Carboxylic Ester Electrolyte for Fast-Charging LFP Cycle Life
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Solution Overview
Problem
Lithium iron phosphate (LFP) batteries have low energy density, which limits their quick charging capabilities and cycle life due to poor compatibility between carboxylate solvents and negative electrodes, and existing electrolytic solutions struggle to meet these demands.
Innovation Solution
An electrolytic solution comprising carboxylic ester and fluorosulfonic acid lactone with specific proportions, which adjusts compatibility and prevents reduction of carboxylic ester, enhancing quick charging performance and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the coating weight of the positive electrode material is improved to increase energy density, then the energy density is improved, but the thickness of the electrode plate is remarkably increased and the lithium-ion transmission path is remarkably increased
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by introducing fluorosulfonic acid lactone with specific molecular structures (Formula I and Formula II) containing fluorine atoms at specific positions. This chemical parameter change enables the electrolyte to effectively dissolve lithium salts and form stable solvation structures, improving lithium-ion conductivity and enabling efficient lithium-ion transmission through thicker electrodes, thus resolving the contradiction between increased coating weight and maintained transmission efficiency.
2Speed
If carboxylate solvent system is used to reduce viscosity and increase conductivity, then the viscosity is reduced and conductivity is increased, but the compatibility with the negative electrode is poor and the cycle life is shortened
Solution Approach 1:
The patent uses fluorosulfonic acid lactone as an intermediary substance that mediates between the carboxylate solvent and the negative electrode. The fluorosulfonic acid lactone forms a stable solvation structure with lithium ions and facilitates the formation of a stable solid electrolyte interface (SEI) on the negative electrode. This intermediary action protects the negative electrode from direct harmful interactions with the carboxylate solvent, maintaining both high conductivity and long cycle life.
Solution Approach 2:
The patent creates a composite electrolytic solution system combining carboxylate solvents (for low viscosity and high conductivity) with fluorosulfonic acid lactone additives (for compatibility and stability). This composite material approach leverages the advantages of both components: the carboxylate provides excellent ionic conductivity while the fluorosulfonic acid lactone ensures electrochemical stability and compatibility with electrodes, particularly the negative electrode, thereby achieving both high speed and long reliability.
3Ease of manufacture
If common carbonate solvent system is used, then the electrolytic solution can be formulated, but it is difficult to meet the quick charging requirement of thick coated LFP battery
Solution Approach 1:
The patent fundamentally changes the solvent system from traditional carbonate-based electrolytes to a carboxylate-based electrolyte system supplemented with fluorosulfonic acid lactone. This parameter change in chemical composition dramatically reduces viscosity and enhances ionic conductivity, enabling rapid lithium-ion transport. The fluorosulfonic acid lactone specifically enhances quick charging performance by forming stable solvation structures that facilitate fast lithium-ion diffusion, meeting the productivity requirements of thick coated LFP batteries.
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 solution enables lithium-ion batteries to achieve excellent quick charging performance and long cycle life by forming an anion-induced ion-solvent complex solvation structure and a compact solid electrolyte interface, improving compatibility and reducing ester reduction.
Implementation Method 1
forming an anion-induced ion-solvent complex solvation structure
Implementation Method 2
prevents reduction of carboxylic ester in the electrolytic solution
Data Source
AI summary
The present disclosure relates to an electrolytic solution for a lithium-ion secondary battery including a solvent, additive, and lithium salt. The solvent includes carboxylic ester, and the additive includes fluorosulfonic acid lactone of Formula I in the description. In the electrolytic solution, a content W of carboxylic ester and a content a of fluorosulfonic acid lactone of Formula I satisfy 430.1>1000*a/W>0.163, optionally 202.02>1000*a/w≥1.635, and further optionally 100.059≥1000*a/w≥4.915, where a and W are both in wt % based on a weight of the electrolytic solution. The secondary battery containing the electrolytic solution has excellent quick charging performance and a long cycle life.