Anode Materials For Next-generation Lithium-ion Batteries Research Articles

Tailoring the Li+ Intercalation Energy of Carbon Nanocage Anodes Via Atomic Al-Doping for High-Performance Lithium-Ion Batteries.

Graphitic carbon materials are widely used in lithium-ion batteries (LIBs) due to their stability and high conductivity. However, graphite anodes have low specific capacity and degrade over time, limiting their application. To meet advanced energy storage needs, high-performance graphitic carbon materials are required. Enhancing the electrochemical performance of carbon materials can be achieved through boron and nitrogen doping and incorporating 3D structures such as carbon nanocages (CNCs). In this study, aluminum (Al) is introduced into CNC lattices via chemical vapor deposition (CVD). The hollow structure of CNCs enables fast electrolyte penetration. Density functional theory (DFT) calculations show that Al doping lowers the intercalation energy of Li+. The Al-boron (B)-nitrogen (N-doped CNC (AlBN-CNC) anode demonstrates an ultrahigh rate capacity (≈300 mAhg-1 at 10 Ag-1) and a prolonged fast-charging lifespan (862.82 mAhg-1 at 5 Ag-1 after 1000 cycles), surpassing the N-doped or BN-doped CNCs. Al doping improves charging kinetics and structural stability. Surprisingly, AlBN-CNCs exhibit increased capacity upon cycling due to enlarged graphitic interlayer spacing. Characterization of graphitic nanostructures confirms that Al doping effectively tailors and enhances their electrochemical properties, providing a new strategy for high-capacity, fast-charging graphitic carbon anode materials for next-generation LIBs.

In Situ TEM Observation of (Cr, Mn, Fe, Co, and Ni)3O4 High-Entropy Spinel Oxide Formation During Calcination at Atomic Scale.

High-entropy oxides (HEOs) are promising anode materials for lithium-ion batteries (LIBs), owing to their stable crystal structure, superionic conductivity, and high capacity. In this study, the (Cr, Mn, Fe, Co, and Ni)3O4 HEO via solid-state reaction is prepared. To improve the synthetic efficiency, it is necessary to understand the formation mechanism. Therefore, a high-resolution transmission electron microscopy (HRTEM) is used to record information during calcination at increasing temperature. The overall formation process included MnO2 and NiO aggregation at 500°C, followed by (Mn, and Ni)3O4 combined with Co3O4 at 600°C to form (Mn, Co, and Ni)3O4. At higher temperatures, Fe2O3 and Cr2O3 sequentially combined with (Mn, Co, and Ni)3O4 and formed the (Cr, Mn, Fe, Co, Ni)3O4 at 900°C. In addition, the valence-state-changing mechanisms and ion arrangements of (Cr, Mn, Fe, Co, and Ni)3O4 are determined using electron energy loss spectroscopy (EELS) and extended X-ray absorption fine structure (EXAFS). This study successfully revealed the formation of HEO at atomic scale. The results provide valuable insights for improving the manufacturing process of (Cr, Mn, Fe, Co, and Ni)3O4 HEOs, which is expected to play a vital role in the development of anode materials for next-generation LIBs.

High-Resolution Nanoanalytical Insights into Particle Formation in SnO2/ZnO Core/Shell Nanowire Lithium-Ion Battery Anodes.

Tin oxide (SnO2)/zinc oxide (ZnO) core/shell nanowires as anode materials in lithium-ion batteries (LIBs) were investigated using a combination of classical electrochemical analysis and high-resolution electron microscopy to correlate structural changes and battery performance. The combination of the conversion materials SnO2 and ZnO is known to have higher storage capacities than the individual materials. We report the expected electrochemical signals of SnO2 and ZnO for SnO2/ZnO core/shell nanowires as well as unexpected structural changes in the heterostructure after cycling. Electrochemical measurements based on charge/discharge, rate capability, and electrochemical impedance spectroscopy showed electrochemical signals for SnO2 and ZnO and partial reversibility of lithiation and delithiation. We find an initially 30% higher capacity for the SnO2/ZnO core/shell NW heterostructure compared to the ZnO-coated substrate without the SnO2 NWs. However, electron microscopy characterization revealed pronounced structural changes upon cycling, including redistribution of Sn and Zn, formation of ∼30 nm particles composed of metallic Sn, and a loss of mechanical integrity. We discuss these changes in terms of the different reversibilities of the charge reactions of both SnO2 and ZnO. The results show stability limitations of SnO2/ZnO heterostructure LIB anodes and offer guidelines on material design for advanced next-generation anode materials for LIBs.

