Cathode Active Material Orientation for High-Ni Thermal Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current high-capacity layered positive active materials for lithium secondary batteries, such as LiNiO2, suffer from structural instability and low thermal stability due to oxidation, making them difficult to commercialize, and ternary NCM materials with substituted Ni, Co, and Mn face reduced thermal safety as Ni content increases.
Innovation Solution
A positive active material with lithium metal oxide particles in a secondary particle form, featuring a controlled structure of planar primary particles on the surface and acicular particles inside, where the angle between the c-axis and the surface normal is optimized to suppress electrolyte decomposition and enhance thermal stability, along with a manufacturing method involving pH control in a co-precipitation reactor to achieve a nickel concentration gradient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity layered positive active materials such as LiNiO2 are used to achieve high battery capacity, then the battery capacity increases, but the structure becomes easily destroyed and thermal stability decreases
Solution Approach 1:
The positive active material is divided into primary particles (acicular inside, planar outside) that aggregate into secondary particles. This segmentation allows the interior to maintain high Ni content for capacity while the exterior provides structural stability and thermal safety, resolving the contradiction between capacity and reliability.
Solution Approach 2:
Different regions of the particle have different compositions and morphologies: the interior contains acicular primary particles with high Ni content for capacity, while the exterior contains planar primary particles with stable composition for reliability. This local differentiation resolves the contradiction between high capacity and thermal stability.
2Quantity of substance
If Ni content is increased in ternary NCM materials to achieve higher capacity, then battery capacity improves, but thermal safety is reduced
Solution Approach 1:
The material is segmented into interior and exterior regions with different Ni contents. The interior has high Ni content (0.8-0.95) for capacity, while the exterior has lower Ni content (0.6-0.8) for thermal safety, resolving the contradiction between capacity and thermal safety.
Solution Approach 2:
Different regions have different chemical compositions optimized for their function: high-Ni interior for capacity and low-Ni exterior for thermal stability. This local quality differentiation allows the material to simultaneously achieve high capacity and thermal safety.
3Reliability
If planar primary particles with specific orientation are formed on secondary particle surface to suppress electrolyte decomposition, then thermal stability improves, but manufacturing precision requirements increase
Solution Approach 1:
The manufacturing process controls the angle parameter of primary particles relative to the secondary particle center. By specifying that the angle between the c-axis and the line connecting the virtual center to the center point ranges from 60-90°, the process achieves the desired planar orientation with manageable precision requirements.
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 approach improves thermal safety by reducing side reactions with the electrolyte, as evidenced by increased peak temperature and reduced total heating value in DSC analysis, while maintaining high power characteristics and battery performance.
Implementation Method 1
a method for preparing a positive active material may include obtaining a metal precursor by inputting a metallic salt aqueous solution into a co-precipitation reactor
Implementation Method 2
wherein, in the obtaining of a metal precursor by inputting a metallic salt aqueous solution into a co-precipitation reactor, a pH condition is changed within a range of a reaction end time of 1 to 30 time % with respect to an entire reaction time of 100 time %
Data Source
AI summary
A positive active material, a manufacturing method thereof, and a lithium secondary battery including the same are disclosed, and a positive active material including lithium metal oxide particles in a secondary particle form including primary particles, wherein the secondary particle surface includes planar primary particles with a narrow angle of 70 to 90° from among angles between a c axis of the primary particles and a straight line connecting a virtual point of a center of the primary particle and a center point of the secondary particle may be provided.