Search

Abstract Selenium (Se)-based materials for sodium (ion) batteries are currently attracting extensive attentions owing to their fast kinetics and excellent cyclability; at the same time, achieving high Se content, which is crucial to maintain the competitive edge over other kinds of electrode materials, still remains a challenge. We developed a confined annealing method which allows us to convert pristine metal-organic frameworks (MOFs) directly into selenium/selenide/carbon composites. It is a simultaneous process of carbonization, selenization and Se vapor deposition, and the combination of elemental Se and selenide results in a record-high Se content of 76 wt%, enhanced capacity and rate capability (490 and 384 mA h g−1 at 0.1 and 2.0 A g−1) exceeding most documented Se-based materials. The produced composites also exhibit excellent cycle stability (no decay for 700 cycles at 2 A g−1), which is correlated to dominant capacitive charge transport mode and the MOF-derived robust structure. Our work not only offers a proof of concept that Se content can be maximized by confining Se through both vapor deposition and chemical bonding with transition metals, but also demonstrates a general and green selenization approach without using any toxic or flammable chemicals. The introduced method will probably prevail for its wide applicability on various metal-containing precursors, and even be expanded to the fabrication of sulfur- and phosphor-based composites. Graphical abstract A selenium/selenide/carbon composite with a record-high selenium content (76 wt%) is fabricated by directly annealing zeolitic imidazole framework-67 in selenium vapor, and delivers superb sodium storage performance. The strategy of confining selenium via both vapor deposition and chemical bonding with metals is demonstrated to be a simple and effective way to produce selenium-based materials. fx1 Highlights • One-step conversion of ZIF-67 into Se/CoSe 2 /C composite is realized via confined annealing in Se vapor. • Se-ZIF composite achieved a record-high (76 wt%) Se contents by combining Se and CoSe 2. • Se-ZIF composite outperformed the most Se-based electrode materials in capacity. • Phase segregation of Se and Co in CoSe 2 after long cycling was revealed. [ABSTRACT FROM AUTHOR]

Abstract Despite advances in traditional lithium-ion batteries in the past decades, its high cost has always been a bottleneck for large-scale applications. In this work, we demonstrate it is possible to replace expensive cathodes such as LiCoO 2 with inexpensive stainless steel to store energy via a stripping/deposition mechanism: during charging, the stainless-steel cathode removes charges by releasing metal ions into the electrolyte, and during discharge, the metal ions re-deposit on the electrode reversibly. An anion exchange membrane allows passage of anions to balance the charge and prevents cross-over of cations. We show here a battery with a stainless-steel cathode and a lithium metal anode with a high discharge voltage of 2.5 V and good reversibility. We also study the mechanism at the stainless-steel electrode, as well as the kinetics of the battery system. Our work can potentially reduce the cost of energy storage by turning common construction materials into cathode materials. In addition, a metal cathode undergoing stripping/deposition gives a theoretical energy density comparable to lithium-sulfur batteries and provides a new exciting direction for future energy storage development. [ABSTRACT FROM AUTHOR]

Interface engineering on 2D layered nanomaterials plays pivotal roles in achieving novel properties and superior device performance. In this work, hierarchical nanotubes consisting of 2D monolayer MoS 2 and carbon (MoS 2 :C) interoverlapped superstructure nanosheets have been synthesized, in which the MoS 2 and carbon layers are alternately sandwiched. The hierarchical architectures assembled from the MoS 2 :C superstructures are beneficial for: (i) providing substantially expanded (002) interlayer spacing (0.98 nm) of 2H-MoS 2 which facilitates fast Na + insertion/extraction reaction kinetics, (ii) improving electrical conductivity of MoS 2 by carbon monolayer insertion with ideal heterointerface contact, (iii) preventing aggregation of MoS 2 nanosheets, and (iv) accommodating volume change upon sodiation/desodiation. The superstructure nanotubes are demonstrated as a robust anode material for sodium storage with superior electrochemical performance. They deliver a high rate-capability and maintain discharge capacities of 295 and 187 mAh g −1 at high current densities of 10.0 and 20.0 A g −1 , respectively. Furthermore, they show durable cycling life (capacity retention of 101.3%, 108.2% and 107.8% after 200 cycles at current densities of 0.2, 0.5 and 1.0 A g −1 , respectively, in comparison to those of the 2 nd cycles), and an initial Coulombic efficiency as high as 84%. The MoS 2 :C superstructure nanotubes perform among the best of current MoS 2 -based electrode materials. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical performance of Cu2MoS4 was evaluated. When the cutoff potential is limited between 1.6 and 3.0V, the material can give stable cycle performance of up to 100mAhg−1. However, the material shows slow kinetics within this region. The material can give a discharge capacity of up to 653mAhg−1 when discharged to 0.6V vs. Li/Li+, with a first cycle efficiency of 61.3%. This corresponds to an insertion of 8.5Li and an extraction of 5.2Li from the material. XRD and XPS measurements both suggest Cu displacement from the material during discharge and charge, which is a possible reason for the poor cycle stability of the material. A reaction mechanism is proposed based on the XPS analysis. Better cycle performance is observed for Cu2MoS4/GO composite. [Copyright &y& Elsevier]

