Core-Shell Electrode Nanoparticles for Fluoride-Ion Cycling Stability
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Solution Overview
Problem
Fluoride-ion batteries face challenges in achieving stable, reliable long-term cycling due to high surface energies of nano-sized metal or metal fluoride active materials, which are reactive with electrolytes, and significant volume changes during electrochemical processes, limiting the effectiveness of conformal protective coatings.
Innovation Solution
The development of core-shell nanoparticles with a metal core surrounded by a metal halide or oxyhalide shell, which protects the active material from side reactions and accommodates volume changes, allowing ion conduction and maintaining conductivity, using a method that involves synthesizing metal nanoparticles in the presence of a removable stabilizer and forming a fluoride-containing shell to encapsulate the core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conformal protective coatings are applied to nano-sized metal or metal fluoride active materials, then the materials are protected from side reactions with electrolytes, but the coatings cannot accommodate significant volume changes during electrochemical processes
Solution Approach 1:
The patent employs a non-conformal shell structure that is decoupled from the core particle, allowing the shell to flex and accommodate volume changes during electrochemical cycling. The shell is attached at discrete attachment points rather than maintaining continuous conformal contact, enabling it to deform elastically as the core expands or contracts during charge-discharge cycles while still providing protective coverage.
2Productivity
If nano-sized metal or metal fluoride active materials are used to increase surface area for ion exchange, then ion exchange efficiency is improved, but surface energy increases making the materials highly reactive with electrolytes
Solution Approach 1:
A protective shell is formed over the nanoparticle core, creating a physical barrier that prevents direct contact between the reactive metal or metal fluoride surface and the electrolyte. This shell maintains the nanoparticle's high surface area for efficient ion exchange while eliminating the harmful reactivity through physical isolation.
Solution Approach 2:
The patent creates a composite structure consisting of a metal or metal fluoride core combined with a protective shell material. This composite architecture combines the desirable properties of the core (high ion exchange efficiency due to nanoparticle size) with the protective properties of the shell (chemical stability and low reactivity with electrolytes).
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 nanoparticles enhance the stability and conductivity of fluoride-ion battery electrodes, enabling reliable long-term cycling and efficient ion exchange, while protecting the active material from environmental degradation and volume changes.
Implementation Method 1
allowing ion conduction and maintaining conductivity
Implementation Method 2
accommodates volume changes
Data Source
Figure 1A
Figure 1B~1C
Figure 1D~1E
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. When the electrochemically active structures are used in secondary batteries, the presence of voids can accommodate dimensional changes of the active material.