Non-aqueous electrolyte, lithium ion battery and electric equipment

Abstract

The invention provides a non-aqueous electrolyte, a lithium ion battery and electric equipment. The non-aqueous electrolyte comprises an electrolyte additive, the electrolyte additive comprises one or more of Li < 3 + x > PO4 <-x > Nx, Li < 3y > La < 2 / 3-y > TiO3 and Li < 1 + z > Al < z > Ti < 2-z > (PO4) 3, x is greater than 0 and less than or equal to 0.5, y is greater than 0 and less than or equal to 0.16, and z is greater than 0 and less than or equal to 0.5. According to the non-aqueous electrolyte, the appropriate electrolyte additive is added into the liquid electrolyte, so that the battery has more excellent low-temperature performance.

Description

Technical Field

[0001] 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 electrical equipment. Background Art

[0002] 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 significantly decline, which is manifested in longer charging time, reduced charge and discharge, smaller battery capacity, faster power loss, etc., which in turn affects the endurance of new energy vehicles and the user experience. This is mainly because the lithium-ion transmission speed inside the lithium-ion battery is reduced, the electrolyte conductivity is reduced, and the battery impedance is increased under low temperature conditions, which leads to serious attenuation of the battery's available energy and power. Summary of the invention

[0003] In view of this, 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.

[0004] In a first aspect, 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, wherein 0 <x≤0.5,0<y≤0.16,0<z≤0.5。

[0005] The present application adds nano-sized solid electrolyte additives such as LiPON, LLTO, LATP, etc. to conventional liquid electrolytes, which can effectively improve the dissociation and ion transport of lithium salts in electrolytes under low temperature conditions and significantly accelerate the desolvation effect, thereby reducing battery impedance and significantly improving battery low temperature performance.

[0006] Optionally, the mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.1%-10%.

[0007] Optionally, the mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.5%-5%.

[0008] Optionally, the particle size D50 of the electrolyte additive is 10nm-300nm.

[0009] Optionally, 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).

[0010] Optionally, the Li 1+z Al z Ti 2-z In (PO4)3, the value range of z is 0.3≤z≤0.5.

[0011] Optionally, the solvent includes one or more of a carbonate solvent, a carboxylate solvent and an ether solvent.

[0012] Optionally, 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, dimethicone ... One or more of methoxymethane, 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.

[0013] Optionally, 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.

[0014] Optionally, the non-aqueous electrolyte further includes 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.

[0015] The second aspect of the present application further provides a lithium-ion battery, the lithium-ion battery comprising an electrolyte, and the electrolyte comprising the non-aqueous electrolyte provided in the first aspect of the present application.

[0016] The third aspect of the present application further provides an electric device, the electric device comprising the lithium-ion battery provided in the second aspect of the present application. Using the lithium-ion battery provided in the present application to power the device can effectively improve the endurance and safety performance of the electric device in a low temperature environment, and enhance its market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a lithium-ion battery provided in one embodiment of the present application.

[0018] Description of Figure Numbers

[0019] 100 - lithium-ion battery; 101 - non-aqueous electrolyte; 102 - diaphragm; 103 - positive electrode plate; 104 - negative electrode plate; 105 - battery casing. DETAILED DESCRIPTION

[0020] The present application is further described in detail below in conjunction with preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments.

[0021] In the present 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 the present application.

[0022] 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 longer charging time, reduced charge and discharge volume, smaller battery capacity, faster power loss, etc., which in turn affects the endurance of new energy vehicles and the user experience.

[0023] The available energy and power characteristics of lithium-ion batteries are seriously degraded in low temperature environments. When the battery is at too low a temperature, the viscosity of the electrolyte is high, the movement of lithium ions is hindered, the transmission speed of lithium ions is slowed down, and the embedding and de-embedding of lithium ions on the negative electrode surface loses balance, causing some lithium ions to deposit on the negative electrode surface, causing lithium precipitation, resulting in battery capacity loss.

[0024] To solve the above technical problems, an embodiment of the present application 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-z (PO4)3, or one or more of them, where 0 < x ≤ 0.5, 0 < y ≤ 0.16, 0 < z ≤ 0.5. In the present application, by adding a nano-level electrolyte additive 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, and thus improve 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 active material, thereby improving the ionic conductivity, significantly reducing the battery impedance, especially suppressing the increase in battery impedance under low-temperature conditions, improving the capacity retention rate of lithium-ion batteries during low-temperature discharge, and thus improving the endurance of lithium-ion batteries in low-temperature environments. In some embodiments of the present application, the electrolyte additive can be, for example, Li 1+z Al z Ti 2-z (PO4)3 (LATP), which can be more helpful for the formation of the SEI film and better improve the low-temperature performance of the battery.

