Question Video: Identifying the Chemical Equation That Represents a Reaction at the Cathode of a Lithium Ion Battery | Nagwa Question Video: Identifying the Chemical Equation That Represents a Reaction at the Cathode of a Lithium Ion Battery | Nagwa

Question Video: Identifying the Chemical Equation That Represents a Reaction at the Cathode of a Lithium Ion Battery Chemistry • Third Year of Secondary School

The following reactions occur in at least one type of mass-manufactured battery. Which equation is related to the cathodic reaction of a lithium-ion battery? [A] LiC₆ (s) ⟶ C₆ (s) + Li⁺ (aq) + e⁻ [B] LiC₆ (s) + CoO₂ (s) ⟶ C₆ (s) + LiCoO₂ (s) [C] Pb (s) + H₂SO₄ (aq) ⟶ PbSO₄ (s) + 2H⁺ (aq) + 2e⁻ [D] CoO₂ (s) + Li⁺ (aq) + e⁻ ⟶ LiCoO₂ (s) [E] PbO₂ (s) + H₂SO₄ (aq) + 2H⁺ (aq) + 2e⁻ ⟶ PbSO₄ (s) + 2H₂O (l)

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Video Transcript

The following reactions occur in at least one type of mass-manufactured battery. Which equation is related to the cathodic reaction of a lithium-ion battery? (A) LiC6 solid reacts to form C6 solid plus Li1+ aqueous plus one electron. (B) LiC6 solid plus CoO2 solid react to form C6 solid plus LiCoO2 solid. (C) Pb solid plus H2SO4 aqueous react to form PbSO4 solid plus two H+ aqueous plus two electrons. (D) CoO2 solid plus Li1+ aqueous plus one electron react to form LiCoO2 solid. (E) PbO2 solid plus H2SO4 aqueous plus two H+ aqueous plus two electrons react to form PbSO4 solid plus two H2O liquid.

Galvanic cells are electrochemical cells that produce electrical energy from spontaneous chemical reactions. There are two types of galvanic cells: primary and secondary. Primary galvanic cells are only for single use, but secondary galvanic cells can be recharged. Secondary galvanic cells can run as both a galvanic and electrolytic cell. Examples of batteries that are secondary galvanic cells include lithium-ion batteries and lead–acid car batteries. In this question, we need to determine the chemical reactions that occur inside a lithium-ion battery.

When looking at the reactants and products in chemical equations (C) and (E), we can recognize that these reactions occur in lead–acid car batteries, not lithium-ion batteries. So let’s go ahead and eliminate these two answer choices and clear them from the screen.

Now, we need to determine which of the remaining answer choices represents the cathodic reaction inside a lithium-ion battery. Let’s take a look inside a lithium-ion battery while it’s running as a galvanic cell, which means it is discharging and powering an external device. In the galvanic cell, the anode is made of lithium graphite, or LiC6. The cathode is made of lithium cobalt oxide, or LiCoO2. The electrolyte liquid inside the cell is lithium hexafluorophosphate, or LiPF6. Knowing this allows us to eliminate answer choice (A), because the reaction shown involves the anode, not the cathode.

At the anode inside the battery, lithium graphite is oxidized, releasing lithium ions and electrons. Electrons flow through the circuit to power an external device, and lithium ions flow from anode to cathode inside the cell. At the cathode, the lithium ions accept electrons and are therefore reduced, as they combine with cobalt oxide to form lithium cobalt oxide. We can see that equation (D) represents this reduction reaction at the cathode and must be the correct answer. However, let’s take a quick look at equation (B). Equation (B) represents the overall reaction during discharging, when the galvanic cell is running.

So which equation is related to the cathodic reaction of a lithium-ion battery? The answer is equation (D). CoO2 solid plus Li1+ aqueous plus one electron react to form LiCoO2 solid.

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