A photo-rechargeable smart textile was able to constantly deliver electric power for 10 min at 0.... more A photo-rechargeable smart textile was able to constantly deliver electric power for 10 min at 0.1 mA after being charged for 1 min under the standard 1-sun condition. It can also work normally under twisted and watery circumstances, and hold stored energy for over 60 days without significant voltage loss. The photo-rechargeable fabric was demonstrated to power a body area sensor network for personalized healthcare.
Inferior charge transport in insulating and bulk discharge products is one of the main factors re... more Inferior charge transport in insulating and bulk discharge products is one of the main factors resulting in poor cycling stability of lithium-oxygen batteries with high overpotential and large capacity decay. Here we report a two-step oxygen reduction approach by pre-depositing a potassium carbonate layer on the cathode surface in a potassium-oxygen battery to direct the growth of defective film-like discharge products in the successive cycling of lithium-oxygen batteries. The formation of defective film with improved charge transport and large contact area with a catalyst plays a critical role in the facile decomposition of discharge products and the sustained stability of the battery. Multistaged discharge constructing lithium peroxide-based heterostructure with band discontinuities and a relatively low lithium diffusion barrier may be responsible for the growth of defective film-like discharge products. This strategy offers a promising route for future development of cathode catalysts that can be used to extend the cycling life of lithium-oxygen batteries.
Keywords: Layered double oxides confined single atoms interlayered confinement Li-CO 2 battery lo... more Keywords: Layered double oxides confined single atoms interlayered confinement Li-CO 2 battery low overpotential A B S T R A C T The operation of Li-air batteries is currently limited to O 2 instead of air, mainly attributed to the formation of wide-bandgap insulator Li 2 CO 3 during discharge caused by the presence of CO 2 in air. A thorough understanding of the decomposition mechanism of Li 2 CO 3 is crucial but challenging owing to the existence of side reactions induced by the large charge overpotential. Here, monodisperse RuO 2 supported on layered double oxide is utilized as cathodes for Li-CO 2 batteries with ultralow charge overpotential (only ~0.4 V larger than equilibrium potential, 2.80 V). The reversibility of Li-CO 2 battery is mainly attributed to the decomposition of Li 2 CO 3 upon charging instead of the degradation of the electrolyte. These results advance the fundamental understanding of the carbonate decomposition in Li-CO 2 batteries and offer a promising route to utilizing agglomeration of layered-confined monodisperse catalyst to enlarge the layered spacings of layered support with complementary catalytic activity for Li-CO 2 batteries with high energy efficiency and superior cycle life.
Inferior charge transport in discharge products is one of the main factors restricting the techno... more Inferior charge transport in discharge products is one of the main factors restricting the technological potential of lithium-oxygen batteries. Here, we propose a strategy to enhance charge transport in discharge products by surface engineering of cathode catalysts with donor and acceptor sites to improve solid-solid interfacial electron transfer properties between catalysts and discharge products. Free-standing layered double oxides loaded with pyrolyzed sodium poly(aminobenzenesulfonate)-derived sulfur-doped carbon nanosheets and carbon nanosheets with sulfoxide groups are synthesized and utilized to investigate donor and acceptor sites effect on the performance of lithium-oxygen batteries. The free-standing cathode with hybrid donor and acceptor sites is capable of operation in oxygen with distinct (dis)charge plateau and superior cycling stability (over 60 cycles at a fixed capacity of 0.53 mAh cm À2). The superior properties are attributed to the enhanced charge transport in lithium peroxide by the formation of hole polarons/Li þ vacancies on acceptor sites and electron polarons/disordered lithium peroxide phase on donor sites. This work provides a promising route to enhance defective charge transport in discharge products by optimization of donor and acceptor sites on cathode catalysts for high-performance lithium-oxygen batteries.
