Lithium Battery Electrolyte Additives for SEI Stability
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Solution Overview
Problem
Rechargeable lithium batteries face challenges in achieving high charge and discharge rate capability, stable cycle-life characteristics, and low-temperature stability, particularly in hybrid batteries like ISG batteries for automobiles, where the formation of a stable Solid Electrolyte Interface (SEI) film is crucial.
Innovation Solution
A non-aqueous electrolyte for rechargeable lithium batteries is developed, comprising a lithium salt, a non-aqueous organic solvent, and specific additives such as lithium difluoro bis(oxalato)phosphate and tris(trimethylsilyl)borate, which are included in specific concentrations to enhance ionic conductivity and suppress side reactions, forming a stable SEI film that improves charge and discharge rate capability and low-temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional electrolytes are used, then basic battery operation is maintained, but charge and discharge rate capability is insufficient
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by introducing specific additives (lithium difluoro bis(oxalato)phosphate and tris(trimethylsilyl)borate) at optimized concentrations. These parameter changes enable the formation of a stable SEI film that simultaneously improves charge/discharge rate capability and extends cycle-life, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent creates a composite electrolyte system by combining multiple components (lithium salt, non-aqueous organic solvent, and specific additives) in a synergistic formulation. This composite approach produces a stable SEI film with enhanced properties that simultaneously addresses both high rate capability and long cycle-life requirements.
2Power
If high power characteristics are achieved, then charge and discharge rate capability improves, but low-temperature stability deteriorates
Solution Approach 1:
The patent adjusts the electrolyte composition parameters by incorporating specific additives that modify the SEI film properties. These changes enable the battery to maintain high power characteristics while improving low-temperature stability, as the stabilized SEI film reduces impedance changes across different temperature conditions.
3Volume of moving object
If compact size is achieved, then energy density improves, but heat management and stability challenges increase
Solution Approach 1:
The patent modifies the electrolyte composition to form a stable SEI film that provides thermal protection. This parameter change allows compact battery design with improved thermal stability, as the stabilized interface reduces unwanted reactions and heat generation in the confined space.
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 electrolyte formulation results in rechargeable lithium batteries with significantly improved charge and discharge rate capability, extended cycle-life, and enhanced low-temperature stability, meeting the demands of hybrid batteries with 5 to 10 times longer cycle-life and high power characteristics in a compact size.
Implementation Method 1
the lithium ions that come out of the positive active material, such as lithium transition metal oxide, transfer to the negative active material and are implanted between the layers of the negative active material
Implementation Method 2
the electrolyte and a lithium salt react with each other on the surface of the negative active material to form a solid electrolyte interface (SEI) film
Implementation Method 3
The SEI film serves as an ion tunnel and allows only lithium ions to pass through. The SEI film prevents organic solvent molecules having a high molecular weight from transferring along with the lithium ions
Implementation Method 4
as the SEI film prevents contact between the organic solvent molecules in the electrolyte and the negative active material, the electrolyte does not decompose
Data Source
AI summary
The invention relates to an electrolyte for a rechargeable lithium battery that comprises a lithium salt, a non-aqueous organic solvent, a first additive represented by the following Chemical Formula 1, and a second additive represented by the following Chemical Formula 2. The invention also relates to a rechargeable lithium battery comprising an electrolyte of the invention.