Non-Aqueous Electrolyte Additive for Stable Low-Resistance SEI Films
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Solution Overview
Problem
Lithium secondary batteries face issues with increased resistance and capacity degradation due to the thermal decomposition of lithium salts, leading to SEI film deterioration and self-discharge reactions, especially under high temperature conditions.
Innovation Solution
A non-aqueous electrolyte solution for lithium secondary batteries is developed, incorporating a compound with a propargyl group and a fluorocarbon functional group, which forms a low-resistance SEI film, reducing the elution of transition metal ions and preventing additional decomposition reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium salts such as LiPF6 are used in the electrolyte solution, then high ionic conductivity and battery performance are achieved, but thermal decomposition occurs at high temperatures generating HF and PF5 that destroy SEI films and cause capacity degradation
Solution Approach 1:
The patent introduces a film-forming additive that reacts preferentially during initial cycles to form a protective SEI film on the negative electrode surface. This pre-formed film acts as a barrier that prevents subsequent decomposition reactions between lithium salts and the electrode, thereby maintaining stability at high temperatures while preserving ionic conductivity.
Solution Approach 2:
The film-forming additive serves as an intermediary substance between the lithium salts and the negative electrode. It forms a stable interface layer that mediates the interaction, allowing lithium ion transport while preventing direct contact and harmful reactions between the electrolyte components and the electrode, thus resolving the contradiction between conductivity and stability.
2Power
If high temperature operation is permitted, then energy density and power output are improved, but thermal decomposition of lithium salts accelerates causing increased resistance and capacity loss
Solution Approach 1:
The patent employs a film-forming additive that creates a protective barrier on the electrode surface before thermal decomposition can occur. This preliminary protective action prevents the harmful effects of heat-induced decomposition, allowing the battery to operate at high temperatures without suffering from increased resistance or capacity loss.
Solution Approach 2:
The invention modifies the chemical composition parameters of the electrolyte by introducing specific film-forming additives with stable molecular structures. These compositional changes enable the system to withstand higher temperatures by altering the decomposition temperature thresholds and reaction kinetics, thus allowing high power output without thermal degradation.
3Productivity
If transition metal ions are eluted from the positive electrode, then electrochemical reactions occur, but lattice structure stability decreases leading to active oxygen generation and electrolyte decomposition
Solution Approach 1:
The film-forming additive creates an intermediary protective layer on the positive electrode surface that facilitates electrochemical reactions while preventing excessive ion elution. This intermediate layer maintains lattice structure stability by controlling the interaction between electrolyte components and the electrode, thereby preventing active oxygen generation and subsequent electrolyte decomposition.
4Ease of operation
If SEI film is destroyed and regenerated continuously, then lithium ion insertion/extraction occurs, but additional lithium ions are consumed causing resistance increase and capacity degradation
Solution Approach 1:
The patent introduces a film-forming additive that performs preliminary SEI film formation during initial cycles. This pre-formed film is more stable and requires less regeneration, thereby reducing continuous lithium ion consumption. The preliminary action establishes a durable interface that maintains lithium ion insertion/extraction functionality while minimizing substance loss.
Solution Approach 2:
The invention changes the compositional parameters of the SEI film by incorporating specific film-forming additives. This compositional modification results in an SEI film with improved stability and lower resistance, reducing the frequency and extent of regeneration reactions. Consequently, lithium ion consumption is minimized while maintaining ease of insertion and extraction.
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 effectively suppresses the increase in initial resistance and enhances output characteristics at room and low temperatures by forming a robust, stable SEI film, thereby improving the battery's performance and lifespan.
Implementation Method 1
the compound represented by Formula 1... may be reduced before the organic solvent to form a low-resistance SEI film including a fluorocarbon component on the surface of the electrode
Implementation Method 2
an electrolyte solution that is a medium for transferring lithium ions
Implementation Method 3
maintaining the passivation ability of a SEI film... form a robust SEI film
Data Source
AI summary
A non-aqueous electrolyte solution for a lithium secondary battery and a lithium secondary battery including the same are described herein. Specifically, the non-aqueous electrolyte solution for a lithium secondary battery includes a lithium salt, an organic solvent and a compound represented by Formula 1 to form a robust SEI film, thereby improving battery performance:Wherein R1 to R3 are described herein.