Vibrationally-resolved RIXS reveals OH-group formation in oxygen redox active Li-ion battery cathodes †

Vibrationally-resolved resonant inelastic X-ray scattering (VR-RIXS) at the O K-edge is emerging as a powerful tool for identifying embedded molecules in lithium-ion battery cathodes. Here, we investigate two known oxygen redox-active cathode materials: the commercial LixNi0.90Co0.05Al0.05O2 (NCA) used in electric vehicles and the high-capacity cathode material Li1.2Ni0.13Co0.13Mn0.54O2 (LRNMC) for next-generation Li-ion batteries. We report the detection of a novel vibrational RIXS signature for Li-ion battery cathodes appearing in the O K pre-peak above 533 eV that we attribute to OH-groups. We discuss likely locations and pathways for OH-group formation and accumulation throughout the active cathode material. Initial-cycle behaviour for LRNMC shows that OH-signal strength correlates with the cathodes state of charge, though reversibility is incomplete. The OH-group RIXS signal strength in long-term cycled NCA is retained. Thus, VR-RIXS offers a path for gaining new insights to oxygen reactions in battery materials

Ethyl 2,2-difluoroacetate as Possible Additive for Hydrogen-Evolution-Suppressing SEI in Aqueous Lithium-Ion Batteries

The performance and lifetime of lithium-ion batteries are strongly influenced by their composition. One category of critical components are electrolyte additives, which are included primarily to stabilize electrode/electrolyte interfaces in the battery cells by forming passivation layers. The presented study aimed to identify and study such an additive that could form a hydrogen-evolution-suppressing solid electrolyte interphase (SEI) in lithium-ion batteries based on aqueous electrolytes. A promising molecular additive, ethyl 2,2-difluoroacetate (EDFA), was found to hold the qualities required for an SEI former and was herein further analyzed electrochemically. Analysis of the battery cells were performed with linear sweep voltammetry and cyclic voltammetry with varying scan rate and EDFA concentrations. Results show that both 1 and 10 w-% EDFA in the electrolyte produced hydrogen-evolution-suppressing SEI:s, although the higher concentration provided no apparent benefit. Lithium-ion full-cells based on LiMn2O4 vs. Li4Ti5O12 active materials displayed poor, though partly reversible, dis-/charge cycling despite the operation of the electrode far outside the electrochemical stability window of the electrolyte. Inclusion of reference electrodes in the lithium-ion cells proved to be immensely challenging with unpredictable drifts in their electrode potentials during operation. To summarize, HER-suppressing electrolyte additives are demonstrated to be a promising approach to stabilize high-voltage operation of aqueous lithium-ion cells although further studies are necessary before any practical application thereof can be realized. Electrochemical evaluation of the reaction mechanism and efficiency of the electrolyte additives relies however heavily on the use of reference electrodes and further development thereof is necessary

DirectX12: A Resource Heap Type Copying Time Analysis

Background The API DirectX 12 allows programmers to have more control over the GPUs memory management. This includes the ability to allocate resources on different types of memory heaps. But there is a lack of research on how these heap types affect the copying performance. Objectives The aim of this thesis is to benchmark the copying performance of the different heap types in DirectX 12 when increasing the data size. The heaps are tested with the three types of command queue that can be used to execute commands to the GPU. Method To answer our research question, a DirectX 12 prototype was implemented and used to copy increasing amount of data between different heap types. The copy operations were also combined with three different types of command queues to see if these have any impact on the performance. The tests ran on three different Nvidia graphic cards on the same computer setup, both to validate our results but also to spot any potential differences. Results The results from this study show that there is a difference in copying speed when copying data between resources that have been allocated on different heap types. The fastest to slowest were as follows: Default to Default, Upload to Default / Default to Readback and Upload to Readback. Using different types of command queues did not have an impact on performance with the exception of when data was copied from Default to Default on an RTX 2080. All of the tests that were carried out showed that the copying time scaled linearly with the data size. Conclusion This study shows the importance of allocating resources on the most suitable heap as there is a difference in copying time between them. In contrast, was the choice of command queue less important as this had no impact on performance in the majority of the tests. The results also show that the copying time scales linearly with the data size

