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All-solid-state lithium-sulfur batteries (ASSB-LiS batteries) are considered among advanced candidates for next-generation energy storage systems, as they break with restrictions and limitations that liquid electrolytes impose on lithium-ion batteries and lithium-sulfur batteries (LiS-batteries), meaning enhanced safety and higher energy densities. However, investigations under realistic conditions on pouch cell level are challenging, as it is necessary to implement a scalable preparation method for sheet-type cathodes with high sulfur utilization and loading. In this study, a solvent-free process to prepare free-standing cathode sheets with low binder content down to 0.1 wt% PTFE is demonstrated. The contribution of binder and electrolyte on the conversion reaction of sulfur is discussed. Sheet-type cathodes reach nearly theoretical sulfur utilization of 1672 mAh gS-1 and outstanding reversible capacity reten-tion with 72% of initial discharge capacity after 400 cycles by adapting cut-off voltages to the stability window of the electrolyte. Furthermore, an all-solid-state pouch cell is demonstrated using the dry-film cathode, which is suc-cessfully tested for 50 cycles at different C-rates. Thickness monitoring of the cell stack gives fundamental insights into the volume change and breathing behavior of both cathode and anode.

The lithium-sulfur (Li−S) technology is the most promising candidate for next-generation batteries due to its high theoretical specific energy and steady progress for applications requiring lightweight batteries such as aviation or heavy electric vehicles. For these applications, however, the rate capability of Li−S cells requires significant improvement. Advanced electrolyte formulations in Li−S batteries enable new pathways for cell development and adjustment of all components. However, their rate capability at pouch cell level is often neither evaluated nor compared to state of the art (SOTA) LiTFSI/dimethoxyethane/dioxolane (LITFSI: lithium-bis(trifluoromethylsulfonyl)imide) electrolyte. Herein, the combination of the sparingly polysulfide (PS) solvating hexylmethylether/1,2-dimethoxyethane (HME/DME) electrolyte and highly conductive carbon nanotube Buckypaper (CNT-BP) with low porosity was evaluated in both coin and pouch cells and compared to dimethoxyethane/dioxolane reference electrolyte. An advanced sulfur transfer melt infiltration was employed for cathode production with CNT-BP. The Li+ ion coordination in the HME/DME electrolyte was investigated by nuclear magnetic resonance (NMR) and Raman spectroscopy. Additionally, ionic conductivity and viscosity was investigated for the pristine electrolyte and a polysulfide-statured solution. Both electrolytes, DME/DOL-1/1 (DOL: 1,3-dioxolane) and HME/DME-8/2, are then combined with CNT-BP and transferred to multi-layered pouch cells. This study reveals that the ionic conductivity of the electrolyte increases drastically over state of (dis)charge especially for DME/DOL electrolyte and lean electrolyte regime leading to a better rate capability for the sparingly polysulfide solvating electrolyte. The evaluation in prototype cells is an important step towards bespoke adaption of Li−S batteries for practical applications.

Lithium sulfur (Li-S) batteries represent an interesting technology due to the high theoretical capacity of sulfur and the low cost of the cathode material. Li-S cells with graphite electrodes could be an option for low-cost stationary energy storage as graphite is cheap and the electrode production process is well established. Unfortunately, in most Li-S electrolytes, graphite is not stable due to solvent co-intercalation and degrades fast. In this work, a new low density electrolyte based on hexyl methyl ether (HME) and 1,3-dioxalane (DOL) is presented, which allows to use graphite as anode material for Li-S batteries. In symmetric graphite vs. graphite cells an averaged Coulombic efficiency of 99.94% per electrode could be reached. For the first time, cycling conditions like voltage window and balancing were optimized for Li-S cells with graphite anodes and the suitability of the concept could be demonstrated in multilayer pouch cellsunder realistic conditions.

The high gravimetric and volumetric capacity of silicon renders it an attractive anode material for lithium-ion solid-state batteries (SSBs). Herein, the partial lithiation (800 mAh g-1) of cost-attractive silicon microparticles (μm-Si) in half- and full cells versus nickel–rich NCM (LiNi0.9Co0.05Mn0.05O2) with Li6PS5Cl as a solid electrolyte (SE) is investigated. As a consequence of the cathode and anode potential curve evolution determined in a three-electrode SSB cell, the charge cut-off potential of the NCM|SE|μm-Si cells is reduced. Thereby, the capacity retention after 50 cycles is more than doubled from 32% to 71% without active pressure control on the cells. This concept addresses both the volume changes and the availability of the anode material on an industrial scale being necessary for the utilization of silicon anodes for electric vehicles and other applications. NCM|SE|μm-Si cells achieve up to 28% higher volumetric energy densities compared to the conventional graphite anode.

Electrolytes with sparingly polysulfide solubility such as 1.5 M LiTFSI in tetramethylene sulfone (TMS) and 1,1,2,2-tetrafluoroethyl- 2,2,3,3-tetrafluoropropyl ether (TTE) are beneficial for the cycle stability of Li-S pouch cells. In this work, this specific electrolyte system and the role of dissolved polysulfides (PS) in symmetrical Li/Li cells is investigated. By studying varying TMS/TTE volume ratios and polysulfide addition aided by both ex situ and operando spectroscopic as well as microscopic techniques, the positive impact of PS on the lithium plating/ stripping behavior is evaluated. The composition of the solid-electrolyte interphase (SEI) as well as the microscopic morphology differs for electrolytes with PS from those without PS addition. These findings are crucial for the development of electrolytes for cycle-stable Li-S prototype cells.

