Non-aqueous Electrolyte Secondary Battery Solvent Mixture
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face issues with metal component elution from the positive electrode due to chlorine ions attacking fluoroethylene carbonate, leading to gas generation and degradation of discharge rate characteristics.
Innovation Solution
A non-aqueous electrolyte secondary battery using a solvent mixture of fluoroethylene carbonate, difluorobutylene carbonate, and at least one fluorinated chain carbonate or fluorinated chain carboxylic acid ester, with a total volumetric content of over 50% to suppress metal elution and gas generation without degrading discharge rate characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If fluoroethylene carbonate is used as an electrolyte solvent to improve cycle characteristics at high battery voltage, then cycle life is improved, but metal component elution from the positive electrode increases
Solution Approach 1:
The patent uses a composite electrolyte solvent system comprising fluoroethylene carbonate (FEC), difluorobutylene carbonate (DFBC), and fluorinated chain carbonate (FEC or FMP) in specific proportions (FEC: 5-30 vol%, DFBC: 5-30 vol%, fluorinated chain carbonate: 60-85 vol%). This composite solvent system synergistically improves cycle life while suppressing metal elution, as the fluorinated chain carbonate provides stable SEI formation and high voltage compatibility, DFBC enhances oxidation resistance, and FEC contributes to cycle stability, collectively resolving the contradiction between extended cycle life and reduced metal elution.
Solution Approach 2:
The patent optimizes the volumetric proportions of each solvent component within specific ranges to achieve the desired balance. By adjusting the concentration parameters of FEC (5-30 vol%), DFBC (5-30 vol%), and fluorinated chain carbonate (60-85 vol%), the electrolyte system achieves optimal performance where cycle life is extended through FEC's stabilizing effect while metal elution is suppressed by the dominant fluorinated chain carbonate's protective film formation and high oxidation potential resistance.
2Duration of action of stationary object
If fluoroethylene carbonate is used to improve cycle characteristics, then battery durability is enhanced, but gas generation at the positive electrode increases
Solution Approach 1:
The composite electrolyte solvent system combines the benefits of multiple solvents: FEC provides durability through stable SEI formation, DFBC enhances oxidation resistance to prevent gas-generating side reactions, and fluorinated chain carbonate (FEC or FMP) suppresses gas generation through its high oxidation potential and ability to form stable protective films on the positive electrode. The synergistic interaction of these components achieves both enhanced battery durability and reduced gas generation.
Solution Approach 2:
By controlling the volumetric ratio of fluorinated chain carbonate to be predominantly high (60-85 vol%), the electrolyte system prioritizes gas suppression while maintaining durability through the complementary effects of smaller amounts of FEC and DFBC. This parameter optimization ensures that the high oxidation potential of fluorinated chain carbonate dominates the electrochemical environment, suppressing gas-generating decomposition reactions while FEC and DFBC contribute to long-term stability.
3Reliability
If fluorinated solvents are used to suppress metal elution, then electrode stability is improved, but discharge rate characteristics may be degraded
Solution Approach 1:
The patent employs a composite solvent system where fluorinated chain carbonate (FEC or FMP) provides electrode stability through stable SEI formation and high voltage compatibility, while the presence of DFBC and controlled amounts of FEC maintains sufficient ionic conductivity and wetting properties. This composite approach balances electrode stability with adequate discharge rate performance, avoiding the extreme stability that would sacrifice kinetic properties.
Solution Approach 2:
The patent carefully controls the proportion of fluorinated chain carbonate within 60-85 vol%, preventing it from being so dominant that it overly stabilizes the electrode at the expense of discharge rate. The balanced formulation ensures that while fluorinated components provide stability, the overall ionic conductivity and electrolyte dynamics remain sufficient for acceptable discharge rate characteristics.
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 reduces metal elution and gas generation at the positive electrode during charging and storage while maintaining preferable discharge rate characteristics, as demonstrated by specific examples with varying solvent ratios.
Implementation Method 1
the non-aqueous electrolyte secondary battery can suppress the gas generation and the metal elution at a positive electrode
Implementation Method 2
chlorine ions generated at a negative electrode attack a fluoroethylene carbonate nucleophilically
Implementation Method 3
The vinylene carbonate is oxidatively decomposed at a positive electrode
Implementation Method 4
the non-aqueous electrolyte secondary battery can suppress the gas generation and the metal elution at a positive electrode
Data Source
AI summary
A non-aqueous electrolyte secondary battery which is one example of an embodiment of the present disclosure is a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte which contains a non-aqueous solvent. The non-aqueous solvent contains a fluoroethylene carbonate, a difluorobutylene carbonate, and at least one of a fluorinated chain carbonate and a fluorinated chain carboxylic acid ester, total volumetric contents of which is more than 50 percent with respect to the total volume of the non-aqueous solvent.