Quiz 2 Energy Storage and Materials

Lectures 5-7

What kind of system is Li/Sulfur?

Is a cathodic systsm

Li/S system has ______ phases

Many

For a multi-phase system such as Li/S, what would the discharge profile look like?

Why is sulfur a good cathode?

• has high specific capacity (1675 mAh/g) and 10x LCO

Why can sulfur be a bad cathode?

• Voltage is pretty low (2V)

• Doesn’t cycle as well and requires as Li metal anode

What kind of things must be transported between the cathode, anode and electrolyte?

Charge, e- and ions

equation to determine the V_cell in terms of IR

What can V_loss be attributed to?

Overpotential, polarization concentration, etc.

Why do devices lose voltage (V_loss)?

Devices try to keep up with transport, sacrificing voltage

Is there electron transport in an open electrolyte?

No, because electrolytes are electronically resistant

Considerations when picking an electrolyte

1. Hosts ionic species

2. Chemical stability

Solvent electrolytes should have a high or low voltage?

Low voltage, to prevent electrolysis from occuring

Large, polar, organic molecules are good electrolytes solvents because of _________ stability

voltage

The ideal electrolyte would look like:

A low-cost liquid that can solvate and lithiate Li, and has a low voltage and is stable

What is an important chemical requirement of a liquid electrolyte

It must not react chemically with any electrodes

Anode and cathode must be stable with liquid electrolyte

For a liquid electrolyte, what liquid should not be present?

Water! Moisture can cause issues and acidic formation of molecules like HF

Resistance

Resistive loss occurs within ion transport

The higher the current, the ______ the voltage drop

Higher, V and I are proportional