Silicon Anode Composition With Carbon Coating for Gas and Swelling Control
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Solution Overview
Problem
Lithium secondary batteries using silicon-based negative electrodes face issues with volume expansion and gas generation, leading to degradation of battery characteristics and reduced energy density due to the rapid expansion of silicon-based compounds during charging and discharging.
Innovation Solution
A negative electrode composition is developed with a silicon-based active material coated with a carbon layer and a binder combination of rubber-based and aqueous binders, where the rubber-based binder is used in higher content to maintain contact between active materials and minimize conductive material usage, thereby reducing volume expansion and gas generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based compounds are used as negative electrode active material to increase capacity, then energy density is improved, but volume expansion occurs during charging leading to conductive path disconnection and battery characteristic degradation
Solution Approach 1:
The patent applies a carbon coating layer (thin film) on the silicon-based active material particles. This carbon shell accommodates the volume expansion of silicon during lithiation while maintaining structural integrity and preventing particle disconnection, thus resolving the contradiction between high capacity and volume stability.
Solution Approach 2:
The patent creates a composite structure by combining silicon-based active material with carbon coating and conductive material. This composite approach allows the silicon to provide high capacity while the carbon and conductive material matrix maintains structural stability and electrical conductivity during volume changes.
2Quantity of substance
If silicon-based compounds are used to achieve high energy density, then capacity increases, but gas generation occurs leading to slurry instability and manufacturing issues
Solution Approach 1:
The patent converts the harmful gas generation reaction into a beneficial process by controlling the carbon coating formation. The carbon coating is formed through controlled carbonization of organic material, and this same carbon layer then prevents subsequent gas generation by isolating the silicon from unwanted reactions with water and oxygen.
Solution Approach 2:
The carbon coating acts as an intermediary layer between the silicon-based active material and the external environment (water, oxygen, conductive material). This intermediate layer prevents direct contact that would cause gas generation while still allowing lithium ion transport.
3Ease of manufacture
If aqueous binders are used for silicon-based negative electrodes, then self-dispersibility issues are addressed, but gas generation problems occur during slurry preparation
Solution Approach 1:
The carbon coating serves as an intermediary that prevents direct reaction between the silicon-based active material and water in the aqueous binder. This allows the use of aqueous binders for improved manufacturability and dispersibility while eliminating gas generation through controlled carbonization.
4Reliability
If rubber-based binders with high ductility are used to maintain connection during volume expansion, then conductive path connectivity is improved, but self-dispersibility of silicon-based active material deteriorates
Solution Approach 1:
The carbon coating layer acts as a flexible shell that maintains particle integrity during volume expansion, reducing the reliance on rubber-based binders for maintaining connectivity. This enables better dispersibility while preserving conductive path connectivity through the carbon-coated particle network.
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 solution enhances the stability and performance of the negative electrode by suppressing gas generation and maintaining better contact between silicon-based active materials, resulting in improved energy density and capacity retention.
Implementation Method 1
the silicon-based active material is hydrated by —OH groups on the surface and gas is generated through electron transfer with the carbon of the conductive material
Implementation Method 2
research has been conducted to apply SBR-CMC-based binders with excellent elongation properties, instead of aqueous binders (PAA, PAM, and the like) having a large modulus applied to existing silicon-based negative electrodes
Data Source
AI summary
A negative electrode composition, a negative electrode including the same, a lithium secondary battery including the negative electrode, and a method of manufacturing the negative electrode composition are provided. The negative electrode composition comprises a silicon-based active material, a negative electrode conductive material, and a negative electrode binder, wherein the silicon-based active material comprises Si and optionally SiOx (0<x<2), and includes 70 parts by weight or more of Si on the basis of 100 parts by weight of the silicon-based active material, a carbon coating layer is formed on the silicon-based active material, the negative electrode binder comprises a rubber-based binder and an aqueous binder, and a content of the rubber-based binder is higher than that of the aqueous binder.