Drastic Volume Change Research Articles

Properties of Thin Lithium Metal Electrode in Carbonate Electrolytes

The utilization of Li anode in Li-ion batteries is still illusive to date: In addition to the significant safety hazard, Li anode suffers from inferior cycle stability. Furthermore, the majority of the lab-scale investigations uses thick Li foils as the study subject, which can behave extremely differently from the practical Li anode. To provide a realistic baseline to evaluate the electrochemical performance of Li anode in liquid electrolytes, the electrochemical and micromorphological properties of thin Li film (50 µm) are investigated in this study. The deposition-stripping coulombic efficiency (CE) of the thin lithium electrode and the cycle life of the symmetric cell under various conditions are measured combined with microscopic and spectroscopic characterizations. The failure mechanism of the symmetric cells is also investigated. Our results indicates the average CE is strongly related to the cycling parameters including area capacity (depth of Li utilization), C rate and cycle number; and indicating loose relationship with the type of Li salts and concentration due to beneficial surface compounds. Meanwhile, CE has no correlation to the cycle lives of the symmetric cells, which is clearly dictated by the areal capacity and C rate. Our results also suggest that the failing of symmetric cells is due to “soft shorting” (direct contact of SEI covered Li) due to the separator breach induced by the drastic volume change of Li electrode during deposition.

Electrospinning Sn@C nanofibers for high-performance flexible lithium ion battery anodes

Lithium ion batteries are considered as one of the most important energy storage devices in the field of portable electronics and electric vehicles. However, exploring novel and high-performance electrode materials are still urgently needed, as the state-of-the-art lithium ion batteries cannot meet the ever-increasing demand for high energy/power densities. Metal tin and its oxides are promising lithium ion battery anodes, but suffering from drastic volume change and crack issues during lithium intercalation/deintercalation cycling. Here we report a feasible technology to fabricate flexible and free-standing Sn@C nanofiber membrane via electrospinning method, consisting of one dimensional carbon matrix with Sn nanoparticles confined inside. Owing to the superior electron/ion transfer ability and confinement effect from the carbon coating, the as-obtained Sn@ C electrode exhibits a capacity of 668 mA h g−1 at 1 A g−1 even after 350 cycles and a reversible capacity of 263 mA h g−1 can be achieved at an ultrahigh current density of 10 A g−1. In all, this work provides a promising anode for practical application on lithium ion batteries.

High performance columnar-like Fe2O3@carbon composite anode via yolk@shell structural design

Abstract Conversion-type reaction anode materials with high specific capacity are attractive candidates to improve lithium ion batteries (LIBs), yet the rapid capacity fading and poor rate capability caused by drastic volume change and low electronic conductivity greatly hinder their practical applications. To circumvent these issues, the successful design of yolk@shell Fe2O3@C hybrid composed of a columnar-like Fe2O3 core within a hollow cavity completely surrounded by a thin, self-supported carbon (C) shell is presented as an anode for high-performance LIBs. This yolk@shell structure allows each Fe2O3 core to swell upon lithiation without deforming the carbon shell. This preserves the structural and electrical integrity against pulverization, as revealed by in situ transmission electron microscopy (TEM) measurement. Benefiting from these structural advantages, the resulting electrode exhibits a high reversible capacity (1013 mAh g−1 after 80 cycles at 0.2 A g−1), outstanding rate capability (710 mAh g−1 at 8 A g−1) and superior cycling stability (800 mAh g−1 after 300 cycles at 4 A g−1). A Li-ion full cell using prelithiated yolk@shell Fe2O3@C hybrid as the anode and commercial LiCoO2 (LCO) as the cathode demonstrates impressive cycling stability with a capacity retention of 84.5% after 100 cycles at 1 C rate, holding great promise for future practical applications.

