NCM Cathode Crystal Ratio Tuning for Thermal Stability and Low-SOC Output
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Solution Overview
Problem
Positive electrodes based on lithium nickel composite oxides tend to have low thermal stability and low-temperature low-SOC output properties, which are compromised when elements are added to improve thermal stability.
Innovation Solution
A nickel-cobalt-manganese-based active material with a specific crystal structure ratio c/a of 4.9631 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 low-temperature low-SOC output properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an added element substitutes for a nickel element to improve thermal stability, then thermal stability is improved, but low-temperature low-SOC output property deteriorates
Solution Approach 1:
The invention changes the crystal structure parameter (c/a ratio) to a specific range (4.9550 or less and 4.9650 or more) to simultaneously achieve high thermal stability and good low-temperature low-SOC output properties without adding elements that would compromise performance
Solution Approach 2:
The invention uses a composite approach by combining specific element ratios (Ni: 0.60-0.80, Co: 0.10-0.30, Mn: 0.10-0.30) with controlled crystal structure parameters to create a material that achieves both thermal stability and electrical performance
2Quantity of substance
If a lithium nickel composite oxide is used to achieve high capacity, then capacity is improved, but thermal stability deteriorates
Solution Approach 1:
The invention controls the c/a ratio parameter within a specific range to stabilize the crystal structure, preventing oxygen release and heat generation while maintaining high nickel content for high capacity
Solution Approach 2:
The invention optimizes the local atomic arrangement by controlling the c/a ratio, which affects the local stability of the crystal structure and prevents thermal degradation while maintaining high capacity
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 both high thermal stability and enhanced low-temperature low-SOC output performance, with a weight decrease ratio per minute of 0.40% or less and low-temperature low-SOC output resistance of 4.670Ω or less, 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
Implementation Method 2
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
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 low-temperature low-SOC output property as well as high thermal stability; the positive electrode including the positive electrode NCM-based active material; and the battery including the positive electrode.