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Summary: Silicon suboxides (SiOx) are considered potential anode materials for high‐energy lithium‐ion batteries (LIBs) owing to their high specific capacity and stable cycling performance. Several structural parameters, such as chemical composition, particle size, surface area, and crystallinity, affect the electrochemical performance of SiOx. In particular, the crystallinity of the Si embedded in the SiO2 matrix significantly influences the electrochemical performance of SiOx, as it directly affects the structural stability of Si during cycling. To optimize the high‐performance synthesis of SiOx, we conduct a comparative study of the heat absorbents (KCl and NaCl) to demonstrate their critical role in determining the crystallinity of SiOx particles during the magnesiothermic reduction of SiO. The different heat capacities of these absorbents induced distinctive structural evolutions of SiO during the process, affecting the electrochemical behavior of SiOx during cycling. When KCl was present, the resulted substance has a lower crystallinity of Si, thereby offering superior electrochemical performance compared to that in the presence of NaCl. KCl‐SiOx exhibited a high reversible capacity of 1862 mAh g−1 and an initial Coulomb efficiency (ICE) of 83.0%. Moreover, a stable cycle performance of up to 200 cycles and high capacity retention of up to 89.1% at a current density of 750 mA g−1 could be achieved. Therefore, we believe that the results obtained herein will provide a basis for the development of high‐performance SiOx anode materials for commercial applications. [ABSTRACT FROM AUTHOR]

Utilization of lithium (Li) metal anode is highly desirable for achieving high energy density batteries. Even so, the unavoidable features of Li dendritic growth and inactive Li are still the main factors that hinder its practical application. During plating and stripping, the solid electrolyte interphase (SEI) layer can provide passivation, playing an important role in preventing direct contact between the electrolyte and the electrode in Li metal batteries. Because of complexities of the electrolyte chemical and electrochemical reactions, the various formation mechanisms for the SEI are still not well understood. What we do know is that a strategic artificial SEI achieved through additives electrolyte can suppress the Li dendrites. Otherwise, the dendrites keep generating an abundance of irreversible Li, resulting in severe capacity loss, internal short‐circuiting, and cell failure. In this minireview, we focus on the phenomenon of dendritic Li‐growth and provide a brief overview of SEI formation. We finally provide some clear insights and perspectives toward practical application of Li metal batteries. [ABSTRACT FROM AUTHOR]

The development of lithium (Li)-metal anode is high priority research to initiate next-generation Li batteries. Applying Li-metal in practical applications as anode still has many hurdles to clear away, such as low Coulombic efficiency and capacity degradation by the continuous formation of dead Li. We demonstrate that cobalt (Co) nanoparticle incorporation in a porous carbon host anode can play a critical role in the formation of a thick lithium fluoride dominated solid-electrolyte interphase in ether-based electrolyte. As a result, the host anode containing Co nanoparticles shows excellent electrochemical performance with high Li-metal reversible capacity and even stable long-term cyclability with no dead Li formation. [ABSTRACT FROM AUTHOR]

