Kai Jia

Solid‐phase regeneration is widely considered as the most promising scalable approach for recycling spent LiFePO ₄ (S‐LFP) cathode. However, the sluggish defect‐repair kinetics in traditional solid‐phase routes remains mechanistically unclear, limiting the practical deployment of this technology. Here, theoretical calculations reveal that the phonon localization in defect‐rich S‐LFP is the essential factor responsible for the sluggish defect‐repair kinetics. Localized phonons retard thermal diffusion, hindering the energy available to overcome defect repair barriers, and concurrently intensify electron‐phonon coupling that suppresses the electron migration necessary for the reduction of Fe(III). Guided by this insight, we employ electric/thermal coupling field strategy to repair the S‐LFP cathode. Carriers driven by the electric field transfer energy to phonons through electron‐phonon scattering, which promotes energy redistribution across disparate phonon modes, collectively enhancing phonon delocalization. As a result, Li‐Fe antisites (Fe _Li ) were repaired within 5 s at 700°C, and the complete structural repair and lithiation are achieved within 60 s. Experimental results indicate that the regenerated cathode delivers a discharge specific capacity of 151.2 mAh g ⁻¹ at 0.1C, and exhibits a capacity retention of 84.3% after 1100 cycles at 1 C. This theoretical breakthrough establishes a solid theoretical foundation for developing advanced S‐LFP restoration technologies.

Solid‐phase regeneration is widely considered as the most promising scalable approach for recycling spent LiFePO ₄ (S‐LFP) cathode. However, the sluggish defect‐repair kinetics in traditional solid‐phase routes remains mechanistically unclear, limiting the practical deployment of this technology. Here, theoretical calculations reveal that the phonon localization in defect‐rich S‐LFP is the essential factor responsible for the sluggish defect‐repair kinetics. Localized phonons retard thermal diffusion, hindering the energy available to overcome defect repair barriers, and concurrently intensify electron‐phonon coupling that suppresses the electron migration necessary for the reduction of Fe(III). Guided by this insight, we employ electric/thermal coupling field strategy to repair the S‐LFP cathode. Carriers driven by the electric field transfer energy to phonons through electron‐phonon scattering, which promotes energy redistribution across disparate phonon modes, collectively enhancing phonon delocalization. As a result, Li‐Fe antisites (Fe _Li ) were repaired within 5 s at 700°C, and the complete structural repair and lithiation are achieved within 60 s. Experimental results indicate that the regenerated cathode delivers a discharge specific capacity of 151.2 mAh g ⁻¹ at 0.1C, and exhibits a capacity retention of 84.3% after 1100 cycles at 1 C. This theoretical breakthrough establishes a solid theoretical foundation for developing advanced S‐LFP restoration technologies.

Simultaneously achieving stable lithium metal batteries (LMBs) under cryogenic and high‐voltage conditions remains a fundamental challenge due to uncontrolled interfacial chemistry at lithium anodes and nickel‐rich cathodes. Here, we report an intramolecular polarization strategy that jointly regulates Li ⁺ solvation dynamics, solid electrolyte interphase (SEI) formation, and cathode electrolyte interphase (CEI) stress dissipation. An intramolecularly polarized electrolyte featuring orthogonally arranged electron donor–acceptor moieties with a dipole moment (∼4.2 D) establishes a potential–dependent solvation screening effect, reducing Li ⁺ desolvation energy to 38.1 kJ mol ⁻¹ , while enabling anodic stability beyond 5.3 V. The tailored solvation chemistry induces spontaneous formation of dual–gradient interphases composed of a LiF–rich SEI and a boroxane–incorporated CEI with an interface modulus ∼20 nN. Consequently, Li||Li symmetric cells exhibit stable cycling over 16 000 h with a minimal polarization of 8.3 mV. Full cells employing LiNi _0.8 Co _0.1 Mn _0.1 O ₂ cathodes retain 90% capacity after 1000 cycles at 4.5 V and maintain 80% at 4.9 V. 3 Ah pouch cells achieve a high energy density of 509 Wh kg ⁻¹ at 30°C with 96.8% capacity retention after 80 cycles, while delivering 439.1 Wh kg ⁻¹ at −30°C. This work establishes a molecular polarization paradigm for electrolyte and interphase engineering toward high–energy–density LMBs under extreme conditions.

