Graphene aerogel supported Fe₅(PO₄)₄(OH)₃·2H₂O microspheres as high performance cathode for lithium ion batteries

Abstract

Three-dimensional (3D) macroporous graphene aerogel-supported Fe5(PO4)4(OH)3·2H2O (iron(iii) hydroxide phosphate dihydrate) microspheres (GA/IHPDs) have been fabricated by the hydrothermal mineralization of Fe3+ and PO43− ions in the presence of graphene oxide (GO).

Mn0.5Co2.5O4 Nanofibers Intercalated into Graphene Frameworks with Mesoporous Structure for Batteries and Supercapacitors

“…The equivalent circuit model of the studied system is also shown in the inset to represent the internal resistance of the test battery, according to reports in the literature . It is clear that the electrodes have lower charge‐transfer impedance after the 1st and 50th cycles than that of the fresh state, which suggests that the initial electrochemical activation and reconstruction of the electrode results in easier and faster lithium‐ion intercalation/charge transfer . The SEI film resistance, R f , and charge‐transfer resistance, R ct , of the first cycle are 91.7 and 68.5 Ω, respectively, which are similar to those after 50 cycles (60.8 and 57.4 Ω).…”

“…It is interesting to note that the capacity increases to 1050 mAh g −1 when the current rate is reduced back to 0.2 A g −1 after 60 cycles, which indicates the good reversibility of the electrode. The increased capacity may be attributed to the reversible growth of a polymeric gel‐like film that results from kinetically activated electrolyte degradation . For comparison, the rate performances of MnCo 2 O 4 @G and MnCo 2 O 4 were further inspected, and the capacities decreased dramatically at each rate, dropping to 60 and 20 mAh g −1 , respectively, at 2.0 A g −1 .…”

“…Graphene has been considered as an appealing electrode material for energy storage owing to its uniquep roperties, such as ultrathin sheet formation, large surface area, high chemical stability,e xcellent electrical conductivity,a nd outstanding mechanical flexibility.H owever, pure graphene layers usually restacka nd aggregate during electrochemical processesb ecause of van der Waals interactions between neighboring layers.F ortunately,g raphene oxide (GO), which is produced by chemically exfoliated methoda nd rich in oxygen-containing functional groups,i sb eneficial to grow and anchor functional nanomaterials, such as metal oxide nanoparticles and electrochemically active polymers. [17][18][19][20][21][22] Thes trong coupling between the graphene layer and metal oxide in ac onfined structure can endow the composite with uniquee lectrochemical and physical properties: [23][24][25][26][27] the flexible graphene layers can buffer the strain caused by volume changes to metal oxide nanoparticles;t hus by reducing damage and improving the utilization of active materials at Self-assembled manganese cobalto xide (Mn 0.5 Co 2.5 O 4 ) nanofibers intercalated into graphene frameworks (Mn 0.5 Co 2.5 O 4 @G) with am esoporous structure are successfully synthesized by ah ydrothermal treatment and annealing process.T he unique structure can effectively preventv olume changes of Mn 0.5 Co 2.5 O 4 nanofibersa nd graphene layers from restacking, and enhance the electrode kinetics,sothe composite demonstrates superiore lectrochemicalp erformances for lithium-ion batteries (LIBs) and supercapacitors.A sa n anode material for LIBs,t he Mn 0.5 Co 2.5 O 4 @G composite shows al arge reversible specific capacity of 950 mAh g À1 after 100cycles at ac urrent density of 0.2 Ag À1 .I nat hreeelectrodes ystem, it achieves specific capacitances of 1926 Fg À1 at ac urrent density of 10 Ag À1 ,a nd capacitances of 1575 and 1211 Fg À1 at ultrahigh current densities of 30 and 40 Ag À1 ,r espectively.F or an asymmetric supercapacitor, Mn 0.5 Co 2.5 O 4 @G//AC( AC = activated carbon) can achieve high energy densities of 64.9 and 14.6 Wh kg À1 at power densities of 75.2 and 3754.3 Wkg À1 ,respectively. the same time,c onductiveg raphene substrates can preserve efficient ion diffusiona nd electron transport, consequently enhancing the rate performance.O nt he other hand, metal oxide loaded on graphene can also decreaset he agglomeration of graphene layers;t hus increasing the electrical doublelayer capacitor (EDLC) energy storage.F or these reasons, metal oxide/graphene composites are attractive for usea s electrodem aterials for LIBs or supercapacitors,s uch as NiCo 2 O 4 nanosheetso ng raphene layers [16,28] and MnCo 2 O 4 nanoflake/graphene nanoplatelets.…”

Conductive framework supported high rate performance of SnO2 hollow nanofibers for lithium battery anodes

“…However, the expansion of the SnO 2 hNFs with conductive framework may be limited due to the coated carbon layer and wrapped GO layers during lithiation process. This suggestion is considered from the reported result that the high Young's module of the graphene related material such as the GO and the reduced GO can be buffers the strain arising from the volume expansion [39,40]. During charge/discharge process, the electrons move along to hNF and transfer through contact point between hNFs.…”

The removal of uranium(VI) from aqueous solution by graphene oxide–carbon nanotubes hybrid aerogels

“…Recently, graphene-based aerogels, composed of tenuous networks of clustered nanoparticles, have been under intense investigation owing to their outstanding properties such as easy separation and large specific surface area [15][16][17][18][19][20]. They have been used as promising sorbents for many environmental applications [21,22].…”