Electrolyte additive and electrolyte and lithium ion battery

Abstract

This application relates to an electrolyte additive, an electrolyte, and a lithium-ion battery. The electrolyte additive includes a first additive and a second additive. The first additive is a pyridine compound, and the second additive is a sulfate ester compound. The second additive and the negative electrode active material satisfy the following condition: 0.75 ≤ (c / 100 + d) / (b / 2 + 2) ≤ 1.5, where the mass percentage of the second additive in the electrolyte is b wt%. The single-sided coating amount of the negative electrode active material is c g / m². 2 The compaction density of the negative electrode active material is dg / cm³. 3 The solution provided in this application combines the coating surface density and compaction density of the negative electrode active material with the adjustment of the amount of electrolyte additives, thereby improving the energy density of the battery, enhancing high-temperature cycle performance, and improving low-temperature discharge performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to electrolyte additives, electrolytes, and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries have advantages such as high operating voltage, long cycle life, low self-discharge, and no memory effect, and are widely used in portable electronic devices, electric vehicles, and other products. With technological advancements, the requirements for lithium-ion batteries are becoming increasingly stringent, demanding not only high energy density but also high-temperature storage stability and superior low-temperature discharge performance.

[0003] In related technologies, there are two main ways to improve the energy density of lithium-ion batteries: one is to increase the upper limit voltage, and the other is to increase the coating density.

[0004] However, increasing the upper limit voltage will worsen the high-temperature performance of the cell, while increasing the coating density or compaction density will worsen the low-temperature discharge performance. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this application provides an electrolyte additive, an electrolyte, and a lithium-ion battery. The amount of electrolyte additive can be adjusted by combining the coating surface density and compaction density of the negative electrode active material, thereby improving the energy density of the battery, enhancing high-temperature cycle performance, and improving low-temperature discharge performance.

[0006] The first aspect of this application provides an electrolyte additive, comprising a first additive and a second additive, wherein the first additive is a pyridine compound and the second additive is a sulfate ester compound; wherein the second additive satisfies the following conditions with the negative electrode active material:

[0007] 0.75≤(c / 100+d) / (b / 2+2)≤1.5

[0008] In the formula, the second additive accounts for b wt% of the electrolyte by mass; the coating surface density of the negative electrode active material is c g / m³. 2 The compaction density of the negative electrode active material is dg / cm³. 3 .

[0009] As an optional embodiment, 0.1 ≤ b ≤ 2.

[0010] As an optional embodiment, the first additive accounts for a wt% of the electrolyte, where 0.1 ≤ a ≤ 1.

[0011] As an optional embodiment, the first additive accounts for a wt% of the electrolyte by mass, and 0.73 ≤ (b+1) / (a+1) ≤ 2.3.

[0012] As an optional embodiment, the first additive comprises a arsenic-based compound of formula one:

[0013]

[0014] In structural formula one, R1, R2, R3, R4, and R5 are each independently selected from H, halogens, C1-C5 alkyl groups substituted or unsubstituted by halogens, C2-C5 olefin groups, and C1-C5 cyano groups.

[0015] As an optional embodiment, the first additive comprises at least one of the following arsenic compounds:

[0016]

[0017]

[0018] As an optional embodiment, the second additive comprises at least one compound selected from vinyl sulfate, propylene sulfate, and vinyl disulfate.

[0019] A second aspect of this application provides an electrolyte comprising: an electrolyte salt, an organic solvent, and an additive, wherein the additive comprises the electrolyte additives described above.

[0020] A third aspect of this application provides a lithium-ion battery, comprising: a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the electrolyte described above.

[0021] As an optional embodiment, the negative electrode comprises a negative electrode sheet and a negative electrode active material coated on at least one surface of the negative electrode sheet, wherein the coating areal density of the negative electrode active material is cg / m². 2 And 60≤c≤120; and / or, the compaction density of the negative electrode active material is dg / cm³. 3 And 1.65≤d≤1.85.

[0022] The technical solution provided in this application may include the following beneficial effects:

[0023] This application uses pyridine compounds and sulfate compounds as electrolyte additives. Pyridine compounds can form a complex film at the positive electrode, giving the cell good high-temperature performance and suppressing gas generation during high-temperature storage, but they deteriorate low-temperature discharge performance. Sulfate compounds can improve low-temperature discharge performance, but they suffer from poor stability and easy decomposition. The pyridine groups in pyridine compounds can inhibit the decomposition of sulfate compounds. The synergistic effect of both can improve high-temperature cycle performance and low-temperature discharge performance. Furthermore, it was found that increasing the coating amount and compaction density of the negative electrode active material also deteriorates low-temperature discharge performance. Therefore, the amount of sulfate compound can be adjusted by combining the coating amount and compaction density of the negative electrode active material to balance the high-temperature and low-temperature performance of the battery while increasing the coating amount and compaction density of the negative electrode material layer.

