An interface modification method for preparing electrodeless lithium metal batteries using ultraviolet-polymerized tannic acid-Ag composite particles.

Abstract

This invention discloses an interface modification method for preparing electrodeless lithium metal batteries using UV-polymerized tannic acid composite Ag particles. This method addresses problems in existing electrodeless lithium metal batteries such as poor lithium affinity of the negative electrode, significant nucleation obstacles, uneven lithium deposition, and poor reversibility of lithium stripping / plating. The specific steps are as follows: A Cu foil is placed in hydrochloric acid and shaken, then repeatedly washed three times with deionized water and ethanol. A phosphate buffer solution is prepared. Tannic acid is dispersed in the phosphate buffer solution to obtain a polymerization solution. The washed Cu foil is placed in the polymerization solution and irradiated with a UV lamp to obtain a Cu foil with a polytannic acid film on its surface. Further, the copper foil with the tannic acid film on its surface is reacted in an AgNO3 solution to obtain a Cu foil with a polytannic acid film interface composed of Ag particles. The polytannic acid film composed of Ag particles in this invention improves the interface of the Cu foil to a certain extent. Compared with existing technologies, this invention reduces lithium nucleation inhibition and overpotential at the Cu foil anode, enhances the reversibility of lithium plating / stripping, and makes the SEI film formed at the anode interface more stable. Furthermore, it effectively suppresses lithium dendrite formation, improves battery cycle performance and safety, and extends battery cycle life.

Description

Technical Field

[0001] This invention relates to an interface modification method for preparing electrodeless lithium metal batteries using ultraviolet-polymerized tannic acid composite Ag particles. Background Technology

[0002] With the improvement of energy density and the decrease of cost of lithium-ion batteries, their applications in electric vehicles and portable electronic devices are increasing. Currently, commercially available lithium-ion batteries typically use graphite, based on a lithium-ion intercalation mechanism, as the anode material. The specific energy density of batteries using this lithium-ion intercalation mechanism has reached approximately 260 Wh / kg in recent years. -1 The peak quickly approached 300Wh / kg. -1 The theoretical limit. The rapid development of electric vehicles has spurred the demand for high energy density (500Wh / kg). -1 The pursuit of high energy density in lithium-ion batteries has become increasingly urgent, as graphite-based anode lithium-ion batteries can no longer meet the demand. Therefore, the development of a new generation of lithium-ion batteries is imperative. Anode-free lithium metal batteries (AFLMB), which do not require additional lithium metal, have come into focus. In AFLMB, only the current collector, such as Cu foil without active materials, is retained on the negative electrode side (using only materials without active materials like Cu foil as the negative electrode), resulting in an N / P ratio close to 0. Compared to graphite anodes, AFLMB reduces the battery's mass and volume, increasing the mass energy density by 38.5% and the volumetric energy density by 85.5%. With NCM as the positive electrode and lithium foil as the negative electrode, the battery's specific energy is 255 Wh / kg. -1 The specific energy of the electrodeless battery system can reach 392Wh / kg. -1 Summary of the Invention

[0003] The purpose of this invention is to address the problems of poor lithiophilicity and reversibility of lithium plating / stripping when preparing anodes for electrodeless lithium metal batteries using existing methods. This invention provides an interface modification method for preparing electrodeless lithium metal batteries using UV-polymerized tannic acid composite Ag particles. A polytannic acid film rich in polar functional groups is constructed on the surface of Cu foil. While the introduction of PTA lowers the lithium nucleation barrier (150 mV for Cu foil, 25 mV for Cu foil), the lower electronic conductivity slows down the kinetics of the reaction on the electrode surface. We utilize the abundant phenolic hydroxyl groups in the polytannic acid film to dissolve Ag in AgNO3 solution. +Reduction was achieved, establishing Ag particle channels in the polytannic acid (PTA) film and on the Cu foil surface. The addition of Ag particles, with their excellent lithiophilic properties, not only further reduced the lithium nucleation barrier (10 mV for PTA film-Ag particle-Cu foil composite) but also optimized the charge transfer process. The synergistic effect of the PTA film and Ag particles formed elastic lithiophilic channels, suppressing lithium dendrite growth. The UV-assisted rapid polymerization process of tannic acid on the Cu surface offers advantages such as good economics, short polymerization time, and low pollution, and is expected to be applied in practical production.

