Three-dimensional carbon fiber as current collector for lithium/sulfur batteries

Ni foam and carbon fiber cloth were tested as three-dimensional (3D) current collectors for a sulfur/polypyrrole composite cathode in lithium batteries. The cell with the carbon fiber current collector has exhibited remarkably enhanced electrochemical performance compared with its Ni foam counterpart, delivering a high initial capacity of 1,278 mAh g^?1 and maintaining a discharge capacity at 810 mAh g^?1 after 40 cycles at 0.06 C. Furthermore, the carbon fiber-based cell demonstrated a better rate capability and delivered a highly reversible discharge capacity of 397 mAh g^?1 after 50 cycles at 0.5 C, representing an increase of 194 mAh g^?1 compared to the Ni foam counterpart. The electrochemical property investigations along with scanning electron microscope studies have revealed that the carbon fiber current collector possesses a three-dimensional network structure, provides an effective electron conduction path, and minimizes the loss of electrical contact within the deposited cathode material during cycling. These results indicate that the carbon fiber cloth can be used as a promising, effective, and inexpensive current collector for Li/S batteries.     

The centrifugally constructed and thermally activated three-dimensional graphene toward a binder-free highly performed anode of the lithium-ion battery

A binder-free three-dimensional porous interconnected graphene (a-3DrGO@NF) was centrifugally constructed and KOH-activated at 800 °C, leading a mechanically strong and pore-developed anode candidate for lithium ion batteries (LIBs). The unique approach of the integration of the mechanical construction and thermal activation demonstrated favorable frameworks to facilitate the stable and fast migrations of both ion and electron during the galvanostatic charge/discharge process, thus significantly improving its durability and electrochemical performance compared to those without the activated and thermal treatment. The a-3DrGO@NF LIBs showed a highly reversible capacity of 1250 mAh g^?1 at a current density of 0.1 A g^?1 after 50 cycles without degradation relative to the first cycle. More importantly, the a-3DrGO@NF LIBs exhibited excellent large current discharge property and cyclic stability of 965 mAh g^?1 in its first cycle and 545 mAh g^?1 after 150 cycles at a current density of 4 A g^?1. Furthermore, it can be quickly charged and discharged in a very short time of 92 s together with high-rate capability of 256 mAh g^?1 after 200 cycles at 10 A g^?1. At both lower and higher its current density as to 10 A g^?1, the coulombic efficiency was close to 100% and showed the reliability of a-3DrGO@NF LIBs.     

Red phosphorus encapsulated in porous carbon derived from cigarette filter solid waste as a promising anode material for lithium-ion batteries

Red phosphorus (RP) is considered to be one of the promising anode materials for lithium-ion batteries (LIBs) on account of its high theoretical capacity (2596 mAh g^?1), abundant resources, and environmental friendliness. However, the intrinsic insulating nature and large volume change during lithium insertion/extraction process lead to drastic capacity loss upon cycling. Recently, great attention has been devoted to constructing P-based composites via mixing with carbon materials. Here, a novel P/C composite, in which red P nanoparticles were homogeneously distributed in cigarette filter-derived porous carbon (CPC), was fabricated by vaporization-condensation method. Due to the unique characteristics of porous carbon, including high specific area, good conductivity, and rich internal porous structure, CPC obtained by means of heat treatment that serves as conductive matrix to load red P could be of great benefits, which can not only improve the overall electrical conductivity but also mitigate the volume expansion issues. As a result, the RP/CPC composite as an anode material for LIBs delivers a good cycling stability (500 mAh g^?1 at 100 mA g^?1 with a high Coulombic efficiency above 99% after 50 cycles) and rate capability (355 mAh g^?1 even at 1000 mA g^?1).     

Design and synthesis of a novel 3D hierarchical mesocarbon microbead as anodes for lithium ion batteries and sodium ion batteries

This work presents a feasible route for the facile synthesis of three-dimensional (3D) hierarchical mesocarbon microbead (MCMB) as anodes for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). The MCMB is oxidized by modified hummers method, and then the precursor is treated by hydrogen reduction to form the HMCMB. The HMCMB with graphene-like architecture has high specific surface, sufficient pore volume, and increased interlayer spacing, which can provide more active insertion/extraction sites and reduce the Li⁺/Na⁺ diffusion resistance. When employed as anode materials for LIBs and SIBs, HMCMB anodes exhibit improved lithium and sodium storage capability. The HMCMB delivers a higher reversible capacity (471.1 and 177.5 mAh g^?1 at 100 mA g^?1 after 100 cycles) and a good rate performance (250 and 121 mAh g^?1 even at 1000 mA g^?1) for LIBs and SIBs, respectively.     

NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> polyhedra with controllable particle size as high-performance anode for lithium-ion battery

Different particle sizes of dodecahedron precursors are synthesized by controlling the polarity of the solution. Through the results of scanning electron microscope (SEM) images, it can be found that different particle sizes of precursors present obvious edge angles and their morphology can be well retained after annealing. X-ray diffraction (XRD) measurements suggest that the annealed polyhedral products are pure single-phase NiCo₂O₄. When tested as lithium-ion battery anode, 0.5 μm NiCo₂O₄ polyhedra exhibits a specific capacity of 1050 mAh g^?1 at 0.1 C at the 60th cycle, which was higher than theoretical capacity of single metal oxide (NiO 718 mAh g^?1 and Co₃O₄ 890 mAh g^?1). It also exhibits the highest rate capability with an average discharge capacity of 890, 700, 490, 330, and 300 mAh g^?1 at 0.5, 2, 4, 8, and 10 C, respectively. Those advantages are attributed to that small-sized particle with great surface areas decrease the actual current density at the surface and inner of the prepared electrode.     

ZnO nanoparticles anchored on nitrogen and sulfur co-doped graphene sheets for lithium-ion batteries applications

Herein, we demonstrate a facile one-step hydrothermal synthesis route to anchor ZnO nanoparticles on nitrogen and sulfur co-doped graphene sheets. The detailed material and electrochemical characterization have been carried out to demonstrate the potential of novel ZnO/NSG nanocomposite in Li-ion battery (LIBs) applications. The structure and morphology of nanocomposite were assessed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-synthesized ZnO/NSG nanocomposite has been studied as anode material in LIBs and delivered a high initial discharge capacity of 1723 mAh g^?1, at the current density of 200 mA g^?1. After 100 cycles, the ZnO/NSG nanocomposites demonstrated a high reversible capacity of 720 mAh g^?1 and coulombic efficiency of 99.8%, which can be attributed to the porous three-dimensional network, constructed by ZnO nanoparticles and nitrogen and sulfur co-doped graphene. Moreover, the designed nanocomposite has shown excellent rate capability and lower charge transfer resistance. These results are promising and encourage further research in the area of ZnO-based anodes for next-generation LIBs.     

A facile synthesis of heteroatom-doped carbon framework anchored with TiO<Subscript>2</Subscript> nanoparticles for high performance lithium ion battery anodes

Titanium dioxide (TiO₂)-based materials have been well studied because of the high safety and excellent cycling performance when employed as anode materials for lithium ion batteries (LIBs), whereas, the relatively low theoretical capacity (only 335 mAh g^?1) and serious kinetic problems such as poor electrical conductivity (~?10^?13S cm^?1) and low lithium diffusion coefficient (~?10^?9 to 10^?13 cm² s^?1) hinder the development of the TiO₂-based anode materials. To overcome these drawbacks, we present a facile strategy to synthesize N/S dual-doping carbon framework anchored with TiO₂ nanoparticles (NSC@TiO₂) as LIBs anode. Typically, TiO₂ nanoparticles are anchored into the porous graphene-based sheets with N, S dual doping feature, which is produced by carbonization and KOH activation process. The as-obtained NSC@TiO₂ electrode exhibits a high specific capacity of 250 mAh g^?1 with a coulombic efficiency of 99% after 500 cycles at 200 mA g^?1 and excellent rate performance, indicating its promising as anode material for LIBs.     

Hierarchical Co<Subscript>3</Subscript>O<Subscript>4</Subscript>@C hollow microspheres with high capacity as an anode material for lithium-ion batteries

Three-dimensional hierarchical Co₃O₄@C hollow microspheres (Co₃O₄@C HSs) are successfully fabricated by a facile and scalable method. The Co₃O₄@C HSs are composed of numerous Co₃O₄ nanoparticles uniformly coated by a thin layer of carbon. Due to its stable 3D hierarchical hollow structure and uniform carbon coating, the Co₃O₄@C HSs exhibit excellent electrochemical performance as an anode material for lithium-ion batteries (LIBs). The Co₃O₄@C HSs electrode delivers a high reversible specific capacity, excellent cycling stability (1672 mAh g^?1 after 100 cycles at 0.2 A g^?1 and 842.7 mAh g^?1 after 600 cycles at 1 A g^?1), and prominent rate performance (580.9 mAh g^?1 at 5 A g^?1). The excellent electrochemical performance makes this 3D hierarchical Co₃O₄@C HS a potential candidate for the anode materials of the next-generation LIBs. In addition, this simple synthetic strategy should also be applicable for synthesizing other 3D hierarchical metal oxide/C composites for energy storage and conversion.     

