Electrolyte additive, electrolyte containing additive and lithium battery

Abstract

The invention specifically discloses an electrolyte additive, an electrolyte containing the additive and a lithium battery. According to the electrolyte additive disclosed by the invention, uniform film formation at a positive electrode and a negative electrode can be promoted, and B in the electrolyte additive can reduce the content of LiF in an electrolyte and reduce impedance between electrode interfaces, so that high temperature resistance and high voltage resistance of a lithium battery are improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to an electrolyte additive and an electrolyte and a lithium battery containing the additive. Background Art

[0002] With the continuous advancement of science and technology and the increasing demand for clean energy, lithium-ion batteries, as an efficient and environmentally friendly energy storage device, are gradually becoming an important part of the future energy field. Driven by the growing electric vehicle market and the development of renewable energy, lithium-ion battery technology is also evolving with human needs. At present, the requirements for the energy density and safety performance of lithium-ion batteries are getting higher and higher. Therefore, how to improve the energy density of lithium batteries is a research hotspot in the field of lithium batteries.

[0003] At present, the use of high-voltage cathode materials is the main way to improve the energy density of lithium-ion batteries. Therefore, high-voltage cathode materials such as LNMO, high-voltage ternary, high-voltage lithium cobalt oxide, layered lithium-rich oxide (LLO), etc. have become research hotspots. As the voltage of lithium-ion batteries continues to increase, the cathode materials will have a higher electrode potential. At this time, the oxidative decomposition of the electrolyte at the cathode and the reaction at the cathode interface will be more intense. As the lithium battery charge and discharge cycle continues, the internal resistance of the lithium battery gradually increases, which will cause the performance of the lithium battery to decline or even fail.

[0004] To this end, there are two main ways in the prior art to improve the high-voltage resistance of the electrolyte: one is to increase the lithium salt concentration in the carbonate electrolyte; the other is to use sulfone solvents, nitrile solvents, ionic liquids and fluorinated electrolytes instead of conventional carbonate solvents. However, the above two methods are still found to have certain limitations during application: increasing the lithium salt concentration in the electrolyte will increase production costs, which is not conducive to large-scale industrial applications, and the high melting points of sulfone solvents and ionic liquids will reduce the low-temperature performance of lithium batteries, and the poor compatibility of nitrile solvents with graphite negative electrodes have limited the practical application of high-voltage electrolytes. Summary of the invention

[0005] In order to solve the problems and deficiencies in the prior art, the present application provides an electrolyte additive and an electrolyte and a lithium battery containing the additive.

[0006] In a first aspect, the present application provides an electrolyte additive, which adopts the following technical solution:

[0007] An electrolyte additive, the structural formula of the electrolyte additive is as follows:

[0008]

[0009] First, the electrolyte additive of the present application has the function of promoting uniform film formation at the interface of the positive and negative electrodes, which helps to form a uniform and dense CEI film and SEI film at the interface of the positive and negative electrodes, inhibiting the dissolution of TMs (transition metal sulfide) metal ions and the release of oxygen, thereby inhibiting the reduction of TMs (transition metal sulfide) metal ions at the negative electrode, thereby reducing the degree of interfacial reaction at the positive and negative electrodes, avoiding the increase of internal resistance of lithium batteries during the cycle, and significantly improving the cycle performance of lithium batteries. Second, LiF in the electrolyte will form a LiF layer covering the electrode surface, and the LiF layer as an insulating layer will hinder the effective transmission of lithium ions and electrons between the electrodes, and B in the electrolyte additive of the present application can dissolve LiF in the electrolyte as an anion receptor, reduce the LiF content in the electrolyte, avoid the formation of a LiF layer at the electrode surface, and help to provide a better propagation path for lithium ion conduction and electron conduction between the electrodes, thereby reducing the interface impedance between the electrodes, which not only helps to improve the high voltage cycle performance of lithium ion batteries, but also helps to improve the thermal stability of lithium batteries and improve the high temperature cycle performance of lithium batteries.

