  We investigate the charging process of quantum battery (QB) systems in an
extended Dicke model with both atomic interactions and an external driving
field. We focus on the effects of the atomic interaction and the external
driving field on the charging performance of QB and find that the maximum
stored energy of QB has a critical phenomenon. We analyze the critical behavior
and obtain the analytical expression of the critical atomic interaction. The
dependence of the maximum stored energy, the energy quantum fluctuations and
the maximum charging power on the number $N$ of the two-level systems are also
discussed. In particular, for the maximum charging power, we obtain the quantum
advantage of the QB, which approximately satisfies a superlinear scaling
relation $P_{max}\propto N^{\alpha}$, where scaling exponent $\alpha$ varies
with the number $N$ of the two-level systems. In the ultra-strong coupling
regime, the atomic interaction can lead to a faster battery charging, and the
quantum advantage $\alpha = 1.88$ can be achieved. While in the deep-strong
coupling regime, the quantum advantage of the QB's maximum charging power is
the same as that of the Dicke QB, i.e., $\alpha=1.5$.
