Modified carboxymethyl cellulose salt, negative electrode dispersant, negative electrode sheet, battery cell, battery, and electrical apparatus

Abstract

A modified carboxymethyl cellulose salt, a negative electrode dispersant, a negative electrode sheet, a battery cell, a battery, and an electrical apparatus. The battery cell comprises a negative electrode sheet; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector; the negative electrode film layer comprises a negative electrode active material and a negative electrode dispersant; the negative electrode dispersant comprises a modified carboxymethyl cellulose salt; the modified carboxymethyl cellulose salt comprises a structural unit represented by formula A, wherein in formula A, Q comprises a hydrogen atom or -CH2COOM1, and M1 comprises at least one of a metal ion or NH4 +; R comprises a hydrogen atom or a flexible group, and the flexible group comprises at least one of a substituted or unsubstituted ether group, substituted or unsubstituted alkyl, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, and a substituted or unsubstituted ester group. The negative electrode film layer has good flexibility and is not prone to cracking.

Description

Modified carboxymethyl cellulose salt, negative electrode dispersant, negative electrode sheet, battery cell, battery and electric device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese Patent Application No. 202410823161.4, filed on June 24, 2024, entitled “Modified carboxymethyl cellulose salt, negative electrode dispersant, negative electrode sheet, battery cell, battery and electric device”, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to a modified carboxymethyl cellulose salt, a negative electrode dispersant, a negative electrode sheet, a battery cell, a battery and an electric device. BACKGROUND

[0004] Battery cells have reliable working performance, and advantages such as no pollution and no memory effect, and are widely used. For example, as environmental protection issues are increasingly valued, new energy vehicles are increasingly popular, and the demand for power battery cells will show explosive growth.

[0005] As the application range of batteries is more and more extensive, the requirements for battery performance are gradually strict. However, in the process of preparing the negative electrode sheet, the negative electrode sheet has a risk of cracking, which leads to the performance of the negative electrode sheet failing to meet the production requirements.

[0006] SUMMARY

[0007] The present application provides a modified carboxymethyl cellulose salt, a negative electrode dispersant, a negative electrode sheet, a battery cell, a battery and an electric device, which can reduce the risk of cracking of the negative electrode film layer in the negative electrode sheet.

[0008] In a first aspect, the present application provides a battery cell, the battery cell comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material and a negative electrode dispersant, the negative electrode dispersant comprising a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprising a structural unit represented by Formula A,

[0009] In Formula A,

[0010] Q comprises a hydrogen atom or -CH2COOM1, M1 comprises a metal ion or NH4 + at least one of the following:

[0011] R comprises a hydrogen atom or a flexible group, the flexible group comprising at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, a substituted or unsubstituted ester group.

[0012] Thus, the negative electrode dispersant of the embodiments of the present application comprises a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprises the structural unit described above, the structural unit increases the carbon chain length in the main chain of the modified carboxymethyl cellulose salt, increases the rotatability of the main chain, increases the flexibility, can improve the flexibility of the modified carboxymethyl cellulose salt, thereby improving the flexibility of the negative electrode film layer, reducing the risk of cracking of the negative electrode film layer, especially reducing the risk of cracking of the thick-coated negative electrode film layer, and improving the energy density of the battery cell;

[0013] Further, the structural unit described above further comprises a flexible group, which can reduce the interaction between molecular chains, thereby further improving the flexibility of the modified carboxymethyl cellulose salt, improving the flexibility of the negative electrode film layer, and reducing the risk of cracking of the negative electrode film layer;

[0014] Moreover, the modified carboxymethyl cellulose salt has good dispersing and leveling effects, can effectively disperse the negative electrode active material, so that the negative electrode active material is uniformly dispersed, and the thickness distribution of the negative electrode film layer is uniform and the performance is uniform;

[0015] Thus, when the negative electrode film layer comprises the modified carboxymethyl cellulose salt, the flexibility of the negative electrode film layer is improved, the risk of cracking is low, and the thickness of the negative electrode film layer is uniform and the performance is uniform.

[0016] In some embodiments, the structural unit represented by formula A comprises a structural unit represented by formula A-1,

[0017] In some embodiments, the structural unit represented by formula A comprises a structural unit represented by formula A-2,

[0018] In some embodiments, the negative electrode dispersant further comprises a structural unit represented by formula B,

[0019] In formula B,

[0020] M2 comprises a metal ion or NH4 + .

[0021] In some embodiments, based on the total number of the structural unit represented by formula A and the structural unit represented by formula B, the proportion of the number of the structural unit represented by formula A is 0.5% to 20%, and optionally 1% to 10%.

