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Separators play an essential role in lithium (Li)-based secondary batteries by preventing direct contact between the two electrodes and providing conduction pathways for Li-ions in the battery cells. However, conventional polyolefin separators exhibit insufficient electrolyte wettability and thermal stability, and in particular, they are vulnerable to Li dendritic growth, which is a significant weakness in Li-metal batteries (LMBs). To improve the safety and electrochemical performance of LMBs, Al2O3 nanoparticles and nanocellulose (NC)-coated non-woven poly(vinylidene fluoride)/polyacrylonitrile separators were fabricated using a simple, water-based blade coating method. The Al2O3/NC-coated separator possessed a reasonably porous structure and a significant number of hydroxyl groups (-OH), which enhanced electrolyte uptake (394.8%) and ionic conductivity (1.493 mS/cm). The coated separator also exhibited reduced thermal shrinkage and alleviated uncontrollable Li dendritic growth compared with a bare separator. Consequently, Li-metal battery cells with a LiNi0.8Co0.1Mn0.1O2 cathode and an Al2O3/NC-coated separator using either liquid or solid polymer electrolytes exhibited improved rate capability, cycle stability, and safety compared with a cell with a bare separator. The present study demonstrates that combining appropriate materials in coatings on separator surfaces can enhance the safety and electrochemical performance of LMBs.

The development of highly efficient catalysts in the cathodes of rechargeable Li-O2 batteries is a considerable challenge. Polyelemental catalysts consisting of two or more kinds of hybridized catalysts are particularly interesting because the combination of the electrochemical properties of each catalyst component can significantly facilitate oxygen evolution and oxygen reduction reactions. Despite the recent advances that have been made in this field, the number of elements in the catalysts has been largely limited to two metals. In this study, we demonstrate the electrochemical behavior of Li-O2 batteries containing a wide range of catalytic element combinations. Fourteen different combinations with single, binary, ternary, and quaternary combinations of Pt, Pd, Au, and Ru were prepared on carbon nanofibers (CNFs) via a joule heating route. Importantly, the Li-O2 battery performance could be significantly improved when using a polyelemental catalyst with four elements. The cathode containing quaternary nanoparticles (Pt-Pd-Au-Ru) exhibited a reduced overpotential (0.45 V) and a high discharge capacity based on total cathode weight at 9130 mAh g-1, which was ∼3 times higher than that of the pristine CNF electrode. This superior electrochemical performance is be attributed to an increased catalytic activity associated with an enhanced O2 adsorbability by the quaternary nanoparticles.

The selection and design of catalysts are key factors in determining the performance of lithium–oxygen (Li–O2) batteries. Among a diverse selection of catalysts, platinum (Pt) is attracting attenti...

Current lithium-ion batteries are vulnerable to fire accidents and explosions because liquid electrolytes have a low flash point and poor thermal stability. This intrinsic problem has led to an ever-growing interest in solid-state polymer electrolytes with high thermal stability. In this study, a solidified polyether-based polymer electrolyte is incorporated into a graphite/LiFePO4 full-cell battery. A liquid precursor, which is prepared by mixing the bisphenol A ethoxylate diacrylate (BisA) crosslinker and the poly(ethylene glycol) dimethyl ether (PEGDME) plasticizer, first wets the anode and cathode, and is then solidified by in situ thermal crosslinking to produce a solid polymer electrolyte. BisA forms a rigid crosslinked network and PEGDME conducts lithium ions within the network. Analysis results, including in situ X-ray diffraction, show that PEGDME in the polymer electrolyte is co-intercalated with lithium ions into the gallery of the graphite electrode, which causes electrode exfoliation and severe capacity fading. Fluoroethylene carbonate is highly effective to prevent the co-intercalation of lithium–PEGDME complex ions into the graphite, via the formation of a solid electrolyte interphase layer, which leads to the ‘absolute intercalation’ of lithium ions. Consequently, the graphite/LiFePO4 full-cell battery based on the solid polymer electrolyte runs stably at a coulombic efficiency higher than 99% for most cycles and the residual capacity of the cell reaches 80% after 100 cycles.

