Toward high performance solid-state lithium-ion battery with a promising PEO/PPC blend solid polymer electrolyte

A promising solid polymer blend electrolyte is prepared by blending of poly(ethylene oxide) (PEO) with different content of amorphous poly(propylene carbonate) (PPC), in which the amorphous property of PPC is utilized to enhance the amorphous/free phase of solid polymer electrolyte, so as to achieve the purpose of modifying PEO-based solid polymer electrolyte. It indicates that the blending of PEO with PPC can effectively reduce the crystallization and increase the ion conductivity and electrochemical stability window of solid polymer electrolyte. When the content of PPC reaches 50%, the ionic conductivity reaches the maximum, which is 2.04 × 10⁻⁵ S cm⁻¹ and 2.82 × 10⁻⁴ S cm⁻¹ at 25°C and 60°C, respectively. The electrochemical stability window increases from 4.25 to 4.9 V and the interfacial stability of lithium metal anode is also greatly improved. The solid-state LiFePO₄//Li battery with the PEO/50%PPC blend solid polymer electrolyte has good cycling stability, which the maximum discharge specific capacity is up to 125 mAh g⁻¹ at a charge/discharge current density of 0.5 C at 60°C.     

Ionanofluid plasticized electrolyte with improved electrical and electrochemical properties for high-performance lithium polymer battery

Herein, the electrochemical characteristics of Li/LiFePO₄ battery, comprising a new class of poly (ethylene oxide) (PEO) hosted polymer electrolytes, are reported. The electrolytes were prepared using lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) dopant salt and imidazolium ionic liquid-based nanofluid (ionanofluid) as the plasticizer. Morphological, thermophysical, electrical, and electrochemical properties of these newly developed electrolytes were studied. Using FT-IR spectroscopy, the interactions between dopant salt plasticizers and the host polymer, within the electrolytes, were evaluated. The optimized 30 wt% ionanofluid plasticized electrolyte exhibits a room temperature ionic conductivity of 6.33 × 10⁻³ S cm⁻¹, wide electrochemical voltage window (~4.94 V vs Li/Li⁺) along with a moderately high value of lithium-ion transference number (0.47). The values are substantially higher than that of similar wt% IL plasticized electrolyte (7.85 × 10⁻⁴ S cm⁻¹, ~4.44 V vs Li/Li⁺ and ~ 0.28, respectively). Finally, the Li/LiFePO₄ battery, comprising optimized 30 wt% ionanofluid plasticized electrolyte, delivers 156 mAh g⁻¹ discharge capacity at 0.1 C rate and able to retain its 92% value after 50 cycles. Such a superior battery performance as compared to the IL plasticized electrolyte cell (137 mAh g⁻¹ and 84% after 50 cycles at the same current rate) would endow this ionanofluid a very promising plasticizer to develop electrolytes for next-generation lithium polymer battery.     

Discharge properties of all-solid sodium–sulfur battery using poly (ethylene oxide) electrolyte

An all-solid sodium/sulfur battery using poly (ethylene oxide) (PEO) polymer electrolyte are prepared and tested at 90 °C. Each battery is composed of a solid sulfur electrode, a sodium metal electrode, and a solid PEO polymer electrolyte. During the first discharge, the battery shows plateau potentials at 2.27 and at 1.76 V. The first discharge capacity is 505 mAh g⁻¹ sulfur at 90 °C. The capacity drastically decreases by repeated on charge–discharge cycling but remains at 166 mAh g⁻¹ sulfur after 10 cycles. The latter value is higher than that reported for a Na/poly (vinylidene difluoride)/S battery at room temperature.     

