Lithium-metal batteries (LMBs) are regarded as the most promising candidate for practical applications in portable electronic devices and electric vehicles because of their high capacity and energy density. However, the uncontrollable growth of lithium dendrite reduces its cycling ability and even causes a severe safety concern, which impedes the development of the technology. Although great efforts have been devoted to solving the lithium dendrite issue in recent years, the contradiction between the high cost of thin Li foil and the severe safety hazard of excess Li still exists. This is precisely the factor that inspired the development of anode-free lithium-metal batteries (AFLMBs). Compared to lithium-metal batteries, AFLMBs with a zero-excess Li anode possess an incredible, conceivable, and specific energy. Additionally, because the use of metal lithium is limited, the battery manufacturing will be safer and simpler, leading to a significant decrease in cost. However, comprehensive reviews on anode-free batteries are rare. Therefore, in this review, we aim to explain the essential development factors influencing the cycle life, energy density, cost, and working mechanism of anode-free batteries. We summarize different strategies to improve the cycling stability of AFLMBs, and we discuss the application of anode-free electrodes in other electrochemical energy storage systems. Moreover, it is believed that the combination of modification techniques, including electrolytes and current collectors, and the application protocols will be the most important solution for future anode-free batteries.

By using pyrazine derivatives, three different types of copper(I) iodide based inorganic–organic hybrid structures, 1D-CuI(2-mo-pz) (1, 2-mo-pz = 2-methoxy-pyrazine), 2D-CuI(2,3-dm-pz)_0.5 (2, 2,3-dm-pz = 2,3-dimethyl-pyrazine), and 2D-Cu₂I₂(2,5-dm-pz)₂ (3, 2,5-dm-pz = 2,5-dimethyl-pyrazine), have been obtained by using a slow-diffusion method. Single crystal and powder X-ray diffraction analyses reveal that these hybrid structures are a one-dimensional (1D) staircase chain based structure, two-dimensional (2D) staircase-chain based structure, and 2D rhomboid dimer based structure, respectively. All of the three compounds show photoluminescence, with the internal quantum yield (IQY) as high as 88.2% for 1. This work provides evidence that for this type of hybrid materials, the structure of the inorganic module could be determined by the selection of the organic ligands and that the substituted group on the organic ligands can influence the luminescence efficiency of the hybrid structures.

To improve the safety and high performance of lithium-ion batteries (LIBs), a novel and heat-resistant fluorinated poly(aryl ether ketone) (FPAEK) compound was successfully synthesized and further fabricated as a nonwoven fibrous separator for LIBs via an electrospinning method. The morphology, thermal properties and electrochemical performances of the as-prepared electrospun FPAEK separators were characterized. The separator had no dimensional shrinkage at 150 °C for 1 h and no disintegration until reaching 500 °C. The electrospun FPAEK porous separators possessed much higher ionic conductivity (3.15 mS cm⁻¹) than that of a commercial polypropylene (PP) separator (0.66 mS cm⁻¹) due to their higher porosity and electrolyte uptake. The LIBs assembled with the electrospun fibrous separators exhibited higher discharge capacity (148.9 mA h g⁻¹) and longer cycle life (with 94.3% capacity retention after 250 cycles) than those assembled with the PP separator, with values of 139.5 mA h g⁻¹ and 88.9%, respectively. The measurements demonstrated that electrospun FPAEK separators may be promising candidates for high-performance LIBs.

A novel CNTs/α-Fe₂O₃/PPy composite with three-dimensional interconnected network structure is successfully synthesized through a solvothermal method and in-situ polymerization. The as-synthesized CNTs/α-Fe₂O₃/PPy composite is characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results indicate that spherical α-Fe₂O₃ particles are densely anchored onto the three-dimensional CNTs conducting network, and the outer PPy layer deposits uniformly on the surface of α-Fe₂O₃ particles. As an anode material for lithium-ion battery, the CNTs/α-Fe₂O₃/PPy composite exhibits a high initial coulombic efficiency of 75.6%, a high specific capacity of 1095.4 mAh·g^–1 at a current rate of 100 mA·g^–1 after 50 cycles, as well as a good rate capability at elevated current rates. Compared with pure α-Fe₂O₃, the improved Li storage property could be ascribed to the synergistic effects of α-Fe₂O₃, CNTs and PPy layer. This unique structure not only possesses excellent conductivity under the joint effect of inner randomly distributed CNTs and outer coated PPy layer, which effectively shortens the transfer paths of lithium ions and reduces the contact resistance, but also the outer PPy protective layer prevents agglomeration of α-Fe₂O₃ upon cont inuous charging/discharging, which withstands huge stresses caused by α-Fe₂O₃ expansion/extraction. T he CNTs/α-Fe₂O₃/PPy composite has the potential for use as high-performance anode electrode for Li-ion batteries.