WO2018149211A1 - Electrolyte containing pyridine ring lithium sulfonyl imide and battery using electrolyte - Google Patents

Abstract

Disclosed is an electrolyte containing a pyridine ring lithium sulfonyl imide, the electrolyte comprising a conductive lithium salt, a non-aqueous organic solvent and additives, wherein the conductive lithium salt comprises a pyridine ring lithium sulfonyl imide, and the general structural formula of the pyridine ring lithium sulfonyl imide is AA, wherein R1-4 = F, CF3, C2F5, C4F9, C6F13, CF3O, CF3CH2O,(CF3)2CHO, or CN; R5 = F, CF3, C2F5, C4F9, C6F13, CF3O, CF3CH2O, (CF3)2CHO, or BB; R1-4 may be the same or different; and a sulfonic acid group on the pyridine ring may be located at the ortho- position, or may also be at the meta- or para- position. The above-mentioned pyridine ring lithium sulfonyl imide has a better thermostability and hydrolysis resistance, and can bind transition metal ions dissolved in the electrolyte and free HF so as to avoid the electrodeposition of these metal ions onto the surface of a negative electrode and also avoid HF damaging an SEI film, this affecting the service life and safety performance of a battery.

Description

Electrolyte containing lithium pyridine ring sulfonimide and battery using the same Technical field

The present invention relates to the field of lithium secondary batteries, and more particularly to an electrolyte containing lithium pyridine ring sulfonimide and a lithium secondary battery using the same.

Background technique

Non-aqueous electrolyte is one of the key materials for energy storage devices such as high-energy lithium-ion batteries. Its comprehensive properties, such as chemical and electrochemical stability, safety, etc., directly affect the use of lithium-ion batteries. At present, the commercial lithium-ion battery electrolyte mainly consists of organic carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), etc., electrolyte conductive salts (mainly LiPF ₆ ) , functional additives, such as vinylene carbonate (VC), 1,3-propane sultone (PS), fluoroethylene carbonate (FEC) and the like. The electrolyte solvent system mainly adjusts the formulation ratio, and the new additive and lithium salt are the key and core technologies of the electrolyte material. LiPF ₆ is widely used in electrolytes, but LiPF _{6 has a} low decomposition temperature (especially when the impurity content is high), and it is prone to hydrolysis reaction, which makes the lithium ion battery work at high temperature (>55 ° C), cycle performance and service life. Greatly reduced. Therefore, research and development of chemical stability (such as thermal stability, water stability, etc.), electrochemical properties (such as high conductivity, wide electrochemical window, non-corrosive to aluminum foil, etc.) excellent new conductive lithium salt electrolyte The replacement of the traditional lithium salt LiPF ₆ by materials is an important research direction for the development of large-scale power batteries and large-scale energy storage electronic devices.

Summary of the invention

In view of the problems of the prior art, it is an object of the present invention to provide a use of lithium pyridine ring sulfonimide, that is, as an electrolyte in lithium batteries and lithium ion batteries.

In order to achieve the above technical solution, the present invention provides an electrolyte containing lithium pyridine ring sulfonimide, comprising a conductive lithium salt, a non-aqueous organic solvent and an additive, and the conductive lithium salt comprises lithium pyridine cyclosulfonimide, pyridine ring sulfonate The structure of lithium imide is:

among them,

R _1-4 =F, CF ₃ , C ₂ F ₅ , C ₄ F ₉ , C ₆ F ₁₃ , CF ₃ O, CF ₃ CH ₂ O, (CF ₃ ) ₂ CHO, CN;

R ₅ =F, CF ₃ , C ₂ F ₅ , C ₄ F ₉ , C ₆ F ₁₃ , CF ₃ O, CF ₃ CH ₂ O, (CF ₃ ) ₂ CHO,

R _1-4 may be the same or different;

The sulfonic acid group on the pyridine ring may be in the ortho position or in the meta or para position.

The conductive lithium salt further includes LiBF ₄ , LiPF ₆ , LiPF ₂ O ₂ , LiAsF ₆ , LiClO ₄ , LiSO ₃ CF ₃ , LiB(C ₂ O ₄ ) ₂ , LiBF ₂ C ₂ O ₄ , LiN (SO ₂ CF ₃ ) ₂ , one or more of LiN(SO ₂ F) ₂ .

The non-aqueous organic solvent is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate. One or more of ester, ethyl propionate, propyl propionate, and butyl propionate.

The additive is vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, 1,3-propane sultone, 1,4-butane sultone, ethylene sulfate One or more of an ester, propylene sulfate, vinyl sulfite, and propylene sulfite.

A lithium secondary battery comprising: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte solution containing lithium pyridine ring sulfonimide according to the present invention; the positive electrode sheet and the negative electrode sheet comprise an active material, a conductive agent, a current collector, and a binder of the active material and a conductive agent in combination with the current collector.

