Flattening of Lithium Plating in Carbonate Electrolytes Enabled by All-In-One Separator

Levelized Electrode Utilization of Silicon-Enriched Pouch-Type Lithium-Ion Batteries from External Stress-Induced Overpotential Modulation

The sectional utilization of the Si negative electrode resulted from the appropriate physical treatment of the pouch cell based on the distribution of electrical resistance. Active materials loaded near the tab have low electrical resistance, leading to a higher degree of lithiation in the Si near the tab. This localized utilization in large pouch cells causes significant polarization growth of the electrode due to mechanical and interphasial degradation. In contrast, the active material loaded farther from the tab does not participate in the electrochemical reaction due to its high electrical resistance. Li plating on near-tab-loaded particles arises from the inhomogeneous failure of the Si negative electrode in a large electrode, causing abrupt discharge capacity fading after cycling. However, the application of external pressure increases the overpotential of near-tab-loaded active materials by constraining their volumetric expansion. Therefore, applying external pressure equalizes the Si utilization across the pouch cell footprint through external stress-induced overpotential modulation, thereby mitigating the sectional failure of the Si negative electrode.

Underlying Mechanism of Electrolyte Compositional Engineering Based on Additive Solvation-Structure Governing Solid Electrolyte Interphase Formation in Lithium-Ion Batteries

Substantial efforts are dedicated to optimizing the additive dosage in the electrolyte and studying its effect on solid electrolyte interphase (SEI) formation in Li-ion batteries (LIBs). This study reveals that the decomposition characteristics of the additive based on its lithium-ion solvation nature significantly contribute to controlling SEI formation. During SEI formation, the strong lithium-ion solvating additive spontaneously migrates to the negative electrode due to negative charge accumulation on the surface, and SEI reinforcement is feasible by increasing the additive dosage. In contrast, population-based SEI formation occurs with a weaker solvating additive, so dosage-dependent modification of the SEI is not effective. These findings demonstrate that compositional electrolyte engineering based on the solvation properties of the additive can be more effective than empirical and experimental studies based on trial and error.

Reinforcement of Positive Electrode-Electrolyte Interface without Using Electrolyte Additives Through Thermoelectrochemical Oxidation of LiPF6 for Lithium Secondary Batteries

Owing to the limited electrochemical stability window of carbonate electrolytes, the initial formation of a solid electrolyte interphase and surface film on the negative and positive electrode surfaces by the decomposition of the electrolyte component is inevitable for the operation of lithium secondary batteries. The deposited film on the surface of the active material is vital for reducing further electrochemical side reactions at the surface; hence, the manipulation of this formation process is necessary for the appropriate operation of the assembled battery system. In this study, the thermal decomposition of LiPF6 salt is used as a surface passivation agent, which is autocatalytically formed during high-temperature storage. The thermally formed difluorophosphoric acid is subsequently oxidized on the partially charged high-Ni positive electrode surface, which improves the cycleability of lithium metal cells via phosphorus- and fluorine-based surface film formation. Moreover, the improvement in the high-temperature cycleability is demonstrated by controlling the formation process in the lithium-ion pouch cell with a short period of high-temperature storage before battery usage.

Lattice modulation strategies for 2D material assisted epitaxial growth

As an emerging single crystals growth technique, the 2D-material-assisted epitaxy shows excellent advantages in flexible and transferable structure fabrication, dissimilar materials integration, and matter assembly, which offers opportunities for novel optoelectronics and electronics development and opens a pathway for the next-generation integrated system fabrication. Studying and understanding the lattice modulation mechanism in 2D-material-assisted epitaxy could greatly benefit its practical application and further development. In this review, we overview the tremendous experimental and theoretical findings in varied 2D-material-assisted epitaxy. The lattice guidance mechanism and corresponding epitaxial relationship construction strategy in remote epitaxy, van der Waals epitaxy, and quasi van der Waals epitaxy are discussed, respectively. Besides, the possible application scenarios and future development directions of 2D-material-assisted epitaxy are also given. We believe the discussions and perspectives exhibited here could help to provide insight into the essence of the 2D-material-assisted epitaxy and motivate novel structure design and offer solutions to heterogeneous integration via the 2D-material-assisted epitaxy method.