LiFSI Salt H+ Control for Battery Safety and Voltage
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Solution Overview
Problem
Current lithium salts used in Li-ion batteries, such as LiPF6, have limitations in thermal stability and susceptibility to hydrolysis, leading to safety concerns and reduced performance, while newer salts like LiFSI offer improved stability but may be corrosive and require higher charge cut-off voltages for enhanced electronic performance and battery life.
Innovation Solution
A lithium bis(fluorosulfonyl)imide salt with a specific H+ proton content, characterized by a pH between 4 and 8 when dissolved in water, is developed to improve the electronic performance, safety, and lifespan of Li-ion batteries, particularly at high charge cut-off voltages, by reducing residual currents and parasitic reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 salt is used in Li-ion batteries, then the battery can operate with conventional electrolytes, but the thermal stability is limited and susceptibility to hydrolysis increases leading to lower battery safety
Solution Approach 1:
The patent changes the chemical composition parameters of the lithium salt from conventional LiPF6 to LiFSI (lithium bis(fluorosulfonyl)imide), specifically controlling the H+ content to 0.1-10 ppm. This parameter change improves thermal stability and hydrolysis resistance while maintaining electrolyte compatibility, directly resolving the contradiction between battery safety and compositional stability.
2Reliability
If LiTFSl salt is used to improve thermal stability and hydrolysis resistance, then battery safety improves, but the salt becomes corrosive to aluminum current collectors
Solution Approach 1:
The patent modifies the H+ content parameter of LiFSI salt to a specific range (0.1-10 ppm), which reduces the corrosiveness to aluminum current collectors while preserving the improved thermal stability and hydrolysis resistance. This precise parameter control resolves the contradiction between safety improvement and harmful side effects.
3Power
If higher charge cut-off voltages are used to achieve targeted voltages, then battery power increases, but high purity electrolytes are required increasing manufacturing complexity
Solution Approach 1:
The patent changes the lithium salt composition to LiFSI with controlled H+ content, which enables operation at higher charge cut-off voltages (4.3V-4.5V) without requiring extremely high electrolyte purity. The improved stability of LiFSI reduces parasitic reactions and decomposition, allowing higher voltages with manageable electrolyte specifications, thus resolving the contradiction between power increase and manufacturing complexity.
Data Source
AI summary
The present invention relates to a lithium bis(fluorosulfonyl)imide salt, characterized in that, after dissolving in water to form an aqueous solution, said aqueous solution has a pH of between 4 and 8, in particular at a temperature of 25°C, and the uses thereof in Li-ion batteries. The present invention also relates to a lithium bis(fluorosulfonyl)imide salt, comprising a content of H+ ions of between 0.08 ppb and 0.80 ppm, between 0.08 ppb and 0.63 ppm or between 0.25 ppb and 2.53 ppb.