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In recent years, solid-state Li metal batteries (SSLBs) have attracted significant attention as the next-generation batteries with high energy and power densities. However, uncontrolled dendrite growth and the resulting pulverization of Li during repeated plating/stripping processes must be addressed for practical applications. Herein, we report a plastic-crystal-based polymer/ceramic composite solid electrolyte (PCCE) to resolve these issues. To fabricate the one-side ceramic-incorporated PCCE (CI-PCCE) film, a mixed precursor solution comprising plastic-crystal-based polymer (succinonitrile, SN) with garnet-structured ceramic (Li7La3Zr2O12, LLZO) particles was infused into a thin cellulose membrane, which was used as a mechanical framework, and subsequently solidified by using UV-irradiation. The CI-PCCE exhibited good flexibility and a high room-temperature ionic conductivity of over 10−3 S cm−1. The Li symmetric cell assembled with CI-PCCE provided enhanced durability against Li dendrite penetration through the solid electrolyte (SE) layer than those with LLZO-free PCCEs and exhibited long-term cycling stability (over 200 h) for Li plating/stripping. The enhanced Li+ transference number and lower interfacial resistance of CI-PCCE indicate that the ceramic-polymer composite layer in contact with the Li anode enabled the uniform distribution of Li+ flux at the interface between the Li metal and CI-PCCE, thereby promoting uniform Li plating/stripping. Consequently, the Li//LiFePO4 (LFP) full cell constructed with CI-PCCE demonstrated superior rate capability (~120 mAh g−1 at 2 C) and stable cycle performance (80% after 100 cycles) than those with ceramic-free PCCE.

The demand for fast-charging lithium-ion batteries (LIBs) with long cycle life is growing rapidly due to the increasing use of electric vehicles (EVs) and energy storage systems (ESSs). Meeting this demand requires the development of advanced anode materials with improved rate capabilities and cycling stability. Graphite is a widely used anode material for LIBs due to its stable cycling performance and high reversibility. However, the sluggish kinetics and lithium plating on the graphite anode during high-rate charging conditions hinder the development of fast-charging LIBs. In this work, we report on a facile hydrothermal method to achieve three-dimensional (3D) flower-like MoS2 nanosheets grown on the surface of graphite as anode materials with high capacity and high power for LIBs. The composite of artificial graphite decorated with varying amounts of MoS2 nanosheets, denoted as MoS2@AG composites, deliver excellent rate performance and cycling stability. The 20−MoS2@AG composite exhibits high reversible cycle stability (~463 mAh g−1 at 200 mA g−1 after 100 cycles), excellent rate capability, and a stable cycle life at the high current density of 1200 mA g−1 over 300 cycles. We demonstrate that the MoS2-nanosheets-decorated graphite composites synthesized via a simple method have significant potential for the development of fast-charging LIBs with improved rate capabilities and interfacial kinetics.

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, Li1+xAlxGe2-x(PO4)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 (B2O3 and Bi2O3) with different functionalities. During synthesis, B2O3 facilitates the grain growth of LAGP, thereby reducing the number of grain boundaries. At the same time, Bi2O3 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.

The Ni-rich LiNi0.8Co0.1Mn0.1O2 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 Li3PO4 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 Li3PO4 nanolayer that inhibits parasitic reactions at the electrode–electrolyte interface. Furthermore, Li3PO4 provides an effective barrier to H2O and CO2 infiltration into the particle agglomerates, thereby suppressing the loss of particle integrity.

A rechargeable lithium–oxygen battery (LOB) operates via the electrochemical formation and decomposition of solid-state Li2O2 on the cathode. The rational design of the cathode nanoarchitectures is thus required to realize high-energy-density and long-cycling LOBs. Here, we propose a cathode nanoarchitecture for LOBs, which is composed of mesoporous carbon (MPC) integrated with carbon nanotubes (CNTs). The proposed design has the advantages of the two components. MPC provides sufficient active sites for the electrochemical reactions and free space for Li2O2 storage, while CNT forests serve as conductive pathways for electron and offer additional reaction sites. Results show that the synergistic architecture of MPC and CNTs leads to improvements in the capacity (~ 18,400 mAh g− 1), rate capability, and cyclability (~ 200 cycles) of the CNT-integrated MPC cathode in comparison with MPC.

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 (, 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.

