Alkali metal m-free batteries and modified current collectors, methods of making and applications thereof

Abstract

This invention belongs to the field of batteries, specifically disclosing an alkali metal M-type electrodeless battery, its modified current collector, preparation method, and application. The preparation method of the modified current collector for the alkali metal M-type electrodeless battery is as follows: a precursor solution is composited on the surface of the current collector to be modified, followed by polymerization treatment to form a modified interface on the surface of the current collector, thus obtaining the modified current collector. The polymerization precursor solution includes ether monomers, modifiers, initiators, crosslinking agents, and alkali metal M salts. The modifiers include at least one of the structural formulas 1 () and 2 (). This invention innovatively uses modifiers of formulas 1 and 2 to participate in in-situ polymerization of the interface and modify the current collector. This can buffer the problem of high expansion of electrodeless current collectors. In addition, it can also solve the problems of poor initial efficiency, low rate capability, and especially unsatisfactory long-cycle stability at high rates in electrodeless batteries.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more specifically to the field of alkali metal non-anode batteries. Background Technology

[0002] With the rapid development of high-energy-density rechargeable batteries, alkali metal anodes such as lithium, sodium, and potassium are considered an important development direction for next-generation high-energy-density battery systems due to their high theoretical specific capacity and lowest reduction potential. However, in actual charge-discharge processes, the deposition and stripping of alkali metals on the anode surface are often accompanied by severe interfacial instability problems, such as dendrite growth, intensified interfacial side reactions, and consumption of active metals. This leads to reduced coulombic efficiency, shortened battery cycle life, and even safety hazards.

[0003] To further improve energy density, electrodeless batteries have gradually attracted attention as a highly promising battery configuration. In this system, no metal active material is pre-placed on the negative electrode side initially. During charging, alkali metals migrate from the positive electrode and deposit directly on the surface of the negative electrode current collector to form the working negative electrode. Although electrodeless batteries can significantly improve energy density and simplify electrode structure, the lack of stable nucleation sites and buffer structures leads to more uneven deposition of alkali metals on the current collector surface, severe interfacial polarization, and generally low cycle stability and first-cycle coulombic efficiency, becoming a key bottleneck restricting the practical application of this system.

[0004] Currently, research has attempted to regulate metal deposition behavior through various approaches to address the interface stability issues of metal anodes and anode-free batteries. Firstly, regarding the construction of artificial interface layers, for example, Chinese patent document CN111463403A discloses an anode material modified with a composite artificial solid electrolyte interface film, attempting to protect the electrode sheet through polymers or inorganic materials. However, these traditional artificial interface layers often lack dynamic mechanical toughness and self-healing capabilities. Faced with the huge volume expansion generated during alkali metal deposition, stress concentration easily occurs, leading to coating debonding, cracking, or powdering failure. Secondly, regarding the modification of current collectors in anode-free batteries, Chinese patent document CN111969212A discloses related anode and battery technologies for inducing uniform lithium metal deposition. However, these conventional modifications mostly rely on static physical morphology or rigid coatings, making it difficult to spatially confine the desolvation process of ions and ion flow at the molecular scale through multi-level confinement.

[0005] Therefore, most existing interface modification technologies lack long-term selective coordination of alkali metal ions, dynamic mechanical toughness, and multi-level spatial confinement capabilities, making it difficult to guide uniform nucleation and deposition processes at the molecular scale for extended periods. Developing an interface layer structure that can stably cover the surface of the negative electrode current collector and possesses good ion conductivity, self-healing toughness, and multi-channel synergistic confinement capabilities is of great significance for overcoming the bottlenecks in cycle stability and safety performance of metal negative electrodes and negative electrodeless batteries. Summary of the Invention

[0006] To address the problems of uneven alkali metal deposition, severe interface polarization, and poor cycle stability in existing metal anode batteries and anode-free batteries, this invention provides a method for preparing a modified current collector adapted to anode-free batteries. The aim is to prepare a current collector that meets the high requirements of anode-free batteries and can achieve excellent first-efficiency, rate capability, and long-term cycle stability.

[0007] The second objective of this invention is to provide the modified current collector prepared by the aforementioned method and its application in alkali metal electrodeless batteries.

[0008] A third objective of this invention is to provide an alkali metal negative electrode-free battery comprising the modified current collector described above.

