Lithium titanate nanotubes as active fillers for lithium-ion polyacrylonitrile solid polymer electrolytes

Mini-Review: Mixed Ionic–Electronic Charge Carrier Localization and Transport in Hybrid Organic–Inorganic Nanomaterials

“…The increment of conducting polymer electronic charge carriers near the interphase could be discussed in view of at least two eventual scenarios: (one or passive ) the dopant stabilizes at the interphase due to strong polar or coulombic interactions with nanoparticles surface, or/and (two or active ) the nanoparticles are also good electronic acceptors, producing in both cases an enhancement on the doping of nearby polymer chains, as schematized in Figure 1C (upper panel). On the other hand, micro-Raman imaging has also been useful to evidence the enhancement of ionic-pair dissociation occurring near the interphase with inorganic nanoparticles, in agreement with the increment of ionic conductivity (Romero et al, 2016 ; Pignanelli et al, 2018 , Pignanelli et al, 2019a ). Analogously, two different scenarios could be discussed for ionic charge carriers: (one or passive ) the counter-ion (in analogy to the dopant anion) stabilizes at the interphase due to strong polar or coulombic interactions with nanoparticles surface yielding an enhancement on the ionic-pair dissociation, or/and (two or active ) the nanoparticles may also possess mobile ionic carriers at the surface (e.g., active filler) that can be injected into the polymer, as schematized in Figure 1C (lower panel).…”

“…An example on the use of Raman imaging to monitor the state of charge for a Li 1−x (Ni y Co z Al 1−y−z )O 2 cathode is shown and described briefly in Figure 1B (Nanda et al, 2011 ). In addition, the use of micro-Raman imaging technique is highly powerful to study simultaneously both compositional and microstructural features, especially for hybrid inorganic–organic materials, as the characteristic Raman signals for inorganic and organic compounds generally lie well-separated at lower (ν < 800 cm −1 ) and higher (ν > 800 cm −1 ) wavenumbers, respectively (Romero et al, 2016 ; Mombrú et al, 2017a , b , c ; Pignanelli et al, 2018 , 2019a , b ). Furthermore, although Raman spectroscopy is quite sensitive to diluted effects such as doping processes of inorganic materials, it is on the other hand, extremely sensitive to doping effects of organic materials such as conducting polymers (Furukawa, 1996 ).…”

“…However, in consonance with the non-homogeneous localization of charge carriers discussed in the previous section, the presence of an organic–inorganic interphase can eventually activate another electronic or/and ionic pathway mediated through the interphase that could be passive or active (Irvine et al, 1990 ). For instance, solid polymer electrolytes with active inorganic nanofillers are the typical case of organic–inorganic interphase-mediated ionic transport (Zheng et al, 2016 ; Yang et al, 2017 ; Pignanelli et al, 2019a ), and a similar behavior will be observed for the electronic counterpart, if there are electronic interactions at the organic–inorganic interphase (Chen et al, 2010 ; Nowy et al, 2010 ; Cai et al, 2012 ; Mombrú et al, 2017b ). This effect, whose associated charge carrier pathway is represented by a curved line in Figure 2C , can also be eventually modeled with (or ) elements connected in series with the electronic (or ionic) part of the mixed ionic–electronic circuit, in analogy to (or ), respectively.…”

Development on Solid Polymer Electrolytes for Electrochemical Devices

“…The CSPE was more thermally stable and showed decreased crystallinity with higher ambient ionic conductivity (1.21 × 10 −4 S cm −1 ) and tensile strength (39.77 MPa) than filler-free electrolyte (σ = 4.72 × 10 −5 S cm −1 ; tensile strength = 38.41 MPa) [13]. Ionic conductivity of PANbased SPE has been shown to increase with the help of an active filler namely lithium titanate nanotubes (LiTNT) [161]. From the vibrational studies, Pignanelli and co-workers observed that the presence of LiTNT in SPE helped in the increment of lithium perchlorate dissociation, whereas the impedance spectroscopy showed two semicircles that are related to lithium-ion conductivity [161].…”

“…Ionic conductivity of PANbased SPE has been shown to increase with the help of an active filler namely lithium titanate nanotubes (LiTNT) [161]. From the vibrational studies, Pignanelli and co-workers observed that the presence of LiTNT in SPE helped in the increment of lithium perchlorate dissociation, whereas the impedance spectroscopy showed two semicircles that are related to lithium-ion conductivity [161]. The semicircle in the higher frequency region is accredited to the bulk resistance of lithium transport across the polymer matrix, whereas the second is ascribed to lithium transport through the interaction with the LiTNT [161].…”