MoS₂/Graphene Composite Paper for Sodium-Ion Battery Electrodes

Abstract

We study the synthesis, electrochemical and mechanical performance of layered freestanding papers composed of acid exfoliated few layer molybdenum disulfide (MoS 2 ) and reduced graphene oxide (rGO) flakes for use as a self-standing flexible electrode in sodium ion batteries. Synthesis was achieved through vacuum filtration of homogenous dispersions consisting of varying wt. % of acid treated MoS 2 flakes in GO in DI water, followed by thermal reduction at elevated temperatures. The electrochemical performance of the crumpled composite paper (at 4 mg.cm -2 ) was evaluated as counter electrode against pure Na foil in a half-cell configuration. The electrode showed good Na cycling ability with a stable charge capacity of approx.230 mAh.g -1 with respect to total weight of the electrode with coulombic efficiency reaching approx. 99 %. In addition, static uniaxial tensile tests performed on crumpled composite papers showed high average strain to failure reaching approx. %.KEYWORDS: TMDC, sodium battery, freestanding electrode, graphene, MoS 2 2 Lithium ion batteries (LIBs) have been extensively studied for energy-storage applications like portable electronic devices and electric vehicles. [1][2][3] However, concerns over the cost, safety and availability of Li reserves 4 for large-scale applications involving renewable energy integration and the electrical grid have to be answered. In this regard, sodium ion batteries (SIBs) have drawn increasing attention because in contrast to lithium, 5-7 sodium resources are practically inexhaustible and evenly distributed around the world while the ion insertion chemistry is largely identical to that of lithium. Also, from electrochemical point of view, sodium has a very negative redox potential (-2.71 V, vs. SHE) and a small electrochemical equivalent (0.86 gAh -1 ), which make it the most advantageous element for battery applications after lithium. However, many challenges remain before SIBs can become commercially competitive with LIBs. For instance, Na ions are about 55% larger in radius than Li-ions, which makes it difficult to find a suitable host material to allow reversible and rapid ion insertion and extraction. 8 To this end, researchers have proposed a number of high-capacity sodium host materials (negative electrode) involving either carbon or group IVA and VA elements that form intermetallic compounds with Na. [9][10][11][12][13] The alloying compounds demonstrate high first cycle Na-storage capacities, such as Na 15 Sn 4 (847 mAhg -1 ), Na 15 Pb 4 (485 mAhg -1 ), Na 3 Sb (600 mAhg -1 ) and Na 3 P (2560 mAhg -1 ), respectively. However, this comes at the cost of very high volume change upon Na-insertion (as much as 500 % in some cases), resulting in formation of internal cracks, loss of electrical contact, and eventual failure of the electrode (particularly for thick electrodes). 14 Novel nanostructured designs that can accommodate large volumetric strains need further exploration. [15][16][17][18] For carbon-based electrode materials, much of the emphasis ...

High‐Performance Sodium‐Ion Batteries and Sodium‐Ion Pseudocapacitors Based on MoS2/Graphene Composites

“…[36] Herein, we report that expanded MoS2/G composite (MoS2/G), which was prepared by the attachment of expanded MoS2 layers onto graphene sheets by a simple hydrothermal method, results in excellent electrochemical properties in both the sodium ion battery and the sodium-ion pseudocapacitor. The sodium ion battery is able to deliver a high capacity of 313 mAh g -1 over 200 cycles at 0.25 C (1 C= 400 mA g -1 ), with capacity retention of 81%.…”

Pure Single‐Crystalline Na1.1V3O7.9 Nanobelts as Superior Cathode Materials for Rechargeable Sodium‐Ion Batteries

“…However, we shall always be prepared for the exhaustion of limited and unevenly distributed Li resources in the Earth's crust. In response, room‐temperature Na‐ion batteries (NIBs) have again aroused a great deal of interest recently because Na resources are practically inexhaustible and ubiquitous, which is extremely favorable for large‐scale stationary electric energy storage applications for renewable energies and smart grids 2, 3, 4, 5. However, partially because Na ion is larger and heavier than Li ion, there is still only very limited number of potential cathode materials for NIBs, and the obtained cathode materials are still far from satisfying in terms of specific capacity, rate capability, and cycling stability 6, 7, 8.…”

Occupied and unoccupied electronic structure of Na doped MoS2(0001)

“…Indeed, alkali metal potassium doping has been used to make an n-doped field effect transistor to construct an inverter based on WSe 2 . 5 The MX 2 -Na interaction is, however, not only relevant for electronic applications but also in several different areas: for instance, sodium-ion batteries (SIBs) have been discussed 6,7 as an alternative to lithium ion batteries and 2-D layered nanomaterials, such as the MX 2 , may be capable of accommodating the large volumetric strains during charging and discharging, while remaining high-capacity sodium host materials. In addition, alkali metal adsorption has significant influence on the catalytic properties of MoS 2 .…”