An electrolyte, a battery

Abstract

The application provides an electrolyte, a battery and an electrolyte, which comprises a lithium salt, an organic solvent and a functional additive; the structural formula of the functional additive is as follows: wherein R1 comprises at least one of a primary amine group, a secondary amine group and a tertiary amine group; and at least one of R4 and R5 comprises a cyano group. The electrolyte has good film forming properties on the positive and negative electrode sides by introducing the specific functional additive, so that the positive and negative electrodes have good interface stability under high voltage, and the long-term cycle performance and high-temperature storage performance of the high-voltage battery are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to an electrolyte and a battery. BACKGROUND

[0002] Developing high-voltage ternary cathode materials is an effective way to improve the energy density of lithium ion batteries. However, as the nickel content in the ternary material increases or the limit voltage continues to increase, the specific capacity of the battery material gradually increases, while the high and low temperature performance of the battery is difficult to balance, the battery is prone to produce gas during high temperature storage, the internal resistance increases rapidly during the cycle process, and the long cycle life cannot be guaranteed.

[0003] The current lithium ion battery electrolyte mainly uses traditional film-forming additives such as vinylene carbonate (VC) or fluoroethylene carbonate (FEC), but VC has poor oxidation resistance, and although FEC is resistant to oxidation, it is prone to decomposition to produce hydrofluoric acid (HF) at high temperatures, which will further exacerbate the dissolution of metal ions in the ternary cathode material and deteriorate the battery performance.

[0004] In addition, for the ternary cathode material, the oxidation states of Ni, Co and Mn are +2, +3 and +4, respectively. During charging, lithium ions will be deintercalated from the cathode, so Ni will be converted from +2 to +3 or even +4, and the cathode will react with the electrolyte to form a layer of solid electrolyte interface (CEI layer), which will protect the cathode (similar to the SEI film of the anode) and hinder the further reaction of the cathode with the electrolyte, thereby improving the stability of the cathode under delithiation conditions. However, the formation of the CEI film will also cause problems such as increased battery impedance, rate decay, capacity decay, and gas generation. Therefore, it is particularly important to optimize the electrolyte composition to form the best cathode CEI film. Of course, the formation of a good SEI film on the anode side is also particularly important for the performance of the battery.

[0005] Therefore, a new ternary high-voltage lithium ion battery electrolyte is developed, which can have good film-forming properties on the cathode and anode sides, and is of great significance for further optimizing the interface stability of the battery and the performance of the battery. SUMMARY

[0006] To solve the problems and deficiencies in the prior art, the application provides an electrolyte and a battery. The electrolyte introduces a specific functional additive, so that the electrolyte has good film-forming properties on the cathode and anode sides, thereby ensuring that the cathode and anode have good interface stability at high voltage, and further improving the long-term cycle performance and high-temperature storage performance of the high-voltage battery.

[0007] According to a first aspect of the application, an electrolyte is provided, comprising a lithium salt, an organic solvent, and a functional additive. The structural formula of the functional additive is:

[0008] wherein R1 comprises at least one of a primary amine group, a secondary amine group, a tertiary amine group; at least one of R4 and R5 comprises a cyano group.

[0009] The introduction of the above-mentioned functional additive with the specific structure effectively improves the overall performance of the electrolyte, and in turn effectively improves the cycle performance and high-temperature storage performance of the battery, and effectively reduces the DCR growth rate of the battery.

[0010] Specifically, first, the functional additive has structures such as benzene rings and double bonds, and the conjugated structure formed by the functional additive can improve the conductivity and ion conductivity of the electrolyte, and reduce the DCR growth rate of the battery; the double bonds can be polymerized during the formation of the battery, which is conducive to the formation of uniform and dense CEI and SEI films at the positive and negative electrode interfaces, improves the stability of the positive and negative electrode interfaces, and in turn optimizes the cycle performance and high-temperature storage performance of the battery; the benzene ring structure and the like can also improve the stability of the molecular structure, which is conducive to improving the overall stability of the electrolyte, thereby improving the high-pressure oxidation resistance and thermal stability of the electrolyte.

