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Lithium alloys have the potential to overcome anode-side challenges in solid state batteries. In this work we synthesize and characterize lithium-rich magnesium alloys, quantifying the changes in mechanical properties, transport, and surface chemistry that impact electrochemical performance. Increases in hardness, stiffness,adhesion, and creep are quantified by nanoindentation as a function of magnesium content. A decrease in diffusivity is quantified with chronopotentiometry and6Li PFG-NMR, and an increase in interfacial impedance due to the presence of magnesium is identified with electrochemical impedance spectroscopy which is correlated with XPS data. Throughout, changes in properties are linked to electrochemical performance. This work provides a framework to investigate other lithium alloy systems.

The fracture of ceramic solid electrolytes, driven by the plating of lithium within cracks, has been identified as one of the fundamental issues to successfully develop solid-state batteries. Understanding the mechanics of lithium at the nanoscale is therefore essential. In this work, the elastic and plastic properties of lithium are measured by nanoindentation within an electron microscope. Lithium metal samples are characterized by electron backscattered diffraction before and after indentation to understand the dependence of the mechanical properties on crystallographic orientationand determine the stiffness tensor components, moduli, and Poisson's ratio using a method first proposed by Vlassak and Nix. The measured stiffness tensor components are C11=13.3, C12=11.2, and C44=8.8GPa. Hardness measurements show a clear size effect with hardness in excess of 100MPa observed for indent depths below 300nm, which could contribute toward observed lithium filament propagation.

The fracture of ceramic solid electrolytes, driven by the plating of lithium within cracks, has been identified as one of the fundamental issues to successfully develop solid-state batteries. Understanding the mechanics of lithium at the nanoscale is therefore essential. In this work, the elastic and plastic properties of lithium are measured by nanoindentation within an electron microscope. Lithium metal samples are characterised by electron backscattered diffraction (EBSD) before and after indentation to understand the dependence of the mechanical properties on crystallographic orientation, and determine the stiffness tensor components, moduli and Poisson’s ratio using a method first proposed by Vlassak and Nix. The measured stiffness tensor components are C11=13.3, C12=11.2, and C44=8.8 GPa. Hardness measurements show a clear size effect with hardness in excess of 100 MPa observed for indent depths below 300 nm, which could contribute toward observed lithium filament propagation.

Colour centres in nanodiamonds provide robust sources of fluorescence and can be used as triggered sources of single photons at room temperature. However, practical devices require stability over thousands of hours of operation, and the use of strong pulsed optical excitation, placing significant burden on the robustness of the emitters that requires bespoke testing. In this work we report the response of single NV centres in nanodiamonds of 50 nm and 100 nm diameter to accelerated lifetime testing, exciting the defects close to saturation around 1013 times to simulate the minimum operational lifetime of a practical device. For nanodiamonds 50 nm in diameter, observed changes in the fluorescence intensity and lifetime suggest a progressive size reduction as a result of the pulsed laser excitation, combined with the introduction of non-radiative centres on or near the nanodiamond surface which affect the quantum efficiency of the NV centre and ultimately lead to photobleaching of the emission. We find examples of NV centres in 100 nm nanodiamonds for which triggered single photon emission remains stable for over these accelerated lifetime tests, demonstrating their suitability for use in practical devices.

Red phosphorus (RP) is a promising anode material for potassium-ion batteries because of its theoretical capacity of 865mAhg–1 delivered at an average potential of 0.5V vs K+/K. However, its alloy reactionto form KP entails a volume expansion of 162% resulting in severe stresses that lead to SEI and electrode fracture, loss of electric contact, and ultimately reduced cycle life. Moreover, its low electronic conductivity (10-14 Scm–1) limits rate capability. Here, we report a RP-graphite composite prepared by a two step ball milling procedure to control particle size and optimize carbon coating. Electrodes prepared with the composites achieve high capacity (723mAhg–1) at C/20 and retaining 75% at 5C. It also shows very good cycling stability, retaining more than 96% of the capacity after 100 cycles at 1C.

Summary Red phosphorus (RP) is a promising anode material for alkali-ion batteries due to a high theoretical capacity at low potentials when alloying with lithium, sodium, and potassium. Most alloy anode materials display large volume changes during cycling, which can lead to particle fracturing, low Coulombic efficiency, loss of electrical contact, and ultimately poor cycle life. In this paper we outline, through comprehensive electrochemo-mechanical characterization and modeling of the cycling stresses, why RP can be cycled at high current densities without fracture. Application of in situ nanoindentation and powder compression allows for measurement of the elastic, plastic, and fracture properties of RP. In situ transmission electron microscopy observation with extreme conditions (anisotropic ion diffusion and high current density) was used to validate the model, observing no catastrophic failure of RP particles. Electrochemo-mechanical characterization with geometry and stress modeling allows for predictions to be made for application of RP in alkali-ion batteries.

Red phosphorus (RP) is a promising anode material for potassium-ion batteries because of its theoretical capacity of 865 mAh/g delivered at an average potential of 0.5 V vs. K + /K. However, its alloy reaction to form KP entails a volume expansion of 162% resulting in severe stresses that lead to SEI and electrode fracture, loss of electric contact, and ultimately reduced cycle life. Moreover, its low electronic conductivity (10 −14 S/cm) limits rate capability. Here, we report an RP-graphite composite prepared by a two-step ball-milling procedure to control particle size and optimize carbon coating. Raman operando on graphite in the composite suggests that the carbon coating reversibly expands and contracts due to the volume expansion of RP particles. Electrodes prepared with the composite achieve high capacity (723 mAh/gP) at C/20 and retaining 75% at 5C. It also shows very good cycling stability, retaining more than 96% of the capacity after 100 cycles at 1C.