A lithium-ion battery

Abstract

This application provides a lithium-ion battery, belonging to the field of lithium-ion battery technology, overcoming the defect of easy migration of Ni ions in existing ternary lithium batteries. The lithium-ion battery of this application includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a ternary material; the general formula of the ternary material is LiNi. x Co y M 1‑x‑ y O2, where 0.5≤x≤0.9, 0.05≤y≤0.3, and M is Mn or Al; the separator includes a base film and a zeolite coating disposed on at least one surface of the base film, the zeolite coating comprising zeolite having micropores with a pore size of F nm; x / F=0.5~2.8; where F=0.3~1.2. The lithium-ion battery of this application has excellent cycle performance and safety performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and specifically relates to a lithium-ion battery. Background Technology

[0002] With the increasing demand for high-energy-density, long-cycle-life batteries in fields such as new energy vehicles, portable electronic devices, and energy storage systems, ternary lithium batteries (especially NCM / NCA systems) have attracted much attention due to their excellent electrochemical performance. However, a key issue facing ternary lithium batteries in practical applications is the migration of Ni ions.

[0003] During the charge-discharge cycle of ternary lithium batteries, especially under high temperature, high voltage, or rapid charge-discharge conditions, Ni ions in the positive electrode active material are prone to migration. This migration not only damages the structure of the positive electrode active material and reduces the battery's electrochemical performance, but may also trigger side reactions, such as reacting with solvents or lithium salts in the electrolyte to form insoluble precipitates that clog the separator pores and affect the normal transport of lithium ions. More seriously, the migrated ions may also penetrate the separator and reach the negative electrode surface, causing corrosion of the negative electrode material and internal short circuits in the battery, thus seriously threatening the battery's safety and lifespan. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect that Ni ions are prone to migration in the prior art ternary lithium battery, thereby providing a lithium-ion battery.

[0005] Therefore, the present invention provides the following technical solution:

[0006] A lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a ternary material.

[0007] The general formula of the ternary material is LiNi. x Co y M 1-x-y O2, where 0.5≤x≤0.9, 0.05≤y≤0.3, and M is Mn or Al;

[0008] The diaphragm includes a base membrane and a zeolite coating disposed on at least one surface of the base membrane, the zeolite coating comprising zeolite having micropores with a pore size of F nm.

[0009] x / F = 0.5–2.8;

[0010] Where F = 0.3 to 1.2.

[0011] In one possible implementation, the zeolite comprises a hierarchical porous zeolite;

[0012] Optionally, the porosity of the hierarchical porous zeolite is C%, 100x / C = 0.8 to 2.5;

[0013] Optional, C = 35–70;

[0014] Optionally, the hierarchical porous zeolite may further include mesopores and / or macropores with a pore size of 2 to 500 nm.

[0015] In one possible implementation, F = 0.3 to 0.7;

[0016] In one possible implementation, x / F = 0.7 to 2.3.

[0017] In one possible implementation, the specific surface area of ​​the zeolite is Am. 2 / g, the particle size Dv501 of zeolite is Bμm, and A / B = 100~1500;

[0018] Optional, A = 20 to 700;

[0019] Optional, B = 0.01 to 5.

[0020] In one possible implementation, the particle size Dv502 of the ternary material is 3–15 μm.

[0021] In one possible implementation, the thickness of the zeolite coating is h μm, and B / h = 0.1 to 0.8;

[0022] Optional, h = 0.5 to 10.

[0023] In one possible implementation, the zeolite has a pore volume of 0.5–1.5 cm³. 3 / g;

[0024] In one possible implementation, the ternary material is a nickel-cobalt-manganese ternary material;

[0025] In one possible implementation, the diaphragm further includes an adhesive layer disposed on at least one side surface of the base membrane and / or the zeolite coating;

[0026] Optionally, the thickness of the adhesive layer is 0.1–4 μm;

[0027] In one possible implementation, the base film comprises one or more of polyethylene, polypropylene, polyimide, polyacrylonitrile, and polyethersulfone;

[0028] Optionally, the thickness of the base film is 3-20 μm;

[0029] Optionally, the pore size of the base membrane is 0.02-0.5 μm.

[0030] In one possible implementation, the zeolite coating contains 10% to 90% zeolite by mass.

[0031] In one possible implementation, the zeolite coating further includes a binder;

[0032] Optionally, the zeolite coating contains 0-90% by mass of binder.

[0033] In one possible implementation, the zeolite coating further includes additives;

[0034] Optionally, the mass percentage of the additives in the zeolite coating is 0-10%.

