Discharge Capacity Retention Research Articles

Co-based and Cu-based MOFs modified separators to strengthen the kinetics of redox reaction and inhibit lithium-dendrite for long-life lithium-sulfur batteries

In this study, two kinds of MOFs nanoparticles including ZIF-67 and Cu-BTC (HKUST-1) were synthesized and the MOFs modified gel F-doped poly-m-phenyleneisophthalamide (PMIA) nanofiber membranes were successfully prepared through blend electrospinning of these synthesized MOFs nanoparticles and PMIA solution. And the electrochemical performance and safety for Li-S cells with the MOFs modified gel PMIA nanofiber separators were systematically researched. Under the synergistic role of F-doped emulsion and MOFs nanoparticles, the modified PMIA-based membranes can produce relatively high porosity, reduced aperture and good electrolyte uptake. And the merits endow the separator with prominent thermal stability, mechanical strength and ionic conductivity, which lays a solid footing stone for high-performance and advanced-safety Li-S battery with fast ion transportation, reduced polarization, good interfacial compatibility and strong catalysis. The batteries with ZIF-67 and Cu-BTC (HKUST-1) modified membranes exhibited high first-cycle discharge capacity of 1267.5 and 1272.2 mAh g−1, outstanding discharge capacity retention of 698.1 and 752.6 mAh g−1 and super-high Coulombic efficiency of 99.75% and 99.82% after 500 cycles at 0.5 C rate, respectively. The outstanding electrochemical properties and safety for the batteries assembled were ascribed to the greatly prevented “shuttle effect” of dissolved lithium polysulfides based on the physical capturing of high-order lithium polysulfides via the prepared jelly-like gel state and strongly chemical adsorbing to lithium polysulfides, and fast redox kinetics based on the strong catalytic conversion. This work proves that the addition of functional MOFs nanoparticles similar with ZIF-67 and Cu-BTC (HKUST-1) in gel F-doped PMIA membrane can inhibit the “shuttle effect” of polysulfides and reduce the growth of lithium dendrites to some extent, which will prompt a great development of Li-S battery with high performance and reassuring safety.

Synthesis and electrochemical performance of Li1+xTi2−xFex(PO4)3/C anode for aqueous lithium ion battery

Aqueous lithium ion batteries (ALIBs) exhibit great application prospects in energy storage system, and the anode materials is the key to the extensive development of ALIBs. In this study, Li1+xTi2−xFex(PO4)3/C (x = 0, 0.05, 0.10, 0.30) composites as anode for ALIBs were synthesized via sol-gel method. The effect of Fe doping on LiTi2(PO4)3/C properties was assessed by electrochemical measurements. In all of these composites, Li1.1Ti1.9Fe0.1(PO4)3/C (LCF-10) presents the best electrochemical properties. LCF-10 exhibits discharge capacity with 120.0 and 80.2 mAh g−1 at 0.5 and 15C, severally, increasing by 1.2 and 1.3 times compared with the original LiTi2(PO4)3/C. Besides, LCF-10 demonstrates remarkable cycling performance, whose discharge capacity retention can keep 70.2% at 5 C for 1000 cycles. Our study demonstrates that Fe doping for LiTi2(PO4)3 lattice can efficiently enhance electrochemical properties of LiTi2(PO4)3/C composite.

Controlling the water absorption and improving the high C-rate stability: a coated Li-ion battery separator using β-cyclodextrin as binder

The water absorption property of the coated separator directly affects the electrochemical performance of a Lithium-ion battery. For the water-based coated separator, the water absorption is directly dependent on the binder and ceramic components. In this work, β-cyclodextrin is chosen as the binder, and its hydrophilicity is regulated by chemical oxidation, while titanium dioxide (TiO2) is used as the ceramic component. It is found that the water absorption of the coated separator using modified β-cyclodextrin is lower than that of commercial aqueous binders such as PVA. In addition, the Li-ion battery assembled with the coated separator shows better discharge capacity retention. At 8 C rate discharge, the discharge capacity of the battery using coated separator is measured at 123 mAhg− 1, and the capacity retention is up to 88%. This work provides a new idea to modify the water-based coated separator with reduced water absorption in the storage stage.

