Denys Butenko

All-solid-state batteries with inorganic solid electrolytes are a global trend in the development of next-generation energy storage devices, promising greatly simplified designs, increased energy density, and, perhaps most importantly, enhanced safety. Currently, the anion-mixed strategy for all-solid-state batteries is the mainstream for developing amorphous halide solid electrolytes, opening up good possibilities for creating conductors with high ionic conductivity and stability. Here, we show the structure evolution of amorphous solid electrolyte, Li_3xZrCl₄N_x (0.17 ≤ x ≤ 1), demonstrating ionic conductivities of up to 3.21 × 10^-3 S∙cm^-1 at 30°C, suggesting that the formation of nitrogen-containing frameworks is crucial for enhancing ionic conductivity. The structural evolution during the mechanochemical reaction, revealed by in situ time-resolved synchrotron X-ray diffraction, highlights the advantages of mixed-anion chemistry and clarifies the formation pathway of the dual-anion electrolyte. In addition, nitrogen incorporation into amorphous electrolyte provides enhanced mechanical deformability and leads to promising electrochemical performance over a wide temperature range. In particular, the dual-anion solid electrolyte maintains stable operation at lower temperatures when coupled with a LiIn negative electrode, highlighting the broader potential of anion-mixed design for all-solid-state batteries.

The design and synthesis of advanced solid electrolytes (SEs) underlie the development of safety and high‐energy density all‐solid‐state batteries (ASSBs). Mechanochemical synthesis stands as the predominant method, yet it faces criticism due to its energy and time‐intensive process (typically spanning several hours to days), presenting a significant obstacle to large‐scale industrial production. Furthermore, ambiguity surrounding the formation mechanisms of SEs during mechanochemical reactions has limited optimization efforts. In addressing these challenges, evidence is presented that the efficiency of mechanochemical SE synthesis can achieve remarkable heights through process optimization. Specifically, the rapid synthesis of the state‐of‐the‐art Li‐Nb‐O‐Cl superionic conductor in only a few hours is highlighted, while concurrently demonstrating its superior electrochemical performance. Notably, for the first time, a structural evaluation during the mechanochemical reaction by time‐resolved in situ synchrotron X‐ray scattering experiments unveils a two‐stage process. This expeditious mechanochemical synthesis of SEs establishes a foundational step toward the commercialization of ASSBs.

Doping with metal ions can significantly enhance the electrochemical performance of Na₃V₂(PO₄)₃ (NVP) as a cathode material for sodium-ion batteries (SIBs). Despite its high reversible capacity and high voltage, practical application of NVP is limited by its poor intrinsic conductivity. Herein, we shed light on a facile sol-gel synthesis method to prepare NVP with ternary doping of potassium K⁺, Al³⁺, and SO₄^2- ions, which accelerates the migration of Na⁺ in the crystal structure, as confirmed by theoretical calculations. The new cathode materials exhibit a notable reversible capacity of 115.3 mA·h g^-1 at 0.5C and retain a substantial initial capacity of 79.1 mA·h g^-1 even at 50C. Additionally, we synthesized NVP with the doping of SO₄^2- ion on the PO₄^3- site, which shows 90.6 and 85 mA·h g^-1 at 0.5 and 10C, respectively. These results perfectly demonstrate the advantages of the superiority of ternary substitution on the NVP cathode. Moreover, sodium anode-free full cells of the cathode paired with Cu/SP foil showed impressive long-term cycling stability. This achievement lays a strong foundation for the use of NASICON cathodes with high charge-discharge rates and high energy density, making them a promising alternative to the next-generation lithium-ion batteries.