Decorating Phosphorus Anode with SnO2 Nanoparticles To Enhance Polyphosphides Chemisorption for High-Performance Lithium-Ion Batteries.

Phosphorus has been regarded as one of the most promising next-generation lithium-ion battery anode materials, because of its high theoretical specific capacity and safe working potential. However, the shuttle effect and sluggish conversion kinetics hamper its practical application. To overcome these limitations, we decorated SnO2 nanoparticles at the surface of phosphorus using an electrostatic self-assembly method, in which SnO2 can participate in the discharge/charge reaction, and the Li2O formed can chemically adsorb and suppress the shuttle of soluble polyphosphides across the separator. Additionally, the Sn/Li-Sn alloy can enhance the electrical conductivity of the overall electrode. Meanwhile, the similar volume changes and simultaneous lithiation/delithiation process in phosphorus and SnO2/Sn are beneficial for avoiding additional particle damage near two-phase boundaries. Consequently, this hybrid anode exhibits a high reversible capacity of ∼1180.4 mAh g-1 after 120 cycles and superior high-rate performance with ∼78.5% capacity retention from 100 to 1000 mA g-1.

Preparation and Electrochemical Characterization of Si@C Nanoparticles as an Anode Material for Lithium-Ion Batteries via Solvent-Assisted Wet Coating Process.

Silicon-based electrodes are widely recognized as promising anodes for high-energy-density lithium-ion batteries (LIBs). Silicon is a representative anode material for next-generation LIBs due to its advantages of being an abundant resource and having a high theoretical capacity and a low electrochemical reduction potential. However, its huge volume change during the charge–discharge process and low electrical conductivity can be critical problems in its utilization as a practical anode material. In this study, we solved the problem of the large volume expansion of silicon anodes by using the carbon coating method with a low-cost phenolic resin that can be used to obtain high-performance LIBs. The surrounding carbon layers on the silicon surface were well made from a phenolic resin via a solvent-assisted wet coating process followed by carbonization. Consequently, the electrochemical performance of the carbon-coated silicon anode achieved a high specific capacity (3092 mA h g−1) and excellent capacity retention (~100% capacity retention after 50 cycles and even 64% capacity retention after 100 cycles at 0.05 C). This work provides a simple but effective strategy for the improvement of silicon-based anodes for high-performance LIBs.

Eliminating Graphite Exfoliation with an Artificial Solid Electrolyte Interphase for Stable Lithium-Ion Batteries.

Although graphite materials with desirable comprehensive properties dominate the anode market of commercial lithium-ion batteries (LIBs), their low capacity during fast charging precludes further commercialization. In the present work, natural graphite (G) is reported not only to suffer from low capacity during fast charging, but also from charge failure after many charging cycles. Using different characterization techniques, severe graphite exfoliation, and continuously increasing solid electrolyte interphase (SEI) are demonstrated as reasons for the failure of G samples. An ultrathin artificial SEI is proposed, addressing these problems effectively and ensuring extremely stable operation of the graphite anode, with a capacity retention of ≈97.5% after 400 cycles at 1 C. Such an artificial SEI modification strategy provides a universal approach to tailoring and designing better anode materials for next-generation LIBs with high energy densities.

