Insights into the Electrochemical Performance of 1.8 Ah Pouch and 18650 Cylindrical NMC:LFP|Si:C Blend Li-ion Cells

Silicon has become an integral negative electrode component for lithium-ion batteries in numerous applications including electric vehicles and renewable energy sources. However, its high capacity and low cycling stability represent a significant trade-off that limits its widespread implementation in high fractions in the negative electrode. Herein, we assembled high-capacity (1.8 Ah) cells using a nanoparticulate silicon–graphite (1:7.1) blend as the negative electrode material and a $LiFePO_{4}–LiNi_{0.5}Mn_{0.3}Co_{0.2}O_{2}$ (1:1) blend as the positive electrode. Two types of cells were constructed: cylindrical 18650 and pouch cells. These cells were subjected both to calendar and cycling aging, the latter exploring different working voltage windows (2.5–3.6 V, 3.6–4.5 V, and 2.5–4.5 V). In addition, one cell was opened and characterised at its end of life by means of X-ray diffraction, scanning electron microscopy, and further electrochemical tests of the aged electrodes. Si degradation was identified as the primary cause of capacity fade of the cells. This work highlights the need to develop novel strategies to mitigate the issues associated with the excessive volumetric changes of Si

A Post-Mortem Study of Stacked 16 Ah Graphite//LiFePO₄ Pouch Cells Cycled at 5 °C

Herein, the post-mortem study on 16 Ah graphite//LiFePO4 pouch cells is reported. Aiming to understand their failure mechanism, taking place when cycling at low temperature, the analysis of the cell components taken from different portions of the stacks and from different positions in the electrodes, is performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS). Also, the recovered electrodes are used to reassemble half-cells for further cycle tests. The combination of the several techniques detects an inhomogeneous ageing of the electrodes along the stack and from the center to the edge of the electrode, most probably due to differences in the pressure experienced by the electrodes. Interestingly, XPS reveals that more electrolyte decomposition took place at the edge of the electrodes and at the outer part of the cell stack independently of the ageing conditions. Finally, the use of high cycling currents buffers the low temperature detrimental effects, resulting in longer cycle life and less inhomogeneities

Adiponitrile-based electrolytes for high voltage, graphite-based Li-ion battery

Operating high voltage lithium-ion batteries (LIB) is still an obstacle due to the limited anodic stability of state-of-the-art alkyl carbonates-based electrolytes which incorporate ethylene carbonate (EC). Thus, we replace here the widely used ethylene carbonate (EC)/dimethyl carbonate (DMC) solvent formulation by adiponitrile (ADN)/DMC (1/1, wt./wt.), to enable room temperature electrolyte formulations with high anodic stabilities. The possibility of operating graphite with 1 M LiDFOB & 1 M LiFSI ADN/DMC (1/1, wt./wt.) without additive is evidenced, with a clear advantage for the LiDFOB electrolyte. The addition of fluoroethylene carbonate (FEC) as a SEI additive results in improved graphite electrode performance in both cases and, less expectedly, in improved anodic stabilities. Cathodes operating above 4.3 V vs Li+/Li have been paired with graphite as well and allowed improved rate capability as compared to graphite half-cells. The safety of the electrolytes versus a charged graphite anode is improved as compared with state-of-the-art, EC-based electrolytes

Aerosol Spray Pyrolysis Synthesis of Doped LiNi_0.5Mn_1.5O₄ Cathode Materials for Next Generation Lithium-Ion Batteries

The autonomy of next generation Electric Vehicles relies on the development of high energy density automotive batteries. LiMn1.5Ni0.5O4 (spinel structure) is a promising active cathode material in terms of charge rate capability, theoretical capacity, cost and sustainability being a cobalt-free material. In the current study pristine and doped (Fe, Al, Mg) LiMn1.5Ni0.5O4 particles were synthesized by an Aerosol Spray Pyrolysis pilot scale unit in a production rate of 100 gr. h−1 and were evaluated for their electrochemical activity in Half Coin Cell form. The doped particles were characterized in terms of their surface area, particle size distribution, crystallite size, morphology and ion insertion of the doping element into the LiNi0.5Mn1.5O4 lattice by Raman spectroscopy. The mixed oxide particles had homogeneous composition which is an inert characteristic of aerosol spray pyrolysis synthesis. The electrochemical activity of the material is attributed both to the nanoscale structure, by successful dopant ion insertion into the spinel lattice as well as to optimization of carbon and spinel particle interface contact in the microscale for increase of electrode conductivity

Insights into the Electrochemical Performance of 1.8 Ah Pouch and 18650 Cylindrical NMC:LFP|Si:C Blend Li-ion Cells

International audienceSilicon has become an integral negative electrode component for lithium-ion batteriesin numerous applications including electric vehicles and renewable energy sources. However, itshigh capacity and low cycling stability represent a significant trade-off that limits its widespreadimplementation in high fractions in the negative electrode. Herein, we assembled high-capacity(1.8 Ah) cells using a nanoparticulate silicon graphite (1:7.1) blend as the negative electrode materialand a LiFePO4 LiNi0.5Mn0.3Co0.2O2 (1:1) blend as the positive electrode. Two types of cells wereconstructed: cylindrical 18650 and pouch cells. These cells were subjected both to calendar andcycling aging, the latter exploring different working voltage windows (2.5 3.6 V, 3.6 4.5 V, and2.5 4.5 V). In addition, one cell was opened and characterised at its end of life by means of X-raydiffraction, scanning electron microscopy, and further electrochemical tests of the aged electrodes. Sidegradation was identified as the primary cause of capacity fade of the cells. This work highlightsthe need to develop novel strategies to mitigate the issues associated with the excessive volumetricchanges of Si

A Post-Mortem Study of Stacked 16 Ah Graphite//LiFePO₄ Pouch Cells Cycled at 5 °C

Herein, the post-mortem study on 16 Ah graphite//LiFePO4 pouch cells is reported. Aiming to understand their failure mechanism, taking place when cycling at low temperature, the analysis of the cell components taken from different portions of the stacks and from different positions in the electrodes, is performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS). Also, the recovered electrodes are used to reassemble half-cells for further cycle tests. The combination of the several techniques detects an inhomogeneous ageing of the electrodes along the stack and from the center to the edge of the electrode, most probably due to differences in the pressure experienced by the electrodes. Interestingly, XPS reveals that more electrolyte decomposition took place at the edge of the electrodes and at the outer part of the cell stack independently of the ageing conditions. Finally, the use of high cycling currents buffers the low temperature detrimental effects, resulting in longer cycle life and less inhomogeneities