[0024] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0025] The embodiments of this application will now be described in more detail. While embodiments of this application are shown below, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0026] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0027] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0028] In related technologies, there are two main ways to improve the energy density of lithium-ion batteries: one is to increase the upper limit voltage, and the other is to increase the coating density.

[0029] However, increasing the upper limit voltage will worsen the high-temperature performance of the cell, while increasing the coating density or compaction density will worsen the low-temperature discharge performance.

[0030] To address the aforementioned issues, this application provides an electrolyte additive that can adjust the amount of the electrolyte additive based on the coating surface density and compaction density of the negative electrode active material, thereby improving the battery's energy density, enhancing high-temperature cycle performance, and improving low-temperature discharge performance.

[0031] This application provides an electrolyte additive, comprising a first additive and a second additive. The first additive is a pyridine compound, and the second additive is a sulfate ester compound. The second additive and the negative electrode active material satisfy the following conditions:

[0032] 0.75≤(c / 100+d) / (b / 2+2)≤1.5

[0033] In the formula, the second additive accounts for b wt% of the electrolyte by mass; the coating surface density of the negative electrode active material is c g / m³. 2 The compaction density of the negative electrode active material is dg / cm³. 3 .

[0034] In this embodiment, the coating density of the negative electrode active material refers to the mass of active material coated per unit area when coating one side, and the compaction density of the negative electrode active material refers to the mass of active material per unit volume after the rolling process.

[0035] In this embodiment, pyridine compounds and sulfate compounds are added as electrolyte additives. Pyridine compounds can form a complex film at the positive electrode, giving the cell good high-temperature performance and suppressing gas generation during high-temperature storage, but they deteriorate low-temperature discharge performance. Sulfate compounds can improve low-temperature discharge performance, but they suffer from poor stability and easy decomposition. The pyridine groups of pyridine compounds can inhibit the decomposition of sulfate compounds. The synergistic effect of both can improve high-temperature cycle performance and low-temperature discharge performance. Furthermore, it was found that increasing the coating amount and compaction density of the negative electrode active material also deteriorates low-temperature discharge performance. Therefore, the amount of sulfate compounds can be adjusted in conjunction with the coating amount and compaction density of the negative electrode active material to balance the high-temperature and low-temperature performance of the battery while increasing the coating amount and compaction density of the negative electrode material layer.

[0036] In the embodiments of this application, the second additive and the negative electrode active material can satisfy the following:

[0037] (c / 100+d) / (b / 2+2) = 0.75, 0.88, 0.96, 1.04, 1.06, 1.18, 1.20, 1.22, 1.27, 1.29, 1.31, 1.49 or any value within the above-mentioned range, which is not limited in this application.

[0038] Although increasing the coating amount and compaction density of the negative electrode active material can improve the energy density, it will deteriorate the low-temperature discharge performance and cycle performance. Moreover, excessive coating amount and compaction density may cause a sharp drop in capacity due to lithium plating in the cell. Therefore, the embodiments of this application control the coating amount and compaction density of the negative electrode active material and reasonably adjust the content of vinyl sulfate compounds to achieve a better balance between the coating amount and compaction density of the negative electrode material layer, as well as high-temperature and low-temperature performance in the system.

[0039] As an optional embodiment, 0.1 ≤ b ≤ 2.

[0040] In this embodiment, if the content of vinyl sulfate compounds is too low, the low-temperature discharge performance cannot be improved effectively; if the content of vinyl sulfate compounds is too high, the excess vinyl sulfate compounds are unstable, leading to excessive side reaction gas production, which will deteriorate the high-temperature storage and cycling performance. Therefore, controlling the content of vinyl sulfate compounds within a suitable range can improve the low-temperature performance without deteriorating the high-temperature storage and cycling performance.

[0041] In the embodiments of this application, the mass percentage of the second additive in the electrolyte can be 0.1wt%, 0.3wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or any value within the above-defined range, and this application does not limit it in this regard.

[0042] As an optional embodiment, the first additive accounts for a wt% of the electrolyte, where 0.1 ≤ a ≤ 1.

