The development of new battery technologies requires them to be well-established given the competition from lithium ion batteries (LIBs), a well-commercialized technology, and the merits should surpass other available technologies’ characteristics for battery applications. Aqueous rechargeable zinc ion batteries (ARZIBs) represent a budding technology that can challenge LIBs with respect to electrochemical features because of the safety, low cost, high energy density, long cycle life, high-volume density, and stable water-compatible features of the metal zinc anode. Research on ARZIBs utilizing mild acidic electrolytes is focused on developing cathode materials with complete utilization of their electro-active materials. This progress is, however, hindered by persistent issues and consequences of divergent electrochemical mechanisms, unwanted side reactions, and unresolved proton insertion phenomena, thereby challenging ARZIB commercialization for large-scale energy storage applications. Herein, we broadly review two important cathodes, manganese and vanadium oxides, that are witnessing rapid progress toward developing state-of-the-art ARZIB cathodes.
Pursuing rechargeable metal-ion batteries with greater energy density is attracting great attention due to increasing demand for energy storage, where alloying anodes can provide very high capacity. [1][2][3][4][5][6][7] This is particularly true since sodium and potassium ion battery technologies offer limited capacity and stability using classic carbon-based anodes compared to lithium ions. [8][9][10][11] However, alloying anodes are notorious for their severe capacity fading, which has hindered their practical applications. The failure mechanism of alloying anodes has always been ascribed to the large volumetric change (~300%) and/or the fragile solid electrolyte interphase (SEI). [12][13][14][15] This interpretation is popular because the pulverization of the alloy-based electrodes can be observed during the reactions. As a result, many strategies have been developed to overcome this issue. These strategies include nano-structural controlling, carbon modification, and improving electrical conductivity. Thus, many nanostructured alloys including particles, 16 fibers/tubes, 5,17 film/membrane, 18,19 and hierarchical material 20,21 are being explored to stabilize alloying anodes. Characteristic, conductive and/or protective materials such as carbon and artificial solid electrolyte interphase (SEI) have been also used to improve alloying anode capacities stabilities. [22][23][24][25] Herein we show that an unprecedented high capacity (>650 mAh g -1 ) and stability (>500 cycles) can be achieved in alloying anodes by simply tuning the electrolyte composition, without the need for nanostructural control, carbon modification, and/or SEI engineering. We confirm that the cation solvation structure (e.g., Na + , K + ), particularly the type and location of the anions present in the metal salt and solvents, plays a critical role in affecting the alloying anode performance. In addition, we present a new anionic model showing that the anion corrosion plays at least an equally important role in alloying anode stability as the volume variation and fragile SEI models. Moreover, we present a new reaction model for alloying anode to make the ASSOCIATED CONTENT Supporting Information. Experimental and simulation section. Figures S1-S17 and Table S1 are included.
In this work we report Na[Li0.05(Ni0.25Fe0.25Mn0.5)0.95]O2 layered cathode materials that were synthesized via a coprecipitation method. The Na[Li0.05(Ni0.25Fe0.25Mn0.5)0.95]O2 electrode exhibited an exceptionally high capacity (180.1 mA h g–1 at 0.1 C-rate) as well as excellent capacity retentions (0.2 C-rate: 89.6%, 0.5 C-rate: 92.1%) and rate capabilities at various C-rates (0.1 C-rate: 180.1 mA h g–1, 1 C-rate: 130.9 mA h g–1, 5 C-rate: 96.2 mA h g–1), which were achieved due to the Li supporting structural stabilization by introduction into the transition metal layer. By contrast, the electrode performance of the lithium-free Na[Ni0.25Fe0.25Mn0.5]O2 cathode was inferior because of structural disintegration presumably resulting from Fe3+ migration from the transition metal layer to the Na layer during cycling. The long-term cycling using a full cell consisting of a Na[Li0.05(Ni0.25Fe0.25Mn0.5)0.95]O2 cathode was coupled with a hard carbon anode which exhibited promising cycling data including a 76% capacity retention over 200 cycles.
The lithium-ion battery is the currently leading energy storage technology for these applications, but will face severe challenges in meeting the increasing energy density demand as the implementation of new chemistries based on high energy density cathodes [2] will require new anode materials in order to overcome the limited energy density of graphite with a low specific capacity of 372 mAh g −1. [3] Lithium metal has an ultra-high theoretical specific capacity (3860 mAh g −1), and the lowest reduction potential (−3.04 V vs standard hydrogen electrode) and is thus considered as a "holy grail" for anode materials for high energy-density battery systems. [2,4] However, the practical application of Li metal batteries (LMBs) has been held back by a low Coulombic efficiency and safety concerns related to use of Limetal anodes. [4a, 5] In general, the problematic issues of Li-metal anodes can be attributed to two main factors, the preferred electrodeposition resulting in a mossy/dendritic morphology and the high reactivity of Li metal toward common liquid electrolytes generating a solid electrolyte interphase (SEI). [6] The mossy/dendritic morphology of Li inevitably results in a structural collapse of the electrode with The application of lithium metal as an anode material for next generation high energy-density batteries has to overcome the major bottleneck that is the seemingly unavoidable growth of Li dendrites caused by non-uniform electrodeposition on the electrode surface. This problem must be addressed by clarifying the detailed mechanism. In this work the mass-transfer of Li-ions is investigated, a key process controlling the electrochemical reaction. By a phase field modeling approach, the Li-ion concentration and the electric fields are visualized to reveal the role of three key experimental parameters, operating temperature, Li-salt concentration in electrolyte, and applied current density, on the microstructure of deposited Li. It is shown that a rapid depletion of Li-ions on electrode surface, induced by, e.g., low operating temperature, diluted electrolyte and a high applied current density, is the underlying driving force for non-uniform electrodeposition of Li. Thus, a viable route to realize a dendrite-free Li plating process would be to mitigate the depletion of Li-ions on the electrode surface. The methodology and results in this work may boost the practical applicability of Li anodes in Li metal batteries and other battery systems using metal anodes.
Potassium (K) is considered to be the most suitable anode material for rechargeable K batteries because of its high theoretical capacity (686 mAh g −1 ) and low redox potential (−2.93 V vs SHE). However, uneven electrodeposition of K during cycling usually leads to the growth of dendrites, resulting in low Coulombic efficiency and compromising battery safety. Herein, we develop a strategy for stabilizing K metal through simple interface control. The conductive passivation layer can be controllably designed by a spontaneous chemical reaction when a K metal foil is kept in contact with a liquid-phase potassium-polysulfide (PPS); this guides the formation of an electronically and ionically conductive solid electrolyte interphase layer including K 2 S compound, enabling dense K plating with a dendrite-free morphology. Compared to the bare K metal anode, the PPS-treated K metal anode demonstrates superior cycling stability in symmetric half cells and full cells using a TiS 2 cathode under practical constraints.
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