Core-Shell Fluoride-Ion Electrodes for Stable Cycling
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Solution Overview
Problem
Existing fluoride-ion battery systems face challenges in achieving stable, reliable long-term cycling due to the reactivity of nano-sized metal or metal fluoride active materials with electrolytes and significant volume changes during charge and discharge.
Innovation Solution
The development of core-shell nanoparticles with a metal core (such as copper) surrounded by a fluoride-containing shell comprising barium and lanthanum, which protects the active material from side reactions and accommodates volume changes during electrochemical processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nano-sized metal or metal fluoride active materials are used in fluoride-ion battery electrodes, then the energy density and electrochemical activity are improved, but the stability and cycling performance deteriorate due to reactivity with electrolytes and volume changes during charge-discharge
Solution Approach 1:
The electrode material is segmented into a core-shell nanoparticle structure where the active metal or metal fluoride core is divided into nano-sized particles (5-50 nm) and surrounded by a protective shell layer. This segmentation allows the interior nano-particles to maintain high electrochemical activity while the exterior shell provides stability and protection against electrolyte degradation.
Solution Approach 2:
A protective shell layer comprising fluorinated compounds (such as metal fluorides, organic fluorinated compounds, or inorganic-organic hybrid fluorinated compounds) is introduced as an intermediary between the active electrode material and the electrolyte. This shell acts as a mediator that prevents direct contact and harmful reactions between the reactive nano-sized active material and the electrolyte, while still allowing ionic conductivity for fluoride ion transport.
2Productivity
If nano-sized active materials are used to increase surface area for electrochemical reactions, then the reaction rate and capacity are improved, but the harmful side reactions with electrolyte increase
Solution Approach 1:
The core-shell structure implements local quality differentiation where the core region maintains nano-sized dimensions for high surface area and fast reaction kinetics, while the shell region provides localized protective properties. The shell's fluorinated compounds are specifically positioned at the interface with the electrolyte to provide chemical stability and prevent side reactions, creating different functional zones within the same particle.
Solution Approach 2:
The electrode material is designed as a composite structure combining the active metal or metal fluoride core with a protective shell of fluorinated compounds. This composite approach integrates the high reactivity of the metal core with the chemical stability of the fluorinated shell, achieving both high productivity and low harmful side reactions.
3Reliability
If solid-state fluoride-conducting electrolytes are used, then the safety characteristics are improved, but the operating temperature must be maintained above room temperature due to limited conductivity
Solution Approach 1:
The patent modifies the electrolyte system by introducing fluoride ion conductive compounds with enhanced ionic conductivity that maintain high performance at lower temperatures. The use of specific fluoride salts and additives changes the conductivity parameter of the electrolyte, enabling safe operation at or near room temperature while maintaining the safety advantages of solid-state systems.
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 core-shell nanoparticle structure enhances the stability and cycling performance of fluoride-ion battery electrodes by preventing unwanted reactions with the electrolyte and allowing for efficient fluoride ion conduction, thereby improving the battery's capacity and longevity.
Implementation Method 1
allowing for efficient fluoride ion conduction
Implementation Method 2
protects the active material from side reactions
Data Source
AI summary
The present disclosure relates to a method of making core-shell and yolk-shell nanoparticles, and to electrodes comprising the same. The core-shell and yolk-shell nanoparticles and electrodes comprising them are suitable for use in electrochemical cells, such as fluoride shuttle batteries. The shell may protect the metal core from oxidation, including in an electrochemical cell. In some embodiments, an electrochemically active structure includes a dimensionally changeable active material forming a particle that expands or contracts upon reaction with or release of fluoride ions. One or more particles are at least partially surrounded with a fluoride-conducting encapsulant and optionally one or more voids are formed between the active material and the encapsulant using sacrificial layers or selective etching. The fluoride-conducting encapsulant may comprise one or more metals. When the electrochemically active structures are used in secondary batteries, the presence of voids can accommodate dimensional changes of the active material.