Gradient Positive Active Material for Lithium Battery Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion batteries face challenges with high cost, safety concerns, and thermal instability due to the use of materials like LiCoO2 and LiNiO2, which have unstable crystal structures and react poorly with electrolytes, limiting their application in high-capacity and high-temperature environments.
Innovation Solution
A positive active material for lithium batteries is developed with a continuous concentration gradient of metal composition, featuring an internal bulk part with high capacity and an external bulk part providing thermal stability, where nickel, manganese, and cobalt are distributed in a controlled gradient to enhance thermal safety and cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 or LiNiO2 is used as positive active material, then high discharge capacity is achieved, but thermal stability deteriorates due to unstable crystal structure and oxygen emission at high temperature
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of metal elements within the positive active material particles. The center region contains higher nickel content for high discharge capacity, while the outer layer has higher cobalt and manganese content for thermal stability. This spatial variation in composition allows different regions to perform different functions simultaneously.
Solution Approach 2:
The patent creates a composite structure within the positive active material by combining multiple metal elements (nickel, cobalt, manganese) in a controlled concentration gradient. This composite approach integrates the high capacity benefits of nickel-rich regions with the thermal stability benefits of cobalt and manganese-rich regions, resolving the contradiction between capacity and stability.
2Quantity of substance
If nickel content is increased to improve discharge capacity, then energy density increases, but reactivity with electrolyte increases causing safety issues
Solution Approach 1:
The patent uses local quality by concentrating nickel in the center region where high energy density is needed, while placing cobalt and manganese in the outer layer that contacts the electrolyte. This spatial separation ensures high energy density without sacrificing safety, as the reactive nickel is protected by the more stable outer layer.
Solution Approach 2:
The patent introduces cobalt and manganese as intermediary elements in the outer layer that act as a buffer between the high-nickel core and the electrolyte. These intermediary elements reduce the direct reactivity between nickel and the electrolyte while maintaining the overall high capacity of the material.
3Reliability
If cobalt is used to improve thermal stability, then safety increases, but cost and toxicity increase
Solution Approach 1:
The patent applies local quality by concentrating cobalt only in the outer layer where thermal stability is most needed, rather than distributing it uniformly throughout the entire material. This localized approach reduces the overall cobalt content and cost while maintaining thermal stability at the critical surface region.
Solution Approach 2:
The patent merges cobalt with manganese in the outer layer to achieve thermal stability. This combination allows for reduced cobalt content since manganese also contributes to stability, thereby lowering cost and improving availability while maintaining the required thermal performance.
4Ease of manufacture
If uniform metal composition is used throughout the particle, then manufacturing is simplified, but surface reactivity with electrolyte increases reducing cycle life
Solution Approach 1:
The patent implements local quality by creating a non-uniform concentration gradient of metal elements within the particles. The outer layer has higher cobalt and manganese content specifically to reduce surface reactivity with the electrolyte, while the center maintains high nickel content for capacity. This targeted composition improvement extends cycle life without making manufacturing prohibitively complex.
Data Source
AI summary
The present invention relates to a positive active material for a lithium battery, a method of preparing the same, and a lithium battery including the same. More particularly, the present invention relates to a positive active material having excellent high-capacity and thermal stability, a method of preparing the same, and a lithium battery including the same.