Lithium Deficient LiCoO2 Core-Shell Structure for Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face rapid life decrease due to low structural stability and poor rate characteristics, especially at high temperatures, with existing positive electrode active materials like LiCoO2 and Li(NixCoyMnz)O2, which limit their high-capacity and high-voltage applications.
Innovation Solution
A positive electrode active material with lithium cobalt oxide particles having a lithium deficient structure (Li/Co molar ratio less than 1) is developed, featuring a core-shell structure with a spinel-like cubic crystal structure for three-dimensional lithium ion transport, enhancing structural stability and rate characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LiCoO2 with layered structure is used as positive electrode active material, then it can be easily synthesized and has good electrochemical properties, but it has low structural stability and is limited for high capacity applications
Solution Approach 1:
The patent uses LiCoO2 as a composite material combining lithium oxide and cobalt oxide in a layered structure. This composite provides both ease of synthesis through conventional ceramic processing and good electrochemical properties, while the layered architecture itself provides structural stability for high capacity applications
2Quantity of substance
If LiNiO2 is used as positive electrode active material, then it provides high discharge capacity, but it is hardly synthesized by simple solid phase reaction and has low thermal stability and cycle property
Solution Approach 1:
The patent changes the chemical composition parameters by substituting nickel with cobalt and manganese in the Li(Ni1-x-yCoxMny)O2 formula. This parameter change maintains high discharge capacity while improving thermal stability and cycle properties through the more stable cobalt and manganese components
3Stability of the object's composition
If LiMn2O4 is used as positive electrode active material, then it has good thermal stability and low cost, but it has limitations of small capacity and inferior properties at high temperatures due to Jahn-Teller distortion
Solution Approach 1:
The patent changes the composition parameters by incorporating lithium nickel manganese cobalt oxide Li(Ni1-x-yCoxMnym)O2 where the specific ratios of nickel, cobalt, and manganese are optimized. This parameter adjustment increases the capacity while maintaining thermal stability by balancing the Jahn-Teller distortion effects through controlled metal ion composition
4Volume of stationary object
If active materials having large size particles are used to increase packing density, then the energy of battery per unit volume is increased, but the surface area is relatively small and rate characteristic and initial capacity are relatively low
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the interior core provides high capacity through large particle volume for high packing density, while the outer shell provides enhanced surface area and improved rate characteristics. This local differentiation of properties resolves the contradiction between volume efficiency and surface reactivity
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 lithium deficient lithium cobalt oxide active material maintains good initial capacity and life properties while improving rate characteristics and thermal stability, enabling high-capacity and high-voltage performance without deteriorating at high temperatures.
Implementation Method 1
featuring a core-shell structure with a spinel-like cubic crystal structure for three-dimensional lithium ion transport
Data Source
AI summary
The present invention relates to a positive electrode active material for a lithium secondary battery, and a lithium secondary battery including the same, and the positive electrode active material includes lithium cobalt oxide particles. The lithium cobalt oxide particles include lithium cobalt oxide having a Li/Co molar ratio of less than 1 in the particles. Good rate property and life property may be obtained without worrying on the deterioration of initial capacity property.