Lithium-ion battery and electrical apparatus

Abstract

The present disclosure relates to the technical field of batteries, and specifically to a lithium-ion battery and an electrical apparatus. The lithium-ion battery comprises a positive electrode plate, a negative electrode plate, a separator, and an electrolyte; the positive electrode plate comprises a positive electrode film layer; the positive electrode film layer comprises a positive electrode active material; the positive electrode active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate; the electrolyte comprises an organic solvent, an electrolyte salt, and an additive; the additive comprises a compound represented by formula (I).

Description

Lithium-ion batteries and electrical devices

[0001] Priority information

[0002] This disclosure claims priority and benefits to patent application No. 2024117420992, filed with the China National Intellectual Property Administration on November 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of battery technology, specifically to lithium-ion batteries and electrical devices. Background Technology

[0004] Polyanionic cathode materials, represented by lithium iron phosphate (LFP) and lithium manganese iron phosphate (LMP), have become one of the most important practical cathode materials due to their high capacity, long cycle life, low cost, environmental friendliness, and high safety. However, in actual use, battery performance degrades significantly under high-temperature conditions. Related technologies use electrolyte additives to improve the high-temperature performance of LFP / LMP batteries, but this also introduces problems such as increased impedance and poor stability. Therefore, based on the need for rapidly and efficiently improving the high-temperature performance of batteries, there is an urgent need to develop novel additives suitable for LFP / LMP systems.

[0005] Public content

[0006] This disclosure proposes a lithium-ion battery that uses a specific electrolyte additive in combination with lithium iron phosphate / lithium manganese iron phosphate. This additive has excellent film-forming properties, and the constructed interfacial film has good high-temperature stability and the property of improving lithium-ion transport. It can effectively suppress lithium dendrite growth and excessive electrolyte consumption and gas generation during the battery's high-rate charge and discharge process, and helps to reduce capacity decay and improve high-temperature stability under low-temperature conditions, or enable the battery to have good fast-charging performance.

[0007] In a first aspect, this disclosure provides a lithium-ion battery. According to an embodiment of this disclosure, the lithium-ion battery includes: a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode includes a positive electrode film layer, the positive electrode film layer including a positive electrode active material, the positive electrode active material including at least one selected from lithium iron phosphate and lithium manganese iron phosphate; the electrolyte includes an organic solvent, an electrolyte salt, and an additive, the additive including a compound represented by Formula 1:

[0008] R1, R2, and R3 are each independently selected from H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C5-C7 cycloalkyl, R4-substituted phenyl, and R5-substituted benzyl; R4 and R5 are each independently selected from H, F, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl, and C2-C4 fluoroalkynyl. This lithium-ion battery, while exhibiting high energy density and good cycle performance, effectively suppresses lithium dendrite growth and excessive electrolyte consumption and gas generation during high-rate charging and discharging. It also helps reduce capacity decay at low temperatures, improves high-temperature stability, and demonstrates excellent high and low temperature performance and fast charging effect.

[0009] A second aspect of this application provides an electrical device. According to an embodiment of this application, the electrical device includes the lithium-ion battery described above. Because it uses the lithium-ion battery described above, the electrical device has good battery life and fast charging performance, and exhibits better performance in high and low temperature environments. Detailed Implementation

[0010] Embodiments of this disclosure are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting it.

[0011] This disclosure is based on the inventors' discoveries and understanding of the following facts and problems:

[0012] To address the increasingly severe energy crisis and environmental pollution, major economies worldwide are accelerating the development of batteries capable of long-term stable storage, high sustainability, long cycle life, and compliance with environmental constraints. Lithium-ion batteries, with their advantages of high operating potential, high specific capacity, long cycle life, stable operating voltage, and low self-discharge, have been widely used in consumer electronics such as mobile phones and computers, embarking on a broad application journey. With further development and deepening of commercialization and scientific research, they are gradually shining brightly in the fields of power batteries and energy storage. For power and energy storage batteries, the most basic requirements are safety and reliability, high energy density, good cycle stability, and resistance to high-temperature storage.

