High conducting multilayer films from poly(acrylic acid) and graphite by layer‐by‐layer self‐assembly

Exfoliated graphite nanoplatelets were modified by hexadecyltrimethylammonium bromide (C₁₆TAB) and were used for the construction of [poly(acrylic acid)/graphite]_n [(PAA/G)_n] multilayer films using a layer‐by‐layer (LBL) self‐assembly method. The film thickness was monitored using X‐ray diffraction technique; the results showed that the thickness depended on pH of PAA. Under a lower pH value such as 1.5, the average bilayer thickness was 1.5 nm. Once the pH of PAA was increased to 6.5, the bilayer thickness was around 30 nm. The C₁₆TAB modified (PAA/G)_n multilayer films showed high thermal stability and electrical conductivity. A percolation phenomenon occurred at bilayer number of 11, and the mechanism was discussed. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Insights on tunneled electrons for electrical and photoelectric behaviors in conducting multilayer films

We demonstrate here the layer‐by‐layer (LbL) self‐assembly of conducting [poly(styrene sulfonate)‐poly(vinyl alcohol)/polypyrrole]_n [(PSS‐PVA/PPy)_n] multilayer film with interesting electrical and photoelectric features. Increments in sheet conductivity and photoelectric response with increasing bilayer number are pioneerly recorded. The fantastic phenomenon is determined as the accumulative electrons tunneled across insulating PSS from bottom to top PPy chains. The resulting multilayer films give a linear growth in bulk conductivity and maximum photocurrent density. Careful examination of data and characterizations indicates that the fantastic effects in electrical conduction and photocurrent are accumulative electrons tunneled across PSS from bottom to top PPy. POLYM. ENG. SCI., 55:107–112, 2015. © 2014 Society of Plastics Engineers     

Comparative electrochemical study of myoglobin loaded in different types of layer-by-layer assembly films

Four different types of layer-by-layer films were assembled on solid surfaces and designated as PDDA/{ZrO₂}_n, {PDDA/ZrO₂}_n, {PDDA/NP-ZrO₂}_n, and {PDDA/PSS}_n, where ZrO₂ stands for zirconia sol-gel formed by vapor-surface sol-gel deposition, NP-ZrO₂ represents ZrO₂ nanoparticles, PDDA is poly(diallyldimethylammonium), and PSS is poly(styrenesulfonate). When these films were immersed in myoglobin (Mb) solutions, Mb could be gradually “absorbed” or loaded into the films, and the Mb-loaded films at pyrolytic graphite (PG) electrodes demonstrated nearly reversible cyclic voltammetric (CV) responses for Mb Fe^III/Fe^II couple and good electrocatalytic property toward H₂O₂. The electrochemical and electrocatalytic activity of Mb in these films exhibited the sequence of PDDA/{ZrO₂}_n-Mb > {PDDA/ZrO₂}_n-Mb > {PDDA/NP-ZrO₂}_n-Mb > {PDDA/PSS}_n-Mb. Among the four types of films, PDDA/{ZrO₂}_n films, formed by repeated vapor-surface sol-gel deposition of ZrO₂ on PDDA surface, demonstrated better porosity and permeability, and thus could load more amounts of Mb from its solutions. Also because of the better porosity of PDDA/{ZrO₂}_n-Mb films, the small counterions in buffer solution could get into and out of the films more easily, also resulting in the better CV responses of the films according to the mechanism of electron hopping. UV-vis and FTIR spectroscopic studies suggest that Mb in these films essentially retains its native structure. The protein-loaded multilayer films are a novel kind of protein layer-by-layer films, which provide a new route to immobilize proteins and may provide a foundation for fabricating the third generation biosensors based on the direct electrochemistry of enzymes.     

Orientation of graphitic planes during annealing of “dip deposited” amorphous carbon film: A carbon K-edge X-ray absorption near-edge study

Annealing effect of amorphous carbon thin films on Si(1 0 0) substrates is studied by normal incidence and angle dependent carbon K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The angle dependence of the XANES signal shows that the graphitic basal planes are oriented perpendicular to the surface when the film is annealed at 1000 °C. Micro-Raman spectroscopy reveals two well-separated bands the D band at 1355 cm⁻¹ and G band at ∼1600 cm⁻¹, and their I_D/I_G intensity ratio indicates the formation of more graphitic film at higher annealing temperatures. X-ray diffraction pattern of 1000 °C temperature annealed film confirms the formation of graphite structure.     

