Plastic–polymer composite electrolytes: Novel soft matter electrolytes for rechargeable lithium batteries

We present here a soft matter solid composite electrolyte obtained by inclusion of a polymer in a semi-solid organic plastic lithium salt electrolyte. Compared to lithium bis-trifluoromethanesulfonimide-succinonitrile (LiTFSI-SN), the (100 − x)%-[LiTFSI-SN]: x%-P (P: polyacrylonitrile (PAN), polyethylene oxide (PEO), polyethylene glycol dimethyl ether (PEG)) composites possess higher ambient temperature ionic conductivity, higher mechanical strength and wider electrochemical window. At 25 °C, ionic conductivity of 95%-[0.4 M LiTFSI-SN]: 5%-PAN was 1.3 × 10⁻³ Ω⁻¹ cm⁻¹ which was twice that of LiTFSI-SN. The Young’s modulus (Y) increased from Y → 0 for LiTFSI-SN to a maximum ∼1.0 MPa for (100 − x)%-[0.4 M LiTFSI-SN]: x%-PAN samples. The electrochemical voltage window for composites was approximately 5 V (Li/Li⁺). Excellent galvanostatic charge/discharge cycling performance was obtained with composite electrolytes in Li|LiFePO₄ cells without any separator.     

‘‘Soggy sand＇＇ polymer composite nanofber membrane electrolytes for lithium ion batteries

A kind of octanol-modifded silica nanoparticle was fabricated and employed as a framework to form‘‘soggy sand’’electrolyte along with 1-butyl-3-methylimidazolium tetrafluoroborate.‘‘Soggy sand’’and poly（vinylidene fluoride-hexafluoropropylene）composite electrolyte membranes were electrospun for the frst time.The properties of this membrane electrolyte have been evaluated by the mechanical test and electrochemical test.The Young’s modulus increased by 275%from 6.8 MPa to 25.5 MPa and the electrical conductivity increased to 7.6 10à5S/cm at 290.15 K when compared to pristine P（VdF-HFP）membrane electrolyte.The conductivity is 3.1 10à4S/cm at 323.15 K.     

Selection of hydrogel electrolytes for flexible zinc–air batteries

Flexible zinc–air batteries attract more attention due to their high energy density, safety, environmental protection, and low cost. However, the traditional aqueous electrolyte has the disadvantages of leakage and water evaporation, which cannot meet application demand of flexible zinc–air batteries. Hydrogels possessing good conductivity and mechanical properties become a candidate as the electrolytes of flexible zinc–air batteries. In this work, advances in aspects of conductivity, mechanical toughness, environmental adaptability, and interfacial compatibility of hydrogel electrolytes for flexible zinc–air batteries are investigated. First, the additives to improve conductivity of hydrogel electrolytes are summarized. Second, the measures to enhance the mechanical properties of hydrogels are taken by way of structure optimization and composition modification. Third, the environmental adaptability of hydrogel electrolytes is listed in terms of temperature, humidity, and air composition. Fourth, the compatibility of electrolyte–electrode interface is discussed from physical properties of hydrogels. Finally, the prospect for development and application of hydrogels is put forward.     

Investigation on the effect of nanosilica towards corn starch–lithium perchlorate-based polymer electrolytes

Biodegradable corn starch–lithium perchlorate (LiClO₄)-based solid polymer electrolytes with addition of nano-sized fumed silica (SiO₂) were prepared by solution casting technique. Ionic conductivity at ambient temperature was measured by AC impedance spectroscopy. Upon addition of nano-sized SiO₂, the ionic conductivity at room temperature is increased. The optimum ionic conductivity value obtained was 1.23?×?10^?4?S?cm^?1 at 4?wt% SiO₂. This may be attributed to the low crystallinity of the polymer electrolytes resulting from the dispersed nanosilica particles. Fourier–transform infrared spectroscopy studies confirmed the complexation between corn starch, lithium perchlorate, and silica. The thermal properties of the prepared samples were investigated with differential scanning calorimetry and thermogravimetric analysis. The surface morphology of the polymer electrolytes confirmed the agglomeration of particles after excess dispersion of inorganic filler. This was proven in the scanning electron microscopy studies.     

