LFP Battery Electrolyte Additives for Iron Elution Suppression
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Solution Overview
Problem
Lithium secondary batteries with lithium iron phosphate (LFP) positive electrodes face electrolyte decomposition and performance degradation due to iron elution, leading to increased resistance and reduced durability, especially at high temperatures.
Innovation Solution
A lithium secondary battery design incorporating a non-aqueous electrolyte solution with specific additives that suppress Lewis acid formation and enhance the solid electrolyte interphase (SEI) film stability, comprising a lithium salt, organic solvents, and additives that control moisture and metal ion elution, thereby improving initial resistance and long-term durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a lithium iron phosphate (LFP) positive electrode is used, then high energy density and working voltage are achieved, but electrolyte decomposition and performance degradation occur due to iron elution at high temperatures
Solution Approach 1:
A coating layer comprising at least one of a metal oxide, a metal phosphate, or a metal fluorosulfonate is formed on the surface of the LFP positive electrode particles. This coating layer acts as an intermediary barrier between the electrode and electrolyte, preventing direct contact and harmful interactions while allowing lithium ion diffusion, thus suppressing iron elution and electrolyte decomposition without compromising the high energy density of the LFP electrode
Solution Approach 2:
The invention changes the surface chemical composition and structure parameters of the LFP electrode by forming a protective coating layer. This modifies the surface properties to be more stable and less prone to iron elution, while maintaining the bulk electrochemical performance that provides high energy density
2Power
If a lithium iron phosphate (LFP) positive electrode is used, then high working voltage is achieved, but transition metals elute into the electrolyte solution causing structural changes and performance degradation
Solution Approach 1:
The coating layer serves as a protective intermediary that stabilizes the electrode structure by preventing direct interaction between the LFP surface and electrolyte, thereby reducing transition metal elution and maintaining structural integrity during charging-discharging cycles at high working voltages
Solution Approach 2:
The invention creates a composite structure where the LFP core material is combined with a protective surface coating layer. This composite structure maintains the high working voltage characteristics of LFP while adding the stability and protection of the coating material, preventing structural degradation
3Temperature
If PF6- anions are thermally decomposed from lithium salt at high temperatures, then Lewis acid is generated which reacts with moisture to generate HF, but this causes electrolyte decomposition and intensified performance degradation
Solution Approach 1:
The coating layer acts as a protective barrier that prevents HF generated from thermal decomposition of LiPF6 from reaching and attacking the electrode structure. This intermediary layer neutralizes or blocks the harmful effects of HF, allowing the battery to operate at high temperatures without severe degradation
Solution Approach 2:
The coating layer transforms the harmful high-temperature environment into a less detrimental condition by providing a stable surface that resists chemical attack from decomposition products like HF and Lewis acids, effectively converting the high-temperature stress into a controlled condition that maintains electrode integrity
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 reduces initial resistance and enhances the lifespan of lithium secondary batteries by suppressing HF formation, stabilizing the SEI film, and preventing metal ion deposition, resulting in improved high-temperature performance and structural stability.
Implementation Method 1
a first additive which is capable of suppressing the formation of additional Lewis acids (HF) by adsorbing moisture
Implementation Method 2
a second additive which is capable of forming a stable film on an electrode
Implementation Method 3
thereby preventing the elution of transition metals into the electrolyte solution
Data Source
AI summary
The present invention relates to a lithium secondary battery including a non-aqueous electrolyte solution containing a lithium salt, an organic solvent, a first additive represented by Formula 1 and a second additive represented by Formula 2, a positive electrode including a lithium iron phosphate-based composite oxide, a negative electrode including a negative electrode active material, and a separator interposed between the positive electrode and the negative electrode, wherein an amount of the first additive and an amount of the second additive are each 0.1 wt% to 5 wt% based on the total weight of the non-aqueous electrolyte solution,wherein R1, R2, Cy1 and L1 are described herein.