Precursor solutions and modified membranes comprising same for lithium-based batteries

Abstract

The present application provides a precursor solution, a modified film comprising the same, and a lithium battery. The modified film is formed on the two poles or the separator film of the battery by a photo-polymerization reaction or thermal curing of the precursor solution. The lithium battery with the modified film can effectively improve the charge-discharge capacity, cycle life and safety. The modified film can be applied to a roll-to-roll process. In the charge-discharge cycle process, the formation of lithium dendrites can be effectively inhibited or reduced, and the modified film has good cycle life and safety. In the state of lithium-sulfur batteries and lithium-iodine batteries, the shuttle effect can be inhibited or reduced. The above characteristics are beneficial to improve the product value of lithium-ion batteries, lithium metal batteries, anode-free lithium batteries, lithium-sulfur batteries and lithium-iodine batteries.

Description

Technical Field

[0001] This invention relates to a precursor solution and a modified film containing the precursor, and to lithium-ion batteries. Background Technology

[0002] In response to energy shortages and soaring electricity demand, significant investment has been made in research on high-efficiency energy storage systems in recent years. Lithium-ion batteries (LIBs), with their high energy density, high power density, and acceptable charge-discharge cycle characteristics, have been widely used in various electronic products. To further improve battery energy density, lithium metal anodes and anode-free (copper foil as the anode) anodes have gained increasing attention. The energy density and safety of batteries also require a suitable cathode system; therefore, the development of lithium-based batteries using lithium metal or copper foil as the anode and various cathode systems is urgent and important.

[0003] Lithium dendrites have long been a problem to be solved in lithium-ion batteries. During the charging and discharging process of lithium-ion batteries, lithium dendrites tend to accumulate on the negative electrode, thereby reducing coulombic efficiency and charge capacity. In severe cases, they may cause internal short circuits in the battery, leading to an explosion and greatly reducing the safety of lithium-ion batteries.

[0004] In the study of lithium-ion battery capacity, it is well known that adding elements such as sulfur and iodine to the cathode system can improve the battery energy density or power density. However, the reduced anions of sulfur and iodine are easily soluble in the electrolyte, resulting in a shuttle effect, which reduces the coulombic efficiency and cycle life of lithium-ion batteries.

[0005] Therefore, there is still room for improvement in the charge-discharge cycle performance and / or safety of lithium-ion batteries. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a precursor solution which forms a modified film through photopolymerization or thermal curing. The lithium battery of the present invention has the modified film, and after charge-discharge cycles, the formation of lithium dendrites can be suppressed or reduced, thus exhibiting good safety.

[0007] On the other hand, the lithium-based battery of the present invention has high coulombic efficiency and cycle life, which is beneficial to improving product value.

[0008] On the other hand, in the presence of sulfur or iodine, the lithium-based battery of the present invention can suppress or mitigate the shuttle effect. Therefore, the lithium-based battery of the present invention is conducive to the development of high-capacity and high-power batteries and has the application potential of lithium-sulfur batteries and lithium-iodine batteries.

[0009] To achieve the aforementioned objectives, the present invention provides a precursor solution comprising an active ingredient, a lithium salt solution, and an initiator;

[0010] The active ingredient is a monomer, oligomer, or a combination thereof;

[0011] The monomer is methacrylate or its lithium salt, acrylate or its lithium salt, or trimethylol propane triacrylate or its lithium salt.

[0012] Among them, the constituent units of oligomers are Or a combination thereof, the terminal structure of the oligomer is or combinations thereof;

[0013] The concentration of the lithium salt solution, expressed as molarity (M), ranges from 0.5 M to 4 M.

[0014] The initiator is 2,2-dimethoxy-2-phenylacetophenone (DMPA), benzoyl peroxide (BPO), 2,2'-azobis(2-methylpropionitrile) (AIBN), 2-hydroxy-2-methyl-1-phenyl-1-propanone (2-hydroxy-2-methyl-1-phenyl-1-propanone), or a combination thereof;

[0015] Of which, by weight percentage, the active ingredient accounts for 5 wt% to 47.5 wt% of the precursor solution, the lithium salt solution accounts for 50 wt% to 94.9 wt% of the precursor solution, and the initiator accounts for 0.1 wt% to 5 wt% of the precursor solution.

[0016] The precursor solution of this invention can form a modified film through photopolymerization or thermal curing. After charge-discharge cycles, lithium dendrite formation in lithium-based batteries with this modified film can be suppressed or reduced, and the lithium-based batteries exhibit high coulombic efficiency and cycle life, which is beneficial for enhancing product value. Furthermore, when applied to lithium-sulfur and lithium-iodine batteries, the modified film can suppress or mitigate the shuttle effect caused by sulfur or iodine, which is beneficial for the development of lithium-sulfur and lithium-iodine batteries.

[0017] Preferably, the constituent units of the oligomer can be Its combination, the terminal structure of the oligomer is Or a combination thereof.

[0018] In one embodiment, the constituent units of the oligomer possess... At least one of them; alternatively, the constituent units of the oligomer may include Or a combination thereof, the terminal structure of the oligomer is Or a combination thereof.

[0019] In one embodiment, the number-average molecular weight (Mn) of the oligomer can be from 200 to 2500; in another embodiment, the number-average molecular weight of the oligomer can be from 500 to 800.

