High-Entropy Polymer Electrolytes Derived from Multivalent Polymeric Ligands for Solid-State Lithium Metal Batteries with Accelerated Li+ Transport.

Solid-state polymer-based electrolytes (SSPEs) exhibit great possibilities in realizing high-energy-density solid-state lithium metal batteries (SSLMBs). However, current SSPEs suffer from low ionic conductivity and unsatisfactory interfacial compatibility with metallic Li because of the high crystallinity of polymers and sluggish Li+ movement in SSPEs. Herein, differing from common strategies of copolymerization, a new strategy of constructing a high-entropy SSPE from multivariant polymeric ligands is proposed. As a protocol, poly(vinylidene fluoride-co-hexafluoropropylene) (PH) chains are grafted to the demoed polyethylene imine (PEI) with abundant -NH2 groups via a click-like reaction (HE-PEIgPHE). Compared to a PH-based SSPE, our HE-PEIgPHE shows a higher modulus (6.75 vs 5.18 MPa), a higher ionic conductivity (2.14 × 10-4 vs 1.03 × 10-4 S cm-1), and a higher Li+ transference number (0.55 vs 0.42). A Li|HE-PEIgPHE|Li cell exhibits a long lifetime (1500 h), and a Li|HE-PEIgPHE|LiFePO4 cell delivers an initial capacity of 160 mAh g-1 and a capacity retention of 98.7%, demonstrating the potential of our HE-PEIgPHE for the SSLMBs.

Superior Li+ Kinetics by "Low-Activity-Solvent" Engineering for Stable Lithium Metal Batteries.

The structure of solvated Li+ has a significant influence on the electrolyte/electrode interphase (EEI) components and desolvation energy barrier, which are two key factors in determining the Li+ diffusion kinetics in lithium metal batteries. Herein, the "solvent activity" concept is proposed to quantitatively describe the correlation between the electrolyte elements and the structure of solvated Li+. Through fitting the correlation of the electrode potential and solvent concentration, we suggest a "low-activity-solvent" electrolyte (LASE) system for deriving a stable inorganic-rich EEI. Nano LiF particles, as a model, were used to capture free solvent molecules for the formation of a LASE system. This advanced LASE not only exhibits outstanding antidendrite growth behavior but also delivers an impressive performance in Li/LiNi0.8Co0.1Mn0.1O2 cells (a capacity of 169 mAh g-1 after 250 cycles at 0.5 C).

Interfacial Modulation of a Self-Sacrificial Synthesized SnO2@Sn Core-Shell Heterostructure Anode toward High-Capacity Reversible Li+ Storage.

Sn-based anodes are promising high-capacity anode materials for low-cost lithium ion batteries. Unfortunately, their development is generally restricted by rapid capacity fading resulting from large volume expansion and the corresponding structural failure of the solid electrolyte interphase (SEI) during the lithiation/delithiation process. Herein, heterostructural core-shell SnO2-layer-wrapped Sn nanoparticles embedded in a porous conductive nitrogen-doped carbon (SOWSH@PCNC) are proposed. In this design, the self-sacrificial Zn template from the precursors is used as the pore former, and the LiF-Li3N-rich SEI modulation layer is motivated to average uniform Li+ flux against local excessive lithiation. Meanwhile, both the chemically active nitrogen sites and the heterojunction interfaces within SnO2@Sn are implanted as electronic/ionic promoters to facilitate fast reaction kinetics. Consequently, the as-converted SOWSH@PCNC electrodes demonstrate a significantly boosted Li+ capacity of 961 mA h g-1 at 200 mA g-1 and excellent cycling stability with a low capacity decaying rate of 0.071% after 400 cycles at 500 mA g-1, suggesting their great promise as an anode material in high-performance lithium ion batteries.

Optimization of Cockpit Ventilation for Polar Cruise Ships in Combination with Windscreen Defogging and Cabin Comfort Considerations.

