Nickel-Rich NCM Cathode Surface Phases for Thermal Stability
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Solution Overview
Problem
Lithium-cobalt oxide-based positive electrode materials face challenges due to high cobalt prices and supply instability, while nickel-rich NCM-based materials suffer from degraded thermal stability and increased resistance due to side reactions, necessitating improved thermal stability and reduced resistance in secondary batteries.
Innovation Solution
A nickel-rich NCM-based lithium composite transition metal oxide is formed as single particles with specific crystal structures and surface characteristics, enhancing thermal stability and suppressing side reactions, thereby improving charge/discharge efficiency and high-temperature lifetime characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel content is increased in NCM-based lithium composite transition metal oxide to increase capacity, then battery capacity is improved, but thermal stability is degraded and side reactions increase
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high nickel content (0.8-0.95) for high capacity, while the surface region contains lower nickel content (0.5-0.8) for improved thermal stability. This spatial differentiation of composition allows each region to optimize its function: the core provides capacity while the surface provides stability.
Solution Approach 2:
The patent uses composite materials by combining nickel-rich NCM phase with lithium nickel oxide (LiNiO2) phase at the surface. This composite structure leverages the high capacity of nickel-rich NCM in the bulk while utilizing the superior thermal stability of LiNiO2 at the surface, creating a synergistic effect that resolves the contradiction between capacity and stability.
2Quantity of substance
If nickel content is increased in NCM-based lithium composite transition metal oxide to increase capacity, then battery capacity is improved, but resistance increases due to side reactions
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the core region contains high nickel content (0.8-0.95) for high capacity, while the surface region contains lower nickel content (0.5-0.8) for improved thermal stability. This spatial differentiation of composition allows each region to optimize its function: the core provides capacity while the surface provides stability.
Solution Approach 2:
The patent uses composite materials by combining nickel-rich NCM phase with lithium nickel oxide (LiNiO2) phase at the surface. This composite structure leverages the high capacity of nickel-rich NCM in the bulk while utilizing the superior thermal stability of LiNiO2 at the surface, creating a synergistic effect that resolves the contradiction between capacity and stability.
3Productivity
If over-firing is performed to minimize secondary particle interface and improve surface characteristics, then charge/discharge efficiency is improved, but performance deterioration occurs if over-firing is not properly controlled
Solution Approach 1:
The patent applies parameter changes by precisely controlling the firing temperature range (900-1000°C) and time (1-24 hours) to achieve the desired phase transformation. By optimizing these parameters, the patent transforms secondary particles into single particles with the specific core-shell structure, improving charge/discharge efficiency while avoiding performance deterioration from excessive firing.
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 results in enhanced thermal stability, reduced resistance, and improved charge/discharge efficiency, output characteristics, and high-temperature lifetime performance of secondary batteries.
Implementation Method 1
a 100-nm region extending from the surface toward the center of a single particle of the lithium composite transition metal oxide has crystal structures of a Fd3M space group and a Fm3m space group
Data Source
AI summary
A positive electrode active material, and a positive electrode and a lithium secondary battery including the same are disclosed herein. In some embodiments, a positive electrode active material includes a lithium composite transition metal oxide containing nickel, cobalt, and manganese and having a nickel content for 60 mol % or more, based on metals (M) excluding lithium, and is in the form of single particles having an average particle diameter (D50) of 1 to 10 μm, wherein a 100-nm region extending from the surface toward the center of a single particle has crystal structures of a Fd3M and a Fm3m space group, and a phase ratio is 0.2 to 0.7, which is a ratio of a first portion of a maximum straight length of the 100-nm region occupied by the crystal structure of the Fd3M space group to a second portion occupied by the crystal structure of the Fm3m space group.