The development of effective synthetic routes is important to manifest proper nature of specific materials. In-situ electrochemical functionalization possesses great advantages over conventional routes, especially facile way and leading to reaching elaborate sites of functional group. Here, we demonstrate the preparation of functionalized carbons by in-situ electrochemical reduction in an argon atmosphere for application in low-cost, environmentally benign, and high-performance oxygen-electrodes for non-aqueous Li–O2 batteries. A Li–O2 battery with functionalized carbon shows a high discharge capacity (100 times that of pristine carbon), high power and cycling stability. The outstanding performance is attributed to the high O2 affinity of the functionalized carbon surface that facilitates the formation of soluble and diffusible superoxide intermediates by the reduction of the remaining O2 competing with surface growth for Li2O2 formation.

Free-standing and binder-free cathodes composed of macroporous carbon nanofiber (MCNF) were fabricated by electrospinning for use in a Li–O2 battery. The use of cross-linked polystyrene colloids as templates enabled the as-prepared samples to have interconnected macropores along the MCNF interior with numerous surface openings. Additionally, Pt nanorods (PtNRs) were grown as catalysts on the MCNF surface (PtNR-MCNF) to enhance the performance of the Li–O2 battery using the cathode. Owing to the open-pore structure of the cathodes, the Li–O2 cells using the cathodes achieved a specific capacity of approximately 7000 mAh gc−1 and even more at a current density of 200 mA gc−1. In particular, the Li–O2 cell using the PtNR-MCNF cathode exhibited higher electrochemical performance in terms of rate capability, energy efficiency, and cycle stability. This study demonstrates that the growth of PtNRs resulted in the formation of poorly crystalized Li2O2, which significantly reduced the overpotentials, both during the discharge and the charge. Additionally, it contributed to the considerably prolonged cycle life of the Li–O2 cell using the PtNR-MCNF (468 cycles) compared to the cell using the MCNF cathode (272 cycles) with a limiting capacity of 1000 mAh gc−1 at a current density of 500 mA gc−1.

Despite the extremely high energy density of the lithium metal, dendritic lithium growth caused by nonuniform lithium deposition can result in low Coulombic efficiency and safety hazards, thereby inhibiting its practical applications. Here, we report a new strategy for adopting a nanopatterned gold (Au) seed on a copper current collector for uniform lithium deposition. We find that Au nanopatterns enhance lithium metal battery performance, which is strongly affected by the feature dimensions of Au nanopatterns (diameter and height).

The structural design and synthesis of sulfur-carbon composite materials with high performance is still a major challenge for rechargeable lithium-sulfur batteries. Interconnected three-dimensional frameworks comprising multi-walled carbon nanotubes, graphene, or carbon particles offer a combination of constituent advantages and can thus be used to achieve superior energy conversion and storage properties. Herein, we designed and prepared free-standing three-dimensional sulfur papers containing interconnected highly conductive carbon materials, which enable to be flexible binder-free cathodes for Li-S batteries. The resultant sulfur-carbon composite paper cathode exhibited high reversible specific capacity of 1386 mAhg−1, good rate capability up to 5C, and excellent cycling performance (a capacity retention 68% after 400 cycles), all of which are significantly improved from those of bare sulfur cathode or sulfur-GO composite only. Rational design of cathode composition, structure, and a simple fabrication process can give insight into the development of various advanced cathode materials for high-performance Li-S batteries.

Tin dioxide (SnO2) is a promising material for use as anodes because of its high theoretical capacity (1,494 mAh g−1). However, a critical limitation is the large change in volume during repeated cycling by pulverization of SnO2, which results in capacity fading. In this study, we enhanced cycle life and reduced capacity fading by introducing the use of three-dimensional SnO2 nanoparticles on carbon nanofibers (CNFs) as an anode material, which is fabricated by simple carbothermal shock through the Joule heating method. Our observations show that the SnO2 nanoparticles are about 50 nm in diameter and are uniformly distributed on CNF, and that the strong connections between SnO2 nanoparticles and CNF are sustained even after repeated cycling. This structural advantage provides high reversible capacity and enhanced cycle performance for over 100 cycles. This study provides insight into the fabrication of anode materials that have strong electric connections between active materials and conductive materials due to the Joule heating method for high-performance lithium ion batteries.

