Improvement in ionic conductivity of self-supported P(MMA-AN-VAc) gel electrolyte by fumed silica for lithium ion batteries

Fumed silica was used as a dopant in the preparation of poly(methyl methacrylate-acrylonitrile-vinyl acetate) (P(MMA-AN-VAc)) to improve the ionic conductivity of the P(MMA-AN-VAc)-based gel polymer electrolyte (GPE). The performance of the P(MMA-AN-VAc) membrane and its GPE for lithium ion battery use were studied by XRD, SEM, TGA, LSV, CA, EIS, and charge/discharge test. It is found that the doping of fumed silica in the P(MMA-AN-VAc) changes the membrane from semi-crystal to amorphous state and the pore structure of the membrane. By the doping of 10 wt.% fumed silica in the membrane, the porosity of the membrane increases with the pore dispersed more uniformly and interconnected and having higher electrolyte uptake, resulting in the improvement in ionic conductivity of the GPE from 3.48 × 10⁻³ to 5.13 × 10⁻³ S cm⁻¹ at ambient temperature. On the other hand, the thermal stability of the membrane, the electrochemical stability of the GPE, and the cyclic performance of the battery are also improved.     

Preparation and properties of gel‐filled PVDF separators for lithium ion cells

Polyether gel‐filled poly(vinylidene fluoride) separators (GF‐PVDF separators) were prepared by means of thermal crosslinking of poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) as gel constituents. The intrinsic properties of GF‐PVDF and their corresponding gel polymer electrolyte (GPE) were characterized by SEM, DSC, and electrochemical methods. It was found a relatively better GPE could be got when the filled polyether content no more than 60 wt % and its ion conductivity could reach 1.3 × 10^?3 S cm^?1. The GPE is compatible with anode and cathode of lithium ion battery at high voltage and its electrochemical window is 4.6 V (vs. Li/Li⁺). The coulombic efficiency could reach 94% after 100 cycles for the cells using such GPE. The results reveal that the composite polymer electrolyte qualifies as a potential application in lithium cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44473.     

Non-woven fabric supported poly(acrylonitrile-vinyl acetate) gel electrolyte for lithium ion battery use

This paper reported on a new gel polymer electrolyte (GPE) based on polyethylene (PE) non-woven fabric supported poly(acrylonitrile-vinyl acetate) (P(AN-VAc)/PE) membrane for lithium ion battery use. The preparation and performances of the P(AN-VAc)/PE membrane and its GPE based on 1 M LiPF₆ in dimethyl carbonate/diethylene carbonate/ethylene carbonate (1:1:1 in volume) were investigated with a comparison of the unsupported P(AN-VAc) membrane. It is found that the P(AN-VAc)/PE membrane shows better mechanical strength and pore structure for electrolyte uptake than the P(AN-VAc) membrane, and subsequently the GPE based on P(AN-VAc)/PE exhibits higher ionic conductivity and electrochemical stability on cathode than the GPE based on P(AN-VAc). With the support of the non-woven fabric, the ionic conductivity of the GPE at room temperature increases from 1.4 to 3.8 mS cm⁻¹, the oxidation decomposition potential of the GPE on a stainless steel is improved from 5.0 to 5.6 V (vs. Li/Li⁺). The mesocarbon microbeads (MCMB)/LiMn₂O₄ battery using P(AN-VAc)/PE as separator retains 94% of its initial discharge capacity after 100 cycles at C/2 rate, showing that the P(AN-VAc)/PE membrane is a possible alternative to the expensive separator for current liquid lithium ion battery.     

Hierarchical nanoarchitecture of vanadium disulfide decorated 3D porous carbon skeleton with improved electrochemical performance toward Li ion battery and supercapacitor

Vanadium disulfide (VS₂) is deemed to be a competitive active material in electrochemical energy storage field in both lithium-ion battery and supercapacitor owing to its unique chemical and physical property. Nevertheless, serious aggregation and structure damage in continuous charge-discharges would result in a decreased capacity, an inferior cycling stability and a poor rate capability, which severly limits the practical application of VS₂. In this current work, a hierarchical porous nanostructured composite composed of VS₂ nanoparticles confined in gelatin-derived nitrogen-doped carbon network (VS₂-NC) was successfully designed and synthesized via a simple freeze drying plus an annealing method. In this VS₂-NC composite, porous architecture is conductive to providing high active surface areas, facilitating the access of electrolyte into active materials and ion diffusion. The confinement of carbon matrix on VS₂ nanoparticles is beneficial to inhibition of the volume change, reinforcement of the structural stability and improvement of the overall electrical conductivity of composite. Benefitting from the advantages mentioned above, the as-prepared VS₂-NC electrode demonstrates outstanding electrochemical performances. Employed as an anode for lithium ion battery, VS₂-NC delivers a relatively high reversible capacity about ～1061 mA h g^?1 in 200-cycle test at 100 mA g^?1. When applied in supercapacitor, VS₂-NC electrode manifests a large pseudocapacitance of 407.3 F g^?1 at a current density of 10 A g^?1 and superior cycling stability.     

