You might like this paper axil, a very good description of charge clusters.
The size of the space that is identified to hold 10^8 to 10^13 electons is 1.9x10^29 m-3. The impossibility to confine this density of an aggregation of electrons is a consequence of the coulomb barrier.
But LENR theorists wrongly insist that extremely high concentrations of electrons are possible. This paper uses the force that such a purported extreme concentration of electrons would trigger the fusion of deuterium. At the time that this paper was written, protium fusion was not widely recognized. This protium fusion is not possible. This removes the basic assumption of fusion as a cause of LENR as put forth by this paper.