Lithium supplement additive and preparation method thereof, electrolyte, electrode plate and lithium ion battery

Abstract

The invention discloses a lithium supplement additive and a preparation method and application thereof. The lithium supplement additive comprises a lithium sulfinate compound, and the lithium sulfinate compound contains an electron withdrawing group. An electron withdrawing group contained in the lithium sulfinate compound in the lithium supplement additive can effectively change electron cloud distribution around sulfur atoms, so that the lithium sulfinate compound is endowed with relatively high lithium supplement capacity; meanwhile, due to the existence of the electron withdrawing group, the electron energy of the lowest unoccupied molecular orbital (LUMO) of the lithium sulfinate compound is reduced, and the energy gap between the highest occupied molecular orbital (HOMO) and the LUMO of the lithium sulfinate compound is reduced, so that the lithium supplement additive can be arranged in an electrode plate to exert the lithium supplement capacity and also can be used as an electrolyte additive; and the material can participate in electrode / electrolyte interface formation.

Description

Technical Field

[0001] This application belongs to the field of batteries, and specifically relates to a lithium supplement additive, a preparation method thereof, an electrolyte, an electrode sheet, and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries are widely used in new energy vehicles, energy storage systems, consumer electronics and other fields, which put forward higher requirements for the energy density and life of the batteries. During the first charging process of lithium-ion batteries, a solid electrolyte interface (SEI film) will form at the interface between the negative electrode and the electrolyte. Although the formation of the SEI film is beneficial to improving the interface stability of the negative electrode material, it will consume a large amount of Li + released from the positive electrode material, resulting in a large capacity loss and a decrease in the first Coulombic efficiency of the lithium-ion battery, thereby reducing the energy density and service life of the battery.

[0003] In order to reduce the capacity loss of lithium-ion batteries and improve the first Coulombic efficiency of lithium-ion batteries, a lithium supplement material is generally added to the lithium-ion battery. This lithium supplement material can de-lithiate during the charging process of the lithium-ion battery monomer, especially during the first charging process, and provide a large amount of irreversible capacity to compensate for the irreversible Li + loss of the negative electrode during the first charging of the lithium-ion battery, thereby improving the capacity and the first Coulombic efficiency of the lithium-ion battery.

[0004] Existing lithium supplement materials are generally binary or ternary lithium-containing lithium supplement materials. Although these existing lithium supplement materials are rich in lithium, after de-lithiation, they will leave residual non-active substances, mostly transition metal compounds, which will react with the electrolyte and cause the electrolyte to decompose and the battery to generate gas. Summary of the Invention

[0005] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art and provide a lithium supplement additive to solve the technical problems such as the side reaction between the residual substances after lithium supplementation of the existing lithium supplement materials and the electrolyte.

[0006] To achieve the above application purpose, in the first aspect, this application provides a lithium supplement additive. The molecular structural formula of the lithium supplement additive of this application is shown as the following general formula (Ⅰ):

[0007]

[0008] Among them, the group represented by R in the general formula (Ⅰ) includes an electron-withdrawing group.

[0009] The lithium supplement additive of the present application contains a lithium sulfinate compound including an electron-withdrawing group and a sulfinic acid group. The lithium sulfinate compound can effectively change the electron cloud distribution around the sulfur atom in the sulfinic acid group through the contained electron-withdrawing group, thereby endowing the lithium sulfinate compound with a high lithium supplement capacity, and further improving the capacity and initial Coulomb efficiency of the lithium-ion battery. Since the lithium sulfinate compound does not contain transition metals, after the lithium sulfinate compound is de-lithiated, the de-lithiated product will not have an adverse side reaction with the electrolyte, so that the capacity performance and safety of the lithium-ion battery can be improved.

[0010] Furthermore, due to the fact that the lithium sulfinate compound contains an electron-withdrawing group, the electron energy of the lowest unoccupied molecular orbital (LUMO) of the lithium sulfinate compound is reduced, and the energy gap between the highest occupied molecular orbital (HOMO) and LUMO of the lithium sulfinate compound is narrowed. When the lithium sulfinate compound is dispersed in the active material layer of the electrode sheet as a lithium supplement additive, the lithium sulfinate compound and other de-lithiated products can undergo a reduction reaction with the infiltrated electrolyte, and a protective film layer can be formed at least on the surface of the electrode active material, which can improve the stability of the electrode active material during the lithium insertion and extraction process; moreover, it can also enable the lithium supplement additive of the present application to be used as an electrolyte additive to participate in the formation of the SEI film at the electrode / electrolyte interface, thereby improving the capacity performance and cycle performance of the lithium-ion battery.

[0011] In the second aspect of the present application, a preparation method of the above-mentioned lithium supplement additive of the present application is provided. The preparation method of the lithium supplement additive of the present application includes the following steps for preparing the lithium sulfinate compound:

[0012] React an organic lithium sulfinate salt and a compound containing an electron-withdrawing group source or an electron-withdrawing group precursor in a first solution to generate a lithium sulfinate compound containing an electron-withdrawing group;

[0013] and / or

[0014] React an organic metal sulfinate salt and a compound containing an electron-withdrawing group source or an electron-withdrawing group precursor in a first solution to generate an organic metal sulfinate salt containing an electron-withdrawing group;

[0015] Perform a first displacement reaction on the metal sulfinate salt and an acid in a second solution to generate a sulfinic acid containing an electron-withdrawing group;

[0016] Perform a second displacement reaction on the sulfinic acid and a soluble lithium salt in a polar solvent to generate a lithium sulfinate compound containing an electron-withdrawing group;

[0017] Wherein, the metal ion contained in the organic metal sulfinate salt is a non-lithium metal ion, and the molecular structural formula of the lithium sulfinate compound is shown as the following general formula (Ⅰ):

[0018]

[0019] The group represented by R in the general formula (I) includes an electron-withdrawing group.

[0020] In the preparation method of the lithium supplement additive of the present application, an R group including an electron-withdrawing group is grafted onto the organic metal sulfinate, so that the prepared lithium sulfinate compound is more likely to release active lithium ions during the charging process, thereby endowing the lithium sulfinate compound with a lithium supplement capacity and avoiding adverse side reactions between the product after de-lithiation and the electrolyte. Moreover, the lithium sulfinate compound is dispersed as a lithium supplement agent in the active material layer of the electrode sheet, and the lithium sulfinate compound and other products after de-lithiation can undergo a reduction reaction with the infiltrated electrolyte, and a protective film layer can be formed on the surface of the electrode active material, which can improve the stability of the electrode active material during the insertion and extraction of lithium ions, and can also enable the lithium sulfinate compound to participate in the formation of the SEI film at the electrode interface as an electrolyte additive, thereby improving the capacity performance and safety of the lithium-ion battery.

[0021] In the third aspect of the present application, an electrolyte is provided. The electrolyte of the present application includes an additive, and the additive includes the lithium supplement additive of the above-mentioned present application or the lithium supplement additive prepared by the preparation method of the lithium supplement additive of the above-mentioned present application.

[0022] The additive in the electrolyte of the present application includes the lithium supplement additive of the above-mentioned present application. The electron-withdrawing group contained in the lithium sulfinate compound can effectively reduce the lowest unoccupied molecular orbital (LUMO) energy of the lithium sulfinate compound and narrow the energy gap between the highest occupied molecular orbital (HOMO) and LUMO, thereby effectively enhancing the electron-accepting ability of the lithium sulfinate compound, which is beneficial to the improvement of the conductivity of the lithium sulfinate compound, enabling the lithium sulfinate compound and its product after de-lithiation to participate in the formation of the SEI film at the electrode / electrolyte interface. Moreover, the lithium sulfinate compound can also release active lithium ions to exert the lithium supplement capacity. Therefore, the electrolyte of the present application can release active lithium ions during the first charging process of the lithium-ion battery, exert the lithium supplement capacity effect, thereby improving the capacity and the first Coulomb efficiency of the lithium-ion battery; and can also participate in the formation of the SEI film at the electrode interface, thereby improving the cycle performance of the lithium-ion battery.

[0023] In the fourth aspect of the present application, an electrode sheet is provided. The electrode sheet of the present application includes a current collector and an active material layer provided on at least one surface of the current collector, and the active material layer includes the lithium supplement additive of the above-mentioned present application or the lithium supplement additive prepared by the preparation method of the lithium supplement additive of the above-mentioned present application.

[0024] The electrode sheet of the present application contains the above-mentioned lithium supplement additive of the present application. Therefore, the electrode sheet of the present application has a high capacity, and alleviates the occurrence of adverse side reactions with the electrolyte during the cycling process of the lithium-ion battery, improving the capacity performance and safety of the lithium-ion battery. Moreover, during the cycling process of the lithium-ion battery, the lithium sulfinate compound contained in the electrode sheet will also undergo a reduction reaction with the infiltrated electrolyte, forming at least a protective film layer on the surface of the electrode active material, which can improve the stability of the electrode active material during the lithium insertion and extraction process, thereby improving the capacity performance and cycling performance of the lithium-ion battery.

[0025] In the fifth aspect of the present application, a lithium-ion battery is provided. The lithium-ion battery of the present application includes a positive electrode sheet and an electrolyte infiltrating the positive electrode sheet, and the positive electrode sheet includes the above-mentioned lithium supplement additive of the present application;

[0026] and / or, the electrolyte is the electrolyte of the present application above.

