L. Persi

Nanocomposite polymer electrolytes for lithium batteries

Ionically conducting polymer membranes (polymer electrolytes) might enhance lithium-battery technology by replacing the liquid electrolyte currently in use and thereby enabling the fabrication of flexible, compact, laminated solid-state structures free from leaks and available in varied geometries. Polymer electrolytes explored for these purposes are commonly complexes of a lithium salt (LiX) with a high-molecular-weight polymer such as polyethylene oxide (PEO). But PEO tends to crystallize below 60 °C, whereas fast ion transport is a characteristic of the amorphous phase. So the conductivity of PEO–LiX electrolytes reaches practically useful values (of about 10−4 S cm−1) only at temperatures of 60–80 °C. The most common approach for lowering the operational temperature has been to add liquid plasticizers, but this promotes deterioration of the electrolytes mechanical properties and increases its reactivity towards the lithium metal anode. Here we show that nanometre-sized ceramic powders can perform as solid plasticizers for PEO, kinetically inhibiting crystallization on annealing from the amorphous state above 60 °C. We demonstrate conductivities of around 10−4 S cm−1 at 50 °C and 10−5 S cm−1 at 30 °C in a PEO–LiClO4 mixture containing powders of TiO2 and Al2O3 with particle sizes of 5.8–13 nm. Further optimization might lead to practical solid-state polymer electrolytes for lithium batteries.

Role of the ceramic fillers in enhancing the transport properties of composite polymer electrolytes

A model to account for the role of the ceramic fillers in enhancing the transport properties of PEO-based composite polymer electrolytes is here proposed. The model is supported by a series of specifically addressed electrochemical tests which included the determination of the conductivity and of the lithium transference number of various composite electrolyte samples differing from the type of the surface states of the ceramic filler.

Impedance Spectroscopy Study of PEO‐Based Nanocomposite Polymer Electrolytes

The addition of nanometric fillers (e.g., , ) to polymer electrolytes induces consistent improvement in the transport properties. The increase in conductivity and in the cation transference number is attributed to the enhancement of the degree of the amorphous phase in the polymer matrix, as well as to some acid‐base Lewis type, ceramic‐electrolyte interactions. This model is confirmed by results obtained from a detailed impedance spectroscopy study carried out on poly(ethylene oxide) [P(EO)]‐based polymer electrolyte samples with and without ceramic fillers.

Transport and interfacial properties of composite polymer electrolytes

Lithium polymer electrolytes formed by dissolving a lithium salt LiX in poly(ethylene oxide) PEO, may find useful application as separators in lithium rechargeable polymer batteries. The main problems, which are still to be solved for a complete successful operation of these materials, are the reactivity of their interface with the lithium metal electrode and the decay of their conductivity at temperatures below 70°C. In this paper we demonstrate that a successful approach for overcoming these problems, is the dispersion of selected ceramic powders in the polymer mass, with the aim of developing new types of composite PEO–LiX polymer electrolytes characterized by enhanced interfacial stability, as well as by improved ambient temperature transport properties.

Enhancement of ion transport in polymer electrolytes by addition of nanoscale inorganic oxides

Abstract The effect of addition of nanoparticle inorganic oxides to poly(ethylene oxide) (PEO) complexed with LiClO 4 on cation transport properties has been explored by electrochemical and 7 Li nuclear magnetic resonance (NMR) methods. The presence of the nanoparticles generally increases the ionic conductivity and the cation transference number, the effect being greatest for TiO 2 . The enhancement in cation transference number is directly correlated with increased Li diffusivity measured by NMR. The NMR results also demonstrate that the increased ionic conductivity is not attributable to a corresponding increase in polymer segmental motion, but more likely a weakening of the polyether-cation association induced by the nanoparticles.

Nanocomposite polymer electrolytes and their impact on the lithium battery technology

Lithium polymer electrolytes formed by dissolving a lithium salt LiX in poly(ethylene oxide) PEO may find useful application as separators in lithium rechargeable polymer batteries. The main problems which are still to be solved for a complete successful operation of these materials are the reactivity of their interface with the lithium metal electrode and the decay of their conductivity at temperatures below 70°C. In this paper we demonstrate that a successful approach for overcoming these problems is the dispersion of selected, low-particle size ceramic powders in the polymer mass with the aim of developing new types of nanocomposite PEO-LiX polymer electrolytes characterized by enhanced interfacial stability as well as by improved ambient temperature transport properties.

Poly(ethylene oxide)-Based, Nanocomposite Electrolytes as Improved Separators for Rechargeable Lithium Polymer Batteries The Li / LiMn 3 O 6 Case

The synthesis and the properties of nanocomposite polymer electrolytes based on low-particle size fillers having a high concentration of surface states are reported. These electrolytes that are formed by dispersing Al 2 O 3 in a P(EO) 20 LiCF 3 SO 3 [PEO is poly(ethylene oxide)] matrix, show higher conductivity and, particularly, much higher lithium transference number than those of common, ceramic-free P(EO) 20 LiCF 3 SO 3 counterparts. These unique properties make the nanocomposite polymer electrolytes of particular interest as improved separators in novel types of lithium rechargeable batteries. This paper reports the performance of a battery using a P(EO) 20 LiCF 3 SO 3 + 10 wt % Al 2 O 3 as the polymer electrolyte and LiMn 3 O 6 as the cathode.

A LiTi2O4–LiFePO4 novel lithium-ion polymer battery

Abstract A new type of lithium-ion polymer cell based on a LiTi 2 O 4 anode, a LiFePO 4 cathode and a PVdF-based gel electrolyte is reported and discussed. The cell operates with a very flat voltage profile evolving around 2 V and cycles with negligible capacity fading and with a high rate. These features, combined with the low cost and the low toxicity of the components make the cell of practical interest as an inexpensive, disposable, thin-layer, plastic-like power source for the 1.5 V consumer electronic market.

Lithium insertion into carbonaceous materials and transition metal oxides from high performance polymer electrolytes

The electrochemical characteristics of gel-type polymer electrolyte membranes of interest for the development of plastic lithium ion batteries are presented and discussed. Particular attention is devoted to the interfacial behavior of both negative (i.e. carbonaceous materials) and positive (i.e. lithium transition metal oxides) electrodes.

Nuclear magnetic resonance studies of nanocomposite polymer electrolytes

The origin of the ionic conductivity enhancement in polymer electrolytes that occurs on adding inorganic oxide powders was explored by 1H and 7Li nuclear magnetic resonance. Ionic and molecular self-diffusion coefficients determined by pulsed field gradient spin-echo measurements demonstrate that lithium ionic diffusivity is enhanced in the composites, but this enhancement is not attributed to polymer segmental mobility. Two different systems were investigated: a high-molecular-mass poly(ethylene oxide)-LiClO4 complex with nanoscale TiO2; and a low-molecular-mass poly(ethylene glycol)-LiClO4 solution with Al2O3. In the latter case the effect of varying the alumina surface acidity or basicity was considered.