Fabrication of Cobalt and Cobalt Oxide/Graphene Composites: Towards High‐Performance Anode Materials for Lithium Ion Batteries

Abstract

Recently, electrochemically active metals and metal oxides, such as Sn, [1] Si, [2] Co 3 O 4 , [3,4] and Fe 2 O 3 , [5] have attracted much attention as anode materials for lithium ion batteries due to their high theoretical capacities and promising potential. However, a large specific volume change commonly occurs in the host matrix of these metals and metal oxides during the cycling process. The resulting partial pulverization of the electrodes leads to a decrease in electrical conductivity and reversible capacity. [1,6] To circumvent these problems, graphitic carbons with high electrical conductivity have been widely used as matrices for metals and metal oxides to improve their cycle performances. [7,8] Although remarkable progress has been made, the metals and metal oxides unavoidably aggregate after long cycles since they are mainly located on the surface of the graphitic carbon. [7] Graphene, an integral part of graphite, is a 2D aromatic monolayer of carbon atoms not only exhibiting superior electrical conductivity and high surface area, [3,9] but also possessing structural flexibility, chemical tolerance, and reassembly properties.[10-13] Such merits suggest that graphene sheets hold promise as matrices for metals and metal oxides to improve their electrochemical performance. Graphene can generally be produced by the chemical reduction of readily available exfoliated graphite oxide with reducing agents, such as hydrazine or dimethylhydrazine. [14][15][16][17] Recently, SnO 2 /graphene, [11] carbon nanotube/graphene, and fullerene/graphene [10] composites were fabricated by the assembly of graphene sheets in the presence of inorganic precursors. Highly reversible capacities and good cycle performances were achieved when using these as anode materials for lithium ion batteries. Nevertheless, these inorganic precursors are still prone to strong aggregation and thus preclude a homogenous dispersion in graphenebased composites.In this Communication, we describe a new strategy by choosing planar metallo-organic molecules, such as cobalt phthalocyanine (CoPc), for the purpose of fabricating organic metal/graphene composites. Due to their pronounced p-interactions with graphene sheets, [18] they enable a homogenous dispersion of cobalt and cobalt oxide into/onto the graphene sheets by a simple pyrolysis and oxidation process. As a consequence, the graphene sheets (GS) in composites can not only efficiently buffer the volume change of cobalt oxide during charging and discharging processes but also preserve the high electrical conductivity of the overall electrode. One thus expects highly reversible capacity, good cycle performance, and good rate capability of the cobalt oxide/graphene composite as anode materials for lithium ion batteries.As illustrated in Scheme 1, graphite oxide was suspended in a solution of ultrapure water and ammonia (25 wt % in water) to create a brown dispersion with a concentration of 0.05 wt %. The dispersion was then homogeneously mixed with CoPc molecules by ultrasonication, in which th...

Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction

“…10,49 Anchoring nanostructured cobalt oxide particles on flexible and electrically conductive graphene nanosheets yields promising alternative electrocatalysts, which can efficiently take advantages of the combinative merits of cobalt oxides and graphene. 50 In addition, by nanocomposite synthesis, the facial functionalized hydroxyl, carboxyl and epoxide can interact with metal precursors, which is helpful for the nucleation and formation of oxide nanoparticles. 24 Co 3 O 4 supported on graphene nanocomposites with 2D or 3D structures exhibited superior ORR electrocatalytic activity in alkaline media.…”

“…In particular, the graphene-based transition metal oxide nanocomposites show outstanding ORR performance in saving cost, thus further decreasing the onset and half-wave potentials, elevating the durability and methanol tolerance. 43,47,48,[50][51][52]55,59,65,66,68,69,74,114,131,132 Iron containing nanoparticles on graphene catalysts have been found to be a group of promising non-noble metal nanocatalysts for the ORR. In a recent work, 43 three-dimensional N-doped graphene aerogel-supported Fe 3 O 4 nanoparticles (Fe 3 O 4 /N-GAs) were synthesized for the efficient catalysis of the ORR.…”

Critical Insight into the Relentless Progression Toward Graphene and Graphene‐Containing Materials for Lithium‐Ion Battery Anodes

“…In 2010, the further progression of graphene-based host structures (i.e., hollow GO spheres, [ 43 ] RGO, [ 37,39,[44][45][46][47][48][49][50] unzipped CNT, [ 51 ] bottom-up-synthesized graphene, [ 52 ] CVD-synthesized graphene [ 40 ] and N-doped graphene [ 40 ] ) only enabled limited progresses (Table 1 ). However, some major advances in understanding the Li-ion storage mechanism in different kinds of graphene were reported.…”

“…Other graphene-based composites, containing metal-oxides (such as Co 3 O 4 , [45][46][47]112 ] Fe 3 O 4 , [113][114][115] Mn 3 O 4 [ 116 ] and CuO [ 117 ] ) or metal hydroxide (i.e., Co(OH) 2 [ 44 ] ), emerged this year but, unfortunately, even though large specifi c gravimetric capacities were achieved, they all showed a generally limited cycle life and, in some cases, an unsatisfactory electrochemical reversibility (see Table 2 ).…”

Graphene-Wrapped Sulfur Particles as a Rechargeable Lithium–Sulfur Battery Cathode Material with High Capacity and Cycling Stability

“…[18][19][20][21][22][23][24][25][26] Recently we have developed a two-step method to grow metal hydroxides and oxides nanocrystals with interesting morphologies and nanoscale sizes on graphene sheets with various degrees of oxidation and surface functional group coverage. [18][19][20][21][22] As a result of controlled nucleation and growth, the hydroxide or oxide nanomaterials are selectively formed on graphene with intimate interaction to the conducting graphene substrate.…”