In-situ fabrication of heterostructured SnOx@C/rGO composite with durable cycling life for improved lithium storage

Due to their ultra-high theoretical capacity and low discharge potential, rich Sn-based materials are considered promising candidates for lithium ion battery (LIB) anodes; however, the development of SnO_x electrodes is restricted by their low conductivity and severe volume change during repeated cycling. In this study, carbon matrix encapsulating heterostructured SnO_x ultrafine nanoparticles (SnO_x@C/rGO) were synthesized in situ through a facile solvent mixing, followed by thermal calcination. During the decomposition of the Sn-organic precursor, the sizes of the as-prepared SnO_x nanoparticles were strictly controlled to 5–10 nm; they were intimately wrapped by the in-situ formation of ultrathin carbon layers, which prevented the agglomeration of nanograins. Furthermore, the SnO_x@C nanoparticles were evenly anchored on the surface of reduced graphene oxide (rGO) to construct a highly conductive carbon framework. It is notable that the carbon matrix prepared in situ can accommodate the volumetric change of SnO_x and facilitate the transport of Li⁺ ions during continuous cycling. Benefiting from the synergistic effect between the SnO_x nanoparticles and carbon matrix prepared in situ, the heterostructured SnO_x@C/rGO will confer improved structural stability and reaction kinetics for lithium storage. It delivers a stable reversible discharge capacity of 1092.2 mAh g⁻¹ at a current rate of 0.1 A g⁻¹, and enhanced cycling retention with a capacity of 447.8 mAh g⁻¹ after 1200 cycles at a current rate of 5.0 A g⁻¹. This strategy provides a rational avenue to design oxide anodes with efficient hierarchical structure for LIB development.     

Ti2Nb10O29@C hollow submicron ribbons for superior lithium storage

Titanium niobate prepared by traditional techniques has the shortcomings of low ion diffusion coefficient as well as poor electrical conductivity, which drastically reduce its applicability. In this work, we prepare carbon coated Ti₂Nb₁₀O₂₉ hollow submicron ribbons (Ti₂Nb₁₀O₂₉@C HSR) using a simple electrospinning procedure. As anode material for lithium-ion batteries (LIBs), it delivers a high charge capacity of 259.7 mAh g^?1 at 1 C with low capacity loss of 0.013% in long-term cycles. Increased the current density to 5 C, Ti₂Nb₁₀O₂₉@C HSR can maintain a reversible capacity of 189.9 mAh g^?1, indicating its good rate performance. Additionally, this work uses in-situ X-ray diffraction (XRD) to provide an explanation for the lithium storage process in Ti₂Nb₁₀O₂₉@C HSR, demonstrating the high reversibility during charge/discharge cycles. Therefore, Ti₂Nb₁₀O₂₉@C HSR has outstanding cycle adaptability and structural reversibility to be a promising anode for LIBs.     

Spherical ferroelectric PbZr0.52Ti0.48O3 nanoparticles with high permittivity: Switchable dielectric phase transition with temperature

The spherical ferroelectric PbZr_0.52Ti_0.48O₃ (PZT 52/48) nanoparticles are prepared via simple and environment friendly high temperature solid state method. The crystal structure and morphology of these particles are characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). XRD analysis and selected area electron diffraction (SAED) pattern of PZT particles revealed its crystalline nature. The energy involved in the synthesis especially during the initiation and termination processes for the formation of PZT particles is found from the high temperature calorimetric study. These particles are spherical in nature with an average diameter of ≤20 nm. The bulk and surface chemical composition of these particles are investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). XPS study reveals that the prepared PZT particles contain titanium ion in two different oxidation states namely Ti³⁺ and Ti⁴⁺. The PZT particles exhibit high permittivity with relatively low dielectric loss. From temperature dependent dielectric analysis, it is seen that there is a switchable dielectric phase transition at or above 80 °C.     