The positive electrode sheet includes a positive electrode active material capable of reversibly intercalating/deintercalating lithium ions, and the positive electrode active material is preferably a composite metal oxide of lithium, and the metal oxide includes an oxide of nickel, cobalt, manganese, and any combination thereof; The positive active material further includes one or several of chemical elements including Mg, Al, Ti, Sn, V, Ge, Ga, B, Zr, Cr, Fe, Sr, and rare earth elements; The active material further includes a polyanionic lithium compound LiM _x (PO ₄ ) _y (M is Ni, Co, Mn, Fe, Ti, V, 0 _{≤ x} ≤ ₅ , 0 _{≤ y ≤} 5).

The negative electrode sheet includes a negative electrode active material capable of accepting or releasing lithium ions, and the negative electrode active material includes lithium metal, lithium alloy, crystalline carbon, amorphous carbon, carbon fiber, hard carbon, soft carbon; wherein the crystalline carbon includes natural graphite, Graphitized coke, graphitized MCMB, graphitized mesophase pitch carbon fiber; the lithium alloy includes an alloy of lithium and aluminum, zinc, silicon, tin, gallium, and ruthenium.

The advantages of the present invention over the prior art are:

(1) The innovation of the present invention is that in the prepared pyridine ring sulfonimide anion, due to the conjugated structure of the SO ₂ -N-SO ₂ group, such anions have negative charge dispersion and good structural flexibility. Moreover, the -SO ₂ - group at both ends can also effectively shield the negative charge on the N atom. Therefore, such an imide anions exhibit weak coordination properties, thereby effectively improving the conductivity, dissociation constant, and migration number of the cation of the pyridine cyclosulfonimide lithium electrolyte.

(2) The anion contains a pyridine ring, and the N atom in the pyridine ring structure has a strong complexing ability, and can combine the transition metal ions dissolved in the electrolyte and the free HF to prevent electrodeposition of these metal ions on the surface of the negative electrode. At the same time, HF is prevented from damaging the SEI film, which affects the service life and safety performance of the battery.

Specific embodiment

The invention is specifically illustrated by the following exemplary embodiments. It is to be understood that the scope of the invention should not be limited to the scope of the embodiments. Any changes or modifications that do not depart from the gist of the invention can be understood by those skilled in the art. The scope of the invention is determined by the scope of the appended claims.

Example 1

(1) Preparation of electrolyte

In an argon atmosphere glove box (H ₂ O <1 ppm), the organic solvent is in a mass ratio of EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 40:40: 20 mixed with lithium (2-pyridinesulfonyl)imide (1.0 M), adding 1% by weight of VC (vinylene carbonate), 2% of PS (propane sultone), 3% of FEC (fluorine Vinyl carbonate), 3% SN (succinonitrile). Each of the above raw materials was sequentially added, and the mixture was thoroughly stirred to obtain a lithium secondary battery electrolyte (free acid <15 ppm, moisture <10 ppm) according to the present invention.

(2) Preparation of positive electrode tab

Dissolving 3% by mass of polyvinylidene fluoride (PVDF) in 1-methyl-2-pyrrolidone solution, adding 94% by mass of LiCoO ₂ and 3% of conductive carbon black to the above solution and mixing well. The mixed slurry was coated on both sides of the aluminum foil, and dried and rolled to obtain a positive electrode tab. Other positive electrode materials LiMn ₂ O ₄ , LiFePO ₄ , LiNi _0.5 Co _0.3 Mn _0.2 , and LiNi _0.3 Co _0.3 Mn _0.3 were prepared in the same manner.

(3) Preparation of negative electrode tab

4% by mass of SBR binder, 1% by mass of CMC thickener dissolved in aqueous solution, 95% by mass of graphite was added to the above solution, uniformly mixed, and the mixed slurry was coated. After being coated on both sides of the copper foil, the negative electrode tab is obtained after drying and rolling. The other negative electrode material Li ₄ Ti ₅ O _{12 was} prepared in a similar manner.

(4) Production of lithium ion battery

The positive electrode piece, the negative electrode piece and the separator prepared above are formed into a square electric core by winding, and the electrolyte prepared by the above is filled with a polymer package, and a lithium ion battery having a capacity of 1600 mAh is formed by a process such as formation. .

(5) Battery performance test

Cyclic test conditions: charge and discharge cycle test of the battery at 1/1C charge and discharge rate; high temperature storage test conditions: firstly, the completed battery is charged and discharged at 1C under normal temperature, and then fully charged with 1C. After high temperature storage, after the battery is completely cooled, the discharged battery is tested for discharge at 1C.

Examples 2 to 16 are the same as in Example 1 except for the following table parameters.