Increasing energy density without sacrificing the lifetime, power and cyclability of electrochemical capacitors is a very important goal. However, most efforts are directed toward the improvement of active charge‐storing materials, while the design of devices and minimization of the weight/volume of the passive component have received less attention. We propose here a mathematical model of a carbon supercapacitor in organic electrolyte, which establishes a relationship between the specific capacitance of a device, the thickness of its electrodes, and the weight of its passive components (case, external current leads, current collectors, etc.). The model was built based on experimentally obtained dependences and has been validated using experiments with electrodes made of two porous carbon materials. Regardless of the pore size distribution in the specified range of electrode thicknesses, the functional dependence of the electrode's specific capacitance on the thickness is well described within the linear approximation. The developed model enables optimization of the electrode thickness, thus maximizing specific energy density for a chosen carbon electrode material.

Lithium (Li) metal solid-state batteries feature high energy density and improved safety and thus are recognized as promising alternatives to traditional Li-ion batteries. In practice, using Li metal anodes remains challenging because of the lack of a superionic solid electrolyte that has good stability against reduction decomposition at the anode side. Here, we propose a new electrolyte design with an antistructure (compared to conventional inorganic structures) to achieve intrinsic thermodynamic stability with a Li metal anode. Li-rich antifluorite solid electrolytes are designed and synthesized, which give a high ionic conductivity of 2.1 × 10^-4 S cm^-1 at room temperature with three-dimensional fast Li-ion transport pathways and demonstrate high stability in Li-Li symmetric batteries. Reversible full cells with a Li metal anode and LiCoO₂ cathode are also presented, showing the potential of Li-rich antifluorites as Li metal-compatible solid electrolytes for high-energy-density solid-state batteries.

Simultaneous study of magnetic and electrocatalytic properties of cobaltites under extreme conditions expands the understanding of physical and chemical processes proceeding in them with the possibility of their further practical application. Therefore, La_0.6Sr_0.4CoO₃ (LSCO) nanopowders were synthesized at different annealing temperatures t_ann = 850-900 °C, and their multifunctional properties were studied comprehensively. As t_ann increases, the rhombohedral perovskite structure of the LSCO becomes more single-phase, whereas the average particle size and dispersion grow. Co³⁺ and Co⁴⁺ are the major components. It has been found that LSCO-900 shows two main Curie temperatures, T_C1 and T_C2, associated with a particle size distribution. As pressure P increases, average ⟨T_C1⟩ and ⟨T_C2⟩ increase from 253 and 175 K under ambient pressure to 268 and 180 K under P = 0.8 GPa, respectively. The increment of ⟨dT_C/dP⟩ for the smaller and bigger particles is sufficiently high and equals 10 and 13 K/GPa, respectively. The magnetocaloric effect in the LSCO-900 nanopowder demonstrates an extremely wide peak δT_fwhm > 50 K that can be used as one of the composite components, expanding its working temperature window. Moreover, all LSCO samples showed excellent electrocatalytic performance for the oxygen evolution reaction (OER) process (overpotentials of only 265-285 mV at a current density of 10 mA cm^-2) with minimal η₁₀ for LSCO-900. Based on the experimental data, it was concluded that the formation of a dense amorphous layer on the surface of the particles ensures high stability as a catalyst (at least 24 h) during electrolysis in 1 M KOH electrolyte.

Single crystals of the langbeinite-type phosphates K_1.65Na_0.35TiFe(PO₄)₃ and K_0.97Na_1.03Ti_1.26Fe_0.74(PO₄)₃ were grown by crystallization from high-temperature self-fluxes in the system Na₂O–K₂O–P₂O₅–TiO₂–Fe₂O₃ using fixed molar ratios of (Na+K):P = 1.0, Ti:P = 0.20 and Na:K = 1.0 or 2.0 over the temperature range 1273–953 K. The three-dimensional framework of the two isotypic phosphates are built up from [(Ti/Fe)₂(PO₄)₃] structure units containing two mixed [(Ti/Fe)O₆] octahedra (site symmetry 3) connected via three bridging PO₄ tetrahedra. The potassium and sodium cations share two different sites in the structure that are located in the cavities of the framework. One of these sites has nine and the other twelve surrounding O atoms.