Lithium-sulfur (Li–S) batteries are among the targeted candidates for future generation secondary batteries with high specific energy. Herein, a scalable synthesis is presented to produce highly porous, nitrogen-doped carbons from a commercial carbon black material by melamine impregnation and subsequent thermolysis. The process up-scaling up was demonstrated at > 100 g batch level. The nitrogen doping was controlled through pyrolysis temperatures and carbon to melamine ratio. The sulfur-carbon cathodes exhibit an enhanced cycle life at a moderate electrolyte to sulfur ratio of 7 μL mgS−1. In particular, under lean conditions at low electrolyte amount of 5 μL mgS−1, the nitrogen functionalities improved active material utilization and capacity retention significantly. The nitrogen-doped scaffold was integrated into five-layered prototype cell (71 × 46 mm2) with a capacity of up to 0.87 Ah reaching a specific energy density of 238 Wh kg−1 on stack level. These results provide new insights into realistic application of nitrogen-doped carbons on pouch cell level.

The lithium-sulfur (Li-S) cell system is promising to satisfy the increasing need for cost-efficient energy storage with high theoretical energies due to the enormous theoretical gravimetrical capacity and the abundance of sulfur. Furthermore, the technology readiness level of Li-S batteries increased steadily in recent years due to extensive research, as well as the number of reported prototype cells. However, an often ignored test parameter is the application of external pressure to the cell stack. In this study, the influence of external pressure on the performance of Li-S cells is investigated. Therefore, five-layered pouch cells with solvent-free processed cathodes are assembled. These cells are tested under lean electrolyte conditions (electrolyte to sulfur ratio of 4.5 µl mg(S)−1). To evaluate the influence of the used electrolyte system either the state-of-the-art 1,2-dimethoxyethane/1,3-dioxolane electrolyte or the sparing polysulfide solvating hexyl methyl ether/1,3-dioxolane electrolyte is deployed. The impact of pressure application is evaluated electrochemically as well as by post-mortem focused ion beam-scanning electron microscopy of the cycled electrodes. Moreover, a technique for infiltration of sulfur into the carbon host matrix is presented, discussed, and successfully implemented.

In the market for next-generation energy storage, lithium-sulfur (Li-S) technology is one of the most promising candidates due to its high theoretical specific energy and cost-efficient ubiquitous active materials. In this study, this cell system was combined with a cost-efficient sustainable solvent-free electrode dry-coating process (DRYtraec®). So far, this process has been only feasible with polytetrafluoroethylene (PTFE)-based binders. To increase the sustainability of electrode processing and to decrease the undesired fluorine content of Li-S batteries, a renewable, biodegradable, and fluorine-free polypeptide was employed as a binder for solvent-free electrode manufacturing. The yielded sulfur/carbon dry-film cathodes were electrochemically evaluated under lean electrolyte conditions at coin and pouch cell level, using the state-of-the-art 1,2-dimethoxyethane/1,3-dioxolane electrolyte (DME/DOL) as well as the sparingly polysulfide-solvating electrolytes hexylmethylether (HME)/DOL and tetramethylene sulfone/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TMS/TTE). These results demonstrated that the PTFE binder can be replaced by the biodegradable sericin as the cycle stability and performance of the cathodes was retained.

Porous carbons are promising anode materials for next generation lithium batteries due to their large lithium storage capacities. However, their high voltage slope during lithiation and delithiation as well as capacity fading due to intense formation of solid electrolyte interphase (SEI) limit their gravimetric and volumetric energy densities. Herein we compare a microporous carbide-derived carbon material (MPC) as promising future anode for all solid-state batteries with a commercial high-performance hard carbon anode. The MPC obtains high and reversible lithiation capacities of 1000 mAh g−1carbon in half-cells exhibiting an extended plateau region near 0 V vs. Li/Li+ preferable for full-cell application. The well-defined micro porosity of the MPC with a specific surface area of >1500 m2 g−1 combines well with the argyrodite-type electrolyte (Li6PS5Cl) suppressing extensive SEI formation to deliver high coulombic efficiencies. Preliminary full-cell measurements vs. nickel-rich NMC-cathodes (LiNi0.9Co0.05Mn0.05O2) provide a considerably improved average potential of 3.76 V leading to a projected energy density as high as 449 Wh kg−1 and reversible cycling for more than 60 cycles. 7Li Nuclear Magnetic Resonance spectroscopy was combined with ex-situ Small Angle X-ray Scattering to elucidate the storage mechanism of lithium inside the carbon matrix. The formation of extended quasi-metallic lithium clusters after electrochemical lithiation was revealed.

