Fluorinated Unsaturated Phosphate Electrolyte Additive for Li-Ion Batteries
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Solution Overview
Problem
Lithium-ion batteries face performance deterioration due to electrolyte decomposition and metal-ion leaching at high temperatures, leading to increased impedance and safety hazards, especially at low temperatures, where conventional unsaturated phosphates fail to provide comprehensive performance improvement.
Innovation Solution
A lithium-ion battery non-aqueous electrolyte containing compounds with unsaturated bonds and hexafluoroisopropyl groups, which form a passivation film on electrodes to suppress decomposition and control polymerization, thereby enhancing both high-temperature and low-temperature performance without increasing internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional unsaturated phosphates are added to improve high-temperature storage and cycle performance, then high-temperature performance is improved, but internal resistance increases and low-temperature performance deteriorates
Solution Approach 1:
The patent introduces fluorine atoms into the unsaturated phosphate structure, changing the chemical parameters of the additive. This modification alters the electrochemical behavior of the phosphate ester, enabling it to form passivation films with different properties that improve high-temperature stability without severely impacting low-temperature performance
Solution Approach 2:
The patent creates a composite electrolyte system combining fluorinated unsaturated phosphate esters with specific non-aqueous solvents (cyclic carbonates, chain carbonates, and cyclic carboxylic acid esters). This composite approach synergistically improves both high-temperature reliability and low-temperature operability
2Quantity of substance
If charging voltage is increased to improve energy density, then energy density is improved, but electrolyte decomposition and metal-ion leaching are exacerbated
Solution Approach 1:
The fluorinated unsaturated phosphate ester performs preliminary protective action by forming a stable passivation film on the positive electrode surface before high-voltage charging begins. This pre-formed film acts as a barrier that prevents subsequent electrolyte decomposition and metal-ion leaching during high-voltage operation
Solution Approach 2:
The passivation film formed by the fluorinated unsaturated phosphate ester acts as an intermediary layer between the positive electrode and the bulk electrolyte. This intermediate film mediates the interaction at the electrode-electrolyte interface, reducing direct contact between high-voltage conditions and the bulk electrolyte, thereby suppressing decomposition reactions
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 effectively inhibits electrolyte decomposition and electrode material destruction, ensuring excellent comprehensive performance by forming a passivation film that maintains battery performance across temperature ranges and reduces lithium precipitation, ensuring safety and efficiency.
Implementation Method 1
the unsaturated bond(s) can form a passivation film on the surface of the positive and negative electrodes, effectively suppressing the decomposition reaction of the electrolyte on the surface of the positive and negative electrodes
Implementation Method 2
due to the steric hindrance relationship of the hexafluoroisopropyl functional group, the degree of polymerization of the unsaturated bond(s) can be suppressed to some extent
Data Source
AI summary
A lithium-ion battery non-aqueous electrolyte and a lithium-ion battery. The non-aqueous electrolyte comprises at least one selected from the compounds represented by structural formula I and II; in formula I, R1 and R2 are independently selected from alkenyl having 2-5 carbon atoms and alkynyl having 2-5 carbon atoms; in formula II, R3 is selected from alkenyl having 2-5 carbon atoms and alkynyl having 2-5 carbon atoms. The compound represented by formula I or II is added in the electrolyte; the compound contains unsaturated bond(s) and hexafluorisopropyl; the unsaturated bond(s) form passivation film on cathode and anode surfaces to inhibit decomposition of the electrolyte on the cathode & anode surface and damage of the cathode material structure; moreover, the polymerization degree of unsaturated bond(s) can be inhibited to some extent due to steric hindrance relationship of fluoroisopropyl functional groups, so as to improve high-temperature performance of the lithium-ion battery while guaranteeing low-temperature performance.