Aqueous Battery Interfacial Tension Control
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Solution Overview
Problem
Nonaqueous lithium secondary batteries face safety concerns due to flammability of organic solvents and high internal resistance, which are exacerbated by electrolysis issues in aqueous solutions, limiting their application in electric vehicles and stationary energy storage.
Innovation Solution
A secondary battery design utilizing an aqueous electrolyte with a titanium-containing oxide negative electrode and a water-soluble organic solvent, maintaining an interfacial tension of 37 mN/m or less, which suppresses water electrolysis and enhances charge-discharge efficiency and cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an organic solvent electrolytic solution is used in a nonaqueous lithium secondary battery, then high electromotive force (2-4.5 V) and oxidation resistance are achieved, but safety deteriorates due to flammability and internal resistance increases
Solution Approach 1:
The patent changes the fundamental parameter of the electrolytic solution from organic-based to aqueous-based, while carefully controlling the pH value (3-11) and composition to prevent water electrolysis. This parameter change allows achieving both safety (non-flammable) and acceptable power output, resolving the contradiction between electromotive force and safety.
2Reliability
If an aqueous electrolytic solution is used to improve safety, then flammability is eliminated, but energy density deteriorates due to limited potential range (1-1.5 V) and water electrolysis
Solution Approach 1:
The patent changes the pH value parameter to a specific range (3-11) and controls the composition ratio of water to organic solvent, which suppresses water electrolysis and enables higher operating potentials. This allows aqueous batteries to achieve both safety and improved energy density, resolving the contradiction between safety and power.
Solution Approach 2:
The patent introduces a specific additive compound as an intermediary substance that mediates between the aqueous electrolyte and electrode materials. This additive prevents water electrolysis and enables stable operation at higher potentials, allowing the system to achieve both safety and high energy density simultaneously.
3Power
If lithium titanium oxide is used as negative electrode material to achieve high electromotive force (2.6-2.7 V) in aqueous solution, then energy density is improved, but water electrolysis increases due to lithium insertion/extraction potential (1.5 V vs. Li/Li+) being close to water decomposition potential
Solution Approach 1:
The patent changes the pH value parameter to a specific range (3-11) and controls the composition ratio of water to organic solvent, which suppresses water electrolysis and enables higher operating potentials. This allows aqueous batteries to achieve both safety and improved energy density, resolving the contradiction between safety and power.
Solution Approach 2:
The patent introduces a specific additive compound as an intermediary substance that mediates between the aqueous electrolyte and electrode materials. This additive prevents water electrolysis and enables stable operation at higher potentials, allowing the system to achieve both safety and high energy density simultaneously.
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 approach results in improved charge and discharge performance, as well as extended cycle life, by reducing water electrolysis and maintaining effective ion insertion/extraction in the battery.
Implementation Method 1
maintaining an interfacial tension of 37 mN/m or less, which suppresses water electrolysis
Implementation Method 2
maintaining effective ion insertion/extraction in the battery
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
According to one approach, there is provided a secondary battery (100) including a positive electrode (5), a negative electrode (3), and an aqueous electrolyte. The negative electrode (3) contains a titanium-containing oxide. The aqueous electrolyte contains a solvent and alkali metal ions or alkaline earth metal ions, the solvent containing water and a water-soluble organic solvent. An interfacial tension of the aqueous electrolyte is 37 mN/m or less.