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Magnesium metal batteries are promising candidates for next‐generation high‐energy‐density and low‐cost energy storage systems. Their application, however, is precluded by infinite relative volume changes and inevitable side reactions of Mg metal anodes. These issues become more pronounced at large areal capacities that are required for practical batteries. Herein, for the first time, double‐transition‐metal MXene films are developed to promote deeply rechargeable magnesium metal batteries using Mo2Ti2C3 as a representative example. The freestanding Mo2Ti2C3 films, which are prepared using a simple vacuum filtration method, possess good electronic conductivity, unique surface chemistry, and high mechanical modulus. These superior electro‐chemo‐mechanical merits of Mo2Ti2C3 films help to accelerate electrons/ions transfer, suppress electrolyte decomposition and dead Mg formation, as well as maintain electrode structural integrity during long‐term and large‐capacity operation. As a result, the as‐developed Mo2Ti2C3 films exhibit reversible Mg plating/stripping with high Coulombic efficiency of 99.3% at a record‐high capacity of 15 mAh cm−2. This work not only sheds innovative insights into current collector design for deeply cyclable Mg metal anodes, but also paves the way for the application of double‐transition‐metal MXene materials in other alkali and alkaline earth metal batteries. [ABSTRACT FROM AUTHOR]

The microstructure of an electrode plays a critical role in the electrochemical performance of lithium‐ion batteries, including the energy and power density. Using a micrometer‐scale Wadsley–Roth phase TiNb2O7 active material with Li intercalation chemistry as a model system, the relationship between electrochemical performance and microstructure of calendared electrodes with same mass loading but different electrode parameters is studied by both experimental investigation and theoretical modeling, providing a paradigm of calendaring‐driven electrode microstructure for balanced battery energy density and power density. Along with the reduction in porosity, ion and electron diffusion distance decreases, which is beneficial for charge transfer and rate capability. Nevertheless, the narrowed ion diffusion pathway increases the resistance for ion diffusion. The rate capability, volumetric capacity, and materials utilization are thus predominantly restricted by the microstructures of the electrode, providing fundamental insights into electrode microstructure design for different applications. As an example, an optimized TiNb2O7 electrode with compaction density of ≈2.5 g cm‐3 and mass loading of ≈8.5 mg cm‐2 provides the highest specific charge capacity of 271.3 mAh g‐1 at 0.2 C in half cell configuration and 70.4% capacity retention at 6 C in full configuration, enabling balanced energy density and power density of batteries. [ABSTRACT FROM AUTHOR]

The transition from fossil fuels to renewable energy represents a grand challenge for humankind. For this vision to come to pass, significant advances in energy storage technologies such as batteries, which solve the intermittency of renewable energy, need to be achieved. Developing new battery materials with higher capacities and longer lifetimes is thus of paramount importance. Moreover, the intermittency of renewable energy presents a significant challenge to smart grid management. To this end, researchers have begun turning to machine learning (ML) techniques: algorithms that learn from datasets and automatically improve through experience. These can be used to make predictions and informed decisions, which can accelerate the process of materials discovery and systems management. Here we discuss key ML concepts that have guided important developments in battery materials discovery and smart grid management. In the process, we also examine critical challenges, future opportunities, and how ML can make a significant impact. [ABSTRACT FROM AUTHOR]