The development of highly efficient catalysts in the cathodes of rechargeable Li-O

Excessive overpotential during charging is a major hurdle in lithium-oxygen (Li-O2) battery technology. NO2-/NO2 redox mediation is an efficient way to substantially reduce the overpotential and to enhance oxygen efficiency and cycle life by suppressing parasitic reactions. Considering that nitrogen dioxide (NO2) is a gas, it is quite surprising that NO2-/NO2 redox reactions can be sustained for a long cycle life in Li-O2 batteries with such an open structure. A detailed study with in situ differential electrochemical mass spectrometry (DEMS) elucidated that NO2 could follow three reaction pathways during charging: (1) oxidation of Li2O2 to evolve oxygen, (2) vaporization, and (3) conversion into NO3-. Among the pathways, Li2O2 oxidation occurs exclusively in the presence of Li2O2, which suggests that NO2 has high reactivity to Li2O2. At the end of the charging process, most of the volatile oxidized couple (NO2) is stored by conversion to a stable third species (NO3-), which is then reused for producing the reduced couple (NO2-) in the next cycle. The dominant reaction of Li2O2 oxidation involves the temporary storage of NO2 as a stable third species during charging, which is an innovative way for preserving the volatile redox couple, resulting in a sustainable redox mediation for a high-performance Li-O2 battery.

Solid-state lithium batteries have been intensively studied as part of research activities to develop energy storage systems with high safety and stability characteristics. Despite the advantages of solid-state lithium batteries, their application is currently limited by poor reversible capacity arising from their high resistance. In this study, we significantly improve the reversible capacity of solid-state lithium batteries by lowering the resistance through the introduction of a graphene and wrinkle structure on the surface of the copper (Cu) current collector. This is achieved through a process of chemical vapor deposition (CVD) facilitating graphene-growth synthesis. The modified graphene/wrinkled Cu current collector exhibits a periodic wrinkled pattern 420 nm in width and 22 nm in depth, and we apply it to a graphite composite electrode to obtain an improved areal loading average value of ∼2.5 mg cm-2. The surface-modified Cu current collector is associated with a significant increase in discharge capacity of 347 mAh g-1 at 0.2 C when used with a solid polymer electrolyte. Peel test results show that the observed enhancement is due to the improved strength of adhesion occurring between the graphite composite anode and the Cu current collector, which is attributed to mechanical interlocking. The surface-modified Cu current collector structure effectively reduces resistance by improving adhesion, which subsequently improves the performance of the solid-state lithium batteries. Our study can provide perspective and emphasize the importance of electrode design in achieving enhancements in battery performance.

Optimized porous structure is a prerequisite for high performance Li‒O2 battery cathode. Macroporous-mesoporous carbon (MMC) is fabricated via a nano-replication method using mesoporous SiO2 (KIT-6) containing NiO as the template. By varying the amount of NiO in the KIT-6/NiO composite template, the amount of macropores inside MMC is easily controlled. The as-prepared MMC exhibits a highly porous structure with abundant ordered mesopores along with macropores that are larger than 200 nm in size. When the MMC is applied as the cathode material in a Li‒O2 battery, the cell exhibits greatly improved electrochemical performance in comparison to a cell using conventional ordered mesoporous carbon (OMC) without macropores. Systematic studies indicate that while mesopores in the OMC are clogged with Li2O2 formed during the early stage of discharge, the MMC sufficiently accommodates a large amount of Li2O2 in the pores. In addition, Li2O2 with poor crystallinity forms on the cathode containing MMC during subsequent discharge processes, which can be due to the accumulated side product and the limited size of pores. The formation of amorphous Li2O2 and the expedited mass transport through the interconnected meso- and macropores of MMC can attribute to the improved electrochemical performance of the MMC cathode material.