Impact of Al Doping and Surface Coating on the Electrochemical Performances of Li-Rich Mn-Rich Li1.11Ni0.33Mn0.56O2 Positive Electrode Material

Li and Mn-rich positive electrode materials, Li[LixTM1−x]O2 (TM = Ni, Co, and Mn), with a single-phase layered structure have been considered for use in next-generation Li-ion batteries for electric vehicles and many advanced applications. Despite their high specific capacity >250 mAh g−1, the commercialization of these materials is hindered by poor rate capability and voltage decay originating from transition metal migration to the lithium layer. Herein, the effect of aluminum doping and aluminum oxide surface coating on the structural and electrochemical performances of Co-free Li1.11Ni0.33Mn0.56O2 was studied. All synthesized materials were single phase with a similar morphology and amount of Ni in the Li layers. Even though the discharge capacity and capacity retention were slightly improved, there was no significant impact of the addition of Al on the rate of voltage fading during charge-discharge cycling as previously reported.

Ultra-Tiny Sb-Doped SnO2 Nanoparticles as a Superior Catalyst for Vanadium Redox Reactions

Herein, ultra-tiny Sb-doped SnO2 nanoparticles were prepared using co-precipitation as superior catalyst for vanadium redox reactions. Different concentrations of Sb in range of 2%, 5%, and 10% were doped in lattice structure of SnO2. The size of nanoparticles decreased, as doping concentration increased. Sb doping also decreased the crystallinity of SnO2, producing structural defects. It is notable that Sb-doped SnO2 showed greatly improved conductivity. However, excessive Sb doping reduced conductivity of SnO2. Sb-doped SnO2 exhibited better electrocatalysis for V3+/V2+ and VO2+/VO2+ reactions. It benefits from Sb-doped SnO2 with smaller size, more structural defects, and higher conductivity, increasing active sites and electron transfer rate for vanadium redox reactions. SnO2/Sb-5% showed the best electrocatalysis. SnO2/Sb-5% was used to modify graphite felt, such that it had better electrochemical performance for vanadium redox reactions. A cell using SnO2/Sb-5% improved electrolyte usage and discharge capacity retention at 50 mA cm−2 for 50 cycles. SnO2/Sb-5% also efficiently reduced electrochemical polarization of cell. The cell using SnO2/Sb-5% had higher energy efficiency compared to pristine cell. At 150 mA cm−2, the energy efficiency of modified cell increased by 9.2% compared with pristine cell (57.3%). Therefore, Sb-doped SnO2 can be used as a promising catalyst for vanadium redox reactions.

4-(Trimethylsilyl) Morpholine as a Multifunctional Electrolyte Additive in High Voltage Lithium Ion Batteries

In this study we characterize 4-(trimethylsilyl) morpholine (TMSML) as a multifunctional electrolyte additive in Li1.03(Ni0.5Mn0.3Co0.2)0.97O2 (NMC532)//Graphite cells operating at 3–4.4 V. This additive completely prevents the hydrolysis of LiPF6 caused by traces of water in a carbonate electrolyte, both ex and in situ. It also inhibits oxidative decomposition of electrolyte on the energized cathode, impedes the formation of electrically insulating deposits on the cathode surface, decreases transition metal loss from the cathode in aged cells, improves the discharge capacity retention, and decreases the rise of cell resistance during aging. We trace these beneficial functions to the ease of nucleophilic substitution and the N–Si bond dissociation in the TMSML. Our results suggest that TMSML could be a promising electrolyte additive in the high voltage lithium ion batteries.

Synthesis and characterization of LiFe1−Mn PO4 (x = 0.25, 0.50, 0.75) lithium ion battery cathode synthesized via a melting process

Abstract Compared to large-scale solid-state and hydrothermal methods, melt synthesis is a simple, fast and low-cost method to synthesize cathode materials with high quality and high electrochemical results. In this paper, melt synthesis is used for the first time to synthesize electrochemically active LiFe1-xMnxPO4 (x = 0.25, 0.50, 0.75) cathode materials with high electrochemical performance. The structure, the morphology and the electrochemical performance of LiFe1-xMnxPO4 materials were characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and galvanostatic charge/discharge cycling. The properties of LiFe1-xMnxPO4 materials synthesized by the molten-state process were compared with those of LiFe1-xMnxPO4 materials synthesized by the well-known solid-state process. The obtained results show that molten- and solid-state syntheses provide similar performances in terms of discharge capacity, capacity retention and rate capability, and even better in the case of LiFe0.25Mn0.75PO4 made from melt synthesis (142 mAh g−1 vs. 130 mAh g−1). This paper offers new perspectives for the large-scale production of high potential cathode materials using melting process that could compete with the current synthetic techniques.