Hierarchically Pomegranate‐Like MnO@porous Carbon Microspheres as an Enhanced‐Capacity Anode for Lithium‐Ion Batteries

AbstractTransition‐metal oxides have attracted much attention as promising anode materials, owing to high theoretical specific capacity for lithium‐ion batteries (LIBs). However, rapid performance degradation derived from poor electrical conductivity and drastic volume changes during the repeated lithium insertion/extraction processes has limited their practical applications. In this work, we design and prepare pomegranate‐like microspheres of nano‐sized MnO particles with gaps among them as the core and porous carbon as the shell (designated as PCMS@MnO) by using a facile three‐step process. In such unique PCMS@MnO, the porous carbon shell from phenolic resin is beneficial for the electronic conductivity and wettability, whereas the nano‐sized MnO particles with gaps among them confined in the porous carbon shell can effectively prevent aggregation and pulverization of active materials. As an anode material for LIBs, the PCMS@MnO with a carbon content of about 12 wt % exhibits remarkably high reversible capability (935 mAh g−1 at 100 mA g−1), outstanding rate performance, and superior cycling stability (527 mAh g−1 of 2000 mA g−1 after 2000 cycles). Our results suggest a great potential of pomegranate‐like transition‐metal oxide‐based composites as anode materials in high‐performance LIBs.

Improving the electrochemical performance of Si-based anode via gradient Si concentration

Silicon (Si) has long been regarded as one of the most promising anode materials for the next-generation lithium-ion batteries (LIBs) due to its exceptional specific capacity and apt working voltage. However, the drastic volume change of Si during lithiation/delithiation processes tends to cause various mechanical failure problems including the delamination between current collector and electrode materials, resulting in poor stability and degradation of LIBs. Inspired by the functional graded design in natural biomaterials, we propose to solve the interfacial delamination problem by reallocating the Si in the electrode in a graded manner. The prepared graded electrodes especially those after gradient optimization are found quite successful in alleviating the interfacial delamination, resulting in higher capacity and capacity retention, higher coulombic efficiency, higher effective mass loading in comparison to the traditional ones. Specifically, the optimal graded electrode shows a charge capacity of 1299 mAh g−1 after 50 cycles, which is much higher than that of the homogeneous electrode (66 mAh g−1). Such a graded electrode can be easily implemented by existing manufacturing techniques and synergize with other strategies for solving the large-volume-change problem of Si. Our work provides a guideline for the design and manufacture of the graded Si-based electrodes for LIBs.

In Situ Cross-linked Carboxymethyl Cellulose-Polyethylene Glycol Binder for Improving the Long-Term Cycle Life of Silicon Anodes in Li Ion Batteries

To increase the energy density of Li-ion batteries (LIBs), silicon has been widely studied due to its relative abundance and high theoretical specific capacity (∼3572 mAh g–1). However, silicon experiences drastic volume changes up to 300% associated with Li. Here, we report an in situ cross-linked carboxymethyl cellulose-polyethylene glycol (CMC-PEG) binder and its application to the silicon anode to improve cycle life. Through in situ cross-linking during the electrode drying process, the cross-linked CMC-PEG binder is simply prepared without an additional process. In particular, the cross-linked CMC-PEG binder is effective in enhancing cohesion between active materials and adhesion between active materials and a current collector. The silicon anode with the cross-linked CMC-PEG binder shows stable cycling performance with a capacity of ∼2000 mAh g–1 up to 350 cycles at 0.5 C. In terms of simplicity, this binder has potential to be used for silicon anodes and other electrodes experiencing volume expansi...

Stabilizing Solid Electrolyte-Anode Interface in Li-Metal Batteries by Boron Nitride-Based Nanocomposite Coating

Summary Solid-state Li-metal batteries are promising to improve both safety and energy density compared to conventional Li-ion batteries. However, various high-performance and low-cost solid electrolytes are incompatible with Li, which is indispensable for enhancing energy density. Here, we utilize a chemically inert and mechanically robust boron nitride (BN) film as the interfacial protection to preclude the reduction of Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte by Li, which is validated by in situ transmission electron microscopy. When combined with ∼1–2 μm PEO polymer electrolyte at the Li/BN interface, Li/Li symmetric cells show a cycle life of over 500 h at 0.3 mA·cm−2. In contrast, the same configuration with bare LATP dies after 81 h. The LiFePO4/LATP/BN/PEO/Li solid-state batteries show high capacity retention of 96.6% after 500 cycles. This study offers a general strategy to protect solid electrolytes that are unstable against Li and opens possibilities for adopting them in solid-state Li-metal batteries.

