In July 2024, Professor Qiao Yu’s research group at Xiamen University published a paper on Achieving High-Capacity Cathode Presodiation Agent Via Triggering in Adavanced Materials (impact factor 27.4) online Anionic Oxidation Activity in Sodium Oxide “, Ni element is precisely implanted into the Na site (functional site) in the Na2O framework by high-energy ball milling process to regulate the band structure, activate the oxidation activity of oxygen anion, and prepare a large-capacity positive sodium supplement. The first author is Chen Yilong, a doctoral student in the School of Chemistry and Chemical Engineering at Xiamen University.
Importing Products and Reference Nodes
Canrd, to help you on the road to scientific research! It is a great honor that the products “Sodium alum phosphate, conductive carbon black, PVDF” from Colud contributed to the results of this research.
Research background
Compensating for the irreversible loss of finite active sodium (Na) is essential to improve the energy density of the full battery of a practical sodium-ion battery (SIBs), especially when using hard carbon negatives with low first loop coulomb efficiency. The introduction of sacrificial positive sodium supplements, especially those with potential anionic oxidation activity and high theoretical capacity, can provide additional sodium sources to compensate for Na losses. The Ni atom was precisely implanted into the Na site within the Na2O framework to obtain (Na0.89Ni0.05□0.06)2O (Ni-NA2O) sodium supplement. The synergistic interaction between Na vacancy and Ni catalyst effectively regulated the band structure, formed a milder NA-O covalent bond, activated the oxidation activity of oxygen anion, and reduced the decomposition overpotential to 2.8 V (vs Na/Na+). A high charging capacity of 710 mAh/g≈Na2O (Na2O decomposition rate >80%) was obtained. By adding the modified sodium supplement to the positive electrode of Na3V2(PO4)3 and Na 2/3Ni2/3Mn1/3O2, the energy density of the corresponding Na ion battery was increased by 23.9% and 19.3%, respectively. In addition, the structure of Ni-Na2O is not limited to the study, but also the structure-function relationship between the anionic oxidation mechanism and the electrode-electrolyte interface manufacturing is deeply analyzed, which provides an example for the development of sacrificial positive sodium supplement.
Research questions
Main point 1: Characteristic analysis of Na2O based large capacity sodium supplement
In order to activate the oxidation activity of oxygen anion and reduce the decomposition potential of Na2O in practical applications, Ni element was successfully implanted into the lattice of Na2O by high-energy ball milling process. The results of synchrotron radiation XRD and neutron diffraction show that Ni replaces the Na site (functional site) in the Na2O framework and introduces Na vacancy. The DFT calculation shows that the injection of Ni atom and the formation of Na vacancy regulate the energy level/band structure of Na2O, enhance the electrical conductivity of the original Na2O, and activate the oxidation activity of O anion. In addition, combined with the catalytic action of NiO, the decomposition kinetics of Na2O was accelerated.
FIG. 1.a) The voltage curve of (Na2O + NiO) composite positive electrode at the upper cut-off potential of 10mAg-1 and 4.5V; The illustration shows the capacity of the pure Na2O positive electrode at a 4.5V cutoff potential (<15mAhg-1). c) sXRD pattern of NNO sodium supplement and d)NPD pattern and the result of Rietveld fine fitting. e) State density (DOS) of Na2O (top) and Ni-Na2O (bottom).
Point 2: Evolution of structure and local covalent environment during the decomposition of sodium supplement.
Synchrotron radiation characterization shows that the tetrahedral Ni-O coordination structure is formed by doping Ni in the Na2O framework. With the irreversible escape of gaseous O2 and the removal of active sodium, its structure has undergone a fundamental evolution. Combined with HR-TEM, it is shown that Ni-Na2O completely decomposes at 4.5V with only a small amount of NiO remaining. The charging and discharging process of NiO in the specified voltage window does not occur Na ejection and embedding.
Figure 2. Fine structure evolution of sodium supplement decomposition process
Point 3: Analysis of oxygen behavior during the oxidation of sodium supplement
In addition, through systematic in situ/in situ characterization techniques (such as OEMS, titration-mass spectrometry, soft X-ray, etc.), we revealed the oxidation pathway of O anion during the decomposition of NNO sodium, and clarified the multi-step reaction process that produces multiple O-O dimers during the decomposition of Na2O. Effective Ni implantation and NiO surface catalysis accelerated the kinetics of NA-O bond cleavage and O-O bond formation, confirming the multi-step transformation pathway of intermediate substances O2−, O22−(O2−) and gaseous O2.
FIG. 3.a) shows the constant current curve of the positive electrode of NNO sodium supplement during the initial charging process when the current density is 50 mAg-1. The charging curve is marked with five different charging states: b) shows the OEMS results of the corresponding time-resolved release rates of O2 and CO2 during the initial charging. c) TMS results: The amount of O2 and CO2 collected from the NNO sodium supplement electrode sheet at different specific voltages. The peak value at 533 eV represents the oxygen in the Na2O antifluorite structure. The peak at 531.4eV represents the * (O-O) peroxide; The peak at 531.2eV represents the hybrid state of the O 2p and Ni 3d orbitals in NiO. e) Ni-Na2O
Kinetic diagram of the electrochemical transfer oxidation process during charging.
