Collateral is the wrong term, apologies for that - what I mean is that expanded bank reserves can be used to back an expansion of credit from the bank in question.
In order to expand credit, banks need borrowers that demand credit. Never mind the number of reserves available if there is nobody asking for credit. That's the reason there is not inflation.
In the current economy, a reactivation of the economy have to come from government spending (fiscal policy). Central Banks (monetary policy) are powerless when the interest rate have gone all the way down.
