Tailoring a Hybrid Functional Layer for Mg Metal Anodes in Conventional Electrolytes with a Low Overpotential.

The development of high-voltage Mg metal batteries is hampered by the incompatibility between a Mg metal anode and conventional electrolyte, leading to a high overpotential for Mg plating/stripping processes. In this work, we tailored a hybrid functional layer consisting of Bi/MgCl2/polytetrahydrofuran (PTHF) by an in situ THF polyreaction during the reaction of the Mg anode with BiCl3 solution. The introduction of PTHF inhibits the growth of Bi particles and fills the layer interstice with MgCl2-containing PTHF, improving the structural integrity of the functional layer and insulation between the electrolyte and Mg anode. As a result, compared to a simply modified Bi/MgCl2 layer, the Bi/MgCl2/PTHF functional layer exhibits a lower polarization voltage of 0.25 V and longer cycling life of more than 2000 h at 0.1 mA cm-2. Mechanism analysis shows that Mg is plated on the surface of Bi particles within the layer. The Mo6S8/Mg full battery with the hybrid functional layer achieved a low voltage hysteresis of ∼0.25 V and long cycling life over 500 cycles at 50 mA g-1. This work provides a facile and effective hybrid functional layer strategy to realize Mg metal batteries in conventional electrolytes.

Modification of a Cu Mesh with Nanowires and Magnesiophilic Ag Sites to Induce Uniform Magnesium Deposition.

The nature of dendrite-free magnesium (Mg) metal anodes is an important advantage in rechargeable magnesium batteries (RMBs). However, this traditional cognition needs to be reconsidered due to inhomogeneous Mg deposits under extreme electrochemical conditions. Herein, we report a three-dimensional (3D) Cu-based host with magnesiophilic Ag sites (denoted as "Ag@3D Cu mesh") to regulate Mg deposition behaviors and achieve uniform Mg electrodeposition. Mg deposition/stripping behaviors are obviously improved under the cooperative effect of nanowire structures and Ag sites. The test results indicate that nucleation overpotentials are reduced distinctly and cycling performances are prolonged, suggesting that the general rules of 3D structures and affinity sites improve the durability and reversibility of Mg deposition/stripping. Besides, a unique concave surface structure can induce Mg to deposit into the interior of the interspace, which utilizes Mg more efficiently and leads to improved electrochemical performances with limited Mg content. Furthermore, in situ optical microscopic images show that the Ag@3D Cu mesh can attain a smooth surface, nearly without Mg protrusions, under 8.0 mA cm-2, which prevents premature short circuits. This report is a pioneering work to demonstrate the feasibility of modification of Cu-based current collectors and the necessity of functional current collectors to improve the possibility of practical applications for RMBs.

Achieving a Stable Solid Electrolyte Interphase and Enhanced Thermal Stability by a Dual-Functional Electrolyte Additive toward a High-Loading LiNi0.8Mn0.1Co0.1O2 /Lithium Pouch Battery.

Li metal batteries with high-capacity cathodes emerge as promising candidates for next-generation battery technologies. However, the poor reversibility of the Li deposition/stripping process severely reduces its lifespan, and safety also remains a major issue for the Li metal anodes. Herein, we propose (ethoxy)-penta-fluoro-cyclo-triphosphazene (DFA) as a dual-functional electrolyte additive to solve the engineering problem of balancing the cycle life and thermal stability of Li metal batteries. The NCM811/lithium metal pouch batteries (2900 mA h) are assembled using the commercial high areal capacity cathode (3.5 mA h cm-2). Compared with the NCM811/Li batteries without DFA, the heat generation and heat generation power of lithium metal batteries with DFA are significantly reduced by half during charging. Moreover, the NCM811/Li pouch batteries with DFA show excellent stability in both hot-oven and adiabatic rate calorimeter experiments. Furthermore, a nonlinear phase field simulation is carried out for mechanism investigation, which confirms that the stable solid electrolyte interphase formed by DFA will improve the cycle life of the NCM811/Li pouch. The DFA is verified to be an effective additive to improve the cycle stability and safety simultaneously, providing new opportunities for developing high energy density Li metal batteries.

Ten Thousand-Cycle Ultrafast Energy Storage of Wadsley-Roth Phase Fe-Nb Oxides with a Desolvation Promoting Interfacial Layer.

Developing advanced electrode materials with enhanced charge-transfer kinetics is the key to realizing fast energy storage technologies. Commonly used modification strategies, such as nanoengineering and carbon coating, are mainly focused on electron transfer and bulk Li+ diffusion. Nonetheless, the desolvation behavior, which is considered as the rate-limiting process for charge-storage, is rarely studied. Herein, we designed a nitridation layer on the surface of Wadsley-Roth phase FeNb11O29 (FNO-x@N) to act as a desolvation promoter. Theoretical calculations demonstrate that the adsorption and desolvation of solvated Li+ is efficiently improved at FNO-x@N/electrolyte interphase, leading to the reduced desolvation energy barrier. Moreover, the nitridation layer can also help to prevent solvent cointercalation during Li+ insertion, leading to advantageous shrinkage of block area and reduced volume change of lattice cell during cycling. Consequently, FNO-x@N exhibits a high-rate capacity of 129.7 mAh g-1 with negligible capacity decay for 10 000 cycles.

Ultralong-Lifespan Magnesium Batteries Enabled by the Synergetic Manipulation of Oxygen Vacancies and Electronic Conduction.

As a potential next-generation energy storage system, rechargeable magnesium batteries (RMBs) have been receiving increasing attention due to their excellent safety performance and high energy density. However, the sluggish kinetics of Mg2+ in the cathode has become one of the main bottlenecks restricting the development of RMBs. Here, we introduce oxygen vacancies to spherical NaV6O15 cross-linked with carbon nanotubes (CNTs) (denoted as SNVOX-CNT) as a cathode material to achieve an impressive long-term cycle life of RMBs. The introduction of oxygen vacancies can improve the electrochemical performance of the NaV6O15-X cathode material. Besides, owing to the introduction of CNTs, excellent internal/external electronic conduction paths can be built inside the whole electrode, which further achieves excellent electrochemical performance. Moreover, such a unique structure can efficiently improve the diffusion kinetics of Mg2+ (ranging from 1.28 × 10-12 to 7.21 × 10-12 cm2·s-1). Simulation calculations further prove that oxygen vacancies can cause Mg2+ to be inserted in NaV6O15-X. Our work proposes a strategy for the synergistic effect of oxygen vacancies and CNTs to improve the diffusion coefficient of Mg2+ in NaV6O15 and enhance the electrochemical performance of RMBs.

Rod-shaped Cu1.81Te as a novel cathode material for aluminum-ion batteries.

Aluminum-ion batteries (AIBs) are supposed to be one of the energy storage systems with great potentialities on account of their high safety, low cost and high theoretical volumetric capacity. Herein, we report a novel rod-shaped Cu1.81Te cathode material for AIBs. At 40 mA g-1, the initial discharge capacity can reach 144 mA h g-1. The diffusion coefficient of Al3+ calculated by the galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV) tests at different scan rates is larger than that in sulfides, indicating that telluride has faster kinetics. The results of ex situ X-ray photoelectron spectroscopy (XPS), ex situ X-ray diffraction (XRD) and 27Al nuclear magnetic resonance (NMR) prove that the mechanism of the charging and discharging processes is the reversible intercalation and deintercalation of Al3+, which is very important for the subsequent researchers to understand and investigate the mechanism of the Al/Cu1.81Te battery. This work also proves that telluride can also be used as a cathode material for aluminum storage.