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This review explores the challenges and advancements in the development of high‐energy lithium‐ion batteries (LIBs), particularly focusing on the electrochemical and structural stability of Ni‐rich cathode materials. Despite their potential to increase the energy density of LIBs, these cathode materials encounter issues such as irreversible phase transitions and structural degradation during cycling, which ultimately affect their electrochemical performance. Elemental doping/substitution has emerged as promising strategies to address these challenges. However, the precise mechanisms underlying their performance enhancement remain unclear. The objective is to elucidate the complex reaction mechanisms triggered by doping and substitution in Ni‐rich cathode materials by employing in situ operando analyses to uncover their effects on electrochemical behavior and structural integrity during cycling. This comprehensive investigation aims to clarify the roles of elemental dopants or substituents in the crystal structures of Ni‐rich cathode materials, thereby offering valuable insights for the structural engineering of cathode materials in high‐energy LIBs. By elucidating these intricate mechanisms, this review provides a practical roadmap for future research and significantly contributes to LIB technology by guiding material design and optimization strategies in the development of advanced LIBs. [ABSTRACT FROM AUTHOR]

Triplite-type LiFeSO4F has attracted considerable attention as a promising cathode for next-generation lithium-ion batteries because of its high redox potential based on earth-abundant Fe2+/3+. However, successful extraction/reinsertion of all the lithium ions in triplite host is challenging even at a low current rate, resulting in a low specific capacity. These experimental findings contrast with previous theoretical works that predicted that the triplite structure would be a fast ionic conductor with low activation barriers for lithium-ion hopping. Origin of this discrepancy is elusive to date. Herein, combined first-principles calculations and high-angle annular dark-field scanning transmission electron microscopy analyses reveal that typical triplite structure is composed of nanodomains consisting of corner-shared FeO4F2 octahedra, whereas their domain boundaries are regions of mixed corner/edge-shared FeO4F2 octahedra. More importantly, these locally disordered domain boundaries significantly reduce the overall lithium diffusivity of the materials. Inspired by these findings, this study redesigns triplite structure with sufficiently small sizes to avoid local bottlenecks arising from the domain boundaries, successfully achieving nearly full lithium extraction/reinsertion with high power and energy density. This work represents the first direct observation of the presence of domain boundaries within a crystalline structure playing a critical role in governing the lithium diffusivity in a battery electrode.

Utilizing hyper‐lithiated materials can offer a variety of options for designing high‐energy lithium‐ion batteries. As sacrificial cathodes, they compensate for the initial loss of Li+ at the anode. During the first delithiation process, a Fe‐substituted Li6CoO4 (Li5.7Co0.7Fe0.3O4) supplies a large amount of Li+. Especially, the peroxide species formation and oxygen evolution are suppressed even though the charge compensation of oxygen is facilitated in Li5.7Co0.7Fe0.3O4. From a structural viewpoint, the anti‐fluorite structure changes to defective disordered phases during the Li+ extraction, and the proportion of the electrochemical‐inactive phase is more dominant in the case of Li5.7Co0.7Fe0.3O4 at the end of the charge. Consequently, the delithiated LixCo0.7Fe0.3O4 is deactivated in subsequent cycles, reducing unexpected electrochemical reactions after the Li+ provision as sacrificial cathodes. These findings provide a comprehensive understanding of the reaction mechanism of hyper‐lithiated materials and represent a significant step forward in developing high‐performance sacrificial cathodes. [ABSTRACT FROM AUTHOR]

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]

The realisation of fast-charging lithium-ion batteries with long cycle lifetimes is hindered by the uncontrollable plating of metallic Li on the graphite anode during high-rate charging. Here we report that surface engineering of graphite with a cooperative biphasic MoOx–MoPx promoter improves the charging rate and suppresses Li plating without compromising energy density. We design and synthesise MoOx–MoPx/graphite via controllable and scalable surface engineering, i.e., the deposition of a MoOx nanolayer on the graphite surface, followed by vapour-induced partial phase transformation of MoOx to MoPx. A variety of analytical studies combined with thermodynamic calculations demonstrate that MoOx effectively mitigates the formation of resistive films on the graphite surface, while MoPx hosts Li+ at relatively high potentials via a fast intercalation reaction and plays a dominant role in lowering the Li+ adsorption energy. The MoOx–MoPx/graphite anode exhibits a fast-charging capability (<10 min charging for 80% of the capacity) and stable cycling performance without any signs of Li plating over 300 cycles when coupled with a LiNi0.6Co0.2Mn0.2O2 cathode. Thus, the developed approach paves the way to the design of advanced anode materials for fast-charging Li-ion batteries. Fast-charging of lithium-ion batteries is hindered by the uncontrollable plating of metallic Li on the graphite anode during cycling. Here, the authors demonstrate the fast chargeability and long cycle lifetimes via surface engineering of graphite with a cooperative biphasic MoOx–MoPx promoter. [ABSTRACT FROM AUTHOR]