[0013] However, in practical applications, the high / low temperature performance of lithium iron phosphate / lithium manganese iron phosphate batteries greatly limits their use, especially under fast charging conditions. In order to improve the fast charging performance of the battery, performance improvements are made to the positive electrode, negative electrode and electrolyte. For example, material structure modification and increased compaction density are carried out for the positive / negative electrode. For the electrolyte, new electrolyte solvents and lithium salts can be used. However, compared with these, using a small amount of new additives to significantly improve performance has a significant cost-effectiveness. The inventors discovered that the reason for this is that in battery systems with high compaction density, the lithium insertion and delithiation reactions in the electrode materials have a significant impact on capacity decay during rate cycling. Because the lithium insertion and delithiation process in the battery is relatively difficult, the capacity decay at higher rates is more severe, especially in systems with easily constructed interface films. Solvated lithium ions still need to complete the desolvation process outside the interface film and ion transport within the interface film. For batteries with high interface film impedance, high-rate charge and discharge processes can lead to lithium plating, internal heat generation, and lithium dendrites promoting electrolyte decomposition. As a result, the properties of the interface film will seriously affect the rate performance and high and low temperature performance of the battery. While related technologies utilize carbonate and sulfate-based electrolyte additives to improve the composition and structure of the SEI (solid electrolyte interphase) film, thereby enhancing battery cycle stability and high / low temperature performance, carbonate additives increase impedance after film formation, negatively impacting the lithium insertion / extraction process. Sulfate-based additives, while providing lower impedance, offer limited improvement in rate performance and cannot effectively suppress lithium plating and dendrite growth during fast charging, leading to high-temperature gas generation and performance degradation. These issues become even more pronounced with the increasing compaction density of lithium iron phosphate / lithium manganese iron phosphate batteries.

[0014] This disclosure aims to at least partially address one of the technical problems in the related art. To this end, in a first aspect, this disclosure provides a lithium-ion battery. According to an embodiment of this disclosure, the lithium-ion battery includes: a positive electrode, a negative electrode, a separator, and an electrolyte; the positive electrode includes a positive electrode film layer, the positive electrode film layer including a positive electrode active material, the positive electrode active material including at least one of lithium iron phosphate and lithium manganese iron phosphate; the electrolyte includes an organic solvent, an electrolyte salt, and an additive, the additive including a compound represented by Formula 1:

[0015] R1, R2, and R3 are each independently selected from H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C5-C7 cycloalkyl, R4 substituted phenyl, and R5 substituted benzyl.

[0016] R4 and R5 are each independently selected from H, F, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl, and C2-C4 fluoroalkynyl.

[0017] It is understandable that lithium-ion batteries will experience lithium plating, internal heat generation, and lithium dendrites promoting electrolyte decomposition during high-rate charging and discharging. As a result, the properties of the interface film will seriously affect the battery's rate performance and high and low temperature performance.

[0018] In this lithium-ion battery, a silicon-based fluorophosphate compound as shown in Formula 1 is used as an electrolyte additive. This compound has a low oxidation potential and preferential reduction over solvents / lithium salts, enabling it to undergo electrochemical reactions on the positive and negative electrode surfaces to construct a stable interfacial film. The film composition includes both organic components of polysiloxanes and inorganic components such as LiIF and Li3PO4. Compared to other film-forming additives, silicon-based fluorophosphate compounds, due to their silicon-based structure, exhibit a higher binding effect on the battery's negative electrode and lithium iron phosphate / lithium manganese iron phosphate positive electrode active materials due to their silicon-based structure. Excellent positive and negative electrode film formation performance: The silicon-based polysiloxane structure possesses dense stability and insulating properties, preventing lithium ions from reducing and depositing lithium dendrites at the negative electrode interface. Silicon-based fluorophosphate compounds help reduce electrolyte viscosity, improve ionic conductivity, and facilitate the desolvation process of solvated lithium ions. Furthermore, the presence of fluorophosphate groups in the structure enriches the interface film with P=O, PF, and lithium salt components, further enhancing ionic conductivity and inhibiting lithium salt solvent decomposition. This results in a higher lithium-ion transport rate under low-temperature conditions or during fast charging, further preventing lithium deposition. In summary, the lithium-ion battery disclosed herein exhibits superior high and low temperature performance and fast-charge cycle performance.