[0043] In this embodiment, if the content of pyridine compounds is too low, it cannot effectively improve the high-temperature performance of the battery; if the content of pyridine compounds is too high, it will increase the film-forming resistance of the negative electrode and affect the electrochemical performance of the battery. Therefore, controlling the content of pyridine compounds within a suitable range can improve high-temperature performance without increasing the film-forming resistance of the negative electrode.

[0044] In the embodiments of this application, the mass percentage of the first additive in the electrolyte can be 0.1wt%, 0.3wt%, 0.5wt%, 0.8wt%, 1wt%, or any value within the above-defined range, and this application does not limit it in this regard.

[0045] As an alternative embodiment, 0.73 ≤ (b+1) / (a+1) ≤ 2.3.

[0046] In the embodiments of this application, the content of the first additive and the second additive can satisfy: (b+1) / (a+1) = 0.73, 1.00, 1.15, 1.33, 1.36, 1.54, 1.67, 1.92 or any value within the above-mentioned range, and this application does not limit it in this regard.

[0047] In a preferred embodiment, the contents of the first additive and the second additive, along with the coating amount and compaction density of the negative electrode active material, satisfy the following conditions:

[0048] 0.75≤(c / 100+d) / (b / 2+2)≤1.5, 0.1≤a≤1, 0.1≤b≤2, 0.73≤(b+1) / (a+1)≤2.3, and 60≤c≤120, 1.65≤d≤1.85.

[0049] As an optional embodiment, the first additive comprises a arsenic-based compound of structural formula one:

[0050]

[0051] In structural formula one, R1, R2, R3, R4, and R5 are each independently selected from at least one of C1-C5 alkyl, C2-C5 olefin, and C1-C5 cyano groups.

[0052] The arsenic compounds in this application are cyanoparidin compounds. The cyano functional groups contained in the cyanoparidin compounds can have a strong complexing effect with the transition metals on the surface of the cathode material, forming a stable CEI film to protect the cathode material and inhibit the dissolution of transition metal elements.

[0053] As an optional embodiment, the first additive comprises at least one of the following arsenic compounds:

[0054]

[0055] Compounds 1 to 4 in the embodiments of this application are cyanopyridine compounds, rich in -CN functional groups. For batteries containing Co3+, their binding energy with Co3+ is low, making them more easily enriched on the positive electrode surface. Simultaneously, the cyano functional group coordinates with high-valence transition metal atoms on the positive electrode surface, working in conjunction with the film structure formed by the pyridine functional group on the positive electrode surface. This reduces side reactions between the positive electrode and the electrolyte, giving the battery cell good high-temperature performance and suppressing gas generation during high-temperature storage. Similarly, in the LiMn2O4, LiMnO2, Li2MnO4, and LiFePO4 systems, the pyridine-cyano functional group can also suppress the dissolution of transition metal ions in the positive electrode and form a more stable SEI film on the negative electrode, inhibiting the damage of transition metal ions to the negative electrode side.

[0056] Compounds 5 and 6 in the embodiments of this application are fluorocyanopyridine compounds, which can be preferentially reduced at the negative electrode. The resulting LiF compound can form a more stable SEI film at the negative electrode, preventing further reduction and decomposition of the electrolyte on the negative electrode surface. As an optional embodiment, the second additive includes at least one compound selected from vinyl sulfate, propylene sulfate, and vinyl disulfate.

[0057] The second additive in this application embodiment is preferably vinyl sulfate, because vinyl sulfate can form films on both the positive and negative electrodes, reducing the overall cell impedance, especially the impedance on the negative electrode side.

[0058] Corresponding to the aforementioned application function implementation method embodiments, this application also provides an electrolyte, a lithium-ion battery, and corresponding embodiments.

[0059] This application provides an electrolyte comprising: an electrolyte salt, an organic solvent, and an additive, wherein the additive includes the aforementioned electrolyte additive.

[0060] In the embodiments of this application, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiODFB), lithium bis(oxalate borate) (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium difluorophosphate (LiPOF2), and the concentration of the electrolyte salt is 0.4 mol / L to 2.2 mol / L.

[0061] In the embodiments of this application, the organic solvent includes two or more of the following: ethylene carbonate EC, propylene carbonate PC, diethyl carbonate DEC, methyl ethyl carbonate EMC, ethyl propionate EP, propyl propionate PP, ethyl fluorocarbonate DFEA, methyl ethyl fluorocarbonate FEMC, dimethyl fluorocarbonate FDMC, and propylene fluorocarbonate FPC. The organic solvent accounts for 20wt% to 70wt% of the mass of the electrolyte.