An Environmental Sustainability Analysis Tool for Next Generation Lithium Ion Batteries of Electric Vehicles

Lithium-ion batteries (LIBs) are widely used in portable electronics and electric vehicles, but are limited in capacity and energy density. Tremendous efforts have been devoted to the research and development of next-generation LIBs with a high capacity and energy density, particularly through adoption of novel nano-structured materials in the LIB electrodes. The synthesis of nanomaterials, however, involves heavy use of toxic chemicals and nanoparticle emissions, which induce grave concerns on the environmental sustainability of next-generation LIBs. Silicon, with a high theoretical specific capacity, has been recognized as one of the most promising anode materials for next-generation LIBs. In this study, a comprehensive analysis tool is developed to evaluate the environmental sustainability of silicon-based LIBs for EVs by incorporating previously published data, and two nanostructured silicon materials, i.e., silicon nanowires (SiNWs) and silicon nanotubes (SiNTs) are chosen as examples. The purpose is to provide decision support for sustainable design of next-generation LIB technologies by providing overall environmental impact results and feedback to next-generation LIB designers to identify the tradeoffs between technical specifications and sustainability performance. Specifically, this tool based on an Excel spreadsheet comprises six modules, i.e., Dashboard, Material Consumptions, Gas and Aqueous Emissions, Nano Particle Emissions, Energy Consumption, and Life Cycle Impacts. The specifications of the battery packs are inputted in the Dashboard and the environmental impact assessment is conducted through the rest modules utilizing the inputted data to compute each modular results using the embedded formula from our previously published work. The conventional emissions and energy consumption data are characterized with the life cycle impact assessment method for design feedback, while the nanoparticle emission data are experimentally measured and directly used. This analysis tool provides insights into material consumptions and environmental impacts of SiNW-and SiNT-based LIBs and can be expanded for future analyses of other nanostructured next-generation LIB technologies for electric vehicles.

Synthesis of porosity controllable nanoporous silicon with a self-coated nickel layer for lithium-ion batteries

Silicon (Si) is a promising anode material for next-generation high-performance lithium-ion batteries (LIBs) owing to its large theoretical capacity. However, its application is limited due to several issues including large volume expansion during the charge–discharge process, causing mechanical pulverization and low electrical conductivity. Herein, we report a scalable method to synthesize nanoporous Si using Al–Si–Ni amorphous precursor alloys. The nanoporous structure is fabricated by selective phase dissolution of crystallized alloys, wherein the pore and ligament sizes in the nanoporous structure are controlled. A thin Ni layer is formed on the surface of the Si ligament by a spontaneous reaction during selective phase dissolution, such that the nanoporous structure fabrication and formation of the conductive coating layer occur simultaneously. The Ni-coated nanoporous Si delivers a high initial coulombic efficiency and high reversible capacity after 500 cycles. This study offers a novel strategy for synthesizing nanostructured Si anode material for next-generation LIBs.

Anode Properties of Cr x V1-x Si2/Si Composite Electrodes for Lithium-Ion Batteries.

We have reported the effects of substituting a transition metal in silicide on the electrochemical performance of the silicide/Si composite anode for lithium-ion batteries (LIBs); the Cr0.5V0.5Si2/Si electrode exhibited much better cyclability compared with CrSi2/Si and VSi2/Si electrodes. Herein, we investigated the electrochemical performance of a CrxV1–xSi2/Si slurry electrode for its application in LIBs, and the results obtained were compared to those of a gas deposition (GD) electrode, which was comprised of only active materials. The slurry electrode exhibited a superior cycling life as with the GD electrode. After charge–discharge cycles, the expansion of the electrode thickness of CrSi2/Si and Cr0.5V0.5Si2/Si was smaller than that of VSi2/Si, and VSi2 was significantly pulverized compared with the other silicides. It is considered that VSi2 deformed easily by the stress from Si expansion and pulverized because the hardness of VSi2 was the smallest among the silicides used in this study. These results reveal that Cr0.5V0.5Si2/Si has great potential as an anode material for next-generation LIBs and hardness is an important property for compositing silicide with Si.

Engineering capacitive contribution in dual carbon-confined Fe3O4 nanoparticle enabling superior Li+ storage capability