Preparation and properties of poly(ethylene oxide) gel filled polypropylene separators and their corresponding gel polymer electrolytes for Li-ion batteries

Poly(ethylene oxide) (PEO) filled polypropylene separators (GFPSs) are designed by means of thermal cross-linking of entrapped poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) as gel constituents. The intrinsic properties of GFPS and their corresponding gel polymer electrolytes (GPE) are characterized by DSC, SEM, contact angle and electrochemical methods. It is found the stability of liquid electrolyte uptake in GPE could be improved obviously. For the GPE prepared from GFPS with filled polyether content of 14.3 wt%, the ionic conductivity could reach 1.12 × 10⁻³ S cm⁻¹ while the electrochemically stable window reach 5.0 V (vs. Li/Li⁺). These primary results show great promise of this simple method to prepare GPE for practical application in lithium ion batteries.     

A high-capacity lithium–air battery with Pd modified carbon nanotube sponge cathode working in regular air

We report a lithium–air battery with a free-standing, highly porous Pd-modified carbon nanotube (Pd–CNT) sponge cathode. The Pd-CNT sponge was synthesized through a chemical vapor deposition growth followed with an electrochemical deposition process. To build a whole lithium–air battery, the air cathode is integrated with a ceramic electrolyte-protected lithium metal anode and non-volatile ionic liquid electrolyte. The lithium anode is stable during the operation and long-time storage and the ionic liquid is chemically inert. By controlling the amount of ionic liquid electrolyte, the sponge is wet but not fulfilled by the electrolyte. Such configuration offers a tricontinuous passage for lithium ions, oxygen and electrons, which is propitious to the discharge reaction. In addition, the existence of Pd nanoparticles improves the catalytic reactivity of the oxygen reduction reaction. The battery is durable to any humidity level and delivers a capacity as high as 9092 mA h g⁻¹.     

A novel electrospun TPU/PVdF porous fibrous polymer electrolyte for lithium ion batteries

Novel blend-based gel polymer electrolyte (GPE) films of thermoplastic polyurethane (TPU) and poly(vinylidene fluoride) (PVdF) (denoted as TPU/PVdF) have been prepared by electrospinning. The electrospun thermoplastic polyurethane-co-poly (vinylidene fluoride) membranes were activated with a 1M solution of LiClO₄ in EC/PC and showed a high ionic conductivity about 1.6 mS cm⁻¹ at room temperature. The electrochemical stability is at 5.0 V versus Li⁺/Li, making them suitable for practical applications in lithium cells. Cycling tests of Li/GPE/LiFePO4 cells showed the suitability of the electrospun membranes made of TPU/PVdF (80/20, w/w) for applications in lithium rechargeable batteries. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Gel Polymer Electrolyte with Anion‐Trapping Boron Moieties via One‐Step Synthesis for Symmetrical Supercapacitors

A novel gel polymer electrolyte (GPE) which is based on new synthesized boron‐containing monomer, benzyl methacrylate, 1 m LiClO₄/N,N‐dimethylformamidel liquid electrolyte solution is prepared through a one‐step synthesis method. The boron‐containing GPE (B‐GPE) not only displays excellent mechanical behavior, favorable thermal stability, but also exhibits an outstanding ionic conductivity of 2.33 mS cm^?1 at room temperature owing to the presence of anion‐trapping boron sites. The lithium ion transference in this gel polymer film at ambient temperature is 0.60. Furthermore, the symmetrical supercapacitor which is fabricated with B‐GPE as electrolyte and reduced graphene oxide as electrode demonstrates a broad potential window of 2.3 V. The specific capacitance of symmetrical B‐GPE supercapacitors retains 90% after 3000 charge–discharge cycles at current density of 1 A g^?1.     