DirectX12: A Resource Heap Type Copying Time Analysis

Background The API DirectX 12 allows programmers to have more control over the GPUs memory management. This includes the ability to allocate resources on different types of memory heaps. But there is a lack of research on how these heap types affect the copying performance. Objectives The aim of this thesis is to benchmark the copying performance of the different heap types in DirectX 12 when increasing the data size. The heaps are tested with the three types of command queue that can be used to execute commands to the GPU. Method To answer our research question, a DirectX 12 prototype was implemented and used to copy increasing amount of data between different heap types. The copy operations were also combined with three different types of command queues to see if these have any impact on the performance. The tests ran on three different Nvidia graphic cards on the same computer setup, both to validate our results but also to spot any potential differences. Results The results from this study show that there is a difference in copying speed when copying data between resources that have been allocated on different heap types. The fastest to slowest were as follows: Default to Default, Upload to Default / Default to Readback and Upload to Readback. Using different types of command queues did not have an impact on performance with the exception of when data was copied from Default to Default on an RTX 2080. All of the tests that were carried out showed that the copying time scaled linearly with the data size. Conclusion This study shows the importance of allocating resources on the most suitable heap as there is a difference in copying time between them. In contrast, was the choice of command queue less important as this had no impact on performance in the majority of the tests. The results also show that the copying time scales linearly with the data size

Abnormal small bowel motility in patients with hereditary transthyretin amyloidosis

Background: Gastrointestinal complications are common in hereditary transthyretin amyloid (ATTRm) amyloidosis. The underlying mechanisms have not been fully elucidated, and the patients' small bowel function remains largely unexplored. The aim of the present study was to compare the small bowel motility in ATTRm amyloidosis patients with that in non-amyloidosis patient controls. Methods: ATTRm amyloidosis patients undergoing evaluation for liver transplantation were consecutively investigated with 24-hour duodenojejunal manometry (n=19). The somatostatin analogue octreotide was used to induce fasting motility. Patients with age at onset of 50years were defined as late-onset cases. For each patient, three age- and sex-matched patient controls (n=57) were selected from the total pool of investigated patients. Key Results: Manometry was judged as abnormal in 58% of the patients and in 26% of the patient controls (P=.01). Patients displayed significantly more daytime phase III migrating motor complexes than patient controls (median 4 vs 2, P<.01), and had a higher frequency of low-amplitude complexes (16% vs 4%; however, this difference did not reach statistical significance, P=.10). Furthermore, late-onset patients showed a delay in octreotide response (5.4 vs 3.8minutes, P<.01), but this was not observed for early-onset patients or within the control group. Conclusions and Inferences: Patients with ATTRm amyloidosis displayed abnormalities in their small bowel motility more frequently than non-amyloidosis patient controls, and the manometric pattern was probably best consistent with a combined neuromyopathic disorder. The delayed octreotide response in late-onset patients warrants further investigation

Vibrationally-resolved RIXS reveals OH-group formation in oxygen redox active Li-ion battery cathodes

Vibrationally-resolved resonant inelastic X-ray scattering (VR-RIXS) at the O K-edge is emerging as a powerful tool for identifying embedded molecules in lithium-ion battery cathodes. Here, we investigate two known oxygen redox-active cathode materials: the commercial LixNi0.90Co0.05Al0.05O2 (NCA) used in electric vehicles and the high-capacity cathode material Li1.2Ni0.13Co0.13Mn0.54O2 (LRNMC) for next-generation Li-ion batteries. We report the detection of a novel vibrational RIXS signature for Li-ion battery cathodes appearing in the O K pre-peak above 533 eV that we attribute to OH-groups. We discuss likely locations and pathways for OH-group formation and accumulation throughout the active cathode material. Initial-cycle behaviour for LRNMC shows that OH-signal strength correlates with the cathodes state of charge, though reversibility is incomplete. The OH-group RIXS signal strength in long-term cycled NCA is retained. Thus, VR-RIXS offers a path for gaining new insights to oxygen reactions in battery materials.Authors in the list of papers of Anastasiia Mikheenkova's thesis: Moritz Hirsbrunner, Anastasiia Mikheenkova, Pontus Törnblom, Robert A. House, Thorsten Schmitt, Håkan Rensmo, Soham Mukherjee, Maria Halin, Laurent Duda</p

The role of oxygen in automotive grade lithium-ion battery cathodes: an atomistic survey of ageing

