The synthesis of cathode materials plays an important role in determining the production efficiency, cost, and performance of lithium‐ion batteries. However, conventional synthesis methods always experience a slow heating rate and involve a complicated multistep reaction process and sluggish reaction dynamics, leading to high energy and long time consumption. Herein, a high‐temperature shock (HTS) strategy is reported for the ultrafast synthesis of cathode materials in seconds. The HTS process experiences an ultrahigh heating rate, leading to a non‐equilibrium reaction and fast reaction kinetics, and avoids high energy and long time consumption. Mainstream cathode materials (such as LiMn2O4, LiCoO2, LiFePO4, and Li‐rich layered oxide/NiO heterostructured material) are successfully synthesized with pure phases, oxygen vacancies, ultrasmall particle sizes, and good electrochemical performance. The HTS process not only provides an efficient synthesis approach for cathode materials, but also can be extended beyond lithium‐ion batteries.

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Global energy crisis and environment pollution have raised ever-growing demand for high-performance energy-storage devices. Supercapacitors (SCs) with fast recharge capability, high power density, and long cycling stability are considered one type of the most promising nextgeneration energy-storage devices. [1,2] Activated porous carbon (APC) with outstanding electrical conductivity, porous structure, and large surface area is the primary electrode materials for SCs. [3] However, the low-energy density of SCs limits their practical application. [4][5][6][7] Generally, APC is prepared by combined carbonization-activation strategies under acidic, alkaline, CO 2 /steam, or other environment at high temperature for a long time. [8,9] To improve the performance of APCbased SCs, a series of strategies have been proposed, such as optimizing the size and distribution pores, [10,11] and impurity doping (N, O, B, S, P) to tune the internal and surface charge properties. [12][13][14][15][16][17][18][19][20][21] These strategies can significantly improve the performance of APC-based SCs under the conditions of long processing time, high temperature, and complex preparation process. These critical conditions can adversely affect the structure of APCs, such as the loss of N and O, which limits the further improvement of the electrochemical performance. Therefore, there is an urgent need for efficient, stable, and safe strategies that can simultaneously optimize the structure of APCs, enlarge the specific surface area, while retain the loss of doping elements.Herein, we propose a strategy to transfer general-purpose carbon into high-energy density SCs carbon with ultrafine structure including high specific surface area and N, O functional groups, within ultrashort time of ≈13 s. [22][23][24][25][26] Typically, APC manufactured by long-term and high-temperature heat treatment of raw carbon (RC) in a tubular furnace (TF) with small amount of N, O element and uneven pores, which has small specific surface area (Figure 1a). By rapid joule heating and subsequent ultrafast cooling (high-temperature shock, HTS), general-purpose carbon can be processed into ultrafine structure with enormous N, O functional groups Supercapacitor (SC) is one of the most promising electrochemical energy-storage devices. However, the practical application of SCs is limited by the low-energy density. Herein, high-temperature shock (HTS)-derived ultrafine structure-activated porous carbon (UAPC) with N, O functional groups is reported as highenergy density SCs carbon. The process of ultrafast joule heating and cooling effectively transfers general-purposed carbon into electrochemical-activated carbon. The UAPC-based SCs exhibit an energy density of up to 129 Wh kg −1 in EMIMBF 4 ionic liquid, which outperform almost all reported and commercial SCs (22 Wh kg −1 ). The outstanding electrochemical performance of UAPC is attributed to the ultrafine structure and N, O functional groups, which enlarges the surface area, improves the surface wettability of UAPC ele...

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