[0010] In a second aspect, the present application provides an electrolyte, which adopts the following technical solution:

[0011] An electrolyte comprises an organic solvent, a carbonate additive, a lithium salt, a lithium salt additive and the electrolyte additive as described above.

[0012] Preferably, the electrolyte additive accounts for 0.3%-1% by mass in the electrolyte.

[0013] When the mass proportion of electrolyte additives in the electrolyte is too low, it will affect the density and thickness uniformity of the CEI film and SEI film generated at the interface of the positive and negative electrodes. In addition, due to the small amount of electrolyte additives used, the coordination effect with other components in the electrolyte is not significant, which will not be conducive to the electrolyte additives to play their due role. When the mass proportion of electrolyte additives in the electrolyte is too high, on the one hand, it will reduce the overall stability of the electrolyte. On the other hand, more violent interfacial reactions will occur at the interface of the positive and negative electrodes, generating thicker CEI and SEI films, which may cause a significant increase in the internal resistance of the lithium battery, thereby reducing the cycle performance of the lithium battery.

[0014] Preferably, the electrolyte further includes a sulfur-containing additive, and the sulfur-containing additive includes at least one of propenyl-1,3-propane sultone PST, 1,3-propane sultone PS, and vinyl sulfate DTD; the mass proportion of the sulfur-containing additive in the electrolyte is 0.5%-3%.

[0015] Preferably, the sulfur-containing additive includes the propenyl-1,3-propane sultone PST and the 1,3-propane sultone PS;

[0016] Or, the sulfur-containing additive includes the propenyl-1,3-propane sultone PST and the vinyl sulfate DTD;

[0017] Or, the sulfur-containing additive includes the 1,3-propane sultone PS and the vinyl sulfate DTD;

[0018] Or, the sulfur-containing additive includes the propenyl-1,3-propane sultone PST, the 1,3-propane sultone PS, and the vinyl sulfate DTD.

[0019] The electrolyte additive in the present application can be combined with the sulfur-containing additive to improve the quality of film formation at the positive electrode, and significantly improve the stability of the electrolyte, especially under high temperature and high pressure conditions, can play a more significant technical effect of inhibiting the gas production of lithium batteries, and improve the wettability of the electrolyte, thereby helping to improve the cycle performance of lithium batteries. When the mass proportion of sulfur-containing additives in the electrolyte is too low, it is not conducive to the formation of a uniform and stable CEI film at the positive electrode, and the stability of the electrolyte in a high temperature and high pressure environment is poor; and when the mass proportion of sulfur-containing additives in the electrolyte is too high, excessive film formation at the positive electrode will reduce the degree of electrolyte wetting of the CEI film and cause the internal resistance of the lithium battery to increase, which is not conducive to the improvement of the cycle performance of the lithium battery.

[0020] Preferably, the carbonate additive includes at least one of vinylene carbonate VC and fluoroethylene carbonate FEC; the mass proportion of the carbonate additive in the electrolyte is 0.01%-1%.

[0021] The electrolyte additives in the present application can be combined with carbonate additives to help generate a SEI film with uniform thickness and stable performance at the negative electrode interface, thereby improving the stability of the lithium battery. In addition, the presence of carbonate additives can also improve the physical and chemical properties of the electrolyte, improve the ion conductivity and stability of the electrolyte, which helps to improve the high-temperature cycle performance of the lithium battery. When the mass proportion of carbonate additives in the electrolyte is too low, it will be unfavorable for uniform film formation at the negative electrode interface, and will also reduce the electrochemical stability of the electrolyte to a certain extent, which will manifest itself as a decrease in the cycle performance of the lithium-ion battery on a macro scale; when the mass proportion of carbonate additives in the electrolyte is too high, the film thickness at the negative electrode will be too large, resulting in an increase in the migration path of ions in the negative electrode membrane, resulting in low concentration polarization discharge capacity, and further affecting the utilization rate of the battery active substances. In addition, excessive film thickness at the negative electrode will lead to a large resistance of the lithium battery, making it easy for the lithium battery to produce gas under high pressure and high temperature during the cycle process, causing damage to the structure of the lithium battery, and seriously, it may even cause the internal pressure of the lithium battery to increase, leakage, and battery expansion, seriously affecting the cycle performance and safety performance of the lithium battery.

