NCM Positive Electrode Material With Magnesium-Stabilized Core-Shell
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Solution Overview
Problem
Lithium-ion secondary batteries face issues such as deterioration due to oxygen release and cation mixing, leading to increased internal resistance and reduced lifetime, particularly in NCM materials with high nickel content, which also have high cobalt costs.
Innovation Solution
Incorporating magnesium into the NCM structure through a coprecipitation method, followed by multiple heat treatments, to stabilize the positive electrode active material and reduce voids between primary particles, enhancing crystallinity and reducing cracks during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the use amount of nickel is increased to reduce cobalt content, then cost is reduced, but oxygen release and deterioration are more likely to occur
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the central core region contains high-nickel NCM material (Ni:Co:Mn=8:1:1) for high capacity, while the outer shell region contains low-nickel NCM material (Ni:Co:Mn=5:2:3) for stability. This spatial differentiation of material composition allows the battery to simultaneously achieve low cobalt content and high deterioration resistance.
2Quantity of substance
If the use amount of nickel is increased, then capacity is improved, but cation mixing is more likely to occur
Solution Approach 1:
The patent implements local quality through a core-shell structure where the core contains high-nickel material (80% Ni) for high capacity, while the shell contains lower-nickel material (50% Ni) that prevents cation mixing. The shell acts as a protective layer that maintains compositional stability during charging and discharging cycles.
3Shape
If primary particles are aggregated to form secondary particles, then electrode structure is formed, but cracks and miniaturization occur during charging and discharging
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core primary particles aggregate to form the secondary particle structure, while the shell provides a protective framework that accommodates volume changes during lithiation and delithiation. This shell structure prevents crack propagation and maintains particle integrity throughout cycling.
Solution Approach 2:
The patent implements beforehand cushioning by forming a shell layer around the core particles that anticipates and compensates for the volume expansion and contraction that occurs during charging and discharging. This shell acts as a buffer that absorbs mechanical stress and prevents crack formation before they can propagate through the particle structure.
4Shape
If voids between primary particles increase due to crystal changes, then secondary particle structure evolves, but lifetime characteristics deteriorate and resistance increases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the shell region with lower nickel content maintains better structural stability during crystal structure evolution. This stable shell prevents excessive void formation between primary particles, maintaining particle integrity and preventing resistance increase over cycling.
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 method results in a more stable positive electrode active material with improved lifetime characteristics and safety, providing a highly reliable secondary battery with reduced internal resistance and enhanced capacity.
Implementation Method 1
Incorporating magnesium into the NCM structure through a coprecipitation method
Implementation Method 2
followed by multiple heat treatments, to stabilize the positive electrode active material and reduce voids between primary particles
Data Source
AI summary
One embodiment of the present invention provides a novel positive electrode active material, or a highly safe secondary battery. The positive electrode active material is manufactured in such a manner that after a nickel compound (also referred to as a precursor) containing nickel, cobalt, and manganese is obtained by a coprecipitation method, a mixture obtained by mixing a lithium compound and the nickel compound is heated at a first heating temperature, the heated mixture is crushed or ground and then heated at a second heating temperature which is higher than the first temperature, and magnesium is mixed and a third heat treatment is performed.