[0027] During the first charging process of the lithium-ion battery of the present application, since the lithium sulfinate compound in the lithium supplement additive contained in at least one of the positive electrode sheet and the electrolyte will de-lithiate to provide active lithium ions, the first efficiency and energy density of the lithium-ion battery are improved. Moreover, when the positive electrode sheet contains the lithium sulfinate compound, itself and its de-lithiated product can undergo a reduction reaction with the infiltrated electrolyte, forming at least a protective film layer on the surface of the positive electrode active material, improving the stability of the positive electrode active material during the lithium insertion and extraction process, and containing no transition metals, thus avoiding adverse side reactions with the electrolyte; when the electrolyte contains the lithium sulfinate compound, it can preferably undergo a reduction reaction with the electrolyte and participate in the formation of the SEI film at the electrode / electrolyte interface, and also avoids adverse side reactions due to the transition metal-containing electrolyte, thereby improving the cycling performance and safety of the lithium-ion battery. Detailed Embodiments

[0028] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] In the present application, the term "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0030] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural item(s). For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can each be single or multiple.

[0031] It should be understood that in various embodiments of this application, the magnitude of the serial numbers of the above - mentioned processes does not imply the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0032] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0033] The weight of the relevant components mentioned in the specification of the embodiments of this application can not only refer to the specific content of each component, but also represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of this application is scaled up or down proportionally, it is within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass described in the specification of the embodiments of this application can be mass units well - known in the chemical industry such as μg, mg, g, kg, etc.

[0034] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of this application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Thus, the features defined with "first" and "second" can explicitly or implicitly include one or more of such features.

[0035] During the first charging process of a lithium - ion battery, a solid electrolyte interface (SEI) film is formed inside it, and the formation of this SEI film will consume a large amount of Li + released from the positive electrode material,

[0036] To compensate for the active lithium ions consumed due to the formation of a solid electrolyte interface (SEI film) during the first charging process of a lithium-ion battery, a lithium supplementing material is generally added to the lithium-ion battery at present. This lithium supplementing material can de-lithiate during the charging process of the lithium-ion battery, especially during the first charging process, and provide a large amount of irreversible capacity to compensate for the irreversible Li + loss during the first charging process of the lithium-ion battery, so as to improve the capacity and first Coulomb efficiency of the lithium-ion battery.

[0037] The commonly used existing lithium supplementing materials are generally binary or ternary lithium-containing lithium supplementing materials. Although these existing lithium supplementing materials are rich in lithium, during or after the de-lithiation process, their crystal phases will change to a certain extent, resulting in changes in the lithium supplementing material particles. Commonly, cracks or crystal structure collapse are likely to occur in the particles of the lithium supplementing material, seriously affecting the lithium supplementing capacity of the inorganic lithium supplementing material, and also causing instability of the SEI film. Moreover, due to the lack of lithium intercalation ability of the lithium supplementing material, the positive effect of the existing lithium supplementing material after de-lithiation in the battery is not obvious. Due to the above deficiencies of the existing lithium supplementing materials, it is difficult for the existing lithium supplementing materials to meet the growing market demand for high-performance batteries.

[0038] Based on the above deficiencies of the existing lithium supplementing agent materials, the following solutions are proposed in the embodiments of this application.

[0039] [Lithium supplementing additive]

[0040] In a first aspect, the embodiments of this application provide a lithium supplementing additive. The lithium supplementing additive in the embodiments of this application includes a lithium sulfinate compound; the lithium sulfinate compound contains an electron-withdrawing group, and its molecular structural formula is shown as the following general formula (Ⅰ):

[0041]

[0042] Among them, the group represented by R in the general formula (Ⅰ) includes an electron-withdrawing group.

[0043] In this way, since the electron-withdrawing group contained in the lithium sulfinate compound in the lithium supplementing additive of the embodiments of this application has strong electron-withdrawing characteristics and is directly or indirectly connected to the sulfur atom in the sulfonic acid group through a chemical bond to form a chemical bond, it can effectively change the electron cloud distribution around the sulfur atom, thereby endowing the lithium sulfinate compound with lithium supplementing capacity, enabling the lithium supplementing additive of the embodiments of this application to exert its lithium supplementing capacity, and thus improving the capacity and first Coulomb efficiency of the lithium-ion battery. Since the lithium sulfinate compound does not contain transition metals, after the lithium sulfinate compound completes de-lithiation, the de-lithiated product thereof will not have an adverse side reaction with the electrolyte, thereby improving the capacity performance and safety of the lithium-ion battery, and effectively overcoming the problems of reduced cycle performance and gas generation of the lithium-ion battery caused by the side reaction between the existing lithium supplementing materials containing transition metals and the electrolyte, which lead to safety performance problems.

[0044] Furthermore, due to the electron-withdrawing groups contained in the lithium sulfinate compound in the lithium supplement additive of the embodiments of the present application, the electron energy of the lowest unoccupied molecular orbital (LUMO) in the lithium sulfinate compound is reduced, and the electron energy gap between the highest occupied molecular orbital (HOMO) and LUMO is narrowed. After being dispersed as a lithium supplement agent in the active material layer of the electrode sheet, the lithium sulfinate compound and other products after de-lithiation can undergo a reduction reaction with the infiltrated electrolyte, and a protective film layer can be formed at least on the surface of the electrode active material, which can improve the stability of the electrode active material during the lithium insertion and extraction process, thereby improving the capacity performance and cycling performance of the lithium-ion battery.

[0045] Meanwhile, since the electron energy of the lowest unoccupied molecular orbital (LUMO) in the lithium sulfinate compound is reduced, and the electron energy gap between the highest occupied molecular orbital (HOMO) and LUMO is narrowed, the lithium supplement additive of the embodiments of the present application can also be used as an additive for the electrolyte, so that the lithium sulfinate compound itself or the product after de-lithiation thickness can participate in the formation of the SEI film at the electrode / electrolyte interface by reacting with the electrolyte.

[0046] Therefore, the lithium supplement additive of the embodiments of the present application can release active lithium ions during the charge and discharge process of the lithium-ion battery, especially during the first charging process, providing a large amount of irreversible capacity to compensate for the irreversible Li + loss during the first charging process of the lithium-ion battery, thereby improving the capacity and first Coulombic efficiency of the lithium-ion battery. Moreover, the lithium sulfinate compound is dispersed in the electrode sheet, and it and its products after de-lithiation can undergo a reduction reaction with the infiltrated electrolyte to form a protective film layer at least on the surface of the electrode active material, which can improve the stability of the electrode active material during the lithium insertion and extraction process; at the same time, it can also make the lithium supplement additive of the embodiments of the present application can be used as an electrolyte additive to participate in the formation of the SEI film at the electrode / electrolyte interface, thereby improving the cycling performance of the lithium-ion battery. In addition, since the lithium supplement additive of the embodiments of the present application does not contain transition metals compared with traditional transition metal-containing lithium supplement agents, the products after de-lithiation of the lithium supplement additive of the embodiments of the present application basically do not undergo adverse side reactions with the electrolyte to cause electrolyte decomposition and battery gas generation, and can also improve the safety of the lithium-ion battery.

[0047] In some embodiments, the electronegativity of the electron-withdrawing group contained in the group represented by R in the above lithium sulfinate compound is 2 to 5, optionally 2 to 4, and further can be 2.7 to 3.5. In exemplary examples, it can be 2.81 (-OCH3), 2.96 (-CN, -CHO), 3.12 (-COOH), 3.28 (-CCl3), 3.64 (-CF3), etc., which are typical but non-limiting electronegativities or ranges between any two electronegativity values. The electron-withdrawing group within this electronegativity range can enhance the influence on the electron cloud distribution around the sulfur atom, thereby improving the ability of the lithium sulfinate compound to release active lithium ions during charging and enhancing the performance of its lithium compensation capacity. At the same time, it can further reduce the electron energy of the lowest unoccupied molecular orbital (LUMO) of the lithium sulfinate compound, further narrowing the energy gap between the highest occupied molecular orbital (HOMO) and LUMO of the lithium sulfinate compound, thereby further enhancing the electron acceptance ability of the lithium sulfinate compound. When used as a lithium compensation additive in the electrode sheet, it can enhance the reduction reaction between itself or its product after lithium deintercalation and the infiltrated electrolyte, thereby forming at least a protective film layer on the surface of the electrode active material, enhancing the stability of the electrode active material during the lithium insertion and extraction process, and also alleviating the migration of transition metals released by the electrode active material into the electrolyte during the cycle; when used as an electrolyte additive, while providing lithium compensation capacity to the lithium-ion battery, the lithium sulfinate compound itself or its product after lithium deintercalation can also preferentially undergo a reduction reaction with the electrolyte and participate in the formation of the solid electrolyte interface (SEI) film at the electrode / electrolyte interface.

[0048] In the embodiments, the above electron-withdrawing group may include at least one of -CN, alkenyl, alkynyl, -OX, aryl, -CCl3, -CF3, -CHO, -COR, -COOH.

[0049] In exemplary examples, when the above electron-withdrawing group contains alkenyl, the alkenyl may include at least one of vinyl, allyl, and 2-butene.

[0050] When the above electron-withdrawing group contains alkynyl, the alkynyl includes at least one of ethynyl, propynyl, and butynyl.

[0051] When the above electron-withdrawing group contains -OX, X in -OX is at least one of methyl, ethyl, and propyl, and -OX may include at least one of -OCH3, -OC2H5, and -OC3H7.

[0052] When the above electron-withdrawing group contains aryl, the aryl includes -C6H5.

[0053] When the above electron-withdrawing group contains -COR, R in -COR is an alkyl group, such as alkyl groups like methyl and ethyl.

