Non-aqueous electrolyte, lithium-ion battery, and electric device

Abstract

A non-aqueous electrolyte, a lithium-ion battery, and an electric device. The non-aqueous electrolyte comprises an electrolyte additive, wherein the electrolyte additive comprises one or more of Li3+xPO4-xNx, Li3yLa2 / 3-yTiO3, and Li1+zAlzTi2-z(PO4)3, wherein 0<x≤0.5, 0<y≤0.16, 0<z≤0.5.

Description

Non-aqueous electrolytes, lithium-ion batteries and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202311870590.9 and invention name “Non-aqueous electrolyte, lithium-ion battery and electrical equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the field of battery technology, and specifically to a non-aqueous electrolyte, a lithium-ion battery, and an electrical device. Background Art

[0003] Lithium-ion batteries are widely used in new energy vehicles due to their excellent performance. However, at low temperatures, their performance degrades significantly, manifesting as longer charging times, reduced charge and discharge capacity, smaller battery capacity, and faster battery drain, which in turn impacts the range of new energy vehicles and the user experience. This is primarily because low temperatures reduce the lithium ion transfer rate within the battery, lower the electrolyte conductivity, and increase the battery impedance, resulting in a significant reduction in the battery's available energy and power.

[0004] Summary of the Invention

[0005] In view of this, the embodiment of the present application provides a non-aqueous electrolyte. The non-aqueous electrolyte is prepared by adding LiPON (Li 3+x PO 4-x N x )、LLTO(Li 3y La 2 / 3-y TiO3), LATP(Li 1+z Al z Ti 2-z (PO4)3) and other electrolyte additives can effectively improve the low-temperature performance of lithium-ion batteries.

[0006] The first aspect of the present application provides a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises an electrolyte additive, wherein the electrolyte additive comprises Li 3+x PO 4-x N x 、Li 3y La 2 / 3-y TiO3、Li 1+z Al z Ti 2-z (PO4)3 one or more, wherein 0 <x≤0.5,0<y≤0.16,0<z≤0.5。

[0007] This application adds nano-sized solid electrolyte additives such as LiPON, LLTO, and LATP to conventional liquid electrolytes, which can effectively improve the dissociation and ion transport of lithium salts in the electrolyte under low temperature conditions and significantly accelerate the desolvation effect, thereby reducing battery impedance and significantly improving the low-temperature performance of the battery.

[0008] In one embodiment, the mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.1%-10%.

[0009] In one embodiment, the mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.5%-5%.

[0010] In one embodiment, the particle size D50 of the electrolyte additive is 10 nm-300 nm.

[0011] In one embodiment, the Li 1+z Al z Ti 2-z In (PO4)3, the value range of z is 0.3≤z≤0.5.

[0012] In one embodiment, the non-aqueous electrolyte further comprises a solvent and an electrolyte salt, and the mass ratio of the solvent, the electrolyte salt and the electrolyte additive is (70-91):(8-20):(1-10).

[0013] In one embodiment, the solvent includes one or more of a carbonate solvent, a carboxylate solvent, and an ether solvent.

[0014] In one embodiment, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate and ethyl propyl carbonate; the carboxylate solvent includes one or more of carboxylate including methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate and butyl butyrate; the ether solvent includes ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,3-dioxolane, dimethoxymethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, isosorbide dimethyl ether, dipropylene glycol dimethyl ether, 1,1, One or more of 2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,3,3-tetrafluoropropyl dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether and 2,2,2-trifluoroethyl ether.

[0015] In one embodiment, the electrolyte salt includes one or more of LiPF6, LiBF4, LiBOB, LiDFOB, LiDFOP, LiPO2F2, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3 and LiN(SO2F)2.

[0016] In one embodiment, the non-aqueous electrolyte further comprises one or more of 1,3-propane sultone, 1,3-propylene sultone, 1,4-butane sultone, vinylene carbonate, fluoroethylene carbonate, methylene methanedisulfonate, and vinyl sulfate.

