Pole piece, preparation method thereof and battery

Abstract

The invention discloses a pole piece, a preparation method thereof and a battery. The pole piece comprises a pole piece main body and an ion-conducting phase change layer arranged on at least one part of the surface of the pole piece main body, and the ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions but not conducting electrons. According to the pole piece disclosed by the invention, the conductive ion phase change layer arranged on the surface of the pole piece main body can actively absorb excessive heat, so that other severe electrochemical or chemical reactions caused by excessive heat accumulation in the battery cell are avoided, and the intrinsic safety of the battery cell is realized. Furthermore, as the ion-conducting phase change layer comprises a material capable of conducting ions and not conducting electrons, on one hand, direct contact of the positive electrode and the negative electrode can be avoided even if the hole breaking temperature of the diaphragm is reached and diaphragm hole breaking occurs, so that thermal runaway caused by short circuit of the positive electrode and the negative electrode is avoided; and on the other hand, the reduction of the ion transmission rate in the battery cell caused by arranging a coating layer on the surface of the pole piece can be avoided to the greatest extent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and relates to a pole piece, a preparation method thereof and a battery. BACKGROUND

[0002] Since lithium ion batteries were introduced by Sony in 1991, they have been widely used in 3C, EV, two-wheeled vehicles, aerospace, photovoltaic energy storage and other fields due to their high energy density, small self-discharge and other characteristics. With the continuous improvement of the energy density and power density of lithium batteries, the academic, industrial and consumer communities have paid more and more attention to the safety of the battery cells. However, there is still a long way to go to improve the overall safety of the battery cells.

[0003] In the research on improving the safety of battery cells, two aspects are often focused on. One is to improve the safety of the battery cells through the optimization of the packaging structure, such as the design of the explosion-proof valve and the packaging design of the aluminum plastic film. The other is to improve the safety of the battery cells through the improvement of the materials, such as the improvement of the heat resistance of the separator and the addition of a flame retardant in the electrolyte. Although these methods can improve the safety of the battery cells to some extent, they cannot avoid the contact between the positive and negative electrodes caused by the shrinkage of the separator, which leads to the occurrence of a violent side reaction.

[0004] Therefore, it is difficult for the existing technical solutions to achieve the intrinsic absolute safety of the battery cells or to improve the safety while causing a loss of other performance.

[0005] Therefore, it is difficult for the existing technical solutions to achieve the intrinsic absolute safety of the battery cells or to improve the safety while causing a loss of other performance. SUMMARY

[0006] In view of the above technical problems in the prior art, the purpose of the present application is to provide a pole piece, a preparation method thereof and a battery.

[0007] In the present application, "comprising" means that in addition to the listed components, some unlisted components can also be included. In some embodiments, only the listed components are included, and in this case, "comprising" can be modified to "consisting of".

[0008] To achieve the above purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a pole piece, which comprises a pole piece body and an ion-conducting phase change layer arranged on at least a portion of the surface of the pole piece body, wherein the ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions and incapable of conducting electrons.

[0010] The following is a preferred technical solution of the present application, but not as a limitation of the technical solutions provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and implemented.

[0011] Preferably, the ionic conductivity of the ion-conducting phase-change layer is σ, σ≥0.5 mS / cm.

[0012] Preferably, the ion-conducting phase-change layer is composed of a phase-change material and a material capable of conducting ions and not capable of conducting electrons.

[0013] Preferably, the mass ratio of the phase-change material to the material capable of conducting ions and not capable of conducting electrons is (5-60):100.

[0014] Preferably, the maximum particle size of the phase-change material is d1, and the maximum particle size of the material capable of conducting ions and not capable of conducting electrons is d2, d1+d2≤10 μm. The reason for such limitation is to prevent excessive thickness from affecting ion transmission.

[0015] In one embodiment, d1 and d2 are obtained by using a focused ion beam scanning electron microscope (FIB-SEM).

[0016] Preferably, the phase-change material includes a phase-change core, and the surface of the phase-change core is coated with a polymer shell to form a microcapsule, wherein the material of the phase-change core includes at least one of an aerogel-based phase-change material, a paraffin-based phase-change material, a fatty acid-based phase-change material, and an alkali metal molten salt-based phase-change material.

[0017] In the present application, the phase-change core is characterized by starting a phase-change reaction at a certain temperature and absorbing heat inside the battery cell.

[0018] In one embodiment, the aerogel-based phase-change material includes a resin-based phase-change aerogel and / or a graphene / polyimide aerogel.

[0019] In one embodiment, the fatty acid-based phase-change material includes stearic acid, and the phase-change point thereof is at 60-80℃.

[0020] In one embodiment, the alkali metal molten salt-based phase-change material includes a nitrate molten salt.

[0021] Preferably, the polymer in the polymer shell includes at least one of a polyethylene-based, a polypropylene-based, and a polymethyl methacrylate-based.

[0022] Preferably, the thickness of the polymer shell is d3, the thickness of the inner core is d4, 10%≤d3 / d4≤67%, d3+d4≤10μm. Exemplarily, d3 / d4 can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 52%, 55%, 57%, 60%, 63%, 65%, 67%, etc.; d3+d4 can be 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm or 1μm, etc.