[0009] Unlike secondary batteries with a negative electrode, batteries without a negative electrode lack active material at the negative electrode. This places higher demands on initial efficiency, rate capability, and the homogenization and deposition of alkali metal elements, making it difficult to simultaneously achieve high rate capability and long-term cycle stability. To address this issue, this invention, after in-depth research, provides the following improvement:

[0010] A method for preparing a modified current collector for an alkali metal anode-free battery involves composite a precursor solution onto the surface of the current collector to be modified, followed by polymerization treatment to form a modified interface on the surface of the current collector, thereby obtaining the modified current collector.

[0011] The polymerization precursor solution comprises ether monomers, modifiers, initiators, crosslinking agents, and alkali metal M salts;

[0012] The modifier includes at least one of the structural formulas 1 and 2.

[0013] Formula 1;

[0014] Formula 2;

[0015] In Formula 1, R is at least one of -OH, C1~C4 hydroxyalkyl, C1~C4 alkyl, C1~C4 alkoxy, C1~C4 sulfonyl, C1~C4 sulfonalkoxy, amino, carboxyl, and alkenyl.

[0016] In Formula 2, R1 and R2 are individually at least one of H, C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, amino, phenyl, cyano, and trifluoromethyl.

[0017] Alternatively, R1 and R2 may cyclize to form a cyclic structure, and the cyclic structure may contain substituents, wherein the substituents include at least one of C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, amino, aminoalkyl, phenyl, cyano, and trifluoromethyl; and the cyclic structure may be a saturated five-membered ring, a saturated six-membered ring, or an aromatic ring.

[0018] n is an integer from 2 to 6;

[0019] The alkali metal M includes at least one of Li, Na, and K.

[0020] To address the unique problems of electrodeless batteries, this invention innovatively employs modifiers of Formula 1 and Formula 2 to participate in in-situ polymerization at the interface and to modify the current collector. This can buffer the problem of high expansion of the current collector in electrodeless batteries. In addition, it can solve the problems of poor initial efficiency, low rate capability, and especially unsatisfactory long-term cycle stability at high rates in electrodeless batteries. It can effectively alleviate the homogenization deposition effect of alkali metal M, improve its adaptability to electrodeless systems, and thus improve the initial efficiency, rate capability, and long-term cycle stability at high rates of electrodeless batteries.

[0021] In this invention, Formula 1 includes at least one of Formula 1A, Formula 1B, Formula 1C, and Formula 1D;

[0022] Formula 1A;

[0023] Formula 1B;

[0024] Formula 1C;

[0025] Formula 1D.

[0026] In this invention, Formula 2 includes at least one of Formula 2A, Formula 2B, Formula 2C, Formula 2D, Formula 2E, and Formula 2F;

[0027] Formula 2A; Formula 2B;

[0028] Formula 2C; Formula 2D;

[0029] Equation 2E; Equation 2F.

[0030] In this invention, the modifier comprises Formula 1 and Formula 2, wherein the weight ratio of Formula 1 to Formula 2 is 1:0.1~5.0; further, it can be 1:0.5~2. Further, Formula 2 comprises at least one of Formula 2C and Formula 2D; and Formula 1 comprises at least one of Formula 1A and Formula 1B.

[0031] The research of this invention shows that the innovative use of Formula 1 and Formula 2 in combination in the interfacial polymerization process can optimize the physicochemical structure of the interface and the control between functional groups, and can further synergistically improve the first efficiency, rate capability, and long-term cycle stability of the electrodeless battery.

[0032] In this invention, the ether monomer is a cyclic ether monomer containing two or more oxygen heteroatoms, including at least one of 1,3-dioxolane, 1,3,5-trioxane, 1,3,5-trioxane, 1,3-dioxane, 1,4-dioxane, 1,2-epoxycyclopentene, or 3,4-epoxy-1-butene; more preferably at least one of 1,3-dioxolane or 1,3-dioxane.

[0033] Preferably, the initiator is a compound capable of generating a Lewis acidic cation in the precursor solution; preferably, it includes at least one of trifluoromethanesulfonic acid, tetrafluoroborate, difluorooxalate borate, hexafluorophosphate, boron trifluoride, phosphorus pentafluoride, or a metal salt of trifluoromethanesulfonic acid. The cation in tetrafluoroborate, difluorooxalate borate, hexafluorophosphate, or the metal salt of trifluoromethanesulfonic acid can be an alkali metal cation, such as at least one of lithium, sodium, or potassium.

