Lithium Storage Rate Performance Research Articles

Revealing the influence of conversion-type Co3O4 dimensionality on cyclic and rate performance for lithium storage

Cobalt tetraoxide (Co3O4) is regarded as a promising anode material for Li-ion batteries owing to its high theoretical capacity (890 mAh g−1), simple preparation, and controllable morphology. Nanoengineering has been proven to be an effective method for producing high-performance electrode materials. However, systematic research on the influence of material dimensionality on battery performance is lacking. Herein, we prepared Co3O4 with various dimensionalities (one-dimensional (1D) Co3O4 nanorod (NR), two-dimensional (2D) Co3O4 nanosheet (NS), three-dimensional (3D) Co3O4 nanocluster (NC), and 3D Co3O4 nanoflower (NF)) using a simple solvothermal heat treatment method, and their morphologies were controlled by varying the precipitator type and solvent composition. The 1D Co3O4 NR and 3D samples (3D Co3O4 NC and 3D Co3O4 NF) exhibited poor cyclic and rate performances, respectively, while the 2D Co3O4 NS exhibited the best electrochemical performance. The mechanism analysis revealed that the cyclic stability and rate performance of the Co3O4 nanostructures are closely related to their intrinsic stability and interfacial contact performance, respectively, and the 2D thin-sheet structure can achieve an optimal balance between the two, resulting in the best performance. This work presents a comprehensive study on the effect of dimensionality on the electrochemical performance of Co3O4 anodes, providing a new concept for the nanostructure design of conversion-type materials.

Sonication-induced electrostatic assembly of an FeCO3@Ti3C2 nanocomposite for robust lithium storage

The sonication-induced electrostatic assembly plays an important role in composite construction and chemical bonding of active FeCO3 nanorods and a Ti3C2 substrate towards superior cycling and rate performance for lithium storage.

High throughput synthesis of defect-rich MoS2 nanosheets via facile electrochemical exfoliation for fast high-performance lithium storage

A facile and cost-effective method to prepare defect-rich MoS2 nanosheets is developed via an electrochemical exfoliation process. By using bucket-like metallic titanium mesh both as inert anode and container for MoS2 powders, defect-rich thin MoS2 nanosheets can be fast exfoliated from the bulk powders in aqueous sodium sulfate electrolyte under positive potentials. The as-obtained MoS2 nanosheets exhibit excellent cycling capability, high specific capacity, and superior rate performance for lithium storage. Furthermore, it provides a novel and effective method to exfoliate insulative or semiconductive layer-structured bulk powders into defect-rich 2D nanosheets.

Composition-dependent lithium storage performances of SnS/SnO2 heterostructures sandwiching between spherical graphene

Heterostructures have broad potential application in energy conversion material and optoelectronic device since of novel interface effect and enhanced electron transport dynamics at heterointerfaces. Herein, we report a heterostructured SnS/SnO2/spherical graphene composite, in which ultrafine SnS/SnO2 nanoparticles with heterostructures are sandwiched between multi-layers of graphene sheets, exhibiting a hollow spherical architecture as a whole. Detailed electrochemical studies indicate that the molar ratio of SnS to SnO2 has great influence on the charge transport efficiency. Theoretical calculation reveals that SnS and SnO2 exhibit different work functions and the Fermi level shift is affected by the SnS/SnO2 molar ratio, thus the hybrid with the ratio close to 1.0 owns the most adsorbed lithium ions, which leads to the highest specific charge-transfer kinetics and lowest ion-diffusion resistance than other samples. Electrochemical tests show that the composite with appropriate composition delivers the best lithium storage rate performance (620 and 312.7 mAh g−1 at 1 C and 10 C). A much stable and high reversible specific capacity of 850 mAh g−1 is obtained after 200 cycles at 0.1 C. The appropriate molar ratio of nano-heterostructures and the novel sandwich hollow spherical composite structure are attributed to the excellent electrochemical performances.

