and have been characterized as high energy density rechargeable positive electrodes for moderate‐temperature Na batteries of the configuration, , . The batteries operate in the temperature range 170°–190°C. Positive electrode reactions during discharge/charge cycles have been characterized. Excellent rechargeability of the batteries has been demonstrated by extended cell cycling. A cell, operating at 190°C, exceeded 600 deep discharge/charge cycles with practically no capacity deterioration. The feasibility of secondary batteries with specific energies ≥ 50 Wh/lb and cycle lifes exceeding 1000 deep discharge/charge cycles has been demonstrated.