Electrolyte, lithium ion battery and electric device

Abstract

The electrolyte, the lithium ion battery and the electric equipment are disclosed, the electrolyte comprises a film-forming additive, the film-forming additive comprises amino borane and / or amino borane metal derivative, the chemical formula of the amino borane metal derivative is M (NH2BH3) n Wherein M is metal, n is positive integer equal to the chemical valence of M.The film-forming additive has high reduction potential and low oxidation potential, can generate dense SEI film and CEI film on the surface of positive and negative electrode by electrochemical reaction, and the generated SEI film and CEI film have the characteristics of low impedance and good high-temperature stability, which is beneficial to improve the high-temperature cycle performance and power performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrolyte, a lithium ion battery and a power utilization device. BACKGROUND

[0002] Lithium ion batteries are widely used in mobile electronic devices, electric vehicles and energy storage systems due to their high energy density and low pollution. During the first charge-discharge cycle of a lithium ion battery, side reactions occur on the surface of the electrode material with the electrolyte, forming a SEI (Solid Electrolyte Interphase) film on the negative electrode and a CEI (Chemical-Electrochemical Interface) film on the positive electrode. The SEI film and the CEI film can prevent electron transmission and allow lithium ion transmission, thereby inhibiting the corrosion of the electrolyte on the electrode material and the occurrence of side reactions. The lithium ion transmission performance and high temperature stability of the SEI film and the CEI film determine the interface performance of the electrode-electrolyte. In order to meet the demand for high energy density, long service life and high power of the battery, it is necessary to form an SEI film and a CEI film with low impedance and good high temperature stability.

[0003] Currently, film-forming additives are often added to the electrolyte of the battery to improve the electrode interface performance. However, existing film-forming additives have relatively single functions. For example, the commonly used negative electrode film-forming additive vinylene carbonate can improve the high temperature stability of the electrode, but the impedance of the SEI film formed is large, and the power performance cannot be considered. The SEI film formed by fluoroethylene carbonate and vinyl sulfate has low impedance and good power performance, but the high temperature stability is insufficient and gas production is serious. Therefore, it is necessary to provide a film-forming additive that can both reduce the impedance of the SEI film and the CEI film and improve the high temperature stability thereof. SUMMARY

[0004] Based on this, the embodiments of the present application provide an electrolyte containing a film-forming additive. The film-forming additive has a high reduction potential and a low oxidation potential, can generate a dense SEI film and a CEI film on the surface of the positive and negative electrodes through electrochemical reaction, and the generated SEI film and CEI film have the characteristics of low impedance and good high temperature stability, which is beneficial to improve the high temperature cycle performance and power performance of the battery.

[0005] In a first aspect, the embodiments of the present application provide an electrolyte, which comprises a film-forming additive, and the film-forming additive comprises amino borane and / or an amino borane derivative; the amino borane derivative comprises an amino borane metal derivative, and the chemical formula of the amino borane metal derivative is M(NH2BH3), wherein M is a metal, and n is a positive integer equal to the chemical valence of M.

[0006] In some embodiments, M is selected from Li, Na, K, Mg, Ca, Al.

[0007] In some embodiments, the aminoborane metal derivative includes at least one of LiNH2BH3, NaNH2BH3, KNH2BH3, Mg(NH2BH3)2, Ca(NH2BH3)2, and Al(NH2BH3)3.

[0008] In some embodiments, the aminoborane and / or aminoborane derivative is present in the electrolyte in a mass percentage of 0.1% to 10%.

[0009] In some embodiments, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, lithium trifluoromethylsulfonate, lithium bis-oxalato-borate, lithium bis-fluoro-oxalato-borate, lithium tetrafluoroborate, and lithium perchlorate.

[0010] In some embodiments, the lithium salt is present in the electrolyte in a molar concentration of 0.1 mol / L to 5 mol / L.

[0011] In some embodiments, the electrolyte further includes a solvent, and the solvent includes at least one of a carbonate solvent, a carboxylate solvent, and an ether solvent.

[0012] In some embodiments, the solvent is present in the electrolyte in a mass percentage of 10% to 90%.