Lithium (Li) metal is regarded as the most attractive anode material for high‐energy Li batteries, but it faces unavoidable challenges—uncontrollable dendritic growth of Li and severe volume changes during Li plating and stripping. Herein, a porous carbon framework (PCF) derived from a metal–organic framework (MOF) is proposed as a dual‐phase Li storage material that enables efficient and reversible Li storage via lithiation and metallization processes. Li is electrochemically stored in the PCF upon charging to 0 V versus Li/Li+ (lithiation), making the PCF surface more lithiophilic, and then the formation of metallic Li phase can be induced spontaneously in the internal nanopores during further charging below 0 V versus Li/Li+ (metallization). Based on thermodynamic calculations and experimental studies, it is shown that atomically dispersed zinc plays an important role in facilitating Li plating and that the reversibility of Li storage is significantly improved by controlled nanostructural engineering of 3D porous nanoarchitectures to promote the uniform formation of Li. Moreover, the MOF‐derived PCF does not suffer from macroscopic volume changes during cycling. This work demonstrates that the nanostructural engineering of porous carbon structures combined with lithiophilic element coordination would be an effective approach for realizing high‐capacity, reversible Li‐metal anodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Defect in graphene-silicon(d-Gr/Si) composites enhances electrochemical performance. • Li adsorption energies in the d-Gr/Si were less than -0.6 eV and 0.25 eV at pristine Gr/Si. • Defected Gr/Si is more thermionically stable than pristine Gr/Si. • Charge transfer on defects improves electrical conduction and mechanical strength at interfaces. • Our analyses elucidate that defect engineering enhances Li capacity and mechanical strength. Carbon-coated silicon materials are considered as promising anode materials in high-capacity lithium-ion batteries (LIBs). Theoretically, using graphene as the anode material in the LIB would afford high electrical conductivity, mechanical stability of Si, and suppression of the unstable solid–electrolyte interface. However, its usage is hindered by its electrochemical characteristic, which is not electrochemically active when combined with lithium. Therefore, research on graphene as the anode and coated material in LIBs has been conducted using defect engineering to enhance the storage capacity of graphene. Although the electrochemical characteristics of various defects in graphene have been studied experimentally and theoretically, graphene-based composite anode materials such as graphene–silicon composite electrodes have rarely been studied from the electrochemical and mechanical perspectives. In this study, lithium adsorptions are conducted on various defected graphene and graphene–silicon composites using density functional theory calculation. The formation energies of Li on the various defected graphene are assessed, and the mechanical strengths of the graphene–silicon composites are analyzed. Our calculations validate that the defects in graphene enhance the electrochemical adsorptions and interfacial mechanical strengths of the graphene and graphene–silicon composites. During lithiation, the defects mediate greater interfacial adhesion of the silicon–graphene composite. Hence, we elucidate that defected graphene increases the electro-chemo mechanical stabilities of silicon composites in high-capacity LIBs. [ABSTRACT FROM AUTHOR]

Nonstoichiometric SiO x -based nanocomposites have gained considerable attention as promising anode materials for lithium-ion batteries because of their high capacity and relatively good cycle performance. However, their commercial use is still limited by some technical problems such as poor thermal reliability, dimensional stability, and safety. Herein we show that surface modification with TiO2 can effectively improve the thermal reliability of SiO x nanocomposites without sacrificing their capacity and cycle performance. We suggest that the TiO2 coating layer could significantly improve the thermal reliability of the SiO x nanocomposites. Even though the TiO2 phase introduced is less active, TiO2-coated nonstoichiometric SiO x nanocomposites showed electrochemical performance comparable with that of bare nonstoichiometric SiO x nanocomposite. We believe that the surface modification approach proposed herein will open up a new route toward high capacity Si-based anode materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

This study presents a simple and effective method of reducing amorphous silica (a-SiO2) with Ti metal through high-energy mechanical milling for improving its reactivity when used as an anode material in lithium-ion batteries. Through thermodynamic calculations, it is determined that Ti metal can easily take oxygen atoms from a-SiO2 by forming a thermodynamically stable SiO2− x/TiO x composite, meaning that electrochemically inactive a-SiO2 is partially reduced by the addition of Ti metal powder during milling. This mechanically reduced SiO2− x/TiO x composite anode exhibits a greatly improved electrochemical reactivity, with a reversible capacity of more than 700 mAh g−1 and excellent cycle performance over 100 cycles. Furthermore, an enhancement in the mechanical and thermal stability of the composite during cycling can be mainly attributed to the in situ formation of the SiO2− x/TiO x phase. These findings provide new insight into the rational design of robust, high-capacity, Si-based anode materials, as well as their reaction mechanism. [ABSTRACT FROM AUTHOR]

Abstract: The material stability of ramsdellite type Li2+x Ti3O7 has been investigated from the view of the correlation between structural and electrochemical behaviors during Li insertion and extraction. The interfacial reaction of Li2+x Ti3O7 is identified by using AC-impedance spectroscopy and various electrochemical measurements are carefully conducted to interpret each elemental reaction of the complicated interfacial reaction. The impedance spectra indicate three semi-circles in the frequency range from 1MHz to 5mHz which fit expectations well. Li+ insertion at the interface is explained by applying the adatom model that includes desolvation and absorption of lithium ions through electron transfer and lattice incorporation. [Copyright &y& Elsevier]

