Self-Assembled Structure Evolution of MnFe Oxides for High Temperature Thermochemical Energy Storage.

Thermochemical energy storage (TCES) materials have emerged as a promising alternative to meet the high-temperature energy storage requirements of concentrated solar power plants. However, most of the energy storage materials are facing challenges in redox kinetics and cyclic stability. Iron-doped manganese oxide attracts raising attention due to its non-toxicity, low cost, and high energy capacity over 800 °C. However, there are few investigations on the reversibility enhancement of the redox reaction from the microstructural-evolution-mechanism point of view. Herein, bixbyite-type (Mn0.8 Fe0.2 )2 O3 is synthesized and extruded into honeycomb units, which can maintain an 85% initial capacity after 100 redox cycles. It is also found that a self-assembled core-shell MnFe2 O4 @Mn2.7 Fe0.3 O4 structure forms during the reduction step, and then transforms into a homogeneous solid solution of (Mn0.8 Fe0.2 )2 O3 in the following oxidation step. During the reduction step, shells are formed spontaneously from the Mn2.7 Fe0.3 O4 with the MnFe2 O4 as cores due to the lower surface energy, which facilitates the oxygen adsorption and dissociation during subsequent oxidation step. Through the density functional theory calculation, it is revealed that the lower formation energy of oxygen vacancies in the shell contributes to the improvement of oxygen diffusion rate. This study can provide a guideline to design prospective materials for high-temperature TCES.

Single-Crystal-Layered Ni-Rich Oxide Modified by Phosphate Coating Boosting Interfacial Stability of Li10 SnP2 S12 -Based All-Solid-State Li Batteries.

All-solid-state lithium batteries (ASSLBs) adopting sulfide electrolytes and high-voltage layered oxide cathodes have moved into the mainstream owing to their superior safety and immense potential in high energy density. However, the poor electrochemical compatibility between oxide cathodes and sulfide electrolytes remains a challenge for high-performance ASSLBs. In this study, a nanoscale Li1.4 Al0.4 Ti1.6 (PO4 )3 (LATP) phosphate coating is reasonably constructed on the surface of single-crystal LiNi0.6 Co0.2 Mn0.2 O2 particles to achieve cathode/electrolyte interfacial stability. The conformal LATP layer with inherent high-voltage stability can effectively suppress the oxidation decomposition of the electrolyte and demonstrate chemical inertness to both the oxide cathode and Li10 SnP2 S12 electrolyte. ASSLBs with an LATP-modified cathode exhibited a high initial discharge capacity (152.1 mAh g-1 ), acceptable rate capability, and superior cycling performance with a capacity retention of 87.6% after 100 cycles at 0.1 C. Interfacial modification is an effective approach for achieving high-performance sulfide-based ASSLBs with superior interfacial stability.

Boosting High-Rate Sodium Storage Performance of N-Doped Carbon-Encapsulated Na3 V2 (PO4 )3 Nanoparticles Anchoring on Carbon Cloth.

The further development of high-power sodium-ion batteries faces the severe challenge of achieving high-rate cathode materials. Here, an integrated flexible electrode is constructed by smart combination of a conductive carbon cloth fiber skeleton and N-doped carbon (NC) shell on Na3 V2 (PO4 )3 (NVP) nanoparticles via a simple impregnation method. In addition to the great electronic conductivity and high flexibility of carbon cloth, the NC shell also promotes ion/electron transport in the electrode. The flexible NVP@NC electrode renders preeminent rate capacities (80.7 mAh g-1 at 50 C for cathode; 48 mAh g-1 at 30 C for anode) and superior cycle performance. A flexible symmetric NVP@NC//NVP@NC full cell is endowed with fairly excellent rate performance as well as good cycle stability. The results demonstrate a powerful polybasic strategy design for fabricating electrodes with optimal performance.

Enhanced Li-Storage of Ni3 S2 Nanowire Arrays with N-Doped Carbon Coating Synthesized by One-Step CVD Process and Investigated Via Ex Situ TEM.

