Nickel-Rich Cathode Surface Layer With 3D CNT Network Stability
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Solution Overview
Problem
Existing nickel-rich positive electrode materials for lithium secondary batteries face limitations in structural and electrochemical stability due to high nickel composition, leading to interfacial reactions with electrolytes and reduced electrical conductivity and thermal stability.
Innovation Solution
A positive electrode active material is developed with a surface layer comprising carbon nanotubes in a three-dimensional reticular form and an organic compound, physically attached to the carbon nanotubes, which enhances electrical conductivity and thermal stability while preventing unnecessary interfacial reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content is increased to increase capacity and reduce cost, then capacity and production cost are improved, but structural and electrochemical stability deteriorate
Solution Approach 1:
The patent applies local quality by creating a surface layer with different composition and properties from the bulk material. The surface layer has reduced nickel content and includes aluminum oxide and carbon components, providing local protection at the critical interface while maintaining high nickel content in the bulk for capacity. This resolves the contradiction by making the surface properties different from the bulk properties.
Solution Approach 2:
The patent uses composite materials by combining nickel-rich lithium transition metal oxide with aluminum oxide and carbon components in a surface layer. This composite structure provides both the high capacity of nickel-rich materials and the stability of aluminum oxide and carbon, resolving the contradiction between capacity and stability.
2Quantity of substance
If nickel content is increased to increase capacity, then capacity is improved, but interfacial reactions with electrolyte increase
Solution Approach 1:
The patent introduces an intermediary surface layer between the nickel-rich positive electrode active material and the electrolyte. This surface layer, containing aluminum oxide and carbon, acts as a mediator that prevents direct contact and harmful reactions between the nickel-rich material and electrolyte, while still allowing ionic transport.
Solution Approach 2:
The patent applies a thin film surface layer (10-100 nm thickness) that flexibly covers the positive electrode active material surface. This thin film provides protection against interfacial reactions while maintaining electrode flexibility and ionic conductivity.
3Quantity of substance
If nickel content is increased to increase capacity, then capacity is improved, but electrical conductivity and thermal stability decrease
Solution Approach 1:
The patent uses composite materials by incorporating carbon components (such as carbon nanotubes or graphene) into the surface layer. This composite structure provides both the high capacity of nickel-rich materials and the electrical conductivity and thermal stability of carbon materials.
Solution Approach 2:
The patent applies local quality by concentrating conductive and thermally stable materials (carbon components, aluminum oxide) at the surface layer, providing local enhancement of electrical conductivity and thermal stability where it is most needed (at the interface and surface) while maintaining high nickel content in the bulk for capacity.
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 proposed solution improves the electrochemical characteristics, cycle stability, and mass production feasibility of lithium secondary batteries by reducing agglomeration, enhancing charge/discharge characteristics, and lowering production costs through reduced binder and conductive material content.
Implementation Method 1
the carbon nanotubes are connected in a reticular form on the surface of the lithium transition metal oxide to form a mutual electrical network
Implementation Method 2
an organic compound physically attached to the carbon nanotubes
Data Source
AI summary
The present invention relates to a positive electrode active material for a lithium secondary battery, comprising a particle-shaped lithium transition metal oxide and a surface layer having a thickness of 10 nm to 100 nm provided on the surface of the lithium-transition metal oxide, wherein: the surface layer comprises carbon nanotubes provided in a three-dimensional reticular form and an organic compound physically attached to the carbon nanotubes; the carbon nanotubes are connected in a reticular form on the surface of the lithium transition metal oxide, forming a mutual electrical network; at least a portion of the carbon nanotubes are spaced apart to provide space in the thickness direction of the surface layer; and 100 parts by weight of the carbon nanotubes contains 30 to 90 parts by weight of the organic compound.