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Solid-state lithium-based batteries offer higher energy density than their Li-ion counterparts. Yet they are limited in terms of negative electrode discharge performance and require high stack pressure during operation. To circumvent these issues, we propose the use of lithium-rich magnesium alloys as suitable negative electrodes in combination with Li6PS5Cl solid-state electrolyte. We synthesise and characterise lithium-rich magnesium alloys, quantifying the changes in mechanical properties, transport, and surface chemistry that impact electrochemical performance. Increases in hardness, stiffness, adhesion, and resistance to creep are quantified by nanoindentation as a function of magnesium content. A decrease in diffusivity is quantified with 6Li pulsed field gradient nuclear magnetic resonance, and only a small increase in interfacial impedance due to the presence of magnesium is identified by electrochemical impedance spectroscopy which is correlated with x-ray photoelectron spectroscopy. The addition of magnesium aids contact retention on discharge, but this must be balanced against a decrease in lithium diffusivity. We demonstrate via electrochemical testing of symmetric cells at 2.5 MPa and 30∘C that 1% magnesium content in the alloy increases the stripping capacity compared to both pure lithium and higher magnesium content alloys by balancing these effects. All-solid-state lithium-based batteries require high stack pressure during operation. Here, we investigate the mechanical, transport, and interfacial properties of Li-rich magnesium alloy and show enhanced performance at low pressure and ambient temperature for alloy-based electrodes with less than 5 at% Mg content. [ABSTRACT FROM AUTHOR]

The O‐type layered nickel oxides suffer from undesired cooperative Jahn–Teller distortion stemming from Ni3+ ions and undergo multiple biphasic structural transformations during the insertion/extraction of large Na+ ions, posing a significant challenge to stabilize the structural integrity. We present here a systematic investigation of the impact of substituting 5 % divalent (Mg2+) or trivalent (Al3+ or Co3+) ions for Ni3+ to alleviate Na+ion ordering and perturb the Jahn–Teller effect to enhance structural stability. We gauge a fundamental understanding of the Mg−O and Na−O or Mg−O−Na bonding interactions, noting that the ionicity of the Mg−O bond deshields the electronic cloud of oxygen from Na+ ions. Furthermore, calculations of the Van Vleck distortion modes reveal a relaxation of NiO6 octahedra from Jahn–Teller distortion and a reduced electron density at the interlayer with Mg2+ substitution. Long‐range (operando X‐ray diffraction) and short‐range (magic angle spinning nuclear magnetic resonance) structural analyses provide insights into reduced ordering, allowing a stable continuous solid solution. Overall, Mg‐substitution results in a high‐capacity retention of ~96 % even after 100 cycles, showcasing the potential of this strategy for overcoming the structural instabilities and enhancing the performance of sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

The O‐type layered nickel oxides suffer from undesired cooperative Jahn–Teller distortion stemming from Ni3+ ions and undergo multiple biphasic structural transformations during the insertion/extraction of large Na+ ions, posing a significant challenge to stabilize the structural integrity. We present here a systematic investigation of the impact of substituting 5 % divalent (Mg2+) or trivalent (Al3+ or Co3+) ions for Ni3+ to alleviate Na+ion ordering and perturb the Jahn–Teller effect to enhance structural stability. We gauge a fundamental understanding of the Mg−O and Na−O or Mg−O−Na bonding interactions, noting that the ionicity of the Mg−O bond deshields the electronic cloud of oxygen from Na+ ions. Furthermore, calculations of the Van Vleck distortion modes reveal a relaxation of NiO6 octahedra from Jahn–Teller distortion and a reduced electron density at the interlayer with Mg2+ substitution. Long‐range (operando X‐ray diffraction) and short‐range (magic angle spinning nuclear magnetic resonance) structural analyses provide insights into reduced ordering, allowing a stable continuous solid solution. Overall, Mg‐substitution results in a high‐capacity retention of ~96 % even after 100 cycles, showcasing the potential of this strategy for overcoming the structural instabilities and enhancing the performance of sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Solid-state lithium-based batteries offer higher energy density than their Li-ion counterparts. Yet they are limited in terms of negative electrode discharge performance and require high stack pressure during operation. To circumvent these issues, we propose the use of lithium-rich magnesium alloys as suitable negative electrodes in combination with Li6PS5Cl solid-state electrolyte. We synthesise and characterise lithium-rich magnesium alloys, quantifying the changes in mechanical properties, transport, and surface chemistry that impact electrochemical performance. Increases in hardness, stiffness, adhesion, and resistance to creep are quantified by nanoindentation as a function of magnesium content. A decrease in diffusivity is quantified with 6 Li pulsed field gradient nuclear magnetic resonance, and only a small increase in interfacial impedance due to the presence of magnesium is identified by electrochemical impedance spectroscopy which is correlated with x-ray photoelectron spectroscopy. The addition of magnesium aids contact retention on discharge, but this must be balanced against a decrease in lithium diffusivity. We demonstrate via electrochemical testing of symmetric cells at 2.5 MPa and 30∘ C that 1% magnesium content in the alloy increases the stripping capacity compared to both pure lithium and higher magnesium content alloys by balancing these effects. [ABSTRACT FROM AUTHOR]

