Boron-Coated Nickel Cathode Particles for Crack-Resistant Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries face issues with structural collapse and reduced long-term life-cycle characteristics due to repeated charging and discharging, leading to decreased capacity and increased resistance in existing positive active materials like lithium nickel-based oxides.
Innovation Solution
A positive active material comprising a mixture of lithium nickel-based composite oxides in the form of secondary and single particles with a boron coating, where the second positive active material has an uneven surface with irregularities and a flat surface, enhancing surface roughness and specific surface area, is developed. This material is prepared by aggregating primary particles, performing heat treatments, and concurrently coating with a boron-containing compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel-based oxide is used as positive active material, then high capacity and high energy density are achieved, but structural collapse and cracks occur during repeated charges and discharges
Solution Approach 1:
A boron coating layer is applied on the surface of the lithium nickel-based composite oxide particles. This thin film coating acts as a protective shell that prevents structural collapse and cracks during repeated charging and discharging, while maintaining the high capacity characteristics of the underlying lithium nickel-based oxide material.
Solution Approach 2:
The positive active material is designed as a composite structure consisting of lithium nickel-based composite oxide particles with boron coating. This composite material combines the high capacity properties of lithium nickel-based oxide with the structural stability provided by the boron coating layer, resolving the contradiction between capacity and structural reliability.
2Quantity of substance
If lithium nickel-based oxide is used as positive active material, then high energy density is achieved, but long-term life-cycle characteristics deteriorate
Solution Approach 1:
The boron coating layer serves as a protective thin film that prevents structural degradation during repeated cycles. This coating maintains the integrity of the lithium nickel-based oxide particles over long periods, thereby improving life-cycle characteristics while preserving the high energy density of the core material.
Solution Approach 2:
The boron coating is applied in advance to the lithium nickel-based oxide particles before they undergo repeated charging and discharging cycles. This pre-protective coating cushions against structural damage that would otherwise occur during cycling, ensuring long-term stability and extended battery life.
3Reliability
If positive active material is coated with boron-containing compound, then life-cycle characteristics are improved, but manufacturing process complexity increases
Solution Approach 1:
The boron coating process is combined with the existing heat treatment step in the manufacturing process. By adding the boron-containing compound to the mixture before heat treatment, the coating and sintering operations are merged into a single processing step, reducing overall process complexity while achieving the desired protective coating.
Solution Approach 2:
The boron-containing compound is mixed with the lithium nickel-based oxide precursor materials before heat treatment, allowing the boron to self-coat the particle surfaces during the heat treatment process itself. This self-service approach eliminates the need for separate coating equipment and processes, simplifying manufacturing while ensuring uniform boron coverage.
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 initial charge/discharge efficiency and life-cycle characteristics, maintaining high capacity and energy density while preventing structural collapse, thus enhancing the overall performance and safety of rechargeable lithium batteries.
Implementation Method 1
performing a third heat treatment on the mixture of the first lithium nickel-based composite oxide, the second lithium nickel-based composite oxide, and the boron raw material
Implementation Method 2
preparing the first lithium nickel-based composite oxide in a form of a secondary particle in which a plurality of primary particles are aggregated by mixing a first nickel-based hydroxide and a lithium raw material and performing a first heat treatment
Data Source
AI summary
A positive active material for a rechargeable lithium battery, a preparation method thereof, and a rechargeable lithium battery including the same are disclosed herein. The positive active material includes a first positive active material including a first lithium nickel-based composite oxide in a form of a secondary particle in which a plurality of primary particles are aggregated and including a boron coating portion on a surface of the secondary particle, and a second positive active material including a second lithium nickel-based composite oxide in a form of a single particle and including a boron coating portion on a surface of the single particle, wherein the second positive active material has an uneven surface with substantial irregularities and a flat surface without substantial irregularities.