Microstructure and electric properties of Pr-doped Pb(Zr0.52Ti0.48)O3 ceramics

Improving the piezoelectric activity of lead zirconate titanate (PZT) ceramics is of great importance for practical applications. In this study, the influence of Pr³⁺ doping on the ferroelectric phase composition, microstructure, and electric properties on the A-site of (Pb_1-1.5xPr_x)(Zr_0.52Ti_0.48)O₃ is extensively investigated. A dense and fine microstructural sample is obtained with the introduction of Pr³⁺. The results show that the morphotropic phase boundary (MPB) moves to the rhombohedral phase region. The rhombohedral and tetragonal phases exhibit an ideal coexistence in the 4 mol.% Pr³⁺ doped (PPZT4) samples. Lead vacancy and the reduction of the potential energy barrier are considered to be the key mechanisms for donor doping, which is upheld by the Pr³⁺ doping. Combining the I-E hysteresis loops with the P-E hysteresis loops, it becomes apparent that both contribution maximums of the domain switching and residual polarisation are in PPZT4. Moreover, the thermal aging resistance of PZT is improved by doping, and the temperature stability is optimised from 83% in PZT to 96% in PPZT4. Hence, an appropriate amount of Pr³⁺ doping can effectively improve the piezoelectric activity of PZT ceramics in the MPB area and optimise the performance stability of the material under application temperatures.     

Tuning the crystal and electronic structure of Li4Ti5O12 via Mg/La Co-doping for fast and stable lithium storage

“Zero-strain” Li₄Ti₅O₁₂ has become one of the most promising anode materials for lithium-ion battery but its low electronic and ionic conductivity lead to the poor rate capability. Herein, the high-rate performance and the cycling stability of Li₄Ti₅O₁₂ have been largely enhanced by replacing Li and Ti with a little amount of Mg and La, respectively. The synergistic modulation mechanism of Mg and La co-doping on the crystal/electronic structure and electrochemical performances has been unveiled. Firstly, Mg and La co-doping enlarges the lattice parameters, unit cell volume and Li1–O bond. These facilitate the lithium-ion migration and enhance the rate capability. Secondly, Ti–O bond is shortened which enhances the structure stability and cyclic performance. Thirdly, the first-principles calculations further confirm that Mg/La co-doping modulates the electronic density of states and decreases the Li⁺ migration barrier. The polarization and charge transfer impedance are effectively alleviated. Moreover, the diffusion coefficient of lithium ions is further improved because of the reduction of much more Ti³⁺. At 10C, it delivers a discharge capacity of 107.8mAh/g after 500cyles which reserves 92.2% of the initial capacity. This study provides some insights into optimizing the electrochemical performances of Li₄Ti₅O₁₂ by tuning the crystal and electronic structure with lattice doping.     

Synthesis of Mn3O4/N-doped graphene hybrid and its improved electrochemical performance for lithium-ion batteries

Mn₃O₄/N-doped graphene (Mn₃O₄/NG) hybrids were synthesized by a simple one-pot hydrothermal process. The scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray powder diffraction (XRD), Thermogravimetric analysis (TG), Raman Spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the microstructure, crystallinity and compositions. It is demonstrated that Mn₃O₄ nanoparticles are high-dispersely anchored onto the individual graphene nanosheets, and also found that, in contrast with pure Mn₃O₄ obtained without graphene added, the introduction of graphene effectively restricts the growth of Mn₃O₄ nanoparticles. Simultaneously, the anchored well-dispersed Mn₃O₄ nanoparticles also play a role as spacers in preventing the restacking of graphene sheets and producing abundant nanoscale porous channels. Hence, it is well anticipated that the accessibility and reactivity of electrolyte molecules with Mn₃O₄/NG electrode are highly improved during the electrochemical process. As the anode material for lithium ion batteries, the Mn₃O₄/NG hybrid electrode displays an outstanding reversible capacity of 1208.4 mAh g⁻¹ after 150 cycles at a current density of 88 mA g⁻¹, even still retained 284 mAh g⁻¹ at a high current density of 4400 mA g⁻¹ after 10 cycles, indicating the superior capacity retention, which is better than those of bare Mn₃O₄, and most other Mn₃O₄/C hybrids in reported literatures. Finally, the superior performance can be ascribed to the uniformly distribution of ultrafine Mn₃O₄ nanoparticles, successful nitrogen doping of graphene and favorable structures of the composites.     

