DISPERSANT FOR LITHIUM ION BATTERY AND PREPARATION METHOD THEREOF, POSITIVE SLURRY, AND LITHIUM ION BATTERY

Abstract

A dispersant for a lithium ion battery and a preparation method thereof, a positive slurry, and a lithium ion battery are provided. The dispersant includes a structural unit A derived from a solvophilic monomer, a structural unit B derived from a conjugated diene monomer, and a structural unit C derived from a high-adhesion monomer. The solvophilic monomer includes one or both of N-vinylpyrrolidone and an acrylamide monomer. The high-adhesion monomer includes one or both of an unsaturated nitrile monomer and an acrylate monomer.

Claims

1. A dispersant for a lithium ion battery, the dispersant comprising a structural unit A derived from a solvophilic monomer, a structural unit B derived from a conjugated diene monomer, and a structural unit C derived from a high-adhesion monomer, wherein the solvophilic monomer comprises one or both of N-vinylpyrrolidone and an acrylamide monomer; and the high-adhesion monomer comprises one or both of an unsaturated nitrile monomer and an acrylate monomer.

2. The dispersant according to claim 1, wherein based on a total amount of the dispersant, a molar proportion of the structural unit A is in a range of 5%-50%, a molar proportion of the structural unit B is in a range of 30%-90%, and a molar proportion of the structural unit C is in a range of 1%-30%.

3. The dispersant according to claim 1, wherein the acrylamide monomer comprises one or more of acrylamide, methylacrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, N-butoxymethylacrylamide, N-hydroxymethylmethylacrylamide, and N-butoxymethylmethylacryl amide.

4. The dispersant according to claim 2, wherein the acrylamide monomer comprises one or more of acrylamide, methylacrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, N-butoxymethylacrylamide, N-hydroxymethylmethylacrylamide, and N-butoxymethylmethylacryl amide.

5. The dispersant according to claim 1, wherein the unsaturated nitrile monomer comprises one or more of acrylonitrile, α-methacrylonitrile, α-ethylacrylonitrile, butenenitrile, 2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile, 4-methyl -3-pentanenitrile, α-chloroacrylonitrile, α-bromoacrylonitrile, 2-ethoxyacrylonitrile, and 3,3-dimethoxy-2-acrylonitrile; the acrylate monomer comprises one or more of alkyl acrylate, alkyl methacrylate, hydroxyalkyl acrylate, and hydroxyalkyl methacrylate; and the conjugated diene monomer comprises one or more of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-decadiene, and 2-methyl-1,5-heptadiene.

6. The dispersant according to claim 2, wherein the unsaturated nitrile monomer comprises one or more of acrylonitrile, α-methacrylonitrile, α-ethylacrylonitrile, butenenitrile, 2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile, 4-methyl-3-pentanenitrile, α-chloroacrylonitrile, α-bromoacrylonitrile, 2-ethoxyacrylonitrile, and 3,3-dimethoxy-2-acrylonitrile; the acrylate monomer comprises one or more of alkyl acrylate, alkyl methacrylate, hydroxyalkyl acrylate, and hydroxyalkyl methacrylate; and the conjugated diene monomer comprises one or more of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-decadiene, and 2-methyl-1,5-heptadiene.

7. The dispersant according to claim 3, wherein the unsaturated nitrile monomer comprises one or more of acrylonitrile, α-methacrylonitrile, α-ethylacrylonitrile, butenenitrile, 2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile, 4-methyl-3-pentanenitrile, α-chloroacrylonitrile, α-bromoacrylonitrile, 2-ethoxyacrylonitrile, and 3,3-dimethoxy-2-acrylonitrile; the acrylate monomer comprises one or more of alkyl acrylate, alkyl methacrylate, hydroxyalkyl acrylate, and hydroxyalkyl methacrylate; and the conjugated diene monomer comprises one or more of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-decadiene, and 2-methyl-1,5-heptadiene.

8. The dispersant according to claim 4, wherein the unsaturated nitrile monomer comprises one or more of acrylonitrile, α-methacrylonitrile, α-ethylacrylonitrile, butenenitrile, 2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile, 4-methyl-3-pentanenitrile, α-chloroacrylonitrile, α-bromoacrylonitrile, 2-ethoxyacrylonitrile, and 3,3-dimethoxy-2-acrylonitrile; the acrylate monomer comprises one or more of alkyl acrylate, alkyl methacrylate, hydroxyalkyl acrylate, and hydroxyalkyl methacrylate; and the conjugated diene monomer comprises one or more of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 1,3-decadiene, and 2-methyl-1,5-heptadiene.

9. The dispersant according to claim 1, wherein a weight average molecular weight of the dispersant is in a range of 100000-600000.