There are increasing demands for large‐scale energy storage technologies for efficient utilization of clean and sustainable energy sources. Solid‐state lithium batteries (SSLBs) based on non‐ or less‐flammable solid electrolytes (SEs) are attracting great attention, owing to their enhanced safety in comparison to conventional Li‐ion batteries. Moreover, SSLBs can provide great benefits in terms of battery performance (power and energy densities) and cost when constructed using a bipolar design. In this review, we introduce the general aspects of the bipolar battery architecture and provide a brief overview of the essential components and technologies for bipolar SSLBs: Li+‐conducting SEs, composite electrodes, and bipolar plates. Furthermore, we review the recent progress in the design and construction of bipolar SSLBs with emphasis on the fabrication techniques of SEs and SSLBs and the engineering approaches to improve their electrochemical properties. [ABSTRACT FROM AUTHOR]

Abstract: Triplite‐type LiFeSO4F has attracted considerable attention as a promising cathode for next‐generation lithium‐ion batteries because of its high redox potential based on earth‐abundant Fe2+/3+. However, successful extraction/reinsertion of all the lithium ions in triplite host is challenging even at a low current rate, resulting in a low specific capacity. These experimental findings contrast with previous theoretical works that predicted that the triplite structure would be a fast ionic conductor with low activation barriers for lithium‐ion hopping. Origin of this discrepancy is elusive to date. Herein, combined first‐principles calculations and high‐angle annular dark‐field scanning transmission electron microscopy analyses reveal that typical triplite structure is composed of nanodomains consisting of corner‐shared FeO4F2 octahedra, whereas their domain boundaries are regions of mixed corner/edge‐shared FeO4F2 octahedra. More importantly, these locally disordered domain boundaries significantly reduce the overall lithium diffusivity of the materials. Inspired by these findings, this study redesigns triplite structure with sufficiently small sizes to avoid local bottlenecks arising from the domain boundaries, successfully achieving nearly full lithium extraction/reinsertion with high power and energy density. This work represents the first direct observation of the presence of domain boundaries within a crystalline structure playing a critical role in governing the lithium diffusivity in a battery electrode. [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]

In lithium-ion batteries (LIBs) comprising spinel cathode materials, the dissolution of transition metals (TMs) in the cathodes causes severe cyclic degradation. We investigate the origin and mechanism of surface TM dissolution in high-voltage spinel oxide (LiNi0.5.Mn1.5O4) nanoparticles to find a practical method for its mitigation. Atomic structures of the LiNi0.5.Mn1.5O4 surfaces are developed, and the electronic structures are investigated by first-principles calculations. The results indicate that titanium is a promising dopant for forming a more stable surface structure by reinforcing metal-oxygen bonds in LiNi0.5.Mn1.5O4. Experimentally synthesized LiNi0.5.Mn1.5O4 with titanium surface doping exhibits improved electrochemical performance by suppressing undesirable TM dissolution during cycles. The theoretical prediction and experimental validation presented here suggest a viable method to suppress TM dissolution in LiNi0.5.Mn1.5O4. [ABSTRACT FROM AUTHOR]

Non-stoichiometric SiO x based materials have gained much attention as high capacity lithium storage materials. However, their anode performance of these materials should be further improved for their commercial success. A conductive polymer, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), is employed as a flexible electrical interconnector to improve the electrochemical performance of Si/SiO x nanosphere anode materials for lithium ion batteries (LIBs). The resulting Si/SiO x-PEDOT:PSS core-shell structured material with the small amount (1 wt %) of PEDOT:PSS shows the improved initial reversible capacity of 968.2 mA h g−1 with excellent long-term cycle performance over 200 cycles. These promising properties can be attributed to the use of the electroconductive and flexible PEDOT:PSS shell layer, which protects the electrical conduction pathways in the electrode from the large volume changes of silicon during cycling. [ABSTRACT FROM AUTHOR]

