Solvothermal synthesis and electrochemical properties of Na2CoSiO4 and Na2CoSiO4/carbon nanotube cathode materials for sodium-ion batteries

The Development and Prospect of Stable Polyanion Compound Cathodes in LIBs and Promising Complementers

Cathode materials are usually the key to determining battery capacity, suitable cathode materials are an important prerequisite to meet the needs of large-scale energy storage systems in the future. Polyanionic compounds have significant advantages in metal ion storage, such as high operating voltage, excellent structural stability, safety, low cost, and environmental friendliness, and can be excellent cathode options for rechargeable metal-ion batteries. Although some polyanionic compounds have been commercialized, there are still some shortcomings in electronic conductivity, reversible specific capacity, and rate performance, which obviously limits the development of polyanionic compound cathodes in large-scale energy storage systems. Up to now, many strategies including structural design, ion doping, surface coating, and electrolyte optimization have been explored to improve the above defects. Based on the above contents, this paper briefly reviews the research progress and optimization strategies of typical polyanionic compound cathodes in the fields of lithium-ion batteries (LIBs) and other promising metal ion batteries (sodium ion batteries (SIBs), potassium ion batteries (PIBs), magnesium ion batteries (MIBs), calcium ion batteries (CIBs), zinc ion batteries (ZIBs), aluminum ion batteries (AIBs), etc.), aiming to provide a valuable reference for accelerating the commercial application of polyanionic compound cathodes in rechargeable battery systems.

Demystifying In Situ Pyrolysis Chemistry for High-Performance Polyanionic Cathodes in Sodium-Ion Batteries

The carbon coating strategy has emerged as an indispensable approach to improve the conductivity of polyanionic cathodes. However, owing to the complex reaction process between precursors of carbon and cathode, establishing a unified screening principle for carbonaceous precursors remains a technical challenge. Herein, we reveal that carbonaceous precursor pyrolysis chemistry undeniably influences the formation process and performance of Na3V2(PO4)3 (NVP) cathodes from in situ insights. By investigating three types of carbonaceous precursors, it is found that O/H-containing functional groups can provide more bonding sites for cathode precursors and generate a reducing atmosphere by pyrolysis, which is beneficial to the formation of polyanionic materials and a uniform carbon coating layer. Conversely, excessive pyrolysis of functional groups leads to a significant amount of gas, which is detrimental to the compactness of the carbon layer. Furthermore, the substantial presence of residual heteroatoms diminishes graphitization. In this case, it is demonstrated that carbon dots (CDs) precursors with suitable functional groups can comprehensively enhance the Na+ migration rate, reversibility, and interface stability of the cathode material. As a result, the NVP/CDs cathode displays outstanding capacity retention, maintaining 92% after 10,000 cycles at a high rate of 50 C. Altogether, these findings provide a valuable benchmark for carbon source selection for polyanionic cathodes.

Recent Advances in Sodium-Ion Batteries: Cathode Materials

Emerging energy storage systems have received significant attention along with the development of renewable energy, thereby creating a green energy platform for humans. Lithium-ion batteries (LIBs) are commonly used, such as in smartphones, tablets, earphones, and electric vehicles. However, lithium has certain limitations including safety, cost-effectiveness, and environmental issues. Sodium is believed to be an ideal replacement for lithium owing to its infinite abundance, safety, low cost, environmental friendliness, and energy storage behavior similar to that of lithium. Inhered in the achievement in the development of LIBs, sodium-ion batteries (SIBs) have rapidly evolved to be commercialized. Among the cathode, anode, and electrolyte, the cathode remains a significant challenge for achieving a stable, high-rate, and high-capacity device. In this review, recent advances in the development and optimization of cathode materials, including inorganic, organometallic, and organic materials, are discussed for SIBs. In addition, the challenges and strategies for enhancing the stability and performance of SIBs are highlighted.

Polyanion-type cathode materials for sodium-ion batteries

This review summarizes the recent progress and remaining challenges of polyanion-type cathodes, providing guidelines towards high-performance cathodes for sodium ion batteries.