SiO Negative Electrode with Fe-SiO2 Coating for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries face issues with irreversible capacity and high electric resistance due to the trapping of Li ions in SiO, leading to poor cycle characteristics and electrolyte consumption, especially with the peeling off of carbon layers during charge and discharge cycles.
Innovation Solution
A lithium ion secondary battery design featuring a negative electrode with SiO cores coated with a composite oxide layer of Fe and SiO2 and an additional carbon coating layer, which reduces dangling bonds and enhances binding strength, preventing peeling and improving conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If SiO is used as negative electrode active material to increase capacity, then battery capacity is improved, but Li ions are trapped during charge producing irreversible capacity and high electric resistance
Solution Approach 1:
An oxide layer is introduced as an intermediary between the SiO active material and the electrolyte. This oxide layer acts as a mediator that prevents direct contact between Li ions and the SiO surface, thereby eliminating the trapping of Li ions that causes irreversible capacity loss, while still allowing efficient Li ion transport for reversible capacity.
Solution Approach 2:
The surface properties of SiO are modified by forming an oxide layer on its surface. This changes the chemical and physical parameters of the SiO surface, transforming it from a state that traps Li ions to a state that allows reversible Li ion insertion and extraction, thereby improving both capacity and reliability.
2Quantity of substance
If SiO is used as negative electrode active material to increase capacity, then battery capacity is improved, but electric resistance increases lowering characteristics at high charge-discharge rate
Solution Approach 1:
The oxide layer serves as a conductive intermediary that facilitates electron and ion transport. It provides a low-resistance pathway for charge transfer between the SiO particles and the electrolyte, thereby reducing overall electric resistance and improving power characteristics at high charge-discharge rates while preserving high capacity.
Solution Approach 2:
A composite structure is formed by combining SiO with an oxide layer. This composite material integrates the high capacity advantage of SiO with the good conductivity of the oxide layer, achieving both high capacity and excellent charge-discharge rate characteristics that neither material could achieve alone.
3Power
If carbon layer is coated on SiO surface to improve conductivity, then electric resistance is reduced, but volume expansion rate difference causes carbon layer to peel off during cycle
Solution Approach 1:
The oxide layer is introduced as an intermediary buffer layer between the SiO core and the carbon coating. This intermediary layer has intermediate expansion characteristics that bridge the gap between the high-expansion SiO and the low-expansion carbon, reducing stress concentration and preventing carbon layer peeling during volume expansion cycles.
Solution Approach 2:
A three-layer composite structure is created: SiO core, oxide intermediate layer, and carbon outer layer. This multi-layer composite design combines the advantages of each material while mitigating their disadvantages, achieving both good conductivity from the carbon layer and stable adhesion through the oxide buffer layer that accommodates volume changes.
4Power
If VC or EFC is added to electrolytic solution to improve conductivity, then electric resistance is reduced, but electrolytic solution is consumed on the surface of active material
Solution Approach 1:
The oxide layer on the SiO surface acts as a mediator that prevents direct interaction between the electrolyte additives (VC or EFC) and the active material surface. This intermediary barrier reduces the consumption of electrolyte additives while still maintaining good interfacial conductivity, thereby improving power characteristics without excessive electrolyte consumption.
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 achieves improved initial charge-discharge characteristics and extended battery life by reducing irreversible capacity and maintaining overall battery performance.
Implementation Method 1
forming an oxide layer that forms a compound with SiO2 on the surface of SiO
Implementation Method 2
coating the surface of SiO with carbon to improve conductivity
Implementation Method 3
making fine metal having a high affinity with carbon be deposited
Data Source
AI summary
The invention addresses the problem of providing a lithium ion secondary battery excellent in initial charge-discharge characteristics and life characteristics. To solve the above problem, the invention provides a lithium ion secondary battery in which an electrode group having a positive electrode and a negative electrode is housed in a battery can, wherein the negative electrode includes a negative electrode active material supported on a negative electrode foil, and the negative electrode active material includes cores having SiO as a main component, a composite oxide coating layer of Fe and SiO2 disposed on the periphery of each of the cores, and a carbon coating layer disposed on the periphery of the composite oxide coating layer of Fe and SiO2.