Si-Composite Lithium Battery Electrolyte for High-Voltage Cycle Life
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Solution Overview
Problem
Rechargeable lithium batteries face performance deterioration and reduced cycle life due to electrolyte solution decomposition and side reactions at high voltage and temperature, leading to increased internal resistance and safety concerns.
Innovation Solution
A rechargeable lithium battery design incorporating a negative electrode with a Si composite and an electrolyte solution containing a specific additive, such as 2-fluoro-1,3,2-dioxaphospholane, and a lithium salt like LiFSI, which suppresses electrolyte solution decomposition and forms a solid electrolyte interface to reduce gas generation and internal resistance.
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 solution oxidization at high voltage
Solution Approach 1:
A coating layer comprising at least one of an oxide, oxyhydroxide, hydroxide, or carbonate of a coating element is formed on the positive electrode surface. This coating layer acts as an intermediary barrier between the electrolyte solution and the positive electrode active material, preventing direct contact and chemical reactions. The coating element is selected from Mg, Al, Co, K, Na, Ca, or a rare earth element, creating a protective interface that maintains electrode performance while allowing high voltage operation for increased capacity
Solution Approach 2:
The invention modifies the surface properties of the positive electrode by changing the chemical composition and structure of the surface layer through coating formation. This parameter change creates a stable interface that resist electrolyte oxidization, enabling the battery to operate at higher voltages to achieve greater energy density without compromising electrode reliability
2Reliability
If LiPF6 is used as the lithium salt in the electrolyte solution, then the electrolyte conductivity is improved, but the solvent depletes and gas is generated at high temperature
Solution Approach 1:
The invention changes the chemical composition parameters of the electrolyte solution by specifying precise proportions of different components: 1,3-propanesultone (0.01-5 wt%), vinylene carbonate (0.1-5 wt%), fluoroethylene carbonate (0.1-5 wt%), lithium bis(fluorosulfonyl)imide (1-10 M), and cyclic carbonate solvents (15-30 vol%). This parameter optimization balances conductivity with thermal stability, preventing solvent depletion and gas generation at high temperatures while maintaining adequate electrolyte conductivity
Solution Approach 2:
The electrolyte solution is formulated as a composite system combining multiple components with complementary functions: sultone compounds for film formation and stability, cyclic carbonates for conductivity, chain carbonates for solubility, and lithium salts for ion transport. This composite approach achieves both high conductivity and thermal stability, eliminating the trade-off between these properties
3Productivity
If the battery operates at high temperature, then the reaction rate increases, but the internal pressure rises due to gas components from side reactions
Solution Approach 1:
A protective film is formed on the positive electrode surface through preliminary coating with oxide, oxyhydroxide, hydroxide, or carbonate of a coating element. This preliminary protective layer prevents side reactions between the electrolyte and electrode at high temperatures, thereby preventing gas generation that would lead to internal pressure increase, while still allowing the battery to operate at elevated temperatures for improved reaction rates
Solution Approach 2:
The invention converts the potentially harmful effect of high temperature (which accelerates unwanted side reactions) into a beneficial operating condition by creating a thermally stable coated electrode. The coating layer enables the battery to safely operate at high temperatures, utilizing the increased reaction rate for improved productivity while the coating prevents the harmful gas generation that would otherwise occur
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 improves battery stability and cycle-life characteristics at both high temperature and room temperature by reducing internal resistance and enhancing ion conductivity, thereby extending the battery's lifespan and safety.
Implementation Method 1
the additive comprises a compound represented by Chemical Formula 1... suppresses decomposition of an electrolyte solution and side reactions with an electrode to suppress an increase in battery internal resistance
Implementation Method 2
the lithium salt comprises a compound represented by Chemical Formula 2... enhances ion conductivity, thereby extending the battery's lifespan and safety
Implementation Method 3
the negative electrode active material comprises a Si composite... improves cycle-life characteristics at high temperature and room temperature due to increased capacity
Data Source
Figure 1
AI summary
Provided is a rechargeable lithium battery comprising a positive electrode comprising a positive electrode active material; a negative electrode comprising a negative electrode active material; and an electrolyte solution comprising a non-aqueous organic solvent, a lithium salt, and an additive, wherein the negative electrode active material comprises a Si composite, the additive comprises a compound represented by Chemical Formula 1, the lithium salt comprises a compound represented by Chemical Formula 2, and the compound represented by Chemical Formula 2 is comprised in an amount of about 5 to about 70 wt% based on 100 wt% of the total amount of the lithium salt. Details of Chemical Formula 1 and Chemical Formula 2 are as described in the specification.