[0017] The second aspect of the present application further provides a lithium-ion battery, which includes the non-aqueous electrolyte according to the first aspect of the present application, a separator, a positive electrode sheet, a negative electrode sheet, and a battery casing.

[0018] In one embodiment, the non-aqueous electrolyte, the separator, the positive electrode sheet, and the negative electrode sheet are housed inside the battery housing.

[0019] In one embodiment, the positive electrode sheet and the negative electrode sheet are stacked, the positive electrode sheet includes a positive electrode collector and a positive electrode active layer arranged on the positive electrode collector, and the negative electrode sheet includes a negative electrode collector and a negative electrode active layer arranged on the negative electrode collector.

[0020] The third aspect of the present application further provides an electrical device, which includes the lithium-ion battery according to the second aspect of the present application.

[0021] Using the lithium-ion battery provided in this application to power the device can effectively improve the endurance and safety performance of the electrical equipment in low-temperature environments, thereby enhancing its market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a schematic structural diagram of a lithium-ion battery provided in one embodiment of the present application.

[0023] Description of reference numerals:

[0024] 100 - lithium-ion battery; 101 - non-aqueous electrolyte; 102 - diaphragm; 103 - positive electrode; 104 - negative electrode; 105 - battery casing. DETAILED DESCRIPTION

[0025] In this application, all professional terms have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this application.

[0026] Lithium-ion batteries are widely used in the field of new energy vehicles due to their excellent performance. Under low temperature conditions, the performance of lithium-ion batteries will decline significantly, which is manifested in extended charging time, reduced charge and discharge volume, smaller battery capacity, and faster power loss, which in turn affects the endurance of new energy vehicles and the user experience.

[0027] Lithium-ion batteries experience significant degradation in available energy and power characteristics at low temperatures. When the battery is exposed to extremely low temperatures, the electrolyte becomes highly viscous, hindering the movement of lithium ions and slowing their transmission. This leads to imbalanced insertion and extraction of lithium ions from the negative electrode surface, causing some lithium ions to deposit on the negative electrode surface, resulting in lithium plating and loss of battery capacity.

[0028] In order to solve the above technical problems, the present invention provides a non-aqueous electrolyte, including an electrolyte additive; the electrolyte additive includes Li 3+x PO 4-x N x 、Li 3y La 2 / 3-y TiO3、Li 1+z Al z Ti 2-zOne or more of (PO4)3, where 0 < x ≤ 0.5, 0 < y ≤ 0.16, and 0 < z ≤ 0.5. In this application, a nano-level electrolyte additive is added to a conventional liquid electrolyte to form a solid-liquid mixed non-aqueous electrolyte. On the one hand, electrolyte additives such as LiPON, LLTO, and LATP can effectively reduce the freezing point of the liquid electrolyte, thereby enhancing the dissociation of lithium salts and ion transport in the electrolyte under low-temperature conditions. On the other hand, electrolyte additives such as LATP will also reduce and generate solid electrolyte interface (SEI) film components such as Li3PO4 and Li2O on the surface of the negative electrode active material, thereby enhancing the ionic conductivity, significantly reducing the battery impedance, especially inhibiting the increase in battery impedance under low-temperature conditions, improving the capacity retention rate of lithium-ion batteries during low-temperature discharge, and thus enhancing the endurance of lithium-ion batteries in low-temperature environments. In some embodiments of this application, the electrolyte additive can be, for example, Li 1+z Al z Ti 2-z (PO4)3 (LATP) can be more conducive to the formation of the SEI film and better improve the low-temperature performance of the battery.

[0029] In the embodiments of this application, the electrolyte additive Li 3+x PO 4-x N x That is, LiPON, where 0 < x ≤ 0.5 refers to a lithium phosphorus oxygen nitrogen solid electrolyte; Li 3y La 2 / 3-y TiO3 is LLTO, where 0 < y ≤ 0.16 refers to a lithium lanthanum titanium oxygen solid electrolyte; Li 1+z Al z Ti 2-z (PO4)3 is LATP, where 0 < z ≤ 0.5 refers to a lithium aluminum titanium phosphate solid electrolyte.

