Co Intercalation Batteries CoIBs Role of TiS2 as Electrode for Storing Solvated Na Ions

The co intercalation of solvent molecules along with Na into the crystal lattice of electrode materials is an undesired process in sodium batteries. An exception is the intercalation of ether solvated alkali ions into graphite, a fast and highly reversible process. Here, reversible co intercalation is shown to also be possible for other layered materials, namely titanium disulfide. Operando X ray diffraction and dilatometry are used to demonstrate different storage mechanisms for different electrolyte solvents. Diglyme is found to co intercalate into the TiS2 leading to a change in the voltage profile and an increase in the interlayer spacing amp; 8776;150 . This behavior is different compared to other solvents, which expand much less during Na storage 24 for tetrahydrofuran [THF] and for a carbonate mixture . For all solvents, specific capacities 2nd cycle exceed 250 mAh g amp; 8722;1 whereas THF exhibited the best stability after 100 cycles. The solvent co intercalation is rationalized by density functional theory and linked to the stability of the solvation shells, which is largest for diglyme. Finally, the TiS2 electrode with diglyme electrolyte is paired with a graphite electrode to realize the first proof of concept solvent co intercalation battery, that is, a battery with two electrodes that both rely on reversible co intercalation of solvent molecule

Tin Graphite Composite as a High Capacity Anode for All Solid State Li Ion Batteries

The use of composites instead of pure metals as negative electrodes is an alternative strategy for making all solid state lithium ion batteries Li SSBs more viable. This study reports on the properties of a composite electrode Sn Graphite consisting of nanosized Sn 17 wt and graphite 83 wt . The theoretical capacity of this material is 478 mAh g Sn Graphite 1. When mixed with Li3PS4 LPS as a solid electrolyte SE , an areal capacity of 1.75 mAh cm 2 active mass loading of 3.8 mg cm 2 is obtained, which can be increased up to 3.0 mAh cm 2 for 7.6 mg cm 2 . At 0.02 mA cm 2 , the Sn Graphite electrode delivers a gravimetric capacity of 470 mAh g Sn Graphite 1, i.e., close to its theoretical value. At 0.1 mA cm 2 , the capacity is 330 mAh g 1 second cycle but drops to 84 mAh g 1 after 100 cycles. Solid state nuclear magnetic resonance spectroscopy ssNMR and X ray photoelectron spectroscopy XPS are used to investigate the stability of the solid electrolyte for this cell configuration. Optimization of the electrode is explored by varying the electrode loading between 3.8 and 7.6 mg cm 2 and the SE content between 0 and 65 . For electrodes without any SE, gravimetric capacities mAh g Sn Graphite 1 and areal capacities mAh cm 2 are lower compared to electrodes with SE; however, their volumetric capacity is higher. This emphasizes the need to optimize the composition of electrodes for SSB

Towards low cost sodium ion batteries electrode behavior of graphite electrodes obtained from spheroidization waste fractions and their structure property relations

Electrode materials for lithium ion batteries LIBs typically show spherical particle shapes. For cathode materials, the spherical shape is obtained through the synthesis method. For graphite, the by far most popular anode material for LIBs, spherical particles are obtained through a spheroidization process. The yield of that process is quite low and limited to about 50 , leaving substantial amounts of by products. Using such lower quality by products would be quite attractive for developing low cost energy stores like sodium ion batteries SIBs , for which the requirements for particle sizes and shapes might be less strict as compared to high performing LIBs. Here, we study three different graphite waste fractions as anode material for SIBs that are obtained from the spheroidization process and how they compare to LIB battery grade material. Only negligible differences between the fractions are found when analyzing them with X ray diffraction, Raman spectroscopy and elemental analysis. More clear differences can be seen from N2 physisorption, scanning electron microscopy and particle size analysis. For example, the surface areas of the waste fractions can become roughly up to twice as large as compared to the battery grade fraction and the d50 values shift by up to 11.9 m to lower numbers. Electrochemical measurements show that the waste fractions can deliver the full electrode capacity and behave similar to the battery grade fraction up to 10C. However, the higher surface areas lead to more irreversible losses in the first cycle. A surprising finding is that all graphite fractions show almost identical discharge voltages, while the charging voltages differ by as much as 200 mV. This asymmetric behavior only occurs in SIBs and not in LIBs, which indicates a more complex storage behavior in case of sodiu