Periodic Reporting for period 1 - Z-ION (Teaming conductivity and chemical functionality in metal-organic frameworks for zinc‑ion batteries)
Berichtszeitraum: 2023-01-01 bis 2025-02-28
The continuous depletion of fossil fuels and their connection to the rising atmospheric CO2 levels have aroused a severe global concern. Therefore, to mitigate these issues, the European Commission has set ambitious targets to make the EU climate-neutral by 2050. In line with this, the next generation of electrochemical energy storage (EES) devices with lower-cost, higher safety, sustainability, eco-friendliness, and performance is the need of an hour. In this direction, zinc-ion batteries (ZIBs) are proving to be an effective EES technology that could meet the future demand for green and safe storage of electric power, which is vital for a low-carbon and fossil-fuel-independent civilization. However, to exploit ZIBs for commercial applications and use them as an alternative to costly and toxic Lithium-ion batteries (LIBs) is very challenging. The commonly used cathodes for ZIBs such as manganese oxides, vanadium oxides, and Prussian blue. limit the rate capability of ZIBs because they severely suffer from decomposition and dissolution in the electrolyte. On the other hand, irregular stripping/plating in pristine Zn anode leads to the formation of Zn dendrites and short circuits, thereby reducing the cycle life of ZIBs severely. Therefore, the overall objectives of this work are to target the alternative anodes and cathodes for ZIBs to minimize the issues associated with the current state of the art based on highly porous and conductive metal-organic frameworks (CMOFs). The first objective is to find, optimize, synthesize, and characterize CMOFs that are suitable for depositing over pristine Zn anodes. The aim is to achieve uniform stripping/plating and minimize the Zn dendrites. The other objective is to select, optimize, synthesize, and characterize CMOF cathodes for ZIBs. The third objective is to synthesize and characterize the covalent interactions of CMOFs and graphene derivatives and use them as a cathode for ZIBs. The fourth objective is to use the optimized CMOF anode and cathode for the assembly of a full aqueous ZIB cell. In this objective, the anode of ZIB is also tested using synchrotron x-ray computed tomography (SXCT) to probe the dendrites and Zn dissolution in pristine and modified Zn anode during secondment in BAM, Berlin. Besides these four objectives, the other objective is planned to two-way transfer of knowledge between an experienced researcher (ER) and the host institute (HI), and also between ER and the secondment host. The final objective is to disseminate and communicate the project results from time to time. Hence, the Z-ION project is expected to offer indispensable knowledge for the advancement of low-cost, sustainable, and safer ZIB and will provide new avenues for EES technologies.
As per the vision of the Z-ION project, the ER first started to synthesize different CMOFs and optimize them as a potential anode and cathode for aqueous ZIBs. The ER has synthesized and characterized CMOFs based on various metals. ER also synthesized the CMOF and graphene acid (GA) composite and tested it as a cathode for ZIBs. Finally, the optimized anode and cathode have been used by ER to assemble the full aqueous ZIB. In addition, the ER also performed SXCT analysis of the cycled anodes and probed the dendrites and Zn dissolution. The main achievements of the Z-ION project are given below:
(i) The successful synthesis and characterization of 2D CMOFs and their hybrid with graphene acid (GA) shows successful covalent interactions between them.
(ii) Different composites of 2DCMOF and GA have been synthesized and characterized but among them 2D Ni3(HHTP)2 CMOF interacts with GA (2DNiGA) more efficiently.
(iii) The 2DNiGA composite as a positive electrode and pristine GA as a negative electrode show extraordinary electrochemical performance for an aqueous asymmetrical supercapacitor resulting in the highest gravimetric (71 W h kg-1) and volumetric (73.8 W h L-1) energy density which is superior than many top-rated literatures.
(iv) Different 2DCMOFs are used to modify the pristine zinc anode for a zinc-ion battery. Our findings show that 2DCo CMOF deposition over a pristine Zn anode works best as an anode by showing uniform stripping/plating and running for long hours by minimizing the dendrites.
(v) Our study also unveils the very first time that graphene derivatives like cyanographene and graphene acid deposition over pristine zinc foil also result in stable cycling and uniform stripping/plating.
