Advanced Materials Science Seminar

Speaker: Filipp Obrezkov, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.

Title: Ultrafast charging polyphenylamine-based cathode material for high rate lithium, sodium and potassium batteries

Abstract: We report the synthesis and investigation of a novel redox-active poly(N,N’-diphenyl-p-phenylenediamine) (PDPPD) polymer obtained via Buchwald-Hartwig C-N cross-coupling reaction. PDPPD has a high density of redox-active amine groups enabling the theoretical specific capacity of 209 mA h g^-1, which is nearly twice higher compared to all other materials of this family reported so far. The obtained polymer was evaluated as a cathode material for dual-ion batteries and demonstrated promising operation voltages of 3.5-3.7 V and decent practical gravimetric capacities of 97, 94 and 63 mA h g^-1 in lithium, sodium and potassium half-cells, respectively, while being tested at the moderate current density of 1C. A specific capacity of 84 mA h g^-1 was obtained for the ultrafast lithium batteries operating at 100C (full charge and discharge takes 36 seconds only), which is, to the best of our knowledge, the highest battery capacity reported so far for such high current densities. The PDPPD//Li batteries also showed promising stability reflected in 67% capacity retention after 5000 cycles.

Speaker: Roman Kapaev, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.

Title: Transition metal coordination polymers for metal-ion batteries

Abstract: Metal-organic polymers might be tuned to have high electrochemical capacity, high electron and ion conductivity and excellent cycling stability, which are necessary for the next generation of metal-ion batteries (MIBs) that are able to charge/discharge quickly over tens of thousands of cycles. In this report, synthesis and characterization of new classes of transition metal coordination polymers, which remain virtually unexplored as active materials for MIBs, are presented. In particular, metal-organic polymers derived from tetraaminobenzene, tetraaminobenzoquinone and dithiooxamide were studied. These compounds were shown to be promising as both ultrastable and ultrafast anode materials (>10 thousand cycles at >10 C) and cathode materials with high capacity and energy density (up to 350 mAh/g in 1.5-4.0 V vs. Li/Li⁺ range) in lithium- and sodium-ion batteries.

Date: December 12, 2018
Time: 16:00-17:00
Place: TPOC-3, Nobel str., 3, Blue Building, CEDL (4^th floor, Room 450)

Passed Seminars:

November, 14, 2018

Speaker: Valeriy Okatenko, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.

Title: Oxide materials with tetrahedrally coordinated d-metal for oxygen electrocatalysis

Abstract: Reversible water decomposition is a promising system for energy storage, e.g. serving as a basis for regenerative alkaline fuel cells. At the same, wide implementation is strongly limited due to kinetic difficulties accompanying oxygen reduction (ORR, water formation) and oxygen evolution (OER, water decomposition) reactions. As the catalysts proven to be reasonably effective and stable are based on precious metals, moderately costed and still efficient catalysts are required.

Bifunctional (effective for both OER and ORR) catalysts based on transition metals oxides have been investigated for some time now, but still no appropriate solution was found. Usually, oxides used in testing contain octahedrally-coordinated d-metal in their crystal structure. At the same time, materials with pure tetrahedral coordination of transition metals were not investigated so wide. Recently, lattice-oxygen mediated mechanism (LOM) was introduced by K. Stevenson’s group, which includes oxygen vacancies transformation during OER and ORR. That leads to the assumption on the necessity of oxygen non-stoichiometry in the bifunctional catalysts.

The talk delivered will cover the investigation of tetrahedrally-coordinated d-metal oxide materials as bifunctional catalysts. In particular, YBaCo₄O₇₊_δ and CaBaCo₄O₇₊_δ are the point of focus, basing on the high oxygen non-stoichiometry index (up to 1.5 and 1.0, respectively, standing for full Co²⁺ to Co³⁺ oxidation) and high electronic conductivity (σ ~ 2,5 S/cm at 50°C).

Speaker: Alexey Akmaev, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.

Title: Hydrothermal synthesis of Na₂FePO₄F and interionic replacement of (PO₄)^3- to (BO₃)^3-

Abstract: Nowadays metal-ion batteries are one of the most perspective systems among other rechargeable electrochemical ones. Metal-ion batteries use in the vast majority of equipment such as electric vehicles, power tools, stationary energy storage, etc. The most important component of metal-ion batteries is the cathode material, which determines the serious parameters of the battery, such as specific energy, specific power, reliability, lifetime and the cost of a unit of stored energy.

The transition metal compounds containing the various polyanionic units like PO₄³, VO₄^3-, SO₄^2-, SiO₄^4-, CO₃^2-, BO₃^3- are considered the most promising cathode materials for the next generation of metal-ion batteries due to the high redox potential caused by the inductive effect and good electrochemical and thermal stability.

In this work polyanionic cathode material Na₂FePO₄F was synthesized by hydrothermal method. It shows a good electrochemical performance. It demonstrates more than 90% of specific capacity at 0.1 C and sufficiently stable work during the long cycling and the cycling rate increasing. There is a PO₄ group which is tetrahedron and has a hanging oxygen atom. In this work we tried to fix this atom through triangle BO₃ group by interionic replacement.

Date: November 14, 2018
Time: 16:00-17:00
Place: TPOC-3, Nobel str., 3, Blue Building, CEDL (4^th floor, Room 450)

October, 10, 2018

Speaker: Aleksandra Boldyreva, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.

Title: Gamma ray induced degradation effects in triple cation perovskite solar cells

Abstract: Solar cells based on complex lead halides with the perovskite structure have attracted particular attention of material scientists and engineers all over the world. Rapid improvement in terms of power conversion efficiencies, which exceeded 22% in combination with potentially low fabrication costs of perovskite solar cells might accomplish a revolution on the PV market. Perovskite solar cells can also be fabricated on ultrathin and lightweight substrates, which makes them particularly attractive for both terrestrial and space applications. Conventional solar cells based on silicon, gallium arsenide or A3B5 type absorbers are usually installed on the satellites. However, these materials rapidly degrade under severe radiation exposure in space. While high-energy particles can be blocked efficiently by the solar cell encapsulation layers, the degradation induced by gamma irradiation from random Sun flares can hardly be avoided. Therefore, development of novel PV materials and solar cell architectures capable of sustaining significant gamma irradiation represents a highly relevant task. In this paper, we will report an experimental evaluation of the gamma radiation tolerance of perovskite solar cells. The effects of the light absorber (triple cation MA(x)FA(y)Cs(z)PbBrnI3-n) formulation and the electron transport materials on the device stability will be discussed in detail. Finally, we will conclude on the potential of the perovskite photovoltaics with respect to the space applications.

Speaker: Maxim Zakharkin, Skolkovo Institute of Science and Technology, Center for Electrochemical Energy Storage, Russia.

Title: Enhancing Na+ Extraction Limit Through High Voltage Activation of the NASICON-type Na4MnV(PO4)3 Cathode

Abstract: Great efforts of battery community were focused on improving performance of a cathode material for sodium-ion batteries Na3V2(PO4)3, however extraction from its structure of more than 2 Na+ ions per formula unit remains the main issue. The presentation will be devoted to a new Na4MnV(PO4)3, where substitution of a part of V3+ by Mn2+ significantly modifies electrochemical properties and reversibly enhances the extraction limit. Our fresh results show how extention of the voltage window changes the (de)intercalation mechanism, activates “locked” Na positions and raises new challenges.