The rapid growth of lithium‐ion batteries has intensified the need for efficient recycling of spent LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM) cathodes. However, direct regeneration is hindered by the high‐spin state of Ni ²⁺ ( S = 1) in degraded surface structures, which impedes Li ⁺ intercalation and limits repair efficiency. Here, we introduce a strong electronegative ligand field to modulate the surface NiO ₆ coordination environment, enabling precise regulation of Ni spin state and electronic structure. This strategy alters the occupancy of Ni e _g orbitals, converting high‐spin Ni ²⁺ (t _{2 g} ⁶ e _g ² , S = 1) to low‐spin Ni ³⁺ (t _{2 g} ⁶ e _g ¹ , S = 1/2) while downshifting the Ni d ‐band center. The resulting electronic reconfiguration weakens Ni‐Li interactions, enabling efficient lithiation and regeneration of the degraded NCM black mass. The regenerated cathode, when assembled into pouch cells, exhibits Ah‐level capacity with electrochemical performance comparable to commercial counterparts. This work establishes a direct correlation between Li ⁺ transport kinetics and the Ni spin‐state regulation, offering a new chemical paradigm for the direct regeneration of degraded cathodes.

The rapid growth of lithium‐ion batteries has intensified the need for efficient recycling of spent LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM) cathodes. However, direct regeneration is hindered by the high‐spin state of Ni ²⁺ ( S = 1) in degraded surface structures, which impedes Li ⁺ intercalation and limits repair efficiency. Here, we introduce a strong electronegative ligand field to modulate the surface NiO ₆ coordination environment, enabling precise regulation of Ni spin state and electronic structure. This strategy alters the occupancy of Ni e _g orbitals, converting high‐spin Ni ²⁺ (t _{2 g} ⁶ e _g ² , S = 1) to low‐spin Ni ³⁺ (t _{2 g} ⁶ e _g ¹ , S = 1/2) while downshifting the Ni d ‐band center. The resulting electronic reconfiguration weakens Ni‐Li interactions, enabling efficient lithiation and regeneration of the degraded NCM black mass. The regenerated cathode, when assembled into pouch cells, exhibits Ah‐level capacity with electrochemical performance comparable to commercial counterparts. This work establishes a direct correlation between Li ⁺ transport kinetics and the Ni spin‐state regulation, offering a new chemical paradigm for the direct regeneration of degraded cathodes.

Direct regeneration of spent lithium‐ion batteries offers economic benefits and a reduced CO₂ footprint. Surface prelithiation, particularly through the molten salt method, is critical in enhancing spent cathode repair during high‐temperature annealing. However, the sluggish Li⁺ transport kinetics, which predominantly relies on thermally driven processes in the traditional molten salt methods, limit the prelithiation efficiency and regeneration of spent cathodes. Here, we introduce a special molecular configuration (benzoate) into molten salts that facilitates rapid Li⁺ transport to the surface of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) via a quasi‐Grotthuss topochemistry mechanism. This approach effectively avoids the phase transitions that could adversely degrade the electrochemical performance due to insufficient lithiation during the repair process. Computational and experimental analyses reveal that the system enables fast Li⁺ migration through the topological hopping of benzoate in organic lithium salt, rather than relying solely on thermally driven diffusion, thereby significantly improving the prelithiation and repair efficiency of spent NCM cathodes. Benefiting from the quasi‐Grotthuss Li⁺ topochemistry transport, the degraded structure and Li vacancies in the spent cathode are effectively eliminated, yieding the regenerated cathode with good cycling stability comparable to commercial counterparts. The proposed Li⁺ transport mechanism presents a promising route for the efficient and sustainable regeneration of spent cathodes.

