Lithium-Ion (and Lithium-Metal) Batteries

Flashcards based on lecture notes about Lithium-Ion and Lithium-Metal Batteries.

Why is Lithium (Li) preferred for batteries compared to Sodium (Na), Potassium (K), Magnesium (Mg) and Calcium (Ca)?

Li, Na, and K are easily ionized making them good charge carriers. Mg and Ca even more so, as they can store 2 charges per atom. Out of all of them, Li is the lightest!

What are the main components of a Li-ion battery?

Anode (Cu foil and active material e.g. graphite), Separator, Cathode (Al foil and active material e.g. LiCoO2), Electrolyte (Organic solvent and Li salt).

What is the role of the separator in a Li-ion battery?

An electrically insulating layer that separates the anode from the cathode, must be porous to allow Li ions to pass and not conduct electrons.

What is the purpose of the binder in a Li-ion battery?

The 'glue' used to hold the active material particles together and fix them onto a metal current collector foil.

What is the main requirement of an electrolyte in a Li-ion battery?

It needs to be stable at the potential of the cathode and anode.

Why are carbonates or ethers typically used as solvents for electrolytes?

Water is not a suitable electrolyte solvent because we are limited by the voltage of water splitting (1.23 V).

What is the Solid Electrolyte Interphase (SEI) in a Li-ion battery?

The layer of decomposition products formed at the surface of the electrode.

What are the characteristics of an ideal SEI?

High ionic conductivity, appropriate thickness, robust mechanical performance, and excellent stability during long-term cycling.

What is the most common anode material for Li-ion batteries?

Graphite.

What are the benefits of using Lithium metal as an anode?

Lithium metal is both the lightest material and the one with the lowest voltage.

What are the challenges associated with using Li metal as the anode?

Dendrite formation leading to short circuits and safety concerns.

What are the Li metal anode protection strategies?

Electrode structuring, electrolyte additives, solid electrolytes, and chemical pre-treatment.

How does structuring the electrode architecture help stabilize Li metal deposition?

Creating a larger surface area, providing porosity, and regulating localized current density.

What is the effect of salt anions in nonaqueous electrolytes on metallic Li anodes?

They strongly affect the surface chemistry of metallic Li anodes, and the composition is determined by the reduction of the anions present in solution.

Why are electrolyte additives used in Li-ion batteries?

To contribute to stable SEI formation.

What are the advantages of using solid electrolytes in Li-ion batteries?

Chemically stable, no leakage, safe, and prevent dendrite formation.

What are the challenges associated with solid inorganic electrolytes?

Brittle and poor interfacial contact with electrodes.

Why are metal oxides preferred for the cathode?

The highest voltage is given by metal oxides.

What are some common materials used as the cathode in Li-ion batteries?

Lithium cobalt oxide (LCO), Lithium nickel manganese cobalt oxides (NMCs), and Lithium iron phosphate (LiFePO4).

What are the advantages of Lithium iron phosphate (LiFePO4) cathodes?

Low cost, high thermal and chemical stability, environmentally friendly.

Why is it difficult to further increase the cell voltage of LIB cathodes?

Higher voltages will lead to electrolyte decomposition.

What is the operating principle of Li-S batteries?

Overall conversion occurs via the formation of polysulfides Li2Sx, 8<x<1.

What are the advantages of using Sulfur (S) as a cathode material?

High theoretical capacity, high theoretical specific energy, relatively lightweight, and sulfur is cheap.

What are the challenges of Li-S batteries?

Polysulfide shuttle effect, large volume expansion, slow kinetics, uncontrolled Li2S precipitation, and low electrical conductivity of sulfur.

How can uncontrolled dissolution and diffusion of polysulfides be suppressed?

Employing functional separators or designing cathode structures.

What role does carbon play in carbon-sulfur composite cathodes?

Provides conductivity, structural scaffold, trapping sites for S and polysulfides, and catalytic/functional surface.

What factors affect sulfur utilization in Li-S batteries?

Porosity, surface area, morphology, and electrolyte loading.

What is the key consideration to compete with current Li-ion technology?

It is essential to consider energy density when designing Li-S cells.

What are the different metrics used to measure battery performance?

Capacity, energy, Coulombic efficiency, life cycle stability, and rate performance.