Aromatic Nitrile Coating for Li-Ion Battery Transition Metal Elution
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Solution Overview
Problem
In non-aqueous liquid electrolyte secondary batteries, the elution of transition metal from the positive electrode active material into the liquid electrolyte leads to increased resistance and reduced battery performance, particularly at high temperatures, due to the instability of the crystal structure during charge/discharge cycles.
Innovation Solution
A method of manufacturing the battery where an aromatic nitrile compound is selectively mixed with the positive electrode active material to form a coating film on its surface, with a mass ratio between 0.1% to 4% by mass, to suppress transition metal elution, and the granular body is disposed on the electrode collector to maintain this coating during the formation of the positive electrode mixture layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aromatic nitrile compound is added to the liquid electrolyte, then a coating film is formed on the positive electrode active material surface, but the coating film cannot be selectively disposed on the surface of the positive electrode active material
Solution Approach 1:
The aromatic nitrile compound is mixed with the positive electrode active material before preparing the positive electrode mixture. This preliminary mixing ensures the compound is positioned on the active material surface before other components are added, enabling selective coating formation that suppresses transition metal elution effectively.
Solution Approach 2:
The aromatic nitrile compound is specifically associated with the positive electrode active material particles, creating a localized coating on the particle surfaces. This local concentration of the compound on the active material surface provides targeted protection against transition metal elution without affecting other electrode components.
2Reliability
If the crystal structure of Li-containing transition metal oxide becomes unstable during charge/discharge, then transition metal elutes into the liquid electrolyte, but the elution cannot be sufficiently suppressed by conventional methods
Solution Approach 1:
The aromatic nitrile compound is incorporated into the positive electrode mixture before battery assembly, creating a protective coating on the active material surface in advance. This preliminary coating formation prevents transition metal elution during subsequent charge/discharge cycles when crystal structure instability occurs.
Solution Approach 2:
The aromatic nitrile compound acts as an intermediary layer between the positive electrode active material and the liquid electrolyte. This intermediate coating film prevents direct contact between the electrolyte and active material surface, thereby suppressing transition metal elution while allowing Li ion transport.
3Loss of substance
If a coating film is formed on the positive electrode active material surface, then transition metal elution is suppressed, but the coating may affect Li ion movement and increase resistance
Solution Approach 1:
The concentration of the aromatic nitrile compound in the positive electrode mixture is precisely controlled within the range of 0.1-4% by mass. This parameter optimization ensures sufficient coating formation to suppress transition metal elution while maintaining adequate Li ion conductivity and avoiding excessive resistance increase.
Solution Approach 2:
The aromatic nitrile compound forms a localized coating on the surface of positive electrode active material particles rather than a thick uniform layer. This localized coating provides effective transition metal suppression while maintaining porosity and Li ion transport pathways, thus avoiding significant resistance increase.
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 approach effectively reduces transition metal elution, minimizing resistance increases and capacity decreases, while maintaining battery performance by ensuring a uniform coating film on the positive electrode active material, even under high-temperature conditions.
Implementation Method 1
mixing the positive electrode active material and an aromatic nitrile compound such that a mass ratio of the aromatic nitrile compound to the positive electrode active material is not less than 0.1% by mass and not more than 4% by mass, to prepare a mixture
Data Source
AI summary
A method of manufacturing a non-aqueous liquid electrolyte secondary battery is to manufacture a non-aqueous liquid electrolyte secondary battery including a positive electrode mixture layer containing a lithium-containing transition metal oxide as a positive electrode active material. The manufacturing method includes: mixing the positive electrode active material and an aromatic nitrile compound such that a mass ratio of the aromatic nitrile compound to the positive electrode active material is not less than 0.1% by mass and not more than 4% by mass, to prepare a mixture; mixing the mixture, a conductive material, a binder, and a solvent to prepare a granular body; and disposing the granular body on a surface of a positive electrode collector to form at least a part of the positive electrode mixture layer.