Large Volume Variation Research Articles

Constructing strain-alleviated structures in ultrathin FeS/C composites for durable lithium and sodium storage

Iron sulfide (FeS) is a competitive anode material for Li-/Na-ion batteries (LIBs/SIBs) with high specific capacity and excellent environmental benignity. Nevertheless, its practical application is greatly hindered by the sluggish charge transfer dynamics and large volume variations upon cycling. Herein, by constructing a strain-alleviated (bubble film-like) structure in an ultrathin FeS/C composite, the sluggish transfer kinetics and huge volume variations of FeS were fundamentally solved. The bubble film-like carbon matrix serves as the protective shell to alleviate the huge volume changes of FeS and enhance its electronic conductivity, as verified by finite element simulation and ex-situ transmission electron microscopy results. Benefiting from this unique design, the as-designed electrode exhibited a significantly enhanced performance with a high discharge capacity of 469 mA h g−1 at 5 A g−1 for LIBs and 354 mA h g−1 after 1500 cycles at 1 A g−1 for SIBs. Moreover, the full cell with this electrode and LiFePO4 cathode can deliver outstanding cycling stability of 558 mA h g−1 even after 100 cycles. We expect that this strategy can also be applied to other anode materials plagued by poor conductivity and huge volume changes and remarkably spur the development of batteries with high rate capability and long lifespan.

Boosted sodium storage of GeS2/GeO2/ZnS composite via heterostructure engineering

Transition metal dichalcogenides exhibit tremendous potential for sodium ion batteries (SIBs), owing to the outstanding specific capacity and aboundant reserves. However, the large ionic radius of sodium and poor conductivity often result in the fast decaying performance and inferior reaction kinetics. Herein, the GeS2/GeO2/ZnS@rGO (GGZ/C) ternary metal-based composite is fabricated as an anode material for SIBs. Notably, the GGZ/C composite is derived from the phase transformation of Zn2GeO4 precursor, which is beneficial for the heterostructure engineering. In this hierarchical structure, the metal phases ZnS and GeO2 are used to form the heterogeneous framework, while graphene is applied to build a conductive network and anchor the host nanoparticles. Therefore, the great Na+ diffusion channels are achieved by the rational design of the huge exquisite interfaces among the heterogeneous mixed phases. Notably, it can almost completely relieve the volume expansion and restrain the internal stress of GGZ/C composite, providing the excellent structural tolerance. As expected, the GGZ/C composite exhibits excellent rate capability, with an impressive reversible capacity of 548 mAh g−1 at a high rate of 5.0 A g−1. Meanwhile, the GGZ/C also displays outstanding cycling performance with a specific capacity of 519 mAh g−1 after 650 cycles at high rate of 5.0 A g−1. This strategy offers the inspiration for rational heterostructure engineering for the energy storage materials with excellent reversible capacity and large volume variation.

Facile fabrication of core-shell α-Fe2O3@PPy imbedded into porous biomass-derived carbon for enhanced lithium storage

Due to the large theoretical capacity (1007mAh/g) and unique electrochemical properties, α-Fe2O3 is regarded as an improved anode for next generation lithium-ion batteries (LIBs). Nevertheless, its numerous applications in lithium storage are constrained by its weak conductivity and large volume variation during cycling. Herein, the unique BPC/α-Fe2O3@PPy composite is synthesized by incorporating α-Fe2O3@PPy into three-dimensional hierarchical porous carbon, which can enhance charge transfer efficiency and decrease its volume variation. As anodes for LIBs, the BPC/α-Fe2O3@PPy electrode displays excellent cycle stability and exceptional high-rate performance. This work offers a sustainable approach of constructing economic and green α-Fe2O3-based composite as novel LIBs anode materials for renewable applications.