[0030] In some embodiments of this application, the mass percentage content of the electrolyte additive in the non-aqueous electrolyte is 0.1% - 10%. Exemplarily, the mass percentage content of the electrolyte additive in the non-aqueous electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. Controlling the content of the electrolyte additive within the above range can, on the one hand, ensure that the electrolyte additive plays a certain role in improving the low-temperature performance of the battery, and on the other hand, avoid the sedimentation phenomenon caused by excessive addition amount, thereby preventing the sharp increase in the impedance between the electrolyte and the negative electrode interface and the significant decrease in the low-temperature performance of the battery due to the reduction decomposition side reaction.

[0031] In some embodiments of the present application, the weight percentage of the electrolyte additive in the non-aqueous electrolyte is 0.5%-5%. For example, the weight percentage of the electrolyte additive in the non-aqueous electrolyte can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%. Controlling the content of the electrolyte additive within the above range can further reduce the low-temperature DC resistance of the battery and improve its low-temperature capacity retention.

[0032] In some embodiments of the present application, the particle size D50 of the electrolyte additive is 10nm-300nm. For example, the particle size D50 of the electrolyte additive can be 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 50nm, 55nm, 60nm, 70nm, 75nm, 80nm, 90nm, 100nm, 125nm, 150nm, 175nm, 200nm, 225nm, 250nm, 275nm, 300nm. By controlling the particle size of the electrolyte additive within the above-mentioned nanoscale range, while ensuring that the electrolyte additive has good dispersibility in the non-aqueous electrolyte, it is possible to obtain as large a specific surface area as possible, better contact with the positive and negative active materials, more conducive to the transmission of lithium ions in the electrolyte, and further increase the liquid retention capacity of the active material, thereby reducing the low-temperature DC resistance of the full battery and further improving the low-temperature performance of the lithium-ion battery. In addition, the solvated ions in the electrolyte are acted upon by the surface of the electrolyte additive particles such as the nano-scale LATP of the present application. The electrolyte additive plays a role of pre-desolvation, reducing the desolvation energy barrier of the solvated ions at the interface between the negative electrode active material and the electrolyte, significantly accelerating the desolvation effect, and improving the stability of lithium deposition / stripping, thereby improving the battery capacity and cycle performance of the battery at low temperatures.

[0033] In some embodiments of the present application, Li 1+z Al z Ti 2-z In (PO4)3, the value of z ranges from 0.3 ≤ z ≤ 0.5. In some specific embodiments of the present application, the value of z can be, for example, 0.3, 0.35, 0.4, 0.45, or 0.5. When x is within the above range, the ionic conductivity and stability of LATP itself are in an optimal range, which is more conducive to reducing battery impedance and enhancing performance. At the same time, the side reaction between the electrolyte and the negative electrode is weak, which does not consume excessive active lithium, and is more conducive to the utilization of battery capacity.

[0034] In some embodiments of the present application, the non-aqueous electrolyte further comprises a solvent and an electrolyte salt, wherein the mass ratio of the solvent, the electrolyte salt, and the electrolyte additive is (70-91):(8-20):(1-10). By controlling the content of each component in the non-aqueous electrolyte within the above range, the electrolyte additive can fully utilize the improvement effect of the battery's low-temperature performance, and can also ensure that the electrolyte has good ion conductivity, thereby improving the battery's low-temperature cycle stability, battery capacity, and safety performance.

[0035] In some embodiments of the present application, the solvent includes one or more of a carbonate solvent, a carboxylate solvent, and an ether solvent. Among them, the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the carboxylate solvent includes one or more of carboxylate including methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate; the ether solvent includes ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,3-dioxolane, dimethoxymethane One or more of alkane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, isosorbide dimethyl ether, dipropylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,3,3-tetrafluoropropyl dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether and 2,2,2-trifluoroethyl ether. Selecting the above solvent as the solvent of the non-aqueous electrolyte of the present application can further promote the dissolution of the electrolyte salt in the non-aqueous electrolyte, further promote the ion migration in the non-aqueous electrolyte, and thus improve the electrochemical performance of the battery.

