High-Nickel Cathode Composition Without Coating-Layer Stability Loss
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Solution Overview
Problem
Lithium nickel cobalt manganese oxides used in lithium secondary batteries face limitations in structural stability and capacity when high nickel content is increased, leading to reduced thermal stability and potential battery rupture due to internal short circuits.
Innovation Solution
A method of preparing a positive electrode active material by mixing a nickel cobalt manganese hydroxide precursor with a lithium-containing raw material and a doping compound represented by Li1+x M2< O2+y, and sintering the mixture to achieve a Li1+x [Ni a Me 1-(a+b) M1< b] 1-x O2 structure, which improves structural stability without forming a coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content in lithium nickel cobalt manganese oxide is increased to increase capacity characteristics, then the reversible capacity is improved, but the structural stability is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the doping amount of lithium-containing metal oxide to be 0.001 to 0.05 based on the total amount of transition metals, and controlling the sintering temperature range of 700 to 900°C. This optimization of parameters allows the material to achieve both high nickel content (0.5 < x ≤ 1.0) for high capacity and sufficient structural stability, resolving the contradiction between capacity and stability.
Solution Approach 2:
The patent creates a composite material system by doping lithium-containing metal oxide (such as Li2SiO3, Li2GeO3, Li2TiO3, Li2NbO3, or Li2TaO3) into the lithium nickel cobalt manganese oxide matrix. This composite approach allows the base material to maintain high nickel content for capacity while the doped oxide phases provide structural stabilization, simultaneously achieving high reversible capacity and structural stability.
2Quantity of substance
If the nickel content is increased to achieve high capacity, then the battery capacity is improved, but the thermal stability is reduced leading to potential battery rupture
Solution Approach 1:
The lithium-containing metal oxide acts as an intermediary substance that mediates between the high-nickel cathode material and the harmful thermal effects. The doped oxide forms a stable structure that prevents direct thermal degradation of the nickel-rich material, thereby maintaining high capacity while improving thermal stability and preventing battery rupture.
Solution Approach 2:
The patent applies beforehand cushioning by pre-doping the lithium-containing metal oxide into the cathode material before battery operation. This creates a protective effect in advance that cushions against thermal runaway and internal short circuit damage, allowing the high-capacity nickel-rich material to operate safely without causing battery rupture.
3Stability of the object's composition
If conventional doping methods are used to improve structural stability, then a coating layer is formed, but the energy density is reduced
Solution Approach 1:
The patent applies segmentation by dividing the doping approach into two distinct methods: (1) doping during the sintering process where the lithium-containing metal oxide is incorporated into the bulk crystal structure, and (2) avoiding post-sintering coating applications. This segmentation allows structural stability to be achieved through bulk modification rather than surface coating, thereby maintaining high energy density without the penalty of reduced active material content.
Solution Approach 2:
The patent uses partial action by applying a small, controlled amount of lithium-containing metal oxide doping (0.001 to 0.05 based on total transition metals), which is sufficient to stabilize the structure but minimal enough to avoid significantly reducing the active lithium nickel cobalt manganese oxide content. This partial doping achieves the necessary structural stability while minimizing the impact on energy density.
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 method enhances structural stability and capacity retention at high temperatures, preventing lithium depletion and swelling, thus improving battery life and output characteristics.
Implementation Method 1
sintering the mixture to prepare a positive electrode active material
Data Source
Figure 1
AI summary
The present invention relates to a method of preparing a positive electrode active material, which includes mixing a nickel cobalt manganese hydroxide precursor containing nickel in an amount of 60 mol% or more based on a total number of moles of transition metals, a lithium-containing raw material, and a compound represented by Formula 2 as a doping raw material, and sintering the mixture to prepare a positive electrode active material represented by Formula 1, a positive electrode active material prepared by the method, and a positive electrode for a lithium secondary battery and a lithium secondary battery which include the positive electrode active material: [Formula 1] Li1+x[NiaMe1-(a+b)M1b]1-xO2 [Formula 2] Li1+x1M2O2+y wherein, in Formula 1, 0≤x≤0.1, 0.6≤a≤0.9995, 0.0005≤b≤0.02, 0.6005≤a+b<1, Me includes at least two selected from the group consisting of cobalt (Co), manganese (Mn), and aluminum (Al), and M1 includes at least one selected from the group consisting of lithium (Li), zirconium (Zr), titanium (Ti), tantalum (Ta), silicon (Si), and niobium (Nb), and wherein, in Formula 2, 0≤x1≤7, 1≤y<6, and M2 includes at least one selected from the group consisting of Li, Zr, Ti, Ta, Si, and Nb.