The recent proliferation of renewable energy generation offers mankind hope, with regard to combatting global climate change. However, reaping the full benefits of these renewable energy sources requires the ability to store and distribute any renewable energy generated in a cost‐effective, safe, and sustainable manner. As such, sodium‐ion batteries (NIBs) have been touted as an attractive storage technology due to their elemental abundance, promising electrochemical performance and environmentally benign nature. Moreover, new developments in sodium battery materials have enabled the adoption of high‐voltage and high‐capacity cathodes free of rare earth elements such as Li, Co, Ni, offering pathways for low‐cost NIBs that match their lithium counterparts in energy density while serving the needs for large‐scale grid energy storage. In this essay, a range of battery chemistries are discussed alongside their respective battery properties while keeping metrics for grid storage in mind. Matters regarding materials and full cell cost, supply chain and environmental sustainability are discussed, with emphasis on the need to eliminate several elements (Li, Ni, Co) from NIBs. Future directions for research are also discussed, along with potential strategies to overcome obstacles in battery safety and sustainable recyclability.

Rechargeable solid-state sodium-ion batteries (SSSBs) hold great promise for safer and more energy-dense energy storage. However, the poor electrochemical stability between current sulfide-based solid electrolytes and high-voltage oxide cathodes has limited their long-term cycling performance and practicality. Here, we report the discovery of the ion conductor Na3-xY1-xZrxCl6 (NYZC) that is both electrochemically stable (up to 3.8 V vs. Na/Na+) and chemically compatible with oxide cathodes. Its high ionic conductivity of 6.6 × 10−5 S cm−1 at ambient temperature, several orders of magnitude higher than oxide coatings, is attributed to abundant Na vacancies and cooperative MCl6 rotation, resulting in an extremely low interfacial impedance. A SSSB comprising a NaCrO2 + NYZC composite cathode, Na3PS4 electrolyte, and Na-Sn anode exhibits an exceptional first-cycle Coulombic efficiency of 97.1% at room temperature and can cycle over 1000 cycles with 89.3% capacity retention at 40 °C. These findings highlight the immense potential of halides for SSSB applications.

To unlock the compact structure of a-V 2 O 5 for the diffusion of K + , we developed single-crystalline bilayered d-K 0.51 V 2 O 5 nanobelts via reconstruction of a-V 2 O 5 . Benefiting from the large interlayer space and optimized growth orientation, d-K 0.51 V 2 O 5 exhibits suitable accommodation sites and fast diffusion paths for K + , enabling high capacity and rate capability. Additionally, the achievement of a high-energy-and high-power-density full K-ion battery proves its feasibility in large-scale energy storage systems. SUMMARYPotassium-ion batteries (KIBs) are a promising alternative to lithium-ion batteries because of the abundance, low cost, and redox potential of K; however, the significantly larger radius of K + inevitably destabilizes the crystal structure of the cathode material, impeding the diffusion of K + . Here, to lower the insertion energetics and diffusion barriers of K + , we synthesizedd-K 0.51 V 2 O 5 nanobelts (KVOs) with a large interlayered structure and optimized growth orientation by reconstructing the V-O polyhedra of orthorhombic V 2 O 5 ; these exhibited a high average voltage (3.2 V), high capacity (131 mAh g À1 ), and superior rate capability even at 10 A g À1 . By coupling the electrochemical experiments with theoretical calculations, we found that the excellent K-ion storage performance of KVO is attributed to its large interlayered structure and unique 1D morphology. Additionally, we assembled a full KIB composed of KVO and graphite with high energy and power densities, proving its feasibility as a promising new battery.

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