In this work, a facile strategy for the construction of single crystalline Ni3 S2 nanowires coated with N-doped carbon shell (NC) forming Ni3 S2 @NC core/shell arrays by one-step chemical vapor deposition process is reported. In addition to the good electronic conductivity from the NC shell, the nanowire structure also ensures the accommodation of large volume expansion during cycling, leading to pre-eminent high-rate capacities (470 mAh g-1 at 0.05 A g-1 and 385 mAh g-1 at 2 A g-1 ) and outstanding cycling stability with a capacity retention of 91% after 100 cycles at 1 A g-1 . Furthermore, ex situ transmission electron microscopy combined with X-ray diffraction and Raman spectra are used to investigate the reaction mechanism of Ni3 S2 @NC during the charge/discharge process. The product after delithiation consists of Ni3 S2 and sulfur, suggesting that the capacity of the electrode comes from the conversion reaction of both Ni3 S2 and sulfur with Li2 S.

Recent Developments of All-Solid-State Lithium Secondary Batteries with Sulfide Inorganic Electrolytes.

Due to the increasing demand of security and energy density, all-solid-state lithium ion batteries have become the promising next-generation energy storage devices to replace the traditional liquid batteries with flammable organic electrolytes. In this Minireview, we focus on the recent developments of sulfide inorganic electrolytes for all-solid-state batteries. The challenges of assembling bulk-type all-solid-state batteries for industrialization are discussed, including low ionic conductivity of the present sulfide electrolytes, high interfacial resistance and poor compatibility between electrolytes and electrodes. Many efforts have been focused on the solutions for these issues. Although some progresses have been achieved, it is still far away from practical application. The perspectives for future research on all-solid-state lithium ion batteries are presented.

Hierarchical MoS2 /Carbon Composite Microspheres as Advanced Anodes for Lithium/Sodium-Ion Batteries.

It is crucial to design advanced electrodes with large Li/Na-ion storage capacities for the development of next-generation battery systems. Herein, hierarchical MoS2 /C composite microspheres were constructed by facile template-free self-assembly sulfurization plus post-carbonization. Cross-linked MoS2 nanosheets and outer carbon layer are organically combined together to form composite microspheres with diameters of 400-500 nm. Due to enhanced electrical conductivity and good structural stability, the MoS2 /C composite microspheres exhibit substantially improved Li/Na-ion storage performance. Compared to unmodified MoS2 , MoS2 /C composite microspheres deliver higher Li/Na-ion storage capacity (Li+ : 1017 mA h g-1 at 100 mA g-1 and Na+ : 531 mA h g-1 at 100 mA g-1 ), as well as better rate capability (Li+ : 434 mA h g-1 at 1 Ag-1 and Na+ : 102 mA h g-1 at 1 Ag-1 ) and capacity retention (Li+ : 902 mA h g-1 after 200 cycles and Na+ : 342 mA h g-1 over 100 cycles). The superior Li/Na-ion storage performance is mainly attributed to the unique porous microsphere architecture with increased electrode/electrolyte interfaces and more diffusion paths for Li/Na ion insertion. Additionally, the carbon coating can not only improve the electronic conductivity, but also suppress the shuttle effect of polysulfides.

A Newly Designed Composite Gel Polymer Electrolyte Based on Poly(Vinylidene Fluoride-Hexafluoropropylene) (PVDF-HFP) for Enhanced Solid-State Lithium-Sulfur Batteries.

Developing high-performance solid-state electrolytes is crucial for the innovation of next-generation lithium-sulfur batteries. Herein, a facile method for preparation of a novel gel polymer electrolyte (GPE) based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) is reported. Furthermore, Li1.5 Al0.5 Ti1.5 (PO4 )3 (LATP) nanoparticles as the active fillers are uniformly embedded into the GPE to form the final PVDF-HFP/LATP composite gel polymer electrolyte (CPE). Impressively, the obtained CPE demonstrates a high lithium ion transference number of 0.51 and improved electrochemical stability as compared to commercial liquid electrolyte. In addition, the assembled solid-sate Li-S battery with the composite gel polymer electrolyte membrane presents a high initial capacity of 918 mAh g-1 at 0.05 C, and better cycle performance than the counterparts with liquid electrolyte. Our designed PVDF-HFP/LATP composite can be a promising electrolyte for next-generation solid-state batteries with high cycling stability.

