Scalable Functionalized Graphene Nano-platelets as Tunable Cathodes for High-performance Lithium Rechargeable Batteries

Abstract

High-performance and cost-effective rechargeable batteries are key to the success of electric vehicles and large-scale energy storage systems. Extensive research has focused on the development of (i) new high-energy electrodes that can store more lithium or (ii) high-power nano-structured electrodes hybridized with carbonaceous materials. However, the current status of lithium batteries based on redox reactions of heavy transition metals still remains far below the demands required for the proposed applications. Herein, we present a novel approach using tunable functional groups on graphene nano-platelets as redox centers. The electrode can deliver high capacity of ~250 mAh g−1, power of ~20 kW kg−1 in an acceptable cathode voltage range, and provide excellent cyclability up to thousands of repeated charge/discharge cycles. The simple, mass-scalable synthetic route for the functionalized graphene nano-platelets proposed in this work suggests that the graphene cathode can be a promising new class of electrode.

Oxygen-containing Functional Groups Enhancing Electrochemical Performance of Porous Reduced Graphene Oxide Cathode in Lithium Ion Batteries

“…5a and b show the chargedischarge curves of the RGO-I and RGO-II electrodes in the 1st, 2nd, 10th, 20th, 50th and 100th cycles, respectively. Obviously, no clear potential plateau is observed in the charge/discharge processes of RGO-I and RGO-II cathodes, as previously reported [26], which results from the existence of electrochemically and geometrically nonequivalent lithium storage sites within the RGO [19]. The initial discharge capacity of the RGO-I is 163 mAh g À1 , and then gradually increase to 220 mAh g À1 , RGO-II with few oxygen-containing functional groups showed much lower electrochemical activity with initial discharge capacity of 49 mAh g À1 .…”

“…During charge/discharge processes, as the redox centers, the oxygen-containing functional surface groups (such as >C-O and -COOH) of RGO can rapidly and reversibly capture lithium ions through surface adsorption and/or surface redox reaction. Thus, functionalized graphene exhibit higher energy density with longlasting cyclability in comparison with the current cathode materials [25,26]. For example, Bor Z. Jang's group proposed a novel LIB using nanostructured graphene as both the anode and the cathode [25].…”

Three Kinds of Energy Storage Devices

“…In the past years, LIBs have dominated the portable electronic markets [11]. However, the power density of LIBs still needs to be further improved to fulfill the demand of the industrial battery products although they have the highest energy density [12,13].…”

“…Nevertheless, further practical applications of these electroactive materials to pseudocapacitors are still limited by the low power density that arises from the poor electrical conductivity restricting fast electron transport, and by the lack of a pure cycling stability owing to the easily damaged structure of the materials during the redox process. Hence, to resolve these problems, carbon-based materials with high electrical conductivity and large SSA are usually used as the backbone materials to combine with these active materials for pseudo-capacitor electrodes [9][10][11][12].…”

“…A promising approach is the combination of lithium-ion battery and supercapacitor. By the aid of hybridization the system can possess energy and power density values between those of lithium ion batteries and supercapacitors as well as a suitable cycle life [12][13][14][15].…”