A combined experimental and computational study of an oxygen-deficient Li2MnO3− δ ( δ≈0.071) cathode for understanding the role and effects of oxygen vacancies on phase transformation and electrochemical activity in Li-ion batteries is presented. The oxygen-deficient Li2MnO3− δ exhibits improved electrochemical reactivity toward Li+ ions without significant loss of structural stability. The oxidation of O during Li+ ion extraction can be suppressed by the enhanced redox reaction of Mn in this material. Furthermore, the inevitable phase transformation of Li2MnO3 can be impeded by the increased kinetic barriers to Mn migration in Li2MnO3− δ (Δ Ebarrier=1.0-2.5 eV), which disfavors the formation of stable intermediate coordination geometries due to the oxygen vacancies. These findings reveal the underlying mechanism on the role of the oxygen vacancies in changing phase transformation and electrochemical activity in inactive Li2MnO3, and provide a scientific insight to the electrochemical reactivity and sustainability of Li-rich oxide cathode materials in Li-ion batteries. [ABSTRACT FROM AUTHOR]

The positive effects of incorporating electrically conductive poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT-PSS) into the negative electrode (NE) of a lithium ion capacitor (LIC) is investigated. The binding material of the NE, styrene-butadiene rubber (SBR), is partially substituted by conductive PEDOT-PSS. The soft carbon NE with 1.0 wt% PEDOT-PSS exhibits enhanced capacity retention of 64% at a current density of 5 C by lowering its electrical and electrochemical charge transfer resistance. The rate capability increased with increasing amounts of PEDOT-PSS, with no variation in the Li + diffusivity. This improved electrochemical performance of the NE is also reflected in the LIC full-cell configuration. An LIC employing a 1.0 wt% PEDOT-PSS NE delivers 6.6 F at a high current density of 100 C, which is higher than the 6.0 F measured for the LIC with a bare NE. Moreover, the LIC with the 1.0 wt% PEDOT-PSS NE retains 85% of its initial capacitance even after 5000 cycles. These results are mainly attributed to the favourable electrical network formed by the incorporation of PEDOT-PSS into the NE. Thus, we believe that the incorporation of conductive PEDOT-PSS is a viable approach for obtaining high-power LICs. [ABSTRACT FROM AUTHOR]

Critical degradation mechanism of many cathode materials for Li-ion batteries is closely related to phase transformations at the surface/interface. Li2MnO3 in x Li2MnO3⋅(1− x) LiMO2 (M=Ni, Co, Mn) provides high capacity, but the Li2MnO3 phase is known to degrade during cycling through phase transformation and O2 evolution. To resolve such degradation problems, it is critical to develop a fundamental understanding of the underlying mechanism. Using first-principles calculations, we identified the surface delithiation potential (<4.5 V vs. Li/Li+) of Li2MnO3, which is significantly lower than the bulk redox potential. A lower Mn oxidation state at the surface would reduce the delithiation potential compared with the fully oxidized Mn4+ in the bulk. As a result, the delithiation would be initiated from the surface, which induces a phase transformation of Li2MnO3 into a spinel-like structure from the surface. These theoretical findings have been confirmed by experimental analyses. Based on these detailed mechanistic understanding, it would be possible to develop rational approaches to modify and coat the surface to suppress degradation mechanisms. [ABSTRACT FROM AUTHOR]

Soft carbon with a high reversible capacity has been proposed as an anode material for high-power lithium ion batteries. In this work, we investigate the effect of phosphoric acid (H 3 PO 4 ) addition during preparation on the microstructure and electrochemical performance of soft carbon. H 3 PO 4 facilitates the formation of nanopores by terminating C-C bonding and forming C-O x -P (0

The effects of electron-beam irradiation on the physicochemical and electrochemical properties of polyethylene (PE) separators are investigated. The high-energy electron-beam irradiation creates carbonyl bands on the surface of bare PE separators, however, it does not affect morphology and pore structure of the separators. In addition, cells employing the electron-beam-irradiated PE separators clearly exhibit better ionic conductivity and rate capability without any degradation in cycling performance compared to cells employing the bare PE separator. This improvement is explained by a formation of new functional group on PE surface-the electron-beam irradiation creates carbonyl group on the surface of the PE separator and it readily facilitates the migration of Li and improves solvent affinity of the PE separators. Furthermore, the thermal stability of PE separators is effectively enhanced by irradiating them with electron beams. The thermal shrinkage of the electron-beam-irradiated PE separators is observed to be much lower than that of bare PE separators, resulting in an increased gap between the shut-down and melting integrity temperatures. From these results, it is believed that the electron-beam irradiation can be considered as an effective approach to enhance electrochemical and thermal properties of PE separator. [ABSTRACT FROM AUTHOR]

