Suppressing the P2–O2 phase transition of P2-type Ni/Mn-based layered oxide by synergistic effect of Zn/Ti co-doping for advanced sodium-ion batteries

Surface Stabilization of O3-type Layered Oxide Cathode to Protect the Anode of Sodium Ion Batteries for Superior Lifespan.

Cu-substituted Prussian white with low crystal defects as high-energy cathode materials for sodium-ion batteries

Electrochemical performance and structural evolution of layered oxide cathodes materials for sodium-ion batteries: A review

Nanoscale surface modification of P2-type Na0.65[Mn0.70Ni0.16Co0.14]O2 cathode material for high-performance sodium-ion batteries

It is desirable to develop alternative electrochemical devices with comparable performance but lower cost to substitute for lithium-ion batteries. Sodium-ion batteries show very similar electrochemical mechanism to lithium-ion batteries. The abundant sodium resource can considerably reduce the cost of energy storage devices as compared with lithium-ion batteries. In this work, a new derivative of sodium iron sulfates, Na6Fe5(SO4)8 (NFS), is developed as cathode material for sodium-ion batteries. The NFS is synthesized from sodium carbonate, sodium sulfate and iron sulfate raw materials, and it shows a high working voltage of 3.7 V vs. Na+/Na. When combined with carbon nanotube (CNT), the NSF@CNT composite demonstrates increased electronic conductivity and superior electrochemical performance. A 3.6 V sodium-ion full battery is constructed based on NFS@CNT cathode and hard carbon (HC) anode materials. Such a full NFS@CNT//HC cell can deliver an energy density towards 350 Wh kg-1 and cycling stability over prolonged 1000 cycles at 2 C. This work offers a low-cost sodium-ion full battery with an impressive high working voltage and energy/power densities for possible stationary energy storage applications.

P2-type Na0.66Ni0.33–xZnxMn0.67O2 as new high-voltage cathode materials for sodium-ion batteries

Insights into the enhanced structure stability and electrochemical performance of Ti4+/F− co-doped P2-Na0.67Ni0.33Mn0.67O2 cathodes for sodium ion batteries at high voltage

P2-type layered transition metal oxide Na0.67Ni0.33Mn0.67O2 is considered as a promising cathode for advanced sodium-ion batteries due to its high theoretical specific capacity. However, the P2-type cathode suffers severe P2-O2 phase transition during cycling process, resulting unsatisfactory cyclic stability and rate capability. Herein, a Ca/Li co-doped P2-type Na0.62Ca0.05Ni0.33Mn0.57Li0.10O2 (NCNMLO) cathode material was synthesized through a simple sol-gel method. With the synergistic effect of Ca-doping at Na sites and Li substitution at transition metal (TM) sites, the cathode achieves an excellent electrochemical performance due to the inhibited P2-O2 phase transition and improved ion diffusion with Na+/vacancy disordering arrangement. The NCNMLO cathode exhibits a good cyclic stability with 70.8 % of capacity retention at 1 C after 200 cycles and excellent rate capability with 40.1 mAh g-1 at 20 C. The dual sites doping strategy provides an effective and simple approach for designing high-performance layered oxide cathode materials for sodium-ion batteries.

Alluaudite-type Na2+2xFe2-x(SO4)3 has been a promising cathode material for sodium-ion batteries (SIBs) due to its high operating voltage and stable structure. However, its actual electrochemical performance suffers from intrinsic sluggish kinetics and poor electronic conductivity. In this work, for the first time, we propose a Na2.48(Fe0.89Mg0.03Sn0.04)1.76(SO4)3 cathode material prepared via a Mg/Sn co-doping strategy. Inactive Mg2+ stabilizes the structure, while Sn4+ inhibits the decomposition of electrolytes under high voltage. The Mg/Sn co-doping strategy enhances the kinetics of sodium ion diffusion reactions, leading to improved electrochemical properties, especially at low temperatures. The optimal NFMS/C-Sn0.03 cathode exhibits a long-term capacity retention of 91.6% after 1500 cycles at 5C and outstanding reversible capacities of 74.3 and 58.3 mAh g-1 at 10C and even at 50C, respectively. Furthermore, the NFMS/C-Sn0.03 cathode demonstrates a high capacity retention of 95.5% at -5 °C and 88.4% at -15 °C, with a remarkable capacity retention of 93.9% after 1000 cycles at room temperature and 85.5% after 700 cycles at -15 °C, respectively. Electron paramagnetic resonance (EPR) and atomic force microscopy (AFM) techniques confirmed that the presence of unpaired electrons and enhanced electronic conductivity could be attributed to the Mg/Sn co-doping. This work provides a feasible approach for designing low-cost, durable, low-temperature, and high-performance cathode materials for SIBs.