[0034] Preferably, the crosslinking agent can be a conventional compound having 1 to 3 branching centers and 2 to 6 crosslinking units modified on the branching centers, wherein the branching centers can be alkyl centers, ether centers, etc. The crosslinking units can be at least one of epoxy, acrylate, and acrylamide. As an optional embodiment, the crosslinking agent can include at least one of ethylene glycol dimethacrylate (EGDMA), 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), neopentyl ditrimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), propoxylated TMPTA, alcohol diacrylate (NPGDA), 1,4-butanediol diacrylate (BDDA), pentaerythritol tetraacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), glycidyl methacrylate (GMA), and trimethylolpropane triglycidyl ether (TTE).

[0035] Preferably, the alkali metal M salt is at least one of the following: bis(trifluoromethanesulfonyl)imide salt, hexafluorophosphate, tetrafluoroborate, perchlorate, bis(oxalate)borate, bis(oxalate)borate, or di(oxalate)phosphate.

[0036] In this invention, the initiator concentration in the precursor solution is 0.1~1M; the concentration of the alkali metal M salt is 0.5~3.0M; the modifier is 5~20wt.% of the total weight of the ether monomer and the alkali metal M salt; and the crosslinking agent is 0.5~10wt.% of the total weight of the ether monomer and the alkali metal M salt.

[0037] Furthermore, in the precursor solution, the initiator concentration is 0.3~0.6M; the alkali metal M salt concentration is 1~3.0M; the modifier is 5~15wt.% of the total weight of the ether monomer and the alkali metal M salt; and the crosslinking agent is 1~5wt.% of the total weight of the ether monomer and the alkali metal M salt.

[0038] Furthermore, in the precursor solution, the initiator concentration is 0.4~0.5M; the alkali metal M salt concentration is 2~2.5M; the modifier is 8~12 wt.% of the total weight of the ether monomer and the alkali metal M salt; and the crosslinking agent is 1.5~3 wt.% of the total weight of the ether monomer and the alkali metal M salt.

[0039] In this invention, the current collector includes at least one of the following: planar conductive metal current collector, 3D conductive metal current collector, carbon material substrate, polymer-based composite metal current collector, and composite current collector with a surface modified with a metalophilic layer;

[0040] Preferably, the precursor solution is applied to the surface of the current collector by means of drop coating, spin coating, spraying, scraping or dipping;

[0041] Preferably, the polymerization temperature is below 150°C, and more preferably 15~60°C;

[0042] Preferably, the polymerization time is less than 200 hours; for example, when the temperature is relatively high, the polymerization time can be shortened to less than 20 hours, and when the temperature is relatively low, such as 15~40℃, the polymerization time can be 40~80 hours.

[0043] Preferably, the thickness of the modified interface is 10 nm to 50 μm; more preferably, it can be 50 nm to 0.5 μm.

[0044] The present invention also provides a modified current collector prepared by the preparation method described above.

[0045] In this invention, the preparation method can endow the modified current collector with special physicochemical properties, and the modified current collector with the aforementioned properties obtained by the preparation method can unexpectedly adapt to the special application requirements without a negative electrode, and can exhibit excellent first-efficiency, rate and long-cycle performance at high rates.

[0046] The present invention also provides an application of the modified current collector prepared by the above preparation method, which is used to prepare an alkali metal M electrodeless battery.

[0047] The present invention also provides an alkali metal M-type electrodeless battery, comprising the modified current collector prepared by the aforementioned preparation method.

[0048] The alkali metal M-type negative electrode-free battery of the present invention, except for the modified current collector described in the present invention, has other components and structural relationships that are well known.

[0049] For example, the aforementioned negative electrode-free battery includes a positive electrode assembly (positive electrode sheet), an electrolyte system, and a negative electrode current collector, wherein the negative electrode current collector is the modified current collector described in this invention.

[0050] The electrolyte system is at least one of liquid electrolyte, gel electrolyte, or solid electrolyte;

[0051] The positive electrode includes a current collector and a positive electrode material composited on its surface. The positive electrode material includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material includes, but is not limited to, lithium cobalt oxide, lithium manganese oxide, ternary nickel-cobalt-manganese lithium, lithium nickel-manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, Prussian blue, sodium vanadium phosphate, and layered oxides such as Na. 0.44 At least one of MnO2;

[0052] Preferably, a separator is allowed between the positive and negative electrodes of the battery cell, including but not limited to at least one of polyurethane (PI) separator, glass fiber (GF) separator, polyethylene (PE) separator, polypropylene (PP) separator, PE-PP composite separator, and surface-coated modified separators.

