Owing to the high theoretical specific capacity,tin-based composites become one of the most potential anode materials for lithium/sodium ion battery.During the cycling process,the drastic volume change leads to plenty of problems,such as the structure collapse,the poor cycling ability and rate performance.Hence,it is the major defect that impedes Sn-based composites as commercial anode materials for lithium ion batteries.In this paper,EG@SnO2@PANI and EG@SnS@PANI composites are synthesized by building the complex dual conductive networks of polyaniline(PANI)and expanded graphite(EG),which are expected to control the morphology,improve the conductivity and structural stability of Sn-based composites.And the main works of this thesis are as follows:Three-dimensional(3D)EG@SnO2@PANI composite is synthesized via solvothermal method followed by in-situ oxidative polymerization.Compared with the bare SnO2 and EG@SnO2 samples,the EG@SnO2@PANI composite as anode material for lithium ion batteries not only delivers the highest initial columbic efficiency of 77.8%,an excellent initial charge capacity of 1021 m Ah g-1 at a current density of 0.1 A g-1,but also still maintains at 408 mAh g-1 after 100 cycles.And it exhibits enhanced rate performance,which remains at 270 mAh g-1with 2 A g-1.In the sodium ion battery,the cycling stability and rate performance of the EG@SnO2@PANI sample also have been enhanced,which can be attributed to the dual conductive networks of PANI with EG that effectively improve conductivity,inhibit of volume expansion,and enhance the internal structural stability.The EG@SnO2 composite is treated with high-temperature then self-sulfureted as EG@SnS composite.We have successfully encapsulated the EG@SnS composite in the PANI and investigated the electrochemical properties of the EG@SnS@PANI composite.In the tests of lithium ion batteries,the EG@SnS@PANI composites could maintain the discharge capacity at 411.9 mAh g-1after 50 cycles with the current of0.1 A g-1,while the discharge capacities of bare SnS and EG@SnS are only 171.7 and271.6 mAh g-1.After a series of large current densities,the EG@SnS@PANI electrode could deliver discharge capacity of 426 mAh g-1with the small current density of 0.1A g-1 again.However,the cycle performance of EG@SnS@PANI composite could not be obviously improved in sodium ion battery with a small current.And the enhanced rate performance is only shown at large current densities.Therefore,the doublemodification of coating PANI and EG is also applied to boost the electrochemical performance and structural stability of the SnS materials in lithium/sodium ion batteries.However,the property of sodium storage is still to be studied and improved. |