[0035] In one possible implementation, the tensile strength of the diaphragm is 2000–5500 gf;

[0036] In one possible implementation, the adhesive force of the diaphragm is 5–30 N / m;

[0037] In one possible implementation, the porosity of the base film is 35-45%;

[0038] In one possible implementation, the puncture strength of the diaphragm is 150–600 gf.

[0039] In one possible implementation, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material;

[0040] The negative electrode active material includes silicon carbide and graphite;

[0041] Optionally, the silicon content in the silicon-carbon is 20-70% by mass;

[0042] Optionally, the particle size Dv503 of the silicon carbide is 5–15 μm.

[0043] The technical solution of this invention has the following advantages:

[0044] 1. The lithium-ion battery of this application includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a ternary material; the general formula of the ternary material is LiNi. x Co y M 1-x-yO2, where 0.5≤x≤0.9, 0.05≤y≤0.3, and M is Mn or Al; the separator includes a base film and a zeolite coating disposed on at least one surface of the base film, the zeolite coating comprising zeolite having micropores with a pore size of F nm; x / F = 0.5~2.8. An appropriate nickel content in the ternary material improves the energy density of the battery, while the suitable pore size of the zeolite coating effectively promotes the rapid transport of lithium ions and significantly inhibits the migration of transition metal ions, thereby ensuring the long lifespan and high safety of the battery. The lithium-ion battery satisfying x / F = 0.5~2.8 in this application exhibits excellent comprehensive performance. Attached Figure Description

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the diaphragm structure.

[0047] Figure label:

[0048] 1-Base film; 2-Zeolite coating; 3-Adhesive layer. Detailed Implementation

[0049] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0050] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0051] During the charge-discharge cycle of lithium batteries, Ni ions in ternary materials are prone to migration, which seriously threatens the safety and lifespan of the battery.

[0052] Based on this, this application provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes a ternary material.

[0053] The general formula of the ternary material is LiNi. x Co y M 1-x-y O2, where 0.5≤x≤0.9, 0.05≤y≤0.3, and M is Mn or Al;

[0054] The diaphragm includes a base membrane and a zeolite coating disposed on at least one surface of the base membrane, the zeolite coating comprising zeolite having micropores with a pore size of F nm.

[0055] x / F = 0.5–2.8;

[0056] Where F = 0.3 to 1.2. Optionally, x / F = 0.7 to 2.3.

[0057] For example, x can be 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, or 0.90. y can be 0.05, 0.1, 0.15, 0.2, 0.25, or 0.3. x / F can be 0.5, 0.6, 0.7, 0.8, 1.0, 1.3, 1.5, 1.8, 2.0, 2.2, 2.5, or 2.8. For example, F can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, or 1.2.

[0058] The higher the Ni content in the positive electrode, the relatively poorer the structural stability of the ternary material. During charge and discharge, especially under high temperature or deep charge and discharge conditions, its crystal structure may undergo slight changes, leading to the migration and redistribution of transition metal ions. These migrated ions may deposit on the surface of the negative electrode, forming a so-called "metal coating," which not only reduces the battery's cycle performance but may also trigger internal short circuits, further exacerbating self-discharge and thermal runaway problems.

[0059] Zeolite is a silicate aluminate with a unique topological structure and microporous channels, enabling effective adsorption of metal ions. Furthermore, the negatively charged zeolite framework attracts positively charged metal ions (such as Ni, Co, and Mn) through electrostatic interactions. This electrostatic interaction helps to block the migration of these metal ions. Functional groups on the zeolite framework (such as hydroxyl and carboxyl groups) can form chemisorption bonds with Ni, Co, and Mn ions, further enhancing the membrane's ability to block these metal ions.

[0060] When the nickel content is relatively low and the zeolite pore size (F) is relatively large, the battery's energy density is limited, while the migration of transition metal ions is exacerbated. The zeolite coating's adsorption and blocking effect on ions weakens, leading to decreased battery cycle stability and accelerated capacity decay. When the nickel content is relatively high and the zeolite pore size is relatively small, although the battery's energy density may be improved to some extent, it results in decreased cycle performance and worsened thermal stability. The migration of transition metal ions becomes difficult to control, exceeding the adsorption capacity of the zeolite coating, leading to damage to the negative electrode SEI film and rapid capacity decay, increasing battery safety risks. Therefore, lithium-ion batteries exhibit excellent overall performance when x / F = 0.5–2.8. An appropriate nickel content in the ternary material increases the battery's energy density, while the suitable pore size of the zeolite coating effectively promotes rapid lithium-ion transport while significantly inhibiting the migration of transition metal ions, thus ensuring long battery life and high safety.