Polar cruise ships are exposed to extreme external conditions during voyages, resulting in cockpit windscreens that are prone to fogging and frosting, seriously affecting the driver's vision and even threatening navigation safety. However, the current research mainly focuses on cabin comfort, ignoring the coupling of defogging and comfort. Accordingly, this paper combines cockpit-windshield-defogging design and cockpit comfort considerations, and proposes 108 orthogonal-ventilation design parameters based on the four basic ventilation methods. The effects of different air supply parameters on comfort and anti-fog characteristics are investigated by using fluid dynamics simulation methods. The entropy weight-TOPSIS algorithm is employed to find the optimal ventilation parameters. The results show that the "Down-supply up-return type vertical jet" air supply method corresponding to an air supply velocity of 1 m/s, an air supply temperature of 297 K, and an air supply relative humidity of 30% has the smallest Euclidean distance di+ from the positive ideal solution, and the largest Euclidean distance di- from the negative ideal solution; thus, it obtains a higher ci and the highest priority. This air supply method provides the best thermal comfort for the drivers, as well as the best anti-fogging and defogging effect. The results can be useful to provide suggestions for the future design of the air-conditioning systems in polar cruise ships.

Multi-Step Phase Transitions of Mn3 O4 During Galvanostatic Lithiation: An In Situ Transmission Electron Microscopic Investigation.

For study of electrochemical reaction mechanisms at nanoscale, in situ electrochemical transmission electron microscopy (EC-TEM) exceeds many other methods due to its high temporal and spatial resolution. However, the limited amount of active materials used in previous in situ TEM studies prevents the model EC cells to operate in the constant-current (galvanostatic) charge/discharge mode that is required for accurate control of electrochemical processes. Herein, a new in situ EC-TEM technique is developed to investigate multi-step phase transitions of Mn3 O4 electrodes under the galvanostatic charge/discharge mode and constant-voltage discharge mode. In galvanostatic mode, the lithiation of Mn3 O4 undergoes multi-step phase transitions following a reaction pathway of Mn3 O4 + Li+ → LiMn3 O4 + Li+ → MnO + Li2 O → Mn + Li2 O. It is also found that lithium ions prefer to enter Mn3 O4 along the {101} direction to form LiMn3 O4 with the help of transitional boundary phase of Lix Mn3 O4 . These results are in sharp contrast to that obtained under a constant-voltage discharge mode, where only a single-step lithiation process of Mn3 O4 + Li+ → Mn + Li2 O is observed.

Freestanding Carbon Nanotube Film for Flexible Straplike Lithium/Sulfur Batteries.

Flexible lithium/sulfur (Li/S) batteries are promising to meet the emerging power demand for flexible electronic devices. The key challenge for a flexible Li/S battery is to design a cathode with excellent electrochemical performance and mechanical flexibility. In this work, a flexible strap-like Li/S battery based on a S@carbon nanotube/Pt@carbon nanotube hybrid film cathode was designed. It delivers a specific capacity of 1145 mAh g-1 at the first cycle and retains a specific capacity of 822 mAh g-1 after 100 cycles. Moreover, the flexible Li/S battery retains stabile specific capacity and Coulombic efficiency even under severe bending conditions. As a demonstration of practical applications, an LED array is shown stably powered by the flexible Li/S battery under flattened and bent states. We also use the strap-like flexible Li/S battery as a real strap for a watch, which at the same time provides a reliable power supply to the watch.

Aerogel-Directed Energy-Storage Films with Thermally Stimulant Multiresponsiveness.

Phase change materials offer enormous potential for thermal energy storage due to their high latent heat and chemical stability. Researchers have developed numerous innovative strategies to overcome the leakage of organic phase change materials and enhance thermal performance. However, the manufacture of form-stable, free-standing energy storage films based on phase change materials with high latent heat remains difficult. Therefore, the present study focused on the production of free-standing, form-stable energy storage films with high phase-change enthalpy and thermally stimulant multiresponsiveness from the simple composite of paraffin with a polytetrafluoroethylene/silica (PTFE/SiO2) aerogel framework, where paraffin was effectively confined in PTFE/SiO2. The resulting paraffin/PTFE/SiO2 films exhibited a large phase change enthalpy (128 J/g) at a paraffin content of 62.8 wt %. The temperature-dependent wettability, transmittance, and mechanical properties of this composite film have also been investigated.

