Non-Aqueous Electrolyte Additives for Stable Low-Impedance SEI Films
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with increased resistance and deteriorated life due to the formation of an SEI film rich in organic components, leading to lithium separation and impaired power and life performance.
Innovation Solution
A non-aqueous electrolyte solution containing cyclic sulfate and cyclic carbonate additives forms a stable SEI film with enhanced electron blocking and elasticity, optimizing the cycle and storage performance by preventing electrolyte decomposition and electrode damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrolyte solution additives are used to form a passivation layer (SEI film) on the negative electrode, then lithium consumption reaction is inhibited and electrode protection is improved, but the impedance of the electrode increases and power performance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the SEI film by introducing fluorinated cyclic carbonate additives with specific molecular structures (formula 1 and formula 2). These additives contain fluorine atoms and specific ring structures that alter the SEI film's properties, achieving lower impedance while maintaining protective function. The fluorine content and molecular structure parameters are optimized to balance protection and conductivity.
Solution Approach 2:
The patent creates a composite SEI film structure by combining fluorinated cyclic carbonate additives with conventional electrolyte components. The SEI film contains both organic components from traditional additives and inorganic fluoride components from the new additives, forming a composite structure that simultaneously provides protection and maintains electron conductivity for power performance.
2Reliability
If the SEI film is made rich in organic components such as alkyl lithium, then the electrode impedance increases, but this may lead to lithium separation at the negative electrode and further deteriorate battery life
Solution Approach 1:
The patent modifies the compositional parameters of the SEI film by incorporating fluorinated cyclic carbonate additives that introduce inorganic fluoride components. This changes the organic-inorganic ratio in the SEI film, reducing excessive organic content that causes high impedance and lithium separation, while maintaining sufficient organic components for battery life protection.
3Power
If the impedance of the electrode is reduced to improve power performance, then the protective function of the SEI film may be compromised, leading to continuous electrolyte decomposition
Solution Approach 1:
The patent creates a composite SEI film with both organic protective components and inorganic fluoride conductive components. The organic parts from fluorinated cyclic carbonate additives provide electrolyte stability and protection, while the inorganic fluoride parts reduce impedance for power performance, achieving both goals 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 SEI film improves battery life and cycling performance by blocking electrons and resisting electrode expansion, while maintaining conductivity, thus enhancing the overall performance of the battery.
Implementation Method 1
the cyclic sulfate additive in the non-aqueous electrolyte solution will generate a more stable SEI film with stronger electron blocking capability on a negative electrode in the first charge process of a secondary battery
Implementation Method 2
the SEI film can more effectively block electrons to relieve continuous decomposition of the electrolyte solution at the negative electrode
Implementation Method 3
saturated cyclic carbonate and unsaturated cyclic carbonate in the non-aqueous electrolyte solution will generate the SEI film with better elasticity on the negative electrode
Implementation Method 4
the SEI film can effectively resist the damage caused by the expansion and contraction of a negative electrode plate
Implementation Method 5
The SEI film is a good conductor of lithium ions and a poor conductor of electrons
Data Source
Figure 1~3
Figure 4~6
AI summary
The present application provides a non-aqueous electrolyte solution, a secondary battery and an electrical apparatus. The non-aqueous electrolyte solution includes additives, the additives include a first additive and a second additive, in which, the first additive is any one or more cyclic sulfate compounds having a structure shown in a general formula (I), and the second additive is any one or more cyclic carbonate compounds having a structure shown in a general formula (III) or general formula (IV),