Solid-state batteries (SSBs) offer a fundamental solution to mitigate the safety and reliability issues of conventional lithium-ion batteries utilizing flammable liquid electrolytes, and enable the bipolar configuration of high-voltage and high-energy storage systems. However, the conventional layer-by-layer (LbL) stacking process using individual electrolyte and electrode layers suffers from poor electrolyte–electrode contacts and challenging process complications for manufacturing multi-layer bipolar SSBs. Herein, we report an electrode-to-electrode (EtE) monolithic integration without a free-standing solid electrolyte layer for high-voltage bipolar SSBs. Positive and negative electrodes seamlessly combined with a thin solid electrolyte are fabricated by the infusion of a plastic-crystal-based polymer electrolyte (PCPE) into porous electrodes with a subsequent ultraviolet-induced solidification process. The infused PCPE in the electrodes forms continuous Li+ conduction channels as well as intimate solid–solid interfaces. The thin PCPE film (∼10 μm) formed in situ on the top of the electrodes during the infusion process provides ultra-high Li+ conductance (∼3.1 S cm−2 at 45 oC) between the two electrodes. SSBs are constructed via direct integration of the PCPE-infused electrodes: a unit cell-type SSB with LiNi0.6Co0.2Mn0.2O2 (positive) and Li4Ti5O12 (negative) show superior capacity (∼160 mAh g−1), rate capability (98 mAh g−1 at 2 C), and stable cyclability (81% after 100 cycles) at 45 oC than the SSB fabricated by the conventional LbL stacking process. Moreover, a 10 V-class, bipolar SSB comprising five unit cells stacked in series is constructed via the EtE monolithic integration of multiple PCPE-infused bipolar electrodes, and its stable cycle performance is corroborated with a capacity retention of 84%. This work demonstrates that the suggested EtE integration process offers a promising strategy to addressing the interfacial contact issues of SSBs, thereby being utilized to realize scalable, low-cost, high-voltage bipolar SSBs.

The use of solid electrolytes provides a technical solution to address the safety issues of lithium-ion batteries and enables a bipolar design of high-voltage and high-energy battery modules. The bipolar design avoids unnecessary components and parts for packaging and electrical connection; therefore, it facilitates an increase in the volumetric energy density of the battery, while enabling easy build-up of total output voltage. Herein, the design and construction of a multilayered, bipolar-type, all-solid-state battery (ASSB) from a biphasic solid electrolyte (BSE) based on inorganic Li0.29 La0.57 TiO3 perovskite and poly(ethylene oxide) (PEO) are reported. A flexible and freestanding BSE membrane exhibits high Li+ conductivity of about 1.2×10-4 S cm-1 , and shows enhanced electrochemical/thermal stability, in comparison to a PEO-only solid electrolyte. A single-layered ASSB assembled with a BSE shows promising electrochemical performance, as evidenced by a high reversible capacity of about 123 mA h g-1 and excellent cycling stability over 100 cycles. Furthermore, a proof-of-concept bipolar ASSB comprising three unit cells connected in series is constructed by using the BSE membrane and Al/Cu-cladded bipolar plates. The bipolar ASSB shows high thermal stability and operates reversibly without any internal short circuit or current leakage during charge-discharge cycles; this demonstrates that BSEs provide a promising approach to the design and fabrication of bipolar ASSBs with improved safety and high energy density.

Ether-based organic liquid electrolytes (OLEs) have been commonly used in lithium–oxygen batteries (LOBs); however, they become unstable and cause rapid performance degradation during LOB operation. To address these problems, in this study we propose an OLE-free cathode architecture based on a Li+-selective solid membrane (LSSM). An LSSM with a seamless duplex (dense/porous) architecture is prepared by a tape casting process combined with co-sintering, and carbon nanotubes (CNTs) decorated with Au nanoparticles (CNT@Au) are directly formed on its porous framework. We show that the duplex-LSSM can effectively protect the metallic Li anode from parasitic reactions with impurity species and improve the cycling stability of Li. Furthermore, an LOB assembled with the duplex-LSSM and CNT@Au components exhibits a discharge capacity as high as 3650 mAh g−1 and improved cycling stability (>140 cycles) compared to a conventional OLE-based LOB; this can be explained in terms of the combined advantages provided by the OLE-free cathode and the LSSM-protected Li anode.

All-solid-state lithium batteries offer notable advantages over conventional Li–ion batteries with liquid electrolytes in terms of energy density, stability, and safety. To realize this technology, it is critical to develop highly reliable solid-state inorganic electrolytes with high ionic conductivities and adequate processability. Li1+xAlxTi2−x(PO4)3 (LATP) with a NASICON (Na superionic conductor)-like structure is regarded as a potential solid electrolyte, owing to its high “bulk” conductivity (ca. 10−3 S cm−1) and excellent stability against air and moisture. However, the solid LATP electrolyte still suffers from a low “total” conductivity, mainly owing to the blocking effect of grain boundaries to Li+ conduction. In this study, an LATP–Bi2O3 composite solid electrolyte shows very high total conductivity (9.4×10−4 S cm−1) at room temperature. Bi2O3 acts as a microstructural modifier to effectively reduce the fabrication temperature of the electrolyte and to enhance its ionic conductivity. Bi2O3 promotes the densification of the LATP electrolyte, thereby improving its structural integrity, and at the same time, it facilitates Li+ conduction, leading to reduced grain-boundary resistance. The feasibility of the LATP–Bi2O3 composite electrolyte in all-solid-state Li batteries is also examined in this study.

Solid electrolytes are key to the evolution of all-solid-state lithium batteries as next-generation energy storage systems. High ionic conductivity and stability of solid electrolytes are critical requirements for designing reliable all-solid-state lithium batteries. Perovskite-type lithium lanthanum titanates Li3xLa(2/3)−x□(1/3)−2xTiO3 (LLTOs) have received much attention as a potential inorganic solid electrolyte to replace current organic liquid electrolytes; however, the practical use of LLTOs is limited by their low total conductivity. With the aim of improving the ionic conductivity, we investigated a correlation between the microstructures and Li+ conducting properties of LLTO perovskites. We show that the total conductivity of LLTOs is dominated by the domain boundary resistance, and the synthesis condition of the electrolyte (sintering temperature and Li concentration) has a crucial role in modifying the microstructure and composition of the domain boundaries to significantly reduce the boundary resistance. By controlling the sintering temperature and Li content, in particular, a total Li+ conductivity as high as 4.8 × 10−4 S cm−1 can be achieved at room temperature. The findings of this study would be essential in understanding Li+ conducting behaviors and in developing highly conductive perovskite-type LLTO solid electrolytes.

