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Energy Storage in the Emerging Era of Smart Grids Part 9

Tham khảo tài liệu 'energy storage in the emerging era of smart grids part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 228 Energy storage in the Emerging Era of Smart Grids The fabricated peptide-amorphous FePC 4 is annealed in adequate condition to remove the inactive peptide template forming the amorphous FePC 4 nanotube as illustrated in Figure 24 a Ryu et al. 2010a . Hollow spaces formed inside the amorphous FePQt resulting in a nanotubular structure as shown in Figure 24 c-d Ryu et al. 2010a . Another purpose for the heat treatment is to remove crystal water because it tends to form a hydrated phase of FePQtgH2O when the FePQt phase is synthesized from aqueous solution. Heat treatment at too high temperature induces the crystallization of the amorphous phase lowering the electrochemical activity Okada et al. 2005 . Thus controlling the temperature is an important factor for the heat treatment. The individual nanotubes are interwoven with one another to form a complex network structure as expected. The peptide leaves a thin amorphous carbon layer inside the tube after heat treatment as which is identified by the FT-IR spectra shown in Figure 24 e Ryu et al. 2010a . Additionally the FT-IR spectra confirm that the FePƠ4 phase is successfullyformed. The residual carbon layer is expected to provide a facile pathway for electron transport. Mineralized hydrogel FePŨ4 nanotubes Fig. 24. Amorphous FePQt nanotube synthesized by a peptide template a schematic diagram for synthesis procedure b-c SEM images d TEM image and e FI-IR spectra Ryu et al. 2010a . Bio-Inspired Synthesis of Electrode Materials for Lithium Rechargeable Batteries 229 As a cathode material the amorphous FePQ nanotube coated by a carbon layer exhibits a high specific capacity as depicted in Figure 25 Ryu et al. 2010a . Its first discharge capacity is approximately 170 mAh g-1 which is comparable to the theoretical capacity 178 mAh gi . Then the specific capacity is saturated to 150 mAh g-1 with excellent reversibility. Similar to the T1O2 nanotube network it is believed th at the nanoscale dimension and unique .