NL…you are right on the mark that NOT all natural flake graphite...

NL…you are right on the mark that NOT all natural flake graphite signatures are alike either chemically or metallurgically. There are many nuances including flake structure, BET, varying levels of Fused Oxides (I.e. SiO2, Fe2O3,) which can affect the SPG processing yield, TAP density, and OAN.
This is discussed in the presentation, yet the issue of cross contamination is relevant and even though a commercial advantage for process multiple signatures, ISO 9001 traceability cannot be completed with a 100% guarantee.
In electrochemistry applications, one natural flake graphite source cannot be substituted for another as each signature sources is subject to the same lengthy and critical raw material qualifications that take months and years to complete as is mandatory by electrochemistry OEM’s. A battery manufacturer will NOT risk consumer safety in the efforts to reduce cost by switching anode grade graphite products without proper homologations.
Cross processing natural flake graphite feedstocks brings into play ISO 9001 traceability of raw materials, product liability and potential violation of governmental consumer safety regulations.
The argument of blending primary synthetic and natural flake graphite powders into anode grade graphite has been presented, yet conversely, years of R & D of testing of a specific natural flake signature with a specific primary synthetic graphite creates a unique product that cannot be altered.
For example, if there are three natural flake feedstocks that are targeted to be processed and let say two of the three have been qualified by a specific battery chemistry and format, yet the third failed to be qualified due to poor TAP density values. By cross processing the three flake feedstocks introduces a level of potential anode grade failure as the processor cannot guarantee with absolute certainty that flake particles have not cross contaminated another flake source, slated to be shipped to a customer that has qualified a specific flake signature.
It is important to note that a specific natural flake graphite feedstock may work well in one battery chemistry or format and fail miserably in another and I have seen this occur with more than one product or customer. This does not mean that specific graphite signature is not good, but is not suitable for a specific battery manufacturer’s product. The variances from one signature to another can be quite significant, yet appear to be close in chemistry. Once a natural flake graphite has been SPG processed, no matter if the PSD’s are the same, the BET’s will vary slightly as well as OAN and TAP density.
Having worked in the battery industry for a couple of decades, I recently discussed this very issue with a consumer goods battery manufacturer and when presented with the potential cross processing contamination of multiple natural flake feedstocks, their first response was any anode graphite processor that does not follow ISO 9001 certification guidelines, introducing a potential for battery chemistry failure, will not be allowed to be a supplier. To risk being identified non-preferred supplier of anode grade graphite is not worth the potential cost savings as a tradeoff for consumer safety, product safety, or potential company liability.
Despite the narrative of the ability to process multiple signatures and potential cost savings for the host company, the possibility of product failure that could potentially create a consumer safety hazard may be viewed as creating a facade of ignoring consumer safety, governmental consumer safety regulations, and violating ISO 9001 guidelines and protocols; all to facilitate a positive commercial result.