[0025] In an embodiment of the present application, the electrolyte additive Li 3+x PO 4-x N x 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.

[0026] In some embodiments of the present application, the mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.1%-10%. Exemplarily, the mass percentage 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, which in turn causes the reduction and decomposition side reaction to cause the impedance of the electrolyte and the negative electrode interface to increase sharply and the low-temperature performance of the battery to decrease significantly.

[0027] In some embodiments of the present application, the mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.5%-5%. For example, the mass percentage of the electrolyte additive in the non-aqueous electrolyte can be, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 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 rate.

[0028] In some embodiments of the present application, the particle size D50 of the electrolyte additive is 10nm-300nm. Exemplarily, 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 nanoscale LATP of the present application, and the electrolyte additive plays a role of pre-desolvation, thereby 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.

[0029] In some embodiments of the present application, Li 1+z Al z Ti 2-zIn (PO4)3, the value range of z is 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, 0.5. When x is within the above range, the ionic conductivity and stability of LATP itself are in a better range, which is more conducive to reducing the impedance and performance of the battery; at the same time, the side reaction between the electrolyte and the negative electrode is weak, and the active lithium will not be consumed too much, which is more conducive to the battery capacity.

[0030] In some embodiments of the present application, 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). By controlling the content of each component in the non-aqueous electrolyte within the above range, the electrolyte additive can give full play to the improvement effect of the low-temperature performance of the battery, and can also ensure that the electrolyte has good ion conductivity, thereby improving the low-temperature cycle stability of the battery, the battery capacity and the safety performance.

[0031] In some embodiments of the present application, the solvent includes one or more of carbonate solvents, carboxylate solvents and ether solvents. Among them, 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; carboxylate solvents include carboxylate esters 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; ether solvents include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, 1,3-dioxolane, dimethoxymethane 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.

[0032] 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.

[0033] In some specific 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 methane disulfonate, and vinyl sulfate. By adding the above additives, the battery can be effectively prevented from overcharging, the SEI film performance can be improved, the positive electrode protection effect can be enhanced, and the overall performance of the battery can be further improved.

[0034] The non-aqueous electrolyte provided in the present application is prepared by directly adding electrolyte additives such as LiPON, LLTO, LATP, etc. to a conventional liquid electrolyte, and controlling the amount of the electrolyte additive added within a suitable range. The 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.

[0035] The present application also provides a lithium-ion battery, including a battery housing and a positive electrode, a negative electrode, a diaphragm and an electrolyte contained in the battery housing, wherein the diaphragm is disposed between the positive electrode and the negative electrode, and the electrolyte is the non-aqueous electrolyte provided in the previous text of the present application. Lithium-ion batteries include, but are not limited to, wound-type lithium-ion batteries and laminated lithium-ion batteries. The positive electrode and the 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 as follows: Figure 1As shown, the lithium-ion battery 100 is a laminated battery, including a battery housing 105 and a non-aqueous electrolyte 101 contained in 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. In order to better deintercalate lithium ions, the outermost side of the lithium-ion battery is the negative electrode sheet 104, that is, the number of negative electrode sheets 104 is one more than the number of positive electrode sheets 103. Among them, the non-aqueous electrolyte 101 is the non-aqueous electrolyte described above in this application; the separator 102 is a high molecular polymer film; the positive electrode plate 103 includes a positive electrode current collector and a positive electrode active layer arranged on the positive electrode current collector; the negative electrode plate 104 includes a negative electrode current collector and a negative electrode active layer arranged on the negative electrode current collector; the battery shell 105 includes but is not limited to materials such as steel shell, aluminum shell, nickel-plated iron shell or aluminum-plastic film. The lithium-ion battery provided in the embodiment of the present application adopts the non-aqueous electrolyte described above, and the lithium-ion battery has good cycle performance in a low temperature environment and a large battery capacity.

[0036] In the embodiment 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. Exemplarily, 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, and 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 of doped or undoped lithium iron phosphate, lithium manganese iron phosphate and other materials, and the transition metal oxide positive electrode active material includes but is not limited to one or more of doped or undoped ternary materials, lithium-rich layered oxides and other materials.

