A New Approach to Stable Cationic and Anionic Redox Activity in O3‐Layered Cathode for Sodium‐Ion Batteries

ion batteries (LIBs) by virtue of their similar charge storage mechanism, as well as the abundance and low cost of Na resources. [1][2][3][4] Compared with lithium ions, sodium ions have a larger radius and heavier mass (1.02 vs. 0.76 Å and ≈23 vs. ≈6.9 g mol −1 ), which makes SIBs compete unfavorably in terms of energy density with LIBs, thus limiting their applications in portable electronics and electric vehicles. However, SIBs show great promise in the applications where cost and sustainability are top priority, such as large-scale energy storage. [5][6][7][8][9] Like LIBs, cathode materials are also the main factor limiting the energy density and cost of SIBs. Finding suitable sodium intercalation hosts is pressing. Until now many types of materials have been explored, including layered transition metal oxides, polyanionic compounds, Prussian blue-based compounds, and organic compounds. [10][11][12] Among these candidates, layered transition metal oxides Na x TMO 2 (TM referring to transition metals) is extremely promising on account of its simple structure, high compositional diversity, easy synthesis and attractive electrochemical performance. According to the oxygen stacking sequence and the Na + coordination environment, Layered transition metal oxide P2-Na 2/3 Ni 1/3 Mn 2/3 O 2 usually suffers from largevolume phase transitions and different Na-vacancy ordering during sodium (de)intercalation, incurring rapid capacity decline and poor rate capability. Herein, an effective strategy based on synergetic effect of selected multiple metal ions is designed for P2-type cathodes with improved performance. The role of tetravalent titanium provides high redox potential, inactive divalent magnesium stabilizes the structure, and the monovalent lithium smooths the electrochemical curves. The combined analysis of in operando X-ray diffraction, in operando X-ray absorption spectroscopy and density functional theory calculations demonstrates the contribution of multi-metal ions converts the unfavorable and large-volume P2 to O2 transition into a moderate "Z"-intergrowth structure by increasing the energy barrier of transition metal slab gliding. As a consequence, the resultant P2-Na 0.7 Li 0.03 Mg 0.03 Ni 0.27 Mn 0.6 Ti 0.07 O 2 electrode delivers a reversible capacity of 134 mAh g −1 , a working voltage of 3.57 V, excellent cycling stability (82% of capacity retention after 200 cycles), and superior rate performance (110 mAh g −1 at 4 C). Full cells fabricated with a hard carbon anode achieve an energy density of 296 Wh kg −1 . This study presents a route to rationally design cathode materials with this functionalization to improve the cell performance for sodium-ion batteries.

show abstract

“…However, SIBs show great promise in the applications where cost and sustainability are top priority, such as large‐scale energy storage. [ 5–9 ]…”

Section: Introductionmentioning

confidence: 99%

“…However, SIBs show great promise in the applications where cost and sustainability are top priority, such as large-scale energy storage. [5][6][7][8][9] Like LIBs, cathode materials are also the main factor limiting the energy density and cost of SIBs. Finding suitable sodium intercalation hosts is pressing.…”

mentioning

confidence: 99%

Mitigating the Large‐Volume Phase Transition of P2‐Type Cathodes by Synergetic Effect of Multiple Ions for Improved Sodium‐Ion Batteries

Cheng

Zhao

Guo

et al. 2022

Advanced Energy Materials

149

View full text Add to dashboard Cite

show abstract

“…[ 8–10 ] Interestingly, such oxygen behavior is also applicable to not only Na‐rich cathodes, [ 11–13 ] which are an analog of Li‐rich materials, but also Na‐deficient TM oxides. [ 14–21 ] The Na‐rich compounds are mainly based on noble and expensive TMs, such as 4 d (Ru) and 5 d (Ir) metals; [ 22–24 ] however, Na‐deficient materials (P2 and P3) are represented by abundant and low‐cost 3 d (Mn). [ 15,16 ] There is a universal notation for oxygen redox: Na x [A y TM 1− y ]O 2 , where TM is Mn, [ 14–20 ] Ru, [ 21,25,26 ] or Ir, [ 23,27,28 ] and A is monovalent Li [ 14,17,18,29,30 ] or divalent Mg [ 20,31–33 ] or Zn.…”

Section: Introductionmentioning

confidence: 99%

“…[8][9][10] Interestingly, such oxygen behavior is also applicable to not only Na-rich cathodes, [11][12][13] which are an analog of Li-rich materials, but also Na-deficient TM oxides. [14][15][16][17][18][19][20][21] The Na-rich compounds are mainly based on noble and expensive TMs, such as 4d (Ru) and 5d (Ir) metals; [22][23][24] however, Na-deficient materials (P2 and P3) are represented by abundant and low-cost 3d (Mn). [15,16] There is a universal notation for oxygen redox:…”

mentioning

confidence: 99%

Hysteresis‐Suppressed Reversible Oxygen‐Redox Cathodes for Sodium‐Ion Batteries

Voronina

Shin

Kim

et al. 2022

Advanced Energy Materials

Self Cite

View full text Add to dashboard Cite

Oxygen‐redox‐based cathode materials for sodium‐ion batteries (SIBs) have attracted considerable attention in recent years owing to the possibility of delivering additional capacity in the high‐voltage region. However, they still suffer from not only fast capacity fading but also poor rate capability. Herein, P2‐Na0.75[Li0.15Ni0.15Mn0.7]O2 is introduced, an oxygen‐redox‐based layered oxide cathode material for SIBs. The effect of Ni doping on the electrochemical performance is investigated by comparison with Ni‐free P2‐Na0.67[Li0.22Mn0.78]O2. The Na0.75[Li0.15Ni0.15Mn0.7]O2 delivers a specific capacity of ≈160 mAh g−1 in the voltage region of 1.5–4.6 V at 0.1 C in Na cells. Combined experiments (galvanostatic cycling, neutron powder diffraction, X‐ray absorption spectroscopy, X‐ray photoelectron spectroscopy, and nuclear magnetic resonance (7Li NMR)) and theoretical studies (density functional theory calculations) confirm that Ni substitution not only increases the operating voltage and decreases voltage hysteresis but also improves the cycling stability by reducing Li migration from transition metal to Na layers. This research demonstrates the effect of Li and Ni co‐doping in P2‐type layered materials and suggests a new strategy of using Mn‐rich cathode materials via oxygen redox with optimization of doping elements for SIBs.

show abstract

“…The most commonly used synthesis method is the solid-state method, which is mainly due to its simple preparation process and easy operation. [34][35][36][37][38] For example, Wang et al 35 used NaCH 3 COOH as the sodium source, mixed it with a certain stoichiometric ratio of K 2 CO 3 and MnO 2 , ball milled for 12 hours, and added a small amount of acetone as a dispersant to make the materials uniformly mixed. The dried powder is calcined at a high temperature to obtain the P2-Na 0. material, it can be found that the sodium content and synthesis temperature have a great impact on the phase of the material.…”

Section: Preparation Of Layer-structured Oxidesmentioning

confidence: 99%