Search for: All records

We propose a real-time path guiding method, Voxel Path Guiding (VXPG), that significantly improves fitting efficiency under limited sampling budget. Our key idea is to use a spatial irradiance voxel data structure across all shading points to guide the location of path vertices. For each frame, we first populate the voxel data structure with irradiance and geometry information. To sample from the data structure for a shading point, we need to select a voxel with high contribution to that point. To importance sample the voxels while taking visibility into consideration, we adapt techniques from offline many-lights rendering by clustering pairs of shading points and voxels. Finally, we unbiasedly sample within the selected voxel while taking the geometry inside into consideration. Our experiments show that VXPG achieves significantly lower perceptual error compared to other real-time path guiding and virtual point light methods under equal-time comparison. Furthermore, our method does not rely on temporal information, but can be used together with other temporal reuse sampling techniques such as ReSTIR to further improve sampling efficiency. 

The lithium-mediated nitrogen reduction reaction (LiNRR) produces ammonia in ambient conditions. This electrochemical pathway is dependent on a catalytic solid–electrolyte interphase—a nanoscale passivation layer formed from reductive electrolyte decomposition on the surface of lithium metal. The catalytic solid–electrolyte interphase is a unique nanostructured environment that exists on reactive metal surfaces and intimately influences product selectivity. Here we explore recent progress made in the field of lithium-mediated nitrogen reduction to ammonia, especially in light of growing knowledge about the nature of the catalytic solid–electrolyte interphase. We systematically analyse the observed chemical species and reactions that occur within the solid–electrolyte interphase. We also summarize key developments in kinetic and transport models, as well as highlight the cathodic and complementary anodic reactions. Trends in ammonia selectivities and rates with varying electrolyte compositions, cell designs and operating conditions are extracted and used to articulate a path forward for continued development of lithium-mediated nitrogen reduction to ammonia. 

Abstract The dynamic behavior of the interface between the lithium metal electrode and a solid-state electrolyte plays a critical role in all-solid-state battery performance. The evolution of this interface throughout cycling involves multiscale mechanical and chemical heterogeneity at the micro- and nano-scale. These features are dependent on operating conditions such as current density and stack pressure. Here we report the coupling of operando acoustic transmission measurements with nuclear magnetic resonance spectroscopy and magnetic resonance imaging to correlate changes in interfacial mechanics (such as contact loss and crack formation) with the growth of lithium microstructures during cell cycling. Together, the techniques reveal the chemo-mechanical behavior that governs lithium metal and Li 7 La 3 Zr 2 O 12 interfacial dynamics at various stack pressure regimes and with voltage polarization. 

In this work we build upon acoustic–electrochemical correlations to investigate the relationships between sound wave structure and chemo-mechanical properties of a pouch cell battery. Cell thickness imaging and wave detection during pouch cell cycling are conducted in parallel. Improved acoustic hardware and signal processing are used to validate the direct measurement of material stiffness, which is an intrinsic physical property. Measurement of cell thickness to micron resolution and wave transmit time to nanosecond resolution in a temperature and pressure controlled acoustic rig allows for estimation of the effective stiffness. We further explore the effects of material type and cell layering on the acoustic signal, demonstrating that the operando acoustic method can accurately measure the changes in physical state properties of a battery with high dynamic temporal and spatial range.