Double-ion regulated aqueous zinc-iodine battery

Abstract

The invention discloses a double-ion regulated aqueous zinc-iodine battery, and belongs to the technical field of zinc ion batteries, the battery comprises an iodine positive electrode, a zinc negative electrode, a diaphragm and an electrolyte solution; the electrolyte solution comprises a zinc sulfate solution and trimethylsulfoxide iodide TMOSI. The problems that in the prior art, Zn deposition / stripping is irreversible, and the service life of the battery is short are solved.

Description

Technical Field

[0001] The invention relates to the technical field of zinc ion batteries, and in particular to a dual-ion-regulated aqueous zinc-iodine battery. Background Art

[0002] As the demand for clean energy and sustainable development continues to grow rapidly, it is crucial to explore safe and reliable large-scale energy storage technologies. Aqueous zinc-ion batteries have attracted much attention due to the safety and sustainability of aqueous electrolytes. However, problems such as hydrogen evolution reaction (HER), surface corrosion, and dendrite formation have seriously hindered their widespread application. HER and surface corrosion lead to rapid battery failure because water decomposition not only consumes electrolyte but also increases the local pH near the Zn electrode, triggering the accumulation of inert byproducts on the Zn electrode surface. The growth of zinc dendrites inevitably leads to serious side reactions and short circuits in the battery. These factors together lead to low Coulombic efficiency (CE), rapid voltage decay, and poor cycling performance of zinc-ion batteries (ZIBs). Therefore, it is crucial to develop efficient zinc anodes that can inhibit dendrite growth and reduce side reactions such as HER and self-corrosion. Typically, the electrolyte is weakly acidic or neutral. Therefore, Zn 2+ and H + The electron competition problem at the electrode interface is inevitable, which significantly affects the deposition / stripping of Zn ions on the Zn electrode surface.

[0003] At present, various strategies have been proposed to change the interfacial behavior of Zn anode, such as surface protection layer engineering, electrode structure optimization and electrolyte additive modification. Among these methods, the electrolyte additive strategy is particularly popular because it is considered to be the simplest and most effective method. Electrolyte additives mainly improve the stability of Zn anode in three ways, including regulating the Zn 2+ The solvation structure of ions, the formation of a solid electrolyte interface (SEI) on the surface of the Zn negative electrode, and the formation of a molecular or ionic adsorption layer on the surface of the Zn negative electrode. Inorganic molecular additives can adjust the Zn by forming an electrostatic shielding layer through the adsorption of cations on the electrode surface. 2+ Organic molecular additives containing atoms with higher electronegativity usually change the deposition behavior of Zn 2+ In addition to anions used to improve the zinc anode, metal cations and quaternary ammonium cations have also been reported to be adsorbed on the zinc anode interface, thereby improving the deposition / stripping behavior of zinc ions. These metal cations include inert monovalent ions Na + 、Divalent ion Mn 2+ Mg 2+ 、Trivalent ion La 3+ 、Ce 3+ , Y 3+etc. Organic cations are usually imidazole-based additives and quaternary ammonium ions. However, the above methods still have defects in regulating the deposition / stripping behavior of zinc ions at the zinc anode interface and reducing side reactions such as dendrite growth, HER and self-corrosion. Therefore, it is necessary to further develop other additives that can improve the zinc anode. Summary of the invention

[0004] The present invention provides a dual-ion regulated aqueous zinc-iodine battery, which solves the problems of irreversible Zn deposition / stripping and short battery life in the prior art.

[0005] In order to solve this technical problem, the present invention provides the following technical solution:

[0006] An ion-regulated aqueous zinc-iodine battery, comprising: an iodine positive electrode, a zinc negative electrode, a separator and an electrolyte solution;

[0007] The electrolyte solution includes zinc sulfate solution and trimethylsulfoxide iodide (TMOSI).

[0008] Preferably, the concentration of trimethyl sulfoxide iodide TMOSI is 0.02-0.06M.

[0009] Preferably, the concentration of trimethylsulfoxide iodide TMOSI is 0.06M.

[0010] Preferably, the concentration of the zinc sulfate solution is 2M.

[0011] Preferably, the iodine positive electrode is obtained by coating positive electrode slurry on carbon paper and drying it; the positive electrode slurry comprises an active material, a conductive agent and a binder; the active material comprises elemental iodine and activated carbon.

[0012] Preferably, the conductive agent is acetylene black.

[0013] Preferably, the adhesive is PVDF.

[0014] Preferably, the weight ratio of the active material, the conductive agent and the binder is 8:1:1.