Unique porous yolk-shell structured Co3O4 anode for high performance lithium ion batteries

This paper introduces a unique porous yolk-shell structured Co₃O₄ microball, which is synthesized by spray pyrolysis from precursor solution with polyvinylpyrrolidone (PVP) additive. PVP acts as an organic template in the pyrolytic reaction facilitating the formation of yolk-shell structure. The electrochemical properties of porous yolk-shell Co₃O₄ microballs evaluated as anode materials for lithium ion batteries exhibit high initial columbic efficiency of 77.9% and high reversible capacity of 1025 mAh g⁻¹ with capacity retention of 98.8% after 150 cycles at 1 A g⁻¹. In contrast, the hollow microballs obtained without PVP addition show obvious capacity decay from 1033 to 748 mAh g⁻¹ after 150 cycles with the capacity retention of 72.3%. In addition, the microballs with porous yolk-shell structure exhibit better rate performance. The superior electrochemical performance is mainly attributed to the unique porous yolk-shell structure which provides large voids to buffer volume expansion and enlarge the contact area with the electrolyte, shortening the diffusion path of the lithium ions.     

Structural and Physical Properties of Nd-Doped Pb(Zr0.52Ti0.48)O3 Ceramics

Lead zirconate titanate (PZT) ceramics (Zr/Ti = 52/48) have been modified with different quantities of neodymium oxide (Nd₂O₃). The preparation was carried out via the solid-state-reaction route. The samples were calcined and sintered at 850°C and 1200°C, respectively. The structural evolution and the microstructure were investigated using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM), respectively. The physical properties such as dielectric constants, piezoelectric coefficients, density etc. were also studied.     

The effect of imprint on remanent piezoelectric properties and ferroelectric aging of PbZr0.52Ti0.48O3 thin films

Ferroelectric films suffer from both aging and degradation under high ac-field drive conditions due to loss of polarization with time. In this study, the roles of defect chemistry and internal electric fields on the long-term stability of the properties of piezoelectric films were explored. For this purpose, lead zirconate titanate (PZT) films with a Zr/Ti ratio of 52/48 doped with Mn- (PMZT) or Nb- (PNZT) were deposited on Pt coated Si substrates by the sol-gel method. It was demonstrated that the magnitude of the internal field is much higher in PMZT films compared to PNZT films after poling in the temperature range of 25-200°C under an electric field of −240 kV/cm. The development of the internal field is thermally activated, with activation energies from 0.5 ± 0.06 to 0.8 ± 0.1 eV in Mn doped films and from 0.8 ± 0.1 to 1.2 ± 0.2 eV in Nb doped films. The different activation energies for imprint suggests that the physical mechanism underlying the evolution of the internal field in PMZT and PNZT films differs; the enhanced internal field upon poling is attributed to (a) alignment of oxygen vacancy—acceptor ion defect dipoles (, ) in PMZT films, and (b) thermionic injection of electron charges and charge trapping in PNZT films. In either case, the internal field reduces back switching, enhances the remanent piezoelectric properties, and dramatically improves the aging behavior. PMZT films exhibited the greatest enhancement, with reduced high temperature (180°C) aging rates of 2%-3%/decade due to improved stability of the poled state. In contrast, PNZT films showed significantly larger high temperature aging rates (15.5%/decade) in the piezoelectric coefficient, demonstrating that the fully poled state was not retained with time.     

Facile synthesis and electrochemical properties of carbon-coated ZnO nanotubes for high-rate lithium storage

ZnO is an important functional material, and a nanotube structure is beneficial for various applications. Here, we report the facile synthesis and electrochemical properties of carbon-coated ZnO nanotube materials as Li rechargeable battery anodes. ZnO nanorod was first synthesized via a simple hydrothermal method. Subsequently, the material was annealed with a carbon precursor, forming free-standing, carbon-coated ZnO nanotubes. The carbon-coated nanotube structure is beneficial to alleviate volume changes of the ZnO active material during Li insertion and extraction processes as well as to improve the electrochemical reaction kinetics. Electrochemical test results demonstrate that the carbon-coated ZnO nanotube electrodes deliver improved the cycling performance compared with ZnO nanorod electrodes. Better rate performance than carbon-coated ZnO nanoparticle electrodes was also achieved.     

