Battery module and assembled battery

A battery module (100) comprises a lithium-ion secondary battery (200) and a control circuit (300). The control circuit (300) has: a measurement unit (310) for measuring the charging/discharging voltage, current and time of the lithium-ion secondary battery (200); a calculation unit (320) for calculating a capacity (Q) on the basis of the voltage, current, and time and calculating a differential value (dQ/dV) obtained by differentiating the capacity (Q) with respect to voltage (V); a threshold voltage setting unit (330) for identifying a peak of the differential value (dQ/dV) on the low capacity side, said peak being generated based on the stage structure of graphite, and for setting the voltage at the peak to a threshold voltage; a termination voltage setting unit (340) for, based on the threshold voltage, setting a discharging termination voltage of the lithium-ion secondary battery (200); and a charging/discharging control unit (360) for, based on the discharging termination voltage, controlling the chargi