Real-Time TEM Study of Nanopore Evolution in Battery Materials and Their Suppression for Enhanced Cycling Performance.

Battery materials, which store energy by combining mechanisms of intercalation, conversion, and alloying, provide promisingly high energy density but usually suffer from fast capacity decay due to the drastic volume change upon cycling. Particularly, the significant volume shrinkage upon mass (Li+, Na+, etc.) extraction inevitably leads to the formation of pores in materials and their final pulverization after cycling. It is necessary to explore the failure mechanism of such battery materials from the microscopic level in order to understand the evolution of porous structures. Here, prototyped Sb2Se3 nanowires are targeted to understand the structural failures during repetitive (de)sodiation, which exhibits mainly alloying and conversion mechanisms. The fast growing nanosized pores embedded in the nanowire during desodiation are identified to be the key factor that weakens the mechanical strength of the material and thus cause a rapid capacity decrease. To suppress the pore development, we further limit the cutoff charge voltage in a half-cell against Na below a critical value where the conversion reaction of such a material system is yet happening, the result of which demonstrates significantly improved battery performance with well-maintained structural integrity. These findings may shed some light on electrode failure investigation and rational design of advanced electrode materials with long cycling life.

A Core‐Shell NiFe2O4@SiO2 Structure as a High‐Performance Anode Material for Lithium‐Ion Batteries

AbstractSmart surface coatings composed of transition‐metal oxides are shown to significantly improve the cycling performance of batteries. Currently, most studies are mainly focused on coating materials such as TiO2 and carbon‐based materials. However, these coating materials face significant challenges, including their low capacity and tedious processing. Herein, a simple and novel amorphous SiO2 coating is successfully used on the surface of NiFe2O4 to form a core‐shell structure. When tested as an anode, it delivers a high initial discharge capacity of 2022.3 mAh g−1 and retains a high specific capacity of 1224.6 mAh g−1 after 100 cycles at a current density of 0.1 C. The superior performance of NiFe2O4@SiO2 is mainly attributed to the SiO2 coatings, which can provide a high capacity, alleviate drastic volume changes in NiFe2O4 and form a stable solid electrolyte interphase (SEI) layer. The results demonstrated that SiO2 can be used as a novel coating material to improve the cycling properties of metal oxide materials.

Germanium Nanoparticle-Dispersed Reduced Graphene Oxide Balls Synthesized by Spray Pyrolysis for Li-Ion Battery Anode

Simple fabrication of a powdered Ge-reduced graphene oxide (Ge-rGO) composite via spray pyrolysis and reduction is introduced herein. Successful incorporation of the rGO nanosheets with Ge hindered the aggregation of Ge and conferred enhanced structural stability to the composite by alleviating the mechanical stress associated with drastic volume changes during repeated cycling. The Li-ion storage performance of Ge-rGO was compared with that of powdered Ge metal. The reversible discharge capacity of Ge-rGO at the 200th cycle was 748 mA h g−1 at a current density of 1.0 A g−1 and Ge-rGO showed a capacity of 375 mA h g−1 even at a high current density of 5.0 A g−1. The excellent performance of Ge-rGO is attributed to the structural robustness, enhanced electrical conductivity, and formation of open channels between the rGO nanosheets, which facilitated electrolyte penetration for improved Li-ion diffusion. Key words: Lithium ion batteries, Germanium, Graphene, Carbon composite, Spray pyrolysis

Ultra-small SnO2 nanoparticles decorated on three-dimensional nitrogen-doped graphene aerogel for high-performance bind-free anode material

