Cobalt-Coated High-Nickel Cathode Material for Battery Durability
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in durability, charge-discharge efficiency, and capacity retention, particularly with high-nickel lithium composite oxides used as positive electrode active materials.
Innovation Solution
A positive electrode active material is developed with a bimodal structure comprising small and large particles coated with a cobalt-rich layer, where the surface area ratio of the coated and uncoated surfaces is optimized to enhance durability and efficiency, and a manufacturing method involving calcination at specific temperatures is employed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-nickel lithium composite oxide is used as positive electrode active material to achieve high energy density, then capacity is improved, but durability and stability deteriorate
Solution Approach 1:
The patent applies local quality by creating a cobalt-rich coating layer specifically on certain surfaces of the positive electrode particles. The coating is not uniformly distributed but concentrated on surfaces with specific orientation ratios (first surface area/second surface area between 0.3-0.8), providing localized protection where it is most needed while maintaining high nickel content in the bulk material for capacity.
Solution Approach 2:
The patent uses composite materials by combining high-nickel lithium composite oxide with a cobalt-rich coating layer. This composite structure allows the core material to provide high capacity while the coating layer provides durability and stability, resolving the contradiction between capacity and reliability.
2Quantity of substance
If high-nickel lithium composite oxide is used to achieve high energy density, then capacity is improved, but charge-discharge efficiency deteriorates
Solution Approach 1:
The cobalt-rich coating layer is selectively applied to surfaces with specific orientation ratios, creating local quality differences. This selective coating improves charge-discharge efficiency at the coated surfaces while maintaining high nickel content elsewhere for capacity, thus resolving the contradiction between capacity and charge-discharge efficiency.
Solution Approach 2:
The patent changes the surface composition parameter by adding cobalt-rich coating layer with different chemical composition than the bulk material. This parameter change at the surface level improves charge-discharge efficiency without compromising the high capacity provided by the high-nickel bulk material.
3Reliability
If surface coating is applied to improve durability, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent controls the coating process by specifying the orientation ratio parameter (first surface area/second surface area between 0.3-0.8) rather than requiring complex multi-step coating procedures. This parameter-based control simplifies manufacturing while achieving the desired durability improvement through selective surface coating.
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 solution improves the charge-discharge efficiency, stability, and capacity retention of rechargeable lithium batteries by optimizing the surface area ratio and coating composition, leading to enhanced battery performance.
Implementation Method 1
The operation of coating the precursor mixture may be performed at about 650° C. to about 900° C.
Data Source
AI summary
Example embodiments include positive electrode active materials, manufacturing methods thereof, and rechargeable lithium batteries. The positive electrode active material includes a positive electrode active material having a first particle that has a first surface and a second surface and includes a lithium composite oxide, and a first coating layer on the first surface. A surface area ratio of the first surface to the second surface is in a range of about 3:7 to about 8:2. The first coating layer has a cobalt amount that is greater than a cobalt amount of the first particle. The cobalt amount of the first coating layer is in a range of about 30 at % to about 100 at %.