Abstract: Electrochemical behaviors of Sn and SnO anodes are studied. Charging/discharging curves show irreversible capacities at the first cycle in both Sn and SnO electrodes. The irreversible capacity loss in Sn electrode is due to the incomplete Li removal from Sn after the first cycle. Although the largest capacity loss in SnO electrode is a result from the lithia formation during the first discharge, additional capacity loss arises from the residual Li in metallic Sn owing to the aggregation of Sn upon repeated cycling. Contrary to the previous studies, Li22Sn5 phase is not observed in the discharge product in Sn and SnO electrodes. The LiSn alloy electrode shows almost 100% cycling efficiency at the first cycle due to the pre-existing Li. [Copyright &y& Elsevier]

Keywords: Lithium metal anode; Lithium dendrite growth; Solid-electrolyte interphase (SEI); Electrolyte additives; Anode-free EN Lithium metal anode Lithium dendrite growth Solid-electrolyte interphase (SEI) Electrolyte additives Anode-free 4008 4008 1 12/15/21 20211213 NES 211213 B Lithium metal anode b is highly desirable for high-energy density batteries. Cover Feature: Strategic Approaches to the Dendritic Growth and Interfacial Reaction of Lithium Metal Anode (Chem. Lithium metal anode, Lithium dendrite growth, Solid-electrolyte interphase (SEI), Electrolyte additives, Anode-free. [Extracted from the article]

[Display omitted] • Graphite anodes were surface-modified with Co 2 P nanoparticles. • The modified anodes exhibited a remarkable charging time of 16.1 min (80 % SOC). • Stable cycling performance > 300 cycles was achieved with the Co 2 P@graphite anode. • LiP and Li 3 P reduced interfacial overpotential and increased reversibility. Natural graphite (NG) is widely utilized as a practical anode in commercial lithium-ion batteries (LIBs) thanks to its high theoretical capacity and low operating voltage as well as high reversibility for Li+ storage. Recently, there has been a strong need to further enhance the fast-charging capability and reduce the charging time of NG for use in expanding electric vehicle applications. To enhance the charging performance of NG, various approaches have been explored to make its surface favorable for fast Li+ intercalation. Herein, we propose a surface modification of NG with functional cobalt phosphide (Co 2 P). Co 2 P nanoparticles can be introduced onto NG particles via a thermally induced phase transition process. Various structural and electrochemical investigations have provided insights into the crucial functions and reaction mechanisms of Co 2 P nanoparticles. We demonstrated that electrochemical conversion reactions of Co 2 P nanoparticles occurred during the first charging process, and the resulting phases induced effective surface stabilization and high-voltage operation during subsequent cycles. In particular, lithium phosphide (LiP and Li 3 P) formation is mainly responsible for reducing the overpotential for interfacial reactions between NG and the electrolyte, leading to the effective Li plating suppression and an increase in reversibility during cycles. In practice, the full-cell employing the Co 2 P@NG anode offered a superior cycling performance over 300 cycles and a charging time of 16.1 min (80 % SOC). We expect our findings make a valuable contribution to the advancement of fast-charging LIBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Track-etched polyimide separator with vertically-aligned nanochannels is designed. • Vertically-aligned nanochannels of the separator allow a fast Li+ migration. • Hydrophilic polyvinylpyrrolidone can regulate Li+ flux uniformly during cycling. The practical application of Li metal is hampered by critical obstacles, such as the indiscriminate dendritic growth of metallic Li and severe dimensional changes during cycling. Effective surface engineering is necessary to stabilize the interfacial reactions of Li metal to resolve these technical issues. Many strategies have been proposed to mitigate this inherent limitation of Li metal. The interfacial stabilization using an electrolyte additive or polymer coating is the most common approach to enable the uniform distribution of Li+ on the surface of Li metal. In parallel, the development of functional separators is also considered a promising alternative strategy for effective suppression of the fatal growth of Li dendrites because it promotes Li+ transfer at the interfaces. The synergistic effect of regulating Li+ flux and promoting Li+ transfer is expected to effectively prohibit the dendritic growth of metallic Li. Herein, we report a track-etched polyimide (TEPI) separator with vertically aligned nanochannels decorated with polyvinylpyrrolidone (PVP) that enables a self-assembled robust protective layer on the surface. From a structural viewpoint, the vertically aligned nanochannels of the TEPI separator allow for fast Li+ migration. Additionally, hydrophilic PVP can regulate Li+ flux uniformly through the nanochannels by forming a stable Li 3 N-dominant solid electrolyte interphase (SEI) layer, thereby enhancing interfacial kinetics and suppressing the Li dendrite growth during cycling. We demonstrate that the TEPI separator decorated with PVP is effective in securing high reversibility and the improved cycle performance of Li-metal batteries (LMBs). [ABSTRACT FROM AUTHOR]

