Rational Design Of Anode Materials Based On Alloy Mechanism And Their Lithium Storage Properties

Lithium-ion batteries（LIBs）are applied widely in portable electric equipment and new energy vehicles because of its high energy density and other advantages.Nowadays,the traditional commercial graphite anode(theoretical capacity:372 m Ah g^-1)cannot meet the ever-increasing demand,so new anode materials with better electrochemical performance need to be explored.Among them,tin-based materials based on alloy mechanism become the research focus because of its higher theoretical capacity.However,huge volume change during alloying/de-alloying process and poor electric conductivity easily give rise to short cyclic life,poor rate performance and other problems,which limits their practical application in Li-ion batteries.To solve the above-mentioned problem,in this thesis,we synthesized a series of tin-based anode materials with better lithium storage performance by modifying their structure and composition,which shows improved cyclic performance.The specific research works are following:（1）We synthesized Sn O₂ composites supported on the S,N co-doped carbon（Sn O₂/SNC）by a simple solid-state method using triphenyltin chloride and L-cysteine.Compared with pristine Sn O₂,the cyclic stability of prepared Sn O₂/SNC composite was improved remarkably.And we also optimized its performance by controlling appropriate carbon content.The Sn O₂/SNC composite displays a stabilized specific capacity of 600m Ah g^-1 after 1000 cycles(current density:2 A g^-1).The corresponding experiment results showed that improved cyclic stability is owing to enhanced conductivity of electrode material.The introduction of carbon could enhance the reaction reversibility efficiently,which will suppress the capacity depression caused by alloying reaction.（2）We constructed Sn S/Sn O₂ heterostructure electrode materials using stannous chloride dihydrate and 2-aminothiazole by a simple hydrothermal method.The heterostructure could improve its structural stability remarkably and relieve the huge volume expansion of Sn O₂ or Sn S during charging and discharging process,which is beneficial to improve materials electrochemical performance.What’s more,ultrathin Sn S nanosheets is beneficial to the transport of ion,which can improve further the cyclic stability and rate performance.（3）The Sn materials coated with carbon（Sn/C）were constructed by calcining at different stages under vacuum condition using ZIF-8 and triphenyltin chloride.The results showed that the reversible capacity of Sn/C composite was up to 725.1 m Ah g^-1 after 400cycles(current density:1 A g^-1).The introduction of carbon can not only improve the electric conductivity but also relieve the structural pulverization causing by huge volume expansion during the alloying process,which improved cyclic stability of electrode materials remarkably.