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Al2O3and SiO2greatly influence the formation of complex calcium ferrite, which is the main bonding phase in high basicity sinters. The effects of Al2O3/SiO2ratios on the morphology of complex calcium ferrite were studied. The main mineral phases in the samples with different Al2O3/SiO2ratios were CaFe2O4with a solid solution of Si or Al atoms and the silico-ferrite of calcium and aluminum. The results showed that the morphology of the complex calcium ferrite changed from lumpy to plate-like and acicular with increases in the SiO2content and the Al2O3/SiO2ratio. When the content of SiO2was 4 wt.%, the main calcium ferrite morphology was acicular, and the number of macropores in the samples increased with the Al2O3/SiO2ratio increasing. The first-principles analysis of the calcium ferrite crystal structure showed that adding SiO2and Al2O3changed the growth mechanism of the CaFe2O4crystal, promoting the formation of platy and acicular complex calcium ferrite. The size of calcium ferrite was significantly smaller due to the increase in CaO–Fe2O3–SiO2–Al2O3viscosity with increasing the Al2O3/SiO2ratio.

The poor interfacial compatibility between solid electrolyte and lithium metal anode is one of the main obstacles to the development of solid lithium metal battery. Herein, the poly (1,3-dioxolane) (PDOL) polymer is combined with g-C3N4powders to form a flexible and dense composite solid electrolyte film, which not only possesses high ionic conductivity of 3.7 × 10−4S·cm−1, high ion migration number up to 0.86, and wide electrochemical stability window of 5.0 V, but also is helpful for inhibiting the growth of lithium dendrites to improve the interfacial stability of the lithium anode and close contact with cathode. The prepared S/g-C3N4-PDOL/Li battery exhibits good rate and cycle performances with a capacity of 550 mAh g−1at 1 C, and 1150 mAh g−1at 0.1 C with a capacity retention rate of 83% after 100 cycles. The dense Li3N layer generated by the reaction between g-C3N4and Li gives g-C3N4/PDOL composite electrolyte a high inhibition ability of lithium dendrites. This composite solid electrolyte film with an interface modification function has good practical application prospects in lithium-sulfur batteries.