Non-aqueous Electrolyte for Lithium Battery Swelling and Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face limitations in high-temperature cycle characteristics, low-temperature output, and swelling due to the high melting point of ethylene carbonate-based electrolytes, and excessive irreversible reactions when propylene carbonate is used with lithium salts like LiPF6.
Innovation Solution
A non-aqueous electrolyte solution comprising propylene carbonate and lithium bis(fluorosulfonyl)imide (LiFSI) is used, with a concentration range of 0.1 to 2 mole/â for LiFSI and a molar ratio of LiPF6 to LiFSI between 1:6 to 1:9, along with additional solvents like dimethyl carbonate and ethylmethyl carbonate, to form a robust solid electrolyte interface (SEI) and prevent decomposition and swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene carbonate-based electrolytes are used, then high-temperature cycle characteristics improve, but low-temperature output deteriorates due to high melting point
Solution Approach 1:
The patent uses a composite electrolyte system combining propylene carbonate (PC) as the main solvent with lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) as dual lithium salts. This composite approach creates synergistic effects where PC provides low-temperature performance while the combination of LiFSI and LiPF6 forms a robust SEI layer that ensures high-temperature stability, resolving the contradiction between low-temperature output and high-temperature cycle characteristics
Solution Approach 2:
The patent optimizes specific parameter ranges: LiFSI concentration at 0.1-2.0 mol/L (preferably 0.5-1.5 mol/L), LiPF6 concentration at 0.01-0.5 mol/L (preferably 0.05-0.1 mol/L), and PC content at 60-95 wt% (preferably 70-90 wt%). These parameter optimizations ensure the electrolyte forms an appropriate SEI layer that maintains ion conductivity across wide temperature ranges while preventing decomposition reactions
2Productivity
If propylene carbonate is used with lithium salts like LiPF6, then low-temperature output improves, but excessive irreversible reactions occur leading to swelling
Solution Approach 1:
Lithium bis(fluorosulfonyl)imide (LiFSI) acts as an intermediary substance that mediates between propylene carbonate and the electrode surfaces. LiFSI preferentially reacts to form a stable SEI layer that prevents direct contact between PC and electrode materials, thereby reducing excessive irreversible reactions and swelling while maintaining PC's low-temperature performance benefits
Solution Approach 2:
The dual-salt system of LiFSI and LiPF6 creates a composite protective interface on electrodes. LiFSI forms the primary stable SEI layer that prevents PC decomposition and swelling, while trace LiPF6 (0.01-0.5 mol/L) enhances overall electrochemical performance. This composite salt approach balances low-temperature conductivity with high-temperature stability
3Reliability
If a robust SEI is formed to prevent lithium ion reactions, then high-temperature cycle characteristics improve, but ion transport resistance increases
Solution Approach 1:
The patent optimizes lithium salt concentrations to control SEI properties: LiFSI at 0.1-2.0 mol/L provides sufficient protective coverage while maintaining ion conductivity, and LiPF6 at 0.01-0.5 mol/L fine-tunes the SEI composition. This parameter optimization ensures the SEI layer is robust enough to prevent decomposition at high temperatures but sufficiently conductive to allow efficient lithium ion transport
Solution Approach 2:
The dual-salt electrolyte system creates a composite SEI layer with optimized properties. LiFSI-rich SEI provides chemical stability and protection against decomposition, while controlled LiPF6 content contributes to ion conductivity. This composite interface structure simultaneously achieves high-temperature cycle stability and efficient ion transport
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 solution improves high-temperature cycle characteristics, low-temperature output, capacity retention, and reduces swelling, enhancing the overall performance and stability of lithium secondary batteries across various temperature ranges.
Implementation Method 1
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 2
The SEI may only pass the lithium ions by acting as an ion tunnel
Implementation Method 3
since lithium is highly reactive, lithium reacts with the carbon electrode to form Li 2 CO 3, LiO, or LiOH
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Provided are a non-aqueous electrolyte solution including propylene carbonate (PC) and lithium bis(fluorosulfonyl)imide (LiFSI), and a lithium secondary battery including the non-aqueous electrolyte solution. The lithium secondary battery including the non-aqueous electrolyte solution of the present invention may improve low-temperature output characteristics, high-temperature cycle characteristics, output characteristics after high-temperature storage, capacity characteristics, and swelling characteristics.