Li-Ion Battery Electrolyte Composition for Stable Negative Electrodes
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving superior battery characteristics due to the frequent use and expanding environmental demands of electronic devices, particularly in maintaining stable electrochemical performance and reducing decomposition reactions.
Innovation Solution
Incorporating a negative electrode active material with a reaction potential of 0.5 V or higher and an electrochemical capacity per unit area less than or equal to that of the positive electrode, combined with an electrolytic solution containing a diphenyl carbonate compound, an unsaturated cyclic carbonate ester, a first maleic anhydride compound, or a second maleic anhydride compound, which forms a protective film on the negative electrode surface, reducing decomposition reactions and enhancing chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolytic solutions are used in lithium-ion secondary batteries with negative electrode active materials having low reaction potential, then the battery can operate, but decomposition reactions occur on the negative electrode surface leading to poor cycle life and unstable electrochemical performance
Solution Approach 1:
The patent introduces a fluorinated cyclic carbonate compound as an intermediary substance in the electrolytic solution. This compound acts as a mediator that preferentially reacts with the negative electrode surface to form a stable protective film, preventing direct contact and harmful decomposition reactions between the conventional electrolytic solution and the negative electrode active material. The fluorinated compound serves as a buffer layer that protects the system while maintaining lithium ion conductivity.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolytic solution by incorporating fluorinated cyclic carbonate compounds with specific molecular structures (Formulae 1-4). This parameter change alters the electrochemical window and reactivity characteristics of the electrolyte, enabling it to form stable solid electrolyte interface (SEI) films on low-potential negative electrodes without causing decomposition. The fluorination and cyclic carbonate structure are key parameter modifications that enable the solution to work with challenging electrode materials.
2Stability of the object's composition
If negative electrode active materials with reaction potential of 0.4 V or higher are used to improve cycle life, then electrochemical stability improves, but the battery design becomes more constrained in terms of capacity balancing
Solution Approach 1:
The patent changes the electrolytic solution composition parameters by adding fluorinated cyclic carbonate compounds, which enables the use of negative electrode active materials with reaction potentials of 0.4 V or higher. This parameter modification in the electrolyte allows access to a broader range of stable negative electrode materials that were previously unusable, thereby reducing design constraints while maintaining electrochemical stability.
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 configuration achieves superior battery characteristics by stabilizing the electrochemical performance, reducing decomposition reactions, and maintaining a balanced discharge and charge capacity, even under severe environmental conditions.
Implementation Method 1
the electrolytic solution includes a fluorinated cyclic carbonate compound... which forms a protective film on the negative electrode surface, reducing decomposition reactions
Implementation Method 2
a negative electrode active material into which lithium is insertable and from which lithium is extractable at 0.4 V or higher versus a lithium electrode
Data Source
AI summary
A lithium-ion secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The negative electrode includes a negative electrode active material having a reaction potential of 0.5 V or higher than a lithium electrode, and has an electrochemical capacity per unit area of less than or equal to an electrochemical capacity per unit area of the positive electrode. The electrolytic solution includes a solvent, an electrolyte salt, and at least one of a diphenyl carbonate compound, an unsaturated cyclic carbonate ester, a first maleic anhydride compound, and a second maleic anhydride compound.