Doped LiCoO2 Cathode Coating for High-Voltage Cycle Stability
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Solution Overview
Problem
Lithium-ion batteries face poor cycling performance at high voltages due to lithium ion deintercalation from the positive electrode active material LiCoO2, leading to reduced reversible capacity and side reactions with the electrolyte, limiting their energy density and application.
Innovation Solution
Doping lithium cobalt oxide particles with elements like Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, or Sc, and applying a coating layer of metal fluoride, oxide, borate, or phosphate compounds to improve structural stability, along with a specific charge and discharge regime to maintain a molar ratio of lithium to cobalt within a certain range (0.62≤(A−B)≤0.655) for enhanced cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the charging voltage of the lithium-ion battery is increased to 4.4 V or more, then the energy density is improved, but the reversible capacity of the positive electrode active material is continuously reduced, causing poor cycling performance
Solution Approach 1:
A coating layer comprising at least one of a metal fluoride, a metal oxide, a metal borate compound, or a metal phosphate compound is applied to the surface of the lithium cobalt oxide particles. This coating layer acts as an intermediary between the positive electrode active material and the electrolyte, preventing direct contact and side reactions, thereby maintaining structural stability and reversible capacity at high charging voltages (4.4V or more) while preserving good cycling performance
Solution Approach 2:
The patent controls the molar ratio of lithium to cobalt in the positive electrode active material within a specific range (0.62≤(A−B)≤0.655, where A is the molar ratio at 0% SOC and B is the molar ratio at 100% SOC). This parameter optimization ensures that the material maintains its hexagonal structure and reversible lithium ion deintercalation capacity even at high charging voltages, resolving the contradiction between energy density and cycling performance
2Quantity of substance
If more lithium ions are deintercalated from the positive electrode active material LiCoO2, then the discharge capacity is improved, but the structural stability is reduced, leading to poor cycling performance
Solution Approach 1:
The coating layer serves as a protective intermediary that stabilizes the surface structure of lithium cobalt oxide particles during repeated lithium ion deintercalation and insertion cycles. This prevents structural degradation and maintains the material's ability to reversibly accommodate high amounts of lithium ion extraction, thereby enabling both high discharge capacity and structural stability
Solution Approach 2:
The patent creates a composite structure by coating lithium cobalt oxide particles with stable inorganic compounds (metal fluorides, oxides, borates, or phosphates). This composite material combines the high capacity characteristics of lithium cobalt oxide with the structural stability of the coating layer, allowing extensive lithium ion deintercalation without compromising the underlying crystal structure
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 approach significantly improves the cycling performance of lithium-ion batteries at high voltages by maintaining structural stability and optimizing the molar ratio of lithium to cobalt, thereby enhancing their energy density and application capabilities.
Implementation Method 1
the positive electrode active material includes lithium cobalt oxide particles doped with one or more elements of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, or Sc
Implementation Method 2
lithium ions in a positive electrode active material LiCoO2 are deintercalated and form Li1-xCoO2 (0≤x≤0.5)
Implementation Method 3
a coating layer of metal fluoride, oxide, borate, or phosphate compounds
Data Source
AI summary
Disclosed is a lithium-ion battery, where the lithium-ion battery includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide particles doped with one or more elements of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, or Sc. When the lithium-ion battery is in an SOC of 0%, a molar ratio of an element lithium to an element cobalt in the positive electrode active material is A, and when the lithium-ion battery is in an SOC of 100%, a molar ratio of the element lithium to the element cobalt in the positive electrode active material is B, where 0.62≤(A−B)≤0.655. The lithium-ion battery provided in the present disclosure has good cycling performance at a high voltage.