Tin dioxide (SnO2) has attracted extensive research attention as promising anode materials for lithium ion batteries due to high theoretical capacity. However, its application is largely hindered by poor electronic conductivity and drastic volume change during the conversion reaction and alloying processes. Herein, we report a three-dimensional nitrogen-doped graphene aerogel decorating ultra-small SnO2 nanoparticles (3–6 nm) by a facile one-step hydrothermal process. Nanoscaled SnO2 nanoparticles facilitate limited volume expansion and shortened lithium diffusion pathways, nitrogen-doping increases the positive charge density of carbon atoms adjacent to the nitrogen atom, while the three-dimensional porous graphene aerogel has excellent electronic conductivity and facile electrolyte infiltration, thus prompting the composite electrode excellent electrochemical performance. When used as bind-free anode electrode, the graphene aerogel/SnO2 composite delivers a high discharge capacity of 1812.0 mAh g−1 in the initial cycle, and the capacity can retain at 778 mAh g−1 after 100 cycles, demonstrating its promising candidate as anode material for energy storage.

Electrochemical Studies on Kinetics and Diffusion of Li-Ions in MnO2 Electrodes

In this work, beta MnO2 nanorods synthesized by one-step microwave assisted solvothermal approach are used as conversion anodes for lithium-ion batteries. The MnO2 electrode exhibits the high initial capacity of 950 mAh g−1 (third cycle) followed by 550 mAh g−1 during the 50th cycle and 1000 mAh g−1 at the end of 200 cycles at C/20 rate. The material also exhibits good capacity at higher C rates of 1C, follows the same capacity retention pattern of C/20 rate and stable over 1000 cycles. The Trasatti procedure has been used to understand the kinetics of the gradual increase in capacity with an increase in cycle number. The increase in capacity is attributed to the enhancement in pseudo capacitive contribution to the overall charge storage from 31% to 75% during 50th and 1000th cycles, respectively. Impedance studies further reveal that MnO2 electrodes exhibit a faster Li-ion diffusion and less resistance with an increase in cycle number. Further, the notable electrochemical performance can be attributed to the unique one-dimensional MnO2 nanorod, which shortens the Li+ diffusion length, and accommodates the strain induced by drastic volume change upon continuous cycling.

A robust aqueous-processable polymer binder for long-life, high-performance lithium sulfur battery

The development of lithium sulfur batteries (LSBs) has significantly suffered from the shuttle of lithium polysulfides (LiPS) and drastic volume change of the active materials during cycling processes. The eco-friendly manufacturing of electrodes based on aqueous slurries is highly desirable for practical applications. To address these challenging issues, a novel aqueous-processable polymer, chitosan sulfate ethylamide glycinamide (CSEG), has been developed as the binder for sulfur cathode. The dual-amide structures endow the CSEG with superior LiPS-trapping capability to impede the diffusion and shuttle of LiPS in electrolyte. The CSEG-based sulfur cathodes demonstrate remarkable cycling performances at 1 C for 700 cycles and 6 C for 450 cycles, with only 0.049%, 0.0895% capacity fading per cycle, respectively. More importantly, the cathode achieves excellent rate performance with a capacity of 194.4 mAh g-1 at an ultrahigh current density of 40.26 mA cm-2 (20 C), which takes only 21 s for one charge or discharge process. The electrochemical performance of the novel CSEG binder, as demonstrated in this work, is superior to all previously reported aqueous-processable binders for sulfur cathode. Such a breakthrough will greatly improve the development of eco-friendly sulfur cathode, paving new ways for the practical application of next-generation LSBs.