[0004] 1. An interface modification method for preparing electrodeless lithium metal batteries using ultraviolet-polymerized tannic acid composite Ag particles, characterized in that the method is carried out according to the following steps:

[0005] I. Pretreatment of Cu Foil

[0006] Place the Cu foil in hydrochloric acid and shake for 5 to 15 minutes, then wash it repeatedly with deionized water and ethanol three times, and then dry it in a vacuum drying oven at 80 to 100°C.

[0007] II. Preparation of Phosphate Buffer Solution

[0008] Prepare a phosphate buffer solution composed of sodium dihydrogen phosphate and disodium hydrogen phosphate, and stir until homogeneous at room temperature;

[0009] III. Preparation of Polymerization Solution

[0010] Add tannic acid to the phosphate buffer solution, controlling the tannic acid concentration to be 0.2–1 g / L. -1 Stir well at room temperature;

[0011] IV. UV-assisted polymerization of tannic acid

[0012] The pretreated Cu foil was placed in the polymerization solution. After irradiating it with an overhead UV lamp for several minutes, it was removed. It was then rinsed three times with deionized water and ethanol, and dried in a vacuum drying oven at 80–100°C.

[0013] V. Preparation of Ag Particle Composite Solution

[0014] Dissolve AgNO3 in water and stir until homogeneous to obtain an AgNO3 solution for later use.

[0015] VI. Ag particle composite

[0016] A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution and reacted for a certain period of time. After the reaction was completed, it was removed and washed three times with deionized water and ethanol, and then dried in a vacuum drying oven at 80–100°C.

[0017] VII. Battery Assembly

[0018] After slicing the Cu foil obtained in step six, first place the negative electrode shell, and then assemble the battery in the following order: Cu foil, electrolyte, separator, electrolyte, Li sheet or lithium iron phosphate electrode sheet, and positive electrode shell.

[0019] The phosphate buffer solution prepared in step two has a concentration of 0.5–1 g / L of hydrogen diphosphate. -1 The concentration of disodium hydrogen phosphate is 1–3 g / L. -1 .

[0020] An appropriate concentration of phosphate buffer solution can provide a more suitable environment for polymerization and promote the polymerization reaction.

[0021] Furthermore, in step four, the Cu foil is pretreated using hydrochloric acid of different concentrations.

[0022] The optimal concentration can be selected by comparing and observing the removal of the oxide film on the Cu foil surface. This can avoid the occurrence of rough Cu foil surface morphology or incomplete oxide film removal due to excessively high or low hydrochloric acid concentration, which would affect the reversibility of lithium plating / stripping in the battery.

[0023] Furthermore, the UV polymerization process in step four is carried out in a dark room.

[0024] The dark chamber design avoids the influence of natural light and artificial light on the polymerization process. It also maximizes the uniformity of the polytannic acid film spread on the Cu foil surface. The high interface uniformity, combined with the buffer solution, reduces silver ions, effectively dispersing Ag nanospheres within the three-dimensional network structure of the polytannic acid. This polymeric three-dimensional network structure, in conjunction with Ag atoms, effectively constructs lithium-affinity channels. These smooth channels are an effective method to ensure the absence of lithium dendrites and dead lithium, because the three-dimensional diffusion channels prevent energy accumulation, and the polymeric framework prevents tip effects. Therefore, it effectively alleviates the uneven lithium plating / stripping caused by localized current density concentrations during battery cycling.

[0025] Furthermore, in step four, the irradiation time of the ultraviolet lamp is controlled to be between 10 and 30 minutes.

[0026] The thickness of the polytannic acid film on the Cu foil can be controlled by adjusting the UV irradiation time. If the film is too thin, its mechanical strength will be poor, leading to cracking after multiple cycles and a decline in cycle performance. If the film is too thick, it will increase the resistance to lithium-ion migration and decrease the reaction rate at the electrode interface.

[0027] Furthermore, in step five, the concentration of the AgNO3 solution is 1–10 mmol·L⁻¹. -1 .

[0028] The concentration of AgNO3 solution is related to the uniformity of Ag particles. Selecting an appropriate concentration can create uniform Ag particle channels in Cu foil and polytannic acid. Uniformly distributed Ag particles can effectively reduce local current density concentration, decrease lithium nucleation barriers, and improve battery cycle stability.

[0029] Furthermore, the electrolyte used in step seven for assembling the battery is 1 mol·L⁻¹. -1 LiPF6 dissolved in DEC / FEC (1:1, V:V) at 1 mol·L⁻¹ -1 LiTFSI is dissolved in one or two of the DOL / DME (1:1, V:V) electrolytes.