Performance Enhancement of a Sulfur/Carbon Cathode by Polydopamine as an Efficient Shell for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are considered to be among the most promising next-generation high-energy batteries. It is a consensus that improving the conductivity of sulfur cathodes and impeding the dissolution of lithium polysulfides are two key accesses to high-performance LSBs. Herein we report a sulfur/carbon black (S/C) cathode modified by self-polymerized polydopamine (pDA) with the assistance of polymerization treatment. The pDA acts as a novel and effective shell on the S/C cathode to stop the shuttle effect of polysulfides. By the synergistic effect of enhanced conductivity and multiple blocking effect for polysulfides, the S/C@pDA electrode exhibits improved electrochemical performances including large specific capacity (1135 mAh g-1 at 0.2 C), high rate capability (533 mAh g-1 at 5 C) and long cyclic life (965 mAh g-1 after 200 cycles). Our smart design strategy may promote the development of high-performance LSBs.

Surface-modified and sulfide electrolyte-infiltrated LiNi0.6Co0.2Mn0.2O2 cathode for all-solid-state lithium batteries.

Sulfide-based all-solid-state lithium batteries (ASSLBs) with high-voltage Ni-rich layered cathodes have shown great potential in energy storage systems. However, the application of ASSLBs is hindered by severe interface issues and poor solid-solid contact between cathodes and sulfide electrolytes. In this work, a suitably thin Li1.5Al0.5Ge1.5(PO4)3 (LAGP) coating (0.41 mS cm-1) is introduced onto the surface of single-crystal LiNi0.6Co0.2Mn0.2O2 particles to mitigate interface side reactions. Subsequently, sheet-type electrodes are fabricated by the infiltration of Li10GeP2S12 to fill the voids and achieve highly dense solid-solid contact, thus preventing contact loss. The Li10GeP2S12-infiltrated ASSLBs with a LAGP buffer layer display a high initial discharge capacity of 141.5 mAh g-1 at 0.05 C and ultrastable cycling for 100 cycles at 0.1 C. An effective fabrication method for highly dense electrodes is proposed in this work, which provides a new direction for scalable industrial production.

Quasi-Solid Electrolyte Interphase Boosting Charge and Mass Transfer for Dendrite-Free Zinc Battery.

The practical applications of zinc metal batteries are plagued by the dendritic propagation of its metal anodes due to the limited transfer rate of charge and mass at the electrode/electrolyte interphase. To enhance the reversibility of Zn metal, a quasi-solid interphase composed by defective metal-organic framework (MOF) nanoparticles (D-UiO-66) and two kinds of zinc salts electrolytes is fabricated on the Zn surface served as a zinc ions reservoir. Particularly, anions in the aqueous electrolytes could be spontaneously anchored onto the Lewis acidic sites in defective MOF channels. With the synergistic effect between the MOF channels and the anchored anions, Zn2+ transport is prompted significantly. Simultaneously, such quasi-solid interphase boost charge and mass transfer of Zn2+, leading to a high zinc transference number, good ionic conductivity, and high Zn2+ concentration near the anode, which mitigates Zn dendrite growth obviously. Encouragingly, unprecedented average coulombic efficiency of 99.8% is achieved in the Zn||Cu cell with the proposed quasi-solid interphase. The cycling performance of D-UiO-66@Zn||MnO2 (~ 92.9% capacity retention after 2000 cycles) and D-UiO-66@Zn||NH4V4O10 (~ 84.0% capacity retention after 800 cycles) prove the feasibility of the quasi-solid interphase.

Nanoparticulate ZrNi: In Situ Disproportionation Effectively Enhances Hydrogen Cycling of MgH2.

High thermal stability and sluggish absorption/desorption kinetics are still important limitations for using magnesium hydride (MgH2) as a solid-state hydrogen storage medium. One of the most effective solutions in improving hydrogen storage properties of MgH2 is to introduce a suitable catalyst. Herein, a novel nanoparticulate ZrNi with 10-60 nm in size was successfully prepared by co-precipitation followed by a molten-salt reduction process. The 7 wt % nano-ZrNi-catalyzed MgH2 composite desorbs 6.1 wt % hydrogen starting from ∼178 °C after activation, lowered by 99 °C relative to the pristine MgH2 (∼277 °C). The dehydrided sample rapidly absorbs ∼5.5 wt % H2 when operating at 150 °C for 8 min. The remarkably improved hydrogen storage properties are reasonably ascribed to the in situ formation of ZrH2, ZrNi2, and Mg2NiH4 caused by the disproportionation reaction of nano-ZrNi during the first de-/hydrogenation cycle. These catalytic active species are uniformly dispersed in the MgH2 matrix, thus creating a multielement, multiphase, and multivalent environment, which not only largely favors the breaking and rebonding of H-H bonds and the transfer of electrons between H- and Mg2+ but also provides multiple hydrogen diffusion channels. These findings are of particularly scientific importance for the design and preparation of highly active catalysts for hydrogen storage in light-metal hydrides.

