Flaviano Garcia Alvarado

Biomass-derived derived carbon has emerged as sustainable and cost-effective candidates for next-generation lithium-ion battery anodes. Herein, we report a silicon-enriched Oat-husk biomass-based composite synthesized via a combined hydrothermal treatment and phosphoric acid–assisted high-temperature activation strategy. Structural and chemical analyses confirm the successful integration of 2D MoS₂ nanosheets within an amorphous, defect-rich carbon matrix, with synergistic contributions from naturally occurring Si and activation-derived P species, forming a hierarchical micro/mesoporous architecture with a specific surface area of 551.7 m² g⁻¹ and abundant redox-active defect sites. Electrochemically, the OH-P-MoS2-1K electrode delivers a high reversible capacity of 828.3 mA h g⁻¹ at 0.1 C, excellent rate capability with 532.4 - 321.4 mA h g⁻¹ retained from 1 to 5 C, and outstanding long-term stability of ~648 mA h g⁻¹ after 1000 cycles at 1 C. Density functional theory calculations show that lithium adsorption is relatively weak only on the stoichiometric MoS2 surface, facilitating fast Li-ion conduction. Full-cell validation using an OH-P-MoS₂-1K//NMC design shows practical viability, with a high capacity of 802 mA h g⁻¹ and an initial CE of 78.9% at an average working voltage of ~3.0 V. The cell shows robust rate-capability and stable cycling performance (249.6 mA h g⁻¹ after 100 cycles).

In this paper we present the electrochemical performance of YSr2Cu2FeO7+δ (YSCF). YSCF was prepared by the combustion method and showed YBaCuO-type structure. Symmetrical cells with YSCF-Ce0.9Gd0.1O2-δ (CGO) electrodes showed a polarization resistance of 0.3 Ω·cm2 at 600 °C. Then, YSCF was incorporated in fuel electrode supported solid oxide cells (SOCs). SOCs were composed by the Ni-8% mol stabilized ZrO2 (YSZ) cermet as fuel electrode, YSZ as electrolyte, CGO as barrier layer and the composite YSCF-CGO as oxygen electrode. A SOC with (La₀.₆Sr₀.₄)₀.₉₅Fe₀.₈Co₀.₂O₃−δ (LSCF)-CGO oxygen electrode was also fabricated as reference cell. At 800 °C under 50:50% H2O:H2 in the fuel electrode and air in the oxygen electrode, YSCF-based cell reached a maximum power output of 0.74 W·cm-2 at 0.5 V in SOFC mode and -1.1 A·cm-2 at thermoneutral voltage (1.3 V) in SOEC mode. In the same conditions, EIS measurements revealed a polarization resistance of 0.17 Ω·cm2.

The perovskite-like materials La_1.60Ce_0.10Sr_0.30NiTiO_6‑δ (LCSNT102000) and La_1.60Ce_0.10Sr_0.20NiTiO_6‑δ (LCSNT101010) are obtained by cosubstituting La³⁺ with Ce⁴⁺ and Sr²⁺ in La₂NiTiO_6‑δ and in the A-site-deficient derivative La_1.90NiTiO_6‑δ, respectively. In both perovskites, conductivity is due to small polarons hopping. In LCSNT101010, which displays lower conductivity and higher activation energy than LCSNT102000, this mechanism is hindered due to fewer Ni–O–Ni conduction paths (because Ni/Ti antisite defects are scarce) and to some kind of defect association, which acts as a charge-carriers trap. The presence of Ce⁴⁺ in LCSNT102000 and LCSNT101010 provides a suitable redox pair, Ce⁴⁺/Ce³⁺, for n-type conduction under reducing conditions, with the activation of the Ti⁴⁺/Ti³⁺ pair ruled out based on the XAS data. The low concentration of Ce⁴⁺ limits the n-type conduction to highly reducing atmospheres (pO₂ < 10^–18 atm) and low conductivity values. This, together with the chemical incompatibility of both materials with YSZ and CGO under reducing conditions, suggests that they can be used as components of the air electrode in reversible SOCs. LCSNT101010 displays performance as a cathode in SOFC comparable to LCSNT102000; however, its behavior as an SOEC anode is much worse, mainly due to its very poor ionic conductivity (estimated oxide diffusion coefficients at 900 °C are 4.9 × 10^–11 and 1.7 × 10^–9 cm² s^–1, respectively). Finally, LCSNT102000 presents similarly low ASR values under anodic and cathodic polarization, which are lower than those corresponding to the OCV. This material could potentially be used as an air electrode in a reversible cell.

