27. Chemical stability of LPS sulfide solid electrolytes : problems in paradise?

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Gasteiger paper on LPS stability with PEO – 2019

LPS and LLZO inorganic solid electrolytes have been the workhorse of solid battery efforts for the past 20 years. LPS (or sulfur based) solid electrolytes have a lithium ion conductivity higher than liquid electrolytes and are softer and easier to process into separators than LLZO. However, their electrochemical stability is quite narrow on the anode as well as on the cathode side which require protective coatings for compatibility. One common method to interface high conductivity LPS with metallic lithium anode is to use a PEO polymer interface between the reactive lithium anode and the LPS solid electrolyte separator. In this podcast i discuss the stability of LPS with the PEO membrane.

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26. The (only) Tesla battery cell patent

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The Tesla patent
Fast charging

Tesla patent link

Arguably the most successful electric car company in the world has (arguably) the fewest battery cell patents: 1. Tesla’s business model so far has not included cell chemistry development. The only patent they claim (in 2019) comes from the Jeff Dahn group and focuses on additives for fast charge and long lifetime of commercial cells. Listen to my podcast to learn more.

25. The dry electrode process of Maxwell Technologies (soon to be Tesla owned)

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Dry electrode process from Maxwell Technologies

Patent 20170098826A1

Capacitor cycle life and operating voltage are governed by the lack of impurities left over from the electrode casting process. Maxwell Technologies claims a solvent – less, dry process can double the cycle life of their capacitors. In this podcast I also discuss the viability of this dry process for manufacturing battery electrodes.

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24. The “R&D” development cycle : the good, the bad and the ugly

Key elements of a successful battery R&D program

I receive a lot of interest regarding setting up R&D programs for lithium ion batteries. In this podcast I dissect the defining elements of a successful battery R&D program. If your company is interested in this type of venture or if you are a student entering this field at an early stage, you may find this episode more interesting than my typical podcast. Enjoy!

23. Cobalt free cathodes: Jeff Dahn (now with Tesla) suggests they are possible and stable

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Cobalt free cathodes

Jeff Dahn paper

The first high voltage cathodes were proposed by John Goodenough in the form of LCO (lithium cobalt oxide) and they were quickly adopted as commercial materials. In an effort to lower costs (cobalt is expensive), analogous LNO (lithium nickel oxide) cathodes have recently been commercialized as doped NCM (nickel, cobalt, manganese) and NCA (nickel, cobalt, aluminum) cathodes. Modern NCM/NCA contain only 5% cobalt and cobalt free derivatives may soon become a reality. Learn how and why in this podcast.

22. Ni rich NCM (cathodes): how we got it, why we use it and how to keep it stable

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Recent twist in the capacity fade mechanism of Ni rich NMC

NCM622 capacity fade paper from Brookhaven National Lab

Currently accepted cathode dogma preaches the root cause of capacity fade in Ni rich NMC is the irreversible phase change of the active material crystalline structure. However, recent findings challenge the status quo. Listen to my podcast to learn more.

20. Stable lithium plating with 3x capacity of commercial Li-ion cells… apparently possible @Stanford

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Stable cycling of lithium metal anodes

Paper link

Yi Cui’s web page

Past podcast on lithium ion separators

The Holy Grail of anodes is a lithium metal anode. Taming this temperamental beast has been unsuccessful so far, but it is bound to change. In this podcast I discuss a composite separator membrane which enables plating lithium with 3x the speed and 3x the quantity (capacity) of commercial lithium ion cells.

19. Can we bypass the energy – fast charge compromise?

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How to break a compromise

Fast charge is limited by the reduction (lithiation) potential and nature of the anode. If charged too fast, graphite anodes may be plated with lithium metal because their lithiation potential is too close to the plating potential of lithium. Faster charge can be accomplished with anodes which lithiate at higher potentials (such as NTO). The trade-off is lower cell energy since there will be a smaller voltage difference between anode and cathode. However, there are anode materials which may bypass this energy – fast charge compromise. Listen to my podcast to learn more.

17. How fast can commercial cells really charge?

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Energy cells vs. power cells – charging rate

Belharouk et al, 2018, Electrochemical Communications – charging limits of NCM811 cathodes and graphite anodes

Bhagat et al, 2018, Electrochimica Acta – charging limits of commercial energy cell

Miller et al, 2017, SAE – charging limits of commercial power cell

In this podcast I discuss the charging rate limits for commercial electrode materials as well as commercial cells. They are faster than you may think.

16. 2 minute charge? Impossible!

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Patent application

Bruce Dunn

This material can charge in 2.5 minutes, > 10,000x.