[0054] The above-mentioned types of electron-withdrawing groups have relatively strong electronegativity, which can further improve the influence on the electron cloud distribution around the sulfur atom, thereby enhancing the ability of the lithium sulfinate compound to release active lithium ions during charging and improving the utilization of its lithium supplement capacity. At the same time, the electron energy of the lowest unoccupied molecular orbital (LUMO) of the lithium sulfinate compound is reduced, and the energy gap between the highest occupied molecular orbital (HOMO) and LUMO of the lithium sulfinate compound is further narrowed, thus further enhancing the electron-accepting ability of the lithium sulfinate compound, enhancing the conductivity of the lithium sulfinate compound, and forming a protective film layer on the surface of the electrode active material by the lithium sulfinate compound itself and its products after de-lithiation (set as a lithium supplement additive in the electrode sheet) and / or being able to participate in the formation of the SEI film at the electrode / electrolyte interface (set as an additive in the electrolyte).

[0055] After testing, in some embodiments, due to the presence of the above-mentioned electron-withdrawing groups in the lithium sulfinate compounds of the above embodiments, the electron energy of their lowest unoccupied molecular orbital (LUMO) is -2 to -5 eV.

[0056] In some embodiments, the energy difference between the electron energy of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the lithium sulfinate compounds of the above embodiments is -2.8 to -7 eV.

[0057] Since the electron energy of the LUMO of the lithium sulfinate compound is reduced, the energy gap between the HOMO and LUMO of the lithium sulfinate compound is further narrowed, thereby further enhancing the electron-accepting ability of the lithium sulfinate compound and enhancing the formation of a protective film layer on the surface of the electrode active material by the products after de-lithiation of the lithium sulfinate compound and / or participating in the formation of the SEI film at the electrode / electrolyte interface.

[0058] In a further embodiment, on the basis of the above embodiments, the lithium supplement additive of the embodiments of the present application may further include other additives. That is, the lithium supplement additive of the embodiments of the present application may be mixed or compounded with other additives. In the embodiments, the other additives may include conductive carbon materials and transition metal oxides, etc. When the other additives include conductive carbon materials, the conductivity of the lithium supplement additive can be improved and the migration rate of lithium ions can be improved; when the other additives include transition metal oxides, the transmission efficiency of lithium ions can be improved. When the transition metal oxide contains lithium ions, through the selection of the transition metal oxide, it can play a synergistic lithium supplement role with the lithium sulfinate compound of the above embodiments of the present application or reduce the de-lithiation voltage, etc., thereby improving the capacity of the electrode sheet.

[0059] In the embodiments, when the lithium supplement additive of the embodiments of the present application further includes the above other additives, the mass ratio of the above lithium sulfinate compound may be greater than 50%. In this way, by increasing the content of the lithium sulfinate compound, the lithium supplement capacity of the lithium supplement additive of the embodiments of the present application can be improved, and the capacity of the electrode sheet and the performance of reducing the internal resistance of the electrode sheet can be further improved.

[0060] In a second aspect, the embodiments of the present application further provide a preparation method of the above lithium supplement additive. In some embodiments, the preparation method of the lithium supplement additive of the embodiments of the present application includes the following steps for preparing the lithium sulfinate compound:

[0061] S10: React an organic lithium sulfinate salt and a compound containing an electron-withdrawing group source or a precursor of an electron-withdrawing group in a first solution to generate a lithium sulfinate compound containing an electron-withdrawing group.

[0062] In the preparation method of the lithium supplement additive of the embodiments of the present application, the electron-withdrawing group source compound in step S10 refers to a compound containing an electron-withdrawing group, and its reaction with the organic lithium sulfinate salt may include a substitution reaction; the electron-withdrawing group precursor refers to a compound containing the elements contained in the electron-withdrawing group but the precursor compound itself does not contain an electron-withdrawing group, and an electron-withdrawing group is generated after its reaction with the organic lithium sulfinate salt. At this time, the reaction of the electron-withdrawing group precursor with the organic lithium sulfinate salt may include an oxidation reaction. The molecular structural formula of the lithium sulfinate compound prepared by step S10 is as shown in the above general molecular structure formula (Ⅰ):

[0063]

[0064] In this way, the preparation method of the lithium supplement additive of the embodiments of the present application directly grafts an R group including an electron-withdrawing group onto the organic lithium sulfinate salt by a one-step method to prepare a lithium sulfinate compound. Therefore, in the prepared lithium sulfinate compound, the strong electron-withdrawing group included in the group represented by R is directly or indirectly connected to the sulfur atom in the sulfonic acid group through a chemical bond, which can effectively change the electron cloud distribution around the sulfur atom, so as to make it easier for the lithium sulfinate compound to release active lithium ions during charging, thereby endowing the lithium sulfinate compound with a lithium supplement capacity, and enabling the prepared lithium supplement additive to exert the lithium supplement capacity.

[0065] Meanwhile, since the prepared lithium sulfinate compound contains an electron-withdrawing group, the electron energy of the lowest unoccupied molecular orbital (LUMO) of the lithium sulfinate compound is reduced, and the energy gap between the highest occupied molecular orbital (HOMO) and LUMO of the lithium sulfinate compound is narrowed, thereby effectively enhancing the electron-accepting ability of the lithium sulfinate compound. As a result, the lithium sulfinate compound can be used as a lithium supplement additive in the electrode sheet, enabling the lithium sulfinate compound and other products after lithium deintercalation to undergo a reduction reaction with the infiltrated electrolyte, and at least forming a protective film layer on the surface of the electrode active material, which can improve the stability of the electrode active material during the lithium intercalation and deintercalation process, or / and be added as an additive to the electrolyte to participate in the formation of the SEI film at the electrode / electrolyte interface.

[0066] In some embodiments, when the reactant in step S10 includes a compound containing an electron-withdrawing group source, the compound containing the electron-withdrawing group source can be a compound containing the electron-withdrawing group in the lithium sulfinate compound as the lithium supplement additive in the above text application embodiment.

[0067] In some embodiments, when the reactant in step S10 includes an electron-withdrawing group precursor, the electron-withdrawing group precursor can also be a precursor compound containing the electron-withdrawing group in the lithium sulfinate compound as the lithium supplement additive in the above text application embodiment. For example, when the electron-withdrawing group precursor includes an organic nitrogen source, an oxidation reaction with an organic lithium sulfinate salt generates an electron-withdrawing group such as -CN. That is, R in the above general molecular structure formula (Ⅰ) can be an electron-withdrawing group such as -CN.

[0068] In the embodiment, when the reactant in step S10 includes an electron-withdrawing group precursor, the first solution of the oxidation reaction system between the electron-withdrawing group precursor and the organic lithium sulfinate salt further includes a catalyst and an oxidant.

[0069] For example, in the embodiment, when the electron-withdrawing group includes a -CN electron-withdrawing group, the electron-withdrawing group precursor includes an organic nitrogen source. At this time, the reaction process of the organic lithium sulfinate salt and the electron-withdrawing group precursor in the first solution is as follows in step S11:

[0070] Step S11: Oxidize and react the organic lithium sulfinate salt, catalyst, oxidant, and organic nitrogen source in the first solution to generate a lithium sulfinate compound containing an electron-withdrawing group.

[0071] Among them, in the oxidation reaction treatment system in step S11, the oxidant and the organic nitrogen source act synergistically. The oxidant produces free radicals, and the organic nitrogen source undergoes a decomposition reaction to generate free radicals and nitric oxide (NO). The free radicals act on the lithium organic sulfinate salt, causing the lithium organic sulfinate salt to lose an electron and generate a sulfonyl radical (-SO2·). The sulfonyl radical (-SO2·) combines with nitric oxide to form an intermediate lithium nitrososulfinate salt (-SO2-NO), which undergoes deoxidation or recombination under the catalysis of a catalyst, and the nitroso group (-NO) contained in the intermediate nitrososulfinate salt is converted into a cyano group (-CN), thereby generating NC-SO2.

[0072] The mechanism of the oxidation reaction treatment in step S11 is specifically as follows:

[0073] Oxidant → Free radicals;

[0074] Organic nitrogen source → Free radicals + Nitric oxide (NO);

[0075] Lithium organic sulfinate salt (Q-SO2 - Li + ) + Free radicals → Organic sulfonyl radical (Q-SO2·Li); where Q is the organic group contained in the lithium organic sulfinate salt.

[0076] Organic sulfonyl radical (Q-SO2·Li) + NO → Intermediate lithium nitrososulfinate salt (Q-SO2(Li)-NO);

[0077] Intermediate lithium nitrososulfinate salt (Q-SO2(Li)-NO) → NC-SO2Li.

[0078] In some embodiments, in the oxidation reaction treatment system of step S11, the addition amount of the oxidant is 5-40 mol% of the lithium organic sulfinate salt, that is, 5-40 mol of the oxidant is added per 100 mol, optionally 25-35 mol%. In the demonstration example, it can be 5 mol%, 7 mol%, 10 mol%, 12 mol%, 15 mol%, 18 mol%, 20 mol%, 23 mol%, 25 mol%, 28 mol%, 30 mol%, 32 mol%, 35 mol%, 38 mol%, 40 mol%, etc. of typical but non-limiting molar ratios or the range between any two molar ratio values. The oxidant within this addition amount range can, on the one hand, generate a sufficient amount of free radicals, thereby increasing the amount of organic sulfonyl radicals (Q-SO2·) generated from the lithium organic sulfinate salt. In this way, the yield of the lithium sulfinate compound can be increased; on the other hand, it can reduce the usage amount of the oxidant, reduce the economic cost and the generation amount of by-products.

[0079] In some embodiments, the oxidant includes at least one of N-hydroxyphthalimide (NHPI) and phthalimide. These oxidants can cooperate with the organic nitrogen source to generate free radicals. For example, when the oxidant includes N-hydroxyphthalimide, it will generate phthalimide-N-oxyl radical (PINO).

