Zirconium-Coated Cathode Material for Crack-Resistant Li-Ion Batteries
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Solution Overview
Problem
Conventional methods of doping or coating lithium transition metal oxides fail to effectively prevent cracks and fine powder formation in positive electrode active materials, leading to capacity reduction and instability during charging/discharging.
Innovation Solution
A method of producing a positive electrode active material by mixing lithium transition metal oxides with a zirconium-containing raw material and a sintering aid, followed by heat treatment to form a zirconium-containing coating film on the surface and inner interfaces of the secondary particle, preventing cracks and fine powder formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional doping or coating methods are used to improve physical properties of positive electrode active material, then thermal stability is improved, but cracks and fine powder generation still occur leading to capacity deterioration
Solution Approach 1:
The patent applies local quality by using a core-shell structure where the inner core contains lithium transition metal oxide with high reversible capacity and the outer shell contains aluminum oxide coating. This shell structure specifically addresses the crack prevention issue at critical locations (particle surfaces and interfaces) without requiring bulk modification of the entire material, thereby preventing cracks and fine powder generation while maintaining thermal stability improvements.
Solution Approach 2:
The patent employs composite materials by combining lithium transition metal oxide (providing high reversible capacity) with aluminum oxide coating (providing structural stability and crack resistance). This composite structure integrates the advantages of both materials: the core provides electrochemical performance while the shell provides mechanical strength and prevents particle degradation, effectively solving both thermal stability and crack prevention requirements.
2Reliability
If non-transition metal elements are doped into lattice to improve physical properties, then thermal stability is enhanced, but capacity properties deteriorate due to substitution at transition metal sites
Solution Approach 1:
The patent applies local quality by concentrating the aluminum oxide coating at the particle surfaces and interfaces rather than doping aluminum into the bulk crystal lattice. This localized approach provides thermal stability enhancement where it is most needed (at surfaces exposed to electrolyte and at interfaces between primary particles) without substituting transition metal atoms in the bulk, thereby preserving the high reversible capacity of the lithium transition metal oxide core.
Solution Approach 2:
The aluminum oxide coating acts as an intermediary layer between the lithium transition metal oxide particles and the external environment (electrolyte, pressure, thermal stress). This shell protects the core material from degradation while allowing lithium ion transport, providing thermal stability without requiring direct substitution of transition metal sites, thus maintaining high reversible capacity.
3Quantity of substance
If lithium nickel composite metal oxide is used to achieve high reversible capacity, then capacity properties are improved, but thermal stability decreases leading to safety issues
Solution Approach 1:
The patent uses composite materials by creating a core-shell structure where lithium nickel composite metal oxide forms the core (providing high reversible capacity of about 200 mAh/g) and aluminum oxide forms the outer shell (providing thermal stability). This composite structure allows the material to simultaneously achieve high capacity from the nickel-based core and improved thermal stability from the aluminum oxide shell, preventing the safety issues associated with low thermal stability of pure lithium nickel oxide.
Solution Approach 2:
The patent applies local quality by placing aluminum oxide coating specifically at the particle surfaces and interfaces where thermal degradation and crack initiation are most likely to occur. This localized protection allows the bulk lithium nickel composite metal oxide to maintain its high reversible capacity while the coated regions provide enhanced thermal stability and structural integrity during charging/discharging cycles.
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 zirconium-containing coating film effectively prevents cracks and fine powder formation, maintaining excellent capacity properties and lifespan characteristics of the positive electrode active material.
Implementation Method 1
heat treating the mixture to form a zirconium-containing coating film on the surface of the lithium transition metal oxide secondary particle and at the interface between the primary particles
Implementation Method 2
heat treating the mixture to form a zirconium-containing coating film
Data Source
AI summary
A positive electrode active material contains a lithium transition metal oxide in the form of a secondary particle in which primary particles are aggregated, wherein a zirconium-containing coating film is formed on the surface of the lithium transition metal oxide secondary particle and at the interface between the primary particles present inside the secondary particle. A method of making the positive electrode active material is also provided.