Non-woven mats constructed from carbon nanofibers with metal (Pt, Co, or Pd) nanoparticles on their surfaces (CNF@metal) were fabricated by coaxial electrospinning for use in non-aqueous lithium‒oxygen (Li‒O2) battery (LOB) cathodes. Through coaxial electrospinning, the metal nanoparticles were evenly distributed on the CNF surfaces, and the samples were directly applied as LOB cathodes. Although the Co and Pd nanoparticles did not promote the desired Li‒O2 reactions, the CNF@Pt exhibited much improved electrochemical performance with highly reversible Li‒O2 operations. Therefore, the Li‒O2 cell using the CNF@Pt cathode exhibited significantly enhanced specific capacity, rate capability, energy efficiency, and cycle stability compared to the other samples. The observed formation of Li2O2 film, rather than toroidal particles, on the CNF@Pt after an early stage of discharge may be attributed to greatly reduced overpotentials both on discharge and charge, as well as a considerably prolonged cycle life (163 cycles) with a limiting capacity of 1000 mAh/gc at a current density of 500 mA/gc. In particular, in-situ differential electrochemical mass spectrometry studies revealed that the cycles of the Pt-catalyzed Li‒O2 cell were mainly based on the reversible formation/decomposition of Li2O2, as evidenced by high O2 evolution and negligible CO2 evolution, even after long-term cycles.

Recently, the achievement of newly designed carbon–sulfur composite materials has attracted a tremendous amount of attention as high-performance cathode materials for lithium–sulfur batteries. To date, sulfur materials have been generally synthesized by a sublimation technique in sealed containers. This is a well-developed technique for the synthesizing of well-ordered sulfur materials, but it is limited when used to scale up synthetic procedures for practical applications. In this study, we suggest an easily scalable, room-temperature/ambient-pressure chemical pathway for the synthesis of highly functioning cathode materials using electrostatically assembled, amine-terminated carbon materials. It is demonstrated that stable cycling performance outcomes are achievable with a capacity of 730 mAhg–1 at a current density of 1 C with good cycling stability by a virtue of the characteristic chemical/physical properties (a high conductivity for efficient charge conduction and the presence of a number of amine g...

To study the effect of different polymer binders on the electrochemical performance of tin electrodes for rechargeable lithium-ion batteries, poly(vinylidene fluoride) (PVDF), conventional polyimide (PI-OB), and synthesized polyimide containing amino benzoquinone (PI-AQOB) were used as the polymer binders for electrodes consisting of commercial powdered Sn particles and Super P. PI-AQOB was converted from polyamic acid (PA-AQOB) synthesized from 2,5-bis(4,4’-oxydianiline)-1,4-benzoquinone (AQODA) and 4,4’-biphthalic dianhydride (BPDA) by condensation polymerization and characterized by Fourier-transform infrared analysis. Compared to the electrode employing the traditional PVDF binder, those with the PI-AQOB binder exhibited significantly enhanced electrochemical performance in terms of rate capability, specific capacity, and cycling behavior. PI-AQOB provided a high initial lithiation capacity of 1529 mAh/g at a current density of 50 mA/g. After 50 cycles, the PI-AQOB electrode maintained a higher specific capacity of 332 mAh/g than the Sn/PVDF electrode (only 65 mAh/g at a current density of 200 mA/g). Furthermore, the Sn/PI-AQOB electrode exhibited good volume restoration compared to the electrodes with Sn/PVDF and Sn/PI, as indicated by scanning electron microscopic analysis. The PI-AQOB binder increased the mechanical and adhesive strength of the electrode by suppressing pulverization of the Sn anode during expansion/contraction of Sn particles in the lithiation/delithiation process.

In spite of several desirable properties such as high stability against superoxide anion and low vapor pressure, N -methyl-2-pyrrolidone (NMP) electrolyte is reported not suitable for use in lithium-oxygen (Li-O 2 ) batteries because of severe degradation upon cycling and low oxygen efficiency. In this work, we find that NMP electrolyte is reactive with O 2 gas in the presence of lithium metal and such O 2 -consuming reaction ( i.e., autoxidation) is a possible cause for the poor performance in Li-O 2 batteries with NMP electrolyte. The autoxidation of NMP is verified by direct measurement of the depletion of O 2 gas in the hermetically sealed symmetric Li/Li cells via in-situ gas pressure analysis. In-situ differential electrochemical mass spectroscopy (DEMS) experiment reveals that the autoxidation resulted in significant O 2 consumption upon discharge, very low O 2 efficiency upon charge, and eventually fast capacity fading. Lithium nitrate (LiNO 3 ), which provides a protective layer on the surface of lithium metal, is employed to suppress the autoxidation, leading to significantly enhanced oxygen efficiency and cycle life.