[0080] In some embodiments, in the oxidation reaction treatment system of step S11, the molar ratio of the organic nitrogen source to the lithium organic sulfinate is 2-5:1, optionally 2.5-3.5:1. In exemplary embodiments, it can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1 and other typical but non-limiting molar ratios or the range between any two molar ratio values. The organic nitrogen source within this addition amount range can, on the one hand, generate a sufficient amount of nitric oxide, thereby increasing the generation amount of the lithium nitrososulfinate intermediate. In this way, the yield of the lithium sulfinate compound can be increased; on the other hand, it can reduce the usage amount of the organic nitrogen source, reducing the economic cost and the generation amount of by-products.

[0081] In some embodiments, the organic nitrogen source includes at least one of tert-butyl nitrite and isopropyl nitrite. These organic nitrogen sources can cooperate with the organic nitrogen source to decompose and generate free radicals and nitric oxide. For example, when the organic nitrogen source includes tert-butyl nitrite, it will generate tert-butoxy radical (t-BuO·) and nitric oxide (NO).

[0082] In some embodiments, in the oxidation reaction treatment system of step S11, the addition amount of the catalyst is 1-15 mol% of the lithium organic sulfinate, that is, 1-15 mol of the oxidant is added per 100 mol, optionally 5-10 mol%. In exemplary embodiments, it can be 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol% and other typical but non-limiting molar ratios or the range between any two molar ratio values. The catalyst within this addition amount range can effectively catalyze the lithium nitrososulfinate intermediate to generate the final product lithium sulfinate compound.

[0083] In some embodiments, the catalyst includes a palladium-based catalyst. In exemplary embodiments, when the catalyst includes a palladium-based catalyst, the palladium-based catalyst can include at least one of palladium acetate, [1,3-bis(diphenylphosphino)propane]palladium(II) trifluoromethanesulfonate, and bis(dibenzylideneacetone)palladium(0). These catalysts have high catalytic activity and can improve the catalytic activity towards the lithium nitrososulfinate intermediate, improving the efficiency of generating the final product lithium sulfinate compound.

[0084] In some embodiments, the temperature of the oxidation reaction treatment in step S11 may be 50 to 90 °C, and the reaction time may be 6 to 48 hours; in exemplary embodiments, the reaction temperature may be typical but non-limiting temperatures such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, or a range between any two temperature values; the reaction time may be typical but non-limiting times such as 6 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 48 hours, or a range between any two time values. This temperature range and time range can effectively increase the yield of the final product and reduce the generation amount of by-products.

[0085] In an embodiment, the oxidation reaction treatment in step S11 may be set as a reflux reaction. For example, at 50 to 90 °C, reflux for 6 to 48 hours.

[0086] In some embodiments, the molar concentration of the lithium organic sulfinate in step S10, such as in step S11, in the first solution is 0.3 to 0.8 mol / L, optionally 0.45 to 0.65 mol / L. In exemplary embodiments, it may be typical but non-limiting molar concentrations such as 0.3 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.8 mol / L, or a range between any two molar concentration values. The concentration of the reactant such as the lithium organic sulfinate within this concentration range can effectively improve the efficiency of the oxidation reaction treatment and reduce the generation amount of by-products.

[0087] In some embodiments, the first solution in step S10, such as in step S11, may include an organic solvent, such as may include at least one of acetonitrile, ethyl acetate, tetrahydrofuran, DMF, and dimethyl sulfoxide. These organic solvents can effectively dissolve each reactant, and can effectively increase the yield of the target product and reduce the generation of by-products.

[0088] In some embodiments, the lithium organic sulfinate in step S10, such as in step S11, includes at least one of lithium trifluoromethanesulfinate, lithium methanesulfinate, lithium benzenesulfinate, and lithium ethanesulfinate. These types of lithium organic sulfinates are rich in lithium and sulfinic acid, and can react with a compound containing an electron-withdrawing group source or an electron-withdrawing group precursor to generate a lithium sulfinate compound containing an electron-withdrawing group.

[0089] In some embodiments, after the reaction treatment in step S10 ends as in step S11, it may further include a step of purifying the lithium sulfinate compound. In the embodiment, the purification treatment may be a solid-liquid separation treatment on the solution system after the oxidation reaction treatment, collecting the filtrate, adding a water remover such as but not limited to anhydrous sodium sulfate to perform water removal and drying treatment on the filtrate, and then removing other solvents to obtain a pure lithium sulfinate compound.

[0090] In some other embodiments, the method for preparing the lithium supplement additive in the embodiments of the present application may further include the following steps for preparing the lithium sulfinate compound:

[0091] S20: React an organic metal sulfinate and a compound containing an electron-withdrawing group source or a precursor of an electron-withdrawing group in a first solution to generate a metal sulfinate containing an electron-withdrawing group;

[0092] S30: Perform a first substitution reaction on the metal sulfinate containing an electron-withdrawing group and an acid in a second solution to generate a sulfinic acid containing an electron-withdrawing group;

[0093] S40: Perform a second substitution reaction on the sulfinic acid containing an electron-withdrawing group and a soluble lithium salt in a polar solvent to generate a lithium sulfinate compound containing an electron-withdrawing group.

[0094] The preparation method of the lithium sulfinate compound in the embodiments of the present application grafts an electron-withdrawing group onto the organic metal sulfinate by the above multi-steps, so that the prepared lithium sulfinate compound, such as the lithium sulfinate compound prepared in step S10 above, makes it easier for the lithium sulfinate compound to release active lithium ions during charging, thereby endowing the lithium sulfinate compound with a lithium supplement capacity. At the same time, the lowest unoccupied molecular orbital (LUMO) energy of the lithium sulfinate compound is reduced, and the energy gap between the highest occupied molecular orbital (HOMO) and LUMO of the lithium sulfinate compound is narrowed, so that the lithium sulfinate compound can be used as a lithium supplement additive and can react with the infiltrating electrolyte during cycling to form a protective film layer on the surface of the electrode active material. It can also be an electrolyte additive and can participate in the formation of the SEI film at the electrode / electrolyte interface. Therefore, the molecular structural formula of the lithium sulfinate compound prepared in this embodiment is also as shown in structural formula (Ⅰ) above.

[0095] Step S20:

[0096] The organic metal sulfinate in step S20 is the same as the organic lithium sulfinate in step S10 above and provides a sulfonic acid group. In this embodiment, the metal ion contained in the organic metal sulfinate in step S20 is a non-lithium metal ion. Therefore, through the reaction treatment of the organic metal sulfinate in step S20, a metal sulfinate containing an electron-withdrawing group is generated, that is, a non-lithium metal sulfinate containing an electron-withdrawing group.

[0097] In addition, the types of reactants and the reaction treatment mechanism in step S20 are the same as those in the above step S10. Therefore, a metal sulfinate containing an electron-withdrawing group (R-SO2M, where M is a metal ion other than lithium). For example, when the electron-withdrawing group precursor of the reactant, such as the electron-withdrawing group precursor includes an organic nitrogen source, then an oxidation reaction occurs with the lithium organosulfinate to generate an electron-withdrawing group including -CN, etc. That is, R in the above general molecular formula (I) can be an electron-withdrawing group including -CN, etc.

[0098] In the examples, when the reactants in step S20 include an electron-withdrawing group precursor, the first solution of the oxidation reaction system between the electron-withdrawing group precursor and the lithium organosulfinate further includes a catalyst and an oxidant. For example, in the examples, when the electron-withdrawing group includes a -CN electron-withdrawing group, the electron-withdrawing group precursor includes an organic nitrogen source. At this time, the reaction between the lithium organosulfinate and the electron-withdrawing group precursor in the first solution is processed as follows in step S21:

[0099] Step S21: Perform an oxidation reaction treatment on the lithium metal sulfinate, catalyst, oxidant, and organic nitrogen source in the first solution to generate a lithium sulfinate compound containing an electron-withdrawing group.

[0100] Among them, in the oxidation reaction treatment system in step S21, the mechanism of the oxidation reaction treatment is the same as that in the above step S11. Specifically, the mechanism of the oxidation reaction treatment in step S21 is as follows:

[0101] Oxidant → Free radical;

[0102] Organic nitrogen source → Free radical + Nitric oxide (NO);

[0103] Lithium metal sulfinate (Q-SO2 - M + ) + Free radical → Organosulfinyl radical (Q-SO2·M); where M is a metal ion other than lithium; Q is the organic group contained in the lithium metal sulfinate;

[0104] Organosulfinyl radical (Q-SO2·M) + NO → Metal organonitrososulfinate intermediate (Q-SO2(M)-NO);

[0105] Metal organonitrososulfinate intermediate (Q-SO2(M)-NO) → NC-SO2M.

[0106] In some examples, in the oxidation reaction treatment system of step S21, at least one of the type and addition amount of the oxidant, the type and addition amount of the organic nitrogen source, the type and addition amount of the catalyst, and the first solution can be the same as or different from those in the above step S11.

[0107] In some embodiments, the temperature of the reaction treatment in step S20, such as the oxidation reaction treatment in step S21, can be 50 - 90 °C, and the reaction time can be 6 - 48 hours; in exemplary embodiments, the reaction temperature can be typical but non-limiting temperatures such as 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, or a range between any two temperature values; the reaction time can be typical but non-limiting times such as 6 hours, 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 48 hours, or a range between any two time values. This temperature range and time range can effectively improve the yield of the metal sulfinate containing an electron-withdrawing group and reduce the generation amount of by-products.

