Long-Term Stable Cycling of Dendrite-Free Lithium Metal Batteries Using ZIF-90@PP Composite Separator.

Lithium metal batteries (LMBs) are anticipated to meet the demand for high energy density, but the growth of lithium dendrites seriously hinders its practical application. Herein, we constructed a kind of composite separator (ZIF-90@PP) consisting of zeolite imidazole framework-90 (ZIF-90) and polypropylene (PP) to promote the uniform deposition of Li+ and inhibit the growth of lithium dendrites. The aldehyde groups interacting with TFSI- and the nitrogen-containing negative groups attracting Li+ of ZIF-90 can facilitate the dissociation of LiTFSI to release more Li+, thus alleviating the influence of space charge near the electrode surface and accelerating the transfer of Li+. Not only does the excellent electrolyte wettability of ZIF-90 enhance the electrolyte retention capacity of the separator, but the orderly nano-channels in ZIF-90 also restrict the free migration of anions and homogenize the distribution of Li+. Consequently, the functional separator achieves a long-term stable Li plating/stripping cycling for over 780 h at 2 mA cm-2. Moreover, an impressive average coulombic efficiency of 98.67% at 0.5 C after 300 cycles is realized by Li || LFP full cells based on ZIF-90@PP with a capacity retention rate of 71.22%. The high-rate and long cycling performance of the modified Li || LFP cells further demonstrates the advantages of the ZIF-90@PP composite separator.

Covalent Organic Framework Enhanced Solid Polymer Electrolyte for Lithium Metal Batteries.

High ionic conductivity, outstanding mechanical stability, and a wide electrochemical window are the keys to the application of solid-state lithium metal batteries (LMBs). Due to their regular channels for ion transport and tailored functional groups, covalent organic frameworks (COFs) have been applied to solid electrolytes to improve their performance. Herein, we report a flexible polyethylene oxide-COF-LZU1 (abbreviated as PEO-COF) electrolyte membrane with a high lithium ion transference number and satisfactory mechanical strength, allowing for dendrite-free and long-time cycling for LMBs. Benefiting from the interaction between bis(triflfluoromethanesulonyl)imide anions (TFSI-) and aldehyde groups in COF-LZU1, the Li+ transference number of the PEO-5% COF-LZU1 electrolyte reached up to 0.43, much higher than that of neat PEO electrolyte (0.18). Orderly channels are conducive to the homogenous Li-+ deposition, thereby inhibiting the lithium dendrites. The assembled LiFePO4|PEO-5% COF-LZU1/Li cells delivered a discharge specific capacity of 146 mAh g-1 and displayed a capacity retention of 80% after 200 cycles at 0.1 C (60 °C). The Li/Li symmetrical cells of the PEO-5% COF-LZU1 electrolyte presented a longer working stability at different current densities compared to that of the PEO electrolyte. Therefore, the enhanced comprehensive performance of the solid electrolyte shows potential application prospects for use in LMBs.

Recent Progress of Biodegradable Polymer Package Materials: Nanotechnology Improving Both Oxygen and Water Vapor Barrier Performance.

Biodegradable polymers have become a topic of great scientific and industrial interest due to their environmentally friendly nature. For the benefit of the market economy and environment, biodegradable materials should play a more critical role in packaging materials, which currently account for more than 50% of plastic products. However, various challenges remain for biodegradable polymers for practical packaging applications. Particularly pertaining to the poor oxygen/moisture barrier issues, which greatly limit the application of current biodegradable polymers in food packaging. In this review, various strategies for barrier property improvement are summarized, such as chain architecture and crystallinity tailoring, melt blending, multi-layer co-extrusion, surface coating, and nanotechnology. These strategies have also been considered effective ways for overcoming the poor oxygen or water vapor barrier properties of representative biodegradable polymers in mainstream research.

Polymeric Electrolytes for Solid-state Lithium Ion Batteries: Structure Design, Electrochemical Properties and Cell Performances.