We developed highly promising solid polymer electrolytes (SPEs) based on a novel cross-linker containing star-shaped phosphazene with poly(ethylene oxide) (PEO) branches with very high ionic conductivity (7.6 × 10−4 S cm−1), improved mechanical stability, and good electrochemical stability for all-solid-state lithium batteries. In particular, allyl groups were introduced at the ends of the cross-linker in order to overcome the easy self-polymerization of existing cross-linking acrylate end groups. A novel semi-interpenetrating network (semi-IPN) SPE was prepared by in-situ radical polymerization of a precursor solution containing lithium salt, poly(ethylene glycol) dimethyl ether as a plasticizer, and a mixture of pentaerythritol tetrakis(3-mercaptopropionate) and a synthesized hexakis(allyloxy)cyclotriphosphazene (thiol-ene PAL) as the cross-linker. Batteries employing LiFePO4 as the cathode, lithium foil as the anode, and the SPE thin film as the electrolyte were assembled and tested. At ambient temperature, the initial discharge capacity was 147 mAh/g at 0.1 °C and 132 mAh/g at 0.5 °C, and 97% of the capacity was retained at the 100th cycle. All-solid-state pouch-package lithium cells assembled with the SPEs exhibited stable electrochemical performance, even under a severely wrinkled state. These outstanding properties of SPEs based on thiol-ene PAL demonstrate feasibility for practical battery applications with improved reliability and safety.

Lithium-Ion Batteries (LIB) are growing in popularity for many applications. Much research has been focusing on battery performance improvement. However, few studies have overcome the disadvantages of the conventional LIB manufacturing processes. Laser cutting of electrodes has been applied. However, the effect of electrodes&rsquo, chemical, physical, and geometrical characteristics on the laser cutting has not been considered. This study proposes the effect of compression of cathode on laser cutting for lithium-ion batteries. The kerf width and top width of the specimens with laser irradiation are measured and the material removal energy is obtained. Observations of SEM photographs and absorptivity measurements are conducted. Increasing volume energies causes logarithmic increases in the kerf and top width. It is observed that the compressed cathode forms a wider kerf width than the uncompressed cathode under the same laser parameters. The top width of the uncompressed cathode is wider than the uncompressed cathode. The compression has a favorable effect on uniform cutting and selective removal of an active electrode.

Despite much research focused on lithium (Li) metal batteries, an important issue concerning Li-dendrite growth on the anode remains unresolved. The intrinsic mechanism of this Li-dendrite formation is related to the non-uniform distribution of Li-ion flux on the anode in charge/discharge caused by irregular structure and energy of anode surface. Here we report upon dendrite-free Li-deposition in a carbonate-based electrolyte using a novel Cu anode structure with sharp wrinkles and a [100] crystal facet. This uniform Li-deposition resulted in long-term electrochemical cyclability in Li/Cu and LiFePO4/Li cell. Our observations revealed that the wrinkled Cu surface and the unifying [100] crystal facet play important roles in enhancing the uniformity of the Li-ion flux and the adsorption energy of the Li-ions on Cu, respectively. We expect that this study will permit the use of a wide range of wrinkled structures and crystal planes to obtain high-energy and long-term cycles of Li-metal batteries.

