LiCoO2 Powder With Co3O4 Coating for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium cobalt oxide cathode materials in lithium ion batteries face challenges with low discharge capacity, poor cycle performance, and high temperature instability due to excessive lithium and residual Co3O4, which react with electrolytes, reducing battery safety and efficiency.
Innovation Solution
A lithium cobalt metal oxide powder with a Co3O4 coating layer is developed, where excess Co is present in a spinel phase both internally and on the surface, controlled through specific molar ratios and sintering processes to enhance energy density and cycle performance, and a method for determining Co3O4 content is provided to optimize material composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cut-off voltage is increased to above 4.3V to increase discharge capacity and energy density, then the discharge capacity increases, but the structure of LiCoO2 becomes unstable causing poor charge and discharge cycling performance and poor storage performance at high temperatures
Solution Approach 1:
A coating layer comprising Co3O4 and Li2SiO3 is applied to the surface of LiCoO2 particles. This coating layer acts as an intermediary barrier between the LiCoO2 cathode material and the electrolyte, preventing direct harmful reactions while allowing ionic transport, thus enabling stable operation at high voltages above 4.3V without compromising cycle performance
Solution Approach 2:
The patent modifies the surface composition and chemical state of the cathode material by controlling the coating process parameters (temperature, time, precursor ratios) to form a stable surface layer. This changes the surface properties to be more resistant to oxidation and electrolyte decomposition at high voltages, enabling safe operation beyond 4.3V
2Volume of stationary object
If Li is used as a fluxing agent to increase crystallinity and particle size thereby increasing press density, then the press density increases, but the material contains a large amount of residual Li which easily induces gas inflation at high temperature and endangers safety performance
Solution Approach 1:
Excess lithium is intentionally added during synthesis and then removed through a controlled reaction process. The coating layer formation process serves to extract and eliminate residual lithium from the particle surfaces, converting it into stable lithium compounds (Li2SiO3) in the coating, thereby eliminating the source of high-temperature gas inflation while preserving the benefits of Li-assisted sintering for high density
Solution Approach 2:
The residual lithium, which is harmful at high temperatures, is converted into a beneficial component of the protective coating layer. The excess Li reacts to form Li2SiO3 within the coating structure, transforming from a safety hazard into a stabilizing element that contributes to the protective function of the coating
3Stability of the object's composition
If Co3O4 is remained on the surface of the cathode material, then the structure is stabilized, but the high concentration Co3O4 reduces the charge and discharge capacities because Co3O4 has no activity in the charge and discharge processes
Solution Approach 1:
The patent creates a non-uniform distribution of Co3O4 within the coating layer, concentrating it where structural stability is needed while maintaining regions with different compositions that facilitate ionic transport. The coating layer has a gradient structure where Co3O4 provides stability at the outer surface while inner regions maintain higher ionic conductivity, thus balancing stability and capacity
4Reliability
If the surface of the cathode material reacts slowly with the electrolyte solution at high temperature or repeated charge and discharge, then the performance of the material gradually reduces, but increasing reactivity would worsen side reactions and reduce cycle life
Solution Approach 1:
The coating layer acts as an intermediary barrier between the LiCoO2 cathode material and the electrolyte. It prevents direct harmful reactions between the electrolyte and the cathode surface while maintaining sufficient ionic conductivity to allow lithium ion transport. This intermediary layer stabilizes the interface, preventing performance degradation over time without requiring high reactivity that would cause harmful side reactions
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 solution improves cycle performance and high temperature safety by preventing electrolyte reactions and maintaining high energy density, while allowing accurate control of residual Co3O4 content for balanced capacity and stability.
Implementation Method 1
The lithium cobalt metal oxide powder includes a Co3O4 coating layer that prevents electrolyte reactions with the cathode material
Implementation Method 2
Co3O4 has no activity in the charge and discharge processes and prevents side reactions with electrolyte
Implementation Method 3
Li can be used as a fluxing agent to increase the crystallinity of particles thereby enlarging the particles in the sintering
Implementation Method 4
increase the crystallinity of particles thereby enlarging the particles in the sintering
Implementation Method 5
By coating with a Co micro powder material and sintering at a high temperature, excess Li can be adsorbed
Implementation Method 6
at a high voltage, with the increase of de-intercalation amount of Li ions, Co3+ can be oxidized into Co4+ and then have a side reaction with the electrolyte
Data Source
AI summary
A lithium cobalt metal oxide powder is disclosed in the present disclosure. The lithium cobalt metal oxide powder has a coating structure. The lithium cobalt metal oxide powder includes a lithium cobalt metal oxide matrix. The lithium cobalt metal oxide powder further includes a Co3O4 coating layer. A general formula of the lithium cobalt metal oxide powder is LiaCo1-x-yMxNyO2·rCo3O4, wherein 0.002<r≤0.05, 1≤a≤1.1, 0<x≤0.02, 0≤y≤0.005, and a<1+3r; M is a doping element; and N is a coating element. A method for making the lithium cobalt metal oxide powder as described above and a method for determining a content of Co3O4 therein are further provided. The material made in the present disclosure has an excellent electrochemical performance.