The time of arrival of people in Australia is an unresolved question. It is relevant to debates about when modern humans first dispersed out of Africa and when their descendants incorporated genetic material from Neanderthals, Denisovans and possibly other hominins. Humans have also been implicated in the extinction of Australia's megafauna. Here we report the results of new excavations conducted at Madjedbebe, a rock shelter in northern Australia. Artefacts in primary depositional context are concentrated in three dense bands, with the stratigraphic integrity of the deposit demonstrated by artefact refits and by optical dating and other analyses of the sediments. Human occupation began around 65,000 years ago, with a distinctive stone tool assemblage including grinding stones, ground ochres, reflective additives and ground-edge hatchet heads. This evidence sets a new minimum age for the arrival of humans in Australia, the dispersal of modern humans out of Africa, and the subsequent interactions of modern humans with Neanderthals and Denisovans.

Sodium-ion batteries are considered as a favorable alternative to the widely used lithium-ion batteries for applications such as grid-scale energy storage. However, to meet the energy density and reliability that is necessary, electrodes that are structurally stable and well characterized during electrochemical cycling need to be developed. Here, we report on how the applied discharge current rate influences the structural evolution of Na 0.67 Mn 0.8 Mg 0.2 O 2 electrode materials. A combination of ex situ and in situ X-ray diffraction (XRD) data were used to probe the structural transitions at the discharged state and during charge/discharge. Ex situ data shows a two-phase electrode at the discharged state comprised of phases that adopt Cmcm and P6 3 /mmc symmetries at the 100 mA/g rate but a predominantly P6 3 /mmc electrode at 200 and 400 mA/g rates. In situ synchrotron XRD data at 100 mA/g shows a solely P6 3 /mmc electrode when 12 mA/g charge and 100 mA/g discharge is used even though ex situ XRD data shows the presence of both Cmcm and P6 3 / mmc phases. The in situ data allows the Na site occupancy evolution to be determined as well as the rate of lattice expansion and contraction. Electrochemically, lower applied discharge currents, e.g., 100 mA/g, produce better capacity than higher applied currents, e.g., 400 mA/g, and this is related in part to the quantity of the Cmcm phase that is formed near the discharged state during a two-phase reaction (via ex situ measurements), with lower rates producing more of this Cmcm phase. Thus, producing more Cmcm phase allows access to higher capacities while higher rates show a lower utilization of the cathode during discharge as less (if any) Cmcm phase is formed. Therefore, this work shows how structural transitions can depend on the electrochemically applied current which has significant ramifications on how sodium-ion batteries, and batteries in general, are analyzed for performance during operation. 50 cathode materials for Na-ion batteries due to their high 51 reversible capacity, and for M = Fe and Mn, cost and safety. 2−4 52 These materials share many common features with their Li-53 counterparts despite the larger size of Na. Sodium layered 54 oxides are typically identified using Delmas' notation 5 P2, P3, 55 O3, etc., where P and O indicate the Na sites (P = trigonal 56 prismatic and O = octahedral) and the number relates to the 57 transition metal layers within the unit cell. From this 58 classification, numerous studies have been reported for P2-59 type Na y MO 2 materials demonstrating their higher capacities, 60 diffusion rate, and better cyclability than that of the O3 61 structure. 6 62 In 1999, Paulsen and Dahn reported an exhaustive study on 63 P2-sodium manganese oxide compounds 7 after reports from

Ambient temperature sodium-ion batteries are emerging as an exciting alternative to commercially dominant lithium-ion batteries for larger scale stationary applications. In order to realize such a sodium-ion battery, electrodes need to be developed, understood, and improved. Here, Na 3 V 2 O 2 (PO 4 ) 2 F is investigated from the perspective of sodium. Reaction mechanisms for this cathode during battery function include the following: a region comprising at least three phases with subtly varying sodium compositions that transform via two two-phase reaction mechanisms, which appears at the lower potential plateau-like region during both charge and discharge; an extended solid solution region for majority of the cycling process, including most of the higher potential plateau; and a second two-phase region near the highest charge state during charge and between the first and second plateau-like regions during discharge. Notably, the distinct asymmetry in the reaction mechanism, lattice, and volume evolution on charge relative to discharge manifests an interesting question: Is such an asymmetry beneficial for this cathode? These reaction mechanisms are inherently related to sodium evolution, which shows complex behavior between the two sodium crystallographic sites in this compound that in turn mediate the lattice and reaction evolution. Thus, this work relates atomiclevel sodium perturbations directly with electrochemical cycling.

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The first time-resolved in situ synchrotron XRD study of a cathode in a functioning sodium-ion battery. We determine the reaction mechanism, lattice parameters, sodium evolution, and the maximum sodium extraction for the fresh and precycled cell.

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The structures of the six perrhenates (AReO4 A = Ag, Na, K, Rb, Cs and Tl) at RT and the phase transitions associated with change in the orientation of the ReO4− tetrahedra seen for A = Rb, Cs and Tl are described.

Cathodes that feature a layered structure are attractive reversible sodium hosts for ambient temperature sodium-ion batteries which may meet the demands for large-scale energy storage devices. However, crystallographic data on these electrodes are limited to equilibrium or quasi-equilibrium information.Here we report the current-dependent structural evolution of the P2-Na 2/3 Fe 2/3 Mn 1/3 O 2 electrode during charge/discharge at different current rates. The structural evolution is highly dependent on the current rate used, e.g., there is significant disorder in the layered structure near the charged state at slower rates and following the cessation of high-current rate cycling. At moderate and high rates this disordered structure does not appear. In addition, at the slower rates the disordered structure persists during subsequent discharge. In all rates examined, we show the presence of an additional two-phase region that has not been observed before, where both phases maintain P6 3 /mmc symmetry but with varying sodium contents. Notably, most of the charge at each current rate is transferred via P2 (P6 3 / mmc) phases with varying sodium contents. This illustrates that the high-rate performance of these electrodes is in part due to the preservation of the P2 structure and the disordered phases appear predominantly at lower rates. Such current-dependent structural information is critical to understand how electrodes function in batteries which can be used to develop optimised charge/discharge routines and better materials.