Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of

Question

Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. Part A Calculate the mass percent lithium in LiMn2O4? Part B Calculate the mass percent lithium in LiCoO2? Part D In a battery that uses a LiCoO2 cathode approximately 50% of the lithium migrates from the cathode to the anode on charging. In a battery that uses a LiMn2O4 cathode what fraction of the lithium in LiMn2O4 would need to migrate out of the cathode to deliver the same amount of lithium to the graphite anode?

Explanation / Answer

molar mass of LiMn2O4 = 180.81 g/mol

molar mass of LiCoO2 = 97.87 g/mol

part A

mass of Li in 1 mol of LiMn2O4 is 6.94 g.

mass of 1 mol of LiMn2O4 is 180.81 g.

mass percent of Li in LiMn2O4 is = (6.94/180.81)x100 = 3.83 %

part B

mass of Li in 1 mol of LiCoO2 is 6.94 g.

mass of 1 mol of LiCoO2 is 97.87 g.

mass percent of Li in LiCoO2 is = (6.94/97.87)x100 = 7.09 %

part D

If 50% of Li migrates from 1 mol of LiCoO2 , then 6.94 /2 = 3.47 g of Li migrates to anode.

If same amount of Li has to migrate from LiMn2O4 toanode, then 3.47 g out of 6.94 g has to migrate.

3.47/6.94 = 0.5

so, again 50% of Li in LiMn2O4 would need to migrate out of the cathode to deliver the same amount of lithium to the graphite anode.

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