[0030] Different electrolytes have different affinity for lithium and different voltage ranges. Selecting an appropriate electrolyte can improve the cycle stability of the battery.

[0031] The present invention has the following beneficial effects:

[0032] A polytannic acid (PPA) film rich in polar functional groups was constructed on the surface of Cu foil. The introduction of the PTA film reduced the lithium nucleation barrier (Cu 150 mV, PTA film Cu foil 25 mV). Utilizing the abundant phenolic hydroxyl groups in the PTA film, Ag particle channels were established between the PTA film and the Cu foil surface. The addition of Ag particles, which possess excellent lithiophilic properties, not only further reduced the lithium nucleation barrier (PPA film combined with Ag particles Cu foil 10 mV), but also optimized the charge transfer process. The synergistic effect of the PTA film and Ag particles formed an elastic lithiophilic channel, inhibiting lithium dendrite growth. This UV-assisted rapid polymerization process of tannic acid on the Cu surface offers advantages such as good economic efficiency, short polymerization time, and low pollution, and is expected to be applied in practical production. Attached Figure Description

[0033] Figure 1 The adsorption energy of Cu foil, Ag particles, and LiAg alloy for lithium ions in an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles.

[0034] Figure 2 This is a diagram showing the nucleation overpotential curve of the negative electrode prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles.

[0035] Figure 3 The image shows the average lithium plating / stripping efficiency of the negative electrode prepared by an interface modification method for preparing negative electrode-free lithium metal batteries using ultraviolet-polymerized tannic acid composite Ag particles.

[0036] Figure 4Tafel curves of a half-cell composed of a negative electrode and a lithium sheet prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles.

[0037] Figure 5 Impedance diagram of a half-cell composed of a negative electrode and a lithium sheet, prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles.

[0038] Figure 6 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 1 of this invention;

[0039] Figure 7 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 2 of this invention;

[0040] Figure 8 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 3 of this invention;

[0041] Figure 9 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 4 of this invention is shown.

[0042] Figure 10 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 5 of this invention;

[0043] Figure 11 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 6 of this invention;

[0044] Figure 12 This is a volt-ampere curve of a full cell consisting of a negative electrode and lithium iron phosphate, prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles.

[0045] Figure 13 This is a cyclic voltammetry curve of the lithium iron phosphate full cell prepared in Comparative Example 1 of this invention;

[0046] Figure 14 This is the in-situ impedance spectrum of a lithium iron phosphate half-cell prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles during the initial cycling process.

[0047] Figure 15 The in-situ impedance spectrum of the lithium iron phosphate half-cell prepared in Comparative Example 1 of this invention during the initial cycling process;

[0048] Figure 16 The electronic conductivity diagram of the negative electrode is obtained by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles.

[0049] Figure 17The negative electrode electronic conductivity diagram prepared in Comparative Example 1 of this invention;

[0050] Figure 18 This is a graph showing the efficiency-specific capacity of a lithium iron phosphate half-cell prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles, under 0.5C cycling conditions.

[0051] Figure 19 The graph shows the efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 1 of this invention under 0.5C cycling.

[0052] Figure 20 The graph shows the efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 2 of this invention under 0.5C cycling.

[0053] Figure 21 The graph shows the efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 3 of this invention under 0.5C cycling.

[0054] Figure 22 The efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 4 of this invention under 0.5C cycling.

[0055] Figure 23 The efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 5 of this invention under 0.5C cycling is shown.

[0056] Figure 24 The efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 6 of this invention under 0.5C cycling.

[0057] Figure 25 This is a specific capacity-voltage curve of a lithium iron phosphate full cell prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles.

[0058] Figure 26 The specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 1 of this invention under 0.5C cycling is shown.

[0059] Figure 27 The specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 2 of this invention under 0.5C cycling is shown.

[0060] Figure 28 The specific capacity-voltage curve of the lithium iron phosphate full cell prepared in Comparative Example 3 of this invention under 0.5C cycling is shown.

[0061] Figure 29 The specific capacity-voltage curve of the lithium iron phosphate full cell prepared in Comparative Example 4 of this invention under 0.5C cycling is shown.

[0062] Figure 30 The specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 5 of this invention under 0.5C cycling is shown.

