SiOx Composite Negative Electrode for Lithium-Ion Batteries
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Solution Overview
Problem
Non-aqueous secondary batteries using SiOx as the negative electrode material face challenges in achieving high capacity and excellent storage characteristics due to volume expansion and contraction issues, poor conductivity, and irreversible capacity increase during charge and discharge cycles.
Innovation Solution
A non-aqueous secondary battery design featuring a negative electrode with a carbon-coated SiOx composite, where the carbon content is optimized between 10 to 30 mass%, and the Si crystallite size is controlled to maintain high capacity while minimizing volume changes, using a carbon coating layer to enhance conductivity and load characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiOx is used as negative electrode material to increase capacity, then charge and discharge capacity is improved, but volume expansion and contraction causes particle pulverization and irreversible capacity increase
Solution Approach 1:
The patent applies the nesting principle by forming a core-shell structure where Si particles are embedded within a SiO2 matrix, and the entire composite is further coated with a carbon layer. This nested structure allows the Si core to expand and contract during lithium insertion/extraction while being constrained and protected by the SiO2 shell and carbon coating, preventing particle pulverization and maintaining cycle stability.
Solution Approach 2:
The patent employs composite materials by creating a SiOx composite where ultrafine Si particles are dispersed in a SiO2 matrix, and further coating it with carbon. This composite structure combines the high capacity of Si with the structural stability of SiO2 and the conductivity/protection of carbon, resolving the contradiction between capacity and reliability.
2Quantity of substance
If SiOx undergoes charge and discharge reactions to store lithium, then capacity is improved, but battery expansion occurs due to volume changes
Solution Approach 1:
The nested core-shell structure of Si particles within SiO2 matrix, further coated with carbon, constrains the volume expansion of Si during lithium insertion. The SiO2 shell and carbon coating act as protective layers that absorb and distribute the mechanical stress, preventing battery expansion while maintaining high lithium storage capacity.
Solution Approach 2:
The patent changes the physical parameters of the SiOx material by controlling the particle size (ultrafine particles), the composition ratio (SiOx where 0.5 ≤ x ≤ 1.5), and the shell thickness. These parameter changes enable the material to accommodate volume changes during charge-discharge while minimizing overall battery expansion.
3Power
If SiOx surface is coated with conductive material to improve load characteristics, then conductivity is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated carbon coating layer that simultaneously provides electrical conductivity for improved load characteristics, structural protection against particle pulverization, and constraint on volume expansion. This consolidation improves power while avoiding the complexity of separate functional layers.
Solution Approach 2:
The carbon-coated SiOx composite integrates the conductive properties of carbon with the structural stability of SiO2 and the high capacity of Si, creating a multi-functional material that improves power characteristics without requiring complex device architecture.
4Quantity of substance
If SiOx is used to achieve high capacity, then charge and discharge capacity is improved, but storage characteristics deteriorate due to reaction between Si and non-aqueous electrolyte solution
Solution Approach 1:
The SiO2 matrix and carbon coating layer act as intermediary barriers between the reactive Si particles and the non-aqueous electrolyte solution. These intermediate layers prevent direct contact and unwanted reactions between Si and the electrolyte, thereby improving storage characteristics while preserving the high capacity of Si.
Solution Approach 2:
The composite structure of Si particles dispersed in SiO2 matrix with carbon coating creates a protective system that isolates the reactive Si from the electrolyte during storage, preventing capacity loss while maintaining high discharge capacity when the battery is in use.
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 battery achieves high capacity and excellent storage characteristics with improved load and cycle performance, maintaining capacity retention even after repetitive charge and discharge cycles.
Implementation Method 1
improving load characteristics by coating the SiOx surface with a conductive material such as carbon
Implementation Method 2
since the aforementioned SiOx undergoes large volume expansion and contraction associated with a charge and discharge reaction
Implementation Method 3
techniques have been proposed of suppressing the volume expansion and contraction of SiOx, which accompanies a charge and discharge reaction, by limiting SiOx utilization
Implementation Method 4
non-aqueous secondary batteries, including lithium ion secondary batteries, provide high voltage and high capacity
Data Source
Figure 1A~1B
Figure 2
AI summary
The non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, the negative electrode contains a negative electrode active material containing a graphitic carbon material and a composite in which a carbon coating layer is formed on a surface of a core material containing Si and O as constituent elements, the composite has a carbon content of 10 to 30 mass%, the composite has an intensity ratio I510/I1343 of a peak intensity I510 at 510 cm-1 derived from Si to a peak intensity I1343 at 1343 cm-1 derived from carbon of 0.25 or less when a Raman spectrum of the composite is measured at a laser wavelength of 532 nm, and the half-width of the (111) diffraction peak of Si is less than 3.0° when the crystallite size of an Si phase contained in the core material is measured by X-ray diffractometry using CuKα radiation.