Internal interface engineering of yolk-shell structure toward fast and robust potassium storage

Advanced anode materials with stable and fast K-ion storage behavior are of great significance for potassium-ion batteries (PIBs) toward large-scale applications, while it still remains a big challenging due to their intrinsic poor conductivity and large volume variation during cycles. Herein, we develop an internal interfacial engineering by encapsulating core-shell NiS2@C nanoparticles within MOF-derived hollow carbon shell for superior PIB anodes. As-prepared yolk-shell NiS2@C@C composite integrates the structure superiority of abundant interior void space, outer protective carbon shell and internal conductive carbon layer. Comprehensive experimental and theoretical methods illuminate that internal NiS2/C interface is conductive to boost charge transport kinetics, enhance pseudocapacitive behavior, and mitigate mechanical stress in outer carbon shell. As a result, it manifests an ultrahigh capacity of 481 mA h g−1 at 0.2 A g−1, and guarantees the rate capability of 306 mA h g−1 at 20 A g−1. Moreover, it presents excellent cycle stability (358 mA h g−1 after 1600 cycles at 1 A g−1), which is extremely competitive among the best reported conversion anodes for PIBs.

A heterogeneous structured C/SnO2/SnSe2@C hybrid: exploring the superior rate performance in sodium ion batteries

Transition metal oxides are regarded as the prospective anode materials for next-generation sodium-ion batteries owing to their high theoretical capacity. Nevertheless, its low conductivity and large volume variation obstruct its practical applications. In this study, a design of heterostructured SnO2/SnSe2 nanoparticles encapsulated by a carbon shell (C/SnO2/SnSe2@C) synthesized through a templating method and in-situ gas-phase selenization process. The rich heterostructures and the interfacial effect induced by a built-in electric field significantly accelerate reaction kinetics and enhance the reaction activity. When employed as an anode for sodium-ion batteries , C/SnO2/SnSe2@C electrodes achieve a superior rate performance (238.4 mAh/g at 5.0 A/g) and cycling performance (422.3 mAh/g at 0.1 A/g after 150 cycles; 289.7 mAh/g at 1.0 A/g after 200 cycles). A quantitative examination into the origin demonstrated that the Na+ storage is dominated by the fast surface redox reaction, which endows the heterostructure with a durable rate performance. Moreover, based on a dQ/dV analysis and in situ X-ray diffraction results, the C/SnO2/SnSe2@C anode has a hybrid mechanism of SnO2 (conversion and alloying reaction) and SnSe2 (intercalation, conversion, and alloying reactions). This strategy of the heterostructure design provides a potential route to develop high-performance sodium-ion storage materials and sheds light on the behavior of Na-storage mechanisms.

Rationally incorporated SnO2/SnS2 nanoparticles on sulfur-doped graphene aerogels for high-performance lithium/sodium-ion batteries

Tin-based anode materials, such as tin oxide and tin sulfide, have received increased attention due to their high theoretical capacity, natural abundance, and adequate operating voltage. But the large volume variation and sluggish reaction kinetics lead to severe structural deterioration and capacity fading during the charge-discharge process, hindering their practical application. Herein, we synthesized a unique ternary hybrid structure to grow SnS2 nanosheets and SnO2 particles on graphene aerogels by hydrothermal method (denoted as SnO2/SnS2/SGA). The SnO2/SnS2/SGA exhibited better cycling stability than SnS2/GA and SnO2/GA. The tight adhesion of SnO2/SnS2 helps to alleviate the undesired electrode materials destruction due to volume expansion. Furthermore, SnO2 and SnS2 quantum dots anchored on graphene aerogels can undergo reversible conversion reaction that profit by synergistic effect. The reversibility of the SnO2/SnS2/SGA material during the transition was also proved by ex-situ high-resolution transmission electron microscopy. The SnO2/SnS2/SGA hybrid was endowed with enhanced electrochemical capability.

Ultrafine FeF3·0.33H2O Nanocrystal-Doped Graphene Aerogel Cathode Materials for Advanced Lithium-Ion Batteries.