[0020] Preferably, the active ingredient may be polyethylene glycol diacrylate (PEGDA), polypropylene glycol diacrylate, lithium methacrylate, lithium acrylate, trimethylolpropane triacrylate, or a combination thereof. In one embodiment, the active ingredient may be a combination of lithium methacrylate and trimethylolpropane triacrylate, with a weight ratio of lithium methacrylate to trimethylolpropane triacrylate of 3:7 to 7:3; in another embodiment, the active ingredient may be a combination of lithium acrylate and trimethylolpropane triacrylate, with a weight ratio of lithium acrylate to trimethylolpropane triacrylate of 3:7 to 7:3.

[0021] In one embodiment, by weight percentage, the active ingredient accounts for 5 wt% to 20 wt% of the precursor solution, the lithium salt solution accounts for 75 wt% to 94.9 wt% of the precursor solution, and the initiator accounts for 0.1 wt% to 5 wt% of the precursor solution.

[0022] Optionally, the lithium salt solution accounts for 60 wt% to 94.5 wt%, 75 wt% to 90 wt%, or 80 wt% to 90 wt% of the precursor solution by weight percentage. Preferably, the concentration of the lithium salt solution is 0.8 M to 2 M by volume molar concentration.

[0023] Preferably, the lithium salt solution comprises a lithium salt and an organic solvent, which may be 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), ethylene carbonate (EC), ethylene methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), tetraethylene glycol dimethyl ether, dimethyl sulfoxide (DMSO), acetonitrile (ACN), or a combination thereof.

[0024] Preferably, the lithium salt may be lithium bis(trifluoromethanesulfonyl)aminoide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (LiOTf), lithium fluoride (LiF), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium nitride (Li3N), or combinations thereof.

[0025] Preferably, the initiator can be 2,2-dimethoxy-phenylacetophenone.

[0026] In one embodiment, the precursor solution further includes an additive, which may be an organic compound or a metal salt;

[0027] The organic compound may be an oligomer having at least one hydroxyl or amino group at the end, polysquarate, succinonitrile, 1,3-propane sultone, prop-1-ene-1,3-sultone, fluoroethylene carbonate, ethylene glycol, polysorbate, or a combination thereof;

[0028] The constituent units of the oligomer having at least one hydroxyl or amino group at the end are: or combinations thereof;

[0029] Among them, the metal salts are lithium nitrate, sodium nitrate, potassium nitrate, or combinations thereof.

[0030] In the embodiment, the lithium salt solution accounts for 50 wt% to 94.5 wt% of the precursor solution by weight percentage, and the additives account for 0.01 wt% to 30 wt%, 0.01 wt% to 20 wt%, or 0.01 wt% to 10 wt% of the precursor solution by weight percentage.

[0031] In another embodiment, the precursor solution further comprises an additive, which may be an oligomer having at least one hydroxyl or amino group at the end;

[0032] The constituent units of the oligomer having at least one hydroxyl or amino group at the end are:

[0033] In another embodiment, the precursor solution further includes an additive, which may be an oligomer having at least one hydroxyl or amino group at the end;

[0034] The oligomer having at least one hydroxyl or amino group at the end is In this context, x can be 1 to 20, y can be 1 to 40, and z can be 1 to 20, and x, y, and z can be the same or different from each other.

[0035] In one embodiment, the precursor solution further comprises filler material, which is titanium dioxide, silicon dioxide, zirconium dioxide, aluminum oxide, indium tin oxide, lanthanum manganite, lithium sulfide-based particles, lithium oxide-based particles, lithium phosphate-based particles, or lithium lanthanum zirconium tantalum oxide. 6.4 La3Zr 1.4 Ta 0.6 O 12 ), Lithium lanthanum aluminum zirconium oxide (Li 6.4 La3Al 0.2 Zr2O 12 Inorganic powders or combinations thereof with lithium-ion conductivity.

[0036] In the embodiment, the lithium salt solution accounts for 50 wt% to 94.5 wt% of the precursor solution by weight percentage, and the filler accounts for 0.01 wt% to 40 wt%, 0.01 wt% to 30 wt%, 0.01 wt% to 20 wt%, or 0.01 wt% to 10 wt% of the precursor solution by weight percentage.

[0037] The present invention also provides a modified membrane, which is formed by photopolymerization or thermal curing of the precursor solution.

[0038] In one embodiment, the modified membrane can be applied to a roll-to-roll process.

[0039] The present invention also provides a lithium-based battery comprising a positive electrode, a negative electrode, a separator, a lithium electrolyte, and at least one modified film, wherein the modified film is formed by curing the aforementioned precursor solution, and the modified film is disposed on the positive electrode, the negative electrode, the separator, or a combination thereof. The lithium-based battery may be a lithium-ion battery, a lithium metal battery, an anode-free lithium battery, a lithium-sulfur battery, or a lithium-iodine battery, but is not limited thereto.

[0040] In one embodiment, the modified membrane may be disposed between the positive electrode and the separator or between the negative electrode and the separator; in another embodiment, the modified membrane may be disposed between the positive electrode and the separator and between the negative electrode and the separator, respectively.

