Lithium Battery Electrolyte Additives for High-Temperature Stability
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Solution Overview
Problem
Lithium batteries with fluorosulfonate in the nonaqueous electrolyte experience side reactions at high temperatures, leading to degradation of output characteristics when stored at high temperatures, which negatively impacts performance at low temperatures.
Innovation Solution
A lithium battery design featuring a positive electrode with manganese oxide or graphite fluoride, a negative electrode with a powdered or fibrous carbon material, and a nonaqueous electrolyte containing LiClO4, LiBF4, and a fluorine-containing sulfur salt, which forms a high-quality solid electrolyte interface to suppress side reactions and maintain output characteristics across temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If fluorosulfonate is dissolved into the nonaqueous electrolyte to improve output characteristics, then the internal impedance is reduced and output characteristics are improved, but side reactions occur at high temperature leading to deposit formation and degradation of output characteristics after high-temperature storage
Solution Approach 1:
LiBF4 is introduced as an intermediary substance that mediates between the fluorosulfonate and the electrode surfaces. It forms a stable solid electrolyte interface (SEI) layer that prevents direct contact between fluorosulfonate and electrodes, thereby suppressing side reactions and deposit formation while maintaining the beneficial low-impedance properties of fluorosulfonate
Solution Approach 2:
The invention changes the compositional parameters of the electrolyte by specifying precise concentration ranges: fluorosulfonate at 0.01-5 wt% and LiBF4 at 1-30 wt%. This parameter optimization ensures sufficient output characteristics from fluorosulfonate while using enough LiBF4 to prevent side reactions during high-temperature storage
2Temperature
If lithium metal is used as the negative electrode to achieve wide operating temperature range, then the battery can function at high temperatures, but significant voltage drop occurs at low temperature
Solution Approach 1:
The invention changes the electrolyte composition parameters by adding fluorosulfonate and LiBF4, which modify the SEI layer properties on the lithium metal surface. This enables the battery to maintain low-temperature voltage by reducing impedance and improving ion transport kinetics, while preserving high-temperature functionality through the stable SEI layer
3Power
If carbon material is attached to the negative electrode surface or LiBF4 is added to improve low-temperature output characteristics, then voltage drop at low temperature is reduced, but deposits still form on positive electrode surface during high-temperature storage
Solution Approach 1:
LiBF4 serves as an intermediary that preferentially reacts to form a stable SEI layer on the positive electrode surface during high-temperature storage. This SEI layer acts as a protective barrier that prevents fluorosulfonate from participating in side reactions that would otherwise form deposits on the positive electrode
Solution Approach 2:
The invention optimizes the concentration ratio between LiBF4 (1-30 wt%) and fluorosulfonate (0.01-5 wt%) to ensure that LiBF4 dominates the SEI formation process at high temperatures, preventing deposit formation, while maintaining sufficient fluorosulfonate concentration to improve low-temperature output characteristics
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 battery maintains excellent output characteristics at low temperatures even after storage at high temperatures, with no significant degradation observed, ensuring reliable pulse discharge performance.
Implementation Method 1
the nonaqueous electrolyte includes a nonaqueous solvent, a solute, a first additive, and a second additive, the solute contains LiClO4, the first additive is LiBF4, and the second additive is a salt having an inorganic anion that contains sulfur and fluorine
Data Source
AI summary
A lithium battery includes a positive electrode, a negative electrode containing lithium, and a nonaqueous electrolyte having lithium-ion conductivity, wherein the positive electrode contains at least one selected from the group consisting of manganese oxide and graphite fluoride, and a powdered or fibrous carbon material is attached to at least part of the surface of the negative electrode opposite the positive electrode. Further, the nonaqueous electrolyte includes a nonaqueous solvent, a solute, a first additive, and a second additive, the solute contains LiClO4, the first additive is LiBF4, and the second additive is a salt having an inorganic anion that contains sulfur and fluorine.