10. The dispersant according to claim 2, wherein a weight average molecular weight of the dispersant is in a range of 100000-600000.

11. The dispersant according to claim 3, wherein a weight average molecular weight of the dispersant is in a range of 100000-600000.

12. The dispersant according to claim 4, wherein a weight average molecular weight of the dispersant is in a range of 100000-600000.

13. The dispersant according to claim 5, wherein a weight average molecular weight of the dispersant is in a range of 100000-600000.

14. The dispersant according to claim 6, wherein a weight average molecular weight of the dispersant is in a range of 100000-600000.

15. A method for preparing a dispersant for a lithium ion battery, comprising: performing a polymerization reaction on a monomer raw material comprising a solvophilic monomer, a conjugated diene monomer, and a high-adhesion monomer to obtain the dispersant for a lithium ion battery, wherein the solvophilic monomer comprises one or both of N-vinylpyrrolidone and an acrylamide monomer; and the high-adhesion monomer comprises one or both of an unsaturated nitrile monomer and an acrylate monomer.

16. The method according to claim 15, wherein the preparation method further comprises: performing a hydrogenation reaction on polymer formed through the polymerization reaction of the monomer raw material.

17. The method according to claim 15, wherein based on a total mass of the monomer raw material, a proportion of the solvophilic monomer is in a range of 5%-50%, a proportion of the conjugated diene monomer is in a range of 40%-90%, and a proportion of the high-adhesion monomer is in a range of 1%-20%.

18. A positive slurry, comprising a positive active material, a conductive agent, a dispersant, and a solvent, wherein the dispersant is the dispersant according to claim 1.

19. The positive slurry according to claim 18, wherein a mass fraction of the dispersant in the positive slurry does not exceed 5%.

20. A lithium ion battery, comprising a positive plate, wherein the positive plate comprises a current collector and a positive material layer arranged on the current collector; the positive material layer comprises a positive active material, a conductive agent, and a dispersant; and the dispersant is the dispersant according to claim 1.

Description

DETAILED DESCRIPTION

[0036] The following provides exemplary implementations of the present disclosure. It should be noted that a person of ordinary skill in the art may make several improvements and refinements without departing from the principles of the present disclosure. These improvements and refinements are considered to fall within the protection scope of the present disclosure.

[0037] The present disclosure is further described below through the following embodiments.

Embodiment 1

[0038] A method for preparing a dispersant for a lithium ion battery includes: dissolving N-vinylpyrrolidone, 1,3-butadiene, and acrylonitrile in N,N-dimethylformamide (DMF) at a mass ratio of 40:40:20, adding an initiator azobisisobutyronitrile and a chain transfer agent dodecyl mercaptan, performing polymerization at 60° C. for 4 hours at a pressure of 4 MPa, performing cooling to terminate the reaction, washing and drying a resulting reactant to obtain a dispersant 1′, and hydrogenating the dispersant 1′ to obtain a dispersant 1. A weight average molecular weight of the dispersant 1 is measured as 500000.

[0039] A method for preparing a positive plate includes: dissolving 1.5 g of binder PVDF in 40 g of N-methylpyrrolidone (NMP), and adding 0.5 g of the above dispersant 1 after full dissolution, and performing stirring for 20 min; adding 20 g of carbon nanotube dispersion (solvent: NMP, solid content: 5 wt %) and performing stirring for 20 min; adding 97 g of lithium iron phosphate positive active material and performing stirring for 1.5 h to obtain a positive slurry; and coating the positive slurry on aluminum foil and performing drying at 130° C. for 30 min to form a positive material layer, thereby completing the production of a lithium iron phosphate positive plate.

Embodiment 2

[0040] A method for preparing a dispersant for a lithium ion battery includes: [0041] dissolving N-vinylpyrrolidone, 1,3-diene, and 2-methyl-2-butenenitrile in DMF at a mass ratio of 5:80:15, adding an initiator azobisisobutyronitrile and a chain transfer agent dodecyl mercaptan, performing polymerization at 60° C. for 4 hours at a pressure of 4 MPa, performing cooling to terminate the reaction, washing and drying a resulting reactant to obtain a dispersant 2′, and hydrogenating the dispersant 2′ to obtain a dispersant 2. A weight average molecular weight of the dispersant 2 is measured as 600000.

[0042] In a method for preparing a positive plate, 0.5 g of dispersant 1 in Embodiment 1 is replaced with 1.5 g of dispersant 2, 1.5 g of binder PVDF is replaced with 0.5 g of PVDF, and other conditions are the same as those in Embodiment 1.

