Design And Fabrication Of Liquid Metal Modified Nanoporous SiGe Alloy And Their Li-stroage Performance

In recent years,lithium-ion batteries（LIBs）have been widely used in portable electronic devices,but with the rapid development of science and technology,higher requirements on the cycle stability and energy density of LIBs have been put forward.At present,the theoretical specific capacity of commercial anode materials is low,which is far from meeting the needs of high specific energy batteries.Therefore,it is urgent to develop anode materials with higher specific capacity and cycle stability.Sianode is considered to be the most promising anode material for high specific energy batteries due to its high theoretical specific capacity(4200 m A h g^-1)and low operating voltage（0.4 V）.However,the cyclic stability of the Sibased anode is poor due to significant volume changes and serious surface side reactions during lithium/delithium processes.In order to solve the above problems about Si,the following studies have been carried out:designing nano-structured Sibased materials and constructing pore structures in Sianode to improve the electrochemical performance of Sibased anodes.Compared with bulk materials,Sinanostructures usually show significantly shortened Li ion and electron transport pathways,which improves the rate capacity.However,there are two basic problems to be solved for the application of Sibase negative electrode direction:i)The huge mechanical stress and surface side reactions of Sibased materials in the process of cycling lead to the loss of electrical contact,and ultimately lead to poor cycling stability.ii)The capacity of Simatrix composites cannot be fully utilized,so its energy density is limited.In order to solve the above two problems,the main work of this paper is as follows:（1）The nanoporous SiGe alloy（NP-SiGe）anode material was designed and prepared by alloying and dealloying technology.SEM test was carried out on the circulating electrode.We observed obvious cracks in the NP-SiGe electrode after cycling,in order to solve the volume change and side reaction problems of the material during the cycling process,We further proposed a preparation strategy for room-temperature liquid metal（LM,Ga In Sn mass ratio 7:2:1）modified nanoporous SiGe alloy（NP-SiGe/LM）composites,which fully utilized the reversible transition between solid and liquid of liquid metal during charge and discharge to achieve self-repair of electrode surface and structure.The morphology and structure characterization showed that the nanocrystalline LM particles were successfully embedded into the porous structure of nanoporous SiGe（NP-SiGe）.It maintains a reversible capacity of～1200m A h g^-1 after 300 cycles at room temperature and maintains a reversible capacity of～746.7 m A h g^-1 after 100 cycles at-20℃.The morphology of the circulating electrode clearly indicate the self-healing properties of LM.This study provides a new idea for the high stability alloy type negative electrode.（2）In order to further improve the capacity of alloy anode,a multistage gradient hole composite anode was constructed at the bottom of copper foam with NP-SiGe/LM as liphilic induction layer to induce uniform deposition of high capacity lithium metal.Because NP-SiGe/LM has better lyophilic properties,the copper foamed has preferential nucleation site at the bottom,which induces uniform deposition of lithium metal at the bottom of the copper foamed.The porous copper frame above effectively accommodates lithium metal deposition,The surface capacity reaches about 5.6 m A h cm^-2 to achieve higher lithium storage capacity.NP-SiGe/Cu terms half cell after 120times of cycle show that the coulomb efficiency is about 97%,we will NP-SiGe/Cu Foam with commercial terms（LFP）assembled fulfill batteries,lithium iron phosphate LFP|NP-SiGe/Cu terms full battery capacity is stable,After 2000 cycles,the cyclic discharge capacity is 112.3 m A h g^-1.NP-SiGe/Cu Foam electrode shows excellent cycling stability in circulation.In this study,NP-SiGe/LM was used to modify the bottom of commercial copper foam to induce The deposition of Li on the bottom of copper foam,which provided an effective way to construct a high specific energy negative electrode..