In Situ Electrochemically Derived Amorphous-Li2 S for High Performance Li2 S/Graphite Full Cell.

High-capacity Li2 S cathode (1166 mAh g-1 ) is regarded as a promising candidate for the next-generation lithium ion batteries. However, its high potential barrier upon the initial activation process leads to a low utilization of Li2 S. In this work, a Li2 S/graphite full cell with the zero activation potential barrier is achieved through an in situ electrochemical conversion of Li2 S8 catholyte into the amorphous Li2 S. Theoretical calculations indicate that the zero activation potential for amorphous Li2 S can be ascribed to its lower Li extraction energy than that of the crystalline Li2 S. The constructed Li2 S/graphite full cell delivers a high discharge capacity of 1006 mAh g-1 , indicating a high utilization of the amorphous Li2 S as a cathode. Moreover, a long cycle life with 500 cycles for this Li2 S/graphite full cell is realized. This in situ electrochemical conversion strategy designed here is inspired for developing high energy Li2 S-based full cells in future.

Prelithiation of Nanostructured Sulfur Cathode by an "On-Sheet" Solid-State Reaction.

A novel "on-sheet" solid-state chemical reaction method is designed to fabricate a nanostructured Li2 S-reduced graphene oxide (rGO) cathode using a semi-sacrificial sulfur-graphene oxide template. The as-fabricated Li2 S-rGO nanocomposite shows a superior electrochemical performance, e.g., high utilization of Li2 S active materials (86.3 wt%), long cell life (1000 cycles), and excellent rate ability.

Synthesis, Crystal Structure, and Electrochemical Properties of a Simple Magnesium Electrolyte for Magnesium/Sulfur Batteries.

Most simple magnesium salts tend to passivate the Mg metal surface too quickly to function as electrolytes for Mg batteries. In the present work, an electroactive salt [Mg(THF)6 ][AlCl4 ]2 was synthesized and structurally characterized. The Mg electrolyte based on this simple mononuclear salt showed a high Mg cycling efficiency, good anodic stability (2.5 V vs. Mg), and high ionic conductivity (8.5 mS cm(-1) ). Magnesium/sulfur cells employing the as-prepared electrolyte exhibited good cycling performance over 20 cycles in the range of 0.3-2.6 V, thus indicating an electrochemically reversible conversion of S to MgS without severe passivation of the Mg metal electrode surface.

High-rate, ultralong cycle-life lithium/sulfur batteries enabled by nitrogen-doped graphene.

Nitrogen-doped graphene (NG) is a promising conductive matrix material for fabricating high-performance Li/S batteries. Here we report a simple, low-cost, and scalable method to prepare an additive-free nanocomposite cathode in which sulfur nanoparticles are wrapped inside the NG sheets (S@NG). We show that the Li/S@NG can deliver high specific discharge capacities at high rates, that is, ∼ 1167 mAh g(-1) at 0.2 C, ∼ 1058 mAh g(-1) at 0.5 C, ∼ 971 mAh g(-1) at 1 C, ∼ 802 mAh g(-1) at 2 C, and ∼ 606 mAh g(-1) at 5 C. The cells also demonstrate an ultralong cycle life exceeding 2000 cycles and an extremely low capacity-decay rate (0.028% per cycle), which is among the best performance demonstrated so far for Li/S cells. Furthermore, the S@NG cathode can be cycled with an excellent Coulombic efficiency of above 97% after 2000 cycles. With a high active S content (60%) in the total electrode weight, the S@NG cathode could provide a specific energy that is competitive to the state-of-the-art Li-ion cells even after 2000 cycles. The X-ray spectroscopic analysis and ab initio calculation results indicate that the excellent performance can be attributed to the well-restored C-C lattice and the unique lithium polysulfide binding capability of the N functional groups in the NG sheets. The results indicate that the S@NG nanocomposite based Li/S cells have a great potential to replace the current Li-ion batteries.

