Nonaqueous Electrolyte Additives for Stable SEI and Low Gas Generation
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Solution Overview
Problem
Existing additives for nonaqueous electrolyte solutions in lithium ion batteries do not sufficiently improve battery characteristics over time and can generate gases, leading to reduced performance.
Innovation Solution
Incorporation of specific compounds represented by Formulas (1a) and (1b) as additives in nonaqueous electrolyte solutions, which form a stable solid electrolyte interface (SEI) to reduce initial resistance and suppress gas generation, thereby enhancing cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional additives (such as cyclic carbonates, chain carbonates, carboxylic acids, or their esters) are used to improve Li ion mobility and charge-discharge characteristics, then the charge-discharge characteristics are improved, but the additives are difficult to dissolve in the electrolyte and precipitate at low temperatures, causing freezing point elevation and performance degradation
Solution Approach 1:
The patent changes the molecular structure parameters of the additive by introducing specific structural features (such as cyclic structures with specific ring sizes, functional group arrangements) to the additive molecules. This structural parameter change enables the additive to maintain solubility across a wide temperature range while preserving its ability to improve Li ion mobility and charge-discharge characteristics.
Solution Approach 2:
The patent creates a composite electrolyte system by combining the specially designed additive with specific solvent mixtures (such as cyclic carbonates and chain carbonates in optimized ratios). This composite approach ensures the additive remains soluble and stable across temperature variations while maintaining enhanced charge-discharge performance.
2Reliability
If the electrolyte uses a conventional composition to achieve good ionic conductivity, then Li ion mobility is improved, but the electrolyte freezes at low temperatures, causing precipitation and performance degradation
Solution Approach 1:
The patent modifies the electrolyte composition parameters by selecting specific solvent combinations and ratios (such as optimizing the proportion of cyclic carbonate to chain carbonate) and incorporating additives with specific molecular structures that lower the freezing point while maintaining ionic conductivity and Li ion mobility.
3Productivity
If existing additives are used to enhance charge acceptance, then fast charging capability is improved, but the additives precipitate at low temperatures, causing performance degradation and potential safety issues
Solution Approach 1:
The patent changes the molecular parameters of the additive to create a structure that maintains solubility at low temperatures while preserving the ability to enhance charge acceptance. This involves optimizing molecular weight, functional group types, and structural configuration to prevent precipitation.
Solution Approach 2:
The patent employs a small, optimized concentration of specifically designed additive molecules that are highly effective at low concentrations. This approach allows the additive to function effectively without requiring large amounts that could precipitate, thereby maintaining reliability at low temperatures while achieving fast charging capability.
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 additives provide low initial resistance and excellent cycle characteristics while minimizing gas generation, improving the performance and longevity of electricity storage devices.
Implementation Method 1
a positive electrode and a negative electrode capable of occluding and releasing lithium ion, and a nonaqueous electrolyte solution allowing the lithium ion to move between the positive electrode and the negative electrode
Implementation Method 2
a porous coating layer formed on the positive electrode or the negative electrode, the porous coating layer having a specific surface area of 0.5 m²/g or more and a pore volume of 0.03 mL/g or more
Data Source
Figure 1
AI summary
Disclosed is an additive for nonaqueous electrolyte solutions, including a compound represented by Formula (1a) or (1b). In Formulae (1a) and (1b), Z represents a monovalent group represented by Formula (2a), (2b), or (2c).