[0019] According to embodiments of this disclosure, the positive electrode active material further includes a ternary positive electrode active material. In some specific embodiments, the positive electrode active material includes lithium manganese iron phosphate and the ternary positive electrode active material. In this disclosure, the mixing ratio of lithium manganese iron phosphate and the ternary positive electrode active material is not particularly limited. Specifically, based on the total mass of the positive electrode active material, the mass percentage of lithium manganese iron phosphate is A, and the mass percentage of the ternary positive electrode active material is B, satisfying: A + B = 1. Specifically, A can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, etc., and correspondingly, B can be 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, etc.

[0020] In some embodiments, the lithium manganese iron phosphate includes LiFe 1-x Mn x For PO4, 0 < x < 1; as an example, 0.3 ≤ x ≤ 0.7. Specifically, x can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. As a specific example, lithium manganese iron phosphate can be LiFe... 0.5 Mn 0.5 PO4, LiFe 0.4 Mn 0.6 PO4, LiFe 0.3 Mn 0.7 PO4, LiFe 0.2 Mn 0.8 PO4, etc.

[0021] In some embodiments, the ternary cathode active material includes LiNi. 1-y-z Co y Mn z For O2, 0 < y < 1, 0 < z < 1. Specifically, y can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc.; z can also be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. As a specific example, the ternary cathode active material can be LiNi. 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.6 Co 0.1 Mn 0.3 O2(NCM613), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), etc.

[0022] According to embodiments of this disclosure, the mass percentage of the additive is 0.05% to 5.0% based on the total mass of the electrolyte. In some embodiments, the mass percentage of the additive is 0.5% to 2.5% based on the total mass of the electrolyte, specifically such as 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, etc. Within the above content range, the additive can achieve better film-forming effects. The constructed interfacial film has good high-temperature stability and improves lithium-ion transport properties, reducing side reactions in the electrolyte (such as side reactions between the cathode material and the electrolyte), while not increasing battery impedance. It significantly improves problems such as lithium dendrite growth, excessive electrolyte consumption and gas generation, and capacity decay during high-rate charge and discharge processes. This results in lithium-ion batteries exhibiting excellent high and low temperature performance and fast charging performance, with virtually no other negative impacts.

[0023] According to embodiments of this disclosure, the compaction density of the positive electrode active material is 2.0 g / cm³. 3 ~4.0g / cm 3 (specifically, 2g / cm) 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 3.4g / cm 3 3.5g / cm 3 3.6g / cm 3 3.7g / cm 3 3.8g / cm 3 3.9g / cm 3 4g / cm 3(etc.). Therefore, this lithium-ion battery possesses both high energy density and cycle stability. Furthermore, as the compaction density of the positive electrode active material continuously increases, the dissolution of Fe / Mn metals in the positive electrode active material and the corrosion of the positive electrode active material by impurities such as water and HF in the electrolyte become more severe. That is, while the battery energy density increases, the negative impacts also become more severe. However, by using the additive shown in Formula 1 in combination with lithium iron phosphate and / or lithium manganese iron phosphate, the excellent film-forming properties of the additive and the good ion conductivity of the formed interfacial film can ensure that the battery has high energy density and good cycle performance, while also exhibiting good high and low temperature performance and fast charging performance.

[0024] It is understandable that the compaction density of the positive electrode active material is closely related to the type of positive electrode active material. In some embodiments, when only lithium iron phosphate is used as the positive electrode active material, the compaction density of the positive electrode active material can be 2.0 g / cm³. 3 ~3.0g / cm 3 When only lithium manganese iron phosphate is used as the positive electrode active material, the compaction density of the positive electrode active material can be 2.8 g / cm³. 3 ~4.0g / cm 3 When lithium manganese iron phosphate and ternary cathode active materials are used, the compaction density of the cathode active material can be 2.8 g / cm³. 3 ~4.0g / cm 3 In actual use, the type and compaction density of the positive electrode active material can be adjusted as needed.

[0025] In actual testing, the high and low temperature performance and rate charge / discharge performance of lithium-ion batteries are not only related to parameters such as the compaction density of the positive and negative electrode materials, but also to the amount of electrolyte and additives used. The inventors found that when the parameters satisfy the following formula 0.0018≤abc / 100d≤0.18, the matching of the positive electrode, negative electrode and electrolyte of the lithium-ion battery is optimal, which can effectively exert the positive effects of additives, greatly suppress lithium dendrite growth, high-temperature electrolyte consumption and gas generation, low-temperature discharge capacity reduction and fast charge cycle stability reduction, and promote the battery to show the most beneficial effect in improving overall performance.