[0053] In this invention, the negative electrode-free battery can be obtained by assembling a modified current collector and a positive electrode, or by preparing it based on an in-situ preparation method. For example, the positive electrode and a current collector coated with a precursor solution can be assembled to form a precursor battery, and then encapsulated for in-situ polymerization to obtain the negative electrode-free battery.

[0054] Beneficial effects

[0055] 1) By constructing the modified interface layer on the surface of the negative electrode current collector, a modifier structural unit with molecular recognition and multi-point coordination ability is introduced, which can selectively coordinate and spatially confine alkali metal ions, which is beneficial to reduce the nucleation overpotential of alkali metals and improve the nucleation uniformity.

[0056] 2) The interface layer can regulate the local ion flux distribution at the negative electrode interface, promote the uniform deposition of alkali metal on the current collector surface and effectively suppress dendrite growth, thereby significantly improving the cycle stability and operational safety of the negative electrode-free battery and the metal negative electrode battery.

[0057] 3) The interface layer forms a continuous covering structure on the surface of the negative electrode current collector through in-situ polymerization. It has a strong interface bond with the current collector and electrolyte system, and has low interface impedance, which is beneficial to reduce polarization and is suitable for high energy density battery systems.

[0058] 4) The interface layer material system of the present invention has both good ion conductivity and structural stability, is suitable for negative electrode-free battery configurations, and is compatible with various electrolyte systems such as liquid, gel and solid states;

[0059] 5) The preparation process of the present invention is simple and can be achieved by conventional coating combined with in-situ polymerization. It is easy to be compatible with existing battery electrode preparation and cell assembly processes and has good potential for large-scale application. Attached Figure Description

[0060] Figure 1 The image shows a SEM image of the coating finally polymerized on the copper foil in Example 1, with the left image being a low magnification (scale bar 50 μm) and the right image being a high magnification (scale bar 20 μm). Detailed Implementation

[0061] The following examples are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the claims of the present invention.

[0062] In this embodiment, a CR2032 button cell was used for electrochemical performance evaluation. The positive electrode material was either lithium iron phosphate (LiFePO4) or nickel-cobalt-manganese ternary material (NCM). The positive electrode preparation method is as follows: 0.32 g of positive electrode active material, 0.04 g of acetylene black conductive agent, and 0.04 g of polyvinylidene fluoride (PVDF) binder were added to 2 g of N-methylpyrrolidone (NMP) and stirred thoroughly to form a uniform slurry. The resulting slurry was coated onto the surface of an aluminum foil current collector, vacuum dried at 80 °C for 12 h, and then punched into positive electrode sheets with a diameter of 12 mm and an areal capacity of approximately 2.0 mAh cm⁻¹. -2 .

[0063] The negative electrode current collector is made of copper foil with a thickness of 10 μm. The interface layer is formed on the surface of the copper foil through in-situ polymerization of the precursor solution. The battery is assembled in an argon glove box (oxygen content < 0.01 ppm, water content < 0.01 ppm).

[0064] Example 1

[0065] The precursor solution has the following composition:

[0066] The ether monomer is 1,3-dioxolane (DOL), the alkali metal salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the modifier is formula 2A, the initiator is lithium difluorooxalate borate (LiDFOB), and the crosslinking agent is trimethylolpropane triglycidyl ether (TTE). It was prepared in an argon glove box (oxygen content less than 0.01 ppm, moisture content less than 0.01 ppm) according to the following steps:

[0067] The preparation method is as follows:

[0068] 1) Dissolve LiTFSI in DOL to form a basic solution with a lithium salt concentration of 2.0 mol / L;

[0069] 2) Add 10 wt.% of Formula 2A and 1.5 wt.% of TTE by weight of the base solution to the base solution, and stir thoroughly to form a homogeneous mixture;

[0070] 3) Add 0.5 mol / L LiDFOB as an initiator to obtain the interfacial layer precursor solution;

[0071] 4) The precursor solution obtained in step (3) is uniformly drop-coated onto the surface of the bare copper foil used as the negative electrode current collector (the coating thickness is 300±20nm) as the negative electrode interface modification layer.

