For the first post of this series, we will focus on Factorial Energy, a Massachusetts solid-state battery company.

The CEO and founder is Dr. Siyu Huang. Her resume was impressive before she founded a battery company with $1B valuation, having both a Ph.D. and an M.B.A. from Cornell University.

*Dr. Siyu Huang speaking at* *Davos in 2024*

Factorial Energy, now located in Methuen, started as a side project while Dr. Huang worked at Johnson & Johnson and spun out of stealth mode in 2021. Previously the two founders (Dr. Siyu Huang and Dr. Alex Yu) started Lionano, and some of the patent portfolio originally started as Lionano patents. Lionano started in 2013 and spun out of the Cornell PhD program.

Lionano became Factorial Energy through a rebranding process. Specifically, Lionano split into two entities: Lionano Inc. (focused on cathodes) and Lionano SE Inc. (focused on solid-state batteries) in 2019. Lionano SE Inc. was rebranded as Factorial Energy in April 2021. Notably Dr. Alex Yu was CEO of Lionano and they switched during the rebrand with Dr. Siyu Huang as the CEO of Factorial.

The Factorial website mentions two products: a “quasi-solid” electrolyte and a sulfide-based all-solid-state electrolyte.

*Factorial’s batteries according to their website.*

*source:* *https://factorialenergy.com/technology/*

Battery company websites can be helpful for customers and investors and non-technical people, but for juicy technical information the proof is in the patents.

Let’s dig in.

Based on the patent verbiage I can say that “quasi-solid electrolyte” means an electrolyte containing polymers and solvents not dissimilar to a gel electrolyte but still including excess solvent.

We have divided the Factorial patents into different segments: polymer containing electrolytes, anode-free, sulfide, cathode, and next-gen. We will start with their “quasi-solid electrolyte” or polymer containing electrolyte patents.

Polymer Containing Electrolyte Patents

In 2019, Factorial filed a patent for electrolyte that now only has one remaining claim. Certainly makes my job easier.

“A polymer solid electrolyte synthesized by crosslinking a mixture comprising a lithium salt, a crosslinkable monomer, an ion dissociation compound, and an additive that can enhance capacity retention of an electrochemical device…wherein the crosslinkable monomer has a formula of:”

Oof I am getting stress flashbacks to organic chemistry. We don’t yet have a polymer person on staff, but as an electrochemist I am pleased with this patent for the verbiage right here: “the polymer solid electrolyte has an oxidation potential of at least 4.5 V with reference to Li/Li+”. A polymer electrolyte with better stability than its liquid counterparts seems like.. a pretty good invention to me.

What about transference number of said electrolyte? If they are mentioning sulfide they are obviously attempting the holy grail of transference numbers (1 for those of you less nerdy than me). Transference number is the ratio of the current carried by a specific ion (in this case Li-ion) in an electrolyte solution relative to the total current. A transference number of 1 means the only current in the system is carried by Li+, love to see it, hard to achieve.

Factorial also has a patent for the electrochemical cells made with polymer electrolytes, and another for the electrodes for lithium-ion batteries. The latter gives us this gem:

*Check out that separator with a ⅜” hole in it, and a catholyte instead of just a cathode. So interesting!*

The Factorial patent attorneys have stayed busy: this 2023 patent shows some Nyquist plots, this 2019 patent reads like another organic chemistry textbook, this 2021 cross-linked polymer electrolyte patent shows some nice capacity retention plots, and we have a recent one with 2024 electrolyte compositions. In 2023 they also patented some cell assembly with this “compressions means for li metal anode cells”.

Anode- free patents

Are you even a solid-state battery company if you don’t use the term “anode-free” or “anode-less”? Factorial stays in the game with this 2022 anode-free battery filing, and another 2022 anode-free battery filing. Seems we know the R&D priorities in 2022.

Sulfide patents

The sulfide-based electrolyte claims start in 2023 with this flexible sulfide solid electrolyte, claiming a lithium-ion conductivity of no less than 0.5 mS/cm. The formula is given as:

“wherein M1 is at least one element of Group 1 or Group 11 other than H or Li of the periodic table, M2 is at least one element of Group 2 of the periodic table, and M3 is at least one element of Group 14 of the periodic table”
“a binder with a weight percentage in a range from 0.05wt% to 10wt% in the flexible electrolyte membrane”

This 2024 sulfide electrolyte patent uses the term “free-standing”, and seems to be for a sulfide-electrolyte that is coated with solvent as a slurry.

“A method of preparing a solid membrane free of a scaffold layer, comprising:
a) mixing a nonfibrillizable binder, a solvent, and particles of a sulfide electrolyte to form a slurry;
b) coating the slurry on a non-stick base;
c) drying the coated slurry to form a dried coating on the non-stick base; and
d) peeling the dried coating from the non-stick base, thereby obtaining a solid electrolyte membrane free of scaffold layer.”

Cathode patents

This 2016 Lionano patent is for a nickel based positive electrode material is super interesting because it has two claims that are still active (and now assigned to Factorial) with an expiration date of 2036.

“A positive electroactive material having a formula Lia[NixMnyCo1−x−y]zM1−zO2, wherein:
M is selected from Samarium (Sm), Silicon (Si), Lanthanum (La) or a combination thereof;”

The patent also included an XRD plot for said active material:

*Now thats a (003) peak if I ever did see one. Looks like a layered oxide structure to me.*

With an impressive span of patent-scope, in 2023 they patented a CAM coating “lithium borate doped lithium carbonate”. I guess if you have an electrolyte stable to 4.5V vs Li, now you need to ensure your CAM is also stable in the same range.

“Disclosed are cathode active material (CAM) coated with a lithium carbonate doped with lithium borate with a formula of Li2+xC1-xBxO3, wherein 0 < x < 0.5 and a preparation method therefor. Also disclosed is a cathode layer comprising the coated CAM in the form of particles. In one embodiment, an all-solid-state battery comprising the cathode layer exhibits improved stability and cycling performance.”

Next gen patents

And then in 2024 we get to solvent-free electrode fabrication! Love to see it.