[0023] Preferably, the material capable of conducting ions and incapable of conducting electrons comprises at least one of a solid-state electrolyte, lithium niobate and a polymer. The solid-state electrolyte comprises at least one of lithium lanthanum zirconium oxide solid-state electrolyte (LLZO) and derivatives thereof, lithium aluminum titanium phosphate solid-state electrolyte (LATP). The derivative of LLZO refers to doping LLZO with ions, such as Ta-doped LLZTO, Al-doped LLZAO, Nb-doped LLZNbO.

[0024] Preferably, the polymer comprises at least one of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA).

[0025] In the present application, the pole piece body is a positive pole piece body or a negative pole piece body.

[0026] Preferably, the positive pole piece body comprises a positive current collector and a positive active layer disposed on the positive current collector, and the positive active layer comprises a positive active material.

[0027] Preferably, the positive active layer further comprises at least one of a conductive agent and a binder.

[0028] Preferably, the negative pole piece body is a lithium metal negative electrode, or the negative pole piece body comprises a negative current collector and a negative active layer disposed on the negative current collector, and the negative active layer comprises a negative active material.

[0029] Preferably, the negative active layer further comprises at least one of a conductive agent and a binder.

[0030] Preferably, the active material in the pole piece body is a positive active material, the thickness of the pole piece body is t1, the thickness of the ion-conducting phase change layer is t2, 5%≤t2 / t1≤20%; or,

[0031] The active material in the pole piece body is a negative active material, the thickness of the pole piece body is t3, the thickness of the ion-conducting phase change layer is t4, 3%≤t4 / t3≤20%.

[0032] In a second aspect, the present invention provides a method for preparing the electrode according to the first aspect, the method comprising the following steps:

[0033] preparing a coating slurry comprising a phase change material and a material that is ion-conducting but not electron-conducting;

[0034] The coating slurry is applied to the surface of the electrode body, and after drying, an ion-conducting phase change layer is formed on at least a portion of the surface of the electrode body. Preferably, the coating slurry also includes a binder.

[0035] In a third aspect, the present invention provides a battery comprising a positive electrode, a negative electrode and a separator, wherein at least one of the positive electrode and the negative electrode adopts the electrode sheet described in the first aspect.

[0036] Preferably, the sum of the thicknesses of the positive electrode, the negative electrode, and the separator is T, and 50 μm ≤ T ≤ 600 μm.

[0037] Preferably, the positive electrode and the negative electrode both use the electrode pieces described in the second aspect, and the thickness of the isolation film is t5, 50 μm≤t1+t2+t3+t4+t5≤600 μm.

[0038] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] In the electrode of the present invention, the ion-conducting phase change layer provided on the surface of the electrode body contains a phase change material, which can actively absorb excessive heat, thereby avoiding other violent electrochemical or chemical reactions caused by excessive heat accumulation inside the battery cell, thereby achieving the intrinsic safety of the battery cell. Furthermore, since the ion-conducting phase change layer includes a material that can conduct ions but cannot conduct electrons, on the one hand, since the material does not conduct electrons, even if the diaphragm ruptures when the rupture temperature of the diaphragm is reached, there is a non-conducting material between the positive and negative electrodes to isolate them, thereby avoiding direct contact between the positive and negative electrodes, thereby avoiding thermal runaway caused by a short circuit between the positive and negative electrodes; on the other hand, since the material can conduct ions, it can allow the normal insertion and extraction of lithium ions, thereby avoiding to the greatest extent the decrease in the ion transmission rate inside the battery cell caused by the coating layer provided on the surface of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a diagram showing the relationship between the positive electrode, negative electrode, and separator after stacking when preparing a battery in Application Example 9;

[0042] Figure 2 is the relationship diagram of the positive electrode, the negative electrode and the separator after being stacked when the battery is prepared according to application example 10;

[0043] Figure 3 is the relationship diagram of the positive electrode, the negative electrode and the separator after being stacked when the battery is prepared according to application example 11;

[0044] wherein 1 is a positive electrode sheet body, 2 is an ion-conducting phase change layer, 3 is a separator, and 4 is a negative electrode sheet body. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be further described below in combination with the drawings and through specific embodiments.

[0046] The specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0047] In one embodiment, the present application provides an electrode sheet, which comprises an electrode sheet body and an ion-conducting phase change layer arranged on at least a portion of the surface of the electrode sheet body, wherein the ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions and incapable of conducting electrons.

[0048] In the electrode sheet provided by one embodiment of the present application, the ion-conducting phase change layer arranged on the surface of the electrode sheet body contains a phase change material, which can actively absorb excessive heat and avoid other severe electrochemical or chemical reactions caused by excessive heat accumulation in the battery cell, thereby achieving the intrinsic safety of the battery cell. Further, since the ion-conducting phase change layer contains a material capable of conducting ions and incapable of conducting electrons, on the one hand, since the material does not conduct electrons, even if the temperature of the hole of the separator is reached and the hole of the separator appears, there is a material incapable of conducting electrons between the positive electrode and the negative electrode to prevent direct contact between the positive electrode and the negative electrode, thereby avoiding thermal runaway caused by short circuit between the positive electrode and the negative electrode; on the other hand, since the material can conduct ions, it can allow normal intercalation and deintercalation of lithium ions, thereby maximizing the avoidance of the decrease in the ion transmission rate in the battery cell caused by the coating layer arranged on the surface of the electrode sheet.

