Limits...
Controlled synthesis of series NixCo3-xO4 products: Morphological evolution towards quasi-single-crystal structure for high-performance and stable lithium-ion batteries.

Zhou Y, Liu Y, Zhao W, Wang H, Li B, Zhou X, Shen H - Sci Rep (2015)

Bottom Line: At the current density of 0.8 A g(-1), it can deliver a high discharge capacities of 1470 mAh g(-1) over 100 cycles (105% of the 2nd cycle) and 590 mAh g(-1) even after 1000 cycles.To better understand what underlying factors lead our QNHMs to achieve excellent electrochemical performance, a series of Ni(x)Co(3-x)O4 products with systematic shape evolution from spherical to polyhedral, and cubic particles as well as circular microtubes consisted of spheres and square microtubes composed of polyhedra have been synthesized.The excellent electrochemical performance of QNHMs is attributed to the unique stable quasi-single-crystal structure, which can both provide efficient electrical transport pathway and suppress the electrode pulverization.

View Article: PubMed Central - PubMed

Affiliation: School of Physics and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China.

ABSTRACT
Transition metal oxides are very promising alternative anode materials for high-performance lithium-ion batteries (LIBs). However, their conversion reactions and concomitant volume expansion cause the pulverization, leading to poor cycling stability, which limit their applications. Here, we present the quasi-single-crystal Ni(x)Co(3-x)O4 hexagonal microtube (QNHM) composed of continuously twinned single crystal submicron-cubes as anode materials for LIBs with high energy density and long cycle life. At the current density of 0.8 A g(-1), it can deliver a high discharge capacities of 1470 mAh g(-1) over 100 cycles (105% of the 2nd cycle) and 590 mAh g(-1) even after 1000 cycles. To better understand what underlying factors lead our QNHMs to achieve excellent electrochemical performance, a series of Ni(x)Co(3-x)O4 products with systematic shape evolution from spherical to polyhedral, and cubic particles as well as circular microtubes consisted of spheres and square microtubes composed of polyhedra have been synthesized. The excellent electrochemical performance of QNHMs is attributed to the unique stable quasi-single-crystal structure, which can both provide efficient electrical transport pathway and suppress the electrode pulverization. It is important to note that such quasi-single-crystal structure would be helpful to explore other high-energy lithium storage materials based on alloying or conversion reactions.

No MeSH data available.


Related in: MedlinePlus

Time dependent morphological and crystal structure evolution of QNHMs.The samples were fabricated by hydrothermal treatment of 0.8 g Ni(NO3)2∙6H2O and 3.2 g Co(NO3)2∙6H2O in 60 mL of ammonia solution (8.3%w/w) at 230 °C for 1–24 h. (a) XRD measurements at various stages, and here some peaks marked with asterisk (*) represent β-Co(OH)2 phase. (b), (c) and (d) Typical SEM images of QNHMs at the reaction time of 1 h, 2 h, and 5 h, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4478471&req=5

f4: Time dependent morphological and crystal structure evolution of QNHMs.The samples were fabricated by hydrothermal treatment of 0.8 g Ni(NO3)2∙6H2O and 3.2 g Co(NO3)2∙6H2O in 60 mL of ammonia solution (8.3%w/w) at 230 °C for 1–24 h. (a) XRD measurements at various stages, and here some peaks marked with asterisk (*) represent β-Co(OH)2 phase. (b), (c) and (d) Typical SEM images of QNHMs at the reaction time of 1 h, 2 h, and 5 h, respectively.