Embodiment 3

[0043] A method for preparing a dispersant for a lithium ion battery includes: [0044] dissolving N-vinylpyrrolidone, 1,3-butadiene, and butyl acrylate in DMF in a mass ratio of 30:65:5, adding an initiator azobisisobutyronitrile and a chain transfer agent isobutanol, performing polymerization at 60° C. for 4 hours at a pressure of 4 MPa, performing cooling to terminate the reaction, and washing and drying a resulting reactant to obtain a dispersant 3. A weight average molecular weight of the dispersant 3 is measured as 150000.

[0045] In a method for preparing a positive plate, 0.5 g of dispersant 1 in Embodiment 1 is replaced with 1 g of dispersant 3, 1.5 g of binder PVDF is replaced with 1 g of PVDF, and other conditions are the same as those in Embodiment 1.

Embodiment 4

[0046] A method for preparing a dispersant for a lithium ion battery includes: [0047] dissolving N-vinylpyrrolidone, 1,3-butadiene, and butyl acrylate in DMF in a mass ratio of 40:40:20, adding an initiator azobisisobutyronitrile and a chain transfer agent isobutanol, performing polymerization at 60° C. for 4 hours at a pressure of 4 MPa, performing cooling to terminate the reaction, washing and drying a resulting reactant to obtain a dispersant 4′, and hydrogenating the dispersant 4′ to obtain a dispersant 4. A weight average molecular weight of the dispersant 4 is measured as 550000.

[0048] In a method for preparing a positive plate, 0.5 g of dispersant 1 in Embodiment 1 is replaced with 1.5 g of dispersant 4, 1.5 g of binder PVDF is replaced with 0.5 g of PVDF, and other conditions are the same as those in Embodiment 1.

Embodiment 5

[0049] A method for preparing a dispersant for a lithium ion battery includes: [0050] dissolving acrylamide, isoprene, and α-ethylacrylonitrile in DMF at a mass ratio of 10:80:10, adding an initiator azobisisobutyronitrile and a chain transfer agent ethyl acetate, performing polymerization at 60° C. for 4 hours at a pressure of 4 MPa, performing cooling to terminate the reaction, washing and drying a resulting reactant to obtain a dispersant 5′, and hydrogenating the dispersant 5′ to obtain a dispersant 5. A weight average molecular weight of the dispersant 5 is measured as 400000.

[0051] A method for preparing a positive plate includes: dissolving 0.8 g of binder PVDF in 30 g of NMP, and adding 0.4 g of dispersant 5 after full dissolution, and performing stirring for 20 min; adding 10 g of carbon nanotube dispersion (solvent: NMP, solid content: 5 wt %) and 1.3 g of carbon black as a conductive agent, and performing stirring for 20 min; adding 97 g of positive active material NCM811 (LiN.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2) and performing stirring for 2 h to obtain a positive slurry; and coating the positive slurry on aluminum foil and performing drying at 130° C. for 30 min to form a positive material layer, thereby completing the production of an NCM ternary positive plate.

Embodiment 6

[0052] A method for preparing a dispersant for a lithium ion battery includes: [0053] dissolving N-vinylpyrrolidone, 1,3-hexadiene, and acrylonitrile in dioxane at a mass ratio of 15:80:5, adding an initiator azobisisobutyronitrile and a chain transfer agent dodecyl mercaptan, performing polymerization at 60° C. for 4 hours at a pressure of 4 MPa, performing cooling to terminate the reaction, washing and drying a resulting reactant to obtain a dispersant 6′, and hydrogenating the dispersant 6′ to obtain a dispersant 6. A weight average molecular weight of the dispersant 6 is measured as 300000.

[0054] In a method for preparing a positive plate, 0.4 g of dispersant 5 in Embodiment 5 is replaced with 0.6 g of dispersant 6, 0.8 g of binder PVDF is replaced with 0.6 g of PVDF, and other conditions are the same as those in Embodiment 5.

Embodiment 7

[0055] A method for preparing a dispersant for a lithium ion battery includes: [0056] dissolving N-hydroxymethylacrylamide, 1,3-butadiene, and acrylonitrile in DMF at a mass ratio of 10:75:15, adding an initiator azobisisobutyronitrile and a chain transfer agent ethyl acetate, performing polymerization at 60° C. for 4 hours at a pressure of 4 MPa, performing cooling to terminate the reaction, washing and drying a resulting reactant to obtain a dispersant 7′, and hydrogenating the dispersant 7′ to obtain a dispersant 7. A weight average molecular weight of the dispersant 7 is measured as 600000.

[0057] In a method for preparing a positive plate, 0.4 g of dispersant 5 in Embodiment 5 is replaced with 0.8 g of dispersant 7, 0.8 g of binder PVDF is replaced with 0.4 g of PVDF, and other conditions are the same as those in Embodiment 5.

