Non-Aqueous Electrolyte Composition for Stable SEI and Low Corrosion
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Solution Overview
Problem
Existing non-aqueous electrolytes in secondary batteries suffer from poor thermal stability, high impedance, and reduced performance due to lithium hexafluorophosphate decomposition, leading to corrosion and degradation of electrode materials, affecting the battery's service life and safety.
Innovation Solution
A non-aqueous electrolyte containing specific concentrations of metal cations (Men+) and difluorooxalate borate anions (DFOB−) within defined ranges, along with other anions, forms a stable SEI film that enhances cycling, safety, and kinetic performance by reducing irreversible lithium consumption and increasing electronic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium hexafluorophosphate is used in non-aqueous electrolyte, then ionic conductivity is improved, but thermal stability deteriorates due to decomposition at high temperatures
Solution Approach 1:
The patent introduces lithium difluoroxalate borate as an intermediary substance that mediates between the electrolyte and electrode materials. This intermediary forms a stable SEI film that prevents direct contact between lithium hexafluorophosphate and electrode materials, thereby preventing decomposition while maintaining ionic conductivity.
Solution Approach 2:
The patent changes the concentration parameters of lithium hexafluorophosphate and lithium difluoroxalate borate within specific ranges (lithium hexafluorophosphate: 0.1-10 mmol/L, lithium difluoroxalate borate: 1-100 mmol/L). By optimizing these parameters, the electrolyte achieves both good ionic conductivity and thermal stability, resolving the contradiction between conductivity and stability.
2Reliability
If lithium hexafluorophosphate concentration is increased to improve conductivity, then electrochemical performance is improved, but decomposition and corrosion of electrode materials increases
Solution Approach 1:
Lithium difluoroxalate borate acts as a protective intermediary that forms a stable SEI film on electrode surfaces. This film prevents harmful interactions between high-concentration lithium hexafluorophosphate and electrode materials, allowing high conductivity without increased corrosion.
Solution Approach 2:
The patent converts the potentially harmful decomposition products of lithium hexafluorophosphate into beneficial components of the SEI film through controlled decomposition at moderate temperatures. The decomposition products contribute to forming a stable protective layer that prevents further harmful reactions.
3Ease of manufacture
If conventional electrolyte composition is used to simplify manufacturing, then manufacturing process is simple, but cycling performance and safety performance are poor
Solution Approach 1:
The patent creates a composite electrolyte system combining lithium hexafluorophosphate and lithium difluoroxalate borate in specific proportions. This composite approach maintains manufacturing simplicity while achieving superior cycling performance and safety through the synergistic effects of the two salts.
Solution Approach 2:
The patent optimizes concentration parameters within practical ranges that do not significantly complicate manufacturing. By selecting concentrations that balance performance and manufacturability (lithium difluoroxalate borate: 1-100 mmol/L), the patent achieves good performance without excessive manufacturing complexity.
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 electrolyte improves capacity retention, reduces volume swelling, and maintains good kinetic performance while ensuring high safety through controlled SEI film formation and thermal stability, preventing decomposition and corrosion.
Implementation Method 1
a difference between a standard reduction potential of Men+ and a standard reduction potential of Li+ is 1.0 V or more... Men+ is reduced before the lithium ions
Implementation Method 2
non-aqueous electrolyte containing a non-aqueous solvent and lithium ions... enables the secondary battery to have good cycling performance, safety performance, and kinetic performance
Data Source
AI summary
Provided are a non-aqueous electrolyte and a preparation method thereof, and a secondary battery and an electric apparatus containing the same. The non-aqueous electrolyte contains a non-aqueous solvent and lithium ions, first cations, and first anions dissolved therein, where the first cation is a metal cation Men+ other than the lithium ion, n representing a chemical valence of the metal cation; the first anion is a difluorooxalate borate anion DFOB−; mass concentration of the first cations in the non-aqueous electrolyte is D1 ppm, and mass concentration of the first anions in the non-aqueous electrolyte is D2 ppm, both based on total mass of the non-aqueous electrolyte; and the non-aqueous electrolyte satisfies that D1 is 0.5 to 870 and that D1/D2 is 0.02 to 2. The non-aqueous electrolyte in this application enables the secondary battery to have good cycling performance, safety performance, and kinetic performance.