Core-Shell Cathode Material to Suppress Microcracks in Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face degradation in life characteristics due to structural deformation and electrolyte decomposition caused by micro cracks in the positive electrode active material, leading to increased resistance and reduced capacity.
Innovation Solution
A core-shell structured positive electrode active material with a smaller average crystallite size in the core portion and a larger size in the shell portion, where nickel accounts for 80% or more of the transition metals, is developed to suppress micro cracks and electrolyte decomposition, maintaining high capacity and improving life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the crystallite size of the positive electrode active material is increased to increase capacity, then the capacity characteristics are improved, but micro cracks occur and life characteristics are rapidly degraded
Solution Approach 1:
The positive electrode active material is divided into core and shell portions with different crystallite sizes. The core portion has a smaller crystallite size (100-180 nm) to prevent micro crack formation, while the shell portion has a larger crystallite size (180-250 nm) to provide high capacity. This segmentation allows both small crystallite benefits (structural stability) and large crystallite benefits (high capacity) to coexist in the same material.
2Quantity of substance
If the crystallite size is increased to increase capacity, then more lithium ions can be stored, but structural deformation occurs during charge and discharge leading to micro cracks
Solution Approach 1:
Different regions of the positive electrode active material are given different crystallite sizes optimized for different functions. The core portion uses small crystallite size (100-180 nm) to maintain crystal lattice stability and prevent deformation during lithium ion insertion/extraction. The shell portion uses large crystallite size (180-250 nm) to maximize lithium ion storage capacity. This local differentiation of crystallite size allows each region to perform its optimal function.
3Quantity of substance
If micro cracks occur in the positive electrode active material, then capacity increases due to larger surface area, but electrolyte solution penetrates through cracks causing decomposition and resistance increase
Solution Approach 1:
The core portion with small crystallite size (100-180 nm) is designed beforehand to prevent micro crack formation during lithium ion intercalation/deintercalation cycles. By maintaining structural integrity through appropriate crystallite size control in the core, the material prevents electrolyte penetration and subsequent decomposition before harmful effects can occur. This proactive structural design cushions against the development of micro cracks that would otherwise lead to electrolyte degradation.
Data Source
AI summary
A positive electrode active material for a lithium secondary battery comprising lithium transition metal oxide particles having a core-shell structure which includes a core portion and a shell portion disposed on a surface of the core portion. Wherein, the average crystallite size of the core portion is smaller than an average crystallite size of the shell portion and an amount of nickel among total transition metals included in the core portion and the shell portion is 80 atm % or more. A positive electrode active material, which suppresses decomposition of an electrolyte solution and occurrence of micro cracks of the positive electrode active material during charge and discharge by forming an average crystallite size of a core portion of the high-nickel positive electrode active material smaller than an average crystallite size of a shell portion, and a method of preparing the same.