Abstract: Co3O4 has shown acceptable electrochemical properties as the anode material of Li secondary batteries. In detail, its capacity reached about 700mAh/g, twice as high as graphite, and 93.4% of initial capacity was retained after 100 cycles. EIS (electrochemical impedance spectroscopy) analyses revealed that after the 1st cycle, the insertion or extraction of Li ions in Co3O4 can occur homogeneously and reversibly (randless-like behavior, homogeneous mixture: Co+Li2O (in the state of Li insertion), Co3O4 (in the state of Li extraction)). In fact, the coulombic efficiency of Co3O4 was almost 100% except for the 1st cycle. According to P. Poizot''s research on several kinds of transition metal oxides, such as Co3O4, CoO, NiO, etc., a small Li2O particle size and catalytic activity of the transition metal are expected to decrease the binding energy of Li2O tremendously. As a result, Li2O should be easy to decompose, and transition metal oxides should be able to charge or discharge reversibly by formation or decomposition of Li2O. However, this assumption has never been confirmed by experimental results. In our results, the CV (cyclic voltammogram) of a Li2O–Co mixture shows much larger oxidation and reduction peaks than that of Li2O. Based on XRD analyses, oxidation and reduction in the CV of Li2O correspond, respectively, to the decomposition and formation of Li2O. So, it can be asserted that Co addition to Li2O facilitates decomposition and formation processes in Li2O and that the catalytic effect of the transition metal must be one of the main causes that make Li2O form or decompose repeatedly. [Copyright &y& Elsevier]

To meet the growing demand for high-power lithium-ion batteries (LIBs), the development of advanced materials is crucial because they play a central role in energy storage technologies. Although graphite is widely used as the most popular anode material, the rate capability and thermal stability of graphite should be further improved for extending the applications of LIBs into emerging markets like electric vehicles and personal mobility devices. With this in mind, we propose off-stoichiometric TiO 2- x -decorated graphite as a potential anode material for practical use in high-power LIBs. Thanks to the high electrical conductivity and thermal resistance of off-stoichiometric TiO 2- x induced by an in situ carbothermal reduction process, the rate capability and thermal stability of graphite can be notably enhanced. The TiO 2- x -decorated graphite offers a high capacity retention of 76.9% even after 100 cycles at a current density of 1C. We believe that this work can provide more opportunities to explore highly reliable anode materials offering high-energy and high-power characteristics for advanced LIBs. A TiO 2-x -decorated graphite is synthesized via an in situ carbon thermal reduction process and its feasibility is thoroughly examined as a potential anode material for practical use in high-power LIBs. The high electrical conductivity and thermal resistance of off-stoichiometric TiO 2-x decorated on the surface of graphite allow the improvement of rate capability and thermal stability of graphite anode. Image 1 • A TiO 2-x -decorated graphite is synthesized via an in situ carbon thermal reduction process as an anode material for LIBs. • The decoration of TiO 2-x nanoparticles is beneficial for improving the rate capability and thermal stability of graphite. • A TiO 2-x -decorated graphite offers a stable cycle performance up to 100 cycle at a current density of 1C. [ABSTRACT FROM AUTHOR]