Aqueous Electrolyte for High-Temperature Battery Stability
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in high-temperature durability and low-temperature output performance, making them unsuitable for vehicle applications, particularly in engine rooms, due to poor ion conductivity and heat stability of nonaqueous electrolytes, which limits their large current discharge performance and cycle life.
Innovation Solution
A secondary battery design incorporating a positive electrode, a negative electrode with titanium-containing oxide, and an aqueous electrolyte containing sodium ions and specific anions like [N(FSO2)2]−, SO32−, and SCN−, which enhances ion conductivity, reduces hydrogen generation, and improves cycle life and discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nonaqueous electrolyte is used in lithium ion secondary battery, then energy density is improved, but ion conductivity is reduced and heat stability is poor
Solution Approach 1:
The patent changes the fundamental parameter of the electrolyte from nonaqueous to aqueous base, while optimizing the concentration of lithium salt (3-8 mol/L) and adding specific additives to achieve both high ion conductivity and improved heat stability. This parameter change resolves the contradiction by selecting water as the solvent base which inherently provides superior ion conductivity and thermal stability.
Solution Approach 2:
The patent creates a composite electrolyte system combining aqueous base with multiple components including lithium salt, cyclic carbonate, chain carbonate, and specific additives (boric acid, sugar alcohols, carboxylic acids). This composite approach maintains high energy density while achieving superior ion conductivity and heat stability through synergistic effects of the components.
2Power
If nonaqueous electrolyte is used, then battery voltage can reach 2-4.5 V, but high-temperature durability is reduced
Solution Approach 1:
The patent changes the electrolyte composition parameters by using aqueous base with optimized lithium salt concentration (3-8 mol/L) and adding heat-stabilizing additives. This enables the battery to maintain high voltage (2-4.5 V) while significantly improving high-temperature durability through the inherent thermal stability of water and the protective effect of additives.
Solution Approach 2:
The patent introduces specific additives (boric acid, sugar alcohols, carboxylic acids) as intermediaries that mediate between the high voltage operation and heat stability requirements. These additives form protective films on electrode surfaces, enabling high voltage operation while protecting against thermal degradation.
3Power
If nonaqueous electrolyte is used, then battery can operate at high voltage, but low-temperature output performance is reduced
Solution Approach 1:
The patent changes the electrolyte from nonaqueous to aqueous base with optimized composition including cyclic and chain carbonates in specific ratios. This parameter change enables the battery to maintain high voltage operation while achieving superior low-temperature output performance due to the lower freezing point and better fluidity of the aqueous electrolyte composition.
4Ease of manufacture
If organic solvent is used in nonaqueous electrolyte, then electrolyte can be formed, but high temperature decomposition occurs and heat stability is poor
Solution Approach 1:
The patent inverts the conventional approach by using aqueous base instead of organic solvent. This inversion fundamentally resolves the heat stability issue since water has much higher boiling point and thermal stability than organic solvents, while still enabling electrolyte formation through high concentration lithium salt dissolution.
Solution Approach 2:
The patent changes the solvent base from organic to aqueous and optimizes the lithium salt concentration to 3-8 mol/L. This parameter change enables the electrolyte to resist high temperature decomposition while maintaining necessary ionic conductivity and electrochemical performance.
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 aqueous electrolyte system significantly improves ion conductivity, cycle life, and large current discharge performance, making the battery more suitable for vehicle applications by addressing the limitations of nonaqueous electrolytes.
Implementation Method 1
The aqueous electrolyte contains a sodium ion having a concentration of 3 mol/L or more and at least one type of first anion selected from the group consisting of [N(FSO2)2]−, SO32−, S2O32− and SCN−
Implementation Method 2
a negative electrode containing a carbonaceous material that allows lithium ions to be inserted and extracted
Implementation Method 3
a secondary battery including a positive electrode, a negative electrode, and an aqueous electrolyte. The negative electrode contains titanium-containing oxide.
Data Source
AI summary
According to one embodiment, a secondary battery includes a positive electrode, a negative electrode and an aqueous electrolyte. The negative electrode includes a titanium-containing oxide. The aqueous electrolyte includes a sodium ion having a concentration of 3 mol/L or more and at least one type of first anion selected from the group consisting of [N(FSO2)2]−, SO32−, S2O32− and SCN−.