Preparation of mesoporous carbon for improved-performance lithium-sulfur battery

A mesoporous carbon (MC) is prepared by the method of hard-template. Cathode materials (S/MC) for Li-S battery were synthesized. Properties of S, MC, and S/MC were characterized by BET, XRD, Raman, HRTEM, and FESEM. Electrochemical performances of the batteries were determined by AC impedance, cyclic voltammetry, and constant-current charging and discharging. Experiments show that MC, prepared with mass ratio CaCO₃/PVA = 1/1.5, is the most suitable for Li-S battery. Thereby, the battery shows initial specific capacity of 1383.6 mAh/g and 881.6 mAh/g after 100 cycles, and the Coulombic efficiencies are both over 98% after 100 cycles at the current rate of 0.5 and 1 C.     

Facile synthesis of N-doped carbon-coated Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode for application in high-rate lithium ion batteries

A facile sol-gel approach for the synthesis of lithium titanate composite decorated with N-doped carbon material (LTO/NC) is proposed. Urea is used as a nitrogen source in the proposed approach. The LTO/NC exhibits superior electrochemical performances as an electrode material for lithium-ion batteries, delivering a discharge capacity of as high as 103 mAh g^?1 at a high rate of 20 C and retaining a stable reversible capacity of 90 mAh g^?1 after 1000 cycles, corresponding to 100% capacity retention. These excellent electrochemical performances are proved by the nanoscale structure and N-doped carbon coating. NC layers were uniformly dispersed on the surface of LTO, thus preventing agglomeration, favoring the rapid migration of the inserted Li ion, and increasing the Li⁺ diffusion coefficient and electronic conductivity. LTO with the appropriate amount of NC coating is a promising anode material with applications in the development of high-powered and durable lithium-ion batteries.     

Sulfur/microporous carbon composites for Li-S battery

A commercial carbon black with microporous framework is used as carbon matrix to prepare sulfur/microporous carbon (S/MC) composites for the cathode of lithium sulfur (Li-S) battery. The S/MC composites with 50, 60, and 72 wt.% sulfur loading are prepared by a facile heat treatment method. Electrochemical performance of the as-prepared S/MC composites are measured by galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), with carbonate-based electrolyte of 1.0 M LiPF₆/(PC-EC-DEC). The composite with 50 wt.% sulfur presents the optimized electrochemical performance, including the utilization of active sulfur, discharge capacity, and cycling stability. At the current density of 50 mA g^?1, it can demonstrate a high initial discharge capacity of 1624.5 mAh g^?1. Even at the current density of 800 mA g^?1, the initial capacity of 1288.6 mAh g^?1 can be obtained, and the capacity can still maintain at 522.8 mAh g^?1 after 180 cycles. The remarkably improved electrochemical performance of the S/MC composite with 50 wt.% sulfur are attributed to the carbon matrix with microporous structure, which can effectively enhance the electrical conductivity of the sulfur cathode, suppress the loss of active material during charge/discharge processes, and restrain the migration of polysulfide ions to the lithium anode.     

Enhanced electrochemical performance of lithium ion battery cathode Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C

Li-ion battery cathode material lithium-vanadium-phosphate Li₃V₂(PO₄)₃ was synthesized by a carbon-thermal reduction method, using stearic acid, LiH₂PO₄, and V₂O₅ as raw materials. And stearic acid acted as reductant, carbon source, and surface active agent. The effect of its content on the crystal structure and electrochemical performance of Li₃V₂(PO₄)₃/C were characterized by XRD and electrochemical performance testing, respectively. The results showed that the content of carbon source has no significant effect on the crystal structure of lithium vanadium phosphate. Lihtium vanadium phosphate obtained with 12.3% stearic acid demonstrated the best electrochemical properties with a typical discharge capacity of 119.4 mAh/g at 0.1 C and capacity retention behavior of 98.5% after 50 cycles. And it has high reversible discharge capacity of 83 mAh/g at 5 C with the voltage window of 3 to 4.3 V.     