Solid-state batteries (SSBs) offer a promising technical solution to meet the key requirements of future energy storage systems, i.e., safety and high energy density. However, the realization of SSBs is hindered by low electrode performance that results from poorly controlled solid-solid contacts. Herein, we propose an effective strategy for tailoring conductive networks and reaction interfaces via the viscosity-controlled infusion of a molten-state polymer electrolyte precursor (polymer ionic conductor, PIC) into a porous composite electrode (CE). A poly(ethylene glycol)-based PIC penetrates a three-dimensional pore network of the CE and transforms to a highly viscous, stable phase under battery operating conditions. The infused PIC enables the formation of percolating Li+ conduction pathways as well as intimate solid-solid reaction interfaces, which leads to the full utilization of the CE at high mass loadings. SSBs assembled with PIC-infused LiFePO4-CEs exhibit superior capacity (154 mAh g−1), rate-capability, and cycling stability than SSBs with unmodified CEs. Moreover, a 10 V-class, bipolar-pouch SSB fabricated using the PIC-infusion technology shows reversible charge–discharge operations without a considerable performance loss. This study demonstrates that the proposed microstructural engineering provides an effective approach to resolving the interfacial solid-solid contact issues of SSBs and can be used to fabricate safe, high-energy, long-cycling SSBs.

Lithium–air battery (LAB) technology is currently being considered as a future technology for resolving energy and environmental issues. During the last decade, much effort has been devoted to realizing state-of-the-art LABs, and remarkable scientific advances have been made in this research field. Although LABs possess great potential for efficient energy storage applications, there are still various technical limitations to be overcome before the full transition. It has been well recognized that the battery performance of LABs is mainly governed by the electrochemical reactions that occur on the surface of the cathode. Thus, the rational design of highly reliable cathodes is essential for building high-performance LABs. In this respect, we introduce recent advances in the development of LABs, particularly focusing on the cathodes based on a fundamental understanding of Li–O2 electrochemistry. Furthermore, we review the remaining technical challenges in order to formulate a strategy for future research and consolidate Li–O2 electrochemistry for successful implementation of LABs in the near future.

A Ge/GeO 2 composite embedded in a carbon matrix (Ge/GeO 2 /C) is synthesized using a one-step mechanical ball-milling method, and its potential as a Li-ion battery anode material is evaluated. Characterization using scanning electron microscopy and transmission electron microscopy reveal that the uniformly distributed germanium and oxygen elements are embedded in the carbon matrix. In situ X-ray diffraction analysis provides insight into the complex conversion reaction as well as the Li–Ge alloy reaction. The Ge/GeO 2 /C composite exhibits a fairly high capacity of 915 mAh g −1 up to 50 cycles (with good cycling and a high rate capability). The improvement in the electrochemical performance arises from the synergistic effects of the reduced particle size, conductive carbon matrix, and catalytic function of Ge to mitigate mechanical strain and provide an efficient network for electron transfer.

To demonstrate an aqueous sodium-polyiodide flow battery (SIFB) for the first time, sodium titanium phosphate (NaTi2(PO4)3) was utilized as the negative electrode and I−/I3− couple was adopted as the positive redox active species. SIFB not only shows advantages of cost-effectiveness and environmental friendliness based on earth-abundant elements of sodium and iodine, but also exhibits a high energy density due to the high solubility of sodium iodide (~12.3 M at room temperature). Although NaTi2(PO4)3 has several advantages such as high Na-ion conductivity and good structural stability, its use as a negative electrode is limited because of intrinsically low electrical conductivity. In this study, NaTi2(PO4)3 nanoparticles were embedded in double carbon networks comprising internal and external carbon layers. Individual effects by the internal and external carbon networks on the electrochemical performance of NaTi2(PO4)3 were clearly distinguished. With the simultaneous formation of the two carbon networks, a SIFB exhibited outstanding electrochemical performance (86.0 mAh•g−1 at a rate of 7 C) and a long cycle life (93.5% capacity retention after 100 cycles).

O3-type Na[Ni1/3Fe1/3Mn1/3]O2 (NaNFM) is considered as a promising cathode material for sodium-ion batteries; however, its poor cycling stability is still a concern. In this study, we discuss the structural, surface and electrochemical properties of Mg-doped NaMgx[Ni1/3Fe1/3Mn1/3]1–xO2 materials and their enhanced cycling performance. The variations of the lattice parameters by substitution of Mg ion and its uniform distribution on the particles are confirmed using X-ray diffraction and transmission electron microscopy. The optimized NaMg0.05[Ni1/3Fe1/3Mn1/3]0.95O2 delivers a discharge capacity of ~120 mAh g−1 and has a diffusion coefficient of Na ranging from 6.5 × 10−13 to 2.7 × 10−10 cm2 s−1. In particular, it shows a relatively high discharge capacity of 42 mAh g−1 even at a high current density of 1200 mA g−1 and exhibits considerably enhanced cycling stability (77% capacity retention after 50 cycles), compared with that of the undoped NaNFM (40%). Based on structural and electrochemical analyses, it is suggested that Mg doping can effectively suppress the irreversible structural degradation and induce more reversible phase transitions; this results in a more stable cycling performance of the Mg-doped NaNFM than that of undoped NaNFM.

