William Robert Brant

Visualising the evolution of buried surfaces and hidden microstructure of components in all-solid-state batteries. A method for operando imaging of solid polymer electrolyte-based lithium-ion batteries, important considerations and future potential.

The sodium iron hexacyanoferrate compound with chemical formula Na_2.04(2)Fe[Fe(CN)₆]·2.24(2)H₂O, also known as Prussian white (PW), contains disordered and dynamic water molecules that have a dualistic effect on its battery performance. Furthermore, the material exhibits severe strain when dehydrated, which over time diminishes the performance. To understand the complex role of water on the sodium ion conduction and the structural changes happening upon dehydration, local structural characterization is needed. Here, we report the first neutron total scattering study of PW. Reverse Monte Carlo (RMC) fitting reveals that local octahedral distortion of the nitrogen-bound iron octahedra contributes to the disorder of the framework. The strain observed in the dehydrated material comes from a combination of the Fe-N bond elongation and a disordered distribution of sodium throughout the larger structure. In the hydrated material, the sodium exhibits more order due to the presence of water, which constrains the sodium movement. However, the sodium ordering affects the orientation of the water molecules. In the low temperature P2₁/n phase, sodium orders into planes with the oxygen atoms in the water molecules being in the plane, while the hydrogen atoms are pointing away from the sodium plane. In the room temperature R-3 phase, the sodium and water are less ordered despite similar frameworks. Sodium can take a wide range of positions, especially if no water molecule blocks its way, to obtain optimal bonding conditions. These results show that the relationship between sodium and water is co-dependent, and demonstrate that the local structure of framework materials has a crucial link to their properties.

Ti-incorporation suppress rock-salt phase formation at particle surfaces, enhancing capacity of aqueous-processed Ni-rich cathodes for LIBs and forming a thinner CEI layer upon cycling.

A slightly thinner CEI layer and lower charge transfer resistance were achieved by H ₃ OP ₄ modification during the water processing of Ni-rich cathodes, compared to non-treated counterparts.

Prussian white (PW), Na_2–xFe[Fe(CN)₆], is an attractive cathode material for sodium-ion batteries due to its porous framework enabling fast sodium-ion extraction and insertion, environmentally safe elements, scalable synthesis, and performance comparable to current lithium-ion technologies. However, PW suffers from large volume changes between rhombohedral and cubic phases during cycling which is suggested to be detrimental over time because of structural degradation and increased ion insertion resistance. In particular, studies on PW hard carbon full cells revealed that most of the capacity is lost from the lower potential plateau, where this phase transition occurs. It is proposed that cycling in a restricted potential range, where the phase transition is avoided, could benefit the cycle lifetime and capacity retention. Here, we show an operando X-ray diffraction study aiming at determining how the structure evolves after prolonged cycling in different restricted potential ranges and how this impacts the cycling stability and capacity fade in PW. No signs of structural degradation were observed independently of the pre-cycling conditions used. In addition, more of the rhombohedral phase and capacity were recovered in the discharged state when a more restricted potential range had been applied. Thus, it was shown that the phase transition and corresponding volume changes have little impact on the capacity fade. Instead, the main source for capacity fade was proved to be sodium inventory loss, especially during the initial cycles, in combination with, to a lesser extent, polarization. This study gives a new perspective on PW-based batteries in that neither volume changes nor phase transitions are detrimental to battery performance. These results aid the development of improved cycling protocols and battery systems comprised of PW where the lifetime of the material is prolonged.

Silicon powder kerf loss from diamond wire sawing in the photovoltaic wafering industry is a highly appealing source material for use in lithium‐ion battery negative electrodes. Here, it is demonstrated for the first time that the kerf particles from three independent sources contain ~50 % amorphous silicon. The crystalline phase is in the shape of nano‐scale crystalline inclusions in an amorphous matrix. From literature on wafering technology looking at wafer quality, the origin and mechanisms responsible for the amorphous content in the kerf loss powder are explained. In order to better understand for which applications the material could be a valuable raw material, the amorphicity and other relevant features are thoroughly investigated by a large amount of experimental methods. Furthermore, the kerf powder was crystallized and compared to the partly amorphous sample by operando X‐ray powder diffraction experiments during battery cycling, demonstrating that the powders are relevant for further investigation and development for battery applications.

Silicon powder kerf loss from diamond wire sawing in the photovoltaic wafering industry is a highly appealing source material for use in lithium-ion battery negative electrodes. Here, it is demonstrated for the first time that the kerf particles from three independent sources contain ~50 % amorphous silicon. The crystalline phase is in the shape of nano-scale crystalline inclusions in an amorphous matrix. From literature on wafering technology looking at wafer quality, the origin and mechanisms responsible for the amorphous content in the kerf loss powder are explained. In order to better understand for which applications the material could be a valuable raw material, the amorphicity and other relevant features are thoroughly investigated by a large amount of experimental methods. Furthermore, the kerf powder was crystallized and compared to the partly amorphous sample by operando X-ray powder diffraction experiments during battery cycling, demonstrating that the powders are relevant for further investigation and development for battery applications.

Two-dimensional TiS2 has been proposed as a versatile host material for various battery chemistries. Nevertheless, its compatibility with aqueous electrolytes has not been thoroughly understood. Herein, we report on a reversible hydration process to account for the electrochemical activity and structural evolution of TiS2 in a dilute electrolyte for sustainable aqueous Li-ion batteries. Solvated water molecules intercalate into TiS2 layers together with Li+ cations, forming a hydrated phase with a nominal formula unit of Li0.38(H2O)2 δTiS2 as the end product. We unambiguously confirm the presence of two layers of intercalated water by complementary electrochemical cycling, operando structural characterization, and computational simulation. Such a process is fast and reversible, delivering 60 mAh g-1 discharge capacity at a current density of 1250 mA g-1. Our work provides further design principles for high-rate aqueous Li-ion batteries based on reversible water co-intercalation.