Lithium Battery Electrolyte Stabilization via Carbon Nanotubes and Cyclic Sulfone
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Solution Overview
Problem
Lithium secondary batteries face performance deterioration and safety issues due to electrolyte solution decomposition at high voltage and temperature, leading to increased internal resistance and reduced cycle life.
Innovation Solution
A lithium secondary battery design incorporating a positive electrode with carbon nanotubes and a cyclic sulfone-based compound in the electrolyte solution, which improves impregnation properties and suppresses electrolyte decomposition, thereby enhancing initial resistance and high-temperature storage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the voltage range is expanded to increase energy density, then the battery capacity is improved, but the positive electrode performance deteriorates due to electrolyte oxidation at high voltage
Solution Approach 1:
A coating layer comprising a cyclic carboxylate and a cyclic sulfone is introduced as an intermediary between the positive electrode and the electrolyte solution. This coating layer acts as a protective barrier that prevents direct contact and harmful oxidation reactions between the electrolyte and the positive electrode, while still allowing lithium ion transport. The coating layer thus mediates the interaction, enabling high voltage operation without electrode deterioration.
Solution Approach 2:
The invention changes the chemical composition and physical state parameters of the electrode surface by forming a specific coating layer with controlled thickness and composition. The coating layer has different chemical properties than the bulk electrode materials, creating a new interface that is resistant to oxidation. This parameter change at the surface level allows the battery to operate at higher voltages without compromising electrode stability.
2Use of energy by moving object
If LiPF6 is used as the lithium salt to achieve high conductivity, then the battery performance is improved, but decomposition products such as HF and PF5 are generated causing electrolyte depletion and safety issues at high temperature
Solution Approach 1:
The coating layer is formed preliminarily on the positive electrode surface before the harmful decomposition reactions can occur. This pre-formed protective barrier prevents the electrolyte from contacting and decomposing at the electrode surface, thereby preventing the generation of harmful decomposition products like HF and PF5. The preliminary protective action thus prevents the harmful effects before they can manifest.
Solution Approach 2:
The invention converts the potentially harmful high-temperature conditions into a benefit by using them to form a stable protective coating layer on the positive electrode. The coating layer, once formed, is more stable at high temperatures and actually protects the electrode from further degradation. The high temperature that would normally accelerate decomposition instead helps create a more robust protective interface.
3Reliability
If the carbon nanotube content is increased to improve conductivity, then the initial resistance is reduced, but the impregnation properties of the positive electrode in the electrolyte solution deteriorate
Solution Approach 1:
The invention optimizes the carbon nanotube content parameter to a specific range (0.5-4 wt%) where the conductivity improvement is maximized while the negative impact on impregnation properties is minimized. Additionally, the coating layer parameters are adjusted to ensure proper electrolyte penetration. By carefully controlling these parameters, the invention achieves the optimal balance between conductivity and impregnation properties.
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 battery exhibits improved initial resistance and high-temperature stability, with enhanced cycle-life characteristics and reduced internal resistance, ensuring better performance and safety.
Implementation Method 1
an additive including a cyclic sulfone-based compound... suppressing decomposition of an electrolyte solution and a side reaction with an electrode
Implementation Method 2
the positive active material layer includes a positive active material and carbon nanotube... improving impregnation properties of a positive electrode in the electrolyte solution
Data Source
AI summary
Provided is a lithium secondary battery including a positive electrode including a positive electrode current collector, and a positive active material layer on the positive electrode current collector; a negative electrode including a negative active material; and an electrolyte solution including a non-aqueous organic solvent, a lithium salt, and an additive, the positive active material layer includes a positive active material and carbon nanotube, an average length of the carbon nanotube is greater than or equal to 1 μm and less than 200 μm, the carbon nanotube is included in an amount of greater than or equal to 0.5 wt % and less than 4 wt % based on the total weight of the positive active material layer, the additive includes a cyclic sulfone-based compound represented by Chemical Formula 1.Details of Chemical Formula 1 are as described in the specification.