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Advanced electrode materials have been intensively explored for next-generation lithium-ion batteries (LIBs), and great progresses have been achieved for many potential candidates at the lab-scale. To realize the commercialization of these materials, industrially-viable synthetic approaches are urgently needed. Spray pyrolysis (SP), which is highly scalable and compatible with on-line continuous production processes, offers great fidelity in synthesis of electrode materials with complex architectures and chemistries. In this review, motivated by the rapid advancement of the given technology in the battery area, we have summarized the recent progress on SP for preparing a great variety of anode and cathode materials of LIBs with emphasis on their unique structures generated by SP and how the structures enhanced the electrochemical performance of various electrode materials. Considering the emerging popularity of sodium-ion batteries (SIBs), recent electrode materials for SIBs produced by SP will also be discussed. Finally, the powerfulness and limitation along with future research efforts of SP on preparing electrode materials are concisely provided. Given current worldwide interests on LIBs and SIBs, we hope this review will greatly stimulate the collaborative efforts among different communities to optimize existing approaches and to develop innovative processes for preparing electrode materials. [ABSTRACT FROM AUTHOR]

A novel anode material for sodium-ion batteries consisting of 3D graphene microspheres divided into several tens of uniform nanospheres coated with few-layered MoS2 by a one-pot spray pyrolysis process is prepared. The first discharge/charge capacities of the composite microspheres are 797 and 573 mA h g−1 at a current density of 0.2 A g−1. The 600th discharge capacity of the composite microspheres at a current density of 1.5 A g−1 is 322 mA h g−1. The Coulombic efficiency during the 600 cycles is as high as 99.98%. The outstanding Na ion storage properties of the 3D MoS2-graphene composite microspheres may be attributed to the reduced stacking of the MoS2 layers and to the 3D structure of the porous graphene microspheres. The reduced stacking of the MoS2 layers relaxes the strain and lowers the barrier for Na+ insertion. The empty nanospheres of the graphene offer voids for volume expansion and pathways for fast electron transfer during repeated cycling. [ABSTRACT FROM AUTHOR]

Composite powders of the configuration Si@carbon@void@graphene were prepared by a one-step spray pyrolysis process, by adding polyvinylpyrrolidone (PVP) to a precursor solution containing graphene oxide (GO) sheets and silicon nanoparticles (NPs). Morphological analysis indicates that the individual Si NPs are coated with amorphous carbon and encapsulated in a micrometer-sized graphene ball structure that offers a large amount of buffer space. The addition of PVP improves the stability of the colloidal spray solution containing the GO sheets and the Si NPs. Consequently, the prepared Si@C@void@graphene composite powders have a relatively more uniform morphology than the Si@void@graphene composite powders prepared from the spray solution without PVP. The first charge and discharge capacities of the Si@C@void@graphene electrode measured at 0.1 A g−1 are as high as 3102 and 2215 mA h g−1, respectively. With an increase in the current rate from 0.5 to 11 A g−1, 46 % of the original capacity (i.e., 2134 mA h g−1) is maintained. After 500 cycles at a high rate of 7 A g−1, the Si@C@void@graphene electrode shows 84 % capacity retention and 99.8 % of the average Coulombic efficiency. The superior cycling and rate capabilities of the prepared Si@C@void@graphene electrode could be attributed to the uniform carbon coating of the Si NPs and the graphene ball structure, which facilitates efficient diffusion of Li ions and prevents the penetration of electrolyte into graphene ball during cycling. [ABSTRACT FROM AUTHOR]

Macroporous Fe3O4/carbon composite and core-shell Fe3O4@carbon composite microspheres have been prepared by means of one-pot spray pyrolysis. The addition of polystyrene (PS) nanobeads to a spray solution containing an iron salt and poly(vinylpyrrolidone) (PVP) led to macroporous Fe3O4/carbon composite microspheres, the carbon and iron components of which are uniformly distributed over the entire composite microsphere. The pore-size distribution curve for the macroporous Fe3O4/carbon composite shows distinct peaks at around 10 and 80 nm. An electrode prepared from the macroporous Fe3O4/carbon composite microspheres showed better cycling and rate performances than an electrode formed from core-shell Fe3O4@carbon composite microspheres. The initial discharge and charge capacities of the macroporous Fe3O4/carbon composite microsphere electrode were determined to be 1258 and 908 mA h g−1 at 2 A g−1, respectively, and the corresponding initial coulombic efficiency was 72 %. The composite microsphere electrode cycled 500 times at 5 A g−1 showed a high discharge capacity of 733 mA h g−1. [ABSTRACT FROM AUTHOR]