Direct regeneration of spent lithium‐ion batteries offers economic benefits and a reduced CO₂ footprint. Surface prelithiation, particularly through the molten salt method, is critical in enhancing spent cathode repair during high‐temperature annealing. However, the sluggish Li⁺ transport kinetics, which predominantly relies on thermally driven processes in the traditional molten salt methods, limit the prelithiation efficiency and regeneration of spent cathodes. Here, we introduce a special molecular configuration (benzoate) into molten salts that facilitates rapid Li⁺ transport to the surface of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) via a quasi‐Grotthuss topochemistry mechanism. This approach effectively avoids the phase transitions that could adversely degrade the electrochemical performance due to insufficient lithiation during the repair process. Computational and experimental analyses reveal that the system enables fast Li⁺ migration through the topological hopping of benzoate in organic lithium salt, rather than relying solely on thermally driven diffusion, thereby significantly improving the prelithiation and repair efficiency of spent NCM cathodes. Benefiting from the quasi‐Grotthuss Li⁺ topochemistry transport, the degraded structure and Li vacancies in the spent cathode are effectively eliminated, yieding the regenerated cathode with good cycling stability comparable to commercial counterparts. The proposed Li⁺ transport mechanism presents a promising route for the efficient and sustainable regeneration of spent cathodes.

Direct recycling technology can effectively solve the environmental pollution and resource waste problems caused by spent lithium‐ion batteries. However, the repaired LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (NCM) black mass by direct recycling technology shows an unsatisfactory cycle life, which is attributed to the formation of spinel/rock salt phases and rotational stacking faults caused by the in‐plane and out‐of‐plane migration of transition metal (TM) atoms during charge/discharge. Herein, local lattice stress is introduced into the regenerated cathode during repair. The resulting stress gradient leads to the localization of the phonon mode and changes the phonon dispersion relation of materials, lowers the bending and stretching vibration frequencies of the TM─O covalent bond in cathode materials, and inhibits the TM atoms migration and the formation of defect structures. Beneficial from the favorable low‐frequency phonon dispersion relation, the regenerated NCM represents remarkably enhanced structural stability during cycling, and exhibits good electrochemical performance. This reconstructed phonon dispersion relation approach broadens the perspective for lattice stress field engineering to suppress the defective structure raised from TM migration and paves the way for the development of regenerated cathodes with long durability.

The rapid growth of electric vehicle use is expected to cause a significant environmental problem in the next few years due to the large number of spent lithium‐ion batteries (LIBs). Recycling spent LIBs will not only alleviate the environmental problems but also address the challenge of limited natural resources shortages. While several hydro‐ and pyrometallurgical processes are developed for recycling different components of spent batteries, direct regeneration presents clear environmental, and economic advantages. The principle of the direct regeneration approach is restoring the electrochemical performance by healing the defective structure of the spent materials. Thus, the development of direct regeneration technology largely depends on the formation mechanism of defects in spent LIBs. This review systematically details the degradation mechanisms and types of defects found in diverse cathode materials, graphite anodes, and current collectors during the battery's lifecycle. Building on this understanding, principles and methodologies for directly rejuvenating materials within spent LIBs are outlined. Also the main challenges and solutions for the large‐scale direct regeneration of spent LIBs are proposed. Furthermore, this review aims to pave the way for the direct regeneration of materials in discarded lithium‐ion batteries by offering a theoretical foundation and practical guidance.

This paper investigates the turning method of fractional-order PID (FOPID) controllers based on neural networks with Borges derivative. The Borges derivative is applied to the controller structure and the turning of parameters in FOPID controllers. To ensure the Borges derivative can be applied for the negative real number as the independent variable, the improved Borges derivative is defined in this paper. Borges derivative is also used to update the coefficients and the orders of a novel type of FOPID controllers with the Borges difference and the Borges sum. In this paper, the selections of the orders in Borges derivative are discussed, and FOPID controllers based on neural networks are improved to gain the higher optimization speed and accuracy than that via the integer-order PID controllers. Finally, we give an example to verify the effeteness of turning method.