CuSbS2 was tested as a negative electrode material for sodium-ion batteries. The material synthesized by ball milling offers a specific charge of 730 mAh g−1, close to the theoretical value ...(751 mAh g−1), over a few cycles. The reaction mechanism was investigated by means of operando X-ray diffraction, 121Sb Mössbauer spectroscopy, and Cu K-edge X-ray absorption spectroscopy. These studies reveal a sodiation mechanism that involves an original conversion reaction in two steps, through the formation of a ternary phase, CuSb(1−x)S(2−y), as well as a NaxS alloy and Sb, followed by an alloying reaction involving the previously formed Sb. The desodiation process ends with the reformation of the ternary phase, CuSb(1−x′)S(2−y′), deficient in Sb and S; this phase is responsible for the good reversibility observed upon cycling.
•A ternary phase CuSbS2 is tested as anode material for sodium ion batteries.•Reversible specific charge of 730 mAh g−1 for few cycles without optimization.•Combination of conversion and alloying reactions mechanism.
Phosphorus is considered as a promising candidate for the replacement of graphite as the active material in Li-ion battery electrodes owing to its 6-fold higher theoretical specific charge. ...Unfortunately, phosphorus-based electrodes suffer from large volume changes upon cycling, leading to poor electrochemical performance. Furthermore, red phosphorus (Pred) is known to release phosphine gas (PH3) once in contact with water (even at the ppm level), and thus, its safety profile needs to be assessed. In this context, the electrolyte/electrode interface of a Pred electrode during the first lithiation is fully investigated using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and online electrochemical mass spectroscopy (OEMS). The XPS analyses reveal that, at potentials higher than 1 V vs Li+/Li, the Pred starts to react via the outermost surface layer, which is mainly composed of the native oxide, P2O5, to form H3PO4. Once this surface oxide is consumed, the Pred reacts with moisture and the electrolyte, resulting in the re-formation of H3PO4 and the release of the toxic PH3 as identified by OEMS. At potential lower than 1 V, a solid electrolyte interphase (SEI) develops on the top of H3PO4 as identified by XPS analyses. This SEI prevents further degradation of the Pred and inhibits PH3 release. Following the lithiation, the reaction of Li with Pred generates particle fracture (identified by SEM) and the transformation of H3PO4 into Li3PO4 is also noticed. Understanding and monitoring the role of the decomposition products and processes within the battery is crucial to further improving battery performance and safety.
Electrochemical performance of Ni2SnP was assessed in Li-ion and Na-ion battery systems. When cycled versus Li, Ni2SnP exhibited a reversible specific charge of 700 mAh.g−1 (theoretical specific ...charge: 742 mAh.g−1). In the Na system, the specific observed charge was ca. 200 mAh.g−1 (theoretical specific charge: 676 mAh.g−1). X-ray diffraction, Ni K-edge X-ray absorption spectroscopy, and 31P and 7Li/23Na nuclear magnetic resonance spectroscopy were used to elucidate the electrochemical mechanisms in both systems. Versus Li, Ni2SnP undergoes a conversion reaction resulting in the extrusion of Ni and the alloying of Li-Sn and Li-P. On delithiation, the material partially recombines into a Sn- and Ni-deficient form. In the Na system, Ni2SnP reacts through the conversion of P into Na3P. These results indicate that the recombination of the pristine material (even partially) increases cycling stability.
Display omitted
•Electrochemical performance of Ni2SnP for Li-ion and Na-ion batteries.•Specific charge close to the theoretical one (742 mAh.g−1) reached in the Li system.•Only 200 mAh.g−1 are obtained in the Na system.•Different electrochemical mechanisms in Li-ion and Na-ion batteries.
The charge and discharge of a Li-ion battery based on conversion type electrode material are investigated
operando by acoustic emission (AE). The AE technique gives a direct evidence of both ...structural and morphological impacts of the electrochemical conversion reaction on the electrode. During the first discharge a huge AE energy is measured not only during the biphasic conversion process, but also during the SEI reaction. On first charge, the cumulated AE energy (CAEE) shows a significant increase, during the back conversion process, while upon further cycling the CAEE fluctuation is smoothed out, but very much reproducible. This demonstrates that a conversion reaction creates an “earthquake” in the electrode during conversion, which is correlated to a strong polarization of the electrochemical curve in the first discharge. More importantly, this study demonstrates that AE is a powerful tool to survey the real-time morphological changes and to discriminate the nature of electrochemical process in the electrode.
In lithium-ion batteries with carbonate electrolytes, the formation of lithium alkoxides at the anode impairs the electrochemical performance and the cycle life of the cells through destabilisation ...of the cathode–electrolyte interface. To fully understand the effect of electrolyte composition on the stability of the cathode–electrolyte interface, and therefore to minimise alkoxide formation and improve cycling stability, we study different carbonate solvents and mixtures thereof. Electrolytes that promote the formation of ethoxide are found to be more detrimental to the cell performance than those forming methoxide. The presence of cyclic carbonates in the electrolyte-solvent mixture alleviates the detrimental effects of ethoxide-forming solvents on the electrochemical performance of Li1.05(Ni0.33Co0.33Mn0.33)0.95O2 by reducing the solubility of the ethoxide.
•Impact of electrolyte composition on the cathode's performance.•The key electrolyte reduction product destabilizing cathode−electrolyte interface.•The role of EC in suppressing overpotential growth at the cathode with cycling.•Importance of solubility of electrochemically formed alkoxides in electrolyte.
Self-supported nickel antimonides/Ni architectured electrodes were prepared by solid state reaction from Ni thin film, Ni foam and Ni nanorods. This specific design is expected to optimize both NiSb
...x
/Ni-current collector and NiSb
x
/electrolyte interfaces of the electrode in the Li ion battery. This new electrode preparation process is based on solid state reaction of antimony with the nickel architectured substrate. Preliminary electrochemical tests of the as-obtained self supported antimonide electrodes show improvement in the capacity retention of the NiSb
x
active material.
PDF