[0062] In the embodiments of this application, necessary additives are also included, including 1,3-propanesulfonate lactone (PS), fluoroethylene carbonate (FEC), and 1,3,6-hexanetrionitrile (HTCN).

[0063] In the embodiments of this application, other additives are also included, including one or more of the following: vinylene carbonate (VC), propylene sulfonate lactone (PST), methane disulfonate (MMDS), vinyl sulfate (DTD), succinate (SN), glutaronitrile (GN), adiponitrile (ADN), ethylene glycol bis(propionitrile) ether (EGBE), glycerol trinitrile, and 3,3',3",3"'(ethane 1,1,2,2 tetraalkyltetra(oxy))tetrapropionitrile. The other additives account for 5 wt% to 15 wt% of the electrolyte by mass.

[0064] This application also provides a lithium-ion battery, including: a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the aforementioned electrolyte.

[0065] In this embodiment, the positive electrode is selected from lithium transition metal oxides such as LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, and LiCo. 1-x-y Mn x Ni y (0≤x<1, 0≤y<1) One or more; the negative electrode is selected from at least one of graphite and silicon-carbon composite materials.

[0066] As an optional embodiment, the negative electrode comprises a negative electrode sheet and a negative electrode active material coated on the negative electrode sheet, wherein the single-layer coating amount of the negative electrode active material is cg / m². 2 And 60≤c≤120, the single-layer compaction density of the negative electrode active material is dg / cm³. 3 And 1.65≤d≤1.85.

[0067] In this embodiment, the single-layer coating amount c of the negative electrode active material can be 60 g / m². 2 90g / m 2 100g / m 2 110g / m 2 120g / m 2 Or any value within the above-mentioned range, but this application does not limit it.

[0068] In this embodiment, the single-layer compaction density d of the negative electrode active material can be 1.65 g / cm³. 3 1.75g / cm 3 1.8g / cm 3 1.85g / cm 3 Or any value within the above-mentioned range, but this application does not limit it.

[0069] To further understand the present invention, the following embodiments are provided to illustrate the present application. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0070] I. Manufacturing of Lithium-ion Batteries

[0071] (1) Production of positive electrode:

[0072] The positive electrode active material lithium cobalt oxide (LiCoO2), conductive agent CNT, and binder PVDF are thoroughly mixed in NMP solvent at a weight ratio of 97:1.5:1.5. This slurry is coated onto aluminum foil with a safety primer. After drying, cold pressing, slitting, sheet forming, welding of tabs, and adhesive bonding, a positive electrode sheet that meets the winding requirements is produced.

[0073] (2) Fabrication of the negative electrode:

[0074] The graphite anode material, conductive agent SP, thickener CMC, and binder SBR were thoroughly mixed in an appropriate amount of deionized water solvent at a mass ratio of 96.3:1:1.2:1.5 to form a uniform anode slurry. This slurry was then coated onto the Cu foil anode current collector according to the coating amount and compaction density in Table 1. After drying, cold pressing, slitting, sheet forming, welding of tabs, and adhesive bonding, anode sheets meeting the winding requirements were produced.

[0075] (3) Preparation of electrolyte:

[0076] The electrolyte preparation steps are as follows: In an argon atmosphere with a water content of <10ppm, EC / PC / DEC / PP are mixed in a glove box at a ratio of 20:20:20:40, 1.2M LiPF6 is added, and then the corresponding additives are added according to the formula and relationship in Table 1 to prepare the electrolyte.

[0077] (4) Manufacturing of lithium-ion batteries:

[0078] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are wound to obtain a bare battery cell. The bare battery cell is placed in a pre-punched aluminum-plastic film to complete the top and side sealing. After high-temperature baking, electrolyte injection, settling, formation, capacity testing, and other processes, the lithium-ion batteries of each embodiment and comparative example are manufactured.

[0079] II. Lithium-ion Battery Performance Testing

[0080] The lithium-ion batteries produced in the above embodiments and comparative examples were subjected to corresponding performance tests according to the following methods, and the test data in Table 2 were calculated.

[0081] (1) 45℃ cyclic test:

[0082] The capacitor was charged at 45°C with a constant current and constant voltage of 0.8C to 4.53V, with a cutoff current of 0.05C. After resting for 10 minutes, it was discharged at 0.5C to 3.0V, and the discharge capacity C0 was recorded as the initial value. This process was repeated for 500 cycles. The final capacity after 500 cycles was C500. Therefore, the capacity retention rate = C500 / C0.

