Non-aqueous Electrolyte with Organophosphorus Additives for SEI Stability
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Solution Overview
Problem
Lithium-ion batteries with traditional electrolytes, such as LiPF6 and carbonates, face issues like rapid capacity fade at elevated temperatures and incompatibility with graphite electrodes, leading to insufficient solid electrolyte interface (SEI) protection and intercalation, limiting their performance and lifespan.
Innovation Solution
A substantially non-aqueous electrolyte solution comprising an alkali metal salt, a polar aprotic solvent, and an organophosphorus compound, specifically designed to prevent SEI formation and decomposition, is used, which includes compounds like ethylene methyl phosphate and tri(2-furyl)phosphine, to enhance the stability and performance of lithium-ion batteries, especially with graphite electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 and EC-based electrolytes are used, then good battery performance is achieved, but capacity fades quickly at elevated temperatures and SEI protection is insufficient
Solution Approach 1:
The patent introduces film-forming additives (cyclic carbonates, carboxylic acid esters, and sulfones) as intermediary substances that mediate between the electrolyte and graphite anode. These additives preferentially decompose to form stable SEI films, preventing direct contact between EC and the anode, thereby reducing further decomposition and improving capacity retention at elevated temperatures.
Solution Approach 2:
The patent modifies the electrolyte composition by adding specific compounds (cyclic carbonates, carboxylic acid esters, and sulfones) in controlled amounts (0.01-5 wt%). This changes the chemical parameters of the electrolyte system, enabling the formation of more stable SEI films that resist decomposition at high temperatures while maintaining good battery performance.
2Temperature
If PC is used to replace EC for high temperature applications, then wider temperature window is achieved, but graphite electrode compatibility is lost due to intercalation
Solution Approach 1:
The patent uses film-forming additives as intermediary layers between the PC electrolyte and graphite anode. These additives form protective SEI films that prevent PC from intercalating into the graphite structure, thereby maintaining electrode compatibility while enabling high-temperature operation.
Solution Approach 2:
The patent applies preliminary anti-action by having the film-forming additives decompose first during initial cycles to create a protective barrier. This preliminary reaction prevents the harmful intercalation of PC into graphite, allowing the use of PC for extended temperature ranges without compromising electrode integrity.
3Ease of manufacture
If simple electrolyte formulations are used, then manufacturing ease is improved, but SEI protection becomes insufficient leading to rapid decomposition
Solution Approach 1:
The patent creates a composite electrolyte system by combining LiPF6 with cyclic carbonates, carboxylic acid esters, and sulfones. This composite formulation maintains the simplicity of handling and manufacturing while the synergistic interaction between components provides enhanced SEI protection and reduced decomposition.
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 proposed electrolyte solution significantly improves capacity retention and reduces interfacial impedance, leading to enhanced performance and stability of lithium-ion batteries at higher temperatures, preventing SEI decomposition and maintaining battery health over long service lives.
Implementation Method 1
a thin passivation layer, also called SEI (solid electrolyte interface), is typically formed during the first charging process and prevents further reactions of the electrolyte on the anode surface
Implementation Method 2
to prevent the intercalation of PC into graphite anodes
Data Source
AI summary
A substantially non-aqueous electrolyte solution includes an alkali metal salt, a polar aprotic solvent, and an organophosphorus compound of Formula IA, IB, or IC:where R1, R2, R3 and R4 are each independently hydrogen, halogen, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heterocyclyl, heteroaryl, alkoxy, alkenoxy, alkynoxy, cycloalkoxy, aryloxy, heterocyclyloxy, heteroaryloxy, siloxyl, silyl, or organophosphatyl; R5 and R6 are each independently alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heterocyclyl, or heteroaryl; R7 isand R8, R9 and R10 are each independently alkyl, cycloalkyl, aryl, heterocyclyl, or heteroaryl; provided that if the organophosphorus compound is of Formula IB, then at least one of R5, and R6 are other than hydrogen, alkyl, or alkenyl; and if the organophosphorus compound is of Formula IC, then the electrolyte solution does not include 4-methylene-1,3-dioxolan-2-one or 4,5-dimethylene-1,3-dioxolan-2-one.