High‐performance solid PEO/PPC/LLTO‐nanowires polymer composite electrolyte for solid‐state lithium battery

Solid polymer composite electrolyte (SPCE) with good safety, easy processability, and high ionic conductivity was a promising solution to achieve the development of advanced solid‐state lithium battery. Herein, through electrospinning and subsequent calcination, the Li_0.33La_0.557TiO₃ nanowires (LLTO‐NWs) with high ionic conductivity were synthesized. They were utilized to prepare polymer composite electrolytes which were composed of poly (ethylene oxide) (PEO), poly (propylene carbonate) (PPC), lithium bis (fluorosulfonyl)imide (LiTFSI), and LLTO‐NWs. Their structures, thermal properties, ionic conductivities, ion transference number, electrochemical stability window, as well as their compatibility with lithium metal, were studied. The results displayed that the maximum ionic conductivities of SPCE containing 8 wt.% LLTO‐NWs were 5.66 × 10^?5 S cm^?1 and 4.72 × 10^?4 S cm^?1 at room temperature and 60°C, respectively. The solid‐state LiFePO₄/Li cells assembled with this novel SPCE exhibited an initial reversible discharge capacity of 135 mAh g^?1 and good cycling stability at a charge/discharge current density of 0.5 C at 60°C.     

Gelled composite electrolyte comprising thermoplastic polyurethane and poly(ethylene oxide) for lithium batteries

Composite polymer electrolyte films consisting of poly(ethylene glycol) based thermoplastic polyurethane blended with poly(ethylene oxide) (denoted as TPU(PEG)/PEO) incorporating LiClO₄–PC have been prepared and their electrochemical properties were studied. The thermal analysis of the composite films were performed to demonstrate the miscibility of the polymer blend by using differential scanning calorimeter (DSC). TPU(PEG)/PEO based polymer electrolyte shows ionic conductivity of the order 6.4×10⁻⁴ S/cm at room temperature, irrespective of time evolution. Cyclic voltammogram shows that this composite electrolyte has good electrochemical stability in the working voltage ranging from 2 to 4.5 V. Cycling performances of Li/polymer electrolyte/LiCoO₂ cells are also followed. From AC impedance results, the recharging ability of the cells is proved to be dominated by the passive layer formation at Li electrode–polymer electrolyte interface.     

A thermo-stable poly(propylene carbonate)-based composite separator for lithium-sulfur batteries under elevated temperatures

Lithium-sulfur (Li-S) batteries have a great potential for the future development of energy industry. However, the high-temperature performance of Li-S batteries is still facing great challenge due to the high flammability of the electrolyte, sulfur cathode as well as the separator. The separator modification is an effective method to improve the thermal stability of separator and the electrochemical performance of Li-S batteries under elevated temperatures. However, the reported methods of separator coating are too complicated to be applied in the industrial production. Here, a novel thermo-stable composite separator (M-Celgard-p), in which a layer of silicon dioxide-poly (propylene carbonate) based electrolyte (nano-SiO₂@PPC) with a high ionic-conductivity of 1.03 × 10⁻⁴ S cm⁻¹ is coated on the commercial Celgard-p separator, is prepared by using a simple dipping method. Compared to the Li-S battery assembled with Celgard-p separator, the M-Celgard-p separator combined with a sulfur/polyacrylonitrile (S/PAN) cathode can improve the electrochemical performance of Li-S batteries, especially their high-temperature stability. As a result, the (S/PAN)/M-Celgard-p/Li cell delivers a high specific capacity of 724.7 mAh g⁻¹ at 1.0 A g⁻¹ after 200 cycles and presents a good rate capability of 1408 mAh g⁻¹ at 1.0 A g⁻¹ and 1216 mAh g⁻¹ at 2.0 A g⁻¹. More importantly, the (S/PAN)/M-Celgard-p/Li cell can exhibit a capacity retention ratio of 69.4% after 200 cycles at 60°C. The M-Celgard-p separator with high Li-ion conductivity can not only block the “shuttle-effect” of polysulfides during cycling but also enhance the thermal stability under elevated temperatures. This work presents a simple dipping method to prepare composite separator with excellent thermal stability, which enhance the rate performance and cyclic stability of Li-S batteries under elevated temperatures. We believe this work can provide a new way to develop more reliable Li-S batteries for practical applications.     