(vi) 2DCMOFs like 2DCu, 2DNi, 2DCo, and 2DMn are explored as cathodes for aqueous zinc-ion batteries in which 2DCu CMOF shows superior specific capacity and cyclic stability as compared to other 2DCMOFs.
(vii) Besides zinc-ion batteries, we have obtained tremendous results for graphene derivatives like Nitrogen-doped graphene (GN3) and graphene acid (including their single metal atom counterparts) as a cathode material for zinc-ion hybrid capacitors. GN3 and GA show extremely high specific capacity, energy density, and cyclic stability when compared to many high-quality literature reports.
(viii) The SXCT testing and analysis during secondment is a breakthrough to observe the location of dendrites and Zn dissolution in pristine Zn anode, and also to observe that with the modification of 2DCo CMOF, the Zn anode becomes free from any dendrites
(i) The successful synthesis and characterization of 2D CMOFs and their hybrid with graphene acid (GA) shows successful covalent interactions between them.
(ii) Different composites of 2DCMOF and GA have been synthesized and characterized but among them 2D Ni3(HHTP)2 CMOF interacts with GA (2DNiGA) more efficiently.
(iii) The 2DNiGA composite as a positive electrode and pristine GA as a negative electrode show extraordinary electrochemical performance for an aqueous asymmetrical supercapacitor resulting in the highest gravimetric (71 W h kg-1) and volumetric (73.8 W h L-1) energy density which is superior than many top-rated literatures.
(iv) Different 2DCMOFs are used to modify the pristine zinc anode for a zinc-ion battery. Our findings show that 2DCo CMOF deposition over a pristine Zn anode works best as an anode by showing uniform stripping/plating and running for long hours by minimizing the dendrites.
(v) Our study also unveils the very first time that graphene derivatives like cyanographene and graphene acid deposition over pristine zinc foil also result in stable cycling and uniform stripping/plating.
(vi) 2DCMOFs like 2DCu, 2DNi, 2DCo, and 2DMn are explored as cathodes for aqueous zinc-ion batteries in which 2DCu CMOF shows superior specific capacity and cyclic stability as compared to other 2DCMOFs.
(vii) Besides zinc-ion batteries, we have obtained tremendous results for graphene derivatives like Nitrogen-doped graphene (GN3) and graphene acid (including their single metal atom counterparts) as a cathode material for zinc-ion hybrid capacitors. GN3 and GA show extremely high specific capacity, energy density, and cyclic stability when compared to many high-quality literature reports.
(viii) The SXCT testing and analysis during secondment is a breakthrough to observe the location of dendrites and Zn dissolution in pristine Zn anode, and also to observe that with the modification of 2DCo CMOF, the Zn anode becomes free from any dendrites
In the current state of the art, ZIBs are too far in performance to be used in commercial applications as compared to other batteries, despite being cost-effective, having tremendous safety, and being a great choice for sustainable energy. This is all due to the limitations associated with the currently used anode and cathode materials in ZIBs. Therefore, Z-ION research is based on finding alternative anode and cathode materials and their possible combinations to minimize the limitations associated with current materials. ER found that the major problem associated with ZIBs is dendrite formation and zinc dissolution during continuous stripping/plating. ER probed this problem during electrochemical anode studies that the pristine Zn anode is only stable upto nearly 60 hours and then gets short-circuited at a current density/specific capacity condition of 1 mA cm 2/1 mAh cm-2. Later, this is also confirmed by SXCT analysis with a clear appearance of plenty of dendrites and severe Zn dissolution using the 3D tool of SXCT for the cycled pristine Zn anode. Therefore, ER performed several optimizations with CMOFs and later found that the 8:2 ratio of Co-CMOF and PVDF binder deposition over pristine Zn anode is appropriate to enhance the stability of the ZIB anode. The electrochemical data show that the CMOF deposited Zn anode is stable upto >250 hours at a similar current density/specific capacity condition of 1 mA cm 2/1 mAh cm-2. Furthermore, the SXCT 3D data also confirmed that there is no observation of dendrites and Zn dissolution after such long cycles. It signifies that CMOF deposition over the zinc anode will be highly beneficial for future ZIB studies to minimize the dendrites, Zn dissolution, and improve the cyclic stability of ZIBs. This will help the ZIB to work for extended cycles, which is impossible for all other batteries.