[0049] In one embodiment, the ion conductivity of the ion-conducting phase change layer is σ, and σ≥0.5 mS / cm, for example, it can be 0.5 mS / cm, 0.6 mS / cm, 0.7 mS / cm, 0.8 mS / cm, 0.9 mS / cm, 1.0 mS / cm, 1.1 mS / cm or 1.2 mS / cm, etc.

[0050] In one embodiment, the ion-conducting phase change layer is composed of a phase change material and a material capable of conducting ions and incapable of conducting electrons.

[0051] In one embodiment, the mass ratio of the phase change material to the material capable of conducting ions and incapable of conducting electrons is (5-60):100, for example, 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, 35:100, 40:100, 45:100, 50:100, 55:100, or 60:100, etc. If the mass ratio is too small, the phase change material is too little, and the absorption of heat in the battery is not enough, which is not conducive to the safety performance. If the mass ratio is too large, the phase change material is too much, which will affect the ion transmission in the battery and affect the electrical performance of the battery.

[0052] In one embodiment, the maximum particle size of the phase change material is d1, and the maximum particle size of the material capable of conducting ions and incapable of conducting electrons is d2, d1+d2≤10μm. For example, d1+d2 can be 10μm, 9μm, 8μm, 7μm, 6μm, 5μm, 4μm, 3μm, 2μm, or 1μm, etc.

[0053] In one embodiment, the phase change material includes a phase change core, and the surface of the phase change core is coated with a polymer shell to form a microcapsule. When the temperature inside the battery reaches the phase transition point of the phase change material, the phase change core starts to absorb heat and reduces the temperature inside the battery. At the same time, the phase change core undergoes phase transition, and through the coating of the polymer shell, it can avoid the side reaction with the main materials (such as electrolyte, separator, positive active material, negative active material, and auxiliary materials) in the battery to reduce the performance of the battery.

[0054] Preferably, the material of the phase change core includes at least one of aerogel phase change material, paraffin phase change material, fatty acid phase change material, and alkali metal molten salt phase change material.

[0055] In one embodiment, the polymer in the polymer shell includes at least one of polyethylene, polypropylene, and polymethyl methacrylate.

[0056] In one embodiment, the thickness of the polymer shell is d3, the thickness of the core is d4, 10%≤d3 / d4≤67%, and d3+d4≤10μm. In the present application, the thickness of the core refers to the distance of the core along the diameter direction of the microcapsule; the thickness of the shell refers to the distance of the shell along the diameter direction of the microcapsule, i.e., the sum of the distance on both sides of the core.

[0057] In the present application, by limiting the type of phase change material, d3 / d4, and d3+d4, the safety performance and electrical performance of the battery can be balanced and adjusted as needed.

[0058] In an embodiment, the ionically conductive and electronically non-conductive material comprises at least one of a solid-state electrolyte, lithium niobate, and a polymer.

[0059] In an embodiment, the solid-state electrolyte comprises at least one of lithium lanthanum zirconium oxide solid-state electrolyte (LLZO) and derivatives thereof, lithium aluminum titanium phosphate solid-state electrolyte (LATP) and derivatives thereof.

[0060] In an embodiment, the polymer comprises at least one of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA).

[0061] In an embodiment, the electrode tab body is a positive electrode tab body or a negative electrode tab body.

[0062] In an embodiment, the positive electrode tab body comprises a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector, the positive electrode active layer comprising a positive electrode active material.

[0063] In an embodiment, the positive electrode active material comprises at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium-rich manganese-based positive electrode material, or lithium cobalt oxide.

[0064] In an embodiment, the positive electrode active layer further comprises at least one of a conductive agent and a binder.

[0065] In an embodiment, the negative electrode tab body is a lithium metal negative electrode, or the negative electrode tab body comprises a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material.

[0066] In an embodiment, the negative electrode active material comprises at least one of graphite, silicon-based material, or a combination of graphite and silicon-based material.

[0067] In an embodiment, the negative electrode active layer further comprises at least one of a conductive agent and a binder.

[0068] In an embodiment, the active material in the electrode tab body is a positive electrode active material, the thickness of the electrode tab body is t1, the thickness of the ionically conductive phase transition layer is t2, and 5%≤t2 / t1≤20%; or,

[0069] the active material in the electrode tab body is a negative electrode active material, the thickness of the electrode tab body is t3, the thickness of the ionically conductive phase transition layer is t4, and 3%≤t4 / t3≤20%.

[0070] Exemplarily, t2 / t1 can be 5%, 7%, 10%, 12%, 14%, 16%, 18% or 20%, etc. t4 / t3 can be 3%, 5%, 7%, 10%, 12%, 13%, 15%, 17% or 20%, etc.