Designable air-stable and dendrite-free Li metal anode via the oligomer layer for in-situ gel polymer batteries

Lithium (Li) metal anode has been an indispensable electrode material in the development of the future battery system, especially in the pursuit of energy density of the solid state battery. However, the poor air stability and dendrite problems are stumbling blocks to the practical application of Li metal anode. Herein, we design the poly(methyl methacrylate) (PMMA) oligomer coating layer for the surface of Li metal anode (Li-PMMA). The Li-PMMA anode can obtain hydrophobic oxygen resistance ability and maintain air stability for 48h in the environment of 70% relative humidity. When applied to the liquid battery, the PMMA oligomer can open the double bond by the catalysis of Li⁺ and repolymerize into the PMMA gel polymer electrolyte (GPE). As a result, the cathode and anode are cohered together by GPE to become an in-situ GPE battery. The GPE displays high ionic conductivity (7.92 mS cm^-1) and perfect interfacial contact with various electrodes. The newly designed in-situ GPE is employed to Li||Li symmetric battery without separator, which can run up to 2000 h with the overpotential of only 2.8 mV. Applications of the in-situ GPE in Li-S battery and 5000mAh LiNi_0.5Co_0.2Mn_0.3O₂/Li pouch cell both obtain excellent electrochemical performance. Our strategy may provide a versatile and practical approach to promote the large-scale application for solid state Li metal batteries.     

Cost effective cation exchange membranes: A review

This paper will look at developments of new polymer electrolyte membranes to replace high cost ion exchange membranes such as Nafion^®, Flemion^® and Aciplex^®. These perfluorinated polymer electrolytes are currently the most commercially utilized electrolyte membranes for polymer electrolyte fuel cells, with high chemical stability, proton conductivity and strong mechanical properties. While perfluorinated polymer electrolytes have satisfactory properties for fuel cell applications, they limit commercial use due to significant high costs as well as reduced performance at high temperatures and low humidity. A promising alternative to obtain high performance proton-conducting polymer electrolyte membranes is through the use of hydrocarbon polymers. The need for inexpensive and efficient materials with high thermal and chemical stability, high ionic conductivity, miscibility with other polymers, and good mechanical strength is reviewed in this paper. Though it is difficult to evaluate the true cost of a product based on preliminary research, this paper will examine several of the more promising materials available as low cost alternatives to ion exchange membranes. These alternative membranes represent a new generation of cost effective electrolytes that can be used in various ion exchange systems. This review will cover recent and significant patents regarding low cost polymer electrolytes suitable for ion exchange membrane applications. Promising candidates for commercial applications will be discussed and the future prospects of cost effective membranes will be presented.     

Study on performances of ZSM-5 doped P(VDF-HFP) based composite polymer electrolyte prepared by steam bath technique

Several novel kinds of poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) based composite polymer electrolyte (CPE) membranes doped with ZSM-5 (Zeolite sieve of molecular porosity) were fabricated by steam bath technique. The desirable CPE membranes were further prepared by immersing them into the liquid electrolyte solution of 1.0?M LiPF₆-ethylene carbonate /dimethyl carbonate/ethylmethyl carbonate (v/v/v:1/1/1) for 1?h to be activated at room temperature. Physical and chemical properties of the as-prepared CPEs are studied by scanning electron microscope, Fourier transform infrared, thermogravimetry and differential scanning calorimetry and electrochemical methods. The results showed that the thermal and electrochemical stabilities of the CPEs can be reached to 350?°C and 5?V, respectively. Reciprocal temperature dependence of corresponding ionic conductivity follows Vogel?CTamman?CFulcher relation, and ionic conductivity at ambient temperature can be up to 5.1?mS?cm^?1. The fabricated Li/CPEs/LiCoO₂ coin cells with the CPE membranes prepared by steam bath technique can achieve a high discharge capacity about 144.97?mAh?g^?1 at 0.1?C. At 1.0?C, the capacity can be kept to 89.84?% of that at 0.1 C for the cell. After 26 cycles, the cell prepared with these CPE membranes can keep 97.5?% of its initial discharge capacity. These excellent physicochemical and battery properties indicate that these novel CPEs can be potentially used as electrolyte in lithium ion polymer battery.     

凝胶聚合物电解质的电化学性能

用化学交联法制备了凝胶聚合物电解质.聚烯烃多孔膜支撑的凝胶聚合物电解质具有优良的电化学性能, 室温电导率为1.01×10^-3S•cm^-1,锂离子迁移数为0.41,在Al电极上的氧化起始电位达到4.2 V以上.采用聚烯烃多孔膜支撑的凝胶聚合物电解质制备了聚合物锂离子电池,并研究了工艺条件对聚合物锂离子电池电化学性能的影响.研究的工艺条件包括：单体添加量和电极组合方式.优化后的聚合物锂离子电池具有良好的电化学性能,1 C放电容量为0.2 C放电容量的93.2%,经100次1 C循环后的剩余容量仍在80%以上.     

