Rechargeable Lithium Battery Composite Electrode Design
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Solution Overview
Problem
Rechargeable lithium batteries face safety concerns due to potential explosions from internal short circuits and thermal runaway, and existing materials like Lithium Iron Phosphate have low average potential and capacity issues.
Innovation Solution
A lithium battery design featuring a positive electrode with composite oxides and a negative electrode with flake-shaped polyethylene particles, optimizing the electrode laminate ratio and incorporating a second positive active material to maintain high voltage and stability, ensuring early shut-down functionality and preventing additional chemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Lithium Iron Phosphate is used as a safety material, then thermal stability is improved, but capacity and voltage decrease
Solution Approach 1:
The patent combines two different positive active materials: LiFePO4 (providing thermal stability and safety) and LiCoO2 (providing high capacity and high voltage). This merging allows the battery to achieve both thermal stability and high capacity simultaneously, resolving the contradiction between safety and performance
Solution Approach 2:
The positive electrode uses a composite material system comprising LiFePO4 and LiCoO2. This composite structure enables the battery to benefit from the low heat-generating characteristics of LiFePO4 while simultaneously achieving the high capacity and high voltage characteristics of LiCoO2
2Use of energy by moving object
If high voltage operation is implemented, then energy density is improved, but safety and stability deteriorate
Solution Approach 1:
The patent merges the high voltage capability of LiCoO2 (operating at 4.3V or higher) with the thermal stability of LiFePO4. This combination enables high voltage operation for improved energy density while maintaining safety through the presence of the thermally stable LiFePO4 material
Solution Approach 2:
The patent changes the operating voltage parameter to 4.3V or higher, which improves energy density. Simultaneously, it introduces LiFePO4 as a stabilizing component that maintains safety at this elevated voltage, thus resolving the contradiction between high voltage operation and safety
3Reliability
If electrode laminate dimensions are optimized, then safety is improved, but manufacturing complexity increases
Solution Approach 1:
The patent specifies a particular L/W ratio range (1.1 to 2.3) for the electrode laminate to ensure safety during thermal runaway. While this adds a dimensional constraint, it provides a clear manufacturing guideline that balances safety requirements with manufacturability
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 design achieves high capacity and stability while preventing explosions by effectively managing thermal runaway and maintaining high voltage operation without capacity degradation.
Implementation Method 1
the negative electrode functional layer includes flake-shaped polyethylene particles... ensuring early shut-down functionality and preventing additional chemical reactions
Implementation Method 2
a rechargeable an electrode laminate including a positive electrode including a positive current collector and a positive active material layer disposed on the positive current collector; a negative electrode including a negative current collector, a negative active material layer disposed on the negative current collector
Data Source
AI summary
A rechargeable lithium battery includes an electrode laminate including a positive electrode including a positive current collector and a positive active material layer disposed on the positive current collector; a negative electrode including a negative current collector, a negative active material layer disposed on the negative current collector, and a negative electrode functional layer disposed on the negative active material layer; and a separator, wherein the electrode laminate has a ratio (L/W) of a height (L), which is a length in a protruding direction of an electrode terminal, relative to a width (W), which is perpendicular to the protruding direction of the electrode terminal and parallel to the laminate surface, is about 1.1 to about 2.3, the positive active material layer includes a first positive active material including at least one of a composite oxide of a metal selected from cobalt, manganese, nickel, and a combination thereof and lithium and a second positive active material including a compound represented by Chemical Formula 1, the negative electrode functional layer includes flake-shaped polyethylene particles, and an operation voltage is greater than or equal to about 4.3 V.LiaFe1-x1Mx1PO4 [Chemical Formula 1]In Chemical Formula 1, 0.90≤a≤1.8, 0≤x1≤0.7, and M is Mn, Co, Ni, or a combination thereof.