In summary, in this paper Jeff Dahn's group showed that Cobalt may play no useful role in the high Nickel NCA cell chemistries used by Tesla.
The significance of this research is it presents solid evidence that >90% Nickel NCA have already reduced cobalt so much it is no longer playing any useful role. Hence, we may only need small changes to current chemistry to remove cobalt - which should be much quicker than other proposals to start from scratch on a whole new cobalt free chemistry.
It presented preliminary evidence that 5% Al, 5% Mn or 5% Mg could all be viable cobalt substitutes, but it hadn't yet found the optimum mix and there is still a lot of work to do before we get a commercial product.
Tesla already uses far less cobalt than its competitors - I think 75% less than the most common NCA chemistry NCA 532.
I think Tesla's current NCA cathode chemistry is Nickel 93% Cobalt 5% and Aluminium 2%. I really don't think it will be long before Tesla moves to something like NA 9.5 0.5 - 95% Nickel, 5% Aluminium.