The development of insertion materials with reduced size offers a promising strategy to increase ... more The development of insertion materials with reduced size offers a promising strategy to increase the energy storage capabilities of K-ion batteries for its extended solid solution composition range. Theoretically, the insertion of cations will induce the volume expansion of the intercalated region with dilatational strain and the compressive stress on the matrix unintercalated portions. The strain-accommodating misfits or dislocations in an ideal solid-solution intercalated compound will retain coherent interfaces and permit “facile phase propagation” to reduce accumulated strains upon insertion. However, to our knowledge, evidence of this “facile phase propagation and dislocation” in solid-solution intercalation compounds has not been confirmed by direct visualization owing to subtle lattice misfit in coherent interface and other release of strain, such as lattice distortion, loss of coherency and grain coarsening. The utilization of stable tunnel-like K2Ti6O13 upon potassiation with large lattice stains is expected to observe the “facile” phase transformation with elastic misfits. In this work, K2Ti6O13 nanowires with different diameters were utilized to explore the size-dependent solid-solution behavior in K-ion battery. K2Ti6O13 nanowires with smaller diameter could deliver a larger reversible depotassiated capacity, which originated mainly from the decrease of the incoherent interface upon potassiation. Maintaining coherence interface within an individual particle upon (de)insertion of K+ is favorable for utilization of coherency strain energy for K-ion batteries with improved performance. In experiment, the presence of intragranular particles was found to be in potassiated large-size K2Ti6O13 fibers. Further preparation of different sizes of fibers for potassiation and analyses of the potassiated sites by DFT calculation revealed the size-dependent solid-solution behavior for intercalated compounds. The insertion materials below critical size to retain coherent interface is proposed to reduce the capacity decay.
Heteroatoms functionalized porous carbon has long been regarded as a
promising electrode material... more Heteroatoms functionalized porous carbon has long been regarded as a promising electrode material to construct high-performance capacitive energy storage devices. However, due to lacking an in-depth understanding of the ion-sorption dynamics, the development of this field is seriously limited. Herein, the component and structure controllable N, O and Cl co-doped bimodal (meso-micro) porous carbons were prepared, and further used as the investigated object for exploring the intrinsic ion-sorption dynamics, which is the root of the enhanced electrochemical response in capacitive energy storage devices. Voltammetry response analysis is employed to quantify the contributions to charge storage from electrostatic adsorption effect (electrical double-layer capacitance) and highly reversible redox process (pseudocapacitance). The existence of electronic capacitance enables a positive correlation between surface capacitance and the ratio of micropores. Besides, an electron-dependent correlation between electroactive functional groups and redox reaction induced capacitance is also explored. This work will advance the capacitive energy storage field by presenting a clear understanding of the ion-sorption dynamics in functionalized porous carbons.
A novel binder-free electrode for lithium–oxygen batteries has been prepared by electrodepositing... more A novel binder-free electrode for lithium–oxygen batteries has been prepared by electrodepositing a Co 3 O 4 layer onto a pretreated TiO 2 fiber mesh, formed on nickel foam by an electrospinning method. The Co 3 O 4 depositing layer is composed of Co 3 O 4 nanoflakes, forming a uniform flower-like porous structure. The Co 3 O 4 nanoflakes within the depositing layer provide a large amount of catalytic active sites for oxygen evolution and reduction reactions. The three-dimensional porous network of the Co 3 O 4 depositing layer can not only facilitate the transportation of ions and electrolyte within the electrode, but also provide plenty of space to accommodate Li 2 O 2 species formed during the discharge process. The Co 3 O 4 spheres embedded in the TiO 2 fiber mesh, formed by the treatment of a suspension of cobalt-ammine precipitate, function as anchors to prevent the detachment of the Co 3 O 4 layer from the current collector, resulting in excellent structural and cycling stability. Only a slight specific capacity decay is observed at full discharge/charge after 80 cycles. This work demonstrates the important factors in the preparation of binder-free cathodes for high performance lithium–oxygen batteries.