[0041] In one embodiment, the lithium salt contained in the modified film is the same as the lithium salt in the lithium electrolyte; in another embodiment, the lithium salt contained in the modified film is different from the lithium salt in the lithium electrolyte. The implementation conditions can be adjusted according to the characteristics of the positive and negative electrodes, further improving the capacity, coulombic efficiency, and cycle life of the lithium-based battery. Specifically, if the positive electrode is lithium nickel manganese cobalt oxide (NMC) material, a lithium salt solution suitable for high voltage can be used as the lithium electrolyte to improve its cycle life and capacity. However, the modified film located at the negative electrode can still use a lithium salt solution with an ether-based lithium salt solution that facilitates lithium metal plating and stripping as a precursor solution, achieving the effect of suppressing lithium dendrite formation at the negative electrode and improving the energy density and cycle life of the lithium metal battery; if the positive electrode is high-voltage lithium nickel manganese oxide (LNMO, such as LiNi... 0.5 Mn 0.5 When using O2) materials, the modified film located at the positive electrode can be a lithium salt solution suitable for high voltage as the precursor solution, and a high-voltage resistant filler (e.g., Li) can be added. 6.4 La3Zr 1.4 Ta 0.6 O 12 LLZTO and additives (such as methyl borate) can improve the cycle life of the positive electrode. However, commercial lithium salt solutions that are conducive to lithium ion insertion / extraction and are often used in combination with graphite negative electrodes can still be used as liquid electrolyte solutions to achieve stable charge and discharge behavior of graphite negative electrodes, thereby improving the energy density and cycle life of lithium-ion batteries.

[0042] In one embodiment, the modified membrane includes fillers, which are titanium dioxide, silicon dioxide, zirconium dioxide, aluminum oxide, indium tin oxide, lanthanum manganese oxide, lithium sulfide particles, lithium oxide particles, lithium phosphate particles, or combinations thereof. The modified membrane of the embodiment can effectively increase the contact between the positive electrode and the electrolyte, and between the negative electrode and the electrolyte, and can further reduce the degradation of the electrolyte during high-voltage charging and discharging.

[0043] In one embodiment, the lithium-ion battery further comprises sulfur or iodine.

[0044] In one embodiment, the positive electrode may be a lithium nickel oxide electrode. Specifically, the lithium nickel oxide electrode may be a lithium nickel manganese cobalt oxide electrode (NMC) or a lithium nickel cobalt aluminum oxide electrode (NCA).

[0045] Furthermore, the modified film of the present invention can also be applied to anode-free lithium batteries. In one embodiment, when the negative electrode surface is modified with the modified film of the present invention, the impedance of lithium metal deposition and stripping on the negative electrode can be significantly reduced after 30 charge-discharge cycles. Therefore, the modified film can improve the charge-discharge cycle performance and / or safety of anode-free lithium batteries. Attached Figure Description

[0046] Figure 1 This is a charge-discharge cycle test diagram of the lithium metal battery in Example 1B.

[0047] Figure 2 This is a charge-discharge cycle test diagram of the lithium metal battery in Example 2B.

[0048] Figures 3A to 3C The following are charge-discharge cycle test diagrams of lithium metal batteries in Examples 3B-1 to 3B-3, in sequence.

[0049] Figure 4 From top to bottom, the lithium-lithium symmetrical batteries of Examples 5B-1, 6B-1, 7B, 8B and Comparative Example 1B are shown at a current density of 0.5 mA / cm². 2 and 1mA / cm 2 The constant current voltage cycle profile.

[0050] Figure 5 The electrochemical impedance spectra of lithium copper batteries of Examples 4B, 5B-2, 6B-2 and Comparative Example 2B are shown.

[0051] Figure 6A This is a constant current charge-discharge diagram of the lithium-iodine battery in Example 6C.

[0052] Figure 6B The constant current charge-discharge diagram is for the lithium-iodine battery of Comparative Example 3C.

[0053] Figure 7A This is a photograph of the negative electrode of the lithium-lithium symmetric battery of Example 9B after 15 minutes of charging and discharging.

[0054] Figure 7B A photograph of the negative electrode of the lithium-lithium symmetric battery of Comparative Example 4B after 15 minutes of charging and discharging. Detailed Implementation

[0055] The following examples illustrate several embodiments of the precursor solution, the modified film solidified therefrom, and the implementation of a lithium-ion battery comprising the aforementioned modified film. Several comparative examples of lithium-ion batteries are also provided for comparison. Those skilled in the art can easily understand the advantages and effects of this invention through the following examples and comparative examples. It should be understood that the embodiments listed in this invention are merely illustrative of the implementation of this invention and are not intended to limit the scope of this invention. Those skilled in the art can make various modifications and alterations based on their ordinary knowledge without departing from the spirit of this invention to implement or apply the content of this invention.

[0056] Reagent instructions

[0057] The relevant descriptions of the active ingredients, lithium salt solutions, initiators, additives, and fillers used in preparing the precursor solutions for each embodiment are as follows:

[0058] 1. Active ingredients:

[0059] (1) PEGDA: Polyethylene glycol diacrylate, model: Merck 437411, Mn: 575;

[0060] (2) TMPTA: Trimethylolpropane triacrylate;

[0061] (3) LiMAA: Lithium methacrylate salt;

[0062] LiMAA is prepared by using methacrylic acid as a raw material, adding a methanol solution of lithium hydroxide to neutralize to a pH of about 7, then removing the solvent by rotary concentration and drying in a vacuum oven to obtain LiMAA.

