Silicon Anode Core-Shell Structure for Battery Cycle Stability
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Solution Overview
Problem
Secondary batteries using silicon as an anode active material face challenges with surface cracking during charge and discharge, leading to increased reactive surface area, electrolyte decomposition, and degraded cycle characteristics.
Innovation Solution
A secondary battery design featuring a core section with Si and O, covered by a low-crystalline or noncrystalline section with a carbon-containing material in its voids, which enhances lithium ion insertion and extraction while preventing surface cracking and electrolyte decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si is used as an anode active material to increase theoretical capacity, then battery capacity is improved, but the anode active material is intensely expanded and shrunk causing surface cracking
Solution Approach 1:
The patent uses a composite structure where Si particles are embedded in a carbon matrix. The carbon matrix provides mechanical strength and structural stability while Si provides high capacity. This composite approach allows the material to withstand expansion and contraction without surface cracking, resolving the contradiction between high capacity and surface integrity.
Solution Approach 2:
The carbon coating layer acts as a flexible shell around the Si particles. This thin film structure allows for volume changes during lithium insertion and extraction while maintaining surface integrity. The flexible carbon shell accommodates the expansion and contraction of Si without causing cracking, thus preserving surface integrity while enabling high capacity.
2Productivity
If surface cracking occurs to increase reactive surface area, then lithium ion insertion and extraction are enhanced, but electrolyte decomposition increases and cycle characteristics deteriorate
Solution Approach 1:
The carbon coating layer serves as an intermediary between the Si particles and the electrolyte. It provides a stable interface that facilitates lithium ion insertion and extraction while preventing direct contact between the electrolyte and the reactive Si surface. This mediator role maintains high productivity while preventing electrolyte decomposition and preserving cycle characteristics.
Solution Approach 2:
The flexible carbon shell maintains surface integrity during lithium ion insertion and extraction cycles. By preventing surface cracking, it avoids the creation of highly reactive new surfaces that would otherwise cause electrolyte decomposition. The shell remains intact throughout cycling, ensuring reliable cycle characteristics while still allowing efficient lithium ion transport.
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
This configuration improves battery performance by maintaining smooth lithium ion insertion and extraction, reducing irreversible capacity, and enhancing electric conductivity and cycle stability.
Implementation Method 1
a core section capable of inserting and extracting lithium ions
Implementation Method 2
a carbon-containing material which contains C as a constituent element is provided in the voids of the covering section
Data Source
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AI summary
A secondary battery capable of obtaining superior battery characteristics is provided. The secondary battery of the present technology includes a cathode, an anode including an active material, and an electrolytic solution. The active material includes a core section and covering section, the core section being capable of inserting and extracting lithium ions, and the covering section being provided in at least part of a surface of the core section and being a low-crystalline or a noncrystalline. The core section includes Si and O as constituent elements, and an atom ratio x (O/Si) of O with respect to Si satisfies 0≤x<0.5. The covering section includes Si and O as constituent elements, and an atom ratio y (O/Si) of O with respect to Si satisfies 0.5≤y≤1.8. The covering section has voids, and a carbon-containing material is provided in at least part of the voids.