[0015] Preferably, the mass ratio of elemental iodine to activated carbon is 3:7.

[0016] Preferably, the diaphragm is glass fiber

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] By adding the electrophilic reagent trimethyl sulfoxide iodide (TMOSI) to the conventional ZnSO4 electrolyte, a long-life aqueous Zn-ion battery with improved performance is realized, which benefits from the trimethyl sulfoxide cation TMOSI formed by the dual ion (TMOSI additive) + and anion I -)’s coordinated regulation.

[0019] I - Ions can not only regulate [Zn(H2O)6] 2+ The solvation structure can also change the properties of the network H2O, because the iodide ion is a Lewis base, which can compete with H2O and react with Zn 2+ In addition, TMOS + Ions and I - Both ions can be adsorbed on the surface of the Zn electrode to form an electrostatic shield and an electrochemical double layer (EDL), respectively, thereby regulating the nucleation growth and deposition behavior of Zn. Under the regulation of dual ions, the Zn / / Cu battery achieves highly reversible Zn deposition / stripping, with initial and average Coulombic efficiencies of up to 93% and 99.8%, respectively.

[0020] In addition, the Zn / / I2 full cell exhibits high capacity (at 2A g -1 180mAh g -1 ) and excellent cycle stability (retention rate is 88.2% after 10000 cycles). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0022] Figure 1 (a) CV curves of Zn / / I2 full cells using ZnSO4 and ZnSO4+TMOSI electrolytes;

[0023] Figure 1 (b) Electrochemical impedance spectroscopy of Zn-I2 full cells using ZnSO4 and ZnSO4+TMOSI electrolytes;

[0024] Figure 1 (c) is the constant current charge-discharge curve of the Zn-I2 full cell using ZnSO4 and ZnSO4+TMOSI electrolytes;

[0025] Figure 1 (d) The rate performance of Zn / / I2 full cell with ZnSO4+TMOSI electrolyte at different current densities;

[0026] Figure 1 (e) Self-discharge characteristics of Zn / / I2 full cell with ZnSO4+TMOSI electrolyte;

[0027] Figure 1 (f) Zn / / I2 full cell with ZnSO4+TMOSI electrolyte at 0.2A g -1 Constant current charge and discharge curves of different cycles;

[0028] Figure 1 (g) Zn / / I2 full cell using ZnSO4 and ZnSO4+TMOSI electrolyte at 0.2A g -1 Long-term cycle performance under

[0029] Figure 2 (a) is H2O-H2O, H2O-I - 、TMOS + -Zn 2+ 、TMOS + -H2O、Zn 2+ -H2O, TMOS + -I - and Zn 2+ -I - The binding energy of

[0030] Figure 2 (b) is the NMR spectra of ZnSO4 in D2O and ZnSO4 containing TMOSI;

[0031] Figure 2 (c) FTIR spectra of ZnSO4 and TMOSI-containing electrolytes;

[0032] Figure 2 (d) Raman spectra of ZnSO4 and TMOSI-containing electrolyte;

[0033] Figure 2 (e) 3D snapshots of ZnSO4-H2O and ZnSO4-H2O-TMOSI and the Zn obtained by MD simulation 2+ A partially magnified snapshot of the solvated structure;

[0034] Figure 2 (f) is the radial distribution function and coordination number of Zn-O(H2O);

[0035] Figure 2 (g) The radial distribution function and coordination number of Zn-I obtained by MD simulation in ZnSO4+TMOSI electrolyte;

[0036] Figure 2 (h) is [Zn(H2O)6] 2+ and [ZnI(H2O)6] + LUMO-HOMO band gap and schematic diagram;

[0037] Figure 3 (a) Coulombic efficiency test of Zn / / Cu battery with different electrolytes;

[0038] Figure 3(b) is the desolvation activation energy of different electrolytes;

[0039] Figure 3 (c) CA curve of Zn / / Zn battery with ZnSO4+TMOSI electrolyte (the inset shows the corresponding Nyquist plot at initial and steady state);

[0040] Figure 3 (d) is the differential capacitance curve of Na2SO4 and Na2SO4+TMOSI electrolyte;

[0041] Figure 3 (e) Chronoamperometry of Zn / / Zn battery with two different electrolytes. The inset shows the Zn / / Zn battery with different electrolytes. 2+ Schematic diagram of the deposition pattern;

[0042] Figure 3 (f) Zn / / Cu battery in different electrolytes at 2.0 mV s -1 CV curves of nucleation overpotential under ;

