An electrode with improved inter-electrode adhesion and a method of making the same

Abstract

The application provides a preparation method of an electric core with improved adhesion between electrodes. Solid polyester diols and polyether diols are respectively coated on the separator near the positive electrode side and the negative electrode side. After mixing a polyisocyanate into an electrolyte, the electrolyte is injected into the electric core to initiate an in-situ polymerization reaction in the battery, so that the positive and negative electrode plates and the separator are integrated to have better adhesion. By designing the types of the coated monomers, a polyester polyurethane binder with strong oxidation resistance can be formed on the positive electrode side, and a polyether polyurethane with strong reduction resistance can be formed on the negative electrode side. Since small molecule monomers are injected into the electric core, the monomers can penetrate into the electrode plates to a greater depth, and the final polyurethane has better contact with the electrode plates. The urethane in the polyurethane can form hydrogen bonds with the positive and negative electrode materials to further improve the adhesion, alleviate the influence of the volume change of the electrode during the charging and discharging process of the battery, and improve the cycle stability of the electric core. The application also provides an electric core with improved adhesion between electrodes.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a battery cell that improves the adhesion between electrodes and its preparation method. Background Technology

[0002] Traditional fossil fuels emit large amounts of CO2 gas during use, leading to the continuous deterioration of the Earth's environment in recent years. In order to reduce dependence on fossil fuels, countries have begun to turn their attention to clean energy and vigorously develop wind power, photovoltaic power, and energy storage technologies. Lithium-ion batteries, due to their high energy density and lack of memory effect, have become an important part of energy storage and are widely used in electric vehicles and energy storage power stations.

[0003] During the charging process of lithium-ion batteries, lithium elements from the positive electrode migrate to the surface of the negative electrode material and form compounds with it. Due to the insertion and extraction of a large number of lithium ions, the electrode thickness expands and contracts significantly. Traditional electrolytes lack adhesion, and after long-term cycling, poor contact occurs between the electrode and the separator, as well as the counter electrode, which affects the electrical performance and can even lead to battery thermal runaway in severe cases.

[0004] Introducing polymers into the battery interior and utilizing their adhesive properties to bond the separator, positive electrode, and negative electrode together helps mitigate the effects of electrode expansion. For example, CN 102332605 B describes adding polyvinylidene fluoride-hexafluoropropylene copolymer powder to the electrolyte. After being injected into the battery, a high-temperature process is performed, causing the polymer to dissolve into the electrolyte and form a physical gel, which bonds the positive and negative electrodes and alleviates the expansion of the battery cell at high temperatures. CN 203690419 U describes assembling a battery cell with a PVDF-coated separator, injecting it into the electrolyte, and using hot pressing to bond the aqueous negative electrode to the separator, suppressing battery deformation during cycling and improving battery cycle stability.

[0005] Traditional methods typically introduce polymers with strong adhesive properties, such as PVDF, into the battery. However, to ensure battery performance, the amount added is often low. Due to the high molecular weight of the polymer, its wetting of the electrode surface is not ideal, ultimately resulting in limited adhesion. The positive and negative electrode voltages of lithium-ion batteries differ significantly. Contact with the positive electrode often requires polymer molecules with excellent oxidation resistance, while contact with the negative electrode requires strong reduction resistance—these two requirements are contradictory and cannot be met by the same material. PVDF has strong oxidation resistance, but it is easily reduced on the negative electrode side; PEO has strong reduction resistance, but it cannot handle high voltages. Therefore, in polymer batteries prepared using traditional methods, the polymer often results in unsatisfactory adhesion due to insufficient addition, poor electrode wetting, and decomposition during cycling. Summary of the Invention

[0006] The purpose of this invention is to provide a battery cell with improved inter-electrode adhesion and its preparation method. This invention utilizes in-situ polymerization to polymerize monomers from the electrolyte with monomers coated on the separator surface to form an adhesion layer. This improves the adhesion between the positive and negative lithium-ion electrodes, reducing the impact of electrode expansion during charging and discharging. Simultaneously, the adhesion layer formed by in-situ polymerization on the separator surface in the battery cell provides both oxidation resistance on the positive electrode side and reduction resistance on the negative electrode side, improving stability during cycling.