In-situ topochemical nitridation derivative MoO2–Mo2N binary nanobelts as multifunctional interlayer for fast-kinetic Li-Sulfur batteries

Li-Sulfur batteries (LSBs) have a wide application foreground for its high energy density and low-cost, however, the shuttle effect, volume fluctuation and irregular Li2S deposition on the cathode side often result in severe capacity decaying during its cycles. It is necessary to design and optimize the conversion route from sulfur (S8) to lithium sulfide (Li2S) to improve the reversibility of Li–S battery. Herein, novel MoO2–Mo2N binary nanobelts synthesized from α-MoO3 through an in situ topochemical nitridation process were employed as the highly efficient interlayer material for LSBs, which not only acted as a physical barrier to alleviate the shuttle effect but also regulated the conversion of lithium polysulfides (LiPSs) across the interface and optimized the nucleation of solid Li2S during cycling. Combining the polarity of MoO2 with the conductivity of Mo2N, such hybrid structure exhibited excellent cycling stability with a very low capacity decay of 0.028% per cycle up to 500 cycles at 1C. Even under the high areal sulfur loadings of 3.1 and 4 mg cm−2, the high discharge capacity and excellent capacity retention ratio can also be obtained. The concept of in-situ binary heterogeneous interfaces construction might also be used in the design and preparation of other electronic devices.

A novel polymer-modified separator for high-performance lithium-ion batteries

In this study, hyperbranched polybenzimidazole (HBPBI) was synthesized and coated on polyethylene membrane surface with terephthaldehyde (TPA) cross-linker to obtain high-performance CHBPBIE separator for application in lithium ion battery (LIB). The introduction of benzimidazole, amino and carboxyl groups to TPA cross-linked HBPBI (CHBPBI) could improve the wettability, electrolyte uptake, heat resistance and thermal stability of CHBPBIE separator. The absorption of the liquid electrolyte is increased from 90% for the control separator to 181% for CHBPBIE separator. More importantly, the cross-linked coating structure can greatly improve the ionic conductivity of CHBPBIE separator, and it is 0.77 mS cm−1 at 25 °C, which is increased by 10.6 times compared with that of the control PE separator. The LIB half cells assembled with CHBPBI modified separator shows 73% increase in power capability at 7 C rate and a discharge capacity retention rate of 91.1% after 400 cycles at 2 C rate. Thus, the modified separator has the potential for use in high-performance LIB.

Effects of Electrolyte Concentration on Electrochemical Properties of Zinc-Air Batteries

The self-discharge behavior of zinc-air batteries is a critical issue induced by corrosion and hydrogen evolution reaction (HER) of zinc anode. The corrosion reaction and HER can be controlled by a gelling agent and concentration of potassium hydroxide (KOH) solution. Various concentrations of KOH solution and polyacrylic acid have been used for gel electrolyte. The electrolyte solution is prepared with different concentrations of KOH (6 M, 7 M, 8 M, 9 M). Among studied materials, the cell assembled with 6 M KOH gel electrolyte exhibits the highest specific discharge capacity and poor capacity retention. Whereas, 9 M KOH gel electrolyte shows high capacity retention. However, a large amount of hydrogen gas is evolved with 9 M KOH solution. In general, the increase in concentration is related to ionic conductivity. At concentrations above 7 M, the viscosity increases and the conductivity decreases. As a result, compared to other studied materials, 7 M KOH gel electrolyte is suitable for Zn-air batteries because of its higher capacity retention (92.00 %) and specific discharge capacity (351.80 mAh/g) after 6 hr storage.

Temperature-Controlled Synthesis of Li- and Mn-Rich Li1.2Mn0.54Ni0.13Co0.13O2 Hollow Nano/Sub-Microsphere Electrodes for High-Performance Lithium-Ion Battery.

The calcination temperature plays a significant role in the structural, textural, and energy-storage performance of metal oxide nanomaterials in Li-ion battery application. Here, we report the formation of well-crystallized homogeneously dispersed Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere architectures through a simple cost-effective coprecipitation and chemical mixing route without surface modification for improving the efficiency of energy storage devices. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 hollow nano/sub-microsphere cathode materials are calcined at 800, 900, 950, and 1000 °C. Among them, Li1.2Mn0.54Ni0.13Co0.13O2 calcined at 950 °C exhibits a high discharge capacity (277 mAh g–1 at 0.1C rate) and excellent capacity retention (88%) after 50 cycles and also delivers an excellent discharge capacity of >172 mAh g–1 at 5C rate. Good electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2-950 is directly related to the optimized size of its primary particles (85 nm) (which constitute the spherical secondary particle, ∼720 nm) and homogeneous cation mixing. Higher calcination temperature (≥950 °C) leads to an increase of the primary particle size, poor cycling stability, and inferior rate capacity of Li1.2Mn0.54Ni0.13Co0.13O2 due to smashing of quasi-hollow spheres upon repeated lithium ion intercalations/deintercalations. Therefore, Li1.2Mn0.54Ni0.13Co0.13O2-950 is a promising electrode for the next-generation high-voltage and high-capacity Li-ion battery application.