[0036] In some embodiments of the present application, the electrolyte salt includes one or more of LiPF6, LiBF4, LiBOB, LiDFOB, LiDFOP, LiPO2F2, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3 and LiN(SO2F)2. The present application makes the solubility of the electrolyte salt in the solvent as large as possible by selecting the combination of the electrolyte salt and the solvent. By selecting a suitable electrolyte salt and controlling the addition amount of the above electrolyte salt within a suitable range, a higher conductivity can be provided for the electrolyte, and electrolyte salts such as LiPF6 can form a suitable SEI film on the negative electrode and effectively passivate the positive electrode, further improving the electrochemical performance of the battery.

[0037] In some embodiments of the present application, the non-aqueous electrolyte further includes other additives, including one or more of 1,3-propane sultone, 1,3-propylene sultone, 1,4-butane sultone, vinylene carbonate, fluoroethylene carbonate, methylene methanedisulfonate, and vinyl sulfate. The addition of these additives can effectively prevent battery overcharge, improve SEI film performance, enhance positive electrode protection, and further improve the overall performance of the battery.

[0038] The non-aqueous electrolyte provided in the present application is prepared by directly adding electrolyte additives such as LiPON, LLTO, and LATP to a conventional liquid electrolyte, and controlling the amount of the electrolyte additives added within an appropriate range. This method is simple in process and can effectively reduce the battery impedance at low temperatures and increase the ion transfer rate, thereby improving the low-temperature performance of lithium-ion batteries.

[0039] The present application also provides a lithium-ion battery, including a battery housing and a positive electrode, a negative electrode, a separator and an electrolyte housed inside the battery housing, the separator being arranged between the positive electrode and the negative electrode, and the electrolyte being the non-aqueous electrolyte provided above in the present application. Lithium-ion batteries include but are not limited to wound lithium-ion batteries and laminated lithium-ion batteries, and the positive electrode and negative electrode in the lithium-ion battery can be one group or multiple groups. In some specific embodiments of the present application, the lithium-ion battery 100 is shown in FIG1 , and the lithium-ion battery 100 is a laminated battery, including a battery housing 105 and a non-aqueous electrolyte 101 housed inside the battery housing 105, a separator 102, a positive electrode sheet 103 and a negative electrode sheet 104, and the positive electrode sheet 103 and the negative electrode sheet 104 are stacked in sequence, and the separator 102 is folded in a "Z" shape to separate the positive electrode sheet 103 and the negative electrode sheet 104. To facilitate lithium ion deintercalation, the outermost layers of the lithium-ion battery are all negative electrode sheets 104, meaning the number of negative electrode sheets 104 exceeds the number of positive electrode sheets 103 by one. The non-aqueous electrolyte 101 is the non-aqueous electrolyte described above in this application; the separator 102 is a polymer film; the positive electrode sheet 103 includes a positive electrode current collector and a positive electrode active layer disposed on the positive electrode current collector; the negative electrode sheet 104 includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector; and the battery housing 105 includes, but is not limited to, materials such as steel, aluminum, nickel-plated iron, or aluminum-plastic film. The lithium-ion battery provided in this embodiment of the application utilizes the non-aqueous electrolyte described above. The lithium-ion battery exhibits good cycle performance in low-temperature environments and has a large battery capacity.

[0040] In the embodiments of the present application, the positive electrode active material in the positive electrode material layer can be any positive electrode active material for lithium-ion batteries known in the art. For example, in some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer stacked on the surface of the positive electrode current collector, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes at least one of a phosphate-based positive electrode active material and a transition metal oxide positive electrode active material. Among them, the phosphate-based positive electrode active material includes but is not limited to one or more materials such as doped or undoped lithium iron phosphate and lithium manganese iron phosphate, and the transition metal oxide positive electrode active material includes but is not limited to one or more materials such as doped or undoped ternary materials and lithium-rich layered oxides.

