Electrolyte Composition for High-Voltage Battery Swelling Control
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Solution Overview
Problem
High-voltage electrochemical devices face issues with cathode material oxidizability, leading to electrolyte decomposition, battery capacity decrease, and reliability problems such as swelling and capacity attenuation due to floating charge.
Innovation Solution
An electrolyte comprising fluorinated cyclic carbonate and a multi-nitrile compound with an ether bond, along with additional additives, forms a stable SEI film that suppresses battery thickness expansion and enhances cycle and floating-charge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-voltage cathode material is used to increase energy density, then battery capacity is improved, but electrolyte decomposition occurs and cathode stability decreases
Solution Approach 1:
The patent introduces a film-forming additive as an intermediary substance between the high-voltage cathode material and the electrolyte. This additive forms a protective interface film that mediates the interaction, preventing direct contact and harmful reactions between the electrolyte and cathode material, thus maintaining cathode stability while enabling high-voltage operation for increased capacity
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding specific film-forming additives and adjusting the solvent mixture ratios. These parameter changes enable the formation of a stable solid electrolyte interface (SEI) film on the cathode surface, which allows the system to operate at higher voltages without decomposition, thereby increasing battery capacity while maintaining reliability
2Duration of action of moving object
If floating charge is applied to maintain full charge state, then battery availability is improved, but thickness expansion and capacity attenuation occur
Solution Approach 1:
The patent applies preliminary action by forming a stable protective film on the cathode surface before floating charge occurs. This pre-formed film acts as a barrier that prevents the swelling and expansion that would otherwise occur during prolonged floating charge, allowing the battery to maintain full charge state without thickness expansion or capacity attenuation
Solution Approach 2:
The film-forming additive acts as a sacrificial component that consumes itself to form the protective interface film. This disposable-like behavior of the additive (consuming small amounts during initial cycles) creates a long-lasting protective layer that prevents the much more costly damage of thickness expansion and capacity loss during floating charge operation
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 stabilizes the electrode interface, reducing internal resistance and thickness expansion, thereby improving the electrochemical device's cycle and storage performance.
Implementation Method 1
forms a stable SEI film that suppresses battery thickness expansion and enhances cycle and floating-charge performance
Implementation Method 2
the oxidizability of the cathode material is increased, and the stability is lowered, which causes the non-aqueous electrolyte to easily decompose on the surface of the cathode
Data Source
Figure 1~3
AI summary
An electrolyte includes a fluorinated cyclic carbonate, and a multinitrile compound having an ether bond. Based on the total weight of the electrolyte, a weight percentage (Cf) of the fluorinated cyclic carbonate is greater than a weight percentage (Cn) of themulti-nitrile compound having the ether bond; and 1< Cf / Cn ≤ 3 or 5.5< Cf / Cn ≤ 20. The electrolyte of the present application can control the expansion of the electrochemical device, so that the electrochemical device has excellent cycle, storage and/or floating-charge performance.