Abstract: Co3O4 nanoparticles are grown on nitrogen modified microwave exfoliated graphite oxide (NMEG) with weight ratio controlled from 10% to 70%. Electrochemical performance reveals that the obtained Co3O4/NMEG composite as Li-ion battery anode exhibits improved cycle stability, excellent reversible capacity, high current rate performance, and reduced irreversible capacity loss in the initial cycle compared to pure Co3O4 without graphene or Co3O4 on thermally reduced graphene oxide (tRG-O). The 70%Co3O4/NMEG composite has initial irreversible capacity of 230mAhg−1 (first cycle efficiency of 77%), and 910mAhg−1 of capacity is retained after 100 cycles. The 70%Co3O4/tRG-O delivers a reversible capacity of 750±20mAhg−1, and the irreversible capacity loss during the first cycle is 700±20mAhg−1. Nitrogen functional groups in NMEG, especially pyridinic and pyrrolic N are advantageous for the Co3O4 growth. Furthermore, the N modification is effective in reducing the oxygen content of chemically prepared graphene and hence is good for Co3O4 dispersion and the amelioration of first cycle efficiency, demonstrating the potential of NMEG based composite as high performance Li-ion battery anode materials. [Copyright &y& Elsevier]

Lithium-ion battery (LIB) is now widely used in the world. However, its unsatisfactory fast-charging performance is limiting its applications. The fast-charging capability of LIB is highly affected by the surface composition of graphite electrode, which can be modified through electrolyte design. Herein we demonstrate that the combination of lithium bis(fluorosulfonyl) imide (LiFSI) salt with methyl acetate (MA) additive in carbonate electrolyte enables fast-charging Li-ion battery. Results from X-ray photoelectron spectroscopy and transmission electron microscopy indicate that the LiFSI-based electrolyte with MA forms a stable and less-resistive solid electrolyte interphase on graphite anode compared to electrolyte with LiPF 6 , facilitating the transport of Li-ion and achieving a superior fast-charging performance with a capacity of 230 mAh g −1 at 2 C. An electrolyte swapping experiment also indicates that the LiFSI salt forms a more stable SEI on graphite than LiPF 6. This work provides a conducive electrolyte design for fast charging Li-ion battery with graphite anode. [ABSTRACT FROM AUTHOR]

Irradiation damage of the materials depends on the irradiation dose and the intrinsic property of the material. In this paper, the high purity hot pressing sintered SiC ceramics with very few second phase and excellent crystallinity were prepared as the target materials, and the high irradiation dose up to 0.95 and 3.16 dpa respectively were chosen. The as-sintered SiC ceramics were irradiated with a 160 keV Ar ion beam at 600 °C. X-ray photoelectron spectroscopy, Raman spectrum, transmission electron microscopy and nanoindentation tests were utilized to analyze the microstructure variations on the surface of irradiated SiC, and it was found that the irradiated crystals kept crystallinity, although amorphization of SiC was generated with 10–25 nm depth, following with a mixture of point defect clusters and extended defects. Furthermore, it is also evident that there is a balance between irradiated-induced damages buildup and dynamic annealing of defects in high temperature. [ABSTRACT FROM AUTHOR]

Dual-ion battery with the use of both cations and anions as means of energy storage promises high power, as the ions do not have to travel from one electrode to another during charge and discharge. Though, actual rate performance of an electrode is highly dependent on material, electrode configuration and electrolyte. Here, we have identified the key parameters governing the rate performance of PF 6 − intercalation into graphite. Capacity is increased by increasing the surface area of the graphite material. Electrical conductivity and stability are enhanced with carbon addition in the electrode with reduced cut-off voltage. Operating voltage is reduced by increasing the salt concentration, and ionic conductivity is improved with the use of carboxymethyl cellulose as binder. Optimized graphite electrode delivers a capacity of about 90 mAh g −1 at 10 mA g −1 , and 90% of it can still be accessible at a rate of 500 mA g −1 , with excellent cycle stability for at least 200 cycles. The dual-ion battery is demonstrated to give power density superior to that of lithium-ion battery, and energy density superior to that of supercapacitor. [ABSTRACT FROM AUTHOR]

