Flexible zinc ion battery and preparation method thereof

Abstract

The invention relates to the technical field of zinc ion batteries, and discloses a preparation method of a flexible zinc ion battery, which comprises the following steps: step 1, preparing a mixed solvent of N, N-dimethylacetamide and lithium chloride, and dissolving a biomass material in the mixed solvent to form a viscous solution; 2, respectively coating the viscous solution on the surfaces of a zinc positive electrode and a manganese dioxide negative electrode, assembling into a battery structure, injecting an electrolyte, and triggering in-situ gelation of a substance material; and step 3, packaging the gelated battery to obtain the flexible zinc ion battery. According to the invention, a seamless electrode-diaphragm interface is realized, and non-uniform ion current distribution is eliminated; self-assembled double-layer SE I (the inner layer accelerates Zn < 2 + > desolvation and blocks electron tunneling, and the cellulose outer layer anchors water molecules to inhibit SE I dissolution); a positive electrode stable layer (hydrogel mediation inhibits MnO2 dissolution); the interface bonding between the in-situ formed gel electrolyte and the electrode is good, and the structural stability of the flexible battery under different deformations can be guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of zinc ion batteries, in particular to a flexible zinc ion battery and a preparation method thereof. BACKGROUND

[0002] Aqueous zinc metal batteries (AZMBs) are considered as an ideal candidate for the next generation of energy storage technology due to their intrinsic safety, low cost and environmental friendliness. The core advantages come from:

[0003] 1. The non-flammability of aqueous electrolyte completely avoids the risk of explosion of organic electrolyte;

[0004] 2. The high theoretical capacity (820 mAh g -1 ) and low redox potential (-0.76 V vs. SHE) of zinc metal can provide high energy density;

[0005] The abundance and easy recyclability of zinc resources meet the needs of sustainable development.

[0006] However, the practical application of AZMBs is restricted by the interface failure mechanism, especially at low current density (<1 mA cm -2 ):

[0007] Hydrogen evolution reaction (HER): In aqueous electrolyte, the zinc negative electrode surface causes severe hydrogen evolution (2H2O + 2e - → H2↑ + 2OH-) due to local pH increase, resulting in electrolyte consumption, interface passivation and battery swelling;

[0008] Dendrite growth and short circuit failure: Zinc ions (Zn 2+ ) are deposited on the electrode surface to form dendrites, which pierce the separator and cause battery short circuit, resulting in a sharp decrease in cycle life.

[0009] SEI absence and dynamic instability: Traditional aqueous electrolyte cannot form a stable SEI similar to lithium batteries, while anion-derived inorganic SEI (such as ZnSO4·3Zn(OH)2, Zn5(OH)8Cl2·H2O) is easily dissolved in water or undergoes phase transition;

[0010] The positive oxide material faces the problems of structural instability, large deformation and easy collapse during charging and discharging, which affects the cycle stability of the battery.

[0011] The existing technology mainly improves the interface stability through the following ways:

[0012] 1. Electrolyte modification: adding corrosion inhibitors (such as Mn 2+ , Bi 3 ) or high-concentration salt ("salt-in-water" electrolyte), but the cost is high and the low-temperature performance is deteriorated;

[0013] 2. Artificial SEI coating: Pre-depositing polymers (such as PVA, PVDF) or inorganic layers (such as TiO2) on the surface of the zinc negative electrode, but the coating has weak bonding with the electrode interface and is easy to fall off during long-term cycling;

[0014] 3. Electrode structure design: Constructing a three-dimensional porous zinc negative electrode (such as zinc foam, Zn@carbon composite material) increases the active area, but intensifies side reactions and reduces energy density. Summary of the Invention

[0015] The purpose of the present invention is to solve the problems existing in the prior art and to propose a flexible zinc ion battery and a preparation method thereof.

[0016] In order to achieve the above object, the present invention adopts the following technical solutions:

[0017] A method for preparing a flexible zinc ion battery comprises the following steps:

[0018] Step 1: preparing a mixed solvent of N,N-dimethylacetamide and lithium chloride, and dissolving the biomass material in the mixed solvent to form a viscous solution;

[0019] Step 2: coating the viscous solution on the surface of the zinc positive electrode and the manganese dioxide negative electrode respectively, assembling them into a battery structure, and injecting the electrolyte to trigger in-situ gelation of the biomass material;

[0020] Step 3: Encapsulate the gelled battery to obtain a flexible zinc-ion battery.

[0021] Preferably, the mass ratio of N,N-dimethylacetamide to lithium chloride is 92:8.

[0022] Preferably, the biomass material is absorbent cotton.

[0023] Preferably, the concentration of the viscous solution is in the range of 0.1% to 1%.

[0024] Preferably, the electrolyte is an aqueous solution containing zinc sulfate.

[0025] Preferably, the in-situ gelation of the triggering biomass material is in-situ gelation of cellulose induced by diffusion of water molecules.

