Lead Fluoride Coated Negative Electrode for Battery Durability
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Solution Overview
Problem
Lithium ion batteries with fluorine-containing solvents suffer from low durability due to reductive decomposition at the negative electrode, leading to decreased cycle characteristics and battery capacity.
Innovation Solution
A negative electrode material with a fluoride ion conductor coating, composed of lead and fluorine, is applied to the surface of the negative electrode active material, preventing electron transfer and reducing reductive decomposition, thereby enhancing durability and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine-containing solvent is used in electrolyte, then oxidation resistance is improved, but reductive decomposition at negative electrode increases
Solution Approach 1:
A fluoride ion conductor coating layer is introduced as an intermediary between the negative electrode active material and the fluorine-containing electrolyte solvent. This coating layer selectively conducts fluoride ions while blocking electron transfer to the solvent, thereby preventing reductive decomposition while maintaining the high oxidation resistance benefits of the fluorine-containing solvent.
Solution Approach 2:
The negative electrode is given different properties at different locations: the inner core (negative electrode active material) provides high electron conductivity for electrochemical reactions, while the outer surface (fluoride ion conductor coating) provides selective ion conductivity and electron blocking properties. This local differentiation allows simultaneous achievement of high oxidation resistance and prevention of reductive decomposition.
2Reliability
If fluoride ion conductor coating is applied to negative electrode, then reductive decomposition is suppressed, but internal resistance increases
Solution Approach 1:
The fluoride ion conductor coating is optimized by controlling key parameters including thickness (1-100 nm), composition ratios (PbF2-SnF2 solid solution with specific x values), and crystalline structure. By adjusting these parameters, the coating achieves optimal balance between blocking electron transfer (preventing decomposition) and conducting fluoride ions (maintaining low resistance).
Solution Approach 2:
The fluoride ion conductor coating is designed as a composite material system based on PbF2-SnF2 solid solution. This composite structure combines the advantages of both components: PbF2 provides high fluoride ion conductivity, while SnF2 enhances structural stability and adjusts the electron blocking properties. The composite material achieves optimal performance in preventing reductive decomposition while maintaining low internal resistance.
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 fluoride ion conductor coating suppresses reductive decomposition, resulting in improved cycle durability and capacity retention, even with fluorine-containing solvents, and increases energy density by reducing internal resistance.
Implementation Method 1
The coating material is a fluoride ion conductor that includes the elements lead and fluorine... This makes it easier for negative charge to build up at the surface of the negative electrode (specifically, the interface of the negative electrode with the electrolyte) in the state of fluoride ions rather than electrons
Data Source
AI summary
One aspect of the invention provides a negative electrode material for use in an electrolyte battery including a negative electrode active material and a coating material disposed on a surface of the negative electrode active material. The coating material is a fluoride ion conductor that includes the elements lead and fluorine.