Analysis of electrochemical mechanism of coprecipitated nano-Ag_4Bi_2O_5 as super high charge-discharge rate cathode materials for aqueous rechargeable battery

摘要

Nano Ag_4Bi_2O_5 as a novel cathode material of rechargeable alkaline batteries was successfully synthesized by precise control of precipitation reaction. KOH solution was used as precipitant and a mixture of AgNO_3 and Bi(NO_3)_3 as Ag-Bi source. The experimental results indicate that concentration of KOH, reaction temperature and PH value have the effects on the structure and electrochemical property of the product. The material was characterized by means of XRD, FSEM and TG-DSC The results show that the sample is single crystals with 50-100 nm in width and 600-800 nm in length. The electrochemical performances of Ag_4Bi_2O_5 in the alkaline electrolyte were measured by galvanostatic method and cyclic voltammetry tests through film electrode. The sample shows three typical procedures during the charge-discharge, corresponding to Ag(II)-Ag(1), Ag(1)-Ag(0) and Bi(III)-Bi(0) transformation processes. This result is also verified by XRD tests. The Ag_4Bi_2O_5 electrode has excellent electrochemical properties. It undergoes a current density as high as 20 A g~(-1), which greatly reduces charge time down to 55.9 s. The electrode offers a cycling capacity of 330 mAh g~(-1) and a cycling life more than 400 cycles at 1-2 A g~(-1).