[0043] Figure 3 (g) is 1 - 、TMOS + and the adsorption energies of H2O molecules on Zn(101), Zn(100), and Zn(002) surfaces;

[0044] Figure 4 (a) is at 1.0 mA cm -2 , 0.5mAh cm -2 Long-term cycling performance of Zn / / Zn batteries with two different electrolytes;

[0045] Figure 4 (b) In situ optical microscopy images of zinc deposition in different electrolytes;

[0046] Figure 4 (c) XRD comparison of zinc negative electrode after cycling in different electrolytes;

[0047] Figure 4 (d) is the SEM image of the zinc negative electrode after cycling in ZnSO4 electrolyte;

[0048] Figure 4 (e) is the SEM image of the zinc negative electrode after cycling in ZnSO4+TMOSI electrolyte. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0050] Example 1

[0051] (a) Preparation of electrolyte

[0052] 2.88 g ZnSO4·7H2O was added to 5 mL water to obtain a 2M ZnSO4 electrolyte. 0.066 g TMOSI was added to 5 mL 2M ZnSO4 solution to obtain a 2M ZnSO4 electrolyte containing 0.06 M TMOSI.

[0053] (b) Preparation of I2 / AC electrode

[0054] First, I2 and activated carbon were diffused at a mass ratio of 3:7 at 90°C for 4 h. Secondly, a cathode slurry was prepared. The I2 / AC material was mixed with PVDF and acetylene black at a mass ratio of 8:1:1 to obtain a slurry. Finally, an I2 / AC cathode was prepared. The cathode slurry was coated on carbon paper and vacuum dried at 90°C for 4 h.

[0055] (c) Assembly of Zn-I2 battery

[0056] A CR2032 button cell was assembled with I2 / AC electrode as the positive electrode, zinc foil as the negative electrode, glass fiber as the separator, and 100μL ZnSO4+TMOSI as the electrolyte, and its electrochemical performance was tested and evaluated. The diameters of the negative electrode, positive electrode, and separator were 14mm, 14mm, and 19mm, respectively. The specific capacity of the battery was calculated based on the mass of iodine.

[0057] Example 2

[0058] The electrolyte was prepared as follows: 2.88 g ZnSO4·7H2O was added to 5 mL water to obtain a 2 M ZnSO4 electrolyte. 0.022 g TMOSI was added to 5 mL 2 M ZnSO4 solution to obtain a 2 M ZnSO4 electrolyte containing 0.02 M TMOSI.

[0059] The preparation of I2 / AC electrode and the assembly of Zn-I2 battery are the same as those in Example 1.

[0060] Example 3

[0061] The electrolyte preparation process is as follows: 2.88g ZnSO4·7H2O was added to 5mL water to obtain a 2M ZnSO4 electrolyte. ZnSO4 electrolytes with different TMOSI contents were prepared by adding 0.044g TMOSI to 5mL 2M ZnSO4 solution to obtain 2M ZnSO4 electrolytes containing 0.04M TMOSI.

[0062] The preparation of I2 / AC electrode and the assembly of Zn-I2 battery are the same as those in Example 1.

[0063] Comparative Example 1

[0064] The difference between Comparative Example 1 and Example 1 is that TMOSI is not added to the electrolyte.

[0065] The preparation process of the electrolyte of Comparative Example 1 is as follows: 2.88 g of ZnSO4·7H2O is added to 5 mL of water to obtain a 2 M ZnSO4 electrolyte.

[0066] The preparation of I2 / AC electrode and the assembly of Zn-I2 battery are the same as those in Example 1.

[0067] In order to evaluate the performance of the TMOSI additive in the full battery, the Zn-I2 batteries assembled in Examples 1-3 and Comparative Example 1 with I2 / AC as the positive electrode and zinc foil as the negative electrode were tested for performance. The results show that the battery performance using the ZnSO4+TMOSI electrolyte of Examples 1-3 is significantly better than the battery performance of the ZnSO4 electrolyte of Comparative Example 1. In order to illustrate the effect of TMOSI, the best performing Example 1 (2M ZnSO4+0.06M TMOSI) and Comparative Example 1 without TMOSI were selected as the test results for comparison. Therefore, unless otherwise stated, the text describing "ZnSO4+TMOSI" below refers to 0.06MTMOSI.

