Unlocking the multi-electron transfer reaction in NASICON-type cathode materials

Abstract

The growing concern about scarcity and large-scale applications of lithium resources has attracted efforts to realize cost-effective phosphate-based cathode materials for next-generation Na-ion batteries (NIBs). In previous work, a series of materials (such as Na4Fe3(PO4)2(P2O7), Na3VCr(PO4)3, Na4VMn(PO4)3, Na3MnTi(PO4)3, Na3MnZr(PO4)3, etc.) with ~120 mAh·g-1 specific capacity and high operating potential have been proposed. However, the mass ratio of the total transition metal in the above compounds is only ~22 wt%, which means that one electron transfer for each transition metal shows a limited capacity (the mass ratio of Fe is 35.4 wt% in LiFePO4). Therefore, a muti-electron transfer reaction is necessary to catch up or beyond the electrochemical performance of LiFePO4. This review summarizes the reported NASICON-type and other phosphate-based cathode materials. On the basis of the aforementioned experimental results, we pinpoint the muti-electron behavior of transition metals and shed light on designing rules for developing high-capacity cathodes in NIBs.

Design of Na3MnZr(PO4)3/Carbon Nanofiber Free-Standing Cathodes for Sodium-Ion Batteries with Enhanced Electrochemical Performances through Different Electrospinning Approaches

“…The tape-cast electrode showed an initial charge and discharge capacity of 105.88 and 67.21 mAh/g, respectively (Figure 12a). The initial capacity loss was typical of the NASICON-structured cathodes containing Zr 4+ or Ti 4+ or Al 3+ , which presented a voltage hysteresis of Al 3+ < Ti 4+ < Zr 4+ [64]. Average discharge capacities of 58.62, 34.61, 21.19, 13.27, 9.01, 5.87, and 3.01 Ah/g at 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, and 5C were obtained, respectively.…”

“…The presence of Zr 4+ was only necessary to unlock the rare Mn 3+ /Mn 4+ redox reaction useful to produce a high-voltage cathode for sodium-ion batteries [64].…”

Towards High-Performance Sodium-Ion Batteries via the Phase Regulation Strategy

“…The overuse of fossil fuels has caused severe energy shortages and environmental contamination problems. Nowadays, building a sustainable development human society via large-scale renewable energy storage technology has become a key to solving these problems. − Sodium-ion batteries (SIBs) had attracted wide attention because they work based on similar principles as lithium-ion batteries but replace lithium with sodium element to eliminate lithium dependence. − In the commercialization process of SIBs, cathode materials played a decisive role. − Up to now, these cathode materials with commercialized prospects were mainly divided into the following three categories: transition-metal oxides, − polyanion compounds, − and prussian blue analogues. − Polyanion-type Fe-based phosphate cathode materials have received extensive interest due to their nontoxic nature, high structural stability, and lower cost. − The widely utilized olivine lithium iron phosphate (LiFePO 4 ), known as LFP, has served as a representative polyanionic iron-based phosphate cathode for lithium-ion batteries (LIBs). However, its counterpart, olivine NaFePO 4 , is not suitable for SIBs due to its complex synthesis route.…”

Realizing Three-Electron Redox Reactions in NASICON-Type NaCrNb(PO4)3 for Sodium Ion Battery Applications

“…Implementing new electrode materials with multielectron redox transitions is a key to the further development of SIBs . Various polyanionic electrode materials for SIBs have been explored, including NASICON-type phosphates, Na x M 1 M 2 (PO 4 ) 3 ( x = 0–4), which appear to be particularly attractive because of their ability to reversibly uptake at least three sodium ions, thereby increasing the specific capacity of electrode materials, and exceptional ability to accommodate a wide range of d elements. − To successfully intercalate 3Na + ions into the Na x M 1 M 2 (PO 4 ) 3 framework, M 1 and M 2 metals should meet the following conditions: (i) at least one of them must be capable of a multielectron reversible redox transfer and (ii) both metals should exhibit redox activity at either high or low potentials for use as a cathode or anode material, respectively.…”