FeF3 has been extensively studied as an alternative positive material owing to its superior specific capacity and low cost, but the low conductivity, large volume variation, and slow kinetics seriously hinder its commercialization. Here, we propose the in situ growth of ultrafine FeF3·0.33H2O NPs on a three-dimensional reduced graphene oxide (3D RGO) aerogel with abundant pores by a facile freeze drying process followed by thermal annealing and fluorination. Within the FeF3·0.33H2O/RGO composites, the three-dimensional (3D) RGO aerogel and hierarchical porous structure ensure rapid diffusion of electrons/ions within the cathode, enabling good reversibility of FeF3. Benefiting from these advantages, a superior cycle behavior of 232 mAh g-1 under 0.1C over 100 cycles as well as outstanding rate performance is achieved. These results provide a promising approach for advanced cathode materials for Li-ion batteries.

Diatom Frustules Decorated with Co Nanoparticles for the Advanced Anode of Li-Ion Batteries.

Silica is regarded as a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. However, large volume variation and poor electrical conductivity are limiting factors for the development of SiO2 anode materials. To solve this problem, combining SiO2 with a conductive phase and designing hollow porous structures are effective ways. In this work, The Co(II)-EDTA chelate on the surface of diatom biosilica (DBS) frustules and obtained DBS@C-Co composites decorated with Co nanoparticles by calcination without a reducing atmosphere is first precipitated. The unique three-dimensional structure of diatom frustules provides enough space for the volume change of silica during lithiation/delithiation. Co nanoparticles effectively improve the electrical conductivity and electrochemical activity of silica. Through the synergistic effect of the hollow porous structure, carbon layer and Co nanoparticles, the DBS@C-Co-60 composite delivers a high reversible capacity of >620mAhg-1 at 100mAg-1 after 270 cycles. This study provides a new method for the synthesis of metal/silica composites and an opportunity for the development of natural resources as advanced active materials for LIBs.

Multilevel spatial confinement of transition metal selenides porous microcubes for efficient and stable potassium storage

Recently, potassium-ion batteries (PIBs) have been considered as one of the most promising energy storage systems; however, the slow kinetics and large volume variation induced by the large radius of potassium ions (K+) during chemical reactions lead to inferior structural stability and weak electrochemical activity for most potassium storage anodes. Herein, a multilevel space confinement strategy is proposed for developing zinc-cobalt bimetallic selenide (ZnSe/Co0.85Se@NC@C@rGO) as high-efficient anodes for PIBs by in-situ carbonizing and subsequently selenizing the resorcinol–formaldehyde (RF)-coated zeolitic imidazolate framework-8/zeolitic imidazolate framework-67 (ZIF-8/ZIF-67) encapsulated into 2D graphene. The highly porous carbon microcubes derived from ZIF-8/ZIF-67 and carbon shell arising from RF provide rich channels for ion/electron transfer, present a rigid skeleton to ensure the structural stability, offer space for accommodating the volume change, and minimize the agglomeration of active material during the insertion/extraction of large-radius K+. In addition, the three-dimensional (3D) carbon network composed of graphene and RF-derived carbon-coated microcubes accelerates the electron/ion transfer rate and improves the electrochemical reaction kinetics of the material. As a result, the as-synthesized ZnSe/Co0.85Se@NC@C@rGO as the anode of PIBs possesses the excellent rate capability of 203.9 mA h g−1 at 5 A g−1 and brilliant long-term cycling performance of 234 mA h g−1 after 2,000 cycles at 2 A g−1. Ex-situ X-ray diffraction (Ex-situ XRD) diffraction reveals that the intercalation/de-intercalation of K+ proceeds through the conversion-alloying reaction. The proposed strategy based on the spatial confinement engineering is highly effective to construct high-performance anodes for PIBs.

Insight into Highly Graphitic Hollow Spheres for Superior Potassium Ion Batteries

AbstractGraphite is an attractive anode material for low‐cost potassium‐ion batteries (PIBs), which are highly promising in addressing the urgent demand for large‐scale energy storage systems. However, the large volume variation of graphite during the potassiation/depotassiation may lead to poor long‐term stability, which is unfavorable for commercialization. Herein, highly graphitic hollow spheres (HGHS) are designed by using D‐ribose as the carbon source and Fe‐based catalysts to address these issues, and the effect of graphitization degree on potassium storage performance is explored, which is rarely reported. Fe‐based catalysts can promote graphitization of carbon layer and function as a hard template for manufacturing hollow and spherical architecture. HGHS possess a high porosity, which provides good contact when the liquid electrolyte infiltrates throughout the material. HGHS synthesized with a suitable amount of Fe‐based catalysts display highly graphitic hollow carbon spheres and show a superior potassium storage performance (264 mAh g−1 at 100 mA g−1). The hollow carbon sphere structure and highly graphitic carbon layer endows HGHS with outstanding stability, retaining 87% of the capacity after 500 cycles at 200 mA g−1. This study provides an effective strategy in designing highly graphitic hollow nanostructures for addressing the instability issues of graphite anode in PIBs.