[0011] Secondly, the sulfate group can further participate in the formation of the negative electrode film, improve the stability of the negative electrode SEI film, and the sulfate group has strong polarity and can interact with lithium ions and the like, promote the dissociation and transmission of lithium ions in the electrolyte, and thus improve the ionic conductivity of the electrolyte. This helps to reduce the internal resistance of the battery and improve the charge and discharge efficiency and rate performance of the battery.

[0012] Thirdly, the cyano group has a wide chemical window, and the strong polar cyano group helps to improve the compatibility between the electrolyte and the electrode, and improve the electrochemical performance of the battery at high temperature and high pressure. The primary amine, secondary amine and tertiary amine have a certain basicity, which can interact with acidic impurities or lithium salts in the electrolyte, adjust the acidity and alkalinity of the electrolyte, reduce side reactions or promote the dissociation and transmission of lithium ions in the electrolyte, improve the stability and performance of the electrolyte, and in turn improve the cycle stability and safety of the battery. In addition, the N group in the cyano group, the primary amine, the secondary amine and the tertiary amine can be complexed with transition metal ions, reducing the damage of transition metal ions to the negative electrode, thereby further improving the stability of the negative electrode interface, and further improving the overall performance of the battery.

[0013] Preferably, R2 comprises at least one of hydrogen, an alkyl chain, a substituted alkyl chain, and a halogen; R3 comprises at least one of an alkyl chain, a substituted alkyl chain, an alkyl chain containing a double bond or a triple bond, and a substituted alkyl chain containing a double bond or a triple bond, and the number of carbon atoms in R3 is ≥ 0.

[0014] It should be noted that when the number of carbon atoms in R3 is 0, the structural formula of the functional additive is:

[0015]

[0016] Preferably, R4, R5 independently include cyano. When the functional additive includes two cyano groups, the electrolyte in which the functional additive is present exhibits better performance, so that the battery has better cycle performance and high-temperature storage performance, and also has a lower DCR growth rate. Therefore, when the functional additive includes two cyano groups, the performance of the electrolyte is more advantageous to play and the performance of the battery is more advantageous to optimize.

[0017] Preferably, R1 includes a primary amine group, hydrogen, R2 includes hydrogen, the number of carbon atoms in R3 = 0, and R4, R5 independently include cyano.

[0018] Preferably, the functional additive has the following structural formula:

[0019]

[0020] Preferably, the mass fraction of the functional additive in the electrolyte is 0.1-0.5%.

[0021] Preferably, the electrolyte further includes a sulfur-containing additive, and the sulfur-containing additive includes at least one of 1,3-propane sulfite (PST), ethylene sulfite (ES), vinyl ethylene sulfite (VES), ethylene sulfite (DTD), methane disulfonic acid methylene ester (MMDS), thiophene derivative (TH), fluorosulfonyloxy benzene (FSOB), phenyl methanesulfonate (PMS), and hydroquinone difluorosulfonate (HBFS). Further, after the electrolyte in the present application introduces the above-mentioned sulfur-containing additive, the battery prepared using the same exhibits better performance. This can be because the introduction of the sulfur-containing additive further promotes the film stability and uniformity of the negative electrode SEI film, effectively reduces the side reaction on the negative electrode side, and the use of the sulfur-containing additive in combination with the above-mentioned functional additive is more advantageous to improve the function of the functional additive on the positive electrode side, and further improves the stability of the positive electrode interface, thereby the stability of the positive and negative electrode interfaces is improved to a certain extent, so that the performance of the battery is further optimized.

[0022] Preferably, the mass fraction of the sulfur-containing additive in the electrolyte is 0.5-1.5 wt%.

