Assembled manganese and its nanostructured manganese dioxide rich electrodes for a new primary battery

Highlights

• New Mn/MnO₂ battery was developed by assembling of Mn metal and its nanostructured dioxide.

• MnO₂ was electrodeposited onto platinum as γ-MnO₂ with particle size <15 nm.

• A Mn/MnO₂ cell presents better performance compared to the classical Zn/MnO₂.

• The voltage of Mn/MnO₂ cell is > 2 V in NH₄Cl, after 3 h of discharge is maintained at 1.89 V.

• A capacity of 1000 mA h.g⁻¹ with energy of 1890 mWh.g⁻¹ was obtained after 3 h at 330 mA g⁻¹.

Abstract

In this work, manganese metal and its nanostructured dioxide (MnO₂) were applied as electrodes for the development of a new Mn/MnO₂ battery. The MnO₂ was deposited onto platinum substrate using electrodeposition technique and collected as powder cathode in the new battery. The influences of temperature and precursor pH on the MnO₂ film properties were investigated. Scanning electron microscopy, X-ray diffraction (XRD), energy dispersive X-ray analysis and transmission electron microscopy (TEM) were used to characterize the MnO₂ deposit. The XRD and TEM demonstrate that the MnO₂ was deposited in its γ-MnO₂ phase with a particle size less than 15 nm. In addition, the pH solution plays a key role in the electrochemical performance of the MnO₂ as a cathode. Indeed, the γ-MnO₂ deposited at pH = 2 provides a high discharge performance in KOH and NH₄Cl aqueous electrolytes. This led to a new Mn/MnO₂ cell with better performance compared to the classical Zn/MnO₂ cell in terms of discharge in NH₄Cl electrolyte. During the discharge process, co-insertion of Mn²⁺ and H⁺ promotes the transformation of MnO₂ into Mn_xMnO₄, MnOOH, and Mn₂O₃. In addition, the Mn/MnO₂ cells exhibits a high output voltage >2 V in NH₄Cl. It reach a high voltage at around 1.89 V after 3 h of continuous discharge. The cells can achieve a discharge capacity of 1000 mA h.g⁻¹ at a current density of 330 mA g⁻¹ with the highest specific energy of 1890 mWh.g⁻¹. Moreover, Mn/MnO₂ cells are more stable in NH₄Cl electrolyte which exhibits a voltage drop of 6% after 3 h of continuous discharge. Such results demonstrate that the assembled Mn/MnO₂ battery can occupy an important place in the energy storage field as a low cost and high performance device.

Introduction

The battery as an energy storage and conversion device has superbly propelled the course of human event. The increasing demand for energy storage and conversion in the modern society is consistently expanding due to the smart environment development including portable devices, electric vehicles, and large-scale networks [1,2]. Particularly, in the last decade, the Lithium-ion batteries (LIBs) have attracted a significant interest, and have registered high progress, and conquered the commercial battery market due to their high energy densities. Despite this, the current LIBs present some disadvantages such as limited resources, high cost, poor safety, and environmentally unfriendly [1]. This led to revive the traditional aqueous batteries, such as Zn/MnO₂, the oldest electrochemical sources of electric power [[3], [4], [5], [6]], because of specific properties of Zn and MnO₂ materials, which are ones of the safest and most abundant materials [4,5,[7], [8], [9]]. Recently, more efforts are undergoing to replace the classical anode material by other low cost metals, including Na, K, Mg, Ca, Mn, Cu and Al, in order to improve the performance of these traditional batteries [1,2,10,11]. Among these metals, Mn seems to be promising because of its electrochemical and thermodynamic properties, its oxidation states (The standard potential for Mn²⁺/Mn is −1.18 V vs. SHE), and its low cost and environmentally friendly [9,[12], [13], [14]]. Moreover, it is well known that the most of current batteries use MnO₂ material as a negative electrode (cathode) [2]. There are various preparation methods of this material namely: sol-gel technique, electrochemical deposition, hydrothermal method, electrolytic deposition, and sonochemistry [8,[13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33]]. Indeed, the MnO₂ structure and morphology strongly depend on the preparation method [8,14,16,27,31,[34], [35], [36], [37], [38], [39], [40], [41]], can exist in several crystallographic structures, such as α, β, γ, λ, and ε [8,9,26,27,33,42]. Commonly, MnO₂ synthesized by electrodeposition (ELD) in acidic electrolytes, has either γ and/or ε crystallographic structures [8,26,33,43]. As reported in the literature, the γ-MnO₂ phase is one of the preferred structures for electrochemical applications as cathode material for batteries [7,8,42,44,45]. In addition, the ELD technique presents another advantage namely the synthesis of a nanostructured MnO₂ film which is desired to achieve a high performance cathode [43].

In this work, a nanostructured film of γ-MnO₂ made of nanoparticle agglomeration was successfully synthesized and collected as powder cathode in battery. Herein, we present for the first time, the Mn as anode material for primary battery. A new Mn/MnO₂ assembled cell was realized and electrochemically characterized in aqueous electrolytes of NH₄Cl and KOH and compared with a typical battery made of Zn/MnO₂.