The author’s solution essentially uses the batteries in the devices themselves to hold the energy.

Their point about power tool usage is a good one, except that they don’t discuss solar power surplus, which can be an issue.

But changing mindset to using electricity while it’s available instead of always assuming there will be a surplus of energy is a good one. The overall piece just seems a bit oversimplified.

like, to be clear: the scope of the article is laid out by those qualifiers, so naturally it's not going to prescribe how to get rid of in-built batteries in consumer electronics since they fall outside of that scope. even so, it addressed the quibble you're getting at here pretty bluntly, i think:

Of course, outsourcing chemical energy storage to the device is not the most sustainable option. The production of lithium-ion batteries requires fossil fuels, and (unlike lead-acid batteries) they are not recycled. The best solution, of course, is to reduce the use of electrical devices. But charging them with direct solar energy is a lot more sustainable and efficient than via other batteries or a fossil-fueled electricity grid. If we use high-tech devices, then preferably in the smartest way possible.

and Low-Tech Magazine has previously covered alternatives to battery technology in other posts. so i'm just not seeing what the objection here is.