[0061] When the zeolite micropore size is 0.3–1.2 nm, it can hinder Ni ions from entering the zeolite micropores, preventing them from shuttling through the zeolite channels and thus inhibiting Ni ion migration. Furthermore, the zeolite framework carries a negative charge, which can attract positively charged metal ions through electrostatic interactions. This electrostatic interaction helps to block the migration of these metal ions. The functional groups on the zeolite framework can form chemisorption bonds with Ni, Co, and Mn ions, and this chemisorption further enhances the membrane's ability to block these metal ions. When the zeolite micropore size is 0.3–1.2 nm, lithium ions can pass through. Therefore, the zeolite used in the membrane of this application can inhibit Ni ion migration while increasing lithium ion transport channels, ensuring rapid and efficient lithium ion transport.

[0062] In one possible implementation, the zeolite comprises a hierarchical porous zeolite;

[0063] Hierarchical porous zeolite is a type of zeolite material with a hierarchical pore structure. Compared with traditional zeolites, hierarchical porous zeolite not only has micropores, but also introduces mesopores (2-50 nm) and / or macropores (greater than 50 nm) to form a hierarchical pore system.

[0064] Optionally, the porosity of the hierarchical porous zeolite is C%, 100x / C = 0.8 to 2.5;

[0065] Optional, C = 35-70.

[0066] For example, C can be 35, 40, 45, 50, 55, 60, 65 or 70; for example, 100x / C can be 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2 or 2.5.

[0067] The hierarchical porous structure increases the specific surface area of ​​zeolite, thereby enhancing its adsorption of transition metals and helping to reduce the risk of battery self-discharge rate and thermal runaway. By uniformly coating hierarchical porous zeolite particles onto the surface of the base film, a three-dimensional hierarchical porous structure is constructed, enhancing the thermal stability, mechanical strength, and puncture resistance of the separator. This ensures that it maintains structural integrity under high-temperature environments, effectively resists internal battery stress, reduces structural damage during charging and discharging, and thus lowers the self-discharge rate.

[0068] Multi-level porous zeolite particles (aluminosilicates) can improve the wettability of the separator to the electrolyte and the liquid retention of the zeolite coating, thereby improving the fluidity of the electrolyte, reducing the mass transfer resistance of lithium ions in the battery, increasing the conductivity of lithium ions, and enhancing the battery dynamics. The increased liquid retention can prevent the electrolyte from evaporating at high temperatures or during long-term use, thereby improving the reliability and lifespan of the battery.

[0069] Applying zeolite coatings to the separator of ternary lithium batteries, with a 100x / C ratio of 0.8–2.5, can effectively suppress the migration of transition metals during high-temperature storage, reduce the dissolution of transition metal elements from the positive electrode to the negative electrode, thereby mitigating the damage to the SEI on the negative electrode surface, reducing the consumption of active lithium ions, and contributing to improved battery storage performance and cycle stability. When 100x / C is less than 0.8, transition metal migration may become relatively easy. Excessively high zeolite porosity may render the zeolite coating's barrier effect on transition metals very limited, and may even lead to the formation of excessively large channels in the zeolite coating, allowing transition metals to migrate more easily through these channels. This migration can also damage the positive and negative electrode structures of the battery, leading to a decrease in battery performance. When 100x / C is greater than 2.5, due to the lower porosity, the separator's barrier effect on transition metals is weakened, making it easier for transition metals to dissolve from the positive electrode material and migrate to the negative electrode via the electrolyte. This migration not only reduces the activity of the cathode material but also forms undesirable deposits on the anode surface, damaging the SEI (solid electrolyte interphase) film and thus accelerating the consumption of active lithium ions and the decay of battery capacity. Meeting the 100x / C ratio of 0.8–2.5 can effectively suppress the migration of Ni, Co, and Mn ions, protect the cathode material structure, and extend battery cycle life. It also improves battery safety and electrochemical performance, providing strong technical support for the further development of ternary lithium batteries. This is expected to drive the lithium-ion battery industry towards higher safety, higher energy density, and longer cycle life.

[0070] In one possible implementation, the hierarchical porous zeolite further includes mesopores and / or macropores with a pore size of 2 to 500 nm; for example, the hierarchical porous zeolite includes mesopores with a pore size of 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm; for example, the hierarchical porous zeolite includes macropores with a pore size of 60 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm.

[0071] In one possible implementation, F = 0.3 to 0.7.

[0072] In one possible implementation, the specific surface area of ​​the zeolite is Am. 2 / g, the particle size Dv501 of zeolite is Bμm, and A / B = 100~1500.

[0073] With an A / B ratio in the range of 100–1500, the separator has sufficient adsorption sites for Ni, Co, Mn, and Al ions, effectively suppressing their migration. Simultaneously, it avoids excessive water absorption by the zeolite, preventing excessive water content inside the battery. High water content accelerates capacity decay during battery cycling, and the decomposition of water during charging and discharging produces gases (such as H2), causing battery bulging and swelling. An A / B ratio of 100–1500 ensures battery cycle performance, reduces the transport resistance of the separator layer, and improves the battery's rate performance.

