Fabrication of VB2/Air Cells for Electrochemical Testing

Summary

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

Abstract

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB₂ is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB₂ particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB₂ anode. Finally, discharge of the completed VB₂/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB₂ anode.

Introduction

Vanadium diboride as an anode has among the highest volumetric charge capacity of any anode material. This protocol introduces a method for studying this fascinating material. Metallic zinc has been the predominant anode material in aqueous primary systems due to zinc metal's high two-electron volumetric and gravimetric charge storage capacities of 5.8 kAh L^-1 and 820 Ah kg^-1, respectively.* The zinc-carbon battery, known as the Leclanché cell, was first introduced in the 19^th century, combining a zinc anode with a manganese dioxide (carbon current collector) cathode in a chloride electrolyte¹. The common a....

Protocol

1. Preparation Nano-VB₂

Nanoscopic VB₂ is directly synthesized from elemental vanadium and boron via ball-milling in a 1:2 mole ration.

1. Clean a 50 ml tungsten carbide milling jar and ten 10-mm tungsten carbide balls. Dry under air in an oven at 100 °C for 1 hr to ensure all water has evaporated.
2. Wipe clean the inside of the milling jar to ensure no residue remains, repeat step 1.1 if residue is visible.
3. Purge the antechamber of a glove box with argon 3x for 10 min each time. Transfer the milling jar, balls, and clean spatula into the argon filled glovebox.
4. Weigh out vanadiu....

Results

Electrochemical testing is performed to determine the performance of VB₂/air batteries. The results obtained for multiple cells provide evidence for reproducibility of the cell performance. Figure 1 compares the VB₂/air batteries during a 3,000 ohm (left) and 1,000 ohm (right) discharge. Note that the discharge voltage, as well as the fraction of the 4,060 Ah kg^-1 intrinsic capacity is higher with the nanoscopic VB₂ anode compared to the macroscopic VB₂

Discussion

Construction of the VB₂/air battery in this way provides the ability to study and probe the eleven electrons per molecule charge transfer that occurs, allowing the possibility for a new high capacity battery. If obtained results do not demonstrate reproducible results, ensure that all of the zinc anode material was removed from the battery, that there is an even dispersion of active material on the cap, and that the cells are properly glued without any leaks. If a problem continues to occur, ensure that the ba.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
MATERIALS
Boron	Alfa Aesar	11337
Diethyl Ether	J.T. Baker	9244-06	4L
Epoxy	Loctite		Heavy Duty 5 min setting time
Isopropyl Alcohol
Panasonic 675 Zinc/Air cell	Panasonic	PR675H	Made in Japan (not German)
C-NERGY Super C65	Timcal		Graphitic carbon black
Vanadium	Aldrich	262935
Vanadium Diboride	American Elements	12007-37-3
Zirconium Chloride	Spectrum	Z20001
EQUIPTMENT
50-mL round bottom flask	Fisher Scientific Co LLC	CG151001
Diagonal cutting pliers	Hardware store
Hot/stir plate	IKA	C-MAG HS 7
Glove box	Labconco	Precision Basic
Ten 10-mm tungsten carbide balls	Lab Synergy	55.0100.08
Tungsten carbide milling jar	Lab Synergy	50.8600.00
Razor blade	Hardware store
Retsch PM 100 planetary ball mill	Retsch	205400003
Stir bar	VWR International	58947-140