Impedance study of protecting film formation on lithium and lithiated graphite induced by bis(fluorosulfonyl) imide anion

The process of Li⁺ reduction from room temperature ionic liquids consisting of N-methyl-N-propylpyrrolidinium cation (MPPyr⁺) and bis(fluorosulfonyl) imide (FSI⁻) or bis(trifluoromethanesulfonyl) imide (TFSI⁻) anions was studied with the use of impedance spectroscopy. Reduction was carried out on both metallic lithium (Li) and graphite (G) electrodes. It has been found that the FSI anion in high amounts is able to form a protective film on both graphite and metallic lithium. The Li⁺/Li couple should rather be represented by a Li⁺/SEI/Li system. The SEI structure depends on the manner of its formation (chemical or electrochemical) and is not stable with time. The rate constant for the Li⁺ + e⁻ → Li process at the Li/SEI/Li⁺ (in MPPyrFSI) interface is k_o = 4.2 × 10⁻⁵ cm/s. In the case of carbon electrodes (G/SEI/Li⁺ interface), lithium diffusion in solid graphite is the rate determining step, reducing current by ca. two orders of magnitude, from ca. 10⁻⁴ A/cm², characteristic of the Li/SEI/Li⁺ electrode, to ca. 10⁻⁶ A/cm².     

Fourier transform infrared spectroscopic study of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by pulsed laser deposition

Nitrogen-doped ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films, which possess n-type conduction with enhanced electrical conductivities, were prepared by pulsed laser deposition and they were structurally studied by Fourier transform infrared (FTIR) spectroscopy. The film with a nitrogen content of 7.9 at.% possessed n-type condition with an electrical conductivity of 18 S/cm at 300 K. The FTIR spectra revealed peaks due to nitrogen impurities, C = N, C-N, and CH_n (n = 1, 2, 3) bands. The sp²-CH_n/(sp²-CH_n + sp³-CH_n), estimated from the area-integration of decomposed peaks, were 24.5 and 19.4% for undoped and 7.9 at.% doped films, respectively. The nitrogen-doping not only form the chemical bonds between carbon and nitrogen atoms such as C = N and C-N bonds but also facilitate the formation of both sp² and sp³ bonds, in particular, the sp³-CH_n bond is preferentially formed. From the analysis of the FTIR spectra, it was found that the hydrogen content in the film is increased with an increase in the nitrogen content. The increased hydrogen content might be owing to the enhanced volume of grain boundaries (GBs) between UNCD grains, and those between UNCD grains and an a-C:H matrix, which is caused by a reduction in the UNCD grain size. The CH_n peaks predominantly come from an a-C:H matrix and GBs. Since the nitrogen-doping for a-C:H has been known to be hardly effective, the n-type conduction with the enhanced electrical conductivities might be attributed to the sp²-CH_n formation at the GBs.     

Hydrogen production from oxidative steam reforming of ethanol in a palladium-silver alloy composite membrane reactor

In this investigation, we studied the oxidative steam reforming reaction of ethanol in a Pd-Ag/PSS membrane reactor for the production of high purity hydrogen. Palladium and silver were deposited on porous stainless steel (PSS) tube via the sequential electroless plating procedure with an overall film thickness of 20 μm and Pd/Ag weight ratio of 78/22. An ethanol-water mixture (n_water/n_ethanol = 1 or 3) and oxygen (n_oxygen/n_ethanol = 0.2, 0.7 or 1.0) were fed concurrently into the membrane reactor packed with Zn-Cu commercial catalyst (MDC-3). The reaction temperatures were set at 593-723 K and the pressures at 3-10 atm. The hydrogen flux in the permeation side increased proportionately with increasing pressure; however, it reduced slightly when increasing oxygen input. This is probably due to the fast oxidation reaction that consumes hydrogen before the onset of the steam reforming reaction. The effect of oxygen plays a vital role on the ethanol oxidation steam reforming reaction, especially for a Pd-Ag membrane reactor in which a higher flux of hydrogen is required. The selectivity of CO₂ increased with increasing flow rate of oxygen, while the selectivity of CO remained almost the same.     

