Electrolyte Composition for Fast-Charging Li-Ion Battery Stability
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Solution Overview
Problem
Lithium-ion batteries face challenges in achieving good fast charging capability, cycling stability, and high-temperature storage performance, particularly due to the decomposition of electrolytes under harsh conditions.
Innovation Solution
An electrolyte comprising a carboxylate ester compound and a compound of Formula (I) is used, where the carboxylate ester reduces lithium salt dissociation and forms a film with unsaturated double bonds on electrodes, while the compound of Formula (I) neutralizes alkalinity and captures water/hydrofluoric acid, enhancing film formation and reducing impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional electrolytes are used, then the battery can operate, but the fast charging capability is poor due to high interfacial impedance
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing carboxylate ester compounds (5-45 mass%) and compound (I) with specific functional groups (anhydride, unsaturated double bonds). This compositional parameter change modifies the interfacial properties, reducing film-forming impedance and enabling faster charging while maintaining stability.
Solution Approach 2:
The patent creates a composite electrolyte system combining carboxylate ester compounds with compound (I) that contains multiple functional groups (anhydride, unsaturated double bonds, ether oxygen). This composite approach allows synergistic effects where the anhydride group neutralizes alkalinity, the unsaturated bonds form protective films, and the ether oxygen coordinates lithium ions, collectively reducing interfacial impedance and improving fast charging capability.
2Reliability
If the battery operates under harsh conditions, then it can function, but cycling stability deteriorates due to electrolyte decomposition
Solution Approach 1:
The patent applies preliminary anti-action by having the anhydride group of compound (I) neutralize alkalinity on the positive electrode surface before electrolyte decomposition can occur. This pre-neutralization prevents base-catalyzed decomposition of the carboxylate ester electrolyte, maintaining composition stability and cycling reliability under harsh conditions.
Solution Approach 2:
The unsaturated double bonds in compound (I) perform preliminary action by polymerizing to form protective films on electrode surfaces before significant electrolyte decomposition occurs. This pre-formed protective layer acts as a barrier, preventing direct contact between the electrolyte and electrode, thereby reducing decomposition reactions and improving cycling stability.
3Reliability
If the battery is stored at high temperature, then it remains functional, but storage performance degrades due to decomposition reactions
Solution Approach 1:
The anhydride group of compound (I) performs preliminary anti-action by neutralizing alkalinity on the positive electrode surface before high-temperature storage can induce decomposition. This pre-neutralization prevents alkaline-catalyzed decomposition reactions that would otherwise occur during high-temperature storage, maintaining electrolyte stability and storage performance.
Solution Approach 2:
The patent converts the potentially harmful alkalinity on the electrode surface into a benefit by having the anhydride group specifically target and neutralize it. The alkalinity that would normally accelerate decomposition is transformed into a driving force for anhydride hydrolysis and neutralization, creating a self-regulating system that protects against high-temperature storage degradation.
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 electrolyte improves fast charging capability and cycling stability by reducing interfacial impedance and inhibiting decomposition, ensuring high-temperature storage performance through synergistic effects.
Implementation Method 1
the carboxylate ester compound can reduce a dissociation degree of lithium salts due to low polarity, so that a solvation structure contains a higher amount of anion
Implementation Method 2
an unsaturated double bond in a molecule can be polymerized on surfaces of positive and negative electrodes to form a film
Implementation Method 3
the anhydride group can capture water and a hydrofluoric acid HF in the electrolyte, to reduce impact of the water and the hydrofluoric acid HF on a cathode electrolyte interface (CEI) film
Data Source
AI summary
An electrolyte includes a carboxylate ester compound and a norbornene anhydride compound. Based on a mass of the electrolyte, a mass percentage of the carboxylate ester compound is A % satisfying 5≤A≤45.