[0013] The electrolyte provided by the embodiments of the present application contains a film-forming additive, which has a higher reduction potential and a lower oxidation potential than common electrolyte solvents, and can generate SEI and CEI films prior to electrolyte solvents in the process of the first charge and discharge, thereby inhibiting the consumption of solvents. The SEI and CEI films formed by the film-forming additive are rich in Li3N and LiF inorganic components on the one hand, and have high lithium ion conductivity and low impedance, which is beneficial to improving the rate performance of the battery. On the other hand, the SEI and CEI films are rich in organic components such as polymer chains, which have high toughness and help to alleviate the volume expansion of electrode materials in the process of charge and discharge, especially the expansion of electrodes under high temperature conditions, which is beneficial to improving the high-temperature cycle stability of the battery. n The SEI and CEI films formed by the film-forming additive are rich in Li3N and LiF inorganic components on the one hand, and have high lithium ion conductivity and low impedance, which is beneficial to improving the rate performance of the battery. On the other hand, the SEI and CEI films are rich in organic components such as polymer chains, which have high toughness and help to alleviate the volume expansion of electrode materials in the process of charge and discharge, especially the expansion of electrodes under high temperature conditions, which is beneficial to improving the high-temperature cycle stability of the battery.

[0014] In a second aspect, the embodiments of the present application provide a lithium ion battery, which includes the electrolyte of the first aspect.

[0015] The lithium ion battery provided by the embodiment of the present application contains a film-forming additive, the film-forming additive can form SEI film and CEI film with low impedance and good high-temperature stability, can improve the stability of the battery electrode interface, and is helpful to improve the high-temperature cycle stability and power performance of the battery.

[0016] In a third aspect, the embodiment of the present application provides a power-using device, which comprises the lithium ion battery of the second aspect.

[0017] The power-using device provided by the embodiment of the present application contains the lithium ion battery of the second aspect, which has good high-temperature stability and power performance, so that the power-using device can be used stably for a long time, and the use performance of the power-using device is improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used by the embodiments of the present application will be described below.

[0019] Figure 1 is a structural schematic diagram of a lithium ion battery 100 in an embodiment of the present application;

[0020] Figure 2 is a cyclic voltammetry curve diagram of a button cell provided by the embodiment 3 and the comparative example 1 of the present application;

[0021] Figure 3 is a linear sweep voltammetry curve diagram of a button half-cell provided by the embodiment 3 and the comparative example 1 of the present application. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described clearly and completely below by combining the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0023] At present, the lithium ion battery mainly has challenges in capacity attenuation, slow charging, low safety and high cost. In order to solve these problems, the lithium ion battery gradually develops towards high specific energy and long service life, which requires the selection of electrode material to be inclined to high-voltage platform or high specific capacity electrode material. With the increase of voltage, the side reaction of the traditional electrolyte with the electrode material also increases, more active lithium is consumed, and the products formed at the same time can cause the SEI film to thicken, the impedance to increase, and the capacity to attenuate. Therefore, the electrode-electrolyte interface stability of the lithium ion battery directly affects the various electrochemical performances and safety of the battery.

[0024] To improve the performance of the battery electrode-electrolyte interface, the most common method is to add a film-forming additive to the battery electrolyte. The film-forming additive can form a stable and effective SEI film and CEI film on the surface of the electrode material. The SEI film and CEI film can maintain good electronic insulation performance while allowing lithium ions to freely enter and exit the electrode, preventing further reaction of the electrode material with the electrolyte and maintaining the stability of the structure, thereby reducing the first irreversible capacity loss of the lithium ion battery and improving the rate performance and cycle life of the battery. However, the existing film-forming additives have the defect of being unable to balance the high-temperature cycle stability and power performance, for example, the commonly used film-forming additive vinylene carbonate can improve the high-temperature stability of the electrode, but the SEI film formed has high impedance and cannot balance the power performance, while the SEI film formed by fluoroethylene carbonate and vinyl sulfate has low impedance and good power performance, but the high-temperature stability is insufficient and gas production is serious. Therefore, it is necessary to provide a film-forming additive that can both reduce the impedance of the SEI film and CEI film and improve its high-temperature stability.

[0025] Based on this, the embodiment of the present application provides an electrolyte, which comprises a film-forming additive, and the film-forming additive comprises aminoborane and / or aminoborane derivative. In the embodiment of the present application, the aminoborane derivative comprises at least one of aminoborane metal derivative and aminoborane alkyl derivative.