Well-Aligned Channels Derived from Wood for Electron and Mass Transportation in Aqueous Flow Batteries

Nature has provided scientists and engineers with tremendous inspirations and resources to design new materials, architectures, and devices. Inspired by the transportation of water and ions in trees, for the first time, a natural wood-derived freestanding electrode with well-aligned channels was designed as an alternative for the pricey electrode in aqueous vanadium redox flow battery (VRFB). The microscale vertically well-aligned channels (the largest channels size are 60 µm) with pit pores on the channel walls work as efficient mass transfer pathways in VRFB. Meanwhile, the designed freestanding wood carbon (WC) electrode is chemically stable, electrically conductive, and has a large specific surface area of 542.28 m2g-1 for fast charge transfer and electrochemical reaction. Furthermore, to improve the wettability and electrochemical catalytic activity, carboxylic groups were introduced on WC via nitric acid (HNO3) treatment (N-WC). Negatively charged carboxylic groups (with a zeta potential of -50.6 mV for N-WC suspension) provide extra driving force for the adsorption of vanadium cations towards the electrode surface, and therefore further enhance the mass transfer. The discharge capacity retention for N-WC electrode is 83.58 % after 100 cycles at 100 mA cm-2, whereas, the corresponding capacity retention is 57.21 % for WC electrode. Moreover, we found that the N-WC electrode has a predominant effect on the positive side of VRFB with the associated half-cell presents voltage efficiency of 92.10 % and energy efficiency of 88.23 % at current density of 40 mA cm-2. Notably, the discharge capacity for the positive half-cell has an excellent cycle stability of 90.19 % retention after 100 cycles at 100 mA cm-2. This work opens a new strategy to apply Nature derived structure and materials for mass and charge transfer in energy storage areas.

In-Situ Arc Discharge-Derived FeSn2/Onion-Like Carbon Nanocapsules as Improved Stannide-Based Electrocatalytic Anode Materials for Lithium-Ion Batteries

Core/shell-structured FeSn2/onion-like carbon (FeSn2/OLC) nanocapsules of confined size range of sub-50 nm are synthesized via an in-situ arc-discharge process, and are evaluated in comparison with FeSn2 nanoparticles as an improved stannide-based electrocatalytic anode material for Li-ion batteries (LIBs). The in-situ arc-discharge process allows a facile one-pot procedure for forming crystalline FeSn2 stannide alloy nanoparticle cores coated by defective OLC thin shells in addition to a confined crystal growth of the FeSn2 nanoparticle cores. The LIB cells assembled using the FeSn2/OLC nanocapsules as the electrocatalytic anodes exhibit superior full specific discharge capacity of 519 mAh·g−1 and specific discharge capacity retention of ~62.1% after 100 charge-discharge cycles at 50 mA·g−1 specific current. The electrochemical stability of FeSn2/OLC nanocapsules is demonstrated from the good cycle stability of the LIBs with a high specific discharge capacity retention of 67.5% on a drastic change in specific current from 4000 to 50 mA·g−1. A formation mechanism is proposed to describe the confined crystal growth of the FeSn2 nanoparticle cores and the formation of the FeSn2/OLC core/shell structure. The observed electrochemical performance enhancement is ascribed to the synergetic effects of the enabling of a reversible lithiation process during charge-discharge of the LIB cells by the FeSn2 nanoparticle cores as well as the protection of the FeSn2 nanoparticle cores from volume change-induced pulverization and solid electrolyte interphase-induced passivation by the OLC shells.