Carbon-decorated single-crystalline Ni2P nanotubes derived from ni nanowire templates: a high-performance material for Li-ion batteries.

Single-crystalline Ni(2)P nanotubes (NTs) were facilely synthesized by using a Ni nanowire template. The mechanism for the formation of the tubular structures was related to the nanoscale Kirkendall effect. These NTs exhibited a core/shell structure with an amorphous carbon layer that was grown in situ by employing oleylamine as a capping agent. Galvanostatic charge/discharge measurements indicated that these Ni(2)P/C NTs exhibited superior high-rate capability and good cycling stability. There was still about 310 mA h g(-1) retained after 100 cycles at a rate of 5 C. Importantly, the tubular nanostructures and the single-crystalline nature of the Ni(2)P NTs were also preserved after prolonged cycling at a relatively high rate. These improvements were attributed to the stable nanotubular structure of Ni(2)P and the carbon shell, which enhanced the conductivity of Ni(2)P, suppressed the aggregation of active particles, and increased the electrode stability during cycling.

MgCr2O4-Modified CuO/Cu2O for High-Temperature Thermochemical Energy Storage with High Redox Activity and Sintering Resistance.

Metal oxides as high-temperature thermochemical energy storage systems with high energy density based on the gas-solid reaction are a critical demand for the future development of concentrated solar power plants. A copper-based system has high enthalpy change and low cost, but its serious sintering leads to poor reactivity. In this study, MgCr2O4 is decorated on the CuO/Cu2O surface to effectively increase the sintering temperature and alleviate the sintering problem. The re-oxidation degree is increased from 46 to 99.9%, and the reaction time is shortened by 3.7 times. The thermochemical energy density of storage and release reach -818.23 and 812.90 kJ/kg, respectively. After 600 cycles, the oxidation activity remains 98.77%. Material characterization elucidates that nanosized MgCr2O4 is uniformly loaded on the surface of CuO/Cu2O during the reversible reaction, and there is a strong interaction between metal oxides and prompter. Density functional theory (DFT) calculation further confirms that CuO/Cu2O-MgCr2O4 has large binding energy and the formation energy of copper vacancy increases, which can effectively inhibit sintering. The modification mechanism of CuO/Cu2O by MgCr2O4 is revealed, which can provide guidance for the reasonable design of thermochemical energy storage materials with sintering resistance and redox activity.

A Novel Ethanol-Mediated Synthesis of Superionic Halide Electrolytes for High-Voltage All-Solid-State Lithium-Metal Batteries.

Halide electrolytes are rising stars among inorganic solid-state electrolytes due to their high ionic conductivity and good compatibility with high-voltage electrodes. However, their traditional synthesis methods including ball-milling annealing are usually energy-intensive and time-consuming compared with liquid-mediated routes. What's more, the only method in aqueous solution is not perfect considering detrimental effect of trace water for battery performances. Here, we propose a novel ethanol-mediated synthesis route for superionic Li3InCl6 electrolyte via energy-friendly dissolution and post-treatment. The organics in ethanol-mediated precursor disappear in form of light gas during post-treatment. And Li3InCl6 with best thermal stability and ionic conductivity (0.79 mS cm-1, 20 °C) can be successfully prepared after postheating for 3 h at 200 °C. Besides, it is also found that the ionic conductivity of Li3InCl6 is positively correlated with peak intensity ratio of (131) plane/(001) plane since crystal plane and preferred orientation can directly affect polyhedrons through which lithium ions migrate in crystalline conductors. The assembled LiNi0.8Co0.1Mn0.1O2/Li3InCl6/Li10GeP2S12/Li-In cell presents high initial charge capacity of 174.8 mAh g-1 at 0.05 C and a good rate performance of 122.9 mAh g-1 at 1 C. Especially, the retention rate of charge capacity can reach 94.8% after 200 cycles. The ethanol-mediated synthesized Li3InCl6 is a novel promising electrolyte which can be coupled with high-voltage cathode for the application of all-solid-state lithium-metal batteries.

