Lithium Manganese Cathode Conductivity via Composite Carbon
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Solution Overview
Problem
Layer-structured lithium manganese-based oxide cathode active materials experience a decrease in electrical conductivity and capacity in the 3V region due to structural changes after the initial charge and discharge cycle, limiting their output and cycle durability in lithium secondary batteries.
Innovation Solution
A composite cathode active material is formed by combining layer-structured lithium manganese-based oxide with different carbon-based conductive materials, where the carbon materials improve electrical conductivity in the 3.5 V or less potential range, achieved through high-energy milling or other synthesis methods, incorporating a first carbon-based material with a particle diameter of 0.3 µm to 30 µm and a second carbon-based material with a diameter of 10 nm to 500 nm, enhancing the material's structural stability and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If layer-structured lithium manganese-based oxide is used as cathode active material, then high capacity can be achieved, but electrical conductivity decreases in the 3V region after initial charge and discharge cycle
Solution Approach 1:
The patent applies composite materials by combining layer-structured lithium manganese-based oxide with spinel-structured lithium-containing manganese oxide to create a composite cathode active material. This composite structure allows the material to achieve high capacity (over 250 mAh/g) while maintaining electrical conductivity in the 3V region through the spinel phase, resolving the contradiction between capacity and conductivity reliability.
2Quantity of substance
If charging is performed at high voltage of 4.4 V or more to achieve high capacity, then capacity increases, but structural transition to spinel-like structure occurs causing conductivity loss
Solution Approach 1:
The patent applies preliminary action by pre-forming the spinel-structured lithium-containing manganese oxide component in the composite structure before the charging process. This pre-existing spinel phase provides a stable structural framework that prevents unwanted structural transitions during high-voltage charging (4.4V or more), allowing the material to maintain both high capacity and structural stability simultaneously.
3Object-affected harmful factors
If spinel-structured lithium-containing manganese oxide is used, then thermal stability and low cost are achieved, but capacity is low and cycle characteristics are poor
Solution Approach 1:
The patent merges two different manganese oxide structures (layer-structured and spinel-structured) into a single composite cathode active material. The layer-structured component provides high capacity, while the spinel-structured component provides thermal stability and maintains electrical conductivity. This merging allows the composite material to simultaneously achieve thermal stability, high capacity, and good cycle characteristics, overcoming the limitations of using either structure alone.
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 material maintains high capacity and improves output and cycle characteristics by preventing a decrease in electrical conductivity, leading to enhanced performance and stability in lithium secondary batteries, particularly in the 3V region.
Implementation Method 1
the different kinds of carbon-based conductive materials improve electrical conductivity of the lithium manganese-based oxide in a potential range of 3.5 V or less after the initial charging
Implementation Method 2
the cathode active material is obtainable by high-energy milling of the layer-structured lithium manganese-based oxide with the first carbon-based material and the second carbon-based material
Implementation Method 3
lithium deintercalation as well as oxygen release occurs during initial charging in a high voltage range of 4.4 V or more
Data Source
Figure 1
AI summary
The present invention relates to a cathode active material including a lithium manganese-based oxide. Particularly, the present invention relates to a cathode active material characterized in that the lithium manganese-based oxide has a layered crystalline structure; Mn is higher in content than (an)other transition metal(s); 1 mol or more of Li is included for 1 mol of a lithium-transition metal oxide; there is a flat level characteristic in which oxygen is released together with release of lithium during first charging in a high voltage range of 4.4V or higher; domains exhibiting electrochemical activity due to a structural change in a voltage range of 3.5V or lower after the first charging are included the layered crystalline structure; and a conductive material is included to improve the electrical conductivity of the lithium manganese-based oxide in the voltage range of 3.5V or lower after the first charging.