Electrode assembly for lithium secondary battery, and lithium secondary battery comprising same
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Solution Overview
Problem
Existing lithium secondary batteries face challenges in achieving high energy density and long battery lifetime due to limitations in negative and positive electrode materials, such as low capacity, high lithium consumption, and safety issues.
Innovation Solution
The electrode assembly incorporates a positive electrode with a specific ratio of lithium metal composite oxide and a positive electrode additive, and a negative electrode with a carbon material and silicon-containing material, controlled within specific weight percentages and ratios, to optimize charging/discharging capacity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-carbon-based negative electrode material (silicon, tin, oxide) is used to achieve high capacity, then capacity is improved, but initial efficiency is low and lithium consumption is large
Solution Approach 1:
A coating layer comprising at least one of silicon oxide and silicon nitride is applied to the surface of the negative electrode active material particles. This coating layer acts as an intermediary that reduces direct contact between lithium and the negative electrode active material, thereby reducing irreversible capacity loss and improving initial efficiency while maintaining high capacity.
Solution Approach 2:
The negative electrode active material uses a composite structure combining silicon or tin with carbon materials (graphite, amorphous carbon, carbon nanotubes, or graphene). This composite approach leverages the high capacity of silicon/tin while the carbon component provides structural stability and reduces lithium consumption, achieving both high capacity and improved initial efficiency.
2Duration of action of stationary object
If LiCoO2 is used as positive electrode material due to excellent cycle characteristics, then cycle characteristics are improved, but safety is low and cost is high
Solution Approach 1:
The positive electrode active material uses a composite structure combining layered lithium-containing metal oxide (such as LiCoO2, LiMnO2, or LiNi1-x-yCoxMnyO2) with spinel lithium-containing metal oxide (such as LiMn2O4 or Li6CoO4). This composite approach maintains excellent cycle characteristics from the layered structure while the spinel component improves safety by suppressing oxygen evolution and thermal runaway.
3Ease of manufacture
If LiNiO2 is used as positive electrode material, then cost is reduced, but lithium plating is induced and charging/discharging capacity is lowered
Solution Approach 1:
The positive electrode active material combines layered lithium-containing metal oxide (such as LiNi1-x-yCoxMnymO2) with spinel lithium-containing metal oxide (such as Li6CoO4 or LiMn2O4). The spinel component suppresses gas generation during charging/discharging, preventing lithium plating on the negative electrode and maintaining high charging/discharging capacity while keeping costs lower than pure LiCoO2.
4Reliability
If graphite is used as negative electrode material, then safety is improved, but capacity per unit mass is low
Solution Approach 1:
The negative electrode active material uses a composite structure combining silicon or tin (providing high capacity) with carbon materials such as graphite, amorphous carbon, carbon nanotubes, or graphene (providing safety and structural stability). This composite approach achieves both high capacity and improved safety compared to using graphite alone.
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
This configuration enhances initial charging/discharging capacity, improves capacity retention, and extends the battery's lifetime by controlling irreversible reactions and reducing lithium consumption.
Implementation Method 1
irreversible reaction occurring during initial charging
Implementation Method 2
lithium consumption during initial charging and discharging
Data Source
AI summary
The present technology relates to an electrode assembly for a lithium secondary battery and a positive electrode for the lithium secondary battery including the electrode assembly. By controlling a ratio (CRLip/CRSi) between a content percentage of a positive electrode additive and a silicon (Si)-containing material that is a negative electrode active material, which are contained in a positive electrode mixture layer and a negative electrode mixture layer, respectively, to a specific range, the electrode assembly has an advantage in that high charging/discharging capacity and charging/discharging efficiency can be realized during initial charging/discharging, a capacity retention rate can be excellent during subsequent charging/discharging, and a lithium secondary battery including the electrode assembly can exhibit a high energy density and long lifetime.