[0026] In the embodiment of the present application, the chemical formula of the aminoborane metal derivative is M(NH2BH3)n n wherein M is a metal, and n is a positive integer. In the embodiment of the present application, M can be selected from Li, Na, K, Mg, Ca and Al. By selecting the aminoborane metal derivative containing a metal element with relatively small element mass, the present application can further ensure that the relative content of the effective component aminoborane in the aminoborane metal derivative is large, and further improve the film-forming performance of the film-forming additive. In some embodiments of the present application, the aminoborane metal derivative can be at least one of LiNH2BH3, NaNH2BH3, KNH2BH3, Mg(NH2BH3)2, Ca(NH2BH3)2 and Al(NH2BH3)3. The above-mentioned aminoborane metal derivative is easy to obtain and is conducive to cost control. In some embodiments of the present application, the aminoborane alkyl derivative can be, for example, ethylenediamine diborane (EDAB), diethylenetriamine triborane (DETAB), triethylenetetramine tetraborane (TETAB) and tetraethylenepentamine pentaborane (TEPAB).

[0027] The electrolyte provided by the embodiment of the present application contains a film-forming additive, which has a higher reduction potential and a lower oxidation potential than common electrolyte solvents, can preferentially undergo electrochemical oxidation and reduction on the electrode surface to generate a dense SEI film and CEI film, inhibit the consumption of solvents, and the generated SEI film and CEI film have the characteristics of low impedance and good high-temperature stability, which is beneficial to improve the high-temperature cycle performance and power performance of the battery. Specifically, first, the film-forming additive contains rich boron-nitrogen bonds in the molecule, which can weaken the solvation interaction between the solvent molecules and Li + , promote the desolvation process of Li + , and improve the diffusion kinetics of lithium ions in the electrolyte, thereby improving the power performance of the battery. Second, the film-forming additive can adjust the solvation sheath by forming a solvent structure rich in anions. Due to the presence of boron-nitrogen bonds, the content of anions in the first solute sheath of Li + is increased, which promotes the decomposition of anions during the charge and discharge cycle, thereby forming an anion-derived SEI film rich in Li3N and LiF. The ionic conductivity of Li3N and LiF is high, which is beneficial to the transfer of lithium ions, and thus the Li + conductivity of the SEI film containing the above inorganic components is enhanced, which can reduce the impedance of the battery, improve the charging speed and charging efficiency of the battery, and further improve the power performance of the battery. Third, the film-forming additive will form [LiNBH]n polymer chains during the film-forming process. This polymer can enhance the toughness of the SEI film, alleviate the swelling of the negative electrode material during the charge and discharge process, especially the swelling under high-temperature conditions, and enhance the high-temperature stability of the SEI film, thereby improving the high-temperature cycle performance of the battery. At the same time, the film-forming additive will also form a CEI film rich in Li3N, LiF and boron-nitrogen bonds ((NH=BH) n ) on the surface of the positive electrode during the film-forming process. The ionic conductivity of these components is high, and the high-temperature stability is good, so that the CEI film has good high-temperature stability and low impedance, thereby improving the high-temperature cycle performance and power performance of the battery.

[0028] In some embodiments of the present application, the mass percentage of the aminoborane and / or aminoborane derivative in the electrolyte is 0.1%-10%. This can effectively improve the stability of the SEI film and CEI film, reduce the impedance of the SEI film and CEI film, and improve the interface performance of the electrode-electrolyte. This can also take into account the specific capacity of the electrolyte, avoid waste of the film-forming additive, and facilitate cost control. In some embodiments, the mass percentage of the aminoborane and / or aminoborane derivative in the electrolyte may, for example, be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.3%, 2.6%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.3%, 4.5%, 5%, 6%, 7%, 8%, 9%, or 10%. In some embodiments of the present application, the film-forming additive comprises aminoborane, and the mass percentage of the aminoborane in the electrolyte is 0.1%-10%. In some embodiments of the present application, the film-forming additive comprises an aminoborane derivative, and the mass percentage of the aminoborane derivative in the electrolyte is 0.1%-10%. In some embodiments of the present application, the film-forming additive comprises aminoborane and an aminoborane derivative, and the total mass percentage of the aminoborane and the aminoborane derivative in the electrolyte is 0.1%-10%.

[0029] In some embodiments of the present application, the film-forming additive further comprises at least one of an unsaturated ester additive and a sulfur-containing additive. The aminoborane and aminoborane metal derivative are used in combination with the above-mentioned additives, which can synergistically improve the interface performance of the electrode and better balance the high-temperature stability and power performance of the battery. Specifically, the unsaturated ester additive may, for example, be one or more of vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate; and the sulfur-containing additive may, for example, be one or more of 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, vinyl sulfate, vinyl sulfite, and propylene sulfite.