[0041] In the embodiments of the present application, the negative electrode active material in the negative electrode material layer can be any negative electrode active material known in the art for lithium-ion batteries. For example, the negative electrode active material can be selected from one or more of a carbon-based negative electrode active material, a silicon-based negative electrode active material, a tin-based negative electrode active material, and a lithium metal negative electrode active material. Carbon-based negative electrodes can include natural graphite, artificial graphite, hard carbon, soft carbon, graphene, etc.; silicon-based negative electrodes can include silicon, silicon-carbon, silicon-oxygen, etc.; and tin-based negative electrodes can include tin, tin-carbon, tin-oxygen, and tin metal compounds, but are not limited thereto.

[0042] This application also provides an electrical device comprising the lithium-ion battery described above. Examples of the electrical device include electric vehicles, mobile phones, tablet computers, laptop computers, wearable devices (watches, bracelets), and digital cameras. Powered by the lithium-ion battery described above, the electrical device exhibits excellent low-temperature performance and cruise control capabilities in low-temperature environments, significantly enhancing user experience and market competitiveness.

[0043] The technical solution of this application is described in detail below with multiple embodiments.

[0044] Example 1

[0045] (1) Preparation of non-aqueous electrolyte: Ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate were mixed in a mass ratio of 1:1:1, and then 1 mol / L lithium hexafluorophosphate was added. Then, 3% of Lithium phosphate with a particle size D50 of 200 nm was added based on the total mass of the non-aqueous electrolyte. 1+z Al z Ti 2-z (PO4)3, (z=0.4), i.e., an electrolyte additive of LATP-0.4, obtains a non-aqueous electrolyte.

[0046] (2) Preparation of the positive electrode: The positive electrode active material lithium iron phosphate, the conductive agent carbon nanotubes, and the binder polyvinylidene fluoride were mixed in a mass ratio of 95.8:1.7:2.5, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on both sides of aluminum foil, dried, rolled, and vacuum-dried, and then welded to aluminum tabs using an ultrasonic welder to obtain the positive electrode.

[0047] (3) Preparation of the negative electrode: The negative electrode active material (artificial graphite), the conductive agent (carbon nanotubes), the binder (polyacrylic acid), and the thickener (carboxymethyl cellulose) were mixed in a mass ratio of 94.2:1.1:4.7:0.5 and then dispersed in deionized water to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of a copper foil, dried, rolled, and vacuum-dried, and then welded with a nickel tab using an ultrasonic welder to obtain the negative electrode.

[0048] (4) Preparation of lithium-ion batteries: Fold the diaphragm into a "Z" shape, and then interlace the positive and negative electrodes to ensure that there are two negative electrodes on the outermost side. Usually, 7 positive electrodes and 8 negative electrodes are used. After the core package is folded, it is fixed with high-temperature tape. Then, the core package is placed in an aluminum foil packaging bag and vacuum-baked at 85°C for 48 hours to obtain a battery cell to be filled with liquid; in a drying room with a dew point controlled below -40°C, the electrolyte prepared above is injected into the battery cell, vacuum-sealed, and left to stand at 45°C for 24 hours. Then, the conventional formation for the first charge was carried out according to the following steps: 0.05C constant current charging for 120 minutes, 0.2C constant current charging for 240 minutes, standing at 45°C for 36 hours, secondary vacuum sealing, and then charging to 3.8V at a constant current and constant voltage of 0.2C. After standing at room temperature for 24 hours, discharging to 3.0V at a constant current of 0.2C, and then cycling 2 times at a current of 0.2C to complete the capacity division and obtain a lithium-ion battery.

[0049] Example 2

[0050] The difference from Example 1 is that the electrolyte additive in step (1) is 0.05% of LATP-0.4 based on the total mass of the non-aqueous electrolyte.

[0051] Example 3

[0052] The difference from Example 1 is that the electrolyte additive in step (1) is 0.1% of LATP-0.4 based on the total mass of the non-aqueous electrolyte.

[0053] Example 4

[0054] The difference from Example 1 is that the electrolyte additive in step (1) is 1% of LATP-0.4 based on the total mass of the non-aqueous electrolyte.

[0055] Example 5

[0056] The difference from Example 1 is that the electrolyte additive in step (1) is 2% of LATP-0.4 based on the total mass of the non-aqueous electrolyte.