Solid-state electrolytes are key to achieving high energy density, safety, and stability for lithium-ion batteries. In this Review, core indicators of solid polymer electrolytes are discussed in detail including ionic conductivity, interface compatibility, mechanical integrity, and cycling stability. Besides, we also summarize how above properties can be improved by design strategies of functional monomers, groups, and assembly of batteries. Structures and properties of polymers are investigated here to provide a basis for all-solid-state electrolyte design strategies of multi-component polymers. In addition, adjustment strategies of quasi-solid-state polymer electrolytes such as adding functional additives and carrying out structural design are also investigated, aiming at solving problems caused by simply adding liquids or small molecular plasticizer. We hope that fresh and established researchers can achieve a general perspective of solid polymer electrolytes via this Review and spur more extensive interests for exploration of high-performance lithium-ion batteries.

One-Step Electrochemical Dealloying of 3D Bi-Continuous Micro-Nanoporous Bismuth Electrodes and CO2RR Performance.

The rapid development of electrochemical CO2 reduction offers a promising route to convert intermittent renewable energy into products of high value-added fuels or chemical feedstocks. However, low faradaic efficiency, low current density, and a narrow potential range still limit the large-scale application of CO2RR electrocatalysts. Herein, monolith 3D bi-continuous nanoporous bismuth (np-Bi) electrodes are fabricated via a simple one-step electrochemical dealloying strategy from Pb-Bi binary alloy. The unique bi-continuous porous structure ensures highly effective charge transfer; meanwhile, the controllable millimeter-sized geometric porous structure enables easy catalyst adjustment to expose highly suitable surface curvatures with abundant reactive sites. This results in a high selectivity of 92.6% and superior potential window (400 mV, selectivity > 88%) for the electrochemical reduction of carbon dioxide to formate. Our scalable strategy provides a feasible pathway for mass-producing high-performance and versatile CO2 electrocatalysts.

A Novel High Temperature Fuel Cell Proton Exchange Membrane with Nanoscale Phase Separation Structure Based on Crosslinked Polybenzimidazole with Poly(vinylbenzyl chloride).

A semi-aromatic polybenzimidazole (DPBI) is synthesized via polycondensation of decanedioic acid (DCDA) and 3,3-diaminobenzidine (DAB) in a mixed phosphorus pentoxide/methanesulfonic acid (PPMA) solvent. Ascribing to in-situ macromolecular crosslinker of ploly((vinylbenzyl chloride) (PVBC), a robust crosslinked DPBI membrane (DPBI-xPVBC, x refers to the weight percentage of PVBC in the membrane) can be obtained. Comprehensive properties of the DPBI and DPBI-xPVBC membranes are investigated, including chemical structure, antioxidant stability, mechanical strength, PA uptake and electrochemical performances. Compared with pristine DPBI membrane, the PA doped DPBI-xPVBC membranes exhibit excellent antioxidative stability, high proton conductivity and enhanced mechanical strength. The PA doped DPBI-10PVBC membrane shows a proton conductivity of 49 mS cm-1 at 160 °C without humidification. Particularly, it reveals an enhanced H2/O2 single cell performance with the maximum peak power density of 405 mW cm-2, which is 29% higher than that of pristine DPBI membrane (314 mW cm-2). In addition, the cell is very stable in 50 h, indicating the in-situ crosslinked DPBI with a macromolecular crosslinker of PVBC is an efficient way to improve the overall performance of HT-PEMs for high performance HT-PEMFCs.

Excavating Anomalous Capacity Increase of Li-S Pouch Cells by Electrochemical Oscillation Formation.

The insufficient activation of a S/C cathode makes insufficient utilization of S in Li-S pouch cells, while the deep activation of a S/C cathode in a formation process is time-consuming and produces lithium polysulfides, which corrode a Li anode. Both situations lead to a low actual capacity of the Li-S pouch cells with a high S loading but are ignored for coin cells. In this work, electrochemical oscillation (EOS) formation employing hundreds of shallow discharge/charge cycles with high frequency was used to replace the resting and/or one deep discharge/charge cycle of traditional (TD) formation protocols. By controlling the discharge/charge capacity separately, symmetric oscillation (SOS) and asymmetric oscillation (ASOS) protocols were performed to facilitate the infiltration of electrolyte into the S cathode and restrict the formed lithium polysulfide in the cathode region. For SOS formation, the batteries were discharged/charged above 2.4 V with the same (symmetric) capacity with 2.78 × 10-3 Hz of oscillation frequency (∼1.4 mAh/g for SOS-500), in which the polysulfide dissolution was suppressed effectively. For ASOS formation, 100% discharge capacity (also ∼1.4 mAh/g for ASOS-500) and 92% charge capacity are set in each oscillation period, which leads to better activation effect but more shuttling polysulfides than SOS. Compared with SOS protocol, for ASOS protocol, more oxidative S (instead of polysulfides) inside original nonactivated cathode will be preferentially reduced in the next discharging process, but all the accumulated polysulfides during discharge of activation are oxidized into elemental S in the final charging process. These efficient formation protocols increase the practical capacity by up to 160% after 50 cycles without any change in pouch cell assembly.