The development of electric vehicles and smart grids necessitates the search for next-generation secondary batteries possessing increased energy densities, with the lithium-sulfur (Li-S) battery being one of the most promising candidates satisfying these demands. Specifically, Li-S batteries are promising energy storage and conversion systems owing to their high theoretical specific energy capacity (1675 mAh g-1) and energy density (2567 kWh kg-1) [1]. However, the practical use of Li-S batteries is hindered by their low specific capacity, low coulombic efficiency, poor rate capability, and poor cycling stability caused by the low conductivity of sulfur (5 x 10-30 S cm-1), dissolution of polysulfides (Li2Sx, 2≤ x ≤ 8) in the electrolyte and their redox shuttling/parasitic reactions and high volume expansion during discharge [2]. To overcome these drawbacks, many studies have focused on developing the design and materials of nanostructured host, electrolyte, interlayers, separators, additives, etc [3]. Interconnected three-dimensional frameworks comprising multi-walled carbon nanotubes, graphene, or carbon particles offer a combination of constituent advantages and can thus be used to achieve superior energy conversion and storage properties. Herein, we designed and prepared various approaches for interconnected highly conductive carbon materials which enable to make sulfur composite materials for Li-S batteries. The resultant sulfur-carbon composite paper cathode exhibited high reversible specific capacity of 1386 mAhg-1, good rate capability up to 5C, and excellent cycling performance (a capacity retention 68% after 400 cycles), all of which are significantly improved from those of bare sulfur cathode or sulfur-GO composite only [5]. Rational design of cathode composition, structure, and a simple fabrication process can give insight into the development of various advanced cathode materials for high performance Li-S batteries. References [1] X. Ji, K.T. Lee, L.F. Nazar, Nat. Mater. 8 (2009) 500. [2] Y. Yang, G.Y. Zheng, Y. Ciu, Chem. Soc. Rev. 42 (2013) 3018. [3] Y.X. Yun, S. Xin, Y.G. Guo, L.J. Wan, Angew. Chem. Int. Ed. 52 (2013) 13186. [4] H.J. Peng, J.Q. Huang, X.B. Cheng, Q. Zhang, Adv. Energy Mater. 7 (2017) 1700260 [5] J. Kim, Y. Kang, S.-W. Song, J. Suk, Electrochimica Acta 299 (2019) 27.

In non-aqueous Li–O 2 batteries, relatively large amounts of discharge products are formed on air cathodes. As such, the expansion of air cathodes is a critical issue that remains to be solved. Here, we report the fabrication of highly porous free-standing graphene paper by introducing macropores within the paper using polystyrene colloidal particles as a sacrificial template. The as-prepared macroporous graphene paper (mp-GP) have a large Brunauer–Emmett–Teller (BET) surface area ( ca . 373 m 2 g −1 ), a large pore volume ( ca . 10.9 cm 3 g −1 ), and a high porosity (91.6%). Owing to the high surface area and large pore volume, the mp-GPs exhibit a high specific capacity of ca . 12,200 mAh g −1 at a current density of 200 mA g −1 , as well as good rate capability, when used as an air cathode in a non-aqueous Li–O 2 battery. Moreover, the mp-GP shows good stability up to 100 and 78 cycles at a current density of 500 mA g −1 and 2000 mA g −1 respectively, with a limiting capacity of 1000 mAh g −1 . It is found that formation and decomposition of the discharge product, Li 2 O 2 , occur within the macropores, and thus, the mp-GP maintains its original structure without considerable expansion during cycling.

Although ether-based electrolytes such as tetraethylene glycol dimethyl ether (TEGDME) have been well recognized and widely employed for lithium–oxygen (Li–O2) cells, researchers do not have a strong confidence in this electrolyte material, because there have been many contradictory results reported. The principal objective of this paper is to clarify whether TEGDME is truly stable and suitable for Li–O2 battery operation. To accomplish the objective, oxygen efficiency and by-product gas evolution during five discharge/charge cycles were determined in a real-time and quantitative manner by in situ differential electrochemical mass spectrometry (DEMS). The amide-based electrolyte dimethylacetamide (DMA), which has recently been considered a promising electrolyte for Li–O2 cells, was also investigated and compared. The quantitative DEMS data during five cycles clearly show that DMA is more stable and exhibits better performance than TEGDME, suggesting that DMA is a more favorable electrolyte for Li–O2 battery applications. DMA exhibits 19% greater oxygen efficiency at charge, 5.1% lower CO2 evolution, and 5% higher energy efficiency than TEGDME during the first cycle. As the discharge/charge operation process continues, the performance gap between the two electrolytes becomes wider. In particular, the gap in the oxygen efficiency at charge grows to 32% at the fifth cycle. Linear sweep voltammetry (LSV)-DEMS analysis with Li2O2-deposited Li–O2 cells demonstrates that the evolutions of O2 and CO2 largely overlap, indicating that the oxidation of Li2O2 is inevitably accompanied by a parasitic reaction during the charge process with the TEGDME electrolyte.