Ultra-Fine Maghemite (γ-Fe2O3) Nanoparticles Anchored on 3D Reduced Graphene Oxide Aerogels for Advanced Lithium-Ion Battery Anodes

Fe2O3 has been widely investigated as anode material for its high theoretical capacity and natural abundance, but the low conductivity, large volume variation and slow kinetics seriously hinder its commercialization. Here, we propose the in situ growth of ultra-fine Maghemite (γ-Fe2O3) NPs on the 3D rGO aerogel with abundant pores by a facile freeze-drying process followed by thermal annealing, which is confirmed by XRD and HR-TEM. This novel 3D porous structure ensures fast electron and ion diffusion within the electrode, which effectively mitigates the volume expansion of Fe2O3 during cycling. Benefiting from these advantages, an excellent cycling performance of 668 mAh g−1 at 0.5 A g−1 over 100 cycles as well as outstanding rate performance are achieved. These results provide a promising approach of advanced anode materials for Lithium-ion batteries.

Preparation of a Flexible Reduced Graphene Oxide-Si Composite Film and Its Application in High-Performance Lithium Ion Batteries

This paper describes a strategy for preparing free-standing reduced graphene oxide@Si nanoparticles (rGO@Si NPs) composite membranes. Graphene oxide (GO) was reduced and self-assembled synchronously with nanoparticles of silicon (Si NPs) on a metal surface and the composite film was subsequently used in a lithium-ion battery (LIB). This work describes several important novel aspects of the reported technology. Firstly, the composite membrane has a flexible self-supporting structure, allowing it to function as an anode material without requiring binders and current collectors. Secondly, the successful assembly of Si NPs and reduced Graphene oxide (rGO) sheets has enabled the production of the rGO@Si NPs composite film with high controllability and orderliness. Thirdly, the conductive nature of graphene has significantly decreased the resistivity while enhancing the electron transport capacity of the battery anode. Lastly, the robust and flexible structure of the graphene sheet has greatly mitigated the large volume variation in Si NPs during charging or discharging, resulting in the rGO@Si NPs composite film exhibiting excellent energy density and high-power density.

Single‐Walled Carbon Nanotube Film as an Efficient Conductive Network for Si‐Based Anodes

AbstractSilicon‐based anodes are considered ideal candidate materials for next‐generation lithium‐ion batteries due to their high capacity. However, the low conductivity and large volume variations during cycling inevitably result in inferior cyclic stability. Herein, a dry method without binders is designed to fabricate Si‐based electrodes with single‐walled carbon nanotubes (SWCNTs) network and to explore the different mechanisms between SWCNT and multiwalled carbon nanotubes (MWCNTs) as a conductive network. As expected, higher initial discharge capacity (1785 mAh g−1), higher initial Coulombic efficiency (ICE, 81.52%) and outstanding cyclic stability are obtained from the SiOx@C|SWCNT anodes. Furthermore, its lithium‐ion diffusion coefficient (DLi+) is 3–4 orders of magnitude higher than that of SiOx@C|MWCNT. The underlying mechanism is clarified by in situ Raman spectroscopy and theoretical analysis. It is found that the SWCNTs can maintain good contact with SiOx@C even under tensile stresses up to 6.2 GPa, while the MWCNTs lose electrical contact due to alternating compressive stress up to 8.9 GPa and tensile stress up to 2.5 GPa during long‐term cycling. Under such very large stresses, the more flexible SWCNTs and their stronger van der Waals forces ensure that SiOx@C still has good contact with SWCNTs.