Carbon nanotubes (CNTs) have been considered as a potential anode material for next generation Lithium-ion batteries (LIBs) due to their high conductivity, flexibility, surface area, and lithium-ion insertion ability. However, the low mass loading and bulk density of carbon nanomaterials hinder their use in large-scale energy storage because their high specific capacity may not scale up linearly with the thickness of the electrode. To address this issue, a novel three-dimensional (3D) architecture is rationally designed by stacking layers of free-standing CNTs with the increased areal density to 34.9 mg cm −2 , which is around three-times higher than that of the state-of-the-art graphitic anodes. Furthermore, a thermal compression process renders the bulk density of the multi-stacked 3D CNTs to be increased by 1.85 g cm −3 , which yields an excellent volumetric capacity of 465 mAh cm −3 at 0.5C. Our proposed strategy involving the stacking of 3D CNT based layers and post-thermal compression provides a powerful platform for the utilization of carbon nanomaterials in the advanced LIB technology.

In the present work, to increase the chemical stability of the lithium-ion-conducting ceramic electrolyte (, LATP) in the strong alkaline solution, the surface of LATP was modified by the nitridation process. The surface and structural properties of nitride LATP solid electrolyte were characterized by X-ray diffraction, X-ray photoelectron spectrometer and scanning electron microscopy and ac-impedance spectroscopy, which were correlated to the chemical stability and electrochemical performance of LATP. The nitrided LATP immersed in the alkaline solution for 30 days exhibits the enhanced chemical stability than the pristine LATP. Moreover, a rechargeable hybrid Li-air battery constructed with the nitrided LATP solid electrolyte shows considerably reduced discharge-charge voltage gaps (enhanced the round-trip efficiency) in comparison to the cell constructed with pristine LATP, which indicate that the surface nitridation process can be the efficient way to improve the chemical stability of solid electrolyte in alkaline media.

To improve the electrochemical performance of Li-S rechargeable batteries, tunable porous carbon materials, which are known as carbide-derived carbons (CDCs), are employed as adsorbents and conductive matrices for the cathodic sulfur materials. A new assembly for Li-S cells was developed by introducing multi-layer membranes as separators. The use of the multi-layer membranes enables the minimization of the shuttle effect by expanding the distance between the separators and blocking the penetration of the polysulfide. The best discharge capacity and cycle life were obtained with ten layers of PP membrane in a sulfur-CDC@1200 composite cathode, resulting in a discharge capacity of 670 mA h g−1 and a minimal gap in the charge-discharge capacity during cell cycling.

Titanium-based oxides have been considered promising anode materials for rechargeable sodium (Na)-ion batteries (NIBs); however, the slow reaction kinetics of TiO2 due to its low electrical conductivity remains a critical problem to be addressed for its practical application in NIBs. Here, we report one-dimensional (1D) TiO2–C composite nanofibers for use as an anode for NIBs, which were fabricated via an electrospinning technique combined with optimized heat-treatment. The TiO2–C composite nanofibers are composed of tiny anatase TiO2 nanocrystals surrounded by and/or embedded in the conducting carbon matrix. When tested in an electrochemical Na cell, the TiO2–C nanofiber electrode retained a high charge capacity of 140 mA h g−1, even after 100 cycles at a current density of 60 mA g−1, and it exhibited excellent rate-capability (105 mA h g−1 at 3 A g−1), proving its feasibility as an NIB anode. The superior Na storage performance of the nanofiber anode is mainly attributed to the unique composite architecture, that is, a large number of active sites per volume due to the high aspect ratios and short lengths for Na transport through 1D nanofibers and TiO2 nanocrystals as well as highly conducting electron paths.

Aluminium doped lithium lanthanum titanate (A-LLTO) powders with various excess Li 2 O content are synthesized using a simple citrate gel method. The obtained A-LLTO powders show an agglomerated form, composed of nano-sized particles of 20–50 nm. The morphology and conductivity of the A-LLTO ceramics are largely affected by the content of excess Li 2 O. The highest total ionic conductivity of 3.17 × 10 −4 S cm −1 is achieved for the A-LLTO sample containing 20% excess Li 2 O, exhibiting a vacancy content of 6%, and a total activation energy of 0.358 eV. The A-LLTO can act as a membrane to protect lithium metal from oxygen and other contaminants diffused through the oxygen electrode part. The Li–O 2 cell employing the A-LLTO solid electrolyte shows a good cycle life of longer than 100 discharge-charge cycles, under the constant capacity mode of 300 mAh g −1 .