Ionic Conductivity Enhancement of Li2ZrCl6 Halide Electrolytes via Mechanochemical Synthesis for All-Solid-State Lithium-Metal Batteries.

Superionic halides have returned to the spotlight of solid electrolytes because of their satisfactory ionic conductivity, soft texture, and stability toward high-voltage electrode materials. Among them, Li2ZrCl6 has aroused interests since abundant Zr element can reduce the cost of large-scale synthesis. However, the related research is very limited, including the detailed parameters during synthesis and the possible strategies for enhancing ionic conductivity. In this work, we have systematically investigated the effects of synthesis parameters on the structure and ionic conductivity of Li2ZrCl6 during the ball-milling annealing process. It is found that mild heat treatment (100 °C) can largely enhance the ionic conductivity of ball-milled electrolytes by 2-3 times, which has not been previously reported. Such enhancement is mainly attributed to the network-like micromorphology composed of nanorods, nanowires, or nanoballs, which is beneficial for lithium ion migration. Finally, the modified Li2ZrCl6 (4.46 × 10-4 S cm-1 @ RT) is also proved to be applicable in LiNi0.8Mn0.1Co0.1O2/ Li2ZrCl6/ Li6PS5Cl/Li-In all-solid-state lithium metal batteries (ASSLMBs). It presents high initial charge capacity of 176.4 mAh g-1 and satisfactory cycle stability since a discharge capacity of 90.8 mAh g-1 is maintained after 40 cycles at 0.1 C. The Li2ZrCl6 electrolytes synthesized via the mechanochemical method is promising to be applied in the high-voltage ASSLMBs, and its ionic conductivity can be enhanced by the strategies provided in our work.

Ultrafast Synthesis of I-Rich Lithium Argyrodite Glass-Ceramic Electrolyte with High Ionic Conductivity.

Lithium argyrodites are one of the most promising sulfide electrolytes due to their high ionic conductivity and ductile feature. Among them, Li6 PS5 I (LPSI) exhibits better stability against Li metal but a rather low ionic conductivity (only ≈10-6 S cm-1 ) because of the absence of S2- /I- disorder. Herein, argyrodite Li6- x PS5- x I1+ x glass-ceramic electrolytes with high iodine content are synthesized using ultimate-energy mechanical alloying method. S2- /I- disorder is successfully introduced into the system by doping LiI during this one-pot process. Determined by 6 Li magic angle spinning nuclear magnetic resonance and ab initio molecular dynamics simulations, the introduction of iodine promotes Li+ inter-cage jumps, leading to an enhanced long-range Li+ conducting. The Li5.6 PS4.6 I1.4 glass-ceramic electrolyte (LPSI1.4 -gc) possesses high ionic conductivity (2.04 mS cm-1 ) and excellent stability against Li metal. The Li symmetric cell with the LPSI1.4 -gc electrolyte demonstrates ultralong cycling stability over 3200 h at 0.2 mA cm-2 . LiCoO2 /Li6 PS5 Cl/Li all-solid-state battery applying LPSI1.4 -gc as the anode interlayer also presents prominent cycling and rate performance. This work provides a novel type of electrolyte with high ionic conductivity and stability against Li metal.

Ionic Liquid-Impregnated ZIF-8/Polypropylene Solid-like Electrolyte for Dendrite-free Lithium-Metal Batteries.

Metal-organic framework (MOF)-based solid-like electrolytes have attracted more prospective due to the combined merits of solid-state electrolytes and liquid electrolytes. However, most MOF-based solid-like electrolytes using organic liquid electrolytes cannot fundamentally solve the safety issues of lithium-metal batteries, and the ionic conductivity and mechanical strength of the electrolytes should be further enhanced. Herein, the ionic liquid-impregnated polypropylene (PP) porous membrane with integrally distributed ZIF-8 nanoparticles is designed. The solid-like electrolyte possesses an increased ionic conductivity of 2.09 × 10-4 S cm-1 at 25 °C, lithium-ion transference number (0.45), mechanical strength, electrochemical window, and excellent nanowetted interfaces. Furthermore, the Li symmetrical cell shows excellent Li plating/stripping properties for 550 h at 0.1 mA cm-2 and 0.1 mA h cm-2. The LiFePO4/Li full battery with the solid-like electrolyte demonstrates an excellent rate capability and cycling stability with the initial discharge capacity of 157.9 mA h g-1 and a capacity retention ratio of 91.23% after 450 cycles at 0.2 C. The work offers a new avenue toward MOF-based solid-like electrolytes for high-safety lithium-metal batteries.