Iron oxides have attracted widespread attention as lithium-ion batteries anode in virtue of abundant resources, high theoretical capacity, and environmental friendliness. However, during the process of charging and discharging, the poor conductivity and large volume expansion of iron oxides lead to the pulverization of the material as well as the rapid capacity fading, which limits further application significantly. Hence, tiny Fe3O4 nanoparticles encapsulated into double layers N-doped hollow carbon nanotubes (NHCNT/Fe3O4) are synthesized by a controllable chemical bath deposition and subsequent carbonization treatment. Benefitting from the double carbon buffer layers and the outstanding N-doped carbon conductive network, the well-designed NHCNT/Fe3O4 electrode delivers an excellent cycling stability with 87% capacity retention at 1 A g−1 after 1000 cycles and a remarkable rate performance. And hollow N-doped carbon nanotubes (NHCNT) displays a favorable reversible capacity of 350 mAh g−1 in the 500th cycle at 1 A g−1. The in-depth kinetic analysis reveals the dominated capacitive contribution facilitate to realize a superior rate capability of NHCNT/Fe3O4 anode. The excellent electrochemical performance exhibited by the NHCNT/Fe3O4 composites material provides great innovative ideas and inspiration for the design of the next-generation lithium-ion battery anode materials.

Dual-metal-organic frameworks derived manganese and zinc oxides nanohybrids as high performance anodes for lithium-ion batteries

Metal-organic framework (MOF) derivatives are attracting increasing interests for next-generation lithium-ion battery anode materials. Here, a novel approach has been applied to synthesize binary Mn–Zn oxides nanohybrids embedded in porous carbon matrix by pyrolysis of dual-metal-organic frameworks. The as-fabricated MnO/ZnO@C nanohybrids exhibit superior lithium storage capabilities, reaching a reversible capacity of 1396 mAh g−1 at 0.2 A g−1 with an initial coulombic efficiency of higher than 75%. When cycled at 2 A g−1, the electrode maintained at 636 mAh g−1 after 1000 cycles, indicating the outstanding high-rate capability and cycling stability. The improved electrochemical performance can be attributed to the interconnected porous structure of carbon frameworks and uniform heterostructure nanohybrids, which efficiently improve the charge transfer and buffer the volume expansion during repeated lithiation process. These findings demonstrate an efficient strategy of using dual-MOF-derived bi-metal oxide nanostructures as high performance anodes for lithium-ion batteries.

Electrochemical performance of porous CaFe2O4 as a promising anode material for lithium-ion batteries

Abstract The performance of existing lithium-ion batteries (LIBs) is greatly hindered by the low specific capacity of graphite-based anodes (372 mAh g−1). Therefore, development of suitable anode materials that exhibit higher and stable capacity is necessary to improve performance. Transition metal oxides have attracted tremendous attention as next-generation anode materials for LIBs due to their high theoretical capacity. Herein, we report the synthesis of a porous CaFe2O4 by a facile and time efficient solution combustion synthesis technique for use in an anode for LIBs. The as-prepared material exhibited improved electrochemical performance with specific discharge capacities of 441 mAh g−1, 518 mAh g−1, and 516 mAh g−1 for the initial three cycles. It achieved stability with a deliverable specific discharge capacity of 551 mAh g−1 after 150 cycles at a current density of 200 mA g−1. The porous CaFe2O4 exhibits improved cyclic performance and rate capability. These improvements are attributed to the porous nature of active material and, more importantly, the presence of CaO, which effectively alleviates the volume changes by acting as a buffer matrix.

In-situ synthesis of Ge/reduced graphene oxide composites as ultrahigh rate anode for lithium-ion battery

Germanium (Ge), as an anode material for lithium-ion batteries (LIBs), has received considerable attention because of its high theoretical capacity and excellent electrochemical performance. However, Ge anode usually undergoes large volume expansion during lithium insertion/extraction, resulting in severe structural pulverization and fast capacity fading. Here, we report an efficient cationic polymer-assisted in-situ reduction method for the preparation of highly uniform Ge/RGO composites (RGO = reduced graphene oxide) using GeO2, instead of expensive and toxic GeXn (X = Cl, Br and I), as Ge source. In this protocol, GeO32− anions are well adsorbed on cationic polymer-modified graphene oxide sheets by electrostatic interaction, followed by in-situ reduction, which results in the growth of ultrafine Ge nanoparticles (ca. 5 nm) on RGO sheets to form highly uniform sandwich-like structure. Benefiting from the tiny size of Ge nanoparticles and the well-conductive RGO sheets, the Ge/RGO anodes exhibit a high reversible capacity of 960 mAh g−1 after 100 cycles at 0.2 A g−1, an excellent rate capability of 631 mAh g−1 at 5 A g−1, and 705 mAh g−1 after 350 cycles at 1 A g−1 (with the capacity fading of only 0.07% per cycle based on the initial discharge capacity of 940 mAh g−1). More impressively, by coupling with LiFePO4 cathode, the full battery also shows a good electrochemical performance in terms of specific capacity and cycling stability. The simple, low-cost and environmental friendly synthesis strategy together with the outstanding lithium-storage performance of Ge/RGO composites affords a promising anode material for next-generation LIBs.