[0063] Figure 31 This is a specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 6 of this invention under 0.5C cycling. Detailed Implementation

[0064] The present invention will be further described below with reference to the preferred embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0065] Experimental drugs

[0066]

[0067]

[0068] Experimental drugs

[0069]

[0070] Experimental Example

[0071] Place Cu foil in 1 mol·L -1 Shake and agitate in hydrochloric acid for 10 minutes, then wash three times repeatedly with deionized water and ethanol, and finally dry in a vacuum drying oven at 80°C. Prepare a concentration of 0.6 g / L. -1 Sodium dihydrogen phosphate and 1.2g L -1 Disodium hydrogen phosphate solution was stirred thoroughly at room temperature. Tannic acid was added to the phosphate buffer solution, controlling the tannic acid concentration to 0.2 g / L. -1 Stir until homogeneous at room temperature. Place the pretreated Cu foil in the polymerization solution. Irradiate with an overhead UV lamp for 10 minutes, then remove. Wash three times repeatedly with deionized water and ethanol, then dry in a vacuum drying oven at 80°C. Prepare a concentration of 5 mmol / L. -1 A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution. After the reaction was complete, it was removed. The foil was washed three times with deionized water and ethanol, and then dried in a vacuum oven at 80°C. The resulting copper foil was sliced ​​and then assembled in an argon-filled glove box in the following order: negative electrode shell, copper foil, separator, lithium sheet or lithium iron phosphate electrode, gasket, spring, and positive electrode shell. A 1 mol·L⁻¹ electrolyte was used. -1 LiPF6 is soluble in DEC / FEC (1:1, V:V).

[0072] Comparative Example 1

[0073] Place Cu foil in 2 mol·L⁻¹-1 Shake and agitate in hydrochloric acid for 10 minutes, then wash three times repeatedly with deionized water and ethanol, and finally dry in a vacuum drying oven at 80°C. Prepare a concentration of 0.6 g / L. -1 Sodium dihydrogen phosphate and 1.2g L -1 Disodium hydrogen phosphate solution was stirred thoroughly at room temperature. Tannic acid was added to the phosphate buffer solution, controlling the tannic acid concentration to 0.2 g / L. -1 Stir until homogeneous at room temperature. Place the pretreated Cu foil in the polymerization solution. Irradiate with an overhead UV lamp for 10 minutes, then remove. Wash three times repeatedly with deionized water and ethanol, then dry in a vacuum drying oven at 80°C. Prepare a concentration of 5 mmol / L. -1 A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution. After the reaction was complete, the foil was removed. It was then washed three times repeatedly with deionized water and ethanol, and finally dried in a vacuum drying oven at 80°C.

[0074] Comparative Example 2

[0075] Place Cu foil in 1 mol·L -1 Shake and agitate in hydrochloric acid for 10 minutes, then wash three times repeatedly with deionized water and ethanol, and finally dry in a vacuum drying oven at 80°C. Prepare a concentration of 0.6 g / L. -1 Sodium dihydrogen phosphate and 1.2g L -1 Disodium hydrogen phosphate solution was stirred thoroughly at room temperature. Tannic acid was added to the phosphate buffer solution, controlling the tannic acid concentration to 0.2 g / L. -1 Stir until homogeneous at room temperature. Place the pretreated Cu foil in the polymerization solution. Irradiate with an overhead UV lamp in a dark room for 10 minutes, then remove. Wash three times repeatedly with deionized water and ethanol, and dry in a vacuum drying oven at 80°C. Prepare a concentration of 5 mmol·L⁻¹. -1 A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution. After the reaction was complete, the foil was removed. It was then washed three times repeatedly with deionized water and ethanol, and finally dried in a vacuum drying oven at 80°C.

[0076] Comparative Example 3

[0077] Place Cu foil in 1 mol·L -1 Shake and agitate in hydrochloric acid for 10 minutes, then wash three times repeatedly with deionized water and ethanol, and finally dry in a vacuum drying oven at 80°C. Prepare a concentration of 0.6 g / L. -1 Sodium dihydrogen phosphate and 1.2g L -1 Disodium hydrogen phosphate solution was stirred thoroughly at room temperature. Tannic acid was added to the phosphate buffer solution, controlling the tannic acid concentration to 0.2 g / L. -1Stir until homogeneous at room temperature. Place the pretreated Cu foil in the polymerization solution. Irradiate with an overhead UV lamp for 30 minutes, then remove. Wash three times repeatedly with deionized water and ethanol, then dry in a vacuum drying oven at 80°C. Prepare a concentration of 5 mmol / L. -1 A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution. After the reaction was complete, the foil was removed. It was then washed three times repeatedly with deionized water and ethanol, and finally dried in a vacuum drying oven at 80°C.