[0030] In some embodiments of the present application, the electrolyte further comprises a lithium salt. In the present application, the main role of the lithium salt is to provide lithium ions, ensuring that there are sufficient lithium ions in the battery during charging and discharging. These lithium ions are transported between the positive and negative electrodes and are embedded and de-embedded in the negative electrode material during charging and discharging. In some embodiments, the lithium salt may, for example, be at least one of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethylsulfonylimide (LiTFSI), lithium trifluoromethylsulfonate (LiOTf), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium tetrafluoroborate (LiBF4), and lithium perchlorate (LiClO4).

[0031] In some embodiments, the molar concentration of the lithium salt in the electrolyte can be, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, or 5 mol / L.

[0032] In some embodiments, the solvent includes at least one of a carbonate solvent, a carboxylic acid ester solvent, and an ether solvent. Specifically, the carbonate solvent can be a cyclic or chain carbonate and derivatives thereof, such as one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, and ethyl butyrate; the carboxylic acid ester solvent can be a straight-chain or branched carboxylic acid ester and derivatives thereof, such as one or more of γ-butyrolactone, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, and ethyl butyrate; and the ether solvent can be one or more of a glycol ether solvent, a diethylene glycol ether solvent, a triethylene glycol ether solvent, and a tetraethylene glycol ether solvent, such as one or more of dimethyl glycol ether, diethyl glycol ether, dimethyl diethylene glycol ether, dimethyl triethylene glycol ether, and dimethyl tetraethylene glycol ether.

[0033] In some embodiments, the mass percentage of the solvent in the electrolyte can be, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

[0034] The present disclosure also provides a lithium ion battery including the electrolyte described above. Specifically, the lithium ion battery can include a positive electrode, a negative electrode, and a separator and an electrolyte between the positive electrode and the negative electrode, wherein the electrolyte includes the electrolyte described above. The lithium ion battery provided by the present disclosure contains a film-forming additive that can form SEI and CEI films with low impedance and good high-temperature stability, thereby improving the stability of the electrode interface of the battery and helping to improve the high-temperature cycle stability and power performance of the battery.

[0035] In some embodiments, the electrolyte includes a lithium salt, a solvent, and a film-forming additive. Figure 1As shown, the lithium ion battery 100 includes a negative electrode 10, an electrolyte 20, a separator 30, a positive electrode 40, and a battery housing 50, the electrolyte 20 and the separator 30 are located between the negative electrode 10 and the positive electrode 40, and the battery housing 50 is used to encapsulate the negative electrode 10, the electrolyte 20, the separator 30, and the positive electrode 40.

[0036] In the embodiments of the present application, the positive electrode 40 can include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the negative electrode 10 can include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the positive electrode active material layer can include a positive electrode active material, a conductive agent, and a binder, and the negative electrode active material layer can include a negative electrode active material, a conductive agent, and a binder, and the present application does not make specific limitations on these materials, and suitable materials can be selected according to actual application requirements.

[0037] In the embodiments of the present application, the positive electrode current collector can be an aluminum foil, and the negative electrode current collector can be a copper foil.

[0038] In the embodiments of the present application, the positive electrode active material can be a phosphate positive electrode active material or a ternary positive electrode active material, specifically, the positive electrode active material can be one or more of lithium cobaltate, lithium iron phosphate, lithium manganate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, fluorinated lithium vanadium phosphate, lithium titanate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminum, and the negative electrode active material can be one or more of a graphite material, a hard carbon material, a soft carbon material, a silicon-based material, and a tin-based material.

[0039] In the embodiments of the present application, the conductive agent can be one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotube. In some embodiments, the mass percentage of the conductive agent in the positive electrode active material layer can be 1%-4%, and the mass percentage of the conductive agent in the negative electrode active material layer can be 1%-4%.

[0040] In the embodiments of the present application, the binder can be one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, butadiene rubber, hydroxypropyl methyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives. In some embodiments, the mass percentage of the binder in the positive electrode active material layer can be 1%-5%, and the mass percentage of the binder in the negative electrode active material layer can be 1%-5%.

[0041] In the embodiments of the present application, the separator can be a polypropylene film (PP), a polyethylene film (PE), or a PP / PE composite film.

