Lithium Battery with Gradient Positive Electrode
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Solution Overview
Problem
Lithium secondary batteries face thermal instability and inadequate lifetime characteristics when used under high temperature conditions due to the separation of metal components from the positive electrode, and existing solutions do not sufficiently enhance storage and lifetime performance.
Innovation Solution
A lithium secondary battery design featuring a positive electrode with a lithium-metal oxide that has a continuous concentration gradient of metals from the center to the surface, combined with a negative electrode using graphite with a specific lattice distance range, which improves thermal stability and extends battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lithium secondary batteries use conventional positive active materials under high temperature conditions, then the battery can operate, but metal components separate from the positive electrode causing thermal instability
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of metal elements within the positive active material particles. The center and surface regions have different metal compositions, with the surface enriched in elements that provide thermal stability while the center maintains high capacity characteristics. This spatial variation in composition allows the material to resist metal component separation and maintain structural integrity at high temperatures.
Solution Approach 2:
The patent uses composite materials by combining multiple metal elements (such as nickel, cobalt, manganese) in a controlled concentration gradient within the same positive active material structure. This composite approach creates a material that exhibits both high capacity and excellent thermal stability, preventing the decomposition and separation issues that occur with conventional single-composition materials at high temperatures.
2Duration of action of moving object
If conventional positive active materials are used, then the battery can function, but lifetime characteristics are insufficient
Solution Approach 1:
The concentration gradient structure creates different local environments within the positive active material particles. The surface region, enriched with specific metal elements, provides enhanced stability and resistance to degradation, while the center region maintains high reactivity. This local differentiation allows the material to sustain long-term cycling without significant capacity loss or structural collapse.
Solution Approach 2:
The patent implements preliminary action by pre-establishing the concentration gradient structure during material synthesis before the battery enters service. This pre-configured compositional distribution prepares the positive active material to resist degradation mechanisms from the outset, preventing metal component separation and structural breakdown that would otherwise occur during high-temperature storage and extended cycling.
3Quantity of substance
If metal components are present in the positive electrode, then high capacity is achieved, but metal separation occurs during high temperature storage
Solution Approach 1:
The patent resolves this contradiction by creating a concentration gradient where metal element distribution varies spatially within the positive active material particles. The surface region is enriched with metal elements that form stable structures at high temperatures, preventing separation, while the center region maintains the composition necessary for high capacity. This local compositional differentiation simultaneously achieves both high capacity and compositional stability.
Solution Approach 2:
The patent employs composite materials by integrating multiple metal elements in a controlled concentration gradient within the positive active material. This composite structure prevents metal component separation by creating a thermodynamically stable distribution where different metal elements are strategically positioned to maintain both high capacity and compositional integrity under high-temperature storage conditions.
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and more particularly, the positive electrode includes a positive active material including lithium-metal oxide in which at least one metal has a continuous concentration gradient from the center to the surface, and the negative electrode includes a negative active material including graphite having an average lattice distance (d002) in the range of 3.356 to 3.365 Å, thereby improving storage characteristics at a high temperature and lifetime characteristics.