[0026] A flexible zinc ion battery is prepared by adopting a preparation method of a flexible zinc ion battery. The surfaces of the zinc metal positive electrode and the manganese dioxide negative electrode are provided with a gel interface layer.

[0027] Preferably, the gel interface layer comprises:

[0028] The outer layer, formed from cellulose into a gel;

[0029] The inner layer is formed of ZnS.

[0030] Preferably, the thickness of the inner layer is 5-15 nm.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention proposes an electrolyte-induced hydrogel interface in situ construction strategy, which induces the gelation of polymer precursors through solvent exchange, and simultaneously achieves:

[0033] 1. Seamless electrode-diaphragm interface eliminates uneven ion flow distribution;

[0034] 2. Self-assembled bilayer SEI (the ZnS inner layer accelerates Zn2+ desolvation and blocks electron tunneling, while the cellulose outer layer anchors water molecules to inhibit SEI dissolution);

[0035] 3. Cathode stabilization layer (inhibiting MnO2 dissolution through hydrogel mediation);

[0036] 4. The interface between the in-situ formed gel electrolyte and the electrode is well bonded, which can ensure the structural stability of the flexible battery under different deformations. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the gelation process of the preparation method of a flexible zinc ion battery proposed in the present invention;

[0038] Figure 2 Schematic diagram of the double-layer SEI of a flexible zinc-ion battery proposed in the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0040] Reference Figure 1 , a method for preparing a flexible zinc ion battery, comprising the following steps:

[0041] Step 1: preparing a mixed solvent of N,N-dimethylacetamide and lithium chloride, and dissolving the biomass material in the mixed solvent to form a viscous solution;

[0042] Step 2: coating the viscous solution on the surface of the zinc positive electrode and the manganese dioxide negative electrode respectively, assembling them into a battery structure, and injecting the electrolyte to trigger the in-situ gelation of the biomass material;

[0043] Step 3: Encapsulate the gelled battery to obtain a flexible zinc-ion battery.

[0044] In this embodiment, the mass ratio of N,N-dimethylacetamide and lithium chloride is 92:8.

[0045] In this embodiment, the biomass material adopts absorbent cotton, which can achieve low cost control. Of course, in other embodiments, lignin, chitin and other biomass materials can also be used.

[0046] In this embodiment, the concentration of the viscous solution is between 0.1% and 1%.

[0047] In this embodiment, the electrolyte is an aqueous solution containing zinc sulfate, and the in-situ gelation of the contact biomass material is water molecule diffusion induced in-situ gelation of cellulose. The solvent exchange induces the in-situ formation of cellulose gel inside the battery, and the battery assembly and interface construction are completed synchronously.

[0048] In other embodiments, temperature-responsive polymers can also be used to trigger gelation by heating. The aqueous solution of ZnSO4 can be replaced by aqueous solutions of ZnCl2, Zn(NO3)2, Zn(CH3COO)2, Zn(CF3SO3)2, and S 2- PO4 3- Zn3(PO4)2inner layer SEI is generated.

[0049] Referring to Figure 2 The present embodiment also proposes a flexible zinc ion battery prepared by the above-mentioned preparation method of a flexible zinc ion battery. The cellulose solution forms a gel interface layer in-situ on the surface of the zinc metal negative electrode and the manganese dioxide positive electrode. In the prior art, the interface between the gel electrolyte and the electrode in the flexible zinc ion battery is weakly bonded, and there is a large interface resistance and structural stability. The present application applies the above-mentioned preparation method of a flexible zinc ion battery on the basis of the prior art, and therefore, the other structures of the flexible zinc ion battery will not be described in detail.

[0050] The traditional aqueous battery has problems of interface instability and interface mismatch due to the intrinsic properties of the aqueous electrolyte, which hinders the transmission of ions across the interface and induces dendrite growth on the surface of the metal negative electrode. This strategy simultaneously constructs a macroscopic seamless interface and a microscopic high-performance double-layer SEI, realizes long-term stability of the negative electrode interface, and thus suppresses dendrite formation.

[0051] In this embodiment, the gel interface layer comprises:

[0052] The inner layer (ZnS) has a thickness of 15 nm, low electronic conductivity, and accelerates Zn 2+ desolvation (activation energy reduction of 45%);

[0053] Outer layer (cellulose gel): Anchors water molecules through hydrogen bonds, inhibits SEI dissolution;

[0054] Therefore, the double-layer SEI can play the following roles:

[0055] The ZnS inner layer inhibits electron tunneling, and the cellulose outer layer inhibits HER and zinc dendrite growth;

[0056] The gel electrolyte formed after in-situ gelation of the cellulose solution can inhibit the solution of the positive electrode MnO2, further improving the cycle stability of the battery;

[0057] The interface between the gel electrolyte formed by in-situ gelation of the cellulose solution and the electrode is better, improving the interface bonding and structural stability of the flexible battery under different deformations.