[0037] In the embodiment of the present application, the negative electrode active material in the negative electrode material layer can be any negative electrode active material for lithium-ion batteries known in the art. Exemplarily, the negative electrode active material can be selected from one or more of carbon-based negative electrode active materials, silicon-based negative electrode active materials, tin-based negative electrode active materials, and lithium metal negative electrode active materials. Among them, the carbon-based negative electrode may include natural graphite, artificial graphite, hard carbon, soft carbon, graphene, etc.; the silicon-based negative electrode may include silicon, silicon carbon, silicon oxygen, etc.; the tin-based negative electrode may include tin, tin carbon, tin oxygen, and tin metal compounds, but is not limited thereto.

[0038] The present application also provides an electric device, which includes the lithium-ion battery described above. The electric device may be, for example, an electric car, a mobile phone, a tablet computer, a laptop computer, a wearable device (a watch, a bracelet), a digital camera, etc. The electric device is powered by the lithium-ion battery described above, has good low-temperature performance, and has good cruising ability in a low-temperature environment, which greatly improves the user experience and market competitiveness.

[0039] The technical solution of the present application is described in detail below with multiple embodiments.

[0040] Example 1

[0041] (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, and then 3% of Li 2+ 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., the electrolyte additive of LATP-0.4, obtains a non-aqueous electrolyte.

[0042] (2) Preparation of 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 the aluminum foil, dried, rolled and vacuum dried, and welded to the aluminum tab with an ultrasonic welder to obtain the positive electrode.

[0043] (3) Preparation of 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 the copper foil, dried, rolled and vacuum dried, and the nickel tab was welded with an ultrasonic welder to obtain the negative electrode.

[0044] (4) Preparation of lithium-ion batteries: Fold the separator 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, and 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 prepared electrolyte is injected into the battery cell, which is vacuum-packaged and left to stand at 45°C for 24 hours. Then, the conventional formation for the first charge is carried out according to the following steps: 0.05C constant current charging for 120 min, 0.2C constant current charging for 240 min, standing at 45°C for 36 h, secondary vacuum sealing, and then charging to 3.8 V at 0.2C constant current and constant voltage, standing at room temperature for 24 h, discharging to 3.0 V at 0.2C constant current, and then cycling 2 times at 0.2C current to complete the capacity division and obtain a lithium-ion battery.

[0045] Example 2

[0046] 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.

[0047] Example 3

[0048] 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.

[0049] Example 4

[0050] 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.

[0051] Example 5

[0052] 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.

[0053] Example 6

[0054] 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.

[0055] Example 7

[0056] 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.

[0057] Example 8

[0058] 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.

[0059] Example 9

[0060] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 20 nm.

[0061] Example 10

[0062] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 50 nm.

[0063] Embodiment 11

[0064] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 100 nm.

[0065] Example 12

[0066] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 300 nm.

[0067] Example 13

[0068] The difference from Example 1 is that the particle size D50 of the electrolyte additive in step (1) is 500 nm.

[0069] Embodiment 14

[0070] The difference from Example 1 is that the non-aqueous electrolyte in step (1) further comprises 3% of vinylene carbonate based on the total mass of the non-aqueous electrolyte.

[0071] Embodiment 15

[0072] 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.

[0073] Example 16

[0074] The difference from Example 1 is that the electrolyte additive in step (1) is 3% Li based on the total mass of the non-aqueous electrolyte. 3+x PO 4-x N x , (x=0.1), that is, LPON-0.1.

[0075] Embodiment 17

[0076] The difference from Example 1 is that the electrolyte additive in step (1) is 3% Li based on the total mass of the non-aqueous electrolyte. 3y La2 / 3-y TiO3, (y=0.11), that is, LLTO-0.11.

[0077] Embodiment 18

[0078] The difference from Example 1 is that the electrolyte additives in step (1) are 1.5% LATP-0.4 and 1.5% LLTO-0.11 based on the total mass of the non-aqueous electrolyte.

[0079] Embodiment 19

[0080] 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.

[0081] Embodiment 20

[0082] 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).

[0083] Embodiment 21

[0084] The difference from Example 1 is that the negative electrode active material in step (3) is silicon carbon.

[0085] Embodiment 22

[0086] 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), i.e. LATP-0.2.

[0087] Embodiment 23

[0088] 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), i.e. LATP-0.3.

[0089] Embodiment 24

[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=0.5), i.e. LATP-0.5.

[0091] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0092] Comparative Example 1

[0093] (1) Preparation of a non-aqueous electrolyte: Ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 1:1:1 were mixed, and then 1 mol / L lithium hexafluorophosphate was added to obtain a non-aqueous electrolyte.

[0094] (2) Preparation of 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 the aluminum foil, dried, rolled and vacuum dried, and welded to the aluminum tab with an ultrasonic welder to obtain the positive electrode.

