Bimetallic selenides are considered to be the promising high-capacity anode materials for potassium ion batteries (PIBs). However, the dramatic volume fluctuation of K+ ions and pulverization during cycling still limit their practical application in PIBs. Herein, the nitrogen, phosphorus, and sulfur tri-doped carbon (SPNC)-coated bimetallic NiCo2Se4 needle arrays grown on carbon cloth (NiCo2Se4⊂SPNC/CC) prepared as a binder-free anode for PIBs. The polyphosphazene (PSZ) was used as ingenious heteroatoms doping carbon source. The coated SPNC layer derived from the PSZ on the surfaces of NiCo2Se4 needle arrays not only effectively alleviate the volume expansion of NiCo2Se4 but also provide abundant active sites for the storage of K+ ions. As the PIB anode, the NiCo2Se4⊂SPNC/CC could deliver a high reversible capacity of 880.9 mA h g−1 at a current density of 0.1 A g−1. After 500 cycles, the NiCo2Se4⊂SPNC/CC anode still maintains a high reversible capacity of 268.1 mA h·g−1 at a current density of 0.5 A g−1.

Solid polymer electrolytes (SPEs) with high ionic conductivity and strong mechanical properties are preconditions for the stable cycling of high-performance Li metal batteries. However, single-polymer SPEs often have low ionic conductivity, which greatly limits their further application. Herein, a SPE composed of polyvinyl alcohol (PVA), reactive aramid nanofibers (RANFs), and lithium bistrifluoromethanesulfonimide (LiTFSI) is prepared using a simple solution-casting method. After introducing the RANFs, the SPE of RANFs/PVA-containing LiTFSI not only exhibits high mechanical properties but also has good thermal stability. The RANFs/PVA SPE constructed from the strong hydrogen bond interaction between rigid RANFs and flexible PVA shows high migration efficiency of lithium ions. When the loading amount of RANFs is 2 wt %, the ionic conductivity of RANFs/PVA reaches ∼7.7 × 10 –4 S·cm–1, and the lithium-ion migration number is ∼0.54 at 60 °C. Toward the Li|RANFs/PVA-2 wt %|LiFePO4 full cell, the discharge specific capacity could reach 162.5 mA h·g–1 at 60 °C and 0.1 C. Meanwhile, the Li|RANFs/PVA-2 wt %|LiFePO4 battery also shows outstanding long-term cycling performance and could maintain 81% of the initial capacity after 1200 cycles at 1 C. The solid-state Li|RANFs/PVA|LiFePO4 cell also exhibits excellent resilience in destructive tests such as cell bending, piercing, and cutting.

Aqueous zinc-ion batteries (AZIBs) use zinc metal as anodes are expected to be used for large-scale energy storage due to their good safety, low cost, environmental friendliness, etc. However, the zinc dendrite growth and associated side reactions seriously cause low Coulomb efficiency and reduce the cycle life of AZIBs, finally hampering further practical application. Herein, the γ-poly(glutamic acid) (γ-PGA)/aramid nanofibers (ANFs)/ MXene (PAM) protection layer was designed toward a dendrite-free Zn metal anode. The PAM layer with a three-dimensional (3D) network formed by strong hydrogen bonding interactions effectively inhibits the growth of zinc dendrites, corrosion of the electrolyte, and hydrogen precipitation due to the reduced nucleation overpotential, which facilitates uniform galvanization/de-zincification. At a current density of 0.1 mA•cm −2 and 0.1 mAh•cm −2 , the cycle life of PAM@Zn//PAM@Zn symmetric cell could extend to 3500 h. Meanwhile, the PAM@Zn//V 2 O 5 full cell could also exhibit a capacity retention of 82.49% after 1500 cycles at 1 C. This strategy of designing a polymer-based composite protection layer by integrating the advantages of different materials opens up more possibilities for the development of a dendrite-free Zn anode.