Study On Controllable Synthesis And Lithium / Sodium Properties Of New Two - Dimensional Carbon - Based Nanosheet Composites

Lithium-ion secondary batteries possess a high energy density、high work voltage and improved safety and environmental benignity, thus have been considered to be the most potential energy storage. However, with the large-scale application of LIBs, the limited resources of lithium is restricting its development. NIBs is considered to be the most promising alternative due to its high abundance of sodium. Battery life、energy density and other properties are mainly determined by the electrode materials, so the development of high-performance electrode materials has become a key factor in battery research. Carbon materials are considered to be one of the most promising commercial materials, and the structure and morphology of carbon materials are the main factors which affect their electrochemical performances. Although currently commercialized graphite has been recognized as the most commonly used anode material for LIBs, its low theoretical capacity of 372 mAh g-1 and poor rate performance can not meet the needs of the development of high energy and power equipment, it is urgent to explore and research a high capacity anode material. The development and research of new carbon material and its compound nanomaterial is a trend to improve the lithium/sodium storage properties for lithium/sodium ion battery. Currently the reported new carbon materials have zero-dimensonal、one-dimensional，two-dimensional、three-dimensional and multi-dimensional compound structure, the compound ways of compound nanomaterials are carbon-coated, carbon-mixed, carbon-loaded and others. But for the development of high performance lithium/sodium ion battery, we should make best of synergistic effect between carbon materials and other lithium/sodium storage materials.In this paper,we take new two-dimensional carbon nanosheets and its compound nanomaterials as a standpoint, to synthesize a series of metal nanoparticle-embedded carbon nanosheets and explore the effect of carbon nanosheet compound materials on storage of lithium and sodium. And two-dimensional carbon nanosheets combine the advantages of carbon material (buffer and electric conduction) and transition metal(high capacity). Compared with traditional carbon material, it exhibits a better charge transfer capability and structural stability.Two-dimensional carbon nanosheets and its compound nanomaterials demonstrate enhanced lithium-storage performance, which can meet the development of LIBs and. NIBs.Herein, we rationally design and synthesize a series of two-dimensional carbon nanosheets and its hybrid nanomaterials by pyrolysis method using NaCl or KC1 as a template and a dispersing agent, glucose or amino acid as carbon and nitrogen source, transition metal salt as metal precursor. Owing to their unique compositional and structural features, the as-prepared two-dimensional carbon nanosheets and its compound nanomaterials demonstrate enhanced lithium/sodium-storage performance in terms of specific capacity, cycling stability, and rate capability. The main innovative results are displayed as follows.(1) By using NaCl as a template and a dispersing agent, glucose as carbon source, Ni(NO3)2 as metal precursor. We rationally design and synthesize Ni nanoparticle-embedded porous graphitic carbon nanosheets by pyrolysis method.the as-synthesized nano compound exhibits enhanced performance in term of cycling stability and good rate performance compared with bare carbon nanosheets. For example, it manifests a very stable high reversible capacity of 740 mAh g-1 after 100 cycles at a current density of 100 mA g-1, Even at ultrahigh current rate of 1000 mA g-1, a large reversible capacity of 400 mAh g-1 can be achieved. We believe that the synthetic strategy outlined here can be extended to other rationally designed anode materials with high performances in LIBs.(2) By using KCI as a template and stabilizer agent, glucose as carbon source, Co(NO3)2 as metal precursor. We rationally design and synthesize Co3O4 active nanoparticle-embedded porous graphitic carbon nanosheets by grinding-dissolution-crystallization process and two step pyrolysis method.the as-synthesized nanohybrid exhibits enhanced performance in term of cycling stability and good rate performance compared with pure carbonsheet and bare Co3O4 nanoparticle.For example, it delivers a remarkable initial specific capacity of 1816 mAh g-1 at a current density of 100 mA g-1. After 100 cycles, the retained capacity is as high as 861.3 mAh g-1. When the current density is increased to 1000 mA g-’, the anode also presents a capacity retention of 415.7 mAh g-1.The Co304@GCNs compound holds promise as an efficient candidate material for anode due to its low-cost, environmentally friendly, high-capacity and stability(3) By using KCl as a template and stabilizer agent, proline as carbon and nitrogen source, Fe(acac)3 as metal precursor. We rationally design and synthesize stable onion-like Fe3C-Fe2O3 nanoparticles embeded in N-Doped carbon nanosheets by grinding-dissolution-crystallization process and two step pyrolysis method.When applied as an anode material for LIBs, the Fe3C-Fe2O3@NGCNs compound material demonstrates high reversible capacities, excellent capacity retention and high rate capability. For example, Benefiting from the flexible and highly conductive N-doped carbon nanosheets material, the composite shows a high discharge capacity of 1698 mAh g-1 at the current density of 100 mA g-1 in the first cycle. It can still deliver a discharge capacity of 857 mAh g-1 after 100 cycles, demonstrating its excellent capacity retention at high charge-discharge rate. The proline biomass material will open a new avenue for producing nanostructured electrode materials from low-cost sustainable sources.(4) By using NaCl as a template and a dispersing agent, glucose as carbon source, Ni(NO3)2 as metal precursor. We rationally design and synthesize porous graphitic carbon nanosheets by pyrolysis method and acid treatment, the as-synthesized porous graphitic carbon nanosheets manifests good sodium-storage performance in terms of specific capacities, cycle life and rate capability. For example, the as-prepared porous nanosheets have excellent Na storage rate capability of 173 mAh·g-1 at 1000 mA·g-1 and exhibit outstanding cycle stability at 100 mA g-1 with 309.4 mAh·g-1 capacity even after 200 cycles running.