Recently, aqueous rechargeable zinc-ion batteries (AZIBs) have attracted much attention owing to their low cost and intrinsic safety. However, the reversibility of AZIBs is limited by dendrite growth on the Zn anode, which leads to low Coulombic efficiency and potential short circuit during cycling. Herein, we develop a new strategy using electrostatic shielding to enable a highly reversible Zn anode. Specifically, a cationic polymeric ionic liquid (PIL) coating layer with a strong positive charge evens out the charge distribution on the surface of the Zn electrode, enabling uniform stripping and deposition of Zn. As a result, a symmetric Zn–Zn cell can sustain stripping-plating for over 2000 h at 1 mA cm−2 with a capacity limit of 1 mAh cm−2, far exceeding the performance of bare Zn electrode. A highly reversible Zn stripping-plating on Cu substrate is also achieved with an average coulombic efficiency of 99.5% over 1100 cycles. PILZ layer can even allow a uniform Zn deposition of up to 30 μm thick, allowing large utilization of the Zn foil. Moreover, the coating layer enables the stable cycling of a MnO 2 –Zn full cell with a high areal capacity of 1 mAh cm−2. [Display omitted] • A functional polymeric interfacial layer is designed to suppress Zn dendrite. • The layer shields the surface electrostatically to enable uniform Zn deposition. • In-situ microscopy shows high utilization of Zn with uniform deposition. • Achieved reversible stripping-plating with high efficiency. • Demonstrated MnO 2 –Zn full cell with high areal loading and long cycle. [ABSTRACT FROM AUTHOR]

• Spinel Na 2 MoO 4 and Na 2 WO 4 can be used as cathode materials for Na-ion batteries despite TMs in the highest oxidation state. • Large initial charge capacity is attributed to anionic redox reactions in the materials. • Negligible structural evolution is observed for both materials during charge and discharge. • Na 2 WO 4 shows a better stability against oxygen loss and structural degradation than Na 2 MoO 4. Two sodium-rich transition metal (TM) oxides with the same spinel structure, Na 2 MoO 4 and Na 2 WO 4 have been investigated as cathode materials for Na-ion batteries for the first time. Although the oxidation state of TMs in the compounds are already at its highest value of 6+, both of them can be activated by anionic redox reaction during initial charge, as revealed by X-ray photoelectron spectroscopy, to give considerable reversible capacity between 1.2 and 4.7 V. In addition, ex-situ X-ray diffractometry (XRD) shows that both cathode materials undergo insignificant structural evolution during Na extraction/insertion, suggesting that the Mo-O 4 and W-O 4 tetrahedral framework are stable even when more than 1 Na is removed from the materials. Overall, Na 2 WO 4 shows larger amount of Na extraction/insertion and better cycle stability than Na 2 MoO 4. This is likely due to better structural integrity and better stability of Na 2 WO 4 against oxygen loss from ex-situ XRD and differential electrochemical mass spectrometry results. [ABSTRACT FROM AUTHOR]

Spinel Li 4 Mn 5 O 12 , a well-known 3 V Li-ion battery (LIB) material with excellent cycling stability and good rate capability, is examined as Na-ion battery (NIB) cathode for the first time. Electrochemical studies clearly show that Na ions can be reversibly inserted into and extracted from the three-dimensional spinel structure. However, unlike in LIB, the available capacity in NIB is strongly dependent on the particle size and current rate due to the sluggish Na-ion transport in solid phase. Cycle performance of Li 4 Mn 5 O 12 in NIB is also inferior to that in LIB. Ex-situ X-ray diffraction study indicates a gradual loss of crystallinity with cycling, and that the crystal lattice undergoes an irreversible expansion during the initial 20 cycles. Inductively coupled plasma spectroscopy shows a decrease of Li/Mn ratio in Li 4 Mn 5 O 12 with cycling. The results suggest that Li ions are removed from the material during the charging process. The charge-discharge mechanism is also discussed in the paper. [ABSTRACT FROM AUTHOR]