[0023] Preferably, the sulfur-containing additive includes 1,3-propane sulfite and fluorosulfonyloxy benzene. When the sulfur-containing additive is a combination of the above two materials, the performance of the sulfur-containing additive in the electrolyte is more obvious, and the function of other components in the electrolyte is not affected, so that the overall performance of the electrolyte can be further improved, and the overall performance of the battery can be further improved.

[0024] Preferably, the mass ratio of 1,3-propane sultone and fluorosulfonyloxybenzene is 3-7:1. When the mass ratio of the above two sulfur-containing additives is within the above range, the combination of the above sulfur-containing additives can further optimize the performance of the electrolyte, and further optimize the cycle performance and high-temperature storage performance of the battery.

[0025] Preferably, a carbonate-based additive is further included, and the carbonate-based additive includes at least one of vinylene carbonate (VC) and fluoroethylene carbonate (FEC).

[0026] Preferably, the mass fraction of the carbonate-based additive in the electrolyte is 0.2-0.8wt%.

[0027] Preferably, the carbonate-based additive includes fluoroethylene carbonate (FEC).

[0028] Preferably, the electrolyte further includes a lithium salt additive, and the lithium salt additive includes at least one of lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), and lithium difluorobis(oxalato)phosphate (LiODFP).

[0029] Preferably, the mass fraction of the lithium salt additive in the electrolyte is 0.5-1.5wt%.

[0030] Preferably, the lithium salt additive includes lithium bis(oxalato)borate (LiBOB). When the lithium salt additive is lithium bis(oxalato)borate, the mutual synergistic effect of the lithium salt additive with the functional additive, the sulfur-containing additive, and the carbonate-based additive, etc. is optimal, that is, the battery prepared using the electrolyte has the best performance, especially in terms of cycle performance and high-temperature storage performance.

[0031] Preferably, the lithium salt includes lithium hexafluorophosphate; and the concentration of lithium hexafluorophosphate in the electrolyte is 1-1.5mol / L.

[0032] Preferably, the organic solvent includes at least one of vinyl carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0033] Preferably, the organic solvent includes at least two or at least three of vinyl carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0034] Preferably, the volume ratio of vinyl carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate is (20-40):(0-20):(0-20):(30-50).

[0035] According to a second aspect of the present application, a battery is provided, characterized in that it includes the above electrolyte.

[0036] Preferably, the battery comprises a positive electrode, and the positive electrode comprises a ternary nickel-cobalt-manganese positive electrode material. In particular, the electrolyte provided by the present application is suitable for a battery with a ternary nickel-cobalt-manganese positive electrode material system, and the resulting battery has better cycle performance and storage performance.

[0037] Preferably, the ternary nickel-cobalt-manganese positive electrode material has a chemical formula of Li(Ni x Co y Mn z )O2, wherein 0.5≤x<0.8, 0<y≤0.3, 0<z≤0.3, and x+y+z=1.

[0038] Preferably, the battery comprises a negative electrode, and the negative electrode comprises graphite. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0040] Embodiment 1

[0041] 1. Electrolyte composition and preparation

[0042] The electrolyte in this embodiment comprises a lithium salt, an organic solvent, a functional additive, a sulfur-containing additive, a carbonate additive, and a lithium salt additive.

[0043] The lithium salt is lithium hexafluorophosphate (LiPF6), and the concentration of lithium hexafluorophosphate in the electrolyte is 1 mol / L.

[0044] The organic solvent is composed of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Taking the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 30%, the volume fraction of diethyl carbonate is 20%, and the volume fraction of methyl ethyl carbonate is 50%.

[0045] The functional additive is The mass fraction in the electrolyte is 0.3wt%.

[0046] The sulfur-containing additive is 1,3-propane sultone (PST), and the mass fraction in the electrolyte is 1wt%.

[0047] The carbonate additive is fluoroethylene carbonate (FEC), and the mass fraction in the electrolyte is 0.5wt%.

