Composite pole piece and preparation method and application thereof

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a composite pole piece as well as a preparation method and application thereof. The composite pole piece comprises a positive pole piece which is provided with two opposite surfaces in the thickness direction of the positive pole piece; the solid electrolyte layer is arranged on the surface of at least one side of the positive pole piece, and the solid electrolyte layer comprises the following raw materials in percentage by mass: 1-12% of inorganic solid electrolyte, 17-56% of plasticizer, 10-20% of lithium salt, 27-59% of photosensitive oligomer, 1-5% of negative pole film-forming additive and 2-3% of photoinitiator. According to the composite pole piece integrating the positive pole piece and the solid-state electrolyte layer provided by the invention, by limiting the composition of the raw materials of the solid-state electrolyte layer, the interface reaction of the negative pole can be well considered, good interface contact with the positive pole is realized, and the cycle and rate performance of the battery is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of secondary batteries, and specifically relates to a composite electrode, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries, with their high energy density, long lifespan, and environmental friendliness, have successfully dominated the energy storage and power equipment markets. Currently, commercial lithium-ion batteries primarily use organic electrolytes, but these electrolytes present safety concerns such as high toxicity, leakage, and flammability. Therefore, replacing liquid electrolytes with non-flammable solid electrolytes is considered one of the most promising strategies for improving lithium-ion battery safety and will become a key technological development direction for next-generation batteries.

[0003] Liquid electrolytes can construct smooth ion migration paths between the positive and negative electrodes due to their good wetting ability with organic solvents. However, there is a solid-solid contact between the solid electrolyte and the electrode, and the effective contact area is insufficient, which seriously hinders ion migration, resulting in excessive internal resistance of the battery and unsatisfactory battery performance. Therefore, the current development of all-solid-state batteries is still limited by the problems of low ionic conductivity and poor interface compatibility. In addition, the negative electrode / solid electrolyte interface faces huge challenges, mainly dendrite growth and interface instability. During the cycle process, uneven deposition of lithium usually leads to the growth of lithium dendrites, which may pierce the solid electrolyte, leading to short circuit and failure. In addition, the rigid properties of the positive electrode material hinder the effective transport of ions, and volume changes may cause cracks, delamination and interface degradation, which in severe cases lead to increased battery resistance and capacity decay.

[0004] In order to solve the above problems, some battery positive electrodes integrating solid electrolytes and positive electrode materials have been disclosed in the prior art. However, these solutions mainly focus on the interface contact problem between the positive electrode and the solid electrolyte, and are unable to take into account the lithium deposition and interface reaction at the negative electrode interface. At the same time, the electrical conductivity needs to be further improved. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present application is to overcome the above-mentioned defects in the prior art, thereby providing a composite electrode and its preparation method and application.

[0006] To this end, this application provides the following technical solutions:

[0007] According to one aspect of the present application, a composite pole piece is provided, comprising:

[0008] The positive electrode sheet has two opposite surfaces in its thickness direction;

[0009] A solid electrolyte layer is provided on at least one side of the positive electrode sheet.

[0010] Among them, based on the total mass of the solid electrolyte layer raw materials, it includes: 1%-12% inorganic solid electrolyte, 17%-56% plasticizer, 10%-20% lithium salt, 27%-59% photosensitive oligomer, 1%-5% negative electrode film-forming additive, and 2%-3% photoinitiator.

[0011] As an example, based on the total mass of the solid electrolyte layer raw material, the mass percentage of the inorganic solid electrolyte can be 1%, 3%, 5%, 7%, 9%, 10%, 12%, or within the range of any of the above values; the mass percentage of the plasticizer can be 17%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 56%, or within the range of any of the above values; the mass percentage of the lithium salt can be 10%, 12%, 14%, 15%, 16%, 18%, 20%, or within the range of any of the above values. The mass percentage of the photosensitive oligomer can be 27%, 30%, 35%, 40%, 45%, 50%, 55%, 59%, or within the range composed of any of the above values; the mass percentage of the negative electrode film-forming additive can be 1%, 2%, 3%, 4%, 5%, or within the range composed of any of the above values; the mass percentage of the photoinitiator can be 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8%, 3%, or within the range composed of any of the above values, as long as the sum of the contents of each component is 100%.