Excellent cyclic performance of electrolytic MnO2 in Li/MnO2 rechargeable batteries

The electrolytic MnO2 particles with α∙γ-MnO2 is successfully prepared using one-step acid constant current electrodeposition method. Scanning electron microscope, N2 adsorption/desorption method and X-ray diffraction are employed for the material characterization. Scanning electron microscope result shows that the diameter of MnO2 particle is about 350–500 nm. A lot of mesoporous exist in the as-prepared MnO2 particles, which exhibit high specific surface area and can provide significantly more electrochemical active sites for the redox reaction. The as-prepared MnO2 particles as cathode in rechargeable Li/MnO2 battery displays high discharge capacity of 202 mAh g−1 in the 1st cycle at a current density of 46 mA g−1, and its discharge capacity retention ratio can achieve 82% over 100 cycles. The discharge capacities of the 100th cycle are 152, 127 and 114 mAh g−1 at different current densities of 151, 350 and 755 mA g−1, respectively, indicating excellent rate capability. The promising electrochemical performance of α∙γ-MnO2 can make researchers focus again on using metal oxide as the cathode materials in the rechargeable Li-ion batteries.

Meso/macroscopically multifunctional surface interfaces, ridges, and vortex-modified anode/cathode cuticles as force-driven modulation of high-energy density of LIB electric vehicles

Modulation of lithium-ion battery (LIB) anodes/cathodes with three-dimensional (3D) topographical hierarchy ridges, surface interfaces, and vortices promotes the power tendency of LIBs in terms of high-energy density and power density. Large-scale meso-geodesics offer a diverse range of spatial LIB models along the geodetically shaped downward/upward curvature, leading to open-ended movement gate options, and diffusible space orientations. Along with the primary 3D super-scalable hierarchy, the formation of structural features of building block egress/ingress, curvature cargo-like sphere vehicles, irregularly located serrated cuticles with abundant V-undulated rigidness, feathery tube pipe conifers, and a band of dagger-shaped needle sticks on anode/cathode electrode surfaces provides high performance LIB modules. The geodetically-shaped anode/cathode design enables the uniqueness of all LIB module configurations in terms of powerful lithium ion (Li+) movement revolving in out-/in- and up-/downward diffusion regimes and in hovering electron density for high-speed discharge rates. The stability of built-in anode//cathode full-scale LIB-model meso-geodesics affords an outstanding long-term cycling performance. The full-cell LIB meso-geodesics offered 91.5% retention of the first discharge capacity of 165.8 mAhg−1 after 2000 cycles, Coulombic efficiency of ~99.6% at the rate of 1 C and room temperature, and high specific energy density of ≈119 Wh kg−1. This LIB meso-geodesic module configuration may align perfectly with the requirements of the energy density limit mandatory for long-term EV driving range and the scale-up commercial manufactures.

Triisopropyl borate as an electrolyte additive for improving the high voltage stability of LiNi0.6Co0.2Mn0.2O2 cathode

Triisopropyl borate electrolyte additive is introduced to improve the cycled stability of LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode operating under 4.5 V charging-cutoff voltage. Through characterizations analysis from SEM, TEM, XPS, ICP, XRD and EIS, it reveals that triisopropyl borate additive can be oxidized on the cathode and form a relatively stable protective film on the NCM622 cathode surface, which has the ability to inhibit the decomposition of carbonate electrolyte solvents and improve the electrochemical stability of LiNi0.6Co0.2Mn0.2O2 cathode. When 1.0 wt% triisopropyl borate additive adding, the NCM622/Li cells achieve the discharge capacity retention of 82.7% after 300 cycles at the voltage of 3.0–4.5 V, while that of the cells without additive is only 50.0%.

Stable cycling of lithium-sulfur batteries by optimizing the cycle condition

Lithium-sulfur (Li–S) batteries suffer from poor utilization of active material and short cycle life due to the complicated multi-step reaction mechanisms. Herein, three conditional cycling methods, i.e. asymmetrical cycling, constant voltage (CV) discharge cycling, and partial cycling are designed in order to increase the cyclability of Li–S batteries. It is found that the solid deposition process that takes place during the lower plateau of discharge is the major limiting step for achieving high discharge capacity and cycle retention, and the cathode surface coverage can be deferred by applying an optimal discharge/charge rate and CV discharge cycling. The asymmetrical cycling renders a specific capacity of ca. 700 mAh g−1 after 200 cycles, 30% higher than that under symmetrical cycling, while applying a CV discharge cycling enables a full retention of target specific capacity of ca. 800 mAh g−1 over 50 cycles. The partial cycling with a low number of phase transformation steps and reduced surface coverage at the end of discharge/charge also enhances cyclability. This work paves the way for understanding and improving the cycling performance of Li–S batteries without increasing the cost of electrode design or changing the configuration of the cell.

