Lithium-Nickel Cathode Doping for Stability
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Solution Overview
Problem
Lithium secondary batteries with high-nickel based cathode active materials face issues with lifespan and operational stability due to side reactions with the electrolyte and cation disorder, leading to reduced capacity and stability, especially at high temperatures.
Innovation Solution
A lithium-nickel composite metal oxide cathode active material is developed with specific doping elements and ratios, including a first doping element with a +2 oxidation number and a second doping element with a +4 oxidation number, which suppresses nickel cation mixing and enhances structural stability, maintaining high-capacity properties at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-nickel based lithium oxide is used to increase battery capacity, then the energy density and charging rate are improved, but the lifespan and operational stability deteriorate due to side reactions with electrolyte and cation disorder
Solution Approach 1:
The patent introduces magnesium (Mg) and titanium (Ti) elements as intermediary dopants in the cathode material structure. These dopants act as mediators that suppress the harmful side reactions between high-nickel lithium oxide and the electrolyte, while also preventing cation disorder. The Mg and Ti elements are incorporated into the crystal lattice at controlled ratios (0.01-0.06 for Mg, 0.005-0.03 for Ti), creating a stabilized structure that maintains high capacity while improving operational stability and lifespan.
2Quantity of substance
If high-nickel based lithium oxide is used to increase battery capacity, then the energy density is improved, but the structural stability deteriorates due to cation disorder when nickel ions are present at lithium ion sites
Solution Approach 1:
The patent applies local quality modification by introducing Mg and Ti dopants at specific locations within the cathode material's crystal lattice. The Mg element (with oxidation number +2) and Ti element (with oxidation number +4) are doped at controlled concentrations (0.01-0.06 and 0.005-0.03 respectively) to locally stabilize the structure around nickel ions. This localized doping prevents nickel ions from occupying lithium ion sites (cation disorder) while maintaining the overall high-nickel composition needed for high energy density.
3Productivity
If high-nickel based lithium oxide is used to achieve high capacity, then the charging rate is improved, but the high-temperature performance deteriorates due to increased side reactions with electrolyte
Solution Approach 1:
The Mg and Ti dopants serve as intermediary protective layers within the cathode structure, reducing the direct contact and harmful interactions between the high-nickel lithium oxide and the electrolyte. This intermediary doping approach allows the battery to maintain high charging rates enabled by the high-nickel composition, while simultaneously suppressing temperature-dependent side reactions that would otherwise degrade performance and stability.
Data Source
Figure 1~2
AI summary
A cathode active material for a lithium secondary battery according to an embodiment of the present invention includes a lithium-nickel composite metal oxide in which an oxidation number of nickel is 2.8 or more. The lithium-nickel composite metal oxide includes a first doping element having an oxidation number of +2 and a second doping element having an oxidation number of +4. A ratio of a molar ratio of the second doping element relative to a molar ratio of the first doping element is greater than 1 and less than 5.