Silicon-based anodes are extensively studied as an alternative to graphite for lithium ion batteries. However, silicon particles suffer larges changes in their volume (about 280%) during cycling, which lead to particles cracking and breakage of the solid electrolyte interphase. This process induces continuous irreversible electrolyte decomposition that strongly reduces the battery life. In this research work, different silicon@graphite anodes have been prepared through a facile and scalable ball milling synthesis and have been tested in lithium batteries. The morphology and structure of the different samples have been studied using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and scanning and transmission electron microscopy. We show how the incorporation of an organic solvent in the synthesis procedure prevents particles agglomeration and leads to a suitable distribution of particles and intimate contact between them. Moreover, the importance of the microstructure of the obtained silicon@graphite electrodes is pointed out. The silicon@graphite anode resulted from the wet ball milling route, which presents capacity values of 850 mA h/g and excellent capacity retention at high current density (≈800 mA h/g at 5 A/g).

Responsible disposal and recycling are essential for the sustainability of the battery market, which has been exponentially growing in the past few years. Under such a scenario, the recycling of materials of less economic value, but environmentally much more sustainable like LiFePO₄, represents an economic challenge. In this paper an approach to recover used FePO₄ electrodes from calendar aged Lithium-ion (Li-ion) batteries and their reuse in Sodium-ion (Na-ion) cells is proposed. The electrochemical performances of the Na-ion cell are shown to be comparable with previously reported values and, since the electrode can retain the original microstructure and distribution, electrode processing can be avoided. A proof of concept of a NaFePO₄//hard carbon full cell using a very high positive electrode loading optimized for Li-ion batteries (≈14 mg cm⁻²) is shown.

Silicon–graphite (Si@G) anodes are receiving increasing attention because the incorporation of Si enables lithium-ion batteries to reach higher energy density. However, Si suffers from structure rupture due to huge volume changes (ca. 300%). The main challenge for silicon-based anodes is improving their long-term cyclabilities and enabling their charge at fast rates. In this work, we investigate the performance of Si@G composite anode, containing 30 wt.% Si, coupled with a LiNi_0.8Co_0.15Al_0.05O₂ (NCA) cathode in a pouch cell configuration. To the best of our knowledge, this is the first report on an NCA/Si@G pouch cell cycled at the 5C rate that delivers specific capacity values of 87 mAh g⁻¹. Several techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and gas chromatography–mass spectrometry (GC–MS) are used to elucidate whether the electrodes and electrolyte suffer irreversible damage when a high C-rate cycling regime is applied, revealing that, in this case, electrode and electrolyte degradation is negligible.

The degradation mechanisms of commercial graphite–SiO_x/NCA battery related to the aging process in full cell under cycling conditions at three different temperatures, namely, 10 °C, 25 °C, and 45 °C, have been studied via post-mortem analysis, emphasizing the high energy density graphite–SiO_x anode behaviour. The aging process of the full battery has been studied by non-destructive electrochemical methods. Then, to gain more understanding on the mechanisms that govern the graphite–SiO_x degradation, full cells are disassembled, and the anodes are studied by physicochemical analysis techniques, electron microscopy techniques, and electrochemical characterizations. The battery cycled at 25 °C, between 2.5 and 4.2 V, shows higher cyclability than those cycled at 45 °C and 10 °C, at SoH 80%. Under these conditions, the structural and morphological changes undergo by graphite–SiO_x and SiO_x particles, respectively, and the loss of active material, together with the SEI growth explain the anode degradation.