Amorphization of Sodium Cobalt Oxide Active Materials for High-Capacity All-Solid-State Sodium Batteries

Abstract

Amorphous Na0.7CoO2–Na x MO y (M = N, S, P, B, or C) positive electrode active materials were synthesized by a mechanochemical technique to achieve high capacities and improved cyclabilities owing to their open and random structures. As none of the X-ray diffraction peaks are attributable to the starting materials, it was clear that the reaction between Na0.7CoO2 and Na x MO y had been successful. The prepared Na0.76Co0.8N0.2O2.2 (80Na0.7CoO2·20NaNO3 (mol %)) was easily densified by pressing at room temperature, and then applied as a positive electrode in bulk-type all-solid-state sodium cells (Na15Sn4/Na3PS4 glass-ceramic/Na0.7CoO2–Na x MO y ). The cell based on the Na0.76Co0.8N0.2O2.2 active material without any conductive additives in an ultrathick positive electrode layer (∼50 μm thickness) operated as a secondary battery at 25 °C. The average discharge voltage was 2.9 V, and the initial discharge capacity was 70 mAh g−1 of the positive electrode. This cell exhibited a higher discharge voltage and a larger capacity than cells employing crystalline Na0.7CoO2 or milled Na0.7CoO2 as the positive electrode. The electrochemical properties of Na0.7CoO2 were therefore improved by amorphization with NaNO3. Furthermore, the cell with the composite electrode containing a conducting additive gave a discharge capacity of 170 mAh g−1 of Na0.76Co0.8N0.2O2.2, which is the highest reported to date for all-solid-state sodium cells based on oxide positive electrodes. Therefore, the amorphization of layered transition-metal oxides with sodium oxy-acids is an effective way to achieve novel active materials with high capacities.

Na 2 TiV ( PO 4 ) 3 @C composite with excellent Na‐storage performance based on a solid‐state polymer electrolyte membrane

“…And at the same time, the pores formed during the preparation process prevent the piercing of the membrane by sodium dendrites and improve the safety performance of the battery. These results confirm that the PFSA-Na membrane promotes the electrochemistry performance of Na 2 TiV F I G U R E 6 A, Nyquist plots of liquid electrolyte battery and quasi-solid battery; B, the relationship between reciprocal square root of angular frequency (ω −1/2 ) and the real impedance (Z 0 ) in the low frequency region of two kinds of batteries; C, morphology of PFSA-Na membrane near Na after cycling; D, morphology of Celgard 2400 near Na after cycling [Colour figure can be viewed at wileyonlinelibrary.com] F I G U R E 7 Comparison of performance of similar types battery 29,50,[54][55][56][57] (PO 4 ) 3 @C and provides a solution for the industrialization of sodium-ion battery in the future.…”

Research Progresses on Interfaces in Solid‐State Sodium Batteries: A Topic Review

“…The amorphous materials have the additional stable sites for cations due to their open and random structures. [ 118–122 ] Therefore, the SSSBs using amorphous TiS 3 (α‐TiS 3 ) electrode with AB showed a reversible capacity of over 300 mAh g −1 for 5 cycles (Figure 7h), which is three times higher than that of the cell using TiS 2 crystal. [ 104 ] The shape of inorganic fillers can also influence the ion conduction of the composite electrolytes.…”

A Review of Battery Materials as CDI Electrodes for Desalination

“…Sodium cobalt oxide (NCO) is a Na-ion battery material with a relatively high theoretical electrochemical capacity (about 235 mAh•g −1 ) that might lead to a good desalination performance and a cost that is not low because of the cobalt [86][87][88]. [89] synthesized Na 0.71 CoO 2 from Co 3 O 4 and Na 2 CO 3 and then used it as the cathode in the flow-by CDI device with a Ag/rGO anode and a cation-exchange membrane separating them.…”