Point 4: Electrochemical properties after pre-natrization
Finally, the NNO sodium supplement was applied to the HC||Na3V2(PO4)3 (NVP) battery to increase the battery capacity from 75.3mAh/gNVP to 93.3 mAh/gNVP. Similarly, in the HC||Na2/3Ni2/3Mn1/3O2 (NNMO) full battery, the initial discharge capacity was significantly improved by 12.1 mAh/gNNMO. This demonstrates the universality of NNO as a sodium supplement and provides a new perspective for improving the energy density of SIBs.
FIG. 4.a) Initial charging curves of Na3V2(PO4)3(NVP) and Na2/3Ni2/3Mn1/3O2(NNMO) at 10mAg-1 (nwt% (n=0%, 5% and 10%) NNO prenatrized positive electrode), The voltage ranges are 2.5 to 4.3V and 2.0 to 4.15V respectively. Illustration: The bar chart corresponds to the charge and discharge capacity of the initial cycle at 10 mag-1. c) Constant current charge and discharge curve of HC||NVP button type full battery without or with 10wt%NNO pre-natrified at 10mAg-1 (1st) and 50mAg-1 (5-50th) in the range 1.0 to 4.2V. e) Constant current charge and discharge curves of HC||NNMO button type full batteries without or containing 10wt% NNO pre-natrified at voltages ranging from 0.5 to 4.0V at 10mAg-1 (1st) and 50mAg-1 (5th to 50th).
Point 5: Effect of pre-sodium on the electrode-electrolyte interface
Time-of-flight secondary ion mass spectrometry (TOF-SIMS) proved that the CEI membrane composition and distribution of the positive electrode were changed by the introduction of sodium supplement. Nucleophilic species in the process of sodium supplement decomposition accelerated the decomposition of electrolyte on the one hand, and promoted the decomposition of electrolyte additive FEC on the other hand, and finally constructed the CEI membrane structure of fluorine-rich components. This multi-layered distribution of internal rigidity helps to form a more robust CEI structure on the positive electrode surface. In addition, the authors not only comprehensively evaluated the decomposition kinetics of sodium supplement, but also comprehensively evaluated the positive-negative shuttle, parasitic reaction, electrode structure stability and safety during the decomposition of sodium supplement, and proposed corresponding solutions.
Figure 5. Effect of sodium supplement on electrode – electrolyte interface and its views
Research summary
In conclusion, the NNO positive sodium supplement was successfully synthesized by doping TM at the functional site (Na site) of Na2O with transition metal (TM) implantation strategy. The researchers demonstrated that Ni atom implantation and Na vacancy adjusted the energy level/band structure of Na2O, enhanced the electrical conductivity of the original Na2O and activated the oxidation activity of the O anion. In addition, combined with the catalytic action of NiO, it also accelerates the decomposition kinetics of Na2O. By adjusting the internal crystal structure of Na2O and the external catalytic action of NiO, the release of active Na and O2 was promoted, and the overpotential of Na2O decomposition was significantly reduced. Finally, the high pre-natritization capacity of 710 mAh/g≈ Na2O and the high decomposition rate of 82% were achieved. Synchrotron radiation characterization shows that doped nickel in Na2O framework forms tetrahedral Ni-O coordination structure. With the irreversible escape of gaseous O2 and the extraction of active sodium, its structure has undergone a fundamental evolution from the original Ni-Na2O antifluorite structure to the residual NiO. In addition, through systematic in situ/in situ characterization techniques (such as OEMS, titration-mass spectrometry, soft X-rays, etc.), the researchers demonstrated the oxidation pathway of O anions during the decomposition of NNO, demonstrating a multi-step reaction process that produces multiple O-O dimers during the decomposition of Na2O. Effective nickel implantation and surface catalysis of nickel oxide accelerated the kinetics of NA-O bond cleavage and O-O bond formation, confirming the multistep transformation path of intermediates including O2-, O22- (O2-) and gaseous O2. Compared to the original NVP positive electrode, the initial charge capacity of the NVP cathode containing 10 wt% NNO was significantly improved by 39.0% (from 103 mAh/gNVP to 143 mAh/gNVP). In addition, the first cycle discharge capacity of HC||NVP and HC||NNMO full batteries with 10 wt% NNO increased by 23.9% and 19.3%, respectively, and the capacity retention rate was not affected. In addition, the researchers also conducted a comprehensive evaluation of positive sodium supplements and advocated the establishment of a standardized research paradigm in future studies to truly realize the efficient use of positive sodium/lithium supplements and significantly improve the energy density of Na/Li ion batteries.
The original link: https://doi.org/10.1002/adma.202407720
Canrd main business
Company introduction
Welcome to Canrd Company (Canrd stands for “Creating Avenues for New Research Development”，website: www.canrd.com ). We specialized in:
- Electrochemical experiment consumables, including coin cell cases, cathodes, anodes, electrodes, electrolytes, and various other materials.
- Battery cell research and development outsourcing, offering Custom-made electrodes, dry cells, finished battery cells, and battery cell testing.
- Test line equipment, such as coin cell equipment lines, pouch cell test lines, cylindrical cell test lines, and more.
We have strong research and development capabilities.If you are interested, please feel free to contact us at any time.
Phone：19867737979
Email：contact@canrd.com
Wechat：contactcanrd
Leave a Reply