[0012] In some optional embodiments, the thickness of the solid electrolyte layer is 50-150 μm. As an example, the thickness of the solid electrolyte layer can be 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or any range thereof.

[0013] In some optional embodiments, the photosensitive oligomer includes at least one of polyethylene glycol dimethacrylate and polyethylene glycol diacrylate; in the present application, the selected photosensitive oligomer can coordinate with lithium ions through the ether oxygen atoms in its molecular chain, thereby further promoting lithium ion transmission.

[0014] In some optional embodiments, the weight average molecular weight of the photosensitive oligomer is 200-600. As an example, the weight average molecular weight of the photosensitive oligomer can be 200, 250, 300, 350, 400, 450, 500, 550, 600, or any range thereof.

[0015] In some optional embodiments, the plasticizer includes at least one nitrile compound. In this application, the conductivity can be further improved by optimizing the plasticizer. This is because these two types of plasticizers have relatively high dielectric constants. During the subsequent ultraviolet (UV) curing process, the plasticizers can form a eutectic system with the lithium salt, thereby improving the conductivity of the solid electrolyte.

[0016] In some optional embodiments, the negative electrode film-forming additive includes a negative electrode film-forming additive containing a 5- to 6-membered heterocyclic ring;

[0017] And / or, the inorganic solid electrolyte includes at least one of an oxide electrolyte, a sulfide electrolyte, and a halide electrolyte. As an example, the inorganic solid electrolyte includes LiAlO2, LiO2, LLZO garnet-type solid electrolyte (such as Li7La3Zr2O 12 )、LATP(Li 1.3 Al 0.3 Ti 1.7 (PO4)3), LISICON (such as Li 14 Zn(GeO4)4), sulfide electrolytes include but are not limited to: Li 10 GeP2S 12 (LGPS), Li5PS5Cl (Argyrodite type), halide electrolytes include but are not limited to: Li3YCl6 / Li3YBr6, etc.

[0018] In some optional embodiments, the plasticizer includes at least one of succinonitrile, adiponitrile, tetracyanoethylene, ethylene glycol dipropionitrile ether, and sulfonyl dipropionitrile;

[0019] And / or, the negative electrode film-forming additive includes at least one of fluoroethylene carbonate, bisfluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, propane sultone, and vinyl sulfate.

[0020] In some optional embodiments, the photoinitiator includes at least one of 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, 2-isopropylthioxanthone, and 1-hydroxycyclohexylphenyl ketone;

[0021] And / or, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium bis(oxalatoborate) (LiBOB), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), and lithium bis(fluorosulfonyl imide) (LiFSI).

[0022] According to another aspect of the present application, a method for preparing a composite electrode is provided, comprising the following steps:

[0023] S1, prepare the positive electrode;

[0024] S2, preparing a slurry according to the raw material composition of the solid electrolyte layer, placing the slurry on at least one side of the positive electrode plate, and curing it with ultraviolet light.

[0025] This application uses ultraviolet light curing technology to cure the solid electrolyte layer. The slurry cures quickly. On the one hand, it can ensure that the organic-inorganic solid electrolyte and other components in the solid electrolyte layer are evenly and densely distributed; on the other hand, the photoinitiator needs to form a cross-linked structure with the help of photocuring to achieve "in-situ curing plasticization" to avoid cracks, delamination and interface degradation that may be caused by volume changes in the positive electrode.

[0026] In some optional embodiments, the parameters of the ultraviolet curing include: an illumination wavelength of 280-400 nm; an illumination time of 10-20 s / time, 3-5 illumination times, and an illumination interval of 2-8 s.

[0027] This application uses intermittent lighting for curing, which can ensure the curing effect and is conducive to a more uniform distribution of components in the raw material formula of the solid electrolyte layer. Continuous curing may lead to uneven curing, excessive surface curing and incomplete curing of the inner layer.

[0028] According to another aspect of the present application, an all-solid-state battery is provided, comprising the above-mentioned composite pole piece.

[0029] According to another aspect of the present application, there is provided an electrical device comprising the above-mentioned all-solid-state battery.