[0074] Optionally, A = 20 to 700; for example, A can be 20, 50, 100, 150, 200, 300, 400, 500, 600 or 700.

[0075] Optionally, B = 0.01 to 5. Exemplary values ​​can be 0.01, 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5. This invention uses zeolite particles (aluminosilicates) with better affinity for the electrolyte, and by controlling the zeolite particle size to 0.01–5 μm, the wettability of the separator to the electrolyte can be improved. Furthermore, by controlling the particle size of the zeolite, a uniform and stable coating is formed, thereby improving the adsorption effect and mechanical stability of transition metal ions, further enhancing the safety performance of the battery.

[0076] In one possible implementation, the particle size Dv502 of the ternary material is 3–15 μm. For example, it can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm.

[0077] Within this range, the particle size of ternary materials avoids the increased liquid phase diffusion resistance and decreased rate performance caused by excessively small particle sizes; simultaneously, it avoids excessively large particle sizes, which can lead to structural stress and material breakage during cycling. When the particle size of ternary materials meets the above-mentioned range, it can improve battery cycle performance and rate performance while suppressing Ni ion migration and enhancing battery safety.

[0078] In one possible implementation, the thickness of the zeolite coating is h μm, and B / h = 0.1–0.8; optionally, h = 0.5–10. For example, B / h can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8. For example, h can be 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0079] With a B / h range of 0.1 to 0.8, the packing density of zeolite particles is moderate, which ensures good porosity of the coating, minimizes the obstruction to ion transport, and at the same time ensures the adsorption of more Ni, Co, Mn, and Al ions, inhibiting their migration and maintaining good cycle performance and rate capability of the battery.

[0080] By controlling the thickness of the hierarchical porous zeolite coating within the aforementioned range, it is possible to maintain good mechanical strength while providing sufficient physical barrier function to further prevent the penetration of transition metal ions.

[0081] In one possible implementation, the zeolite is a lithium-exchange zeolite; optionally, the lithium exchange rate in the lithium-exchange zeolite is 90% to 99%. For example, the lithium exchange rate in the lithium-exchange zeolite can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%.

[0082] Lithium-exchanged zeolites are zeolites in which at least a portion of the cations (such as Na, K, Ca, etc.) contained in the zeolite matrix are replaced with lithium ions. The replacement amount is the amount of lithium exchanged.

[0083] Using lithium-exchange zeolite can effectively replenish lithium while preventing lithium adsorption during battery cycling, thereby increasing the free lithium content, improving ionic conductivity, kinetics, rate performance, and cycle performance. It also enhances the chemical stability of the zeolite coating, allowing it to maintain good performance under extreme conditions such as high temperature and high pressure. Lithium-exchange zeolite not only provides additional lithium ions to the battery system but also significantly improves ion transport efficiency. Simultaneously, it effectively suppresses the dissolution and migration of transition metal ions such as Ni, Co, and Mn, preventing these ions from depositing dendrites on the negative electrode and avoiding battery self-discharge problems caused by dendrites piercing the separator.

[0084] In one possible implementation, the zeolite has a pore volume of 0.5–1.5 cm³.3 / g; for example, it could be 0.5cm 3 / g, 0.6cm 3 / g, 0.7cm 3 / g, 0.8cm 3 / g, 0.9cm 3 / g, 1.0cm 3 / g, 1.1cm 3 / g, 1.2cm 3 / g, 1.3cm 3 / g, 1.4cm 3 / g or 1.5cm 3 / g. Zeolites with high pore volume can effectively adsorb transition metal ions, with pore volumes ranging from 0.5 to 1.5 cm³. 3 / g can further inhibit the migration of transition metal elements.

[0085] In one possible implementation, the ternary material is a nickel-cobalt-manganese ternary material.

[0086] In one possible implementation, the diaphragm further includes an adhesive layer disposed on at least one side surface of the base membrane and / or the zeolite coating;

[0087] Optionally, the thickness of the adhesive layer (the thickness of the adhesive layer on one side surface) is 0.1 to 4 μm; for example, the thickness of the adhesive layer can be 0.1 μm, 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, or 4 μm.

[0088] In one possible implementation, the base film comprises one or more of polyethylene, polypropylene, polyimide, polyacrylonitrile, and polyethersulfone;

[0089] Optionally, the thickness of the base film is 3-20 μm; for example, it can be 3 μm, 4 μm, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 18 μm or 20 μm.

