Focused Practice

I. Answer the following questions:

1. What does the treatment of water by membrane technology imply?

2. What is a survival strategy in oligotrophic systems?

3. What will the organisms do when they colonize the surface?

4. When is the term “biofouling” applied?

5. Why if biofouling the “Achilles heel” of the process in membrane systems?

6. How is the biofouling potential represented?

II. Analyse the grammar structures underlined in the above text.

III. Speak on: The vertical transport vector.

Unit 16 Grammar: Modal Verbs Word List:

1. compatibility	совместимость
2. host	первичный материал, минерал-«хозяин»
3. a solid-state battery	твердотельная батарея
4. a voltage window (a voltage range)	диапазон напряжений
5. overcharge	избыточный заряд
6. availability	наличие
7. unstrained bonds	недеформированные связи (соединения)
8. both....and	как...так и; и...и
9. primarily	в первую очередь
10. until recently	до недавнего времени

What Materials Are Suitable as Polymer Electrolytes?

As the electrolyte must function as both a separator and an electrolyte in a solid-state battery (still seen as the major application for these materials), then a number of properties are critical for its success. The electrolyte must satisfy a minimum of requirements from an electrochemical point of view:

• Conductivity: the electrolyte must have sufficient ionic conductivity to allow a reasonable current density; 10 S/cm would be ideal at room temperature although a lower value may be acceptable (Armand originally quoted 10 S/cm minimum practical value).

• Electrochemical stability: the electrolyte should be electrochemically stable in a voltage window that is at least as wide as the voltage window defined by the electrode reactions (it should preferably be wider, to accommodate overcharge and discharge reactions).

• Compatibility: they must be chemically and electrochemically compatible with electrode materials.

• Thermal stability: electrolytes must have good thermal stability, especially in contact with a lithium electrode.

• Mechanical stability: the mechanical stability becomes important as battery technology moves from laboratory into process development, pilot production and, finally, full, production.

• Availability: raw materials must be readily available and inexpensive. Exotic materials have many uses as model compounds but may be impractical at a production level.

While many electrochemists throughout the 1980s preferred to study simple PEO-based polymer electrolyte systems using phase diagrams as a guide to suitable salt concentrations and temperature ranges, polymer chemists began to design more appropriate electrolyte constituents, primarily polymer hosts. The lain advantage of PEO as a host is it is chemically and electrochemically stable, since it contains only strong unstrained C-О, C-C, and C-H bonds. It is not surprising therefore that alternative host polymers have tended to incorporate ether units. It has perhaps been unfortunate that, with the bulk conductivity as the prime motivator of polymer electrolyte design, the other five factors listed above have not, until relatively recently, had the attention they deserve. As a result, the vast majority of alternative polymer hosts synthesized will have little practical application.