Facile synthesis of MoS2@TiNb2O7 nanocomposite anode materials with superior electrochemical performance for Li-ion batteries

Novel hierarchical MoS2@TiNb2O7 (MS@TNO) hetero-nanostructures consisted of TiNb2O7 nanorods and ultrathin MoS2 nanosheets were successfully synthesized by simple sol-gel/hydrothermal processes. The synergistic effects of the two constituents benefited to the lithium-ion transport kinetics of the MS@TNO hetero-nanostructure for lithium-ion batteries (LIBs). In the potential range of 0.01~3.00 V vs. Li/Li+, the MS@TNO-based LIBs exhibited high capacities of 925 and 771 mAh g−1 after 50 and 200 cycles at a current density of 0.5 A g−1, respectively, and excellent rate performance of 579 mAh g−1 at 4 A g−1. The obtained anode materials exhibited excellent electrochemical performance with superior reversible capacity, rate capability, and cyclic stability. The outstanding electrochemical property of 3D MS@TNO hetero-nanostructures allows their application in high-performance anode materials for next-generation LIBs.

Nitrogen-doped hierarchically porous carbonaceous nanotubes for lithium ion batteries

By a novel two-step activation of the polypyrrole nanotube (PPyNT) precursor, nitrogen-doped hierarchically porous carbonaceous nanotubes (HPCNT) are successfully prepared. The as-prepared HPCNT not only exhibits an ultrahigh specific surface area of 2180 m2 g−1 and a large total pore volume of 1.22 cm3 g−1, but also possesses a rich N-doping content of 8.2 wt% which especially includes a high pyridinic-N content of 30%. As an anode for lithium-ion batteries (LIBs), the HPCNT delivers an ultrahigh reversible capacity of 1372 mAh g−1 and keeps a high retention of 89.3% over 100 cycles at 0.1 A g−1. Even at a large current rate of 1 A g−1, the reversible capacity is still as high as 630 mAh g−1 after 700 cycles. Compared with either the commercial graphite or the state-of-the-art LIB carbons in the literature, the HPCNT is quite competitive, which makes it a promising anode material for next-generation LIBs. Also, the outstanding performances of the HPCNT exhibit a great potential of this novel activation strategy for commercial application on LIBs.

A novel durable double-conductive core-shell structure applying to the synthesis of silicon anode for lithium ion batteries

Si/C composites are currently the most commercially viable next-generation lithium-ion battery anode materials due to their high specific capacity. However, there are still many obstacles need to be overcome such as short cycle life and poor conductivity. In this work, we design and successfully synthesis an excellent durable double-conductive core-shell structure p-Si-Ag/C composites. Interestingly, this well-designed structure offers remarkable conductivity (both internal and external) due to the introduction of silver particles and carbon layer. The carbon layer acts as a protective layer to maintain the integrity of the structure as well as avoids the direct contact of silicon with electrolyte. As a result, the durable double-conductive core-shell structure p-Si-Ag/C composites exhibit outstanding cycling stability of roughly 1000 mAh g−1 after 200 cycles at a current density of 0.2 A g−1 and retain 765 mAh g−1 even at a high current density of 2 A g−1, indicating a great improvement in electrochemical performance compared with traditional silicon electrode. Our research results provide a novel pathway for production of high-performance Si-based anodes to extending the cycle life and specific capacity of commercial lithium ion batteries.