Synthesis and electrochemical performance of Li4Ti5O12/Ag composite prepared by electroless plating

To improve the electrochemical and anti flatulence performance of Li₄Ti₅O₁₂, Ag modified Li₄Ti₅O₁₂ (LTO) with high electrochemical performance as anode materials for lithium-ion battery was synthesized successfully by two-step solid phase sintering and subsequent electroless plating process in the presence of silver. The effect of Ag modification on the physical and electrochemical properties were investigated by the extensive material characterization of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM). The results showed that the samples possessed single spinel structure, it could be observed that the LTO/Ag composite and the pure LTO shared the same vibration frequencies, which indicated that the crystal structure of LTO didn’t change after electroless plating process, and the particles were uniformly and regularly shaped within 0.5–1.0 µm. Electrochemical performance of the samples were evaluated by the charging and discharging, cyclic voltammetry, electrochemical impedance spectroscopy, cycling and rate tests. It's obvious that the LTO/Ag composite prepared at the 10 min of electroless plating showed the highest performance with capacitance of 182.3 mA h/g at 0.2 C current rates. What's more, the LTO/Ag composites still maintained 92% of its initial capacity even after 50 charge/discharge cycles. Modification of appropriate Ag not only benefits the reversible intercalation and deintercalation of Li⁺, but also improves the diffusion coefficient of lithium ion. Besides, modification of appropriate Ag lower electrochemical polarization leads to higher conductivity and cycle performance of LTO, which is consistent with the results of the best reversible capacities.     

One-dimensional Ti2Nb10O29 nanowire for enhanced lithium storage

Among a variety of host materials for lithium storage, titanium-niobium oxides exhibit great potential in application. Herein, Ti₂Nb₁₀O₂₉ nanowire is synthesized via an electrospinning method. Compared with bulk Ti₂Nb₁₀O₂₉ prepared by solid-state approach, the electrochemical properties of Ti₂Nb₁₀O₂₉ nanowire is better. According to the galvanostatic charging-discharging test, the initial capacity of 232.8 mAh g^?1 for Ti₂Nb₁₀O₂₉ nanowire is displayed. Besides, it exhibits superior rate performance. With the current density set as 0.5, 1, 2, 3, 4 and 5 C, the Ti₂Nb₁₀O₂₉ nanowire can deliver the specific capacity of 251.3, 240.3, 221.8, 205.3, 188.1 and 174.5 mAh g^?1, respectively. Furthermore, its cycling performance is superior. The capacity retention of Ti₂Nb₁₀O₂₉ nanowire is 85.90% after 900 cycles at 12 C, which is obviously superior than that of bulk Ti₂Nb₁₀O₂₉ (25.16%). Finally, a Ti₂Nb₁₀O₂₉/LiCoO₂ full cell is fabricated, which exhibits excellent electrochemical performance, demonstrating its potential for practical application.     

Electrochemical performance of Li4Ti5O12 anode materials synthesized using a spray-drying method

In this study, spinel lithium titanate (Li₄Ti₅O₁₂, LTO) anode materials were synthesized from two titanium sources (P25 TiO₂, 100% anatase TiO₂) using a spray-drying method and subsequent calcination at various temperatures. The electrochemical performance of both a Li/LTO half cell and a LiNi_0.5Mn_1.5O₄/LTO (LNMO/LTO) full cell were investigated. The electrochemical performance of the LTO material prepared from P25 TiO₂ was superior to that of the LTO prepared from 100% anatase TiO₂. After modification of LTO material with AlPO₄, the LTO coated with 2 wt% of AlPO₄ (denoted “2%AlPO₄-LTO”) provided the best performances. The specific (delithiation) capacities of the 2%AlPO₄-LTO anode material was 189.7 mA h g⁻¹ at 0.1C/0.1C, 184.5 mA h g⁻¹ at 1C/1C, 178.8 mA h g⁻¹ at 5C/5C, and 173.1 mA h g⁻¹ at 10C/10C. From long-term cycling stability tests, the specific capacity at the first cycle and the capacity retention after cycling were 185.5 mA h g⁻¹ and 98.06%, respectively, after 200 cycles at 1C/1C and 182.1 mA h g⁻¹ and 99.18%, respectively, after 100 cycles at 1C/10C. For the LNMO/2%AlPO₄-LTO full cell, the average specific capacity (delithiation) and coulombic efficiency after the first five cycles were 164.8 mA h g⁻¹ and 93.30%, respectively, at 0.1C/0.1C. The specific capacities at higher C-rates were 156.1 mA h g⁻¹ at 0.2C/0.2C, 135.7 mA h g⁻¹ at 1C/1C, 97.5 mA h g⁻¹ at 3C/3C, and 46.5 mA h g⁻¹ at 5C/5C. After twenty-five cycles, the C-rate returned to 1C/1C and the specific capacity, coulombic efficiency, and capacity retention were maintained at 134.1 mA h g⁻¹, 99.17%, and 98.82%, respectively.     