[0007] This invention provides a method for preparing a battery cell with improved inter-electrode adhesion, comprising the following steps:

[0008] A) The first component solution and the second component solution are coated on both sides of the diaphragm respectively to obtain a double-sided coated diaphragm;

[0009] The first component solution includes polyester polyol and / or polycarbonate polyol; the second component solution includes polyether polyol and / or polysiloxane polyol.

[0010] B) Assemble the double-coated separator, positive electrode, and negative electrode into a battery cell, inject electrolyte, and initiate an in-situ polymerization reaction inside the battery cell to obtain a battery cell with a functionalized separator.

[0011] The electrolyte comprises a third component, a catalyst, a lithium salt, and a solvent; the third component is a polyisocyanate.

[0012] Preferably, the first component is one or more of polyethylene adipate diol, 1,4-butanediol adipate diol, 1,6-hexanediol adipate diol, polycarbonate diol, polycaprolactone diol, and polyphthalate diol.

[0013] Preferably, the mass fraction of the solute in the first component solution is 0.1% to 100%.

[0014] Preferably, the second component is one or more of polyethylene glycol, polypropylene glycol, polytetrahydrofuran ether glycol, trihydroxy polyether, hydroxyl silicone oil, and polydimethylsiloxane.

[0015] Preferably, the mass fraction of the solute in the second component solution is 0.1% to 100%.

[0016] Preferably, the first component solution is coated on the side of the separator near the positive electrode, and the second component solution is coated on the side of the separator near the negative electrode.

[0017] Preferably, the third component is one or more of toluene diisocyanate, isoflurone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, terephthalic diisocyanate, MDI trimer, and TDI trimer.

[0018] Preferably, the mass fraction of the third component in the electrolyte is 0.1% to 20%.

[0019] Preferably, the catalyst is one or more of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylene diamine, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, triethanolamine, N,N'-dimethylpyridine, dibutyltin dilaurate, stannous octoate, triethylphosphorus, triphenylphosphorus, tri-n-butylphosphorus, tributyltin oxide, tetrabutyl titanate, tetrabutyl zirconate, trialkyltin alkoxide, and dialkyltin oxide;

[0020] The mass of the catalyst in the electrolyte accounts for 0.5 to 5% of the total mass of the first, second, and third components.

[0021] Preferably, the polymerization temperature is 40–90°C and the polymerization time is 1–120 hours.

[0022] Preferably, after assembling the double-coated separator, positive electrode, and negative electrode, the mixture is brought into contact with the electrolyte and then immersed at room temperature for 2 to 36 hours before polymerization is initiated.

[0023] This invention provides a battery cell with improved inter-electrode adhesion, prepared according to the method described above.

[0024] This invention provides a method for preparing a battery cell with improved inter-electrode adhesion, comprising the following steps: A) coating a first component solution and a second component solution onto both sides of a separator to obtain a double-sided coated separator; the first component solution includes polyester polyol and / or polycarbonate polyol; the second component solution includes polyether polyol and / or polysiloxane polyol; B) assembling the double-sided coated separator, positive electrode, and negative electrode, and then contacting them with an electrolyte to initiate a polymerization reaction to obtain a functionalized battery cell; the electrolyte includes a third component, a catalyst, a lithium salt, and a solvent; the third component is a polyisocyanate. This invention involves coating solid polyester diol and polyether diol onto the separator near the positive and negative electrodes, respectively. Polyisocyanate is then mixed into the electrolyte and injected into the battery cell, initiating an in-situ polymerization reaction inside the battery. This integrates the positive and negative electrodes with the separator, resulting in better adhesion. Furthermore, by designing the type of monomers used for coating, a polyester-based polyurethane adhesive with extremely strong oxidation resistance can be formed on the positive electrode side, while a polyether-based polyurethane with extremely strong reduction resistance can be formed on the negative electrode side. Because small-molecule monomers are injected into the battery cell, the penetration depth into the electrodes is deeper, resulting in better contact between the final polyurethane and the electrodes. The urethane in the polyurethane can form hydrogen bonds with the positive and negative electrode materials, further improving their adhesion, mitigating the impact of electrode volume changes during battery charging and discharging, and improving the cycle stability of the battery cell. Detailed Implementation

[0025] This invention provides a method for preparing a battery cell with improved inter-electrode adhesion, comprising the following steps:

[0026] A) The first component solution and the second component solution are coated on both sides of the diaphragm respectively to obtain a double-sided coated diaphragm;

[0027] The first component solution includes polyester polyol and / or polycarbonate polyol; the second component solution includes polyether polyol and / or polysiloxane polyol.