Effects of surface lithiated TiO2 nanorods on room-temperature properties of polymer solid electrolytes

Polymer solid electrolyte with high ionic conductivity at room-temperature is most likely to be widely used in solid-state lithium batteries. In this work, the novel surface lithiated TiO₂ nanorods were firstly used as ionic conductor in polymer solid electrolyte. The surface lithiated TiO₂ nanorods-filled polypropylene carbonate polymer composite solid electrolyte (CSE) has an uniform composite structure with a thickness of about 60 μm. The ionic conductivity at room-temperature is 1.21 × 10⁻⁴ S cm⁻¹ and the electrochemical stability window is up to 4.6 V (vs Li⁺/Li). The assembled NCM622/CSE/Li solid-state battery shows a stable cycle performance with a retention capacity of 120 mAh g⁻¹ after 200 cycles at the current density of 0.3 C and a high coulomb efficiency of 99%. Compared with TiO₂ particles, this novel surface lithiated TiO₂ nanorods can provide more continuous ion transport channels and more Lewis acid-base reactive sites, provide a novel way to enhance the lithium ion transport in polymer solid electrolyte.     

Ionic liquid doped PEO-based solid polymer electrolytes for lithium-ion polymer batteries

The influence of adding the room-temperature ionic liquid 1-ethyl-3-methyllimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) to poly(ethylene oxide) (PEO)–lithium difluoro(oxalato)borate (LiDFOB) solid polymer electrolyte and the use of these electrolytes in solid-state Li/LiFePO₄ batteries has been investigated. Different structural, thermal, electrical and electrochemical studies exhibit promising characteristics of these polymer electrolyte membranes, suitable as electrolytes in rechargeable lithium-ion batteries. The crystallinity decreased significantly due to the incorporation of ionic liquid, investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The ion–polymer interaction, particularly the interaction of cations in LiDFOB and ionic liquid with ether oxygen atom of PEO chains, has been evidenced by FT-IR studies. The polymer electrolyte with ～40 wt% of ionic liquid offers a maximum ionic conductivity of ～1.85 × 10^?4 S/cm at 30 °C with improved electrochemical stabilities. The Li/PEO-LiDFOB-40 wt% EMImTFSI/LiFePO₄ coin-typed cell cycled at 0.1 C shows the 1st discharge capacity about 155 mAh g^?1, and remains 134.2 mAh g^?1 on the 50th cycle. The addition of the ionic liquid to PEO₂₀-LiDFOB polymer electrolyte has resulted in a very promising improvement in performance of the lithium polymer batteries.     

Electrochemical properties of lithium sulfur cells using PEO polymer electrolytes prepared under three different mixing conditions

Lithium sulfur cells were prepared by composing with sulfur cathode (PEO)₆LiBF₄ polymer electrolyte and lithium anode. (PEO)₆LiBF₄ polymer electrolyte was prepared under three different mixing conditions: stirred polymer electrolyte (SPE), ball-milled polymer electrolyte (BPE) and ball-milled polymer electrolyte with 10 wt%Al₂O₃ (BCPE). The effects of ball milling and additive were investigated by discharge test according to depth of discharge. The initial discharge capacity of lithium sulfur cell using BCPE was 1670 mAh g⁻¹-sulfur, which was better than those of SPE and BPE, and approximately equal to the theoretical capacity. The cycle performance of Li/(PEO)₆LiBF₄/S cell was remarkably improved by the addition of Al₂O_3.     

Phase-separated polymer electrolyte based on poly(vinyl chloride)/poly(ethyl methacrylate) blend

The characteristics of polymer electrolytes based on a poly(vinyl chloride) (PVC)/poly(ethyl methacrylate) (PEMA) blend are reported. The PVC/PEMA based polymer electrolyte consists of an electrolyte-rich phase that acts as a conducting channel and a polymer-rich phase that provides mechanical strength. The dual phase was simply developed by a single-step coating process. The mechanical strength of the PVC/PEMA based polymer electrolyte was found to be much higher than that of a previously reported PVC/PMMA-based polymer electrolyte (poly(methyl methacrylate), PMMA) at the same PVC content, and even comparable with that of the PVC-based polymer electrolyte. The blended polymer electrolytes showed ionic conductivity of higher than 10⁻³ S cm⁻¹ and electrochemical stability up to at least 4.3 V. A prototype battery, which consists of a LiCoO₂ cathode, a MCMB anode, and PVC/PEMA-based polymer electrolyte, gives 92% of the initial capacity at 100 cycles upon repeated charge–discharge at the 1 C rate.     

