Yes, the capacity of lithium batteries degrades over time, as is the case with most battery chemistries (flow batteries and liquid metal batteries being exceptions). The root cause of much of the degradation is from cycling of the battery cell - moving of lithium ions from the cathode to the anode. The anode in lithium ion batteries is typically made from graphite. The graphite is a significant part of the overall battery mass and volume. Silicon-based anodes can store much more lithium per unit of volume and mass than graphite anodes, but suffer from faster capacity degradation than graphite anodes used in most lithium batteries today. Talga (and Tesla and others) are working to mitigate this issue, in Talga's case using graphene + silicon anodes. I note that Talga reported 5% capacity degradation in their test graphene+silicon cells after 45 cycles, so perhaps not yet about to wipe out current graphite-anode batteries with 30% degradation after 10 years (Tesla Model 3 LR battery warranty is 70% capacity after 8 years or 192,000 km, whichever comes first).
Yes there is abundant lithium in sea water, but at very low concentrations compared to ORE's brine resources or GXY's spodumene. I'm not aware of any proposed project for economically extracting lithium from sea water - can you point me at any?
I don't believe hydrogen is a viable alternative to lithium batteries, except perhaps in long-haul trucking. Lithium battery round-trip efficiency is 90% or more. Producing hydrogen from electrolysis is around 80% efficient, but producing electricity from a hydrogen fuel cell is only 40-60% efficient, so in the end it will take at least twice as much input electricity to power a fuel cell vehicle than a battery-powered vehicle. (Not to mention the cost of building out a hydrogen distribution network).
You say "Graphene holds 6 times more energy than lithium". As discussed above, I think the correct statement would be "a graphene-silicon anode can store 6 times more lithium (ions) than the same weight of graphite". You are absolutely correct that this has the potential to greatly reduce the size (volume) and weight of lithium batteries, and thus further accelerate the transition away from ICE vehicles.
ORE Price at posting:
$9.04 Sentiment: Hold Disclosure: Held