Thermal stability of a lithium-rich layered oxide cathode material with composition 0.5Li 4/3 Mn 2/3 O 2 –0.5LiNi 1/3 Co 1/3 Mn 1/3 O 2 (LMO–NCM) is investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Investigated material shows higher thermal stability (higher onset temperature) than LiCoO 2 . The state of charge and previous cycling history of LMO–NCM, particularly activation of lithium manganese oxide (LMO) “component” during first charge, affect its thermal stability. Activation of LMO has an ambivalent effect on cathode thermal stability: on the one hand, the onset temperature of cathode decomposition is increased, probably due to the change in oxidation states of Ni, Co and Mn after the first cycle. On the other hand, the enthalpy of decomposition increases, presumably due to formation of unstable oxygen in the lattice. X-ray diffraction (XRD) analyses of cathodes before and after thermal decomposition at 600 °C indicate differences in decomposition reactions of charged cathodes, depending on state of charge and cycling history. [ABSTRACT FROM AUTHOR]

Abstract: Thermal stability of charged LiCoO2 cathodes with various surface areas of active material is investigated in order to quantify the effect of LiCoO2 surface area on thermal stability of cathode. Thermogravimetric analyses and calorimetry have been conducted on charged cathodes with different active material surface areas. Besides reduced thermal stability, high surface area also changes the active material decomposition reaction and induces side reactions with additives. Thermal analyses of LiCoO2 delithiated chemically without any additives or with a single additive have been conducted to elaborate the effect of particle size on side reactions. Stability of cathode–electrolyte system has been investigated by accelerating rate calorimetry (ARC). Arrhenius activation energy of cathode decomposition has been calculated as function of conversion at different surface area of active material. [Copyright &y& Elsevier]

Silicon monoxide (SiO) is a promising anode material for Li-ion batteries because of its high capacity. Though, its low first Coulombic efficiency (FCE) due to the formation of inactive Li–Si–O compounds during lithiation hinders its practical application. Herein, we report a facile pre-sodiation technique by annealing SiO with a small amount of Na 2 CO 3 (≤ 5 wt%) under 850 °C, which improves FCE of pristine SiO from 61.4% to 86.0% without the use of lithium metal, solvent and disassembling and re-assembling of cells. Transmission electron microscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance demonstrate that the incorporation of Na facilitates the disproportionation of SiO into crystalline Si and SiO 2 through nucleophilic substitution, and reduces the reactivity of the oxygen atoms with lithium and thereby suppresses the irreversible capacity during initial lithiation. The pre-sodiation process also improves thermal stability of SiO. Since the Na-containing SiO material is not sensitive to moisture in ambient condition, special handling of the material is not necessary. Combining with a LiFePO 4 cathode, the full cell shows a FCE of 85.8% with good cycle stability. The energy density of lithium-ion battery can even reach 900 Wh L−1 based on a theoretical calculation with high-capacity Ni-based metal-oxide cathode. • First Coulombic efficiency of SiO is increased to 86% by heat-treating with Na 2 CO 3. • Na 2 CO 3 facilitates disproportionation of SiO to SiO 2 , inactivating the oxygen atoms in the lattice. • Thermal stability of pre-treated SiO is enhanced with less heat generation. • The treated material is stable in air and exhibits remarkable water compatibility. • A LIB with volumetric energy density of 900 Wh L−1 can be achieved with optimization. [ABSTRACT FROM AUTHOR]

