1,3-Dioxane Electrolyte Additive for Lithium-Ion Cell Gas Suppression
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Solution Overview
Problem
Non-aqueous electrolyte secondary cells face challenges with ethylene carbonate (EC) and propylene carbonate (PC) due to low oxidative decomposition potential and lithium ion conductivity issues, leading to reduced discharging capacity and gas generation.
Innovation Solution
A non-aqueous electrolyte secondary cell with a solvent mixture of ethylene carbonate and propylene carbonate in a specific ratio (0.40 to 0.78) and the addition of a 1,3-dioxane compound (0.1 to 5.0 mass %) to inhibit oxidative decomposition and form a stable coating film, minimizing gas generation and maintaining high discharging capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene carbonate (EC) is used as the non-aqueous solvent, then a stable covering film with high lithium ion conductivity is formed on the negative electrode, but the low oxidative decomposition potential causes decomposition at the positive electrode, generating gas and reducing discharging capacity
Solution Approach 1:
The patent introduces a 1,3-dioxane compound as an intermediary substance that preferentially reacts with the positive electrode to form a protective coating film. This intermediary layer acts as a barrier, preventing direct contact between EC and the positive electrode, thereby inhibiting oxidative decomposition and gas generation while allowing lithium ion transport.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by adding the 1,3-dioxane compound at specific concentrations (0.1 to 5.0 mass%). This parameter change alters the reaction sequence and coating formation behavior, enabling the system to achieve both stable negative electrode coverage and reduced positive electrode decomposition.
2Object-generated harmful factors
If propylene carbonate (PC) is used as the non-aqueous solvent, then the high oxidative decomposition potential prevents gas generation, but the coating film formed on the negative electrode has low lithium ion conductivity, reducing discharging capacity
Solution Approach 1:
The patent creates a composite electrolyte system combining EC, PC, and 1,3-dioxane compound. The EC provides high lithium ion conductivity through its reaction product on the negative electrode, while the 1,3-dioxane compound provides oxidative decomposition resistance. This composite approach integrates the advantages of both solvents while mitigating their individual disadvantages.
3Reliability
If the ratio of ethylene carbonate to total mass of ethylene carbonate and propylene carbonate is increased, then the lithium ion conductivity of the coating film improves, but the oxidative decomposition at the positive electrode increases, leading to more gas generation
Solution Approach 1:
The 1,3-dioxane compound serves as a protective intermediary that enables the use of higher EC concentrations. By forming a stable coating on the positive electrode first, it allows EC to dominate the negative electrode coating formation (improving lithium ion conductivity) without causing excessive oxidative decomposition and gas generation.
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 provides superior cycle characteristics and minimized gas generation, with discharging capacity preservation rates ranging from 64 to 81% and reduced gas production, outperforming cells outside the specified 1,3-dioxane concentration range.
Implementation Method 1
the 1,3-dioxane compound being represented by Formula 1... DOX to react with the positive electrode before EC does so that DOX is oxidative-decomposed to form a stable coating film on the positive electrode surface
Implementation Method 2
The coating film acts to inhibit decomposition of EC. This minimizes the amount of gas generated as a result of decomposition of EC
Implementation Method 3
EC has the advantage of providing a stable covering film with high lithium ion conductivity as a result of reaction with the negative electrode
Data Source
AI summary
A non-aqueous electrolyte secondary cell with superior cycle characteristics is provided. The non-aqueous electrolyte secondary cell has a positive electrode, a negative electrode, and a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt. The non-aqueous solvent contains ethylene carbonate and propylene carbonate. The ratio of the ethylene carbonate to the total mass of the ethylene carbonate and the propylene carbonate is from 0.40 to 0.78. The non-aqueous electrolyte contains a 1,3-dioxane compound at a mass % of from 0.1 to 5.0. The 1,3-dioxane compound is represented by Formula 1:where R1 to R4 independently denote a hydrogen atom, a methyl group, or an ethyl group.