Hollow Nickel Cathode Particles With Cobalt Coating Against Aggregation
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Solution Overview
Problem
Lithium secondary batteries with high energy density face issues of particle aggregation in single-crystal cathode active materials due to high-temperature heat treatment, leading to reduced productivity and deteriorated crystallinity, along with surface defects and residual impurities from pulverization processes.
Innovation Solution
A cathode active material comprising nickel-based lithium metal oxide secondary particles with a hollow structure and a cobalt compound-containing coating layer, which suppresses particle aggregation and improves surface resistance without a pulverization process, utilizing a co-precipitation method to create pores and control synthesis rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high-temperature heat treatment is performed for single crystallization, then crystallinity is improved, but particle aggregation occurs and productivity is reduced
Solution Approach 1:
The heat treatment process is divided into two distinct stages: a first heat treatment at a relatively low temperature (700-900°C) to form a precursor, and a second heat treatment at a high temperature (900-1100°C) to achieve single crystallization. This segmentation allows the crystallization process to occur without excessive particle aggregation, as the lower initial temperature prevents premature sintering while still enabling crystal formation.
Solution Approach 2:
A cobalt compound coating layer is applied to the surface of the cathode active material particles before the heat treatment process. This preliminary coating prevents particle aggregation during the high-temperature single crystallization by acting as a barrier, allowing the particles to maintain their individual identities while still achieving the desired crystalline structure.
2Volume of moving object
If pulverization process is performed to solve particle aggregation, then particle size is reduced, but crystallinity deteriorates and surface defects occur
Solution Approach 1:
Instead of applying pulverization to break down aggregated particles after heat treatment, the invention inverts the approach by preventing aggregation in the first place through the cobalt compound coating. This eliminates the need for mechanical breakdown that would damage the crystal structure and create surface defects.
3Reliability
If cobalt compound coating layer is applied before heat treatment, then particle aggregation is suppressed, but process complexity increases
Solution Approach 1:
The cobalt compound coating application is merged with the heat treatment process into a single integrated operation. The coating is applied immediately before heat treatment, and the entire process is optimized as one sequence, reducing the need for separate handling steps and minimizing additional equipment requirements.
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 enhances the lifespan and capacity characteristics of lithium secondary batteries by preventing particle aggregation and maintaining crystallinity, resulting in improved electrochemical properties and reduced surface resistance.
Implementation Method 1
a cobalt compound-containing coating layer on surfaces of the nickel-based lithium metal oxide secondary particles
Implementation Method 2
utilizing a co-precipitation method to create pores
Data Source
AI summary
A cathode active material for lithium secondary batteries, a method of preparing the same, a cathode including the same, and a lithium secondary battery including the cathode are provided. The cathode active material includes nickel-based lithium metal oxide secondary particles each including a plurality of large primary particles, the nickel-based lithium metal oxide secondary particles having a hollow structure having pores therein, each of the plurality of large primary particles having a size of about 2 μm to about 6 μm, and each of the nickel-based lithium metal oxide secondary particles having a size of about 10 μm to about 18 μm; and a cobalt compound-containing coating layer on surfaces of the nickel-based lithium metal oxide secondary particles.