Controllable Fabrication of CoMn2O4 Microflowers and Microspheres As High-Performance Lithium Ion Battery Anode Material

The growing electric vehicle requirements have attracted great interest in development of lithium ion batteries (LIBs) with large gravimetric and volumetric capacities, long cycle lifespan. To meet these applications, high quality electrode materials are needed. However, conventional bulk electrode materials cannot fully reach the increasing demands due to their inherent limits in performance. In recent years, nanostructured electrode materials with higher rate capability have been acknowledged by low lithium-ion diffusion distance and high electrode/electrolyte area. However, electrode made from nanostructured electrode materials meets these challenges. (1) Nanoparticles tend to self-aggregate and the side reaction with the electrolyte due to high specific surface area, which lead to low initial coulombic efficiency and poor cycling life. (2) Nanoparticles have a huge volume changes during Li+ insertion/ extraction that result in fracture of nanostructured particle, delaminating of the conductive coating and low capacity with cycle increasing. (3) Nanostructured particles have low tap density which results in a low volumetric energy density.Therefore, the electrode materials with optimal structure should be developed to deal with above-mentioned problems. Micro-/nanostructures with controlled size and morphology have attracted considerable attention as high-performance anode materials for next-generation LIBs. This micro-/nanostructure should be a porous microstructure composed of primary nanocrystallines tightly compacted to form 3D channels for ion diffusion. Moreover, this structure can exploit many advantages of nanostructure for lithium ion batteries due to the reduction of side reactions with electrolyte, leading to high density and long cycling life with high safety. Some simple micro-/nano-structured metal oxides such as Mn-based oxides, Co-based oxides, Fe-based oxides and Sn-based oxides, have been recently reported for use in LIBs. Mn-based oxide electrodes (MnO, MnO2, Mn2O3, Mn3O4, ZnMn2O4, NiMn2O4 and CoMn2O4) are developed due to low operating voltages (1.3-1.5 V for lithium extraction) and high energy density. Among these Mn-based anodes, CoMn2O4 has been considered for substitution of the conventional graphite anode in LIBs. The shape and micro/nanostructure of CoMn2O4 material play an important role in the electrochemical performances. In this paper, uniform hierarchical porous CoMn2O4 microspheres and microflowers were realized by adjusting the urea concentration through a solvothermal process followed by a post-annealing treatment. In the low urea concentration, the microflower with diameter size of around 10 μm is composed of porous nanosheets with a thickness of about 20 nm. In the high urea concentration, a large amount of uniform CoMn2O4 microspheres is obtained with average diameter of about 8 μm. CoMn2O4 microsphere is highly porous and composed of numerous primary nanoparticles. As expected, the distribution of the O, Mn and Co elements is homogeneously distributed on the surface for CoMn2O4 microflower and microsphere. The actual molar ratios of Mn and Co for CoMn2O4 microflower and microspheres obtained from energy-dispersive X-ray (EDX) analysis are close to 2, which are consistent with the ratio of that in the precursor solution. The chemical compositional and crystalline structural changes of as-prepared samples were characterized using X-ray diffraction (XRD) and thermogravimetric analysis (TGA). These results show the precursor in the low urea concentration is a MnCo-complex structure (including CoMn-layered double hydroxide and CoMn-glycolates or alkoxide derivatives) in an alkaline environment under this solvothermal conditions. Meanwhile, in the high urea concentration, the precursor Co1/3Mn2/3CO3 sample is formed. The possible formation mechanism of as-prepared CoMn2O4 microsphere and microflower precursors is explained due to the presence of CO2 pressure into the reaction solution. When used as anode materials for lithium-ion batteries, the porous CoMn2O4 microflower and microspheres exhibited good long-life cycling performance at high rate density. At a current density of 100 mA g-1, the CoMn2O4 microflower and microspheres exhibit an initial capacity of 1200 and 1225 mA h g-1 and the capacity is maintained at 710 and 220 mAh g-1 after 50 cycles. Excellent rate capabilities (~813 mAh g-1 at 200 mA g-1 and ~612 mAh g-1 at 600 mA g-1) are observed for CoMn2O4 microspheres. Based on these results, the good electrochemical properties can result from the porous CoMn2O4 microspheres. On the one hand, the micro-/nano porous structured CoMn2O4 microspheres could significantly enhance the electrode integrity by buffering the volume changes with repeating Li+ insertion/ extraction, which is contributed to good cycling stability. On the other hand, the micro-/nano porous structured CoMn2O4 microspheres provide extra active position for Li+ storage and short Li+ ion diffusion length, contributing to the high specific capacity and better rate capability. The CoMn2O4 hierarchical porous microspheres, which have good electrochemical performance and ease of fabrication, hold the great promise as the anode materials for high-performance LIBs. Figure 1

