Electrolyte Additive for Lithium Secondary Battery
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Solution Overview
Problem
Lithium secondary batteries face challenges in improving low-temperature output characteristics, high-temperature cycle characteristics, and swelling due to non-uniform solid electrolyte interface (SEI) formation and decomposition issues, especially when using electrolyte solutions without effective additives.
Innovation Solution
A non-aqueous electrolyte solution containing lithium difluorophosphate, vinylene carbonate-based compounds, and sultone-based compounds, with specific weight ratios and concentrations, is used to form a robust SEI, preventing cathode decomposition and oxidation reactions, thereby enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electrolyte solution additives are used to improve low-temperature output characteristics, then low-temperature output is improved, but high-temperature cycle characteristics and swelling characteristics deteriorate due to non-uniform SEI formation and decomposition
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration ratios of multiple electrolyte additives (vinylene carbonate at 0.01-5 wt%, dimethyl carbonate at 0.01-5 wt%, and lithium difluorophosphate at 0.01-1 wt%) to achieve optimal SEI formation that performs well across both low-temperature and high-temperature conditions
Solution Approach 2:
The patent uses a composite electrolyte additive system combining multiple compounds (vinylene carbonate, dimethyl carbonate, and lithium difluorophosphate) that work synergistically to form a robust SEI layer, where each component contributes different properties that collectively resolve the temperature-dependent performance contradiction
2Power
If electrolyte solution additives are increased to improve SEI formation, then low-temperature output improves, but cathode decomposition and oxidation reactions increase at high temperatures
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration ratios of multiple electrolyte additives (vinylene carbonate at 0.01-5 wt%, dimethyl carbonate at 0.01-5 wt%, and lithium difluorophosphate at 0.01-1 wt%) to achieve optimal SEI formation that performs well across both low-temperature and high-temperature conditions
Solution Approach 2:
The patent uses dimethyl carbonate as an intermediary substance that mediates between the SEI-forming additives and the cathode, preventing direct harmful interactions while maintaining beneficial SEI formation properties
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 solution improves low-temperature output, high-temperature cycle, and swelling characteristics by forming a robust SEI, maintaining capacity retention and reducing irreversible capacity, leading to better battery performance and longevity.
Implementation Method 1
a process of intercalating and deintercalating lithium ions from a lithium metal oxide cathode into and out of a graphite anode is repeated. In this case, since lithium is highly reactive, lithium reacts with the carbon electrode to form Li 2 CO 3 , LiO, or LiOH. Thus, a film may be formed on the surface of the anode. The film is denoted as 'solid electrolyte interface (SEI)'
Implementation Method 2
The SEI formed at an initial stage of charging may prevent a reaction of the lithium ions with the carbon anode or other materials during the charge and discharge. Also, the SEI may only pass the lithium ions by acting as an ion tunnel
Implementation Method 3
Charge and discharge of the lithium secondary battery is performed while a process of intercalating and deintercalating lithium ions from a lithium metal oxide cathode into and out of a graphite anode is repeated
Implementation Method 4
the co-intercalation of the carbon anode and organic solvents of an electrolyte solution having a high molecular weight which solvates lithium ions and moves therewith
Data Source
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AI summary
Provided is an electrolyte solution additive including lithium difluorophosphate (LiDFP), a vinylene carbonate-based compound, and a sultone-based compound. Also, a non-aqueous electrolyte solution including the electrolyte solution additive and a lithium secondary battery including the non-aqueous electrolyte solution are provided. The lithium secondary battery including the electrolyte solution additive of the present invention may improve low-temperature output characteristics, high-temperature cycle characteristics, output characteristics after high-temperature storage, and swelling characteristics.