Lithium–oxygen batteries with an exceptionally high theoretical energy density
have triggered wor... more Lithium–oxygen batteries with an exceptionally high theoretical energy density have triggered worldwide interest in energy storage system. The research focus of lithium–oxygen batteries lies in the development of catalytic materials with excellent cycling stability and high bifunctional catalytic activity in oxygen reduction and oxygen evolution reactions. Here, a hierarchically porous fl ower-like cobalt–titanium layered double oxide on nickel foam with interca- lated anions of bistrifl uoromethane sulfonamide (TFSI) is designed and pre- pared. When used as a binder-free cathode for lithium–oxygen batteries, this material exhibits low polarization (initial polarization of 0.45 V) and superior cycling stability (80 cycles at a current density of 100 mA g −1 at full discharge/ charge). The high electrochemical performance of the cathode material is attributed to the good dispersion of binary elements in its host layer and good compatibility with lithium bistrifl uoromethane sulfonamide electrolyte induced by intercalated guest anions of TFSI within its interlayer. This work provides a novel strategy for the fabrication of binder-free cathodes based on layered double oxides for high-performance lithium–oxygen batteries.
Cathode design is indispensable for building Li-O 2 batteries with long cycle
life. A composite o... more Cathode design is indispensable for building Li-O 2 batteries with long cycle life. A composite of carbon-wrapped Mo 2 C nanoparticles and carbon nano- tubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo 2 C nanoparticles with well-controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/ OER) catalyst. The carbon coating can prevent the aggregation of the Mo 2 C nanoparticles. The even distribution of Mo 2 C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li-O 2 batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g −1 and a low average charge voltage of ≈4.0 V at 200 mA g −1 . With a cutoff capacity of 1000 mAh g −1 , the Li-O 2 bat- teries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo 2 C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li-O 2 batteries.
Free-standing macroporous air electrodes with enhanced interfacial contact, rapid mass transport,... more Free-standing macroporous air electrodes with enhanced interfacial contact, rapid mass transport, and tailored deposition space for large amounts of Li 2 O 2 are essential for improving the rate performance of Li-O 2 batteries. An ordered mesoporous carbon membrane with continuous&&ok?&& macroporous channels was prepared by inversely topological transformation from ZnO nanorod array. Utilized as a free-standing air cathode for Li-O 2 battery, the hierarchically porous carbon membrane shows superior rate performance. However, the increased cross-sectional area of the continuous macropores on the cathode surface leads to a kinetic over-potential with large voltage hysteresis and linear voltage variation against Butler–Volmer behavior. The kinetics were investigated based on the rate-determining step of second electron transfer accompanied by migration of Li + in solid or quasi-solid intermediates. These discoveries shed light on the design of the air cathode for Li-O 2 batteries with high-rate performance.
A photo-rechargeable smart textile was able to constantly deliver electric power for 10 min at 0.... more A photo-rechargeable smart textile was able to constantly deliver electric power for 10 min at 0.1 mA after being charged for 1 min under the standard 1-sun condition. It can also work normally under twisted and watery circumstances, and hold stored energy for over 60 days without significant voltage loss. The photo-rechargeable fabric was demonstrated to power a body area sensor network for personalized healthcare.
Inferior charge transport in insulating and bulk discharge products is one of the main factors re... more Inferior charge transport in insulating and bulk discharge products is one of the main factors resulting in poor cycling stability of lithium-oxygen batteries with high overpotential and large capacity decay. Here we report a two-step oxygen reduction approach by pre-depositing a potassium carbonate layer on the cathode surface in a potassium-oxygen battery to direct the growth of defective film-like discharge products in the successive cycling of lithium-oxygen batteries. The formation of defective film with improved charge transport and large contact area with a catalyst plays a critical role in the facile decomposition of discharge products and the sustained stability of the battery. Multistaged discharge constructing lithium peroxide-based heterostructure with band discontinuities and a relatively low lithium diffusion barrier may be responsible for the growth of defective film-like discharge products. This strategy offers a promising route for future development of cathode catalysts that can be used to extend the cycling life of lithium-oxygen batteries.
