Dynamic Transport in Li‐Conductive Polymer Electrolytes Plasticized with Poly(ethylene glycol)–Borate/Aluminate Ester

Abstract

The addition of plasticizers into Li(+)-conductive solid polymer electrolytes (SPEs) is a commonly known technique to enhance the ionic conductivity. Among the used plasticizers, alkoxides of group-13 elements [such as poly(ethylene glycol) (PEG)-borate ester] are promising candidates due to the Lewis acidity of the elements of this group (i.e. B, Al, and so on), which interact with the anions and may increase the degree of dissociation of the salts and the transport number of the SPEs. By means of pulsed-gradient stimulated-echo NMR (PGStE-NMR) and AC impedance measurements, we investigate the effect of Lewis acidity originated from group-13 elements on the transport number and the dissociation rate of SPEs containing various plasticizers. Our results show that the degree of salt dissociation is significantly enhanced by the addition of plasticizers including group-13 elements, whereas only a small or negligible increase of the transport number is observed for these SPEs. We infer that the plasticizers exhibiting Lewis acidity associate with the anions, and that the associated pairs can migrate in the SPEs as fast as free anions, which results in a lower transport number than expected.

Salt-in-Polymer Electrolytes for Lithium Ion Batteries Based on Organo-Functionalized Polyphosphazenes and Polysiloxanes

“…Similar experiments combining related esters with other polymer electrolytes can be found in the literature [64][65][66]. The electron deficient boron atom acts as a Lewis acid and will therefore interact with Lewis bases and, in particular, with anions.…”

“…Apart from that, one observes a considerable concentration of undissociated ion pairs [23,24,66,84]. The typical transference numbers of lithium ions in such salt-in-polymer electrolytes are markedly below 0.5, typically 0.2-0.3 [84].…”

“…4 of Kunze et al [24]). Under these conditions, the net lithium ion transport in the steady state may be dominated by a coupled countertransport of ion pairs and anions (which show considerably faster diffusion than the lithium cations as proved by NMR measurements for polysiloxanes [23,24] and PEO [66]). Under these conditions, mass conservation leads to the following net partial current densities of cations and anions which include the a contribution of neutral ion pairs LiX (an extended treatment of the background within the framework of irreversible thermodynamics can be found in [85,86]):…”

Transport Mechanisms of Ions in Graft-Copolymer Based Salt-in-Polymer Electrolytes

“…Detailed characterizations were carried out by methods like infrared spectroscopy [29][30][31], nuclear magnetic resonance (NMR) [32][33][34][35][36][37][38][39][40] and viscosimetry [41][42][43][44] in order to clarify the interaction of the cations with a polymer network and their associated transport dynamics.…”

Development of nonflammable lithium ion battery using a new all-solid polymer electrolyte

“…The polymerization process of the monomer mixture was analyzed by DSC (Bruker AXS 3100SA) from a room temperature to about 120°C at heating rate 10°C/min under N 2 atmosphere putting a small amount of monomer mixture in a small aluminum-made sealed container with a very small hole in the top of the center part. CV measurement and AC impedance experiments besides NMR measurement were examined using similar techniques previously reported [11][12][13][14][15][16][17]. The SPE film (thickness, about 1 mm) was newly prepared for the measurements.…”