[0068] from Figure 1 From the CV curve of (a), it can be seen that the redox potential difference of the battery using ZnSO4+TMOSI electrolyte (ΔV=63mV) is smaller than that of the battery using ZnSO4 electrolyte (ΔV=95mV), which indicates that it has good reversible performance in ZnSO4+TMOSI electrolyte. Figure 1 The EIS spectrum of (b) shows that the impedance of the battery using ZnSO4+TMOSI electrolyte (50Ω) is lower than that of the battery using ZnSO4 electrolyte (85Ω), which indicates that a faster charge transfer rate can be obtained in ZnSO4+TMOSI electrolyte. Figure 1 The charge-discharge curve of (c) shows a charging platform of 1.3 V and a discharging platform of 1.2 V, which is consistent with the CV results. Figure 1 As shown in (d), when tested at different current densities, the battery using ZnSO4+TMOSI electrolyte also exhibited excellent performance, outperforming the battery using ZnSO4 electrolyte.

[0069] The self-discharge test of Zn / / I2 battery is an important indicator. Figure 1(e) shows that the battery containing TMOSI electrolyte has a higher capacity retention rate than the battery containing zinc sulfate electrolyte (91.6% vs. 70.7%). More importantly, Figure 1 (f) and Figure 1 (g) at 0.2A g -1 The long-term cycling stability under the condition of 1.5 % NH 2 O 2 showed that the battery containing TMOSI electrolyte exhibited stable cycling performance over 1900 cycles with a capacity of 220 mAh g -1 The capacity retention rate is 88%. In contrast, the capacity of the battery containing ZnSO4 electrolyte decays faster, from 185 mAh g to 100 mAh g after 1100 cycles. -1 Down to 114mAh g -1 , the capacity retention rate is only 62%. Obviously, since the oxidation of iodine ions in TMOSI contributes to the total battery capacity, the total capacity of the battery using ZnSO4+TMOSI electrolyte is larger than that of the battery using ZnSO4 electrolyte. This shows that the TMOSI additive can not only enhance the durability of the zinc anode, but also improve the stability of the Zn / / I2 full battery.

[0070] Due to the interaction between Zn ions and H2O molecules and between H2O molecules, there are solvated H2O, network H2O and free H2O in the ZnSO4 solution. For the solvated H2O, the electrons on the O atoms in the H2O molecules bonded to the Zn ions are transferred to the Zn ions in the Zn-O bonds, which weakens the OH bonds of H2O and makes HER more likely to occur at the Zn negative electrode. For the network H2O, the O and H atoms in the H2O molecules act as electron donors and acceptors, respectively, to form a continuous H2O molecular network connected by hydrogen bonds. It mainly affects the working potential range, boiling point and freezing point of the electrolyte. Free H2O in the electrolyte is a factor that affects the charge transfer resistance, Zn 2+ TMOSI is an important medium for ion transport and diffusion, but too much free H2O can easily trigger side reactions. Fortunately, the properties of natural solvation structure, network H2O or free H2O can be adjusted by some special additives that induce different local interactions. TMOSI is known to be a commonly used electrophilic reagent in organic synthesis reactions with high solubility and chemical stability. In aqueous TMOSI, anion I - With strong nucleophilicity, cationic TMOS + It has high electrophilicity. Adding TMOSI to the electrolyte may change the local interactions between ions and molecules. The O atoms and I atoms in TMOSI accumulate more negative charges (-0.549 eV and -0.720 eV, respectively) than the O atoms in the H2O molecules (-0.541 eV). This suggests that adding TMOSI molecules to the solution can change the hydrogen bonds of the network H2O.

[0071] To study TMOS + Ions and I - Ion pair Zn 2+ The influence of ion solvation structure was considered and their interactions were calculated (Materials Studio software was used to calculate the molecular interaction energy between different molecules. Specifically, the DMol3 package was used to calculate the binding energy and adsorption energy. The exchange-correlation interaction was described by the Perdew-Burke-Ernzerhof (PBE) functional method of the generalized gradient approximation (GGA). The global orbital cutoff radius was set to The orbital occupancy was broadened by 0.005 Ha and the energy threshold was 1×10 -5 Hartree, maximum force is The displacement is To achieve accurate electronic convergence, a self-consistent field (SCF) procedure was performed on the total energy with a convergence criterion of 1×10 -6 Ha. Binding energy between Zn atoms, H2O and TMOSI (E b ) is calculated by the following formula:

[0072] E b =E T-substance -(E T +E substance )

[0073] Where E T-substance is the energy of the entire system, E T is the energy of TMOSI, E substance is the energy of Zn atoms and H2O in the system). Figure 2 As shown in (a), TMOS + With Zn 2+ The binding energy of is 0.43 eV, indicating that they repel each other, so TMOS + The effect on the solvation structure is weak. However, I - With Zn 2+ The binding energy of H2O and Zn is -18.79eV, which is significantly lower than that of 2+ The binding energy of I - Ions may enter the solvation structure and reduce the solvation structure water. It is worth noting that whether TMOS + Cation (-0.60 eV) or I - anions (-0.81 eV), all of which have lower binding energies with water than H2O molecules (-0.24 eV), verifying that the addition of TMOSI tends to alter the hydrogen bonds of network H2O.