[0057] Example 6

[0058] The difference from Example 1 is that the electrolyte additive in step (1) is 5% of LATP-0.4 based on the total mass of the non-aqueous electrolyte.

[0059] Example 7

[0060] The difference from Example 1 is that the electrolyte additive in step (1) is 7% of LATP-0.4 based on the total mass of the non-aqueous electrolyte.

[0061] Example 8

[0062] The difference from Example 1 is that the electrolyte additive in step (1) is 10% of LATP-0.4 based on the total mass of the non-aqueous electrolyte.

[0063] Example 9

[0064] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 20 nm.

[0065] Example 10

[0066] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 50 nm.

[0067] Example 11

[0068] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 100 nm.

[0069] Example 12

[0070] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 300 nm.

[0071] Example 13

[0072] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 500 nm.

[0073] Example 14

[0074] The difference from Example 1 is that the non-aqueous electrolyte in step (1) further includes 3% of vinylene carbonate based on the total mass of the non-aqueous electrolyte.

[0075] Example 15

[0076] The difference from Example 1 is that the non-aqueous electrolyte in step (1) further comprises 3% of fluoroethylene carbonate based on the total mass of the non-aqueous electrolyte.

[0077] Example 16

[0078] The difference from Example 1 is that the electrolyte additive in step (1) is 3% of Li 3+x PO 4-x N x , (x=0.1), that is, LPON-0.1.

[0079] Example 17

[0080] The difference from Example 1 is that the electrolyte additive in step (1) is 3% of Li 3y La2 / 3-y TiO3, (y=0.11), that is, LLTO-0.11.

[0081] Example 18

[0082] The difference from Example 1 is that the electrolyte additives in step (1) are 1.5% of LATP-0.4 and 1.5% of LLTO-0.11 based on the total mass of the non-aqueous electrolyte.

[0083] Example 19

[0084] The difference from Example 1 is that the electrolyte additives in step (1) are 1.5% of LATP-0.4 and 1.5% of LPON-0.1 (x=0.1) based on the total mass of the non-aqueous electrolyte.

[0085] Example 20

[0086] The difference from Example 1 is that the positive electrode active material in step (2) is LiNi 0.6 Mn 0.2 Co 0.2 O2(NCM622).

[0087] Example 21

[0088] The difference from Example 1 is that the negative electrode active material in step (3) is silicon carbon.

[0089] Example 22

[0090] The difference from Example 1 is that the electrolyte additive in step (1) is Li 1+z Al z Ti 2-z (PO4)3, (z=0.2), that is, LATP-0.2.

[0091] Example 23

[0092] The difference from Example 1 is that the electrolyte additive in step (1) is Li 1+z Al z Ti 2-z (PO4)3, (z=0.3), that is, LATP-0.3.

[0093] Example 24

[0094] The difference from Example 1 is that the electrolyte additive in step (1) is Li 1+z Al z Ti 2-z (PO4)3, (z=0.5), i.e. LATP-0.5.

[0095] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0096] Comparative Example 1

[0097] (1) Preparation of a non-aqueous electrolyte: Ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate were mixed in a mass ratio of 1:1:1, and then 1 mol / L lithium hexafluorophosphate was added to obtain a non-aqueous electrolyte.

[0098] (2) Preparation of the positive electrode: The positive electrode active material lithium iron phosphate, the conductive agent carbon nanotubes, and the binder polyvinylidene fluoride were mixed in a mass ratio of 95.8:1.7:2.5, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on both sides of aluminum foil, dried, rolled, and vacuum-dried, and then welded to aluminum tabs using an ultrasonic welder to obtain the positive electrode.

[0099] (3) Preparation of the negative electrode: The negative electrode active material (artificial graphite), the conductive agent (carbon nanotubes), the binder (polyacrylic acid), and the thickener (carboxymethyl cellulose) were mixed in a mass ratio of 94.2:1.1:4.7:0.5 and then dispersed in deionized water to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of a copper foil, dried, rolled, and vacuum-dried, and then welded with a nickel tab using an ultrasonic welder to obtain the negative electrode.

