Battery electrodes are complex mesoscale systems comprised of electroactive components, conductive additives, and binders. In this report, methods for processing electrodes with dispersion of the ...components are described. To investigate the degree of material dispersion, a spin-coating technique was adopted to provide a thin, uniform layer that enabled observation of the morphology. Distinct differences in the distribution profile of the electrode components arising from individual materials physical affinities were readily identified. Hansen solubility parameter (HSP) analysis revealed pertinent surface interactions associated with materials dispersivity. Further studies demonstrated that HSPs can provide an effective strategy to identify surface modification approaches for improved dispersions of battery electrode materials. Specifically, introduction of surfactantlike functionality such as oleic acid (OA) capping and P3HT-conjugated polymer wrapping on the surface of nanomaterials significantly enhanced material dispersity over the composite electrode. The approach to the surface treatment on the basis of HSP study can facilitate design of composite electrodes with uniformly dispersed morphology and may contribute to enhancing their electrical and electrochemical behaviors. The conductivity of the composites and their electrochemical performance was also characterized. In conclusion, the study illustrates the importance of considering electronic conductivity, electron transfer, and ion transport in the design of environments incorporating active nanomaterials.
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IJS, KILJ, NUK, PNG, UL, UM
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•One-pot co-precipitation is described for silver ferrite/maghemite composite preparation.•One-pot Ag0.2FeO1.6 delivers an energy density ∼2× higher than the mechanical ...mixture.•Non-stoichiometric, low temperature, one-pot synthesis may translate well to industrial scales.
A series of silver ferrite/maghemite composite materials (AgxFeOy, where AgxFeOy=composites of xAgFeO2+(1−x)/2 γ-Fe2O3 and y=2−(1−x)/2) have been prepared via a non-stoichiometric, one-pot co-precipitation strategy. The impact of a one-pot composite preparation on electrochemistry was determined by comparison to a mechanical mixture of nanocrystalline AgFeO2 and γ-Fe2O3 powders, which were combined to afford an overall composition of Ag0.2FeO1.6. Notably, following 30 discharge-charge cycles, the one-pot Ag0.2FeO1.6 composite delivers an energy density (156mWh/g) profoundly higher than the mechanical mixture Ag0.2FeO1.6 (67mWh/g). AgxFeOy composites with the lowest Ag (x) content and smallest crystallite size, Ag0.2FeO1.6, deliver twice the discharge energy density (169mWh/g) of stoichiometric AgFeO2 with no maghemite component and exhibited good capacity retention over 50 cycles. The notable electrochemistry of one-pot AgxFeOy composites may involve reduced AgFeO2 and γ-Fe2O3 aggregate sizes and a concomitant increase in AgFeO2/γ-Fe2O3 crystallite contact not achievable through mechanical mixing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In situ
,
in operando
characterization of electrochemical cells can provide insight into the complex discharge chemistries of batteries which may not be available with destructive methods. In this ...study,
in situ
energy-dispersive X-ray spectroscopy (EDXRD) measurements are conducted for the first time on active lithium/silver vanadium diphosphate, Li/Ag
2
VP
2
O
8
, electrochemical cells at several depths of discharge allowing depth profiling analysis of the reduction process. This technique enables non-destructive,
in operando
imaging of the reduction process within a battery electrode over a millimeter scale interrogation area with micron scale resolution. The discharge of Ag
2
VP
2
O
8
progresses
via
a reduction displacement reaction forming conductive silver metal as a discharge product, a high
Z
material which can be readily detected by diffraction-based methods. The high energy X-ray capabilities of NSLS beamline X17B1 allowed spatially resolved detection of the reduction products forming conductive pathways providing insight into the discharge mechanism of Ag
2
VP
2
O
8
.
In situ
energy dispersive x-ray spectroscopy (EDXRD) measurements on active lithium/silver vanadium diphosphate, Li/Ag
2
VP
2
O
8
, electrochemical cells allowed spatial depth profiling of the reduction process with micron resolution over the entire cathode.
In situ, in operandocharacterization of electrochemical cells can provide insight into the complex discharge chemistries of batteries which may not be available with destructive methods. In this ...study, in situenergy-dispersive X-ray spectroscopy (EDXRD) measurements are conducted for the first time on active lithium/silver vanadium diphosphate, Li/Ag sub(2)VP sub(2)O sub( 8), electrochemical cells at several depths of discharge allowing depth profiling analysis of the reduction process. This technique enables non-destructive, in operandoimaging of the reduction process within a battery electrode over a millimeter scale interrogation area with micron scale resolution. The discharge of Ag sub(2)VP sub(2)O sub(8) progresses viaa reduction displacement reaction forming conductive silver metal as a discharge product, a high Zmaterial which can be readily detected by diffraction-based methods. The high energy X-ray capabilities of NSLS beamline X17B1 allowed spatially resolved detection of the reduction products forming conductive pathways providing insight into the discharge mechanism of Ag sub(2)VP sub(2)O sub(8).
The novel use of heat-treatment in flowing Ar to systematically affect particle and crystallite dimensions of synthetic graphite LK-702 is reported. Samples were characterized by percent mass loss, ...X-ray powder diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface area, and methylene blue adsorption surface area measurements. The treated graphites were studied as possible electrode materials for Li-ion cells. The BET and methylene blue surface areas increased for treatment times up to 48 h, then remained constant. For times up to 48 h, At treatment was demonstrated to break apart larger graphite particles, narrowing the particle size distribution. The irreversible capacity of the graphite decreased substantially with increased Ar treatment time, while the reversible capacity remained unchanged.
Fe3O4 nanoparticles (NPs) with an average size of 8-10 nm and a loading ratio of 50 wt% have been successfully attached onto the external surfaces of multi-walled carbon nanotubes (MWNTs) by means of ...three different preparative approaches, namely a sonication method, a covalent attachment protocol, as well as a non-covalent π-π interaction strategy. Specifically, the Fe3O4 NPs associated with the sonication method lie directly on the outer surfaces of the MWNTs. Particles covalently attached onto the MWNTs formed amide chemical bonds through the mediation of the amorphous (3-aminopropyl) triethoxysilane (APTES) linker. Finally, particles were anchored non-covalently onto the underlying conjugated MWNTs via an aromatic 4-mercaptobenzoic acid (4-MBA) linker. Both structural and electrochemical characterization protocols have been used to systematically correlate the electrode performance with the corresponding attachment strategies. Fe3O4-MWNT composites generated by the π-π interaction strategy delivered 813, 768, 729, 796, 630, 580, 522, and 762 mAh/g under rates of 200, 400, 800, 100, 1200, 1600, 2000, and 100 mA/g, with 72% retention between cycles 2 and 80, demonstrating both higher capacity and better cycling stability as compared with analogues derived from the physical sonication as well as covalent attachment strategies. This finding may be attributed to the enhanced charge and ion transport coupled with retention of physical contact with the underlying MWNTs after a large volume change during cycling. Our collective results suggest that the non-covalent π-π attachment modality is a more effective preparative strategy for enhancing the performance of MWNT-Fe3O4 composite electrodes after a full discharge process.
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