LFP Positive Electrode Electrolyte Additive Against F− Side Reactions
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Solution Overview
Problem
Rechargeable lithium batteries face degradation in lifespan characteristics and stability due to side reactions caused by F− ions, particularly when using lithium-iron-phosphate-based oxides as positive electrode active materials and LiPF6 as lithium salt in the electrolyte, which decomposes into HF and induces degradation at room and high temperatures.
Innovation Solution
Incorporating a positive electrode with lithium-iron-phosphate-based oxide and an electrolyte containing an additive represented by Chemical Formula 1, which suppresses side reactions and enhances chemical and physical stability by stabilizing PF5 and reducing the impact of F− ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as lithium salt in the electrolyte, then electrical conductivity and battery performance are improved, but side reactions occur due to decomposition into HF and F− ions, causing degradation in lifespan and stability
Solution Approach 1:
A compound of Formula 1 is introduced as an intermediary substance in the electrolyte. This compound acts as a mediator between LiPF6 and the positive electrode active material, preventing direct harmful interactions. The compound stabilizes PF5 generated during LiPF6 decomposition and prevents F− ions from attacking the positive electrode, thereby eliminating the harmful side reactions while maintaining the electrical conductivity benefits of LiPF6.
Solution Approach 2:
The invention converts the harmful decomposition products of LiPF6 (PF5 and F− ions) into beneficial components. PF5, which would normally cause harm, is stabilized by the compound of Formula 1 to form a protective layer. The F− ions are prevented from causing degradation and instead contribute to forming a stable interface. This transforms the harmful decomposition into a beneficial protective mechanism that enhances lifespan and stability.
2Quantity of substance
If lithium-iron-phosphate-based oxide is used as positive electrode active material, then capacity and energy density are improved, but chemical stability deteriorates due to reactions with F− ions from electrolyte decomposition
Solution Approach 1:
The compound of Formula 1 serves as a protective intermediary between the lithium-iron-phosphate-based oxide and the electrolyte. It prevents F− ions from directly contacting and reacting with the positive electrode active material, thereby preserving the chemical stability of the lithium-iron-phosphate structure while allowing the high capacity and energy density benefits to be fully realized.
Solution Approach 2:
The compound of Formula 1 performs preliminary protective action by forming a stable interface layer on the positive electrode before harmful F− ion attacks can occur. This pre-formed protective barrier prevents the chemical degradation that would otherwise occur during battery operation, ensuring long-term chemical stability while maintaining high capacity.
3Reliability
If conventional electrolyte composition is used, then manufacturing simplicity is maintained, but lifespan characteristics and stability deteriorate at room and high temperatures due to side reactions
Solution Approach 1:
The compound of Formula 1 is added in a specific optimal amount (0.01-5 wt% based on total electrolyte weight) to create a localized protective effect at the electrode-electrolyte interface. This small, targeted addition provides substantial protection against side reactions and degradation without significantly complicating the overall electrolyte formulation or manufacturing process.
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 improves the lifespan characteristics and stability of rechargeable lithium batteries at both room temperature and high temperatures by minimizing side reactions, thereby enhancing overall performance.
Implementation Method 1
the additive represented by Chemical Formula 1, which suppresses side reactions and enhances chemical and physical stability by stabilizing PF5 and reducing the impact of F− ions
Implementation Method 2
The positive electrode and the negative electrode include an active material in which intercalation and deintercalation may occur. The rechargeable lithium battery generates electrical energy through oxidation and reduction reactions if (e.g., when) lithium ions are intercalated and deintercalated.
Implementation Method 3
The rechargeable lithium battery generates electrical energy through oxidation and reduction reactions if (e.g., when) lithium ions are intercalated and deintercalated.
Implementation Method 4
A lithium salt dissolved in a non-aqueous (e.g., water-insoluble) organic solvent is used as the electrolyte of the rechargeable lithium battery.
Data Source
AI summary
A positive electrode and a rechargeable lithium battery including the positive electrode are disclosed. The rechargeable lithium battery may include a positive electrode that includes a positive electrode active material, a negative electrode that includes a negative electrode active material, and an electrolyte that includes a non-aqueous (e.g., water-insoluble) organic solvent, a lithium salt, and an additive represented by Chemical Formula 1. The positive electrode active material may include lithium-iron-phosphate-based oxide.