Fluorinated Nickel-Cobalt-Manganese Cathode for Gelation Control
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Solution Overview
Problem
Lithium-based composite oxides, such as LiNiO2, face issues with gelation when kneaded with binder resins and have poor capacitance characteristics, while lithium cobaltate is expensive and prone to reduced crystallinity and electrolyte decomposition, limiting their suitability for lithium secondary batteries.
Innovation Solution
A positive electrode active material is developed by mixing nickel, cobalt, and a transition metal with a lithium compound and a calcium compound, followed by firing, to incorporate calcium atoms on the surface and reduce residual Li2CO3, enhancing cycle characteristics and safety by suppressing gelation and improving coating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LiNiO2 or lithium composite oxide with nickel replacement is used as positive electrode material, then cost is reduced compared to lithium cobaltate, but gelation occurs during kneading with binder resin causing poor coating properties
Solution Approach 1:
The patent applies fluorination treatment to the surface of LiNi0.8Co0.1Mn0.1O2 particles, changing the surface chemical composition by introducing fluorine atoms. This surface modification reduces residual Li2CO3 and improves wettability with binder resin, preventing gelation during kneading while maintaining the cost advantage of nickel-based materials
Solution Approach 2:
The patent creates a composite structure with a LiNi0.8Co0.1Mn0.1O2 core and a fluorinated surface layer. This composite material combines the high capacity benefits of nickel-based oxides with the improved surface properties of fluorinated compounds, achieving both cost reduction and good coating properties
2Ease of manufacture
If LiNiO2 is used as positive electrode material, then cost is reduced, but residual Li2CO3 remains causing gelation during kneading
Solution Approach 1:
The patent converts the harmful effect of residual Li2CO3 on the surface into a beneficial process by applying fluorination treatment. The fluorine reacts with residual Li2CO3 to form volatile LiF and CO2, eliminating the harmful residue and improving material stability during subsequent processing
Solution Approach 2:
The fluorination treatment changes the surface chemical parameters by introducing fluorine atoms and removing carbon-containing residues. This parameter change transforms the surface from a gelation-prone state to a stable, processable state while maintaining the cost benefits of nickel-based materials
3Reliability
If lithium cobaltate is used as positive electrode material, then excellent electrical properties are achieved, but raw material cobalt is rare and expensive
Solution Approach 1:
The patent changes the compositional parameters by replacing 80% of cobalt with nickel in the LiNi0.8Co0.1Mn0.1O2 formula. This parameter change dramatically reduces cobalt content and cost while the fluorination treatment compensates for any electrical property degradation, achieving a balance between cost and performance
Solution Approach 2:
The patent creates a composite material LiNi0.8Co0.1Mn0.1O2 that combines multiple transition metals. This composite approach reduces dependence on expensive cobalt while the fluorinated surface layer maintains good electrical properties by improving interfacial contact and reducing resistance
4Quantity of substance
If lithium cobaltate is charged with 0.7 electron or more, then capacity is increased, but crystallinity is reduced and electrolyte solution is decomposed
Solution Approach 1:
The fluorination treatment changes the surface electrochemical parameters by introducing fluorine atoms that stabilize the surface structure. This allows the material to withstand higher charging levels (0.7 electron or more) without severe crystallinity loss or electrolyte decomposition, enabling higher capacity operation
Solution Approach 2:
The fluorinated surface layer acts as a protective cushion before high-capacity charging occurs. This pre-applied surface modification prevents direct contact between the high-voltage charged state and the electrolyte, cushioning against decomposition reactions and maintaining crystallinity even at high charge levels
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 resulting lithium secondary battery exhibits excellent cycle characteristics and safety, with reduced gas generation and improved initial discharge capacity, maintaining capacity over multiple cycles.
Implementation Method 1
mixing a compound containing nickel, cobalt, a transition metal atom other than these and the like with a lithium compound and a calcium compound; and firing the resulting mixture
Data Source
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AI summary
There is provided a positive electrode active material for lithium secondary batteries which suppresses gelation when kneaded with a binder resin in producing a positive electrode material and provides excellent coating properties. The positive electrode active material for lithium secondary batteries comprises a lithium composite oxide represented by the following general formula (1) and a Ca atom contained in the lithium composite oxide. When the positive electrode active material is analyzed by X-ray diffraction using Cu- Kα radiation as a radiation source, the intensity ratio (b/a) of (b) the diffraction peak at 2θ = 18.7 ± 0.2° to (a) the diffraction peak at 2θ = 37.4 ± 0.2° derived from CaO is from 10 to 150. LixNi1-y-zCoyMezO2 (1) In the formula, Me represents a metal element having an atomic number of 11 or more other than Co and Ni; and x, y, and z are represented by the formulae 0.98 ≤ x ≤ 1.20, 0 < y ≤ 0.5, and 0 < z ≤ 0.5, respectively, provided that y + z < 1.