Dual-Additive Electrolyte for Stable SEI and CEI at High Voltage
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Solution Overview
Problem
Traditional electrolytic solutions in electrochemical devices suffer from decomposition reactions under high voltage, leading to increased internal resistance and poor high-temperature cycle and storage performance due to side reactions and gas generation.
Innovation Solution
A combination of compounds represented by formulas 1 and 2 is used as electrolyte additives, where compound 2 preferentially forms a stable SEI film on the negative electrode and compound 1 forms a stable CEI film on the positive electrode, reducing side reactions and decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the upper limit charging voltage is raised to increase energy density, then the energy density is improved, but the electrolytic solution decomposes and side reactions occur, increasing internal resistance and reducing high-temperature cycle performance
Solution Approach 1:
The patent introduces a dual-component additive system comprising a cyclic carboxylate compound (formula 1) and a chain carboxylate compound (formula 2) as intermediary substances. These additives mediate the interaction between the electrolyte and electrode at high voltage, forming protective interphase films that prevent direct contact and harmful reactions. The cyclic carboxylate forms a stable CEI film on the positive electrode, while the chain carboxylate forms an stable SEI film on the negative electrode, acting as protective intermediaries that enable high-voltage operation without decomposition
Solution Approach 2:
The patent employs a composite additive system combining two different carboxylate compounds with specific structural characteristics. The cyclic carboxylate (formula 1) provides rigidity and stability for CEI film formation, while the chain carboxylate (formula 2) provides flexibility and stability for SEI film formation. This composite approach creates synergistic effects where the two additives work together to form a comprehensive protective interface system that addresses both positive and negative electrode issues simultaneously
2Quantity of substance
If nickel content in positive electrode material is increased to increase energy density, then the energy density is improved, but side reactions between positive electrode material and electrolyte occur, affecting structural stability and increasing internal resistance
Solution Approach 1:
The cyclic carboxylate compound (formula 1) acts as an intermediary substance between the high-nickel positive electrode material and the electrolyte. It preferentially reacts with the electrolyte to form a stable cathode electrolyte interphase (CEI) film that serves as a protective barrier, preventing direct contact between the electrolyte and the structurally vulnerable high-nickel cathode material, thereby maintaining structural stability while enabling high energy density
3Reliability
If a large amount of compound 1 is used to form stable SEI and CEI films, then the interface stability is improved, but the initial film-forming impedance increases and internal resistance rises during cycling
Solution Approach 1:
The patent segments the film-forming function into two distinct components: the cyclic carboxylate (formula 1) responsible for CEI film formation on the positive electrode, and the chain carboxylate (formula 2) responsible for SEI film formation on the negative electrode. This segmentation allows each additive to work at optimized low concentrations (0.01-5 wt% each), forming thin, stable, and low-impedance films without the need for excessive amounts that would cause high initial impedance
Solution Approach 2:
The patent applies different additive components to different locations (electrodes) based on their specific requirements. The cyclic carboxylate targets the positive electrode interface where high-voltage stability is needed, while the chain carboxylate targets the negative electrode interface where low-impedance SEI formation is critical. This local quality approach ensures each region receives the appropriate protective film with optimal properties for its specific function
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
This combination stabilizes both electrode interfaces, reducing internal resistance growth and improving high-temperature cycle and storage performance by inhibiting electrolyte decomposition and gas generation.
Implementation Method 1
The compound represented by formula 2 is preferentially reduced on the surface of the negative electrode over the compound represented by formula 1 and other components of the electrolytic solution, which allows the formation of a solid electrolyte interphase (SEI) film rich in alkyl sulfonate on the surface of the negative electrode
Implementation Method 2
the compound represented by formula 1 can form interphase films at the positive and negative electrode interfaces when used as the electrolyte additive
Implementation Method 3
Traditional electrolytic solution systems are prone to decomposition reactions under high voltage, and side reactions are likely to occur between the positive electrode material and the electrolytic solution
Data Source
AI summary
The present application provides an electrolyte additive, an electrolytic solution, and an electrochemical device. The electrolyte additive includes a compound represented by formula 1 and a compound represented by formula 2, and the compound represented by formula 2 is selected from the group consisting of a compound represented by formula 2-A, a compound represented by formula 2-B, and a combination thereof. Through the above configuration, when the compound represented by formula 1 and the compound represented by formula 2 of the present application are used in combination as electrolyte additives, it is beneficial to form a stable solid electrolyte interface film at the negative electrode interface, and also beneficial to form a stable cathode electrolyte interface film at the positive electrode interface. This improves the stability of both the positive and negative electrode interfaces, reduces side reactions between the electrolytic solution and the electrode active materials, effectively inhibits the further decomposition of the electrolytic solution, reduces gas generation, decreases the growth rate of the internal resistance of the electrochemical device, and improves the high-temperature cycle performance and high-temperature storage performance of the electrochemical device.