Lithium Battery Cathode Gradient Ceramic Separator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face issues with thermal instability and safety due to metal component desorption from the cathode electrode at high temperatures and potential ignition from internal short circuits, which affect their lifespan and safety performance.
Innovation Solution
A lithium secondary battery design featuring a cathode electrode with lithium-metal oxide having a concentration gradient of metals between the core and surface parts, combined with a separation film coated with a ceramic layer, enhances both lifespan and safety by reducing thermal instability and preventing rapid heating during external impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium secondary battery uses lithium transition metal oxide or composite oxide as cathode active material, then the battery can provide high capacity and energy density, but the metal component desorbs from the cathode electrode during storage at high temperature, causing thermal instability
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of metal elements within the cathode active material particles. The core region has a different metal composition (higher in stabilizing elements like Mn or Co) compared to the surface region, allowing the core to maintain structural stability at high temperatures while the surface provides high capacity. This spatial variation in composition resolves the contradiction between capacity and thermal stability.
Solution Approach 2:
The patent uses composite materials by combining multiple metal elements (Ni, Co, Mn, and other transition metals) in a controlled concentration gradient within the same cathode active material particle. This composite structure allows different regions of the particle to contribute different properties: the core provides structural stability while the surface provides high capacity, thereby resolving the contradiction between thermal stability and capacity.
2Power
If a forced internal short circuit occurs due to external impact, then the heating value inside the battery rapidly increases, but this causes ignition and safety issues
Solution Approach 1:
The patent applies beforehand cushioning by forming a protective coating layer on the surface of the cathode active material particles before the short circuit occurs. This coating layer, composed of stable metal oxides or compounds, acts as a thermal barrier that slows down the heat generation rate during internal short circuits caused by external impacts. By cushioning the thermal effect in advance, the battery prevents rapid temperature rise and ignition, thereby improving safety while maintaining energy density.
3Stability of the object's composition
If a cathode active material with core-shell structure made of different lithium transition metal oxides is used, then some improvement in stability is achieved, but life-span property and safety still lack sufficient improvement
Solution Approach 1:
The patent applies parameter changes by optimizing the concentration gradient profile of metal elements within the cathode active material particles. Instead of using a sharp core-shell structure, the patent creates a gradual concentration gradient where the composition changes continuously from the core to the surface. This parameter optimization allows for better ion transport kinetics and reduced mechanical stress during cycling, thereby improving life-span property while maintaining the stability benefits of the core-shell structure.
Data Source
AI summary
A lithium secondary battery includes a cathode electrode, an anode electrode, and a separation film installed between the cathode electrode and the anode electrode, wherein the cathode electrode includes a cathode active material containing lithium-metal oxide of which at least one of metals has a concentration gradient region between a core part and a surface part thereof, and the separation film includes a base film and a ceramic coating layer formed on at least one surface of the base film, such that it is possible to achieve a significantly improved effect in both of the lifespan property and penetration durability.