Polybenzimidazole Confined in Semi-Interpenetrating Networks of Crosslinked Poly (Arylene Ether Ketone) for High Temperature Proton Exchange Membrane.

As a traditional high-temperature proton exchange membrane (HT-PEM), phosphoric acid (PA)-doped polybenzimidazole (PBI) is often subject to severe mechanical strength deterioration owing to the "plasticizing effect" of a large amount of PA. In order to address this issue, we fabricated the HT-PEMs with a crosslinked network of poly (arylene ether ketone) to confine polybenzimidazole in semi-interpenetration network using self-synthesized amino-terminated PBI (PBI-4NH2) as a crosslinker. Compared with the pristine linear poly [2,2'-(p-oxdiphenylene)-5,5'-benzimidazole] (OPBI) membrane, the designed HT-PEMs (semi-IPN/xPBI), in the semi-IPN means that the membranes with a semi-interpenetration structure and x represent the combined weight percentage of PBI-4NH2 and OPBI. In addition, they also demonstrate an enhanced anti-oxidative stability and superior mechanical properties without the sacrifice of conductivity. The semi-IPN/70PBI exhibits a higher proton conductivity than OPBI at temperatures ranging from 80 to 180 °C. The HT-PEMFC with semi-IPN/70PBI exhibits excellent H2/O2 single cell performance with a power density of 660 mW cm-2 at 160 °C with flow rates of 250 and 500 mL min-1 for dry H2 and O2 at a backpressure of 0.03 MPa, which is 18% higher than that of OPBI (561 mW cm-2) under the same test conditions. The results indicate that the introduction of PBI containing crosslinked networks is a promising approach to improve the comprehensive performance of HT-PEMs.

Construction of KB@ZIF-8/PP Composite Separator for Lithium-Sulfur Batteries with Enhanced Electrochemical Performance.

Lithium-sulfur batteries (LSBs) have attracted wide attention, but the shuttle effect of polysulfide hinders their further practical application. Herein, we develop a new strategy to construct a Ketjen black@zeolite imidazole framework-8/polypropylene composite separator. Such a separator consists of Ketjen black (KB), zeolite imidazole framework-8 (ZIF-8) and polypropylene (PP) with a low coating load of 0.06 mg cm-2 and is denoted as KB@ZIF-8/PP. KB@ZIF-8/PP can absorb polysulfides because of the Lewis acid-base interaction between ZIF-8 and polysulfides. This interaction can reduce the dissolution of polysulfides and suppress the shuttle effect, thereby enhancing the electrochemical performance of the battery. When tested at a current density of 0.1 C, an LSB with a KB@ZIF-8/PP separator exhibits low polarization and achieves a high initial capacity of 1235.6 mAh/g and a high capacity retention rate of 59.27% after 100 cycles.

Interphase Building of Organic-Inorganic Hybrid Polymer Solid Electrolyte with Uniform Intermolecular Li+ Path for Stable Lithium Metal Batteries.