[0090] Optionally, the pore size of the base film is 0.02-0.5 μm. For example, it can be 0.02 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm or 0.5 μm.

[0091] In one possible implementation, the tensile strength of the diaphragm is 2000 to 5500 gf; within this range, the tensile strength can effectively suppress the expansion of the silicon anode while avoiding a decrease in diaphragm dynamics.

[0092] In one possible implementation, the adhesive force of the diaphragm is 5–30 N / m;

[0093] In one possible implementation, the porosity of the base film is 35% to 45%. Exemplary examples include 35%, 38%, 40%, 42%, or 45%.

[0094] In one possible implementation, the puncture strength of the diaphragm is 150–600 gf.

[0095] In one possible implementation, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material;

[0096] The negative electrode active material includes silicon carbide and graphite.

[0097] The zeolite coating enhances the puncture resistance of the separator. This design better accommodates the volume expansion of the silicon-carbon anode, reduces potential damage to the battery structure, and further reduces the self-discharge rate.

[0098] Optionally, the silicon content in the silicon-carbon is 20% to 70% by mass; for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%.

[0099] Optionally, the particle size Dv503 of the silicon carbide is 5 to 15 μm; for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0100] Optionally, the average sphericity of the silicon-carbon is 0.5 to 1. For example, it can be 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

[0101] Through the optimized combination of these parameters, the hierarchical porous zeolite coating can significantly reduce the migration of transition metal ions, thereby reducing the side reactions caused by these ions with the electrolyte, avoiding the formation of an unstable solid electrolyte interphase (SEI) film that affects the lithium ion insertion and extraction process, and improving battery performance; at the same time, it reduces dendrite formation, ultimately reducing the battery's self-discharge rate and improving the overall performance and stability of the battery.

[0102] In summary, this invention uses LiNi x Co y M 1-x-y O2, where 0.5≤x≤0.9 is the positive electrode active material. By adjusting the coating thickness and pore size of the multi-hole zeolite coating in the battery separator, and by adjusting the particle size of the zeolite particles, the problems of poor cell wetting, low liquid retention and high self-discharge rate can be effectively solved.

[0103] In one possible implementation, the configuration of the hierarchical porous zeolite includes one or more of MEI, BEA, DDR, STT, MWW, MFI, LTA, FAU, SOD, CHA, and MOR.

[0104] By controlling the zeolite synthesis method, zeolite particles with multiple pore structures can be prepared, such as hierarchical porous zeolite MFI, which includes macropores larger than 100 nm and micropores of 0.58 nm.

[0105] In one possible implementation, the adhesive layer comprises at least one polymer selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene modified and copolymerized thereof, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, styrene-butadiene rubber (SBR), polyvinyl alcohol and its copolymerized polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, waterborne polyurethane, ethylene vinyl acetate copolymer, multi-component acrylic copolymer, lithium polystyrene sulfonate, pure styrene latex, polyvinylidene fluoride trichloroethylene, polyvinylidene fluoride chlorotrifluoroethylene, polyvinylpyrrolidone, polyethylene oxide, cellulose acetate, cellulose butyl acetate, cellulose propyl acetate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose.

[0106] In one possible embodiment, the adhesive is a polymer adhesive, optionally selected from polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, polyacrylonitrile, poly(meth)acrylate, aramid resin, poly(meth)acrylic acid, styrene-butadiene rubber (SBR), polyvinyl alcohol, polyvinyl acetate, carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose (CMCNa), carboxyethyl cellulose, polyacrylamide, phenolic resin, epoxy resin, waterborne polyurethane, ethylene-vinyl acetate copolymer, multi-component acrylic copolymer, lithium polystyrene sulfonate, waterborne silicone resin, nitrile-polyvinyl chloride blend, styrene-acrylic latex, pure styrene latex, etc., and one or more combinations of blends and copolymers derived from the aforementioned polymer modifications.

[0107] In one possible implementation, the adjuvant includes at least one of branched alcohols, triethyl phosphate, polyethylene glycol, fluorinated polyethylene oxide, polyethylene oxide, stearic acid, sodium dodecylbenzene sulfonate, sodium hexadecyl sulfonate, fatty acid glycerides, sorbitan fatty acid esters, and polysorbates.

[0108] The electrolyte can be a conventional electrolyte in the art. In one possible embodiment, the electrolyte is a non-aqueous electrolyte, which includes a carbonate solvent and a lithium salt.

[0109] In one possible implementation, the carbonate solvent is selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC).

[0110] In one possible implementation, the negative current collector is selected from one or more of aluminum foil, carbon-coated aluminum foil, and perforated aluminum foil.

[0111] In one possible implementation, the positive current collector is selected from one or more of aluminum foil, carbon-coated aluminum foil, and perforated aluminum foil.