Facile synthesis of porous hollow Co3O4 microfibers derived-from metal-organic frameworks as an advanced anode for lithium ion batteries

Co₃O₄, as a promising anode material for the next generation lithium ion batteries to replace graphite, displays high theoretical capacity (890 mAh g⁻¹) and excellent electrochemical properties. However, the drawbacks of its poor cycle performance caused by large volume changes during charge-discharge process and low initial coulombic efficiency due to large irreversible reaction impede its practical application. Herein, we have developed a porous hollow Co₃O₄ microfiber with 500 nm diameter and 60 nm wall thickness synthesized via a facile chemical precipitation method with subsequent thermal decomposition. As an advanced anode for lithium ion batteries, the porous hollow Co₃O₄ microfibers deliver an obviously enhanced electrochemical property in terms of lithium storage capacity (1177.4 mA h g⁻¹ at 100 mA g⁻¹), initial coulombic efficiency (82.9%) and cycle performance (76.6% capacity retention at 200th cycle). This enhancement could be attributed to the well-designed microstructure of porous hollow Co₃O₄ microfibers, which could increase the contact surface area between electrolyte and active materials and accommodate the volume variations via additional void space during cycling.     

A high ionic conductive glass fiber-based ceramic electrolyte system for magnesium‒ion battery application

The rechargeable magnesium-ion batteries are one of the emerging alternatives of lithium-ion batteries as it has a high volumetric capacity, non-toxic nature and a divalent charge of Mg-ions. The design of an excellent performing magnesium-ion battery requires a stable electrolyte system with high ionic conductivity. However, there is a lack of understanding of how different materials affect the properties of separators in terms of ionic conductivity and stability. In the present study, an attempt has been made to compare the physical and electrochemical characteristics of glass-ceramic and polypropylene membranes as separators in the magnesium-ion battery, using magnesium bis(trifluoromethanesulfonimide) and propylene carbonate as an organic electrolyte. The characterization like X-ray diffraction, field emission electron microscopy, electrolyte uptake, ionic conductivity, voltage stability, thermal stability and transference number are thoroughly examined for both the membranes. The glass-ceramic electrolyte system showed significantly higher ionic conductivity of 9.22 mS cm⁻¹ at room temperature as compared to the polypropylene membrane. Additionally, the glass-ceramic electrolyte system showed higher thermal and voltage stability.     

Semi-interpenetrating gel polymer electrolyte based on PVDF-HFP for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolyte (GPE) is considered one of the promising candidate electrolytes in the polymer lithium ion battery (LIB) because of its free standing, shape versatility, security, flexibility, lightweight, reliability, and so on. However, the pristine PVDF-HFP GPE cannot still meet the requirement of large-scale LIBs and other electrochemical devices due to its relatively low ionic conductivity and deterioration of mechanical strength caused by the incorporation of organic liquid electrolyte into the polymer matrix as well as high cost. In order to overcome above deficiencies of PVDF-HFP based GPE, ultraviolet (UV)-curable semi-interpenetrating polymer network is designed and synthesized through UV-irradiation technique, and the as-prepared semi-interpenetrating matrix is constituted by pentaerythritol tetracrylate polymer network and PVDF-HFP. The ionic conductivity of the optimized GPE is as high as 5 × 10⁻⁴ S/cm and electrochemical window is up to 4.8 V at room temperature. Especially, the LIB prepared by GPE shows the high initial discharge specific capacity of 151 mAh/g at 0.5 C and good rate capability. Therefore, the semi-interpenetrating GPE based on PVDF-HFP exhibits a promising prospect for the application of rechargeable LIBs.     

Boosting lithium-ion transport capability of LAGP/PPO composite solid electrolyte via component regulation from ‘Ceramics-in-Polymer’ to ‘Polymer-in-Ceramics'

The design and regulation of the ion transport channels in the polymer electrolyte is an important means to improve the lithium ion transport behavior of the electrolyte. In this work, we for the first time combined the high ionic conductive inorganic ceramic electrolyte Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) with flexible polypropylene oxide (PPO) polymer electrolyte to synthesize a high-filling LAGP/PPO composite solid electrolyte film and regulated the ion transport channels from ‘Ceramics-in-Polymer’ mode to ‘Polymer-in-Ceramics' mode by optimizing the ratio of LAGP vs. PPO. The results reveal that when the LAGP content <40%, the electrolyte belongs to ‘LAGP-in-PPO’, and then changes to ‘PPO-in-LAGP’ when the LAGP content exceeds 40%. Compared with ‘LAGP-in-PPO’, the ‘PPO-in-LAGP’ shows better comprehensive properties, especially for the 75% LAGP-filled PPO electrolyte, the room-temperature ionic conductivity is as high as 3.46 × 10^?4 Scm^?1, the ion migration number and voltage stable window reach 0.83 and 4.78 V respectively. This high-filled composite electrolyte possesses high tensile stress of 40 MPa with a strain of 46% and withstands working environment up to 200 °C. The NCM622/Li solid-state battery composed of this electrolyte also presents good rate and cycle performances with a capacity retention of 80% after 230 cycles at 0.3C because of its high ion transport capability and good inhibition of lithium dendrites. This composite structural design is expected to develop high-performance solid-state electrolytes suitable for high-voltage solid-state lithium batteries.     

