Researchers from Tokyo University of Science (TUS) are developing high-capacity electrode materials for sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) to compete with lithium-ion batteries (LIBs).

In the study published in Advanced Energy Materials, the researchers reported a new synthesis strategy for nanostructured hard carbon (HC) electrodes. HC lacks a crystalline structure—unlike graphene or diamond—and it is also strong and resistant. Researchers examined zinc oxide (ZnO) and calcium carbonate (CaCO₃) HC samples and compared them to magnesium oxide (MgO) samples. 

ZnO showed potential for negative electrodes in preliminary experiments. By optimizing ZnO concentration in the HC matrix during synthesis, researchers achieved a reversible capacity of 464 mAh g^–1, high initial Coulombic efficiency of 91.7% and low average potential of 0.18 V vs Na+/Na. When integrated into a KIB, the ZnO-templated HC also showed a capacity of 381 mAh g^–1, highlighting its potential.

“The NIB fabricated using the optimized ZnO-templated HC as the negative electrode exhibited an energy density of 312 Wh kg^–1,” said Professor Komaba, research team leader. “This value is equivalent to the energy density of certain types of currently commercialized LIBs with LiFePO₄ and graphite and is more than 1.6 times the energy density of the first NIBs (192 Wh kg^–1), which our laboratory reported back in 2011.”

Source: Tokyo University of Science