Lithium (Li) metal has been generally noticed as the most prospective anode for next-generation batteries attributed to its outstanding theoretical capacity and low electrochemical potential. Nevertheless, the unstable solid-electrolyte interphase (SEI) and uncontrollable dendrite growth cause poor reversibility and fetter the practical application of Li metal anodes. Herein, a new organic-inorganic hybrid polymer artificial SEI (POSS-LiBMAB) layer with uniform lithium-ion paths at a molecular level is designed to stabilize Li metal anodes. The SEI layer is constructed by the thiol-ene "click chemistry" reaction between inorganic polyhedral oligomeric silsesquioxane containing eight-mercaptopropyl (POSS-SH) with lithium bis (allylmalonato) borate (LiBMAB) on Li foil. What is more, the POSS-LiBMAB film can be cross-linked and self-reinforced via intermolecular SC bonds. Benefiting from its flexible polymeric covalent structure and noble inorganic Si8 O16 -type cubes, the organic-inorganic hybrid polymer layer is flexible and effectively tolerates the volume change of Li metal anodes during plating/stripping cycles. In addition, this layer shows loose and uniformly distributed electrostatic interaction between Li+ and charge delocalized sp3 boron-oxygen anions, which aids to form a uniform intermolecular Li+ path regulating the homogeneous distribution of Li+ flux on Li anodes. Finally, the designed POSS-LiBMAB layer has high ionic conductivity and lithium-ion transference number, which can effectively promote Li+ diffusion and guide Li deposition beneath the SEI layer. Therefore, with the protection of the POSS-LiBMAB layer, the Li metal anode exhibits stable cycling at 5 mA cm-2 for more than 1000 h, and the LFP//Li full cells also present outstanding cycling stability.

Covalent Organic Frameworks with Low Surface Work Function Enabled Stable Lithium Anode.

Uniform deposition and distribution of lithium ion (Li+ ) on the surface of lithium metal anode is crucial for long-life and high-safety lithium metal batteries. However, the preparation of stable solid-electrolyte interphase (SEI) is mostly based on trial and error in the absence of guideline. Herein, covalent organic framework (COF) with high Young's modulus and low surface work function is in situ synthesized on Li anode to stabilize Li|electrolyte interface. Notably, Young's modulus, mechanical index for Li dendrite resistance, and surface work function, electrical index for Li+ distribution, can be regarded as macroscopically detectable indicators to evaluate the artificial SEI before battery assembly. The COFTpPa modified Li metal anodes delivered stable cycling over 1000 (2000) h at high current density of 5 (2) mA cm-2 in the ether-based electrolyte, and the full cells with commercial LiFePO4 electrode (mass loading of 16.5 mg cm-2 ) demonstrate remarkably enhanced cycling performance with a high reversible capacity of 152.3 mAh g-1 (retention of 96.8%) after 300 cycles.

A Robust Composite Proton Exchange Membrane of Sulfonated Poly (Fluorenyl Ether Ketone) with an Electrospun Polyimide Mat for Direct Methanol Fuel Cells Application.

As a key component of direct methanol fuel cells, proton exchange membranes with suitable thickness and robust mechanical properties have attracted increasing attention. On the one hand, a thinner membrane gives a lower internal resistance, which contributes highly to the overall electrochemical performance of the cell, on the other hand, strong mechanical strength is required for the application of proton exchange membranes. In this work, a sulfonated poly (fluorenyl ether ketone) (SPFEK)-impregnated polyimide nanofiber mat composite membrane (PI@SPFEK) was fabricated. The new composite membrane with a thickness of about 55 µm exhibited a tensile strength of 35.1 MPa in a hydrated state, which is about 65.8% higher than that of the pristine SPFEK membrane. The antioxidant stability test in Fenton's reagent shows that the reinforced membrane affords better oxidation stability than does the pristine SPFEK membrane. Furthermore, the morphology, proton conductivity, methanol permeability, and fuel cell performance were carefully evaluated and discussed.

Transparency Change Mechanochromism Based on a Robust PDMS-Hydrogel Bilayer Structure.

Hydrogels and polydimethylsiloxane (PDMS) are complementary to each other, since the hydrophobic PDMS provides a more stable and rigid substrate, while the water-rich hydrogel possesses remarkable hydrophilicity, biocompatibility, and similarity to biological tissues. Herein a transparent and stretchable covalently bonded PDMS-hydrogel bilayer (PHB) structure is prepared via in situ free radical copolymerization of acrylamide and allylamine-exfoliated-ZrP (AA-e-ZrP) on a functionalized PDMS surface. The AA-e-ZrP serves as cross-linking nano-patches in the polymer gel network. The covalently bonded structure is constructed through the addition reaction of vinyl groups of PDMS surface and monomers, obtaining a strong interfacial adhesion between the PDMS and the hydrogel. A mechanical-responsive wrinkle surface, which exhibs transparency change mechanochromism, is created via introducing a cross-linked polyvinyl alcohol film atop the PHB structure. A finite element model is implemented to simulate the wrinkle formation process. The implication of the present finding for the interfacial design of the PHB and PDMS-hydrogel-PVA trilayer (PHPT) structures is discussed.

