Quasi-Frobenius algebras in finite tensor categories

We introduce the notion of a quasi-Frobenius algebra in a finite tensor category $\mathcal{C}$ and give equivalent conditions for an algebra in $\mathcal{C}$ to be quasi-Frobenius. A quasi-Frobenius algebra in $\mathcal{C}$ is not necessarily Frobenius, however, we show that an algebra $A$ in $\mathcal{C}$ is quasi-Frobenius if and only if $A$ is Morita equivalent to a Frobenius algebra in $\mathcal{C}$. We also show that the class of symmetric Frobenius algebras in $\mathcal{C}$ is closed under the Morita equivalence provided that $\mathcal{C}$ is pivotal so that the symmetricity makes sense.