Compositing SrLi2Ti6O14 with chemical deposited silver for enhancing lithium ion storage

One of the main issues for titanium-based anode materials is their poor electronic conductivity and this issue can affect their rate performance. For conquering this drawback, many approaches have been proposed. In this report, SrLi₂Ti₆O₁₄ as one of the titanium-based anode materials is prepared via a facile sol–gel method and subsequently it has been composited with silver to elevate its electronic conductivity. Upon the analysis of electrochemical results, the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag can deliver an initial capacity of 164.9?mAh?g^?1. After 50 cycles, the sample can still retain 154.6?mAh?g^?1 with 93.8% retention of the first cycle. Meanwhile, the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag can also exhibit good rate capacities, even at 300?mA?g^?1, its capacity can be firmly kept at 140.0?mAh?g^?1. In addition, in situ X-ray diffraction characterization shows the structural reversibility of the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag during cycling. All the electrochemical results indicate that the SrLi₂Ti₆O₁₄/Ag composite with 6?wt% Ag can be a promising anode material for lithium ion batteries.     

Carbon-coated Bi5Nb3O15 as anode material in rechargeable batteries for enhanced lithium storage

Bismuth can alloy with lithium to generate Li₃Bi with the volumetric capacity of about 3765 mAh cm^?3 (386 mAh g^?1), rendering bismuth-based materials as attractive alloying-type electrode materials for rechargeable batteries. In this work, bismuth-based material Bi₅Nb₃O₁₅ @C is fabricated as anode material through a traditional solid-state reaction with glucose as carbon source. Bi₅Nb₃O₁₅ @C composite is well dispersed, with small particle size of 0.5–2.0?µm. The electrochemical performance of Bi₅Nb₃O₁₅ @C is reinforced by carbon-coated layer as desired. The Bi₅Nb₃O₁₅ @C exhibits a high specific capacity of 338.56 mAh g^?1 at a current density of 100?mA?g^?1. And it also presents an excellent cycling stability with a capacity of 212.06 mAh g^?1 over 100 cycles at 100?mA?g^?1. As a comparison, bulk Bi₅Nb₃O₁₅ without carbon-coating only remains 319.62 mAh g^?1 at 100?mA?g^?1, revealing poor cycle and rate performances. Furthermore, in-situ X-ray diffraction experiments investigate the alloying/dealloying behavior of Bi₅Nb₃O₁₅ @C. These insights will benefit the discovery of novel anode materials for lithium-ion batteries.     

Defect engineering on the defluorinated MWCNTs@SnO2@N-doped carbon composite for enhanced lithium storage performance

When tin oxide (SnO₂) is used in the anode of lithium-ion batteries, its capacity decreases dramatically due to poor conductivity and volume effects during the electrochemical cycle. Although composites with traditional carbon-based materials can improve this shortcoming, the low capacitance of such materials still limits the capacity of the composites. Therefore, we applied defect engineering to SnO₂/C composite electrodes for the first time, and prepared D-MWCNTs@SnO₂@N–C composite electrodes with hollow rod structures. Defects were constructed in the carbon materials to promote electron diffusion and ion storage active sites. The hollow structure can adapt to the volume change that occurs during Li-ion insertion/desorption. In addition, the detachment of F atoms and the insertion of N atoms, which are chemical processes that occur on the surface of carbon materials, promote an increase in surface porosity and defect density, thereby providing additional lithium storage sites. The double carbon effect caused by defect engineering provides a multidimensional transport path and rapid migration rate for Li-ions, which enables the electrode to display excellent electrochemical performance; thus, this work could lead to the preparation of next-generation anode materials with high energy storage capacity, high rate capability and high cycle stability.     