[0074] In order to further understand the effect of TMOSI additives on [Zn(H2O)6]2+ The effects of the solvation structure and the hydrogen bonding network of H2O were investigated using NMR, FTIR and Raman spectroscopy. Figure 2 In (b), after adding ZnSO4 to D2O, the 1H peak shifts downfield, indicating that [Zn(H2O)6] 2+ Zn in the solvated structure 2+ The charge transfer between H2O and 1H2O reduces the electron density of hydrogen. However, after adding TMOSI to the solution, the 1H peak slightly shifts to the high field, indicating that the electron density of hydrogen increases, which is related to the interaction between water molecules and the change of solvation structure. Therefore, the addition of TMOSI changes the strong hydrogen bonding interaction between H2O-H2O, resulting in the formation of weak hydrogen bonding interaction between TMOSI and H2O. At the same time, after adding TMOSI, due to the I - With Zn 2+ The binding energy of I - Enter [Zn(H2O)6] 2+ The solvation structure of the H2O in the partial solvation structure is changed from [Zn(H2O)6] 2+ Since the stretching vibration of OH- is sensitive to changes in hydrogen bonding, the study of OH- vibration can be used to evaluate hydrogen bonding. In the FTIR spectrum, the OH stretching vibration of H2O is located at 2750-3750cm -1 .exist Figure 2 In (c), the decrease in strong hydrogen bonds and the increase in weak hydrogen bonds mean that the TMOSI additive can form weak hydrogen bonds with H2O molecules, thereby destroying the strong interaction between H2O and reducing the activity of H2O in the bulk electrolyte. The solvent-separated ion pairs (SSIP, Zn 2+ (H2O)6·SO4 2- ) and contacting ion pairs (CIP, Zn 2+ (H2O)5·OSO3 2- ).like Figure 2 As shown in (d), when TMOSI was added to the electrolyte, SSIP increased from 33.3% to 74.3%, while CIP decreased from 66.7% to 25.7%, indicating that the solvation structure changed. In addition, the decrease in the proportion of DAA and free OH also indicates a decrease in active water.

[0075] MD simulations were used to further analyze and quantify the changes in the solvation structure (the solvation structure of Zn ions was calculated and evaluated using the molecular dynamics (MD) package. First, a model system was established, which contained 8 TMOSI, 159 ZnSO4, and 4400 H2O. After geometry optimization, the model system was annealed for 5 cycles in the range of 300K to 500K. Secondly, a 1ns NPT ensemble simulation was performed at 1atm and 298K. The temperature and pressure of the system were adjusted using the Nose heat bath and the Berendsen pressure bath. At the same time, the electrostatic interaction was calculated using the Ewald summation, and the van der Waals interaction cutoff radius was Finally, a 10 ns NVT combined simulation was performed and a Nose heat bath was used to characterize the Zn 2+ Coordination). The statistical results are as follows Figure 2 As shown in (e), typical hydrated ion solvation structures were detected in both electrolytes. Through radial distribution function (RDFs) analysis, the coordination number and average bond length, which are two important parameters describing the geometric arrangement of solvent molecules, can be obtained. Figure 2 (f) and Figure 2 As shown in (g), Zn in ZnSO4 electrolyte 2+ The coordination number of the solvation structure formed by -H2O coordination is 5.45, corresponding to the Zn-O pair at about and After adding TMOSI to the ZnSO4 electrolyte, Zn 2+ The corresponding coordination number with H2O is reduced to 5.39. 2+ with I - The coordination numbers are 0.002 and 0.02, respectively, and the Zn-I peaks are located at about and If Figure 2 (h), with the solvated structure [Zn(H2O)6] 2+ (-9.56 eV) compared to the reconstructed [ZnI(H2O)5] + It has a higher LUMO energy band (-5.45 eV), indicating that the probability of water being reduced is lower. - Not only to Zn 2+ Inject electrons to change the charge of Zn from [Zn(H2O)6] 2+ 0.847eV in [ZnI(H2O)5] + 0.640eV in the solution, and also injected into the solvated H2O, reducing the [ZnI(H2O) 5 ] + From H2O to Zn 2+ Electron transfer. [ZnI(H2O)5] +and [Zn(H2O)6] 2+ The differential charge density analysis shows that [ZnI(H2O)5] + Medium Zn 2+ The electron density increment around [Zn(H2O)6] 2+ , which is attributed to the fact that the I element has a stronger electron-donating ability than the O in H2O. - The participating solvation structure can reduce from H2O to Zn 2+ The electron transfer of TMOS enhances the stability of water, thereby inhibiting HER. + It can accumulate on the surface of electrode protrusions to form an electrostatic protection barrier to hinder dendrite growth.