[0058] Compared with the prior art, the present application has the following effects:

[0059] 1. Improved interface stability: Eliminate electrode-separator interface voids, achieve uniform distribution of ion flow, and better interface bonding between the gel electrolyte formed by in-situ gelation and the electrode;

[0060] 2. Multifunctionality of double-layer SEI: ZnS inner layer blocks electron leakage, HER rate reduced to 0.012 μmol h - 1 cm -2 (1 / 100 of traditional SEI), stabilizing the SEI structure;

[0061] 3. Performance breakthrough of full battery: Ultra-low N / P ratio soft pack battery can improve the cycle life and overall energy density of the battery;

[0062] 4. Green and environmentally friendly: The raw material cellulose of the gel electrolyte is a natural polymer material, which is renewable, biodegradable, and environmentally friendly.

[0063] It should be noted here that the related terms involved in this embodiment are explained as follows:

[0064] SEI (Solid Electrolyte Interphase): Protective layer formed on the surface of the electrode, affecting ion transport and interface stability.

[0065] HER (Hydrogen Evolution Reaction): Side reaction during water electrolysis, leading to electrolyte consumption and battery failure.

[0066] Dendrite: Inhomogeneous deposition behavior of metal negative electrode during reaction, resulting in tree-like deposits on the surface of the negative electrode, which can easily pierce the separator and cause short circuit failure of the battery.

[0067] N / P ratio (Negative / Positive Capacity Ratio): the ratio of the capacity of the negative electrode to that of the positive electrode, a low N / P ratio can improve the energy density of the battery;

[0068] English meanings are as follows:

[0069] Carbon cloth: carbon cloth;

[0070] Separator: separator;

[0071] Zinc metal: zinc metal negative electrode;

[0072] Electrolyte-triggered gelation chemistry: electrolyte-triggered gelation chemistry;

[0073] Cellulose: cellulose;

[0074] CPS: cellulose precursor solution;

[0075] In-CH: in-situ cellulose hydrogel;

[0076] Methylene: methylene stretching vibration;

[0077] Hydrogen bonds: hydrogen bonds;

[0078] Dendrite deposition: dendritic deposition;

[0079] Interfacial mismatch: interfacial mismatch;

[0080] In situ construct hydrogel interphase: in situ construct hydrogel interphase;

[0081] Unstable SEI: unstable solid electrolyte interphase;

[0082] Bilayer SEI: bilayer structure solid electrolyte interphase;

[0083] Uniform deposition: uniform deposition;

[0084] Seamless interface: seamless interface.

[0085] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing a flexible zinc ion battery, characterized in that: The following steps are involved: Step 1: preparing a mixed solvent of N,N-dimethylacetamide and lithium chloride, and dissolving the biomass material in the mixed solvent to form a viscous solution; Step 2: coating the viscous solution on the surface of the zinc positive electrode and the manganese dioxide negative electrode respectively, assembling them into a battery structure, and injecting the electrolyte to trigger the in-situ gelation of the biomass material; Step 3: Encapsulate the gelled battery to obtain a flexible zinc-ion battery.

2. The method for preparing a flexible zinc ion battery according to claim 1, wherein: The mass ratio of the N,N-dimethylacetamide to lithium chloride is 92:

8.

3. A flexible zinc ion battery and a preparation method thereof according to claim 2, characterized in that: The biomass material is selected from at least one of absorbent cotton, lignin or chitin.

4. A flexible zinc ion battery and a preparation method thereof according to claim 3, characterized in that: The concentration of the viscous solution ranges from 0.1% to 1%.

5. A flexible zinc ion battery and a preparation method thereof according to claim 4, characterized in that: The electrolyte is an aqueous solution containing at least one of zinc sulfate, zinc chloride, zinc nitrate, zinc acetate or zinc trifluoromethanesulfonate.

6. A flexible zinc ion battery and a preparation method thereof according to claim 3, characterized in that: The in-situ gelation of the triggering biomass material comprises:

1. Water molecule diffusion induces in situ gelation of cellulose, lignin, and chitin; or 2. Heating to 40-60°C activates the temperature-responsive polymer to trigger gelation.

7. A flexible zinc ion battery and a method for preparing the same according to claim 6, characterized in that: The temperature-responsive polymer is poly (N-isopropylacrylamide).

8. A flexible zinc ion battery, prepared by the method for preparing a flexible zinc ion battery according to any one of claims 1 to 7, characterized in that: A gel interface layer is provided on the surfaces of the zinc metal positive electrode and the manganese dioxide negative electrode.

9. A flexible zinc ion battery according to claim 8, characterized in that: The gel interface layer comprises: the outer layer, which forms a gel from cellulose, lignin, or chitin; The inner layer is formed of ZnS or Zn3(PO4)2.

10. A flexible zinc ion battery according to claim 9, characterized in that: The thickness of the inner layer is 5-15 nm.

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