Dandelion-shaped manganese sulfide in ether-based electrolyte for enhanced performance sodium-ion batteries

Metal sulfide materials serve as environment-friendly, sustainable, and effective electrode materials for green-energy storage systems. However, their capacity-fading issues related to low electrical conductivity and drastic volume changes during electrochemical cycling have generally limited their application to sodium ion batteries. Here we show that with the combination of an ether-based NaPF6/diglyme electrolyte, the dandelion-shaped manganese sulfide electrode displays enhanced reversible capacity, cycle life, and rate capability. The capacity of 340 mAh g−1 is maintained over more than 1000 cycles at a current density of 5.0 A g−1. Furthermore, discharge capacities of 277 and 230 mAh g−1 at 10 and 20 A g−1 current densities, respectively, are obtained. Our work demonstrates the formation of a protective solid electrolyte interface layer along the surface of the primary seed particle that limits polysulfide dissolution and hence the preservation of the active material during reaction with sodium.

High-rate and long-cycle life performance of nano-porous nano-silicon derived from mesoporous MCM-41 as an anode for lithium-ion battery

Nano-porous nano-silicon (npn-Si) anode for Li-ion battery is a great promise to mitigate problems associated with large volume expansion and pulverization during the charging-discharging cycle. Here we report the synthesis of highly porous Si from MCM-41, through a magnesiothermic reduction ((MR) method. Structural studies confirm the complete conversion of MCM-41 to crystalline silicon from the particle core to the surface. Morphological studies reveal the retention of porous network in the parent compound after reduction. The silicon anode is fabricated using two types of aqueous binders viz Na salt of carboxymethyl cellulose (Na-CMC), alginate (Na-Alg) demonstrates good cycling stability and rate performance. Among these, porous silicon with former binder shows a higher initial charge capacity of 2767 mAhg−1 even at a current rate of C/2 and retains 705 mAhg−1 capacity after 500 cycles. While, alginate binder showed much higher initial capacity of 3000 mAhg−1 and retained almost the same capacity as Na-CMC after 10 cycles and beyond. High capacity and reasonably good retention of nano-porous nano-silicon is attributed to (i) the accommodation of the drastic volume change in porous Si to effectively mitigate the mechanical stress, (ii) enhanced electrochemical kinetics and (iii) high Li flux in the porous structure.

Tip-welded ferric-cobalt sulfide hollow nanoneedles on highly conductive carbon fibers for advanced asymmetric supercapacitors

The ever-increasing concerns about global environmental problems and depletion of fossil resources have stimulated intensive research on low-cost and high-performance energy storage materials. Here, we introduce the two-step sulfidation of hierarchical ferric-cobalt sulfide hollow nanoneedles on electrical conductive carbon fiber paper (CFP) for high-performance supercapacitor electrodes. Under the growth regulation of macroporous CFP substrate, prepared free-standing composite paper with tip-welded ferric-cobalt sulfide hollow nanoneedles can offer substantial exposed electroactive sites for Faradaic redox reaction and effectively buffer the drastic volume change during long-term charge-discharge, and also provide fast charge transfer paths through the carbon skeleton for efficient energy storage. Due to these unique features, obtained composite paper electrode delivers a higher specific capacitance (2282 F g−1 at current density of 1 A g−1) than those of the previously reported MCo2S4 based electrodes. Asymmetric supercapacitor assembled using the composite paper as the binder-free positive electrode also shows a high energy density of 86.8 Wh kg−1 at a power density of 800 W kg−1, and an impressive 82.3% capacitance retention after 5000 cycles, demonstrating the great potential of this low-cost and free-standing electrodes towards high-performance energy storage.

Thin films as model system for understanding the electrochemical reaction mechanisms in conversion reaction of MgH2 with lithium

Metal hydrides are promising high-capacity anode materials for Li-ion batteries but their conversion reaction with lithium suffers from low reversibility at room temperature (RT). Irreversibility issues in magnesium hydride MgH2 thin films are investigated, as well-defined model system. Films are deposited over Cu current collectors by means of microwave plasma-assisted sputtering and coated with aluminum to minimize formation of passivating MgO native oxide. Structural and chemical properties of the electrodes have been analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS). Galvanostatic cycling reversibility at RT and C/50 regime is limited to 25% in the first cycle for 1 μm thick films. The lithiation of the thin film is complete and doubles its thickness. Despite drastic volume changes, neither cracks, voids, nor detachment of the thin film from the substrate are noticed. Moreover, electronic resistivity decreases upon lithiation due to the formation of metallic Mg. The origin of irreversibility phenomena in MgH2 films is attributed to sluggish mass transport of species within the electrode at RT.