[0028] B) After assembling the double-coated separator, positive electrode, and negative electrode, the mixture is brought into contact with the electrolyte and an in-situ polymerization reaction is initiated under certain conditions to obtain a functionalized battery cell.

[0029] The electrolyte comprises a third component, a catalyst, a lithium salt, and a solvent; the third component is a polyisocyanate.

[0030] The present invention first prepares a first component solution and a second component solution. Preferably, the first component is soluble to obtain the first component solution. The solvation can be achieved by directly heating and melting the first component to obtain the first component solution; or the first component can be mixed with a solvent to obtain the first component solution.

[0031] In this invention, the first component is preferably polyester polyol and / or polycarbonate polyol, more preferably one or more of polyethylene adipate diol, 1,4-butanediol adipate diol, 1,6-hexanediol adipate diol, polycarbonate diol, polycaprolactone diol and polyphthalate diol.

[0032] In this invention, the heating and melting temperature is preferably 40-90°C, more preferably 50-80°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and preferably any of the above values ​​as the upper or lower limit.

[0033] The solvent is preferably N-methylpyrrolidone (NMP), water, small molecule ethers, small molecule esters, etc. The mass concentration of the first component solution obtained by adding the solvent for solubilization is preferably 1-90%, more preferably 10-80%, such as 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, preferably within the range of any of the above values ​​as the upper or lower limit.

[0034] The present invention preferably involves solubilizing the second component to obtain a second component solution. The solubilization can be achieved by directly heating and melting the second component to solubilize it, or by mixing the second component with a solvent to obtain a second component solution.

[0035] In this invention, the second component is preferably a polyether polyol and / or a polysiloxane polyol, more preferably one or more of polyethylene glycol, polypropylene glycol, polytetrahydrofuran ether glycol, trihydroxy polyether, hydroxyl silicone oil and polydimethylsiloxane.

[0036] In this invention, the heating and melting temperature is preferably 40-90°C, more preferably 50-80°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and preferably any of the above values ​​as the upper or lower limit.

[0037] The solvent is preferably N-methylpyrrolidone (NMP), water, small molecule ethers, small molecule esters, etc. The mass concentration of the first component solution obtained by adding the solvent for solubilization is preferably 1-90%, more preferably 10-80%, such as 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, preferably within the range of any of the above values ​​as the upper or lower limit.

[0038] After obtaining the first component solution and the second component solution, the present invention coats the first component solution and the second component solution onto the two sides of the diaphragm respectively to obtain a double-sided coated diaphragm.

[0039] In this invention, the coating method is not particularly limited, and commonly used methods such as blade coating, transfer coating, slot extrusion coating, and spraying can all be applied to this invention.

[0040] Preferably, in this invention, the first component solution is coated onto the side of the separator near the positive electrode, and after drying, a functional coating with antioxidant properties is formed; the second component solution is coated onto the side of the separator near the negative electrode, and after drying, a functional coating with anti-reduction properties is formed.

[0041] In this invention, the method of drying and forming film can be either drying or cooling.

[0042] In this invention, the thickness of the functional coating formed by the first component solution is preferably 1–10 μm, more preferably 3–8 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and preferably within a range where any of the above values ​​are the upper or lower limits. The thickness of the functional coating formed by the second component solution is preferably 1–10 μm, more preferably 3–8 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and preferably within a range where any of the above values ​​are the upper or lower limits.

[0043] After obtaining the double-sided coated separator, the present invention assembles the double-sided coated separator with the positive electrode and the negative electrode to form a battery cell, injects electrolyte, impregnates at room temperature for 12 to 36 hours, and then initiates polymerization under certain conditions to obtain a functionalized battery cell.

