Monoclinic Lithium Metal Oxide Coating for Cathode Stability
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Solution Overview
Problem
Lithium ion batteries experience capacity loss and poor cycling life due to irreversible changes in cathode active materials during charging and discharging cycles, primarily caused by reactions between the cathode active material and organic solvents, which affect the stability and conductivity of the materials.
Innovation Solution
A cathode composite material is developed by coating a lithium metal oxide with a monoclinic crystal structure onto the surface of lithium transition metal oxide particles, forming a core-shell structure that prevents direct contact with the electrolyte and enhances chemical and thermal stability, using a method involving a composite precursor and lithium source chemical compounds to create a uniform and integrated coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cathode active material is left untreated, then the manufacturing process is simple, but the cycling stability and conductivity are poor
Solution Approach 1:
The patent applies composite materials by coating lithium metal oxide (such as Li2TiO3, Li2SnO3, Li2PbO3, Li2TeO3, Li2RuO3, Li2HfO3, or Li2ZrO3) on the surface of the cathode active material particles. This creates a core-shell structure where the core is the cathode active material and the shell is the lithium metal oxide coating layer, combining the high capacity of the core material with the stability and conductivity enhancement of the coating layer.
Solution Approach 2:
The patent uses a thin film coating approach where lithium metal oxide forms a protective shell on the cathode active material surface. This thin film structure maintains the electrochemical activity of the core material while providing a stable interface with the electrolyte, preventing direct contact and unwanted reactions between the cathode material and organic solvent.
2Reliability
If carbon coating is applied to improve conductivity, then the conductive properties are enhanced, but the cycling stability problem is not properly solved
Solution Approach 1:
The lithium metal oxide coating layer acts as an intermediary between the cathode active material and the organic solvent electrolyte. It provides a stable interface that prevents direct harmful reactions between the cathode material and electrolyte, while still allowing lithium ion transport. The coating materials mentioned (Li2TiO3, Li2SnO3, Li2PbO3, Li2TeO3, Li2RuO3, Li2HfO3, Li2ZrO3) all serve as effective intermediaries.
Solution Approach 2:
The lithium metal oxide coating creates an inert environment around the cathode active material, protecting it from direct contact with the organic solvent electrolyte. This inert barrier prevents oxidation and other unwanted side reactions, especially when the cathode material is in a lithium ion deintercalation state with high oxidability.
3Stability of the object's composition
If a coating layer is formed to prevent reactions, then the chemical stability is improved, but the lithium ion mobility may be reduced
Solution Approach 1:
The patent optimizes the coating thickness and composition to balance chemical stability and lithium ion mobility. The coating layer thickness is controlled to be sufficient for protection but thin enough to allow efficient lithium ion transport. The specific lithium metal oxide materials selected (such as Li2TiO3, Li2SnO3, etc.) have crystal structures that facilitate lithium ion diffusion, maintaining good rate performance while providing stability.
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 cathode composite material significantly improves the cycle performance and stability of lithium ion batteries, maintaining discharge specific capacities even at high current rates and after multiple charge/discharge cycles, while reducing side reactions and enhancing lithium ion mobility.
Implementation Method 1
coating a lithium metal oxide with a monoclinic crystal structure onto the surface of lithium transition metal oxide particles, forming a core-shell structure that prevents direct contact with the electrolyte
Implementation Method 2
using a method involving a composite precursor and lithium source chemical compounds to create a uniform and integrated coating layer
Data Source
AI summary
A cathode composite material includes a cathode active material and a coating layer coated on a surface of the cathode active material. The cathode active material includes a layered type lithium nickel cobalt manganese oxide. The coating layer comprises a lithium metal oxide having a crystal structure belonging to C2/c space group of the monoclinic crystal system. The present disclosure also relates to a lithium ion battery including the cathode composite material.