Gradient-Coated Cathode Material for High-Temperature Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining capacity and lifespan stability, especially at high temperatures, due to non-uniform chemical structures in lithium metal oxide cathode active materials, which can lead to short-circuiting and degradation.
Innovation Solution
A lithium secondary battery with a cathode active material featuring a concentration gradient in lithium metal oxide particles coated with aluminum, titanium, and zirconium, along with a specific composition ratio, is developed to enhance thermal stability and performance retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal oxide is used as cathode active material to achieve high capacity and high output, then energy density and power are improved, but thermal stability and chemical uniformity deteriorate leading to short-circuiting and degradation
Solution Approach 1:
The patent applies local quality by creating a concentration gradient within the lithium metal oxide particles, where the composition varies from the core to the surface. This gradient structure allows different regions of the same material to have different properties - the core maintains high lithium content for capacity while the surface has reduced lithium content for improved thermal stability and chemical uniformity, thus resolving the contradiction between energy density and reliability
Solution Approach 2:
The patent uses composite materials by combining lithium metal oxide with other metal oxides (such as nickel, cobalt, manganese) in specific ratios and configurations. This composite approach allows the cathode active material to simultaneously achieve high capacity from lithium metal oxide while gaining thermal stability and structural integrity from the other metal oxides, preventing degradation and short-circuiting
2Quantity of substance
If lithium metal oxide structure is optimized for high capacity, then energy storage capability is improved, but structure transforms or damages during repeated charging-discharging operations degrading lifespan stability
Solution Approach 1:
The concentration gradient structure creates a protective surface layer with reduced lithium content that maintains structural integrity during repeated charging-discharging operations. This surface layer acts as a buffer that prevents structural transformation and damage while allowing the high-capacity core to function, thus maintaining both capacity and lifespan stability
Solution Approach 2:
The patent applies preliminary action by pre-forming the concentration gradient structure and surface modification before the battery enters service. This pre-engineered structure proactively prevents structural degradation during subsequent cycling operations, rather than attempting to repair damage after it occurs, thereby ensuring long-term lifespan stability
Data Source
AI summary
A lithium secondary battery includes a cathode formed of a cathode active material including a lithium metal oxide particle having a concentration gradient, and a coating formed on the lithium metal oxide particle, the coating including aluminum, titanium and zirconium, an anode, and a separator interposed between the cathode and the anode. The cathode active material includes 2,000 ppm to 4,000 ppm of aluminum, 4,000 ppm to 9,000 ppm of titanium and 400 ppm to 700 ppm of zirconium, based on the total weight of the cathode active material. The performance of the secondary battery may be maintained under a high temperature condition.