[0063] (4) LiAA: Lithium acrylate salt;

[0064] LiAA is obtained by using acrylic acid as a raw material, adding a methanol solution of lithium hydroxide to neutralize it to a pH of about 7, then removing the solvent by rotary concentration and drying in a vacuum oven.

[0065] (5) PU oligomer: polyurethane oligomer;

[0066] Polyether oligomer (model: Pluronic) Hereinafter referred to as L61), 1,4-phenylene diisocyanate was dissolved in methyl ethyl ketone solvent, and dibutyltin dilaurate (DBTDL) was added as a catalyst. Nitrogen gas was introduced as a protective gas during the reaction, and the reaction was carried out at 60°C for 6 hours to obtain a polyurethane oligomer intermediate. Then the temperature was lowered to 40°C, and polypropylene glycol acrylate was added to the solution. The reaction was carried out at 40°C for 2 hours, and then the solvent was removed by rotary concentration to obtain the polyurethane oligomer. The reaction is shown in the following formula.

[0067]

[0068] 2. Lithium salt solution:

[0069] (1) 1M LiTFSI DOL / DME solution: An appropriate amount of bis(trifluoromethanesulfonyl)aminolithium is dissolved in 1,3-dioxolane and ethylene glycol dimethyl ether in a volume ratio of 1:1 to prepare a 1M LiTFSI DOL / DME solution.

[0070] (2) 1M LiPF6 DMC / EC solution: Dissolve an appropriate amount of lithium hexafluorophosphate in dimethyl carbonate and ethylene carbonate in a volume ratio of 1:1 to prepare a 1M LiPF6 DMC / EC solution.

[0071] (3) 1M LiPF6 EC / EMC / DMC solution (containing 1 vol% VC): An appropriate amount of lithium hexafluorophosphate was dissolved in ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a volume ratio of 1:1:1 to prepare a 1M LiPF6 EC / EMC / DMC solution (containing 1 vol% VC), wherein the volume of ethylene carbonate (VC) accounted for 1% of the mixture.

[0072] 3. Initiator: DMPA: 2,2-dimethoxy-phenylacetophenone.

[0073] 4. Additives:

[0074] (1) LiNO3: Lithium nitrate;

[0075] (2) L61: Pluronic

[0076] 5. Filler: Al2O3: alumina.

[0077] Precursor Solution

[0078] Examples 1 to 9 (E1 to E9)

[0079] The precursor solutions of Examples 1 to 9 were all prepared by mixing monomers or oligomers with different lithium salt solutions and initiators, and selectively adding additives and fillers. After stirring uniformly for 0.5 to 6 hours, the precursor solutions of each example were obtained. For ease of explanation, the composition ratios of Examples 1 to 9 are shown in Table 1 below.

[0080] Table 1: Composition ratio of precursor solutions in Examples 1 to 9 (E1 to E9)

[0081]

[0082] Modified membrane

[0083] Examples 1A to 9A (E1A to E9A)

[0084] The precursor solutions of Examples 1 to 9 can be uniformly dropped onto the positive electrode, negative electrode, or separator as needed, and cured under appropriate light to form the modified membranes of Examples 1A to 9A.

[0085] Lithium-ion Batteries

[0086] The modified membranes of each embodiment can be further combined with the negative electrode, the separator, and the positive electrode to form lithium metal batteries, lithium copper batteries, lithium-lithium symmetrical batteries, and lithium-iodine batteries of Embodiments 1B to 9B, and the modified membranes of Embodiment 6C. The configurations of the lithium metal batteries, lithium copper batteries, lithium-lithium symmetrical batteries, and lithium-iodine batteries of each embodiment and their modified membranes are described below.

[0087] Example 1B

[0088] The lithium metal battery in Example 1B is a coin cell, with its positive electrode being a lithium nickel manganese cobalt oxide electrode (LiNi). 0.6 Mn 0.2 Co 0.2 O2 (hereinafter referred to as NMC622), lithium foil (purchased from Xuneng Co., Ltd.), commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN), and electrolyte 70 μL of 1M LiPF6 DMC / EC solution (v / v = 1 / 1). 10 μL of the precursor solution from Example 1 was uniformly dropped onto the lithium foil surface and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form the modified film of Example 1A. The modified film of Example 1A is located between the lithium foil and the separator.

[0089] Example 2B

[0090] The lithium metal battery of Example 2B is a button cell, with NMC622 as the positive electrode, lithium foil (purchased from Xuneng Co., Ltd.) as the negative electrode, and commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN) as the separator. The electrolyte is 60 μL of 1M LiPF6 DMC / EC solution (v / v = 1 / 1). 10 μL of the precursor solution from Example 1 was uniformly dropped onto the lithium foil surface and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form the modified film of Example 1A. Similarly, 10 μL of the precursor solution from Example 2 was uniformly dropped onto the NMC622 surface and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form the modified film of Example 2A. The modified film of Example 1A is located between the lithium foil and the separator, while the modified film of Example 2A is located between the NMC622 and the separator.

