Core-Shell Precursor for High-Capacity Lithium Battery
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Solution Overview
Problem
Current lithium secondary batteries face challenges in achieving high capacity and output while maintaining structural stability and low production costs, with existing materials like LiNiO2 experiencing issues such as high production costs, chemical instability, and swelling due to gas generation.
Innovation Solution
A precursor for a lithium composite transition metal oxide with a core-shell double-layer structure is developed, comprising a core unit with a high nickel content and a shell unit with a high cobalt content, optimized with specific mole ratios and the inclusion of zirconium and hydroxyl ions, which is prepared using a coprecipitation method and plasticized at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2 is used as positive electrode active material to achieve high discharge capacity and low cost, then reversible capacity exceeds 200 mAh/g and energy density improves, but chemical stability deteriorates and swelling occurs due to gas generation
Solution Approach 1:
The patent uses a core-shell composite structure where the core is LiNiO2 providing high capacity and the shell is LiCoO3 providing chemical stability. This composite structure allows the battery to achieve both high reversible capacity (exceeding 200 mAh/g) and improved chemical stability, preventing the swelling and gas generation issues that occur with pure LiNiO2.
Solution Approach 2:
The patent applies different materials to different regions of the positive electrode particles. The core region uses LiNiO2 for high capacity while the outer shell region uses LiCoO3 for chemical stability. This local differentiation allows each region to perform its optimal function, resolving the contradiction between capacity and stability.
2Duration of action of stationary object
If LiCoO2 is used as positive electrode active material to achieve excellent cycle characteristics, then cycle life improves, but production cost increases due to cobalt resource limitation
Solution Approach 1:
The patent concentrates the expensive cobalt-containing LiCoO3 material only in the outer shell region rather than throughout the entire particle. This allows the positive electrode to achieve excellent cycle characteristics from the stable shell while reducing overall cobalt content and production cost compared to using pure LiCoO2.
Solution Approach 2:
The patent creates a composite positive electrode active material combining LiNiO2 and LiCoO3 in a core-shell structure. This composite approach allows the system to achieve the excellent cycle characteristics of LiCoO2 while reducing production costs by using less cobalt overall and incorporating cheaper LiNiO2 in the core region.
3Ease of manufacture
If lithium manganese oxides are used as positive electrode active material to achieve low cost and environmental friendliness, then production cost decreases and environmental impact improves, but capacity is reduced and cycle characteristics deteriorate
Solution Approach 1:
The patent creates a composite structure where LiNiO2 core provides high capacity (exceeding 200 mAh/g) and LiCoO3 shell provides excellent cycle characteristics. This composite approach overcomes the limitations of lithium manganese oxides, achieving both high capacity and good cycle life while maintaining cost-effectiveness.
Solution Approach 2:
The patent assigns different functional roles to different regions: the LiNiO2 core region is optimized for high capacity while the LiCoO3 shell region is optimized for cycle stability. This local optimization resolves the contradiction between capacity and cycle characteristics that plagues single-material systems like lithium manganese oxides.
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
This approach results in a positive electrode active material with enhanced capacity, output, and structural stability, reducing resistance and improving the life characteristics of the battery, while minimizing byproduct issues like gelation and high-temperature swelling.
Implementation Method 1
a precursor for a lithium composite transition metal oxide... is prepared using a coprecipitation method
Implementation Method 2
which is prepared using a coprecipitation method and plasticized at high temperatures
Data Source
AI summary
Provided herein is a precursor of a transition metal oxide, including a core unit and a shell unit, wherein the core unit includes a compound of chemical formula 1 below, and the shell unit includes a compound of chemical formula 2 below.NiaMnbCo1−(a+b+c)Mc[OH(1−x)2−y]A(y/n) [Chemical formula 1]Nia′Mnb′Co1−(a′+b′+c′)M′c′[OH(1−x′)2−y′]A′(y′/n) [Chemical formula 2]