[0044] In this invention, the electrolyte is a blend of a third component and a catalyst. The electrolyte includes the third component, a catalyst, a lithium salt, and a solvent. The third component is preferably a polyisocyanate, more preferably one or more of toluene diisocyanate, isoflurane diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, terephthalic diisocyanate, MDI trimer, and TDI trimer. The mass fraction of the third component in the electrolyte is preferably 0.1% to 20%, more preferably 1% to 15%, such as 0.1%, 0.5%, 1%, or 1%. 5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0045] In this invention, the catalyst is preferably one or more of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylene diamine, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, triethanolamine, N,N'-dimethylpyridine, dibutyltin dilaurate, stannous octoate, triethylphosphorus, triphenylphosphorus, tri-n-butylphosphorus, tributyltin oxide, tetrabutyl titanate, tetrabutyl zirconate, trialkyltin alkoxide, and dialkyltin oxide; the mass of the catalyst in the electrolyte accounts for 0.5% to 5% of the total mass of the first component, the second component, and the third component, more preferably 1% to 4%, such as 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0046] In this invention, the lithium salt is preferably one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium dioxaborate, lithium bis(fluorosulfonyl)imide, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluorophosphate; the mass fraction of the lithium salt in the electrolyte is preferably 0.2–1.5 mol / L, more preferably 0.5–1 mol / L, such as 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, and 1.5 mol / L, preferably within a range where any of the above values ​​is the upper or lower limit.

[0047] In this invention, the solvent is preferably one or more of ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), butenyl carbonate, methyl propyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, dimethyl glycol ether (DME), tetraethylene glycol dimethyl ether, δ-valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane, 1,3-dioxolane (DOL), sulfolane, and dimethyl sulfoxide. Specifically, in one embodiment of this invention, the solvent may be a mixed solvent composed of EC, EMC, and DEC in a volume ratio of 1:1:1.

[0048] In this invention, the positive electrode sheet is a commonly used positive electrode sheet in the art, obtained by coating and drying a positive electrode slurry containing a positive electrode active material, a binder, and a conductive agent on the surface of the current collector. For example, a positive electrode sheet containing LiCo... 0.1 Ni 0.8 Mn 0.1 The positive electrode is obtained by coating a solution of O2, polyvinylidene fluoride (PVDF) and conductive carbon black in NMP form onto a current collector.

[0049] The negative electrode sheet is a commonly used negative electrode sheet in this field, which is obtained by coating and drying a negative electrode slurry containing negative electrode active material, binder and conductive agent on the surface of the current collector. For example, an NMP solution containing graphite, polyvinylidene fluoride (PVDF) and conductive carbon black is used as the negative electrode slurry and coated on the current collector to obtain the negative electrode.

[0050] During assembly, the side of the separator coated with the first composition is brought into contact with the positive electrode, and the side of the separator coated with the second composition is brought into contact with the negative electrode. Then, the electrolyte containing the third composition and the catalyst is injected, and the mixture is immersed at room temperature for 24 hours. Then, the mixture is heated to initiate polymerization and solidify it to obtain a functionalized battery cell.

[0051] This invention improves the adhesion between the separator and the positive and negative electrodes by coating the positive electrode side of the separator with an oxidation-resistant binder monomer and the negative electrode side with a reduction-resistant binder monomer, and then polymerizing them with a third component in the electrolyte to form a polymer binder, thereby reducing the impact of electrode volume expansion during battery charging and discharging.

[0052] In this invention, the polymerization temperature is preferably 40–90°C, more preferably 50–80°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, and 90°C, preferably within a range where any of the above values ​​are the upper or lower limits; the polymerization time is preferably 1–120 hours, more preferably 5–100 hours, such as 1 hour, 5 hours, 10 hours, 15 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 110 hours, and 120 hours, preferably within a range where any of the above values ​​are the upper or lower limits.

[0053] The present invention also provides a battery cell with improved inter-electrode adhesion prepared according to the preparation method described above.