Atom-Level Tandem Catalysis in Lithium Metal Batteries.

High-energy-density lithium metal batteries (LMBs) are limited by reaction or diffusion barriers with dissatisfactory electrochemical kinetics. Typical conversion-type lithium sulfur battery systems exemplify the kinetic challenges. Namely, before diffusing or reacting in the electrode surface/interior, the Li(solvent)x + dissociation at the interface to produce isolated Li+, is usually a prerequisite fundamental step either for successive Li+ "reduction" or for Li+ to participate in the sulfur conversions, contributing to the related electrochemical barriers. Thanks to the ideal atomic efficiency (100 at%), single atom catalysts (SACs) have gained attention for use in LMBs toward resolving the issues caused by the five types of barrier-restricted processes, including polysulfide/Li2S conversions, Li(solvent)x + desolvation, and Li0 nucleation/diffusion. In this perspective, the tandem reactions including desolvation and reaction or plating and corresponding catalysis behaviors are introduced and analyzed from interface to electrode interior. Meanwhile, the principal mechanisms of highly efficient SACs in overcoming specific energy barriers to reinforce the catalytic electrochemistry are discussed. Lastly, the future development of high-efficiency atomic-level catalysts in batteries is presented.

Enhanced photocatalytic activity of titanium oxide nanotubes after heating treatment.

Titanium oxide nanotubes were obtained by an electrochemical anodization method. Scanning electron microscope results demonstrate that the diameter of the tubes is about 120 nm and the length of the tubes is around 13 microm. Transmission electron microscope results indicate that the nanotubes are assembled by numerous nanoparticles and tube-like structure remains well after heat treatment at 400-600 degrees C. The photocatalysis performance of the nanotubes was evaluated in terms of the decomposition rate of methyl orange under UV irradiation. The results show that the photocatalytic activity was enhanced through the heating treatment of the nanotubes, and the nanotubes heated at 600 degrees C exhibits the best photocatalytic activity. X-ray diffraction patterns indicate that there is no phase transformation during the heat treatment. Therefore, the enhanced activity can be attributed to the improvement of nanotubes crystallinity, which may provide more insights about the effect of the crystallinity on the photocatalytic performance.

Anion Receptor Enhanced Li Ion Transportation for High-Performance Lithium Metal Batteries.

High-potential lithium metal batteries (LMBs) are still facing many challenges, such as the growth of lithium (Li) dendrites and resultant safety hazards, low-rate capabilities, etc. To this end, electrolyte engineering is believed to be a feasible strategy and interests many researchers. In this work, a novel gel polymer electrolyte membrane, which is composed of polyethyleneimine (PEI)/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) cross-linked membrane and electrolyte (PPCM GPE), is prepared successfully. Due to the fact that the amine groups on PEI molecular chains can provide the rich anion receptors and strongly pin the anions of electrolytes and thus confine the movement of anions, our designed PPCM GPE owns a high Li+ transference number (0.70) and finally contributes to the uniform Li+ deposition and inhibits the growth of Li dendrites. In addition, the cells with PPCM GPE as a separator behave the impressive electrochemical performances, i.e., a low overpotential and an ultralong and stable cycling performance in Li∥Li cells, a low overvoltage of about 34 mV after a stable cycling for 400 h even at a high current density of 5 mA/cm2, and, in Li∥LFP full batteries, a specific capacity of 78 mAh/g after 250 cycles at a 5 C rate. These excellent results suggest a potential application of our PPCM GPE in developing high-energy-density LMBs.

Interfacial "Single-Atom-in-Defects" Catalysts Accelerating Li+ Desolvation Kinetics for Long-Lifespan Lithium-Metal Batteries.