Applications of advanced cathode materials with well designed chemical components and or optimized nanostructures promoting the sulfur redox kinetics and suppressing the shuttle effect of polysulfides are highly valued. However, in the case of actual lithium sulfur Li amp; 8722;S batteries under practical working conditions, one long term obstacle still exists, which is mainly due to the difficulties in massive synthesis of such nanomaterials with low cost and ease of control on the nanostructure. Herein, we develop a facile synthesis of carbon coated Ti4O7 hollow nanoparticles C amp; 8722;Ti4O7 using spherical polymer electrolyte brush as soft template, which is scalable via utilizing a minipilot reactor. The C amp; 8722;Ti4O7 hollow nanoparticles provide strong chemical adsorption to polysulfides through the large polar surface and additional physical confinement by rich micro amp; mesopores and have successfully been employed as an efficient sulfur host for multilayer pouch cells. Besides, the sluggish kinetics of the sulfur and lithium sulfide redox mechanism can be improved by the highly conductive Ti4O7 via catalyzation of the conversion of polysulfides. Consequently, the C amp; 8722;Ti4O7 based pouch cell endows a high discharge capacity of 1003 amp; 8197;mAh amp; 8201;g amp; 8722;1 at 0.05 amp; 8197;C, a high capacity retention of 83.7 amp; 8201; after 100 amp; 8197;cycles at 0.1 amp; 8197;C, and a high Coulombic efficiency of 97.5 amp; 8201; at the 100th cycle. This work proposes an effective approach to transfer the synthesis of hollow Ti4O7 nanoparticles from lab to large scale production, paving the way to explore a wide range of advanced nanomaterials for multilayer Li amp; 8722;S pouch cells

The successful transfer of room temperature sodium sulfur (RT-Na-S) technology from coin cell to pouch cell level is demonstrated. The general cell design is based on a previously developed RT-Na-S concept implementing hard carbon based anodes. Scalable technologies known from lithium ion battery production are utilized for electrode production. The electrolyte composition, the voltage window as well as the balancing is evaluated on coin cell level leading to optimized parameters. For scaled electrodes and electrolytes, a specific capacity of 418 mAh gS−1 coupled with a high coulombic efficiency of 95.3% can be still obtained in RT-Na-S coin cells after a total of 549 cycles. Residual carbonates in the HC-anode were found to deteriorate the cycling performance. An increased cut-off voltage (1.5 V) significantly raises the coulombic efficiency. Finally, the design is successfully transferred to a 10-layered pouch cell leading to a high energy efficiency of 88.6% and a capacity of 387 mAh gS−1 after a total of 937 cycles. Hence, the present work shows the principle feasibility of a stationary energy storage technology based on RT-Na-S pouch cell technology.

Silicon carbon void structures (Si-C) are attractive anode materials for Lithium-ion batteries to cope with the volume changes of silicon during cycling. In this study, Si-C with varying Si contents (28 ‑ 37 %) are evaluated in all-solid-state batteries (ASSBs) for the first time. The carbon matrix enables enhanced performance and lifetime of the Si-C composites compared to bare silicon nanoparticles in half-cells even at high loadings of up to 7.4 mAh cm-2. In full cells with nickel-rich NCM (LiNi0.9Co0.05Mn0.05O2, 210 mAh g-1), kinetic limitations in the anode lead to a lowered voltage plateau compared to NCM half-cells. The solid electrolyte (Li6PS5Cl, 3 mS cm-1) does not penetrate the Si-C void structure resulting in less side reactions and higher initial coulombic efficiency compared to a liquid electrolyte (72.7 % vs. 31.0 %). Investigating the influence of balancing of full cells using 3-electrode ASSB cells revealed a higher delithiation of the cathode as a result of the higher cut-off voltage of the anode at high n/p ratios. During galvanostatic cycling, full cells with either a low or rather high overbalancing of the anode showed the highest capacity retention of up to 87.7 % after 50 cycles.

For decades graphite has been used as the anode material of choice for lithium batteries since porous carbons were believed to be inappropriate because of their high potential slope during lithiation as well as capacity losses due to intense formation of solid electrolyte interphase (SEI). However, in this work we demonstrate a microporous carbide-derived carbon material (HCmicro) to provide a high-capacity anode framework for lithium storage in all solid-state batteries. Half-cell measurements of HCmicro exhibit exceptionally high and reversible lithiation capacities of 1000 mAh g-1carbon utilizing an extremely long voltage plateau near 0 V vs. Li/Li+. The defined microporosity of the HCmicro combined well with the argyrodite-type electrolyte (Li6PS5Cl) suppressing extensive SEI formation to deliver high coulombic efficiencies. Preliminary full-cell measurements vs. NMC-cathodes (LiNi0.9Co0.05Mn0.05O2) obtained a considerably improved average potential of 3.76 V leading to a projected energy density as high as 443 Wh kg-1. 7Li Nuclear Magnetic Resonance spectroscopy was combined with ex-situ Small Angle X-ray Scattering and further electrochemical investigations to elucidate the storage mechanism of lithium inside the carbon matrix revealing the formation of extended quasi-metallic lithium clusters.

