The practical application of Na metal anode is plagued by the dendrite growth, unstable solid electrolyte interphase (SEI) formation and volume change during the cycling process. Herein, poly(tetrafluoroethylene) (noted as PTFE) coating microcrystalline graphite is designed as the sodium metal anode host by a facile and cost-effective strategy. The isotropous microcrystalline graphite (MG) is conducive to guiding Na⁺ to form a co-intercalation structure into MG. And the PTFE coating layer can form NaF as artificial SEI film for uniform ion transport and deposition. As a result, the gained PTFE coating MG electrode can deliver a long-life span over 1,200 cycles with an average Coulombic efficiency (CE) of 99.88%. To note, almost the CE in each cycle is around 99.8%–100%. When assembled with Na₃V₂(PO₄)₂F₃ cathode as full cells, the full cell paired with PTFE coating MG electrode can operate much stable than that of MG electrode for the existence of PTFE coating layer. Even utilized as sodium-free Na metal anode paired with Na₃V₂(PO₄)₂F₃ cathode, it can also deliver a high initial CE of 76.27% at 0.5 C. After 100 cycles, it still has a high discharge capacity of 83.5 mAh·g⁻¹.

The K metal batteries are emerged as promising alternatives beyond commercialized Li-ion batteries. However, suppressing uncontrolled dendrite is crucial to the accomplishment of K metal batteries. Herein, an oxygen-rich treated carbon cloth (TCC) has been designed as the K plating host to guide K homogeneous nucleation and suppress the dendrite growth. Both density function theory calculations and experimental results demonstrate that abundant oxygen functional groups as K-philic sites on TCC can guide K nucleation and deposition homogeneously. As a result, the TCC electrode exhibits an ultra-long-life over 800 cycles at high current density of 3.0 mA·cm^-2 for 3.0 mA·h·cm^-2. Furthermore, the symmetrical cells can run stably for 2,000 h with low over-potential less than 20 mV at 1.0 mA·cm^-2 for 1.0 mA·h·cm^-2. Even at a higher current of 5.0 mA·cm^-2, the TCC electrode can still stably cycle for 1,400 h.

Bismuth (Bi)-based electrode has aroused tremendous interest in potassium-ion batteries (PIBs) on account of its low cost, high electronic conductivity, low charge voltage and high theoretical capacity. However, the rapid capacity fading and poor lifespan induced by the normalized volume expansion (up to ~ 406%) and serious aggregation of Bi during cycling process hinder its application. Herein, bismuth molybdate (Bi₂MoO₆) microsphere assembled by 2D nanoplate units is successfully prepared by a facile solvothermal method and demonstrated as a promising anode for PIBs. The unique microsphere structure and the self-generated potassium molybdate (K-Mo-O species) during the electrochemical reactions can effectively suppress mechanical fracture of Bi-based anode originated from the volume variation during charge/discharge of the battery. As a result, the Bi₂MoO₆ microsphere without hybridizing with any other conductive carbon matrix shows superior electrochemical performance, which delivers a high reversible capacity of 121.7 mAh·g^-1 at 100 mA·g^-1 over 600 cycles. In addition, the assembled perylenetetracarboxylic dianhydride (PTCDA)//Bi₂MoO₆ full-cell coupled with PTCDA cathode demonstrates the potential application of Bi₂MoO₆ microsphere. Most importantly, the phase evolution of Bi₂MoO₆ microsphere during potassiation/depotassiation process is successfully deciphered by ex situ X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM) technologies, which reveals a combination mechanism of conversion reaction and alloying/dealloying reaction for Bi₂MoO₆ anode. Our findings not only open a new way to enhance the performance of Bi-based anode in PIBs, but also provide useful implications to other alloy-type anodes for secondary alkali-metal ion batteries.