Lithium-Ion Electrolyte Additives for Low-Impedance Protective Films
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Solution Overview
Problem
Existing lithium ion batteries face issues with electrolyte oxidation and decomposition at high temperatures, affecting high temperature storage performance and low temperature discharge performance.
Innovation Solution
A lithium ion battery electrolyte containing specific additives, such as compounds represented by structural formulas (1)-(7), which form protective films on electrode surfaces to improve conductivity and stability, reducing impedance and enhancing both high and low temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluoroethylene carbonate is used as electrolyte additive to form stable SEI film on silicon carbon negative electrode, then film-forming capability is improved, but high temperature storage performance deteriorates due to decomposition and flatulence
Solution Approach 1:
The patent introduces organic dinitrile substances (NC-(CH2)n-CN where n=2-4) as intermediary compounds that mediate between the fluoroethylene carbonate additive and the electrolyte system. These dinitrile substances suppress the decomposition of fluoroethylene carbonate at high temperatures, preventing flatulence while maintaining the beneficial SEI film-forming capability. The dinitrile acts as a stabilizing intermediary that resolves the contradiction between film stability and high temperature performance.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte system by adding specific organic dinitrile substances with controlled chain lengths (n=2-4). This parameter change modifies the thermal stability characteristics of the electrolyte system, enabling it to maintain both good SEI film formation and high temperature storage performance by adjusting the molecular structure parameters of the additive components.
2Temperature
If nitrile compounds are added to suppress flatulence at high temperature, then high temperature storage performance is improved, but low temperature discharge performance and cycle performance deteriorate due to increased polarization
Solution Approach 1:
The patent precisely controls the concentration parameters of dinitrile substances within the range of 0.01-5 wt% to optimize performance. This parameter optimization ensures sufficient high temperature storage performance while minimizing polarization effects that would harm low temperature discharge performance and cycle life. The controlled parameter range resolves the contradiction by finding the optimal balance point.
Solution Approach 2:
The patent applies dinitrile substances selectively to address the specific high temperature storage issue without uniformly affecting all temperature ranges. The localized application of this additive strategy targets the high temperature decomposition problem while preserving low temperature performance characteristics, achieving local optimization of temperature-dependent performance.
3Quantity of substance
If silicon carbon composite material is used as negative electrode to increase capacity, then energy density is improved, but volume expansion and pulverization occur leading to poor cycle performance
Solution Approach 1:
The patent employs electrolyte additives (fluoroethylene carbonate combined with dinitrile substances) that perform preliminary action by forming stable protective SEI films on the silicon carbon composite surface before electrode degradation can occur. This preliminary film formation prevents subsequent volume expansion and pulverization during cycling, thereby improving cycle performance while maintaining high capacity.
Solution Approach 2:
The patent creates a composite protective interface layer through the interaction of fluoroethylene carbonate and dinitrile substances, forming a composite SEI film structure that combines the film-forming capability of fluoroethylene carbonate with the thermal stability enhancement from dinitrile substances. This composite material approach at the interface level protects the silicon carbon composite electrode from degradation.
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 additives significantly enhance cycle performance, low temperature discharge performance, and overall output performance of lithium ion batteries.
Implementation Method 1
the additive comprises at least one of compounds represented by structural formulas (1)-(7)... which form protective films on electrode surfaces to improve conductivity and stability
Implementation Method 2
reducing impedance and enhancing both high and low temperature performance
Data Source
AI summary
An additive for a battery electrolyte, including at least one of compounds represented by structural formulae in the present application text. The additive for a battery electrolyte provided in the present application can form low-impedance protective films on electrode surfaces, suppress side reactions between the electrodes and the electrolyte, reduce interface impedances, consider both high and low temperature performances, and improve an overall output performance of the lithium ion battery.