[0091] Examples 3B-1, 3B-2, and 3B-3

[0092] Example 3B-1's lithium metal battery is a button cell, with NMC622 as the positive electrode, lithium foil (purchased from Xuneng Co., Ltd.) as the negative electrode, and commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN) as the separator. The electrolyte is 70 μL of 1M LiPF6 DMC / EC solution (v / v = 1 / 1). 10 μL of the precursor solution from Example 3 was uniformly dropped onto the lithium foil surface and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form the modified film of Example 3A. The modified film of Example 3A is located between the lithium foil and the separator.

[0093] The lithium metal battery of Example 3B-2 is largely the same as the lithium metal battery of Example 3B-1, except that 10 microliters of the precursor solution of Example 3 is uniformly dropped onto the surface of NMC622 and irradiated with UV light at a wavelength of 365 nanometers for 2 minutes, and the modified film of Example 3A is located between NMC622 and the separator.

[0094] The lithium metal battery of Example 3B-3 is largely the same as the lithium metal battery of Example 3B-1, except that 10 microliters of the precursor solution of Example 3 is uniformly dropped onto the surface of the separator and irradiated with UV light at a wavelength of 365 nanometers for 2 minutes, and the modified film of Example 3A is located between the lithium foil and the separator.

[0095] Example 4B

[0096] The lithium-copper battery of Example 4B is a button cell, with lithium foil (purchased from Xuneng Co., Ltd.) as the negative electrode, copper foil (purchased from Xuneng Co., Ltd., model: 1092011) as the positive electrode, and commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN) as the separator. The electrolyte is 80 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.8 μL of VC). 15 μL of the precursor solution of Example 4 was uniformly dropped onto the surface of the copper foil, and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form the modified film of Example 4A. The modified film of Example 4A is located between the copper foil and the separator.

[0097] Example 5B-1, Example 5B-2

[0098] Example 5B-1's lithium-lithium symmetric battery is a button cell, with lithium foil as both the positive and negative electrodes (purchased from Xuneng Co., Ltd.), a commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN), and an electrolyte of 65 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.65 μL of VC). Two 15 μL portions of the precursor solution from Example 5 were uniformly dropped onto the surfaces of the positive and negative electrodes, respectively, and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form two modified films of Example 5A. One modified film of Example 5A is located between the positive electrode and the separator, while the other modified film of Example 5A is located between the negative electrode and the separator.

[0099] Example 5B-2's lithium-copper battery is a button cell, with lithium foil (purchased from Xuneng Co., Ltd.) as the negative electrode, copper foil (purchased from Xuneng Co., Ltd., model: 1092011) as the positive electrode, and commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN) as the separator. The electrolyte is 80 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.8 μL of VC). 15 μL of the precursor solution from Example 5 was uniformly dropped onto the copper foil surface and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form the modified film of Example 5A. The modified film of Example 5A is located between the copper foil and the separator.

[0100] Example 6B-1, Example 6B-2

[0101] Example 6B-1's lithium-lithium symmetric battery is a button cell, with lithium foil as both the positive and negative electrodes (purchased from Xuneng Co., Ltd.), a commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN), and an electrolyte of 65 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.65 μL of VC). Two 15 μL portions of the precursor solution from Example 6 were uniformly dropped onto the surfaces of the positive and negative electrodes, respectively, and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form two modified films of Example 6A. The two modified films of Example 6A are located between the positive electrode and the separator, and between the negative electrode and the separator, respectively.

[0102] Example 6B-2's lithium-copper battery is a button cell, with lithium foil (purchased from Xuneng Co., Ltd.) as the negative electrode, copper foil (purchased from Xuneng Co., Ltd., model: 1092011) as the positive electrode, and commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN) as the separator. The electrolyte is 80 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.8 μL of VC). 15 μL of the precursor solution from Example 6 was uniformly dropped onto the copper foil surface and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form the modified film of Example 6A. The modified film of Example 6A is located between the copper foil and the separator.

[0103] Example 7B

[0104] The lithium-lithium symmetric battery of Example 7B is a button cell, with lithium foil as both the positive and negative electrodes (purchased from Xuneng Co., Ltd.), a commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN), and an electrolyte of 65 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.65 μL of VC). Two 15 μL portions of the precursor solution from Example 7 were uniformly dropped onto the surfaces of the positive and negative electrodes, respectively, and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form two modified films of Example 7A. The two modified films of Example 7A are located between the positive electrode and the separator, and between the negative electrode and the separator, respectively.

[0105] Example 8B

[0106] The lithium-lithium symmetric battery of Example 8B is a button cell, with lithium foil as both the positive and negative electrodes (purchased from Xuneng Co., Ltd.), a commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN), and an electrolyte of 65 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.65 μL of VC). Two 15 μL portions of the precursor solution from Example 8 were uniformly dropped onto the surfaces of the positive and negative electrodes, respectively, and then irradiated with UV light at a wavelength of 365 nm for 2 minutes to form two modified films of Example 8A. The two modified films of Example 8A are located between the positive electrode and the separator, and between the negative electrode and the separator, respectively.

