  Lithium depletion and enrichment in the cosmos is not yet well understood. To
help tighten constraints on stellar and Galactic evolution models, we present
the largest high-resolution analysis of Li abundances A(Li) to date, with
results for over 100 000 GALAH field stars spanning effective temperatures
$5900\,\mathrm{K} \lesssim \rm{T_{eff}} \lesssim7000\,\mathrm{K}$ and
metallicities $-3 \lesssim \rm[Fe/H] \lesssim +0.5$. We separated these stars
into two groups, on the warm and cool side of the so-called Li-dip, a localised
region of the Kiel diagram wherein lithium is severely depleted. We discovered
that stars in these two groups show similar trends in the A(Li)-[Fe/H] plane,
but with a roughly constant offset in A(Li) of 0.4 dex, the warm group having
higher Li abundances. At $\rm[Fe/H]\gtrsim-0.5$, a significant increasing in Li
abundance with increasing metallicity is evident in both groups, signalling the
onset of significant Galactic production. At lower metallicity, stars in the
cool group sit on the Spite plateau, showing a reduced lithium of around 0.4
dex relative to the primordial value predicted from Big Bang nucleosynthesis
(BBN). However, stars in the warm group between [Fe/H] = -1.0 and -0.5, form an
elevated plateau that is largely consistent with the BBN prediction. This may
indicate that these stars in fact preserve the primordial Li produced in the
early Universe.
