Search

Rechargeable magnesium batteries (RMBs) have the potentials in terms of high energy density, resource abundancy and safety beyond current lithium‐ion batteries. However, the bare Mg metal electrode is prone to be passivated by solvents, suffering from the extremely high overpotential and short life during cycling. Herein, a facile chloride‐free solution pretreatment method for Mg anode is developed to construct the fluoride‐rich artificial interphase. Driven by the strong‐Lewis‐acidity trifluoromethanesulfonate anion, the interphase consisting of magnesiophilic and fluoride‐rich components are constructed by the substitution reaction of Mg metal with antimony trifluoride. The formed porous Sb‐based skeletons can uniform the electric‐field distribution and Mg ions flux at anode side, inducing the self‐adapting dendrite‐free Mg deposition even under large current density. The generated alloyable metal fluoride enables to lower the desolvation energy barrier for Mg ions and sustainedly release metallic antimony to compensate for the potentially invalid magnesiophilic sites during cycling. Therefore the symmetric cells with modified Mg anodes achieve the excellent cycling over 2000 h at 1 mA cm−2 and under a high areal capacity of 5 mAh cm−2. The full cells with CuS cathodes exhibit a superior high voltage stability (2.6 V vs Mg/Mg2+) and high coulombic efficiency close to 100%. [ABSTRACT FROM AUTHOR]

Conversion‐reaction metal fluoride cathodes have the advantages of low cost, environmental friendliness, and high energy density. However, their tailored synthesis and structure design under safe, facile, and scalable conditions have always been a puzzle, which limits the popularization of conversion‐type cathodes in lithium metal batteries. To address these challenges, here an iron fluoride heterostructure with FeF2 and FeF3 binary phases is proposed and prepared by deep eutectic solvent method under the assistance of cobalt cation as an oxidization promoter. The compact heterogeneous contact between tetragonal FeF2 and hexagonal tungsten bronze FeF3 phases enables the promotion and stabilization of interface charge transfer and topotactic conversion reaction. The narrower band gap of FeF2, higher theoretical capacity and thermodynamic potential of FeF3 synergistically contribute to the balance between cycling reversibility and capacity. The heterostructure cathode with an optimized molar ratio of FeF2/FeF3 can realize a highly reversible capacity of ≈520 mAh g−1 in the first tens of cycles and 305 mAh g−1 after 200 cycles. The typical two‐stage reaction plateaus are well preserved even under the high current density of 1000 mA g−1. The green synthesis strategy and heterostructure fluoride design open a new horizon for the development of high‐energy‐density metal fluoride batteries. [ABSTRACT FROM AUTHOR]

Lithium metal is a potential candidate for anode material in next‐generation rechargeable batteries with high energy and power densities. However, the huge volume change caused by the uneven deposition of metallic Li leads to the cracking of the solid electrolyte interphase (SEI), which cannot prevent the reaction of inner fresh Li with electrolyte, resulting in severe dendrite growth and electrochemical degradation. Herein, a freestanding protein film derived from eggshell is reported as the protective layer on the electrode surface to form a robust artificial SEI layer. Benefiting from its 3D interconnected fiber framework along with good mechanical stiffness and softness, the Li‐ion flow is uniformly modulated, leading to the suppression of Li dendrite growth. The electrochemical performance of corresponding symmetric, asymmetric, and full cells is significantly enhanced. A high coulombic efficiency above 95% for nearly 700 cycles is achieved for the modified Cu/Li asymmetric cell at a current density of 3 mA cm−2 (with a capacity of 1 mAh cm−2). This study indicates a SEI reinforcement approach for the stabilization of the Li metal anode based on the freestanding structure derived from biomaterials. [ABSTRACT FROM AUTHOR]

The polyethylene oxide (PEO) based solid-state batteries are considered as promising candidates for the next-generation Li metal batteries with high energy density and safety. However, the low Li-ion conductivity and high-voltage endurability hinder the further applications of PEO-based electrolytes. To overcome these issues, herein two-dimensional (2D) CeF3 nanoplates with maximally exposed [001] crystal faces are introduced into the PEO matrix to expand the electrochemical window and improve Li-ion conduction and transport. The optimized crystal shape and crystal face anisotropy of CeF3 nanoplate filler reduce the crystallinity of composite solid polymer electrolyte (CSPE) via its Lewis acid-base interaction with ether oxygen of PEO. The Li-affinity [100] and Li-repellent [001] crystal faces of CeF3 nanoplates synergistically realize the dissociation of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), fast Li-adsorption/desorption, and Li+ migration. The optimized CSPE-0.1CeF3 membrane enables the achievement of Li metal batteries with high endurability and stability, from the kinetically favorable Li/Li symmetric cells with long-term cycling over 8000 h. The highly reversible Li/LiFePO4 cells exhibit a capacity retention of 109.2 mAh·g−1 after 1000 cycles at 1 C, corresponding to a low capacity fading rate of 0.026% per cycle. The conversion-type all-solid-state Li/CSPE-0.1CeF3/FeF3 cells show a high reversible capacity of 201.9 mAh·g−1 after long-term 600 cycles and of 231.1 mAh·g−1 at an ultra-high rate of 5 C. [ABSTRACT FROM AUTHOR]

[Display omitted] Pursuing all-solid-state lithium metal batteries with dual upgrading of safety and energy density is of great significance. However, searching compatible solid electrolyte and reversible conversion cathode is still a big challenge. The phase transformation at cathode and Li deformation at anode would usually deactivate the electrode–electrolyte interfaces. Herein, we propose an all-solid-state Li-FeF 3 conversion battery reinforced by hierarchical microsphere stacked polymer electrolyte for the first time. This g-C 3 N 4 stuffed polyethylene oxide (PEO)-based electrolyte is lightweight due to the absence of metal element doping, and it enables the spatial confinement and dissolution suppression of conversion products at soft cathode-polymer interface, as well as Li dendrite inhibition at filler-reinforced anode-polymer interface. Two-dimensional (2D)-nanosheet-built porous g-C 3 N 4 as three-dimensional (3D) textured filler can strongly cross-link with PEO matrix and LiTFSI (TFSI: bistrifluoromethanesulfonimide) anion, leading to a more conductive and salt-dissociated interface and therefore improved conductivity (2.5 × 10–4 S/cm at 60 °C) and Li+ transference number (0.69). The compact stacking of highly regular robust microspheres in polymer electrolyte enables a successful stabilization and smoothening of Li metal with ultra-long plating/striping cycling for at least 10,000 h. The corresponding Li/LiFePO 4 solid cells can endure an extremely high rate of 12 C. All-solid-state Li/FeF 3 cells show highly stabilized capacity as high as 300 mAh/g even after 200 cycles and of ~200 mAh/g at extremely high rate of 5 C, as well as ultra-long cycling for at least 1200 cycles at 1 C. High pseudocapacitance contribution (>55%) and diffusion coefficient (as high as 10–12 cm2/s) are responsible for this high-rate fluoride conversion. This result provides a promising solution to conversion-type Li metal batteries of high energy and safety beyond Li-S batteries, which are difficult to realize true "all-solid-state" due to the indispensable step of polysulfide solid–liquid conversion. [ABSTRACT FROM AUTHOR]