Excellent long-term electrochemical performance of graphite oxide as cathode materials for lithium-ion batteries

A facile, scalable route has been adopted to synthesize graphite oxides with different degrees of oxidation. Subsequently, graphite oxides with rationally designed functional groups have been utilized as cathode materials for lithium-ion batteries (LIBs). The electrodes deliver the initial and second discharge capacities of 332 and 172 mAh g^?1 at a current density of 0.1 A g^?1, respectively. More importantly, a remarkable long-term cycling performance of 130 mAh g^?1 after 800 cycles has been gathered, with an ultralow capacity fading of 0.03% per cycle from the second cycle. The root cause of excellent cycling stability should be ascribed to the admirable reversibility of epoxy and carbonyl groups in graphite oxides during the Li-cycling. Meanwhile, the deep study has provided a novel way to avoid complex and expensive post-treatment process of graphite oxides, whose synthesis conditions are also optimized. Those striking features make graphite oxides as promising cathode materials for lithium-ion batteries.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> quantum dots on 3D-framed graphene aerogel as an advanced anode material in lithium-ion batteries

Three-dimensional fabricated Fe₃O₄ quantum dots/graphene aerogel materials (Fe₃O₄ QDs/GA) were obtained from a facile hydrothermal strategy, followed by a subsequently heat treatment process. The Fe₃O₄ QDs (2–5 nm) are anchored tightly and dispersed uniformly on the surface of three-dimensional GA. The as-prepared anode materials exhibit a high reversible capacity of 1078 mAh g^?1 at a current density of 100 mA g^?1 after 70 cycles in lithium-ion batteries (LIBs) system. Moreover, the rate capacity still remains 536 mAh g^?1 at 1000 mA g^?1. The enhanced electrochemical performance is attributed to that the GA not only acts as a three-dimensional electronic conductive matrix for the fast transportation of Li⁺ and electrons, but also provides with double protection against the aggregation and pulverization of Fe₃O₄ QDs during cycling. Apparently, the synergistic effects of the three-dimensional GA and the quantum dots are fully utilized. Therefore, the Fe₃O₄ QDs/GA composites are promising materials as advanced anode materials for LIBs.     

Synergistic effect of magnesium and fluorine doping on the electrochemical performance of lithium-manganese rich (LMR)-based Ni-Mn-Co-oxide (NMC) cathodes for lithium-ion batteries

Mg-doped-LMR-NMC (Li_1.2Ni_0.15-xMg_xMn_0.55Co_0.1 O₂) is synthesized by combustion method followed by fluorine doping by solid-state synthesis. In this approach, we substituted the Ni²⁺ by Mg²⁺ in varying mole percentages (x = 0.02, 0.05, 0.08) and partly oxygen by fluorine (LiF: LMR-NMC = 1:50 wt%). The synergistic effect of both magnesium and fluorine substitution on electrochemical performance of LMR-NMC is studied by electrochemical impedance spectroscopy and galvanostatic-charge-discharge cycling. Mg-F-doped LMR-NMC (Mg 0.02 mol) composite cathodes shows excellent discharge capacity of ~300 mAh g^?1 at C/20 rate whereas pristine LMR-NMC shows the initial capacity around 250 mAh g^?1 in the voltage range between 2.5 and 4.7 V. Mg-F-doped LMR-NMC shows lesser Ohmic and charge transfer resistance, cycles well, and delivers a stable high capacity of ~280 mAh g^?1 at C/10 rate. The voltage decay which is the major issue of LMR-NMC is minimized in Mg-F-doped LMR-NMC compared to pristine LMR-NMC.     

Synthesis of carbon microtubules core structure LiFePO4 via a template-assisted method

The carbon microtubules core structure LiFePO₄ is synthesized using a cotton fiber template-assisted method. The crystalline structure and morphology of the product is characterized by X-ray diffraction and field emission scanning electron microscopy. The charge–discharge kinetics of the LiFePO₄ electrode is investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The result shows that the well-crystallized carbon microtubules core structure LiFePO₄ is successfully synthesized. The as-synthesized material exhibits a high initial discharge capacity of 167 mAh g^?1 at 0.2 C rate. The material also shows good high-rate discharge performance and cycling stability, about 127 mAh g^?1 and 94.7 % capacity retention after 100 cycles even at 5.0 C rate.     