Currently commercial lithium ion batteries typically charge in 1.5 – 2 hours. ‘Fast charge’ is limited to 30 – 45 minutes and with harsh consequences on cycle life and safety. However, there are battery electrode materials which blur the capacitor/battery line. MoS2 has been claimed by professor Dunn (UCLA) to be such a “pseudocapacitor”. This podcast discusses a patent claiming a pseudocapacitor electrode material which can charge in 2.5 minutes for > 10,000x and with a capacity > 120mAh/g.

> 10,000 cycles with no capacity fade at a charge/discharge rate of 23C (which corresponds to 2.5 minute charge). Capacity is stable > 120 mAh/g.

15. Amprius: silicon anodes by CVD

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Amprius grows silicon directly off current collectors by CVD

Patent

Amprius website

Yi Cui – Stanford

Growing silicon directly off current collectors (by CVD) offers a rich library of strategies to solve traditional problems associated with silicon anodes. However, it also raises a few new ones. Find out more in my latest podcast.

Silicon active material (340) is grown onto nickel silicide template (310) and may be coated by carbon or lithium conducting shell (330). The silicide template is hard rooted onto the copper current collector (320) for enhanced electron conductivity.

14. 1D Silicon anodes from Sila Nanotechnologies

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Why is BMW investing in this company?

2017 Sila US9673448

Professor Gleb Yushin’s page

Sila Nanotechnology

Secondary particle of Sila’s silicon anode depicting the 1D carbon whiskers for electron conductivity and the silicon nanoparticles for lithium capacity

Anodes with silicon active materials may offer more than 2x the capacity of anodes with graphite active materials and improved rates of operation due to a low risk of lithium plating. A 1D architecture consists of ultrathin wires or whiskers as opposed to ultrathin sheets (2D). Emerging from the lab of professor Gleb Yushin, Sila Nanotechnologies focuses on such electron conductive wires (carbon based) decorated with silicon nanoparticles. This concept provides a highly porous secondary structure where the silicon particles have room to expand and contract without cracking the overall anode structure and is claimed to work well with liquid electrolyte systems. This podcast dissects a 2018 patent which claims Sila’s core silicon anode technology.

13. The magic of 2D current collectors

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2D mxene light current collectors to replace heavy copper current collectors, from Gogotsi group.

Gogotsi paper on mxene current collectors

Gogotsi page at Drexel University

2D current collector on the left (sheets of d-Ti3C2Tx) and cathode (particles of LFP+CB+PVDF) on the right. Inset shows bending of such electrode.

Current collectors are the substrates on which anode and cathode active materials are deposited in a lithium ion battery. They do NOT contribute to battery energy density. Their role is to transport electrons from the location of redox reactions in the active material towards wiring tabs and through the load (cell phone or electric motor, etc). Traditionally, current collectors need high transverse electron conductivity parallel to the sheet plane as well as flexibility and high mechanical strength to allow for tight electrode winding into cells, under high tension. In addition, current collectors need to block any ion transport across the foil which would short the cell. These requirements have traditionally limited a choice of current collector materials to metallic foils such as copper and aluminum, circa 10 micron in thickness. It is desirable to reduce the weight of current collectors which currently can account for as high as 50% of electrode weight in a lithium ion cell. This podcast discusses professor Gogotsi’s invention of mxene based, 2D, light current collectors.

12. Bipolar Madness

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2005 Amine: wound bipolar cells US6858345B2

2013 Nissan: non metallic bipolar current collector US8445139B2

2014 Nissan: no bubbles US8734984

2016 CEA: U shaped wind/stack hybrid US9318748

2018 CEA: copolymer, temp dependent US10044068

Monopolar (left) vs bipolar (right) battery cell design

A bipolar design solves a major problem in lithium ion batteries: fast charging. Typical commercial cells have a monopolar design which means that each current collector has either a cathode or an anode applied on either side. By contrast, a bipolar design has both the anode and cathode applied to opposite sides of the same current collector. In this podcast, I explain how this design lowers battery resistance and increases energy density. I also discuss several patents which claim solutions to some of the challenges of bipolar designs.

10. Fast Silicon anodes from Enevate

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Can silicon anodes provide BOTH higher capacity AND faster rates?
Free standing, 5 micron, flexible, strong anode with >70% silicon from Enevate


Patent link

Enevate website poster

Enevate website

There is a lot of talk on the subject of fast charging in the electric vehicle world. In principle, you cannot have both high energy density AND fast charging built into the same battery. There are many reasons for this, however, the graphite anode is the main block to fast charging. Currently “power” cells with graphite anodes can charge as fast as 75% in 15 minutes while “energy” cells require >1.5 hours. Future anodes such as silicon may bring larger capacities AS WELL AS faster rates of charging. Enevate discloses how in this patent. Listen to my podcast to learn more.