Core-Shell Metal Fluoride Cathode for High-Capacity Lithium Batteries
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Solution Overview
Problem
Current metal-ion batteries, particularly those using fluoride-based cathodes, face challenges such as poor stability, volume changes, slow charging, high impedance, and rapid irreversible capacity losses due to limitations in electrical and ionic conductivity, as well as degradation mechanisms like metal dissolution and electrolyte decomposition, which hinder their practical application in high-energy density applications.
Innovation Solution
The development of a Li metal or Li-ion battery with a conversion-type metal fluoride cathode comprising core-shell particles and a solid electrolyte with a Li transference number between 0.7 and 1.0, which enhances electrical and ionic conductivity, stability, and capacity utilization by using composite cathode materials with a core-shell architecture and specific electrolyte compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conversion-type metal fluoride cathodes are used to achieve high energy density, then gravimetric and volumetric capacities are improved, but electrical conductivity and ionic conductivity deteriorate
Solution Approach 1:
The patent employs composite cathode materials consisting of metal fluoride particles coated with conductive materials (such as carbon coatings or metal nanoparticle shells). This composite structure combines the high capacity of metal fluorides with the high conductivity of the coating materials, simultaneously achieving both high energy density and good electrical/ionic conductivity.
Solution Approach 2:
The patent applies different materials to different parts of the cathode structure: the core metal fluoride particles provide high capacity, while the surface coating layers provide high conductivity. This local differentiation of material properties allows each region to optimize its function, resolving the contradiction between capacity and conductivity.
2Quantity of substance
If metal fluoride cathodes operate at high potentials to achieve high energy density, then capacity is improved, but metal dissolution and electrolyte decomposition increase
Solution Approach 1:
The patent introduces a protective coating layer as an intermediary between the metal fluoride cathode and the electrolyte. This coating acts as a barrier that prevents direct contact and harmful reactions, blocking metal dissolution and electrolyte decomposition while still allowing lithium ion transport, thus enabling high potential operation without the associated degradation.
Solution Approach 2:
The patent converts the harmful high potential that causes metal dissolution into a beneficial feature by coating the cathode with materials that are stable at high potentials. The coating material's stability at high potentials becomes the protective mechanism that enables the system to operate at high energy density without the harmful side effects.
3Ease of manufacture
If conventional electrolytes are used with metal fluoride cathodes, then cell assembly is simplified, but irreversible capacity losses and degradation increase
Solution Approach 1:
The patent modifies the electrolyte composition by adjusting parameters such as salt concentration, solvent ratios, and additive types to optimize performance with metal fluoride cathodes. These parameter changes improve cycle stability and reduce irreversible capacity losses while maintaining ease of cell assembly and manufacturing.
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
This solution improves the stability, energy density, and rate performance of fluoride-based cathodes, enabling higher capacity and energy storage while minimizing irreversible capacity losses and degradation, thus making them suitable for advanced applications like electric vehicles and energy grids.
Implementation Method 1
a solid electrolyte with a Li transference number in the range from around 0.7 to around 1.0 impregnating at least the cathode
Implementation Method 2
Conversion-type electrodes, such as metal fluorides, metal chlorides, metal iodides, metal sulfides, sulfur, oxides, metal nitrides, metal phosphides, metal hydrides and others for Li-ion batteries offer high gravimetric and volumetric capacities. In these electrodes, so-called conversion reactions take place when metal ions such as Li are inserted or extracted during battery operation.
Data Source
AI summary
An embodiment is directed to a Li metal or Li-ion battery, including a conversion-type metal fluoride comprising cathode capable of storing and releasing Li ions during battery operation, a conversion-type type or Li metal-type anode capable of storing and releasing Li ions during battery operation, a separator membrane ionically coupling and electronically insulating the cathode and the anode, and a solid electrolyte with a Li transference number in the range from around 0.7 to around 1.0 impregnating at least the cathode, wherein the cathode comprises composite a core-shell particle and has an areal capacity loading that ranges from around 2 mAh/cm2 to around 12 mAh/cm2.