The spatial uniformity and electromechanical stability of transparent, conductive films of single walled nanotubes

We have prepared thin films of arc discharge single walled nanotubes by vacuum filtration. For film thicknesses greater than 40 nm, the films are of high optical quality; the optical transmission varies by <2% over the film area when measured with a spatial resolution of 4 μm. However, the films become spatially non-uniform for film thickness below 40 nm. The in-plane DC conductivity correlates with the uniformity, increasing from ∼3800 S/m for a 10 nm thick film to ∼2-2.5 × 10⁵ S/m for films of thickness >40 nm. Conductive atomic force microscopy maps show reasonably uniform current flow out of the plane of the film. For all thicknesses, the optical transmittance scales with film thickness as expected for a thin conducting film with optical conductivity of 1.7 × 10⁴ S/m (λ = 550 nm). For films with t > 40 nm the ratio of DC to optical conductivity was σ_DC/σ_Op = 13.0, leading to values of transmittance and sheet resistance such as T = 80% and R_s = 110 Ω/□ for the t = 40 nm film. Electromechanically, these films were very stable showing conductivity changes of <5% and <2% when cycled over 2000 times in compression and tension respectively.     

Improvement of the electrochemical behavior of steel surfaces using a TiN[BCN/BN]n/c-BN multilayer system

The aim of this work is to improve the electrochemical behavior of AISI 4140 steel substrates by using a TiN[BCN/BN]_n/c-BN multilayer system as a protective coating. We grew TiN[BCN/BN]_n/c-BN multilayers via reactive r.f. magnetron sputtering technique, systematically varying the length period (Λ) and the bilayer number (n), maintaining constant the total thickness of the coating and all other growth parameters. The coatings were characterized by FTIR spectroscopy that showed bands associated to h-BN bonds, and c-BN stretching vibrations centered at 1385 cm^− 1 and 1005 cm^− 1, respectively. Film composition was studied via X-ray photoelectron spectroscopy where typical signals for C1s, N1s and B1s are shown. The electrochemical properties were studied by electrochemical impedance spectroscopy and Tafel curves. In this work, the maximum corrosion resistance for the coating with (Λ) equal to 80 nm was obtained, corresponding to n = 25 bilayers. The polarization resistance and corrosion rate were around 10.1 kOhm cm² and 0.22 mm/year; these values were 83 and 15 times higher, respectively, than uncoated AISI 4140 steel substrate (0.66 kOhm cm² and 18.51 mm/year). Optical microscopy was used for surface analysis after corrosive attack. The improvement of the electrochemical behavior of the AISI 4140 coated with this TiN[BCN/BN]_n/c-BN multilayer system can be attributed to the presence of several interfaces that offer resistance to diffusion of Cl⁻ of the electrolyte toward the steel surface.     

Hydrated Mn(IV) oxide-exfoliated graphite composites for electrochemical capacitor

Commercially available low cost exfoliated graphite (EG, nominal diameter 130 μm) was used as a conductive substrate for electrochemical capacitor of hydrated Mn(IV) oxide, MnO₂·nH₂O. The MnO₂·nH₂O-EG composites were prepared by addition of EG to potassium permanganate solution, followed by 1 h stirring and then slow addition of manganese(II) acetate solution. By this procedure submicrometer or smaller sized MnO₂·nH₂O particles having mesopores of 6-12 nm in diameter were formed on the graphite sheets of EG. Although EG alone showed only about 2 F g⁻¹, the composites showed good rectangular cyclic voltammograms at 2-20 mV s⁻¹ in 1 mol L⁻¹ Na₂SO₄. The capacitance per net amount of MnO₂ increased proportionally with EG content, that is, utilization ratio of MnO₂ increased with EG content. The composites of MnO₂·nH₂O and smaller diameter of EG (nominal diameter 45 μm) or artificial graphite powder (average diameter 3.7 μm) showed fairly good performance at 2 mV s⁻¹, but with increasing potential scan rate the rectangular shape was distorted and capacitance decreased drastically. The results implies that sheet-like structure is more effective than small particles as conductive materials, when the formation procedure of composite is the same. Large sized EG may be a promising conductive material for electrochemical capacitors.     

