| Solid-state lithium batteries have attracted much attention because of their high energy density and high safety,and are one of the future directions of energy storage technology.The main problems are the low room temperature ionic conductivity and poor interfacial compatibility of the key material,solid-state electrolyte,especially the strong activity of lithium metal,which can easily react with the solid-state electrolyte and generate a continuously growing unstable interface,thus leading to the extremely fast decay of battery performance.Thus,in this paper,to address the problem of the anode-side interface of solid-state lithium-metal batteries,a process innovation was used to prepare graphite and graphene oxide carbon material modified layers at the interface between the polypropylene carbonate（PPC）/La2Zr2O7（LZO）/Li TFSI composite solid-state electrolyte and the anode-side of lithium metal,respectively,to obtain a relatively stable interface modified layer by using the spontaneous reaction between carbon material and lithium metal.improve the cycle stability and multiplier performance of solid-state lithium-metal batteries.The main research results are as follows.（1）A graphene oxide（GO）-modified PPC-based composite solid-state electrolyte（SE）was prepared by the scratch-coating method to obtain GO-SE with a total thickness of 26μm.GO-SE can reach a maximum electrochemical window of 4.8 V,room temperature ionic conductivity of 2.22×10-4 S·cm-1,lithium ion migration number of up to 0.90,and tensile strength of 53.79 MPa.The rGO layer generated by the spontaneous reaction between the GO-modified layer and Li greatly improves the interfacial contact and stability of SE and Li,and reduces the impedance of the NCM622/SE/Li cell.This GO-modified film is suitable for high-voltage solid-state lithium batteries,and the assembled NCM622/GO-SE/Li cells have an initial capacity of 170 m Ah/g at 0.5C,and the capacity is still above 100 m Ah/g after 210 cycles.The discharge specific capacity of GO-SE is much higher than that of the unmodified electrolyte film at multiplicities from 0.1 C to 2 C.（2）Graphite-modified PPC/LZO/Li TFSI composite solid electrolyte films（G-SE）with a total thickness of 28-34μm were prepared by the scratch-coating method,and the effects of different thicknesses of graphite coating on the electrolyte film performance and battery performance were investigated.The electrochemical stability window can reach more than 4.6 V,the room temperature ionic conductivity reaches3.08×10-4S·cm-1,and the tensile strength reaches 76.19 MPa when the thickness of graphite modified layer is 4μm.Meanwhile,the graphite modified solid electrolyte has good lithium dendrite suppression ability and interfacial stabilization.The spontaneous reaction of graphite with lithium metal to generate Li C6 interfacially modified layer was demonstrated by Raman spectroscopy and X-ray photoelectron spectroscopy analysis,and the assembled NCM622/G-SE/Li cell had an initial capacity of 160 m Ah/g at 0.5C and maintained a capacity of 100 m Ah/g after 200cycles,compared with the discharge specific capacity of the unmodified electrolyte film at 2C multiplicity of Compared with the discharge capacity of unmodified electrolyte film at 2C rate of 45 m Ah/g,the discharge capacity of G-SE at the same rate can be more than 110 m Ah/g,which has a significant improvement effect.（3）The mechanism of GO and graphite modification of the electrolyte/lithium cathode interface was clarified by means of test characterization.rGO and Li C6 were formed by the spontaneous reaction of GO and graphite with Li metal,and their interfacial modification of PPC-based all-solid-state lithium metal batteries was mainly reflected in the following three aspects:（a）Improved interfacial contact between the solid electrolyte（SE）and the lithium metal cathode and reduced interfacial impedance;（b）The formation of interfacial intermediate layer inhibits the interfacial side reactions and improves the cycle stability;（c）It promotes the current homogenization and stress uniformity distribution at the interface,inhibits the abnormal growth of lithium dendrites,and improves the cycle life. |