A Silk Protein-Based Eutectogel as a Freeze-Resistant and Flexible Electrolyte for Zn-Ion Hybrid Supercapacitors.

A eutectogel (ETG) based on immobilizing a zinc salt deep eutectic solvent (DES) in a silk protein backbone is prepared by a coagulating bath method as a solid electrolyte for Zn-ion hybrid supercapacitors (ZHSCs). The Zn salt DES is composed by ethylene glycol (EG), urea, choline chloride (ChCl), and zinc chloride (ZnCl2) with a molar ratio of 6:10:3:3. A strong bonding of the DES liquid to the silk protein backbone is formed between protein macromolecules and the DES due to plenty of hydrogen bonds in both materials. The as-prepared ETG membrane is dense and has no obvious void defects, which possesses a fracture strength of 7.58 MPa and environmental stability. As a solid electrolyte, the ETG membrane exhibits a higher Zn2+ transference number of about 0.60 and a high ionic conductivity (12.31 mS cm-1 at room temperature and 3.63 mS cm-1 at -20 °C). A ZHSC (Zn∥ETG∥C) with the silk protein-based ETG electrolyte is assembled by Zn and active carbon as the anode and the cathode, respectively, which delivers a specific capacitance of 342.8 F g-1 at a current density of 0.2 A g-1 and maintains excellent cycling stability with 80% capacitance retention after 20,000 cycles at a high current rate (5 A g-1) at room temperature. Moreover, the Zn∥ETG∥C device can safely work under a lower temperature of about -18 °C and damaging situations, such as folding states and even cutting tests. The interface evolutions between the Zn anode and the ETG electrolyte are explored, and it was found that a ZnCO3/Zn(CH2OCO2)2 solid electrolyte interphase is in situ formed on the Zn anode, which can inhibit the growth of Zn dendrites. This work provides a new way to fabricate advanced electrolytes for applications in Zn-ion hybrid supercapacitors.

Graphene sheet/porous NiO hybrid film for supercapacitor applications.

We report the preparation of a nickel-foam-supported graphene sheet/porous NiO hybrid film by the combination of electrophoretic deposition and chemical-bath deposition. The obtained graphene-sheet film of about 19 layers was used as the nanoscale substrate for the formation of a highly porous NiO film made up of interconnected NiO flakes with a thickness of 10-20 nm. The graphene sheet/porous NiO hybrid film exhibits excellent pseudocapacitive behavior with pseudocapacitances of 400 and 324 F g(-1) at 2 and 40 A g(-1), respectively, which is higher than those of the porous NiO film (279 and 188 F g(-1) at 2 and 40 A g(-1)). The enhancement of the pseudocapacitive properties is due to reinforcement of the electrochemical activity of the graphene-sheet film.

One-step fabrication of nanostructured Ni film with lotus effect from deep eutectic solvent.

We report a procedure to fabricate nanostructured Ni films via programmed electrochemical deposition from a choline-chloride-based ionic liquid at a high temperature of 90 °C. Three electrodeposition modes using constant voltage, pulse voltage, and reverse pulse voltage produce a variety of nanostructured Ni films with micro/nanobinary surface architectures, such as nanosheets, aligned nanostrips, and hierarchical flowers. The nanostructured Ni films possess face-centered cubic crystal structure. Amazingly, it is found that the electrodeposited Ni films deliver the superhydrophobic surfaces without any further modifications by low surface-energy materials, which might be attributed to the vigorous micro/nanobinary architectures and the surface chemical composition. The electrochemical measurements reveal that the superhydrophobic Ni film exhibit an obvious passivation phenomenon, which could provide enhanced corrosion resistance for the substrate in the aqueous solutions.