Aqueous lithium ion secondary battery
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Solution Overview
Problem
Aqueous lithium ion secondary batteries face challenges with energy density and safety due to the narrow potential window of aqueous electrolyte solutions, which restricts the use of active materials and affects cycle stability when aluminum is used as a current collector, leading to decomposition and instability during charging and discharging.
Innovation Solution
Employing a negative electrode current collector with a surface made of materials like Mg and Zr, which have a work function of 4.5 eV or less, to expand the reduction side potential window and ensure cycle stability by maintaining a passive state and reducing electrochemical activity changes during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high concentration aqueous electrolyte solution is used to expand the potential window, then the energy density and available active materials are improved, but electrolysis may still proceed at potentials above LTO charging/discharging potential, consuming current and preventing proper battery operation
Solution Approach 1:
The patent changes the chemical composition parameters of the aqueous electrolyte solution by using high concentration lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at 7.5-12.5 mol per kg water, which shifts the electrolysis potential to values above the LTO charging/discharging potential, preventing current consumption and enabling reliable battery operation while maintaining an expanded potential window
2Quantity of substance
If Al is used as a negative electrode current collector to reduce overvoltage and expand the reduction side potential window, then charging and discharging become possible, but cycle stability deteriorates due to changes in surface activity during charging and discharging
Solution Approach 1:
The patent changes the material parameter of the current collector surface from Al to materials with work functions of 4.5 eV or less (such as Mg, Zr, Ti, or their alloys), which maintains low overvoltage for an expanded reduction side potential window while ensuring stable surface properties and passive state during cycling, thereby achieving both wide potential window and excellent cycle 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
The use of Mg and Zr in the negative electrode current collector expands the reduction side potential window and enhances cycle stability, allowing for stable charging and discharging of the battery while maintaining electrochemical stability, even after multiple cycles.
Implementation Method 1
a surface in contact with the aqueous electrolyte solution, the surface including a material containing at least one selected from the group consisting of Mg and Zr as a main component... which have a work function of 4.5 eV or less, to expand the reduction side potential window and ensure cycle stability by maintaining a passive state and reducing electrochemical activity changes
Implementation Method 2
Electrolysis of a general aqueous electrolyte solution generally proceeds at a potential above a charging and discharging potential of LTO... in a high concentration aqueous electrolyte solution... although a potential window is expanded due to addition of LiTFSI, electrolysis may proceed at a potential above a charging and discharging potential of LTO in some cases
Implementation Method 3
the electrolyte contains lithium bis(trifluoromethanesulfonyl)imide, and the aqueous electrolyte solution contains the lithium bis(trifluoromethanesulfonyl)imide such that an amount of substance of the lithium bis(trifluoromethanesulfonyl)imide is within a range of 7.5 mol to 12.5 mol per kg of the water
Data Source
Figure 1A~1C
Figure 2~3
Figure 4A~4E
AI summary
There is provided a negative electrode current collector (10, 10a, 10b, 10c) that is used in contact with an aqueous electrolyte solution (50) in an aqueous lithium ion secondary battery (1000), including a surface in contact with the aqueous electrolyte solution (50), the surface including a material (11) containing at least one selected from the group consisting of Ti, Pb, Zn, Sn, Mg, Zr and In as a main component.