Date | May 2009 | Marks available | 2 | Reference code | 09M.3.sl.TZ2.C3 |
Level | SL | Paper | 3 | Time zone | TZ2 |
Command term | Describe | Question number | C3 | Adapted from | N/A |
Question
The high activity of lithium metal leads to the formation of an oxide layer on the metal which decreases the contact with the electrolyte in a battery.
Describe how this is overcome in the lithium-ion battery.
Describe the migration of ions taking place at the two electrodes in the lithium-ion battery when it produces electricity.
Anode (–):
Cathode (+):
Discuss one similarity and one difference between fuel cells and rechargeable batteries.
Similarity:
Difference:
Markscheme
contains no lithium/metal / uses lithium salt in an organic solvent (as electrolyte);
involves movement of lithium ions (between electrodes);
Anode (–):
\({\text{Li}}{{\text{C}}_{\text{6}}} \to {\text{L}}{{\text{i}}^ + } + {\text{6C}} + {{\text{e}}^ - }/{\text{L}}{{\text{i}}^ + }\) ions dissociate from anode (and migrate to cathode);
Cathode (+):
\({\text{L}}{{\text{i}}^ + } + {{\text{e}}^ - } + {\text{Mn}}{{\text{O}}_{\text{2}}} \to {\text{LiMn}}{{\text{O}}_{\text{2}}}\) / \({\text{L}}{{\text{i}}^ + } + {{\text{e}}^ - } + {\text{Co}}{{\text{O}}_{\text{2}}} \to {\text{LiCo}}{{\text{O}}_{\text{2}}}\) / \({\text{L}}{{\text{i}}^ + } + {{\text{e}}^ - } + {\text{FeP}}{{\text{O}}_{\text{4}}} \to {\text{LiFeP}}{{\text{O}}_{\text{4}}}\) / \({\text{L}}{{\text{i}}^ + } + {{\text{e}}^ - } + {\text{Ni}}{{\text{O}}_{\text{2}}} \to {\text{LiNi}}{{\text{O}}_{\text{2}}}\) / \({\text{L}}{{\text{i}}^ + }\) ions are inserted into metal oxide/phosphate (structure);
Award [1] if electrodes are reversed.
Similarity:
both convert chemical energy directly into electrical energy / both use spontaneous redox reactions (to produce energy) / both are electrochemical cells/voltaic cells/galvanic cells;
Difference:
fuel cells are energy conversion devices and rechargeable batteries are energy storage devices / fuel cells require constant supply of reactants and batteries have stored chemical energy/provide power until stored chemicals are used up / batteries can be recharged and fuel cells do not need recharging (have a continuous supply of fuel) / fuel cells are more expensive than rechargeable batteries / the reactions in a rechargeable battery are reversible and in a fuel cell are not;
Examiners report
Only the better candidates described how the lithium-ion battery overcomes the reactivity of lithium.
The description of the migration of ions was poor.
The similarity and difference of fuel cells and rechargeable cells had better resposes.