The electrochemical performance of a rutile with high niobium content (Ti _0.33 Nb _0.66 O ₂ ) has been investigated as Li host material in Li half cells. Electrochemical features are typical of an intercalation pseudocapacitive material. It allows for a highly reversible specific capacity that is kept upon cycling (ca. 170 mAh g ⁻¹ after 200 cycles). This rutile can insert lithium through a solid solution down to 1 V, thus extending the solid solution region 0.2 V with respect to TiO ₂ . On the other hand, the considerable increase in a lattice parameter due to the larger size of Nb widens the tunnel of the rutile structure, thus allowing for a faster insertion reaction. In this work, we report for the first time that the origin of the good performance of the Nb‐substituted TiO ₂ rutiles can be attributed to a high lithium‐ion diffusion coefficient, in the order of 10 ⁻¹⁰ – 10 ⁻¹¹ cm ² s ⁻¹ . These are four orders of magnitude higher than that of TiO ₂ rutile, thus explaining the intercalation pseudocapacitive behavior of the Nb‐derivatives of TiO ₂ .

The synthesis of materials in the La_2–x (CeSr) _m Sr _n □ _p NiTiO_6‑δ series (where □ denotes vacancies, with m, n, and p ranging from 0 to 0.2, and x = 2m + n + p taking values of 0.4 and 0.6) was attempted using a modified Pechini method. A comprehensive chemical, structural, and microstructural characterization was carried out using X-ray diffraction (conventional and synchrotron), neutron powder diffraction, selected area electron diffraction, high-resolution transmission electron microscopy, and X-ray absorption spectroscopy. The results highlight that single-phase samples are obtained for compositions with low cerium and low vacancy contents (m ≤ 0.1 and p ≤ 0.1). The structural study reveals that the compounds present monoclinic symmetry, space groups P2 ₁ /n or P2 ₁ , with Ni and Ti cations exhibiting different degrees of disorder or short-range order, influenced by the existence of A-site vacancies and the contents of Ce⁴⁺ and Sr²⁺ ions. The magnetic behavior is closely related to the cationic disorder at the B-site. The presence of antisite defects and short-range Ni–O–Ni interactions contribute to a lack of three-dimensional antiferromagnetic ordering, probably forming instead of random Ni²⁺ antiferromagnetic clusters at low temperatures.

High-pressure β-V₂O₅ is a positive electrode material for sodium-ion batteries offering a remarkable high capacity of ∼150 mAh g^–1. Despite its attractive electrochemical properties and interesting crystal chemistry due to the existence of several sodiated phases, the sodium intercalation mechanism that provides reversible insertion is still largely unclear. In this work, we conducted a comprehensive investigation of the structural evolution, oxidation state and local structural changes of high-pressure β-V₂O₅ during sodium intercalation. Operando synchrotron diffraction and operando X-ray absorption spectroscopy together with X-ray photoelectron spectroscopy, reveal the reversibility of sodium (de)­intercalation and allowed us to gain a complete picture of the crystal structure evolution and oxidation state changes during cycling. A full crystal structure determination of the sodiated phases Na _x V₂O₅ (0 ≤ x ≤ 1) was performed for the first time directly from operando synchrotron diffraction and ex situ transmission electron microscopy. Our findings reveal a fully reversible phase transition sequence, P2₁/m → C2/m → P2₁/m, during sodium intercalation, driven by the facile slab-gliding of V₂O₅ layers along the crystallographic b direction to accommodate varying amounts of sodium ions. This storage mechanism was further supported with first-principles density functional theory (DFT) calculations.

This study presents the synthesis of biomass‐derived carbon‐metal organic framework (C‐MOF) using modified sawdust as a sustainable precursor and elucidates its electrochemical performance as an anode material for sodium‐ion batteries (SIBs). Optimization at a pyrolysis temperature of 1000 °C with 7.5% catalyst concentration, C‐MOF achieves a high surface area of 312 m⁻²g⁻¹ and electrical conductivity of 28 S cm⁻¹, contributing to its long cycling electrochemical performance compared to commercial hard carbon (HC). The C‐MOF delivers a maximum discharge capacity of 348.5 mAh g⁻¹ at 25 mA g⁻¹ and exhibits an outstanding cycling stability over 600 cycles with minimal degradation. Electrochemical techniques (cyclic voltammetry, impedance, and galvanostatic charge–discharge) reveal efficient sodium‐ion intercalation and favorable ion diffusion characteristics within the porous C‐MOF structure. These findings position C‐MOF as a promising, sustainable, and long‐standing anode material for advanced SIB applications, offering enhanced rate capability, durability, and effective sodium‐ion kinetics.