[0030] Those skilled in the art will appreciate that the all-solid-state battery provided herein includes, in addition to the aforementioned composite electrode sheet, a negative electrode sheet, a housing, and other structural components. During the battery's charge and discharge process, lithium ions are intercalated and released back and forth between the positive and negative electrode sheets. The solid electrolyte layer conducts ions between the positive and negative electrode sheets, preventing a short circuit between the positive and negative electrodes while allowing lithium ions to pass through.

[0031] As an example, a positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector. The materials, composition, and manufacturing methods of the positive electrode sheet used in the all-solid-state battery of the present application may include any technology disclosed in the prior art.

[0032] In the present application, the positive electrode active material layer may include positive electrode active materials, conductive agents, binders, etc. The mass ratio of each component is conventional in the field and is not specifically limited in this application. The positive electrode active material may include one or more of lithium cobalt oxide and its modified materials, lithium iron phosphate and its modified materials, lithium manganese iron phosphate and its modified materials, lithium nickel cobalt manganese oxide and its modified materials, lithium nickel cobalt aluminum oxide and its modified materials, lithium nickel oxide and its modified materials, lithium manganese oxide and its modified materials. The modified materials of each of the above-mentioned positive electrode active materials may be doping modification and / or surface coating modification of the positive electrode active material.

[0033] As an example, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector has two surfaces facing each other in the thickness direction of the negative electrode current collector, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector. The negative electrode plate of the present application may also be a metal sheet, such as a lithium sheet or a lithium alloy sheet. The materials, composition, and manufacturing method of the negative electrode plate used in the all-solid-state battery of the present application may include any technology disclosed in the prior art.

[0034] In the present application, the negative electrode active material layer may include a negative electrode active material, a conductive agent, a binder, etc. The mass ratio of each component is conventional in the field and is not specifically limited in this application. The negative electrode active material may include one or more of graphite, graphene, carbon nanotubes, mesophase microcarbon beads, soft carbon, hard carbon, silicon-based materials, etc.

[0035] The present application does not specifically limit the preparation method of the all-solid-state battery. The all-solid-state battery can be prepared using conventional preparation methods in the art. The assembly methods of the all-solid-state battery include but are not limited to button batteries, mold batteries, square shell batteries, soft-pack batteries, etc.

[0036] It is understood that in the electrical equipment provided in this application, the all-solid-state battery can be used as a power source for the electrical equipment, or as an energy storage unit for the electrical equipment. The electrical equipment may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0037] The electrical equipment provided in this application has the same advantages as the above-mentioned all-solid-state batteries due to the use of the all-solid-state batteries provided in this application, which will not be repeated here.

[0038] The technical solution of this application has the following advantages:

[0039] 1. The composite electrode provided by the present application comprises: a positive electrode having two opposing surfaces in the thickness direction thereof; a solid electrolyte layer disposed on at least one surface of the positive electrode, wherein, based on the total mass of the raw materials of the solid electrolyte layer, the composite electrode comprises: 1%-12% inorganic solid electrolyte, 17%-56% plasticizer, 10%-20% lithium salt, 27%-59% photosensitive oligomer, 1%-5% negative electrode film-forming additive, and 2%-3% photoinitiator. The composite electrode provided by the present application, which integrates the positive electrode and the solid electrolyte layer, can well take into account the negative electrode interface reaction and achieve good interface contact with the positive electrode by limiting the composition of the raw materials of the solid electrolyte layer. Specifically, on the one hand: the introduction of the negative electrode film-forming additive into the solid electrolyte layer, which is pioneered by the present application, can form a dense and uniform solid electrolyte interface (SEI) on the negative electrode surface, build a close contact interface with the negative electrode, reduce contact impedance, avoid negative electrode interface reaction, and extend battery life. On the other hand: under the action of photoinitiator, inorganic solid electrolyte and photosensitive oligomer can obtain a composite electrode integrating organic-inorganic solid electrolyte and positive electrode, which can achieve good interface contact with the positive electrode and improve conductivity and rate performance; the addition of plasticizer can improve the mechanical flexibility of the solid electrolyte layer, and the flexibility of the electrolyte can alleviate the volume effect caused by the expansion stress of the positive electrode, which is beneficial to the effective transmission of lithium ions and ensure the long life of the all-solid-state battery; the addition of lithium salt plays a positive role in improving conductivity. In addition, the polar bonds in the plasticizer can also be Li + It provides a migration path for the transport of ions and improves the conductivity.

