Imidazolone Electrolyte Additive for Li-Ion High-Temperature Stability
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Solution Overview
Problem
Lithium-ion batteries face challenges with electrolyte oxidation and decomposition at high temperatures, leading to poor high-temperature storage and low-temperature discharge performance due to the limitations of existing additives like fluoroethylene carbonate.
Innovation Solution
An additive with an imidazolone structure, represented by formulas I and II, is introduced into the battery electrolyte, which forms a low-impedance protective film on electrodes, inhibiting oxidative decomposition and improving thermal stability by reacting with PF5 and suppressing HF and H2O, thus enhancing both high and low-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluoroethylene carbonate is used as film forming additive, then SEI film formation on silicon-carbon negative electrode is improved, but electrolyte decomposition at high temperature occurs
Solution Approach 1:
The patent introduces organic dinitriles as intermediary substances that mediate between the fluoroethylene carbonate and the electrode/electrolyte system. The dinitriles preferentially react to form protective films that prevent fluoroethylene carbonate decomposition at high temperatures, while still allowing effective SEI formation at the negative electrode. This intermediary action resolves the contradiction by decoupling the film-forming function from the high-temperature stability requirement.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolyte by adding organic dinitriles with specific molecular structures (where n=2-4). This parameter change modifies the electrolyte's behavior at high temperatures, suppressing the decomposition reactions that normally occur with fluoroethylene carbonate alone, while maintaining the necessary film-forming properties for SEI creation on silicon-carbon electrodes.
2Temperature
If nitrile compounds are added to suppress battery inflation, then high temperature storage performance is improved, but battery polarization increases and low temperature characteristics deteriorate
Solution Approach 1:
The patent applies local quality by using organic dinitriles that preferentially act at specific locations and conditions. The dinitriles primarily suppress inflation and stabilize the electrolyte at high temperatures, while their structure and concentration are optimized to minimize their impact at low temperatures. This localized action resolves the contradiction by making the additive's effect position and condition-dependent.
Solution Approach 2:
The patent creates a composite electrolyte system combining fluoroethylene carbonate, organic dinitriles, and other electrolyte components. This composite formulation achieves synergistic effects where the dinitriles suppress high-temperature inflation and stabilize the system, while the overall composition maintains good low-temperature performance through careful balancing of all components. The composite approach allows multiple functions to be achieved simultaneously.
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 significantly improves cycle performance, high-temperature storage, and low-temperature discharge performance by forming a protective film that reduces interface impedance and suppresses side reactions, leading to better overall output performance of lithium-ion batteries.
Implementation Method 1
The additive significantly improves cycle performance, high-temperature storage, and low-temperature discharge performance by forming a protective film that reduces interface impedance
Implementation Method 2
improving the thermal stability of LiPF6 and suppressing oxidative decomposition of the electrolyte
Implementation Method 3
the silicon-containing groups in R1 and R2 can undergo hydrolysis or polymerization with HF and H2O containing active proton hydrogen in the electrolyte to achieve the purpose of removing H2O and suppressing HF
Implementation Method 4
the carbonyl group in the imidazolone structure can react with PF5 (a decomposition product of LiPF6), which can be preferentially reduced to form a low-impedance SEI film on the negative electrode
Implementation Method 5
the N atoms in the imidazolone structure contain lone pairs of electrons, which easily lose electrons at the battery positive electrode to oxidize into a protective film, inhibit the oxidative decomposition of the electrolyte at the positive electrode
Data Source
AI summary
An additive for battery electrolyte, the additive at least including a structure represented by formula I or formula II as shown below,in formula I, R1 and R2 are independently selected from silicon-containing groups, and X is selected from organic groups with carbon atoms of 2 to 20; andin formula II, R1 and R2 are independently selected from silicon-containing groups, and X1 and X2 are independently selected from organic groups with carbon atoms of 2 to 20.