[0026] According to embodiments of this disclosure, the lithium-ion battery satisfies the following condition: 0.0018 ≤ abc / 100d ≤ 0.18. As an example, abc / 100d can specifically be 0.0018, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, etc. Wherein, 'a' is the ratio of the mass of the electrolyte to the compaction density of the negative electrode film in the lithium-ion battery, where the mass of the electrolyte is in grams (g) and the compaction density of the negative electrode film is in g / cm³. 2 b represents the compaction density of the positive electrode active material in the lithium-ion battery, in g / cm³. 3 c represents the mass percentage of the additive in the electrolyte, in %; d represents the moisture content in the lithium-ion battery, in ppm.

[0027] According to the embodiments of this disclosure, a is 0.1 to 3. In some embodiments, a can be 0.25-2, specifically such as 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.5, 2, 2.5, 3, etc.

[0028] According to embodiments of this disclosure, d ≤ 400ppm, and in some embodiments, d ≤ 300ppm. Specifically, d can be 400ppm, 350ppm, 300ppm, 250ppm, 200ppm, 150ppm, 100ppm, 50ppm, etc.

[0029] When the parameters satisfy the above relationship, an interface film with good corrosion resistance and high lithium-ion conductivity can be generated on the surface of the positive / negative electrode, providing good protection for the positive and negative electrode interfaces, especially for suppressing lithium plating at the negative electrode interface. Since the constructed interface film can quickly transport lithium ions, combined with the desolvation effect of additives on solvated lithium ions in the electrolyte, it can effectively suppress the growth of lithium dendrites, suppress electrolyte consumption and gas generation under high temperature conditions, capacity reduction under low temperature conditions, and battery capacity decay during rate cycling, thereby improving the overall high / low temperature and fast charging performance of the battery.

[0030] In this article, the units of the parameters involved in the above formulas are explained. It is important to understand that these units only indicate that calculations should be performed using the values ​​corresponding to the units specified above. They do not mean that the parameters in the formulas can only be expressed in these units. For example, the mass of the electrolyte can be expressed in units such as mg, g, and kg. As an example, 100g of electrolyte can be described as 100000mg, 100g, or 0.1kg. When using it in the above formulas, the value of 100 (in g) should be used. Other parameters are similar and will not be elaborated upon further.

[0031] In this article, the areal density of the positive electrode film layer refers to the areal density of a single positive electrode film layer. Specifically, the positive electrode sheet typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The areal density of the positive electrode film layer mentioned above refers to the areal density of the positive electrode film layer on one side surface of the positive current collector.

[0032] It is understood that, in addition to the lithium iron phosphate and / or lithium manganese iron phosphate, and / or ternary cathode materials mentioned above, the cathode film may also include binders and conductive agents; depending on the actual use requirements, it may further include functional additives, etc. The binders, conductive agents and functional additives are conventional choices in the field, and will not be described in detail here.

[0033] According to embodiments of this disclosure, the additive includes at least one of the following compounds:

[0034] Therefore, the additive has excellent film-forming properties and can better cooperate and synergize with lithium iron phosphate / lithium manganese iron phosphate cathode active materials, thereby enabling lithium-ion batteries to have high energy density, good high-temperature performance, long cycle life and good fast charging performance.

[0035] Compounds 18 to 22 were prepared according to the preparation method of Example 14 in patent CN114728992A, specifically, the dichlorophenylsilane in the reference document was replaced with the raw materials shown below.

[0036] The raw material is trivinylchlorosilane (1871-21-2).

[0037] The raw material is dimethylethynyl butylchlorosilane (2069196-19-4).

[0038] The raw material is dimethyl(trifluoropropylene)chlorosilane (89705-02-2).

[0039] The raw material is tris(pentafluoroethyl)chlorosilane (1620665-21-5).

[0040] The raw material is dimethyl(p-methylbenzyl)chlorosilane (1833-28-9).

[0041] According to embodiments of this disclosure, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium difluorodi(oxalate)phosphate, lithium tetrafluorooxalate phosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perfluorobutylsulfonate, and lithium fluorinated fatty acids.