[0040] 2. In the composite electrode provided in this application, the thickness of the solid electrolyte layer is 50-150 μm. In this application, by limiting the thickness of the solid electrolyte layer, it is avoided that the thickness is too thin, which will have a poor buffering effect on the electrode stress, and the thickness is too thick, which will lead to increased impedance.

[0041] 3. The preparation method of the composite electrode provided in the present application comprises the following steps: S1, preparing a positive electrode; S2, preparing a slurry according to the raw material composition of the above-mentioned solid electrolyte layer, placing the slurry on at least one side of the surface of the positive electrode, and curing it with ultraviolet light. The preparation method of the present application is simple to operate, does not require complicated processing or steps such as preparing the solid electrolyte layer in steps, and is easy to promote and apply. At the same time, the selection of photoinitiators and photosensitive oligomers in the raw materials can be cured by ultraviolet light curing process, avoiding the formation of holes in the organic-inorganic solid electrolyte due to solvent volatilization during the preparation process, thereby obtaining a highly dense, defect-free uniform surface and further improving the conductivity.

[0042] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. DETAILED DESCRIPTION

[0043] The following examples are provided to further better understand the present application, but are not limited to the best implementation mode described herein, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the scope of protection of the present application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application text are intended to cover non-exclusive inclusions.

[0045] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0046] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values ​​and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter can be, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0048] In the description of the embodiments of the present application, the term "at least one" refers to one or more than two (including two).

[0049] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0050] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0051] The present application is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present application in any way.

[0052] Example 1

[0053] This embodiment provides a composite electrode sheet, including a positive electrode sheet and a solid electrolyte layer disposed on the surface of the positive electrode sheet. The specific composition and preparation method of the composite electrode sheet are as follows:

[0054] 1) Preparation of positive electrode sheet. The positive electrode material is mixed with N-methylpyrrolidone (NMP) in the following mass ratio: lithium iron phosphate: conductive agent (SuperP): carbon nanotubes (CNT): binder (PVDF) = 95:0.8:0.4:3.8, and stirred to obtain positive electrode slurry. The positive electrode slurry is then evenly coated on one side of the positive electrode current collector aluminum foil with a single-side surface density of 180-220 g / m 2 (The single-sided density in this embodiment is 200g / m 2 ), and dried at 60°C for 4h to obtain a positive electrode sheet.

[0055] 2) Preparation of composite electrolyte slurry. Weigh polyethylene glycol dimethacrylate (Mw = 550), succinonitrile, photoinitiator 2-hydroxy-2-methylphenylpropane-1-one, lithium salt LiFSI, inorganic solid electrolyte LiO2, and negative electrode film-forming additive fluoroethylene carbonate (FEC) in proportion. Specific amounts are shown in Table 1. Add the weighed components to a brown glass bottle and mix thoroughly using ultrasonic mixing at constant temperature to obtain a uniformly mixed liquid electrolyte slurry.

[0056] 3) Preparation of the Composite Electrode. A uniformly mixed liquid electrolyte slurry was poured onto one side of the positive electrode, covered with a glass plate, and then exposed to a 300nm UV lamp for 15 seconds each, followed by three intermittent exposures with 5-second intervals. The thickness of the solid electrolyte layer was controlled to 100μm, resulting in an integrated composite electrode.

[0057] Example 2-Example 11

[0058] The composition of the solid electrolyte layer raw materials of Examples 2 to 11 is shown in Table 1 below, where the curing parameters of Example 8 are: irradiation under a 300nm wavelength ultraviolet lamp for 15 seconds and static curing; the curing parameters of Example 9 are: the irradiation wavelength is adjusted to 600nm, the irradiation time is 15s / time, and intermittent irradiation is performed 3 times with an interval of 5s.

