Popular Post Jason McNeil Posted January 27 Popular Post Share Posted January 27 (edited) For all of us battery nerds, stumbled upon this awesome presentation by Prof. Jeff Dahn, lab has deep ties with Tesla & the battery industry. Skip to timestamp 12:00 of intros, we're all going to die from climate change... Key Takeaways: 1) Current NMC cells have the potential to reach 100,000 cycles /100 year of useful life, e.g. 80% retention by substituting the LiPF6 electrolyte with a commercially available LiFSI salts 2) Restricting the charging voltage to 3.8V, results in a ~27% reduction of maximal nameplate capacity, but yielding at least a >10x increase in longevity 3) Temperature is important, but not critical 4) LFPs , on every metric [total ownership cost, longevity, energy density] are lame 5) NMC cell chemistries, of this type, will exceed the lifespan of everything else they're connected to: vehicle, electronics, BMS, etc - NMC LiNi1xy MnxCoyO2, for NMC532, NMC811, & LiFePO4. The numbers in NMC refer to the relative ratios of Nickel, Manganese & Colbolt. - High energy design, long lifetime, no self-discharge, affordable, short recharge time - Three years of continuous testing of single crystal NMC532/graphite cell with appropriate electrolyte added. If every cycle is 350km, represent 3.5 million km & still retains >96% capacity. - Developing long lifetime Li-ion cells: 1) Avoid large volume changes in positive electrode materials 2) Use the best graphites 3) Use appropriate electrolytes 4) Keep the upper cutoff voltage down - Delta Polarization: gap between the charge & discharge curve shown in graphic. Measure of the internal impedance of the cell - If using the battery in a vehicle-to-grid setting, longer 10,000 cycles will be required. - LiFSI yields issues with aluminum corrosion at elevated temperature when the full cell voltage exceed 4.0V - By 2030 expected to be 130 million EVs, average pack size of 40kWhs. Production capacity estimates are in the range of 2-6 TWh/year Lots of great slides!!! After 5 years, 92-93% capacity after 16,500 cycles with virtually no degradation - These lifecycles are pretty decent, but how do we make them even better? To avoid the volumetric changes in 811, charge to 4.06V capacity. Commercially available NMC charged to 4.3V better than the best LFP LFP is a low voltage system charged to only 3.65V. Why is it worse than NMC 811 to 4.06V & NMC 532 to 4.3V LiFSI yields issues with aluminum corrosion at elevated temperature when the full cell voltage exceed 4.0V What would happen if we made NMC cells balanced for lower voltage & then used LiFSI? Their lifetime cost of energy storage will be much less than LFP cells. Initial $/kWh is not a meaningful metric when incredible lifetime cells are in discussion. The importance of single crystal anodes, virtually no cracking over time. Comparison of different use of electrolytes, Ecker = LiPF6 To accelerate testing the label ran the same tests at higher temperatures. Fractional Slippage per hour: proportional to the degradation rate at the positive electrode As the voltage is reduced, degradation rate becomes less & less. Reducing the cell voltage to 4V allows the use of a more thermally stable Lithium salt called LiFSI instead of LiPF6 Even charging to 3.8V, a NMC has vastly more energy than an LFP Sacrificed 27% in initiatal energy density, with at least a 10x increase in longevity Upper right slide: loss of only 5% capacity to 3.8V in 9 months testing @ 70°C is incredible! No impedance growth & transition metals found on the negative electrode. Extrapolated with the LiFSI electrolyte, NMC 532 will last for over 100 years. 1600hr of testing @ 85°C 96% capacity, amazing! Ramped up to 85°C to accelerate aging, but still the cell won't die! Energy penalty charging at 3.8V vs regular 4.3V Can produce a pretty good sodium ion battery with sodium, manganese, & iron. At the scale of 400TWh, have to work with sodium ion. Volumetric density of sodium ion is way less than NMC. Picture of cells ofthe same capacity, but Na is twice as thick! Current lifespan is pretty weak [compared to NMC] even with alternative electrolytes Edited January 27 by Jason McNeil 10 Quote Link to comment Share on other sites More sharing options...
UniVehje Posted January 27 Share Posted January 27 The question we all have in mind: when? 1 Quote Link to comment Share on other sites More sharing options...
joyrider Posted January 27 Share Posted January 27 I concur. 1 Quote Link to comment Share on other sites More sharing options...
Popular Post macgyvercanada Posted January 27 Popular Post Share Posted January 27 Jeff Dahn's from my home city so I hear a lot of news about his work. He's been involved in several battery collabs with industry. I guess the question is whether battery manufacturers want to make batteries that never need to be replaced... 2 1 1 Quote Link to comment Share on other sites More sharing options...
RagingGrandpa Posted January 27 Share Posted January 27 But for EUC's, we want more energy density! Our packs are already outlasting our machines today... 2 Quote Link to comment Share on other sites More sharing options...
alcatraz Posted January 27 Share Posted January 27 It's great to have more options. Let's see how it holds up in real life and if it's worth the money. Doomsday preppers may find it interesting but in euc there are different priorities. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.