In recent years, the technology readiness level of next generation lithium sulfur Li S batteries has shifted from coin cell to pouch cell dimensions. Promising optimizations of the electrodes, electrolytes, active materials, and additives lead to improved performance and cycling stability. However, new challenges arise with the pouch cell design and engineering including electrode stacking and electrolyte filling , which influence the mechanistic processes of the cell. This study presents an unprecedented multimodal operando investigation of Li S batteries on a pouch cell level and provides an inside view of material transformations during battery cycling, using X ray radiography, electrochemical impedance spectroscopy, and spatially resolved temperature monitoring. With the comparison of two different electrolytes, new experimental details about sulfur and lithium sulfide deposition and dissolution processes are revealed and related to electrolyte and temperature distribution. Operando impedance measurements on monolayer pouch cells yield a clear correlation of electrochemical and macroscopic radiographic observations. Understanding the monolayer cells behavior represents an optimal foundation for further studies on multilayer pouch cell prototypes and demonstrators with the developed operando setup. Herein the proof of principle for correlated measurement methods on pouch cell level is shown, and the experimental proof of concept for sulfur crystal suppression in sparingly solvating electrolyte is visualized

Nitrogen-doped carbons were synthesized by a solvent-free mechanochemically induced one-pot synthesis by using renewable biomass waste. Three solid materials are used: sawdust as a carbon source, urea and/or melamine as a nitrogen source, and potassium carbonate as an activation agent. The resulting nitrogen-doped porous carbons offer a very high specific surface area of up to 3000 m2 g-1 and a large pore volume up to 2 cm3 g-1 . Also, a high nitrogen content of 4 wt % (urea only) up to 12 wt % (melamine only) is generated, depending on the nitrogen and carbon sources. The mechanochemical reaction and the impact of different wood components on the porosity and surface functionalities are investigated by nitrogen physisorption and high-resolution X-ray photoelectron spectroscopy (XPS). These N-doped carbons are highly suitable as cathode materials for Li-S batteries, showing high initial discharge capacities of up to 1300 mAh gsulfur-1 (95 % coulombic efficiency) and >75 % capacity retention within the first 50 cycles at low electrolyte volume.

We report expansion-tolerant architectures in ultrahigh-loading sulfur cathodes inspired by particle agglomeration theories., Lithium-sulfur batteries can displace lithium-ion by delivering higher specific energy. Presently, however, the superior energy performance fades rapidly when the sulfur electrode is loaded to the required levels—5 to 10 mg cm−2— due to substantial volume change of lithiation/delithiation and the resultant stresses. Inspired by the classical approaches in particle agglomeration theories, we found an approach that places minimum amounts of a high-modulus binder between neighboring particles, leaving increased space for material expansion and ion diffusion. These expansion-tolerant electrodes with loadings up to 15 mg cm−2 yield high gravimetric (>1200 mA·hour g−1) and areal (19 mA·hour cm−2) capacities. The cells are stable for more than 200 cycles, unprecedented in such thick cathodes, with Coulombic efficiency above 99%.

Application-relevant data such as cycle life, rate capability, and energy density are inaccessible via electrochemical standard tests in today's Li-S-lab cells due to electrolyte and anode excess masking major degradation mechanisms. Because of the gap of lab cell characterization and prototype cell development, misinterpretations and false expectations of material development are frequently reported, and electrode porosity as well as pressure on cell stack are neglected. Rapid transfer of new concepts on multilayer-pouch cell level is essential, especially for electrolytes working in lean electrolyte regime. Fundamental studies should concentrate on fundamental scientific questions related to the main bottlenecks of Li-S-cells: first, understanding anode and electrolyte degradation phenomena and realistic evaluation of stabilizing interfaces is crucial. Further, new analytical tools allowing electrochemical studies under lean electrolyte conditions and in situ studies of electrolyte and additive depletion pose tremendous chances for impactful research. In addition, tap density and the accompanied swelling and compaction behavior of cathodes in different electrolytes should be further addressed. Consequently, pressure distribution in pouch cells should be monitored and adapted to the respective mechanical properties of the cathode and anode. These guidelines help to realize a breakthrough of the Li-S technology as a sustainable, safe, and lightweight energy storage option in the near future.

With the lithium-ion technology approaching its intrinsic limit with graphite-based anodes, lithium metal is recently receiving renewed interest from the battery community as potential high capacity anode for next-generation rechargeable batteries. In this focus paper, we review the main advances in this field since the first attempts in the mid-1970s. Strategies for enabling reversible cycling and avoiding dendrite growth are thoroughly discussed, including specific applications in all-solid-state (polymeric and inorganic), Lithium-sulphur and Li-O2 (air) batteries. A particular attention is paid to review recent developments in regard of prototype manufacturing and current state-ofthe-art of these battery technologies with respect to the 2030 targets of the EU Integrated Strategic Energy Technology Plan (SET-Plan) Action 7.

Rapid decay of silicon anodes during lithiation poses a significant challenge in application of silicon as an anode material in lithium ion batteries. In situ Raman spectroscopy is a powerful method to study the relationship between structural and electrochemical data during electrode cycling and to allow the observation of amorphous as well as liquid and transient species in a battery cell. Herein, we present in situ Raman spectroscopy on high capacity electrode using uncoated and carbon-coated silicon nanowires during first lithiation and delithiation cycle in an optimized lithium ion battery setup and complement the results with operando X-ray reflection diffraction measurements. During lithiation, we were able to detect a new Raman signal at 1859 cm−1 especially on uncoated silicon nanowires. The detailed in situ Raman measurement of the first lithiation/delithiation cycle allowed to differentiate between morphology changes of the electrode as well as interphase formation from electrolyte components.

