Li Metal‐Free Rechargeable Batteries Based on Li1 + x Mn2 O 4 Cathodes  ( 0 ≤ x ≤ 1 )  and Carbon Anodes

We show that the spinel , can also be used as the cathode in rechargeable rocking‐chair batteries based on lithium intercalation anodes (carbon, either graphite or petroleum coke). At room temperature, such cells show promising cycle life, an average open‐circuit voltage of 3.7 V and a specific energy of 250 Wh/kg of electrode materials . In addition, we report a novel easily reproducible solution technique for synthesizing , at low temperatures (<100°C), using as a mild reducing agent. The cycling behavior of rocking‐chair cells using this lithiated phase as the starting cathode is presented. appears to be a promising practical "air stable" Li‐bearing cathode for rocking‐chair‐type rechargeable cells.