Abstract: Graphene-MnO composite and hollow-structured MnO powders are prepared by a simple one-pot spray pyrolysis process. The graphene content in the graphene-MnO composite powder is estimated to be 10wt.%. The fine MnO crystals of size several tens of nanometers are uniformly distributed all over the graphene. The BET specific surface areas of the graphene-MnO composite and hollow-structured MnO powders are found to be 20 and 5 m2 g−1, respectively. The graphene-MnO composite powders have high initial discharge and charge capacities of 1207 and 849mA h g−1, respectively, at a current density of 500mAg−1. The initial discharge and charge capacities of the hollow-structured MnO powders are 1004 and 673mA h g−1, respectively. The discharge capacities of the graphene-MnO composite and hollow-structured MnO powders for the 130th cycle are 1313 and 701mA h g−1, respectively. [Copyright &y& Elsevier]

VO2-decorated reduced graphene balls were prepared by a one-pot spray-pyrolysis process from a colloidal spray solution of well-dispersed graphene oxide and ammonium vanadate. The graphene-VO2 composite powders prepared directly by spray pyrolysis had poor electrochemical properties. Therefore, the graphene-VO2 composite powders were transformed into a reduced graphene ball (RGB)-V2O5 (RGB) composite by post-treatment at 300 °C in an air atmosphere. The TEM and dot-mapping images showed a uniform distribution of V and C components, originating from V2O5 and graphene, consisting the composite. The graphene content of the RGB-V2O5 composite, measured by thermogravimetric analysis, was approximately 5 wt %. The initial discharge and charge capacities of RGB-V2O5 composite were 282 and 280 mA h g−1, respectively, and the corresponding Coulombic efficiency was approximately 100 %. On the other hand, the initial discharge and charge capacities of macroporous V2O5 powders were 205 and 221 mA h g−1, respectively, and the corresponding Coulombic efficiency was approximately 93 %. The RGB-V2O5 composite showed a better rate performance than the macroporous V2O5 powders. [ABSTRACT FROM AUTHOR]

A spray-pyrolysis process is introduced as an effective tool for the preparation of yolk-shell-structured materials with electrochemical properties suitable for anode materials in Li-ion batteries (LIBs). Yolk-shell-structured ZnO-Mn3O4 systems with various molar ratios of the Zn and Mn components are prepared. The yolk-shell-structured ZnO-Mn3O4 powders with a molar ratio of 1:1 of the Zn and Mn components are shown to have high capacities and good cycling performances. [ABSTRACT FROM AUTHOR]

In this study, we report the first preparation of phase-pure Co9S8 yolk-shell microspheres in a facile two-step process and their improved electrochemical properties. Yolk-shell Co3O4 precursor microspheres are initially obtained by spray pyrolysis and are subsequently transformed into Co9S8 yolk-shell microspheres by simple sulfidation in the presence of thiourea as a sulfur source at 350 °C under a reducing atmosphere. For comparison, filled Co9S8 microspheres were also prepared using the same procedure but in the absence of sucrose during the spray pyrolysis. The prepared yolk-shell Co9S8 microspheres exhibited a Brunauer-Emmett-Teller (BET) specific surface area of 18 m2 g−1 with a mean pore size of 16 nm. The yolk-shell Co9S8 microspheres have initial discharge and charge capacities of 1008 and 767 mA h g−1 at a current density of 1000 mA g−1, respectively, while the filled Co9S8 microspheres have initial discharge and charge capacities of 838 and 638 mA h g−1, respectively. After 100 cycles, the discharge capacities of the yolk-shell and filled microspheres are 634 and 434 mA h g−1, respectively, and the corresponding capacity retentions after the first cycle are 82 % and 66 %. [ABSTRACT FROM AUTHOR]

Li2TiO3–LiCrO2 cathode powders of various compositions are prepared by spray pyrolysis. Pure Li2TiO3 powder and Li2TiO3–LiCrO2 composite cathode powder have a spherical shape, nonaggregated structure, and fine sizes even after post-treatment at 700 °C under nitrogen atmosphere. The optimum post-treatment temperature to obtain composite powders with high initial discharge capacity, high coulombic efficiency, and good cycle properties is 700 °C. The initial charge capacities increase when the LiCrO2 content of the composite increase. However, the 0.55Li2TiO3–0.45LiCrO2 composite cathode powders have the highest initial discharge capacity of 203 mAh g−1, in which the capacity retention after 30 cycles is 96%. The dQ/dV curve of the first charge curve has a distinct oxidation peak at approximately 3.9 V, which corresponds to Cr oxidation. The oxidation peak shifts to a lower voltage range at approximately 3.6 V after the first cycling because an irreversible reaction takes place in the initial charge process. The composite cathode powders with low LiCrO2 content have low initial charge/discharge capacities and good cycle properties because of the stabilizing effect of high amounts of an inactive Li2TiO3 component. [ABSTRACT FROM AUTHOR]