[0107] Example 9B

[0108] The lithium-lithium symmetric battery of Example 9B is a self-designed closed-loop in-situ optical microscope battery observation cell. Both its positive and negative electrodes are lithium foil (purchased from Xuneng Co., Ltd.), without a separator. The electrolyte is a 1M LiPF6 DMC / EC solution (v / v = 1 / 1), which needs to fill the entire observation cell (approximately 8 to 10 ml). 2 to 3 μL of the precursor solution from Example 9 is uniformly dropped onto the negative electrode, and then irradiated with UV light at a wavelength of 365 nm for 1.5 minutes to form the modified film of Example 9A. The modified film of Example 9A is located on the negative electrode and faces the positive electrode.

[0109] Lithium-iodine batteries

[0110] The lithium-iodine battery of Example 6C is a button cell. Its positive electrode is activated carbon fiber (ACF) containing 36 wt% iodine, its negative electrode is lithium foil (purchased from Xuneng Co., Ltd.), its separator is a commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN), and its electrolyte is 70 μL of 1M LiTFSI DOL / DME solution (v / v = 1 / 1) containing 2 wt% lithium nitrate (LiNO3). 10 μL of the precursor solution from Example 6 was uniformly dropped onto the surface of the activated carbon fiber, and then irradiated with UV light at a wavelength of 365 nm for 1.5 minutes to form the modified film of Example 6A. The modified film of Example 6A is located between the activated carbon fiber and the separator.

[0111] Comparative Examples 1B, 2B, 3C, 4B (C1B, C2B, C3C, C4B)

[0112] Comparative Example 1B

[0113] Comparative Example 1B's lithium-lithium symmetric battery is a button cell, with both its positive and negative electrodes being lithium foil (purchased from Xuneng Co., Ltd.), its separator being a commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN), and its electrolyte being 95 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.95 μL of VC). Comparative Example 1B's lithium-lithium symmetric battery does not have a modified membrane structure.

[0114] Comparative Example 2B

[0115] Comparative Example 2B's lithium copper battery is a button cell, with lithium foil (purchased from Xuneng Co., Ltd.) as the negative electrode, copper foil (purchased from Xuneng Co., Ltd., model: 1092011) as the positive electrode, commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN) as the separator, and 95 μL of 1M LiPF6 EC / EMC / DMC solution (v / v / v = 1 / 1 / 1) (containing 0.95 μL of VC) as the electrolyte. Comparative Example 2B's lithium copper battery does not have a modified membrane structure.

[0116] Comparative Example 3C

[0117] Comparative Example 3C's lithium-iodine battery is a button cell with an active carbon fiber containing 36 wt% iodine as the positive electrode, a lithium foil (purchased from Xuneng Co., Ltd.) as the negative electrode, a commercial polyethylene separator (purchased from Asahi Kasei, model: SUNFIN) as the separator, and an 80 μL DOL / DME solution of 1M LiTFSI (v / v = 1 / 1) containing 2 wt% lithium nitrate (LiNO3) as the electrolyte. Comparative Example 3C's lithium-iodine battery does not have a modified membrane structure.

[0118] Comparative Example 4B

[0119] Comparative Example 4B's lithium-lithium symmetric battery is a self-designed closed-loop in-field optical microscope observation cell. Both its positive and negative electrodes are lithium foil (purchased from Xuneng Co., Ltd.), without a separator. The electrolyte is a 1M LiPF6 DMC / EC solution (v / v = 1 / 1), which needs to fill the entire observation cell (approximately 8 to 10 ml). Comparative Example 4B's lithium-lithium symmetric battery does not have a modified membrane structure.

[0120] Test Example 1: Charge-Discharge Cycle Performance

[0121] This test example uses lithium metal batteries from Examples 1B, 2B, 3B-1, 3B-2, and 3B-3 as samples. Under 1 atmosphere, the charging rate for the first cycle was 0.1C, and the charging rate after the second cycle was 0.5C; the discharge rate for all cycles was 0.5C; the voltage ranged from 3.0 volts (V) to 4.2V. The results are as follows: Figure 1 , Figure 2 , Figures 3A to 3C As shown.

[0122] from Figure 1 It can be seen that after 118 charge-discharge cycles, the lithium metal battery of Example 1B still has a total capacity of 137 mAh / g, a coulombic efficiency of 98%, and a capacity retention of 92.4%.

[0123] from Figure 2 It can be seen that after 170 charge-discharge cycles, the lithium metal battery of Example 2B still has a total capacity of 128 mAh / g, a coulombic efficiency of 96%, and a capacity retention rate of 87%.

[0124] from Figure 3A It can be seen that after 90 charge-discharge cycles, the lithium metal battery of Example 3B-1 still has a total capacity of 135 mAh / g, a coulombic efficiency of 98.3%, and a capacity retention rate of 99.5%.

[0125] from Figure 3B It can be seen that after 90 charge-discharge cycles, the lithium metal battery of Example 3B-2 still has a total capacity of 137 mAh / g, a coulombic efficiency of 98.9%, and a capacity retention rate of 94.3%.

[0126] from Figure 3C It can be seen that after 88 charge-discharge cycles, the lithium metal battery of Example 3B-3 still has a total capacity of 142 mAh / g, a coulombic efficiency of 98.5%, and a capacity retention rate of 96.0%.

[0127] Depend on Figure 1 , Figure 2 It is known that the lithium metal battery of the present invention, in the state in which a modified film is disposed between the negative electrode and the separator, or in the state in which two modified films are disposed between the negative electrode and the separator, and between the positive electrode and the separator, respectively, can have a coulombic efficiency of more than 95% and a capacity retention of more than 85% after more than 100 charge-discharge cycles, showing that applying the precursor solution to the preparation of lithium metal batteries to form modified films can enable the lithium metal batteries of the two states to have good cycle performance.

