The Effect of Barium Hydroxide on the Rechargeable Performance of Alkaline γ-MnO₂

Abstract

A series of controlled current cycling experiments have been conducted to investigate the effect of barium hydroxide on the rechargeable performance of the alkaline manganese dioxide cathode. Analysis of the resulting discharge behavior revealed that the inclusion of Ba(OH) 2 suppresses the dissolution of Mn 3+ ions during the latter stages of discharge. This in turn gave rise to improved rechargeable performance, with electrodes containing Ba(OH) 2 exhibiting both improved capacity retention and higher cumulative capacities. Similar effects were observed during the cycling of manganese dioxide in the presence of soluble Ba(II) ions, and the implications in terms of its underlying role considered. In both cases barium hydroxide was also noted to inhibit the formation of δ-MnO 2 , and this was confirmed by X-ray diffraction and transmission electron microscopy.Electrochemical energy storage.-With the increased prevalence of portable electronic devices a higher demand is being placed on both the performance and efficiency of their electrochemical power sources. With global sales exceeding $10 billion per year, 1 batteries are the power source of choice due to their portability, reliability and excellent performance characteristics. Within this domain the alkaline Zn/MnO 2 system is prominent due to its low cost and strong performance in a wide variety of applications. While still widely regarded as a primary system, significant progress has been made in the development of rechargeable manganese dioxide (RAM) cells. 2-4 Despite the excellent performance of presently available cells, 5 there remains significant scope for improvement in terms of cathodic rechargeability under deep discharge conditions. Structure and discharge mechanism of γ-MnO 2 .-The preferred cathode material for use in both primary and secondary alkaline Zn/MnO 2 cells is that of electrolytic manganese dioxide (EMD). EMD has the γ-MnO 2 structure which is built up of edge-and cornersharing [MnO 6 ] octahedra in a manner consistent with a random microscopic intergrowth of pyrolusite (1×1) and ramsdellite (2×1) forms of MnO 2 . 6,7 Its structure has been considered in depth by Chabre and Pannetier, 8 who outlined a method for the calculation of the pyrolusite content (denoted P r ), and the level of microtwinning (denoted T w ) present in the (021) and (061) growth planes. Other key features associated with the γ-MnO 2 structure include cation vacancies, lower valent manganese cations (Mn 3+ ), and structural water present as protons associated with the oxide anions that compensate for the charge deficiency incurred by Mn 3+ ions and cation vacancies. 9-11

Rechargeability and economic aspects of alkaline zinc–manganese dioxide cells for electrical storage and load leveling

“…All battery characteristics are taken from Chen and coworkers [41], but it should be noted that capital cost and cycle life estimates show wide variation depending on source [42e44]. The lifetime investment cost was calculated based on cycle life and DC round-trip energy efficiency as: Lifetime Investment Costð¢=kWh per cycleÞ ¼ capital costð$=kWhÞ cycle life  energy efficiencyð%Þ (16) Many of these technologies, such as Pb-acid, NieCd, NaeS, Vredox, and the various types of Li-ion batteries, have been suggested for grid-scale storage applications. However, many of these technologies have drawbacks related to cycle life, complexity, toxicity, or safety.…”

“…Anode effects were treated empirically by assuming the separator resistance R s was a linear function with cycle number as shown in Equation (5). R s ¼ 0:0001ðcycle numberÞ þ 0:55 (14) This resistance was included to account for the increase in cell resistance caused by ZnO buildup and clogging at the separator by Equation (16).…”

Facile synthesis of ternary MnO2/graphene nanosheets/carbon nanotubes composites with high rate capability for supercapacitor applications

“…However, MnO 2 has the disadvantage of low cyclic life and stability due to crystal shrinkage/expansion induced drawback of the material during repetitive charge/discharge cycles [8].…”

Chemical Charging on a MnO2 Electrode of a Fuel Cell/Battery System in a Highly O2-Dissolved Electrolyte

“…The crystal structure of the EMD during chemical charging is likely to have changed in the same manner as discussed in section 3.1. We found that the crystal structure of the chemically charged EMDs was in the process of ramsdellite formation because the potential was around À0.1 V [16][17][18][19]. The electrode potentials after electrochemical charging were lower than those of the chemically charged electrodes.…”

“…The structure of EMD consists of the intergrowth of two different structural domains: a complex tunnel of ramsdellite (1 Â 2) and pyrolusite (1 Â1) [15][16][17][18][19]. From the dQ/dV curve obtained during charging, three peaks were also obtained near À0.28 V, 0.02 V, and 0.4 V. These correspond to oxidation reactions at the pyrolusite and ramsdellite domains, and the oxygen evolution reaction upon the electrolysis of the electrolyte, respectively [15][16][17][18][19].…”