Lithium-Ion Active Materials

The performance of Ni-foam pasted Ni(OH)2 prepared from co-precipitated Ni(OH)2 with Zinc (Zn) and Cobalt (Co) as the positive electrode active material of an asymmetric electrochemical capacitor (EC) is studied for the enhancement of the capacitor’s specific energy and power densities. A co-precipitated Ni(OH)2/activated carbon (AC) composite material and AC were used as a positive and negative electrode material. The AC in the positive electrode is used as an electrolyte reservoir to reduce ionic diffusion resistance regardless of charge/discharge current density. In addition, the simultaneous presence of Zn and Co ions in the Ni(OH)2 layer improves the efficiency of the active material and reduces the resistance of the unit cell. It was observed that through the effects of the additives in the positive electrode, the asymmetric EC exhibits a high energy density with 35.7 Wh/kg, based on the active material. Furthermore, the energy density decreasing behavior at a high discharge current density was retarded.

Hierarchical carbon-decorated Fe3O4 on hollow CuO nanotube array: Fabrication and used as negative material for ultrahigh-energy density hybrid supercapacitor

All-solid-state batteries (SSBs) using lithium metal anode are expected to realize SSBs with high energy density. This is because lithium metal anode has the lowest redox potential and the theoretical capacity of 3861 mA h g-1 is ca. ten times larger than that of commonly-used graphite anode (372 mA h g-1). In fact, lithium metal anode has been successfully used in thin-film-type SSBs and stable charge-discharge reactions are reported [1]. In SSBs, both positive and negative electrode materials are combined with solid electrolytes, and they are assembled from the initial state in general. On the other hand, conventional SSBs apply lithium transition metal oxides (LiCoO2, etc.) as the positive electrode material, and lithium metal is electrochemically plated during the charging process. Appling electrochemically-plated lithium as a anode material can simplify the battery manufacturing process and will be an effective way to form pure lithium metal anode. Such “Li-free” SSBs has been successfully prepared in thin-film-type SSBs [2]. Also, this anode-less idea has been applied to develop large-sized SSBs in recent years [3].In this presentation, the author will talk about the factors for lithium plating morphology on inorganic solid electrolytes, such as current collector species, current densities, temperature, etc. [4]. The model solid electrolytes are LiPON-coated LATP or garnet-structured Ta-doped LLZ. Also, several problems for applying electrochemically-plated lithium anode and the issues arising during the stripping processes will be discussed.

A symmetric sodium-ion battery based on P2-Na0.67[ZnxMn1-x]O2 as both positive and negative electrode materials