[0128] Depend on Figures 3A to 3C It is known that the precursor solution of the present invention, regardless of whether it is coated on the positive electrode, negative electrode or separator of the lithium metal battery, forms a modified film that enables the lithium metal battery to have high coulombic efficiency and high capacity retention after multiple charge-discharge cycles. Specifically, the three types of lithium metal batteries can have a coulombic efficiency of more than 98% and a capacity retention of more than 94% after more than 80 charge-discharge cycles, showing that applying the precursor solution to the preparation of lithium metal batteries to form a modified film can enable the three types of lithium metal batteries to have good cycle performance.

[0129] Furthermore, the inventors discovered in experiments that regardless of whether the precursor solution is dropped onto the side of the separator that contacts the negative electrode to form a modified film as in Example 3A, or whether the precursor solution is dropped onto the side of the separator that contacts the positive electrode so that the modified film is located between the positive electrode and the separator, the cycle performance of the lithium metal batteries of the former and the latter is comparable; that is, the latter lithium metal battery can still have a coulombic efficiency of more than 98% and a capacity retention of more than 94% after more than 80 charge-discharge cycles.

[0130] Experimental Example 2: Galvanostatic cycling voltage profile

[0131] This test example uses lithium-lithium symmetric batteries from Examples 5B-1, 6B-1, 7B, 8B, and Comparative Example 1B as samples, with a charge / discharge capacity of 1 mAh / cm². 2Under the condition of ), at a current density of 0.5 mA / cm², respectively 2 ) and 1mA / cm 2 Polarization tests were conducted, and the results are as follows: Figure 4 As shown.

[0132] Because the lithium-lithium symmetrical batteries of Examples 5B-1, 6B-1, 7B, and 8B differ from the lithium-lithium symmetrical battery of Comparative Example 1B, they have modified films between the positive electrode and the separator, and between the negative electrode and the separator. Figure 4 It can be seen that the lithium-lithium symmetrical batteries of Examples 5B-1, 6B-1, 7B, and 8B have smoother voltage cycle profiles compared to the lithium-lithium symmetrical battery of Comparative Example 1B, indicating that the internal resistance of the lithium-lithium symmetrical batteries of Examples 5B-1, 6B-1, 7B, and 8B can remain constant during the charging and discharging process; and the absolute value of the voltage cycle profile of the lithium-lithium symmetrical batteries of Examples 5B-1, 6B-1, 7B, and 8B deviating from 0V is smaller, indicating that the overvoltage of lithium plating and lithium stripping during the charging and discharging process is lower, which is conducive to achieving uniform lithium plating and lithium stripping behavior and enabling the interface to reach stability more quickly.

[0133] Experimental Example 3: Electrochemical Impedance Spectroscopy (EIS)

[0134] This test used lithium-copper batteries from Examples 4B, 5B-2, 6B-2, and Comparative Example 2B as samples. These batteries simulated the lithium plating (charging) and lithium stripping (discharging) behavior of the copper foil negative electrode in an anode-free lithium battery, and can be considered as half-batteries. Each sample was analyzed using an AC impedance analyzer (purchased from CHInstruments, model: CHI6273e) after 30 charge-discharge cycles. The voltage used for analysis was open-loop potential, and the AC frequency ranged from 100 kHz to 0.01 Hz.

[0135] like Figure 5 As shown, the semicircle diameters of the curves for the lithium copper batteries of Examples 4B, 5B-2, and 6B-2 are smaller than those for the lithium copper battery of Comparative Example 2B, indicating that the lithium copper batteries of Examples 4B, 5B-2, and 6B-2 have lower charge transfer resistance. Therefore, it can be seen that the lithium copper battery of the present invention can indeed maintain a low internal resistance after multiple charge-discharge cycles.

[0136] Experimental Example 4: Galvanostatic charge-discharge (GCD)

[0137] Currently, it is known that the shuttle effect caused by the dissolution of iodides or polysulfides at the positive electrode during the charging and discharging process of lithium-iodine and lithium-sulfur batteries is one of the problems that needs to be solved by those skilled in the art. This experimental example uses lithium-iodine batteries as an example, taking the lithium-iodine batteries of Example 6C and Comparative Example 3C mentioned above as samples, and testing the voltage range from 2.0V to 3.6V under the condition of a charge / discharge rate of 0.5C. Figure 6A As shown, in Example 6C, the capacity in the voltage range of 2.0V to 3.6V remained above 220mAh / g for the first three charge-discharge cycles; Figure 6B As shown, the capacity of Comparative Example 3C in the voltage range of 2.0V to 3.6V decreased to below 200mAh / g in the second charge-discharge cycle.

[0138] The lithium-iodine batteries of Example 6C and Comparative Example 3C were further tested for coulombic efficiency. The coulombic efficiency of Example 6C was 93%, while that of Comparative Example 3C was 76.9%.

