Preparation And Characterization Of A Doped Graphene Lithium Ion Battery Anode

Currently,graphite is the most widely-used anode material due to its excellent cycling stability.However,the Li storage capacity of graphite is relatively low since its theoretical specific capacity is only 372 m A h g-1,the main purpose of our research is to improve the performance of LIBs graphene anode materials.In order to combine the merits of graphite and the single-layered heteroatomdoping graphene,here we report an oxydic intercalation and thermal reduction process,followed by the CO2 supercritical fluid exfoliation method to synthesize the multilayered(3-6 layers)S-doped graphene(SG)and P&S dual-doped graphene(PSG).To evaluate the effect the synthesized method,X-Ray diffraction(XRD)coupled with Raman analysis testified the exfoliated effect between the graphite layers formed by the thermal reduction process,and further confirmed the defects introduced by heteroatom doping.The EDS mapping confirmed that the heteroatoms are uniformly distributed on the graphene surface,the X-ray photoelectron spectroscopy(XPS)analyses confirm that the P and S atoms have been successfully incorporated into the graphite networks,and the content doping into carbon matrix of P and S is up to 1.34 and 2.01 atom%,respectively.As the anode material for LIBs,the PSG exhibits extremely high Li storage capacity(532 m A h g-1 at the current density of 50 mA g-1)and excellent cycling stability(remaining a reversible capacity of 150 mA h g-1 at 1000 mA g-1 after 100 cycles),showing much better electrochemical performance as compared to the virgin NG anode material.The stable voltage plateaus are also observed during the lithiation and delithiation process at 0-0.3 V and contribute large capacity,which is over 80 percent.The full cell batteries is assembled with PSG as anode and LiFePO4 as cathode,exhibit high reversible capacity(165 mA h g-1 at 0.2 C)and excellent cycling stability(remains 94.4% after 100 cycles at 2 C)with stable voltage plateau.Aluminum lithium alloy was mixed with organic electrolyte to fill up some active points for lithium ion storage.In this way,the 1st coulombic efficiency was dramatically enhanced to nearly 100%,compared to the original ones about 60-70%.Phosphorus and sulfur dual-doped multi-layered graphene are synthesized via oxidation intercalation and CO2 supercritical fluid exfoliation and exhibited supreme performance as the anode material for LIBs.At the same time,the application of aluminum lithium alloy evidently improve the 1st reversible capacity for graphite anode in LIBs,which is practical worthiness.