[0071] By limiting t2 / t1 and t4 / t3, on one hand, the ion-conducting phase transition layer with a suitable thickness can well insulate the positive and negative electrodes, avoiding short circuit after the damage of the separator; on the other hand, the lithium ion transmission of the battery can be regulated, and the performance of the battery can be improved.

[0072] In another embodiment, the application provides a method for preparing the electrode tab as described above, comprising the following steps:

[0073] Preparation of a coating slurry containing a phase transition material and a material capable of conducting ions and not capable of conducting electrons;

[0074] Coating the coating slurry to the surface of the electrode tab body, and drying to form an ion-conducting phase transition layer on at least a portion of the surface of the electrode tab body.

[0075] In one embodiment, the solvent used for preparing the coating slurry is NMP and / or DMF.

[0076] In one embodiment, the coating slurry further comprises a binder.

[0077] In another embodiment, the application provides a battery comprising a positive electrode, a negative electrode and a separator, at least one of the positive electrode and the negative electrode being the electrode tab as described above.

[0078] In one embodiment, the positive electrode in the battery is the electrode tab of the first aspect, comprising a positive electrode tab body and an ion-conducting phase transition layer arranged on at least a portion of the surface of the positive electrode tab, at least a portion of the ion-conducting phase transition layer facing the negative electrode. The negative electrode in the battery is a prior art negative electrode.

[0079] In another embodiment, the negative electrode in the battery is the electrode tab of the first aspect, comprising a negative electrode tab body and an ion-conducting phase transition layer arranged on at least a portion of the surface of the negative electrode tab, at least a portion of the ion-conducting phase transition layer facing the positive electrode. The positive electrode in the battery is a prior art positive electrode.

[0080] In yet another embodiment, the positive electrode in the battery is the electrode tab of the first aspect, comprising a positive electrode tab body and an ion-conducting phase transition layer arranged on at least a portion of the surface of the positive electrode tab. The negative electrode in the battery is the electrode tab of the first aspect, comprising a negative electrode tab body and an ion-conducting phase transition layer arranged on at least a portion of the surface of the negative electrode tab. At least a portion of the ion-conducting phase transition layer is located between the positive electrode tab body and the negative electrode tab body.

[0081] In the embodiment of the present application, the ion-conducting phase-change layer in the pole piece can be arranged on one side or both sides of the pole piece body. If arranged on one side, the ion-conducting phase-change layer is preferably arranged on the side close to the inside of the battery cell.

[0082] The type of the battery is not specifically limited in the embodiment of the present application, and can be a full-solid-state battery, a semi-solid-state battery or a liquid battery. In the full-solid-state battery, no electrolyte is contained, and the separator is a solid electrolyte membrane. In the liquid battery or the semi-solid-state battery, an electrolyte is contained, and the separator is a diaphragm.

[0083] In one embodiment, the battery is a liquid battery, and the separator is a diaphragm. The material of the diaphragm includes, but is not limited to, at least one of polyimide (PI), aramid, polyethylene (PE) or polypropylene (PP).

[0084] In one embodiment, the sum of the thicknesses of the positive electrode, the negative electrode and the separator is T, and 50 μm≤T≤600 μm. Exemplarily, T can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, 300 μm, 325 μm, 350 μm, 370 μm, 400 μm, 450 μm, 500 μm, 550 μm or 600 μm, etc.

[0085] In one embodiment, the positive electrode and the negative electrode both adopt the pole piece described above, and the thickness of the separator is t5, and 50 μm≤t1+t2+t3+t4+t5≤600 μm. Exemplarily, t1+t2+t3+t4+t5 can be 50 μm, 60 μm, 70 μm, 80 μm, 100 μm, 120 μm, 150 μm, 170 μm, 180 μm, 200 μm, 220 μm, 250 μm, 275 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm or 600 μm, etc.

[0086] Based on the above embodiment, the following typical but non-limiting examples are provided:

[0087] In the embodiment of the present application, the maximum particle size of the phase-change material is d1, and the maximum particle size of the material capable of conducting ions and incapable of conducting electrons is d2, and d1+d2≤10 μm. Within this range, the electrochemical performance is improved.

[0088] Example 1

[0089] The embodiment provides a positive electrode, which comprises a positive electrode sheet body and an ion-conducting phase change layer arranged on one side surface of the positive electrode sheet body, the ion-conducting phase change layer is opposite to a negative electrode, the ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions and incapable of conducting electrons, the material capable of conducting ions and incapable of conducting electrons is LLZO (with an average particle size of 200 nm), and the mass ratio of the phase change material to the material capable of conducting ions and incapable of conducting electrons is 10:100.

[0090] The phase change material comprises a phase change core, and the phase change core is coated with a polymer shell to form a microcapsule. The phase change core is paraffin, the polymer shell is polyethylene, the diameter of the microcapsule is 5 microns, the thickness of the polymer shell is 2 microns, and the thickness of the phase change core is 3 microns, so that the ratio of the thickness of the polymer shell to the thickness of the phase change core is 66.7%.

