NCM Cathode Crystal Structure for Thermal Stability and Cycle Life
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Solution Overview
Problem
Positive electrodes based on lithium nickel composite oxides tend to have low thermal stability and cycling performance when an added element substitutes for nickel, leading to heat generation and oxygen release during charging or discharging.
Innovation Solution
A nickel-cobalt-manganese-based active material with a specific crystal structure ratio c/a of 4.9625 or less, aggregated particle size of 14 μm to 18 μm, and controlled weight decrease in thermal mass spectrometry, ensuring high thermal stability and improved cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an added element substitutes for nickel in lithium nickel composite oxide to improve thermal stability, then thermal stability is improved, but cycling performance becomes lower
Solution Approach 1:
The patent changes the crystal structure parameter (c/a ratio) to a specific range (4.9625 or less) to simultaneously achieve high thermal stability and good cycling performance. This parameter optimization allows the material to maintain structural integrity during cycling while resisting thermal degradation, resolving the contradiction between stability and performance.
Solution Approach 2:
The patent uses a composite lithium nickel cobalt manganese oxide structure where multiple elements work synergistically. The specific composition ratio and crystal structure create a composite material that combines the thermal stability benefits of added elements with the high capacity characteristics of nickel-rich compounds, achieving both improved thermal stability and cycling performance.
2Use of energy by moving object
If lithium nickel composite oxide is used for high capacity, then energy density is improved, but heat generation and oxygen release increase during charging or discharging
Solution Approach 1:
The patent optimizes the c/a ratio parameter to 4.9625 or less, which stabilizes the crystal structure and prevents oxygen release during charging/discharging. This structural parameter control allows the material to maintain high nickel content for energy density while suppressing the harmful effects of heat generation and oxygen release through enhanced structural stability.
Solution Approach 2:
The patent converts the potential harm of nickel-rich materials (heat generation and oxygen release) into benefits by carefully controlling the crystal structure. The optimized c/a ratio transforms the unstable nickel-rich structure into a stable configuration that maintains high capacity while eliminating the harmful thermal and oxygen release effects.
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 solution achieves high thermal stability and cycling performance retention, with a weight decrease ratio per minute of 0.40% or less and cycle capacity retention of 93.3% or more, effectively addressing the limitations of existing materials.
Implementation Method 1
a ratio c/a of a length of an a-axis to a length of a c-axis in a crystal structure as obtained from an X-ray diffraction pattern analysis result is 4.9625 or less
Implementation Method 2
comprising an aggregated particle in which a diameter (D50) of a secondary particle is 14 μm or more and 18 μm or less
Implementation Method 3
a weight decrease amount in thermal mass spectrometry at a temperature of 120 to 600° C. and a temperature increase rate of 5° C./min is 12 mass % or less
Data Source
AI summary
The present disclosure relates to: a positive electrode NCM (nickel-cobalt-manganese)-based active material in which a ratio c/a of a length of an a-axis to a length of a c-axis in a crystal structure as obtained from an X-ray diffraction pattern analysis result is 4.9625 or less; a positive electrode including the positive electrode NCM-based active material; and a battery including the positive electrode. According to the present disclosure, there are provided: the positive electrode NCM-based active material that can exhibit an improved cycling performance as well as high thermal stability; the positive electrode including the positive electrode NCM-based active material; and the battery including the positive electrode.