[0078] Comparative Example 4

[0079] Place Cu foil in 1 mol·L -1 Shake and agitate in hydrochloric acid for 10 minutes, then wash three times repeatedly with deionized water and ethanol, and finally dry in a vacuum drying oven at 80°C. Prepare a concentration of 0.6 g / L. -1 Sodium dihydrogen phosphate and 1.2g L -1 Disodium hydrogen phosphate solution was stirred thoroughly at room temperature. Tannic acid was added to the phosphate buffer solution, controlling the tannic acid concentration to 0.2 g / L. -1 Stir until homogeneous at room temperature. Place the pretreated Cu foil in the polymerization solution. Irradiate with an overhead UV lamp for 10 minutes, then remove. Wash three times repeatedly with deionized water and ethanol, then dry in a vacuum drying oven at 80°C. Prepare a concentration of 10 mmol·L⁻¹. -1 A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution. After the reaction was complete, the foil was removed. It was then washed three times repeatedly with deionized water and ethanol, and finally dried in a vacuum drying oven at 80°C.

[0080] Comparative Example 5

[0081] Place Cu foil in 1 mol·L -1 Shake and agitate in hydrochloric acid for 10 minutes, then wash three times repeatedly with deionized water and ethanol, and finally dry in a vacuum drying oven at 80°C. Prepare a concentration of 0.6 g / L. -1 Sodium dihydrogen phosphate and 1.2g L -1 Disodium hydrogen phosphate solution was stirred thoroughly at room temperature. Tannic acid was added to the phosphate buffer solution, controlling the tannic acid concentration to 0.2 g / L. -1 Stir until homogeneous at room temperature. Place the pretreated Cu foil in the polymerization solution. Irradiate with an overhead UV lamp for 10 minutes, then remove. Wash three times repeatedly with deionized water and ethanol, then dry in a vacuum drying oven at 80°C. Prepare a concentration of 5 mmol / L. -1 A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution and reacted for 30 minutes. After the reaction, the foil was removed, washed three times with deionized water and ethanol, and then dried in a vacuum drying oven at 80°C.

[0082] Comparative Example 6

[0083] Place Cu foil in 1 mol·L -1 Shake and agitate in hydrochloric acid for 10 minutes, then wash three times repeatedly with deionized water and ethanol, and finally dry in a vacuum drying oven at 80°C. Prepare a concentration of 0.6 g / L. -1 Sodium dihydrogen phosphate and 1.2g L -1 Disodium hydrogen phosphate solution was stirred thoroughly at room temperature. Tannic acid was added to the phosphate buffer solution, controlling the tannic acid concentration to 0.2 g / L. -1 Stir until homogeneous at room temperature. Place the pretreated Cu foil in the polymerization solution. Irradiate with an overhead UV lamp for 10 minutes, then remove. Wash three times repeatedly with deionized water and ethanol, then dry in a vacuum drying oven at 80°C. Prepare a concentration of 5 mmol / L. -1 A Cu foil with a tannic acid film polymerized on its surface was placed in an AgNO3 solution and then removed. It was then washed three times with deionized water and ethanol, and dried in a vacuum oven at 80°C. The resulting copper foil was sliced ​​and assembled sequentially in an argon-filled glove box in the following order: negative electrode shell, copper foil, separator, lithium sheet (lithium iron phosphate positive electrode sheet), gasket, spring contact, and positive electrode shell. A 1 mol·L⁻¹ electrolyte was used. -1 LiTFSI dissolves in DOL / DME (1:1, V:V).

[0084] Figure 1 In an interface modification method for preparing electrodeless lithium metal batteries using UV-polymerized tannic acid composite Ag particles, the adsorption energies of Cu foil, Ag particles, and LiAg alloy for lithium ions were analyzed. Density functional theory calculations showed that the adsorption energy of lithium ions on the copper surface was only -0.54 eV, significantly lower than that on Ag (-1.53 ​​eV) and LiAg (-1.43 eV) surfaces. This higher adsorption energy indicates that Ag and LiAg have good lithiophilicity, resulting in a smaller barrier during lithium deposition. During deposition, lithium ions initially combine with Ag to form LiAg alloys. Once all Ag particles have been converted to LiAg alloys, the low nucleation barrier of LiAg can continue to contribute to uniform lithium deposition.