[0100] (4) Preparation of lithium-ion batteries: Fold the diaphragm into a "Z" shape, and then interlace the positive and negative electrodes to ensure that there are two negative electrodes on the outermost side. Usually, 7 positive electrodes and 8 negative electrodes are used. After the core package is folded, it is fixed with high-temperature tape. Then, the core package is placed in an aluminum foil packaging bag and vacuum-baked at 85°C for 48 hours to obtain a battery cell to be filled with liquid; in a drying room with a dew point controlled below -40°C, the electrolyte prepared above is injected into the battery cell, vacuum-sealed, and left to stand at 45°C for 24 hours. Then, the conventional formation for the first charge was carried out according to the following steps: 0.05C constant current charging for 120 minutes, 0.2C constant current charging for 240 minutes, standing at 45°C for 36 hours, secondary vacuum sealing, and then charging to 3.8V at a constant current and constant voltage of 0.2C. After standing at room temperature for 24 hours, discharging to 3.0V at a constant current of 0.2C, and then cycling 2 times at a current of 0.2C to complete the capacity division and obtain a lithium-ion battery.

[0101] Comparative Example 2

[0102] The difference from Comparative Example 1 is that the non-aqueous electrolyte in step (1) further comprises 3% of vinylene carbonate (VC) based on the total mass of the non-aqueous electrolyte.

[0103] Comparative Example 3

[0104] The difference from Comparative Example 1 is that the non-aqueous electrolyte in step (1) further comprises 3% of fluoroethylene carbonate (FEC) based on the total mass of the non-aqueous electrolyte.

[0105] Comparative Example 4

[0106] The difference from Comparative Example 1 is that the positive electrode active material in step (2) is LiNi 0.6 Mn 0.2 Co 0.2 O2(NCM622).

[0107] Comparative Example 5

[0108] The difference from Comparative Example 1 is that the negative electrode active material in step (3) is silicon carbon.

[0109] Comparative Example 6

[0110] The difference from Example 1 is that the electrolyte additive in step (1) is LATP-0.6.

[0111] Performance Testing

[0112] (1) Low temperature DCIR (direct current resistance) test:

[0113] The lithium-ion batteries of each embodiment and comparative example were capped to 50% SOC (capacity referenced to the rated capacity during the capping stage) at 25°C, then placed in a -20°C high-low temperature chamber for at least 8 hours to ensure the battery body temperature remained stable at -20°C. They were then discharged at a current of 1.5C for 30 seconds. The discharge DC resistance was calculated as follows: Discharge DCIR = (Pre-discharge voltage - Post-discharge voltage) / Discharge current * 1000 (voltage and current are expressed in volts (V) and amperes (A), respectively). The results are summarized in Table 1.

[0114] (2) Low temperature capacity retention test:

[0115] The lithium-ion batteries of each embodiment and comparative example were capped to 100% SOC at 25°C (the capacity refers to the rated capacity during the capping stage), then placed in a -20°C high-low temperature chamber for at least 8 hours to ensure that the battery body temperature remained stable at -20°C. They were then discharged at a current value of 0.33C to 2.0V. The low-temperature capacity retention rate was calculated as follows: Low-temperature capacity retention rate = 0.33C discharge capacity (-20°C) / 0.33C discharge capacity (25°C) * 100%. The calculation results are summarized in Table 1.

[0116] Table 1

[0117] From the data in Table 1, it can be found that compared with the lithium-ion batteries of Comparative Examples 1-5 without the addition of electrolyte additives, the lithium-ion batteries obtained by using the non-aqueous electrolytes provided in Examples 1-21 of the present application with the addition of electrolyte additives have significantly reduced low-temperature DC resistance and a relatively higher low-temperature capacity retention rate, that is, the low-temperature performance of the battery is better.

[0118] Comparing the data from Examples 1-8, it can be found that when the electrolyte additive content is between 0.05% and 5%, the low-temperature DC resistance of the battery decreases and the low-temperature capacity retention rate increases as the electrolyte additive content increases. Among them, the low-temperature performance improvement effect of the battery in Example 1, which adds 3% of the electrolyte additive, is the most obvious. When the electrolyte additive content exceeds 5%, the low-temperature performance of the battery deteriorates to a certain extent.