Keywords: Layered double oxides confined single atoms interlayered confinement Li-CO 2 battery lo... more Keywords: Layered double oxides confined single atoms interlayered confinement Li-CO 2 battery low overpotential A B S T R A C T The operation of Li-air batteries is currently limited to O 2 instead of air, mainly attributed to the formation of wide-bandgap insulator Li 2 CO 3 during discharge caused by the presence of CO 2 in air. A thorough understanding of the decomposition mechanism of Li 2 CO 3 is crucial but challenging owing to the existence of side reactions induced by the large charge overpotential. Here, monodisperse RuO 2 supported on layered double oxide is utilized as cathodes for Li-CO 2 batteries with ultralow charge overpotential (only ~0.4 V larger than equilibrium potential, 2.80 V). The reversibility of Li-CO 2 battery is mainly attributed to the decomposition of Li 2 CO 3 upon charging instead of the degradation of the electrolyte. These results advance the fundamental understanding of the carbonate decomposition in Li-CO 2 batteries and offer a promising route to utilizing agglomeration of layered-confined monodisperse catalyst to enlarge the layered spacings of layered support with complementary catalytic activity for Li-CO 2 batteries with high energy efficiency and superior cycle life.
Inferior charge transport in discharge products is one of the main factors restricting the techno... more Inferior charge transport in discharge products is one of the main factors restricting the technological potential of lithium-oxygen batteries. Here, we propose a strategy to enhance charge transport in discharge products by surface engineering of cathode catalysts with donor and acceptor sites to improve solid-solid interfacial electron transfer properties between catalysts and discharge products. Free-standing layered double oxides loaded with pyrolyzed sodium poly(aminobenzenesulfonate)-derived sulfur-doped carbon nanosheets and carbon nanosheets with sulfoxide groups are synthesized and utilized to investigate donor and acceptor sites effect on the performance of lithium-oxygen batteries. The free-standing cathode with hybrid donor and acceptor sites is capable of operation in oxygen with distinct (dis)charge plateau and superior cycling stability (over 60 cycles at a fixed capacity of 0.53 mAh cm À2). The superior properties are attributed to the enhanced charge transport in lithium peroxide by the formation of hole polarons/Li þ vacancies on acceptor sites and electron polarons/disordered lithium peroxide phase on donor sites. This work provides a promising route to enhance defective charge transport in discharge products by optimization of donor and acceptor sites on cathode catalysts for high-performance lithium-oxygen batteries.
The development of insertion materials with reduced size offers a promising strategy to increase ... more The development of insertion materials with reduced size offers a promising strategy to increase the energy storage capabilities of K-ion batteries for its extended solid solution composition range. Theoretically, the insertion of cations will induce the volume expansion of the intercalated region with dilatational strain and the compressive stress on the matrix unintercalated portions. The strain-accommodating misfits or dislocations in an ideal solid-solution intercalated compound will retain coherent interfaces and permit “facile phase propagation” to reduce accumulated strains upon insertion. However, to our knowledge, evidence of this “facile phase propagation and dislocation” in solid-solution intercalation compounds has not been confirmed by direct visualization owing to subtle lattice misfit in coherent interface and other release of strain, such as lattice distortion, loss of coherency and grain coarsening. The utilization of stable tunnel-like K2Ti6O13 upon potassiation with large lattice stains is expected to observe the “facile” phase transformation with elastic misfits. In this work, K2Ti6O13 nanowires with different diameters were utilized to explore the size-dependent solid-solution behavior in K-ion battery. K2Ti6O13 nanowires with smaller diameter could deliver a larger reversible depotassiated capacity, which originated mainly from the decrease of the incoherent interface upon potassiation. Maintaining coherence interface within an individual particle upon (de)insertion of K+ is favorable for utilization of coherency strain energy for K-ion batteries with improved performance. In experiment, the presence of intragranular particles was found to be in potassiated large-size K2Ti6O13 fibers. Further preparation of different sizes of fibers for potassiation and analyses of the potassiated sites by DFT calculation revealed the size-dependent solid-solution behavior for intercalated compounds. The insertion materials below critical size to retain coherent interface is proposed to reduce the capacity decay.