Spectroscopic and structural studies of di-ureasils doped with lithium perchlorate

Di-urea cross-linked POE/siloxane hybrid ormolytes (di-ureasils) doped with a wide concentration range of lithium perchlorate trihydrate (LiClO₄·3H₂O) (200 ≥ n ≥ 0.5, where n expresses the salt content in terms of the number of ether oxygen atoms per Li⁺ ion) have been analysed by Fourier transform infrared and Raman (FT-IR and FT-Raman, respectively) spectroscopies and X-ray diffraction (XRD). The results obtained lead us to conclude that the xerogels with n ≥ 5 are totally amorphous. At n ≤ 1 free salt is observed. “Free” ClO₄⁻ ions appear to be the main charge carriers at the conductivity maximum located within the 25 ≤ n ≤ 8 composition range of this family of ormolytes. At n = 15 ClO₄⁻ ions coordinated in mono/tridentate (C_3v symmetry) and bidentate (C_2v symmetry) configurations were detected. In salt-rich samples with n < 15 there is a marked tendency for ionic association. The resulting decrease that occurs in the concentration of “free” ions is consistent with the observed significant decrease of the ionic conductivity. The analysis of the “amide I” and “amide II” regions provided solid proof that the Li⁺ ions bond to the urea carbonyl oxygen atoms over the entire range of salt concentration studied.     

Synthesis and characterization of highly soluble 9,10-diphenyl-substituted poly(2,6-anthracenevinylene)

We report the synthesis and optoelectronic properties of highly soluble poly(9,10-bis(3′,4′-di(2″-ethylhexyloxy))phenyl)-2,6-anthracenevinylene) (HSM-PAV). The key intermediate for the synthesis of HSM-PAV is 2,6-dimethyl-9,10-dibromoanthracene, and the high solubility of HSM-PAV is from the incorporation of lateral 3,4-di(2-ethylhexyloxy)phenyl moieties into the 9,10-positions of anthracene units. The increase of side alkyloxy groups endows HSM-PAV with higher molecular weight (M_n = 3.2 × 10⁴) and better electroluminescence performances (L_max = 590 cd/m², LE_max = 0.27 cd/A) compared with the poly(2,6-anthracenevinylene) with lateral monoalkyoxy moieties (M_n = 1.9 × 10⁴, L_max = 340 cd/m², LE_max = 0.17 cd/A). The electrical conductivity of doped HSM-PAV film with iodine is 5 × 10⁻² S cm⁻¹ that is several order higher than that of doped 9,10-anthracene-based polymers, further demonstrating that linkage position has a dramatic effect on the optoelectronic properties of anthracene-based conjugated polymers.     

Mg-doped poly(?-caprolactone)/siloxane biohybrids

Ionically conducting materials based on a poly(?-caprolactone) (PCL)/siloxane organic/inorganic host framework doped with magnesium triflate (Mg(CF₃SO₃)₂) were synthesized by the sol-gel process. In this matrix short PCL chains are covalently bonded to the siliceous network via urethane linkages. In this study the salt content of samples was identified using the conventional notation n, where n indicates the number of (C(O)(CH₂)₅O) PCL repeat units per Mg²⁺ ion. Xerogels with compositions ranging from n = ∞ to 1 were prepared. The only composition studied that was not entirely amorphous was that prepared with n = 1. Xerogels with n ≥ 7 are thermally stable up to at least 200 °C. The composition with the highest conductivity of the series is that with n = 34 (5.9 × 10⁻⁹ and 9.8 × 10⁻⁷ S cm⁻¹ at 24 and 104 °C, respectively).     

Layer-by-layer assembly of poly(sodium 4-styrenesulfonate) wrapped multiwalled carbon nanotubes with polyaniline nanofibers and its electrochemistry

A simple and versatile method based on noncovalent supramolecular attachment and layer-by-layer (LBL) assembly is proposed to prepare nanostructured hybrid conducting polymer. The negatively charged poly(sodium 4-styrenesulfonate) (PSS) wrapped multiwalled carbon nanotubes (MWCNTs) is doped with cationic polyaniline (PANI) nanofibers via LBL assembly, and a well-defined PANI/MWCNTs composite was obtained. The LBL assembly process is characterized by scanning electron microscopy, energy dispersive spectrometry and electrochemical methods. It was found that PSS wrapped MWCNTs inside the multilayer film can dope nanostructured PANI effectively and shift its electroactivity to a neutral pH environment. Moreover, the conducting composites show amperometric response for hydrogen peroxide with a linear range of 2.0 × 10⁻⁷-1.0 × 10⁻³ mol L⁻¹.     