[0119] It can be seen from the data of Comparative Examples 2 and 3 and Examples 14 and 15 that the electrolyte additive LATP can improve the deterioration of low-temperature performance caused by the addition of other conventional film-forming additives such as VC and FEC.

[0120] It can be seen from the data of Comparative Example 6 and Examples 22-24 that the present application can further enhance the improvement of the low-temperature performance of the battery by controlling the various elemental components in the electrolyte additive LATP within a suitable range.

[0121] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A non-aqueous electrolyte (101), characterized in that, including an electrolyte additive, the electrolyte additive comprising Li 3+x PO 4-x N x 、Li 3y La 2 / 3-y TiO3, Li 1+z Al z Ti 2-z (PO4)3, where 0 < x ≤ 0.5, 0 < y ≤ 0.16, 0 < z ≤ 0.

5.

2. The non-aqueous electrolyte (101) according to claim 1, characterized in that, The mass percentage content of the electrolyte additive in the non-aqueous electrolyte (101) is 0.1% - 10%.

3. The non-aqueous electrolyte (101) according to claim 1 or 2, characterized in that, The mass percentage content of the electrolyte additive in the non-aqueous electrolyte (101) is 0.5% - 5%.

4. The non-aqueous electrolyte (101) according to any one of claims 1-3, characterized in that, The particle size D50 of the electrolyte additive is 10 nm - 300 nm.

5. The non-aqueous electrolyte (101) according to any one of claims 1-4, characterized in that, The Li 1+z Al z Ti 2-z In (PO4)3, the value range of z is 0.3 ≤ z ≤ 0.

5.

6. The non-aqueous electrolyte (101) according to any one of claims 1-5, characterized in that, The non-aqueous electrolyte (101) further includes a solvent and an electrolyte salt, and the mass ratio of the solvent, the electrolyte salt, and the electrolyte additive is (70 - 91):(8 - 20):(1 - 10).

7. The non-aqueous electrolyte (101) according to claim 6, characterized in that, The solvent includes one or more of carbonate solvents, carboxylate solvents, and ether solvents.

8. The non-aqueous electrolyte (101) according to claim 7, characterized in that, The carbonate solvents include one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; the carboxylate solvents include one or more of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butyl butyrate; the ether solvents include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,3-dioxolane, dimethoxymethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, isosorbide dimethyl ether, dipropylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,3,3,3-pentafluoropropyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,3,3-tetrafluoropropyl dimethyl ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, and 2,2,2-trifluoroethyl ether.

9. The non-aqueous electrolyte (101) according to claim 6, characterized in that, The electrolyte salt includes one or more of LiPF6, LiBF4, LiBOB, LiDFOB, LiDFOP, LiPO2F2, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, and LiN(SO2F)2.

10. The non-aqueous electrolyte (101) according to any one of claims 1-9, characterized in that, The non-aqueous electrolyte (101) further includes one or more of 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, vinylene carbonate, fluoroethylene carbonate, methylene methanedisulfonate, and ethylene sulfate.

11. A lithium-ion battery (100), characterized in that, The lithium-ion battery (100) comprises: The non-aqueous electrolyte (101) according to any one of claims 1 - 10; a separator (102); a positive electrode sheet (103); a negative electrode sheet (104); and a battery case (105).

12. The lithium-ion battery (100) according to claim 11, characterized in that, The non-aqueous electrolyte (101), the separator (102), the positive electrode sheet (103), and the negative electrode sheet (104) are housed inside the battery case (105).

13. The lithium-ion battery (100) according to claim 11 or 12, characterized in that, The positive electrode sheet (103) and the negative electrode sheet (104) are stacked. The positive electrode sheet (103) includes a positive electrode current collector and a positive electrode active layer provided on the positive electrode current collector. The negative electrode sheet (104) includes a negative electrode current collector and a negative electrode active layer provided on the negative electrode current collector.

14. An electrical device, characterized in that, The electrical device includes the lithium-ion battery (100) according to any one of claims 11-13.

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