[0048] The lithium salt additive is lithium difluorophosphate (LiPO2F2), and the mass fraction in the electrolyte is 1.0wt%.

[0049] The preparation of the electrolyte solution is carried out according to the following steps: under an argon atmosphere, the formula amount of carbonate additives, lithium salt additives, sulfur-containing additives and functional additives are added to the organic solvent, and then the lithium salt is added, and the mixture is stirred at a temperature of 10°C to obtain the electrolyte solution.

[0050] 2. Preparation of the battery

[0051] Preparation of the lithium ion battery

[0052] (1) Preparation of the positive electrode sheet

[0053] The ternary positive electrode material NCM523, the binder PVDF (polyvinylidene fluoride), and the conductive agent SP (conductive carbon black Super-P) are mixed and stirred uniformly at a mass ratio of 94:3:3 to obtain a positive electrode slurry, and then the positive electrode slurry is coated on an aluminum foil through a coating process, vacuum dried, and cold pressed to obtain a positive electrode sheet.

[0054] (2) Preparation of the negative electrode sheet

[0055] The negative electrode material graphite, the conductive agent SP (conductive carbon black Super-P), the binder CMC (carboxymethyl cellulose), and SBR (styrene-butadiene rubber) are mixed and stirred uniformly at a mass ratio of 94:1:2:3 to obtain a negative electrode slurry, and then the negative electrode slurry is coated on a copper foil through a coating process, vacuum dried, and cold pressed to obtain a negative electrode sheet.

[0056] (3) Selection of the electrolyte solution

[0057] The electrolyte solution prepared in this example is used.

[0058] (4) Selection of the separator film

[0059] Celgard 2400 is selected as the separator film of the lithium ion battery.

[0060] (5) Preparation of the lithium ion battery

[0061] The above-mentioned positive electrode sheet, the separator film (Celgard 2400), and the negative electrode sheet are stacked in order, with the separator film between the positive electrode sheet and the negative electrode sheet to play a separating role, the bare battery cell is placed in an outer packaging shell, dried, and then the electrolyte solution is injected, and the lithium ion battery is obtained after vacuum packaging, standing, formation, shaping, and other processes.

[0062] Example 2

[0063] The difference between this example and Example 1 is that the functional additive in the prepared electrolyte solution is adjusted to CAS No. 122533-89-5; the rest is consistent with Example 1.

[0064] Example 3

[0065] The difference between this embodiment and embodiment 1 is that in the prepared electrolyte, the functional additive is adjusted to CAS No. 116396-16-8; the rest is consistent with embodiment 1.

[0066] Embodiment 4

[0067] The difference between this embodiment and embodiment 1 is that in the prepared electrolyte, the functional additive is adjusted to CAS No. 137996-26-0; the rest is consistent with embodiment 1.

[0068] Embodiment 5

[0069] The difference between this embodiment and embodiment 1 is that in the prepared electrolyte, the mass fraction of the functional additive in the electrolyte is adjusted to 0.6wt%; the rest is consistent with embodiment 1.

[0070] Embodiment 6

[0071] The difference between this embodiment and embodiment 1 is that in the prepared electrolyte, the sulfur-containing additive is adjusted to 1,3-propane sulfone and fluorosulfonyloxybenzene, and the mass ratio of the two is 5:1, and the total amount of the sulfur-containing additive is unchanged; the rest is consistent with embodiment 1.

[0072] Embodiment 7

[0073] The difference between this embodiment and embodiment 1 is that in the prepared electrolyte, the sulfur-containing additive is adjusted to 1,3-propane sulfone and fluorosulfonyloxybenzene, and the mass ratio of the two is 5:1, and the total amount of the sulfur-containing additive is unchanged; the rest is consistent with embodiment 1.

