Two-Step Electrolyte Injection for Lithium-Ion SEI Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries face challenges in maintaining high energy efficiency and long cycle life under conditions of low electrolyte injection volume, particularly at low temperatures and during high-temperature cycling.
Innovation Solution
A two-step electrolyte injection method is employed, utilizing a first electrolyte with 0.5 wt % to 2 wt % vinylene carbonate, 5 wt % to 15 wt % lithium salt, and non-aqueous organic solvent, followed by a second electrolyte with 5 wt % to 20 wt % vinylene carbonate, 5 wt % to 15 wt % lithium salt, 0.005 wt % to 30 wt % infiltrant stabilizer, and non-aqueous organic solvent, along with additives like 1,3-propane sultone and fluoroethylene carbonate to enhance SEI film stability and battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If electrolyte injection volume is reduced to meet high capacity and high energy density requirements, then energy density is improved, but low-temperature and long-cycle performance deteriorates
Solution Approach 1:
The electrolyte injection process is divided into two distinct stages: first injecting a small volume of electrolyte (3.5-4.0 g/Ah) to form initial SEI film, then after formation and replenishment, injecting a second volume (3.5-4.0 g/Ah) to repair and stabilize the SEI film. This segmentation allows optimized electrolyte distribution for both energy density and long-cycle performance.
Solution Approach 2:
The first electrolyte injection and formation process create an initial SEI film structure before the battery is fully assembled and sealed. This preliminary action prepares the electrode surfaces to receive the second electrolyte injection, which then repairs and stabilizes the SEI film under optimized conditions, ensuring long-term reliability with reduced electrolyte volume.
2Duration of action of stationary object
If vinylene carbonate content is increased to improve SEI film stability, then cycle life is improved, but interfacial impedance increases
Solution Approach 1:
Vinylene carbonate is applied in two periodic stages with different concentrations. The first injection uses low VC content (0.5-2.0 wt%) to form initial SEI with low impedance. After formation and replenishment, the second injection uses high VC content (5.0-20.0 wt%) to repair and stabilize the SEI film, reducing impedance growth during cycling while maintaining low initial impedance.
Solution Approach 2:
The concentration parameter of vinylene carbonate is dynamically changed between two injection stages. The first stage uses 0.5-2.0 wt% VC to minimize impedance, while the second stage uses 5.0-20.0 wt% VC to maximize stability. This parameter change allows the system to achieve both low initial impedance and long cycle life.
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 method achieves a balance between low interfacial impedance and long cycle stability of the battery, while maintaining a low total electrolyte usage, thereby improving the battery's performance and lifespan under various temperature conditions.
Implementation Method 1
performing a formation process on the initial cell to form an initial SEI film
Implementation Method 2
the first electrolyte includes: 0.5 wt % to 2 wt % vinylene carbonate... the second electrolyte includes: 5 wt % to 20 wt % vinylene carbonate
Implementation Method 3
Electrolyte, as an important component of the lithium-ion battery system, serves as a bridge connecting the positive and negative electrodes to transmit lithium ions
Implementation Method 4
0.005 wt % to 30 wt % infiltrant stabilizer... where the infiltrant stabilizer is one of poly(ethyleneglycol) 2-[ethyl[(heptadecafluorooctyl)sulfonyl]amino]ethyl ether, 2-(N-Ethylperfluorooctanesulfonamido)ethyl methacrylate, fluorobenzene
Data Source
AI summary
Disclosed is a method for preparing lithium-ion batteries including: winding or sheet-stacking a positive electrode sheet, a negative electrode sheet, and a separator, and then placing them into a case to form an initial cell; injecting a first electrolyte into the initial cell, where the first electrolyte includes: 0.5 wt % to 2 wt % vinylene carbonate, 5 wt % to 15 wt % lithium salt, and non-aqueous organic solvent (all by weight); performing a formation process on the initial cell to form an initial solid electrolyte interphase film; injecting a second electrolyte into the initial cell, where the second electrolyte includes: 5 wt % to 20 wt % vinylene carbonate, 5 wt % to 15 wt % lithium salt, 0.005 wt % to 30 wt % infiltrant stabilizer, and non-aqueous organic solvent (all by weight); where the first electrolyte or the second electrolyte further includes: at least one of 1,3-propane sultone or fluoroethylene carbonate.