Tannic Acid Coating for Silicon Anodes Under Volume Expansion
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Solution Overview
Problem
Silicon-based negative electrode active materials in secondary batteries are prone to breaking due to volume expansion during charging and discharging, leading to reduced lifespan and performance.
Innovation Solution
A composition comprising tannic acid and a tris buffer solution is used to form cross-linked tannic acid-based coating films on primary particles of a silicon-based negative electrode active material, creating secondary particles through agglomeration and crosslinking, thereby reducing volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to increase theoretical capacity, then capacity increases, but volume expansion occurs during lithium intercalation
Solution Approach 1:
The patent applies the nesting principle by forming a coating film on the surface of silicon-based negative electrode active material particles. The coating film acts as an outer layer that encapsulates the silicon core, allowing the high-capacity silicon material to be utilized while the coating layer accommodates and buffers the volume expansion during lithium intercalation, preventing direct mechanical damage to the electrode structure.
Solution Approach 2:
The patent employs a coating film that functions as a flexible shell around the silicon-based active material. This thin film structure allows it to deform elastically during volume expansion and contraction cycles, maintaining structural integrity and preventing particle breakage while still enabling lithium ion transport to the silicon core.
2Quantity of substance
If silicon volume increases by up to 300% due to lithium intercalation, then capacity is achieved, but negative electrode breaks and cycling characteristic deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming a coating film on the silicon-based negative electrode active material before electrode assembly. This coating film serves as a cushioning layer that absorbs and distributes the mechanical stress generated during volume expansion, preventing direct transmission of stress to the electrode binder and current collector, thereby maintaining electrode integrity throughout cycling.
Solution Approach 2:
The patent utilizes composite materials by combining silicon-based active material with a coating film material that has complementary properties. The composite structure leverages the high capacity of silicon while the coating film provides mechanical strength, flexibility, and stability, creating a material system that exhibits both high capacity and excellent cycling characteristics.
3Reliability
If coating film is formed to control volume expansion, then electrode integrity is maintained, but manufacturing process complexity increases
Solution Approach 1:
The patent applies self-service by utilizing a coating formation process that leverages the inherent properties of the coating materials and the silicon surface. The coating film forms through self-assembly or spontaneous chemical reactions between the coating precursors and the silicon surface, eliminating the need for complex external equipment or multi-step deposition processes, thereby simplifying manufacturing while ensuring uniform coverage and adhesion.
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 tannic acid-based coating film effectively controls volume expansion and prevents damage to the negative electrode active material, enhancing the resistance and lifespan characteristics of the secondary battery.
Implementation Method 1
crosslinks between tannic acid-based coating films
Implementation Method 2
secondary particles of agglomerated primary particles
Implementation Method 3
effectively controls volume expansion and prevents damage to the negative electrode active material
Data Source
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AI summary
The present invention relates to a composition for coating a negative electrode active material, a negative electrode active material for a secondary battery, a negative electrode containing the same, and a lithium secondary battery containing the negative electrode. Particularly, a composition for coating a negative electrode active material, which includes tannic acid, a negative electrode active material for a secondary battery whose surface is coated with a tannic acid-based coating film, a negative electrode for a secondary battery, which includes the negative electrode active material, and a lithium secondary battery including the negative electrode may reduce volume expansion and prevent damage in charging/discharging of the negative electrode active material. Therefore, the secondary battery including the negative electrode of the present invention ultimately improves resistance and life span characteristics.