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Organic cathode materials for lithium-ion batteries are becoming increasingly popular because of their structural flexibility, resource abundance, and environmental friendliness. However, their application is limited by their solubility in electrolytes, which leads to the rapid decay of cycling performance. Herein, we synthesize crosslinked polyimides by condensation polymerization between 3,4,9,10-perylenetetracarboxylic dianhydride and 1,2-ethanediamine in the presence of a trifunctional crosslinker of diethylenetriamine. The synthesized crosslinked polyimides present a porous structure with a high surface area. The crosslinked polyimide cathode materials used in lithium metal half-cells have a high discharge capacity of 160.3 mA h g–1 at a current density of 30 mA g–1, and the assembled lithium-ion batteries maintain 77% capacity after 2000 cycles at a current density of 150 mA g–1, which is much better than that of lithium-ion batteries employing linear polyimides, demonstrating that crosslinked polyimides may be potential cathode materials for high-performance lithium-ion batteries.

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The xLi[Li[Formula: see text]Mn[Formula: see text]]O[Formula: see text](1−x)Li[Ni[Formula: see text]Mn[Formula: see text]Co[Formula: see text]]O2 was prepared by coprecipitation method in this paper. Co(NO3)2, NiCO[Formula: see text]Ni(OH)[Formula: see text]H2O, LiOH⋅H2O and MnSO[Formula: see text]H2O were used as the sources of cobalt, nickel, lithium and manganese. In the process of calcining and sintering, the temperature and time of the material were studied. The optimum conditions for the coprecipitation method synthesis were determined: precursor was pre-sintered at 500[Formula: see text]C for 5 h, then the precursor was successively sintered at 850[Formula: see text]C for 9 h to get the final product. The results of XRD and SEM showed that the composite particles and crystal structure of the particles exhibited basic integrity and high degree of crystallinity with [Formula: see text]-NaFeO2-type structure. The first charging and discharging capacities were 183.14 mA[Formula: see text]⋅[Formula: see text]h[Formula: see text]⋅[Formula: see text]g[Formula: see text] and 171.11 mA[Formula: see text]⋅[Formula: see text]h[Formula: see text]⋅[Formula: see text]g[Formula: see text] at 0.1 C with a discharge efficiency of 93%. The capacity retention rate was 95% over 20 cycles. It had a good electrochemical cycling performance.

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