[0022] Preferably, the organic solvent comprises cyclic carbonate, chain carbonate, and chain carboxylic acid ester; the mass proportion of the organic solvent in the electrolyte is 80%-90%.

[0023] Preferably, in the organic solvent, the mass ratio of the cyclic carbonate, the chain carbonate, and the chain carboxylic acid ester is 1-15:20-70:5-20.

[0024] By selecting the above three organic solvents for combination, it helps to improve the stability of the electrolyte system, and helps the sulfur-containing additives and the electrolyte additives used in this application to play an efficient coordination effect, which also helps to improve the cycle performance of lithium-ion batteries in high temperature and high pressure environments.

[0025] Preferably, the lithium salt additive includes at least one of lithium bis(fluorosulfonyl)imide LiFSI, lithium difluorophosphate LiPO2F2, lithium bis(oxalatoborate) LiBOB, and lithium difluorobis(oxalatophosphate) LiDFOP; the mass proportion of the lithium salt additive in the electrolyte is 0.5%-1%.

[0026] Preferably, the lithium salt includes lithium hexafluorophosphate LiPF6; the mass proportion of the lithium salt in the electrolyte is 10%-15%.

[0027] By doping the electrolyte with a suitable type of lithium salt additive, the dissolution of metal ions at the positive and negative electrodes can be inhibited, the destructive effect of metal ion dissolution on the CEI membrane and SEI membrane can be reduced, and the stability of the CEI membrane and SEI membrane can be improved; and the loss of active lithium can also be compensated during the cycle of lithium-ion batteries, which helps to improve the cycle performance of lithium-ion batteries.

[0028] In a third aspect, the present application provides a lithium battery, which adopts the following technical solution:

[0029] A lithium battery comprises the electrolyte as described above. DETAILED DESCRIPTION

[0030] For better understanding and implementation, the technical solution of the present application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0032] Unless otherwise indicated, all numerical values ​​expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties desired to be obtained.

[0033] As used herein, "and / or" means one or all of the mentioned elements.

[0034] As used herein, “including” and “comprising” encompasses the case where only the stated elements are present as well as the case where there are other elements other than the stated elements.

[0035] All percentages in this application are by weight unless otherwise stated.

[0036] Unless otherwise indicated, "a", "an", "an" and "the" used in this specification are intended to include "at least one" or "one or more". For example, "a component" means one or more components, so more than one component may be considered and may be employed or used in the implementation of the embodiment.

[0037] The electrolyte additive used in the following examples and comparative examples has the following structural formula: The CAS number is 865869-27-8.

[0038] Example 1

[0039] 1. Electrolyte and preparation of electrolyte

[0040] The electrolyte in this embodiment includes an organic solvent, a carbonate additive, a lithium salt, a lithium salt additive, an electrolyte additive, and a sulfur-containing additive in a mass ratio of 81.5%: 0.5%: 15%: 0.5%: 0.5%: 2%;

[0041] The organic solvent is composed of cyclic carbonate (fluoroethylene carbonate FEC and ethylene carbonate EC in a mass ratio of 1:1), chain carbonate (diethyl carbonate DEC), and chain carboxylic acid ester (ethyl difluoroacetate DFAE) in a mass ratio of 10:70:20.

[0042] The carbonate additive is vinylene carbonate VC,

[0043] The lithium salt is lithium hexafluorophosphate LiPF6,

[0044] The lithium salt additive is lithium difluorophosphate LiPO2F2,

[0045] Electrolyte additive (structural formula:

[0046] The sulfur-containing additive is 1,3-propane sultone PS.