Recent Progress in SiC Nanostructures as Anode Materials for Lithium- Ion Batteries

Abstract: Large volume variation during charge/discharge of silicon (Si) nanostructures applied as the anode electrodes for high energy lithium-ion batteries (LIBs) has been considered the most critical problem, inhibiting their commercial applications. Searching for alternative high performance anodes for LIBs has been emphasized. Silicon carbide (SiC) nanomaterials, a wide bandgap semiconductor with excellent mechanical properties, have been investigated as anode electrode materials even as active materials, protective layers, or inactive buffer stuff. In this mini review, we briefly summarize the synthesis of SiC nanostructures, the application of SiC/C anode materials, and SiC/Si composite anodes in LIBs.

A new target localization method for image-guided radiation therapy of prostate cancer

In imaged-guided radiation therapy (IGRT), target localization is usually done with rigid-body registration based on anatomy matching. Problems arise when the target volume can only be matched partially due to inter-fractional organ motion and deformation, resulting in deteriorated target coverage and critical structure sparing. A new target localization method is investigated in which the treatment target volume is aligned with the prescription isodose surface. Our study included 15 prostate patients previously treated with intensity-modulated radiation therapy (IMRT). Patient setup and target localization were performed using a CT-on-rails system before and after the IMRT treatment. IMRT plans were generated on the original simulation CTs (15) and the same MUs and leaf sequences were used to compute the dose distributions on post-treatment CTs (98) with the isocenter adjustments based on either anatomical structure matching or prescription isodose surface alignment. When patients were aligned with the traditional anatomy matching method, the dose to 95% of the CTV, D95, received 74.0 – 77.6 Gy and the minimum CTV dose, Dmin, was 61.9 – 71.6 Gy, respectively, in the cumulative dose distributions. The rectal dose-volume constraints were violated in 35.7% of the treatment fractions. When patients were aligned using the new localization method, the dose to 95% of the CTV, D95, received 74.0 – 78.2 Gy and the minimum CTV dose, Dmin, was 68.4 – 71.6 Gy, respectively, in the cumulative dose distributions. The rectal dose-volume constraints were violated in 17.3% of the treatment fractions. Traditional IGRT target localization based on anatomy matching is effective for population-based PTV margins but not ideal for those patients with large inter-fractional prostate rotation/deformation due to large rectal and bladder volume variation. The new method using the prescription isodose surface to align the target volume could improve the target coverage and rectal sparing for these patients, which can be implemented clinically to improve target dose delivery accuracy.

Dealloyed Porous NiFe2O4/NiO with Dual-Network Structure as High-Performance Anodes for Lithium-Ion Batteries

As high-capacity anode materials, spinel NiFe2O4 aroused extensive attention due to its natural abundance and safe working voltage. For widespread commercialization, some drawbacks, such as rapid capacity fading and poor reversibility due to large volume variation and inferior conductivity, urgently require amelioration. In this work, NiFe2O4/NiO composites with a dual-network structure were fabricated by a simple dealloying method. Benefiting from the dual-network structure and composed of nanosheet networks and ligament-pore networks, this material provides sufficient space for volume expansion and is able to boost the rapid transfer of electrons and Li ions. As a result, the material exhibits excellent electrochemical performance, retaining 756.9 mAh g-1 at 200 mA g-1 after cycling for 100 cycles and retaining 641.1 mAh g-1 after 1000 cycles at 500 mA g-1. This work provides a facile way to prepare a novel dual-network structured spinel oxide material, which can promote the development of oxide anodes and also dealloying techniques in broad fields.

Recent Advances in the Structural Design of Silicon/Carbon Anodes for Lithium Ion Batteries: A Review

As the capacity of lithium-ion batteries (LIBs) with commercial graphite anodes is gradually approaching the theoretical capacity of carbon, the development of silicon-based anodes, with higher energy density, has attracted great attention. However, the large volume variation during its lithiation/de-lithiation tends to lead to capacity decay and poor cycling performance. While rationally designed silicon/carbon (Si/C) anodes can exhibit higher specific capacity by virtue of silicon and high electrical conductivity and volume expansion suppression by virtue of carbon, they still show poor cycling performance with low initial coulombic efficiency. This review focuses on three strategies for structural design and optimization of Si/C anodes, i.e., carbon-coated structure, embedded structure and hollow structure, based on the recent researches into Si/Canodes and provides deeper insights into the problems that remain to be addressed.

