Cobalt-Coated Ni-Rich Cathode Particles for Longer Battery Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rechargeable lithium batteries face issues with long-term cycle-life and capacity due to structure collapse and increased resistance in positive active materials like lithium nickel-based oxides during repeated charging and discharging.
Innovation Solution
A positive active material for lithium batteries is developed, comprising a lithium nickel-based composite oxide with a cobalt coating on secondary particles and single particles, where the cobalt content is optimized to achieve a specific ratio, enhancing structural stability and reducing surface side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium nickel-based oxide is used as positive active material to achieve high capacity and high energy density, then energy density is improved, but structure collapses and cracks occur during repeated charges and discharges leading to deteriorating long-term cycle-life
Solution Approach 1:
The patent uses a composite material structure consisting of lithium nickel-based composite oxide particles coated with a lithium phosphate layer. This composite structure combines the high capacity properties of lithium nickel-based oxide with the protective and stabilizing properties of lithium phosphate coating, thereby achieving both high energy density and improved long-term cycle-life characteristics
Solution Approach 2:
The patent optimizes specific parameters including the thickness of the lithium phosphate coating layer (controlled to be 1-10 nm), the composition ratios of the lithium nickel-based composite oxide, and the particle size distribution. These parameter optimizations balance the high capacity needs with structural stability during cycling, resolving the contradiction between energy density and cycle-life
2Quantity of substance
If lithium nickel-based oxide is used to achieve high capacity, then capacity is improved, but resistance increases during repeated charges and discharges leading to deteriorating capacity characteristics
Solution Approach 1:
The lithium phosphate coating forms a protective composite layer on the surface of the lithium nickel-based oxide particles. This composite structure prevents direct exposure of the active material to the electrolyte, reducing surface side reactions and resistance increase during cycling, thereby maintaining capacity characteristics over time
Solution Approach 2:
The lithium phosphate coating is applied beforehand to cushion and protect the lithium nickel-based oxide particles from structural degradation and resistance increase during subsequent charging and discharging cycles. This protective layer prevents harmful interactions between the active material and electrolyte, preserving capacity characteristics
3Ease of manufacture
If conventional positive active materials are used, then manufacturing is simple, but surface side reactions occur leading to gas generation during high-temperature storage
Solution Approach 1:
The patent creates a composite structure with lithium phosphate coating on lithium nickel-based oxide particles. This composite material effectively suppresses surface side reactions and gas generation during high-temperature storage while maintaining a relatively simple manufacturing process involving coating and heat treatment steps
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed are a positive active material for a rechargeable lithium battery, a preparation method thereof, and a rechargeable lithium battery including the same. The positive active material for a rechargeable lithium battery includes a first positive active material including a lithium nickel-based composite oxide and including a secondary particle in which a plurality of primary particles are aggregated and a cobalt coating portion on the surface of the secondary particle, and a second positive active material including a lithium nickel-based composite oxide and including a single particle and a cobalt coating portion on the surface of the single particle, wherein a cobalt content (at%) based on the total amount of nickel and cobalt in the cobalt coating portion of the first positive active material is about 1.45 times to about 1.60 times a cobalt content (at%) based on the total amount of nickel and cobalt in the cobalt coating portion of the second positive active material.