The rising demand for high-performance lithium-ion batteries, pivotal to electric transportation, hinges on key materials like the Ni-rich layered oxide LiNi$_x$Co$_y$Al$_z$O$_2$ (NCA) used in cathodes. The present study investigates the redox mechanisms, with particular focus on the role of oxygen in commercial NCA electrodes, both fresh and aged under various conditions (aged cells have performed >900 cycles until a cathode capacity retention of ∼80%). Our findings reveal that oxygen participates in charge compensation during NCA delithiation, both through changes in transition metal (TM)–O bond hybridization and formation of partially reversible O$_2$, the latter occurs already below 3.8 V vs. Li/Li$^+$. Aged NCA material undergoes more significant changes in TM–O bond hybridization when cycling above 50% SoC, while reversible O$_2$ formation is maintained. Nickel is found to be redox active throughout the entire delithiation and shows a more classical oxidation state change during cycling with smaller changes in the Ni–O hybridization. By contrast, Co redox activity relies on a stronger change in Co–O hybridization, with only smaller Co oxidation state changes. The Ni–O bond displays an almost twice as large change in its bond length on cycling as the Co–O bond. The Ni–O$_6$ octahedra are similar in size to the Co–O$_6$ octahedra in the delithiated state, but are larger in the lithiated state, a size difference that increases with battery ageing. These contrasting redox activities are reflected directly in structural changes. The NCA material exhibits the formation of nanopores upon ageing, and a possible connection to oxygen redox activity is discussed. The difference in interaction of Ni and Co with oxygen provides a key understanding of the mechanism and the electrochemical instability of Ni-rich layered transition metal oxide electrodes. Our research specifically highlights the significance of the role of oxygen in the electrochemical performance of electric-vehicle-grade NCA electrodes, offering important insights for the creation of next-generation long-lived lithium-ion batteries

The Role of Oxygen in Automotive Grade Lithium-Ion Battery Cathodes : An Atomistic Survey of Ageing

The rising demand for high-performance lithium-ion batteries, pivotal to electric transportation, hinges on key materials like the Ni-rich layered oxide LiNixCoyAlzO2 (NCA) used in cathodes. The present study investigates the redox mechanisms, with particular focus on the role of oxygen in commercial NCA electrodes, both fresh and aged under various conditions (aged cells have performed &gt;900 cycles until a cathode capacity retention of ∼80%). Our findings reveal that oxygen participates in charge compensation during NCA delithiation, both through changes in transition metal (TM)–O bond hybridization and formation of partially reversible O2, the latter occurs already below 3.8 V vs. Li/Li+. Aged NCA material undergoes more significant changes in TM–O bond hybridization when cycling above 50% SoC, while reversible O2 formation is maintained. Nickel is found to be redox active throughout the entire delithiation and shows a more classical oxidation state change during cycling with smaller changes in the Ni–O hybridization. By contrast, Co redox activity relies on a stronger change in Co–O hybridization, with only smaller Co oxidation state changes. The Ni–O bond displays an almost twice as large change in its bond length on cycling as the Co–O bond. The Ni–O6 octahedra are similar in size to the Co–O6 octahedra in the delithiated state, but are larger in the lithiated state, a size difference that increases with battery ageing. These contrasting redox activities are reflected directly in structural changes. The NCA material exhibits the formation of nanopores upon ageing, and a possible connection to oxygen redox activity is discussed. The difference in interaction of Ni and Co with oxygen provides a key understanding of the mechanism and the electrochemical instability of Ni-rich layered transition metal oxide electrodes. Our research specifically highlights the significance of the role of oxygen in the electrochemical performance of electric-vehicle-grade NCA electrodes, offering important insights for the creation of next-generation long-lived lithium-ion batteries

The Role of Oxygen in Automotive Grade Lithium-Ion Battery Cathodes: An Atomistic Survey of Ageing

The rising demand for high-performance lithium-ion batteries, pivotal to electric transportation, hinges on key materials like the Ni-rich layered oxide LiNixCoyAlzO2 (NCA) used in cathodes. The present study investigates the redox mechanisms, with particular focus on the role of oxygen in commercial NCA electrodes, both fresh and aged under various conditions (aged cells have performed > 900 cycles until cathode capacity retention ∼80%). Our findings reveal that oxygen participates in charge compensation during NCA delithiation, both through changes in transition metal (TM) - O bond hybridization and formation of partially reversible O2, the latter occurs already below 3.8 V vs Li/Li+. Aged NCA material undergoes more significant changes in TM - O bond hybridization when cycling above 50% SoC while reversible O2> formation is maintained. Nickel is found to be redox active throughout the entire delithiation, and shows a more classical oxidation state change during cycling with smaller changes in the Ni-O hybridization. By contrast, Co redox activity relies on a stronger change in Co-O hybridization, with only smaller Co oxidation state changes. The Ni-O bond displays an almost twice as large change in its bond length on cycling as the Co-O bond. The Ni-O6 octahedra are similar in size as the Co-O6 octahedra in the delithiated state, but are larger in the lithiated state, a size difference that increases with battery ageing. These contrasting redox activities are reflected directly in structural changes. The NCA material exhibits the formation of nanopores upon ageing, and a possible connection to oxygen redox activity is discussed. The difference in interaction of Ni and Co with oxygen provides a key understanding of the mechanism and the electrochemical instability of Ni-rich layered transition metal oxide electrodes. Our research specifically highlights the significance of the role of oxygen in the electrochemical performance of electric-vehicle-grade NCA electrodes, offering important insights for the creation of next-generation long-lived lithium-ion batteries