[0047] The preparation steps of the electrolyte are as follows: in an argon atmosphere, add a formulated amount of carbonate additives, sulfur-containing additives, lithium salt additives and electrolyte additives to an organic solvent, then add lithium salt, and stir and mix at 10°C to obtain an electrolyte.

[0048] 2. Preparation of lithium batteries

[0049] The lithium battery of this embodiment includes a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0050] Preparation of positive electrode sheet: positive electrode active material (0.25Li2MnO3 · 0.75LiMn 0.375 Ni 0.375 Co 0.25 O2), conductive agent (acetylene black) and binder (PVDF) are prepared into positive electrode slurry in a mass ratio of 94:3:3; the positive electrode slurry is coated on an aluminum foil current collector and vacuum dried to obtain a positive electrode sheet.

[0051] Preparation of negative electrode sheet: negative electrode active material (graphite), conductive agent (acetylene black) and binder (CMC), binder (SBR) are prepared into negative electrode slurry in a mass percentage of 94:1:2:3; the negative electrode slurry is coated on the copper foil current collector, and vacuum dried to obtain a negative electrode sheet.

[0052] After assembling the above-mentioned positive electrode plate, negative electrode plate and Celgard2400 separator to obtain a battery cell, the battery cell is transferred into a casing, and then the electrolyte prepared in this embodiment is injected, formed, and constant in volume to obtain the battery of this embodiment.

[0053] Example 2

[0054] 1. Electrolyte and preparation of electrolyte

[0055] The electrolyte in this embodiment includes an organic solvent, a carbonate additive, a lithium salt, a lithium salt additive, an electrolyte additive, and a sulfur-containing additive in a mass ratio of 84%: 1%: 10%: 1%: 1%: 3%;

[0056] The organic solvent is composed of cyclic carbonate (fluoroethylene carbonate FEC and ethylene carbonate EC in a mass ratio of 1:1), chain carbonate (diethyl carbonate DEC), and chain carboxylic acid ester (ethyl difluoroacetate DFAE) in a mass ratio of 15:65:20.

[0057] The carbonate additive is fluoroethylene carbonate FEC,

[0058] The lithium salt is lithium hexafluorophosphate LiPF6,

[0059] The lithium salt additive is lithium difluorophosphate LiFSI,

[0060] Electrolyte additive (structural formula: ),

[0061] The sulfur-containing additive is propenyl-1,3-propane sultone PST.

[0062] The preparation steps of the electrolyte are as follows: in an argon atmosphere, add a formulated amount of carbonate additives, sulfur-containing additives, lithium salt additives and electrolyte additives to an organic solvent, then add lithium salt, and stir and mix at 10°C to obtain an electrolyte.

[0063] 2. Preparation of lithium batteries

[0064] The lithium battery of this embodiment includes a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0065] Preparation of positive electrode sheet: positive electrode active material (0.25Li2MnO3 · 0.75LiMn 0.375 Ni 0.375 Co 0.25 O2), conductive agent (acetylene black) and binder (PVDF) are prepared into positive electrode slurry in a mass ratio of 94:3:3; the positive electrode slurry is coated on an aluminum foil current collector and vacuum dried to obtain a positive electrode sheet.

[0066] Preparation of negative electrode sheet: negative electrode active material (graphite), conductive agent (acetylene black) and binder (CMC), binder (SBR) are prepared into negative electrode slurry in a mass percentage of 94:1:2:3; the negative electrode slurry is coated on the copper foil current collector, vacuum dried to obtain a negative electrode sheet.

[0067] After assembling the above-mentioned positive electrode plate, negative electrode plate and Celgard2400 separator to obtain a battery cell, the battery cell is transferred into a casing, and then the electrolyte prepared in this embodiment is injected, formed, and constant in volume to obtain the battery of this embodiment.

