Hierarchically porous Fe3O4/C microspheres, with complex microstructures and excellent electrochemical performances as anode materials in LIBs, have been successfully prepared thanks to the self-aggregation of CO2 nano-bubbles confined by PVP and Fe(OH)3 nanoparticles decorated by citrate groups via the molecular chain entanglements during the condensation and carbonization of glucose.

ZnCo 2 O 4 /C microhydrangeas with controllable microstructure are successfully synthesized through a simple citrate-guided solvothermal method and following thermal decomposition. The experimental results reveal that the citratedirected self-regulation of Zn-Co-EG agglomerates play a critical role in the formation of the hydrangea-like precursors. When applied as anode material in lithium ion batteries (LIBs), ZnCo 2 O 4 /C microhydrangeas exhibited high available capacities of 964.6 mAh g −1 at 1 A g −1 after 200 cycles and 704.4 mAh g −1 at 4 A g −1 over 1000 cycles. The excellent reliability is attributed to the superior microstructure that provides many benefits including enhanced electron or ion transport and improved structure stability, etc. KEYWORDScitrate-assisted solvothermal process, composite pattern, cyclic reliability, high rate performance, lithium ion batteries, ZnCo 2 O 4 /C microhydrangeas

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Porous Fe3O4/C composite nanofoils, characterized by a thickness of ∼20 nm and with ∼8 nm open pores and ∼5 nm Fe3O4 nanoparticles embedded in the carbon matrix, were prepared for the first time using Na-citrate to mediate the growth of hexagonal Fe-ethylene glycolate nanosheets and subsequently annealing them at 350 °C in N2. It has been found that the Fe-ethylene glycolate nanosheets can be effectively slimmed by increasing the concentration of Na-citrate, and the microstructures of Fe3O4/C nanocomposites may be tailored by the annealing temperature. When tested as the anode materials in LIBs, the Fe3O4/C nanofoils obtained after annealing at 350 °C were found to exhibit superior electrochemical performance due to its optimal microstructure, featured by a reversible capacity of 1314.4 mAh g(-1) at 0.4 A g(-1) over 100 cycles, 1034.2 mAh g(-1) at 1 A g(-1), and 686.4 mAh g(-1) at 5 A g(-1) after 500 cycles, whereas the annealing treatments at 450 and 550 °C render the Fe3O4/C nanocomposites with the inferior electrochemical performances as a result of shrinking porous microstructures and coarsening of Fe3O4 nanoparticles in the carbon matrix. With a particle-size control model proposed herein, the cycle discharging behaviors of the Fe3O4/C nanocomposites with different microstructures are well explained from the perspective of the local confinement of Fe3O4 nanoparticles inside the carbon matrix and their evolution in size and composite microstructure during the charge/discharge cycling.

A new-type binder-free Sn/C composite membrane with densely stacked Sn-in-carbon nanosheets was prepared by vacuum-induced self-assembly of graphene-like Sn alkoxide and following in situ thermal conversion. The successful implementation of this rational strategy is based on the controllable synthesis of graphene-like Sn alkoxide by using Na−citrate with the critical inhibitory effect on polycondensation of Sn alkoxide along the a and b directions. Density functional theory calculations reveal that graphene-like Sn alkoxide can be formed under the joint action of oriented densification along the c axis and continuous growth along the a and b directions. The Sn/C composite membrane constructed by graphene-like Sn-in-carbon nanosheets can effectively buffer volume fluctuation of inlaid Sn during cycling and much enhance the kinetics of Li + diffusion and charge transfer with the developed ion/electron transmission paths. After temperature-controlled structure optimization, Sn/C composite membrane displays extraordinary Li storage behaviors, including reversible half-cell capacities up to 972.5 mAh g −1 at a density of 1 A g −1 for 200 cycles, 885.5/729.3 mAh g −1 over 1000 cycles at large current densities of 2/4 A g −1 , and terrific practicability with reliable fullcell capacities of 789.9/582.9 mAh g −1 up to 200 cycles under 1/4 A g −1 . It is worthy of noting that this strategy may open up new opportunities to fabricate advanced membrane materials and construct hyperstable self-supporting anodes in lithium ion batteries.