[0085] Figure 2 This is a diagram showing the nucleation overpotential curve of the negative electrode prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles. The assembled Li||Cu battery was tested at 1 mAh·cm⁻¹. -2The lithium nucleation overpotential of the electrode was tested at a current density of [value missing]. The nucleation overpotential of the bare Cu foil was 150 mV. Thanks to the abundant lithiophilic groups and good wettability of tannic acid, the lithium nucleation overpotential was reduced to 25 mV after polymerizing a polytannic acid film on the Cu surface. After the introduction of Ag particles, a clear alloying process was observed on the nucleation curve, which is the process of Ag combining with lithium ions to form LiAg. The nucleation overpotential of the Cu foil with polytannic acid film composite Ag particles was further reduced to 10 mV. This means that lithium deposition on the surface of the Cu foil with polytannic acid film composite Ag particles is minimally hindered, and the growth of lithium dendrites and dead lithium will be suppressed.

[0086] Figure 3 This image shows the average lithium plating / stripping efficiency of a cathode prepared using an interface modification method for fabricating electrodeless lithium metal batteries using UV-polymerized tannic acid composite Ag particles. The faster reaction kinetics and smaller lithium nucleation barrier result in higher average CE (calculation efficiency) for lithium plating / stripping on both polytannic acid film / Cu foil (99.1%) and polytannic acid film / Ag particle composite Cu foil (98.2%), compared to Cu (91.7%), demonstrating superior reversibility in lithium plating. The average CE decreases after introducing Ag particles because during lithium plating, some lithium ions are first consumed in an alloying reaction with Ag to form a LiAg alloy, which will not detach further. Figure 3 It can also be seen that the polarization level of the polytannic acid film composite Ag particle Cu foil is the lowest during lithium plating / stripping, which indicates that its interfacial reaction is more stable.

[0087] Figure 4 This is a Tafel curve of a half-cell consisting of a negative electrode and a lithium sheet, prepared using an interface modification method for preparing a negative electrode-free lithium metal battery by UV polymerization of tannic acid composite Ag particles. The Tafel curve also shows that polytannic acid film Cu foil and polytannic acid film composite Ag particle Cu foil can effectively improve the reaction kinetics during lithium plating / stripping. When the exchange current density is high, the redox reaction rate at the electrode is faster, and the polarization level is lower. The exchange current density of the polytannic acid film Cu foil is 12.5 mA·cm⁻¹. -2 Much higher than Cu's 5.2 mA·cm -2 Building upon this, the polytannic acid film composite Ag particle Cu foil further increased the exchange current density to 20.1 mA·cm⁻¹. -2 .

[0088] Figure 5 The impedance diagram of a half-cell consisting of a negative electrode and a lithium sheet prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles is shown. ct =157.3Ω.

[0089] Figure 6The impedance diagram of the negative electrode half-cell prepared in Comparative Example 1 of this invention is shown below. ct =68.1Ω.

[0090] Figure 7 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 2 of this invention is shown below. ct =34.4Ω.

[0091] Figure 8 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 3 of this invention is shown below. ct =23.7Ω.

[0092] Figure 9 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 4 of this invention is shown below. ct =58.6Ω.

[0093] Figure 10 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 5 of this invention is shown below. ct =51.7Ω.

[0094] Figure 11 The impedance diagram of the negative electrode half-cell prepared in Comparative Example 6 of this invention is shown below. ct =18.2Ω.

[0095] Figure 12 This document describes an interface modification method for preparing electrodeless lithium metal batteries using ultraviolet-polymerized tannic acid-Ag composite particles. It presents the volt-ampere curves of a full cell consisting of an anode and lithium iron phosphate, obtained at a scan rate of 0.8 mV·s. -1 The redox peak positions differed by 1.02V.

[0096] Figure 13 This is the cyclic voltammogram of the lithium iron phosphate full cell prepared in Comparative Example 1 of this invention, at a scan rate of 0.8 mV·s. -1 The difference between the redox peaks was 0.62V, indicating that cleaning with an appropriate concentration of hydrochloric acid can effectively remove the oxide film on the Cu foil surface and accelerate the reaction rate at the electrode interface.