Aqueous superconcentrated electrolyte solutions have recently attracted attention for aqueous high-voltage Li-ion batteries due to their wider potential window than that of conventionally concentrated aqueous ones. According to literatures, 21 mol kg-1 LiN(SO2CF3)2 (LiTFSA)/H2O and 27.8 mol kg-1 Li(TFSA)0.7[N(SO2C2F5)2 (BETI)]0.3/H2O electrolytes show potential window wider than 2 V and 3.5 V, respectively (1, 2). As well as the Li electrolytes, superconcentrated aqueous Na and K electrolytes have been recently studied. Thanks to weak Lewis acidity of Na+ and K+ ions, aqueous Na and K solutions show higher ionic conductivity than Li counterparts in principle. Indeed, 17 mol kg-1 NaClO4/H2O solution exhibits a very high ionic conductivity of 108 mS cm-1; however, potential window wider than 2 V is still challenging in aqueous Na-ion batteries (3). In this study, we have developed superconcentrated mixed cation electrolytes demonstrating wide potential window and high ionic conductivity based on NaN(SO2F)2 (NaFSA), KFSA, and H2O system to realize 2 V-class aqueous Na/K multi-ion batteries. Ionic conductivities of the electrolytes were measured at 25 °C. NaTi2(PO4)3 carbon composite (NTP/C) (4) and Na3V2(PO4)3 (NVP) (5) were used as negative electrode materials, and K2Mn[Fe(CN)6] (6) was as a positive electrode material. Al and Ti foils were used as a current collector for the negative and positive electrodes, respectively. Figure 1a shows water content of saturated aqueous K x Na1-x FSA solutions. The concentration of the saturated NaFSA and KFSA solutions as endmembers is 20 mol kg-1 and 31 mol kg-1, respectively. Higher concentration is realized at eutectic or close to eutectic composition of NaFSA - KFSA: 35 mol kg-1 for Na0.55K0.45FSA/H2O and 33 mol kg-1 for Na0.45K0.55FSA/H2O. Both Na/K mixed electrolytes show ionic conductivity of 20–25 mS cm-1 which is much higher than 3 mS cm-1 of 27.8 mol kg-1 Li(TFSA)0.7(BETI)0.3 (2). Figure 1b shows the LSV curves of Al and Ti foil for a cathodic and anodic scan, respectively, in the superconcentrated Na, K, and mixed electrolytes. 20 mol kg-1 NaFSA/H2O and 31 mol kg-1 KFSA/H2O as endmembers show potential window of 3.2 V and 3.4 V, respectively. As expected, the Na/K mixed electrolytes demonstrate a wider potential window of 3.5 V. NTP//K2Mn[Fe(CN)6] and NVP//K2Mn[Fe(CN)6] cells were fabricated using 33 mol kg-1 K0.55Na0.45FSA/H2O electrolyte. The NTP//K2Mn[Fe(CN)6] cell shows reversible charge/discharge curves with mainly two discharge voltage plateaus located at 1.7 V and 1.3 V and delivers reversible capacity of ca. 130 mAh g (positive electrode)-1 and 70 mAh g (negative electrode)-1 with excellent capacity retention over 30 cycles as shown in Fig. 1c. On the other hand, the NVP//K2Mn[Fe(CN)6] cell demonstrate 2 V-class operation as shown in Fig. 1d. Electrochemical performance and charge/discharge mechanism of the electrode materials in terms of insertion/extraction of Na/K multi-ions will be discussed in the presentation. References L. Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang and K. Xu, Science, 350, 938 (2015).Y. Yamada, K. Usui, K. Sodeyama, S. Ko, Y. Tateyama and A. Yamada, Nat. Energy, 1, 16129 (2016).K. Nakamoto, R. Sakamoto, Y. Sawada, M. Ito and S. Okada, Small Methods, 1800220 (2018).S. I. Park, I. Gocheva, S. Okada and J. Yamaki, J. Electrochem. Soc., 158, A1067 (2011).K. Saravanan, C. W. Mason, A. Rudola, K. H. Wong and P. Balaya, Adv. Energy Mater., 3, 444 (2013).T. Hosaka, K. Kubota, H. Kojima and S. Komaba, Chem. Commun., 54, 8387 (2018). Figure 1