[0112] In one possible implementation, the battery casing may include one of aluminum-plastic film, aluminum alloy, and stainless steel.

[0113] In the examples and comparative examples, "parts" refers to "parts by mass".

[0114] The preparation method of lithium-exchange zeolite in the embodiment includes: soaking the zeolite in a lithium salt solution, which can replace the original cations with lithium ions, centrifuging and washing to obtain lithium-exchange zeolite, and controlling the amount of lithium exchange by controlling the soaking time.

[0115] Example 1

[0116] This embodiment provides a lithium-ion battery, the preparation method of which includes:

[0117] 85 parts of lithium-exchanged hierarchical porous FAU zeolite particles (particle size Dv501 1 μm, micropore size 0.5 nm, macropore size 204 nm, Li exchange content in the zeolite 95%), 10 parts of polyvinylidene fluoride-hexafluoropropylene, and 5 parts of polyethylene glycol were added to 860 parts of DMAC (N,N-dimethylacetamide). After uniform mixing, a slurry was obtained. The slurry was coated onto one side of a base membrane 1 (base membrane 1 thickness 7 μm, pore size 0.05 μm, porosity 38%) using a microgravure printing method. After drying, a membrane with a hierarchical porous FAU zeolite coating 2 with a thickness of 3 μm was obtained. The obtained membrane was then coated with a 1 μm thick polyvinylidene fluoride-hexafluoropropylene coating layer 3 on both sides using gravure printing. The puncture strength of the membrane prepared in this example is 350 gf.

[0118] The negative electrode uses artificial graphite: a silicon-carbon composite graphite material with a silicon-carbon mass ratio of 90:10 is used as the negative electrode active material. The silicon content in the silicon-carbon is 40% by mass, and the particle size (Dv503) of the silicon-carbon is 8 μm. The positive electrode uses ternary material LiNi. 0.8 Co 0.1 Mn 0.1O2 is the positive electrode active material. The above-mentioned separator, positive electrode sheet, and negative electrode sheet are stacked and wound in the order of negative electrode sheet, separator, positive electrode sheet, separator to prepare a lithium-ion battery cell. After baking, electrolyte injection, formation, and packaging, a high-safety lithium-ion battery is obtained.

[0119] This application also provides lithium-ion batteries of Examples 2-25 and Comparative Examples 1 and 21, which are basically the same as those of Example 1, except for the different parameters, as shown in Tables 1 and 2.

[0120] Comparative Example 3 is basically the same as Example 1, except that a conventional diaphragm is used (alumina is used instead of lithium-exchanged multi-level porous FAU zeolite particles).

[0121] The testing methods for each parameter are as follows:

[0122] (1) Base film thickness: Measure the thickness of the base film using a micrometer.

[0123] (2) Thickness of zeolite coating (hμm): The cross-section of the coated diaphragm was observed using a scanning electron microscope (SEM). The coating thickness was measured three times and the average value was taken using SEM image measurement software.

[0124] (3) Thickness of the adhesive layer: The cross-section of the coated diaphragm was observed using a scanning electron microscope (SEM). The thickness of the adhesive layer was measured three times using SEM image measurement software, and the average value was taken.

[0125] (4) Pore size of the base membrane: obtained by testing with a PMI membrane micropore analyzer.

[0126] (5) Diaphragm puncture strength: can be tested using a universal tensile testing machine, referring to GB / T 36363-2018.

[0127] (6) Test method for tensile strength of diaphragm: Tensile testing machine is used to test the tensile strength at a strain rate of 1 mm / min.

[0128] (7) Test method for the adhesion of the diaphragm: Cut samples with a width of 20 mm and a length of 80 mm from the diaphragm prepared in the examples and comparative examples and the positive or negative electrode sheet, and press them together on a hot press at a temperature of 65°C and a pressure of 1 MPa for 30 s. Fix one end of the diaphragm and one end of the electrode sheet to the left and right clamps of a universal tensile testing machine respectively, and peel them at a constant speed of 10 mm / min. Repeat the experiment 5 times and take the average value.

[0129] (8) Pore diameter F μm and specific surface area (Am) of zeolite micropores 2Test methods for pore size ( / g) and pore volume: Using a specific surface area and pore size analyzer, 0.1g of sample is placed in the analyzer. The pore size, specific surface area and pore volume of the zeolite micropores are calculated by utilizing the adsorption-desorption behavior of nitrogen molecules in the zeolite channels.

[0130] (9) Pore size of mesopores and macropores in hierarchical zeolite: Take 1g of hierarchical zeolite sample and put it into the expansion chamber of mercury porosimeter. Apply different pressures to make mercury penetrate into the pores of the powder sample. Based on the relationship between the volume of mercury entering the pores and the pressure, calculate the size distribution of the pores using the Washburn equation.