[0054] This invention provides a method for preparing a battery cell with improved inter-electrode adhesion, comprising the following steps: A) coating a first component solution and a second component solution onto both sides of a separator to obtain a double-sided coated separator; the first component solution includes polyester polyol and / or polycarbonate polyol; the second component solution includes polyether polyol and / or polysiloxane polyol; B) assembling the double-sided coated separator, positive electrode, and negative electrode, and then contacting them with an electrolyte to initiate a polymerization reaction to obtain a functionalized battery cell; the electrolyte includes a third component, a catalyst, a lithium salt, and a solvent; the third component is a polyisocyanate. This invention involves coating solid polyester diol and polyether diol onto the separator near the positive and negative electrodes, respectively. Polyisocyanate is then mixed into the electrolyte and injected into the battery cell, initiating an in-situ polymerization reaction inside the battery. This integrates the positive and negative electrodes with the separator, resulting in better adhesion. Furthermore, by designing the type of monomers used for coating, a polyester-based polyurethane adhesive with extremely strong oxidation resistance can be formed on the positive electrode side, while a polyether-based polyurethane with extremely strong reduction resistance can be formed on the negative electrode side. Because small-molecule monomers are injected into the battery cell, the penetration depth into the electrodes is deeper, resulting in better contact between the final polyurethane and the electrodes. The urethane in the polyurethane can form hydrogen bonds with the positive and negative electrode materials, further improving their adhesion, mitigating the impact of electrode volume changes during battery charging and discharging, and improving the cycle stability of the battery cell.

[0055] To further illustrate the present invention, the following detailed description of a functionalized battery cell, its preparation method, and the battery provided by the present invention is provided in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] ① Dissolve 2g of polycarbonate diol (PCDL2000) with a molecular weight of 2000 in 5g of NMP solvent, coat it on the side of the separator near the positive electrode, and then dry it to form a single-sided coated separator with a coating thickness of 5um; heat polyethylene glycol (PEG2000) with a molecular weight of 2000 to 60℃ to melt it, coat it on the side of the single-sided separator near the negative electrode, and then cool it to form a double-sided coated separator with a coating thickness of 5um.

[0058] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0059] ③ Dissolve 2g of diphenylmethane diisocyanate (MDI) and 0.2g of dibutyltin dilaurate in 10g of electrolyte (EC / EMC / DEC = 1 / 1 / 1, 1M LiPF6), mix well, and obtain a blended electrolyte.

[0060] ④ The battery cell is assembled using the separator from step ① and the electrode from step ②. The blended electrolyte from step ③ is injected, and the battery is soaked at room temperature for 24 hours and then placed in a 60°C oven for 5 hours to cure.

[0061] The battery obtained in step ④ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0062] Example 2

[0063] ① Dissolve 2g of poly(1,4-butanediol adipate) diol (PBA2000) with a molecular weight of 2000 in 5g of NMP solvent, coat it on the side of the separator near the positive electrode, and then dry it to form a single-sided coated separator with a coating thickness of 5um; heat polytetrahydrofuran ether diol (PTMG1000) with a molecular weight of 1000 to 60℃ to melt it, coat it on the side of the single-sided separator near the negative electrode, and then cool it to form a double-sided coated separator with a coating thickness of 5um.

[0064] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0065] ③ Dissolve 2g of isophorone diisocyanate (IPDI) and 0.2g of dibutyltin dilaurate in 10g of electrolyte (EC / EMC / DEC = 1 / 1 / 1, 1M LiPF6), mix well, and obtain a blended electrolyte.

[0066] ④ The battery cell is assembled using the separator from step ① and the electrode from step ②. The blended electrolyte from step ③ is injected, and the battery is soaked at room temperature for 24 hours and then placed in a 60°C oven for 5 hours to cure.

[0067] The battery obtained in step ④ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0068] Example 3

[0069] ① Dissolve 2g of 1,4-butanediol adipate (PBA2000) with a molecular weight of 2000 and 2g of polycarbonate diol (PCDL2000) with a molecular weight of 2000 in 10g of NMP solvent, coat the membrane near the positive electrode side, and then dry to form a single-sided coated membrane with a coating thickness of 5um; heat 5g of polyethylene glycol (PEG2000) with a molecular weight of 2000 and 5g of polytetrahydrofuran ether diol (PTMG1000) with a molecular weight of 1000 to 60℃ to melt and mix evenly, coat the single-sided membrane near the negative electrode side, and then cool to form a double-sided coated membrane with a coating thickness of 5um.