[0059] Example 12

[0060] Compared with Example 1, the difference is that in step 2) the preparation of the composite electrolyte slurry, the selection of various raw materials is different. In this embodiment, the photosensitive oligomer is polyethylene glycol diacrylate (Mw = 500), the plasticizer is tetracyanoethylene (replacing succinonitrile) and the photoinitiator is 2,2-dimethoxy-2-phenylacetophenone, the lithium salt LiPF6, the inorganic solid electrolyte LiAlO2, and the negative electrode film-forming additive is difluoroethylene carbonate (replacing FEC).

[0061] Comparative Example 1

[0062] The difference between Comparative Example 1 and Example 1 is that the composition of the raw materials of the solid electrolyte layer is different and the raw materials do not include lithium salt.

[0063] Comparative Example 2

[0064] The difference between Comparative Example 2 and Example 1 is that the composition of the raw materials of the solid electrolyte layer is different and the raw materials do not include a plasticizer.

[0065] Comparative Example 3

[0066] The difference between Comparative Example 3 and Example 1 is that the composition of the raw materials of the solid electrolyte layer is different, see Table 1 for details.

[0067] Comparative Example 4

[0068] The difference between Comparative Example 4 and Example 1 is that the composition of the raw materials of the solid electrolyte layer is different, and the raw materials do not include negative electrode film-forming additives.

[0069] Table 1

[0070]

[0071] Test Case

[0072] The performance of the composite electrode sheets prepared in each embodiment and comparative example was tested. The specific testing method is as follows:

[0073] 1) Lithium Ion Conductivity Test: A symmetrical Li / composite electrode / Li cell was constructed using a lithium metal sheet and a composite electrode (thickness T, area A). Electrochemical impedance spectroscopy (EIS) analysis was performed at 5 mV over a frequency range of 0.03 kHz to 500 kHz to obtain the bulk resistance, Rs, of the composite solid polymer electrolyte membrane. The lithium ion conductivity, C, was then calculated using the formula, C = (T·A) / Rs.

[0074] 2) Cycling performance test. The composite electrodes prepared in each embodiment and comparative example were assembled into CR2032 button-type full batteries together with lithium metal sheets in an argon glove box. Three button-type full batteries were taken from each group and charged at 1 / 3C constant current to the charging cut-off voltage at 30°C. Then, they were charged at constant voltage until the current dropped to 0.05C, allowed to stand for 5 minutes, and then discharged at 0.1C constant current to the lower limit cut-off voltage. Then, they were allowed to stand for 5 minutes. This procedure was repeated 500 times. The capacity retention rate (%) after N cycles = discharge capacity of the Nth cycle / discharge capacity of the first cycle × 100%, and the average value was taken.

[0075] 3) Rate Performance Test. Four button-type full-cell batteries were taken from each group and charged at 1 / 3C constant current at 30°C to the charge cutoff voltage. The batteries were then charged at constant voltage until the current dropped to 0.05C, allowed to rest for 5 minutes, and then discharged at 0.1C (or 1C) constant current to the lower discharge cutoff voltage of 2.0V. The batteries were then allowed to rest for another 5 minutes. This procedure was repeated 10 times. 1C / 0.1C rate discharge capacity ratio (%) = discharge capacity at 1C discharge in the 10th cycle / discharge capacity at 0.1C discharge in the 10th cycle × 100%.

[0076] The specific test results are shown in the table below:

[0077] Table 2

[0078]

[0079] From the above test results, it can be seen that by comparing Examples 1 to 3, it is found that the addition of inorganic solid electrolyte has a significant effect on the cycle performance of the battery cell. The battery cells of Examples 1 and 3 still have a cycle retention rate of more than 95% after 500 cycles. This is mainly because the addition of inorganic solid electrolyte is conducive to the formation of solid SEI film, but the amount of inorganic solid electrolyte added is not as much as possible. Combining Examples 1 to 3 and Comparative Example 3, it is found that as the amount of inorganic solid electrolyte added increases by more than 12%, the conductivity and cycle performance both decrease significantly. This may be due to the excessive amount of Li in the inorganic solid electrolyte. +The complexation with negatively charged groups (including ether oxygen groups in photosensitive oligomers) is too strong, which hinders the transmission of ions.

[0080] By comparing Example 3, Example 4, Example 5, and Comparative Example 1, it was found that the addition of lithium salt has a significant enhancing effect on lithium ion conductivity. The lithium ion conductivity increases with the increase in the amount of lithium salt added. The improvement in conductivity also significantly improves the rate performance of the prepared lithium ion battery.