Insight into demand-driven preparation of single-atomic mediators for lithium–sulfur batteries

Lithium-sulfur(Li-S) batteries have attracted considerable attention as one of the most appealing energy storage systems.Strenuous efforts have been devoted to tackling the tremendous challenges,mainly pertaining to the severe shuttle effect,sluggish redox kinetics and lithium dendritic growth.Single-atomic mediators as promising candidates exhibit impressive performance in addressing these intractable issues.Related research often utilizes a trial-and-error approach,proposing solutions to fabri...     

Enhanced performance of lithium polymer batteries using a V2O5–PEG composite cathode

A new concept is proposed to realize solid-state high-performance lithium polymer batteries in which two different polymers are used as ionically conductive matrices in the cathode and in the separator. A solid, low molecular weight poly(ethylene glycol) was used in the cathode while a blend with a higher molecular weight poly(ethylene oxide) (PEO) was used in the separator. The enhanced transport properties in the cathodic compartment allow us to discharge the battery (190 mAh g⁻¹) at a moderate temperature (65°C) in a reasonable time (about 3.3 h). Batteries cycled at 100°C showed enhanced performance with respect to PEO-based batteries. At a power density of about 416 W kg⁻¹, energy density as high as 460 Wh kg⁻¹, based on the weight of the active material, was achieved in about 1 h of discharge. The work was developed within the ALPE (Advanced Lithium Polymer Electric Vehicle Battery) project, an Italian integrated project devoted to the realization of lithium polymer batteries for electric vehicle applications, in collaboration with the Osaka National Research Institute.     

An odyssey of lithium metal anode in liquid lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries exhibit outstanding energy density and material sustainability. Enormous effects have been devoted to the sulfur cathode to address redox kinetics and polysulfide intermediates shuttle. Recent attentions are gradually turning to the protection of the lithium metal anodes, since electrochemical performances of Li–S batteries are closely linked to the working efficiency of the anode side, especially in pouch cells that adopt stringent test protocols. This Perspective article summarizes critical issues encountered in the lithium metal anode, and outlines possible solutions to achieve efficient working lithium anode in Li–S batteries. The lithium metal anode in Li–S batteries shares the common failure mechanisms of volume fluctuation, nonuniform lithium flux, electrolyte corrosion and lithium pulverization occurring in lithium metal batteries with oxide cathodes, and also experiences unique polysulfide corrosion and massive lithium accumulation. These issues can be partially addressed by developing three-dimensional scaffold, exerting quasi-solid reaction, tailoring native solid electrolyte interphase (SEI) and designing artificial SEI. The practical evaluation of Li–S batteries highlights the importance of pouch cell platform, which is distinguished from coin-type cells in terms of lean electrolyte-to-sulfur ratio, thin lithium foil, as well as sizable total capacity and current that are loaded on pouch cells. This Perspective underlines the development of practically efficient working lithium metal anode in Li–S batteries.     

Nano-wire networks of sulfur–polypyrrole composite cathode materials for rechargeable lithium batteries

Polypyrrole (PPy) nanowire was synthesized through a surfactant mediated approach. The sulfur–polypyrrole (S–PPy) composite materials were prepared by heating the mixture of element sulfur and polypyrrole nanowire. The materials were characterized by FTIR, SEM. PPy with special morphology serves as conductive additive, distribution agent and absorbing agents, which effectively enhanced the electrochemical performance of sulfur. The initial discharge capacity of the active materials was 1222 mA h g⁻¹ the remaining capacity is 570 mA h g⁻¹ after 20th cycles.     

P_4S_(10) modified lithium anode for enhanced performance of lithium–sulfur batteries

To address the corrosion and dendrite issues of lithium metal anodes, a protective layer was ex-situ constructed by P_4S_(10) modification. It was determined by X-ray photoelectron spectroscopy and Raman spectra that the main constituents of the protective layer were P_4S_(10), Li_3PS_4 and other LixPySztype derivatives. The protective layer was proved to be effective to stabilize the interphase of lithium metal. With the modified Li anodes, symmetric cells could deliver stable Li plating/stripping for 16000 h; Li–S batteries exhibited a specific capacity of 520 m A h g~(-1) after 200 cycles at 1000 m A g~(-1) with average Coulombic efficiency of 97.9%. Therefore, introducing LixPySzbased layer to protect Li anode provides a new strategy for the improvement of Li metal batteries.     

