Single-Particle Cathode With Rock-Salt Surface for High-Nickel Stability
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Solution Overview
Problem
Current lithium nickel cobalt metal oxides used in lithium secondary batteries suffer from low structural stability and capacity due to nickel oxidation and rapid oxygen desorption, especially when the nickel content is increased to enhance capacity characteristics.
Innovation Solution
A positive electrode active material is developed, comprising a lithium transition metal oxide doped with specific amounts of doping elements like aluminum, titanium, or strontium, with nickel content of 60 mol % or more. This material is synthesized in a single particle form with a layered structure at the center and a rock-salt structure on the surface, and is prepared through a method involving mixing transition metal precursors, lithium sources, and doping element-containing raw materials, followed by sintering at 800° C to 1,000° C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the nickel content is increased to enhance capacity characteristics, then the reversible capacity is improved, but the thermal stability deteriorates and structural stability is reduced
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the center portion has a layered structure optimized for high capacity while the surface portion has a rock-salt structure optimized for stability. This allows different regions of the same particle to have different properties, enabling high nickel content (60-80 mol%) in the bulk for capacity while maintaining a stable surface for thermal reliability.
Solution Approach 2:
The patent uses composite materials by combining two different crystal structures (layered and rock-salt) within the same particle. The layered structure provides high reversible capacity while the rock-salt structure provides thermal and structural stability. This composite approach allows the material to simultaneously achieve high capacity and high reliability.
2Quantity of substance
If the nickel content is increased to enhance capacity characteristics, then the reversible capacity is improved, but the structural stability deteriorates due to nickel oxidation and rapid oxygen desorption
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the center portion has a layered structure optimized for high capacity while the surface portion has a rock-salt structure optimized for stability. This allows different regions of the same particle to have different properties, enabling high nickel content (60-80 mol%) in the bulk for capacity while maintaining a stable surface for thermal reliability.
Solution Approach 2:
The patent uses composite materials by combining two different crystal structures (layered and rock-salt) within the same particle. The layered structure provides high reversible capacity while the rock-salt structure provides thermal and structural stability. This composite approach allows the material to simultaneously achieve high capacity and high reliability.
3Quantity of substance
If LiCoO2 is used to achieve high operating voltage and excellent capacity characteristics, then the capacity is improved, but the cost increases and thermal properties deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the cathode material. Instead of using pure LiCoO2, the patent uses lithium nickel cobalt metal oxide with specific compositional ranges (60-80 mol% nickel, 5-20 mol% cobalt, 5-20 mol% manganese) to achieve a balance between capacity, voltage, and thermal stability.
Solution Approach 2:
The patent uses composite materials by combining nickel, cobalt, and manganese in specific proportions within the lithium nickel cobalt metal oxide structure. This composite approach reduces cobalt content (lowering cost) while maintaining capacity and improving thermal stability through the synergistic effects of multiple metal elements.
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 doped lithium transition metal oxide exhibits improved structural stability and high-capacity characteristics, leading to enhanced life characteristics and reduced risk of thermal instability and internal short circuits in lithium secondary batteries.
Implementation Method 1
a positive electrode active material including a lithium transition metal oxide doped with doping element M2
Implementation Method 2
sintering at 800° C to 1,000° C
Implementation Method 3
sintering at 800° C to 1,000° C
Data Source
AI summary
A positive electrode active material includes a lithium transition metal oxide and a coating element M3-containing coating layer formed on a surface of the lithium transition metal oxide, wherein M3 comprises at least one of Al, Ti, Mg, Zr, W, Y, Sr, or Co, wherein the lithium transition metal oxide is doped with a doping element M2, wherein M2 includes at least one of Al, Ti, Mg, Zr, W, Y, Sr, Co, F, Si, Na, Cu, Fe, Ca, S, or B, wherein the lithium transition metal oxide has a single particle form, and includes a center portion having a layered structure and a surface portion having a rock-salt structure, and the total amount of the doping element M2 and the coating element M3 is in a range of 4,580 ppm to 9,120 ppm based on a total weight of the positive electrode active material.