Functionalized fullerenes for highly efficient lithium ion storage: Structure-property-performance correlation with energy implications

Here, we report that spherical C60 derivatives with well-defined molecular structures hold great promise to be advanced anode materials for lithium-ion batteries (LIBs). We studied four C60 molecules with various functional groups, including pristine, carboxyl, ester, and piperazine C60. The comparison of these C60s elucidated a strong correlation between functional group, overall packing (crystallinity), and the anode performance in LIBs. Specifically, carboxyl C60 and neutral ester C60 showed higher charge capacities than pristine C60, whereas positively-charged piperazine C60 exhibited lower capacity. The highest charge capacity was achieved on the carboxyl C60 (861mAhg−1 at 100th cycle), which is five times higher than that of pristine C60 (170mAhg−1), more than double the theoretical capacity of commercial graphite (372mAhg−1), and even higher than the theoretical capacity of graphene (744mAhg−1). Carboxyl C60 also showed a high capacity at a fast discharge-charge rate (370mAhg−1 at 5C). The exceptional performance of carboxyl C60 can be attributed to multiple key factors. They include the complex formation between lithium ions and oxygen atoms on the carboxyl group, the improved lithium-binding capability of C60 cage due to electron donating from carboxylate groups, the electrostatic attraction between carboxylate groups and lithium ions, and the large lattice void space and high specific area due to carboxyl functionalization. This study indicates that, while maintaining the basic C60 electronic and geometric properties, functionalization with desired groups can achieve remarkably enhanced capacity and rate performance for lithium storage.

Free-standing graphene/carbon nanotubes/CuO aerogel paper anode for lithium ion batteries

Three-dimensional porous graphene/carbon nanotubes (CNTs)/CuO (GCC) hybrid aerogel was constructed through hydrothermal treatment. After been mechanically compressed, the aerogel showed a paper form and revealed a relatively ordered layer by layer structure with CuO and CNTs intercalated. When used as anode for lithium ion batteries, the unique structure not only provided electrically conducting channels to promote electrolyte penetration, but also could buffer the volume expansion during lithium ion insertion/extraction process. Thus, the resultant binder-free GCC aerogel paper anodes demonstrated excellent cyclic retention with the specific capacity of 636.9mAhg−1 after 80 cycles compared to pure CuO, as well as excellent rate performance for lithium storage.

One-dimensional NiCo2O4 nanowire arrays grown on nickel foam for high-performance lithium-ion batteries

With the ever-increasing power and energy needs in application of advanced consumer electronics and related technologies, developing electrode materials with both high energy and power densities holds the key for satisfying the urgent demand of energy storage worldwide. Herein, we report the successful preparation of NiCo2O4 nanowire arrays that are grown on nickel foam via a simple hydrothermal method followed by an annealing process. The electron microscopy images of the obtained NiCo2O4 nanowires reveal that the NiCo2O4 nanowires are uniformly distributed and anchored on the surface of nickel foam. Benefited from the unique structure of NiCo2O4 nanowires on a nickel foam substrate, the as prepared materials exhibit a high reversible capacity of 1048.8 mAh g−1 at 100 mA g−1 and show excellent rate performance for lithium storage.

One-Pot Synthesis of Three-Dimensional Graphene/Carbon Nanotube/SnO2 Hybrid Architectures with Enhanced Lithium Storage Properties.

Three-dimensional (3D) graphene/carbon nanotube (CNT)/SnO2 (GCS) hybrid architectures were constructed by a facile and cost-effective self-assembly method through hydrothermal treatment of a mixture of Sn(2+), CNTs, and graphene oxide (GO). The resultant GCS displayed a 3D hierarchically porous structure with large surface area and excellent electrical conductivity, which could effectively prevent the aggregation and volume variation of SnO2 and accelerate the transport of ions and electrons through 3D pathways. Benefiting from the unique structure and the synergistic effect of different components in the hybrid architectures, the GCS exhibited a remarkably improved reversible capacity of 842 mAh g(-1) after 100 cycles at 0.2 A g(-1) and excellent rate performance for lithium storage compared with that of graphene/SnO2 (GS) hybrid architectures. Hence, the impressive results presented here could provide a universal platform for fabricating graphene/CNT-based hybrid architectures with promising applications in various fields.

Self-assembly of 2D sandwich-structured MnFe2O4/graphene composites for high-performance lithium storage

In this study, two-dimensional (2D) sandwich-structured MnFe2O4/graphene (MFO/GN) composites are synthesized by a facile in situ solvothermal approach, using cetyltrimethylammonium bromide (CTAB) as cationic surfactant. As a consequence, the nanocomposites of MFO/GN self-assembled into a 2D sandwich structure, in which the interstitial cluster structure of microsphere-type MnFe2O4 is sandwiched between the graphene layers. This special structure of the MFO/GN composites used as anodes for lithium-ion batteries will be favorable for the maximum accessible surface of electroactive materials, fast diffusion of lithium ions and migration of electron, and elastomeric space to accommodate volume changes during the discharge–charge processes. The as-synthesized MFO/GN composites deliver a high specific reversible capacity of 987.95mAhg−1 at a current density of 200mAg−1, a good capacity retention of 69.27% after 80 cycles and excellent rate performance for lithium storage.