[0081] By comparing Example 6, Example 7 and Comparative Example 2, it can be found that the addition of plasticizer is also beneficial to the improvement of lithium ion conductivity, which may be attributed to the fact that the plasticizer can provide more migration paths.

[0082] Examples 8 and 9 studied the effects of UV curing parameters on the lithium ion conductivity and electrical properties of the prepared battery cells. Comparing Example 8 (UV time 15s, then static curing) with Example 9 (curing wavelength 600nm), it was found that UV curing parameters play an important role in the organic-inorganic solid electrolyte prepared in this application. Its preparation process not only shortens the preparation time, but also has a significant effect on the performance. In a shorter time and within a more suitable wavelength range, it is more conducive to the photoinitiator to play a role, ensuring uniform curing of the prepared electrolyte, and improving the lithium ion conductivity, cycle and rate performance of the prepared battery cell.

[0083] By comparing Example 1, Example 10, Example 11 and Comparative Example 4, it was found that the addition of the negative electrode film-forming additive is beneficial to the improvement of the rate discharge performance. This is mainly due to the fact that the negative electrode film-forming additive improves the ionic conductivity of the solid electrolyte and improves the charge and discharge efficiency of the battery. At the same time, a stable solid electrolyte (SEI) is formed on the negative electrode side, ensuring the stability of the interface during the cycle, and the cycle performance of the battery cell is improved.

[0084] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A composite pole piece, characterized in that: include: The positive electrode sheet has two opposite surfaces in its thickness direction; A solid electrolyte layer is provided on at least one side of the positive electrode sheet. Among them, based on the total mass of the solid electrolyte layer raw materials, it includes: 1%-12% inorganic solid electrolyte, 17%-56% plasticizer, 10%-20% lithium salt, 27%-59% photosensitive oligomer, 1%-5% negative electrode film-forming additive, and 2%-3% photoinitiator.

2. The composite pole piece according to claim 1, characterized in that: The thickness of the solid electrolyte layer is 50-150 μm.

3. The composite pole piece according to claim 2, characterized in that: The photosensitive oligomer includes at least one of polyethylene glycol dimethacrylate and polyethylene glycol diacrylate; And / or, the weight average molecular weight of the photosensitive oligomer is 200-600.

4. The composite pole piece according to any one of claims 1 to 3, characterized in that: The plasticizer includes at least one nitrile compound; And / or, the negative electrode film-forming additive includes a negative electrode film-forming additive containing a 5- to 6-membered heterocyclic ring; And / or, the inorganic solid electrolyte includes at least one of an oxide electrolyte, a sulfide electrolyte, and a halide electrolyte.

5. The composite pole piece according to claim 4, characterized in that: The plasticizer includes at least one of succinonitrile, adiponitrile, tetracyanoethylene, ethylene glycol dipropylene glycol ether, and sulfonyl dipropylene glycol nitrile; And / or, the negative electrode film-forming additive includes at least one of fluoroethylene carbonate, bisfluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, propane sultone, and vinyl sulfate.

6. The composite pole piece according to any one of claims 1 to 3, characterized in that: The photoinitiator includes at least one of 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, 2-isopropylthioxanthone, and 1-hydroxycyclohexyl phenyl ketone; And / or, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalatoborate), lithium bis(trifluoromethanesulfonyl imide), and lithium bis(fluorosulfonyl imide).

7. A method for preparing a composite electrode, characterized in that: The steps include: S1, prepare the positive electrode; S2, preparing a slurry according to the raw material composition of the solid electrolyte layer according to any one of claims 1 to 5, placing the slurry on at least one side of the positive electrode plate, and curing it with ultraviolet light.

8. The method for preparing a composite electrode according to claim 7, characterized in that: The parameters of the ultraviolet curing include: an illumination wavelength of 280-400 nm; an illumination time of 10-20 s / time, 3-5 illumination times, and an illumination interval of 2-8 s.

9. An all-solid-state battery, characterized in that: A composite pole piece comprising the composite pole piece according to any one of claims 1 to 8.

10. An electrical device, characterized in that: Including the all-solid-state battery according to claim 9.

Images