Roger G. Linford

The effect of plasticiser on zinc polymer electrolytes

Abstract The compounds Eu x ZrSe 1.95 have been prepared by reaction of the zirconium diselenide and europium metal using the liquid ammonia technique. The 1T structural type of pristine ZrSe 1.95 is apparently retained for x lying in the range 0–0.40 (+/− 0.02). For x>0.40, Eu amide is formed. No significant change in the cell parameter values related to size effects is observed as x increases. From magnetic susceptibility measurements together with Mossbauer spectroscopy, discrete Eu 2+ and Eu 3+ valence states are evidenced. The question whether these compounds are real intercalation compounds is discussed.

Novel solid state polymeric batteries

Abstract AC conductivity measurements have been performed on a number of polymeric electrolytes containing Mg, Ca, Sr and Zn perchlorates and Mg and Ca thiocyanates. The electrolytes were characterised using DSC. Results are reported of preliminary tests of cells incorporating anodes of the above metals.

EXAFS and related studies of mixed ion polymer electrolytes

Abstract EXAFS studies on polymer electrolyte systems have provided a unique means of addressing local structure-conductivity relationships. Most polymer electrolytes are anion as well as cation conductors, but it is often desirable to enhance the cation contribution. Conductivity can be enhanced by plasticizers or alternatively by incorporation of two inorganic salts, rather than one, in the polymer matrix. Results are described for the following: (i) PEO 12 : (0.5 ZnBr 2 ), (0.5 CaBr 2 ); (ii) PEO 15 : (0.5 ZnI 2 ), (0.5 CaI 2 ); (iii) (PEO 8 : ZnCl 2 ), (0.7 ethylene carbonate); (iv) PEO 12 : (0.5 ZnBr 2 ), (0.5 ZnI 2 ).

EXAFS and thermal studies on zinc polymeric electrolytes

Abstract(PEO)n:ZnX2 (X = I, Br) complexes were formed at room temperature with values ofn ranging from 8 to 30. Differential scanning calorimetry (DSC) results indicate that none of them contained any crystalline phases that can be associated with the formation of a complex (i.e. it can be assumed that all the salt is in the amorphous phase). EXAFS studies carried out on these samples suggest that the zinc cation is co-ordinated to two of the halide ions and, in addition, to 4 oxygen atoms whereX = I and 6 oxygen atoms whereX = Br. The DSC results confirm that the zinc cation is in an environment independent of overall stoichiometry, as the glass transition temperatures of the samples were found to be similar throughout. By comparing these with those of annealed samples (made by heating the above samples to 150°C and cooling to −80°C at 320°C min−1) it was found that the stoichiometry of the amorphous phase was roughly 6∶1 forX=I and 8∶1 forX = Br.

Thermal history and polymer electrolyte structure: Implications for solid-state battery design

Abstract Studies on PEO/LiCF 3 SO 3 polymeric electrolytes using polarising microscopy, SEM/EDX, DSC and complex plane analysis show that thin electrolyte films prepared by slow evaporation from CH 3 CN solution are spherulitic in nature. More than one type of spherulite is present across the composition range and each spherulite type contains both amorphous and crystalline regions. The structural behaviour on heating and cooling is discussed with particular reference to electrolyte films of overall composition PEO 20 :LiCF 3 SO 3 . For these high ratio triflate films, in contrast to similar PEO/LiClO 4 films, high melting salt-rich regions are unexpectedly present in conjunction with low melting, low salt spherulites. No evidence is found for the presence of pure PEO spherulites, but the low melting spherulites may have a crystalline skeleton of pure PEO. Evidence is presented for the dependence of conductivity on thermal history.

EXAFS studies of divalent polymeric electrolytes: An investigation of PEO4:CaI2 at room temperature

Abstract The first EXAFS study of a divalent polymeric electrolyte film is reported. The samples were prepared and handled under conditions which do not exclude water. The results indicate an absence of ion pairing within the first two neighbour shells of the cation, and the probable presence of a cation hydration shell. The Ca 2+ ions are surrounded by 10 oxygen atoms as nearest neighbours.

Applications of solid state ionics for batteries

An overview is presented of solid state battery systems, especially those based on inorganic materials such as AgI, CuI and LiI. Emphasis is focussed on the structural and other modifications that are required to produce room temperature, compacted powder electrolytes with enhanced conductivity. The implications for primary batteries of discharge-induced changes of the local structure surrounding the mobile species are considered with reference to cuprous electrolytes. The use of these materials for other applications is discussed.

Structure-conductivity relationships in divalent polymer electrolytes

Abstract The potential influence of averaging caused by spherulite morphology on local structures deduced from EXAFS studies of crystallisable films is discussed. Evidence is presented to show that only high-melting, polymer-salt complexes interfere significantly with studies of the ionic environment within the amorphous conducting region. The possible modifications to the amorphous matrix that could result from the proximity of spherulites are considered. Results are presented for EXAFS studies of the local environment surrounding Zn in PEO n ·ZnBr 2 ( n =4, 8) prepared by three different drying procedures, at room temperature, -20°C and -70°C. Structural differences between amorphous and glassy forms were observed. The results suggest the presence of neutral ZnBr 2 entities.

Local structure studies of PEO-based NiBr2 electrolytes

Abstract The local atomic arrangements surrounding Ni(II) and Br(-I) in a high molecular weight PEO (mol.wt = 5 × 10 6 ) electrolyte of composition, NiBr 2 (PEO) 8 , were determined using K -edge EXAFS [Ni(II)] and AXS techniques [Br(-I)]. The results show that the first nearest neighbors of Ni(II) include, on average, four oxygens and two bromides, at distances from Ni(II) of 2.09 and 2.48 A, respectively. Around Br(-1) are, on average, one Ni(II) ion and four carbons at distances of 2.48 and 2.58 A, respectively. The two techniques yield consistent results and clearly show that ion pairing occurs in the electrolyte. The results indicate that Br(-I) ions are bonded more weakly in their local environments and thus likely to be more mobile than Ni(II) ions.

Changes in electrolyte structure in solid state cells during discharge: Extended x-ray absorption fine structure study

Abstract The first EXAFS study of a solid state battery system is reported. The working cell is based on a copper(I) iodide-sulphonium iodide electrolyte. The EXAFS results clearly indicate that cell modification occurs during cell discharge.