[0076] In order to gain a deeper understanding of the effect of TMOSI additives on zinc deposition and stripping, ZnSO4 and ZnSO4+0.06M TMOSI were used as electrolytes to assemble Zn / / Zn batteries to evaluate long cycle performance, and Zn / / Cu batteries to study coulombic efficiency. -1 Cyclic voltammetry (CV) curves were measured under open circuit voltage. Electrochemical impedance spectroscopy (EIS) was measured at a frequency range of 100 mHz to 0.1 Hz and an AC voltage amplitude of 5 mV. The ionic conductivity of electrolytes of different concentrations was measured by two Ti foil (Ti / / Ti) symmetric button cells in different electrolyte systems. The Zn deposition / stripping process was also carried out on the Zn / / Cu button cell. HER was tested using linear sweep voltammetry (LSV) in a three-electrode system, with Ti foil, Pt foil and Ag / AgCl as the working electrode, counter electrode and reference electrode, respectively.

[0077] To investigate the electrochemical performance of electrolytes with or without TMOSI additives, the deposition and stripping of Zn on Cu foil in different electrolytes were tested in coin cells. It is well known that higher Coulombic efficiency means longer cycling stability. Figure 3 (a) shows that the Zn / / Cu cells with TMOSI additive can be cycled for more than 1000 times with an average Coulombic efficiency value of 99.8%. However, the Zn / / Cu cells with only ZnSO4 can only be cycled a few times. Compared with their first galvanostatic deposition and stripping cycles, it was found that the Coulombic efficiency increased from 73% to 93% after adding TMOSI additive, indicating that the deposition / stripping performance of zinc on copper foil was improved. However, at the same time, the polarization voltage also increased with the increase of additive concentration. This may be due to the TMOSI during the deposition process. + The competitive adsorption of cations on the electrode surface forms an interfering Zn 2+ ion deposition shielding layer. Of course, this may also be related to the change of Zn 2+The solvation sheath is related to the Zn 2+ The solvated structure leads to strong interactions, which increase the polarization voltage.

[0078] In order to determine the effect of additives on Zn 2+ The effect of desolvation on the solvation structure Figure 3 The desolvation activation energy (E a ). [Zn(H2O)6] 2+ The desolvation process is the rate-determining step of the interfacial kinetics and can be described by the Ea value. The results show that the desolvation energy is slightly reduced after adding TMOSI, indicating that the TMOSI additive has a positive effect on the desolvation process. Figure 3 (c) shows that due to the addition of TMOSI additive, Zn 2+ The migration number increased from 0.18 to 0.23, indicating that it has excellent Zn 2+ ion transport capability, which can guide the uniform Zn 2+ Ion deposition. Figure 3 In (d), the differential capacitance value increases with the addition of TMOSI additive, which means that the adsorption of iodine ions on the Zn electrode surface changes the double layer structure of the electrode surface.