[0072] Electrodeless battery assembly and electrochemical performance testing:

[0073] Assembly conditions: In a high-purity glove box filled with argon, a CR2032 coin cell was assembled using copper foil coated with a precursor solution as the negative electrode (without pre-placed active lithium metal material), a commercial lithium iron phosphate (LiFePO4) electrode as the positive electrode, and a Celgard 2400 polypropylene microporous membrane as the separator. During assembly, an appropriate amount (e.g., 30-50 μL) of a conventional ether-based liquid electrolyte (such as the base solution from step 1) was added dropwise to the positive electrode and separator side to fully wet the positive electrode. The above components were sequentially assembled into a CR2032 coin cell. After sealing, the cell was allowed to stand at room temperature (25 °C) for 72 h for in-situ ring-opening polymerization, allowing the polymer electrolyte to solidify in-situ on the copper foil surface and at the separator interface, forming a continuously covering interface layer.

[0074] Cyclic performance test of the electrodeless battery: At 25 ℃, with the charge and discharge voltage range set to 2.5 V ~ 4.0 V, constant current charge and discharge test was conducted at a rate of 0.5 C. The coulombic efficiency of the electrodeless battery reached 89.3% in the first cycle; after 80 charge and discharge cycles, the battery capacity retention rate still reached 82.6%.

[0075] Example 2

[0076] Compared with Example 1, the only difference is that the type of modifier in the precursor solution was changed (the total amount of modifier added was kept at 10 wt.% of the weight of the base solution). The experimental groups were set as follows:

[0077] Group A: The modifier is Formula 2B;

[0078] Group B: The modifier is Formula 2D;

[0079] Group C: The modifier is Formula 2C;

[0080] Group D: The modifier is Formula 1A;

[0081] Group E: The modifier is Formula 1B;

[0082] Group F: The modifier is a mixture of Formula 2D and Formula 1A in a weight ratio of 1:1;

[0083] Group G: The modifier is a mixture of Formula 2C and Formula 1A in a weight ratio of 1:1.

[0084] Other assembly operations and electrochemical test parameters were the same as in Example 1. The electrochemical test results of each group of full cells without a negative electrode are summarized in Table 1:

[0085]

[0086]

[0087] As can be seen from Examples 1 and 2, the modifiers described in this invention, especially the modifiers combining Formula 1 and Formula 2, can achieve synergy, optimize the network structure of the electrolyte, and improve its first-efficiency and cycle stability.

[0088] Example 3

[0089] Compared with Example 1, the difference is that the concentration of LiTFSI in the base solution is increased to 2.5 mol / L; the modifier is replaced with a composite modifier of Formula 2C and Formula 1A in a weight ratio of 2:1, and the total amount of the composite modifier added is 12 wt.% of the mass of the base solution. Other operations and parameters are the same as in Example 1.

[0090] Electrochemical tests were conducted using the method described in Example 1. The results showed that the first-cycle coulombic efficiency of the electrodeless battery was as high as 92.8%; after 100 cycles at 0.5 C rate and 25 °C, the capacity retention was 88.5%.

[0091] Example 4

[0092] Compared with Example 1, the difference is that the modifier is replaced with a composite system of Formula 2D and Formula 1B in a mass ratio of 1:1 (total addition amount 10 wt.%); the amount of crosslinking agent TTE is increased to 3.0 wt.%.

[0093] Electrochemical tests were conducted using the method described in Example 1. The results showed that the first-cycle coulombic efficiency of the electrodeless battery was 93.5%; after 120 cycles at 0.5 C rate and 25°C, the capacity retention was still as high as 89.2%.

[0094] Example 5

[0095] Compared with Example 1, the difference is that: in the precursor solution, the modifier adopts a composite system of Formula 2C and Formula 1A (mass ratio 1:1), and the total addition amount is reduced to 8 wt.% of the base solution mass; the concentration of the initiator LiDFOB is slightly adjusted to 0.4 mol / L. The assembly method is the same as in Example 1.

[0096] The test conditions were adjusted to: at room temperature of 25 ℃, the charge and discharge voltage range was 2.5 V ~ 4.0 V, and the charge and discharge rate was significantly increased to 1.0 C for high-intensity constant current cycle testing.

[0097] Test results show that even under harsh conditions of high current density, the first-cycle coulombic efficiency of this electrodeless battery can still be maintained at 91.5%; after 150 high-rate cycles, the capacity retention rate reaches 85.6%.