Cauliflower-like WO 3 was synthesized by a hydrothermal reaction without a surfactant, followed by firing, and was investigated as an anode material for lithium-ion battery applications. The scanning electron microscope (SEM) and transmission electron microscope (TEM) characterization indicated that WO 3 nanorods had an aggregation framework and built a cauliflower morphology. With the objective of understanding the charge–discharge process within a voltage range of 0–3 V vs. Li + /Li, in situ X-ray diffraction was used and a complex reaction of intercalation and conversion of WO 3 was revealed for the first time. The cauliflower-like WO 3 after being decorated with carbon provides a high gravimetric capacity of >635 mA h/g (Li 5.5 WO 3 ) with good cycling and a high rate capability when used as an anode in lithium-ion batteries. Based on our studies, we attribute the high electrochemical performance to the nanoscopic WO 3 particles and a conductive carbon layer, which makes them a potential candidate for lithium-ion batteries.

A nitrate/urea mixture was used as fuel to simply combustion-synthesize LiNi0.6Co0.2Mn0.2O2 as a high-capacity cathode material for lithium ion batteries. The reaction formulas and physical properties of the resultant cathode materials sintered at various temperatures were examined using thermogravimetric analysis/simultaneous differential thermal analysis, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectrometry, and inductively coupled plasma/atomic emission spectrometry. The influence of sintering temperature on the electrochemical performance was evaluated by analyzing the charge/discharge profiles and cycling and rate-capability performances. The LiNi0.6Co0.2Mn0.2O2 cathode sintered at 800 C exhibited a discharge capacity of 170 mA h g � 1 measured at a constant 20 mA g � 1 , 98.2% capacity retention after 30 cycles, and better rate capability than the cathodes sintered at 700, 900, and 1000 C. The experimental results suggest that the enhanced electrochemical performance of the LiNi0.6Co0.2Mn0.2O2 cathode sintered at 800 C is attributable to the pure, well-organized layered structure containing few mixed cations and to the shorter diffusion path resulting from the uniformly distributed nanoparticles.

To improve the electrochemical performance of natural graphite anodes, we have designed a facile, scalable carbon-coating process using coal-tar pitch and ammonium hexafluorophosphate (NH4PF6) as a structural modifier. NH4PF6 effectively modifies the microstructure of amorphous carbon, coated on the surface of the natural graphite, leading to better, reversible Li+-storage characteristics within a wide operating-temperature range (from −20 to 60 °C). The COP linkage introduced as a result of the thermal decomposition of NH4PF6 assists the formation of open nanopores in the amorphous carbon layer. The integrated nanopores act as additional reversible Li+-storage sites, which minimize the reversible capacity loss and improve the cycle performance of natural graphite. Moreover, the thermal stability of natural graphite can also be improved while maintaining the improved electrochemical performance. Thus, this approach is a step toward the practical use of natural graphite anodes for lithium-ion batteries for electric-vehicle applications.

An important component in lithium–air batteries is the oxygen electrode, which facilitates the oxygen reduction reaction during the discharge process and the oxidation reaction of Li 2 O 2 during the charge process. The performance of the oxygen electrode strongly depends upon the activity of the materials employed. Herein, we report the catalytic activity of the graphene/zirconium doped ceria (ZDC) nano-blend prepared by mixing graphene, which is prepared using the modified Hummers method followed by H 2 reduction, and ZDC, chemically prepared. With merely 10% loading of ZDC on the graphene, Li-O 2 cells showed a threefold increase in their discharge capacities. The well exfoliated layered structure of graphene and the mesoporous structure of ZDC facilitated the diffusion of the electrolyte and oxygen in the inner electrode to enhance the catalytic efficiency and also offered ample volume for the accumulation of discharge product. The synergistic effect of the fast kinetics of electron transport provided by the graphene support and the high electro-catalytic activity provided by the ZDC resulted in the excellent performance of the oxygen electrode in the Li-O 2 batteries.

All-solid-state-batteries (ASSBs) provide technical solution to address the challenges of high safety and high energy density for future energy storage. However, their practical applications have been mainly hindered by the interfacial issues, since it is very challenging to construct intimate contact between the solid electrode and electrolyte due to their rigidity in conventional ASSBs, which leads to high polarization and low utilization of active materials. Herein, we demonstrate a simple but effective interfacial engineering approach to mitigate the poor interfacial contact via incorporating deformable polymer solid electrolyte (PSE) into the composite electrode. For the purpose, the poly(ethylene glycol)-based PSE was directly casted on and thermally infiltrated into the composite cathode (LiFePO4). From the various physicochemical and microstructural analyses, it was found that PSE exhibits the moderate Li+ conductivity (~ 6.6 × 10-4 S cm-1 at 65 oC) and wide electrochemical window (~ 4.5 V vs. Li/Li+), and its rheological properties are strongly dependent on the temperature. It was also observed that micro-pores in the composite electrode are completely filled without any cracking and the active components are fully covered by the deformable PSE. The cells assembled with PSE-incorporated cathode clearly exhibited the superior storage capacity, rate-capability and cyclablity in comparison with the pristine composite electrode. Moreover, 10 V-class bipolar ASSB (~10 mAh) comprising three unit cells connected in series was designed and constructed by using PSE-incorporated cathode, and its stable electrochemical performance was also demonstrated. Those results suggest that the PSE-infiltration process is considerably helpful for promoting the Li+ transport in the composite electrode by establishing intimate contacts between the solid electrolyte and active materials, and continuous ionic path through the whole composite electrode.

