Novel layered K0.7Mn0.7Ni0.3O2 cathode material with enlarged diffusion channels for high energy density sodium-ion batteries

Abstract

As promising, low-cost alternatives of lithiumion batteries for large-scale electric energy storage, sodiumion batteries (SIBs) have been studied by many researchers. However, the relatively large size of Na + leads to sluggish diffusion kinetics and poor cycling stability in most cathode materials, restricting their further applications. In this work, we demonstrated a novel K +-intercalated Mn/Ni-based layered oxide material (K 0.7 Mn 0.7 Ni 0.3 O 2 , denoted as KMNO) with stabilized and enlarged diffusion channels for high energy density SIBs. A spontaneous ion exchange behavior in forming K 0.1 Na 0.7 Mn 0.7 Ni 0.3 O 2 between the KMNO electrode and the sodium ion electrolyte was clearly revealed by in situ X-ray diffraction and ex situ inductively coupled plasma analysis. The interlayer space varied from 6.90 to 5.76 Å, larger than that of Na 0.7 Mn 0.7 Ni 0.3 O 2 (5.63 Å). The enlarged ionic diffusion channels can effectively increase the ionic diffusion coefficient and simultaneously provide more K + storage sites in the product framework. As a proof-of-concept application, the SIBs with the as-prepared KMNO as a cathode display a high reversible discharge capacity (161.8 mA h g −1 at 0.1 A g −1), high energy density (459 W h kg −1) and superior rate capability of 71.1 mA h g −1 at 5 A g −1. Our work demonstrates that the K + pre-intercalation strategy endows the layered metal oxides with excellent sodium storage performance, which provides new directions for the design of cathode materials for various batteries.

Sodium-Storage Performance of K+-Intercalated NaxCu0.2Mn0.8O2

“…As discussed in the introduction part, Na + is easier to intercalate into the KCM structure, while it is more difficult for K + to intercalate into NaCM. The larger interlayer spacing of KCM and the smaller ion radius of Na + may be the main reasons. , The crystalline structure of KCM-Na turns to the desired P2 phase with a significant K + residue, which may improve the electrochemical performance …”

“…The larger interlayer spacing of KCM and the smaller ion radius of Na + may be the main reasons. 17,18 The crystalline structure of KCM-Na turns to the desired P2 phase with a significant K + residue, which may improve the electrochemical performance. 17 The position of K + in the crystal structure has vital importance to the sodium storage of the material.…”

“…This route suffers from insufficient stability of the P3 phase. According to previous reports, 17,18 irreversible phase transformation occurs in P3-K x TMO 2 even after immersing it in NaClO 4 electrolyte for 12 h, making the battery unstable in the operation. Another route is to dope K + into an existing P2-Na x TMO 2 by high-temperature treatment in a K + -rich environment.…”

Constructing a Composite Structure by a Gradient Mg2+ Doping Strategy for High-Performance Sodium-Ion Batteries

“…Sodium-ion batteries (SIBs) have been deemed as an appealing alternative for electrochemical energy storage systems on a large scale by virtue of the analogous working principle with lithium-ion batteries (LIBs), abundant reserves, and attractive cost. − Moreover, cathode materials are of great significance in determining the operating voltage and energy density. − Among many cathode materials, layered transition metal oxides possess high specific capacity, cost effectiveness, and convenience for large-scale preparation. − In particular, P2-type Na 0.67 Mn 0.67 Ni 0.33 O 2 (P2-NMNO) materials are supposed to be an attractive cathode alternative for commercialization due to the high voltage profile (average voltage ≥3.5 V), high specific capacity, and good stability in an ambient atmosphere and moisture. , Nevertheless, bulk failure caused by the high-voltage P2–O2 phase transformation (4.2 V vs Na + /Na) results in large volume expansion and contraction. This not only causes inferior Na + diffusion kinetics but also gives rise to the initiation and propagation of cracks .…”

A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion storage

“…For KIB technologies, several families have been explored as anode materials with high capacity and long cyclability, including intercalation-type, conversion-type, and alloying type materials [8][9][10][11][12][13][14][15][16]. In comparison, the development of ideal cathode materials, such as Prussian blue analogues (PBAs), oxides, polyanions, and organics [17][18][19][20][21][22] are sluggish. For instance, despite of enormous investigations on PBAs, of which the three-dimensional (3D) open framework structure is promising for K-ion storage, the preparation of defect-free and water-free PBAs is difficult, which deteriorates the electrochemical performance of PBAs in terms of kinetics, Coulombic efficiency (CE), and cycling life [23][24][25][26].…”