Electrolyte Additive Composition for High-Temperature Li-Ion Stability
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Solution Overview
Problem
Lithium secondary batteries face performance deterioration in high-temperature environments due to metal ion dissolution, electrolyte decomposition, and instability of ethylene sulfate, leading to acidity and chromaticity increases, which damage electrode interfaces and reduce cycle performance.
Innovation Solution
An electrolyte additive composition comprising a fluorine-containing pyridine compound and a phosphite compound at a specific mass ratio, which inhibits electrolyte decomposition and metal ion dissolution, forming a stable passivation film to enhance battery performance at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene sulfate (DTD) is used as a functional electrolyte additive, then low-resistance and high-performance are achieved, but hydrolysis occurs causing increases in acidity and chromaticity
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance that mediates between the ethylene sulfate additive and the electrolyte system. This compound prevents direct harmful interactions by forming a protective interface layer, thereby reducing acidity generation while maintaining the performance benefits of ethylene sulfate
Solution Approach 2:
The patent creates a composite electrolyte system combining ethylene sulfate with fluorinated cyclic carbonate compounds. This composite approach allows the system to leverage the low-resistance properties of ethylene sulfate while the fluorinated compound provides stability against hydrolysis and acidity formation
2Duration of action of stationary object
If lithium transition metal oxides are used as positive active materials, then high operating voltage and long cycle life are achieved, but metal ion dissolution occurs in high-temperature environments
Solution Approach 1:
The patent applies preliminary action by having the fluorinated cyclic carbonate compound pre-form a stable protective film on the electrode surface before metal ion dissolution can occur. This pre-formed protective layer acts as a barrier that prevents metal ion release into the electrolyte during high-temperature operation
Solution Approach 2:
The fluorinated cyclic carbonate compound serves as an intermediary layer between the lithium transition metal oxide and the electrolyte. This intermediate film prevents direct contact and harmful interactions, thereby suppressing metal ion dissolution while allowing ionic transport for maintaining cycle life
3Reliability
If the electrolyte contains increased acidity, then DTD functional performance is enhanced, but electrode interface damage and transition metal ion dissolution occur
Solution Approach 1:
The patent converts the potential harm of acidity by using fluorinated cyclic carbonate compounds that can tolerate or even utilize trace acidity to form more stable protective films. The compound transforms the harmful acidic environment into a beneficial condition for forming robust interface protection layers
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 additive composition significantly reduces electrolyte decomposition and acidity, improves cycle and high-temperature performance, and forms a stable passivation film, enhancing the battery's capacity retention and interface stability.
Implementation Method 1
forming a stable passivation film to enhance battery performance at high temperatures
Data Source
AI summary
The present application relates to an electrolyte additive composition, an electrolyte, and a lithium secondary battery. The electrolyte additive composition includes a fluorine-containing pyridine compound having a structure represented by formula ( ) and a phosphite compound having a structure represented by formula (I), where R1, R2, R3, and R4 are each independently selected from hydrogen, halogen, C1 to C20 alkyl, C1 to C20 halogenated alkyl, C6 to C26 aryl, C6 to C26 halogenated aryl, amino, isocyano, and alkoxy; and R5, R6, and R7 are each independently selected from C1 to C20 alkyl, C1 to C20 halogenated alkyl, C6 to C26 aryl, and C6 to C26 halogenated aryl. A mass ratio of the fluorine-containing pyridine compound to the phosphite compound is (3 to 10):1.