Table 1 Examples 2 to 14 and Comparative Examples 1 to 7

From the results of Examples 1 to 10 and Comparative Examples 1 to 7, it can be seen that the battery using lithium pyridine cyclosulfonimide has higher cycle performance and storage performance than the battery using LiPF ₆ in the case where the solvent and the additive components are the same. It’s better. From the results of Examples 11, 12 and Comparative Examples 1, 4, it can be seen that lithium pyridine cyclosulfonimide and LiPF _{6 are} used as a conductive lithium salt, and the cycle performance and storage performance of the corresponding battery are also higher than those of LiPF ₆ alone. The battery is superior. From the results of Examples 13, 14 and Comparative Examples 6, 7, it can be seen that the chemical and electrochemical stability of the lithium salt has a more pronounced effect on the performance of the battery in the case where the additive in the electrolyte formulation is less. The difference in battery performance between Examples 1 to 11 and Comparative Examples 1 to 5 is mainly due to the fact that lithium pyridine cyclosulfonimide has more stable chemical properties than LiPF ₆ during the operation of the battery, especially in It can maintain its own chemical stability at high temperatures, and does not produce Lewis acid impurities such as PF ₅ , which affects the service life of the battery. The difference in battery performance between Examples 11 and 12 and Comparative Examples 1 and 4 is mainly due to the fact that the pyridine ring in the lithium pyridine sulfonimide structure can adsorb hydrofluoric acid which is free in the electrolyte, effectively avoiding hydrogen. Fluoric acid destroys the SEI film and affects the life of the battery.

Claims (10)

1. An electrolyte containing lithium pyridine ring sulfonimide, the electrolyte comprising a conductive lithium salt, a non-aqueous organic solvent and an additive, wherein the conductive lithium salt comprises lithium pyridine cyclosulfonimide, a pyridine ring The structural formula of lithium sulfonimide is:

   
2. The electrolyte containing lithium pyridine ring sulfonimide according to claim 1, wherein R _1-4 = F, CF ₃ , C ₂ F ₅ , C ₄ F ₉ , C ₆ F ₁₃ , CF ₃ O, CF ₃ CH ₂ O, (CF ₃ ) ₂ CHO, CN, R _1-4 may be the same or different.
3. The electrolyte containing lithium pyridine ring sulfonimide according to claim 1 or 2, wherein R ₅ = F, CF ₃ , C ₂ F ₅ , C ₄ F ₉ , C ₆ F ₁₃ , CF ₃ O, CF ₃ CH ₂ O, (CF ₃ ) ₂ CHO,

   
4. The electrolyte containing lithium pyridine ring sulfonimide according to claim 1, wherein the sulfonic acid group on the pyridine ring may be in the ortho position or may be in the meta or para position.
5. The electrolyte containing lithium pyridine ring sulfonimide according to claim 1, wherein the conductive lithium salt further comprises LiBF ₄ , LiPF ₆ , LiPF ₂ O ₂ , LiAsF ₆ , LiClO ₄ , LiSO ₃ CF ₃ , one or more of LiB(C ₂ O ₄ ) ₂ , LiBF ₂ C ₂ O ₄ , LiN(SO ₂ CF ₃ ) ₂ , and LiN(SO ₂ F) ₂ .
6. The electrolyte containing lithium pyridine ring sulfonimide according to claim 1, wherein the non-aqueous organic solvent is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and carbonic acid. Ethyl ester, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate or one or more.
7. The electrolyte containing lithium pyridine ring sulfonimide according to claim 1, wherein the additive is vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate. , one or more of 1,3-propane sultone, 1,4-butane sultone, vinyl sulphate, propylene sulfate, vinyl sulfite, propylene sulfite.
8. A lithium secondary battery comprising: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte solution containing lithium pyridine ring sulfonimide according to any one of claims 1 to 7; wherein the positive electrode sheet and the negative electrode sheet comprise an active material a conductive agent, a current collector, a binder that binds the active material and the conductive agent to the current collector.
9. The lithium secondary battery according to claim 8, wherein the positive electrode sheet comprises a positive electrode active material capable of reversibly intercalating/deintercalating lithium ions, and the positive electrode active material is a composite metal oxide of lithium, the metal oxide The material includes an oxide of nickel, cobalt, manganese and any combination thereof in proportion; the positive active material further includes one or several of chemical elements including Mg, Al, Ti, Sn, V , Ge, Ga, B, Zr, Cr, Fe, Sr and rare earth elements; the positive active material further comprises a polyanionic lithium compound LiM _x (PO ₄ ) _y (M is Ni, Co, Mn, Fe, Ti, V, 0 ≤ x ≤ 5, 0 ≤ y ≤ 5).
10. The lithium secondary battery according to claim 8, wherein the negative electrode sheet comprises a negative electrode active material capable of accepting or releasing lithium ions, and the negative electrode active material comprises lithium metal, lithium alloy, crystalline carbon, amorphous carbon. Carbon fiber, hard carbon, soft carbon; wherein the crystalline carbon comprises natural graphite, graphitized coke, graphitized MCMB, graphitized mesophase pitch carbon fiber; the lithium alloy comprises lithium and aluminum, zinc, silicon, tin, gallium , an alloy of base metals.