Self-Oxygenated Blood Protein-Embedded Nanotube Catalysts for Longer Cyclable Lithium Oxygen-Breathing Batteries

Because of the increasing demand for energy, Li–O2 batteries have emerged as encouraging energy storage systems, because of their exceptional energy potential. However, the sluggish reactions caused by the inactive decomposition of the insulating discharge products are primarily responsible for disrupting their reversible operation. Herein, we report the direct application of hemoglobin (Hb) protein into carbon nanotubes (CNTs) via a facile fabrication way for efficient Li–O2 cell reactions. Our research indicated that Hb protein is an emerging environmentally friendly and abundant catalyst candidate with auto-oxygen binding properties. The protein was successfully infiltrated into CNTs via capillary force to fabricate proteinated CNT cathode materials. Compared with the cells featuring pristine CNTs, those featuring proteinated CNTs presented reversible performance and stable cyclability with low overpotential, because of the protein sources serving as a catalyst in the charge region. Our results suggest that proteins can be used to develop catalysts using an economic and environmentally friendly method. Moreover, our findings contribute to the progress of Li–O2 batteries as next-generation energy storage

Theoretical Evidence for Low Charging Overpotentials of Superoxide Discharge Products in Metal–Oxygen Batteries

Li–oxygen and Na–oxygen batteries are some of the most promising next-generation battery systems because of their high energy densities. Despite the chemical similarity of Li and Na, the two systems exhibit distinct characteristics, especially the typically higher charging overpotential observed in Li–oxygen batteries. In previous theoretical and experimental studies, this higher charging overpotential was attributed to factors such as the sluggish oxygen evolution or poor transport property of the discharge product of the Li–oxygen cell; however, a general understanding of the interplay between the discharge products and overpotential remains elusive. Here, we investigated the charging mechanisms with respect to the oxygen evolution reaction (OER) kinetics, charge-carrier conductivity, and dissolution property of various discharge products reported in Li–oxygen and Na–oxygen cells. The OER kinetics were generally faster for superoxides (i.e., LiO₂ and NaO₂) than for peroxides (i.e., Li₂O₂ and Na₂O₂). The electronic and ionic conductivities were also predicted to be significantly higher in superoxide phases than in peroxide phases. Moreover, systematic calculations of the dissolution energy of the discharge products in the electrolyte, which mediate a solution-based OER reaction, revealed that the superoxide phases, particularly NaO₂, exhibited markedly low dissolution energy compared with the peroxide phases. These results imply that the formation of superoxides instead of peroxides during discharge may be the key to improving the energy efficiency of metal–oxygen batteries in general

Electrochemically Induced Metallization of NaCl: Use of the Main Component of Salt as a Cost-Effective Electrode Material for Sodium-Ion Batteries

Sodium chloride (NaCl), a typical stoichiometric ionic compound, breaks all of the basic rules of chemistry at high pressures and can form new metallic compounds with different stoichiometries of NaxCl at x > 1. However, the electrochemical phase transition of NaCl from an insulating state to a metallic state without pressurization has not been achieved to date. In this study, we first demonstrate that nonmetallic NaCl can be transformed to a metallic compound through an electrochemical activation process. Subsequently, the activated NaCl electrode was shown to intercalate/deintercalate sodium ions into the structure, with a discharge capacity of 267 mAh/g by reversibly accommodating 0.6 Na ions. We believe that this method may represent a new approach for designing inexpensive electrode materials using the main component of table and sea salt for sodium-ion batteries. In addition, these results will contribute to the development of low-cost and sustainable rechargeable batteries that can be operated at a room temperature

Self-Constructed Intimate Interface on a Silicon Anode Enabled by a Phase-Convertible Electrolyte for Lithium-Ion Batteries

Promising high-capacity anodes of Si-based materials suffer from large volume expansions, thereby limiting their practical applications, especially in combination with safe inorganic solid electrolytes. Here, to achieve a high level of safety by applying Si anodes, we introduced a quasi-solid-state succinonitrile-based electrolyte (QS-SCN) that enables the practical application of the anode with long-term cycling performance. By exploiting the unique phase-convertible property of QS-SCN, the Si electrode was successfully impregnated with the liquid-state electrolyte above its melting temperature, and a simple cooling process was then used to form a quasi-solid-state Li–Si cell. Additionally, through a precycling process, the formation of a stable and rigid solid–electrolyte interphase (SEI) was induced, and the intimate contacts between the QS-SCN and Si particles were preserved. The soft QS-SCN played an important role as a buffer in the large volume expansions while maintaining favorable interface contacts, and the formation of the SEI layers contributed to the reversible lithiation and delithiation in the Si particles. As a result, the quasi-solid-state Li–Si cell fabricated with QS-SCN exhibited significantly improved capacity retention compared with an all-solid-state cell

Reversible Mg-Metal Batteries Enabled by a Ga-Rich Protective Layer through One-Step Interface Engineering