[0042] The embodiment of the present application also provides a power-using device, which comprises the lithium ion battery in any of the above embodiments. Specifically, the power-using device can be an electric vehicle, an electric motorcycle, an electric bicycle, a mobile power source, a drone, a mobile phone, a computer, a camera, an electric tool, a smart home or a wearable device.

[0043] The power-using device provided by the embodiment of the present application comprises the lithium ion battery, which has good high-temperature stability and power performance, so that the power-using device can be used stably for a long time, and the use performance of the power-using device is improved.

[0044] The technical solutions of the present application are further described below through specific embodiments and comparative examples.

[0045] Embodiment 1

[0046] (1) Preparation of electrolyte

[0047] In an argon-filled glove box, ethylene carbonate (EC), diethyl carbonate (EMC) and dimethyl carbonate (DMC) are mixed in a volume ratio of 1:1:1, then lithium hexafluorophosphate (LiPF6) is added to prepare an electrolyte base solution, then a film-forming additive, aminoborane, is added to the electrolyte base solution to obtain an electrolyte. In the electrolyte, the concentration of LiPF6 is 1 mol / L, and the mass percentage of aminoborane is 0.1%.

[0048] (2) Preparation of battery

[0049] Preparation of negative electrode sheet: graphite, conductive agent conductive carbon black (Super P), thickening agent carboxymethyl cellulose sodium (CMC) and adhesive styrene-butadiene rubber (SBR) are mixed in a mass ratio of 50:1:1:1.5 to form a slurry, which is uniformly coated on a copper foil as a negative electrode current collector. After drying at 85°C under vacuum for 24h, cold pressing is performed, then the edges are cut, the sheet is cut, and the strip is separated, and then drying is performed at 110°C under vacuum for 4 hours, and the tabs are welded to prepare a negative electrode sheet;

[0050] Preparation of positive electrode sheet: lithium cobalt oxide LiCoO2 (LCO), conductive agent conductive carbon black (Super P) and adhesive polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 50:1:1 to form a uniform positive electrode slurry, which is uniformly coated on an aluminum foil as a positive electrode current collector. After drying at 80°C under vacuum for 24h, cold pressing is performed, then the edges are cut, the sheet is cut, and the strip is separated, and then drying is performed at 110°C under vacuum for 4 hours, and the tabs are welded to prepare a positive electrode sheet;

[0051] Preparation of soft package battery: the prepared positive and negative electrode sheets and the separator are wound to prepare an LCO / graphite soft package battery. In an argon glove box with a water content of less than 5 ppm, the prepared electrolyte is injected into the soft package battery with an air bag, and then left to stand for 24 hours, and then subjected to a cycle test.

[0052] Preparation of button cell: The prepared negative electrode sheet, lithium sheet, electrolyte and separator were assembled into a CR2016 button cell for testing the reduction potential of the electrolyte. The lithium sheet was assembled into a button half-cell with a stainless steel sheet for testing the oxidation potential of the electrolyte;

[0053] Formation process: The full cell was first charged to 1.9 V at a current of 0.05 C and maintained at 1.9 V for 10 h to fully wet the electrode sheet of the cell. After the constant voltage was completed, the cell was initially charged at a small current of 0.01 C for 10 h to form a stable and dense SEI film, then charged to 4.4 V at a current of 0.05 C, and finally discharged to 2.75 V.

[0054] Example 2

[0055] (1) Preparation of electrolyte

[0056] The difference from Example 1 is that the mass percentage content of aminoborane in the electrolyte is 0.5%.

[0057] (2) Preparation of battery

[0058] The same as Example 1.

[0059] Example 3

[0060] (1) Preparation of electrolyte

[0061] The difference from Example 1 is that the mass percentage content of aminoborane in the electrolyte is 1%.

[0062] (2) Preparation of battery

[0063] The same as Example 1.

[0064] Example 4

[0065] (1) Preparation of electrolyte

[0066] The difference from Example 1 is that the mass percentage content of aminoborane in the electrolyte is 2%.

[0067] (2) Preparation of battery

[0068] The same as Example 1.

[0069] Example 5

[0070] (1) Preparation of electrolyte

[0071] The difference from Example 1 is that the mass percentage content of aminoborane in the electrolyte is 5%.

[0072] (2) Preparation of battery

[0073] The same as Example 1.

[0074] Example 6

[0075] (1) Preparation of electrolyte

[0076] The difference from Example 1 is that the mass percentage of aminoborane in the electrolyte is 10%.

[0077] (2) Preparation of battery

[0078] The same as Example 1.