Improved performance of Li hybrid solid polymer electrolyte cells

The seminal research by Wright et al. on polyethylene oxide (PEO) solid polymer electrolyte (SPE) generated intense interest in all solid-state rechargeable lithium batteries. Following this a number of researchers have studied the physical, electrical and transport properties of thin film PEO electrolyte containing Li salt. These studies have clearly identified the limitations of the PEO electrolyte. Chief among the limitations are a low cation transport number (t₊), high crystallinity and segmental motion of the polymer chain, which carries the cation through the bulk electrolyte. While low t₊ leads to cell polarization and increase in cell resistance high T_g reduces conductivity at and around room temperatures. For example, the conductivity of PEO electrolyte containing lithium salt is <10⁻⁷ S cm⁻¹ at room temperature. Although modified PEO electrolytes with lower T_g exhibited higher conductivity (∼10⁻⁵ S cm⁻¹ at RT) the t₊ is still very low ∼0.25 for lithium ion. Numerous other attempts to improving t₊ have met with limited success. The latest approach involves integrating nano domains of inorganic moieties, such as silcate, alumosilicate, etc. within the polymer component. This approach yields an inorganic–organic component (OIC) based polymer electrolyte with higher conductivity and t₊ for Li⁺_. This paper describes the improved electrical and electrochemical properties of OIC-based polymer electrolyte and cells containing Li anode with either a TiS₂ cathode or Mag-10 carbon electrode. Several solid polymer electrolytes derived from silicate OIC and salt-in-polymer constituent based on Li triflate (LiTf) and PEO are studied. A typical composition of the SPE investigated in this work consists of 600 kDa PEO, lithium triflate (LiTf, LiSO₃CF₃) and 55% of silicate based on (3-glycidoxypropyl)trimethoxysilane and tetramethoxysilane at molar ratio 4:1 and 0.65 mol% of aluminum(tri-sec-butoxide) (GTMOS-Al1-900k-55%). Several pouch cells consisting of Li/OIC-based–SPE/cathode containing OIC-based–SPE–LiTf binder were fabricated and tested, these cells are called modified cells. The charge/discharge and impedance characteristics of the new cells (also called modified cells) are compared with that of the pouch cells containing the conventional PEO–LiTf electrolyte as the cathode binder, these cells are called non-modified cells. The new cells can be charged and discharged at 70 °C at higher currents. However, the old cells can be charged and discharged only at 80 °C or above and at lower currents. The cell impedance for the new cells is much lower than that for the old cells.     

High reversible capacities of graphite and SiO/graphite with solvent-free solid polymer electrolyte for lithium-ion batteries

The combination of graphite or silicon monoxide (SiO)/graphite = 1/1 mixture with a solvent-free solid polymer electrolyte (SPE) was fabricated using a new preparation process, involving precoating the electrode with vapor-grown carbon fiber (VGCF) and binders (polyvinyl difluoride: PVdF or polyimide: PI), followed by the overcoating of the SPE. The reversible capacity of [graphite | SPE | Li] and [SiO/graphite | SPE | Li] cells were >360 and >1000 mAh g⁻¹ with 78% and 77% for the 1st Coulombic efficiency, respectively. The reversible capacities were 75% at the 250th cycle for [graphite | SPE | Li] and 72% at the 100th cycle for [SiO/graphite | SPE | Li]. The electrode used was compatible with that of the conventional liquid electrolyte system, and the SPE film could be formed on the electrode by the continuous overcoating process, which will lead to a low-cost electrodes and low-cost battery production. The solid-state lithium-ion polymer battery (SSLiPB) developed in this study, which consisted of [LiFePO₄ | SPE | graphite], showed the reversible capacity of 128 mAh g⁻¹ (based on the LiFePO₄ capacity) with favorable cycle performance.     