Charging up the batteries: The preparation and electrochemical properties of the yolk–shell LiV3O8 powders (see scheme) have been described for the first time. These powders have superior rate and cycling performances as a direct result of their unique particle structure and stability during cycling. [ABSTRACT FROM AUTHOR]

The electrochemical properties of yolk-shell-structured, multi-component, transition-metal oxides have not yet been properly compared to those of hollow-structured or nanoscale powders. In this study, yolk-shell, hollow, and single-crystalline ZnCo2O4 powders with uniform compositions are prepared by using simple gas-phase reaction methods. Double-shelled ZnCo2O4 yolk-shell powder is prepared directly from the spray solution by using spray pyrolysis. Single-crystalline ZnCo2O4 nanopowder is prepared by means of flame spray pyrolysis. The yolk-shell ZnCo2O4 powder shows higher charge and discharge capacities than the hollow and single-crystalline powders. The yolk-shell, hollow, and single-crystalline ZnCo2O4 powders deliver discharge capacities of 753, 586, and 206 mAh g−1, respectively, after 200 cycles at a charge/discharge rate of 3 A g−1, and the corresponding capacity retentions measured after the first cycle are 99, 74, and 27 %, respectively. The yolk-shell ZnCo2O4 powders are structurally stable during cycling and have good electrochemical properties even at high current densities. [ABSTRACT FROM AUTHOR]

Abstract: The preparation of precursors of BaTiO3 nanopowders with various amounts of Ag by spray pyrolysis is reported. The precursor powders obtained with hollow and thin-wall particles are composed of uniformly dispersed Ba, Ti, and Ag components. After post-treatment and a simple milling process, the precursor powders, irrespective of the amount of Ag, are transformed into Ag–BaTiO3 composite nanoparticles. The mean particle size of the Ag (10mol%)–BaTiO3 powders is 142nm. BaTiO3 pellets containing Ag exhibit dense structures even at a low sintering temperature of 1000°C. BaTiO3 pellets with 10mol% Ag show the highest dielectric constant of 2950, as opposed to the pure BaTiO3 pellets (without Ag), whose dielectric constant is 1827. [Copyright &y& Elsevier]

Abstract: Nanometer-sized 0.6Li2MnO3·0.4LiNi0.5Mn0.5O2 composite cathode powders are prepared directly by high-temperature flame spray pyrolysis. The precursor powders and the powders post-treated at 800°C exhibit mixed-layered crystal structures comprising layered Li2MnO3 and layered LiNi0.5Mn0.5O2 phases. The discharge capacity of the precursor powders decreased from 193mAhg−1 to 96mAhg−1 by the 9th cycle, corresponding to a capacity retention of 49.7%. Post-treatment at 800°C increases the capacity retention of the post-treated composite powders to 94.6% after 50 cycles, corresponding to a decrease in the discharge capacity from 225 to 213mAhg−1. The post-treated composite powders that contain a high amount of the Li2MnO3 phase have a high initial discharge capacity and good cyclability. [Copyright &y& Elsevier]

Abstract: Li2O–2B2O3 glass-modified LiMn2O4 cathode powders are prepared using spray pyrolysis. The powders with 1 and 5wt% glass material have a spherical shape, dense structure, and large grain size. The BET surface areas of LiMn2O4 powders with 0 and 1wt% glass material are 15.0 and 5.9m2 g−1, and their mean crystallite sizes are 29 and 49nm. The lithium boron oxide (LBO) glass material improves the cycle properties as well as the initial discharge capacities of the LiMn2O4 powders at a constant current density of 1C. The discharge capacity of LiMn2O4 powders without any glass material decreases from 116.3 to 92.6mAhg−1 after 100 cycles, the reduced capacity being 80% of the initial capacity. However, the discharge capacity of the LiMn2O4 powders with 1wt% glass material decreases from 131.0 to 113.2mAhg−1 after 100 cycles; thus, the capacity retention is 86% of the initial capacity. [Copyright &y& Elsevier]