[0074] Embodiment 8

[0075] The difference between this embodiment and embodiment 1 is that in the prepared electrolyte, the sulfur-containing additive is adjusted to hydroquinone difluorosulfonate (HBFS); the rest is consistent with embodiment 1.

[0076] Embodiment 9

[0077] The difference between this embodiment and embodiment 1 is that in the prepared electrolyte, the carbonate additive is adjusted to vinylene carbonate (VC); the rest is consistent with embodiment 1.

[0078] Embodiment 10

[0079] The difference between this embodiment and embodiment 6 is that in the prepared electrolyte, the carbonate additive is adjusted to vinylene carbonate (VC); the rest is consistent with embodiment 6.

[0080] Example 11

[0081] The difference between this example and Example 1 is that in the prepared electrolyte, the lithium salt additive is adjusted to lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), and the mass ratio of the two is 2:1, and the total amount of lithium salt additive is unchanged; the rest is consistent with Example 1.

[0082] Example 12

[0083] The difference between this example and Example 1 is that in the prepared electrolyte, the lithium salt additive is adjusted to lithium bis(oxalato)borate (LiBOB); the rest is consistent with Example 1.

[0084] Example 13

[0085] The difference between this example and Example 6 is that in the prepared electrolyte, the lithium salt additive is adjusted to lithium bis(oxalato)borate (LiBOB); the rest is consistent with Example 6.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 1 is that in the prepared electrolyte, no functional additive is added; the rest is consistent with Example 1.

[0088] Comparative Example 2

[0089] The difference between this comparative example and Example 1 is that in the prepared electrolyte, the functional additive is adjusted to CAS No. is 99-97-8; the rest is consistent with Example 1.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 1 is that in the prepared electrolyte, the functional additive is adjusted to CAS No. is 825-44-5; the rest is consistent with Example 1.

[0092] Comparative Example 4

[0093] The difference between this comparative example and Example 1 is that in the prepared electrolyte, the functional additive is adjusted to CAS No. is 58068-69-2; the rest is consistent with Example 1.

[0094] Test Example

[0095] 1. Experimental construction method

[0096] The electrolyte prepared in all the above examples and comparative examples was subjected to HF content determination, and the battery prepared in all the above examples and comparative examples was subjected to cycle performance test, DCR growth rate test and high temperature storage performance test, and the specific test methods were as follows.

[0097] (1) Cycle performance test and DCR growth rate test

[0098] Cycle performance: at 45°C, the lithium ion battery was charged to 4.4V at 1.0C (nominal capacity) constant current, and then charged to 4.4V constant voltage until the current was less than or equal to 0.05C, and then discharged to the cut-off voltage of 2.8V at 1C constant current after 10min of standing, which was one charge-discharge cycle. The lithium ion battery was subjected to 45°C 300 times of charge-discharge cycle according to the above conditions.

[0099] Capacity retention rate (%) of lithium ion battery after N cycles = (discharge capacity of the Nth cycle / first discharge capacity) x 100%, and N was the cycle number of the lithium ion battery.

[0100] DCR growth rate: at 45°C, the battery was subjected to DCR growth rate test according to the following steps, ① 1C charged to 4.2V, (1 / 50)C cut-off, charged to 100% SOC; ② standing for 1h, and taking the last standing voltage as U1; ③ 2C discharging for 30s, and taking the voltage at the end of the 10th s as U2; ④ calculation, DCIR calculation formula: DCIR = (U2-U1) / 2C*1000; DCIR growth rate calculation formula: DCIR growth rate = DCIR / initial DCIR.