Stabilization of covalent organic frameworks (COFs) by post-synthetic locking strategies is a powerful tool to push the limits of COF utilization, which are imposed by the reversible COF linkage. Here we introduce a sulfur-assisted chemical conversion of a two-dimensional imine-linked COF into a thiazole-linked COF, with full retention of crystallinity and porosity. This post-synthetic modification entails significantly enhanced chemical and electron beam stability, enabling investigation of the real framework structure at a high level of detail. An in-depth study by electron diffraction and transmission electron microscopy reveals a myriad of previously unknown or unverified structural features such as grain boundaries and edge dislocations, which are likely generic to the in-plane structure of 2D COFs. The visualization of such real structural features is key to understand, design and control structure–property relationships in COFs, which can have major implications for adsorption, catalytic, and transport properties of such crystalline porous polymers., Stabilization of covalent organic frameworks (COFs) by post-synthetic locking is a powerful tool to push the limits of COF utilization. Here the authors demonstrate a sulfur-assisted conversion of an imine-linked COF into a thiazole-linked COF, with retention of crystallinity and porosity, allowing for direct imaging of defects in COFs.

The lithium-sulfur chemistry provides a next generation battery technology on the verge of commercialization with significantly increased specific energy. However, the cycle life mainly suffers from dendrite and continuous SEI formation in lithium anodes inducing active material and electrolyte depletion. Here, we report on a silicon-carbon composite anode as a stable alternative anode for safe Li-S cells. Well-defined sulfur coatings generate a shell for a silicon core (Si@S) to further form a carbon shell (Si@S@sucrose). After sulfur removal the void structure (Si@void@C) allows to compensate the mechanical stress imposed by the huge volume change during the lithiation of the silicon. In this case, sulfur is not only used as a low cost and high capacity cathode material but also as a template to create free volume. It is easily removed during the pyrolysis and no acid leaching steps are required. In half cell tests vs. lithium a high capacity of 2270 mA h gSi -1 (690 mA h g-1) was achieved in the 10th cycle and the reversible lithiation of the silicon particles could be ensured for more than 50 cycles. The prelithiated Si-C anode with a high areal capacity of 2 mA h cm-2 was successfully matched with a sulfur cathode in a SLS full cell on coin cell and on pouch cell levels. A high capacity of about 807 mA h gsulfur -1 (2nd cycle) was reached with a low lithium excess of only 76% compared to 2000% lithium excess in state-of-the-art Li-S cells.

Nano energy 54, 116 - 128 (2018). doi:10.1016/j.nanoen.2018.09.065, The lithium-sulfur (Li–S) battery is a promising alternative to overcome capacity and specific energy limitations of common lithium-ion batteries. Highly porous, nitrogen-doped carbons as conductive host structures for sulfur/lithium sulfide deposition are shown herein to play a critical role in reversible cycling at low electrolyte/sulfur ratio. The pore geometry is precisely controlled by an efficient, scalable ZnO hard templating process. By using an electrolyte volume as low as 4 μL mg$^{-1}_S$ , the beneficial nitrogen functionality leads to a twofold increased cell lifetime turning our findings highly favorable for real applications. Stable cycling of up to 156 cycles (59 cycles with undoped carbon) with high sulfur loadings of 3 mg cm$^{-2}$ is achieved. Operando X-ray diffraction measurements during cycling show the transformation pathway of the sulfur – polysulfide – Li$_2$S species. The observed intermediates critically depend on the nitrogen doping in the cathode carbon matrix. Nitrogen-doped carbons facilitate polysulfide adsorption promoting the nucleation of crystalline Li$_2$S. These results provide new insights into the significant role of heteroatom doping for carbons in Li-S batteries with high specific energy., Published by Elsevier, Amsterdam [u.a.]

Hierarchically structured biomorphic carbide-derived carbon (CDC) materials are obtained by applying a combined activation- and CDC approach on abundantly available, renewable and cheap raw materials. For the synthesis of these materials we mimic nature by using wood structures as templates which are already optimized for mass transport during their long-term evolutional process. The impregnation of steam- or carbon dioxide-pre-activated wood templates with a polycarbosilane precursor and the subsequent halogen treatment yields a hierarchical material that exhibits longitudinally orientated macropores from the wood structure as well as well-defined and narrowly distributed micro- and meso-pores derived from the activation and CDC approach. These materials offer specific surface areas up to 1750 m2 g−1, micro-/meso-pore volumes up to 1.0 cm3 g−1 and macropore volumes of 1.2 cm3 g−1. This sophisticated hierarchical pore system ensures both efficient mass transfer and high specific surface area, ideal for mass transport limited applications, such as the lithium sulfur battery. Testing steam activated wood-CDCs as cathode materials for Li–S batteries reveals excellent performance, especially a highly stable discharge capacity and sulfur utilization. Stable capacities of over 580 mA h gsulfur−1 at current densities exceeding 20 mA cm−2 (2C) are possible using only very low amounts of electrolyte of 6.8 μL mgsulfur−1.