[0098] Comparative Example 1

[0099] Compared to Example 1, the only difference is that no modifier is added to the precursor solution. All other operations and parameters are the same as in Example 1.

[0100] Test results: The first-cycle coulombic efficiency of this electrodeless battery was only 75.2%, and after 50 cycles at 0.5C rate and 25℃, the capacity retention dropped sharply to 32.4%.

[0101] Comparative Example 2

[0102] Compared to Example 1, the only difference is that no crosslinking agent is added to the precursor solution. All other operations, parameters, and components are the same as in Example 1.

[0103] Test results: The first-cycle coulombic efficiency of this electrodeless battery was 85.4%, but after 80 cycles at 0.5C rate and 25℃, the capacity retention plummeted to 48.6%. Disassembly and observation revealed severe cracking and pulverization of the negative electrode interface layer.

[0104] Comparative Example 3

[0105] Compared with Example 1, the only difference is that no crosslinking agent (TTE) and initiator (LiDFOB) are used in the precursor solution. Instead, the same amount of modifier is directly dissolved as a free additive in a conventional liquid electrolyte (1,3-dioxolane / ethylene glycol dimethyl ether volume ratio 1:1, containing 2.0 mol / L LiTFSI) and directly injected into the assembled negative electrode-free battery.

[0106] Test results: The first-cycle coulombic efficiency of this electrodeless battery is 83.1%, and after 80 cycles at 0.5C rate and 25℃, the capacity retention is only 52.3%.

[0107] Comparative Example 4

[0108] Compared with Example 1, the only difference is that α-D-glucose is used as a modifier in the precursor solution, while the other operations, parameters and components are the same as in Example 1.

[0109] Test results: The first-cycle coulombic efficiency of this electrodeless battery is 80.5%, and after 80 cycles at 0.5 C rate and 25℃, the capacity retention rate is only 55.2%.

[0110] Comparative Example 5

[0111] Compared to Example 1, the only difference is that a traditional non-in-situ solution casting method is used to construct the PEO (polyethylene oxide)-based interface layer, replacing the in-situ polymerization process of this application. The specific operation is as follows:

[0112] 1) Dissolve high molecular weight PEO (Mw≈600,000), LiTFSI (in a molar ratio of EO:Li of 18:1) and an equal amount (10 wt.%) of modifier (Formula 2A) in acetonitrile solvent and stir until homogeneous to form a slurry. No crosslinking agent or initiator is added to this system.

[0113] 2) The above slurry is evenly coated onto the surface of bare copper foil using a scraper, and then placed in a vacuum drying oven at 60 ℃ for 24 h to completely evaporate the acetonitrile solvent, thus obtaining a pre-cured PEO-based composite solid interface film.

[0114] 3) Assemble the copper foil with the non-in-situ PEO interface film, along with the separator and the positive electrode, into a negative electrode-free battery. Other electrochemical testing conditions are the same as in Example 1.

[0115] Test results: The negative electrode-free battery is extremely polarized at room temperature (25 ℃), with a coulombic efficiency of only 68.5% in the first cycle. After 80 cycles at 0.5 C rate, the capacity retention rate plummeted to 41.2%.

Claims

1. A method for preparing a modified current collector for an alkali metal negative electrode-free battery, characterized in that, A precursor solution is composited on the surface of the current collector to be modified, followed by polymerization treatment to form a modified interface on the surface of the current collector, thereby obtaining the modified current collector. The polymerization precursor solution comprises ether monomers, modifiers, initiators, crosslinking agents, and alkali metal M salts; The modifier includes at least one of the structural formulas 1 and 2. Formula 1; Formula 2; In Formula 1, R is at least one of -OH, C1~C4 hydroxyalkyl, C1~C4 alkyl, C1~C4 alkoxy, C1~C4 sulfonyl, C1~C4 sulfonalkoxy, amino, carboxyl, and alkenyl. In Formula 2, R1 and R2 are individually at least one of H, C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, amino, aminoalkyl, phenyl, cyano, and trifluoromethyl. Alternatively, R1 and R2 may cyclize to form a cyclic structure, and the cyclic structure may contain substituents, wherein the substituents include at least one of C1-C6 alkyl, C1-C6 alkoxy, halogen, hydroxyl, amino, phenyl, cyano, and trifluoromethyl; and the cyclic structure may be a saturated five-membered ring, a saturated six-membered ring, or an aromatic ring. n is an integer from 2 to 6; The alkali metal M includes at least one of Li, Na, and K.