Abstract: We introduce an effective way to improve the electrochemical and thermal stabilities of natural graphite anodes of lithium ion batteries. Through a thermal decomposition of H3PO4 and H3BO3, phosphorus and boron can be successfully incorporated into the surface of natural graphite by the formation of chemical bonds with carbon. By incorporation of these heteroatoms, the electrochemical stability of natural graphite can be significantly improved, even under severe operating conditions. From the results of various structural and electrochemical analyses, the incorporated heteroatoms are thought to be affecting the physicochemical properties of the solid electrolyte interphase (SEI) by promoting additional Li+ consumption and thus making it more stable. In addition, we found that the heteroatoms also have potential to improve the thermal resistivity of the natural graphite anode. These findings could be helpful for developing natural graphite anodes with a good electrochemical as well as thermal properties for use in lithium ion batteries. [Copyright &y& Elsevier]

Abstract: The positive effect of AlF3 (Al–F) coating on the over-lithiated transition metal oxide with a composition of 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 has been investigated to address its potential use in lithium ion batteries. On the basis of various structural and electrochemical characterizations, we elucidate a correlation between surface structure and its electrochemical performance. After the controlled coating with AlF3 (Al–F), we observed notable improvements on cyclic performance and rate capability as well as thermal stability. We found that uniformly introduced AlF3 (Al–F) not only preserves the electrochemical kinetics at the surface of the oxide but also stabilizes its surface as a protective layer against electrolyte oxidation during the high voltage charging. Such improvements will provide a further progress on the development of high-capacity cathode materials fulfilled with the stringent safety requirements. [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]

Abstract: The electrochemical lithiation–delithiation reaction was examined for LiMnPO4 in which different cations were substituted for part of Mn. The X-ray diffraction analysis indicated that LiMnPO4 is tolerant, to some extent, to substitution of Mg2+, Ca2+ and Zr4+. The substitution of Mg2+ and/or Zr4+ led to an increased reversible capacity and a reduced polarization, whereas Ca2+ substitution had a detrimental effect on the electrochemical properties. The potential transient analysis showed that LiMn0.88Mg0.1Zr0.02PO4 has higher lithium diffusivities than pure LiMnPO4, indicating facilitated diffusion kinetics in the substituted material. Upon the first charge–discharge cycle, LiMn0.88Mg0.1Zr0.02PO4 suffered less irreversible capacity loss when compared with LiMnPO4, and smaller amounts of electrolyte salt-based species were detected on the electrode surface of LiMn0.88Mg0.1Zr0.02PO4. [Copyright &y& Elsevier]

Abstract: Si–carbon composite prepared by mechanical milling showed good cyclic capacity retention until the utilization of Si was limited below 32%, whereas the retention of a Si–Cu–carbon composite obtained by two-step mechanical milling was maintained up to 55%. A comparison between the first charge curves of a Si–carbon composite and a Si–Cu–carbon composite at 0.1C, indicated that the Si–carbon composite underwent a much higher polarization than the Si–Cu–carbon composite, leading to the difference in utilization of Si. Impedance spectroscopy let us confirm that the electrochemical alloying between Si and Li+ is much easier in the Si–Cu–carbon composite than in the Si–carbon composite. The superiority of the Si–Cu–carbon composite in kinetics enabled its electrode to have a more homogeneous Li+ concentration after Li+ insertion. Because this phenomenon means that the Si–Cu–carbon composite has a more homogeneous volume expansion than the Si–carbon composite, the disparity in electrochemical performance between the Si–carbon composite and the Si–Cu–carbon composite was attributed to enhanced Li+ transfer in the Si–Cu–carbon composite. [Copyright &y& Elsevier]

A VOx-impregnated oxide cathode for lithium ion batteries exhibits a substantial drop in oxygen evolution during high voltage operation. An electrolyte was found to catalyze the gas evolution, and the VOxlayer could protect the cathode oxide surface from the electrolyte and stabilize the surface oxide ions during their electrochemical oxidation. [ABSTRACT FROM AUTHOR]