Silicon anodes offer a very promising approach to boost the energy density of lithium-ion batteries. While silicon anodes show a high capacity and, depending on the system, a good cycle stability in half-cells vs lithium, their integration in industrially applicable lithium-ion full-cells is still challenging. Balancing described as the capacity ratio of negative and positive electrode (n/p ratio) is a crucial necessity for the successful design of lithium-ion batteries. In this work, three different silicon based anode systems, namely carbon coated silicon nanowires, columnar silicon thin films and silicon-carbon void structures are compared in LIB full cells containing NMC111 cathodes. By varying the areal capacity of the NMC111 cathode, the influence of the balancing was investigated over a broad n/p range of 0.8−3.2. The aim was to find an ideal compromise between lithium plating suppression, high cycling stability and maximized energy density. To underline the high volumetric energy density, the columnar silicon thin films are additionally analyzed in multilayered pouch cells with NMC622 and NMC811 cathodes resulting in 605 Wh L−1 and 135 Wh kg−1 and even 806 Wh L−1 and 183 Wh kg−1 as demonstrated on stack level.

Polydopamine, formed by oxidation of dopamine, is a bioinspired polymer developed for multifunctional coatings by Lee et al. in 2007 by drawing inspiration from the adhesive proteins found in mussels. Due to their high versatility and substrate-independence, polydopamine coatings are gaining considerable attention in a plethora of research fields, particularly in the coating of particles, but systematic investigations of the polydopamine coating process are lacking in the literature. In this study, we explore by TEM and thermogravimetric analysis the polydopamine coating process on alumina microparticles, tungsten carbide microparticles and tungsten carbide nanoparticles. By choosing two substrates with similar size but different material (Al 2 O 3 and WC), as well as two substrates of the same material but different size (WC micro- and nanoparticles) we investigate the effects of both substrate material and substrate size, in order to gain some insights into the polydopamine particle coating process. As opposed to what is generally assumed in the literature, we found that the polydopamine coating thicknesses on particles, as well as the thickness growing trend, depend on the particles size and material. In particular, after 24 h of polymerization time the polydopamine coatings reached a thickness of 65 ± 10 nm in the case of Al 2 O 3 microparticles, 18 ± 4 nm in the case of WC microparticles and 33 ± 6 nm in the case of WC nanoparticles.

In the past four years major improvement of the lithium sulfur battery technology has been reported. Novel carbon cathode materials offer high sulfur loading, sulfur utilization and cycle stability. An often neglected aspect is that sulfur loading and amount of electrolyte strongly impact the performance. In this paper, we demonstrate how the amount of electrolyte, sulfur loading, lithium excess and cycling rate influences the cycle stability and sulfur utilization. We chose vertically aligned carbon nanotubes (VA-CNT) as model system with a constant areal loading of carbon. For a high reproducibility, decreased weight of current collector and good mechanical adhesion of the VA-CNTs we present a layer transfer technique that enables a light-weight sulfur cathode. The sulfur loading of the cathode was adjusted from 20 to 80 wt.-%. Keeping the total amount of electrolyte constant and varying the C-rate, we are able to demonstrate that the capacity degradation is reduced for high rates, high amount of electrolyte and low sulfur loading. In addition idle periods in the cycling regiment and lower rates result in an increased degradation. We attribute this to the redox-reaction between reactive lithium and polysulfides that correlates with the cycling time, rather than cycle number.

This study reports on the electrochemical oxidation of highly concentrated sulfuric acid by Diachem ® boron-doped diamond electrodes. The scope of this work was to evaluate a proposed continuous electrooxidation process in order to prepare a resist removal bath that contains equivalent amounts of peroxosulfuric compounds as a common SPM (sulfuric acid and hydrogen peroxide mixture) bath. The electrochemical processes at the electrode surface were investigated by cyclic voltammetry and by titration of the reaction products under real working conditions (> 80 wt% H 2 SO 4 ). Furthermore, an alternative electrolysis test cell setup, exhibiting a thin and mechanically stable ion exchange membrane will be used. For this process only one electrolyte circuit is performed. The initial electrolysis product H 2 S 2 O 8 immediately undergoes hydrolysis and forms H 2 SO 5 . The obtained concentration of H 2 SO 5 was similar to a reference SPM bath (> 0.14 mol l −1 H 2 SO 5 in 90 wt% H 2 SO 4 ), even though the current efficiency was lower than for more diluted solutions. This can be attributed to a complex interplay of side and consumption reactions of peroxosulfuric compounds. This electrolysis bath has the potential to be a very promising alternative to standard SPM baths, as it operates as a continuous and sustainable process.

Nanoparticles (NPs) can improve mechanical properties of construction elements. However, the integration is not trivial due to the nanoscopic nature of the particles and the different material properties of particle and device: new processing routes have to be found for homogeneous incorporation. Therefore, a wet chemical synthesis is established to incorporate various ceramic NPs such as TiO2, TiC, SiC, and WC in copper films in desired concentrations. Depending on the kind and concentration of NPs, hardness and wear resistance of copper are enhanced. The resulting metal matrix composite films are thus of high interest for various applications such as reinforced electrical contacts and in aerospace and automotive technology. The energy released in an exothermic reaction of a reactive multilayer system (RMS) can be used as a precise and well-defined local heat source for joining the surface of polymers. In this case, a RMS consisting of alternating layers of nickel and aluminum is used. The design of the RMS is adjusted in a way that despite the intensive but very short reaction no damaging of the polymers occurs. The joining process takes only milliseconds and does not require any pre- or post-treatment of the polymers. With the optimal joining parameters, e.g., the joining load, for fiber non-reinforced polymers tensile strengths can be achieved, which lead to a material failure by tensile attempts. Preliminary tests of fiber reinforced polymers result in a tensile strength that is characteristic for adhesive polymer bonding. Model simulations show that only the first few micrometers of the materials surface are in a liquid state for a very short period of time. In addition to the applied joining load, the materials composition and specifically the resulting solidification process of the liquid polymer phase result in a strong bond between polymer samples that have to be joined. Materials with different thermal expansion coefficients are difficult to join thermally. Among them is the joining of solar cells. It is conventionally carried out by heating the whole assembly. Due to the thermal differences between tabbing wire and silicon, deformations as well as changes in the microstructure can occur. In the worst case, damage of the whole assembly is possible. Upon inspection of the joining process, the high energy consumption of the process itself is also critical.

