Porous Coordination Polymer Coated Lithium Composite Cathode
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Solution Overview
Problem
Lithium secondary batteries face limitations in high electrode density, lifetime properties, and high-temperature stability due to degradation of active materials and increased internal resistance, particularly in nickel-based materials like LiNiO2, which have poor structural stability and low thermal stability.
Innovation Solution
A positive electrode active material is developed with a core of lithium composite metal oxide coated with a porous coordination polymer, where the central metal ion is coordinate-bonded with an organic ligand, enhancing structural stability and thermal properties through a surface treatment layer that reduces material resistance and improves output properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-based positive electrode active materials (LiNiO2) are used to achieve high discharge capacity, then initial discharge capacity is improved (180-200 mAh/g), but structural stability deteriorates causing rapid capacity decrease during continuous charging and discharging
Solution Approach 1:
The patent applies composite materials by combining nickel-based active material with a surface coating layer consisting of lithium transition metal oxide. This composite structure allows the core nickel-based material to provide high discharge capacity while the outer coating layer provides structural stability and prevents degradation during charging-discharging cycles, thus resolving the contradiction between high capacity and structural stability.
Solution Approach 2:
The patent applies local quality by creating a concentration gradient in the surface coating layer, where the composition varies from the core to the surface. The coating layer has a gradient structure with different lithium and transition metal oxide concentrations, providing enhanced structural stability at the surface while maintaining the high-capacity nickel-based core, thus resolving the contradiction between capacity and stability.
2Temperature
If lithium manganese oxides (LiMnO2, Li2MnO3, LiMn2O4) are used to achieve excellent thermal stability and low cost, then thermal stability is improved, but capacity deteriorates with low discharge capacity
Solution Approach 1:
The patent applies composite materials by creating a core-shell structure where the core is lithium manganese oxide providing thermal stability and the shell is a nickel-rich lithium transition metal oxide providing high discharge capacity. This composite structure allows simultaneous achievement of thermal stability from the manganese oxide core and high capacity from the nickel-based shell.
3Stability of the object's composition
If cobalt is added to LiNiO2 to achieve structural stability, then structural stability is improved, but capacity deteriorates with a relative decrease in capacity when cobalt content is at least 30 mol %
Solution Approach 1:
The patent applies local quality by creating a concentration gradient where cobalt content varies spatially within the material. The surface coating layer has a different composition than the core, with the gradient structure allowing structural stability to be concentrated at the surface while maintaining high nickel content in the core for high capacity, thus resolving the contradiction between stability and capacity.
4Duration of action of stationary object
If LiCoO2 with layered structure is used to achieve excellent lifetime properties and charge-discharge efficiency, then lifetime properties are improved, but capacity deteriorates with low discharge capacity compared to nickel-based materials
Solution Approach 1:
The patent applies composite materials by combining LiCoO2 layers with nickel-rich lithium transition metal oxide in a core-shell or layered composite structure. The LiCoO2 component provides excellent lifetime properties and charge-discharge efficiency, while the nickel-based component provides higher discharge capacity, thus resolving the contradiction between lifetime and capacity.
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 surface treatment layer with porous coordination polymer significantly enhances the battery's lifetime properties and high-temperature stability, leading to improved discharge capacity and capacity retention, making it suitable for applications in vehicles and power tools.
Implementation Method 1
a surface treatment layer which is positioned on the surface of the core, wherein the surface treatment layer includes a porous coordination polymer in which a central metal ion is coordinate-bonded with an organic ligand
Data Source
AI summary
In the present invention is provided a positive electrode active material for a secondary battery, wherein the positive electrode active material includes a core including a lithium composite metal oxide, and a surface treatment layer positioned on the surface of the core, and the surface treatment layer includes a porous coordination polymer in which a central metal ion is coordinate-bonded with an organic ligand such that high electrode density may be exhibited when an electrode is manufactured, and consequently, battery properties may be significantly enhanced. Also provided are a positive electrode, which is for a secondary battery and includes the positive electrode active material, and a secondary battery.