The influence of polytetrafluorethylene reduction on the capacity loss of the carbon anode for lithium ion batteries

To date, the lithium ion battery has become the focus of secondary battery studies. A considerable capacity loss during the first lithiation of its carbon electrode is a severe drawback of this kind of battery. It has been suggested frequently that the capacity loss was caused by the decomposition of the electrolyte on the surface of the carbon electrode. However, the contribution of binder reduction to this capacity loss has never been considered until now. This paper deals with the binder polytetrafluorethylene (PTFE) reduction and finds that it plays an important part in the capacity loss. It is found that (1) the capacity loss increased with increasing PTFE binder content, (2) the X-ray diffraction peaks corresponding to the PTFE, binder became weaker, while more of the lithium was consumed by the carbon electrode, and disappeared when the consumed amount of lithium exceeded the theoretical value of 1070 mAh per gram of PTFE and (3) the height of the high voltage plateau of the electrochemical titration curves was just a function of storage time, and the length of the plateau was a function of the PTFE content.     

Synthesis of hierarchical MoS<Subscript>2</Subscript> microspheres composed of nanosheets assembled via facile hydrothermal method as anode material for lithium-ion batteries

A hierarchical MoS₂ architecture composed of nanosheet-assembled microspheres with an expanded interplanar spacing of the (002) planes was successfully prepared via a simple hydrothermal reaction. Electron microscopy studies revealed formation of the MoS₂ microspheres with an average diameter of 230 nm. It was shown that the hierarchical structure of MoS₂ microspheres possesses both the merits of nanometer-sized building blocks and micrometer-sized assemblies, which offer high surface area for fast kinetics and buffers the volume expansion during lithium insertion/deinsertion, respectively. The micrometer-sized assemblies were found to contribute to the enhanced electrochemical stabilities of the electrode materials. The mentioned advantages of the MoS₂ electrode prepared in this work allowed enhanced cyclability and high rate capability of the material. Along with this, the material delivered a high initial discharge capacity of 1206 mAh g^?1 and a reversible discharge capacity of 653 mAh g^?1 after 100 cycles at a current density of 100 mA g^?1. Furthermore, the material delivered a high reversible capacity of 480 mAh g^?1 at a high current density of 1000 mA g^?1.     

Effects of carbon content on the electrochemical properties of spherical pyrrhotine/carbon nanocomposites

Spherical pyrrhotine/carbon nanocomposites with different carbon contents were synthesized by a solvothermal method followed by heat treatment. The carbon content of the nanocomposites was controlled by changing the amount of the carbon precursor. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM); the influence of carbon layer thickness on the electrochemical performance was analyzed by charge/discharge cycling and X-ray photoelectron spectroscopy (XPS). Results show that the moderate carbon layer displays a positive effect in improving reversible capacity and the rate capability. The optimal carbon content in the pyrrhotine/carbon nanocomposites was about 15 wt.%, which can retain a high reversible capacity of 689.5 mAh/g even after 50 cycles at 0.1 C and an excellent rate capability of 393.4 mAh/g at 5 C. The synthesized nanocomposites show a promising potential as a novel anode material for lithium-ion batteries.     

Pickering emulsion polymerization of polyaniline/LiCoO2 nanoparticles used as cathode materials for lithium batteries

