Why are two MOSFETs used in series in the Lithium-ion secondary battery protection circuit?

Two MOSFET are used to realize both the charge and discharge functions.

To realize both the charge and discharge functions, two MOSFET are used as shown in Fig. 1.

The case of only one MOSFET is used as shown in Fig. 2., even if the MOSFET is turned off, reverse current of MOSFET flow through the body diode in discharge of Lithium-ion secondary battery.
This case will not be a function as a charge-discharge switch.

Fig. 1: Circuitry with two MOSFET
Fig. 1: Circuitry with two MOSFET
Fig. 2: Circuitry using only one MOSFET
Fig. 2: Circuitry using only one MOSFET

Please also refer to the following page.

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