[0101] (3) High temperature storage performance test

[0102] The battery was subjected to 5 times of charge-discharge cycle test at 1C charge-discharge rate at room temperature, and then charged to full state of charge at 1C rate. The 1C capacity Q0 and the battery volume V0 were recorded respectively. The battery in full state of charge was stored at 60°C for 90 days, and the battery volume V1 and 1C discharge capacity Q1 were recorded, and then the battery was charged at 1C rate for 5 weeks at room temperature, and the 1C discharge capacity Q2 was recorded, and the experimental data such as high temperature storage capacity retention rate, capacity recovery rate and volume change rate of the battery were calculated, and the results were recorded as follows. The calculation formula used was as follows: capacity retention rate (%) = Q1 / Q0 x 100%; capacity recovery rate (%) = Q2 / Q0 x 100%; volume change rate (%) = (V1-V0) / V0 x 100%.

[0103] The above charge-discharge cycle at 1C charge-discharge rate or 1C rate charge refers to

[0104] 1.0C (nominal capacity) constant current charge to 4.4V, then 4.4V constant voltage charge to current <0.05C, after 10min rest, 1C constant current discharge to 2.8V, above is one charge-discharge cycle or one charge.

[0105] 2. Experimental results

[0106] The relevant performance test results of the batteries prepared in all the above examples and comparative examples are shown in Table 1.

[0107] Table 1. The relevant performance test results of the batteries prepared in examples and comparative examples

[0108]

[0109] From Table 1, it can be seen that the battery prepared by using the electrolyte provided by the application not only has good high-temperature (45℃) cycle performance, but also has good high-temperature (60℃) storage performance, so the electrolyte provided by the application can realize the effect of further optimizing the performance of the battery, for reference to Examples 1-13.

[0110] The electrolyte of Comparative Example 1 has no functional additive, the functional additive of the electrolyte of Comparative Example 2 has a cyano group, a sulfate group and a benzene ring connected with the sulfate group, the functional additive of the electrolyte of Comparative Example 3 has no cyano group, amine group and benzene ring connected with the amine group, and the functional additive of the electrolyte of Comparative Example 4 has no sulfate group and benzene ring connected with the sulfate group; these factors cause a more obvious decrease in the performance of the battery, especially the electrolyte of Comparative Example 1 has no functional additive, which leads to a more obvious decrease in the high-temperature cycle performance and high-temperature storage performance of the battery. Therefore, the above results show that the introduction of the specific functional additive in the application plays a key role in optimizing the performance of the electrolyte and the battery, and the specific functional groups of the functional additive also have a greater impact on the performance of the electrolyte and the battery.

[0111] Further comparing Examples 1 and 2-4, the alkyl chain after the secondary amine in the functional additive of Example 2 is longer, the alkyl chain after the secondary amine in the functional additive of Example 3 is longer, and there is also an alkenyl group in R3, the amine group in the functional additive is primary amine, and there is also a methyl group in R1, finally the high-temperature cycle performance of Examples 2-4 is higher than that of Example 1, the DCR growth rate is higher than that of Example 1, and in the high-temperature storage performance, the volume expansion rate is higher than that of Example 1, and the capacity retention rate and the capacity recovery rate are worse than those of Example 1. This shows that even a small change in the structural formula of the functional additive will affect the performance of the functional additive in the electrolyte, and then affect the overall performance of the electrolyte, and finally lead to a certain deterioration of the performance of the battery.

[0112] Comparing example 1 and example 5, the content of the functional additive in example 5 is too high, which also causes the high-temperature cycle performance and high-temperature storage performance of the battery in example 5 to decrease. This is because too high content of the functional additive affects the solubility of the functional additive and the function of other components of the electrolyte, thereby causing the overall performance of the battery to decrease, and finally causing the battery performance to deteriorate.

