Lithium Battery Negative Electrode Functional Layer Safety
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Solution Overview
Problem
Rechargeable lithium batteries face safety concerns due to potential explosions from internal short circuits, overcharge, and over-discharge, which can lead to thermal runaway and capacity degradation, especially with lithium iron phosphate's low heat generation and capacity issues.
Innovation Solution
A rechargeable lithium battery design incorporating a positive electrode with a composite oxide of cobalt, manganese, nickel, and lithium, along with a second active material and a negative electrode functional layer featuring flake-shaped polyethylene particles to enhance safety and capacity by improving reaction rates and preventing additional electrical/chemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium iron phosphate is used as a safety material, then thermal safety is improved, but capacity decreases
Solution Approach 1:
The patent combines lithium iron phosphate particles (providing thermal safety) with conductive carbon particles and binder to form a composite negative electrode active material layer. This merging approach allows the battery to maintain thermal safety while the conductive carbon network compensates for capacity loss, achieving both safety and acceptable capacity performance
Solution Approach 2:
The negative electrode uses a composite material system consisting of lithium iron phosphate particles dispersed in a matrix of conductive carbon and binder. This composite structure allows the insulating lithium iron phosphate to coexist with conductive elements, maintaining electrical conductivity and capacity while preserving the thermal safety benefits of lithium iron phosphate
2Quantity of substance
If high energy density materials are used, then capacity is improved, but safety risk increases
Solution Approach 1:
The patent introduces a negative electrode functional layer containing flake-shaped polyethylene particles as an intermediary safety mechanism. This layer acts as a thermal barrier and shutdown mechanism that prevents thermal runaway from propagating to the positive electrode, thereby reducing explosion risk while allowing high energy density materials to be used in the positive electrode
Solution Approach 2:
The flake-shaped polyethylene particles in the negative electrode functional layer serve as a pre-positioned safety cushion. These particles are strategically placed before potential thermal events occur, creating a physical and thermal barrier that activates during thermal runaway to prevent catastrophic failure, thus cushioning against the harmful effects of high energy density materials
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 power characteristics while improving safety by preventing thermal runaway and capacity degradation, ensuring the battery operates effectively at high voltages and maintaining cycle-life characteristics.
Implementation Method 1
the negative electrode functional layer includes flake-shaped polyethylene particles... As the reaction rate depending on a temperature is improved, an early shut-down function may be implemented
Implementation Method 2
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
Data Source
AI summary
A rechargeable lithium battery includes a positive electrode including a positive current collector and a positive active material layer disposed on the positive current collector; and 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, 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 at least one of compounds represented by Chemical Formula 1 to Chemical Formula 4, and the negative electrode functional layer includes flake-shaped polyethylene particles andLix2Mn1-y2M′y2A2 [Chemical Formula 1]Lix2Mn1-y2M′yO2-z2Xz2 [Chemical Formula 2]Lix2Mn2O4-z2Xz2 [Chemical Formula 3]Lix2Mn2-y2M′y2M″z2A4 [Chemical Formula 4]wherein, 0.9≤x2≤1.1, 0≤y2≤0.5, 0≤z2≤0.5, M′ and M″ are the same or different and are selected from Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, Sr, V, and a rare earth element, andwherein A is selected from O, F, S, and P and X is selected from F, S, and P.