Lithium ion batteries (LIBs) have been successfully utilized as power sources for various electronic devices (e.g. mobile phone, remote controller, lab-top, etc.). Recently, the application of LIBs is extending to emerging markets such as electric vehicles (EVs) and energy storage systems (ESSs) for grid-supporting. Unfortunately, conventional LIBs still suffer from safety issues associated with the use of flammable organic electrolytes. To overcome such limitation of LIBs, many attentions have been devoted to the development of all-solid-state batteries (ASBs) that are employing solid electrolytes with excellent structural and electrochemical stabilities. Li1+xAlxGe2–x(PO4)3 (LAGP) is a kind of potential solid electrolytes with a NASICON structure. It offers relatively high bulk ionic conductivity (~10-4 Scm-1) with a wide electrochemical window and great moisture tolerance.[2] Owing to these advantages, LAGP can be a great option as a practical solid electrolyte for realizing ASBs. However, there are some technical issues to be resolved before commercial use of LAGP solid electrolytes as follow; i) a low ionic conductivity arising from the high boundary resistance and ii) a high synthesis temperature (i.e. energy consumable process). In this work, the microstructures of LAGP solid electrolyte are tailored by addition of Bi2O3 and B2O3 with a purpose of improving the ionic conductivity and reducing the fabrication temperature. Based on various structural and electrochemical analyses, we investigate the correlation between microstructure and ionic conductivity of LAGP. In practice, Bi2O3 is able to improve the structural integrity of LAGP with turning down of the sintering temperature, leading to the densification of LAGP [1] and, on the other hand, B2O3 facilitates the grain growth of LAGP during synthesis.[3] As a result of co-addition of Bi2O3 and B2O3, the ionic conductivity of LAGP solid electrolyte increases about one order of magnitude higher than pristine LAGP. This work will provide a practical guideline to develop a highly reliable solid electrolytes for ABSs. (Figure 1 image) SD Lee and KN Jung, ChemSusChem 10, 2175 (2017) Masashi Kotobuki, Keigo Hoshina, Yasuhiro Isshiki, Phosphorus Research Bulletin 24, 061 (2010) Harsharaj S. Jadhav, Ramchandra S. Kalubarme, Seong-Yong Jang, KN Jung, Mo, Dalton Trans. 43, 11723 (2014) Figure 1

Driven by strong demands for long-range electric vehicles, extensive efforts have been devoted to design and develop advanced cathode materials with high capacity and high operating voltages. Given the commercialization possibility on an industrial scale, Ni-rich layered transition metal oxides, such as LiNi0.8Co0.1Mn0.1O2 (NCM811), with a high specific capacity, may be a reasonable choice. 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 Li3PO4 nanolayer via phosphate treatment. The accelerated storage stability test (ASST) 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. Based on the ASST studies combined with material characterizations (SEM, TEM, and XPS), the enhanced cycling and storage stability of phosphate-modified NCM811 is explained as follows. First, phosphate treatment eliminates Li residues that can easily be transformed to undesirable impurity phases such as Li2CO3 and LiOH. Second, a thin Li3PO4 nanolayer produced by the chemical reaction between residual Li and (NH4)2HPO4 effectively mitigates the parasitic electrolyte decomposition by preventing the direct contact between NCM811 and electrolyte. Third, the formation of Li3PO4 contributes to the increased ordering of the layered structure (i.e., reduced cation mixing). Finally, Li3PO4 serves as an effective protecting layer for H2O and CO2 infiltration during storage, thereby suppressing the deterioration of particle integrity.

The increasing number of fire/explosion incidents related to lithium-ion batteries (LIBs) for mobile devices and electric vehicles (EVs) in the recent years have raised significant concerns regarding their safety and reliability. The use of solid electrolytes provides a technical solution to address the safety issues of lithium-ion batteries and enables a bipolar design of high-voltage and high-energy battery modules. The bipolar design avoids unnecessary components and parts for packaging and electrical connection; therefore, it facilitates an increase in the volumetric energy density of the battery, while enabling easy build-up of total output voltage. Here, we report the design and construction of a multi-layered bipolar ASSB using a hybrid solid electrolyte (HSE) membrane. The HSE membrane proposed in this work consists of inorganic Li0.29La0.57TiO3 (LLTO) perovskite and poly(ethylene oxide) (PEO). The perovskite-structured LLTO was selected as an inorganic solid electrolyte specifically as a result of its high Li+ conductivity, excellent mechanical strength, and high chemical stability against moisture. The hybridization of LLTO with PEO allows for the fabrication of thin and large-area electrolyte membranes with high ionic conductivity, without the need for high-temperature sintering. Moreover, the soft and adhesive PEO improves the interfacial contact between the electrolyte and electrode, resulting therefore in enhanced electrochemical performance of the prepared ASSBs. Although the concept of hybridization between inorganic material (garnet-Li7La3Zr2O12 and NASICON-Li1.5Al0.5Ge1.5(PO4)3) and polymer has been proposed previously, the focus in these earlier studies has been predominantly on optimizing the electrolytes to improve their Li+-conducting and/or mechanical properties and/or demonstrating their applications in the monopolar-type, small-sized ASSB. By contrast, little attention has been given to the design and fabrication of bipolar ASSBs with HSEs, which is essential for demonstrating the feasibility of HSEs in large-scale ASSBs with high voltage and energy. In this study, the HSE membranes based on LLTO and PEO were synthesized in the form of flexible and freestanding sheets with a thickness of ~30 mm using a simple casting method. The optimized HSE membrane exhibits remarkably enhanced Li+ conductivity, electrochemical window, and thermal stability when compared to a solid PEO-only membrane, facilitating reversible charge–discharge operations of ASSBs. Finally, a proof-of-concept bipolar ASSB comprising three unit cells connected in series was designed and constructed using the HSE membrane, and its electrochemical performance was investigated.

