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

Etude de nouveaux matériaux phosphates de lithium et d'élément de transition comme électrode positive pour batteries LI-ION

Since the discovery of highly interesting properties for LiFePO4 as a positive electrode material in lithium ion batteries, the search for novel polyanion-based insertion hosts is intense. Actually, cathodic materials based on iron phosphates exhibit high stability and economical and environmental interests. In this context, we were interested in Na3Fe3(PO4)4 with a lamellar structure and in alluaudite-like iron and manganese phosphates LiXNa1-XMnFe2(PO4)3 which structure exhibits tunnels. This work deals, in one hand, on the synthesis and the structural characterisation of these materials and in the other hand on their physical and electrochemical properties as positive electrode for lithium and sodium batteries.Depuis la mise en évidence des potentialités du phosphate LiFePO4 comme électrode positive de batteries lithium-ion, un très fort regain d'intérêt pour les phosphates de fer est actuellement observé. Dans cette optique de recherche de nouveaux matériaux, notre intérêt s'est porté sur la phase Na3Fe3(PO4)4 et sur des monophosphates de fer et de manganèse de type alluaudite LiXNa1-XMnFe2(PO4)3. Leurs structures, respectivement en couche et en chaines, en font de bons candidats pour des applications en tant que matériau d'électrode pour des batteries au lithium ou au sodium. Notre étude porte donc, d'une part, sur la synthèse et la caractérisation structurale de ces phases, et d'autre part sur leurs propriétés physiques et électrochimiques

Iron phosphates with original structures used as positive electrode materials in lithium and sodium batteries

Depuis la mise en évidence des potentialités du phosphate LiFePO4 comme électrode positive de batteries lithium-ion, un très fort regain d’intérêt pour les phosphates de fer est actuellement observé. Dans cette optique de recherche de nouveaux matériaux, notre intérêt s’est porté sur la phase Na3Fe3(PO4)4 et sur des monophosphates de fer et de manganèse de type alluaudite LiXNa1-XMnFe2(PO4)3. Leurs structures, respectivement en couche et en chaines, en font de bons candidats pour des applications en tant que matériau d’électrode pour des batteries au lithium ou au sodium. Notre étude porte donc, d’une part, sur la synthèse et la caractérisation structurale de ces phases, et d’autre part sur leurs propriétés physiques et électrochimiques.Since the discovery of highly interesting properties for LiFePO4 as a positive electrode material in lithium ion batteries, the search for novel polyanion-based insertion hosts is intense. Actually, cathodic materials based on iron phosphates exhibit high stability and economical and environmental interests. In this context, we were interested in Na3Fe3(PO4)4 with a lamellar structure and in alluaudite-like iron and manganese phosphates LiXNa1-XMnFe2(PO4)3 which structure exhibits tunnels. This work deals, in one hand, on the synthesis and the structural characterisation of these materials and in the other hand on their physical and electrochemical properties as positive electrode for lithium and sodium batteries

Iron phosphates with original structures used as positive electrode materials in lithium and sodium batteries

Depuis la mise en évidence des potentialités du phosphate LiFePO4 comme électrode positive de batteries lithium-ion, un très fort regain d'intérêt pour les phosphates de fer est actuellement observé. Dans cette optique de recherche de nouveaux matériaux, notre intérêt s'est porté sur la phase Na3Fe3(PO4)4 et sur des monophosphates de fer et de manganèse de type alluaudite LiXNa1-XMnFe2(PO4)3. Leurs structures, respectivement en couche et en chaines, en font de bons candidats pour des applications en tant que matériau d'électrode pour des batteries au lithium ou au sodium. Notre étude porte donc, d'une part, sur la synthèse et la caractérisation structurale de ces phases, et d'autre part sur leurs propriétés physiques et électrochimiques.Since the discovery of highly interesting properties for LiFePO4 as a positive electrode material in lithium ion batteries, the search for novel polyanion-based insertion hosts is intense. Actually, cathodic materials based on iron phosphates exhibit high stability and economical and environmental interests. In this context, we were interested in Na3Fe3(PO4)4 with a lamellar structure and in alluaudite-like iron and manganese phosphates LiXNa1-XMnFe2(PO4)3 which structure exhibits tunnels. This work deals, in one hand, on the synthesis and the structural characterisation of these materials and in the other hand on their physical and electrochemical properties as positive electrode for lithium and sodium batteries

Iron phosphates with original structures used as positive electrode materials in lithium and sodium batteries

Depuis la mise en évidence des potentialités du phosphate LiFePO4 comme électrode positive de batteries lithium-ion, un très fort regain d’intérêt pour les phosphates de fer est actuellement observé. Dans cette optique de recherche de nouveaux matériaux, notre intérêt s’est porté sur la phase Na3Fe3(PO4)4 et sur des monophosphates de fer et de manganèse de type alluaudite LiXNa1-XMnFe2(PO4)3. Leurs structures, respectivement en couche et en chaines, en font de bons candidats pour des applications en tant que matériau d’électrode pour des batteries au lithium ou au sodium. Notre étude porte donc, d’une part, sur la synthèse et la caractérisation structurale de ces phases, et d’autre part sur leurs propriétés physiques et électrochimiques.Since the discovery of highly interesting properties for LiFePO4 as a positive electrode material in lithium ion batteries, the search for novel polyanion-based insertion hosts is intense. Actually, cathodic materials based on iron phosphates exhibit high stability and economical and environmental interests. In this context, we were interested in Na3Fe3(PO4)4 with a lamellar structure and in alluaudite-like iron and manganese phosphates LiXNa1-XMnFe2(PO4)3 which structure exhibits tunnels. This work deals, in one hand, on the synthesis and the structural characterisation of these materials and in the other hand on their physical and electrochemical properties as positive electrode for lithium and sodium batteries

