Fluorine-Coated LiNiCoMnO4 Cathode for High-Temp Stability
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face a significant decrease in discharge capacity when exposed to high temperatures, particularly when stored in a charged state, due to decomposition reactions between the positive electrode and electrolyte, which affects their performance and longevity.
Innovation Solution
A positive electrode active material is developed by mixing lithium nickel cobalt manganate with lithium cobaltate, where a compound containing fluorine and elements like zirconium, magnesium, titanium, or rare earth elements is adhered to the surface, maintaining a specific ratio of lithium nickel cobalt manganate within the active material to suppress decomposition and enhance discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge voltage of the battery is increased to achieve higher capacity, then the battery capacity is improved, but decomposition of the electrolyte is accelerated
Solution Approach 1:
A coating layer containing fluorine and at least one of zirconium, magnesium, titanium, aluminum, or rare earth elements is applied to the surface of the positive electrode active material particles. This coating layer acts as an intermediary between the electrolyte and the positive electrode active material, preventing direct harmful interactions while allowing beneficial lithium ion insertion/extraction reactions to proceed, thereby suppressing electrolyte decomposition even at high charge voltages
Solution Approach 2:
The positive electrode active material is formed as a composite structure combining lithium nickel cobalt manganate (providing high capacity) with lithium cobaltate (providing structural stability), with a fluorine-containing compound coating on the surface. This composite material approach allows the battery to achieve high capacity while maintaining stability and suppressing electrolyte decomposition
2Ease of operation
If the battery is stored at high temperature in a charged state, then the battery can be kept ready for use, but decomposition reactions between the positive electrode and electrolyte occur
Solution Approach 1:
The fluorine-containing coating layer serves as a protective intermediary that remains stable at high temperatures, preventing direct contact and reaction between the positive electrode active material and the electrolyte during high-temperature storage, thereby suppressing decomposition reactions while maintaining battery readiness
Solution Approach 2:
The fluorine-containing compound is pre-applied to the surface of the positive electrode active material particles before battery assembly. This preliminary coating action creates a stable protective layer that prevents decomposition reactions from occurring during subsequent high-temperature storage, addressing the issue before it can manifest
3Quantity of substance
If lithium nickel cobalt manganate is used as positive electrode active material to increase capacity, then the battery capacity is improved, but decomposition and elution of the positive electrode active material occur
Solution Approach 1:
The fluorine-containing coating layer acts as a protective intermediary that prevents direct exposure of lithium nickel cobalt manganate to the electrolyte, thereby suppressing decomposition and elution of the active material while preserving its high-capacity properties
Solution Approach 2:
The positive electrode active material is designed as a composite combining lithium nickel cobalt manganate (high capacity) with lithium cobaltate (high stability), creating a material that inherently balances capacity and stability requirements
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
This configuration effectively reduces the decrease in discharge capacity during low-temperature discharge after high-temperature storage, improving the battery's capacity retention and overall performance by inhibiting electrolyte decomposition and metal elution.
Implementation Method 1
a compound containing fluorine and at least one selected from zirconium, magnesium, titanium, aluminum, and a rare earth element is adhered to part of a surface of the lithium nickel cobalt manganate and the lithium cobaltate
Implementation Method 2
a nonaqueous electrolyte secondary battery that is charged and discharged through migration of lithium ions between a positive electrode and a negative electrode
Data Source
AI summary
A positive electrode for a nonaqueous electrolyte secondary battery that does not undergo a decrease in discharge capacity in low-temperature discharge during charge and discharge after the battery is left standing at high temperature in a charged state, for example. The positive electrode for a nonaqueous electrolyte secondary battery includes a positive electrode active material. The positive electrode active material includes a mixture of lithium nickel cobalt manganate and lithium cobaltate having a compound adhered to part of a surface thereof, the compound containing fluorine and at least one selected from zirconium, magnesium, titanium, aluminum, and a rare earth element; and a ratio of the lithium nickel cobalt manganate relative to a total amount of the positive electrode active material is 1% by mass or more and less than 70% by mass.