A Highly Immobilized Organic Anode Material for High Performance Rechargeable Lithium Batteries.

Organic conjugated carbonyl materials have attracted considerable attention in the field of high-capacity and green energy storage technologies. However, the high solubility in organic electrolyte restrains their further application. In this work, an organic terephthalate compound (Li2M) with propargyl groups is synthesized innovatively and then used to prepare a highly cross-linked anode material (X-Li2M) by simple hydrothermal treatment for rechargeable lithium batteries. The electrochemical properties are enhanced significantly by in situ constructing an interpenetrating network of X-Li2M and the conductive carbon nanotubes (CNTs). The as-synthesized X-Li2M@CNTs composite anode delivers a reversible capacity of ∼200 mAh g-1 at 0.1 C after 200 cycles and exhibits excellent cycle stability at a high rate of 1 C with ∼150 mAh g-1 retention capacity after 1000 cycles and nearly 100% average Coulombic efficiency. Additionally, the superior rate capability is obtained at the high rate of 2 and 10 C and with specific discharge capacities of 140 and 100 mAh g-1, respectively. Highly reversible redox reaction of the electrochemical active site carbonyl group (C═O) is ascertained by ex-situ infrared spectroscopy and X-ray photoelectron spectroscopy. The described approach provides a novel direction for the immobilization of organic electrode molecules and is intended to serve as a universal guide for the research and fabrication of high-performance organic batteries.

Addressing Passivation of a Sulfur Electrode in Li-S Pouch Cells for Dramatically Improving Their Cyclic Stability.

The effective passivation of a sulfur electrode in Li-S pouch cells is addressed by increasing the discharging cutoff voltage from 1.6 to 2.0 V. This simple method can effectively suppress the generation of solid and insulated Li2S deposition while reserves the majority of capacity and improves the cyclic stability of Li-S pouch cells. Upon increasing the discharging cutoff voltage from 1.6 to 2.0 V, the Li-S pouch cell loses only 8% of the initial discharge capacity and remarkably promotes the capacity retention rate from 62.4 to 91.6% within 40 cycles at 0.05C. The analysis of electrochemistry and physics of a sulfur cathode demonstrates that the less Li2S deposition under the discharging cutoff voltage of 2.0 V can ensure fast reaction kinetics in Li-S pouch cells with high areal sulfur loadings and lean electrolyte. The mechanism of the passivation of a sulfur electrode is studied and discussed in detail. This brand new methodology may provide an effective approach to enhance the cyclic stability of a Li-S battery.

Design of dental implants at materials level: An overview.

Due to the excellent restoration of masticatory function, satisfaction on aesthetics and other superiorities, dental implants represent an effective method to resolve tooth losing and damaging. Current dental implant systems still have problems waiting to be addressed, and problems are centralized on the materials of implant bodies. This review aims to summarize major developments in the field of dental implant materials, starting with an overview on structures, procedures of dental implants and challenges of implant materials. Next, implant materials are examined in three categories, that is, metals, ceramics, and polymers, their mechanical properties, biocompatibility, and bioactivity are summarized. And as an important aspect, strategies of surface modification are also reviewed, along with some finite element analysis to guiding the research direction of implant materials. Finally, the conclusive remarks are outlined to provide an outlook on the future research directions and prospects of dental implants.

Synergetic Covalent and Spatial Confinement of Sulfur Species by Phthalazinone-Containing Covalent Triazine Frameworks for Ultrahigh Performance of Li-S Batteries.

Lithium-sulfur (Li-S) batteries severely suffer from the shuttling of soluble polysulfides intermediates, insulation of sulfur and lithium sulfides, and volumetric expansion of sulfur electrodes, which result in the fast capacity decay and low utilization of active materials. To overcome these issues, a new type of porous phthalazinone-based covalent triazine frameworks (P-CTFs) with inherent N and O atoms has been in situ grown onto conductive reduced graphene oxide (rGO) by the sulfur-mediated cyclization of dinitrile monomers to afford the S/P-CTF@rGO hybrids. The well-designed structure endows the S/P-CTF@rGO composites with several features for enhanced Li-S batteries: (i) the nanoporous structure can spatially trap the sulfur species within the P-CTFs; (ii) the covalent binding of sulfur and polar groups of phthalazinone and triazine in P-CTFs exhibits strong chemical attachment and adsorption with polysulfides and further limits the diffusion of polysulfides; (iii) the conductive rGO and semiconductive P-CTFs help faster electronic transportation and accelerate the electrochemical process. Therefore, the S/P-CTF@rGO cathodes show greatly enhanced electrochemical performances with a high initial specific capacity of 1130 mAh g-1 at 0.5C and a good capacity retention of 81.4% after 500 cycles, indicating only 0.04% degradation per cycle.