Recent progress in fluorinated electrolytes for improving the performance of Li–S batteries

Lithium–sulfur(Li–S) batteries represent a "beyond Li-ion" technology with low cost and high theoretical energy density and should fulfill the ever-growing requirements of electric vehicles and stationary energy storage systems. However, the sulfur-based conversion reaction in conventional liquid electrolytes results in issues like the so-called shuttle effect of polysulfides and lithium dendrite growth, which deteriorate the electrochemical performance and safety of Li–S batteries. Optimization of conventional organic solvents(including ether and carbonate) by fluorination to form fluorinated electrolytes is a promising strategy for the practical application of Li–S batteries. The fluorinated electrolytes, owing to the high electronegativity of fluorine, possesses attractive physicochemical properties, including low melting point,high flash point, and low solubility of lithium polysulfide, and can form a compact and stable solid electrolyte interphase(SEI) with the lithium metal anode. Herein, we review recent advancements in the development of fluorinated electrolytes for use in Li–S batteries. The effect of solvent molecular structure on the performance of Li–S batteries and the formation mechanism of SEI on the cathode and anode sides are analyzed and discussed in detail. The remaining challenges and future perspectives of fluorinated electrolytes for Li–S batteries are also presented.     

Synthesis and electrochemical performance of sulfur–carbon composite cathode for lithium–sulfur batteries

In this paper, porous carbon was synthesized by an activation method, with phenolic resin as carbon source and nanometer calcium carbonate as activating agent. Sulfur–porous carbon composite material was prepared by thermally treating a mixture of sublimed sulfur and porous carbon. Morphology and electrochemical performance of the carbon and sulfur–carbon composite cathode were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and galvanostatic charge–discharge test. The composite containing 39 wt.% sulfur obtained an initial discharge capacity of about 1,130 mA?h g^?1 under the current density of 80 mA?g^?1 and presented a long electrochemical stability up to 100 cycles.     

Thermal,electrical and electrochemical properties of ionic liquid-doped poly(ethylene oxide)–LiTDI polymer electrolytes for Li-ion batteries

Journal of Solid State Electrochemistry - In the present study, we report the synthesis and characterisation of solid polymer electrolytes (SPEs) based on polymer poly(ethylene oxide) (PEO), salt...     

P(VDF-HFP)-poly(sulfur-1,3-diisopropenylbenzene) functional polymer electrolyte for lithium–sulfur batteries

Lithium–sulfur(Li–S)battery as a high-energy density electrochemical energy storage system has attracted many researchers’attention.However,the shuttle effect of Li–S batteries and the challenges associated with lithium metal anode caused poor cycle performance.In this work,the organosulfide poly(sulfur-1,3-diisopropenylbenzene)(PSD)was prepared as cathode material and additive of P(VDFHFP)polymer electrolyte(P(VDF-HFP)).It was verified that P(VDF-HFP)polymer electrolyte with 10%PSD(P(VDF-HFP)-10%PSD)showed a higher ionic conductivities than that of liquid electrolyte up to2.27×10-3 S cm-1 at room temperature.The quasi-solid-state Li-S batteries fabricated with organosulfide cathode material PSD and P(VDF-HFP)based functional polymer electrolyte delivered good cycling stability(780 m Ah g-1 after 200 th cycle at 0.1 C)and rate performance(613 m Ah g-1 at 1 C).The good cycling performance could be attributed to the synergistic effect of components,including the interaction between polysulfides and polymer main chain in the organosulfide cathode,the sustained organic/inorganic hybrid stable SEI layer formed by polymer electrolyte additive PSD,the improved cathode/electrolyte interface and the good affinity between P(VDF-HFP)based functional polymer electrolyte and Li metal surface.This strategy herein may provide a new route to fabricate high-performance Li–S batteries through the organosulfide cathode and functional polymer electrolyte.     

