Lithium Metal Polymer Batteries Research Articles

Electrochemical characteristics of multi-functional polymer electrolyte based on dual-layer membrane for lithium metal polymer battery

A novel dual-layer type polymer electrolyte was prepared by impregnating the interconnected pores with an ethylene carbonate(EC)/dimethyl carbonate(DMC)/lithium hexafluorophosphate(LiPF 6) solution. An incompatible layer is based on a micro-porous polyethylene(PE) and a compatible layer, based on a poly(vinylidenefluoride-co-hexafluoropropylene)(P(VdF-co-HFP)), is submicro-porous and compatible with an electrolyte solution. To enhance the ionic conductivity in the compatible layer, inorganic type Li + single ion conductor particle based on hydrophilic silica has been synthesized. The maximum apparent ionic conductivity of the dual-layer polymer electrolyte is 7.7 × 10 −3 S/cm at the ambient temperature. High rate capability of the Li/the dual-layer polymer electrolytes/Li[Ni 0.15Li 0.23M n0.62]O 2 cell was significantly improved as the incompatible layer thickness decreases.

Recent developments in the ENEA lithium metal battery project

Solvent-free P(EO) 20LiTFSI + PYR 14TFSI polymer electrolyte films with PYR 14 +/Li + mole ratios ranging from 0.96 to 3.22 were prepared by hot-pressing mixtures composed of PEO, LiTFSI and PYR 14TFSI of selected stoichiometries. The PYR 14TFSI room temperature ionic liquid (RTIL) is homogeneously incorporated into the P(EO) 20LiTFSI membrane without phase separation. For a PYR 14 +/Li + mole ratio of 3.22, the ionic conductivity was about 2 × 10 −4 S/cm at 20 °C, i.e., more than one order of magnitude higher than that of the RTIL-free electrolyte. The electrochemical stability window of the polymer electrolyte containing the RTIL was about 6 V (versus Ag/Ag +). Li/V 2O 5 cells with the polymer electrolyte (PYR 14 +/Li + = 1.92) showed a 60% capacity retention after 80 cycles at 40 °C (the initial capacity was 210 mA h/g). Li/V 2O 5 cells (PYR 14 +/Li + = 1.28) held at 30 °C delivered about 93 mA h/g (at 0.057 mA/cm 2), which corresponds to approximately 34% utilization of the active material. These results suggest that the incorporation of the RTILs into PEO-based polymer electrolytes is very promising for the future realization of solid-state lithium metal polymer batteries operating near ambient temperatures.

Preparation and Characterization of Asymmetric Composite Polymer Electrolytes for Lithium Metal Polymer Batteries

An asymmetric composite polymer electrolyte composed of porous polymer matrix which micro-porous layer based on the polyethylene acts as a support and submicro-porous layer is introduced on one side of the micro-porous layer through a coating process and ethylene carbonate/dimethyl carbonate/LiPF6 liquid solution occupying the pores has been prepared. The maximum ionic conductivity of this system was 7.0 × 10-3 S/cm at the ambient temperature. The conductivity seems to be significantly affected by the uptake amount of liquid electrolyte within the matrix.

Towards room-temperature performance for lithium–polymer batteries

Recent work on molecular simulations of the mechanisms of lithium ion conductance has pointed towards two types of limiting process. One has involved the commonly cited segmental motion while the other is related to energy barriers in the solvation shell of polymeric ether oxygens around the lithium ions. Calculations of the barriers to lithium ion migration have provided important indicators as to the best design of the polymer. The theoretical work has coincided with and guided some recent developments on polymer synthesis for lithium batteries. Structural change of the polymer solvation shell has been pursued by the introduction of trimethylene oxide (TMO) units into the polymer. The conductivity measurements on polymers containing TMO unit are encouraging. The architecture of the polymer networks has been varied upon which the solvating groups are attached and significant improvements in sub-ambient performance are observed as a result. However, the above-ambient temperature performance appears controlled by an Arrhenius process that is not completely consistent with the theoretical calculations described here and may indicate the operation of a different mechanism. The new polymers possess significantly lower T g values in the presence of lithium salts, which indicates weaker binding of the lithium ions by the polymers. These properties provide considerable improvement in the transport properties close to the electrode surfaces resulting in decreased impedances at the surfaces both at lithium metal and in composite electrodes. The greater flexibility of the solvation groups combined with appropriate architecture not only has applications in lithium metal–polymer batteries but also in lithium ion liquid and gel systems as well as in fuel cell electrodes.

Improved composite materials for rechargeable lithium metal polymer batteries

Abstract The performance of several polymer electrolytes for lithium metal batteries for electric vehicle applications are reported. The best performing electrolyte is the composite PEO 20 LiCF 3 SO 3 –γLiAlO 2 , which was prepared by a solvent-free procedure. It showed coulombic efficiency values of the lithium deposition–stripping process of 94%–96%. Electrochemical tests of lithium polymer battery (LPB) prototypes based on a 3 V LiMn 2 O 4 composite cathode material laminated together with the PEO 20 LiCF 3 SO 3 –γLiAlO 2 electrolyte gave promising results for electric vehicle applications. Even under non-optimized battery design, the prototypes delivered, at the C/3 rate and at 94°C, 40%–30% of theoretical capacity over 100 charge–discharge cycles.

An Improved Composite Polymer Electrolyte for Lithium Metal Batteries

ABSTRACTWe have demonstrated that PEO-based polymer electrolytes prepared by solvent-free procedures and with the addition of particle-size ceramic powder have very stable lithium interface properties—a very important feature for the development of successful lithium metal polymer batteries (LPBs). The results of cyclability tests at different charge-discharge rates carried out on prototypes of LPBs assembled with the dry prepared PEO20-LiCF3SO3-20%w/w λLiAlO2 composite electrolyte and with a composite cathode based on LiMn204 spinel operating at 3V are reported and discussed.