Nanosheets of Earth-Abundant Jarosite as Novel Anodes for High-Rate and Long-Life Lithium-Ion Batteries

Nanosheets of earth-abundant jarosite were fabricated via a facile template-engaged redox coprecipitation strategy at room temperature and employed as novel anode materials for lithium-ion batteries (LIBs) for the first time. These 2D materials exhibit high capacities, excellent rate capability, and prolonged cycling performance. As for KFe3(SO4)2(OH)6 jarosite nanosheets (KNSs), the reversible capacities of above 1300 mAh g(-1) at 100 mA g(-1) and 620 mAh g(-1) after 4000 cycles at a very high current density of 10 A g(-1) were achieved, respectively. Moreover, the resulting 2D nanomaterials retain good structural integrity upon cycling. These results reveal great potential of jarosite nanosheets as low-cost and high-performance anode materials for next-generation LIBs.

Large-scale low temperature fabrication of SnO2 hollow/nanoporous nanostructures: the template-engaged replacement reaction mechanism and high-rate lithium storage.

The morphology-controlled synthesis of SnO2 hollow/nanoporous nanostructures (nanotubes, urchin-like morphologies and nanospheres) was achieved via a template-engaged replacement reaction at a mild temperature (lower than 80 °C). The formation mechanism of hollow interior and nanoporous walls for the obtained SnO2 nanostructures (SnO2 nanotubes were used as an example) was investigated based on TEM and HRTEM observations during different reaction stages. It is found that bridge voids firstly form at the MnO2/SnO2 interface, followed by the inward development of voids before the MnO2 core is completely consumed. Two types of short-circuited galvanic cells, MnO2/Mn(2+)∣SnO2/Sn(2+) and concentration cell-SnO2/Sn(2+) (interior)∣SnO2/Sn(2+) (exterior), are probably responsible for the formation of SnO2 nanotubes and outward growth of SnO2 along MnO2. Moreover, the calculation result of the outer diameter of SnO2 nanotubes is in good agreement with the observation results by SEM and TEM. When evaluated as anodes for lithium ion batteries (LIBs), the three SnO2 nanostructures exhibit superior rate capability and cycling performance. Especially, SnO2 nanotubes present the best rate capability: specific capacities of above 800 mA h g(-1) at 200 mA g(-1) and about 500 mA h g(-1) at 4000 mA g(-1) were achieved, respectively. Importantly, the 1D morphology of SnO2 nanotubes can be well preserved after prolonged cycling at a relatively high current density, indicating good structural stability of the resulting nanotubes during the Li(+) insertion/extraction process. These results indicate that the obtained SnO2 hollow/nanoporous nanostructures would be promising anode materials for next-generation LIBs.

Full-Field Synchrotron Tomography of Nongraphitic Foam and Laminate Anodes for Lithium-Ion Batteries

Nondestructive methods that allow researchers to gather high-resolution quantitative information on a material's physical properties from inside a working device are increasingly in demand from the scientific community. Synchrotron-based microcomputed X-ray tomography, which enables the fast, full-field interrogation of materials in functional, real-world environments, was used to observe the physical changes of next-generation lithium-ion battery anode materials and architectures. High capacity, nongraphitic anodes were chosen for study because they represent the future direction of the field and one of their recognized limitations is their large volume expansion and contraction upon cycling, which is responsible for their generally poor electrochemical performance. In this work, Cu6Sn5 coated on a three-dimensional copper foam was used to model a high power electrode while laminated silicon particles were used to model a high energy electrode. The electrodes were illuminated in situ and ex situ, respectively, at Sector 2-BM of the Advanced Photon Source. The changes in electrode porosity and surface area were measured and show large differences based on the electrode architecture. This work is one of the first reports of full-field synchrotron tomography on high-capacity battery materials under operating conditions.