A Low-Carbon Strategy to Synthesize Cobalt-Free Cathode Materials of Lithium-Ion Batteries

Given the high uncertainty of cobalt supply and related ethical concerns, the development of cobalt-free cathode materials has become an urgent priority for lithium-ion battery industry. Nevertheless, manufacturing cobalt-free cathode materials involves energy-intensive processes such as long-time high-temperature lithiation, which significantly contributes to the carbon footprint of cathode material production. As such, establishing low-carbon manufacturing strategies is crucial to improve the sustainability of energy storage applications, including electric vehicles and renewable energy grid storage. In this study, we propose a low-carbon technique, termed Flame-Assisted Spray Pyrolysis (FASP), characterized by its reduced synthesis time and utilization of hydrogen as an energy source. The FASP method demonstrated its efficacy in synthesizing cobalt-free cathode materials, particularly layered structure nickel-rich cathode materials. Using an inexpensive aqueous solution of metal nitrates as a precursor, FASP saves a significant amount of time and energy by reducing the calcination process from over 20 hours to just 40 minutes. Furthermore, with hydrogen as a supplementary fuel, FASP further mitigates carbon emissions compared to traditional heating methods.<br/>Comparison with long-time calcinated samples in full cells using graphite as the anode confirms that the electrochemical performance of the newly synthesized cobalt-free cathode materials is maintained. This work also investigated the detailed material formation mechanism through X-ray diffraction and transmission electron microscopy. We found that uniform lithium distribution in the as-synthesized material prior to calcination was the key to shortening lithium diffusion, fastening layered structure formation, and preventing impurity phases. Furthermore, inhibiting the generation of hard-to-decompose lithium compounds, particularly lithium carbonate, was also critical in ensuring the desired electrochemical performance of fast-calcinated samples. Moreover, emission analysis shows that the carbon emission could be reduced by more than 30% with this novel synthesis route. The current work underscores the potential for FASP to significantly contribute to a low-carbon future in the manufacturing of cobalt-free lithium-ion batteries.