[0058] The following comparative examples 1-2 are set up below to highlight the beneficial effects of the present disclosure.

Comparative Example 1

[0059] A main difference between a positive plate in Comparative example 1 and that in Embodiment 1 is that no dispersant is added, 2 g of PVDF is used, and a larger amount of solvent is used during the preparation of the lithium iron phosphate positive plate.

[0060] A method for preparing a lithium iron phosphate positive plate in Comparative example 1 includes: fully dissolving 2 g of binder PVDF in 50 g of NMP; adding 20 g of carbon nanotube NMP dispersion (solid content: 5 wt %), and performing stirring for 20 min; adding 97 g of lithium iron phosphate positive active material and performing stirring for 3 h to obtain a positive slurry; and coating the positive slurry on aluminum foil and performing drying at 130° C. for 30 min to form a positive material layer, thereby completing the production of a lithium iron phosphate positive plate.

Comparative Example 2

[0061] A main difference between a ternary positive plate in Comparative example 2 and that in Embodiment 2 is that no dispersant is added, 1.2 g of PVDF is used, and a larger amount of solvent is used during the preparation of the NCM ternary positive plate.

[0062] A method for preparing a ternary positive plate in Comparative example 2 includes: fully dissolving 1.2 g of binder PVDF in 40 g of NMP; adding 10 g of carbon nanotube dispersion (solid content: 5 wt %) and 1.3 g of carbon black as a conductive agent, and performing stirring for 20 min; adding 97 g of positive active material NCM811 (LiNi.sub.0.8Co.sub.0.1Mn.sub.0.1O.sub.2) and performing stirring for 3 h to obtain a positive slurry; and coating the positive slurry on aluminum foil and performing drying at 130° C. for 30 min to form a positive material layer, thereby completing the production of an NCM ternary positive plate.

[0063] In order to support the beneficial effects of the present disclosure, the tested viscosity and solid content of the positive slurry in each embodiment and comparative example, content of the positive active material in the positive material layer, and peeling force of the positive plate are summarized in the following Table 1.

TABLE-US-00001 TABLE 1 Summary of results of embodiments and comparative examples Viscosity of Solid content of Content of positive active Peeling force of positive slurry positive slurry material in positive positive plate (mPa .Math. s) (%) material layer (%) (N/mm) Embodiment 1 3430 63.0 97.0 32 Embodiment 2 3560 63.0 97.0 28 Embodiment 3 3280 63.0 97.0 25 Embodiment 4 3300 63.0 97.0 23 Comparative 3390 59.2 97.0 21 example 1 Embodiment 5 2560 71.7 97.0 30 Embodiment 6 2470 71.7 97.0 28 Embodiment 7 2600 71.7 97.0 33 Comparative 2710 66.9 97.0 25 example 2

[0064] The viscosities of the positive slurries in the above Table 1 are measured by using a rheometer with a reference model of Anton Paar MCR 302. The flexibilities of the positive plates are obtained through visual observation after folding the positive plates in half. The peeling force of the positive plate is tested by using a pressure sensitive binder tape peeling test, with a reference standard GB/T 2792-1998.

[0065] It may be learned from Table 1 that the viscosities of the positive slurries in Embodiments 1-4 approximate that in Comparative example 1, and the viscosities of the positive slurries in Embodiments 5-7 approximate that in Comparative example 2, both of which satisfy corresponding plate preparation requirements. Through comparison between Embodiments 1-4 and Comparative example 1 and between Embodiments 5-7 and Comparative example 2, it may be learned that the positive slurry including the dispersant provided in the embodiments of the present disclosure has a higher solid content and a shorter time is spent in producing a positive slurry with a desirable dispersion effect in a case that the content of the positive active material in the positive material layer remains unchanged. Moreover, only a small amount of binder PVDF is used, which indicates that the dispersant provided in the present disclosure may partially replace PVDF to provide a bonding function. In addition, the peeling force of the positive plate in the embodiments of the present disclosure is greater than the peeling force of the positive plate in the corresponding comparative example.

[0066] In addition, it may be learned through the comparison between Embodiment 1 and Embodiment 4 that when mass ratios of all components in the monomer raw material are the same, the peeling force of the positive plate using the dispersant prepared using acrylonitrile is slightly greater than that of the positive plate using the dispersant prepared using acrylate.

[0067] The foregoing embodiments show only several implementations of the present disclosure and are described in detail, which, however, are not to be construed as a limitation to the patent scope of the present disclosure. It should be noted that a person of ordinary skill in the art may make several transformations and improvements can be made without departing from the idea of the present disclosure. The transformations and improvements belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the appended claims.