[0079] Example 7

[0080] (1) Preparation of electrolyte

[0081] The difference from Example 1 is that aminoborane is replaced by lithium ammonia borane LiNH2BH3, and the mass percentage of lithium ammonia borane in the electrolyte is 2%.

[0082] (2) Preparation of battery

[0083] The same as Example 1.

[0084] Example 8

[0085] (1) Preparation of electrolyte

[0086] The difference from Example 1 is that aminoborane is replaced by sodium ammonia borane NaNH2BH3, and the mass percentage of sodium ammonia borane in the electrolyte is 2%.

[0087] (2) Preparation of battery

[0088] The same as Example 1.

[0089] Example 9

[0090] The difference from Example 1 is that aminoborane is replaced by magnesium ammonia borane Mg(NH2BH3)2, and the mass percentage of magnesium ammonia borane in the electrolyte is 2%.

[0091] (2) Preparation of battery

[0092] The same as Example 1.

[0093] Example 10

[0094] The difference from Example 1 is that aminoborane is replaced by aluminum ammonia borane Al(NH2BH3)3, and the mass percentage of aluminum ammonia borane in the electrolyte is 2%.

[0095] (2) Preparation of battery

[0096] The same as Example 1.

[0097] Comparative Example 1

[0098] (1) Preparation of electrolyte

[0099] The difference from Example 1 is that the electrolyte does not contain aminoborane.

[0100] (2) Preparation of battery

[0101] The same as Example 1.

[0102] Comparative Example 2

[0103] (1) Preparation of electrolyte

[0104] The difference from Example 1 is that aminoborane is replaced by vinylene carbonate (VC), and the mass percentage content of vinylene carbonate (VC) in the electrolyte is 2%.

[0105] (2) Preparation of battery

[0106] The same as Example 1.

[0107] Comparative Example 3

[0108] (1) Preparation of electrolyte

[0109] The difference from Example 1 is that aminoborane is replaced by 1,3-propane sultone (PS), and the mass percentage content of 1,3-propane sultone (PS) in the electrolyte is 2%.

[0110] (2) Preparation of battery

[0111] The same as Example 1.

[0112] The electrolytes, soft package batteries and button batteries of Examples 1-10 and Comparative Examples 1-3 are subjected to the following performance tests:

[0113] (1) Reduction-oxidation potential test

[0114] The button batteries of the examples and comparative examples are subjected to cyclic voltammetry test, the scanning speed is 0.2 mV / s, and the scanning range is 0.005 V-3 V. The reduction potential test results of the electrolytes are shown in Table 1, and the cyclic voltammetry test results of the button batteries of Example 3 and Comparative Example 1 are shown in Figure 2 From Figure 2 it can be seen that aminoborane in the electrolyte of Example 3 has a reduction peak at about 1.36 V, while carbonate solvent in the electrolyte of Comparative Example 1 has a reduction peak at about 0.8 V, indicating that the reduction potential of aminoborane is higher than that of carbonate solvent.

[0115] The linear sweep voltammetry test of the button half-cells of the examples and the comparative examples was carried out at a scanning speed of 0.2 mV / s and a scanning range of 3.0 V-6 V, and the obtained oxidation potential test results of the electrolytes are shown in Table 1, and the linear sweep voltammetry test results of the button half-cells of Example 3 and Comparative Example 1 are shown in Figure 3 Figure 3 It can be seen that the aminoborane in the electrolyte of Example 3 has an oxidation peak at 4.0 V, while the carbonate solvent in the electrolyte of Comparative Example 1 has an oxidation peak at 4.5 V, indicating that the oxidation potential of the aminoborane is lower than that of the carbonate solvent.

[0116] Table 1 Reduction potential and oxidation potential of the electrolytes of Examples 1-10 and Comparative Examples 1-3

[0117] Group Reduction potential (vs. Li + / Li, V) Oxidation potential (vs. Li + / Li, V) Example 1 1.36 4.01 Example 2 1.37 4.01 Example 3 1.36 4.01 Example 4 1.36 4.0 Example 5 1.34 3.99 Example 6 1.34 3.99 Example 7 1.41 4.03 Example 8 1.38 4.02 Example 9 1.38 4.05 Example 10 1.38 4.05 Comparative Example 1 0.8 4.5 Comparative Example 2 1.1 4.25 Comparative Example 3 1.2 4.1

[0118] It can be seen from Table 1 that the reduction potential of the film-forming additive provided by the examples of the present application is between 1.34 V and 1.41 V, which is higher than the reduction potential of the carbonate solvent, and the oxidation potential is between 3.99 V and 4.05 V, which is lower than the oxidation potential of the carbonate solvent. Therefore, the film-forming additive provided by the examples of the present application can preferentially oxidize and reduce the carbonate solvent to form SEI film and CEI film, thereby protecting the solvent and reducing the consumption of the solvent.