[0091] The thickness of the ion-conducting phase change layer is 10 microns, and the thickness of the positive electrode sheet body is 120 microns, so that the ratio of the thickness of the ion-conducting phase change layer to the thickness of the positive electrode sheet body is 8.33%.

[0092] The embodiment further provides a preparation method of the positive electrode.

[0093] (1) LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P and PVDF are dispersed in NMP at a mass ratio of 90:5:5 to form a positive electrode slurry, the positive electrode slurry is coated on an aluminum foil, and the positive electrode sheet body is obtained after drying.

[0094] (2) The microcapsule, LLZO and PVDF are dissolved in DMF, the mass ratio of the microcapsule, LLZO, PVDF and DMF is 1:10:5:20, and the coating slurry is obtained after uniform mixing and stirring.

[0095] (3) The coating slurry is coated on one side surface of the positive electrode sheet body, and the positive electrode is obtained after drying.

[0096] Embodiment 2

[0097] The embodiment provides a positive electrode, which comprises a positive electrode sheet body and an ion-conducting phase change layer arranged on one side surface of the positive electrode sheet body, the ion-conducting phase change layer is opposite to a negative electrode, the ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions and incapable of conducting electrons, the material capable of conducting ions and incapable of conducting electrons is LLZO (with an average particle size of 1 micron), and the mass ratio of the phase change material to the material capable of conducting ions and incapable of conducting electrons is 50:100.

[0098] The phase change material includes a phase change core, and a polymer shell is coated on the surface of the phase change core to form a microcapsule. The phase change core is a sodium nitrate molten salt, the polymer shell is polypropylene, the diameter of the microcapsule is 5.5 μm, the thickness of the polymer shell is 0.5 μm, and the thickness of the phase change core is 5 μm. The ratio of the thickness of the polymer shell to the thickness of the phase change core is 10%.

[0099] The thickness of the ion-conducting phase change layer is 9.1 μm, and the thickness of the positive electrode sheet body is 130 μm. The ratio of the thickness of the ion-conducting phase change layer to the thickness of the positive electrode sheet body is 7.02%.

[0100] The embodiment also provides a preparation method of the positive electrode, which includes the following steps:

[0101] (1) Lithium iron phosphate and PVDF are dispersed in NMP at a mass ratio of 90:5:5 to form a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil, and a positive electrode sheet body is obtained after drying.

[0102] (2) The microcapsules, LLZO, and PVDF are dissolved in DMF, and the mass ratio of the microcapsules, LLZO, PVDF, and DMF is 1:2:1:4. After uniform mixing and stirring, a coating slurry is obtained.

[0103] (3) The coating slurry is coated on one side surface of the positive electrode sheet body, and a positive electrode is obtained after drying.

[0104] Embodiment 3

[0105] The embodiment provides a positive electrode, which includes a positive electrode sheet body and an ion-conducting phase change layer arranged on one side surface of the positive electrode sheet body. The ion-conducting phase change layer is opposite to a negative electrode. The ion-conducting phase change layer includes a phase change material and a material capable of conducting ions and incapable of conducting electrons. The material capable of conducting ions and incapable of conducting electrons is LLZO (with an average particle size of 100 nm). The mass ratio of the phase change material to the material capable of conducting ions and incapable of conducting electrons is 10:100.

[0106] The phase change material includes a phase change core, and a solid-state electrolyte layer is coated on the surface of the phase change core to form a microcapsule. The phase change core is graphene aerogel, the polymer shell is polyethylene, the diameter of the microcapsule is 9 μm, the thickness of the polymer shell is 3 μm, and the thickness of the phase change core is 6 μm. The ratio of the thickness of the polymer shell to the thickness of the phase change core is 50%.

[0107] The thickness of the ion-conducting phase change layer is 10 μm, and the thickness of the positive electrode sheet body is 120 μm. The ratio of the thickness of the ion-conducting phase change layer to the thickness of the positive electrode sheet body is 8.33%.

[0108] The embodiment also provides a preparation method of the positive electrode, and the preparation method comprises the following steps:

[0109] (1) LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P and PVDF are dispersed in NMP according to a mass ratio of 90:5:5 to form a positive electrode slurry, the positive electrode slurry is coated on an aluminum foil, and a positive electrode piece body is obtained after drying.

[0110] (2) The microcapsules, LLZO and PVDF are dissolved in DMF, the mass ratio of the microcapsules, LLZO, PVDF and DMF is 1:10:9:20, and the mixture is uniformly stirred to obtain a coating slurry.

[0111] (3) The coating slurry is coated on one side surface of the positive electrode piece body, and a positive electrode of embodiment 4 is obtained after drying.

[0112] The embodiment provides a positive electrode, which comprises a positive electrode piece body and an ion-conducting phase change layer arranged on one side surface of the positive electrode piece body, the ion-conducting phase change layer material faces a negative electrode, the ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions and incapable of conducting electrons, the material capable of conducting ions and incapable of conducting electrons is LATP (the average particle size is 600 nm), and the mass ratio of the phase change material to the material capable of conducting ions and incapable of conducting electrons is 30:100.