A uniform surface coating and control over residual Li on the surface of high-Ni layered transition metal oxides is crucial for development of highly reliable and high-performance cathode materials for lithium ion batteries (LIBs). To suppress undesirable side reactions at the surface of high-Ni layered transition metal oxides, we propose a one-pot TiO 2 surface coating process using a bifunctional hybrid solution. We demonstrate that the uniformity and thickness of a TiO 2 coating layer can be controlled, and residual Li can be simultaneously reduced during the surface coating process. Structural and electrochemical characterizations support the utilization of an essential bifunctional hybrid solution composed of titanium (IV) isopropoxide (TTIP) in isopropyl alcohol (IPA) and tetrabutyl-ammonium hydroxide (TBAOH) in water for introducing a uniform TiO 2 coating layer and eliminating undesirable Li residues on the surface without yielding significant structural degradation. Our approach provides a practical guide to develop advanced cathode materials and simplify the synthetic process for mass production. A one-pot TiO 2 surface coating process using a bifunctional hybrid solution composed of titanium (IV) isopropoxide (TTIP) in isopropyl alcohol (IPA) and tetrabutyl-ammonium hydroxide (TBAOH) in water for introducing a uniform TiO 2 coating layer and eliminating undesirable Li residues on the surface without yielding significant structural degradation. Image 1 • A one-pot TiO 2 surface coating process using a bifunctional hybrid solution is proposed. • A bifunctional hybrid solution is essential for introducing a uniform TiO 2 coating and eliminating undesirable Li residues. • TiO 2 coated NCM811 exhibits a high reversible capacity of more than 200 mAh g−1 and stable cycle performance. [ABSTRACT FROM AUTHOR]

The Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 layered oxide (NCM811) is attracting considerable attention as a high-capacity cathode material for rechargeable Li-ion batteries. However, due to its inherent structural/chemical/electrochemical instability, NCM811 with high Ni content suffers from significant performance degradation upon storage even in ambient atmospheres as well as during charge–discharge cycling. Herein, we demonstrate a simple but effective surface-tuning approach to mitigate storage-induced degradation of NCM811, which is based on the conversion of undesirable Li residues to a protective Li 3 PO 4 nanolayer via phosphate treatment. The accelerated storage stability test shows that phosphate-modified NCM811 exhibits remarkably improved electrochemical performance (capacity, cycle life, and rate capability) over the pristine one after being stored under harsh environmental conditions. A combined analytical study indicates that surface tuning through phosphate treatment enhances the storage stability of NCM811 by eliminating impurity-forming Li residues and producing a Li 3 PO 4 nanolayer that inhibits parasitic reactions at the electrode–electrolyte interface. Furthermore, Li 3 PO 4 provides an effective barrier to H 2 O and CO 2 infiltration into the particle agglomerates, thereby suppressing the loss of particle integrity. [ABSTRACT FROM AUTHOR]

Sodium ion batteries are being highlighted as a promising energy storage system to resolve the critical issues associated with lithium ion battery usage due to a limited quantity of lithium resources on the earth. Although recent advances in sodium ion battery technology have been remarkable, the reversible capacities and cyclic performance of sodium ion batteries should be further advanced prior to their successful implementation. Herein, we demonstrate dual-textured Prussian blue nanocubes prepared via simple acid etching as a reliable sodium storage material. Taking advantage of their hybrid microstructure composed of porous and non-porous domains, dual-textured Prussian blue nanocubes exhibit high reversible capacities, good rate capabilities, and stable cyclic performance. Moreover, the nanocubes exhibit excellent dimensional stability even after 100 cycles, offering new opportunities for the development of robust and high-performance sodium rechargeable batteries. [ABSTRACT FROM AUTHOR]