Embedding antimony nanoparticles into metal–organic framework derived TiO2@carbon nanotablets for high-performance sodium storage

Titanium dioxide (TiO2) has been widely investigated as a candidate for anode materials of sodium-ion batteries (SIBs) due to its low cost and high abundance. However, the intrinsic sluggish ion/electron transfer rate hinders its practical applications for high energy density storage devices. In contrast, antimony (Sb) shows high specific theoretical capacity (660 mAh/g) as well as excellent electron conductivity, but the large volume variation upon cycling usually leads to severe capacity fading. Herein, with the objective of achieving high-performance sodium storage anode materials, TiO2@C-Sb nanotablets with a small amount of Sb content (6.4 wt%) are developed through calcination Ti-metal–organic framework (MIL-125) derived TiO2@C/SbCl3 mixture under reductive atmosphere. Benefitting from the synergetic effect of well-dispersed Sb nanoparticles as well as robust porous TiO2@C substrate, the TiO2@C-Sb shows enhanced electron/ion transfer rate and predominantly pseudocapacitive sodium storage behavior, delivering a reversible capacity of 219 mAh/g at 0.5 A/g even after 1000 cycles. More significantly, this method may be commonly used to incorporate other alloy-based high-theoretical materials into MIL-125-derived TiO2@C, which is promising for developing high-energy-density TiO2-based energy storage devices.

Porous bismuth nanocrystals with advanced sodium ion storage property

Bismuth-based materials are ideal electrodes for sodium-ion batteries (SIBs) due to their high capacity and low cost. However, conventional solid bismuth materials still suffer from severe volume expansion during the reaction process, which hinders its application. Herein, single-crystal bismuth nanospheres with diameters in the range of 200–400 ​nm were successfully prepared with the Na–Bi alloying mechanism studied using in-situ XRD, which confirms a stepwise process of Bi→NaBi→Na3Bi with large volume variation. To address the volume change issue, we introduce a porous structure into the bulk of Bi crystals, which alleviated its volume expansion and suppressed its cyclic failure. An in-situ TEM experiment is further carried out to verify this effective structure-modification strategy, demonstrating its applicable feature for electrode design and performance enhancement.

Sulfur-Bridged Bonds Heightened Na-Storage Properties in MnS Nanocubes Encapsulated by S-Doped Carbon Matrix Synthesized via Solvent-Free Tactics for High-Performance Hybrid Sodium Ion Capacitors.

The exploitation of electrode materials with ability to balance capacity and kinetics between cathode and anode is a challenge for sodium-ion hybrid capacitors (SIHCs). Mn-based anode materials are limited by poor electrical conductivity, sluggish reaction kinetics, large volume variation, weak cycling stability, and inferior reversible capacity. Herein, MnS nanocubes encapsulated in S-doped porous carbon matrix (MSC) with strong sulfur-bridged bond interactions (CSMn) are successfully synthesized by solvent-free tactics. The CSMn bonds generated between MnS and carbon significantly inhibit the aggregation of nanostructural MnS cubes, restrict the volume expansion, and stabilize the nanostructure, which improves the Na+ storage reversibility and stability. Moreover, S-doped porous carbon enhances the electrical conductivity and electrons/ions diffusion rate, which boosts a fast kinetic reaction. As expected, MSC anode presents an outstanding reversible capacity of 600 mAh g-1 at 0.2 A g-1 and a long-term stable capacity of 357 mAh g-1 for 1000 cycles at a high current density of 10 A g-1 in sodium-ion batteries (SIBs). The as-assembled SIHCs delivera high energy density of 109W h kg-1 and a high power output of 98W kg-1 , with 88% capacity retention at 2 A g-1 after 2000 cycles and practical applications (55 LEDs can be lighted for 10 min).