[0108] In an embodiment, the reaction treatment in step S20, such as the oxidation reaction treatment in step S21, can be set as a reflux reaction. For example, at 50 - 90 °C, reflux for 6 - 48 hours.

[0109] In some embodiments, after the reaction treatment in step S20, such as the reaction treatment in step S11, is completed, it may further include a step of purifying the metal sulfinate containing an electron-withdrawing group. In an embodiment, this purification treatment can be to perform solid-liquid separation on the reaction-treated solution system, collect the filtrate, then add a water remover such as but not limited to anhydrous sodium sulfate to perform water removal and drying treatment on the filtrate, and then remove other solvents to obtain a pure metal sulfinate containing an electron-withdrawing group.

[0110] Step S30:

[0111] During the first displacement reaction treatment in step S30, the metal ions contained in the metal sulfinate containing an electron-withdrawing group prepared in step S20 react with the hydrogen ions contained in the acid to generate a sulfinic acid containing an electron-withdrawing group. The specific chemical reaction formula is as follows:

[0112] R-SO2M + H-Y → R-SO2H + M-Y;

[0113] Among them, M is a metal ion other than lithium, and Y is an acid radical ion in the acid.

[0114] In some embodiments, in the first displacement reaction treatment system of step S30, the addition amount of the acid can be: for every 50 - 1000 mmol of the metal sulfinate containing an electron-withdrawing group, 5 - 100 ml of the acid is added. The acid within this addition amount range can effectively displace the metal in the metal sulfinate containing an electron-withdrawing group with hydrogen, thereby increasing the yield of the sulfinic acid containing an electron-withdrawing group; at the same time, on the basis of ensuring appropriate excess of the acid, reducing the amount of the acid used can reduce the economic cost.

[0115] In some embodiments, the acid may include at least one of an organic acid and an inorganic acid. In exemplary embodiments, the organic acid may include at least one of acetic acid and formic acid; the inorganic acid may include at least one of hydrochloric acid and sulfuric acid. These acids can effectively displace epoxy with a metal sulfinate containing an electron-withdrawing group to generate a sulfinic acid containing an electron-withdrawing group.

[0116] In some embodiments, the molar concentration of the metal sulfinate containing an electron-withdrawing group in the second solution is 0.8 - 2 mol / L, optionally 0.8 - 1.2 mol / L. In exemplary embodiments, it can be 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L and other typical but non-limiting molar concentrations or the range between any two molar concentration values. The concentration of the reactant such as the metal sulfinate containing an electron-withdrawing group within this concentration range can effectively improve the efficiency of the first displacement reaction treatment and reduce the generation amount of by-products.

[0117] In some embodiments, the second solution may include an organic solvent, such as at least one of acetonitrile, ethyl acetate, tetrahydrofuran, DMF and dimethyl sulfoxide. These organic solvents can effectively dissolve the metal sulfinate containing an electron-withdrawing group and the acid, and can effectively increase the yield of the target product of the sulfinic acid containing an electron-withdrawing group and reduce the generation of by-products.

[0118] In some embodiments, the temperature of the first displacement reaction in step S30 may be 25 - 40 °C, and the reaction time is 0.5 - 6 hours. In exemplary embodiments, the reaction temperature can be 25 °C, 28 °C, 30 °C, 32 °C, 35 °C, 38 °C, 40 °C and other typical but non-limiting temperatures or the range between any two temperature values; the reaction time can be 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours and other typical but non-limiting times or the range between any two time values. This temperature range and time range can effectively increase the yield of the sulfinic acid containing an electron-withdrawing group and reduce the generation amount of by-products.

[0119] In some embodiments, after the first displacement reaction treatment in step S30 is completed, it may further include a step of purifying the sulfinic acid containing an electron-withdrawing group. In an embodiment, the purification treatment may be to perform solid-liquid separation on the solution system after the first displacement reaction treatment, collect the filtrate, then add a water remover such as but not limited to anhydrous sodium sulfate to perform water removal and drying treatment on the filtrate, and then remove other solvents to obtain pure sulfinic acid containing an electron-withdrawing group.

[0120] Step S40:

[0121] In the first displacement reaction process in step S40, the hydrogen ions contained in the sulfinic acid with an electron-withdrawing group prepared in step S30 react with the lithium contained in the soluble lithium salt to generate a lithium sulfinate compound as shown in the molecular structural formula (Ⅰ). The specific chemical reaction formula is as follows:

[0122] R-SO2H+Li-X→R-SO2Li+M-X;

[0123] Among them, X is the anion contained in the soluble lithium salt.

[0124] In some embodiments, in the second displacement reaction treatment system of step S40, the molar ratio of the sulfinic acid with an electron-withdrawing group to the soluble lithium salt is 50-1000:(50-2000), optionally 50-300:(50-300). This molar ratio range of the sulfinic acid with an electron-withdrawing group to the soluble lithium salt can effectively displace the hydrogen in the sulfinic acid with an electron-withdrawing group with lithium, thereby increasing the yield of the lithium sulfinate compound; at the same time, on the basis of ensuring that the soluble lithium salt is appropriately in excess, reducing the amount of the soluble lithium salt used can reduce the economic cost.

[0125] In some embodiments, the soluble lithium salt may include at least one of lithium hydroxide, lithium carbonate, and lithium acetate. These soluble lithium salts can effectively react with the sulfinic acid with an electron-withdrawing group to generate a lithium sulfinate compound.

[0126] In some embodiments, the molar concentration of the sulfinic acid with an electron-withdrawing group in the polar solvent is 0.8-2 mol / L, optionally 0.8-1.2 mol / L. In exemplary embodiments, it can be 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, etc. typical but non-limiting molar concentrations or the range between any two molar concentration values. The concentration of the reactant such as the sulfinic acid with an electron-withdrawing group in this concentration range can effectively improve the efficiency of this second displacement reaction treatment and reduce the generation amount of by-products.

[0127] In some embodiments, when the soluble lithium salt is added to the polar solvent, the temperature of the polar solvent can be 0-10 °C. In exemplary embodiments, it can be 0 °C, 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, 10 °C, etc. typical but non-limiting temperatures or the range between any two temperature values. When adding the soluble lithium salt, controlling the temperature of the polar solvent within this range can prevent the solution temperature from rising rapidly. If the temperature is not controlled, the solution may be close to boiling, generating steam or splashing, increasing the operation risk.

[0128] In some embodiments, the polar solvent may include at least one of water, ethanol, and N,N-dimethylformamide. These polar solvents can effectively dissolve the sulfinic acid containing an electron-withdrawing group and the lithium salt, and can effectively improve the yield of the target product of the lithium sulfinate compound and reduce the generation of by-products.

[0129] In some embodiments, the temperature of the second substitution reaction in step S40 may be 25 to 60 °C, and the reaction time may be 0.5 to 3 hours. In exemplary embodiments, the reaction temperature may be typical but non-limiting temperatures such as 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, etc. or a range between any two temperature values; the reaction time may be typical but non-limiting times such as 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc. or a range between any two time values. This temperature range and time range can effectively improve the yield of the final product lithium sulfinate compound and reduce the amount of by-products generated.

[0130] In some embodiments, after the second substitution reaction in step S40 is completed, it may further include a step of purifying the lithium sulfinate compound. In an embodiment, the purification treatment may be a solid-liquid separation treatment of the solution system after the second substitution reaction, collecting the filter residue, and washing the filter residue, such as washing the filter residue with anhydrous ethanol multiple times, and then performing a drying treatment to obtain the final product and then adding the lithium sulfinate compound. Among them, the drying treatment may be a vacuum drying treatment, such as vacuum drying at 50 to 80 °C for 6 to 24 hours.

[0131] [Electrolyte]

[0132] In a third aspect, an embodiment of the present application further provides an electrolyte. The electrolyte of the embodiment of the present application includes an organic solvent and an electrolyte and an additive dissolved in the organic solvent, wherein the additive includes the lithium supplement additive in the above embodiment of the present application or the lithium supplement additive prepared by the preparation method of the lithium supplement additive in the above embodiment of the present application, that is, the additive contained in the electrolyte of the embodiment of the present application includes the above lithium sulfinate compound.

[0133] Thus, since the electrolyte of the embodiment of the present application contains the lithium supplement additive in the above embodiment of the present application. Therefore, the electrolyte of the embodiment of the present application contains the above lithium sulfinate compound, and the lithium sulfinate compound can release active lithium ions during the charge and discharge process of the lithium-ion battery, especially during the first charging process, providing a large amount of irreversible capacity to compensate for the irreversible Li consumed during the first charging process of the lithium-ion battery. +Losses are thus reduced, thereby improving the capacity and first Coulombic efficiency of the lithium-ion battery. At the same time, due to the electron-withdrawing groups contained in the lithium sulfinate compound, the electronic energy of the lowest unoccupied molecular orbital (LUMO) is reduced, the electronic energy gap between the highest occupied molecular orbital (HOMO) and LUMO is narrowed, and the conductivity of the lithium sulfinate compound is increased. It can preferentially react with the electrolyte in the electrolyte and participate in the formation of the SEI film at the electrode contact interface, thereby improving the cycling performance of the lithium-ion battery.

[0134] In some embodiments, the mass content of the lithium sulfinate compound in the electrolyte of the embodiments of the present application can be 0.05% to 5%, optionally 0.5% to 3%. In exemplary examples, it can be 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., typical but non-limiting contents or ranges between any two content values. The lithium sulfinate compound within this range of content can effectively increase the lithium supplement capacity, improve the stability and conductivity of the SEI film formed at the electrolyte-electrode contact interface, and improve the cycling performance of the battery.