[0079] Further electrochemical experiments proved that TMOS + and I - The linear polarization experiment shows that TMOS + and I - The adsorption on the electrode surface can prevent the self-corrosion of the Zn electrode surface. The reason is that after adding TMOSI additive, the corrosion potential increases from -0.017V to -0.008V. The charge transfer resistance (R ct ). After adding TMOSI additive to 2M ZnSO4 electrolyte, its R ct The value does not change much. 2+ The deposition behavior of Zn depends on the deposition kinetics. 2+ The first deposition of Zn is crucial to the stability of subsequent cycles. In order to characterize the nucleation and growth of Zn, chronoamperometry (CA) was used. The reason is that the change of current over time in the CA curve can reveal the change of Zn surface morphology during the deposition process. Figure 3 As shown in (e), for pure ZnSO4 electrolyte, the current density gradually increased during the test (600s). However, for the electrolyte containing TMOSI, after the transient current rise at the beginning of deposition (within 50s), the current density remained relatively stable until the end. These two different phenomena are related to the nucleation and growth process of Zn deposition. During the deposition process, Zn2+ It tends to diffuse horizontally along the surface of Zn crystal and form initial crystal nuclei, which follows the principle of minimum surface energy and minimum exposed area. 2+ The continuous diffusion of TMOS and the disturbed electric field around the protrusions grow rapidly, forming messy dendrites. + Cations and Zn 2+ In the nucleation stage, the initial nuclei are smaller and denser. In the nucleus growth stage, the non-redox TMOS + The cations accumulate electrostatically at the protrusions, which 2+ Forming a shielding layer effect, Zn 2+ ions can be deposited on the smooth area of ​​the Zn anode. 2+ The disordered diffusion of Zn was blocked and the tip effect was suppressed, and the Zn deposition layer became flat. In addition, CV experiments were performed to study the nucleation overpotential. Figure 3 As shown in (f), the results show that the nucleation overpotential in ZnSO4+TMOSI electrolyte is similar to that in ZnSO4 electrolyte. DFT shows that TMOS + and I - The adsorption energy on the Zn anode is higher than that of H2O on the Zn anode (to optimize the adsorption energy, the lattice constant is used Construct Zn(002), Zn(100) and Zn(101) layers. Create approx. The vacuum layer is used to eliminate the interaction between the periodic Zn atoms in the upper layer. During the optimization process, the atoms in the bottom layer are frozen and the atoms in the top layer are allowed to relax. The adsorption energy (E) of A on each slab layer a ) is calculated by the following formula: a =E slab+A -(E slab +E A );

[0080] Among them, E slab+A is the energy of the entire system, E slab is the energy of the Zn plate, E A is the energy of Zn atoms, H2O and TMOSI in the system), such as Figure 3 (g). Therefore, these ions are more easily adsorbed on the surface of the Zn anode, thereby reducing the contact between H2O molecules and the Zn anode during the deposition process, further hindering HER. The charge density difference further confirms that I - and TMOS + Strong electrostatic adsorption to Zn crystal surface, because I - and TMOS +The charge transfer on Zn(002), Zn(100) and Zn(101) planes is more than that of H2O on Zn planes. 2+ The adsorption energy of ions on the Zn(002) plane is lower than that on the Zn(100) and Zn(101) planes, which indicates that the Zn(002) plane grows preferentially in the ZnSO4+TMOSI electrolyte.

[0081] Zn / / Zn batteries were assembled using ZnSO4 and ZnSO4+TMOSI electrolytes for charge and discharge tests to evaluate the battery kinetics and electrochemical stability. Figure 4 (a) shows the -2 Current density and 0.5 mAh cm -2 Figure 2. Voltage-time curves of Zn / / Zn cells in ZnSO4 and ZnSO4+TMOSI electrolytes at specific capacity. In the ZnSO4 electrolyte, the voltage curve began to fluctuate at the 262nd cycle. In contrast, the voltage curve in the ZnSO4+TMOSI electrolyte remained stable for more than 3500 cycles (3500 h) with no signs of short circuiting, indicating that the electrolyte containing the TMOSI additive has longer cycling stability. At lower current densities (0.5 mA cm -2 ) and higher current density (4 mA cm -2 ), the cycle time of Zn / / Zn battery using ZnSO4+TMOSI electrolyte can reach 3800h and 1800h, respectively. In addition, at higher current density, Zn / / Zn battery using ZnSO4+TMOSI electrolyte also shows better cycle performance than that of battery using ZnSO4 electrolyte. The improvement in cycle performance is attributed to the suppression of Zn dendrites and the alleviation of side reactions by the TMOSI additive added to the ZnSO4 electrolyte.