[0070] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0071] ③ Dissolve 2g of isoflurane diisocyanate (IPDI), 2g of diphenylmethane diisocyanate (MDI), and 0.2g of dibutyltin dilaurate in 20g of electrolyte (EC / EMC / DEC = 1 / 1 / 1, 1M LiPF6), mix well, and obtain a blended electrolyte.

[0072] ④ The battery cell is assembled using the separator from step ① and the electrode from step ②. The blended electrolyte from step ③ is injected, and the battery is soaked at room temperature for 24 hours and then placed in a 60°C oven for 5 hours to cure.

[0073] The battery obtained in step ④ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0074] Comparative Example 1

[0075] ① Dissolve 1g of polyurethane 1 (obtained by polymerization of PCDL2000+MDI) in 10g of NMP solvent and coat it near the positive electrode side. Dissolve 1g of polyurethane 2 (obtained by polymerization of PEG2000+MDI) in 10g of NMP solvent and coat it near the negative electrode side. Then dry it to form a coated membrane with a coating thickness of 5um.

[0076] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0077] ③ Assemble the battery cell using the separator from step ① and the electrode from step ②, inject electrolyte (EC / EMC / DEC = 1 / 1 / 11MLiPF6), soak at room temperature for 24 hours, and then place it in a 60℃ oven for 5 hours to gel and obtain the battery.

[0078] The battery obtained in step ③ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0079] Comparative Example 2

[0080] ① Dissolve 1g of polyvinylidene fluoride (PVDF) in 10g of NMP solvent, coat it on both sides of the diaphragm, and then dry it to form a coated diaphragm with a coating thickness of 5um.

[0081] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0082] ③ Assemble the battery cell using the separator from step ① and the electrode from step ②, inject electrolyte (EC / EMC / DEC = 1 / 1 / 11MLiPF6), soak at room temperature for 24 hours, and then place it in a 60℃ oven for 5 hours to gel and obtain the battery.

[0083] The battery obtained in step ③ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0084] Comparative Example 3

[0085] ① Dissolve 1g of polyethylene oxide (PEO) in 10g of NMP solvent, coat it on both sides of the diaphragm, and then dry it to form a coated diaphragm with a coating thickness of 5um.

[0086] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0087] ③ Assemble the battery cell using the separator from step ① and the electrode from step ②, inject electrolyte (EC / EMC / DEC = 1 / 1 / 11MLiPF6), soak at room temperature for 24 hours, and then place it in a 60℃ oven for 5 hours to gel and obtain the battery.

[0088] The battery obtained in step ③ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0089] Comparative Example 4

[0090] ① Dissolve 1g of polyvinylidene fluoride (PVDF) in 10g of NMP solvent, coat it on the side of the separator near the positive electrode, and then dry it to form a single-sided coated separator with a coating thickness of 5um; heat 5g of polyethylene oxide (PEO) to 60℃ to melt it, mix it evenly, coat it on the side of the single-sided separator near the negative electrode, and then cool it to form a double-sided coated separator with a coating thickness of 5um.

[0091] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0092] ③ Assemble the battery cell using the separator from step ① and the electrode from step ②, inject electrolyte (EC / EMC / DEC = 1 / 1 / 11MLiPF6), soak at room temperature for 24 hours, and then place it in a 60℃ oven for 5 hours to gel and obtain the battery.

[0093] The battery obtained in step ③ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0094] Comparative Example 5

[0095] ① Dissolve 2g of polycarbonate diol (PCDL2000) with a molecular weight of 2000 in 5g of NMP solvent, coat it on the side of the separator near the positive electrode, and then dry it to form a single-sided coated separator with a coating thickness of 5um.

[0096] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo.0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0097] ③ Dissolve 1g of diphenylmethane diisocyanate (MDI) and 0.1g of dibutyltin dilaurate in 10g of electrolyte (EC / EMC / DEC = 1 / 1 / 1, 1M LiPF6), mix well, and obtain a blended electrolyte.

[0098] ④ The battery cell is assembled using the separator from step ① and the electrode from step ②. The blended electrolyte from step ③ is injected, and the battery is soaked at room temperature for 24 hours and then placed in a 60°C oven for 5 hours to cure.

