tell me

E⁰cell is a standard value for any two half-cells, just like co-efficient of friction [1].

At equilibrium,concentration of both reactants and products becomes
same.=>Reduced and Oxidised products are in equal quantity. and since equilibrium is directly realted to stablity,so reaction within cell
ceases and cell stops producing emf(becoz reactants and products would not like to lose equilibrium condition).=>E_cell=0
whereas E° is a combined characteristic feature of the cations and
anions present within the cell.It is calculated theoritically and so
it exists even at equilibrium becoz it is independent of reaction
kinetics....

In a nutshell at equilibrium net work done by cell is ZERO ,so
E_cell=0

I may be wrong with what i just said...........so plzzzzzzz dont get angry with me.......[1]