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This work reports the synthesis of a NaSICON-type structure material, a cost-efficient electrode for lithium-ion batteries, by the substitution of vanadium with cost-effective and eco-friendly iron. Li 3.27 FeII 0.19 FeIII 0.81 V(PO 4) 3 was synthesized using sol-gel followed by a calcination at 450 °C under argon. XRD has confirmed the successful preparation of a compound isostructural to Li 3 V 2 (PO 4) 3 which crystallizes in a monoclinic structure with the P 2 1 / c space group. The electrochemical properties of the novel phosphate were explored at different cut-off voltage windows (2.0–4.2 V, 2.8–4.5 V, 1.4–4.5 V, and 1.0–4.6 V), and using three electrolytes (LP30, LP40, and LP50). The best electrochemical performance was obtained at C/2 over 1.4–4.5 V voltage range and using LP40 delivering a reversible capacity of 150 mAh g−1 after 55 cycles with coulombic efficiency and capacity retention of 99% and 79%, respectively. 57Fe Mӧssbauer spectroscopy evidenced the contribution of Fe2+/Fe3+ redox couple upon the electrochemical reaction. Magnetic measurements revealed the oxidation of the transition metals during the charge process. XAFS study around V and Fe at K-edge revealed the successful substitution of Fe in the V site with a reorganization of the local structure at short and medium range order. • Synthesis of Li 3.27 FeII 0.19 FeIII 0.81 V(PO 4) 3 cathode using sol-gel at 450 °C under Ar. • Improvement of the electrochemical properties of Li 3.27 FeII 0.19 FeIII 0.81 V(PO 4) 3. • Optimization of the cut-off voltage and electrolyte. • Reversible capacity of 150 mAh g−1 was delivered at C/2-rate after 55 cycles. • Characterization using XAFS, 57Fe Mössbauer spectroscopy and magnetic measurements. [ABSTRACT FROM AUTHOR]

Nickel-rich LiNi x Mn y Co 1−x−y O 2 (NMC, with x ≥ 0.6) layered oxides are regarded as cathode candidates for high-energy density lithium-ion batteries (LIBs). However, this technology faces several challenges due to the scarcity of crucial raw materials such as cobalt precursors and the negative environmental impact of their extraction process. It is therefore, it becomes imperative to develop low cobalt content cathode compositions that offer alternative options with comparable electrochemical performance. Herein, we have used a systematic approach to modify the composition while keeping all other properties (particle size and morphology) constant to synthesise low-Co-cathode materials, namely LiNi 0·8 Mn 0·1 Co 0·1 O 2 (NMC-10 %) and LiNi 0·8 Mn 0·15 Co 0·05 O 2 (NMC-5%). A co-precipitation route using a continuous stirred thank reactor was used for synthesis. The physico-chemical properties, electrochemical performances, cycling stability, and rate capabilities of NMC-5% materials are comparable to those of NCM-10 % materials. NMC-10 % and NMC-5% half cells show initial specific discharge capacities of 191 mAh.g−1, and 185 mAh.g−1, respectively, in a voltage range of 2.8–4.3 V (vs. Li+/Li). The NMC-5% exhibits excellent thermal stability, characterized by a predominant exothermic peak at 432 °C and significantly lower total heat energy when compared to NMC-10 % counterpart, which displayed its main exothermic peak at 339 °C. The structural and electronic changes of both materials were evaluated through in operando synchrotron-based X-ray techniques. Regardless of the cobalt content, both materials show comparable structural and electronic evolution upon the de-intercalation/intercalation of Li+ ions. An irreversible phase transition at the first delithiation was observed as emphasized by diffraction of synchrotron radiations. [Display omitted] • LiNi 0·8 Mn 0.1+y Co 0.1-y O 2 (y = 0, 0.05) were synthesized using the co-precipitation. • Capacities of 191 and 185 mAh.g-1 were recorded for y = 0 and 0.05 respectively. • y = 0.05 shows better thermal stability comparing to NMC811. • Reduction of 50 % of Cobalt rate have no effect on the structural properties. [ABSTRACT FROM AUTHOR]

Sodium Mn-doped iron fluorophosphate Na 2 Fe 0·5 Mn 0·5 PO 4 F is a potential positive electrode material for lithium-ion and sodium-ion batteries. This study outlines the synthesis of Na 2 Fe 0·5 Mn 0·5 PO 4 F powder through a simplified and more accessible production method. The X-rays diffraction (XRD) technique showed a pure phase with monoclinic symmetry (S.G. P2 1 /n). The resulting uncoated material (labeled as NFeMPF) was ball-milled with dopamine hydrochloride (mentioned as dopamine hereafter) as a carbon source to enhance the specific surface and improve its electronic conductivity. Raman spectra confirmed the presence of residual carbon after the pyrolysis process. Thermogravimetric analysis (TGA) demonstrated the stability of Mn-doped iron fluorophosphate up to 1000 °C. Additionally, Mössbauer spectroscopy disclosed structural improvements in the material, indicating the reduction of all Fe(III) when coated with dopamine. The uncoated material discharge capacity when cycled against sodium exhibits reversible capacities of only 80, 67, and 38 mAh/g during the first cycle at C/20, C/16, and C/5, respectively. The coated NFeMPF@D delivered improved capacities of 272 and 202 mAh/g at C/20 and C/16, respectively. This highlights the considerable promise of the investigated phosphate-based electrode material as a cathode composite for the next generation of sodium-ion batteries. • Physicochemical and electrochemical properties of Na 2 Fe 0·5 Mn 0·5 PO 4 F are deeply analyzed as cathode material. • Structural and electrochemical properties of pristine Na 2 Fe 0·5 Mn 0·5 PO 4 F were markedly enhanced by adding dopamine. • The Na 2 Fe 0·5 Mn 0·5 PO 4 F/dopamine cathode works as a pseudocapacitor, delivering high discharge capacities with low cycling stability that needs to be improved. [ABSTRACT FROM AUTHOR]