新型固态聚合物电解质在锂硫电池中的性能研究

本工作采用（氟磺酰）（三氟甲基磺酰）亚胺锂{Li[(FSO2)(CF3SO2)N],LiFTFSI}和聚氧乙烯（PEO）分别作为导电锂盐和聚合物主链,通过简单的溶液浇铸法制备了新型固态聚合物电解质（SPEs）,并采取示差扫描量热（DSC）、热重（TGA）、线性扫描伏安（LSV）、交流阻抗（EIS）和恒电位直流（DC）极化等方法研究了LiFTFSI/PEO （EO/Li+摩尔比为16）电解质的理化性质和电化学性质。结果表明,LiFTFSI/PEO电解质具有较高的室温离子电导率（σ ≈10−5 S/cm）,较高的氧化电位（4.63 V vs. Li/Li+）,并且耐热温度高达256 ℃。锂硫电池测试结果表明,该类SPEs展现出相对高的首周放电比容量（881 mA•h/g）,有效地抑制了多硫离子的“穿梭效应”,表现出良好的电池循环性能。     

Electrochemical characterization of blend polymer electrolytes based on poly(oligo[oxyethylene]oxyterephthaloyl) for rechargeable lithium metal polymer batteries

Solid polymer electrolytes composed of poly(ethylene oxide)(PEO), poly(oligo[oxyethylene]oxyterephthaloyl) and lithium perchlorate have been prepared and characterized. Addition of poly(oligo[oxyethylene]oxyterephthaloyl) to PEO/LiClO₄ reduced the degree of crystallinity and improved the ambient temperature ionic conductivity. The blend polymer electrolyte containing 40 wt.% of poly(oligo[oxyethylene]oxyterephthaloyl) showed an ionic conductivity of 2.0 × 10⁻⁵ S cm⁻¹ at room temperature and a sufficient electrochemical stability to allow application in the lithium batteries. By using the blend polymer electrolytes, the lithium metal polymer cells composed of lithium anode and LiCoO₂ cathode were assembled and their cycling performances were evaluated at 40 °C.     

Lithium-ion rechargeable cells with polyacenic semiconductor (PAS) and LiCoO2 electrodes

Polyacenic semiconductor (PAS), heat-treated at 700°C, has a lithium intercalation capacity as high as 438 mAh g⁻¹ which is higher than the theoretical capacity of 372 mAh g⁻¹ for graphite. The electrochemical behaviour of PAS is examined by studying Li/PAS and Li/graphite cells. In a PAS or graphite anode, three reactions are distinguished: (i) reaction of lithium with the Teflon binder; (ii) decomposition of electrolyte, and (iii) intercalation of Li⁺ ions. Two laboratory cells with liquid organic electrolyte or polymer electrolyte and PAS as the anode demonstrate that PAS is a promising anode material for lithium-ion batteries.     

Photocured PEO-based solid polymer electrolyte and its application to lithium–polymer batteries

A solid polymer electrolyte (SPE) based on polyethylene oxide (PEO) is prepared by photocuring of polyethylene glycol acrylates. The conductivity is greatly enhanced by adding low molecular weight poly(ethylene glycol) dimethylether (PEGDME). The maximum conducticity is 5.1×10⁻⁴ S cm⁻¹ at 30°C. These electrolytes display oxidation stability up to 4.5 V against a lithium reference electrode. Reversible electrochemical plating/stripping of lithium is observed on a stainless steel electrode. Li/SPE/LiMn₂O₄ as well as C(Li)/SPE/LiCoO₂ cells have been fabricated and tested to demonstrate the applicability of the resulting polymer electrolytes in lithium–polymer batteries.     

Alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte for Zn–air battery

An alkaline composite PEO–PVA–glass-fibre-mat polymer electrolyte with high ionic conductivity (10⁻² S cm⁻¹) at room temperature has been prepared and applied to solid-state primary Zn–air batteries. The electrolyte shows excellent mechanical strength. The electrochemical characteristics of the batteries were experimentally investigated by means of ac impedance spectroscopy and galvanostatic discharge. The results indicate that the PEO–PVA–glass-fibre-mat composite polymer electrolyte is a promising candidate for application in alkaline primary Zn–air batteries.     