Influence of post-calcination treatment on the spinel lithium titanium oxide anode material for lithium ion batteries

The influence of post-calcination treatment on spinel Li₄Ti₅O₁₂ anode material is extensively studied combining with a ball-milling-assisted rheological phase reaction method. The post-calcinated Li₄Ti₅O₁₂ shows a well distribution with expanded gaps between particles, which are beneficial for lithium ion mobility. Electrochemical results exhibit that the post-calcinated Li₄Ti₅O₁₂ delivers an improved specific capacity and rate capability. A high discharge capacity of 172.9 mAh g^?1 and a reversible charge capacity of 171.1 mAh g^?1 can be achieved at 1 C rate, which are very close to its theoretical capacity (175 mAh g^?1). Even at the rate of 20 C, the post-calcinated Li₄Ti₅O₁₂ still delivers a quite high charge capacity of 124.5 mAh g^?1 after 50 cycles, which is much improved over that (43.9 mAh g^?1) of the pure Li₄Ti₅O₁₂ without post-calcination treatment. This excellent electrochemical performance should be ascribed to the post-calcination process, which can greatly improve the lithium ion diffusion coefficient and further enhance the electrochemical kinetics significantly.     

Advanced LiTi<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C anode by incorporation of carbon nanotubes for aqueous lithium-ion batteries

Inferior rate capability is a big challenge for LiTi₂(PO₄)₃ anode for aqueous lithium-ion batteries. Herein, to address such issue, we synthesized a high-performance LiTi₂(PO₄)₃/carbon/carbon nanotube (LTP/C/CNT) composite by virtue of high-quality carbon coating and incorporation of good conductive network. The as-prepared LTP/C/CNT composite exhibits excellent rate performance with discharge capacity of 80.1 and 59.1 mAh g^?1 at 10 C and 20 C (based on the mass of anode, 1 C = 150 mA g^?1), much larger than that of the LTP/C composite (53.4 mAh g^?1 at 10 C, and 31.7 mAh g^?1 at 20 C). LTP/C/CNT also demonstrates outstanding cycling stability with capacity retention of 83.3 % after 1000 cycles at 5 C, superior to LTP/C without incorporation of CNTs (60.1 %). As verified, the excellent electrochemical performance of the LTP/C/CNT composite is attributed to the enhanced electrical conductivity, rapid charge transfer, and Li-ion diffusion because of the incorporation of CNTs.     

Facile synthesis of a sulfur/multiwalled carbon nanotube nanocomposite cathode with core–shell structure for lithium rechargeable batteries

A novel sulfur/multiwalled carbon nanotube nanocomposite (S/MWCNT) was prepared by a facile quasi-emulsion template method in an O/W system. Transmission and scanning electronic microscopy show the formation of a highly developed core–shell tubular structure consisting of S/MWCNT composite with uniform sulfur coating on its surface. The homogenous dispersion and integration of MWCNT in the S/MWCNT composite create a highly conductive and mechanically flexible framework, enhancing the electronic conductivity and consequently the rate capability of the material. The S/MWCNT composite cathode could deliver a stable discharge (the fifth cycle) capacity of about 903 mAh g^?1 at 0.1 C, 751 mAh g^?1 at 0.5 C, and 631 mAh g^?1 at 1 C.     

New-type low-cost cathode materials for Li-ion batteries: Mikasaite-type Fe2(SO4)3

In the present work, a new-type low-cost lithium ion battery cathode material, the Mikasaite-type iron sulfate, has been studied. It can be prepared by heating the water-containing iron sulfate raw chemicals in air atmosphere. The experimental results have shown that the oxidation and the reduction peaks are 3.92 and 3.37 V in the cyclic voltammogram, respectively, when the scanning rate is 0.05 mV s^?1. The galvanostatic measurements have explored that the voltage plateau during charging is slightly less than 3.70 V and the discharge voltage plateau is 3.40 V for the first cycle and 3.50 V for the following cycles at 0.1 C rate. The discharge capacity in the first cycle can reach 116 mAh g^?1, about 87 % of the theoretical capacity (134 mAh g^?1). It is believed that the product in the fully discharged state is Li₂Fe₂(SO₄)₃. However, the insertion reaction is reversible only for the second lithium ion. During cycling, the reversible capacity remains about 60 mAh g^?1. Further capacity fade is not found in the 20 discharge–charge cycles. The electrochemical impedance measurements have shown that there are two compressed semicircles in the Nyquist plots and a Warburg impedance in the low-frequency domain. The high-frequency semicircle is related with the electrode’s structural factor and the intermediate-frequency semicircle corresponds to the charge-transfer process.     

