Heightened Integration of POM‐based Metal–Organic Frameworks with Functionalized Single‐Walled Carbon Nanotubes for Superior Energy Storage

Abstract

To increase the conductivity of polyoxometalate‐based metal–organic frameworks (POMOFs) and promote their applications in the field of energy storage, herein, a simple approach was employed to improve their overall electrochemical performances by introducing a functionalized single‐walled carbon nanotubes (SWNT‐COOH). A new POMOF compound, [Cu18(trz)12Cl3(H2O)2][PW12O40] (CuPW), was successfully synthesized, then the size‐matched functionalized SWNT–COOH was introduced to fabricate CuPW/SWNT–COOH composite (PMNT–COOH) by employing a simple sonication‐driven periodic functionalization strategy. When the PMNT–COOH nanocomposite was used as the anode material for Lithium‐ion batteries (LIBs), PMNT–COOH(3) (CuPWNC:SWNT‐COOH=3:1) showed superior behavior of energy storage, a high reversible capacity of 885 mA h g−1 up to a cycle life of 170 cycles. The electrochemical results indicate that the uniform packing of SWNT–COOH provided a favored contact between the electrolyte and the electrode, resulting in enhanced specific capacity during lithium insertion/extraction process. This fabrication of PMNT–COOH nanocomposite opens new avenues for the design and synthesis of new generation electrode materials for LIBs.

Polyoxometalates (POMs): from electroactive clusters to energy materials

“…Recently, MOFs are also investigated as host to immobilize POMs to prevent their solubility in organic electrolytes. [105][106][107][108][109][110][111] The combination of POM and MOFs is hereafter referred as POMOFs. The unique combination of features of both POMs and MOFs such as open porous structures and redox-rich chemistry makes them potential materials for LIBs.…”

“…111 Among those, PMo 10 V 2 -ILs@MIL-100 crystals showed an excellent cycling stability with a high capacity of 1248 mAh.g -1 at 0.1 A.g -1 after 100 cycles as LIB-anode material. Likewise, Li et al 106 O 40 ]) as anode materials where SWNTs were utilized as a conductive scaffold. The material showed a reversible capacity of 885 mAh.g -1 after 170 cycles at 100 mA.g -1 .…”

Carbon Nanotube Based Metal–Organic Framework Hybrids From Fundamentals Toward Applications

“…In the case of CNT@MOF composites, the value of the I D /I G ratio was employed to confirm that the electronic and structural integrity of the composites remained unchanged in comparison with functionalized CNTs since both materials had similar values of the I D /I G ratio. [53] Moreover, Raman spectroscopy can indicate the graphitic nature of pyrolized CNT@MOF hybrids. [57] Surface topography of materials is usually studied by scanning electron microscopy (SEM).…”

Covalently Linked Polyoxometalate–Polypyrrole Hybrids: Electropolymer Materials with Dual-Mode Enhanced Capacitive Energy Storage

“…16 Coupled with their facility for rapid electron transfer, this makes them an excellent basis for electrochemical energy storage in batteries and supercapacitors, 17−20 as demonstrated by the use of [PMo 12 O 40 ] 3− and [PW 12 O 40 ] 3− as cathode materials for lithium-ion batteries. 20 However, the direct use of POMs in both these and other devices is restricted by high solubility and low conductivity as they are typically salts with negligible conductivity. 21 Interfacing of POMs with devices can be achieved by electrically "wiring" the POM to conductive substrates, such as conductive polymers (CPs).…”

“…Among the most important is their ability to act as stable, multielectron acceptors (up to 24 electrons in the solid state) with structures and properties that can be tailored for specific demands at the molecular level, e.g., by connection of organic moieties − or inclusion of almost any heterometal . Coupled with their facility for rapid electron transfer, this makes them an excellent basis for electrochemical energy storage in batteries and supercapacitors, − as demonstrated by the use of [PMo 12 O 40 ] 3– and [PW 12 O 40 ] 3– as cathode materials for lithium-ion batteries . However, the direct use of POMs in both these and other devices is restricted by high solubility and low conductivity as they are typically salts with negligible conductivity …”