[0042] According to embodiments of this disclosure, the mass percentage of the electrolyte salt is 6% to 25% based on the total mass of the electrolyte. In some embodiments, the mass percentage of the electrolyte salt is 10% to 15% based on the total mass of the electrolyte, such as 6%, 10%, 15%, 20%, 25%, etc.

[0043] According to embodiments of this disclosure, the organic solvent includes at least one of cyclic carbonates, linear carbonates, and linear carboxylic acid esters. In some embodiments, cyclic carbonates include, but are not limited to, at least one of ethylene carbonate (EC) and propylene carbonate (PC); linear carbonates include, but are not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); and linear carboxylic acid esters include, but are not limited to, at least one of ethyl acetate (EA), propyl acetate (PA), ethyl propionate (EP), and propyl propionate (PP).

[0044] According to embodiments of this disclosure, the organic solvent has a mass percentage content of 60% to 92% based on the total mass of the electrolyte. In some embodiments, the organic solvent has a mass percentage content of 65% to 85% based on the total mass of the electrolyte, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, etc.

[0045] According to embodiments of this disclosure, the negative electrode sheet includes a negative electrode film layer, wherein the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes at least one of carbon-based materials, silicon-based materials, and lithium-containing metal composite oxides. In some embodiments, carbon-based materials include, but are not limited to, graphite (natural graphite, artificial graphite, etc.), soft carbon, hard carbon, etc.; silicon-based materials include, but are not limited to, silicon particles, silicon-oxygen materials, silicon-carbon materials, etc.; and lithium-containing metal composite oxides include, but are not limited to, lithium titanate, etc.

[0046] It is understood that the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one side surface of the negative electrode current collector. The negative electrode film layer may include the aforementioned negative electrode active material, binder and conductive agent. Depending on the actual use requirements, the negative electrode film layer may further include thickener, functional additives, etc. The aforementioned conductive agent, binder, thickener and functional additive can be conventionally selected in the art, and will not be described in detail here.

[0047] According to embodiments of this disclosure, the diaphragm comprises at least one of polyolefin, aromatic polyamide, polytetrafluoroethylene, and polyethersulfone.

[0048] A second aspect of this disclosure provides an electrical device. According to an embodiment of this disclosure, the electrical device includes the lithium-ion battery described above. Because it uses the lithium-ion battery described above, the electrical device has good battery life and fast charging performance, and exhibits better performance in high-temperature environments.

[0049] It is understood that the lithium-ion battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0050] It is understandable that, in addition to the battery mentioned above, the electrical equipment may also include the necessary structures and components of conventional electrical equipment. Taking electric vehicles as an example, it may include the body, windows, chassis, engine, seats, tires, and other necessary structures and components, which will not be elaborated here.

[0051] The embodiments of this disclosure are described in detail below.

[0052] Example 1

[0053] 1. Electrolyte preparation: The electrolyte in this embodiment is prepared according to the following components by mass fraction: 12.5% ​​LiPF6, non-aqueous organic solvents including ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a solvent mass ratio of 3:7, and 0.5 wt% compound 1.

[0054] 2. Cathode Preparation: LiFePO4 cathode material (LFP), conductive agent SuperP (conductive carbon black), and binder PVDF (polyvinylidene fluoride) were mixed evenly at a mass ratio of 96:2:2 and vacuum stirred until the fluidity was uniform. This slurry was then evenly coated onto both sides of an aluminum foil, and subsequently dried at 85℃, cold-pressed, trimmed, cut into sheets, slit, and vacuum-dried at 85℃ for 12 hours. After welding the tabs, an electrode with an areal density of 35 mg / cm³ was obtained.2 The positive electrode sheet.

[0055] 3. Anode Preparation: Graphite anode material, conductive agent Super P (conductive carbon black), thickener CMC-Na (sodium carboxymethyl cellulose), and binder SBR (styrene-butadiene rubber latex) are thoroughly mixed in a mass ratio of 95:1.5:1.5:2 to form a uniform slurry. After coating both sides of copper foil, it is dried at 85℃, followed by cold pressing, edge trimming, cutting, and slitting. Finally, it is dried under vacuum at 85℃ for 12 hours, and the electrode tabs are welded to obtain a surface density of 15.8 mg / cm³. 2 The negative electrode sheet.