We present a cost-effective synthesis process for producing a carbon-coated nano-Si@Graphite (n-Si@G-C) anode, in which nano-sized Si (n-Si) particles (∼50 nm in size) are anchored onto natural graphite particles by a carbothermal shock through microwave induction. During the carbothermal shock process, graphite undergoes a fast increase in temperature resulting in micron-sized Si (m-Si) particles (∼4 μm in size) to undergo stress fractures due to rapid thermal expansion. This process leads to the formation of abundant n-Si particles onto graphite particles. Subsequently, a thin carbon shell is introduced by a wet-coating process combined with a thermal decomposition of coal-tar pitch. The amorphous carbon shell offers multiple functionalities: i) preventing direct exposure of n-Si particles to the electrolyte, ii) accommodating their volume expansion, and iii) maintaining electron conduction pathways. The resulting n-Si@G-C anode allows a high reversible capacity (500.8 mAh g−1) as well as fast-charging characteristics. When utilized in a full-cell configured with a commercial-grade LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, it achieves a notable reduction in charging time (approximately 10.1 min@80 % state of charge). After 300 cycles, a high capacity retention (71.3 %) can be retained under 3C charging. Moreover, the distinctive structural features of the n-Si@G-C anode effectively suppress undesirable Li plating. [Display omitted] • The n-Si@G-C composite is synthesized by a carbothermal shock by microwave induction. • This offers an efficient, non-contact powder process for cost-effective mass production. • The n-Si@G-C anode demonstrates both a high reversible capacity and fast-charging capability. • A full-cell exhibits a high capacity retention (71.3 %) under 3C charging after 300 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyborosiloxane (PBS) layer enhances moisture resistance and ionic conductivity of Li 2 NiO 2. • The PBS layer significantly diminishes the interfacial resistance and improves the cycling performance of Li 2 NiO 2. • The full-cell containing PBS@LNO outperformed, preserving 71.8 % capacity after 300 cycles. Li 2 NiO 2 has garnered considerable interest as a Li-excess cathode additive for high-energy lithium-ion batteries (LIBs), attributed to its high irreversible capacity during the initial cycle and an operating voltage comparable with that of commercial cathode materials. However, its integration into practical applications is limited by its suboptimal cycling performance owing to moisture instability and gas evolution. To surmount these obstacles, we developed a hybrid surface coating strategy employing polyborosiloxane (PBS)—a structural derivative of polydimethylsiloxane (PDMS) synthesized with boric acid (H 3 BO 3)—applied to a Li 2 NiO 2 cathode additive. The bi-functional of the PBS layer enhances moisture resistance and ionic conductivity on the Li 2 NiO 2 surface. A hydrophobic, elastic PDMS matrix offers conformal coverage, forestalling adverse moisture-induced side reactions. The introduction of H 3 BO 3 into the PDMS matrix on the Li 2 NiO 2 surface fosters the formation of Li–B–O bonds, thus augmenting the ionic conductivity of the coating. This innovative approach with the PBS layer significantly diminishes the interfacial resistance and improves the cycling performance of Li 2 NiO 2 while preventing substantial structural degradation. In a full-cell configuration incorporating a PBS-coated Li 2 NiO 2 cathode additive with a LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode and a SiO x /Graphite anode, the enhanced energy density and sustained stable cycling performance exceed 300 cycles. This hybrid layer can aid in producing longer-lasting, more efficient LIBs that can fulfill the requirements for use in high-energy storage solutions. [ABSTRACT FROM AUTHOR]

Abstract: The physical effects of a polyethylene (PE) surface on the electrochemical and thermal properties of a PE separator coated with polyvinylidene fluoride (PVDF)–12wt% hexafluoropropylene (HFP) co-polymer have been investigated for use in lithium ion batteries. To change the surface property of the PE separator, it is treated using gamma ray irradiation. In comparison with the non-irradiated separator, the irradiated separator shows strong affinity for polar solvents due to the carbonyl band formed during gamma ray irradiation. And the PVDF–12wt%HFP co-polymer is coated on the both sides of the non-irradiated and irradiated separators using a dip-coating process. It is clearly observed that the ionic conductivity of the irradiated separator coated with PVDF–12wt%HFP is higher than that of the non-irradiated separator coated with the same one. Based on the activation energy calculation, the ionic conductivity is found to strongly depend on the characteristics of the interfaces between them. In addition, rate discharge property and thermal stability of the irradiated separator coated with PVDF–12wt%HFP are much better than those of the non-irradiated one. The improvement of the thermal stability could be attributed to cross-linking of the support PE separator using gamma ray irradiation. [Copyright &y& Elsevier]

[Display omitted] • LiTaO 3 surface layer is integrated onto SNCM cathode for high-energy LIBs and ASSBs. • The crystallinity of LiTaO 3 affects the reversibility and long-term cycling performance of SNCM cathode. • Tailoring the crystallinity of LiTaO 3 is beneficial for effective surface stabilization of SNCM cathode. Various functional materials have been explored as surface-coating layers for Ni-rich cathode materials used in lithium-ion batteries (LIBs) aiming to enhance their long-term cycling performance and electrochemical stability under high-voltage operation. In particular, lithium tantalate (LiTaO 3) has received considerable attention as a promising candidate due to its distinct physicochemical properties, including high ionic conductivity, wide voltage window, low band-gap energy, and excellent mechanical strength. These characteristics are beneficial for effective surface stabilization of Ni-rich cathode materials, which currently suffer from poor cycling performance, mainly due to issues related to structural instability with elevated Ni concentrations. In this respect, we report the benefits of surface coating with LiTaO 3 on the electrochemical properties of single-crystalline Ni-rich cathode materials (SNCM) for successful implementation in high-energy LIBs. The controlled crystallinity of the LiTaO 3 surface layer directly affects the reversibility as well as interfacial stability of the SNCM cathode under various operating conditions. The tailored crystallinity of LiTaO 3 surface layer is mainly responsible for enhancing the cycle performance of SNCM cathodes under high-temperature (60 °C) and high-voltage (4.5 V vs. Li/Li+) operations. Our findings will significantly contribute to the development of robust and reliable cathode materials for high-energy LIBs. [ABSTRACT FROM AUTHOR]