[0131] (10) Dv501 (Bμm), Dv502, Dv503: measured using a laser particle size analyzer.

[0132] (11) Test method for base membrane porosity: Porosity was tested using a PMI AAQ series water pressure tester. Specifically, the produced base membrane was sampled: 1.5-2.0g base membrane samples were cut; the thickness, length, and width of the samples were recorded, and the density of the base membrane was calculated as: density = weight / (length * width * thickness), in g / cm³, and basis weight = weight / (length * width), in g / m³. 2 The sample was then placed in a pure water bath to expel the gas; the test was then conducted. The porosity value was read from the output report.

[0133] (12) Test method for porosity C% of hierarchical zeolite: Mercury is forced into the pores of hierarchical zeolite by applying external pressure. The smaller the pore size, the greater the pressure required. By measuring the volume of mercury entering the pores under different pressures, the pore volume and pore size distribution can be calculated, thereby obtaining the porosity of the material.

[0134] (13) Lithium exchange capacity test method: First, 0.1 g of zeolite sample was dissolved in an appropriate acid to extract lithium ions from the zeolite structure. The sample was tested using ICP-MS (inductively coupled plasma mass spectrometry) to obtain the molar concentrations of lithium and sodium ions in the sample.

[0135] Lithium exchange capacity = Lithium ion molar concentration / (Lithium ion molar concentration + Sodium ion molar concentration)

[0136] The parameters for each embodiment and comparative example are shown in Tables 1-2.

[0137] Table 1

[0138]

[0139]

[0140] Table 2

[0141]

[0142] Separator and Lithium-ion Battery Performance Testing Methods

[0143] (1) Ion conductivity meter

[0144] The membrane, fully immersed in electrolyte, is placed in an ionic conductivity meter. The wetted membrane sample is sandwiched between identical stainless steel electrodes to form a button cell or similar test unit. An appropriate scanning frequency range (e.g., 0.1–100,000 Hz) is set on an electrochemical workstation, and impedance testing is performed to obtain the ionic conductivity of the membrane.

[0145] (2) After the lithium-ion battery is charged at 2C and discharged at 1C for 1000 cycles, the battery is disassembled and the metal content in the separator is tested:

[0146] The content of metal elements in the battery separator was determined using X-ray fluorescence spectroscopy (XRF). The battery separator sample was cut into a square with a side length of 10 mm, fixed in place using a clamp, and then analyzed using XRF.

[0147] The test results of Example 1 are shown in Table 3.

[0148] Table 3. Content (%) of each metal in the diaphragm

[0149] Example 1 36.2 35.3 4.6 15.7 3.8 4.1

[0150] As shown in Table 3, the membrane of this application can successfully inhibit the migration of Ni, Co, and Mn ions.

[0151] Based on the total mass of metals in the diaphragm, the Al content is 33.5-44%, the Li content is 33-37%, the Na content is 4-5.1%, the Ni content is 12-16%, the Co content is 3.5-4.2%, and the Mn content is 3.5-4.2%.

[0152] (3) 25℃ Cyclic Capacity Retention Rate and Thickness Expansion Rate Test

[0153] The initial voltage and initial thickness of the incoming battery were measured. The lithium-ion battery was then placed at 25°C and charged at a constant current of 2C to the upper limit voltage (4.5V), followed by constant voltage charging at 4.5V to 0.05C, recording the initial thickness P0. Then, it was discharged at a constant current of 1C to 3.0V, with the initial discharge capacity recorded as C0. After resting for 5 minutes, this constituted one charge-discharge cycle. This charging / discharging cycle was repeated, and the discharge capacity after 1000T cycles was recorded as C1, and the final thickness P1 was recorded. Capacity retention rate: C = C1 / C0 * 100%, Thickness expansion rate: P = (P1 - P0) / P0 * 100%.

[0154] (4) Liquid retention test: The liquid retention of the battery is calculated by the difference between the weight after packaging and the weight before liquid injection.

[0155] (5) Wetting test: The contact angle of the diaphragm is tested using a contact angle tester to obtain its wettability.

[0156] The test results are shown in Tables 4 and 5.