To exploit LIBs to their maximum applications, innovative electrode materials should be developed and existing materials should be improved. As negative electrode materials are needed in excess in comparison with positive electrode materials (in terms of specific capacity) in a lithium-ion battery, it is important to reduce their amounts so as to reduce the cell size and production cost[1]. Moreover, innovative negative electrode material classes delivering high capacity and offering fast Li diffusion kinetics should be developed. Parallel to this, research in alternative low cost energy storage systems became more intensive. Due to the high abundance and cost effectiveness of the electrode materials used, Na-ion batteries have become one of the best alternative energy storage systems to LIBs. Many of the attractive Li-insertion electrode materials are also tested for Na-insertion as a part of developing this system further. As different from the wide variety of positive electrode materials, there are only few choices for negative electrode materials for Na-ion batteries[2]. Na does not insert into graphite. Binary alloys of Na with Sn, Pb or other metals and conversion metal oxides are expected to have very high gravimetric capacity[3]. However, the enormous volume changes are supposed to bring out poor cycling behavior of these materials. SnO2 is a promising negative electrode material for Li-ion batteries due to its high theoretical specific capacity of 1491 mAh g-1 [4]. The first step in the Li insertion of SnO2 is a conversion reaction involving 4 Li, where metallic Sn particles are formed in a matrix of Li2O. In the second step, metallic Sn alloys with Li and produce Li4.4Sn. Hence in total 8.4 Li ions can be inserted per formula unit of SnO2 [4]. Nevertheless, this material suffers from extreme volume changes which can lead to a drop in the electric contact and further to severe capacity fading during cycling. This can be overcome by preparing nanocrystalline materials, composite materials with carbon derivatives etc. In the present work, SnO2 nanoparticles are synthesized via a hydrothermal process. The obtained SnO2 material has a particle size of ~50 nm. The material was investigated as negative electrode candidate for both Li- and Na-ion batteries in corresponding half cells. The respective electrochemical mechanism was investigated by in situ and quasi in situ X-ray absorption spectroscopy. It was observed that at the end of discharge, SnO2 was converted to metallic Sn nanoparticles in a Li-ion cell (see Figure 1). Meanwhile, no complete reduction of the SnO2 was observed in the Na-ion cell at the end of discharge. The details of the electrochemical mechanism of SnO2 as negative electrode material for Li-ion and Na-ion batteries will be discussed. Acknowledgement: Financial support from DFG within the Research Priority Program SPP 1473, “Materials with new design for improved Li ion batteries-WeNDeLIB” under grant no EH183/16-2 is gratefully acknowledged. This work has benefitted from beam time allocation by the core-level absorption and emission spectroscopies (CLAESS) beamline, ALBA, Barcelona.

Redox active organic molecule-Emodin modified graphene for high-performance supercapacitors

Construction of asymmetric flexible-solid state supercapacitors based on Mo-MnO2 nanoflowers and MoO3-x nanobelts

<div class="section abstract"><div class="htmlview paragraph">A major challenge in the development of the next generation electric and hybrid electric vehicle (EV and HEV) technology is the control and management of heat generation and operating temperatures. Vehicle performance, reliability and ultimately consumer market adoption are integrally dependent on successful battery thermal management designs. In addition to this, crucial to thermal modeling is accurate thermo-physical property input. Therefore, to design a thermal management system and for thermal modeling, a designer must study the thermal characteristics of batteries. This work presents a purely experimental thermal characterization of thermo-physical properties of a lithium-ion battery utilizing a promising electrode material, LiFePO<sub>4</sub>, in a prismatic pouch configuration. In this research, the thermal resistance and corresponding thermal conductivity of prismatic battery materials is evaluated. The experiment was designed to measure the thermal conductivity of both the individual electrode layers, and the overall thermal resistance of the sealed prismatic structure. For this experiment, the first step was battery dissection, the second step was sample preparation and the third step was the measurement of thermal resistance. Thermal resistance measurements were made using specially constructed battery samples. The thru-plane thermal conductivity of LiFePO<sub>4</sub> positive electrode and negative electrode materials was found to be 1.79 ± 0.18 W/m°C and 1.17 ± 0.12 W/m°C, respectively.</div></div>

A new secondary battery technology: Electrode structure and charge–discharge mechanism of all-solid-state zinc-graphite batteries

A simple strategy of pre-doping lithium ion into carbon negative electrode for lithium ion capacitor was introduced. In this strategy, a kind of Li-containing compound was added directly into the positive electrode of the lithium ion capacitor (LIC). When the lithium ion capacitor was charging first time, the Li-containing compound releases Li+, and the pre-doping of lithium ion into the negative electrode was performed. Here, we developed a lithium ion capacitor using Meso-carbon microbeads (MCMB)/activated carbon (AC) as the negative and positive electrode materials, respectively and use the lithium iron phosphate (LiFePO4) as the Li-containing compound, which supply the Li+ ions for pre-doping. The results demonstrated that, by adding 20 percent of LiFePO4 into the positive electrode, the efficiency of the capacitor increases from lower than 60% up to higher than 90%, and the capacitor shows good capacitance characteristics and high capacity.