[0139] The lithium-iodine battery of Example 6C possesses the modified film formed by curing the precursor solution of the present invention, which suppresses the iodine ions (I₂O₃) dissolved in the electrolyte. - ) and triiodine anion (I3) - The shuttle effect caused by the movement of the polysulfide (C) maintains a stable capacity. In contrast, the lithium-iodine battery of Comparative Example 3C shows a significant decrease in capacity after the second charge-discharge cycle. Similarly, the lithium-sulfur battery equipped with the modified film can also suppress the shuttle effect of negatively charged polysulfides during charge and discharge, thereby improving its coulombic efficiency and maintaining a stable capacity.

[0140] Experimental Example 5: Observation of Lithium Dendrites

[0141] This test used lithium-lithium symmetric batteries from Example 9B and Comparative Example 4B as samples, with a charge / discharge current density of 0.5 mA / cm². 2 After 15 minutes of the first lithium plating, in other words, the areal capacity of the lithium plating reached 0.125 mAh / cm². 2 At that time, the lithium foil negative electrode was photographed, and the results were as follows: Figure 7A and Figure 7B .

[0142] like Figure 7A As shown, in Example 9B, no lithium dendrite formation was observed on the lithium foil anode of the lithium-lithium symmetric battery after 15 minutes of lithium plating; as Figure 7B As shown, in Comparative Example 4B, lithium dendrites were clearly observed forming on the lithium foil anode of the lithium-lithium symmetric battery after 15 minutes of lithium plating. The size of the lithium dendrites was approximately 35 to 50 micrometers. Therefore, the modified film of the present invention can effectively suppress the formation of lithium dendrites on the lithium electrode during the charging and discharging process.

[0143] In summary, the lithium-based battery of the present invention, due to the modified film formed by the curing of the precursor solution, can improve the lithium dendrite problem generated by the lithium metal electrode during the charging and discharging process, thereby improving safety and cycle life. The modified film can also be applied to lithium-sulfur batteries and lithium-iodine batteries to suppress the shuttle effect during the charging and discharging process, which is beneficial to improving product value.

Claims

1. A method for manufacturing a modified film for lithium-ion batteries using a precursor solution, characterized in that: Prepare the precursor solution, which comprises an active ingredient, a lithium salt solution, and an initiator; The active ingredient is a monomer, oligomer, or a combination thereof; The monomer is a methacrylate or its lithium salt, or an acrylate or its lithium salt; Among them, the constituent units of oligomers are , , , , , , , , Or a combination thereof, the terminal structure of the oligomer is , , or combinations thereof; The concentration of the lithium salt solution, expressed as a volumetric molar concentration, ranges from 0.5 M to 4 M. The initiator is 2,2-dimethoxy-phenylacetophenone, benzoyl peroxide, azobisisobutyronitrile, 2-hydroxy-2-methyl-1-phenyl-1-propanone or a combination thereof; Of which, by weight percentage, the active ingredient accounts for 5 wt% to 47.5 wt% of the precursor solution, the lithium salt solution accounts for 50 wt% to 94.9 wt% of the precursor solution, and the initiator accounts for 0.5 wt% to 5 wt% of the precursor solution. The precursor solution is subjected to photopolymerization or thermal curing to form a modified film for lithium batteries; The lithium-ion battery comprises a positive electrode, a negative electrode, a separator, a lithium electrolyte, and at least one modified film, wherein the modified film is formed by curing the precursor solution on the positive electrode, the negative electrode, the separator, or a combination thereof.

2. The method as described in claim 1, characterized in that, The building blocks of oligomers are , , Or a combination thereof, the terminal structure of the oligomer is , Or a combination thereof.

3. The method as described in claim 1, characterized in that, The concentration of the lithium salt solution ranges from 0.8M to 2M.

4. The method as described in claim 1, characterized in that, The lithium salt solution contains a lithium salt and an organic solvent, wherein the organic solvent is 1,3-dioxolane, ethylene glycol dimethyl ether, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, vinylene carbonate, tetraethylene glycol dimethyl ether, dimethyl sulfoxide, acetonitrile, or a combination thereof.

5. The method as described in claim 4, characterized in that, The lithium salt is lithium bis(trifluoromethanesulfonyl)amino, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium fluoride, lithium difluorophosphate, lithium dioxazone borate, lithium difluorooxazone borate, lithium nitride, or a combination thereof.

6. The method as described in claim 1, characterized in that, The precursor solution also contains additives, which are organic compounds or metal salts; Among them, the organic matter is an oligomer having at least one hydroxyl or amino group at the end, polysaccharide, succinic acid, 1,3-sulfonolactone, propylene-1,3-sulfonolactone, fluoroethylene carbonate, ethylene glycol, polysorbate, or a combination thereof. The constituent units of the oligomer having at least one hydroxyl or amino group at the end are: , , , , , , , , or combinations thereof; Among them, the metal salts are lithium nitrate, sodium nitrate, potassium nitrate, or combinations thereof.

7. The method as described in claim 1, characterized in that... The precursor solution further comprises filler material, which is titanium dioxide, silicon dioxide, zirconium dioxide, aluminum oxide, indium tin oxide, lanthanum manganese oxide, lithium sulfide particles, lithium oxide particles, lithium phosphate particles, lithium lanthanum zirconium tantalum oxide, lithium lanthanum aluminum zirconium oxide, or a combination thereof.

8. The method as described in claim 1, characterized in that... The lithium-based battery also contains sulfur or iodine.

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