New anhydrous proton exchange membranes based on fluoropolymers blend imidazolium poly (aromatic ether ketone)s for high temperature polymer electrolyte fuel cells

The blend polymer membranes were synthesized from the methylimidazolium poly (aromatic ether ketone) (MeIm-PAEK) and fluoropolymers (PVDF and PVDF-HFP) with excellent thermal stability and improved dimensional stabilities for high-temperature polymer electrolyte fuel cells. The MeIm-PAEK exhibited good compatibility with PVDF or PVDF-HFP without phase separation. High phosphoric acid doping contents of the blend membranes were achieved at elevated temperatures with acceptable swellings. The acid doped blend membranes displayed lower dimensional swellings and higher mechanical strength compared to the MeIm-PAEK membrane, which allowed the blend membranes to obtain higher acid doping contents and proton conductivities. The MeIm-PAEK/10%PVDF membrane with a phosphoric acid doping content of 700 wt% showed a proton conductivity as high as 0.192 S cm^?1 at 180 °C under the non-humidified condition and a tensile strength of 4.3 MPa at room temperature.     

Cobalt-doped layered lithium nickel oxide as a three-in-one electrode for lithium-ion and sodium-ion batteries and supercapacitor applications

Layered LiNi_0.94Co_0.06O₂ (LNCO) was prepared and explored as an energy-storage material for Li-ion (LIBs), Na-ion (SIBs) batteries as well as supercapacitor application for the first time. All the physical and morphological characterizations were studied for the sample LNCO. The result displays good thermal stability, phase purity in the crystal structure, appreciable Brunauer-Emmett-Teller (BET) surface area (5.53 m² g⁻¹) and possesses cubic morphology. The cobalt was identified in lithium nickel oxide with binding energies at 794.02, 779.04 and 784.30 eV, respectively. In the case of LIBs, LNCO exists with a minimal difference of 5 mAh g⁻¹, even when cycled from 2C to 0.1C. After 200 cycles, the specific capacity, 247 mAh g⁻¹, is obtained for the cell with retention of 97.8% (efficiency 99.8%) at 0.1C. In SIBs, at 0.1C, the discharge capacity of 182 mAh g⁻¹ was restored even when cycled after 2C. After 200 cycles, a discharge capacity of 204 mAh g⁻¹ is ensured with retention of 96.6% (efficiency of 99.4% at 0.1C). In supercapacitor, the electrode, LNCO, delivered a specific capacity of 300 F g⁻¹ at 0.5 A g⁻¹. Therefore, LNCO is highly recommended as a suitable electrode material for fulfilling the requirement of energy-storage applications.     

Simultaneously enhancing the thermal stability and electrochemical performance of solid polymer electrolytes by incorporating rod-like Zn2(OH)BO3 particles

Solid polymer electrolytes provide high safety and good electrochemical stability in solid-state lithium batteries (SSLBs) compared with conventional liquid electrolytes. In this work, a novel solid polymer composite electrolyte based on poly (ethylene oxide) (PEO) filled with rod-like Zn₂(OH)BO₃ particles was prepared by a grinding process followed with a heating treatment process and a cold pressing process. The effect of the incorporation amount of rod-like Zn₂(OH)BO₃ particles on the ionic conductivity was investigated systemically. It is found that 10 mol% of rod-like Zn₂(OH)BO₃ particles addition resulted in a highest ionic conductivity of 2.78 × 10⁻⁵ at 30 °C and the improved ionic conductivity was considered to be caused by the reducing of PEO crystallinity and the increasing of Li ion migrating pathway on the interface between the Zn₂(OH)BO₃ and PEO. In addition, the optimum composite electrolyte exhibited a high electrochemical stability window of 4.51 V (vs. Li/Li⁺), good lithium stability and excellent thermal stability.