[0099] The battery obtained in step ④ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0100] Example 6

[0101] ① Heat polyethylene glycol (PEG2000) with a molecular weight of 2000 to 60℃ to melt it, apply it to the membrane near the negative electrode side, and then cool it down to form a single-sided coated membrane with a coating thickness of 5um.

[0102] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0103] ③ Dissolve 1g of diphenylmethane diisocyanate (MDI) and 0.1g of dibutyltin dilaurate in 10g of electrolyte (EC / EMC / DEC = 1 / 1 / 1, 1M LiPF6), mix well, and obtain a blended electrolyte.

[0104] ④ The battery cell is assembled using the separator from step ① and the electrode from step ②. The blended electrolyte from step ③ is injected, and the battery is soaked at room temperature for 24 hours and then placed in a 60°C oven for 5 hours to cure.

[0105] The battery obtained in step ④ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0106] Comparative Example 7

[0107] ① Dissolve 2g of polycarbonate diol (PCDL2000) with a molecular weight of 2000 in 5g of NMP solvent, coat it on both sides of the membrane, and then dry it to form a double-sided coated membrane with a coating thickness of 5um;

[0108] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0109] ③ Dissolve 1g of diphenylmethane diisocyanate (MDI) and 0.1g of dibutyltin dilaurate in 10g of electrolyte (EC / EMC / DEC = 1 / 1 / 1, 1M LiPF6), mix well, and obtain a blended electrolyte.

[0110] ④ The battery cell is assembled using the separator from step ① and the electrode from step ②. The blended electrolyte from step ③ is injected, and the battery is soaked at room temperature for 24 hours and then placed in a 60°C oven for 5 hours to cure.

[0111] The battery obtained in step ④ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0112] Example 8

[0113] ① Heat polyethylene glycol (PEG2000) with a molecular weight of 2000 to 60℃ to melt it, apply it to the diaphragm side, and then cool it down to form a double-sided coated diaphragm with a coating thickness of 5um.

[0114] ② The positive electrode slurry contains 50% wt of the solvent N-methylpyrrolidone, and the solid component ratio is LiCo. 0.1 Ni 0.8 Mn 0.1 O2:PVDF:conductive carbon black = 8:1:1; after coating and drying, the positive electrode is obtained. The negative electrode slurry contains 50% wt of solvent N-methylpyrrolidone, and the solid component ratio is graphite:PVDF:conductive carbon black = 8:1:1; after coating and drying, the negative electrode is obtained.

[0115] ③ Dissolve 1g of diphenylmethane diisocyanate (MDI) and 0.1g of dibutyltin dilaurate in 10g of electrolyte (EC / EMC / DEC = 1 / 1 / 1, 1M LiPF6), mix well, and obtain a blended electrolyte.

[0116] ④ The battery cell is assembled using the separator from step ① and the electrode from step ②. The blended electrolyte from step ③ is injected, and the battery is soaked at room temperature for 24 hours and then placed in a 60°C oven for 5 hours to cure.

[0117] The battery obtained in step ④ was subjected to a 0.3C charge-discharge cycle. After the cycle, the battery was disassembled and the peel force between the separator and the electrode was tested using a tensile testing machine.

[0118] Table 1. Performance parameters of the batteries obtained from the embodiments and comparative examples of the present invention.

[0119]

[0120]

[0121] The experimental results of Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 show that the cycle stability of the multifunctional membrane cell using the method of the present invention is significantly improved compared with the traditional polymer coating method. This is because the adhesive layer formed by the present invention is oxidation-resistant on the positive electrode and reduction-resistant on the negative electrode, so the adhesive layer itself has high electrochemical stability. However, the results of Examples 1 and 4 show that simply coating the positive electrode with an oxidation-resistant adhesive layer and the negative electrode with a reduction-resistant adhesive layer cannot achieve the effect of the present invention. This is because the present invention uses in-situ polymerization to form an adhesive layer on the surface of the membrane inside the cell, resulting in better adhesion between the positive and negative electrodes and the membrane. Since small molecule monomers are injected into the cell, the penetration depth of the electrode is deeper, and the adhesion between the electrode and the membrane is significantly stronger. Therefore, it is better able to adapt to the effects of the expansion of the positive and negative electrodes during long-term cycling.