Lawn-like FeCo2S4 hollow nanoneedle arrays on flexible carbon nanofiber film as binder-free electrodes for high-performance asymmetric pseudocapacitors

Herein, we report the rational design and synthesis of a novel flexible supercapacitor electrode consisting of lawn-like FeCo2S4 hollow nanoneedle arrays (FeCo2S4 HNNA) on electrospun carbon nanofiber (CNF) film via a two-step sulfidation method. In this work, the macroporous CNF film served as flexible/conducting substrate not only promotes the homogeneous distribution of FeCo2S4 hollow nanoneedles, but also enhance the electrical conductivity of the composite film. Especially, the tip-welded FeCo2S4 nanoneedles with unique interior channels and perpendicular orientation possess numerous accessible electroactive sites and short electrolyte transfer paths for efficient energy storage, and also buffer the drastic volume change during the repetitive charge-discharge process. As a result, prepared FeCo2S4 HNNA/CNF composite electrode exhibits a high specific capacitance of 2476 F g−1 at 1 A g−1, and excellent capacitance retention of 93% after 5000 cycles, which is competitive among those previously reported ternary metal sulfide-based electrodes. Asymmetric supercapacitor device fabricated using FeCo2S4 HNNA/CNF as positive electrode also delivers a high energy density of 88.5 Wh kg−1 at a power density of 800 W kg−1, as well as a superior cycling stability of 81.2% capacity retention after 5000 cycles.

Nitrogen-doped carbon-coated MnO nanoparticles anchored on interconnected graphene ribbons for high-performance lithium-ion batteries

The construction of the anode materials with high-rate and long-life performance for lithium-ion batteries (LIBs) still remains a great challenge due to their poor electronic conductivity and drastic volume changes during the lithiation and delithiation processes. Herein, we report nitrogen-doped carbon-coated MnO nanoparticles anchored on the interconnected graphene ribbons (IGR-MnO-C) as a anode for LIBs. As a result, the IGR-MnO-C exhibits a high reversible capacity (1055 mAh g−1 at 0.1 A g−1), excellent rate capability (547 mAh g−1 at 2 A g−1) and stable cycling performance (550 cycles with 113% capacity retention at 0.5 A g−1). The strategy proposed in this work can be further extended to other transition metal oxides for the applications in supercapacitors, sodium-ion batteries and fuel cell.

Self-assembled 3D network GeOx/CNTs nanocomposite as anode material for Li-ion battery

Ge-based materials are promising alternative anode materials for Li-ion batteries (LIBs) because of their high theoretic specific capacity, as well as high intrinsic electronic conductivity and Li-ion diffusivity compared with Si-based materials. However, their industrial application has been limited by their inherent problem of volume expansion (~260%) upon Li+ insertion/extraction. Here, we report a GeOx/CNT nanocomposite with a self-assembled three-dimensional (3D) network structure that can be applied as an anode material in LIBs. The nanocomposite is synthesised through an in situ reduction route wherein GeOx particles are selectively grown on the surface of CNTs. The material is studied through X-ray diffraction, X-ray photoelectron spectrometry, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and electrochemical techniques. When used as an anode material for LIBs, the cycling performance and rate capability of the synthesised GeOx/CNTs nanocomposite are superior to those of pure GeOx particles. The GeOx/CNT composite can deliver a discharge capacity of 753.8 mAh g−1 after 100 charge/discharge cycles at 160 mA g−1 even under the high current density of 3.2 A g−1 and achieves a reversible capacity of 554.8 mAh g−1. The excellent Li storage performance of the material is attributed to its unique self-assembled 3D network structure, which provides a stable conductive network and effectively buffers the drastic volume changes experienced by GeOx particles during charge–discharge cycling.