Titanium-Doped NMC Cathode Material for Capacity and Thermal Stability
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Solution Overview
Problem
Existing lithium ion secondary batteries face challenges in achieving both high battery capacity and thermal stability, particularly with high nickel ratios, and existing methods for enhancing thermal stability often compromise battery performance or are difficult to scale industrially.
Innovation Solution
A positive electrode active material comprising lithium-nickel-manganese composite oxide with specific mole ratios and containing titanium, fired under high oxygen concentration, followed by water-washing and drying, to ensure titanium is solid-solved within the particles, enhancing thermal stability while maintaining high capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel ratio is increased to enlarge battery capacity, then the battery capacity is improved, but the thermal stability decreases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior contains high-nickel content for high capacity while the surface is modified with titanium-containing compounds for thermal stability. This allows different regions of the particle to have different compositions optimized for their specific functions.
Solution Approach 2:
The patent uses composite materials by combining lithium-nickel-manganese composite oxide with titanium-containing compounds to create a multi-component system. The titanium-containing compound forms a coating or surface modification layer that provides thermal stability while the bulk material maintains high nickel content for capacity.
2Reliability
If a heterogeneous element such as niobium is added to improve thermal stability, then the thermal stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating titanium at specific ratios (0.01 ≤ z ≤ 0.05 in the molar ratio Li:Ni:Mn:M:Ti = a:(1-x-y-z):x:y:z) to achieve thermal stability. This controlled parameter adjustment allows for systematic optimization without excessive complexity.
3Reliability
If a coating layer is applied to enhance thermal stability, then the thermal stability is improved, but the battery performance decreases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior contains high-nickel content for high capacity while the surface is modified with titanium-containing compounds for thermal stability. This allows different regions of the particle to have different compositions optimized for their specific functions.
Solution Approach 2:
The patent optimizes the thickness and composition of the surface layer by controlling titanium content within specific ranges, ensuring the coating is thin enough to maintain performance while sufficient to provide thermal stability.
4Reliability
If the firing temperature is increased to solid-solve titanium within particles, then the thermal stability is improved, but the energy consumption increases
Solution Approach 1:
The patent optimizes the firing temperature parameter within a specific range (700-950°C) to achieve sufficient solid-solution of titanium without excessive energy consumption. This controlled parameter adjustment balances thermal stability achievement with energy efficiency.
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 proposed material achieves both high thermal stability and battery capacity, suitable for industrial-scale production, by suppressing oxygen release and improving particle structure through controlled firing and washing processes.
Implementation Method 1
a firing step of firing the mixture in an oxidizing atmosphere having an oxygen concentration of 80 vol% or more and 100 vol% or less at 700°C or higher and 950°C or lower so as to obtain the lithium-nickel-manganese composite oxide
Implementation Method 2
firing the mixture in an oxidizing atmosphere having an oxygen concentration of 80 vol% or more and 100 vol% or less
Implementation Method 3
a water-washing step of mixing water at a ratio of 50 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the lithium-nickel-manganese composite oxide and stirring the mixture so as to perform solid-liquid separation
Implementation Method 4
a drying step of drying the water-washed lithium-nickel-manganese composite oxide
Implementation Method 5
the lithium-nickel-manganese composite oxide has a hexagonal layered structure and contains lithium (Li), nickel (Ni), manganese (Mn), an element M, and titanium (Ti)... achieving both high thermal stability and battery capacity
Data Source
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AI summary
There is provided a positive electrode active material with which a lithium ion secondary battery with both high battery capacity and high thermal stability achieved at a high level is obtainable. A positive electrode active material for a lithium ion secondary battery, containing a lithium-nickel-manganese composite oxide configured by secondary particles with a plurality of aggregated primary particles, in which the lithium-nickel-manganese composite oxide has a hexagonal layered structure and contains lithium (Li), nickel (Ni), manganese (Mn), an element M (M), and titanium (Ti), a mole number ratio of elements is represented as Li : Ni : Mn : M : Ti = a : (1 - x - y - z) : x : y : z, provided that 0.97 ≤ a ≤ 1.25, 0.03 ≤ x ≤ 0.15, 0 ≤ y ≤ 0.15, and 0.01 ≤ z ≤ 0.05, a ratio of a total amount of peak intensities of most intense peaks of a titanium compound to a (003) diffraction peak intensity that is the most intense peak of the hexagonal layered structure is 0.2 or less, a crystallite diameter at (003) plane is 80 nm or more and less than 160 nm, and a specific surface area is 0.7 m2/g or more and 4.0 m2/g or less.