[0068] Example 3

[0069] 1. Electrolyte and preparation of electrolyte

[0070] The electrolyte in this embodiment includes an organic solvent, a carbonate additive, a lithium salt, a lithium salt additive, an electrolyte additive, and a sulfur-containing additive in a mass ratio of 87.9%: 0.1%: 10%: 0.5%: 0.3%: 1.2%;

[0071] The organic solvent is composed of cyclic carbonate (fluoroethylene carbonate and ethylene carbonate in a mass ratio of 3:1) with a mass ratio of 5:50:8, chain carbonate (diethyl carbonate) and chain carboxylic acid ester (ethyl difluoroacetate).

[0072] The carbonate additive is vinylene carbonate VC,

[0073] The lithium salt is lithium hexafluorophosphate LiPF6,

[0074] The lithium salt additive is lithium bis(oxalatoborate) LiBOB.

[0075] Electrolyte additive (structural formula: ),

[0076] The sulfur-containing additive is vinyl sulfate DTD.

[0077] The preparation steps of the electrolyte are as follows: in an argon atmosphere, add a formulated amount of carbonate additives, sulfur-containing additives, lithium salt additives and electrolyte additives to an organic solvent, then add lithium salt, and stir and mix at 10°C to obtain an electrolyte.

[0078] 2. Preparation of lithium batteries

[0079] The preparation of lithium battery is consistent with that in Example 1.

[0080] Example 4

[0081] The difference between this embodiment and embodiment 1 is that the mass proportion of the electrolyte additive in the electrolyte is adjusted to 0.1%, and the part less than 100% in the electrolyte can be obtained by adaptively adjusting the amount of the organic solvent (one or more of the organic solvents can be adjusted). Other steps and parameter settings are consistent with embodiment 1.

[0082] 2. Preparation of lithium batteries

[0083] The preparation of lithium battery is consistent with that in Example 1.

[0084] Example 5

[0085] The electrolyte in this embodiment is different from that in Embodiment 1 in that the mass fraction of the electrolyte additive in the electrolyte is adjusted to 5%, and the portion exceeding 100% in the electrolyte can be obtained by adaptively adjusting the amount of the organic solvent (one or more of the organic solvents can be adjusted). Other steps and parameter settings are consistent with those in Embodiment 1.

[0086] 2. Preparation of lithium batteries

[0087] The preparation of lithium battery is consistent with that in Example 1.

[0088] Example 6

[0089] The difference between this embodiment and embodiment 1 is that the sulfur-containing additive in the electrolyte is adjusted to consist of propenyl-1,3-sultone PST and 1,3-propanesultone PS, and the mass proportions of PST and PS in the electrolyte are 1.5% and 0.5%, respectively. The other steps and parameter settings are consistent with those in embodiment 1.

[0090] 2. Preparation of lithium batteries

[0091] The preparation of the battery in this example is consistent with that in Example 1.

[0092] Example 7

[0093] The difference between this embodiment and embodiment 1 is that the sulfur-containing additive in the electrolyte is adjusted to consist of 1,3-propane sultone PS and vinyl sulfate DTD, and the mass proportions of PS and DTD in the electrolyte are 1.5% and 1% respectively. The other steps and parameter settings are consistent with those in embodiment 1.

[0094] 2. Preparation of lithium batteries

[0095] The preparation of the battery in this example is consistent with that in Example 1.

[0096] Example 8

[0097] The difference between this embodiment and embodiment 1 is that the sulfur-containing additive in the electrolyte is adjusted to consist of propenyl-1,3-sultone PST and vinyl sulfate DTD, and the mass proportions of PST and DTD in the electrolyte are 0.5% and 1.5%, respectively. The other steps and parameter settings are consistent with those in embodiment 1.

[0098] 2. Preparation of lithium batteries

[0099] The preparation of the battery in this example is consistent with that in Example 1.