Heteroatoms functionalized porous carbon has long been regarded as a
promising electrode material... more Heteroatoms functionalized porous carbon has long been regarded as a promising electrode material to construct high-performance capacitive energy storage devices. However, due to lacking an in-depth understanding of the ion-sorption dynamics, the development of this field is seriously limited. Herein, the component and structure controllable N, O and Cl co-doped bimodal (meso-micro) porous carbons were prepared, and further used as the investigated object for exploring the intrinsic ion-sorption dynamics, which is the root of the enhanced electrochemical response in capacitive energy storage devices. Voltammetry response analysis is employed to quantify the contributions to charge storage from electrostatic adsorption effect (electrical double-layer capacitance) and highly reversible redox process (pseudocapacitance). The existence of electronic capacitance enables a positive correlation between surface capacitance and the ratio of micropores. Besides, an electron-dependent correlation between electroactive functional groups and redox reaction induced capacitance is also explored. This work will advance the capacitive energy storage field by presenting a clear understanding of the ion-sorption dynamics in functionalized porous carbons.
A novel binder-free electrode for lithium–oxygen batteries has been prepared by electrodepositing... more A novel binder-free electrode for lithium–oxygen batteries has been prepared by electrodepositing a Co 3 O 4 layer onto a pretreated TiO 2 fiber mesh, formed on nickel foam by an electrospinning method. The Co 3 O 4 depositing layer is composed of Co 3 O 4 nanoflakes, forming a uniform flower-like porous structure. The Co 3 O 4 nanoflakes within the depositing layer provide a large amount of catalytic active sites for oxygen evolution and reduction reactions. The three-dimensional porous network of the Co 3 O 4 depositing layer can not only facilitate the transportation of ions and electrolyte within the electrode, but also provide plenty of space to accommodate Li 2 O 2 species formed during the discharge process. The Co 3 O 4 spheres embedded in the TiO 2 fiber mesh, formed by the treatment of a suspension of cobalt-ammine precipitate, function as anchors to prevent the detachment of the Co 3 O 4 layer from the current collector, resulting in excellent structural and cycling stability. Only a slight specific capacity decay is observed at full discharge/charge after 80 cycles. This work demonstrates the important factors in the preparation of binder-free cathodes for high performance lithium–oxygen batteries.
Lithium–oxygen batteries with an exceptionally high theoretical energy density
have triggered wor... more Lithium–oxygen batteries with an exceptionally high theoretical energy density have triggered worldwide interest in energy storage system. The research focus of lithium–oxygen batteries lies in the development of catalytic materials with excellent cycling stability and high bifunctional catalytic activity in oxygen reduction and oxygen evolution reactions. Here, a hierarchically porous fl ower-like cobalt–titanium layered double oxide on nickel foam with interca- lated anions of bistrifl uoromethane sulfonamide (TFSI) is designed and pre- pared. When used as a binder-free cathode for lithium–oxygen batteries, this material exhibits low polarization (initial polarization of 0.45 V) and superior cycling stability (80 cycles at a current density of 100 mA g −1 at full discharge/ charge). The high electrochemical performance of the cathode material is attributed to the good dispersion of binary elements in its host layer and good compatibility with lithium bistrifl uoromethane sulfonamide electrolyte induced by intercalated guest anions of TFSI within its interlayer. This work provides a novel strategy for the fabrication of binder-free cathodes based on layered double oxides for high-performance lithium–oxygen batteries.
Cathode design is indispensable for building Li-O 2 batteries with long cycle
life. A composite o... more Cathode design is indispensable for building Li-O 2 batteries with long cycle life. A composite of carbon-wrapped Mo 2 C nanoparticles and carbon nano- tubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel composed of ammonium heptamolybdate tetrahydrate and hydroquinone resin. The Mo 2 C nanoparticles with well-controlled particle size act as a highly active oxygen reduction reactions/oxygen evolution reactions (ORR/ OER) catalyst. The carbon coating can prevent the aggregation of the Mo 2 C nanoparticles. The even distribution of Mo 2 C nanoparticles results in the homogenous formation of discharge products. The skeleton of porous carbon with carbon nanotubes protrudes from the composite, resulting in extra voids when applied as a cathode for Li-O 2 batteries. The batteries deliver a high discharge capacity of ≈10 400 mAh g −1 and a low average charge voltage of ≈4.0 V at 200 mA g −1 . With a cutoff capacity of 1000 mAh g −1 , the Li-O 2 bat- teries exhibit excellent charge–discharge cycling stability for over 300 cycles. The average potential polarization of discharge/charge gaps is only ≈0.9 V, demonstrating the high ORR and OER activities of these Mo 2 C nanoparticles. The excellent cycling stability and low potential polarization provide new insights into the design of highly reversible and efficient cathode materials for Li-O 2 batteries.