In this work, detailed studies on Li dendrite formation in Li–S Batteries are reported. Li dendrites can grow rapidly, may pierce through or can easily grow around the separator. Dendrites can even lead to short circuits when cathode and/or anode are wrapped with the separator. By replacing the Li metal anode with a pre-lithiated Si anode, these dendrite problems could be successfully prevented and were not observed for more than 200 cycles. The here used Si microwire array anodes are examined with ether and carbonate based electrolytes and different charging conditions vs. a Li metal counter electrode and demonstrate very high capacities matching the theoretical values. Electrochemical pre-lithiated Si microwire array anodes are examined in full cells with binder free, sulfur infiltrated carbon nanotube cathodes (CNT-S) and various polysulfide or Li 2 S containing electrolytes. The average polysulfide chain length and the presence of LiNO 3 in the electrolyte have a great impact on the cycle stability of the cell, next to the charging conditions.

The limited abundance of lithium on the Earth forces the search of alternative battery systems for mobile and stationary applications. Sodium-ion batteries could be a reasonable replacement for lithium-ion ones if a compromise between electrochemical performance and cost can be found. Since the ionic radius of Na+ is larger than of Li+, the choice for electrode materials is more restricted compared to Li-ion batteries, despite the similar chemistry of Na- and Li-compounds in many cases. The reason for that is a lower stability of crystalline phases with Na in fully charged or discharged states because of a larger volume change upon sodiation/desodiation. Anode materials like metallic alloys on the basis of Sn, Sb or Ge represent the most crucial point in Na-ion batteries because of a huge volume difference between sodiated and desodiated states, resulting in fast capacity fading due to reducing the particle size and contact loss. Hence, nowadays solely hard carbons (HC) can exhibit electrochemical performance suitable for a potential application. The structure of hard carbon consists of amorphous areas (sp 3-hybridization of carbon) embedding and partially crosslinking layered graphitic segments of low dimensional graphene layers (sp 2-hybridization of carbon). Electrochemical insertion of sodium into hard carbon involves two steps: a slope potential region resulting from very stable intercalation of Na-ions between graphitic layers, and a plateau in potentials from adsorption of ions in micropores. Upon desodiation, a large irreversible capacity up to 70 % of the total first discharging capacity is usually observed, which includes the solid-electrolyte interface (SEI) formation, and Na-ions being stably trapped between graphitic layers [1]. In our present work, we studied electrochemical performance of full Na-ion batteries with olivine-like NaFePO4 or layered-type NaNi0.5Ti0.5O2 cathodes, and HC anode materials. In order to overcome the problem with irreversible capacity loss, hard carbon materials were partially or fully sodiated (discharged) prior to electrochemical tests. A NaPF6-containing electrolyte modified with 1-butyl-1-methylpyrrolidinium hexafluorophosphate was used. The observed specific capacities of about 150 mAh g-1 for NaFePO4/HC batteries after 20 cycles are comparable with half NaFePO4/Na cells [2], while NaNi0.5Ti0.5O2/HC batteries show about 75 mAh g-1 (Fig. 1). The reason for a lower capacity retention of NaNi0.5Ti0.5O2 upon cycling is discussed. Figure 1. Specific capacity of full Na-ion batteries with NaFePO4 (NFPO) and NaNi0.5Ti0.5O2 (NNTO) cathodes and hard carbon (HC) anodes, normalized on the cathode weight, at C/10 rate meaning 1Na intercalated during 10 h. References [1] E. Irisarri et al., J. Electrochem. Soc., 162 (2015) A2476-A2482. [2] G. Ali et al., ACS Appl. Mater. Interfaces, 8 (2016) 15422−15429. Figure 1

A new approach for fabricating copper coated silica and alumina nanoparticles by a mercaptosilane-based coating and subsequent electroless plating is reported. Mercaptosilane covalently binds to the particle surface via hydrolysis and condensation reactions, while the mercapto group promotes a selective metal deposition during the electroless plating process due to its high affinity towards metal ions. The combination of an organic-based treatment process with electroless plating ensures a scalable and homogeneous metal coating strategy. Moreover, no further activation and sensitization steps with palladium-based solutions are required, thus overcoming the high costs and complexity of the state of the art metallization procedures. Metal coated nanoparticles synthesized with this procedure show a uniform and conformal coating and are particularly well suited for the production of metal matrix composites. The metal coating facilitates the integration and compatibility of the ceramic particles within the metal matrix, and can act as a barrier layer preventing undesired reactions between the two phases. Such composites are potential components for a wide range of applications including components for the automotive and aerospace industries, electromagnetic interference shielding, cutting tools, reinforced electrodes and coatings.

