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Survey of Types of Solid Electrolytes
Published in P.J. Gellings, H.J.M. Bouwmeester, Electrochemistry, 2019
One of the end members, NaZr2(PO4)3, itself has a framework structure provided with three-dimensional channels suitable for ionic conduction. However, its conductivity is not excellent (~10−4 S cm−1 at 300°C) because one of the two kinds of Na sites (Nal and Na2) along the conduction channel is preferentially occupied with Na+ ions and all are fixed at Nal. The structure of NASICON, rhombohedral at high temperature and monoclinic at low temperature, consists of a similar framework based on comer sharing of a ZrO6 octahedron with a PO4 or SiO4 tetrahedron, in which two kinds of Na sites exist, the Na2 sites being separated into two nonequivalent sites in the monoclinic form. As x is increased, the Na+ions also partially occupy Na2 sites, giving the compound a better conductivity. It is believed that diffusion takes place due to exchange of Na+ between Nal and Na2 sites. The maximum conductivity is obtained at x = 2, at which composition the activation energy for ionic conduction shows a minimum. Hydrothermally synthesized NASICON, with approximately this composition, shows a conductivity comparable with that of β″-alumina,74 as shown in Figure 6.8. A kink in the conductivity is due to the transition from monoclinic to rhombohe-dral. Though NASICON shows excellent conductivity, there is the problem that they are unstable with respect to liquid sodium.
Solid Polymer Electrolytes for Solid State Batteries
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Tariq Altalhi, Polymers in Energy Conversion and Storage, 2022
Anukul K. Thakur, Mandira Majumder, Archana Patole, Shashikant P. Patole
The NASICON kind of ceramics, that is Na ionic conductors, have garnered much attention of materials scientists owing to their properties, including remarkable stability, high ionic conductivity in ambient conditions, and practical applicability [63]. As a result of the replacement of Na by Li, NASICON-type materials, it was observed that the original morphology is retained together with conversion in an inorganic filler based on Li-ions [64, 65]. In general, these materials are denoted by the chemical formula LiM2(PO4)3, where filling of M sites is observed by Ge, Zr, or Ti. Zhai et al. [66] reported the production of SPCEs to where there was vertical alignment and connection between the NASICON-type ceramic Li1+xAlxTi2−x(PO4)3 (LATP). The matrix comprising PEO was considered as the ceramic structure with high porosity to introduce flexibility in the electrolyte membrane. In the mentioned research work, the nanoparticles of LATP were first dispersed in water, followed by deposition on a substrate. The ice was sublimated after, followed by sintering of the LATP particles and hence the formation of the channels, which were vertically aligned straightaway. As a result, Li-ion passageways were created by vertical arrangement and interwoven channels. Getting advantage from the proposed ice-template approach, Liao and co-workers introduced a different NASICON like ceramic, Li1.5Al0.5Ge1.5(PO4)3 (LAGP), effecting the creation of a vertically arranged polymer/ceramic composite electrolyte related to PEO [67]. To highlight the solid electrolyte with large, outstanding, satisfactory fracture resilience and mechanical strength simultaneously, Li et al. [68] made a composite exhibiting distinctive “brick-and-mortar” small-scale structures.
Effect of Nb substitution on structural, electrical and electrochemical properties of LiTi2(PO4)3 as electrolyte materials for lithium ion batteries
Published in Journal of Asian Ceramic Societies, 2018
M. Koteswara Rao, K. Vijaya Babu, V. Veeraiah, K. Samatha
Aono et al. and Good Enough et al. reported in 1976 a high ionic conducting skeleton structure having polyhedral units popularly known as NASICON (Na Super Ionic CONductors) [1,2]. The NASICON structure consists of a rigid (immobile) sub-array (sub-lattice) of ions which render a large number of three dimensionally connected interstitial sites suitable for long range motion of small monovalent cations. Since 1970, a good number of studies focusing on the synthesis and characterization of solid electrolytes appeared. Search for the lithium–ion conductors is motivated by the small ionic radii of lithium–ion by its lower weight, easy of handling and its potential use in high energy density batteries. Li2SiO4, LiZr2(PO4)3 and LiTi2(PO4)3 are some the earliest solid electrolytes which show high ionic conductivity and have been the subject of many interesting properties. Understanding of the structure, morphology and ion conduction in solid electrolyte materials is a challenge one. Among the various types of solid electrolytes, the NASICON-type materials have shown interesting features such as remarkable structure, good chemical stability, electrical and electrochemical properties and a promising material for solid electrolyte. In the present paper, we focused on structural, morphological, electrical and electrochemical properties of Nb-doped LiTi2(PO4)3 and the results are systematically discussed. From these studies, we report the high conductivity NASICON-type solid electrolyte material at x = 0 is 2.0715 × 10−6 which is in good agreement with previous result [3–8].