The lithium-metal anode is a promising candidate for realizing high-energy-density batteries owing to its high capacity and low potential. However, several rate-limiting kinetic obstacles, such as the desolvation of Li+ solvation structure to liberate Li+ , Li0 nucleation, and atom diffusion, cause heterogeneous spatial Li-ion distribution and fractal plating morphology with dendrite formation, leading to low Coulombic efficiency and depressive electrochemical stability. Herein, differing from pore sieving effect or electrolyte engineering, atomic iron anchors to cation vacancy-rich Co1- x S embedded in 3D porous carbon (SAFe/CVRCS@3DPC) is proposed and demonstrated as catalytic kinetic promoters. Numerous free Li ions are electrocatalytically dissociated from the Li+ solvation complex structure for uniform lateral diffusion by reducing desolvation and diffusion barriers via SAFe/CVRCS@3DPC, realizing smooth dendrite-free Li morphologies, as comprehensively understood by combined in situ/ex situ characterizations. Encouraged by SAFe/CVRCS@3DPC catalytic promotor, the modified Li-metal anodes achieve smooth plating with a long lifespan (1600 h) and high Coulombic efficiency without any dendrite formation. Paired with the LiFePO4 cathode, the full cell (10.7 mg cm-2 ) stabilizes a capacity retention of 90.3% after 300 cycles at 0.5 C, signifying the feasibility of using interfacial catalysts for modulating Li behaviors toward practical applications.

Tailoring Electrolyte Solvation for LiF-Rich Solid Electrolyte Interphase toward a Stable Li Anode.

A solid electrolyte interphase (SEI) with robust mechanical property and high ionic conductivity is imperative for high-performance lithium metal batteries since it can efficiently impede the growth of notorious lithium dendrites. However, it is difficult to form such a SEI directly from an electrolyte. In this work, a crowding dilutant modified ionic liquid electrolyte (M-ILE) has been developed for this purpose. Simulations and experiments indicate that the 1,2-difluorobenzene (1,2-dfBen) dilutant not only creates a crowded electrolyte environment to promote the interaction of Li+-FSI-, leading to abundant aggregate ion pairs (AGGs), but also participates in the reduction to construct a robust and high ionic-conductive SEI. With this M-ILE, Li/LiFePO4 cells achieve a capacity retention of 96% over 250 cycles with 9.5 mg cm-2 mass loading, and Li/LiNi0.5Co0.2Mn0.3O2 cells also deliver a discharge capacity of 132 mAh g-1 with a high retention of 88% after 100 cycles. Therefore, the use of a crowding diluent is considered to be an efficient way to construct an advanced SEI for a Li anode.

Kinetics of electron recombination of dye-sensitized solar cells based on TiO2 nanorod arrays sensitized with different dyes.

The performance and electron recombination kinetics of dye-sensitized solar cells based on TiO(2) films consisting of one-dimensional nanorod arrays (NR-DSSCs) which are sensitized with dyes N719, C218 and D205, respectively, have been studied. It has been found that the best efficiency is obtained with the dye C218 based NR-DSSCs, benefiting from a 40% higher short-circuit photocurrent density. However, the open circuit photovoltage of the N719 based cell is 40 mV higher than that of the organic dye C218 and D205 based devices. Investigation of the electron recombination kinetics of the NR-DSSCs has revealed that the effective electron lifetime, τ(n), of the different dye based NR-DSSCs shows the sequence of C218 > D205 > N719. The higher V(oc) with the N719 based NR-DSSC is originated from the more negative energy level of the conduction band of the TiO(2) film. In addition, in comparison to the DSSCs with the conventional nanocrystalline particles based TiO(2) films, the NR-DSSCs have shown over two orders of magnitude higher τ(n) when employing N719 as the sensitizer. Nevertheless, the τ(n) of the DSSCs with the C218 based nanorod arrays is only ten-fold higher than that of the nanoparticles based devices. The remarkable characteristic of the dye C218 in suppressing the electron recombination of DSSCs is discussed.