[0100] Example 9

[0101] The difference between this embodiment and embodiment 1 is that the sulfur-containing additive in the electrolyte is adjusted to consist of propenyl-1,3-sultone PST, 1,3-propanesultone PS, and vinyl sulfate DTD, and the mass proportions of PST, PS, and DTD in the electrolyte are 0.5%, 0.5%, and 1%, respectively. The other steps and parameter settings are consistent with those in embodiment 1.

[0102] 2. Preparation of lithium batteries

[0103] The preparation of the battery in this example is consistent with that in Example 1.

[0104] Example 10

[0105] The difference between this embodiment and embodiment 1 is that the organic solvent in the electrolyte is adjusted to be cyclic carbonate (fluoroethylene carbonate) and chain carbonate (diethyl carbonate) in a mass ratio of 15:85. The other steps and parameter settings are consistent with those in embodiment 1.

[0106] Comparative Example 1

[0107] The difference between this comparative example and Example 1 is that the electrolyte does not contain electrolyte additives, and the electrolyte less than 100% can be obtained by adaptively adjusting the amount of organic solvent (one or more of the organic solvents can be adjusted). Other steps and parameter settings are consistent with Example 1.

[0108] 2. Preparation of lithium batteries

[0109] The preparation of lithium battery is consistent with that in Example 1.

[0110] Test Method

[0111] 1. Lithium battery room temperature cycle performance test

[0112] At 25°C, the lithium-ion battery is charged at a constant current of 0.5C (nominal capacity) to a voltage of 4.6V, then charged at a constant voltage of 4.6V to a current ≤ 0.05C, left for 10 minutes, and then discharged at a constant current of 1C to a cut-off voltage of 2.5V. The above is one charge and discharge cycle. The lithium-ion battery is charged and discharged 1000 times at 25°C under the above conditions.

[0113] The capacity retention rate (%) of a lithium-ion battery after N cycles = (discharge capacity at the Nth cycle / initial discharge capacity) × 100%, where N is the number of cycles of the lithium-ion battery.

[0114] The average voltage (V) of a lithium-ion battery after N cycles = discharge energy of the Nth cycle / discharge capacity of the Nth cycle, where N is the number of cycles of the lithium-ion battery.

[0115] 2. Lithium battery high temperature cycle performance test

[0116] At 45°C, the lithium-ion battery is charged at a constant current of 1.0C (nominal capacity) to a voltage of 4.6V, then charged at a constant voltage of 4.6V to a current ≤ 0.05C, left for 10 minutes, and then discharged at a constant current of 1C to a cut-off voltage of 2.5V. The above is one charge and discharge cycle. The lithium-ion battery is subjected to 800 charge and discharge cycles at 45°C under the above conditions.

[0117] The capacity retention rate (%) of a lithium-ion battery after N cycles = (discharge capacity at the Nth cycle / initial discharge capacity) × 100%, where N is the number of cycles of the lithium-ion battery.

[0118] The average voltage (V) of a lithium-ion battery after N cycles = discharge energy of the Nth cycle / discharge capacity of the Nth cycle, where N is the number of cycles of the lithium-ion battery.

[0119] Table 1

[0120]

[0121]

[0122] In combination with Examples 1-3, Comparative Example 1 and Table 1, it can be seen that after adding the electrolyte additive of the present application to the electrolyte, the room temperature cycle performance and high temperature cycle performance of the lithium-ion battery can be significantly improved. This is because, on the one hand, the electrolyte additive can promote the formation of dense CEI film and SEI film at the positive and negative electrodes, which can avoid the increase of internal resistance of the lithium battery during the cycle. On the other hand, the boron in the electrolyte additive can dissolve LiF in the electrolyte, thereby avoiding the appearance of an insulating LiF layer on the electrode surface, further reducing the interface impedance, which helps to improve the cycle performance and high temperature resistance of the lithium battery.

[0123] In Comparative Example 1, no electrolyte additive was used, and the cycle performance of the lithium battery at room temperature and high temperature deteriorated, and the voltage decay was significant.