Influences of Liquid‐Phase Sintering on Structure,Grain Growth,and Dielectric Behavior of PbZr0.52Ti0.48O3 Ceramics

In this work, to formulate piezoceramic systems such as PbZr_0.52Ti_0.48O₃ (PZT) for low‐temperature co‐fired ceramic (LTCC)‐based devices, liquid‐phase sintering approach is demonstrated. ZnO–B₂O₃ (ZB) binary glass system is used as sintering aid. X‐ray diffraction (XRD) study confirms the formation of morphotropic phase boundary (MPB; tetragonal + rhombohedral) in PZT prepared by hydrothermal route. ZB is found to induce change in tetragonal/rhombohedral ratio in MPB of PZT. 1%ZB in PZT is found to raise the tetragonality from 71% to 92% in MPB region of PZT. ZB addition in PZT has reduced the sintering temperature from 1250 to 825°C for relative density about 91% with sustaining MPB phase. 1% ZB content is optimal percentage to enhance sinterability and relative density. Uniform dispersion of glass in PZT matrix is confirmed by SEM images. ZB content in PZT is found to controlling grain growth during sintering. Highest dielectric constant and lowest dielectric loss with low sintering temperature (825°C) of 1%ZB among all glass added in PZT exhibit technical suitability of 1%ZB + PZT to use as LTCC‐based energy storage devices.     

Synthesis of CuGeO3/reduced graphene oxide nanocomposite by hydrothermal reduction for high performance Li-ion battery anodes

Nowadays, Lithium-ion batteries (LIBs) are prevalently applied in numerous areas, leading to increasing demand of innovative electrodes with high specific capacities. An advanced CuGeO₃/reduced graphene oxide (rGO) structure is designed and fabricated as the anode material taking the advantage of considerable capacity offered by CuGeO₃ and stable framework constructed by rGO. The as-prepared CuGeO₃ with 30 wt% GO addition exhibits the best electrochemical performance. Specifically, a reversible charge capacity of 909 mAh·g⁻¹ with high coulombic efficiency of 91.49% at the current density of 100 mA g⁻¹ after 200 cycles is demonstrated, and the rate capacity retains 747.6 mAh·g⁻¹ with 91.59% capacity retention. These results indicate that the CuGeO₃/rGO composite holds great potential in next-generation LIBs.     

Ag enhanced electrochemical performance for Na2Li2Ti6O14 anode in rechargeable lithium-ion batteries

Due to the characteristics of an electronic insulator, Na₂Li₂Ti₆O₁₄ always suffers from low electronic conductivity as anode material for lithium storage. Via Ag coating, Na₂Li₂Ti₆O₁₄@Ag is fabricated, which has higher electronic conductivity than bare Na₂Li₂Ti₆O₁₄. Enhancing the Ag coating content from 0.0 to 10.0 wt%, the surface of Na₂Li₂Ti₆O₁₄ is gradually deposited by Ag nanoparticles. At 6.0 wt%, a continuous Ag conductive layer is formed on Na₂Li₂Ti₆O₁₄. While, particle growth and aggregation take place when the Ag coating content reaches 10.0 wt%. As a result, Na₂Li₂Ti₆O₁₄@6.0 wt% Ag displays better cycle and rate properties than other samples. It can deliver a lithium storage capacity of 131.4 mAh g⁻¹ at 100 mA g⁻¹, 124.9 mAh g⁻¹ at 150 mA g⁻¹, 119.1 mAh g⁻¹ at 200 mA g⁻¹, 115.8 mAh g⁻¹ at 250 mA g⁻¹, 111.9 mAh g⁻¹ at 300 mA g⁻¹ and 109.4 mAh g⁻¹ at 350 mA g⁻¹, respectively.