[0082] Next, the deposition behavior of Zn in ZnSO4 and ZnSO4+TMOSI electrolytes was observed using in situ optical microscopy. Figure 4 As shown in (b), after 60 minutes of deposition in ZnSO4 electrolyte, the surface of the Zn electrode showed a loose, porous and irregular morphology. There were many small protrusions of different sizes on the surface, which gradually grew into Zn dendrites. In contrast, under the same deposition conditions, the surface of the Zn electrode in ZnSO4+TMOSI electrolyte was almost flat, indicating that the deposition of zinc was uniform. XRD detection was further performed to view the deposits on the surface of the Zn electrode used in ZnSO4 and ZnSO4+TMOSI electrolytes. Figure 4As shown in (c), the byproduct Zn4SO4(OH)6·4H2O (JCPDS 44-0673) was generated on the surface of the Zn electrode after circulation in the ZnSO4 electrolyte, but this byproduct was not found on the surface of the Zn electrode after circulation in the ZnSO4+TMOSI electrolyte. In addition, the Zn(002) crystal plane of the Zn electrode in the ZnSO4+TMOSI electrolyte was different from the Zn(100) crystal plane (I 002 / 100 ) and Zn(101) plane (I 002 / 101 ) are 3.66 and 0.77, respectively, which are larger than the corresponding ratios in ZnSO4 electrolyte (II 002 / 100 =3.29, I 002 / 101 =0.62). These findings suggest that the TMOSI additive is beneficial for the preferential growth of the Zn(002) plane. Figure 4 (d) and Figure 4 (e) shows that the deposited Zn in the ZnSO4 electrolyte is very loose and uneven, accompanied by uneven pits, indicating the presence of severe Zn dendrites and corrosion reactions. In contrast, the surface of the Zn electrode used in the ZnSO4+TMOSI electrolyte exhibits a layered stacking morphology. It is worth noting that the hexagonal morphology of the deposited Zn matches the unique morphology of the Zn (002) crystal plane, which is consistent with the XRD and DFT calculation results. Therefore, due to the addition of TMOSI, the side reactions are greatly reduced, while inducing high-quality Zn (002) crystal plane growth. In summary, the electrochemical performance of the Zn anode is improved by introducing TMOSI into the electrolyte, which is attributed to the TMOS + Cations and I - The combined effects of anions include changes in the solvation structure of zinc ions, changes in the H2O hydrogen bonding network, electrostatic shielding effects to reduce zinc dendrites, and inducing the growth of the Zn(002) crystal plane.

[0083] In summary, TMOSI was introduced as a dual-ion additive into the conventional ZnSO4 electrolyte. In the electrolyte containing TMOSI additive, the performance of zinc-ion batteries was improved, with a Coulombic efficiency of up to 99.8% and a cycle durability of more than 3500 h (1 mA cm -2 , 0.5mAh cm -2 ). On the one hand, I - ions can change the solvation structure of Zn ions and hydrogen bonds in solution. On the other hand, TMOS + and I -The ions can be adsorbed on the Zn electrode surface, not only forming electrostatic shielding and electrochemical double layers to change the nucleation growth and deposition behavior of Zn ions, but also inducing the selective growth of Zn(002) crystal planes. These results lead to good Zn ion deposition / stripping, reduced Zn dendrites and side reactions, and improved electrochemical performance of Zn-ion batteries. The complete Zn / / I2 cell was constructed to demonstrate the positive effect of TMOSI, enabling it to be used at 2A g -1 High capacity (180mAh g -1 ) and excellent cycling stability (retention rate is 88.2% after 10000 cycles). The dual-ion regulation strategy based on TMOSI additive provides a simple and innovative approach for the optimization of zinc ion electrolyte.

[0084] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A dual-ion controlled aqueous zinc-iodine battery, characterized in that: include: It includes an iodine positive electrode, a zinc negative electrode, a separator and an electrolyte solution; The electrolyte solution includes zinc sulfate solution and trimethylsulfoxide iodide (TMOSI).

2. The dual-ion controlled aqueous zinc-iodine battery according to claim 1, characterized in that: The concentration of trimethylsulfoxide iodide (TMOSI) is 0.02-0.06M.

3. The dual-ion controlled aqueous zinc-iodine battery according to claim 2, characterized in that: The concentration of trimethylsulfoxide iodide (TMOSI) was 0.06M.

4. The dual-ion controlled aqueous zinc-iodine battery according to claim 1, characterized in that: The concentration of the zinc sulfate solution is 2M.

5. The dual-ion controlled aqueous zinc-iodine battery according to claim 1, characterized in that: The iodine positive electrode is obtained by coating positive electrode slurry on carbon paper and drying it; the positive electrode slurry comprises active materials, conductive agents and adhesives; the active materials comprise iodine monomers and activated carbon.

6. The dual-ion controlled aqueous zinc-iodine battery according to claim 5, characterized in that: The conductive agent is acetylene black.

7. The dual-ion controlled aqueous zinc-iodine battery according to claim 5, characterized in that: The adhesive is PVDF.

8. The dual-ion controlled aqueous zinc-iodine battery according to claim 5, characterized in that: The weight ratio of the active material, the conductive agent and the binder is 8:1:

1.

9. The dual-ion controlled aqueous zinc-iodine battery according to claim 5, characterized in that: The mass ratio of elemental iodine to activated carbon is 3:

7.

10. The dual-ion controlled aqueous zinc-iodine battery according to claim 5, characterized in that: The diaphragm is fiberglass.

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