Cobalt-Coated Nickel Cathode Blend for Longer Battery Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing positive active materials for rechargeable lithium batteries, such as lithium nickel-based oxides, suffer from structural collapse and cracking during charge and discharge cycles, leading to reduced cycle-life and capacity characteristics.
Innovation Solution
A positive active material composed of a first nickel-based material with secondary particles formed by aggregated primary particles and a second nickel-based material in single crystal form, both coated with cobalt, is developed. This material is prepared through a three-step heat-treatment process involving mixing nickel-based hydroxides with lithium raw materials and cobalt compounds to enhance structural integrity and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional positive active materials (lithium nickel-based oxide, lithium nickel manganese cobalt composite oxide) are used, then high capacity and high energy density can be achieved, but the structure collapses or cracks during repeated charge and discharge cycles, reducing cycle-life
Solution Approach 1:
The positive active material is divided into two distinct components: first positive active material in the form of secondary particles comprising aggregated primary particles, and second positive active material in single crystal form. This segmentation allows each component to contribute different properties - the secondary particles provide high capacity while the single crystals maintain structural integrity during cycling, thus resolving the contradiction between capacity and cycle-life.
Solution Approach 2:
The invention creates a composite positive active material combining two different nickel-based materials with distinct morphologies (secondary particles and single crystals). Both materials are coated with cobalt to enhance structural stability. This composite structure leverages the high capacity of secondary particles and the structural robustness of single crystals, simultaneously achieving high capacity and long cycle-life.
2Quantity of substance
If conventional positive active materials are used, then high capacity can be achieved, but resistance increases during repeated charge and discharge cycles, reducing long-term performance
Solution Approach 1:
Cobalt coating is applied as an intermediary layer on both the first and second positive active materials. This cobalt coating acts as a protective intermediary that prevents direct contact between the nickel-based materials and the electrolyte, thereby reducing resistance increase during cycling while maintaining the high capacity characteristics of the nickel-based materials.
3Quantity of substance
If nickel-based positive active materials are used, then high energy density can be achieved, but structural collapse occurs during charge and discharge cycles
Solution Approach 1:
The invention applies different local qualities to different components: the first positive active material uses secondary particle morphology with aggregated primary particles, while the second uses single crystal form. Both are locally coated with cobalt to enhance structural stability. This local differentiation allows the material to maintain high energy density while resisting structural collapse during cycling.
Solution Approach 2:
The invention changes the morphological parameters of the nickel-based materials by creating two distinct forms (secondary particles and single crystals) and modifies the surface composition by adding cobalt coating. These parameter changes enhance structural stability while preserving the high energy density characteristics of nickel-based materials.
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 cobalt-coated nickel-based materials exhibit improved cycle-life characteristics, high capacity, and high energy density, with enhanced charge and discharge efficiency.
Implementation Method 1
This material is prepared through a three-step heat-treatment process involving mixing nickel-based hydroxides with lithium raw materials and cobalt compounds to enhance structural integrity and surface roughness.
Implementation Method 2
mixing the first nickel-based oxide, the second nickel-based oxide in a single crystal form, and a cobalt compound together and performing a third heat-treatment to coat the first nickel-based oxide and the second nickel-based oxide with cobalt
Data Source
AI summary
Disclosed are a positive active material for a rechargeable lithium battery, a method of preparing the same, and a rechargeable lithium battery including the same. The positive active material includes a first positive active material in a form of secondary particles including a plurality of primary particles that are aggregated together, and a second positive active material having a single crystal form, wherein both of the first positive active material and the second positive active material are nickel-based positive active materials, each of the first positive active material and the second positive active material is coated with cobalt, and a maximum roughness of a surface of the second positive active material is greater than or equal to about 15 nm.