Both Phosphonic Acid- and Fluorine-Containing Poly(aryl ether)-hydroxyapatite Biocomposites: Toward Enhanced Biocompatibility and Bonelike Elastic Modulus.

Metal-based implants possess excellent mechanical strength, corrosion resistance, and biocompatibility and can deliver favorable performances in clinic treatments. However, modulus mismatching is considered a common defect for metal-based materials, while polymer-based materials with a bonelike elastic modulus have been regarded as one of the most promising candidates for bone replacement implants. In this work, a phosphonic acid- and fluorine-containing poly(aryl ether) (PAE) resin is designed and synthesized, which is determined to be an amorphous polymer with excellent thermostability. The elastic modulus of composites is improved to 15.7 GPa by reinforcing with 60 wt % hydroxyapatite (HA), which demonstrates admirable protein adsorption and hydrophilicity. After 14 days of immersion in simulated body fluid, a layer of HA deposition can be observed, indicating favorable bioactivity in advance, and the preliminary in vitro cell experiments also suggest that PAE-HA composites possess favorable cell responses on adhesion, proliferation, and differentiation, which reveal the feasibility of synthesized polymers to be employed as bone replacement materials, while the adjustability in molecular chains also leaves room for further investigations.

CO2 Nanoenrichment and Nanoconfinement in Cage of Imine Covalent Organic Frameworks for High-Performance CO2 Cathodes in Li-CO2 Batteries.

The Li-CO2 battery is an emerging green energy technology coupling CO2 capture and conversion. The main drawback of present Li-CO2 batteries is serious polarization and poor cycling caused by random deposition of lithium ions and big insulated Li2 CO3 formation on the cathode during discharge. Herein, covalent organic frameworks (COF) are identified as the porous catalyst in the cathode of Li-CO2 batteries for the first time. Graphene@COF is fabricated, graphene with thin and uniform imine COF loading, to enrich and confine CO2 in the nanospaces of micropores. The discharge voltage is raised by higher local CO2 concentration, which is predicted by the Nernst equation and realized by CO2 nanoenrichment. Moreover, uniform lithium ion deposition directed by the graphene@COF nanoconfined CO2 can produce smaller Li2 CO3 particles, leading to easier Li2 CO3 decomposition and thus lower charge voltage. The graphene@COF cathode with 47.5% carbon content achieves a discharge capacity of 27833 mAh g-1 at 75 mA g-1 , while retaining a low charge potential of 3.5 V at 0.5 A g-1 for 56 cycles.

Low-Carbon and Nanosheathed ZnCo2O4 Spheroids with Porous Architecture for Boosted Lithium Storage Properties.

Multielectronic reaction electrode materials for high energy density lithium-ion batteries (LIBs) are severely hindered by their inherent sluggish kinetics and large volume variations, leading to rapid capacity fade. Here, a simple method is developed to construct low-carbon and nanosheathed ZnCo2O4 porous spheroids (ZCO@C-5). In this micro/nanostructure, an ultrathin amorphous carbon layer (~2 nm in thickness) is distributed all over the primary nanosized ZCO particles (~20 nm in diameter), which finally self-assembles into porous core (ZCO)-shell(carbon) micron spheroids. The nanoencapsulation and macro/mesoporous architecture can not only provide facile electrolyte penetration and rapid ion/electron transfer but also better alleviate volumetric expansion effect to avoid pulverization of ZCO@C-5 spheroids during repeat charge/discharge processes. As expected, the three-dimensional porous ZCO@C-5 composites exhibit high reversible capacity of 1240 mAh g-1 cycle at 500 mA g-1, as well as excellent long-term cycling stability and rate capability. The low-carbon and nanoencapsulation strategy in this study is simple and effective, exhibiting great potential for high-performance LIBs.