The structural design and synthesis of cathode materials with superior catalytic activity is still a major challenge for rechargeable lithium–oxygen batteries. Here we prepared hierarchical Ru- and RuO2-foams as binder- and carbon-free electrocatalysts via an electrodeposition process using a hydrogen bubble template. The as-prepared Ru- and RuO2-foams were grown vertically on stainless steel mesh, with a dendritic bracken-like structure and highly divided thin branches. These freestanding Ru- and RuO2-foams provide high catalytic activity, large space to accommodate the discharge products, short ion diffusion lengths and channels for rapid transport of oxygen and electrolytes. The hierarchically dendritic cathodes without carbon and binders present low charge/discharge overpotential, remarkable cyclability, good oxygen efficiency and reduced irreversible formation/decomposition. The excellent performance of these foams, as characterized by systematic analysis and the facile fabrication approach provide an alternative method to develop advanced cathodes for Li–O2 batteries.

In this study, free-standing porous graphene papers for high-capacity and reversible Li-O2 battery cathodes are investigated. The graphene paper-like films were fabricated by the assembling of graphene nanoplatelets (GNPs) with the aid of graphene oxides (GOs) as a stabilizer, using a vacuum-assisted filtration method. By using GOs as a stabilizer, the GNP/GO films were fabricated with a paper-like form and they exhibited a highly wrinkled and disordered morphology. Moreover, the use of GNPs as a basic material eliminated the need for a post-annealing to recover the intrinsic electrical conductivity of graphene sheets. Subsequently, the GNP/GO paper could be directly used as a Li-O2 battery cathode without any conducting additives and binders. The GNP/GO paper electrode showed a much higher discharge capacity in comparison to the reduced-GO paper and commercially available carbon papers. We also found that toroidal Li2O2 mainly nucleated and grew on discharge, and decomposed on charge with a relatively high O2 evolution/consumption efficiency of 87%. However, a large number of Li2O2 particles grew inside the GNP/GO paper electrode, resulting in severe volume expansion of the electrode. This volume expansion could be the primary reason for the capacity fading on cycling.

Lithium polymer batteries (LPBs) are considered to be the most promising alternatives to current lithium-ion batteries (LIBs), which have been known to exhibit certain safety issues. However, the relatively poor electrochemical performances of LPBs hinder their practical usage, particularly at high C-rates, moderate temperatures, and/or with high loading densities. Therefore, this study analyzes the use of a novel composite electrode for manufacturing room-temperature operable LPBs with high loading densities. Rapid decay in the rate capabilities of LPBs at high C-rates is found to be attributable to the increased electrical resistance in an electrode. To account for this, this study modified the composite electrode with various conducting fillers. Subsequently, the effect of the type and content of the conducting fillers on the performance of LPBs was systematically investigated using the composite electrode. The incorporation of the conducting fillers in the lithium iron phosphate (LFP) composite electrode was found to effectively reduce the electrical resistance and consequently improve the electrochemical performance of LPBs. Furthermore, LFP composite electrodes with a mixture of structurally different graphene (G) and carbon nanotube (CNT) (1 wt%) were observed to demonstrate synergistic effects on improving the electrochemical performance of LPBs. The results obtained in this study elucidate that the facilitated electrical conduction within a composite electrode is critically important for the performance of LPBs and the expedited diffusion of Li+.

