Electrochemical Properties of Spinel Cobalt Ferrite Nanoparticles with Sodium Alginate as Interactive Binder

Abstract

AbstractWe introduce a process of making high‐capacity and rate‐capable metal‐ferrite‐based conversion anodes for lithium‐ion batteries. Cobalt ferrite (CoFe2O4) exhibits a discharge capacity that is two‐times higher compared to the state‐of‐the‐art graphite anode, but at the same time it shows high volume change (ca. 95 %) during conversion reaction with lithium in an electrochemical environment. This large volume expansion is responsible for the particle–particle and conductive‐carbon particles–active materials detachment, which leads to cyclic instability during subsequent cycles. As observed in our earlier work, any kind of weak or strong chemical interaction between active materials and binder is necessary to achieve excellent electrochemical performance in case of conversion or alloying reactions. To compare the electrochemical activity of CoFe2O4 nanoparticles against lithium, we use conventional polyvinylidene fluoride and sodium alginate binder to fabricate electrodes. Fourier‐transform infrared measurements reveal weak hydrogen‐bond formation between surface OH groups of CoFe2O4 and COOH groups of the alginate binder. Indentation tests further confirm the increased hardness of the alginate/CoFe2O4‐based electrode films. CoFe2O4–alginate–carbon anode exhibits a high specific capacity of 890 mAh g−1 at 0.1 C rate (91.4 mA g−1) after 50 charge–discharge cycles. Even at high rate cycling with current densities such as 18280 mA g−1 (20 C), the same electrode material exhibits a specific capacity of 470 mAh g−1, which is much higher than that of conventional graphite anode at the same electrochemical conditions.