2. The preparation method according to claim 1, characterized in that, Formula 1 includes at least one of Formula 1A, Formula 1B, Formula 1C, and Formula 1D; Formula 1A; Formula 1B; Formula 1C; Formula 1D.

3. The preparation method according to claim 1, characterized in that, Formula 2 includes at least one of Formula 2A, Formula 2B, Formula 2C, Formula 2D, Formula 2E, and Formula 2F; Formula 2A; Formula 2B; Equation 2C; Formula 2D; Equation 2E; Equation 2F.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The modifier comprises Formula 1 and Formula 2, wherein the weight ratio of Formula 1 and Formula 2 is 1:0.1~5.

0.

5. The preparation method according to claim 1, characterized in that, The ether monomers are cyclic ether monomers containing two or more oxygen heteroatoms, including at least one of 1,3-dioxolane, 1,3,5-trioxane, 1,3,5-trioxane, 1,3-dioxane, 1,4-dioxane, 1,2-epoxycyclopentene, or 3,4-epoxy-1-butene; more preferably at least one of 1,3-dioxolane or 1,3-dioxane. Preferably, the initiator is a compound capable of generating Lewis acidic cations in the precursor solution; preferably, it includes at least one of trifluoromethanesulfonic acid, tetrafluoroborate, difluorooxalate borate, hexafluorophosphate, boron trifluoride, phosphorus pentafluoride, or a metal salt of trifluoromethanesulfonic acid. Preferably, the crosslinking agent comprises at least one of polyfunctional glycidyl ether compounds or polyfunctional acrylate compounds; more preferably, it comprises at least one of ethylene glycol dimethacrylate (EGDMA), 1,6-hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), neopentyl ditrimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), propoxylated TMPTA, alcohol diacrylate (NPGDA), 1,4-butanediol diacrylate (BDDA), pentaerythritol tetraacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), glycidyl methacrylate (GMA), and trimethylolpropane triglycidyl ether (TTE). Preferably, the alkali metal M salt is at least one of the following: bis(trifluoromethanesulfonyl)imide salt, hexafluorophosphate, tetrafluoroborate, perchlorate, bis(oxalate)borate, bis(oxalate)borate, or di(oxalate)phosphate.

6. The preparation method according to any one of claims 1 to 5, characterized in that, In the precursor solution, the initiator concentration is 0.1~1M; the alkali metal M salt concentration is 0.5~3.0M; the modifier is 5~20 wt.% of the total weight of the ether monomer and the alkali metal M salt; and the crosslinking agent is 0.5~10 wt.% of the total weight of the ether monomer and the alkali metal M salt. Further, in the precursor solution, the initiator concentration is 0.3~0.6M; the alkali metal M salt concentration is 1~3.0M; the modifier is 5~15wt.% of the total weight of the ether monomer and the alkali metal M salt; and the crosslinking agent is 1~5wt.% of the total weight of the ether monomer and the alkali metal M salt. Furthermore, in the precursor solution, the initiator concentration is 0.4~0.5M; the alkali metal M salt concentration is 2~2.5M; the modifier is 8~12 wt.% of the total weight of the ether monomer and the alkali metal M salt; and the crosslinking agent is 1.5~3 wt.% of the total weight of the ether monomer and the alkali metal M salt.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The current collector includes at least one of the following: planar conductive metal current collector, 3D conductive metal current collector, carbon material substrate, polymer-based composite metal current collector, and composite current collector with a surface modified with a metal-philic layer; Preferably, the precursor solution is applied to the surface of the current collector by means of drop coating, spin coating, spraying, scraping or dipping; Preferably, the polymerization temperature is below 150°C; Preferably, the polymerization time is less than 200 hours; Preferably, the thickness of the modified interface is 10 nm to 50 μm.

8. A modified current collector prepared by the preparation method according to any one of claims 1 to 7.

9. The application of a modified current collector prepared by the method according to any one of claims 1 to 7, characterized in that, It was used to prepare alkali metal M-type negative electrode-free batteries.

10. An alkali metal M-type electrodeless battery, characterized in that, The modified current collector is prepared by the preparation method according to any one of claims 1 to 7.

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