Mentions: To gain more insight into the growth mechanism of QNHMs, the time-dependent experiments were also performed at the hydrothermal temperature of 230 °C with the reaction time changing from 1 h to 24 h, as shown in Fig. 4. While the reaction time was less than 5h, the crystal phase is predominantly NixCo3-xO4, and trace amounts of brucite-like β-Co(OH)2 whose peaks at 32.5° and 37.9°, and 51.4° were also detected. After 5 h of reaction, the β-Co(OH)2 impurity disappeared and only a pure NixCo3-xO4, phase was produced, which illustrate that β-Co(OH)2 is the intermediate product, and it would completely decomposed to water and NixCo3-xO4 crystal with the increase of the reaction time. Surprisingly, similar to temperature-dependent evolution of NixCo3-xO4 products (see Fig. 2), time-dependent XRD measurements (Fig. 4a) show that the ratio of the intensity of (400) peak to that of (111) peak increased from 0.03 at 1 h to 0.06 at 2 h, to 0.15 at 4 h, and to 1.02 at 5 h with the increase of reaction time, indicating the building blocks for hexagonal microtubes were also evolved from particles with mostly exposed {111} plane to cubes with exposed {100} plane. After 5 h of reaction, the ratio of the intensity of (400) peak to that of the (111) peak is in the range of 0.8–1.0, revealing the texture of QNHMs were almost unchanged. Time dependent SEM images of products also confirm that the primary building blocks for hexagonal tubes are transformed from the particles exposed {111} plane to cubes exposed {100} plane with the increase of reaction time (Fig. 4b–d). At the early reaction stage of 1 h, large scale and well separated hexagonal microtubes containing nanoparticles inside began to form (Fig. 4b and the inset). With an increase of reaction time up to 2 h, the nanoparticles inside the microtubes disappeared and the tube wall obviously became thick (Fig. 4c and the inset). When the growth time was further extended to 5 h, the building blocks for microtubes were developed into well crystallized submicron-cubes (Fig. 4d and the inset). Based on the above experiments, we propose a possible growth process involving multi-step formation of QNHMs. Initially, Ni and Co precursor was dissolved in ammonia solution, resulting in the formation of a lot of nucleus. Subsequently, many nanocrystals aggregated into hexagonal tubular structures with the help of fast out-diffusion of NH3 bubbles via the decomposition of ammonia solution under the hydrothermal condition. With the increase of reaction time, nanoparticles inside the hexagonal microtube disappeared, and then the tube wall became thick following the Ostwald ripening process35. Finally, the building blocks of hexagonal microtubes evolved from the particles with mostly exposed {111} plane to cubes with exposed {100} plane via the dissolution and recrystallization process.


Controlled synthesis of series NixCo3-xO4 products: Morphological evolution towards quasi-single-crystal structure for high-performance and stable lithium-ion batteries.

Zhou Y, Liu Y, Zhao W, Wang H, Li B, Zhou X, Shen H - Sci Rep (2015)

Time dependent morphological and crystal structure evolution of QNHMs.The samples were fabricated by hydrothermal treatment of 0.8 g Ni(NO3)2∙6H2O and 3.2 g Co(NO3)2∙6H2O in 60 mL of ammonia solution (8.3%w/w) at 230 °C for 1–24 h. (a) XRD measurements at various stages, and here some peaks marked with asterisk (*) represent β-Co(OH)2 phase. (b), (c) and (d) Typical SEM images of QNHMs at the reaction time of 1 h, 2 h, and 5 h, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4478471&req=5

