As modern society becomes more dependent on technology and more concerned about minimizing our impact on the environment, the need for reliable energy storage is becoming more and more important. Due to the reason of environmental concerns, batteries have become the dominant device for energy storage. Batteries are now expected to be able to power vehicles for the efficient use of energy[ Armand M, Tarascon JM. Nature 2008;451:652.], the efficient use of energy includes efficient storage of electricity, which means one needs to have high energy density batteries that have low energy losses during storage, electrical charging and discharging[ Wolfgang H. Meyer,”Polymer Electrolytes for Lithium-Ion Batteries”,Advanced Materials 1998,10,No.6.].
Since the introduction of the first generation rechargeable lithium battery by Sony in 1990, the performance of such batteries has improved significantly, especially in the auto industry[ Martinus Nijhoff, Dordrecht, “For a survey see for example: Solid State Batteries” (Eds: C. A. C. Sequeira, A. Hooper), NATO ASI Series E, Vol. 101, the Netherlands 1985]. Among all kinds of batteries, the lithium-ion battery is considered to be most promising and thus its development is significantly supported[ J. Krieger, Chem. Eng. News 1992, 16, 17].
Especially, the development of new and efficient solid state electrolytes plays an important role for the advances of lithium batteries. This report is focused on the subject of solid electrolytes of lithium-ion batteries. Lithium-ion batteries are now commonly used in consumer electronics, like laptops and mobile phones8. Figure 1.1 shows examples of different lithium ion batteries available in the market.
Figure 1.1 Examples of lithium-ion batteries[ Veidhes R. Basrur,”New Electrolyte and Electrode Materials for Use in Lithium- Ion Batteries”, University of Maryland, College Park,2010].
In order to know what exactly are these batteries, and what makes them so much better than everyday alkaline batteries, and more importantly, understand how solid state electrolytes work, we need to know the components and the function mechanism.
1.2 Structure of an Electrochemical Cell
A Li-ion battery is composed of two electrodes (cathode and anode), they are separated by electrolyte, Figure 1.2 shows the operation of a Li-ion cell. Upon discharge, lithium ions travel through the electrolyte from anode to cathode, the electron traveling in the external circuit is used to perform external work[ G.Ceder, G.Hautier, A.Jain and S.P.Ong, Recharging lihtium battery research with first principles methods, Materials Research Society, Volume 36, March 2011]. During charge, an external potential is applied, the process is reversed.
Fig1.2: Schematic of lithium battery[ Recent developments in lithium ion batteries, Masataka Wakihara, Materials Science and Engineering R33(2001)109-134]
The electrode materials are both lithium intercalation compounds. The most common used...