Improved electrochemical properties and thermal stability of Li1.20Mn0.54Ni0.13Co0.13O2 cathode material by Li2ZrO3 coating for Lithium-ion batteries

To ameliorate the electrochemical properties and thermal stability of the Layered Li-rich and Mn-based oxides, the Li2ZrO3 nanoparticles with different contents were coated on the surface of Li1.20Mn0.54Ni0.13Co0.13O2 via using the sol-gel method. The effect of the Li2ZrO3 coating modification on the microstructure, morphology and electrochemical properties of the Li1.20Mn0.54Ni0.13Co0.13O2 cathode have been investigated by the XRD, SEM, TEM, galvanostatic discharge-charge tests and electrochemical impedance spectroscopy techniques. The results demonstrated the Li2ZrO3 coating layer not only could keep cathode away from HF and corrosive electrolyte, but also contributed to enhancing the Li+ migration speed across the interfacial regions. The 2 wt% Li2ZrO3 coated Li1.20Mn0.54Ni0.13Co0.13O2 delivered about 25.6 mAh g(-1) larger than that of the pristine one at 5C high rate. In addition, the 2 wt% Li2ZrO3 coated material retained a much higher discharge capacity retention of 92.6% after 200 cycles. Whereas, the pristine cathode showed only 85.0% of the capacity retention under identical conditions. These results indicated that Li2ZrO3 coating modification could effectively enhance the electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2.

Functional double-layer membrane as separator for lithium-sulfur battery with strong catalytic conversion and excellent polysulfide-blocking

Lithium-sulfur (Li-S) battery with promising specific capacity and high energy density has attracted wide attention in recent years. However, the rapid capacity fading of the batteries caused by the “shuttle effect” of soluble polysulfides restricted its applications. Here, a novel thermostable double-layer membrane based on F-doped poly-m-phenyleneisophthalamide (PMIA) membrane and F-mangano-manganic oxide (Mn3O4) co-doped PMIA membrane is fabricated through electrospinning method. The F-PMIA membrane and F-Mn3O4-co-doped PMIA membrane in the double-layer membrane can act as the matrix to prepare gel polymer electrolyte (GPE). More importantly, the F-doped PMIA membrane in combination with F-Mn3O4-co-doped PMIA membrane, render the engineered functional separator with extraordinary high electrolyte uptake and eminent preserving liquid electrolyte, excellent thermal stability and shrinkage resistance, strong catalytic conversion, forceful chemisorption and physical blocking the “shuttle effect” of lithium polysulfides for Li-S battery. Based on these merits, the assembled batteries with the novel separator exhibited a high first-cycle discharge capacity with 1237.1 mAh g−1, excellent discharge capacity retention of 814.0 mAh g−1 and high Coulombic efficiency of 98.83% after 1000 cycles at the current density of 0.5 C rate. In addition, the obtained Li-S battery with GPE presented a low interfacial resistance and high rate capacity (624.1 mA h g−1 at 2 C rate after 600 cycles). The reasons of these excellent electrochemical performances for the battery using the prepared membrane were ascribed to the suppressed “shuttle effect” through both the physical trapping of lithium polysulfides by the GPE based as matrix on F-doped PMIA membrane and chemical binding of intermediates by F-Mn3O4-co-doped membrane. The new separator will open up an effective avenue to enhance the capability and cyclability of Li-S batteries.

Hierarchical hollow microcuboid LiNi0.5Mn1.5O4 as cathode material with excellent rate and cycling performance for lithium-ion batteries

The rational design of the structure is the key to engineering spinel LiNi0.5Mn1.5O4 cathode material to enhance Li+/electron transport and relieve the structural damage during the reduplicative Li+ intercalation/deintercalation, which is closely to the rate and cycling performance. Here, we report hollow microcuboid LiNi0.5Mn1.5O4 composed of interconnected nanoparticles which can simultaneously achieve the easy Li+ diffusion and high structure robustness. The hollow microcuboid has been fabricated by a facile solvothermal reaction followed by a lithiation process. It is found that the morphology and the size can be easily controlled, which depends on the initial nucleation process. The obtained hollow microcuboid LiNi0.5Mn1.5O4 presents excellent rate and cycling performance. It delivers a capacity of 125 mAh g−1 at the discharge rate of 1 C. Even at a high discharge rate of 30 C, the capacity of 109 mAh g−1 and a discharge capacity retention of 94.4% after 900 cycles can be achieved. The excellent performance should be ascribed to its intrinsic hierarchical hollow structure, which not only benefits the diffusion of Li+ but also provides pore spaces to relieve the volume expansion during the high rate charge/discharge process. The result suggests the potential application of hollow microcuboid LiNi0.5Mn1.5O4 cathode material for high-rate and long-life Li ion batteries.