NiCo-layered double hydroxide with cation vacancy defects for high-performance supercapacitors

Amorphous solid electrolytes were prepared in the compositions 75 {(1-x)Li2O⋅xLi2S}⋅5P2S5 (mol%) by using a high-energy ball-milling process. The amorphous materials showed lithium ion conductivities higher than 10-3 Sm-1 at room temperature. The amorphous 7.5Li2O⋅67.5Li2S⋅5P2S5 (mol%) sample showed the highest lithium ion conductivity σ298K=2.7×10-2 Sm-1 at room temperature among the obtained samples. An all-solid-state battery was assembled by using the amorphous 7.5Li2O⋅67.5Li2S⋅5P2S5 sample as solid electrolytes. In the battery, TiS2 and Li4.4Si were employed as positive and negative electrode materials, respectively. The discharge-charge cycling test of the battery was carried out at room temperature under a constant current density of 64μAcm-2 with the discharge-charge criteria of voltages 1.1 and 2.6 V. The battery showed successive reversibility with a large specific capacity; the specific capacity calculated on the base of the weight of the TiS2 positive electrode materials was about 170 mAhg-1.

Deep eutectic electrolytes (DEEs) are a combination of two or more components, usually solid powders, that when mixed exhibit significantly lower melting points than the pure materials due to hydrogen bonding, Lewis acid-base, and other intermolecular interactions. Since DEEs have unique properties and can be prepared using low-cost materials, they have attracted attention as new electrolytes for Li-ion batteries (LIBs) .1, 2 Earlier this year, we reported the preparation of DEEs containing lithium bis(fluorosulfonyl)amide (LiFSA) and urea-derivatives, and tested them with positive and negative electodes.3 However, we found the range of concentrations that form liquid phase DEEs with urea was quite limited. In this study, we explored the usage of urea with an alternative electrolyte salt, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)amide (LiFTFSA), and a binary salt of LiFSA and lithium bis(trifluoromethanesulfonyl)amide (LiTFSA), which show lower melting points than LiFSA. The physicochemical and electrochemical properties of these electrolytes were thoroughly investigated for application in lithium-ion batteries.To prepare the DEEs, a 6:4 (mol/mol) mixture of LiFSA and LiTFSA (LiFSA0.6TFSA0.4) or LiFTFSA was mixed with urea at room temperature. Compared to the previously reported LiFSA:urea (1:3.8) – (1:4.2),3 the composition range for forming room temperature liquids was extended to LiFSA0.6TFSA0.4:urea (1:2.5) – (1:4) and LiFTFSA:urea (1:1.5) – (1:4). The oxidation and reduction stability was evaluated by voltammetry (LSV or CV) using Pt foil or Al foil as the working electrode, respectively. All electrolytes showed good reduction stability and reversible Li-Al alloying or Li plating reactions (Fig. 1). Furthermore, DEEs prepared with higher Li salt concentrations exhibited higher oxidation stability.Galvanostatic charge-discharge tests were performed in three-electrode cells with LiTi4O5 (LTO) or LiFePO4 (LFP) working electrodes. For LTO negative electrodes (Fig. 2), capacity fading and low average Coulombic efficiencies below 80% were observed after 50 cycles in the LiFSA0.6TFSA0.4:urea (1:2.5) and LiFTFSA:urea (1:4) electrolytes. The cell containing LiFSA0.6TFSA0.4:urea (1:4) achieved the highest capacity retention of ~90% and average Coulombic efficiency of 85% after 50 cycles. In contrast to LTO, LFP positive electrodes exhibited stable charge/discharge behavior and achieved nearly 100% capacity retention in early cycles using LiFSA0.6TFSA0.4:urea (1:2.5) and (1:4) electrolytes (Fig. 3). These results indicate some of the DEEs are compatible for both practical positive and negative electrode materials and could be candidates for new electrolytes for LIBs. The impact of these new electrolyte salts on LIB performance, as well as the thermal stability and solution structure of DEEs will be discussed.

Graphite, a suitable positive electrode material for high-energy electrochemical capacitors