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The microstructure of an electrode plays a critical role in the electrochemical performance of lithium‐ion batteries, including the energy and power density. Using a micrometer‐scale Wadsley–Roth phase TiNb2O7 active material with Li intercalation chemistry as a model system, the relationship between electrochemical performance and microstructure of calendared electrodes with same mass loading but different electrode parameters is studied by both experimental investigation and theoretical modeling, providing a paradigm of calendaring‐driven electrode microstructure for balanced battery energy density and power density. Along with the reduction in porosity, ion and electron diffusion distance decreases, which is beneficial for charge transfer and rate capability. Nevertheless, the narrowed ion diffusion pathway increases the resistance for ion diffusion. The rate capability, volumetric capacity, and materials utilization are thus predominantly restricted by the microstructures of the electrode, providing fundamental insights into electrode microstructure design for different applications. As an example, an optimized TiNb2O7 electrode with compaction density of ≈2.5 g cm‐3 and mass loading of ≈8.5 mg cm‐2 provides the highest specific charge capacity of 271.3 mAh g‐1 at 0.2 C in half cell configuration and 70.4% capacity retention at 6 C in full configuration, enabling balanced energy density and power density of batteries. [ABSTRACT FROM AUTHOR]

The electrode–electrolyte interface is one of the major components enabling Li‐ion batteries (LIBs) to function reversibly. Often, the solid–electrolyte interphase (SEI) at the anode is regarded as the key interface that determines the cycle life, capacity fade, and overall safety of batteries. There are a plethora of SEI literatures that exist; however, the cathode–electrolyte interphase (CEI) remains relatively unexplored. Unlike in the case of SEI, a detailed understanding of CEI formation and its association with battery performance is not present. This review gives insight into the recent progress in understanding the CEI in LIBs. Though there is a relative dearth of literature, the CEI is generally considered as a heterogeneous multicomponent film formed due to the decomposition of electrolyte at the cathode surface. Besides understanding the thermodynamic properties and relevant kinetic reactions, one of the main challenges lies in developing and stabilizing the CEI layer due to its complex structural composition. Extensive research efforts to engineer a stable CEI are reviewed, including the use of electrolyte additives, artificial engineering, and heteroatom doping of cathode. Furthermore, promising characterization techniques and future outlook in forming a robust CEI for both existing LIB and post‐LIB systems are highlighted. [ABSTRACT FROM AUTHOR]

SiO–based materials are promising alloys and conversion‐type anode materials for lithium‐ion batteries and are recently found to be excellent dendrite‐proof layers for lithium‐metal batteries. However, only a small fraction of the Li–Si–O compositional space has been reported, significantly impeding the understanding of the phase transition mechanisms and the rational design of these materials both as anodes and as protection layers for lithium‐metal anodes. Herein, we identify three new thermodynamically stable phases within the Li–Si–O ternary system (Li2SiO5, Li4SiO6, and Li4SiO8) in addition to the existing records via first‐principle calculations. The electronic structure simulation shows that Li2SiO5 and Li4SiO8 phases are metallic in nature, ensuring high electronic conductivity required as electrodes. Moduli calculations demonstrate that the mechanical strength of Li–Si–O phases is much higher than that of lithium metal. The diffusion barriers of interstitial Li range from 0.1 to 0.6 eV and the interstitial Li hopping serves as the dominating diffusion mechanism in the Li–Si–O ternary systems compared with vacancy diffusion. These findings provide a new strategy for future discovery of improved alloying anodes for lithium‐ion batteries and offer important insight towards the understanding of the phase transformation mechanism of alloy‐type protection layers on lithium‐metal anodes. [ABSTRACT FROM AUTHOR]

Room‐temperature Na metal batteries represent an emerging energy storage technology beyond Li‐ion batteries, owing to the high specific capacity and high natural abundance of Na. However, Na metal anodes are plagued with multiple challenges including unstable solid electrolyte interphase, undesirable dendrite growth, and large volumetric expansion, leading to low Coulombic efficiency during Na plating and stripping. To this end, mechanically stable and sodiophilic hosts with nano‐ or micro‐structured materials have been investigated to accommodate Na in the structured spacing or gaps for enhanced cyclability. In this concept, we will discuss the key concepts and latest developments in guiding uniform Na deposition through host modification, especially carbon, inorganic and polymeric materials. Future prospects and outlook will also be provided, including artificial interphase design, solid‐state electrolytes, and precise nanoscale characterization to improve our fundamental understanding of Na deposition and spur this burgeoning field in Na metal batteries. [ABSTRACT FROM AUTHOR]

A Li/KNO3 composite (LKNO), with KNO3 uniformly implanted in bulk metallic Li, is fabricated for battery anode via a facile mechanical kneading approach, which exhibits high Coulombic efficiency and prolonged cycle life. The mechanism behind the enhanced electrochemical performance of the "salt‐in‐metal" composite is investigated, where KNO3 in metallic Li composite electrode would be sustainably released into the electrolyte. The presence of NO3– stabilizes the solid electrolyte interphase by producing functional Li3N, LiNxOy, and Li2O species. K+ from KNO3 also helps to form an electrostatic shield after its adsorption on the electrode protrusions, which suppresses the dendritic growth of metallic Li. With the above advantages, uniform Li plating with dense and planar structure is realized for the LKNO electrode. These findings reveal a deep understanding of the effect of the "salt‐in‐metal" anode and provide new insights into the use of nitrate additives for high‐energy‐density Li metal batteries. [ABSTRACT FROM AUTHOR]

Lithium‐ion batteries (LIBs) have changed lives since their invention in the early 1990s. Further improvement of their energy density is highly desirable to meet the increasing demands of energy storage applications. Active lithium loss in the initial charge process appreciably reduces the capacity and energy density of LIBs due to the formation of a solid electrolyte interface (SEI) on the anode surface, especially for Si based anodes in high‐energy‐density batteries. To solve this issue, prelithiation to provide additional active lithium into the battery has been widely accepted as one of the most promising strategies. Here, key parameters/issues for the practical implementation of prelithiation approaches in LIBs are discussed, including donable lithium‐ion capacity/prelithiation efficiency, chemical and ambient stability of the prelithiation materials/reagents, safety hazards of prelithiation, residues and side reactions during prelithiation, potential effect on electrochemical performance, industrial compatibility, and scalability of the prelithiation, many of which are often overlooked in academic literature. Moreover, insights are offered regarding the potential future directions in the development of this burgeoning field. Continuous progress in prelithiation is essential and urgent to enable next‐generation high‐energy‐density LIBs in the near future. [ABSTRACT FROM AUTHOR]

Li2S/metal nanocomposites are synthesized via chemical conversion reactions, and their properties as cathode prelithiation additives have been investigated to offset the initial lithium loss in lithium‐ion batteries. The Li2S/Co nanocomposite shows good stability, and delivers a high “donor” lithium‐ion specific capacity of 670 mAh g−1 in the cutoff potential range of existing cathode materials in a carbonate‐based electrolyte. [ABSTRACT FROM AUTHOR]

A novel sulfur cathode with pomegranate‐like cluster structure is developed for high‐energy lithium–sulfur batteries. It has stable cycling stability, high volumetric energy density, and excellent rate capability. [ABSTRACT FROM AUTHOR]