Monolithic Graphene Trees as Anode Material for Lithium Ion Batteries with High C‐Rates

Abstract

Monolithically structured reduced graphene oxide (rGO), prepared from a highly concentrated and conductive rGO paste, is introduced as an anode material for lithium ion batteries with high rate capacities. This is achieved by a mixture of rGO paste and the water-soluble polymer sodium carboxymethylcellulose (SCMC) with freeze drying. Unlike previous 3D graphene porous structures, the monolithic graphene resembles densely branched pine trees and has high mechanical stability with strong adhesion to the metal electrodes. The structures contain numerous large surface area open pores that facilitate lithium ion diffusion, while the strong hydrogen bonding between the graphene layers and SCMC provides high conductivity and reduces the volume changes that occur during cycling. Ultrafast charge/discharge rates are obtained with outstanding cycling stability and the capacities are higher than those reported for other anode materials. The fabrication process is simple and straightforward to adjust and is therefore suitable for mass production of anode electrodes for commercial applications.

Graphene‐Based Nanocomposites for Energy Storage

“…A Li‐ion battery provides capacities through Li intercalation with an active electrode material, and therefore, its high‐rate performance is largely governed by Li + diffusivity and electron conductivity . However, using a traditional procedure to prepare the electrode usually leads to a low electrical conductivity caused by many factors such as the poor contact resistances by random pore structures, poor adhesion to the current collector, etc.…”

Chemically doped three-dimensional porous graphene monoliths for high-performance flexible field emitters

“…This was because of the effect of the doping of monovalent ions in the rGO sheets as well as the high dispersion stability of the ions in the solution. A 3D porous rGO structure [22][23][24] was prepared by the simple bar coating of the rGO paste and its subsequent freeze-drying, as illustrated in Fig. 1b.…”

Polymer/Graphene Hybrids for Advanced Energy‐Conversion and ‐Storage Materials

“…Recently, Lee et al. have prepared novel monolithic graphene trees as a LIB anode material through direct freeze drying of a mixture of rGO paste and the water‐soluble polymer SCMC . The monolithic graphene trees have large surface areas, short diffusion lengths, and high electrical conductivities, all of which lead to ultrafast charge/discharge rates of 718 mA h g −1 at 5 C (i.e., 12 min) and 550 mA h g −1 at 100 C (36 s).…”

“…Recently,L ee et al have prepared novel monolithic graphene trees as aL IB anode material throughd irect freeze drying of am ixture of rGO paste and the water-soluble polymerS CMC. [96] The monolithic graphene trees have large surface areas, short diffusion lengths, and high electrical conductivities, all of which lead to ultrafast charge/discharge rates of 718 mA hg À1 at 5C(i.e.,1 2min) and 550 mA hg À1 at 100 C(36 s). To study their electrochemical performances as LIB anodes, ap ouch-type half cell of monolithic rGO (M-rGO) electrodes has been fabricated and cycled between 0.005 and 2V at various charge/discharge rates (C rates).T ypical voltage profiles for M-rGO anodesa re shown in Figure10a:t he specific capacity increases with an increase in the Crate, and the Coulombic efficiencyo fM -rGO reaches 52.5 %i nt he first cycleo wing to irreversible capacities (Figure 10 b), whichc an probably be attributed to the fact that the stable structured and highly conductive rGO paste electrolyte restrains decomposition and surface side reactions through the formationo fasolid-electrolyte interface .T he M-rGO anodes possess ah igher capacity (817 mA hg À1 )a t0 .2 C ( Figure 10 Song and co-workers [97] report PF-grafted rGO (rGO-g-PF) as ah ighly stable anode materialf or LIBs.…”