Lithium-ion batteries are actively used for many applications due to many advantages. Although electrodes are important during laser cutting, most laser cutting studies use commercially available electrodes. Thus, effects of electrodes characteristics on laser cutting have not been effectively studied. Since the electrodes&rsquo, characteristics can be manipulated in the laboratory, this study uses an uncompressed anode on laser cutting for the first time. Using the lab-made anode, this study identifies laser cutting characteristics of the uncompressed anode. First, the absorption coefficients of graphite and copper in the ultraviolet, visible, and infrared range are measured. The measured absorptivity of the graphite and copper at the wavelength of 1070 nm is 88.25% and 1.92%, respectively. In addition, cutting phenomena can be categorized in five regions: excessive cutting, proper cutting, defective cutting, excessive ablation, and proper ablation. The five regions are composed of a combination of multi-physical phenomena, such as ablation of graphite, melting of copper, evaporation of copper, and explosive boiling of copper. In addition, the top width varies in the order of 10 &mu, m and 1 &mu, m when applying high and low volume energy, respectively. The logarithmic relationship between the melting width and the volume laser energy was found.

Nitrogen-incorporated honeycomb-like nanoporous carbons (n-hC) are synthesized through the hydrothermal carbonization of a lignin precursor, subsequent KOH activation, and a post-doping process. The as-obtained n-hC exhibits a large surface area (2071 m2 g−1) and pore volume (1.11 cm3 g−1) and a high N content (3.47%). The n-hC is used as an S-hosting material with a mass loading of 64.1 wt% (S@n-hC) through the in situ redox reaction of Na2S2O3. The S@n-hC achieves a high initial discharge capacity of 1295.5 mAh g−1 at 0.1C and retains 647.2 mAh g−1 after 600 cycles, and shows excellent cycling stability (with the capacity fading of 0.05% per cycle over 900 cycles at 1C). The strong confinement of S in the N-incorporated micropores leads to the electrochemical and thermal stabilization of S, providing different redox environments. The facile and reversible redox kinetics of the S@n-hC are confirmed by deriving the lowest exchange current density and redox charge-transfer resistance from Tafel and Nyquist plots and through the prominent redox and charge/discharge profiles. The improved performance of the S@n-hC is attributed to the S confinement in the micropores, the honeycomb-like hierarchical structure, and the N incorporation for the inhibition of polysulfide dissolution and the efficient utilization of S.

Controlling the pore structure of cathodes has a decisive effect on the performance of lithium (Li)-O2 batteries. In this work, macroporous carbon nanofiber (MCNF) decorated with Pt nanoparticles (PtNPs) (PtNP-MCNF) are successfully fabricated. Their electrochemical performance as cathodes for a Li-O2 battery is evaluated. The MCNF mats are fabricated through an electrospinning and templating method using cross-linked polystyrene particles. PtNPs are grown on the surface of the MCNF through a solvothermal reaction. As-prepared PtNP-MCNF has interconnected macropores along the MCNF interior and abundant surface openings. These macropores are also connected to larger pores between individual MCNFs through the orifices on the MCNF surface, rendering a hierarchical porous structure. Owing to the highly porous structure and catalytic activity of PtNPs, Li-O2 cells using PtNP-MCNF cathodes exhibit considerably improved performance. In particular, with regard to cycle stability, the Li-O2 cell using PtNP-MCNF attains over 470 cycles in total while discharging at a capacity of 1000 mAh gc −1 with a current density of 500 mA gc −1. Such a high performance of the Li-O2 cell can be attributed to a facilitated Li+ and O2 transportation through the highly porous structure, and highly reversible Li-O2 operation over its life-cycle by means of catalytic activity of PtNPs.

N-doped carbon materials were prepared by in situ electrochemical pre-treatment of a carbon electrode in a deaerated non-aqueous electrolyte containing lithium nitrate. Li–O2 batteries, applying the novel N-doped carbon electrode, show a significantly reduced overpotential and enhanced O2-evolution efficiency.

In this report, we introduce electrospun silicon nanoparticle and carbon nanotube loaded carbon nanofibers (SCNFs) as anode materials in lithium-ion batteries (LIBs). The one-dimensional structure of electrospun nanofibers provides porosity for the anode material. Carbon nanotubes (CNTs) in the electrospun fibers reduce the volume expansion of silicon nanoparticles (SiNPs) and improve mechanical stability of the electrode. Both CNTs and carbon nanofibers enhance electronic conduction by connecting SiNPs in SCNFs for electrode reactions. These contribute to improved electrochemical performance of SCNF anode-based LIBs resulting in the enhancement of capacity and cycling ability.