Lithium Storage Characteristics and Possible Applications of Graphene Materials

Graphene materials are materials with a flat mono/few layer of carbon atoms tightly packed to a two-dimensional honeycomb lattice. Graphene materials are expected to be applied in lithium ion batteries due to their unique structural, mechanical and electrical properties. As an anode material, the charge/discharge characteristics of graphene materials is similar to those of low-temperature soft carbon materials, such as high capacity, low initial efficiency and large voltage hys- teresis. Although attractive results have been achieved for graphene as anode materials for LIBs, detailed lithium storage mechanisms are still not clear. The effects of the following several structural parameters including disorder degree, surface area, micropores, interlayer spacing, C/O ratio and layer number on the lithium storage properties are discussed. Thermally reduced graphene materials with a highly disordered structure and high surface area has exceptionally high reversible capac- ity. Micropores in graphene materials have a great impact on their electrochemical performance. Although these micropores can provide additional sites for increased reversible lithium storage, it can also results in severe capacity fading and voltage hysteresis. Oxygen functional groups and larger interlayer spacing may provide higher reversible capacity of graphene, but the micropores and defect-based reversible storage may be the main contribution. Effect of layer number on lithium storage mechanisms of graphene and the conclusion are still in debate. Graphene with rich oxygen functional groups is a promising cathode material with high capacity and rate performance for lithium storage. High specific capacity of graphene cathode is mainly ascribed to lithiation reaction of oxygen functional groups, such as epoxide and carbonyl groups. Lithiation of oxygen functional groups still requires further study for a full understanding. Based on the lithium storage characteristics of graphene anode and cathode, lithium ion capacitors with high energy density and graphene composite cathode materials for lithium ion batteries may be designed and developed in the future. Graphene based lithium ion capacitors facilitate the reversible lithium storage, which significantly improves the energy density of lithium ion capacitors compared to those of conventional systems based on activated carbon. LiFePO4 modified with graphene layers has reached 208 mAh/g in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoli- ated graphene flakes.

Two-Dimensional Carbon-Coated Graphene/Metal Oxide Hybrids for Enhanced Lithium Storage

Metal oxides (MOs) have been widely investigated as promising high-capacity anode material for lithium ion batteries, but they usually exhibit poor cycling stability and rate performance due to the huge volume change induced by the alloying reaction with lithium. In this article, we present a double protection strategy by fabricating a two-dimensional (2D) core-shell nanostructure to improve the electrochemical performance of metal oxides in lithium storage. The 2D core-shell architecture is constructed by confining the well-defined graphene based metal oxides nanosheets (G@MO) within carbon layers. The resulting 2D carbon-coated graphene/metal oxides nanosheets (G@MO@C) inherit the advantages of graphene, which possesses high electrical conductivity, large aspect ratio, and thin feature. Furthermore, the carbon shells can tackle the deformation of MO nanoparticles while keeping the overall electrode highly conductive and active in lithium storage. As the result, the produced G@MO@C hybrids exhibit outstanding reversible capacity and excellent rate performance for lithium storage (G@SnO(2)@C, 800 mAh g(-1) at the rate of 200 mA g(-1) after 100 cycles; G@Fe(3)O(4)@C, 920 mAh g(-1) at the rate of 200 mA g(-1) after 100 cycles).

A Novel Type of Ge Nanotube Arrays for Lithium Storage Material

Amorphous Ge nanotubes, featured of a top-closed tubular structure, were synthesized directly on metallic current collector substrates via a template technique. Measurement of electrochemical cycling reveals that these nanotubes can deliver reversible capacities of -1300 mAh/g (81% of the theoretical capacity) at the current density of C/20 (1C = 1600 mAh/g) and retain -700 mAh/g at 2C with columbic efficiencies over 99%. Such performance is comparable to that of the recently reported Ge nanowire anodes grown directly on the metallic substrates by the chemical vapor deposition, indicating that the present Ge nanotubes are a type of anode materials with high capacity and good rate performance for lithium storage.