The origins of low reversibility for Cu–Al battery were revealed. Components modifications solve irreversibility issues for Cu–Al battery. The polyacrylonitrile coating on Cu cathode reduces self-discharge. Polyvinylpyrrolidone modified 3M LiTFSI FEC inhibits the dendrite growth. The graphene oxide layer on Al anode suppresses side reaction between FEC and anode. 3 V rechargeable Cu–Al batteries are highly desirable for large-scale energy storage owing to the low cost and excellent scalability of the two metal electrodes. However, they still undergo irreversible processes such as the crossover of Cu ions, dendrite growth during alloy reaction at Al anode, and side reaction between AlLi and the electrolyte. In this work, we solve the poor reversibility of the battery by modifying the cathode, anode and electrolyte. Specifically, a polyacrylonitrile coating on the copper cathode anchors the dissolved Cu ions, polyvinylpyrrolidone additive in the electrolyte enables dendrite-free AlLi alloy formation and a graphene oxide layer on the Al anode suppresses reductive decomposition of the electrolyte, thereby improving average Coulombic efficiency. Our work overcomes some of the critical challenges in Cu–Al batteries and opens new opportunities for the development of low-cost, high-performance rechargeable metal-metal batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Dual-ion battery (DIB) can potentially provide higher power, lower cost and faster charging capability than traditional lithium-ion batteries. Even though graphite can effectively accommodate anions as a cathode for DIB, the high working voltage of around 5 V vs. Li/Li+ leads to continuous side reactions, yielding to low Coulombic efficiency (CE < 90%) and poor cycle life. Here, we demonstrate that fluoroethylene carbonate (FEC) additive can induce a protective cathode electrolyte interface (CEI) on the graphite cathode, effectively suppressing electrolyte decomposition and stabilizing the graphite surface. This CEI enables a high CE (~99.0%) and an excellent cycle stability of 5000 cycles with capacity retention of 85.1% at the cutoff voltage of 5.1 V. The CEI layer can also reduce the self-discharge of the battery. Furthermore, the DIB exhibits a high-rate capability with 93.3% utilization at 30C (3000 mA g−1), enabling an ultrafast charging time within two minutes. This work sheds light on the features of CEI on graphite cathodes and provides a facile and economically effective strategy to achieve highly reversible/stable cycling of DIBs with high power capability. Image 1 • A protective cathode electrolyte interface is constructed on the graphite cathode. • The graphite surface is effectively stabilized for PF 6 − de-/intercalation process. • The cathode electrolyte interface significantly suppresses electrolyte decomposition. • The graphite-based dual-ion batteries with FEC additive exhibits low self-discharge. • Highly reversible/stable cycling and ultrahigh power capability are achieved. [ABSTRACT FROM AUTHOR]

Binder plays a key role in maintaining the integrity of battery electrodes. In this work, we investigate the relationship between binder properties and performances of Si electrodes in a lithium-ion battery (LIB). We learn from nature and use borax as a crosslinker between strands of polyacrylic acid (PAA) to form a network in the binder. By adding different amounts of borax, we can control the degree of crosslinking and thus the mechanical and chemical properties of the binder. We find that increasing the amount of borax crosslinker increases the modulus of the polymer network and the stability of the corresponding Si electrode up to about 5 wt% borax. Even with Si microparticles with an electrode density of 1.25 g cm−3, we obtain a capacity of about 2470 mA h g−1 (3.1 mA h cm−2) and a capacity retention of 91.2% after 50 cycles. Cycle performance is extended beyond 500 cycles with a capacity limitation of 1000 mA h g−1. Though, excessive amount of borax consumes the functional groups of PAA and compromises electrode adhesion, resulting in a decrease in cycle stability. Striking a balance between mechanical strength and adhesion of the binder is important for further development of alloy-based anode materials for LIBs. PAA-borax crosslinked polymer provides high mechanical strength and enables high areal capacity anode using bulk Si as active material. Image 1 • PAA binder can be crosslinked with the addition of borax. • Crosslinking increases modulus and hardness of the polymer binder. • Use of micron-sized Si particles enables electrode with high packing density of 1.25 g cm−3 • Excellent cycle stability obtained for micron-sized Si with 5 wt% borax in PAA. • A tradeoff between binder strength and electrode adhesion is observed. [ABSTRACT FROM AUTHOR]

Silicon monoxide (SiO) with a high Li storage capacity is an attractive material for next-generation lithium-ion batteries. Though, micron-size SiO, which is easier to handle and manufacture, undergoes particle cracking during charge and discharge, leading to fast capacity fading. In this work, we design a robust coating system to accommodate the large volume change of the SiO particles using a self-assembled monolayer (SAM) to covalently bond the active material with a high-modulus polyimide (PI) coating. The SAM is essential as it enhances the adhesion between the particles and the coating, preventing the delamination of the PI coating. The SiO material with the coating demonstrates a stable capacity of 1310.7 mAh g−1 under a current rate of 150 mA g−1 for 100 cycles. The electrode is stable even for 300 cycles at a current rate of 1000 mA g−1. Full cell test with LiFePO 4 positive electrode also shows stable cycle performance with 86% capacity retention after 200 cycles. • Micron-sized SiO particles coated with self-assemble monolayer and polyimide. • Self-assemble monolayer covalently bonded with surface of SiO and polyimide. • Coating system reduces thickness change of electrode during charge and discharge. • Cycle stability significantly improved with coating system. • Stability is verified by full cell tests. [ABSTRACT FROM AUTHOR]