Abstract: Nano-sized Ba0.7Sr0.3TiO3 powders are prepared by post-treatment of the precursor powders with hollow and thin wall structure at temperatures between 900 and 1100°C. Ethylenediaminetetraacetic acid and citric acid improve the hollowness of the precursor powders prepared by spray pyrolysis. The mean sizes of the powders post-treated at temperatures of 900, 1000 and 1100°C are 42, 51 and 66nm, respectively. The densities of the Ba0.7Sr0.3TiO3 pellets obtained from the powders post-treated at 900, 1000 and 1100°C are each 5.36, 5.55 and 5.38gcm−3 at a sintering temperature of 1300°C. The pellet obtained from the powders post-treated at 1000°C has higher maximum dielectric constant than those obtained from the powders post-treated at 900 and 1100°C. [Copyright &y& Elsevier]

Abstract: Nanosized BaO–B2O3–SiO2 glass powders are directly prepared by flame spray pyrolysis. The mean size of the BaO–B2O3–SiO2 glass powders with amorphous phase and spherical shape is 30nm. The effects of glass powders on the sintering characteristics of the BaTiO3 pellet formed from the nanosized BaTiO3 powders are investigated. The mean size and BET surface area of the BaTiO3 powders prepared by spray pyrolysis are 110nm and 9.1m2/g. The BaTiO3 pellet with glass additive has large grain size with several microns, dense structure and pure tetragonal crystal structure at a sintering temperature of 1000°C. The XRD pattern of the pellet has distinct split of (200) and (002) peaks at 2θ ≈44.95°. The dielectric constant of the pellet without glass additive is 2180. However, the dielectric constants of the pellets with 1, 3, 5 and 7wt% glass additive with respect to BaTiO3 are 2496, 2514, 2700 and 2225, respectively. [Copyright &y& Elsevier]

Nickel sulfide-reduced graphene oxide (RGO) composite powders with spherical shapes are prepared by a one-pot spray pyrolysis process. The optimum mole ratio of nickel nitrate and thiourea to obtain nickel sulfide–RGO composite powders with high initial capacities and good cycling performance is 1:8. The bare nickel sulfide and nickel sulfide–RGO composite powders prepared directly by spray pyrolysis have mixed crystal structures of hexagonal α-NiS and cubic Ni 3 S 4 phases. The bare nickel sulfide powders are prepared from the spray solution without graphene oxide sheets. The nickel sulfide–RGO composite powders have sharp mesopores approximately 3.5 nm in size. The discharge capacities of the nickel sulfide–RGO composite powders for the 1st and 200th cycles at a current density of 1000 mA g −1 are 1046 and 614 mA h g −1 , respectively, and the corresponding capacity retention measured from the second cycle is 89%. However, the discharge capacities of the bare nickel sulfide powders for the 1st and 200th cycles at a current density of 1000 mA g −1 are 832 and 16 mA h g −1 , respectively. The electrochemical impedance spectroscopy (EIS) measurements reveal the high structural stability of the nickel sulfide–RGO composite powders during cycling. [ABSTRACT FROM AUTHOR]

Highlights: [•] The xLi2MnO3–(1− x)Li(Ni1/3Mn1/3Co1/3)O2 (0≤ x ≤1) composite cathode powders are prepared by spray pyrolysis. [•] The initial discharge capacities of the composite cathode powders are 242, 283, 291, and 234mAhg−1 when x =0.2, 0.4, 0.5, and 0.8, respectively. [•] The cathode powders with appropriate proportions of Li2MnO3 and Li(Ni1/3Mn1/3Co1/3)O2 have good cycling properties. [ABSTRACT FROM AUTHOR]

Abstract: Spherically shaped vanadium pentoxide (V2O5) cathode powders with porous or dense morphologies are prepared directly via spray pyrolysis by varying the preparation temperatures between 600 and 1000°C. The powders prepared at 600°C consist of nanometer-sized rod-shaped crystals with porous structures. The V2O5 powders prepared at 1000°C have spherical shapes, clean surfaces, and dense structures, because of complete melting of the powders that occurs inside the hot-wall reactor. The Brunauer–Emmett–Teller (BET) surface areas of the V2O5 powders decrease from 24.7 to 3.2m2 g−1 when the preparation temperature increases from 600 to 1000°C. The V2O5 powders prepared at 1000°C have better cycle properties than those prepared at 600 and 800°C. The discharge capacity of the V2O5 powders prepared at 1000°C decreases from 432mAhg−1 to 263mAhg−1 after 20 cycles, in which the capacity retention is 61%. [Copyright &y& Elsevier]