Free-standing macroporous air electrodes with enhanced interfacial contact, rapid mass transport,... more Free-standing macroporous air electrodes with enhanced interfacial contact, rapid mass transport, and tailored deposition space for large amounts of Li 2 O 2 are essential for improving the rate performance of Li-O 2 batteries. An ordered mesoporous carbon membrane with continuous&&ok?&& macroporous channels was prepared by inversely topological transformation from ZnO nanorod array. Utilized as a free-standing air cathode for Li-O 2 battery, the hierarchically porous carbon membrane shows superior rate performance. However, the increased cross-sectional area of the continuous macropores on the cathode surface leads to a kinetic over-potential with large voltage hysteresis and linear voltage variation against Butler–Volmer behavior. The kinetics were investigated based on the rate-determining step of second electron transfer accompanied by migration of Li + in solid or quasi-solid intermediates. These discoveries shed light on the design of the air cathode for Li-O 2 batteries with high-rate performance.
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Papers by Shumao Xu
promising electrode material to construct high-performance capacitive energy storage
devices. However, due to lacking an in-depth understanding of the ion-sorption
dynamics, the development of this field is seriously limited. Herein, the component and
structure controllable N, O and Cl co-doped bimodal (meso-micro) porous carbons
were prepared, and further used as the investigated object for exploring the intrinsic
ion-sorption dynamics, which is the root of the enhanced electrochemical response in
capacitive energy storage devices. Voltammetry response analysis is employed to
quantify the contributions to charge storage from electrostatic adsorption effect
(electrical double-layer capacitance) and highly reversible redox process
(pseudocapacitance). The existence of electronic capacitance enables a positive
correlation between surface capacitance and the ratio of micropores. Besides, an
electron-dependent correlation between electroactive functional groups and redox
reaction induced capacitance is also explored. This work will advance the capacitive
energy storage field by presenting a clear understanding of the ion-sorption dynamics
in functionalized porous carbons.
have triggered worldwide interest in energy storage system. The research
focus of lithium–oxygen batteries lies in the development of catalytic materials
with excellent cycling stability and high bifunctional catalytic activity in oxygen
reduction and oxygen evolution reactions. Here, a hierarchically porous
fl ower-like cobalt–titanium layered double oxide on nickel foam with interca-
lated anions of bistrifl uoromethane sulfonamide (TFSI) is designed and pre-
pared. When used as a binder-free cathode for lithium–oxygen batteries, this
material exhibits low polarization (initial polarization of 0.45 V) and superior
cycling stability (80 cycles at a current density of 100 mA g
−1 at full discharge/
charge). The high electrochemical performance of the cathode material is
attributed to the good dispersion of binary elements in its host layer and
good compatibility with lithium bistrifl uoromethane sulfonamide electrolyte
induced by intercalated guest anions of TFSI within its interlayer. This work
provides a novel strategy for the fabrication of binder-free cathodes based on
layered double oxides for high-performance lithium–oxygen batteries.
life. A composite of carbon-wrapped Mo 2 C nanoparticles and carbon nano-
tubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel
composed of ammonium heptamolybdate tetrahydrate and hydroquinone
resin. The Mo 2 C nanoparticles with well-controlled particle size act as a
highly active oxygen reduction reactions/oxygen evolution reactions (ORR/
OER) catalyst. The carbon coating can prevent the aggregation of the Mo 2 C
nanoparticles. The even distribution of Mo 2 C nanoparticles results in the
homogenous formation of discharge products. The skeleton of porous carbon
with carbon nanotubes protrudes from the composite, resulting in extra voids
when applied as a cathode for Li-O 2 batteries. The batteries deliver a high
discharge capacity of ≈10 400 mAh g −1 and a low average charge voltage of
≈4.0 V at 200 mA g −1 . With a cutoff capacity of 1000 mAh g −1 , the Li-O 2 bat-
teries exhibit excellent charge–discharge cycling stability for over 300 cycles.