Etude de nouveaux matériaux phosphates de lithium et d'élément de transition comme électrode positive pour batteries LI-ION

Depuis la mise en évidence des potentialités du phosphate LiFePO4 comme électrode positive de batteries lithium-ion, un très fort regain d intérêt pour les phosphates de fer est actuellement observé. Dans cette optique de recherche de nouveaux matériaux, notre intérêt s est porté sur la phase Na3Fe3(PO4)4 et sur des monophosphates de fer et de manganèse de type alluaudite LiXNa1-XMnFe2(PO4)3. Leurs structures, respectivement en couche et en chaines, en font de bons candidats pour des applications en tant que matériau d électrode pour des batteries au lithium ou au sodium. Notre étude porte donc, d une part, sur la synthèse et la caractérisation structurale de ces phases, et d autre part sur leurs propriétés physiques et électrochimiques.Since the discovery of highly interesting properties for LiFePO4 as a positive electrode material in lithium ion batteries, the search for novel polyanion-based insertion hosts is intense. Actually, cathodic materials based on iron phosphates exhibit high stability and economical and environmental interests. In this context, we were interested in Na3Fe3(PO4)4 with a lamellar structure and in alluaudite-like iron and manganese phosphates LiXNa1-XMnFe2(PO4)3 which structure exhibits tunnels. This work deals, in one hand, on the synthesis and the structural characterisation of these materials and in the other hand on their physical and electrochemical properties as positive electrode for lithium and sodium batteries.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

A new set of K3Fe3(PO4)4·yH2O (0 ≤ y ≤ 1) layered phases obtained by topotactic reactions

K3Fe3(PO4)4·H2O powder was synthesized by Na+/K+ exchange reaction from Na3Fe3(PO4)4 in aqueous medium. The replacement of the sodium cations by the potassium larger ones and water molecules causes a structural distortion leading to P2/n monoclinic K3Fe3(PO4)4·H2O. This new layered phase was characterized by XRD, Mössbauer spectroscopy and magnetic measurements. The study of its thermal stability reveals that other new layered K3Fe3(PO4)4·yH2O with (0 ≤ y ≤ 1) phases can be stabilized up to 600 °C and finally at higher temperature a new K3Fe3(PO4)4 polymorph with a different structural type is irreversibility formed

Study of layered iron(III) phosphate phase Na3Fe3(PO4)4 used a positive electrode in lithium batteries

The layered Na3Fe3(PO4)4 phase prepared by solid-state reaction was studied as positive electrode in lithium batteries. Up to 1.9 Li+ ions/f.u. could be intercalated, and only 1.7 Li+ ions could be extracted between 4.5 and 2 V vs Li+/Li with an average voltage of around ~2.8  V. In situ and ex situ X-ray diffraction data and Mössbauer spectroscopy measurements indicate that the intercalation/deintercalation process occurs through a solid solution process and is reversible. To improve its electrochemical performances, Na3Fe3(PO4)4 was also prepared via a hydrothermal method that leads to a significant particle size reduction. However, no clear improvements of the cycling performances were observed using this material as positive electrode in sodium and lithium batteries

Li0.75Mn1.50Fe1.75(PO4)3: First alluaudite-type iron phosphate containing only Li+ as alkaline ions

A new iron phosphate Li0.75Mn1.50Fe1.75(PO4)3 has been prepared by the flux method and its structure was characterized from single crystal X-ray diffraction data. It crystallizes as an alluaudite type structure, characterized by the A(2)A(2)’A(1)A(1)’A(1)”M(1)M(2)2(PO4)3 general formula with a = 12.002(9) Å, b = 12.509(9) Å, c = 6.404(7) Å, β = 115.07(7)° in the monoclinic C2/c space group. The 3D framework consists of infinite chains of edge-sharing M(2)2O10 dimers and M(1)O6 octahedra connected by phosphate tetrahedra leading to two sets of hexagonal tunnels. The Li+ and Mn2+ ions partially occupy one of them, the other tunnel being empty. The Mössbauer spectroscopy confirmed the occurrence of only Fe3+ ions in octahedral environment. Electrochemical cycling tests in Li cells were performed using Li0.75MnII1.50FeIII1.75(PO4)3 powder as electrode material. Only a small amount of Li+ ions can be reversibility deintercalated/intercalated corresponding to a capacity as low as 30 mAh/g with a 3.2 V average voltage. Moreover, a strong polarization due to low electronic and ionic conductivities is observed. The presence of Mn2+ ions in the same tunnel as Li+ probably hinders a good Li+ ionic diffusion