Rechargeable Lithium Battery with Flake-Shaped Polyethylene Functional Layer
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Solution Overview
Problem
Rechargeable lithium batteries face safety concerns due to thermal runaway and explosion risks from internal short circuits, and existing materials like lithium iron phosphate have low average potential and decreasing capacity during discharge.
Innovation Solution
A rechargeable lithium battery design incorporating a positive electrode with composite oxides of cobalt, manganese, and nickel, and a negative electrode with a flake-shaped polyethylene particle functional layer, enhancing stability and capacity while preventing thermal runaway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium iron phosphate is used as the positive active material, then safety is improved, but capacity decreases
Solution Approach 1:
The patent combines lithium iron phosphate (safe but low capacity) with lithium nickel cobalt manganese oxide (high capacity but less safe) in a composite positive active material. This merging allows the battery to achieve both improved safety from the LFP component and high capacity from the NCM component, resolving the contradiction between safety and capacity.
Solution Approach 2:
The patent uses a composite material approach by creating a positive active material that contains both lithium iron phosphate particles and lithium nickel cobalt manganese oxide particles. This composite structure allows the beneficial properties of both materials to coexist, providing both the safety of LFP and the high capacity of NCM.
2Quantity of substance
If lithium nickel cobalt manganese oxide is used to increase capacity, then energy density is improved, but thermal stability deteriorates
Solution Approach 1:
The patent merges lithium nickel cobalt manganese oxide (providing high energy density) with lithium iron phosphate (providing thermal stability) in a composite structure. The LFP component acts as a thermal buffer that stabilizes the NCM component, allowing high energy density to be achieved without sacrificing thermal stability.
Solution Approach 2:
The patent changes the compositional parameters of the positive active material by controlling the ratios of different metal elements (Fe, Ni, Co, Mn) and adjusting the particle size distribution. By optimizing these parameters, the battery achieves both high energy density and thermal stability.
3Reliability
If internal short circuit prevention measures are added, then safety is improved, but device complexity increases
Solution Approach 1:
The patent extracts the safety function from complex external protection systems and integrates it directly into the electrode structure itself. By incorporating safety features at the material level rather than adding external protection mechanisms, the patent improves safety without significantly increasing device complexity.
Solution Approach 2:
The patent implements self-service safety mechanisms where the electrode materials themselves provide protection against internal short circuits. The composite structure of LFP and NCM creates inherent thermal and electrical stability, allowing the battery to protect itself without requiring complex external safety systems.
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 battery achieves high capacity and stability, with improved safety features that delay thermal shutdown and prevent additional electrical/chemical reactions, effectively addressing the risks of explosion and maintaining energy density.
Implementation Method 1
the negative electrode functional layer includes flake-shaped polyethylene particles
Implementation Method 2
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
Implementation Method 3
high electrical energy stored in each electrode is conducted through the shorted positive electrode and negative electrode
Data Source
AI summary
A rechargeable lithium battery including an electrode assembly includes 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 positive active material layer includes a first positive active material including at least one of a composite oxide of 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 a battery capacity is greater than or equal to about 3.5 Ah.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.