Electrolyte Additive Pairing for Stable SEI and CEI Films
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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, gas generation, and poor high-temperature cycle and storage performance due to side reactions between the positive electrode material and the electrolytic solution.
Innovation Solution
A combination of compounds represented by formulas 1 and 2 is used as electrolyte additives, where compound 2 is preferentially reduced on the negative electrode, forming a stable SEI film, and compound 1 forms a stable CEI film on the positive electrode, reducing side reactions and decomposition, thereby improving the stability of both electrode interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the upper limit charging voltage is raised or nickel content in positive electrode material is increased to increase energy density, then energy density is improved, but decomposition reactions occur in traditional electrolytic solution systems leading to increased internal resistance and poor high-temperature 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 between the electrolytic solution and electrode materials, forming protective interface films that prevent direct harmful interactions. The cyclic carboxylate forms a stable CEI film on the positive electrode, while the chain carboxylate forms a stable SEI film on the negative electrode, enabling high energy density operation without the decomposition issues of traditional electrolytes.
Solution Approach 2:
The patent employs a composite additive system combining two different carboxylate compounds with complementary functions. The cyclic carboxylate (formula 1) and chain carboxylate (formula 2) work synergistically to form a composite protective interface structure. This composite approach allows the system to simultaneously achieve high voltage stability and low temperature performance, resolving the contradiction between energy density and reliability.
2Stability of the object's composition
If a relatively large amount of compound 1 is used to form stable SEI and CEI films, then interface stability is improved, but initial film-forming impedance increases and internal resistance grows during cycling
Solution Approach 1:
The patent segments the film-forming function between two different compounds: compound 1 (cyclic carboxylate) and compound 2 (chain carboxylate). Compound 1 preferentially forms the CEI film on the positive electrode at lower concentrations, while compound 2 forms the SEI film on the negative electrode. This segmentation allows each compound to optimize its film-forming behavior without the harmful side effects of using excessive amounts of a single compound, thereby reducing initial impedance while maintaining stability.
Solution Approach 2:
The patent applies different compounds to different locations (electrodes) to achieve optimal local film properties. Cyclic carboxylate (compound 1) is targeted at the positive electrode interface to form CEI, while chain carboxylate (compound 2) is targeted at the negative electrode interface to form SEI. This local quality approach ensures that each interface receives the most appropriate protective film composition, minimizing overall impedance while maximizing stability.
3Device complexity
If traditional electrolytic solution systems are used under high voltage conditions, then device simplicity is maintained, but side reactions occur between positive electrode material and electrolytic solution leading to gas generation and increased internal resistance
Solution Approach 1:
The patent introduces carboxylate compounds as intermediary substances that mediate between the traditional electrolytic solution and the positive electrode material. These intermediaries form protective CEI films that prevent direct contact and harmful side reactions between the electrolyte and electrode, thereby eliminating gas generation while maintaining the simplicity of the overall electrolytic solution system.
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 synergistic effect of these compounds reduces the growth rate of internal resistance, enhances high-temperature cycle and storage performance by stabilizing electrode interfaces, and inhibiting 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
Implementation Method 2
the compound represented by formula 1 of the present application can form interphase films at the positive and negative electrode interfaces
Implementation Method 3
the stability of the positive and negative electrode at both electrode interfaces is improved, side reactions between the electrolytic solution and electrode active materials are reduced, and the further decomposition of the electrolytic solution is effectively inhibited
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.