Nonaqueous Battery Electrode Coating for Gas Suppression
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in maintaining discharge characteristics and preventing gas generation during continuous charging, especially at high temperatures, due to electrolyte decomposition and increased internal pressure.
Innovation Solution
A nonaqueous electrolyte secondary battery design featuring a positive electrode with a rare earth element compound deposited in dispersed form and a nitrile compound with a chain saturated hydrocarbon group, which forms a protective coating to inhibit electrolyte decomposition, combined with a nitrile compound in the electrolyte solution to prevent gas generation and maintain discharge performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge voltage is increased to achieve higher capacity, then the energy density is improved, but the electrolytic solution decomposes more easily causing gas generation and increased internal pressure
Solution Approach 1:
A protective film is introduced as an intermediary layer between the electrolytic solution and the positive electrode. This film, formed by compounds containing nitrile groups or carboxyl groups, acts as a mediator that prevents direct contact and harmful reactions while allowing lithium ion transport, thus enabling high voltage operation without electrolyte decomposition
Solution Approach 2:
The invention changes the chemical composition parameters of the protective film by selecting specific compounds with nitrile groups (–C≡N) or carboxyl groups (–COOH). These parameter changes in molecular structure enable the film to provide adequate protection against electrolyte decomposition at high charging voltages
2Power
If the battery is stored or continuously charged at high temperatures, then the power output is maintained, but the electrolytic solution decomposes to produce gas causing swelling and increased internal pressure
Solution Approach 1:
The protective film serves as a thermal intermediary that stabilizes the interface between the electrolyte and electrode at high temperatures. Compounds with nitrile or carboxyl groups form this protective layer that prevents thermal decomposition of the electrolyte and subsequent gas generation, while maintaining power output characteristics
Solution Approach 2:
The invention converts the potentially harmful high-temperature conditions into a beneficial effect by using the heat to form a stable protective film on the electrode surface. This film, once formed, prevents further thermal decomposition and gas generation, thus converting the harmful thermal energy into a protective mechanism
3Quantity of substance
If the capacity of the active material is increased to achieve higher battery capacity, then the energy storage is improved, but the discharge characteristics deteriorate after continuous charging
Solution Approach 1:
The protective film acts as an intermediary that stabilizes the electrode-electrolyte interface during continuous charging cycles. This film prevents direct harmful interactions that would otherwise deteriorate the active material, thereby maintaining reliable discharge characteristics even when the active material capacity is increased for higher energy storage
4Quantity of substance
If the amount of active material packed is increased to achieve higher packing density, then the battery capacity is improved, but the internal pressure increases due to electrolyte decomposition
Solution Approach 1:
The protective film formed by nitrile-containing or carboxyl-containing compounds serves as an intermediary barrier that prevents electrolyte decomposition. This elimination of decomposition reactions prevents gas generation and subsequent internal pressure increases, allowing higher packing densities to be achieved safely
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 effectively reduces gas generation and deterioration in discharge characteristics during continuous charging, enhancing the battery's capacity and safety by forming a protective coating on the positive electrode, thereby maintaining performance and reducing voltage drops.
Implementation Method 1
the nitrile groups bind to the surface of the positive electrode at high temperatures to form a complex, and the complex serves as a protective film
Implementation Method 2
particles of a rare earth element compound are deposited in dispersed form on the surface of the positive electrode
Data Source
AI summary
In a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode and a nonaqueous electrolytic solution, the nonaqueous electrolytic solution contains a nitrile compound having a chain saturated hydrocarbon group and a nitrile group, the number of carbon atoms in the nitrile compound is four or more, and the positive electrode contains a positive-electrode active material on the surface of which particles of a rare earth element compound are deposited in dispersed form.