[0119] (2) High-temperature cycle test

[0120] The soft pack batteries of the examples and the comparative examples (10 for each condition, and the results are averaged) were cycled at a current of 1C between 2.75 V and 4.4 V for 200 times. The high-temperature cycle test was carried out in a 45℃ constant temperature box. The capacity retention rate (%) was calculated by dividing the discharge capacity at the 200th cycle by the initial discharge capacity of the first cycle. The high-temperature cycle test results are shown in Table 2.

[0121] (3) Battery impedance test

[0122] The soft pack batteries of the examples and the comparative examples (10 for each condition, and the results are averaged) were cycled at a current of 500 mA (1C) between 2.75 V and 4.5 V for 120 times, and the battery was discharged to 2.75 V, and then the alternating current impedance at a temperature of -10℃ was measured. The low-temperature alternating current impedance test results are shown in Table 2.

[0123] Table 2 High-temperature cycle test and low-temperature alternating current impedance test results

[0124]

[0125] ​As can be seen from Table 2, the capacity retention rates of the pouch batteries of Examples 1-10 at high temperature are all higher than that of Comparative Example 1, indicating that the film-forming additive provided in the examples of the present application can effectively improve the high-temperature cycle performance of the battery. As can also be seen from Table 2, the AC impedance of the pouch batteries of Examples 1-10 at low temperature are all lower than those of Comparative Examples 2 and 3, indicating that the film-forming additive provided in the examples of the present application, compared with the existing film-forming additives such as vinylene carbonate and 1,3-propane sultone, can better inhibit the increase of impedance while improving the high-temperature cycle performance of the battery, so as to better balance the high-temperature cycle performance and power performance of the battery.

[0126] As can be seen from Comparative Examples 4, 7-10 and Comparative Examples 2 and 3, compared with the existing film-forming additives vinylene carbonate and 1,3-propane sultone, the novel film-forming additive provided in the examples of the present application has a better effect in improving the high-temperature cycle performance of the battery, and can obtain a lower low-temperature impedance. As can be seen from Comparative Examples 1-6, selecting a moderate value of the content of the film-forming additive in the electrolyte in the range of 0.1%-10% is conducive to balancing the high-temperature cycle performance and low-temperature impedance of the battery.

[0127] The above-described examples only express several embodiments of the present application, and the description is relatively specific and detailed, but it should not be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A lithium-ion battery, characterized by, The lithium ion battery includes an electrolyte, the electrolyte includes a film-forming additive, the film-forming additive includes an aminoborane and / or an aminoborane derivative; the aminoborane derivative includes an aminoborane metal derivative, the aminoborane metal derivative has a chemical formula of M(NH2BH3) n wherein M is a metal, and n is a positive integer equal to the chemical valence of M.

2. The lithium-ion battery of claim 1, wherein, The M is selected from at least one of Li, Na, K, Mg, Ca, Al.

3. The lithium-ion battery of claim 1 or 2, wherein, The amino borane metal derivative includes at least one of LiNH2BH3, NaNH2BH3, KNH2BH3, Mg(NH2BH3)2, Ca(NH2BH3)2 and Al(NH2BH3)3.

4. The lithium-ion battery of claim 1, wherein, The mass percentage of the amino borane and / or amino borane derivative in the electrolyte is 0.1%-10%.

5. The lithium-ion battery of claim 1, wherein, The electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, lithium trifluoromethylsulfonate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium tetrafluoroborate and lithium perchlorate.

6. The lithium-ion battery of claim 5, wherein, The molar concentration of the lithium salt in the electrolyte is 0.1mol / L-5mol / L.

7. The lithium-ion battery of claim 1, wherein, The electrolyte further includes a solvent, and the solvent includes at least one of carbonate solvents, carboxylate solvents and ether solvents.

8. The lithium-ion battery of claim 7, wherein, The mass percentage of the solvent in the electrolyte is 10%-90%.

9. An electric device, characterized by The power consuming device includes the lithium ion battery of any one of claims 1-8.

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