[0083] (2) Store at 85℃ for 6 hours:

[0084] Charge the battery to 4.53V at 0.8C constant current and constant voltage at 25℃, cut off current 0.05C, let stand for 10 minutes, test cell thickness H0, then store at 85±2℃ for 6 hours, thermally measure thickness H6, thickness expansion = (H6-H0) / H0.

[0085] (3) Discharge at -10℃:

[0086] The capacitor is fully charged at 0.8C at 25℃ with a cutoff current of 0.05C, left to stand for 10 minutes, and then discharged at 0.2C to 3.0V at 25℃. The discharge capacity C0 is recorded. The capacitor is fully charged at 0.8C at 25℃ with a cutoff current of 0.05C, left to stand at -10℃ for 2 hours, and then discharged at 0.2C to 3.4V. The discharge capacity C1 is recorded. The capacity retention rate at 3.4V is C1 / C0.

[0087] Table 1. Formulas and Relationships

[0088]

[0089]

[0090] Table 2 Test Results

[0091]

[0092]

[0093] Note: "Plummeting" refers to a sharp drop in capacity caused by factors such as lithium plating in battery cells.

[0094] Based on the data in Tables 1 and 2, and by comparing Examples 28 and 29, as well as Comparative Examples 1 and 2, it was found that by adding pyridine compounds and sulfate compounds as electrolyte additives, when the ratio of the second additive to the negative electrode active material satisfies 0.75 ≤ (c / 100 + d) / (b / 2 + 2) ≤ 1.5, the high and low temperature performance of the battery is improved. Furthermore, by comparing Examples 28 and Comparative Example 12, and Examples 29 and Comparative Example 13, it was found that when the coating amount and compaction density of the negative electrode active material are large, and the battery energy density is high, it may cause cell cycle degradation. Adding pyridine compounds and sulfate compounds as electrolyte additives can significantly improve the high and low temperature performance of the battery. When the coating amount and compaction density of the negative electrode active material are small, and the battery energy density is low, adding pyridine compounds and sulfate compounds as electrolyte additives can also improve the high and low temperature performance of the battery to some extent.

[0095] Comparative studies in Examples 3, 6 to 12 revealed that, compared to alkyl- and olefin-based arsenic compounds, arsenic compounds selected from cyano- and fluorocyano-arsenic compounds exhibited superior high- and low-temperature performance in the battery. This is likely because the cyano and fluorine groups contained in cyano- and fluorocyano-arsenic compounds can participate in the film-forming reactions of the positive and negative electrodes, increasing the stability of the positive and negative electrode films and thus improving the high- and low-temperature performance of the battery.

[0096] Comparative studies of Examples 1 to 5 and Comparative Examples 3 and 4 revealed that as the content of pyridine compounds increased, the high-temperature cycle performance of the battery improved, while the low-temperature discharge performance deteriorated. Furthermore, with a continued increase in the content of pyridine compounds, the high-temperature cycle performance of the battery also worsened. This is because excessive pyridine compound content increases the negative electrode film-forming resistance, affecting the battery's electrochemical performance. The content 'a' of pyridine compounds must satisfy the condition: 0.1 ≤ a ≤ 1.

[0097] Comparative studies of Examples 2, 13 to 16, and Comparative Examples 5 and 6 revealed that while increasing the vinyl sulfate content improved the battery's low-temperature discharge performance, it worsened its high-temperature storage and cycle performance. This is because excess vinyl sulfate is unstable, leading to excessive side reactions and gas production. Furthermore, the vinyl sulfate content b must satisfy the following condition: 0.1 ≤ b ≤ 2.

[0098] By comparing Comparative Examples 7 and 14, and Comparative Examples 9 and 15, it was found that due to the smaller coating amount and compaction density of the negative electrode active material in Comparative Examples 7 and 9, the corresponding energy density of the battery was smaller, resulting in better high and low temperature performance of the battery. Furthermore, the high and low temperature performance of the battery can be further improved by adding pyridine compounds and sulfate ester compounds as electrolyte additives.

[0099] Comparative examples 2, 17-20, and Comparative Examples 7 and 8, or comparative examples 2, 21-23, and Comparative Examples 9 and 10, revealed that as the coating amount and compaction density of the negative electrode active material increase, the energy density of the battery increases accordingly, and the high-temperature cycle performance and low-temperature discharge performance of the battery decrease slightly. However, as the coating amount and compaction density of the negative electrode active material continue to increase, the high-temperature cycle performance and low-temperature discharge performance of the battery will continue to deteriorate. Excessively high coating amount and compaction density may even cause a drop in cycle performance. Furthermore, the coating amount c and compaction density d of the negative electrode active material must satisfy: 60 ≤ c ≤ 120, 1.65 ≤ d ≤ 1.85.