The average potential polarization of discharge/charge gaps is only ≈0.9 V,
demonstrating the high ORR and OER activities of these Mo 2 C nanoparticles.
The excellent cycling stability and low potential polarization provide new
insights into the design of highly reversible and efficient cathode materials for
Li-O 2 batteries.
promising electrode material to construct high-performance capacitive energy storage
devices. However, due to lacking an in-depth understanding of the ion-sorption
dynamics, the development of this field is seriously limited. Herein, the component and
structure controllable N, O and Cl co-doped bimodal (meso-micro) porous carbons
were prepared, and further used as the investigated object for exploring the intrinsic
ion-sorption dynamics, which is the root of the enhanced electrochemical response in
capacitive energy storage devices. Voltammetry response analysis is employed to
quantify the contributions to charge storage from electrostatic adsorption effect
(electrical double-layer capacitance) and highly reversible redox process
(pseudocapacitance). The existence of electronic capacitance enables a positive
correlation between surface capacitance and the ratio of micropores. Besides, an
electron-dependent correlation between electroactive functional groups and redox
reaction induced capacitance is also explored. This work will advance the capacitive
energy storage field by presenting a clear understanding of the ion-sorption dynamics
in functionalized porous carbons.
have triggered worldwide interest in energy storage system. The research
focus of lithium–oxygen batteries lies in the development of catalytic materials
with excellent cycling stability and high bifunctional catalytic activity in oxygen
reduction and oxygen evolution reactions. Here, a hierarchically porous
fl ower-like cobalt–titanium layered double oxide on nickel foam with interca-
lated anions of bistrifl uoromethane sulfonamide (TFSI) is designed and pre-
pared. When used as a binder-free cathode for lithium–oxygen batteries, this
material exhibits low polarization (initial polarization of 0.45 V) and superior
cycling stability (80 cycles at a current density of 100 mA g
−1 at full discharge/
charge). The high electrochemical performance of the cathode material is
attributed to the good dispersion of binary elements in its host layer and
good compatibility with lithium bistrifl uoromethane sulfonamide electrolyte
induced by intercalated guest anions of TFSI within its interlayer. This work
provides a novel strategy for the fabrication of binder-free cathodes based on
layered double oxides for high-performance lithium–oxygen batteries.
life. A composite of carbon-wrapped Mo 2 C nanoparticles and carbon nano-
tubes is prepared on Ni foam by direct hydrolysis and carbonization of a gel
composed of ammonium heptamolybdate tetrahydrate and hydroquinone
resin. The Mo 2 C nanoparticles with well-controlled particle size act as a
highly active oxygen reduction reactions/oxygen evolution reactions (ORR/
OER) catalyst. The carbon coating can prevent the aggregation of the Mo 2 C
nanoparticles. The even distribution of Mo 2 C nanoparticles results in the
homogenous formation of discharge products. The skeleton of porous carbon
with carbon nanotubes protrudes from the composite, resulting in extra voids
when applied as a cathode for Li-O 2 batteries. The batteries deliver a high
discharge capacity of ≈10 400 mAh g −1 and a low average charge voltage of
≈4.0 V at 200 mA g −1 . With a cutoff capacity of 1000 mAh g −1 , the Li-O 2 bat-
teries exhibit excellent charge–discharge cycling stability for over 300 cycles.
The average potential polarization of discharge/charge gaps is only ≈0.9 V,
demonstrating the high ORR and OER activities of these Mo 2 C nanoparticles.
The excellent cycling stability and low potential polarization provide new
insights into the design of highly reversible and efficient cathode materials for
Li-O 2 batteries.