Silicon Negative Electrode Carbon Coating for Lithium Battery
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Solution Overview
Problem
Silicon negative electrodes in lithium batteries face challenges such as irreversible electric capacity loss due to alloying and de-alloying with lithium ions, volume changes causing structural issues, and reactions with the electrolyte that form a solid electrolyte interphase (SEI) film, leading to reduced charge/discharge efficiency.
Innovation Solution
A lithium battery design incorporating a silicon negative electrode coated with a carbon film, a lithium mixed metal oxide positive electrode, a separator, and an electrolytic solution containing an organic solvent, lithium salt, and additives like maleimides or vinylene carbonate to form a stable SEI film, reducing irreversible capacity loss and enhancing conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon negative electrode is used to achieve high electric capacity, then electric capacity increases, but irreversible capacity loss increases due to alloying and de-alloying reactions with lithium ions
Solution Approach 1:
The patent applies preliminary action by pre-coating the silicon negative electrode with a carbon film before battery operation. This carbon coating layer is formed in advance to prevent direct contact between the silicon electrode and electrolyte, thereby preventing irreversible capacity loss that would otherwise occur during alloying and de-alloying reactions. The carbon coating is applied before the battery undergoes its first charge/discharge cycle, establishing protective measures beforehand.
Solution Approach 2:
The patent uses a carbon coating layer as an intermediary between the silicon negative electrode and the electrolyte. This intermediate layer allows lithium ions to pass through while preventing direct alloying reactions between silicon and electrolyte components. The carbon coating acts as a mediator that enables beneficial ion transport while blocking harmful direct reactions that cause irreversible capacity loss.
2Quantity of substance
If silicon negative electrode undergoes alloying and de-alloying with lithium ions to achieve high capacity, then electric capacity increases, but volume changes cause electrode structure to peel
Solution Approach 1:
The patent employs a carbon coating thin film as a flexible shell that envelops the silicon negative electrode. This carbon film layer is designed to accommodate the volume expansion and contraction of silicon during alloying and de-alloying cycles while maintaining structural integrity. The flexible carbon coating prevents the electrode structure from peeling by providing a compliant protective layer that moves with the silicon substrate.
Solution Approach 2:
The patent creates a composite structure by combining silicon negative electrode material with a carbon coating layer. This composite material approach integrates the high-capacity silicon core with the structurally stable carbon shell, forming a hybrid electrode that benefits from both materials' properties. The composite structure maintains electrode integrity during volume changes while preserving the high capacity characteristics of silicon.
3Productivity
If silicon negative electrode reacts with electrolyte to form SEI film, then initial charge/discharge capacity is achieved, but irreversible capacity loss increases
Solution Approach 1:
The patent extracts or removes the harmful direct reaction between silicon and electrolyte by introducing a carbon coating barrier. Instead of allowing the silicon electrode to directly form SEI film with the electrolyte (which causes irreversible capacity loss), the carbon coating is extracted as an intermediate layer that prevents this harmful interaction while still permitting necessary ion transport for charge/discharge functionality.
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 proposed design improves the charge/discharge efficiency of silicon negative electrodes by reducing irreversible capacity loss and maintaining electrode structure integrity, as evidenced by higher charge/discharge capacities and efficiencies in experimental results.
Implementation Method 1
the silicon powder for manufacturing the silicon negative electrode is covered by carbon film
Implementation Method 2
an organic electrolytic solution in which a lithium salt is dissolved is used instead
Implementation Method 3
the lithium ions of the electrolytic solution and the silicon negative electrode will alloy and de-alloy during charging and discharging, respectively
Implementation Method 4
the re-crystallized silicon surface and the electrolyte reacts to form an SEI film
Data Source
AI summary
Disclosed is a lithium battery including a silicon negative electrode, a lithium mixed metal oxide positive electrode, a separator disposed between the negative and positive electrodes to define a reservoir region, an electrolytic solution filled in the reservoir region, and a sealant structure wrapped around the silicon negative electrode, the lithium mixed metal oxide positive electrode, the separator, and the electrolytic solution. The electrolytic solution includes an organic solvent, a lithium salt, and an additive. The additive includes a maleimide compound and vinylene carbonate. The silicon negative electrode of the lithium battery employing the described electrolytic solution has higher cycle efficiency and longer operating lifespan.