Rechargeable lithium–oxygen batteries have attracted considerable attention due to their high energy density. The critical challenges that limit the practical use of this technology include sluggish kinetics of the electrochemical oxygen reactions on the cathode during discharging and charging. Here, urchin-like α-MnO2 materials decorated with Au and Pd nanoparticles are developed for use as a cathode catalyst for rechargeable Li–O2 batteries with hybrid electrolytes. Au and Pd particles as large as 3–8 nm are uniformly dispersed on the vertically aligned nanorods of α-MnO2. The Au/α-MnO2 and Pd/α-MnO2 catalysts show excellent bi-functional activity for both oxygen reduction and evolution. A rechargeable Li–O2 battery with a hybrid electrolyte is constructed using the nanostructured composite catalysts. Charging and discharging experiments of the batteries indicate that the metal-decorated, urchin-like α-MnO2 can be used as an efficient bi-functional catalyst for rechargeable hybrid Li–O2 batteries.

The effects of B 2 O 3 addition on the properties of the Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) glass ceramic have been studied. The crystallization temperature of the LAGP decreases with the addition of B 2 O 3 . The glasses are crystallized at different temperatures and characterized for microstructure and ionic conductivity. The highest total conductivity of the glass ceramic material, 6.9 × 10 −4 S cm −1 at 25 °C is achieved by crystallizing the glass at 825 °C for 5 h with the addition of 0.05 wt% B 2 O 3 . Non-linearity in Arrhenius plot is observed due to the characteristics of AlPO 4 dielectric phase. In addition, the B 2 O 3 added LAGP glass ceramic is stable in weak acidic and neutral solutions, but highly corroded in strong acidic and basic solutions.

Carbide-derived carbons (CDCs), part of a large family of carbon materials derived from carbide, are attractive for energy-related applications, such as batteries, supercapacitors, and fuel cells. Pore textures (micro-, meso-, and macro-pores) and structures (from amorphous to highly ordered graphite) of CDCs can be controlled by changing the synthesis conditions and carbide precursor. Adequate control of the carbon structure, and the porosity in terms of application as an anode can be exploited to maximize the electrochemical capacity in a lithium ion batteries. In this study, the use of CDC as anodes by chlorine treatment of B 4 C and TiC 7 N 3 in a synthesis temperature range from 600 °C to 1200 °C has been explored. The discharge capacity of TiC 7 N 3 -CDC reaches the highest value, 462 mA h g −1 , at 100 cycles, which is 25% higher than the theoretical capacity of graphite (375 mA h g −1 ). B 4 C-CDC meanwhile affords a value of 453 mA h g −1 at 100 cycles. These results show that B 4 C-CDC and TiC 7 N 3 -CDC have excellent potential as the negative electrode in Li battery applications, and can be exposed to a practical low synthesis temperature range of 600–1200 °C. B 4 C-CDC and TiC 7 N 3 -CDC can also provide 2–3 times better performance than existing graphite or hard carbon for lithium battery systems.

N-doped mesoporous carbon decorated TiO2 nanofibers were synthesized for the first time by a facile electrospinning process combined with subsequent heat treatment and investigated as an anode material for lithium-ion battery applications. The N-doped mesoporous carbon decorated TiO2 nanofibers had continuous one-dimensional (1-D) geometry with a smooth surface and an average thickness of ∼250 nm. The nanofibers comprised both interconnected polycrystalline TiO2 and numerous mesopores in N-doped carbon. After 100 cycles at current density of 33 mA/g, the N-doped mesoporous carbon decorated TiO2 nanofibers still exhibited a high capacity of 264 mAh/g. This superior electrochemical performance is attributed to small TiO2 crystallites, N-doped mesoporous carbon, favorable 1-D nanostructures, and smooth accommodation of the strain occurring during the charge–discharge process.

Lithium–air battery (LAB) technology is currently being considered as a future technology for resolving energy and environmental issues. During the last decade, much effort has been devoted to realizing state-of-the-art LABs, and remarkable scientific advances have been made in this research field. Although LABs possess great potential for efficient energy storage applications, there are still various technical limitations to be overcome before the full transition. It has been well recognized that the battery performance of LABs is mainly governed by the electrochemical reactions that occur on the surface of the cathode. Thus, the rational design of highly reliable cathodes is essential for building high-performance LABs. In this respect, we introduce recent advances in the development of LABs, particularly focusing on the cathodes based on a fundamental understanding of Li–O2 electrochemistry. Furthermore, we review the remaining technical challenges in order to formulate a strategy for future research and consolidate Li–O2 electrochemistry for successful implementation of LABs in the near future.