[0135] In some embodiments, when the additives contained in the electrolyte of the embodiments of the present application contain other additives in addition to the lithium sulfinate compound, the other additives can be conventional electrolyte additives in the field of lithium-ion batteries, and can be specifically added according to needs.

[0136] The organic solvent contained in the electrolyte of the embodiments of the present application should be an organic solvent that can dissolve the electrolyte and additive components. For example, in the embodiments, the organic solvent can include at least one of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and ethyl methyl carbonate. These organic solvents have good stability and can effectively dissolve the lithium supplement additive of the embodiments of the present application above, specifically, can dissolve the lithium sulfinate compound.

[0137] The electrolyte contained in the electrolyte of the embodiments of the present application can be a conventional electrolyte for lithium-ion batteries.

[0138] [Electrode sheet]

[0139] Fourthly, the embodiments of the present application also provide an electrode sheet. The electrode sheet of the embodiments of the present application includes a current collector and an active material layer provided on at least one surface of the current collector. The active material layer includes an electrode active material and a lithium supplement agent, and the lithium supplement agent includes the lithium supplement additive of the embodiments of the present application above.

[0140] Since the electrode sheet in the embodiment of the present application contains the lithium supplement additive in the above-mentioned embodiment of the present application, the lithium sulfinate compound in the lithium supplement additive in the embodiment of the present application can exert the lithium supplement capacity, thereby improving the capacity and the first Coulombic efficiency of the lithium ion battery. Since the lithium sulfinate compound does not contain transition metals, after the lithium sulfinate compound is delithiated, the delithiated product thereof will not have an adverse side reaction with the electrolyte, thereby improving the capacity performance and safety of the lithium ion battery, effectively overcoming the problems of reduced cycle performance and gas generation of the lithium ion battery caused by the side reaction between the existing lithium supplement materials containing transition metals and the electrolyte, which lead to safety performance problems.

[0141] Meanwhile, since the electron-withdrawing group contained in the lithium sulfinate compound reduces the electron energy of its lowest unoccupied molecular orbital (LUMO) and narrows the electron energy gap between the highest occupied molecular orbital (HOMO) and LUMO, and it is arranged as a lithium supplement agent in the active material layer of the electrode sheet, the lithium sulfinate compound and other delithiated products can react with the infiltrated electrolyte to form a protective film layer at least on the surface of the electrode active material, which can improve the stability of the electrode active material during the insertion and extraction of lithium ions, thereby improving the capacity performance and cycle performance of the lithium ion battery.

[0142] In some embodiments, the mass ratio of the lithium sulfinate compound in the lithium supplement additive in the electrode sheet to the electrode active material in the electrode sheet can be 0.002-0.2:1, optionally 0.02-0.12:1. In exemplary examples, it can be 0.002:1, 0.01:1, 0.02:1, 0.05:1, 0.1:1, 0.12:1, 0.15:1, 0.2:1 and other typical but non-limiting mass ratios or the range between any two mass ratio values. The lithium sulfinate compound within this content range can effectively exert the lithium supplement capacity and improve the energy density and cycle performance of the lithium ion battery. When the electrode sheet is a positive electrode sheet, the mass ratio of the lithium sulfinate compound contained in the electrode sheet to the electrode active material in the electrode sheet is the mass ratio of the lithium sulfinate compound to the positive electrode active material in the electrode sheet.

[0143] In addition, the electrode active material contained in the electrode sheet in the embodiment of the present application can be a positive electrode active material. At this time, the electrode sheet in the embodiment of the present application is a positive electrode sheet. In the embodiment, the positive electrode current collector of the positive electrode sheet can be, but not limited to, any one of copper foil and aluminum foil. The positive electrode active material layer of the positive electrode sheet includes components such as a positive electrode active material, a binder, and a conductive agent. The content and material types of the positive electrode active material, the binder, and the conductive agent can be the conventional content and material types in the field of lithium ion batteries.

[0144] In the embodiments, the cathode active material in the cathode active material layer may include one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium fluorovanadate phosphate, lithium titanate, lithium nickel manganate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate.

[0145] In the embodiments, the content of the binder in the cathode active material layer may be 2 wt% - 4 wt%. In specific embodiments, the content of the binder may be typical but non-limiting contents such as 2 wt%, 3 wt%, 4 wt%, etc. In specific embodiments, the binder includes one or more of polyvinylidene fluoride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives.

[0146] In the embodiments, the content of the conductive agent in the cathode active material layer may be 3 wt% - 5 wt%. In specific embodiments, the content of the conductive agent may be typical but non-limiting contents such as 3 wt%, 4 wt%, 5 wt%, etc. In specific embodiments, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes.

[0147] In the embodiments, the preparation process of the cathode sheet may be: mixing the cathode active material, the conductive agent, the binder, and the lithium supplement additive to obtain a cathode slurry, coating the cathode slurry on a current collector, and preparing the cathode sheet through steps such as drying, rolling, and die-cutting.

[0148] [Battery]

[0149] In a fifth aspect, the embodiments of the present application further provide a lithium-ion battery. The lithium-ion battery in the embodiments of the present application includes necessary components such as a cathode sheet, an anode sheet, a separator disposed between the cathode sheet and the anode sheet, and an electrolyte, and of course also includes other necessary or auxiliary components. Among them, the cathode sheet includes the lithium supplement additive in the above embodiments of the present application, or / and the electrolyte is the electrolyte in the above embodiments of the present application.

[0150] Since the positive electrode sheet of the lithium-ion battery in the embodiment of the present application contains the lithium supplement additive in the above-mentioned embodiment of the present application, or the electrolyte contains the lithium supplement additive in the above-mentioned embodiment of the present application, or both the positive electrode sheet and the electrode liquid contain the lithium supplement additive in the above-mentioned embodiment of the present application. In this way, during the first charging process of the lithium-ion battery in the embodiment of the present application, the lithium sulfinate compound contained in at least one of the positive electrode sheet and the electrolyte will de-lithiate to provide active lithium ions, thereby improving the first efficiency and energy density of the lithium-ion battery. When the lithium sulfinate compound is contained in the positive electrode sheet, it and its product after de-lithiation can undergo a reduction reaction with the infiltrated electrolyte to form a protective film layer at least on the surface of the positive active material, improving the stability of the positive active material during the lithium insertion / extraction process, and it does not contain transition metals, thus avoiding adverse side reactions with the electrolyte; when the electrolyte contains the lithium sulfinate compound, it can preferably undergo a reduction reaction with the electrolyte and participate in the formation of the SEI film at the electrode / electrolyte interface. Therefore, the lithium supplement additive in the positive electrode sheet or / and the electrolyte in the embodiment of the present application effectively improves the cycle performance and safety of the lithium-ion battery.

[0151] The negative electrode sheet contained in the battery in the embodiment of the present application can be a conventional negative electrode sheet. When the negative electrode sheet is a lithium metal foil, the lithium battery in the embodiment of the present application can be a lithium metal battery.

[0152] The battery in the embodiment of the present application can be assembled according to the existing assembly methods of wound core batteries, cylindrical batteries, or laminated core batteries.

[0153] The following uses multiple specific examples to illustrate the lithium sulfinate compound, its preparation method, and the battery, etc. in the embodiment of the present application.

[0154] 1. Embodiment of the lithium supplement additive and its preparation method:

[0155] Embodiment A1:

[0156] This embodiment provides a lithium supplement additive and its preparation method. The lithium supplement additive includes a lithium sulfinate compound, and the molecular structural formula of the lithium sulfinate compound is shown as follows (Ⅰ1):

[0157]

[0158] The preparation method of the lithium sulfinate compound in this embodiment includes the following steps:

[0159] S1. Preparation of sodium cyanosulfinate: Under a nitrogen atmosphere, 1 mol of commercial lithium trifluoromethanesulfinate is dispersed in 1 L of acetonitrile solvent. 50 mmol of palladium acetate catalyst, 400 mmol of N-hydroxyphthalimide oxidant, and 3 mol of tert-butyl nitrite nitrogen source are all dispersed in the above acetonitrile solvent. The reaction temperature is controlled at 70 °C, and the reflux oxidation reaction is carried out for 24 hours. After the oxidation reaction is completed, filtration is carried out to remove the filter residue, the filtrate is collected, anhydrous sodium sulfate is added for drying, and the solvent is removed to obtain the lithium sulfinate compound containing a cyano group shown in the above molecular structural formula (Ⅰ1).

[0160] Example A2:

[0161] This example provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive includes a lithium sulfinate compound, and the molecular structural formula of the lithium sulfinate compound is as shown below (Ⅰ1):

[0162]

[0163] The preparation method of the lithium sulfinate compound in this example includes the following steps:

[0164] S1. Preparation of sodium cyanosulfinate: Under a nitrogen atmosphere, 1 mmol of commercial sodium trifluoromethanesulfinate is dispersed in 1 L of acetonitrile solvent. 50 mmol of palladium acetate catalyst, 400 mmol of N-hydroxyphthalimide oxidant, and 3 mol of tert-butyl nitrite nitrogen source are all dispersed in the above acetonitrile solvent. The reaction temperature is controlled at 70 °C, and the reflux oxidation reaction is carried out for 12 hours. After the oxidation reaction is completed, filtration is carried out to remove the filter residue, the filtrate is collected, anhydrous sodium sulfate is added for drying, and the solvent is removed to obtain sodium cyanosulfinate;

[0165] S2. Preparation of cyanous sulfonic acid: Take 200 mmol of sodium cyanosulfinate and add it to 200 ml of organic solvent, stir evenly, slowly dropwise add 10 ml of acid, and stir for 3 hours. After the reaction is completed, filtration is carried out to remove the precipitate, the filtrate is collected, anhydrous sodium sulfate is added for drying, and the solvent is removed to obtain cyanous sulfonic acid;

[0166] S3. Preparation of lithium cyanosulfinate: Dissolve the obtained 200 mmol of cyanous sulfonic acid in 200 ml of deionized water, add 200 mmol of lithium hydroxide at 5 °C, and stir at 40 °C for 2 hours. After the reaction is completed, filtration is carried out to obtain the filter residue solid, and the filter residue solid is washed three times with anhydrous ethanol. The obtained filter residue solid is placed in a vacuum oven and dried at 70 °C under vacuum for 15 hours to obtain the lithium sulfinate compound containing a cyano group shown in the molecular structural formula (Ⅰ1).