[0100] Comparisons of Comparative Examples 3 and 5, and Comparative Example 11, revealed that when the coating amount and compaction density of the negative electrode active material are large, and the energy density of the battery is correspondingly high, the high-temperature cycle performance of the battery can be improved by adding only pyridine compounds, and the low-temperature discharge performance of the battery can be improved by adding only vinyl sulfate. Further comparisons of Examples 1 to 16, and Comparative Example 11, showed that when the additive contains both pyridine compounds and vinyl sulfate, both the high and low temperature performance of the battery can be improved. However, excessive vinyl sulfate content can affect the high-temperature storage performance of the battery, and excessive pyridine compound content may cause cycle drops. Therefore, the synergistic effect of pyridine compounds and vinyl sulfate compounds can achieve both high and low temperature performance and high-temperature storage performance. Furthermore, the content of pyridine compounds and vinyl sulfate must satisfy the following conditions: 0.1 ≤ a ≤ 1, 0.1 ≤ b ≤ 2, 0.73 ≤ (b+1) / (a+1) ≤ 2.3.

[0101] In summary, the contents of pyridine compounds and vinyl sulfate in the embodiments of this application, as well as the coating amount and compaction density of the negative electrode active material, need to meet the following conditions: 0.75≤(c / 100+d) / (b / 2+2)≤1.5, 0.1≤a≤1, 0.1≤b≤2, 0.73≤(b+1) / (a+1)≤2.3, and 60≤c≤120, 1.65≤d≤1.85. The high and low temperature performance of the battery can be improved simultaneously.

[0102] All scopes disclosed in this application include endpoints, and endpoints can be combined with each other.

[0103] The solution of this application has been described in detail above. In the above embodiments, the descriptions of each embodiment have their own emphasis; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. Those skilled in the art should also understand that the actions and modules involved in the specification are not necessarily essential to this application. Furthermore, it is understood that the steps in the method of this application embodiment can be adjusted, combined, and deleted according to actual needs, and the modules in the device of this application embodiment can be combined, divided, and deleted according to actual needs.

[0104] Although this application has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for the elements, as long as they do not depart from the scope of this application. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this application, as long as they do not depart from the essential scope of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed as the best mode of carrying out this application as conceived, but rather this application will include all embodiments falling within the scope of the appended claims.

[0105] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An electrolyte additive, characterized in that, It includes a first additive and a second additive, wherein the first additive is a pyridine compound and the second additive is a sulfate ester compound; wherein the second additive and the negative electrode active material satisfy the following conditions: 0.1≤a≤1； 0.1≤b≤2； 0.75≤(c / 100+d) / (b / 2+2)≤1.5; 0.73≤(b+1) / (a+1)≤2.3; In the formula, the first additive accounts for a wt% of the electrolyte by mass; the second additive accounts for b wt% of the electrolyte by mass; and the coating surface density of the negative electrode active material is c g / m³. 2 The compaction density of the negative electrode active material is dg / cm³. 3 .

2. The electrolyte additive according to claim 1, characterized in that, The first additive comprises a arsenic compound of structural formula one: Structural Formula 1 In structural formula one, R1, R2, R3, R4, and R5 are each independently selected from H, halogens, C1-C5 alkyl groups substituted or unsubstituted by halogens, C2-C5 olefin groups, and C1-C5 cyano groups.

3. The electrolyte additive according to claim 2, characterized in that, The first additive comprises at least one of the following arsenic compounds: 。 4. The electrolyte additive according to claim 1, characterized in that, The second additive contains at least one compound selected from vinyl sulfate, propylene sulfate, and vinyl disulfate.

5. An electrolyte, characterized in that, include: Electrolyte salts, organic solvents, and additives, wherein the additives comprise the electrolyte additives according to any one of claims 1 to 4.

6. A lithium-ion battery, characterized in that, include: A positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the electrolyte according to claim 5.

7. The lithium-ion battery according to claim 6, characterized in that, The negative electrode comprises a negative electrode sheet and a negative electrode active material coated on at least one surface of the negative electrode sheet, wherein the coating areal density of the negative electrode active material is cg / m². 2 And 60≤c≤120; and / or, the compaction density of the negative electrode active material is dg / cm³. 3 And 1.65≤d≤1.85.

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