f4: Time dependent morphological and crystal structure evolution of QNHMs.The samples were fabricated by hydrothermal treatment of 0.8 g Ni(NO3)2∙6H2O and 3.2 g Co(NO3)2∙6H2O in 60 mL of ammonia solution (8.3%w/w) at 230 °C for 1–24 h. (a) XRD measurements at various stages, and here some peaks marked with asterisk (*) represent β-Co(OH)2 phase. (b), (c) and (d) Typical SEM images of QNHMs at the reaction time of 1 h, 2 h, and 5 h, respectively.
Mentions: To gain more insight into the growth mechanism of QNHMs, the time-dependent experiments were also performed at the hydrothermal temperature of 230 °C with the reaction time changing from 1 h to 24 h, as shown in Fig. 4. While the reaction time was less than 5h, the crystal phase is predominantly NixCo3-xO4, and trace amounts of brucite-like β-Co(OH)2 whose peaks at 32.5° and 37.9°, and 51.4° were also detected. After 5 h of reaction, the β-Co(OH)2 impurity disappeared and only a pure NixCo3-xO4, phase was produced, which illustrate that β-Co(OH)2 is the intermediate product, and it would completely decomposed to water and NixCo3-xO4 crystal with the increase of the reaction time. Surprisingly, similar to temperature-dependent evolution of NixCo3-xO4 products (see Fig. 2), time-dependent XRD measurements (Fig. 4a) show that the ratio of the intensity of (400) peak to that of (111) peak increased from 0.03 at 1 h to 0.06 at 2 h, to 0.15 at 4 h, and to 1.02 at 5 h with the increase of reaction time, indicating the building blocks for hexagonal microtubes were also evolved from particles with mostly exposed {111} plane to cubes with exposed {100} plane. After 5 h of reaction, the ratio of the intensity of (400) peak to that of the (111) peak is in the range of 0.8–1.0, revealing the texture of QNHMs were almost unchanged. Time dependent SEM images of products also confirm that the primary building blocks for hexagonal tubes are transformed from the particles exposed {111} plane to cubes exposed {100} plane with the increase of reaction time (Fig. 4b–d). At the early reaction stage of 1 h, large scale and well separated hexagonal microtubes containing nanoparticles inside began to form (Fig. 4b and the inset). With an increase of reaction time up to 2 h, the nanoparticles inside the microtubes disappeared and the tube wall obviously became thick (Fig. 4c and the inset). When the growth time was further extended to 5 h, the building blocks for microtubes were developed into well crystallized submicron-cubes (Fig. 4d and the inset). Based on the above experiments, we propose a possible growth process involving multi-step formation of QNHMs. Initially, Ni and Co precursor was dissolved in ammonia solution, resulting in the formation of a lot of nucleus. Subsequently, many nanocrystals aggregated into hexagonal tubular structures with the help of fast out-diffusion of NH3 bubbles via the decomposition of ammonia solution under the hydrothermal condition. With the increase of reaction time, nanoparticles inside the hexagonal microtube disappeared, and then the tube wall became thick following the Ostwald ripening process35. Finally, the building blocks of hexagonal microtubes evolved from the particles with mostly exposed {111} plane to cubes with exposed {100} plane via the dissolution and recrystallization process.

Bottom Line: At the current density of 0.8 A g(-1), it can deliver a high discharge capacities of 1470 mAh g(-1) over 100 cycles (105% of the 2nd cycle) and 590 mAh g(-1) even after 1000 cycles.To better understand what underlying factors lead our QNHMs to achieve excellent electrochemical performance, a series of Ni(x)Co(3-x)O4 products with systematic shape evolution from spherical to polyhedral, and cubic particles as well as circular microtubes consisted of spheres and square microtubes composed of polyhedra have been synthesized.The excellent electrochemical performance of QNHMs is attributed to the unique stable quasi-single-crystal structure, which can both provide efficient electrical transport pathway and suppress the electrode pulverization.

View Article: PubMed Central - PubMed

Affiliation: School of Physics and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275, China.

ABSTRACT
Transition metal oxides are very promising alternative anode materials for high-performance lithium-ion batteries (LIBs). However, their conversion reactions and concomitant volume expansion cause the pulverization, leading to poor cycling stability, which limit their applications. Here, we present the quasi-single-crystal Ni(x)Co(3-x)O4 hexagonal microtube (QNHM) composed of continuously twinned single crystal submicron-cubes as anode materials for LIBs with high energy density and long cycle life. At the current density of 0.8 A g(-1), it can deliver a high discharge capacities of 1470 mAh g(-1) over 100 cycles (105% of the 2nd cycle) and 590 mAh g(-1) even after 1000 cycles. To better understand what underlying factors lead our QNHMs to achieve excellent electrochemical performance, a series of Ni(x)Co(3-x)O4 products with systematic shape evolution from spherical to polyhedral, and cubic particles as well as circular microtubes consisted of spheres and square microtubes composed of polyhedra have been synthesized. The excellent electrochemical performance of QNHMs is attributed to the unique stable quasi-single-crystal structure, which can both provide efficient electrical transport pathway and suppress the electrode pulverization. It is important to note that such quasi-single-crystal structure would be helpful to explore other high-energy lithium storage materials based on alloying or conversion reactions.

No MeSH data available.


Related in: MedlinePlus