Zeolites as Solid Electrolytes in Batteries

Aluminosilicate zeolites because of their structure, composition, and properties offer a superior ionic strength environment [172,173], Even though these materials are electronic insulators, when hydrated, they are solid solutions of high ionic mobility, and when dehydrated exhibit fair ionic conductivity (see Section 8.2.7) [38,112,119,172], The properties of aluminosilicate zeolites that are responsible for affecting the charge-transfer reactions in electrochemical systems are [172,174]  

The Physical Chemistry of Materials Energy and Environmental Applications 

When zeolites are hydrated shows a notable ionic conductivity [112], Consequently, since all electrode processes depend on the transport of charged species zeolites provide an excellent solid matrix for ionic conduction [172], In 1965 [175], Freeman established the possibility of using zeolites in the development of a functional solid-state electrochemical system, that is, a battery where a zeolite, X, was used as the ionic host for the catholyte, specifically, Cu2, Ag+, or Hg2+, and as the ionic separator in its sodium-exchanged form, that is, Na-X. Pressed pellets of Cu-X and Na-X were sandwiched between a gold current collector and a zinc anode. Then, the half-cell reactions are the oxidation of Zn — Zn2+ + 2e and the reduction of Cu2+ + 2e — Cu, with type X providing a solid-state ionic path for cationic transport [175], The electrochemical system obtained can be represented as follows (Au I Cu11 -XI Na-X I Zn). 

The role of zeolites as solid electrolytes is linked to water adsorption in the zeolite secondary porosity (see Section 8.2.7), which can be evidenced in the use of natural or synthetic zeolites as solid electrolytes, since the cationic conduction of zeolites is highly enhanced by the adsorption of water in the secondary porosity [112], 

Zeolite-based solid electrolytes have been used in the manufacture of Li secondary batteries with the zeolite acting as the host for Li ions [174,176], These materials were applied as hosts for Zn11, in Zn-Mn02 batteries [177], and in Pb11 in lead acid batteries [178]. 

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