[0122] As can be seen from Comparative Examples 1, 2, and 3, polyurethane adhesive layers have stronger adhesion than PVDF and PEO. This is because the urethane in polyurethane can form hydrogen bonds with the positive and negative electrode materials, further improving its adhesion.

[0123] The test results of Example 1 and Comparative Examples 5, 6, 7, and 8 show that in-situ polymerization to form an adhesive layer only on one side of the separator, or in-situ polymerization on both sides of the separator to form an adhesive layer with the same function (oxidation resistance or reduction resistance), improves the adhesion of the electrode sheet. However, the subsequent cycle performance is not as good as the battery provided by this invention, which forms adhesive layers with different functions in-situ polymerization on both sides of the separator. This is because the present invention forms a polycarbonate ester polyurethane near the positive electrode and a polyether polyurethane on the negative electrode, taking into account the oxidation resistance of the positive electrode and the reduction resistance of the negative electrode. During charging and discharging, it is less likely to have side reactions that affect the electrical performance.

[0124] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a battery cell with improved inter-electrode adhesion, comprising the following steps: A) Mix the first component with a solvent to obtain a solution of the first component; heat the second component to melt it and solidify it to obtain a solution of the second component. The first component solution and the second component solution are sequentially coated on both sides of the diaphragm to obtain a double-sided coated diaphragm; The first component solution includes polyester polyol and / or polycarbonate polyol; the second component solution includes polyether polyol and / or polysiloxane polyol. B) Assemble the double-coated separator, positive electrode, and negative electrode into a battery cell, inject electrolyte, and initiate an in-situ polymerization reaction inside the battery cell to obtain a battery cell with a functionalized separator. The electrolyte comprises a third component, a catalyst, a lithium salt, and a solvent; the third component is a polyisocyanate.

2. The preparation method according to claim 1, characterized in that, The first component is one or more of polyethylene adipate diol, 1,4-butanediol adipate diol, 1,6-hexanediol adipate diol, polycarbonate diol, polycaprolactone diol, and polyphthalate diol.

3. The preparation method according to claim 2, characterized in that, The mass fraction of the solute in the first component solution is 0.1% to 100%.

4. The preparation method according to claim 1, characterized in that, The second component is one or more of polyethylene glycol, polypropylene glycol, polytetrahydrofuran ether glycol, trihydroxy polyether, hydroxyl silicone oil and polydimethylsiloxane.

5. The preparation method according to claim 4, characterized in that, The mass fraction of solute in the second component solution is 0.1% to 100%.

6. The preparation method according to claim 1, characterized in that, The first component solution is coated on the side of the separator near the positive electrode, and the second component solution is coated on the side of the separator near the negative electrode.

7. The preparation method according to claim 1, characterized in that, The third component is one or more of toluene diisocyanate, isoflurone diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, terephthalic diisocyanate, MDI trimer, and TDI trimer.

8. The preparation method according to claim 7, characterized in that, The mass fraction of the third component in the electrolyte is 0.1% to 20%.

9. The preparation method according to claim 1, characterized in that, The catalyst is one or more of N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, N,N,N',N'-tetramethylalkylene diamine, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, triethanolamine, N,N'-dimethylpyridine, dibutyltin dilaurate, stannous octoate, triethylphosphorus, triphenylphosphorus, tri-n-butylphosphorus, tributyltin oxide, tetrabutyl titanate, tetrabutyl zirconate, trialkyltin alkoxide, and dialkyltin oxide; The mass of the catalyst in the electrolyte accounts for 0.5 to 5% of the total mass of the first, second, and third components.

10. The preparation method according to claim 1, characterized in that, The polymerization temperature is 40–90°C; the polymerization time is 1–120 hours.

11. The preparation method according to claim 10, characterized in that, After assembling the double-coated separator, positive electrode, and negative electrode, the mixture is brought into contact with the electrolyte and immersed at room temperature for 2–36 hours, after which polymerization is initiated.

12. A battery cell for improving inter-electrode adhesion, prepared according to the preparation method of any one of claims 1 to 11.

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