...but unfortunately, we will need lithium ion batteries to reduce CO2 emissions until we can develop better portable energy storage systems.

Maybe if we had stopped using fossil fuels when Mrs. O'Leary's cow started the Chicago Fire in 1871 we wouldn't be in this mess now, but of course, even when we do get away from using fossil fuels to generate our electricity, we'll probably still have the problem of rodents starting about 25% of unknown-origin house fires just from chewing on electrical wiring and equipment.

but not as energy dense.

Lots of new battery stations (or whatever they're called) are now LiFePO4 (Lithium Iron Phosphate)

I have a gaming laptop computer with a LIon battery that I do a lot of 3D work with (so making heavy use of the GPU). Especially if a computer is put away without turning it off, the laptop can get hot enough to cause blistering and potentially catch its backpack carrier on fire.

There are a number of interesting alternatives to Lithium batteries, most notably Sodium batteries (which is part of the same Class I elements that hydrogen and lithium are part of). I recently saw a report of a anode-less sodium that, if it can be scaled, could render LiON batteries obsolete - they have a slightly lower energy density than lithium, but they are much less expensive to produce, and because they don't require a dedicated anode, they also run much cooler. Expect to see them in production in the next 3-4 years.

The sodium batteries have an edge in that they're already in limited production.

I've also read about magnesium water (less energy dense than lithium ion) and iron-air systems that sound too good to be true. We know that lithium ion batteries are showing their unintended consequences like EEK FIRE!

We might always use the small ones, they seem ideal for cell phones and small tablets. We do need better solutions for things that require more power, like gaming computers and the electrical grid.