How to differentiate a time domain signal in the complex transfer function?
The transfer function is commonly defined as output divided by input, and not so often the other way around (as you did in your question). Also Matlab uses that more common definition. So the transfer function $H(s)$ between current $I(s)$ (input) and velocity $V(s)$ (output) would be defined by

$$H(s)=\frac{V(s)}{I(s)}\tag{1}$$

Since acceleration $A(s)$ is the derivative of velocity, we have

$$A(s)=sV(s)\tag{2}$$

Consequently, the transfer function between current and acceleration is

$$G(s)=\frac{A(s)}{I(s)}=\frac{sV(s)}{I(s)}=sH(s)\tag{3}$$