Recent Progress of P2‐Type Layered Transition‐Metal Oxide Cathodes for Sodium‐Ion Batteries

Abstract

Sodium‐ion batteries (SIBs) have attracted much attention due to their abundance, easy accessibility, and low cost. All of these advantages make them potential candidates for large‐scale energy storage. The P2‐type layered transition‐metal oxides (NaxTMO2; TM=Mn, Co, Ni, Ti, Fe, V, Cr, and a mixture of multiple elements) exhibit good Na+ ion conductivity and structural stability, which make them an excellent choice for the cathode materials of SIBs. Herein, the structural evolution, anionic redox reaction, some challenges, and recent progress of NaxTMO2 cathodes for SIBs are reviewed and summarized. Moreover, a detailed understanding of the relationship of chemical components, structures, phase compositions, and electrochemical performance is presented. This Review aims to provide a reference for the development of P2‐type layered transition‐metal oxide cathode materials for SIBs.

A Scalable Approach to Na2FeP2O7@Carbon/Expanded Graphite as a Low‐Cost and High‐Performance Cathode for Sodium‐Ion Batteries

“…[15] Conversely, there is still an absence of suitable cathode materials. As is well known, typical P2 and O3 layer oxide cathodes still suffer serious capacity decay during the discharge/charge process, [16] and organic cathodes are inescapably hindered by the toxic raw material. Nevertheless, the polyanionic materials with stable threedimension (3D) crystal frame structure have attracted extensive attention as a type of SIBs cathodes.…”

Na‐Ion Batteries—Approaching Old and New Challenges

“…Following this strategy, introducing Ni into the structure, greater stability of the P2 phase and better cyclability are obtained since Mn acts as an inactive redox structural element, while Ni 2+ /Ni 4+ couple participates in the redox reaction. [38] A higher Na content (>2/3) in the structure allows a reduction of the average oxidation state of Ni, promoting the oxidation of Ni 2+ [39] The use of Ni as an active redox element results in higher working average voltage, although the charging voltage must be limited to avoid detrimental phase transitions (≈3.5 V). In addition, the presence of Ni reduces sensitivity to air making it difficult to insert harmful species such as CO 3 2− in the transition metal layer.…”

“…Following this strategy, introducing Ni into the structure, greater stability of the P2 phase and better cyclability are obtained since Mn acts as an inactive redox structural element, while Ni 2+ /Ni 4+ couple participates in the redox reaction. [ 38 ] A higher Na content (>2/3) in the structure allows a reduction of the average oxidation state of Ni, promoting the oxidation of Ni 2+ to Ni 4+ at lower charge voltages, leading to higher structural stability of the P2 phase, as observed in P2‐type Na 45/54 Li 4/54 Ni 16/54 Mn 34/54 O 2 . [ 39 ] The use of Ni as an active redox element results in higher working average voltage, although the charging voltage must be limited to avoid detrimental phase transitions (≈3.5 V).…”

Multifunctional Metal Phosphides as Superior Host Materials for Advanced Lithium‐Sulfur Batteries

“…In the past decades, our society has witnessed a huge change (the novel industrial revolution). In this industrial revolution, technological innovations in things such as electric automobiles, smart‐grids, unmanned aerial vehicles, and internet‐of‐things applications are urgently need to exploration a novel energy storage system with excellent performance and safety tolerance [1–7] . Today, the most widely used energy storage devices are lithium‐ion batteries (LIBs); however, after decades of development, both the traditional cathode and anode materials of LIBs are based on insertion mechanism and nearly realized their theoretical energy density (420 W h kg −1 ) [8–10] .…”