Interfacial stability is one of the crucial factors for long-term cyclability of lithium (Li) metal batteries (LMBs). While cross-contamination phenomena have been well-studied in Li-ion batteries (LIBs), similar phenomena have rarely been reported in LMBs. Here, we investigated cathode failure triggered by chemical crossover from the anode in LMBs. In contrast to LIBs, the cathode in LMBs suffers more significant capacity fading, and its capacity cannot be fully recovered by replacing the Li anode. In-depth surface characterization reveals severe deterioration related to the accumulation of highly resistive polymeric components in the cathode–electrolyte interphase. The soluble byproducts generated by extensive electrolyte decomposition at the Li metal surface can diffuse toward the cathode side, resulting in severe deterioration of the cathode and separator surfaces. A selective Li-ion permeable separator with a polydopamine coating has been developed to mitigate the detrimental chemical crossover and enhance the cathode stability.

the energy density of LIBs because Si has ten times higher theoretical capacity (3579 mAh g −1 ) comparing with those of conventional graphite (372 mAh g −1 ). [9][10][11] However, large-scale applications of Si anodes still face several significant challenges, including pulverization of Si particles, continuous growth of a solid electrolyte interface (SEI) layer during the charge/discharge processes, and large swelling of the Si-based anode. [12,13] Without successfully overcoming those challenges, Si can be used only as a limited additive in graphite-based anodes to incrementally increase the energy density of LIBs.Several approaches have been developed in recent years to address those challenges. [14][15][16][17] In this regard, Si nanocomposites stabilized by heterogeneous elements has been used as one of most effective approaches to accommodate large volume changes and prevent side reactions between the electrolyte and Si. [15,16,[18][19][20] Moreover, practical issues associated with the use of nanoengineered Si anodes [21] (e.g., high surface area, low density, and high interparticle resistance) have been addressed by building the nanostructure in a local scale within micrometersized particles. [14,[22][23][24] Representative design of nanostructured Si includes the pomegranate-inspired Si/C anode [23] and Si nanolayer embedded graphite. [24] These nanostructure materials form micrometer (µm) size particles that can be used in practical applications and that are compatible with conventional battery manufacturing process. However, as the primary particle size decreases to nanometer-scale, it is increasingly difficult to assemble nanostructured Si into micrometer-sized material. [25][26][27][28] In this work, we demonstrate a facile method for preparing a Si/C composite containing micrometer-sized nanoporous Si (denoted Np-Si) that is protected by pitch-derived carbon (denoted PC). The resulting PC/Np-Si not only successfully retains its single nanometer-sized Si primary particle without sintering in micrometer-scale, but also exhibits favorable powder properties for conventional battery manufacturing process such as narrow particle size distribution, high density, strong mechanical strength, and small surface area. It also exhibits low swelling upon lithiation at both particle-and Porous silicon (Si)/carbon nanocomposites have been extensively explored as a promising anode material for high-energy lithium (Li)-ion batteries (LIBs). However, shrinking of the pores and sintering of Si in the nanoporous structure during fabrication often diminishes the full benefits of nanoporous Si. Herein, a scalable method is reported to preserve the porous Si nano structure by impregnating petroleum pitch inside of porous Si before high-temperature treatment. The resulting micrometer-sized Si/C composite maintains a desired porosity to accommodate large volume change and high conductivity to facilitate charge transfer. It also forms a stable surface coating that limits the penetration of electrolyte into nanoporous Si and ...

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Although Li–O2 batteries are promising next‐generation energy storage systems with superior theoretical capacities, they have a serious limitation regarding the large overpotential upon charging that results from the low conductivity of the discharge product. Thus, various redox mediators (RMs) have been widely studied to reduce the overpotential in the charging process, which should promote the oxidation of Li2O2. However, RMs degrade the Li metal anode through a parasitic reaction between the RM and the Li metal, and a solution for this phenomenon is necessary. In this study, an effective method is proposed to prevent the migration of the RM toward the anode side of the lithium using a separator that is modified with a negatively charged polymer. When DMPZ (5,10‐dihydro‐5,10‐dimethylphenazine) is used as an RM, it is found that the modified separator suppresses the migration of DMPZ toward the counter electrode of the Li metal anode. This is investigated by a visual redox couple diffusion test, a morphological investigation, and an X‐ray diffraction study. This advanced separator effectively maximizes the catalytic activity of the redox mediator. Li–O2 batteries using both a highly concentrated DMPZ and the modified separator exhibit improved performance and maintained 90% round‐trip efficiency up to the 20th cycle.

α-Fe 2 O 3 submicron spheres with different internal structures were prepared as anode materials for lithium ion batteries (LIBs). Using sulfonated polystyrene (SPS) microspheres as a template, we designed a hollow and macroporous α-Fe 2 O 3 particle structure. The sulfonation degree of polystyrene (SPS) microspheres was controlled by sulfonation reaction time in the range of 24−36 h. After introducing Fe metal precursors by adsorption of ferrous ions into the SPS particles and adding a reduction agent, α-Fe 2 O 3 submicron spheres with hollow and macroporous structures were obtained by heat treatment in an air atmosphere. The internal structure of particles was characterized by scanning electron microscopy, transmission electron microscopy, focused ion beam-scanning electron microscopy, and X-ray diffraction. The electrochemical properties of the hollow and macroporous α-Fe 2 O 3 composite electrodes were investigated by galvanostatic cycling at both constant and variable current rates. The α-Fe 2 O 3 submicron spheres with hollow and macroporous structures exhibited excellent cyclability and rate capability. Electrical impedance spectroscopy was employed to prove the structural effects on the cell performances.

A stable electrolyte is critical for practical application of lithium–oxygen batteries (LOBs). Although the ionic conductivity and electrochemical stability of the electrolytes have been extensively investigated before, their oxygen solubility, viscosity, volatility, and the stability against singlet oxygen (1O2) still need to be comprehensively investigated to provide a full picture of the electrolytes, especially for an open system such as LOBs. Herein, a systematic investigation is reported on the localized high‐concentration electrolytes (LHCEs) using different fluorinated diluents in comparison with those of conventional electrolytes. The physical properties and activation energies for reactions with singlet oxygen (1O2) of these electrolytes are calculated by density functional theory. The electrochemical performances of LOBs using these electrolytes are compared. This study reveals that the correlation between the stability of the electrolytes and their physical and electrochemical properties depends strongly on the diluents in LHCEs. Therefore, it shines light on the rational design of new electrolytes for LOBs.

Developing a safe and long-lasting lithium (Li) metal battery is crucial for high-energy applications. However, its poor cycling stability due to Li dendrite formation and excessive Li pulverization is the major hurdle for its practical applications. Here, we present a silica (SiO2) nanoparticle-dispersed colloidal electrolyte (NDCE) and its design principle for suppressing Li dendrite formation. SiO2 nanoclusters in the NDCE play roles in enhancing the Li+ transference number and increasing the Li+ diffusivity in the vicinity of the Li-plating substrate. The NDCE enables less-dendritic Li plating by manipulating the nucleation-growth mode and extending Sand’s time. Moreover, SiO2 can interplay with the electrolyte components at the Li-metal surface, enriching fluorinated compounds in the solid electrolyte interface layer. The initial control of the Li plating morphology and SEI structure by the NDCE leads to a more uniform and denser Li deposition upon subsequent cycling, resulting in threefold enhancement of the cycle life. The efficacy of the NDCEs has been further demonstrated by the practical battery design, featuring a commercial-level cathode and thin Li-metal (40 μm) anode.

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