[0113] Comparing example 1 and examples 6-8, the sulfur-containing additive in example 6 is 1,3-propane sultone and fluorosulfonyloxybenzene, and the mass ratio is in the range of 3-7:1; the sulfur-containing additive in example 7 is 1,3-propane sultone and fluorosulfonyloxybenzene, but the mass ratio is not in the range of 3-7:1; the sulfur-containing additive in example 8 is hydroquinone difluorosulfonate (HBFS); and the performance of the battery in example 6 is better than that in example 1, and the performance of the battery in examples 7 and 8 is worse than that in example 1. Comparing example 1 and example 9, the carbonate additive in example 9 is vinylene carbonate (VC), and the performance of the battery in example 9 is worse than that in example 1. Comparing example 6 and example 10, the carbonate additive in example 10 is vinylene carbonate (VC), and the performance of the battery in example 10 is worse than that in example 6. Comparing example 1 and examples 11-12, the lithium salt additive in example 11 is lithium difluorophosphate (LiPO2F2) and lithium bis(oxalato)borate (LiBOB), and the lithium salt additive in example 12 is lithium bis(oxalato)borate (LiBOB), and the performance of the battery in example 11 is better than that in example 1, and the performance of the battery in example 12 is worse than that in example 1. Comparing example 6 and example 13, the lithium salt additive in example 13 is lithium bis(oxalato)borate (LiBOB), and the performance of the battery in example 13 is better than that in example 6. The above results show that the selection of the type and / or mass ratio of the sulfur-containing additive, the carbonate additive, and the lithium salt additive will have a certain influence on the performance of the electrolyte, and thus will have a certain influence on the performance of the final battery. Therefore, further optimization of the respective materials of the sulfur-containing additive, the carbonate additive, and the lithium salt additive or the collocation of the respective materials of the sulfur-containing additive, the carbonate additive, and the lithium salt additive, and limitation of specific ratios, can be more conducive to the overall performance of the electrolyte, and thus can further optimize the performance of the battery.

[0114] The above examples are only used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the above examples, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents, but these modifications or replacements are within the protection scope of the present application.

Claims

1. An electrolyte, characterized by, The lithium salt, the organic solvent, and the functional additive; The functional additive has a structural formula as follows: ； R1 includes at least one of a primary amine group, a secondary amine group, and a tertiary amine group; R2 includes at least one of hydrogen, an alkyl chain, a substituted alkyl chain, and a halogen; R3 includes at least one of an alkyl chain, a substituted alkyl chain, an alkyl chain containing a double bond or a triple bond, and a substituted alkyl chain containing a double bond or a triple bond, and the number of carbon atoms in R3 is greater than or equal to 0; At least one of R4 and R5 includes a cyano group. The functional additive has a mass fraction of 0.1-0.5% in the electrolyte.

2. The electrolyte of claim 1, wherein: R4 and R5 independently include a cyano group.

3. The electrolyte of claim 1, wherein The functional additive has a structural formula as follows: 。 4. The electrolyte of claim 1, wherein: The sulfur-containing additive includes at least one of 1,3-propane sulfite, ethylene sulfite, vinyl ethylene sulfite, vinyl sulfate, methane disulfide methylene, a thiophene derivative, a fluorosulfonyloxy benzene, a benzene methanesulfonate, and a hydroquinone difluorosulfonate. The sulfur-containing additive has a mass fraction of 0.5-1.5% in the electrolyte.

5. The electrolyte of claim 4, wherein: The sulfur-containing additive includes the 1,3-propane sulfite and the fluorosulfonyloxy benzene. The mass ratio of the 1,3-propane sulfite to the fluorosulfonyloxy benzene is 3-7:

1.

6. The electrolyte of claim 1, wherein: The carbonate additive includes at least one of vinylene carbonate and fluoroethylene carbonate. The carbonate additive has a mass fraction of 0.2-0.8% in the electrolyte.

7. The electrolyte as described in claim 1, characterized in that: The lithium salt additive includes at least one of lithium difluorophosphate, lithium bisoxalate borate, and lithium difluorobisoxalate phosphate. The lithium salt additive has a mass fraction of 0.5-1.5% in the electrolyte.

8. The electrolyte of claim 7, wherein: The lithium salt additive includes the lithium bisoxalate borate.

9. A battery, characterized by: The electrolyte includes the electrolyte according to any one of claims 1-8.

Images