The oil in water (o/w) emulsions were prepared using aniline dissolved in toluene and LiCoO₂ particles as stabilizers (Pickering emulsions). Pickering emulsions are stabilized by adsorbed solid particles instead of emulsifier molecules. The mean droplet diameter of emulsions was controlled by the mass ratio M (oil)/M (solid particles). The emulsions showed great stability during 3 days. The composite materials containing LiCoO₂ and the conductive polymer polyaniline (PANI) have been prepared by means of polymerization of aniline emulsion stabilized by LiCoO₂ particles. The composite materials were characterized by nanosphere and nanofiber-like structures. The nanofiber-like morphology of the powdered material was distinctly different of the morphologies of the parent materials. The electrochemical reactivity of PANI/LiCoO₂ composites as positive electrode in a lithium battery was examined during lithium ion deinsertion and insertion by galvanostatic charge–discharge testing; PANI/LiCoO₂ (1:4) composite materials exhibited the best electrochemical performance by increasing the reaction reversibility and capacity compared to that of the pristine LiCoO₂ cathode. The first discharge capacity of PANI/LiCoO₂ (1:4) was 167 mAh/g, while that of LiCoO₂ was136 mAh/g.     

Sulfur cloaked with different carbonaceous materials for high performance lithium sulfur batteries

Carbon matrices have attracted the attention enthusiastically as the improver materials of sulfur for rechargeable lithium-sulfur battery. In this work, various morphologies (sphere, fiber, tube and layer) based carbon materials have been used for preparing the sulfur-carbon binary composites via melt diffusion method for lithium-sulfur battery application. The prepared binary composites have been characterized for its structural and morphological information using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and, Scanning and Transmission electron microscopy. The electrochemical studies are characterized by cyclic voltammetry, charge-discharge and cycle life after being assembled as lithium-sulfur cell. The S-prGO composite exhibits the initial discharge capacity of 893 mAh g⁻¹ and it sustains over 50 cycles (598 mAh g⁻¹) at 0.1C, with low capacity fading rate when compared to the other composites studied. A remarkable electrochemical performance indicates that the sheet like morphology can accommodate the volume expansion of sulfur and the oxygen groups containing GO minimize the dissolution of lithium polysulfides.     

Nano Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> as sulfur host for high-performance Li-S battery

S/Li₄Ti₅O₁₂ cathode with high lithium ionic conductivity was prepared for Li-S battery. Herein, nano Li₄Ti₅O₁₂ is used as sulfur host and fast Li⁺ conductor, which can adsorb effectively polysulfides and improve remarkably Li⁺ diffusion coefficient in sulfur cathode. At 0.5 C, S/Li₄Ti₅O₁₂ cathode has a stable discharge capacity of 616 mAh g^?1 at the 700th cycle and a capacity loss per cycle of 0.0196% from the second to the 700th cycle, but the corresponding values of S/C cathode are 437 mAh g^?1 and 0.0598%. Even at 2 C, the capacity loss per cycle of S/Li₄Ti₅O₁₂ cathode is only 0.0273% from the second to the 700th cycle. The results indicate that Li₄Ti₅O₁₂ as the sulfur host plays a key role on the high performance of Li-S battery due to reducing the shuttle effect and enhancing lithium ionic conductivity.     

Spray pyrolysis-deposited TiO<Subscript>2</Subscript> thin films as high-performance lithium ion battery anodes

Focusing on additive-free electrodes, thin films are of typical interest as electrodes for lithium ion battery application. Herein, we report the fabrication of TiO₂ thin films by spray pyrolysis deposition technique. X-ray diffraction and transmission electron microscopic analysis confirms the formation of anatase TiO₂. Electrochemical evaluation of these sub-micron TiO₂ thin films exhibits high-rate performance and long cycling stability. At 1C rate (1C?=?335 mA/g), the electrode delivered discharge capacity of 247 mAh/g allowing about 0.74 lithium into the structure. The electrodes also delivered specific capacities of 122 and 72 mAh/g at 10 and 30C rates, respectively. Without conductive additives, this excellent performance can be attributed to the nanosize effect of TiO₂ particles combined with the uniform porous architecture of the electrode. Upon cycling at high rates (10 and 30C), the electrode exhibited excellent cycling stability and retention, specifically only <?0.6% capacity loss per cycle over 2500 cycles.     

