900°C thermal-force coupling carbonization tailoring hard carbon microstructures enables high performance sodium-ion...

Hard carbon materials are promising candidates for advancing large-scale energy storage in sodium-ion batteries. However, a fundamental trade-off often exists between sodium storage sites and fast diffusion kinetics in hard carbon. Herein, we overturn this long-standing constraint through a machine learning design paradigm and low-temperature thermal-force coupling carbonization that enables the microstructure in hard carbon of both abundant sodium storage sites and rapid Na⁺ diffusion. Benefiting from this low-temperature construction, the sodium-ion pouch cell exhibits a high specific energy (based on the entire cell) of 208.1 Wh kg^-1 at 1.5-4.3 V. Besides, the required carbonization temperature reduces from 1300 °C to 900 °C, leading to an energy consumption reduction of 49.7% and a carbon emission reduction of 47.5%. This work not only provides a double-field regulation strategy to prepare high-performance hard carbon under low temperature, but also contributes a viable pathway toward sustainable sodium-ion batteries.