SiOx-Graphite Composite Negative Electrode for Battery Swelling
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Solution Overview
Problem
Non-aqueous secondary batteries using silicon oxide (SiOx) as a negative electrode material face issues with volumetric expansion and shrinkage during charge and discharge cycles, leading to battery swelling and reduced cycle characteristics due to its low conductivity and high reactivity with solvents.
Innovation Solution
A composite negative electrode material is developed, combining SiOx with carbon and graphite, where SiOx is coated with a conductive carbon material to form a conductive network, and the SiOx crystallite diameter is controlled to 50 nm or less, with a specific atom ratio of O to Si and a graphite content of 70-95 mass%, to enhance conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiOx is used as negative electrode material to increase capacity, then charge discharge capacity is improved, but volumetric expansion and shrinkage cause battery swelling and reduced cycle characteristics
Solution Approach 1:
The patent embeds ultrafine Si particles (average particle diameter 0.01 to 1 μm) within a SiO2 matrix structure, creating a nested configuration where the active Si cores are protected by the more stable SiO2 shell. This nested structure allows the high-capacity Si to undergo volumetric changes while being constrained and protected by the SiO2 matrix, preventing particle crushing and maintaining structural integrity during charge-discharge cycles.
Solution Approach 2:
The patent employs a composite material system consisting of Si particles dispersed in a SiO2 matrix, combined with carbonaceous materials and conductive agents. This composite structure integrates the high capacity of Si with the structural stability of SiO2 and the conductivity of carbon materials, achieving both high charge-discharge capacity and good cycle characteristics while suppressing battery swelling.
2Speed
If SiOx particles are made ultrafine to improve load characteristics, then load characteristic is improved, but conductivity remains low and reactivity with solvent increases
Solution Approach 1:
The patent introduces carbonaceous materials (such as graphite, amorphous carbon, or carbon nanotubes) as intermediary components that form conductive networks around and between the SiOx particles. These carbon materials act as mediators that provide electrical pathways, compensating for the low intrinsic conductivity of ultrafine SiOx particles while maintaining their high surface area and fast reaction kinetics for improved load characteristics.
3Reliability
If SiOx surfaces are coated with conductive material to improve conductivity, then load characteristic is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines multiple functional components (Si particles, SiO2 matrix, carbonaceous materials, and conductive agents) into a single integrated composite material system that can be processed together as one unit. This merging approach eliminates the need for separate coating steps, as all components are mixed and formed simultaneously into electrode structures, simplifying the manufacturing process while achieving both high conductivity and structural stability.
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 composite electrode material improves charge discharge cycle characteristics and suppresses battery swelling by maintaining conductivity and structural integrity during cycles, while maintaining a high capacity retention rate over 500 cycles.
Implementation Method 1
combining SiOx with carbon and graphite, where SiOx is coated with a conductive carbon material to form a conductive network
Implementation Method 2
SiOx exhibits large volumetric expansion and shrinkage associated with the charge and the discharge reaction
Implementation Method 3
The material containing Si and O as constitution elements has a crystallite diameter of 50 nm or less
Data Source
AI summary
[Objectives] The present invention provides a non-aqueous secondary battery in which a material containing Si and O as constituent elements is used in a negative electrode. The present invention provides a non-aqueous secondary battery having good charge discharge cycle characteristics, and suppressing the battery swelling associated with the charge and the discharge. Also, the present invention relates to a negative electrode that can provide the non-aqueous secondary battery. [Solution] The negative electrode includes a negative electrode active material, including a composite of a material containing Si and O as constitution elements (atom ratio x of O to Si is 0.5≦x≦1.5) in combination with a carbon material, and graphite. The graphite has an average particle diameter dg (μm) of 4 to 20 μm. The material containing Si and O as constitution elements has an average particle diameter ds (μm) of 1 μm or more. The ratio ds/dg (i.e., ds to dg) is 0.05 to 1. The material containing Si and O as constitution elements has a crystallite diameter of 50 nm or less, the crystallite diameter is calculated from a half width at a (220) plane of Si obtained by an X-ray diffraction method, using Scherrer Formula. In 100 mass % of the composite of the material containing Si and O as constitution elements, and the carbon material, a ratio of the material containing Si and O as constitution elements is 70 to 95 mass %.