Due to the limited distribution of lithium resources, the high cost disadvantage of lithium-ion battery gradually affects its large-scale application. In contrast, sodium resources are abundant in the world, as a substitute for lithium gradually gained widespread attention. However, due to the large radius of sodium ions, the material will undergo a large volume change during electrode insertion/removal, resulting in structural collapse. Therefore, in order to realize the high performance application of sodium electricity, it is necessary to develop cathode materials with long cycle life and good magnification performance. A novel polyanionic compound, niobium phosphate oxide Nb(PO₄)O, was synthesized by one-step calcination with phytate-melamine supramolecular polymer assisted strategy. First of all, the material has a stable large frame structure to ensure the rapid transmission of sodium ions. Secondly, the loose sheet structure of the surface is conducive to the mass transfer between the electrolyte and the electrode, effectively shortening the diffusion path. When used as a sodium anode, the group of sodium ion batteries, in 1 000 mA·g^-1 current density, 3000 cycles after reversible discharge capacity can reach 133.7 mA·h·g^-1, in 4 000 mA·g^-1 high current density, reversible specific capacity is still 117.9 mA·h·g^-1. Compared with Nb₂O₅, it has obvious magnification performance and long cycle stability.

The performance of lithium-sulfur battery is restricted by the lower value of electrode conductance and the sluggish LiPSs degradation kinetics. Unfortunately, the degradation rate of polysulfides was mostly attributed to the catalytic energy barrier in previous, which is unable to give accurate predictions on the performance of lithium-sulfur battery. Thereby, a quantitative framework relating the battery performance to catalytic energy barrier and electrical conductivity of the cathode host is developed here to quantitate the tendency. As the model compound, calculated-Ti₄O₇ (c-Ti₄O₇) has the highest comprehensive index with excellent electrical conductivity, although the catalytic energy barrier is not ideal. Through inputting the experimental properties such as impedance and charge/discharge data into the as-build model, the final conclusion is still in line with our prediction that Ti₄O₇ host shows the most excellent electrochemical performance. Therefore, the accurate model here would be attainable to design lithium-sulfur cathode materials with a bottom–up manner.

As a novel class of porous crystalline solids, covalent organic frameworks (COFs) based electrolyte can combine the advantages of both inorganic and polymer electrolytes, leading to such as higher structural stability to inhibit lithium dendrites and better processing facility for improving interfacial contact. However, the ionic components of Li salt tend to be closely associated in the form of ion pairs or even ionic aggregates in the channel of COFs due to strong coulombic interactions, thus resulting in slow ionic diffusion dynamics and low ionic conductivity. Herein, we successfully designed and synthesized a novel single-ion conducting nitrogen hybrid conjugated skeleton (NCS) as all solid electrolyte, whose backbone is consisted with triazine and piperazine rings. A loose bonding between the triazine rings and cations would lower the energy barrier during ions transfer, and electrostatic forces with piperazine rings could “anchor” anions to increase the selectivity during ions transfer. Thus, the NCS-electrolyte exhibits excellent room temperature lithium-ion conductivity up to 1.49 mS·cm⁻¹ and high transference number of 0.84 without employing any solvent, which to the best of our knowledge is one of the highest COF-based electrolytes so far. Moreover, the fabricated all-solid-state lithium metal batteries demonstrate highly attractive properties with quite stable cycling performance over 100 cycles with 82% capacity reservation at 0.5 C.