[0097] Figure 14 This is the in-situ impedance spectrum of a lithium iron phosphate half-cell prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles during the initial cycling process. During the charging and discharging process, the battery impedance value is large and the impedance variation range is large.

[0098] Figure 15 The image shows the in-situ impedance spectrum of the lithium iron phosphate half-cell prepared in Comparative Example 1 of this invention during the initial cycling process. The battery impedance value is small, and the impedance change range is small during the charging and discharging process, indicating that the electrode is more stable during the reaction process.

[0099] Figure 16 The electronic conductivity diagram of the negative electrode is obtained by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles. s =0.34A.

[0100] Figure 17 The electron conductivity diagram of the negative electrode prepared in Comparative Example 1 of this invention is shown in Figure I. s =0.35A.

[0101] Figure 18 This is a graph showing the efficiency-specific capacity curve of a lithium iron phosphate half-cell prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles; the capacity retention rate after 50 cycles is 17.5%.

[0102] Figure 19 The graph shows the efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 1 of this invention at 0.5C. After 50 cycles, the capacity retention rate is 21.2%. Using hydrochloric acid of appropriate concentration to remove the oxide film avoids the reaction between lithium ions and copper oxide, thereby increasing the reversibility of electrode cycling.

[0103] Figure 20 The graph shows the efficiency-specific capacity curve of the lithium iron phosphate full cell prepared in Comparative Example 2 of this invention at 0.5C cycling; the capacity retention rate after 50 cycles is 35.3%. Darkroom polymerization can improve the uniformity of the polytannic acid film, reduce the occurrence of localized current density concentrations, and improve the reversibility of lithium plating on the electrodes.

[0104] Figure 21 The graph shows the efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 3 of this invention at 0.5C cycling; the capacity retention rate after 50 cycles is 36.1%. Controlling the UV polymerization time can control the thickness of the polytannic acid film; a suitable thickness can effectively protect the electrodes and promote lithium-ion migration.

[0105] Figure 22 This is the efficiency-specific capacity curve of the lithium iron phosphate full cell prepared in Comparative Example 4 of this invention at 0.5C cycling; the capacity retention rate after 50 cycles is 38.1%. The concentration of AgNO3 solution affects the aggregation degree of Ag particles. Too high a concentration will cause Ag particles to aggregate, resulting in local current density concentration and the formation of lithium dendrites. Too low a concentration will reduce the content of Ag particles in the negative electrode, affecting electrode performance.

[0106] Figure 23This is the efficiency-specific capacity curve of the lithium iron phosphate full battery prepared in Comparative Example 5 of this invention at 0.5C cycling; the capacity retention rate after 50 cycles is 40.1%. The reaction time in AgNO3 directly affects the Ag particle content in the negative electrode. Too short a reaction time will lead to uneven Ag particle distribution. An appropriate reaction time can achieve a uniform Ag particle distribution and improve electrode surface uniformity.

[0107] Figure 24 The graph shows the efficiency-specific capacity of the lithium iron phosphate full battery prepared in Comparative Example 6 of this invention at 0.5C cycling; the capacity retention rate after 50 cycles is 49.4%. Using a suitable electrolyte can provide more favorable conditions for lithium-ion migration during battery cycling, improving the reversibility of electrode lithium plating.

[0108] Figure 25 This is a specific capacity-voltage curve of a lithium iron phosphate full cell prepared by an interface modification method for preparing a negative electrode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles. The battery polarization voltage is 0.68 after 50 cycles.

[0109] Figure 26 This is a specific capacity-voltage curve of the lithium iron phosphate full cell prepared in Comparative Example 1 of this invention under 0.5C cycling. After 50 cycles, the battery polarization voltage is 0.63V. Using a higher concentration of hydrochloric acid can more completely remove the oxide layer on the copper foil surface, accelerate the electrode interface reaction rate, and reduce the polarization voltage.

[0110] Figure 27 This is a specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 2 of this invention under 0.5C cycling. After 50 cycles, the battery polarization voltage is 0.28V. Ultraviolet polymerization in a dark room can induce a more uniform formation of polytannic acid film on the Cu foil surface, which is beneficial for reducing the battery polarization voltage.

[0111] Figure 28 This is a specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 3 of this invention under 0.5C cycling. After 50 cycles, the battery polarization voltage is 0.17V. Extending the UV irradiation time can construct a more complete and robust polytannic acid film on the copper foil surface, and there are also more elastic Ag particle channels during the reaction, which is beneficial to reducing the battery polarization voltage.