Vanadium doped ceramic matrix Li6.7La3Zr1.7V0.3O12 enabled PEO-based solid composite electrolyte with high lithium ion transference number and cycling stability

Solid polymer electrolytes (SPEs) have attracted much attention because of their potential in improving energy density and safety. Vanadium doped ceramic matrix Li_6.7La₃Zr_1.7V_0.3O₁₂ (LLZVO) was synthesized by high-temperature annealing, and formed a composite electrolyte with polyethylene oxide (PEO). Compared with pure PEO electrolyte membrane, the composite electrolyte membrane exhibited better ionic conductivity (30 °C: 3.2 × 10^?5 S cm^?1; 80 °C: 3.6 × 10^?3 S cm^?1). The combination of LLZVO was beneficial to improve the lithium ion transference number (t_Li⁺) of SPE, which was as high as 0.81. The Li/SPE/LiFePO₄ battery shows good cycling ability, with a specific capacity of 142 mAh g^?1 after a stable cycle of 150 cycles. Meanwhile, the symmetrical lithium battery with composite electrolyte can work continuously for 1200 h without short circuit at the current density of 0.1 mA cm^?2 at 50 °C, and the capacity is 0.176 mAh. Vanadium doped ceramic matrix LLZVO as an active ionic conductor, improved the overall performance of solid electrolyte.     

Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium‐ion battery

The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium‐ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the T_g and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10⁻³ S cm⁻¹ at room temperature and 1.42 × 10⁻² S cm⁻¹ at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3O₂ cell were evaluated at a current rate of 0.1C and in voltage range of 2.8–4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi_1/3Co_1/3Mn_1/3 O₂ cell is 115.3 mAh g⁻¹. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Highly uniform silicon nanoparticle/porous carbon nanofiber hybrids towards free-standing high-performance anodes for lithium-ion batteries

Novel silicon nanoparticle/porous carbon nanofiber (Si/PCNF) hybrids with high Si loading (52 wt.%) have been designed and fabricated through a simple electrospinning. The Si/PCNF of uniform fiber diameter has exhibited high specific surface area and unique porous structure. The continuous three-dimensional porous carbon networks have effectively provided strain relaxation for Si volume expansion/shrinkage during lithium insertion/extraction. In addition, the carbon matrix could largely minimize the direct exposure of Si to the electrolyte, thus substantially improving the structural stability of Si. Moreover, the porous structure could also create efficient channels for the fast transport of lithium ions. As a consequence, this novel Si-based hybrid material has exhibited stable cycling performance (ca. 870 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles) in the absence of binders and conducting additives, promising great potential as a free-standing anode for lithium ion batteries.     

The Enhanced Performance of Polyethylene Composite Separators by the Modification of Lithium Salt@SiO2 Nanoparticles

Improving the dimensional thermal stability and electrochemical performance of polyethylene (PE) membrane is critical to enhance the safety performance of lithium-ion battery. In this paper, PE membranes are modified by lithium bis(trifuoromethanesulfonyl)imide (LiTFSI) solution and then coated with nano-SiO₂/polyvinyl alcohol solution to obtain composite membranes (PE@LnSiO₂, where n represents the concentration of LiTFSI solution). The obtained PE@L4SiO₂ (LiTFSI solution concentration is 4%) composite membrane possesses a thermal shrinkage rate of only 17% at 150 °C, which is far superior to that of the PE separator. The ionic conductivity of the composite membrane is 16.9 × 10⁻⁴ S cm⁻¹ at room temperature (RT), and the battery impedance decreases to 154 Ω, which is remarkably better than that of the PE membrane (188 Ω). The battery delivers a reversible discharge capacity of 164 mAh g⁻¹ at 0.2 C under RT after 250 cycles, and the coulomb efficiency remains above 99%. The battery also has a high discharge capacity of 132 mAh g⁻¹ at 2 C, which indicates that it has excellent rate performance. Therefore, this research successfully explores a simple method to effectively improve the dimensional thermal stability of PE separator, as well as the electrochemical and safety performance of lithium battery.