[0056] 4. Separator: A 16μm thick double-layer polypropylene porous polymer film.

[0057] 5. Lithium-ion battery manufacturing:

[0058] The positive electrode, separator, and negative electrode are sequentially stacked and then wound to form a bare cell with a theoretical capacity of 1300mAh. The bare cell is placed in an outer packaging aluminum foil and vacuum baked at 75°C for 10 hours before being injected with the electrolyte. After vacuum sealing, settling, formation, aging, and capacity testing, the lithium-ion battery manufacturing process is complete.

[0059] Examples 2-51

[0060] Same as Example 1, the differences are shown in Table 1.

[0061] Comparative Example 1

[0062] Same as Example 1, the differences are shown in Table 1.

[0063] Table 1

[0064] Note: In Table 1, 0.4LMFP+0.6NCM523 indicates that the positive electrode active material is a mixture of LMFP and NCM523. Based on the total mass of the positive electrode active material, the mass percentage of LMFP is 40% and the mass percentage of NCM523 is 60%. Other similar descriptions have the same meaning.

[0065] Performance testing:

[0066] The prepared lithium-ion batteries were subjected to impedance, cycle, and high-temperature performance tests. The test methods are as follows, and the test results are shown in Table 2:

[0067] 25℃ ambient temperature cycling test: At 25℃, charge the battery at a constant current of 4.0C to 3.65V, then charge it at a constant voltage of 3.65V to the cutoff current of 0.05C. Then discharge the battery at a constant current of 4.0C to 2.0V. Repeat the charge and discharge cycle for 1500 cycles. Record the discharge capacity of the 1500th cycle and the 1st cycle. Divide the two values ​​to obtain the capacity retention rate.

[0068] -10℃ Low Temperature Discharge Test: At 25℃, the battery was charged at a constant current of 1.0C to 3.65V, then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The battery was then discharged at a constant current of 1.0C to 2.0V, and the discharge capacity was recorded as C3. At 25℃, the battery was charged at a constant current of 1.0C to 3.65V, then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The battery was then transferred to -10℃ and left to stand for 240 minutes. The battery was then discharged at a constant current of 0.3C to 2.0V, and the discharge capacity was recorded as C4. The -10℃ discharge rate = C4 / C3*100%.

[0069] 30-day storage test at 60℃: At 25℃, the battery was charged at a constant current of 1.0C to 3.65V, then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The battery was then discharged at a constant current of 1.0C to 2.0V, and the discharge capacity was recorded as C1. At 25℃, the battery was charged at a constant current of 1.0C to 3.65V, then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The battery was then transferred to 60℃ and stored for 30 days. The battery was then discharged at a constant current of 1.0C to 2.0V, and the discharge capacity was recorded as C2. The capacity retention rate after 30 days of storage at 60℃ = C2 / C1 × 100%.

[0070] Initial DCIR test: The lithium-ion battery was charged at 25℃ with a constant current of 1.0C to 3.65V, and then charged at a constant voltage of 3.65V to the cutoff current of 0.05C. The battery was then discharged at a constant current of 1.0C for 30 minutes, and after resting for 1 hour, it was discharged at a constant current of 2.0C for 10 seconds. The DCIR impedance value of the battery at 50% SOC was calculated (the voltage difference before and after 10 seconds of 2C discharge divided by the discharge current).

[0071] High-Temperature DCIR Test: The lithium-ion battery was charged at 25℃ with a constant current of 1.0C to 3.65V, then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The battery was then discharged at a constant current of 1.0C for 30 minutes, allowed to rest for 1 hour, and then discharged at a constant current of 2.0C for 10 seconds. The DCIR at 50% SOC was calculated and recorded as D1. For batteries that had completed a 30-day storage test at 60℃, the battery was charged at 25℃ with a constant current of 1.0C to 3.65V, then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The battery was then discharged at a constant current of 1.0C for 30 minutes, allowed to rest for 1 hour, and then discharged at a constant current of 2.0C for 10 seconds. The DCIR at 50% SOC was calculated and recorded as D2. Battery impedance change rate = D2 / D1 × 100%.