[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]

Although lithium-ion batteries are recognized as the most suitable power source for electric vehicles, they continue to pose a severe safety issue mainly arising from the use of flammable electrolytes. To improve safety, various types of solid electrolytes are explored as potential alternatives due to their non-flammability, high stability, and a wide electrochemical window. In particular, Li 1+ x Al x Ge 2- x (PO 4) 3 (LAGP) has many strengths such as a high total Li+ conductivity and low sensitivity against Li metal anode. Despite these benefits, practical use of LAGP is hindered by a significant loss of total Li+ conductivity due to large grain boundary resistance and interfacial resistance. As an effective way to increase the total Li+ conductivity of LAGP, we propose microstructural engineering with the structural modifiers (B 2 O 3 and Bi 2 O 3) with different functionalities. During synthesis, B 2 O 3 facilitates the grain growth of LAGP, thereby reducing the number of grain boundaries. At the same time, Bi 2 O 3 promotes the densification of LAGP with the advancement of its structural integrity. As a result of synergetic effect, the total Li+ conductivity of LAGP can be effectively improved at room temperature. Furthermore, we demonstrate positive effects of the tailored microstructure of LAGP on the electrochemical performance of all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Improving cycle performance and rate-capability of lithium ion batteries is necessary in moving toward their use in electric vehicles. Working towards this goal, we propose an amorphous Li-Zr-O coating on the surface of a high-Ni layered transition metal oxide (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) via a simple wet process. By using residual Li on the surface of as-prepared LiNi 0.8 Co 0.1 Mn 0.1 O 2 particles as a Li source, a non-stoichiometric Li-Zr-O compound can be successfully formed on the surface of LiNi 0.8 Co 0.1 Mn 0.1 O 2 particles at a low temperature of 400 °C. The formation of an amorphous Li-Zr-O layer is beneficial in minimizing undesirable side reactions associated with residual Li at the surface and, by extension, improving the cycle performance and rate-capability of LiNi 0.8 Co 0.1 Mn 0.1 O 2 . The amorphous Li-Zr-O coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 exhibits a high reversible capacity of more than 190 mAh g −1 with improved cycle performance. This simple approach offers easy control of the surface characteristics of LiNi 0.8 Co 0.1 Mn 0.1 O 2 , improving the surface stability and enhancing the thermal stability. [ABSTRACT FROM AUTHOR]

The thermal stability of a fully delithiated cathode, coupled with an inorganic salt, organic solvents, and electrolyte, was evaluated with differential scanning calorimetry (DSC) to address the safety issue of lithium-ion batteries. The DSC experiments revealed that vinylene carbonate (VC)-based systems exhibit decreased thermal stability compared to other coexisting systems. The DSC analysis of the cathode and electrolyte in the presence of VC, employed as additives, confirmed the reduction in thermal stability. Our results suggested that VC additives, which have been recently employed to enhance the electrochemical performance in anodes, negatively affect the thermal properties and safety characteristics of the cathode in lithium-ion batteries. [ABSTRACT FROM AUTHOR]

