3D thick electrode design is a promising strategy to increase the energy density of lithium-ion batteries but faces challenges such as poor rate and limited cycle life. Herein, a coassembly method is employed to construct low-tortuosity, mechanically robust 3D thick electrodes. LiFe 0.7 Mn 0.3 PO 4 nanoplates (LFMP NPs) and graphene are aligned along the growth direction of ice crystals during freezing and assembled into sandwich frameworks with vertical channels, which prompts fast ion transfer within the entire electrode and reveals a 2.5-fold increase in ion transfer performance as opposed to that of random structured electrodes. In the sandwich framework, LFMP NPs are entrapped in the graphene wall in a "plate-on-sheet" contact mode, which avoids the detachment of NPs during cycling and also constitutes electron transfer highways for the thick electrode. Such vertical-channel sandwich electrodes with mass loading of 21.2 mg cm −2 exhibit a superior rate capability (0.2C-20C) and ultralong cycle life (1000 cycles). Even under an ultrahigh mass loading of 72 mg cm −2 , the electrode still delivers an areal capacity up to 9.4 mAh cm −2 , ≈2.4 times higher than that of conventional electrodes. This study provides a novel strategy for designing thick electrodes toward high performance batteries.
The
large-scale application of graphene–polymer composites
needs a simple, low-cost method that simplifies the preparation process
of graphene and optimizes the structure and properties of composites.
We propose the first interlayer polymerization in chemically expanded
graphite (CEG) with large specific surface areas, which allows CEG
to be spontaneously exfoliated into single- and few-layer graphene
in poly(methyl methacrylate) (PMMA). Our results demonstrate that
besides weakened interlayer interactions, the surface wettability
of CEG to monomers is a critical prerequisite for the desired graphene
exfoliation, dispersion, and performance optimization of composites.
The slightly oxidized CEG (LCEG) improved to some extent the affinity
for the monomer but is not sufficient to achieve complete exfoliation
of LCEG, so that the resulting composites reveal the mechanical and
electrical properties that are far poorer than those of the surface-modified
LCEG-based composites. The latter not only exhibit a significantly
enhanced elastic modulus, increased as much as 3-fold relative to
that of the neat PMMA, but also show an extremely high electrical
conductivity, of >1700 S/m. Such a novel interlayer polymerization
approach is expected to accelerate the use of industrial applications
of a wide range of graphene-based composites.
The
large-scale preparation of ultralarge graphene oxide (ULGO)
is urgently needed for developing advanced devices and high-performance
nanocomposites. However, it is extremely difficult to produce ULGO
in an industrially viable, high-efficiency manner because of the inevitable
sheet fragmentation and significant gelation behavior occurred in
existing methods. We propose a stationary oxidation-monolithic crystalline
swelling strategy that can completely convert graphite to ULGO. This
new stationary oxidation method minimizes the sheet fracture and prevents
the exfoliation of oxidized layers without sacrificing the oxidation
rate, resulting in oxidized flakes with high crystalline and lateral
sizes the same as raw graphite. The oxidized graphite flakes undergo
a monolithic crystalline swelling during the purification, leading
to the formation of a three-dimensional ordered structure without
peeling. This enables graphite oxide to be purified by spontaneous
sedimentation within 1 h as gelation is avoided and to be exfoliated
exhaustively into single-layered ULGO sheets through mild mechanical
shaking, with an average size of 108 μm and the largest size
of 256 μm. These ULGO sheets can form liquid crystals at a record
dispersion concentration (as low as 0.2 mg/mL). The ULGO papers show
outstanding mechanical properties and electrical conductivities (after
HI reduction) that outperform the reported results.
Polymer-tethered nanoparticles with different geometric shapes are very useful fillers of polymer nanocomposites. Herein, a universal approach for the fabrication of such nanoparticles with precisely controlled shape and composition is reported. By microphase separation of poly(3-(triethoxysilyl)propyl methacrylate)-block-polystyrene (PTEPM-b-PS) in the presence of oligomers, o-TEPM (oT) and/or o-S (oS), followed by cross-linking and dispersion in PS solvent, precisely tailored PS-grafted nanoparticles were prepared. These particles include those with varied shapes but identical PS shells, particles with varied core sizes but the same PS shell, and particles with fixed shapes but varied PS shells. These particles are ideal model nanofillers to study the dynamics and reinforced mechanism of polymer nanocomposites.
The UV-initiated RAFT polymerizations of a series of poly(ethylene glycol) dimethacrylates (PEGDMA) were investigated using differential scanning photocalorimetry (DPC) at room temperature. The rate of the RAFT system was much lower than that of a conventional free radical polymerization. A mild autoacceleration occurred as the addition reaction became diffusion controlled. The influence of the spacer length (CH 2 CH 2 O) x between the vinyl moieties of the dimethacrylates on the polymerization kinetics was examined. The polymerization rate of PEGDMA decreased with an increased x value from 4 to 9, but it increased with a further increased x value from 9 to 14. Mechanical properties of the resulting polymers were also examined by dynamic mechanical analysis (DMA). It was concluded that the presence of the RAFT agent during polymerization of multifunctional monomers did not have an effect on the heterogeneity of the polymer network. In comparison with three different PEGDMAs, the PEGDMA with the longest spacer formed the most homogeneous networks with a lower crosslinking density.
We present a systematic investigation of static and dynamic properties of block copolymer micelles with crosslinked cores, representing model polymer-grafted nanoparticles, over a wide concentration range from dilute regime to an arrested (crystalline) state, by means of light and neutron scattering, complemented by linear viscoelasticity. We have followed the evolution of their scattering intensity and diffusion dynamics throughout the non-ergodicity transition and the observed results have been contrasted against appropriately coarse-grained Langevin Dynamics simulations. These stable model soft particles of the core-shell type are situated between ultrasoft stars and hard spheres, and the wellknown star pair interaction potential is not appropriate to describe them. Instead, we have found that an effective brush interaction potential provides very satisfactory agreement between experiments and simulations, offering insights into the interplay of softness and dynamics in spherical colloidal suspensions.
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