Novel synthesis and characterization of ZnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoflakes grown on nickel foam as efficient electrode materials for electrochemical supercapacitors

ZnCo₂O₄ nanoflakes were directly grown on Ni foam via a two-step facile strategy, involving cathodic electrolytic electrodeposition (ELD) method and followed by a thermal annealing treatment step. The results of physical characterizations exhibit that the mesoporous ZnCo₂O₄ nanoflakes have large electroactive surface areas (138.8 m² g^?1) and acceptable physical stability with the Ni foam, providing fast electron and ion transport sites. The ZnCo₂O₄ nanoflakes on Ni foam were directly used as integrated electrodes for supercapacitors and their electrochemical properties were measured in 2 M KOH aqueous solution. The ZnCo₂O₄ nanoflake electrode exhibits a high capacitance of 1781.7 F g^?1 at a current density of 5 A g^?1 and good rate capability (62% capacity retention at 50 A g^?1). Also, an excellent cycling ability at various current densities from 5 to 50 A g^?1 was obtained and 92% of the initial capacitance maintained after 4000 cycles. The results demonstrate that the proposed synthesis route is cost-effective and facile and can be developed for preparation of electrode materials in other electrochemical supercapacitors.     

Nitrogen-doped carbon nanofiber decorated LiFePO<Subscript>4</Subscript> composites with superior performance for lithium-ion batteries

Nitrogen-doped carbon nanofiber (NCNF) decorated LiFePO₄ (LFP) composites are synthesized via an in situ hydrothermal growth method. Electrochemical performance results show that the embedded NCNF can improve electron and ion transfer, thereby resulting in excellent cycling performance. The as-prepared LFP and NCNF composites exhibit excellent electrochemical properties with discharge capacities of 188.9 mAh g^?1 (at 0.2 C) maintained at 167.9 mAh g^?1 even after 200 charge/discharge cycles. The electrode also presents a good rate capability of 10 C and a reversible specific capacity as high as 95.7 mAh g^?1. LFP composites are a potential alternative high-performing anode material for lithium ion batteries.     

Effect of milling time on the performance of bowl-like LiFePO4/C prepared by wet milling-assisted spray drying

LiFePO₄/C was prepared by wet milling-assisted spray drying. The effects of ball-milling time on the characteristics of LiFePO₄/C were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, cyclic voltammograms, electrochemical impedance spectra, and galvanostatic charge–discharge testing. Bowl-like material was obtained, surrounded by a network of carbon, which display larger specific surface area. The specific surface area of particle first increased and then decreased, as the increasing of ball-milling time; when ball-milling time reach 2.5 h, it showed the largest specific surface area of 29.350 m² g^?1, primary particles with size of ～50 nm, delivered a discharge capacity of 162 mAh g^?1 at 0.5 C and 123 mAh g^?1 at 10 C, and with no capacity loss.     

Preparation and characterization of Li1.2Ni0.13Co0.13Mn0.54O2 cathode materials for lithium-ion battery

Lithium-rich cathode materials Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ with (sample SF) and without (sample SP) formamide was synthesized by a spray-dry method. The crystalline structure and particle morphology of as-prepared materials were characterized by X-ray diffraction and scanning electron microscope. The specific surface area (SSA) of the Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ prepared from different routes was determined by a five-point Brunauer–Emmett–Teller (BET) method using N₂ as absorbate gas. Being compared with the material synthesized without spray-drying process (sample CP), sample SP has much higher SSA. The additive formamide is helpful to form regular and solid precursor particles in spray-drying process, which results in a slightly aggregation of grains and reduction of SSA for sample SF. The electrochemical activities of the materials are closely related to their morphology and SSA. In the voltage range of 2–4.8 V at 25 °C, sample SP present a discharge capacity of 257 mAh g^?1 at 0.1 C rate and 170 mAh g^?1 at 1 C rate. The sample CP delivered only 136 mAh g^?1 when discharged at 1 C rate. The elevated specific capacity and rate capability are attributed to smaller primary particle and higher SSA. Both cycle performance and rate capability of Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ were improved when formamide was used in spray-dry process. Discharge capacity of SF is 140.5 mAh g^?1 at 2 C rate, and that of SP is 132.3 mAh g^?1. Overlarge SSA of SP may provoke serious side reaction, so that its electrochemical performance was deteriorated.