Absolutely‐Zero‐Expansion Behavior Enables Ultra‐Long Life for Stationary Energy Storage

Abstract

AbstractUltra‐long‐life (at least 10 000 cycles) lithium‐ion batteries are very effective for stationary energy‐storage applications. However, even “zero‐strain” materials with small unit‐cell‐volume changes of <1% cannot last for ultra‐long cycles due to gradually accumulated intracrystal strain/stress. Here, Li[Li0.2Cr0.4Ti1.4]O4 is explored as the first absolutely‐zero‐expansion material with unit‐cell‐volume variations of zero during Li+ storage. Its absolutely‐zero‐expansion mechanism is intensively studied, revealing that 16c‐octahedron shrinkage fully offsets 16d‐octahedron expansion through reversible O2− movement. It delivers better cycling stability than, as far as  we  know, all electrochemical energy‐storage materials previously reported. Its capacity retention at 10 C and 1.0 mg cm−2 after 17 000 cycles reaches 91.5%. When the active‐material loading significantly increases to 6.4 mg cm−2, its capacity retention at 5 C after 500 cycles reaches 95.7%. At an elevated temperature of 45 °C, it not only keeps excellent cycling stability but also exhibits significantly enhanced rate capability. Therefore, Li[Li0.2Cr0.4Ti1.4]O4 is especially suitable for stationary energy storage.