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Active-Site-Specific Structural Engineering Enabled Ultrahigh Rate Performance of the NaLi3Fe3(PO4)2(P2O7) Cathode
Li-Ming Zhang1, Jing-Chao Xiao1, Jun-Ru Wang1
1CAS Key Laboratory of Materials for Energy Conversions, Department of Materials Science and Engineering & Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Anhui Hefei 230026, China.
ACS Applied Materials & Interfaces
|February 23, 2022
Summary
A new sodium-based cathode material, NaLi3Fe3(PO4)2(P2O7) (NLFPP), was synthesized using electrochemical ion exchange. This advanced cathode demonstrates high capacity and stability for lithium-ion batteries.
Area of Science:
- Materials Science
- Electrochemistry
- Solid-State Chemistry
Background:
- Iron-based mixed-polyanionic cathodes, such as Na4Fe3(PO4)2(P2O7) (NFPP), offer environmental benefits, facile synthesis, high theoretical capacity, and good stability.
- Developing advanced cathode materials is crucial for enhancing the performance of lithium-ion batteries.
Purpose of the Study:
- To synthesize a novel lithium-substituted material, NaLi3Fe3(PO4)2(P2O7) (NLFPP), from NFPP via active Na-site structural engineering.
- To investigate the electrochemical performance and structural properties of the NLFPP cathode.
- To evaluate the potential of NLFPP as a cathode material for high-performance lithium-ion batteries.
Main Methods:
- Electrochemical ion exchange was employed to synthesize the NLFPP material from NFPP.
- Electrochemical performance was evaluated through galvanostatic cycling at various rates.
- Density functional theory (DFT) calculations and in situ X-ray powder diffraction (XRD) were used to analyze structural and energetic properties.
Main Results:
- The synthesized NLFPP cathode exhibited high reversible capacities of 103.2 mAh g-1 at 0.5C and 90.3 mAh g-1 at 5C.
- NLFPP demonstrated excellent rate capability, retaining 81.5 mAh g-1 at an ultrahigh rate of 30C.
- DFT calculations confirmed that NLFPP has the lowest formation energy, indicating thermodynamic favorability, and revealed structural changes upon Li substitution.
- An NLFPP//hard carbon (HC) full cell achieved a reversible capacity of 91.1 mAh g-1 at 2C, maintaining 82.4% capacity after 200 cycles.
Conclusions:
- The active-site-specific structural tailoring via electrochemical ion exchange is an effective strategy for designing high-performance cathode materials.
- NaLi3Fe3(PO4)2(P2O7) (NLFPP) shows significant promise as a cathode material for advanced lithium-ion batteries due to its superior electrochemical performance and stability.
- This approach provides new insights into the rational design of next-generation battery materials.