[0112] Figure 29 This is a specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 4 of this invention, showing a polarization voltage of 0.89V after 50 cycles. Using a higher concentration of AgNO3 solution accelerates the reduction process, resulting in a significantly uneven distribution of Ag particle channels on the copper foil, which in turn increases the battery polarization voltage.

[0113] Figure 30 This is a specific capacity-voltage curve of the lithium iron phosphate full battery prepared in Comparative Example 5 of this invention under 0.5C cycling. After 50 cycles, the battery polarization voltage is 0.22V. Extending the immersion time in AgNO3 solution allows sufficient Ag particle channels to be constructed in the polytannic acid film on the copper foil surface, thereby reducing the battery polarization voltage.

[0114] Figure 31 This is the specific capacity-voltage curve of the lithium iron phosphate full cell prepared in Comparative Example 6 of this invention under 0.5C cycling. After 50 cycles, the battery polarization voltage is 0.38V. Using 1 mol·L⁻¹ -1 LiTFSI dissolved in DOL / DME (1:1, V:V) as an electrolyte has a better affinity for lithium metal, forming a more stable SEI film and reducing the polarization voltage of the battery.

Claims

1. An interface modification method for preparing electrodeless lithium metal batteries using ultraviolet-polymerized tannic acid composite Ag particles, characterized in that... The method is performed according to the following steps: I. Pretreatment of Cu Foil Place the Cu foil in hydrochloric acid and shake for 5-15 minutes, then wash it repeatedly with deionized water and ethanol three times, and then dry it in a vacuum drying oven at 80-100℃. II. Preparation of Phosphate Buffer Solution Prepare a phosphate buffer solution composed of sodium dihydrogen phosphate and disodium hydrogen phosphate, and stir until homogeneous at room temperature; III. Preparation of Polymerization Solution Add tannic acid to the phosphate buffer solution, controlling the tannic acid concentration to be 0.2~1 g / L. -1 Stir well at room temperature; IV. UV-assisted polymerization of tannic acid The pretreated Cu foil was placed in a polymerization solution, irradiated with a UV lamp, removed, washed three times with deionized water and ethanol, and then dried in a vacuum drying oven at 80~100℃. V. Preparation of Ag Particle Composite Solution Dissolve AgNO3 in water and stir until homogeneous to obtain an AgNO3 solution for later use. VI. Ag particle composite Cu foil with a tannic acid film polymerized on its surface was placed in AgNO3 solution and reacted for a certain period of time. After the reaction was completed, it was taken out, washed three times with deionized water and ethanol, and then dried in a vacuum drying oven at 80~100℃. VII. Battery Assembly After slicing the Cu foil obtained in step six, first place the negative electrode shell, and then assemble the battery in the following order: Cu foil, electrolyte, separator, electrolyte, Li sheet or lithium iron phosphate electrode sheet, and positive electrode shell.

2. The interface modification method for preparing a cathode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles according to claim 1, characterized in that... The concentration of sodium dihydrogen phosphate in the polymerization solution is 0.5~1 g / L. -1 The concentration of disodium hydrogen phosphate is 1~3 g / L. -1 .

3. The interface modification method for preparing a cathode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles according to claim 1, characterized in that... The concentration of hydrochloric acid in step one is 0.1~2 mol·L⁻¹ -1 .

4. The interface modification method for preparing a cathode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles according to claim 1, characterized in that... The UV polymerization process in step four is carried out in a dark room.

5. The interface modification method for preparing a cathode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles according to claim 1, characterized in that... In step four, irradiate with a UV lamp for 10-30 minutes.

6. The interface modification method for preparing a cathode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles according to claim 1, characterized in that... The concentration of the AgNO3 solution prepared in step five is 1~10 mmol·L. -1 .

7. The interface modification method for preparing a cathode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles according to claim 1, characterized in that... In step six, react in AgNO3 solution for 1 to 30 minutes.

8. The interface modification method for preparing a cathode-free lithium metal battery using ultraviolet-polymerized tannic acid composite Ag particles according to claim 1, characterized in that... The electrolyte used in step seven is 1 mol·L⁻¹. -1 LiPF6 dissolves in DEC / FEC (1:1, V : V Neutralize 1 mol·L -1 LiTFSI dissolves in DOL / DME (1:1). V : V One or two of these electrolytes.

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