Hierarchically porous nitrogen-doped carbon as cathode for lithium–sulfur batteries

Porous nitrogen-doped carbon is an especially promising material energy storage due to its excellent conductivity, stable physicochemical properties, easy processability, controllable porosity and low price.Herein, we reported a novel well-designed hierarchically porous nitrogen-doped carbon(HPNC) via a combination of salt template(ZnCl_2) and hard template(SiO_2) as sulfur host for lithium–sulfur batteries. The low-melting ZnCl_2 is boiled off and leaves behind micropores and small size mesopores during pyrolysis process, while the silica spheres are removed by acid leaching to generate interconnected 3D network of macropores. The HPNC-S electrode exhibits an initial specific capacity of 1355 mAh g~(–1) at 0.1 C(1 C = 1675 m Ah g~(–1)), a high-rate capability of 623 m Ah g~(–1) at 2 C, and a small decay of 0.13% per cycle over 300 cycles at 0.2 C. This excellent rate capability and remarkable long-term cyclability of the HPNC-S electrode are attributed to its hierarchical porous structures for confining the soluble lithium polysulfide as well as the nitrogen doping for high absorbability of lithium polysulfide.     

Mg–Al hydroxide intercalated ionic liquids for quasi-solid-state lithium batteries

Journal of Solid State Electrochemistry - Solid -state lithium batteries are considered safer energy storage, but their payload and energy density are limited due to the large interfacial impedance...     

Critical aspects in the development of lithium–air batteries

Intensive research has been done on lithium–air batteries, especially in the last few years. Due to their very high theoretical specific energy, lithium–air batteries are one of the most promising candidates to power future electric vehicles. However, this new technology is in a very early stage of development, and several challenges must be overcome before there will be a commercially viable product. This review describes the most important critical aspects in the development of lithium–air batteries: the electrocatalysis of the oxygen electrode reactions, the degradation of the electrolyte and the oxygen electrode components, the structure of the oxygen electrode, and the passivation of the oxygen electrode during the discharge of the battery. Recent works in these areas are critically reviewed, and suitable research strategies to address these issues are discussed.     

CoNi-embedded nitrogen-enriched porous carbon framework for long-life lithium–sulfur batteries

Journal of Solid State Electrochemistry - Metal–organic framework (MOF) derivatives are excellent energy storage devices such as lithium–sulfur batteries. Here, a bimetallic...     

Enhancing electrochemical conversion of lithium polysulfide by 1T-rich MoSe2 nanosheets for high performance lithium–sulfur batteries

The sluggish conversion kinetics and shuttle effect of lithium polysulfides (LiPSs) severely hamper the commercialization of lithium–sulfur batteries. Numerous electrocatalysts have been used to address these issues, amongst which, transition metal dichalcogenides have shown excellent catalytic performance in the study of lithium–sulfur batteries. Note that dichalcogenides in different phases have different catalytic properties, and such catalytic materials in different phases have a prominent impact on the performance of lithium–sulfur batteries. Herein, 1T-phase rich MoSe₂ (T-MoSe₂) nanosheets are synthesized and used to catalyze the conversion of LiPSs. Compared with the 2H-phase rich MoSe₂ (H-MoSe₂) nanosheets, the T-MoSe₂ nanosheets significantly accelerate the liquid phase transformation of LiPSs and the nucleation process of Li₂S. In-situ Raman and X-ray photoelectron spectroscopy (XPS) find that T-MoSe₂ effectively captures LiPSs through the formation of Mo-S and Li-Se bonds, and simultaneously achieves fast catalytic conversion of LiPSs. The lithium–sulfur batteries with T-MoSe₂ functionalized separators display a fantastic rate performance of 770.1 mAh/g at 3 C and wonderful cycling stability, with a capacity decay rate as low as 0.065% during 400 cycles at 1 C. This work offers a novel perspective for the rational design of selenide electrocatalysts in lithium–sulfur chemistry.