SiOx Negative Electrode for Lithium-Ion Battery
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in maintaining battery characteristics such as cycle characteristics and safety due to the extreme expansion and contraction of silicon (Si) negative-electrode active material during charge and discharge, leading to surface cracking and increased irreversible capacity.
Innovation Solution
A negative electrode with a negative-electrode active material composed of Si, O, and at least one element M1 (such as Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, Na, and K), where the atomic ratio of O to Si is between 0.5 and 1.8, is used, forming a compound Si-M1-O that reduces irreversible capacity and electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si is used as negative-electrode active material to increase battery capacity, then battery capacity is improved, but cycle characteristics deteriorate due to surface cracking and electrolytic solution decomposition
Solution Approach 1:
The patent uses a composite material consisting of Si and O (forming SiOx) as the negative-electrode active material. This composite structure combines the high capacity advantage of Si with the stability of oxidized silicon, reducing volume expansion and surface cracking while maintaining improved battery capacity compared to traditional graphite materials.
Solution Approach 2:
The patent changes the chemical composition parameters of the negative-electrode active material by controlling the oxygen content in SiOx. By adjusting the oxidation state of silicon (forming different SiOx compositions), the material achieves a balance between capacity retention and structural stability during charge-discharge cycles, thereby improving cycle characteristics.
2Quantity of substance
If Si is used as negative-electrode active material to increase battery capacity, then battery capacity is improved, but safety deteriorates due to extreme expansion and contraction
Solution Approach 1:
The SiOx composite material reduces the extreme expansion and contraction behavior of pure Si by incorporating oxygen atoms in the silicon structure. This composite structure provides better mechanical stability and reduces safety issues related to electrode degradation while maintaining high battery capacity.
Solution Approach 2:
By changing the chemical composition (adding oxygen to form SiOx), the patent modifies the physical and chemical properties of the active material, reducing volume change during lithiation-delithiation cycles and improving safety performance.
3Reliability
If oxygen content in SiOx is increased to improve cycle characteristics, then cycle characteristics are improved, but battery capacity decreases
Solution Approach 1:
The patent optimizes the oxygen content parameter in SiOx to achieve a balance between cycle characteristics and battery capacity. By controlling the Si:O ratio, the material maintains sufficient structural stability for good cycle life while retaining enough silicon content to provide high battery capacity.
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 solution enhances battery performance by improving cycle characteristics, initial charge-discharge characteristics, and load characteristics, while reducing the risk of surface cracking and maintaining battery capacity.
Implementation Method 1
lithium-ion secondary batteries that utilize the occlusion and release of lithium ions
Implementation Method 2
forming a compound Si-M1-O that reduces irreversible capacity and electrical resistance
Data Source
AI summary
A lithium-ion secondary battery includes a positive electrode, a negative electrode containing an active material, and an electrolytic solution, in which the active material contains, as constituent elements, Si, O, and at least one element M1 selected from Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, Na, and K, and the atomic ratio x (O/Si) of O to Si is 0.5≦x≦1.8.