Recently, NEU Professor Gao Bo's team published a paper titled "Graphene nanonetwork embedded with polyaniline nanoparticles as anode of Li-ion battery" in the Chemical Engineering Journal, proposing a simple, solvent-free method to prepare graphene nanonetwork polyaniline (PANI) nanocomposites with stronger conductivity and lithium ion storage performance. The first author of this paper is Fu Haiyang, a PhD at the School of Metallurgy at NEU, and the corresponding authors are Professor Gao Bo and Professor Ali Kamali.
In order to prepare this advanced composite material, acidic graphene oxide (AGO) and PANI were first ball milled, followed by low-temperature chemical expansion to form chemically expanded graphene (CEG), forming a mesoporous nanonet with a lattice layer spacing of 0.362 nm, and embedding PANI nanoparticles. The performance of CEG-PANI nanocomposites is superior to CEG, with a specific reversible capacity of 664mAh g-1 after 150 cycles at 200mA-g-1 and a discharge capacity of 253 mAh g-1 after 350 cycles at 2000mA-g-1. The improvement in electrochemical performance of CEG-PANI is attributed to its large specific surface area, mesostructure, and conductive homogeneous graphene nanonetwork doped with N heteroatoms of polyaniline, which provide sufficient active sites for rapid storage of lithium ions. Nanostructured CEG-PANI is an ideal candidate material for lithium-ion battery anodes.
Figure 1. Graphical representation of the synthesis process of CEG-PANI.
Figure 2. SEM micrographs of (a) CEG-PANI (1:0.1), (b) CEG-PANI (1:0.2), (c) CEG-PANI (1:0.5) and (d) CEG-PANI (1:1); (e) Adsorption/desorption isotherms of N2CEG-PANI (1:0.2). (f) Pore size distribution of CEG-PANI (1:0.2).
Figure 3. (a, b) TEM morphological characteristics of CEG-PANI (1:0.2). (c) High resolution transmission electron microscopy micrographs show that the crystal plane with a interlayer spacing of 0.36 corresponds to the (002) plane of lonsdaleite. (d) The diffraction pattern recorded on the graphene sheet, where the bright ring corresponds to the (002) crystal plane of graphene in CEG-PANI (1:0.2). (e-i) Display the corresponding element diagram images of materials with distributions of (f) C, (h) N, and (i) O.
Figure 4. XRD spectra of (a) AGO, PANI, CEG, CEG-PANI (1:0.1), CEG-PANI (1:0.1), CEG-PANI (1:0.5), and CEG-PANI (1:1) powders. (b) Raman spectra of AGO, PANI, CEG, CEG-PANI (1:0.1), CEG-PANI (1:0.2), CEG-PANI (1:0.5), and CEG-PANI (1:1) powders; (c) Fourier transform infrared spectroscopy.
Figure 5. (a) C1s of AGO; (b) C1s of PANI; (c) C1s of CEG; (d) C1s of CEG-PANI (1:0.2); (e) X-ray photoelectron spectroscopy characterization of the N1s spectra of PANI and (f) CEG-PANI (1:0.2).
Figure 6. Electrochemical performance of nanocomposites
Figure 7. (a) CV curves of CEG-PANI (1:0.2) at different scanning rates.(b) B values under different peak currents after linear fitting.(c) The contribution ratio of pseudo capacitance and diffusion capacity under different scanning rates.(d) The CV curve of the composite material and the calculated false capacitance contribution rate in the shaded area at a scanning rate of 1.0 mV-s-1.(e) The GITT curve and Li+diffusion coefficient of CEG-PANI (1:0.2) anode during (f) petrification and (g) decalcification processes.(h) Nyquist diagram of electrode materials for AGO, PANI, CEG-PANI (1:0.1,1:0.2,1:0.5,1:1).
This study explores a new, low-cost, and quite environmentally friendly low-temperature chemical expansion method for preparing high-quality nitrogen doped graphene nanonetworks embedded in polyaniline nanoparticles to inhibit the re accumulation of graphene layers. The CEG-PANI nanocomposite material has a mesoporous structure, a specific surface area of 383 m2-g-1, and a pore size of 3.82 nm. Through Fourier transform infrared spectroscopy and XPS, it was demonstrated that nitrogen was successfully introduced in the form of pyridine nitrogen, pyrrolidone nitrogen, and a small amount of graphite nitrogen. In addition, compared to AGO (515 mAh g-1) and CEG (765 mAh g-1), the maximum specific capacity of CEG-PANI (1:0.2) after 10 cycles is 822 mAh g-1 (0.1 A-g-1). Under the condition of a current density of 2000 mA-g-1, CEG-PANI can still maintain good cycling stability (253 mAh g-1) after 350 cycles. The CEG-PANI material prepared in this study can be regarded as another high-performance negative electrode material for lithium-ion batteries.
