  In this paper we study the evolution of 7Li in the Galaxy considering the
contributions of various stellar sources: type II supernovae, novae, red giant
stars, and asymptotic giant branch (AGB) stars. We present new results for the
production of 7Li in AGB stars via the hot bottom burning process, based on
stellar evolutionary models by Frost (1997). In the light of recent
observations of dense circumstellar shells around evolved stars in the Galaxy
and in the Magellanic Clouds, we also consider the impact of a very high
mass-loss rate episode (superwind) before the evolution off the AGB phase on
the 7Li enrichment in the interstellar medium. We compare the Galactic
evolution of 7Li obtained with these new 7Li yields (complemented with a
critical re-analysis of the role of supernovae, novae and giant stars) with a
selected compilation of spectroscopic observations including halo and disk
field stars as well as young stellar clusters. We conclude that even allowing
for the large uncertainties in the theoretical calculation of mass-loss rates
at the end of the AGB phase, the superwind phase has a significant effect on
the 7Li enrichment of the Galaxy.