Influence of metal coordination on conductivity behavior in poly(butadiene-acrylonitrile)-CoCl2 system

The metal complex formation and the electrical properties of amorphous solid polymer electrolytes, based on poly(butadiene-acrylonitrile) copolymer (PBAN) and CoCl₂, have been studied over the homogeneity region of the system limited by the CoCl₂ concentration of 1.89 mol kg⁻¹. It has been found that ionic conductivity is carried out by the unipolar anion transfer at lower CoCl₂ concentrations (up to 0.10 mol kg⁻¹). As the CoCl₂ concentration increases, electronic conductivity appears in addition to ionic conductivity, and the former becomes dominant, starting from 0.38 mol kg⁻¹. It has been shown that the nature of charge carriers is determined by the composition of metal complexes formed by CoCl₂ and the macromolecular solvent PBAN. At lower concentrations, the [Co₂L₂Cl₄]⁰ dimers are the predominant species (L being macromolecule side groups CN), and their dissociation is followed by the formation of mobile Cl⁻ anions and immobile binuclear [Co₂Cl₃]⁺ complexes. As CoCl₂ concentration increases, polynuclear [Co_nL₂Cl_2n]⁰ (n > 2) complexes appear (L being CN and CC groups of PBAN). Specific features of chemical bonds in π-complexes of transition metals result in the appearance of electronic charge carriers. The abrupt increase in conductivity observed at the highest CoCl₂ concentration is connected with the formation of a percolation network of polynuclear [Co_nL₂Cl_2n]⁰ complexes.     

Physicochemical characterization of the layer-by-layer self-assembly of polyphenol oxidase and chitosan on glassy carbon electrode

This paper demonstrates the feasibility to build up layer-by-layer (L-b-L) self-assemblies of polyphenol oxidase (PPO) and quaternized chitosan (CHI⁺) on a glassy carbon (GC) rotating disk electrode. This work highlights the promising properties of this modified polysaccharide to immobilize PPO in self-assembled structures under conditions that preserve its catalytic activity. The film consists of a diffusional underlayer coupled with an outermost active layer of (PPO/CHI⁺)_n. UV-vis spectroscopy and quartz crystal microbalance (QCM) were used to follow the multilayer film formation. Referring to the low amount of enzyme immobilized in the multilayer structure, the amperometric response of the biosensor reached an excellent sensitivity of about 2000 A mol⁻¹ cm, proving that an important part of the entrapped enzyme is accessible to the substrate molecule while keeping a good level of activity. The experimental validation of the theoretical model that was carried out on the basis of the catechol and phenol-polyphenol oxidase model system shows that the amperometric responses are in excellent agreement with the model. From a comparison of the experimental results with theory, we were able to characterize the diffusion through the film which includes two different areas and extract its enzymatic activity related to catechol and phenol substrates.     

Effect of BNBTKNN on the electrical properties of bismuth ferrite thin films

BiFeO₃/[0.93(Bi_0.50Na_0.50TiO₃)-0.05BaTiO₃-0.02K_0.50Na_0.50NbO₃] (BFO/BNBTKNN) bilayered thin films were fabricated on Pt/TiO₂/SiO₂/Si substrates without any buffer layers by a combined sol-gel and radio frequency sputtering route. Effect of BNBTKNN on electrical properties of BFO/BNBTKNN thin films was investigated. A higher phase purity and a denser microstructure are induced for the BFO/BNBTKNN bilayered thin film by using the bottom BNBTKNN layer, resulting in its lower leakage current density. Moreover, the enhancement in dielectric behavior is also demonstrated for such a bilayer, where a high dielectric constant and a low dielectric loss are obtained. The BFO/BNBTKNN bilayered thin film has an improved multiferroic behavior: 2P_r ∼ 76.8 μC/cm², 2E_c ∼ 378.1 kV/cm, 2M_s ∼ 52.6 emu/cm³, and 2H_c ∼ 453.6 Oe, together with a low fatigue rate up to ∼1 × 10⁹ switching cycles.     

