Silicon-Anode Electrolyte Additive for High-Temperature Storage
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Solution Overview
Problem
Lithium ion batteries with silicon-based negative electrodes face challenges in high-temperature storage performance due to volume expansion and impedance increase, leading to reduced energy density and stability.
Innovation Solution
A secondary battery design incorporating a silicon-based negative electrode material layer and a non-aqueous electrolyte with a specific additive, represented by structural formula 1, which forms a solid electrolyte interface film containing sulfur, replacing carbonate lithium salts to prevent impedance and gas generation during high-temperature storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode material is used to improve energy density, then theoretical specific capacity increases, but volume expansion reaches up to 300% and solid electrolyte interface film is destroyed
Solution Approach 1:
The patent applies preliminary action by pre-forming a stable solid electrolyte interface film containing lithium sulfonate and lithium sulfate compounds before silicon volume expansion occurs. This pre-formed film acts as a protective barrier that accommodates the 300% volume expansion of silicon during lithiation, preventing film destruction and maintaining electrode integrity throughout charge-discharge cycles.
Solution Approach 2:
The patent employs composite materials by creating a solid electrolyte interface film with a composite chemical composition containing both lithium sulfonate (from sultone compound decomposition) and lithium sulfate (from electrolyte salt). This composite film structure provides enhanced mechanical stability and chemical resistance to accommodate silicon's volume expansion while maintaining ionic conductivity.
2Quantity of substance
If silicon-based negative electrode material is used to improve energy density, then theoretical specific capacity increases, but high-temperature storage performance deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the solid electrolyte interface film to include lithium sulfonate and lithium sulfate compounds in specific ratios. This compositional parameter change increases the film's thermal stability and resistance to decomposition at elevated temperatures, thereby improving high-temperature storage performance while maintaining silicon's high capacity characteristics.
Solution Approach 2:
The patent uses sultone compound as a sacrificial additive that decomposes during battery formation to form the stable interface film. This disposable organic compound serves its purpose by providing the precursor for lithium sulfonate formation, then is consumed in the process, leaving behind a stable inorganic-rich film that protects the silicon electrode during high-temperature storage.
3Reliability
If conventional electrolyte additives are used, then solid electrolyte interface film forms, but impedance increases and CO2 gas generation occurs during high-temperature storage
Solution Approach 1:
The patent converts the harmful side reactions of conventional electrolyte additives into beneficial effects by using sultone compound decomposition to form lithium sulfonate in the interface film. Instead of generating CO2 gas and increasing impedance as conventional additives do, the sultone-derived film components create a stable, low-impedance interface that prevents further parasitic reactions and eliminates gas generation during high-temperature storage.
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 achieves improved high-temperature storage performance while maintaining excellent energy density, with the additive's decomposition forming a stable interface film that inhibits volume expansion and reaction with the silicon-based material, enhancing the battery's stability and capacity retention.
Implementation Method 1
the additive will be reduced and decomposed at the negative electrode before the solvent in the formation process to form a solid electrolyte interface film (SEI)
Implementation Method 2
form a solid electrolyte interface film (SEI), and the formed interface film also contains element S
Implementation Method 3
the additive will be reduced and decomposed at the negative electrode before the solvent in the formation process
Implementation Method 4
the alloying of silicon and lithium in the charging state leads to serious volume expansion of the negative electrode
Data Source
AI summary
The present application provides a secondary battery, including a positive electrode, a negative electrode with a negative electrode material layer, and a non-aqueous electrolyte, the negative electrode material layer comprises a negative electrode active material, and the negative electrode active material comprises a silicon-based material;the non-aqueous electrolyte comprises a solvent, an electrolyte salt and an additive, the additives comprises a compound represented by structural formula 1;wherein n is 0 or 1, A is selected from C or O, X is selected fromR1 and R2 are each independently selected from H,R1 and R2 are not selected from H at the same time, and X, R1 and R2 comprise at least one sulfur atom;the secondary battery meets the following requirements:0.21≤m*n*rS≤40;and 40%≤m≤90%, 0.05%≤n≤2%, 1.2 g/cm3≤r≤1.8 g/cm3, 5%≤S≤30%.