Why direct recycling beats leaching and smelting

Lithium-ion battery manufacturing is expanding rapidly, yet recycling still relies mainly on two routes: hydrometallurgical leaching and pyrometallurgical smelting. Both work, in the sense that they recover metal content. Both also discard the cathode's existing crystal structure in the process, and with it, much of the energy that was already spent building that structure in the first place (Roy et al., Carbon Energy, 2024).

What leaching and smelting actually do

Hydrometallurgical leaching breaks the cathode down into individual dissolved metal salts, which then have to be re-precipitated and re-synthesised into fresh cathode material. Pyrometallurgical smelting goes further, reducing the material to a metal alloy and slag, recovering some metals well, but losing others (like manganese and lithium) to the slag almost entirely.

Both routes work at the level of "get the elements back." Neither preserves the layered crystal structure that took real energy and real engineering to build in the first place.

What direct recycling does instead

Direct recycling avoids this by relithiating the existing structure in place, instead of dissolving or smelting it down and starting over. Done well, it should mean recovering a cathode material that's already most of the way to production-ready, without the leaching, solvent-based dissolution, or smelting of the active material that the conventional routes require.

This is the engineering problem HSCR is working on: not just measuring how much conventional recycling helps, but building a genuinely better recycling process. Our own process is still in development; see the R&D & Battery Recycling page for where things stand, including the qualitative literature comparison across all three routes and the modeled techno-economic estimates for our approach.