Lithium Ion Battery Electrolyte Oxidative Decomposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to develop a lithium ion secondary battery that uses an amide-based solvent as an electrolyte, which has high electric conductivity but a low oxidation potential, limiting its application due to oxidative decomposition issues, especially with lithium complex oxides.
Innovation Solution
The battery configuration includes a positive electrode with a lithium complex oxide and a binder like polytetrafluoroethylene, polyethylene oxide, or carboxymethylcellulose, and an electrolyte solution with a high concentration of lithium salt in N,N-dimethylformamide or dimethylacetamide, ensuring the lithium carbonate content is sufficient to prevent oxidative decomposition, and the lithium complex oxide has a lamellar rock salt structure for enhanced stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an amide-based solvent (such as N,N-dimethylformamide) is used as an electrolyte solvent, then the electric conductivity of the electrolyte solution is improved, but the oxidation potential decreases leading to oxidative decomposition
Solution Approach 1:
A lithium carbonate layer is formed as an intermediary protective coating on the surface of the lithium complex oxide positive electrode material. This layer acts as a barrier that prevents direct contact between the amide-based electrolyte solvent and the positive electrode material, thereby suppressing oxidative decomposition while allowing ionic conduction to proceed. The lithium carbonate layer serves as a mediator that enables the use of high-conductivity amide-based solvents without suffering from their low oxidation potential.
2Reliability
If a high concentration of lithium salt (more than or equal to 1.9 mol/l) is used in the electrolyte solution, then the electric conductivity is enhanced, but the oxidative decomposition risk increases
Solution Approach 1:
The concentration of lithium salt in the amide-based electrolyte solution is optimized to a specific range (1.9-2.3 mol/l). This parameter change achieves a balance between maintaining high electric conductivity and suppressing oxidative decomposition. The specific concentration range ensures sufficient ionic conductivity while the presence of lithium carbonate on the electrode surface provides protective effects against oxidation.
3Stability of the object's composition
If conventional binder materials like polyvinylidene fluoride (PVdF) are used in the positive electrode, then the electrode structure is compromised due to dissolution in amide-based solvents, but alternative binders may reduce conductivity
Solution Approach 1:
The binder material in the positive electrode is changed from conventional PVdF to amide-based soluble polymers such as polyacrylonitrile, polyacrylic acid, or carboxymethyl cellulose. This parameter change in material selection ensures the binder remains soluble and effective in amide-based electrolyte solvents, maintaining electrode structure stability. These alternative binders provide adequate structural support without dissolving, thereby preserving both structural integrity and electrical conductivity.
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 maintains the structural integrity of the positive electrode and enhances the oxidative resistance of the electrolyte solution, allowing the lithium ion secondary battery to function effectively within a high potential environment, achieving high electric conductivity and improved input/output characteristics.
Implementation Method 1
the lithium carbonate is adhered to the surface of the lithium complex oxide. Since the lithium carbonate protects the surface of the lithium complex oxide, the oxidative decomposition of DMF etc. is considered to be suppressed.
Implementation Method 2
the electrolyte solution includes a high concentration of the Li salt. Accordingly, the oxidative decomposition of DMF etc. can be suppressed.
Implementation Method 3
An electrolyte solution including an amide-based solvent (such as N,N-dimethylformamide) can have a high electric conductivity. This is presumably because the amide-based solvent has a high polarity and a low viscosity.
Data Source
AI summary
A lithium ion secondary battery at least includes a positive electrode, a negative electrode, and an electrolyte solution. The positive electrode at least includes a positive electrode active material and a binder. The positive electrode active material includes more than or equal to 0.08 mass % of a lithium carbonate and a remainder of a lithium complex oxide. The binder is at least one selected from a group consisting of polytetrafluoroethylene, polyethylene oxide, and carboxymethylcellulose. The electrolyte solution at least includes a solvent and a lithium salt. The solvent is at least one of N,N-dimethylformamide and dimethylacetamide. A concentration of the lithium salt in the electrolyte solution is more than or equal to 1.9 mol/l and less than or equal to 2.3 mol/l.