[0157] Table 4

[0158] Example 1 86.21 15.36 Example 2 85.25 17.99 Example 3 85.49 17.33 Example 4 83.85 21.82 Example 5 82.97 24.23 Example 6 84.36 20.42 Example 7 84.05 21.27 Comparative Example 1 80.4 31.26 Comparative Example 2 81.2 29.07 Comparative Example 3 75.1 30.42 Example 8 84.61 19.74 Example 9 85.26 17.96 Example 10 84.87 19.03 Example 11 82.58 25.29 Example 12 82.34 25.95 Example 13 83.11 23.84 Example 14 82.68 25.02 Example 15 82.35 25.92 Example 16 82.26 26.17 Example 17 83.59 22.53 Example 18 82.47 25.60 Example 19 82.34 25.95 Example 20 82.38 25.84 Example 21 82.05 26.74 Example 22 82.12 26.55 Example 23 83.72 22.17 Example 24 83.28 23.38 Example 25 82.49 25.54

[0159] As can be seen from the comparison of the embodiments and comparative examples in Table 4, the capacity retention rate of the battery of this application at 1000T is significantly increased, the cycle life is extended, the expansion rate is reduced, and the safety performance of the battery is improved.

[0160] Table 5

[0161] Example 1 1.48 8.57 62 Example 25 0.95 8.31 67

[0162] The smaller the contact angle of the separator, the better the wettability. As shown in Table 5, the use of hierarchical porous zeolite can significantly improve the ionic conductivity, electrolyte retention, and wettability of the battery.

[0163] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode material layer includes a ternary material; The general formula of the ternary material is LiNi. x Co y M 1-x-y O2, where 0.5≤x≤0.9, 0.05≤y≤0.3, and M is Mn or Al; The diaphragm includes a base membrane and a zeolite coating disposed on at least one surface of the base membrane, the zeolite coating comprising zeolite having micropores with a pore size of F nm. x / F = 0.5~2.8; Where F = 0.3~1.2; The zeolite comprises hierarchical porous zeolite particles; the porosity of the hierarchical porous zeolite particles is C%, 100x / C = 0.8~2.5; C=35~70。 2. The lithium-ion battery according to claim 1, characterized in that, The hierarchical porous zeolite also includes mesopores and / or macropores with a pore size of 2~500nm.

3. The lithium-ion battery according to claim 1 or 2, characterized in that, At least one of the following conditions must be met: （1）F=0.3~0.7； (2) x / F = 0.7~2.

3.

4. The lithium-ion battery according to claim 1 or 2, characterized in that, The specific surface area of ​​the zeolite is Am. 2 / g, the particle size Dv501 of zeolite is Bμm, A / B=100~1500.

5. The lithium-ion battery according to claim 4, characterized in that, A=20~700。 6. The lithium-ion battery according to claim 4, characterized in that, B=0.01~5。 7. The lithium-ion battery according to claim 1 or 2, characterized in that, The particle size Dv502 of the ternary material is 3~15μm.

8. The lithium-ion battery according to claim 1 or 2, characterized in that, The thickness of the zeolite coating is h μm, and B / h = 0.1~0.

8.

9. The lithium-ion battery according to claim 8, characterized in that, h=0.5~10。 10. The lithium-ion battery according to claim 1 or 2, characterized in that, At least one of the following conditions must be met: (1) The pore volume of the zeolite is 0.5~1.5 cm. 3 / g; (2) The ternary material is a nickel-cobalt-manganese ternary material; (3) The diaphragm further includes an adhesive layer disposed on at least one side of the base membrane and / or zeolite coating; (4) The base film includes one or more of polyethylene, polypropylene, polyimide, polyacrylonitrile, and polyethersulfone.

11. The lithium-ion battery according to claim 10, characterized in that, The thickness of the adhesive layer is 0.1~4μm.

12. The lithium-ion battery according to claim 10, characterized in that, The thickness of the base film is 3-20 μm.

13. The lithium-ion battery according to claim 10, characterized in that, The pore size of the base membrane is 0.02-0.5 μm.

14. The lithium-ion battery according to claim 1 or 2, characterized in that, At least one of the following conditions must be met: (1) The zeolite content in the zeolite coating is 10%~90% by mass; (2) The zeolite coating also includes a binder.

15. The lithium-ion battery according to claim 14, characterized in that, The binder in the zeolite coating has a mass percentage content of 0-90%.

16. The lithium-ion battery according to claim 1 or 2, characterized in that, At least one of the following conditions must be met: (1) The tensile strength of the diaphragm is 2000~5500 gf; (2) The adhesive force of the diaphragm is 5~30 N / m; (3) The porosity of the base membrane is 35-45%; (4) The puncture strength of the diaphragm is 150~600 gf.

17. The lithium-ion battery according to claim 1 or 2, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer includes a negative electrode active material; The negative electrode active material includes silicon carbide and graphite.

18. The lithium-ion battery according to claim 17, characterized in that, The silicon carbon contains 20-70% silicon by mass.

19. The lithium-ion battery according to claim 17, characterized in that, The particle size Dv503 of the silicon carbide is 5~15μm.

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