A Polar and Ordered-Channel Composite Separator Enables Antidendrite and Long-Cycle Lithium Metal Batteries.

Lithium (Li) metal as an anode replacing the traditional graphite could largely enhance the specific energy density of Li batteries. However, the repeated formation of solid electrolyte interfaces on the surface of Li metal upon plating/stripping leads to a low Coulombic efficiency, and the growth of Li dendrites upon cycling probably causes the short circuit or even explosion of the batteries, both of which block the commercial application of Li metal in lithium metal batteries (LMBs). Herein, we report an antidendrite AAO@PVDF-HFP composite separator fabricated by a two-step method, which features the ordered pore channels and the polar groups in the channels. This novel composite separator has a good wettability to the electrolyte, high mechanical properties, and high ionic conductivity. Expectedly, the assembled batteries based on our novel composite separator show many impressive performances. In Li-Li cells, the cycling life up to 1600 h at an areal current density of 2 mA/cm2 can be realized; in Li-Cu cells, the cycling life of more than 1000 h with a high Coulombic efficiency of 99.9% at 1 mA/cm2 can be achieved. More interestingly, the Li/LiFePO4 full batteries constructed by the novel AAO@PVDF-HFP composite separators show a high discharge capacity of 140 mAh/g and weak capacity decays even after 360 cycles. The novel design of the separator with ordered channels and polar groups presents an effective route for developing the next-generation LMBs.

Coupling Niobia Nanorods with a Multicomponent Carbon Network for High Power Lithium-Ion Batteries.

High power lithium-ion batteries require highly conductive electrodes. For an active electrode material that has limited electron conductivity, it is critical to build a carbon network that is not only highly conductive itself but also highly compatible with the electroactive material for efficient interfacial charge transfer. Herein, we design a multicomponent carbon network that is optimized for electrical coupling with the electroactive Nb2O5 nanorods for efficient electron injection. The self-support electrode is constructed by using 0D polypyrrole-derived (Ppy) carbon nanoparticles as glue to bind the Nb2O5 nanorods with 1D carbon nanotubes (CNTs) and 2D graphene nanosheets (GNSs). The 0D carbon nanoparticles also cross-link 1D CNTs with 2D GNSs, which can effectively prevent the GNSs from aggregation and form the 3D CNT/GNS network that provides continuous electronic and ionic pathways. This 3D Nb2O5@C self-support electrode exhibits a high discharge capacity of 246.3 mA h g-1 at 0.5 C and 100 mA h g-1 at 20 C and excellent Coulombic efficiency of 99.98% at 20 C. Even increasing the mass loading to 7.1 mg cm-2, the Nb2O5@C electrode can still reach a discharge capacity of 172.4 mA h g-1 at 0.5 C after 100 cycles. A high power density of 1043 W kg-1 can be achieved at an energy density of 104.3 W h kg-1 based on the electrode weight, which is among the highest values demonstrated so far for Nb2O5 electrodes. The results pave the way toward practical applications of Nb2O5 anodes in high-power lithium-ion batteries.

Reducing lithium deposition overpotential with silver nanocrystals anchored on graphene aerogel.

Li metal as an anode for high-energy-density batteries is actively pursued due to its high specific capacity and ultralow electrochemical potential. Unfortunately, Li dendrite growth might induce a short circuit creating safety hazards that limit the practical applications of Li metal anode batteries. Herein, a novel anode of graphene aerogel (GA) decorated with silver nanocrystals (AgNCs@GA) is reported for effective suppression of lithium dendrite growth and improvement in coulombic efficiency at various current densities. This improved performance is attributed to AgNCs. This loaded AgNCs with high Li affinity serve as Li deposition sites, which deeply reduce the overpotential of Li nucleation and electrodeposition. Therefore, it successfully realizes stable Li deposition/stripping processes with enhanced coulombic efficiency at various current densities and areal capacities. The pre-lithiated AgNCs@GA is evaluated as an anode in a Li battery and demonstrates remarkable performance in comparison with a commercial lithium foil.