[0124] In combination with Example 1, Examples 4-5 and Table 1, it can be seen that if the mass proportion of the electrolyte additive in the electrolyte is too low (Example 4), the density and thickness uniformity of the CEI film and SEI film generated at the positive and negative electrode interfaces will be affected, and the side reactions cannot be effectively reduced; if the mass proportion of the electrolyte additive in the electrolyte is too high (Example 5), not only will the stability of the electrolyte be reduced, but also violent interfacial reactions will occur at the positive and negative electrodes, causing the cycle capacity retention rate of the lithium-ion battery to decrease and the voltage to decay rapidly.

[0125] In combination with Example 1, Examples 6-9 and Table 1, it can be seen that by adjusting the combination of sulfur-containing additives, the sulfur-containing additives can work together with the electrolyte additives to improve the film formation quality at the positive electrode and improve the stability of the electrolyte, which is beneficial to improving the high-temperature cycle capacity retention rate of the lithium battery and reducing the high-temperature voltage decay of the lithium battery.

[0126] In combination with Example 1, Example 10 and Table 1, it can be seen that by selecting the organic solvent in the scheme of the present application, it is beneficial to the stability of the sulfur-containing additive, the electrolyte additive, and the carbonate additive in the electrolyte and the effect of the coordination of the three, significantly improving the film formation quality at the positive and negative electrodes, significantly improving the high temperature cycle performance of the lithium battery and alleviating the voltage attenuation of the lithium battery.

[0127] The above embodiments are only used to illustrate the technical solution of the present application rather than to limit the protection scope of the present application. Although the present application is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the technical solution of the present application can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present application.

Claims

1. An electrolyte additive, characterized in that: The structural formula of the electrolyte additive is as follows:

2. An electrolyte, characterized in that: The electrolyte additive comprises an organic solvent, a carbonate additive, a lithium salt, a lithium salt additive and the electrolyte additive as claimed in claim 1.

3. The electrolyte according to claim 2, characterized in that: The electrolyte additive accounts for 0.3%-1% by mass in the electrolyte.

4. The electrolyte according to claim 2, characterized in that: The electrolyte further includes a sulfur-containing additive, wherein the sulfur-containing additive includes at least one of propenyl-1,3-propane sultone, 1,3-propane sultone, and vinyl sulfate; The sulfur-containing additive accounts for 0.5%-3% by mass in the electrolyte.

5. The electrolyte according to claim 4, characterized in that: The sulfur-containing additive includes the propenyl-1,3-propane sultone and the 1,3-propane sultone; Or, the sulfur-containing additive includes the propenyl-1,3-propane sultone and the vinyl sulfate; Or, the sulfur-containing additive includes the 1,3-propane sultone and the vinyl sulfate; Or, the sulfur-containing additive includes the propenyl-1,3-propane sultone, the 1,3-propane sultone, and the vinyl sulfate.

6. The electrolyte according to claim 2, characterized in that: The carbonate additive includes at least one of vinylene carbonate and fluoroethylene carbonate; The carbonate additive accounts for 0.01%-1% by mass in the electrolyte.

7. The electrolyte according to claim 2, characterized in that: The organic solvent includes cyclic carbonate, chain carbonate, and chain carboxylic acid ester; The mass proportion of the organic solvent in the electrolyte is 80%-90%.

8. The electrolyte according to claim 7, characterized in that: In the organic solvent, the mass ratio of the cyclic carbonate, the chain carbonate and the chain carboxylic acid ester is 1-15:20-70:5-20.

9. The electrolyte according to claim 2, characterized in that: The lithium salt additive includes at least one of lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium bis(oxalatoborate), and lithium difluorobis(oxalatophosphate); The lithium salt additive accounts for 0.5%-1% by mass in the electrolyte.

10. A lithium battery, characterized in that: Comprising the electrolyte as described in any one of claims 2-9.

Images