[0072] High-temperature expansion test: The lithium-ion battery was charged at 25°C with a constant current of 1.0C to 3.65V, and then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The initial thickness of the lithium-ion battery at this point was measured and recorded as T1. The battery was then stored at 60°C for 30 days, and the thickness under 60°C conditions was measured and recorded as T2. Battery expansion rate (%) = (T2 - T1) / T1 × 100%.

[0073] Table 2

[0074] In the description of this disclosure, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0075] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0076] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. A lithium-ion battery, comprising: Positive electrode, negative electrode, separator, and electrolyte; The positive electrode sheet includes a positive electrode film layer, and the positive electrode film layer includes a positive electrode active material, which includes at least one of lithium iron phosphate and lithium manganese iron phosphate. The electrolyte comprises an organic solvent, an electrolyte salt, and additives, wherein the additives include compounds represented by Formula 1: R1, R2, and R3 are each independently selected from H, F, C1-C4 alkyl, C1-C4 fluoroalkyl, C2-C4 alkenyl, C2-C4 fluoroalkenyl, C2-C4 alkynyl, C5-C7 cycloalkyl, R4 substituted phenyl, and R5 substituted benzyl. R4 and R5 are each independently selected from H, F, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 fluoroalkyl, C2-C4 fluoroalkenyl, and C2-C4 fluoroalkynyl.

2. The lithium-ion battery according to claim 1, wherein, The positive electrode active material also includes ternary positive electrode active materials.

3. The lithium-ion battery according to claim 2, wherein, The positive electrode active material includes lithium manganese iron phosphate and the ternary positive electrode active material.

4. The lithium-ion battery according to claim 3, wherein at least one of the following conditions is met: The lithium manganese iron phosphate includes LiFe 1-x Mn x PO4, 0 < x < 1; The ternary cathode active material includes LiNi. 1-y-z Co y Mn z O2, 0 < y < 1, 0 < z < 1.

5. The lithium-ion battery according to any one of claims 1 to 4, wherein, Based on the total mass of the electrolyte, the mass percentage of the additive is 0.05% to 5.0%.

6. The lithium-ion battery according to claim 5, wherein, Based on the total mass of the electrolyte, the mass percentage of the additive is 0.5% to 2.5%.

7. The lithium-ion battery according to any one of claims 1 to 6, wherein, The compaction density of the positive electrode active material is 2.0 g / cm³. 3 ~4.0g / cm 3 .

8. The lithium-ion battery according to claim 7, wherein, The compaction density of the positive electrode active material is 2.1 g / cm³. 3 ~3.5g / cm 3 .

9. The lithium-ion battery according to any one of claims 1 to 8, wherein: 0.0018 ≤ abc / 100d ≤ 0.18; in, 'a' represents the ratio of the mass of the electrolyte in the lithium-ion battery to the compaction density of the negative electrode film, where the mass of the electrolyte is in grams (g) and the compaction density of the negative electrode film is in g / cm³. 3 ; b is the compaction density of the positive electrode active material in the lithium-ion battery, in g / cm³. 3 ; c represents the mass percentage content of the additive in the electrolyte; d represents the moisture content in the lithium-ion battery.

10. The lithium-ion battery according to claim 9, wherein, a is 0.1 to 3; and / or d≤400ppm.

11. The lithium-ion battery according to claim 10, wherein, a is 0.25 to 2; and / or d≤300ppm.

12. The lithium-ion battery according to any one of claims 1 to 11, wherein, The additive includes at least one of the following compounds:

13. The lithium-ion battery according to any one of claims 1 to 12, wherein, The electrolyte salt comprises at least one of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium difluorodi(oxalate)phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium perfluorobutylsulfonate, and lithium fluorinated fatty acids; and / or Based on the total mass of the electrolyte, the mass percentage of the electrolyte salt is 6% to 25%; and / or The organic solvent includes at least one of cyclic carbonates, linear carbonates, and linear carboxylic acid esters; and / or Based on the total mass of the electrolyte, the organic solvent has a mass percentage content of 60% to 92%.

14. The lithium-ion battery according to claim 13, wherein, Based on the total mass of the electrolyte, the mass percentage of the electrolyte salt is 10% to 15%; and / or Based on the total mass of the electrolyte, the organic solvent has a mass percentage content of 65% to 85%.

15. An electrical device comprising a lithium-ion battery according to any one of claims 1 to 14.

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