[0113] The phase change material comprises a phase change core, and the phase change core is coated with a polymer shell to form a microcapsule. The phase change core is a potassium nitrate molten salt, the polymer shell is polyethylene, the diameter of the microcapsule is 6 microns, the thickness of the polymer shell is 1.5 microns, the thickness of the phase change core is 4.5 microns, and the ratio of the thickness of the polymer shell to the thickness of the phase change core is 33.3%.

[0114] The thickness of the ion-conducting phase change layer is 17 microns, and the thickness of the positive electrode piece body is 120 microns, and the ratio of the thickness of the ion-conducting phase change layer to the thickness of the positive electrode piece body is 14.2%.

[0115] The embodiment also provides a preparation method of the positive electrode, and the preparation method comprises the following steps:

[0116] (1) LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P and PVDF are dispersed in NMP according to a mass ratio of 90:5:5 to form a positive electrode slurry, the positive electrode slurry is coated on an aluminum foil, and a positive electrode piece body is obtained after drying.

[0117] (2) Dissolve the microcapsule, LATP and PVDF in DMF, the mass ratio of the microcapsule, LLZO, PVDF and DMF is 3.3:10:5:15, mix and stir uniformly to obtain a coating slurry.

[0118] (3) Apply the coating slurry to one side surface of the positive electrode sheet body, and after drying, obtain a positive electrode.

[0119] Example 5

[0120] The embodiment provides a positive electrode and a preparation method thereof, and the difference from the embodiment 1 is that the mass ratio of the phase change material and the material capable of conducting ions and incapable of conducting electrons is 65:100, and the total mass of the two is the same as that in the embodiment 1.

[0121] Example 6

[0122] The embodiment provides a positive electrode and a preparation method thereof, and the difference from the embodiment 1 is that the ratio of the thickness of the polymer shell to the thickness of the phase change core is 52%, and the diameter of the microcapsule is the same as that in the embodiment 1.

[0123] Example 7

[0124] The embodiment provides a positive electrode and a preparation method thereof, and the difference from the embodiment 1 is that the thickness of the ion-conducting phase change layer is changed, so that the ratio of the thickness of the ion-conducting phase change layer to the thickness of the positive electrode sheet body is 5%.

[0125] Example 8

[0126] The embodiment provides a positive electrode and a preparation method thereof, and the difference from the embodiment 1 is that the thickness of the ion-conducting phase change layer is changed, so that the ratio of the thickness of the ion-conducting phase change layer to the thickness of the positive electrode sheet body is 20%.

[0127] Example 9

[0128] The embodiment provides a negative electrode, which comprises a negative electrode sheet body and an ion-conducting phase change layer arranged on one side surface of the negative electrode sheet body, and the ion-conducting phase change layer is opposite to a positive electrode. The ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions and incapable of conducting electrons, the material capable of conducting ions and incapable of conducting electrons is LLZO (particle size is 800 nm), and the mass ratio of the phase change material to the material capable of conducting ions and incapable of conducting electrons is 10:100.

[0129] The phase change material comprises a phase change core, and the surface of the phase change core is coated with a polymer shell to form a microcapsule. The phase change core is paraffin, the polymer shell is polyethylene, the diameter of the microcapsule is 5 μm, the thickness of the polymer shell is 2 μm, and the thickness of the phase change core is 3 μm, so that the ratio of the thickness of the polymer shell to the thickness of the phase change core is 66.7%.

[0130] The thickness of the ion-conducting phase transition layer is 5 pm, and the thickness of the negative electrode piece body is 130 pm, so the ratio of the thickness of the ion-conducting phase transition layer to the thickness of the negative electrode piece body is 3.85%.

[0131] The embodiment also provides a preparation method of the negative electrode, and the preparation method comprises the following steps:

[0132] (1) graphite, Super P and SBR are dispersed in water at a mass ratio of 90:5:5 to form a negative electrode slurry, the negative electrode slurry is coated on a copper foil, and a positive electrode piece body is obtained after drying.

[0133] (2) the microcapsules, LLZO and PVDF are dissolved in DMF, the mass ratio of the microcapsules, LLZO, PVDF and DMF is 110:5:20, and the coating slurry is obtained after uniform mixing and stirring.

[0134] (3) the coating slurry is coated on one side surface of the negative electrode piece body, and a negative electrode is obtained after drying.

[0135] Embodiment 10

[0136] The embodiment provides a negative electrode, which comprises a negative electrode piece body and an ion-conducting phase transition layer arranged on one side surface of the negative electrode piece body, the ion-conducting phase transition layer material faces a positive electrode, the ion-conducting phase transition layer comprises a phase transition material and a material capable of conducting ions and incapable of conducting electrons, the material capable of conducting ions and incapable of conducting electrons is LLZO (with a particle size of 1.2 pm), and the mass ratio of the phase transition material to the material capable of conducting ions and incapable of conducting electrons is 50:100.

[0137] The phase transition material comprises a phase transition core, and the phase transition core is coated with a polymer shell to form a microcapsule. The phase transition core is paraffin, the polymer shell is polypropylene, the diameter of the microcapsule is 5.5 pm, the thickness of the polymer shell is 0.5 pm, and the thickness of the phase transition core is 5 pm, so the ratio of the thickness of the polymer shell to the thickness of the phase transition core is 10%.

