Composite Cathode Coated with Carbon Nanostructures and Inert Shell
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Solution Overview
Problem
Lithium ion batteries face challenges in maintaining high energy density and long lifetime due to issues with cathode active materials, including decreased specific capacity, increased interfacial resistance, and oxidation of electrolytes at high voltages, which affect charge/discharge rate and lifetime characteristics.
Innovation Solution
A composite cathode active material is developed, comprising a lithium-intercalation capable composite oxide core coated with a shell of carbon nanostructures and a chemically inert material, such as Al2O3 or AlF3, to prevent electrolyte oxidation and improve conductivity, thereby enhancing charge/discharge rate and lifetime characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating material such as electrochemically stable oxide or phosphate is used to coat the cathode surface, then structural stability and thermostability are improved, but specific capacity decreases due to the coating material not being directly involved in charge/discharge reaction
Solution Approach 1:
The patent applies composite materials by combining carbon nanostructures (graphite, amorphous carbon, carbon nanotubes) with the cathode active material to form a composite structure. This composite approach provides both structural stability and maintains high specific capacity through the carbon component's involvement in lithium intercalation, resolving the contradiction between stability and capacity.
Solution Approach 2:
The patent uses thin film coatings of carbon nanostructures on the cathode surface. These thin film shells provide protective functionality while minimizing the volume occupied by non-active material, thereby maintaining high specific capacity compared to bulk coating materials.
2Reliability
If a coating material is applied to the cathode surface, then ion elution and oxygen ion dissolution are prevented, but active reaction area decreases and interfacial resistance increases
Solution Approach 1:
The patent employs porous carbon nanostructure coatings that provide a high surface area-to-volume ratio. The porous structure maintains numerous active reaction sites while providing protective functionality, thereby preventing ion elution without significantly increasing interfacial resistance or reducing active reaction area.
Solution Approach 2:
Thin film carbon coatings are applied to the cathode surface, providing a protective barrier against ion elution while minimizing the thickness to maintain adequate active reaction area and low interfacial resistance.
3Use of energy by moving object
If high-voltage cathode active material is used to increase energy density, then energy density is improved, but electrolyte oxidation and conductivity deterioration occur
Solution Approach 1:
The patent introduces carbon nanostructures as an intermediary layer between the high-voltage cathode active material and the electrolyte. This intermediary provides electrochemical stability, prevents electrolyte oxidation, and maintains conductivity, enabling the use of high-voltage materials to achieve high energy density without the associated harmful effects.
4Use of energy by moving object
If high-voltage cathode active material is used to increase energy density, then energy density is improved, but conductivity deteriorates
Solution Approach 1:
The patent creates composite materials by combining high-voltage cathode active material with conductive carbon nanostructures. The carbon component compensates for conductivity deterioration while allowing the high-voltage material to maintain high energy density, effectively resolving the contradiction between energy density and conductivity.
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 composite cathode active material improves charge/discharge rate and lifetime characteristics by preventing electrolyte oxidation and reducing interfacial resistance, maintaining high energy density and stability even at high temperatures.
Implementation Method 1
The coating material blocks direct contact between a cathode surface and an electrolyte
Implementation Method 2
a composite oxide core capable of intercalation and deintercalation of lithium
Implementation Method 3
a material which is chemically inert to lithium
Data Source
AI summary
A composite cathode active material including: a composite oxide capable of intercalation and deintercalation of lithium; a carbon nanostructure; and a material which is chemically inert to lithium.