Non-Aqueous Electrolyte Additives for Durable Silicon-Anode SEI
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Solution Overview
Problem
Lithium secondary batteries using silicon-based active materials face issues with volume expansion and contraction during charging and discharging, leading to reduced conductivity, accelerated electrolyte side reactions, and decreased lifespan and storage performance, particularly at high temperatures.
Innovation Solution
A non-aqueous electrolyte comprising specific additives, including a coumarin-based compound for rapid ring-opening reactions and a cyclic siloxane-based compound for high shear modulus, forms a flexible and durable solid electrolyte interphase (SEI) film on the negative electrode, enhancing durability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are used as negative electrode materials, then battery capacity is improved, but volume expansion and contraction occur during charging and discharging leading to reduced conductivity and decreased lifespan
Solution Approach 1:
The patent applies preliminary action by forming a stable SEI film on the silicon-based negative electrode before the battery enters normal operation. The electrolyte contains specific additives (vinylene carbonate at 0.01-5 wt% and fluoroethylene carbonate at 0.01-5 wt%) that preferentially react during initial charging cycles to create a protective interface layer. This pre-formed SEI film prevents subsequent electrolyte decomposition and maintains electrode integrity during volume expansion/contraction, thereby extending battery lifespan while preserving high capacity
Solution Approach 2:
The patent uses the SEI film as an intermediary layer between the silicon-based negative electrode and the electrolyte. This intermediate layer mediates the interaction by providing a stable interface that accommodates silicon's volume changes while preventing direct contact between the electrolyte and silicon surface. The controlled composition of additives in the electrolyte enables formation of this intermediary protective layer that resolves the contradiction between maintaining high capacity and ensuring long lifespan
2Quantity of substance
If silicon-based active materials are used as negative electrode materials, then battery capacity is improved, but conductivity decreases due to volume expansion and contraction
Solution Approach 1:
The patent employs the SEI film as a flexible protective shell on the silicon-based negative electrode. This thin film layer is formed by controlled decomposition of vinylene carbonate and fluoroethylene carbonate additives during initial cycles. The flexible nature of this SEI shell allows it to accommodate the volume expansion and contraction of silicon during charging and discharging without cracking or detaching, thereby maintaining continuous electrical conductivity and preventing exposure of fresh silicon surfaces that would cause further electrolyte decomposition and conductivity loss
3Ease of operation
If conventional electrolytes are used, then battery operation is simple, but storage performance deteriorates at high temperatures
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the electrolyte. Specifically, it incorporates vinylene carbonate at 0.01-5 wt% and fluoroethylene carbonate at 0.01-5 wt% into the electrolyte formulation. These compositional parameter changes enable the formation of a thermally stable SEI film on the negative electrode that resists decomposition at high temperatures during storage, thereby improving storage performance while maintaining simple battery operation. The modified electrolyte composition creates a more stable interface that prevents capacity fade during high-temperature storage conditions
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 SEI film improves the lifespan and storage performance of lithium secondary batteries, especially at high temperatures, by preventing electrolyte side reactions and maintaining conductivity.
Implementation Method 1
the first additive has strong reducibility at the negative electrode to cause a rapid ring-opening reaction during formation of an initial SEI film
Implementation Method 2
the first additive has strong reducibility at the negative electrode
Implementation Method 3
the second additive may form a siloxane-based SEI film during cathodic reduction
Implementation Method 4
radicals formed when the first additive is decomposed promote the ring-opening reaction of the second additive
Implementation Method 5
radicals formed when the first additive is decomposed
Data Source
AI summary
The present disclosure relates to a non-aqueous electrolyte including lithium salts, an organic solvent, and an additive including a first additive and a second additive. Each of the first additive and the second additive includes a compound represented by a specific Formula.