The exponential growth of the lithium‐ion (LIB) market is causing a significant disparity between the supply chain and demand for its resources. In this regard, sodium‐ion and potassium‐ion batteries are promising alternatives to LIBs due to their low cost. However, the larger sizes of Na+ and K+ ions create challenges that prevent them from achieving energy densities comparable to LIBs while maintaining an acceptable cycle life. In this perspective, the aim is to evaluate the status of Na‐ion and K‐ion batteries and the challenges associated with them on both fundamental and commercial levels. The focus is on the structural instability arising from phase transitions during cycling, intricate chemical degradation processes, and potential avenues for enhancing their performance with a specific goal of improving their viability for grid‐scale energy storage. Materials production and abundance limitations for the chemistries of the state‐of‐the‐art materials and account for critical parameters from both the perspective of researchers and investors are analyzed. This analysis aims to provide insights into the strategic trade‐offs required to effectively implement the technology in real‐world applications, such as grid‐scale storage and other areas. Furthermore, the utilization of metals with low or no supply‐chain problems as an important aspect of these trade‐offs is considered. [ABSTRACT FROM AUTHOR]

P3-type layered K0.48Mn0.4Co0.6O2 was synthesized using a solid-state method. By stabilising into a rhombohedral structure [s.g. R3m (#160)], it delivers a reversible capacity of 64 mA h g−1 with a nominal voltage of ∼3.0 V (vs. K/K+) and it has good cycling stability. It involves a solid-solution redox mechanism, and forms an economical and stable oxide insertion material for potassium-ion batteries. [ABSTRACT FROM AUTHOR]

Aqueous rechargeable zinc-ion batteries have immense commercial potential in the primary battery market, which is largely occupied by alkaline zinc/manganese oxide batteries. These storage systems are desirable for large-scale applications due to their superior safety, high capacity, fast ionic conductivity and low cost. Pursuing new Mn-based cathodes for Zn-ion batteries, cryptomelane with a specific chemical composition of K1.33Mn8O16 was synthesized using a simple sonochemical technique. The formation of phase pure tetragonal K1.33Mn8O16 with I4/m symmetry was confirmed by X-ray diffraction. When tested as a cathode for Zn-ion batteries, cryptomelane K1.33Mn8O16 demonstrated a high reversible capacity of 312 mA h g−1 at a rate of C/10. Robust cycling stability was observed retaining more than 80% of initial capacity after 650 cycles with ∼99% coulombic efficiency. The intercalation chemistry of Zn–MnO2 systems is very rich involving polymorphism and phase transformations during charge/discharge cycles. Synergizing ex situ X-ray diffraction and spectroscopy with the electrochemical titration technique, we have examined the detailed mechanism of (de)intercalation of Zn2+ into cryptomelane K1.33Mn8O16, which is proposed as a potential cathode for Zn-ion batteries. [ABSTRACT FROM AUTHOR]

Noble-metal-free, bifunctional catalysts are essential to develop high-performance, cost-effective water-splitting systems. The current work explores the bifunctional electrocatalytic behavior of two sodium cobalt phosphate systems, namely, NaCoPO4 and Na2CoP2O7, prepared by solution combustion synthesis (SCS) for the first time. Formation of phase-pure orthorhombic maricite NaCoPO4 (space group: Pnma) and orthorhombic Na2CoP2O7 (space group: Pna21) was confirmed by Rietveld refinement. The electrocatalytic activity of maricite NaCoPO4 and Na2CoP2O7 was investigated by using linear sweep voltammetry with a rotating disk electrode (RDE). The oxygen reduction reaction (ORR) activities of these sodium cobalt phosphates are comparable to Vulcan carbon black and Pt/C. Oxygen evolution reaction (OER) activity of Na2CoP2O7 is dominant compared to NaCoPO4 and Pt/C. The Tafel slope, electron-transfer number, and stability of the sodium-metal phosphates were calculated in different concentrations of Na+-containing aqueous electrolyte. The bifunctional activity and good stability of the sodium cobalt phosphates stem from cobalt ions and stabilization of the catalytic centers by the phosphate frameworks. The present work demonstrates sodium cobalt phosphates as alternate cost-effective, novel electrocatalysts for efficient OER/ORR activity in alkaline solution. [ABSTRACT FROM AUTHOR]

Reversible electrochemical potassium-ion intercalation in P2-type NaxCoO2 was examined for the first time. Hexagonal Na0.84CoO2 platelets prepared by a solution combustion synthesis technique were found to work as an efficient host for K+ intercalation. They deliver a high reversible capacity of 82 mA h g−1, good rate capability and excellent cycling performance up to 50 cycles. [ABSTRACT FROM AUTHOR]