Higher Capacity, Improved Conductive Matrix VB₂/Air Batteries

Abstract

Transition metal borides, such as VB 2 , have been investigated as alternative, higher capacity anode materials. The VB 2 high capacity is due to the capability to undergo a 4060 mAh/g formula weight multiple electron (11 e − ) alkaline oxidative discharge at a singular discharge potential plateau. With a comparable formula weight (10% higher) to zinc, VB 2 has an intrinsic gravimetric capacity five fold higher than the 2 e − oxidation of the widely used zinc alkaline anode. One challenge to the implementation of VB 2 /air batteries is that resistive oxide products impede the discharge depth, and only thin anode batteries (for example 10 mAh in a 1 cm diameter cell) had been demonstrated to discharge effectively. This study demonstrates that (i) smaller particle size (nano-VB 2 , as opposed to macroscopic VB 2 ) helps to alleviate this effect and (ii) a stacked anode compartment configurations improve the anode conductive matrix significantly, resulting in an increase in the coulombic efficiency of high capacity, thicker anodes in VB 2 /air batteries. Combined, these effects provide a 50% relative increase in the coulombic efficiency (from 50% to 75% at an 0.4 V discharge cutoff) of a 30 mAh coin cell, and increase the coulombic efficiency of the 100 mAh cell to 50%. Higher energy density portable power is needed for consumer electronic, medical, and military devices, and drives the need for increased energy density batteries. Zinc-air batteries are primary batteries with the highest commercial energy capacity. They provide a practical capacity of up to 1,756 Wh/L, which is 5-fold higher than that of rechargeable Li-ion batteries and 10-fold higher than conventional alkaline primary (zinc anode/manganese dioxide cathode) batteries. 1,2The capacity of zinc is limited by its oxidative discharge, which releases two electrons per zinc, leading to an intrinsic capacity of 820 mAh/g (=2 * FW/Faraday * mAh). Transition metal borides have been investigated as alternative, potentially higher capacity anode materials due to their ability to undergo oxidative discharge processes that release multiple electrons per molecule. The highest capacity of these materials, vanadium diboride, has an alkaline capacity per VB 2 (FW 72.561 g/mol) intrinsic capacity of 4060 mAh/g (charge/FW), approximately five times that of zinc. [3][4][5][6][7][8][9] As with the zinc anode, the borides can chemically react to generate hydrogen, and this causes a parasitic loss of battery capacity. In 2007, we noted that a zirconia overlayer impedes this parasitic reaction and promotes the battery discharge reaction.3,8 VB 2 coupled with an air cathode results in a battery material that is among the highest energy density of any primary battery (5,300 kWh/kg). 8 The VB 2 anode discharges all 11 of its electrons at a singular voltage plateau, in accordance with: [8][9][10] Anode :The thermodynamic (intrinsic battery) potential of Equation 3 is 1.55 V. [8][9][10] The experimental VB 2 /air battery is observed to discharge at a fraction of this intrinsic ...

Synthesis of Vanadium Diboride Nanoparticles via Reaction of VCl3 with NaBH4

“…Vanadium diboride, VB 2 , a typical Group V metal diboride, has a high melting point (2745°C) and high hardness, strength, wear resistance, and impact strength. Owing to this, it is a promising material for high-temperature engineering, vanadium boride-air batteries, and catalysts for the liquid-phase oxidation of various organic compounds, for example, cyclooctene, with molecular oxygen [1][2][3][4][5][6].…”

Suppressing Self-Discharge of Vanadium Diboride by Zwitterionicity of the Polydopamine Coating Layer

“…As shown in eq , the VB 2 –air battery adopts alkali media as electrolyte, such as KOH, NaOH, or a mixture of NaOH and KOH. Just like metal anodes, the VB 2 anode can chemically react with hydroxide ions in the alkaline electrolyte, which involves corrosion reaction and hydrogen evolution reaction . This self-discharge phenomenon of VB 2 anode causes a direct loss of battery capacity and predominantly impedes the practical application of VB 2 –air battery.…”

“…Just like metal anodes, the VB 2 anode can chemically react with hydroxide ions in the alkaline electrolyte, which involves corrosion reaction and hydrogen evolution reaction. 15 This self-discharge phenomenon of VB 2 anode causes a direct loss of battery capacity and predominantly impedes the practical application of VB 2 −air battery. The current effort on stabilizing VB 2 against corrosion was conducted by Licht et al 16 A thin zirconia coating on VB 2 not only guarantees charge transfer during the anodic discharge process, but can effectively prevent corrosion at the surface of the boride.…”

Reaction Synthesis and Discharge Performance of Binary Vanadium Borides

“…料电池的长处, 其比能量高、结构简单、放电电压 平稳, 是未来很有发展和应用前景的一类新兴绿色 能源 [1] 。 金属空气电池以活泼金属作为阳极, 空气中 的氧气作为阴极, 氧气通过气体扩散电极到达气-液-固三相界面与金属负极发生反应而放出电能 [2] 。 与现有的铅酸、镍氢和锂离子电池相比, 金属空气 电池可实现更高的能量密度和比容量, 而且安全性 更高 [3][4] 。目前商业中应用最广的锌空气电池, 其能 量密度可以达到 1756 Wh/L, 是锂离子电池能量密 度的 5 倍多, 更是传统碱性 Zn-MnO 2 电池的 10 倍 以上 [5][6] 。其中金属硼化物作为负极材料具有超高的 理论放电容量和能量密度, 近年来正在引起人们的 关注。 VB 2 在碱性溶液中可以发生 11 电子氧化反应, 理论放电比容量为 4060 mAh/g [7][8][9] , 几乎是锌空气 电池理论放电比容量(820m Ah/g)的 5 倍, 能量密度 为 32000 Wh/L [10] (6270 Wh/kg), 这是目前水溶液体 系金属化合物放电性能的最高水平。 上世纪末, 美国 Steven Amendola 等 [11] 提出了 以硼化物作为电极材料的高能量电池体系。 2004 年, 我国杨汉西等 [12]…”