LiTaO 3 has a high ionic conductivity (10−5−10−6 S cm−1), mechanical strength, and excellent moisture stability. Such characteristics would make it more valuable for reducing the interfacial resistance and promoting the surface stabilization of Li 2 NiO 2. The positive effects of the LiTaO 3 surface layer towards improving the structural stability and electrochemical performance of Li-excess Li 2 NiO 2 are demonstrated for practical use. [Display omitted] • Li 2 NiO 2 offers surplus Li+ for compensating the irreversible Li+ loss in the anode. • LiTaO 3 coating layer can suppress the formation of impurities after air exposure. • The gas evolution and mechanical cracking can be minimized during cycling. • A full-cell with LiTaO 3 @Li 2 NiO 2 shows stable cycling performance up to 200 cycles. Silicon based anodes are known to have a high specific capacity and low operating voltage (less than 0.5 V vs. Li/Li+). Even so, the solid electrolyte interphase (SEI) formation induces the severe capacity loss at the first cycle, known as a critical factor in reducing the energy density of lithium-ion batteries (LIBs). To improve the energy density by compensating the initial Li+ loss, the utilization of Li-excess cathode additives has been considered as the most practical strategy for supplying surplus Li+ during the initial charge. Li 2 NiO 2 is an ideal cathode additive thanks to its large charge capacity (≥320 mAh g−1) and low Coulombic efficiency (∼35%) at the first cycle. Surface protection of Li 2 NiO 2 is still required, however, due to its vulnerability to moisture (H 2 O) and carbon dioxide (CO 2) in the ambient atmosphere. In addition, Li 2 NiO 2 becomes more structurally unstable due to oxygen (O 2) gas evolution, leading to the formation of microcracks. Herein, we introduce a functional LiTaO 3 coating layer onto the surface of Li 2 NiO 2 for structural stabilization. The LiTaO 3 coating layer can effectively suppress the formation of impurities (i.e. , LiOH and Li 2 CO 3) after air exposure. Furthermore, the gas evolution and mechanical cracking can be minimized by enhancing the structural integrity of Li 2 NiO 2 during cycling. [ABSTRACT FROM AUTHOR]

Utilizing the unparalleled theoreticalcapacity of sulfur reaching1675 mAh/g, lithium–sulfur (Li–S) batteries have beencounted as promising enablers of future lithium ion battery (LIB)applications requiring high energy densities. Nevertheless, most sulfurelectrodes suffer from insufficient cycle lives originating from dissolutionof lithium polysulfides. As a fundamental solution to this chronicshortcoming, herein, we introduce a hierarchical porous carbon structurein which meso- and macropores are surrounded by outer micropores.Sulfur was infiltrated mainly into the inner meso- and macropores,while the outer micropores remained empty, thus serving as a “barricade”against outward dissolution of long-chain lithium polysulfides. Onthe basis of this systematic design, the sulfur electrode delivered1412 mAh/gsulfurwith excellent capacity retention of 77%after 500 cycles. Also, a control study suggests that even when sulfuris loaded into the outer micropores, the robust cycling performanceis preserved by engaging small sulfur crystal structures (S2–4). Furthermore, the hierarchical porous carbon was produced in ultrahighspeed by scalable spray pyrolysis. Each porous carbon particle wassynthesized through 5 s of carrier gas flow in a reaction tube. [ABSTRACT FROM AUTHOR]

The mechanical properties of cathode materials are among the critical factors that directly affect the lifespan of lithium-ion batteries (LIBs). However, a significant challenge remains in understanding the exact mechanism of mechanical degradation of present cathode materials that results in significant loss of performance during long-term operation. Herein, a comparative study on the correlation between mechanical strength (e.g. particle hardness) and cycle performance of the cathode materials (particularly those with layered structures) is presented. By improving the particle hardness of cathode materials via Mg doping, the formation of undesirable microcracks within the particles during cycling can be effectively suppressed, thus improving cycle performance. Structural and electrochemical analyses are performed in order to further elucidate the mechanical degradation mechanism of LIBs during repeat cycles, and identify a possible approach to the enhancement of electrochemical performance and long-term durability in present cathode materials. Image 1 • A strategy for improving the cycle performance of NCM cathode is presented. • The particle hardness of NCM can be effectively enhanced by Mg doping. • The enhanced particle hardness of Mg-NCM positively affects the cycle performance. • The formation of microcracks within Mg-NCM can be suppressed during cycles. [ABSTRACT FROM AUTHOR]

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]

Among the silicon (Si)-based anode materials, Si/SiO x is likely to be the best candidate for maintaining structural stability while taking advantage of the high capacity of Si as well as the compatible functionality between Si and SiO x. The oxygen content of SiO x is an especially significant factor for obtaining better performance, because it directly affects electrochemical properties such as reversible capacity, structural stability, and electrical conductivity. Herein, we have synthesized SiO x materials with different oxygen contents via magnesiothermic reduction of silica. The theoretical capacities of a series of Si/SiO x samples were estimated by using X-ray photoelectron spectroscopy, and then those results were compared with empirical results. This work paves the way to predicting the electrochemical performances of lithium-ion battery anodes based on oxygen content in the nonstoichiometric Si/SiO x structure. Image 1 • Si/SiO x materials with various oxygen contents via magnesiothermic reduction of silica had been prepared. • The theoretical capacities of a series of Si/SiO x samples had been estimated by using X-ray photoelectron spectroscopy. • The optimum oxygen content of Si/SiO x material as a lithium-ion battery anode had been proposed. [ABSTRACT FROM AUTHOR]