A novel approach for the fabrication of metal coated micro- and nanoparticles by functionalization with a thin polydopamine layer followed by electroless plating is reported. The particles are initially coated with polydopamine via self-polymerization. The resulting polydopamine coated particles have a surface rich in catechols and amino groups, resulting in a high affinity toward metal ions. Thus, they provide an effective platform for selective electroless metal deposition without further activation and sensitization steps. The combination of a polydopamine-based functionalization with electroless plating ensures a simple, scalable, and cost-effective metal coating strategy. Silver-plated tungsten carbide microparticles, copper-plated tungsten carbide microparticles, and copper-plated alumina nanoparticles were successfully fabricated, showing also the high versatility of the method, since the polymerization of dopamine leads to the formation of an adherent polydopamine layer on the surface of particles of any material and size. The metal coated particles produced with this process are particularly well suited for the production of metal matrix composites, since the metal coating increases the wettability of the particles by the metal, promoting their integration within the matrix. Such composite materials are used in a variety of applications including electrical contacts, components for the automotive industries, magnets, and electromagnetic interference shielding.

In the present study, the electrochemical deposition (ECD) of platinum particles on aligned multiwalled carbon nanotube (MWCNT) arrays as novel membrane electrode assembly (MEA) in polymer electrolyte membrane fuel cells was investigated. The ECD was performed using the pulse plating technique and an electrolyte based on potassium tetranitroplatinate(II) salt. The MWCNTs were produced on thin nickel foils by chemical vapour deposition. The MWCNT arrays were electrochemically characterised by cyclic voltammetry in sulphuric acid. The platinum functionalisation of the MWCNT arrays was also investigated by cyclic voltammetry and by scanning electron microscopy. The final preparation of the MEA functionalised MWCNT on Nafion was performed by a hot pressing process.

A scalable process at atmospheric pressure for direct growth of vertical aligned carbon nanotube (VA-CNT) on aluminum substrates has been developed including dip-coating steps for the wet-chemical buffer and catalyst layer deposition and a subsequent chemical vapor deposition step. Up to 80 μm high vertical aligned carbon nanotube forests were obtained on catalyst-coated aluminum foil in a thermal plasma-free CVD process at atmospheric pressure and 645 °C using ethene as carbon source. The influence of two catalyst compositions (Fe:Co 2:3 and Fe:Mo 47:3) and the effect of the catalyst concentration on growth rate, morphology and density of resulting CNT films were investigated. Additionally, the binder-free VA-CNT/aluminum system was electrochemically tested as supercap electrode and the feasibility of tailoring the specific capacity varying the catalyst layer thicknesses was shown. The specific capacitance of electrodes deduced from impedance spectra varied between 25.6 and 61.2 F g−1 depending on the catalyst complex mixture composition and concentration. The VA-CNT/Al electrodes have a very low value of effective serial resistance (0.42–0.15 mΩ g) indicating a potential candidate as electrode material for high power supercapacitor application. Excellent cycle stability of supercapacitors has been demonstrated up to 300,000 cycles.

Li-S cells have a low voltage (about 2.1 V), but their potentially high energy density (200-500 Wh/kg) makes them a promising system for next generation batteries. To obtain high energy densities on cell level, the weight fraction and load of the active material should be as high as possible, while inactive material is reduced to a minimum. Conventionally, sulfur slurry cathodes with an aluminum current collector are used. However, binder-free CNT-coated carbon structures are a promising method of achieving higher loads and higher ratios of active material. Using a specially designed test cell it was demonstrated that sulfur cathodes without a metal current collector can deliver enough power to meet the requirements of consumer electronics at simultaneously high capacities of up to 600 m Ah g-1 for the entire electrode and current collector. A literature study compared various equivalent circuits used for Li-S electrochemical impedance spectroscopy (EIS), and enabled the selection of the most suitable one for the system used here. EIS measurements during charge and discharge delivered vital information about the specific resistances of the sulfur cathodes with a carbon current collector.

To obtain information about the Li-S reaction mechanism through spectroscopy, a Raman literature study, polysulfide vibrational mode calculations and experimental in-situ measurements were performed. A special test cell was constructed to examine in-situ Raman spectra in the spectral range from 100 cm-1 to 600 cm-1during charge and discharge in the voltage range of 1.5 V to 3.0 V. In order to assign the in-situ Raman data and to support the interpretation of the observed changes in the overall Raman-spectrum, several reference measurements on well-defined substances were conducted. The reference measurements included pure solvents, electrolytes and polysulfide solutions prepared from stoichiometric mixtures of S8 and Li2S powders. The assignment of the observed Raman-spectra was fürther based on a comparison with purely theoretical data for the vibrational modes of the polysulfide di-anions Sn2- and radical mono-anions Sn- calculated at the B3PW91/6-311G(2df,p) level o f density functional theory (DFT). The DFT data for the vibrational spectra, corrected for solvent effects in the framework of the polarizable continuum model (PCM), allowed an identification of several characteristic features in the in-situ Raman spectra.