[0138] The thickness of the ion-conducting phase transition layer is 45 pm, and the thickness of the negative electrode piece body is 280 pm, so the ratio of the thickness of the ion-conducting phase transition layer to the thickness of the negative electrode piece body is 16.07%.

[0139] The embodiment also provides a preparation method of the negative electrode, and the preparation method comprises the following steps:

[0140] (1) graphite, silicon nanoparticles, Super P and SBR are dispersed in water at a mass ratio of 88:2:5:5 to form a negative electrode slurry, the negative electrode slurry is coated on a copper foil, and a positive electrode piece body is obtained after drying.

[0141] (2) Dissolve the microcapsule, LLZO and PVDF in DMF, the mass ratio of the microcapsule, LLZO, PVDF and DMF is 1:2:1:4, mix and stir uniformly to obtain a coating slurry.

[0142] (3) Apply the coating slurry to one side surface of the negative electrode sheet body, and after drying, obtain a negative electrode.

[0143] Example 11

[0144] The example provides a negative electrode, which comprises a negative electrode sheet body and an ion-conducting phase change layer arranged on one side surface of the negative electrode sheet body, the ion-conducting phase change layer material faces the positive electrode, the ion-conducting phase change layer comprises a phase change material and a material capable of conducting ions and not capable of conducting electrons, the material capable of conducting ions and not capable of conducting electrons is LLZO (particle size is 650 nm), and the mass ratio of the phase change material to the material capable of conducting ions and not capable of conducting electrons is 10:100.

[0145] The phase change material comprises a phase change core, and the surface of the phase change core is coated with a polymer shell to form a microcapsule. The phase change core is paraffin, the polymer shell is polypropylene, the diameter of the microcapsule is 9 μm, the thickness of the polymer shell is 3 μm, and the thickness of the phase change core is 6 μm, so the ratio of the thickness of the polymer shell to the thickness of the phase change core is 50%.

[0146] The thickness of the ion-conducting phase change layer is 5 μm, and the thickness of the negative electrode sheet body is 46 μm, so the ratio of the thickness of the ion-conducting phase change layer to the thickness of the negative electrode sheet body is 10.87%.

[0147] The example also provides a preparation method of the above-mentioned negative electrode, which comprises the following steps:

[0148] (1) Take a lithium metal foil as the negative electrode sheet body.

[0149] (2) Dissolve the microcapsule, LLZO and PVDF in DMF, the mass ratio of the microcapsule, LLZO, PVDF and DMF is 1:10:9:20, mix and stir uniformly to obtain a coating slurry.

[0150] (3) Apply the coating slurry to one side surface of the negative electrode sheet body, and after drying, obtain a negative electrode

[0151] Comparative Example 1

[0152] The comparative example provides a positive electrode, which is different from the example 1 in that no ion-conducting phase change layer is arranged.

[0153] Comparative Example 2

[0154] The comparative example provides a negative electrode, which is different from the example 11 in that no ion-conducting phase change layer is arranged.

[0155] Comparative Example 3

[0156] The present comparative example provides a positive electrode, which is different from Example 1 in that the LLZO in the ion-conducting phase-change layer is removed, so that the phase-change layer is not ion-conducting.

[0157] Application Examples 1-12

[0158] An electric core is provided, and a preparation method thereof is as follows:

[0159] After stacking the positive electrode, the negative electrode and the separator, winding is performed to obtain a winding core, and after packaging, injecting electrolyte, formation and aging, an electric core is obtained. The separator is an aramid separator with a thickness of 15 μm. The corresponding relationship of the positive electrode and the negative electrode is shown in Table 1.

[0160] The electric core in the present application can be used to prepare a battery, and a preparation method thereof is a known method. The electrochemical performance of the battery can be characterized by performance testing of the electric core.

[0161] When the battery is prepared according to Application Example 9, the relationship diagram of the stacked positive electrode, negative electrode and separator is shown in Figure 1 , when the battery is prepared according to Application Example 10, the relationship diagram of the stacked positive electrode, negative electrode and separator is shown in Figure 2 , and when the battery is prepared according to Application Example 11, the relationship diagram of the stacked positive electrode, negative electrode and separator is shown in Figure 3 , wherein 1 is the positive electrode sheet body, 2 is the phase-change ion-conducting layer, 3 is the separator, and 4 is the negative electrode sheet body.

[0162] Table 1

[0163]

[0164] After the batteries of Application Examples 1-12 are fully charged, a hot box test is performed. The electric core is heated at a heating rate of 5℃ / min to observe the phenomenon. The electric core is heated to 200℃ and observed for 30 min to observe whether it catches fire or explodes. The results are shown in Table 2, and the rate performance is represented by the 1C / 0.1C capacity retention rate.

[0165] Table 2

[0166]

[0167]

[0168] Application Example 5 differs from Application Example 1 in that the positive electrode of Example 5 is used to replace the positive electrode of Example 1. The results show that the phase-change material is too much, resulting in a decrease in the rate performance of the battery.

