon Dioxide Control
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using lithium titanate as a negative electrode active material face issues with gas generation and increased internal resistance due to insufficient SEI coating formation, leading to battery expansion and capacity retention ratio deterioration, especially when stored at high temperatures.
Innovation Solution
Incorporating carbon dioxide into the negative electrode active material and nonaqueous electrolyte, with specific concentration ranges, to promote moderate SEI coating formation while suppressing gas generation, and using carbon monoxide in the electrolyte to enhance coating stability and reduce electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium titanate is used as negative electrode active material, then battery performance is improved, but SEI coating formation is insufficient leading to electrolyte decomposition
Solution Approach 1:
The patent applies preliminary action by forming a SEI coating through initial charge-discharge cycles before the battery enters normal operation. The coating is formed in advance to prevent subsequent electrolyte decomposition during storage and use, particularly when the battery is stored at high temperatures near full charge.
Solution Approach 2:
The patent applies parameter changes by controlling the concentration of carbon dioxide in the electrolyte (50-1000 ml/L) and controlling the amount of carbon dioxide released by the negative electrode active material (0.01-3 ml/g). These parameter adjustments optimize SEI coating formation while suppressing excessive gas generation.
2Quantity of substance
If SEI coating formation is insufficient, then battery capacity is maintained, but gas generation increases causing battery expansion
Solution Approach 1:
The patent applies parameter changes by precisely controlling the carbon dioxide concentration in the electrolyte (50-1000 ml/L) and the carbon dioxide release amount from the negative electrode active material (0.01-3 ml/g). This optimization achieves moderate SEI coating formation that suppresses gas generation and battery expansion while maintaining capacity.
Solution Approach 2:
The patent converts the potentially harmful effect of carbon dioxide (which can cause gas generation) into a beneficial effect. By controlling carbon dioxide release and concentration, the patent utilizes it to form protective SEI coating, transforming a harmful factor into a protective mechanism.
3Power
If SEI coating formation is insufficient, then initial battery performance is good, but internal resistance increases over time
Solution Approach 1:
The patent applies preliminary action by forming a stable SEI coating through controlled carbon dioxide release during initial charge-discharge cycles. This pre-formed coating prevents subsequent electrolyte decomposition that would increase internal resistance, thereby maintaining capacity retention ratio over time and improving long-term reliability.
4Reliability
If carbon dioxide concentration in electrolyte is increased, then SEI coating formation is improved, but gas generation may increase
Solution Approach 1:
The patent applies parameter changes by optimizing the carbon dioxide concentration in the electrolyte to a specific range (50-1000 ml/L) and controlling the carbon dioxide release amount from the negative electrode active material (0.01-3 ml/g). This dual parameter control achieves moderate SEI coating formation while suppressing excessive gas generation.
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 approach effectively suppresses battery expansion and resistance rise, improving capacity retention ratio by controlling gas generation and electrolyte decomposition, maintaining battery performance over charge/discharge cycles.
Implementation Method 1
This coating is formed due to the reductive decomposition of an electrolyte on a negative electrode at the time of an initial charge and discharge
Implementation Method 2
The negative electrode active material layer contains carbon dioxide and releases the carbon dioxide in the range of 0.01 ml to 3 ml per 1 g when heated at 400° C. for 1 minute
Implementation Method 3
using carbon monoxide in the electrolyte to enhance coating stability and reduce electrolyte decomposition
Data Source
AI summary
According to the embodiment, there is provided a nonaqueous electrolyte secondary battery comprising a positive electrode; a negative electrode including a negative electrode active material layer; and a nonaqueous electrolyte. The negative electrode active material layer contains carbon dioxide and releases the carbon dioxide in the range of 0.01 ml to 3 ml per 1 g when heated at 400° C. for 1 minute. The nonaqueous electrolyte contains carbon dioxide of 50 ml/L to 1000 ml/L.