Practical applications of Mg-metal batteries (MMBs) have been plagued by a critical bottleneckthe formation of a native oxide layer on the Mg-metal interfacewhich inevitably limits the use of conventional nontoxic electrolytes. The major aim of this work was to propose a simple and effective way to reversibly operate MMBs in combination with Mg(TFSI)2-diglyme electrolyte by forming a Ga-rich protective layer on the Mg metal (GPL@Mg). Mg metal was carefully reacted with a GaCl3 solution to trigger a galvanic replacement reaction between Ga3+ and Mg, resulting in the layering of a stable and ion-conducting Ga-rich protective film while preventing the formation of a native insulating layer. Various characterization tools were applied to analyze GPL@Mg, and it was demonstrated to contain inorganic-rich compounds (MgCO3, Mg(OH)2, MgCl2, Ga2O3, GaCl3, and MgO) roughly in a double-layered structure. The artificial GPL on Mg was effective in greatly reducing the high polarization for Mg plating and stripping in diglyme-based electrolyte, and the stable cycling was maintained for over 200 h. The one-step process suggested in this work offers insights into exploring a cost-effective approach to cover the Mg-metal surface with an ion-conducting artificial layer, which will help to practically advance MMBs

Magnesiophilic Graphitic Carbon Nanosubstrate for Highly Efficient and Fast-Rechargeable Mg Metal Batteries

The high volumetric energy density of rechargeable Mg batteries (RMBs) gives them a competitive advantage over current Li ion batteries, which originates from the high volumetric capacity (∼3833 mA h cm–3) of bivalent Mg metal anodes (MMAs). On the other hand, despite their importance, there are few reports on research strategies to improve the electrochemical performance of MMAs. This paper reports that catalytic carbon nanosubstrates rather than metal-based substrates, such as Mo, Cu, and stainless steel, are essential in MMAs to improve the electrochemical performance of RMBs. In particular, three-dimensional macroporous graphitic carbon nanosubstrates (GC-NSs) with high electrical conductivities can accommodate Mg metal with significantly higher rate capabilities and Coulombic efficiencies than metal substrates, resulting in a more stable and longer-term cycling performance over 1000 cycles. In addition, while metal-based substrates suffered from undesirable Mg peeling-off, homogeneous Mg metal deposition is well-guided in GC-NSs owing to the better affinity of the Mg2+ ion. These results are supported by density functional theory calculations and ex-situ characterization

<i>Operando</i> Visualization of Morphological Evolution in Mg Metal Anode: Insight into Dendrite Suppression for Stable Mg Metal Batteries

Rechargeable Mg-metal batteries (RMBs) are considered promising alternatives to conventional Li-ion batteries owing to their high volumetric capacity and low cost. In addition, Mg anodes for RMBs do not suffer from metal dendritic growth or internal short circuit. However, the notion that Mg anodes are indeed dendrite-free has recently been under debate, and further clarification is crucial for advancing practical RMBs. In this work, we closely investigated Mg dendrite behaviors under various electrochemical test conditions using operando observation techniques. The critical current density inducing fatal Mg dendritic growth was defined by directly monitoring the dendritic growth process leading to a short circuit. We further propose a new strategy to regulate the dendrite growth by introducing magnesiophilic sites of Au nanoseeds on a substrate. We not only elucidated the effect of the applied current density and capacity utilization on the Mg growth behaviors but also demonstrated the effect of magnesiophilic seeds in suppressing Mg dendrite growth

<i>Operando</i> Visualization of Morphological Evolution in Mg Metal Anode: Insight into Dendrite Suppression for Stable Mg Metal Batteries

Rechargeable Mg-metal batteries (RMBs) are considered promising alternatives to conventional Li-ion batteries owing to their high volumetric capacity and low cost. In addition, Mg anodes for RMBs do not suffer from metal dendritic growth or internal short circuit. However, the notion that Mg anodes are indeed dendrite-free has recently been under debate, and further clarification is crucial for advancing practical RMBs. In this work, we closely investigated Mg dendrite behaviors under various electrochemical test conditions using operando observation techniques. The critical current density inducing fatal Mg dendritic growth was defined by directly monitoring the dendritic growth process leading to a short circuit. We further propose a new strategy to regulate the dendrite growth by introducing magnesiophilic sites of Au nanoseeds on a substrate. We not only elucidated the effect of the applied current density and capacity utilization on the Mg growth behaviors but also demonstrated the effect of magnesiophilic seeds in suppressing Mg dendrite growth

<i>Operando</i> Visualization of Morphological Evolution in Mg Metal Anode: Insight into Dendrite Suppression for Stable Mg Metal Batteries

Rechargeable Mg-metal batteries (RMBs) are considered promising alternatives to conventional Li-ion batteries owing to their high volumetric capacity and low cost. In addition, Mg anodes for RMBs do not suffer from metal dendritic growth or internal short circuit. However, the notion that Mg anodes are indeed dendrite-free has recently been under debate, and further clarification is crucial for advancing practical RMBs. In this work, we closely investigated Mg dendrite behaviors under various electrochemical test conditions using operando observation techniques. The critical current density inducing fatal Mg dendritic growth was defined by directly monitoring the dendritic growth process leading to a short circuit. We further propose a new strategy to regulate the dendrite growth by introducing magnesiophilic sites of Au nanoseeds on a substrate. We not only elucidated the effect of the applied current density and capacity utilization on the Mg growth behaviors but also demonstrated the effect of magnesiophilic seeds in suppressing Mg dendrite growth