[0167] Example A3:

[0168] This embodiment provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive includes a lithium sulfinate compound, and the molecular structural formula of the lithium sulfinate compound is shown as follows (Ⅰ2):

[0169]

[0170] The preparation method of the lithium sulfinate compound in this embodiment includes the following steps:

[0171] S1. Dissolve 1 mol of sodium methylsulfinate in 1.5 L of 10% dilute sulfuric acid, cool it in an ice bath to 0 - 5 °C, and slowly add it dropwise to 300 mL of a 5 mol / L potassium dichromate (K2Cr2O7) solution. Control the temperature below 10 °C to prevent the excessive oxidation of the aldehyde group (-CHO) to carboxylic acid. Stir and react for 4 hours, and quench with 500 mL of saturated sodium sulfite solution until the orange - red color disappears (Cr 6+ is reduced to Cr 3+ ), extract with ethyl acetate, dry with 100 g of anhydrous sodium sulfate, concentrate under reduced pressure, add 200 mL of ether for recrystallization, and filter to obtain sodium aldehyde sulfinate (OHC - SO2Na);

[0172] S2. Prepare aldehyde sulfinic acid: Add 200 mmol of sodium nitrosulfinate to 200 ml of an organic solvent, stir evenly, slowly add 10 ml of acid dropwise, and stir for 3 hours; after the reaction is completed, filter to remove the precipitate, collect the filtrate, add anhydrous sodium sulfate for drying, and remove the solvent to obtain aldehyde sulfinic acid;

[0173] S3. Prepare lithium aldehyde sulfinate: Dissolve the obtained 200 mmol of aldehyde sulfinic acid in 200 ml of deionized water, add 200 mmol of lithium hydroxide at 5 °C, and stir at 40 °C for 2 hours; after the reaction is completed, filter to obtain the filter residue solid, and wash the filter residue solid three times with anhydrous ethanol; place the obtained filter residue solid in a vacuum oven and dry it at 70 °C under vacuum for 15 hours to obtain the lithium sulfinate compound containing an aldehyde group shown in the molecular structural formula (Ⅰ2).

[0174] Example A4:

[0175] This embodiment provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive includes a lithium sulfinate compound, and the molecular structural formula of the lithium sulfinate compound is shown as follows (Ⅰ3):

[0176]

[0177] The preparation method of the lithium sulfinate compound in this embodiment includes the following steps:

[0178] S1. React 1 mol of sodium methylsulfinate with 1.5 mol of sodium methoxide in 30 mL of DMF under argon protection at 120 °C for 24 hours. After cooling, add ether to obtain a precipitate, filter by suction and wash with ether to obtain sodium methoxysulfinate (CH3O-SO2Na).

[0179] S2. Prepare methoxysulfinic acid: Take 200 mmol of sodium methoxysulfinate and add it to 200 ml of an organic solvent, stir evenly, slowly dropwise add 10 ml of acid, and stir for 3 hours; after the reaction is completed, filter to remove the precipitate, collect the filtrate, add anhydrous sodium sulfate for drying, and remove the solvent to obtain methoxysulfinic acid;

[0180] S3. Prepare lithium methoxysulfinate: Dissolve the obtained 200 mmol of methoxysulfinic acid in 200 ml of deionized water, add 200 mmol of lithium hydroxide at 5 °C, and stir at 40 °C for 2 hours; after the reaction is completed, filter to obtain the solid residue, and wash the solid residue with absolute ethanol three times; place the obtained solid residue in a vacuum oven and dry it under vacuum at 70 °C for 15 hours to obtain the lithium sulfinate compound containing a methoxy group shown in the molecular structural formula (Ⅰ3).

[0181] Example A5:

[0182] This example provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive includes a lithium sulfinate compound, and the molecular structural formula of the lithium sulfinate compound is as shown below (Ⅰ4):

[0183]

[0184] The preparation method of the lithium sulfinate compound in this example includes the following steps:

[0185] S1. Mix 1 mol of sodium phenylsulfinate with 1.2 mol of bromobenzene in 500 mL of acetone, add 3 mol of potassium carbonate, and reflux and stir at 70 °C for 24 hours. After the reaction is completed, cool, filter to remove the inorganic salt, concentrate the filtrate under reduced pressure to dryness, and recrystallize the residue with ethanol:water = 1:1 to obtain sodium benzenesulfinate (C6H5SO2Na).

[0186] S2. Prepare benzenesulfinic acid: Take 200 mmol of sodium benzenesulfinate and add it to 200 ml of an organic solvent, stir evenly, slowly dropwise add 10 ml of acid, and stir for 3 hours; after the reaction is completed, filter to remove the precipitate, collect the filtrate, add anhydrous sodium sulfate for drying, and remove the solvent to obtain benzenesulfinic acid;

[0187] S3. Preparation of lithium phenylsulfinate: Dissolve 200 mmol of phenylsulfinic acid obtained in 200 ml of deionized water, add 200 mmol of lithium hydroxide at 5°C, and stir at 40°C for 2 hours; after the reaction is completed, filter to obtain the filter residue solid, and wash the filter residue solid three times with absolute ethanol; place the obtained filter residue solid in a vacuum oven and dry it under vacuum at 70°C for 15 hours to obtain the lithium sulfinate compound containing phenyl as shown in the molecular structural formula (Ⅰ4).

[0188] Example A6:

[0189] This example provides a lithium supplement additive and a preparation method thereof. The lithium supplement additive includes a lithium sulfinate compound, and the molecular structural formula of the lithium sulfinate compound is as shown below (Ⅰ5):

[0190]

[0191] The preparation method of the lithium sulfinate compound in this example includes the following steps:

[0192] S1. React 1 mol of sodium methylsulfinate, 1.5 mol of vinyl bromide, 0.05 mol of Pd(OAc)2 and 3 mol of triethylamine in 500 mL of dimethylacetamide under nitrogen protection at 110°C for 12 hours, decolorize with activated carbon and recrystallize with ethanol to obtain sodium vinylsulfinate (CH2=CH-SO2Na).

[0193] S2. Preparation of vinylsulfinic acid: Take 200 mmol of sodium vinylsulfinate and add it to 200 ml of organic solvent, stir evenly, slowly dropwise add 10 ml of acid, and stir for 3 hours; after the reaction is completed, filter to remove the precipitate, collect the filtrate, add anhydrous sodium sulfate for drying, and remove the solvent to obtain vinylsulfinic acid;

[0194] S3. Preparation of lithium vinylsulfinate: Dissolve 200 mmol of vinylsulfinic acid obtained in 200 ml of deionized water, add 200 mmol of lithium hydroxide at 5°C, and stir at 40°C for 2 hours; after the reaction is completed, filter to obtain the filter residue solid, and wash the filter residue solid three times with absolute ethanol; place the obtained filter residue solid in a vacuum oven and dry it under vacuum at 70°C for 15 hours to obtain the lithium sulfinate compound containing vinyl as shown in the molecular structural formula (Ⅰ5).

[0195] 2. Examples of lithium supplement additives, electrolytes and lithium-ion batteries:

[0196] Examples B1 to B7 and Comparative Examples B1 to B3 in this example respectively provide a lithium-ion battery. Each lithium-ion battery is assembled according to the following method:

[0197] 1) Positive electrode sheet:

[0198] Positive electrode sheets of lithium-ion batteries in Examples B1 to B7:

[0199] Using the lithium sulfinate compounds provided in Examples A2 to A6 as the positive electrode lithium supplement additives in the lithium-ion batteries of Examples B1 to B6 respectively, under the same conditions, according to the mass ratio of lithium iron phosphate cathode material: Su-P conductive agent: PVDF binder: positive electrode lithium supplement additive of 8:1:1:0.24, they were mixed and treated in an appropriate amount of NMP to prepare a positive electrode slurry; then, through the operations of homogenization - coating - drying - cutting, positive electrode sheets were prepared respectively, and the positive electrode sheets were baked in a vacuum oven at 100 °C to remove trace water. Among them, compared with the positive electrode sheet of Example B1, the positive electrode sheet of Example B7 does not contain a positive electrode lithium supplement additive.

[0200] Positive electrode sheets of lithium-ion batteries in Comparative Examples B1 to B3:

[0201] Positive electrode sheet of Comparative Example B1: Compared with the positive electrode sheet of the lithium-ion battery in Example B1, the Li5FeO4 lithium supplement additive was used to replace the lithium sulfinate compound in Example B1.

[0202] Positive electrode sheets of Comparative Examples B2 to B3: Compared with the positive electrode sheet of the lithium-ion battery in Example B1, no lithium supplement agent was added;

[0203] 2) Negative electrode sheet: The negative electrode active material graphite, conductive agent Super P, thickening agent carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) were mixed evenly in deionized water to prepare a negative electrode slurry, where the mass ratio of graphite: Super P: CMC: SBR was 95:2:0.5:2.5. The negative electrode slurry was coated on the current collector copper foil, and after drying - rolling - secondary drying processes, a negative electrode sheet was made.

