Silicon Oxide Negative Electrode Material with Carbon Coating
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Solution Overview
Problem
Conventional silicon oxide negative electrode materials for lithium ion secondary batteries exhibit low initial charge and discharge efficiency and capacity, limiting their utilization in high-performance mobile devices due to significant cubical expansion and capacity degradation over cycles.
Innovation Solution
A negative electrode material comprising silicon oxide with a specific crystallite size range (2.0 nm to 8.0 nm) and surface-coated with carbon, where the carbon content is between 0.5% to 5.0% by mass, providing improved initial discharge capacity and charge/discharge efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon oxide is used as negative electrode material to achieve high theoretical capacity, then the battery capacity is improved, but the initial charge and discharge efficiency becomes low
Solution Approach 1:
The patent changes the physical and chemical parameters of the silicon oxide by controlling the crystallite size to 2.0 nm to 8.0 nm and adjusting the oxidation state, which improves the initial charge and discharge efficiency while maintaining high capacity
Solution Approach 2:
The patent creates a composite structure where silicon oxide with controlled crystallite size is combined with carbon coating (0.5% to 5.0% by mass), forming a composite material that achieves both high capacity and high initial charge and discharge efficiency
2Quantity of substance
If silicon oxide is used to achieve high capacity, then the battery performance is improved, but significant cubical expansion occurs leading to structure destruction
Solution Approach 1:
The patent controls the crystallite size parameter within 2.0 nm to 8.0 nm, which is small enough to accommodate expansion without destroying the overall structure, yet large enough to maintain electrical conductivity
Solution Approach 2:
The carbon-coated silicon oxide composite structure allows the silicon oxide core to expand during lithium insertion while the carbon shell maintains structural integrity and electrical conductivity, preventing capacity degradation
3Quantity of substance
If silicon oxide is used to achieve high theoretical capacity, then the battery energy density is improved, but capacity degradation occurs over cycles
Solution Approach 1:
By optimizing the crystallite size to 2.0 nm to 8.0 nm, the patent reduces the mechanical stress during cycling that leads to structure degradation, thereby improving cycle life while maintaining high capacity
Solution Approach 2:
The carbon coating on silicon oxide creates a stable composite structure that prevents direct contact between silicon oxide and electrolyte, reducing side reactions and capacity fading over cycles
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 proposed solution enhances the initial discharge capacity and charge/discharge efficiency of lithium ion secondary batteries, reducing cubical expansion and capacity degradation, thereby improving the battery's performance and longevity.
Implementation Method 1
a negative electrode material for a lithium ion secondary battery, the negative electrode material comprising a silicon oxide and having a diffraction peak attributable to Si (111) in an X-ray diffraction spectrum, in which a size of a silicon crystallite calculated from the diffraction peak is from 2.0 nm to 8.0 nm
Implementation Method 2
the silicon oxide, which is one material of the specific element substances, is used as a negative electrode material, the initial charge and discharge efficiency is low... a negative electrode material comprising a silicon oxide and having a diffraction peak attributable to Si (111)
Data Source
AI summary
A negative electrode material for a lithium ion secondary battery includes a silicon oxide and having a diffraction peak attributable to Si (111) in an X-ray diffraction spectrum, in which a size of a silicon crystallite calculated from the diffraction peak is from 2.0 nm to 8.0 nm.