Sodium-ion batteries (SIBs) are evolving as a low-cost alternative to the state-of-the-art lithium-ion batteries (LIBs). Elementary properties of sodium, high abundance and low cost associated with sodium precursors made it a realistic alternative to lithium-ion chemistry [1, 2]. Research activities on SIBs are growing worldwide and still require a great deal of basic research. Currently, the research on SIBs is focused on the development of new cathode and anode materials or combinations with improved properties such as high energy density, sustainability, and safety. Sodium insertion in hard carbon is strongly debated, and a full and consistent picture of the underlying mechanism is still missing. By combining in-situ Raman spectra obtained during sodium insertion in hard carbon with detailed ab initio studies, for the first time we provide a complete description of the Na insertion process in hard carbon [3]. On the cathode side, we propose weberite-type sodium metal fluorides (SMF), a new class of high voltage and high energy density materials which are so far unexplored as cathode materials for SIBs [4]. Weberite-type is highly favorable for sodium-containing transition metal fluorides, with a large variety of transition metal combinations (M, M’) adopting the corresponding Na2MM’F7 structure. A series of known and hypothetical compounds with weberite-type structure were computationally investigated to evaluate their potential as cathode materials for SIBs. Weberite-type SMFs show quasi-three-dimensional pathways for Na+ diffusion with surprisingly low activation barriers. The high energy density combined with low diffusion barriers for Na+ makes this type of compounds promising candidates for cathode materials in SIBs. We also present the synthesis and electrochemical properties of new sodium vanadium oxy phosphate (NaVOP), Na2+xV3P2O13 (0 ≤ x ≤ 2). NaVOP shows a reversible capacity of 150 mAh g-1 at an average voltage of 2.5 V vs. Na/Na+, with high cycling stability [5]. The post-structural analysis shows Na2+xV3P2O13 (0 ≤ x ≤ 2) is structurally stable over a wide range of sodium extraction and reinsertion demonstrating its potential as cathode material for SIBs.

P2-Na2/3[Fe1/2Mn1/2]O2 layered oxide is a promising high energy density cathode material for sodium-ion batteries. However, one of its drawbacks is the poor long-term stability in the operating voltage window of 1.5–4.25 V vs Na+/Na that prevents its commercialization. In this work, additional light is shed on the origin of capacity fading, which has been analyzed using a combination of experimental techniques and theoretical methods. Electrochemical impedance spectroscopy has been performed on P2-Na2/3[Fe1/2Mn1/2]O2 half-cells operating in two different working voltage windows, one allowing and one preventing the high voltage phase transition occurring in P2-Na2/3[Fe1/2Mn1/2]O2 above 4.0 V vs Na+/Na; so as to unveil the transport properties at different states of charge and correlate them with the existing phases in P2-Na2/3[Fe1/2Mn1/2]O2. Supporting X-ray photoelectron spectroscopy experiments to elucidate the surface properties along with theoretical calculations have concluded that the formed electrode-electrolyte interphase is very thin and stable, mainly composed by inorganic species, and reveal that the structural phase transition at high voltage from P2- to “Z”/OP4-oxygen stacking is associated with a drastic increased in the bulk electronic resistance of P2-Na2/3[Fe1/2Mn1/2]O2 electrodes which is one of the causes of the observed capacity fading.

Na3CoZr(PO4)3 as high-voltage cathode material for sodium-ion batteries

Sodium diffusion and redox properties of alluaudite Na2+2xM2−x(MoO4)3 (M = Fe, Co, Ni) from DFT+U study

Suppressed O3–P3 phase transition of Cu/Fe/Mn-based layered oxides as cathode materials for high performance sodium-ion batteries

Improved high-rate performance of Na3V2(PO4)3 with an atomic layer deposition-generated Al2O3 layer as a cathode material for sodium-ion batteries