[0095] (3) Preparation of 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 the copper foil, dried, rolled and vacuum dried, and the nickel tab was welded with an ultrasonic welder to obtain the negative electrode.

[0096] (4) Preparation of lithium-ion batteries: Fold the separator 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, and 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 prepared electrolyte is injected into the battery cell, which is vacuum-packaged and left to stand at 45°C for 24 hours. Then, the conventional formation for the first charge is carried out according to the following steps: 0.05C constant current charging for 120 min, 0.2C constant current charging for 240 min, standing at 45°C for 36 h, secondary vacuum sealing, and then charging to 3.8 V at 0.2C constant current and constant voltage, standing at room temperature for 24 h, discharging to 3.0 V at 0.2C constant current, and then cycling 2 times at 0.2C current to complete the capacity division and obtain a lithium-ion battery.

[0097] Comparative Example 2

[0098] 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.

[0099] Comparative Example 3

[0100] 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.

[0101] Comparative Example 4

[0102] 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).

[0103] Comparative Example 5

[0104] The difference from Comparative Example 1 is that the negative electrode active material in step (3) is silicon carbon.

[0105] Comparative Example 6

[0106] The difference from Example 1 is that the electrolyte additive in step (1) is LATP-0.6.

[0107] Performance Testing

[0108] (1) Low temperature DCIR (direct current resistance) test:

[0109] The lithium-ion batteries of the embodiments and comparative examples were set to 50% SOC (capacity refers to the rated capacity in the set-capacity stage) at 25°C, and then placed in a high-low temperature box at -20°C for more than 8 hours to ensure that the temperature of the battery body is stable at -20°C, and then discharged at a current value of 1.5C for 30 seconds. The calculation formula of the discharge DC resistance is: discharge DCIR = (voltage value before discharge - voltage value after discharge) / discharge current value * 1000 (the units of voltage and current are volts V and amperes A, respectively), and the calculation results are summarized in Table 1.

[0110] (2) Low temperature capacity retention test:

[0111] The lithium-ion batteries of the embodiments and comparative examples were set to 100% SOC (capacity refers to the rated capacity in the set capacity stage) at 25°C, and then placed in a -20°C high and low temperature box for more than 8 hours to ensure that the battery body temperature is stable at -20°C, and then discharged to 2.0V at a current value of 0.33C. The calculation formula for the low temperature capacity retention rate is: low temperature capacity retention rate = 0.33C discharge capacity (-20°C) / 0.33C discharge capacity (25°C) * 100%, and the calculation results are summarized in Table 1.

[0112] Table 1

[0113]

[0114]

[0115] From the data in Table 1, it can be found that compared with the lithium ion batteries of Comparative Examples 1-5 without adding electrolyte additives, the low-temperature DC resistance of the lithium ion batteries obtained by using the non-aqueous electrolyte with added electrolyte additives provided in Examples 1-21 of the present application is significantly reduced, and the low-temperature capacity retention rate is relatively higher, that is, the low-temperature performance of the battery is better.

[0116] By comparing the data of Examples 1-8, it can be found that when the electrolyte additive content is 0.05%-5%, as the content of the electrolyte additive increases, the low-temperature DC resistance of the battery decreases and the low-temperature capacity retention rate increases. Among them, the low-temperature performance improvement effect of the battery in Example 1 with an electrolyte additive content of 3% is the most obvious. When the electrolyte additive content is higher than 5%, the low-temperature performance of the battery deteriorates to a certain extent.

[0117] 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.

[0118] 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 components of each element in the electrolyte additive LATP within a suitable range.

[0119] 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, characterized in that: The non-aqueous electrolyte includes an electrolyte additive, and 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-z (PO4)3, wherein 0 <x≤0.5,0<y≤0.16,0<z≤0.5。 2. The non-aqueous electrolyte according to claim 1, characterized in that The mass percentage of the electrolyte additive in the non-aqueous electrolyte is 0.1%-10%.

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

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

5. The non-aqueous electrolyte according to any one of claims 1 to 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 according to any one of claims 1 to 5, characterized in that: 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).

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

8. The non-aqueous electrolyte according to claim 7, characterized in that 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, dimethoxybenzene ... The invention can be selected from the group consisting of methane, 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 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 according to any one of claims 1 to 9, characterized in that: The non-aqueous electrolyte further includes 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.

11. A lithium ion battery, characterized in that: The lithium-ion battery comprises an electrolyte, and the electrolyte comprises the non-aqueous electrolyte according to any one of claims 1 to 10.

12. An electrical equipment, characterized in that: The electrical device comprises the lithium-ion battery as claimed in claim 11.

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