[0204] 3) Separator: A polyethylene (PE) separator was used.

[0205] 4) Electrolytes of lithium-ion batteries in Examples B1 to B6 and Comparative Examples B1 to B2: The electrolyte was a 1 mol / L LiPF6 solution, and the solvent was composed of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1;

[0206] Electrolyte of the lithium-ion battery in Example B7: The electrolyte was 1 mol / L LiPF6, the additive was 0.5% of the cyanolithium sulfinate compound (cyanolithium sulfinate in Example A2), and the solvent was composed of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1;

[0207] Electrolyte of the lithium-ion battery in Comparative Example B3: The electrolyte is a 1 mol / L LiPF6 solution, the additive is 0.5% lithium methylsulfonate, and the solvent is composed of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1;

[0208] 5) Assembly of the secondary battery:

[0209] Assemble the above positive electrode sheet, negative electrode sheet, electrolyte and separator into a lithium-ion battery according to the assembly requirements of the lithium-ion battery.

[0210] Detection of relevant performance of the lithium-ion battery:

[0211] Conduct the relevant performance tests on the positive electrode slurries and lithium-ion batteries of each example and comparative example assembled in Section 5) as shown in Table 2 below, and the measured results are shown in Table 1 below.

[0212] Among them, the relevant performance test methods in Table 1 are as follows:

[0213] Detection method for the initial Coulomb efficiency of the lithium-ion battery: In a constant temperature environment of 25 °C, charge the battery at a current of 0.1C in the voltage range of 2.0V to 4.1V until the voltage reaches 4.1V, then charge the battery at a constant voltage of 4.1V until the current reaches 0.01C, and record the capacity as C1; Let the battery stand for 5 minutes, then discharge the battery at a current of 0.1C until the voltage reaches 2.0V, and record the capacity of the lithium-ion battery at a discharge rate of 0.1C as D1; The initial cycle Coulomb efficiency is calculated as: Initial Coulomb efficiency = D1 / C1.

[0214] Detection method for the capacity retention rate of the lithium-ion battery: Conduct the first charge-discharge cycle in a constant temperature environment of 25 °C, charge the battery at a constant current of 1C (the current at which the nominal capacity of the battery is completely discharged within 2 hours) until the voltage reaches the upper limit of 4.1V, then charge at a constant voltage until the current reaches 0.05C, let the battery stand for 5 minutes, and then discharge the battery at a constant current of 1C until the voltage finally reaches 2.0V and record the discharge capacity of the first cycle; Subsequently, continuously repeat the charge and discharge cycles; Calculate the capacity retention rate at the end of the 2000th cycle of the fully charged battery cycled at 25 °C, that is, 2000-cycle capacity retention rate = (discharge capacity at the 2000th cycle / discharge capacity of the first cycle) × 100%.

[0215] High-temperature storage gas generation test method: After assembling the gas generation battery device, perform formation on the battery to discharge the generated gas, place the formed gas generation battery device in a constant temperature environment of 45 °C for 48h, and use differential electrochemical mass spectrometry to detect the amount of gas generated inside the gas generation battery device to obtain the total gas generation amount.

[0216] Table 1

[0217]

[0218] It can be seen from the test results in Table 1 that: from the results of Example B1 and Comparative Example B2, it can be seen that adding a lithium sulfinate compound as a lithium supplement is beneficial to increasing the initial discharge capacity and improving the capacity retention rate.

[0219] It can be seen from Example B1 and Comparative Example B1 that the initial discharge capacity and capacity retention rate of Comparative Example B1 are higher than those of Example B1. This is because Li5FeO4 added in Comparative Example B1 has a relatively high theoretical capacity, so it has a better lithium supplement effect. However, it can be seen from the gas generation amount during high-temperature aging that the gas generation amount of Comparative Example B1 during high-temperature aging is much larger than that of Comparative Example B2 and Example B1. This indicates that the residue after the decomposition of Li5FeO4 will undergo side reactions with the electrolyte at high temperatures, while there is no significant difference in the gas generation amount during high-temperature aging between Example B1 and Comparative Example B2, indicating that most of the lithium sulfinate lithium supplement decomposes into gases and the residue does not react with the electrolyte.

[0220] It can be seen from the results of Example B1 and Example B2 that there is no significant difference in the initial discharge capacity, capacity retention rate, and gas generation amount during high-temperature aging between the two, indicating that the preparation method has no significant effect on the lithium supplement effect of the lithium sulfinate lithium supplement.

[0221] It can be seen from Example B1 to Example B6 that as the mass of the substituent group increases, the initial discharge capacity and capacity retention rate decrease. This is because as the mass of the substituent group increases, the theoretical capacity of the lithium sulfinate lithium supplement material decreases, so the lithium supplement effect weakens.

[0222] It can be seen from Example B1 to Example B6 that as the electron-withdrawing ability of the substituent group increases, the charging voltage platform of the pure lithium supplement material decreases. This is because the electron-withdrawing group is beneficial to the decrease of the LUMO value, thereby reducing the gap between the LUMO value and the HOMO value and improving the conductivity of the material.

[0223] It can be seen from Example B2 and Example B7 that directly adding the same lithium sulfinate lithium supplement to the cathode material has a better lithium supplement effect than adding it to the electrolyte. This is because the solubility of the lithium sulfinate lithium supplement in the electrolyte is limited, so the addition amount is relatively low and the lithium supplement capacity is relatively low.

[0224] From the LSV test results of Example B7, Comparative Example B2, and Comparative Example B3, it can be seen that with the introduction of the electron-withdrawing group -CN, the reduction peak advances to 2.3 V, indicating that the decomposition products of lithium cyanosulfinate undergo reduction reaction earlier than the electrolyte components and participate in the formation of SEI. This is because the cyano group is an electron-withdrawing group, which is beneficial to the reduction of the LUMO value. A lower LUMO value means that it is easier to accept electrons, can participate in the formation of the electrode / electrolyte interface, and enables the substances remaining after the de-lithiation of lithium cyanosulfinate to play a role.

[0225] The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A lithium supplement additive, characterized in that, It includes a lithium sulfinate compound, and the molecular structural formula of the lithium sulfinate compound is shown as the following general formula (I): Among them, the group represented by R in the general formula (I) includes an electron-withdrawing group.

2. The lithium supplement additive according to claim 1, wherein The electronegativity of the electron-withdrawing group is 2 to 5; and / or The electron-withdrawing group includes at least one of -CN, alkenyl, alkynyl, -OX, aryl, -CCl3, -CF3, -CHO, -COR, -COOH; among them, X in -OX is at least one of methyl, ethyl and propyl, and R in -COR is an alkyl group.

3. The lithium supplement additive according to claim 2, wherein The alkenyl includes at least one of vinyl, allyl and 2-butene; and / or The alkynyl includes at least one of ethynyl, propynyl and butynyl; and / or The -OX includes at least one of -OCH3, -OC2H5 and -OC3H7.

4. The lithium supplement additive according to any one of claims 1 to 3, characterized in that, The electron energy of the lowest unoccupied molecular orbital of the lithium sulfinate compound is -2 to -5 eV; and / or The difference between the electron energy of the highest occupied molecular orbital and the electron energy of the lowest unoccupied molecular orbital of the lithium sulfinate compound is -2.8 to -7 eV.

5. The lithium supplement additive according to any one of claims 1 to 3, characterized in that The lithium supplement additive further includes at least one of a conductive carbon material and a transition metal oxide.

6. A preparation method of a lithium supplement additive, characterized in that, It includes the following steps for preparing a lithium sulfinate compound: Reacting an organic lithium sulfinate salt with a compound containing an electron-withdrawing group source or an electron-withdrawing group precursor in a first solution to generate a lithium sulfinate compound containing an electron-withdrawing group; and / or Reacting an organic metal sulfinate salt with a compound containing an electron-withdrawing group source or an electron-withdrawing group precursor in a first solution to generate a metal sulfinate salt containing an electron-withdrawing group; Performing a first displacement reaction on the metal sulfinate salt and an acid in a second solution to generate a sulfinic acid containing an electron-withdrawing group; Performing a second displacement reaction on the sulfinic acid and a soluble lithium salt in a polar solvent to generate a lithium sulfinate compound containing an electron-withdrawing group; Among them, the metal ion contained in the organic metal sulfinate salt is a non-lithium metal ion, and the molecular structural formula of the lithium sulfinate compound is shown as the following general formula (I): The group represented by R in the general formula (I) includes the electron-withdrawing group.

7. An electrolyte, comprising an additive, characterized in that, The additive includes the lithium supplement additive according to any one of claims 1 to 4 or the lithium supplement additive prepared by the preparation method according to claim 6.

8. The electrolyte according to claim 7, wherein The mass ratio of the lithium sulfinate compound in the electrolyte is 0.05% to 5%.

9. An electrode sheet, characterized in that: It includes a current collector and an active material layer provided on at least one surface of the current collector, and the active material layer includes the lithium supplement additive according to any one of claims 1 to 5 or the lithium supplement additive prepared by the preparation method according to claim 6.

10. The electrode sheet according to claim 9, wherein, The mass ratio of the lithium sulfinate compound in the lithium supplement additive to the electrode active material in the active material layer is 0.005 to 0.1:

1.

11. A lithium-ion battery, comprising a positive electrode sheet and an electrolyte infiltrating the positive electrode sheet, characterized in that, The positive electrode sheet is an electrode sheet including the one according to claim 9, and the active material layer includes a positive electrode active material; and / or, the electrolyte is the electrolyte according to claim 7 or 8.

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