[0169] The difference between application example 6 and application example 1 is that the positive electrode of example 6 is used to replace the positive electrode of example 1, and the results show that the thickness ratio of the polymer shell is too large, which leads to the decrease of the rate performance of the battery.

[0170] The difference between application examples 7-8 and application example 1 is that the positive electrode of example 7 and example 8 is used to replace the positive electrode of example 1, respectively, and the results show that the thickness ratio of the ion-conducting phase change layer to the positive electrode sheet body in the range of 5% to 20% makes the battery have good safety performance, and the relatively thin ion-conducting phase change layer is more conducive to improving the rate performance of the battery.

[0171] In the battery of application example 9, the positive electrode does not contain the phase change ion-conducting layer, and the negative electrode contains the phase change ion-conducting layer. In the battery of application example 10, the negative electrode does not contain the phase change ion-conducting layer, and the positive electrode contains the phase change ion-conducting layer. The batteries of application example 9 and application example 10 both have good safety performance and good rate performance. In the battery of application example 11, the positive electrode and the negative electrode do not contain the ion-conducting phase change layer, and the battery does not pass the hot box test and explodes.

[0172] In the battery of application example 12, the non-ion-conducting phase change layer is used to replace the ion-conducting phase change layer, which can ensure the safety performance, but the rate performance is greatly decreased, only 70%.

[0173] The applicant declares that the above examples are used to illustrate the detailed method of the present application, but the present application is not limited to the above detailed method, that is, it does not mean that the present application must rely on the above detailed method to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A pole piece, characterized in that: The pole piece includes a pole piece body and an ion-conducting phase change layer provided on at least a portion of a surface of the pole piece body. The ion-conducting phase change layer includes a phase change material and a material that can conduct ions but cannot conduct electrons.

2. The pole piece according to claim 1, characterized in that: The ionic conductivity of the ion-conducting phase change layer is σ, σ≥0.5mS / cm; And / or, the ion-conducting phase change layer is composed of a phase change material and a material that can conduct ions but cannot conduct electrons; And / or, the mass ratio of the phase change material to the material capable of conducting ions but not conducting electrons is (5-60):100; And / or, the maximum particle size of the phase change material is d1, the maximum particle size of the material that can conduct ions but cannot conduct electrons is d2, and d1+d2≤10 μm.

3. The pole piece according to claim 1 or 2, characterized in that: The phase change material comprises a phase change core, the surface of the phase change core is covered with a polymer shell to form a microcapsule; The phase change core material includes at least one of an aerogel phase change material, a paraffin phase change material, a fatty acid phase change material, and an alkali metal molten salt phase change material. and / or, the polymer in the polymer shell comprises at least one of polyethylene, polypropylene and polymethyl methacrylate; And / or, the thickness of the polymer shell is d3, the thickness of the core is d4, 10%≤d3 / d4≤67%, d3+d4≤10 μm.

4. The pole piece according to any one of claims 1 to 3, characterized in that: The material capable of conducting ions but not conducting electrons comprises at least one of a solid electrolyte, lithium niobate, and a polymer; wherein the solid electrolyte comprises at least one of a lithium lanthanum zirconium oxide solid electrolyte and its derivatives, a lithium aluminum titanium phosphate solid electrolyte, and its derivatives; And / or, the polymer includes at least one of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile and polymethyl methacrylate.

5. The pole piece according to any one of claims 1 to 4, characterized in that: The electrode body is a positive electrode body or a negative electrode body; And / or, the positive electrode sheet main body includes a positive electrode current collector and a positive electrode active layer provided on the positive electrode current collector, and the positive electrode active layer includes a positive electrode active material; And / or, the negative electrode sheet main body is a lithium metal negative electrode, or the negative electrode sheet main body includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, and the negative electrode active layer includes a negative electrode active material.

6. The pole piece according to any one of claims 1 to 5, characterized in that: The active material in the electrode body is a positive electrode active material, the thickness of the electrode body is t1, the thickness of the ion-conducting phase change layer is t2, and 5%≤t2 / t1≤20%; or, The active material in the pole piece body is a negative electrode active material, the thickness of the pole piece body is t3, the thickness of the ion-conducting phase change layer is t4, and 3%≤t4 / t3≤20%.

7. A method for preparing a pole piece according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: preparing a coating slurry comprising a phase change material and a material that is ion-conducting but not electron-conducting; The coating slurry is applied to the surface of the pole piece body, and after drying, an ion-conducting phase change layer is formed on at least a portion of the surface of the pole piece body.

8. The method for preparing a pole piece according to claim 7, characterized in that: The coating slurry also includes a binder.

9. A battery comprising a positive electrode, a negative electrode and a separator, characterized in that: At least one of the positive electrode and the negative electrode adopts the electrode sheet according to any one of claims 1 to 6.

10. The battery according to claim 9, characterized in that The sum of the thicknesses of the positive electrode, the negative electrode, and the separator is T, 50 μm ≤ T ≤ 600 μm; Preferably, the positive electrode and the negative electrode both adopt the electrode piece according to any one of claims 1 to 5, and the thickness of the isolation film is t5, 50 μm≤t1+t2+t3+t4+t5≤600 μm.

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