There is a great deal of current interest in the development of rechargeable sodium (Na)-ion batteries (SIBs) for low-cost, large-scale stationary energy storage systems. For the commercial success of this technology, significant progress should be made in developing robust anode (negative electrode) materials with high capacity and long cycle life. Sn-P compounds are considered promising anode materials that have considerable potential to meet the required performance of SIBs, and they have been typically prepared by high-energy mechanical milling. Here, we report Sn-P-based anodes synthesised through solvothermal transformation of Sn metal and their electrochemical Na storage properties. The temperature and time period used for solvothermal treatment play a crucial role in determining the phase, microstructure, and composition of the Sn-P compound and thus its electrochemical performance. The Sn-P compound prepared under an optimised solvothermal condition shows excellent electrochemical performance as an SIB anode, as evidenced by a high reversible capacity of ~560 mAh g−1 at a current density of 100 mA g−1 and cycling stability for 100 cycles. The solvothermal route provides an effective approach to synthesising Sn-P anodes with controlled phases and compositions, thus tailoring their Na storage behaviour.

A sulfur-microporous (S-MIP) carbon composite was prepared for use as a cathode for rechargeable Li/S batteries. Two sulfur-embedded methods, S-impregnation (IS) and S-liquefied pore filling (LS), were applied for the preparation of the S-MIP carbon composites. The pristine elemental S of the polycrystalline α-S8 undergoes a structural change to an amorphous-S (a-S) structure in the S-MIP carbon composite created by the IS method. During sulfur loading of 40–50 wt %, the S-MIP carbon composite created by the IS method showed a BET SSA value of around 500 m2 g−1 and a pore volume of 0.2 cm3 g−1. However, after the LS process was applied to the S-MIP carbon composite, at 160 °C and 10 h, the a-S structure in the S-MIP carbon composite became recrystalline α-S8. Little remained of the porosity in the S-MIP carbon composite prepared by the LS method due to the large portion of the S crystalline phase. The best discharge capacity was obtained with an S-MIP carbon composite created by the IS method, with the result of 680 mA h g−1 after 50 cycles at 0.1 °C, i.e., ~47 % higher than that by the LS method.

Nitrided MoO 2 has been synthesized by hydrothermal processing followed by post-nitridation with NH 3 and investigated as alternative anode materials for rechargeable lithium batteries. Characterization data reveal the presence of molybdenum nitride (γ-Mo 2 N and δ -MoN) and molybdenum oxynitride (MoO x N y ). The nitrided MoO 2 exhibits a capacity of >420 mAh/g after 100 cycles and good rate capability. The improved electrochemical performance of the nitrided MoO 2 compared to that of molybdenum oxide (MoO 2 ) is attributed to high electrical conductivity provided by nitrogen doping/or substitution in the oxygen octahedral site of MoO 2 structure.

A LiNi 0.8 Co 0.15 Al 0.05 O 2 –graphene composite has been synthesized by a high energy mechanical ball milling (HEMM) process. The structural and morphological features of the synthesized samples are characterized by various techniques. Electrochemical studies on the LiNi 0.8 Co 0.15 Al 0.05 O 2 –graphene composite are conducted using of the galvanostatic charge–discharge process and electrochemical impedance spectroscopy methods by constructing a lithium-ion cell. The LiNi 0.8 Co 0.15 Al 0.05 O 2 –graphene composite exhibits a high capacity of >180 mA h/g with good cyclability and high rate capability. The improved electrochemical performance is attributed to increased electrical contact provided by the graphene layer, which reduces the cell polarization.

In order to understand the nature of dendritic zinc growth, electrochemical zinc redox reaction on nickel plate was investigated in aqueous solutions containing different concentrations, 0.2, 0.1 and 0.02 (M), of zinc sulfate () or zinc chloride (). Zinc ion was efficiently reduced and oxidized on nickel in the high-concentration (0.2 M) solution, whereas relatively poor efficiency was obtained from the other low-concentration solutions (0,1 and 0.02 M). Cyclic voltammetry (CV) analysis revealed that the 0.2 M electrolyte solution decomposes at more positive potentials than the 0.1 and the 0.02 M solutions. These results suggested that the concentration of electrolyte solution and anion would be an important factor that suppresses the reaction of the zinc dendrite formation. Scanning Electron Microscopy (SEM) data revealed that the shape of dendritic zinc and its growing behavior were also influenced by electrolyte concentration.

A sulfur-multi walled carbon nanotubes (MWCNTs) composite is prepared by the direct precipitation method as a cathode material for lithium sulfur batteries. The microstructure and morphology of the sulfur-MWCNTs composite are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) mapping and thermogravimetric analysis (TGA). From these results, it is found that the synthesized sulfur has an orthorhombic phase and the MWCNTs are chemically well-dispersed over the whole surface of the synthesized sulfur. Electrochemical charge–discharge tests demonstrated that the sulfur-MWCNTs composite exhibits better capacity retention (63%) than that (16%) of the precipitated sulfur, which is also prepared by the direct precipitation method without MWCNTs. The enhanced cycle performance of the sulfur-MWCNTs is mainly attributed to the formation of highly conductive electron path due to the uniformly dispersed MWCNTs. Furthermore, in order to investigate the electrochemical reaction mechanism for the Li–S cell during the discharge process, the ac-impedance spectra as a function of the state of discharge are measured and analyzed.