Vertically aligned α-MnO<Subscript>2</Subscript> nanosheets on carbon nanotubes as cathodic materials for aqueous rechargeable magnesium ion battery

In this work, vertically aligned α-MnO₂ nanosheets on carbon nanotubes are synthesized simply by a solution process and the electrochemical performance as host materials of magnesium ion is tested in aqueous solution. Cyclic voltammetry analysis confirms the enhanced electrochemical activity of carbon nanotube-supported samples. Moreover, carbon nanotubes skeleton could reduce the charge transfer resistant of the cathode materials, which is confirmed by electrochemical impedance spectroscopy. Furthermore, when tested as magnesium ion batteries cathodic electrode, the α-MnO₂/carbon nanotube sample registers a prominent discharge capacity of 144.6 mAh g^?1 at current density of 0.5 A g^?1, which is higher than the discharge capacity of α-MnO₂ (87.5 mAh g^?1) due to the synergistic effect of insertion/deinsertion reaction and physical adsorption/desorption process. After the 1000th cycle, a remarkable discharge capacity of 48.3 mAh g^?1 is collected for α-MnO₂/carbon nanotube at current density of 10 A g^?1, which is 85% of the original. It is found that the carbon skeleton not only improved the capacity but also enhanced the cycling performance of the α-MnO₂ electrode significantly. Therefore, α-MnO₂/carbon nanotube is a very promising candidate for further application in environmentally benign magnesium ion batteries.     

Synthesis and characterization of Li4Ti5O12/graphene composite as anode material with enhanced electrochemical performance

The use of graphene as a conductive additive to enhance the rate capability and cycle stability of Li₄Ti₅O₁₂ electrode material has been demonstrated. Li₄Ti₅O₁₂ and its composite with graphene (1.86 wt%) are prepared by ball milling and simple chemical method, respectively. Among the as-synthesized composites, Li₄Ti₅O₁₂ particles uniformly clung to the graphene sheets. When used as an electrode material for lithium ion battery, the composite presents excellent rate performance and high cyclic stability. It is found that the composite displayed high-rate capacity of 118.7 mAh?g^?1 at 20 C. Furthermore, the composite exhibits good cycle stability, retaining over 96 % of its initial capacity after 50 cycles at 10 C. The excellent electrochemical performance is attributed to a decrease in the charge-transfer resistance.     

Carbon@SnS<Subscript>2</Subscript> core-shell microspheres for lithium-ion battery anode materials

A novel unique C@SnS₂ core-shell structure composites consisting of well-dispersity carbon microspheres and ultrathin tin disulfide nanosheets were successfully synthesized for the first time through a simple solvothermal method. The thin SnS₂ nanosheets grew onto the carbon microspheres surfaces perpendicularly and formed the close-knit porous structure. When it was used as anode materials for lithium-ion batteries, the hybrid C@SnS₂ core-shell structure composites showed a remarkable electrochemical property than pure SnS₂ nanosheets. Typically, the hybrid composites with SnS₂ nanosheet shells and carbon microsphere’s core exhibited an excellent initial discharge capacity of 1611.6 mAh/g. Moreover, the hybrid composites exhibited capacities of 474.8–691.6 mAh/g at 100 mA/g over 50 battery cycles, while the pure SnS₂ could deliver capacities of 243–517.6 mAh/g in the tests. The results indicated that the improvement of lithium storage performance of the core-shell structure C@SnS₂ anode materials in terms of rate capability and cycling reversibility owing to the introduction of the smooth carbon microspheres and special designing of core-shell structure.     

