Mobility management is an important part of the analysis and design of ultra-dense LiFi networks. This paper thus presents a two-tier LiFi network and analyses the cross-tier handover rate between the primary and secondary cells. For different conditions of semiangle at half illuminance of the primary and secondary cells, we propose three different coverage models for the secondary cells. Using stochastic geometry, closed-form expressions are derived for the cross-tier handover rate, ping-pong rate, and sojourn time in terms of the received optical signal intensity, time-to-trigger, and user mobility. The analytical models are validated with simulation results.