| The ever-growing renewable energy storage calls for advanced anodes to substitute for commercial graphite anodes.Among the numerous anode materials,Si has been regarded as the next-generation anode material due to its highest known theoretical capacity and relatively low potential plateau,but its disadvantages of large irreversible loss,serious volume effect and poor conductivity have also been criticized.In this paper,the electrochemical deposition synthesis technology is mainly used to prepare composite silicon film electrode materials on three kinds of substrate materials:commercial copper foil,nickel foam,and commercial graphite/copper foil.The main contents and conclusions of this paper are as follows:?1?First,copper foil is used as the substrate material by LSV,and the deposited voltage was-1.85 V.After investigating the effect of deposited time and silicon source concentration on the electrodeposited silicon/copper foil composite electrode,the results showed that when the deposition time was 1 h and the silicon source concentration was 0.5M,the electrochemical performance of the composite electrode was the best.The obtained electrode has excellent flexibility and mechanical properties.XRD and Raman results showed that the deposited silicon film was amorphous.SEM observation showed that the thickness of the deposited silicon film was about 500 nm.The Si pieces were tightly connected to each other and the sizes were uniform.The constant current charge and discharge test showd that at a current density of 100 m A·g-1,the first discharge/charge capacity is 4393/1460 m Ah·g-1,and the discharge specific capacity of 1036 m Ah·g-1 was obtained after 100 cycles,and the capacity decay rate was 0.36%/time.Amorphous silicon anodes can effectively relieve volume expansion after lithiated alloys and improve cycle performance.?2?A three-electrode system with high-purity platinum sheets as assistant electrode and reference electrode,nickel foam as the working electrode was used to electrodeposit a silicon film.The deposition time was 1 hours.The LSV test determined that the deposition voltage was-1.48 V.The SEM found that the surface of the amorphous silicon film was composed with the small Si particles,the particle size was uniform,and the silicon film was flat.XRD and Raman results showed that the deposited silicon film was amorphous.Electrochemical tests showed a specific discharge capacity of about 1004 m Ah·g-1 after100 cycles can be achieved,and its cyclic stability was effectively improved compared with ordinary commercial silicon.The three-dimensional foamed nickel can buffer the volume change of Si during the Si alloying/dealloying process,which can improving the electrochemical performance of silicon materials.?3?A commercial graphite/copper foil two-dimensional carbon substrate was used as substrate to deposite Si,and the deposition voltage was-1.65 V according to LSV result.SEM observation of the silicon/graphite/copper foil composite electrode shows that the silicon can completely be coated to the surface and gaps of graphite.XRD and Raman results showed that the deposited silicon film was amorphous.The constant current charge/discharge result shows that the specific discharge capacity of the second cycle is1262 m Ah·g-1,and it is still 517 m Ah·g-1 after 80 cycles.The average capacity decay rate of 79 cycles is 0.74%/time.It can be found that the specific capacity decays fastly in the first 25 cycles and the capacity decay rate reaches 1.8%/time,and the capacity decay rate after 55 cycles is 0.43%/time.The structure and performance of the electrode material have not yet stabilized during the initial several charge and discharge cycles due to the activation reaction caused during the lithiation process.The stable discharge performance can be achieved after 25 cycles,and its cyclic stability was effectively improved compared with ordinary commercial silicon.The introduction of graphite effectively improved the conductivity of the composite material,and enhanced the rate performance and impedance performance. |
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