  An explanation is provided for the heavy quasiparticle excitations in
LiV_2O_4. It differs considerably from that of other known heavy-fermion
systems. Main ingredients of our theory are the cubic spinel structure of the
material and strong short-range correlations of the d electrons. The large
gamma-coefficient is shown to result from excitations of Heisenberg spin 1/2
rings and chains. The required coupling constant is calculated from LDA+U
calculations and is found to be of the right size. Also the calculated
Sommerfeld-Wilson ratio is reasonably close to the observed one.