Porous NiO hollow quasi-nanospheres derived from a new metal-organic framework template as high-performance anode materials for lithium ion batteries

Porous hollow metal oxides derived from nanoscaled metal-organic framework (MOF) have drawn tremendous attention due to their high electrochemical performance in advanced Li-ion batteries (LIBs). In this work, porous NiO hollow quasi-nanospheres were fabricated by an ordinary refluxing reaction combination of a thermal decomposition of new nanostructured Ni-MOF, i.e., {Ni₃(HCOO)₆·DMF}_n. When evaluated as an anode material for lithium ion batteries, the MOF derived NiO electrode exhibits high capacity, good cycling stability and rate performance (760 mAh g^?1 at 200 mA g^?1 after 100 cycles, 392 mAh g^?1 at 3200 mA g^?1). This superior lithium storage performance is mainly attributed to the unique hollow and porous nanostructure of the as-synthesized NiO, which offer enough space to accommodate the dramstic volume change and alleviate the pulverization problem during the repeated lithiation/delithiation processes, and provide more electro-active sites for fast electrochemical reactions as well as promote lithium ions and electrons transfer at the electrolyte/electrode interface.     

High-performance hierarchical cypress-like CuO/Cu<Subscript>2</Subscript>O/Cu anode for lithium ion battery

Composite CuO/Cu₂O/Cu anode for lithium ion battery was designed and synthesized via facile electrodeposition and the subsequent in situ thermal oxidation in air at 300 °C for 1 h. The as-prepared composite CuO/Cu₂O/Cu anode was studied in terms of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), galvanostatic charge/discharge, cyclic voltammetry (CV), and AC impedance. As expected, the composite CuO/Cu₂O/Cu with CuO-rich surface displayed hierarchical cypress-like morphology; furthermore, the hierarchical cypress-like CuO/Cu₂O/Cu anode also delivered satisfactory electrochemical performances. For example, the reversible discharge capacity remained at 534.1 mAh/g even after 100 cycles. The enhanced electrochemical performances were attributed to the hierarchical cypress-like porous structure and the synergistic effect among the composite active copper oxides and highly conductive Cu current collector.     

Oxalate precursor preparation of Li1.2Ni0.13Co0.13Mn0.54O2 for lithium ion battery positive electrode

Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ powders have been prepared through co-precipitation of metal oxalate precursor and subsequent solid state reaction with lithium carbonate. X-ray diffraction pattern shows that the massive rock-like structure has a good layered structure and solid solution characteristic. Scanning electron microscope and transition electron microscope images reveal that the Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ composed of nanoparticles have the size of 1–2 μm. As a lithium ion battery positive electrode, the Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ has an initial discharge capacity of 285.2 mAh g^?1 at 0.1 C within 2.0–4.8 V. When the cutoff voltage is decreased to 4.6 V, the cycling stability of product can be greatly improved, and a discharge capacity of 178.5 mAh g^?1 could be retained at 0.5 C after 100 cycles. At a high charge–discharge rate of 5 C (1,000 mAh g^?1), a stable discharge capacity of 121.4 mAh g^?1 also can be reached. As the experimental results, the Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ prepared from oxalate precursor route is suitable as lithium ion battery positive electrode.     

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.     

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.     

PAN-based carbon fiber@SnO<Subscript>2</Subscript> for highly reversible structural lithium-ion battery anode

The carbon fiber (CF) is frequently preferred because it is considered as a multifunctional lightweight composite, where the CF is not only acted as one completely integrated part of the device with high-performance structural reinforcement, but also served as one of the battery electrode to storage energy. However, the limitation of electrochemical capacity of commercial CFs for the structural lithium-ion battery (SLIB) is an urgent issue should be solved. Therefore, in this work, a novel strategy to fabricate CF@SnO₂ composite is developed by employing one-step tin tetrachloride solvothermal method. The performance of the CFs could be improved by growing the stannic oxide firmly on each CF to form a synergetic electrode. When tested as anode materials, a high reversible capacity of 510 mAh g^?1 at a current density of 100 mAh g^?1 is maintained without obvious decay up to 150 cycles (a huge increase as high as 637.5% than that of the pure CFs). Furthermore, our strategy reveals an attainable route, which could be as a promising way to make a sustainable anode for SLIBs and carbon-based multi-functional composite for other practical applications.