Nickel (Ni)-rich layered cathode materials—such as composites of Ni, lithium, manganese, cobalt, and oxygen, commonly called Ni-rich NMC (LiNi_1-x-yM_xCo_yO₂, 1 – x – y ≥ 0.6)—hold promise for high-energy batteries. Ni-rich NMC cathodes boast high discharge capacity and improved energy density compared to traditional lithium-cobalt-oxygen materials (LiCoO₂). Unfortunately, challenges hinder the use of these Ni-rich materials. Cracks degrade structural integrity, and aggressive thermal reactions raise safety concerns. No approach has adequately addressed these challenges, until now.

Researchers at Pacific Northwest National Laboratory have developed a novel process to synthesize cathode materials that could help batteries—such as those needed for electric cars—last longer and perform better. The key is the infusion of lithium phosphate into the Ni-rich NMC cathode materials. Conventional methods merely coat the surface of the cathodes with lithium phosphate or other materials, like icing on a cake, protecting the materials but not strengthening them. The patented PNNL approach binds the lithium phosphate to the NMC material under high temperatures in a few hours, joining the boundaries of the small primary particles in the vicinity by a solid electrolyte that prevents strain and cracking.

These lithium-infused materials have high energy density and improved discharge capacity, increasing structural integrity without observable cracking. Furthermore, the materials retain more than 90 percent of their high capacity after 200 charge/discharge cycles at room temperature, a 15 percent increase over traditional materials. The fusing of the lithium phosphate and Ni-rich cathode materials also prevents the undesirable thermal reactions in traditional materials. 

APPLICABILITY

The approach paves the way for advanced battery cathodes, such as those needed for electric cars. The process can be used for all types of cathode materials, not just Ni-rich NMC.