Polypyrrole and La1−xSrxMnO3 (0≤ x ≤0.4) composite electrodes for electroreduction of oxygen in alkaline medium

Composite G/PPy/PPy(La_1−xSr_xMnO₃)/PPy electrodes made of the perovskite La_1−xSr_xMnO₃ embedded into a polypyrrole (PPy) layer, sandwiched between two pure PPy films, electrodeposited on a graphite support were investigated for electrocatalysis of the oxygen reduction reaction (ORR). PPy and PPy(La_1−xSr_xMnO₃) (0≤ x ≤0.4) successive layers have been obtained on polished and pretreated graphite electrodes following sequential electrodeposition technique. The electrolytes used in the electrodeposition process were Ar saturated 0.1 mol dm⁻³ pyrrole (Py) plus 0.05 mol dm⁻³ K₂SO₄ with and without containing a suspension of 8.33 g L⁻¹ oxide powder. Films were characterized by XRD, SEM, linear sweep voltammetry, cyclic voltammetry (CV) and electrochemical impedance (EI) spectroscopy. Electrochemical investigations were carried out at pH 12 in a 0.5 mol dm⁻³ K₂SO₄ plus 5 mmol dm⁻³ KOH, under both oxygenated and deoxygenated conditions. Results indicate that the porosity of the PPy matrix is considerably enhanced in presence of oxide particles. Sr substitution is found to have little influence on the electrocatalytic activity of the composite electrode towards the ORR. However, the rate of oxygen reduction decreases with decreasing pH of the electrolyte from pH 12 to pH 6. It is noteworthy that in contrast to a non-composite electrode of the same oxide in film form, the composite electrode exhibits much better electrocatalytic activity for the ORR.     

Processing and performance of solid oxide fuel cell with Gd-doped ceria electrolyte

Fuel Cell performance was measured at 792-1095 K for Ni-GDC (Gd-doped ceria) anode-supported GDC film (60 μm thickness) with a (La_0.8Sr_0.2)(Co_0.8Fe_0.2)O₃ cathode using H₂ fuel containing 3 vol% H₂O. A maximum power density, 436 mW/cm², was obtained at 1095 K. The electrical conductivity of GDC electrolyte in N₂ atmosphere of 10⁻¹⁵-10⁰ Pa oxygen partial pressures (Po₂) at 773-1073 K was independent of Po₂, which indicated the diffusion of oxide ions. The conductivity of GDC in H₂O/H₂ atmosphere increased because of the further formation of electrons due to the dissociation of hydrogen in GDC (H₂ → 2H⁺ + 2e⁻). The hole conductivity was observed at 873 K in Po₂ = 10⁰-10⁴ Pa. The key factors in increasing power density are the increase of open circuit voltage and the suppression of H₂ fuel dissolution in GDC electrolyte. These are controlled by the cathode material and Gd-dopant composition.     

Comb-shaped single ion conductors based on polyacrylate ethers and lithium alkyl sulfonate

Comb-shaped single ion conductors have been synthesized by (1) sulfonation of small molecule chloroethyleneglycols, which, after ion exchange to the Li⁺ salt were then converted to the acrylate by reaction with acryloyl chloride and copolymerized with polyethylene glycol monomethyl ether acrylate (Mn = 454, n = 8) (PAE₈-co-E₃SO₃Li); (2) sulfonation of chloride end groups grafted on to prepolymers of polyacrylate ethers (PAE₈-g-E_nSO₃Li, n = 2, 3). The highest conductivity at 25 °C of 2.0 × 10⁻⁷ S cm⁻¹ was obtained for the PAE₈-co-E₃SO₃Li with a salt concentration of EO/Li = 40. The conductivity of PAE₈-g-E₃SO₃Li is lower than that of PAE₈-co-E₃SO₃Li at similar salt concentrations, which is related to the incomplete sulfonation of the grafted polymer that leads to a lower concentration of Li⁺. The addition of 50 wt.% of plasticizer, PC/EMC (1/1, v/v), to PAE₈-g-E₂SO₃Li increases the ambient conductivity by three orders of magnitude, which is due to the increased ion mobility in a micro-liquid environment and an increase concentration of free ions as a result of the higher dielectric constant of the solvent. A symmetrical Li/Li cell with an electrolyte membrane consisting of 75 wt.% PC/EMC (1/1, v/v) was cycled at a current density of 100 μA cm⁻² at 85 °C. The cycling profile showed no concentration polarization after a break-in period during the first few cycles, which was apparently due to reaction of the solvent at the lithium metal surface that reacted with lithium metal to form a stable SEI layer.