[0022] Thus, when the proportion of the number of the structural unit represented by formula A in the embodiments of the present application is in the above range, the modified carboxymethyl cellulose salt has excellent hydrophobic effect, can have excellent dispersing effect on the negative electrode active material such as graphite material, and can effectively improve the flexibility of the carboxymethyl cellulose salt.

[0023] In some embodiments, the flexible group includes at least one of a substituted or unsubstituted C3 to C150 ether group, a substituted or unsubstituted C3 to C150 alkyl group, a substituted or unsubstituted C3 to C150 polyolefin group, a substituted or unsubstituted C3 to C150 amide group, and a substituted or unsubstituted C3 to C150 ester group. The above groups enable the modified carboxymethyl cellulose salt to have excellent flexibility, which can improve the flexibility of the negative electrode film layer.

[0024] In some embodiments, the substituted or unsubstituted C3 to C150 ether group includes at least one of a structural formula of Formula 1,

[0025] In Formula 1,

[0026] R 11 to R 17 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0027] m includes any positive integer of 5 to 60.

[0028] In some embodiments, the substituted or unsubstituted C3 to C150 ether group includes at least one of a structural formula of Formula 1-1 to a structural formula of Formula 1-14,

[0029] wherein m1 includes any positive integer of 1 to 30.

[0030] Thereby, the ether group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0031] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes a structural formula of Formula 2,

[0032] In Formula 2,

[0033] R 21 to R 27 each independently includes at least one of a hydrogen atom, a halogen atom, and a substituted or unsubstituted C1 to C10 alkyl group;

[0034] s includes any positive integer of 5 to 60.

[0035] Thereby, the alkyl group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0036] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes at least one of a structural formula represented by Formula 2-1 to a structural formula represented by Formula 2-11,

[0037] wherein s1 includes any positive integer of 1 to 30.

[0038] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group includes a structural formula represented by Formula 3,

[0039] In Formula 3,

[0040] R 31 to R 34 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group;

[0041] R 35 includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0042] p includes any positive integer of 5 to 60.

[0043] Thereby, the polyalkylene group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0044] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group includes at least one of a structural formula represented by Formula 3-1 to a structural formula represented by Formula 3-8,

[0045] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes a structural formula represented by Formula 4,

[0046] In Formula 4,

[0047] R 41 includes at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0048] R 42 to R 46 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, a substituted or unsubstituted C2 to C10 alkynyl group;

[0049] a includes any positive integer of 1 to 30.

[0050] Thus, the ester group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0051] In some embodiments, R 41 including a single bond, the substituted or unsubstituted C3 to C150 amide group includes a structural formula represented by Formula 4-1,

[0052] In some embodiments, the substituted or unsubstituted C3 to C150 amide group includes at least one of a structural formula represented by Formula 4-11 to a structural formula represented by Formula 4-15,

[0053] In some embodiments, R 41 including a substituted or unsubstituted C1 to C5 methylene group, the substituted or unsubstituted C3 to C150 amide group includes a structural formula represented by Formula 4-2,

[0054] a1 includes any positive integer of 1 to 5.

[0055] In some embodiments, the substituted or unsubstituted C3 to C150 amide group includes at least one of a structural formula represented by Formula 4-21 to a structural formula represented by Formula 4-24,

[0056] In some embodiments, the substituted or unsubstituted C3 to C150 ester group includes a structural formula represented by Formula 5,

[0057] In Formula 5,

[0058] R 51 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0059] R 52 including a substituted or unsubstituted C1 to C5 alkyl group;

[0060] R 53 to R 55 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0061] b includes any positive integer of 1 to 30.

[0062] Thus, the ester group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0063] In some embodiments, R 51including a single bond, a substituted or unsubstituted C3 to C150 ester group includes a structural formula represented by formula 5-1,

[0064] In some embodiments, the substituted or unsubstituted C3 to C150 ester group includes at least one of a structural formula represented by formula 5-11 to a structural formula represented by formula 5-16,

[0065] In some embodiments, R 51 including a substituted or unsubstituted C1 to C5 methylene group, a substituted or unsubstituted C3 to C150 ester group includes a structural formula represented by formula 5-2,

[0066] b1 includes any positive integer from 1 to 5.

[0067] In some embodiments, the substituted or unsubstituted C3 to C150 ester group includes at least one of a structural formula represented by formula 5-21 to a structural formula represented by formula 5-28,

[0068] In some embodiments, the weight average molecular weight of the negative electrode dispersant is 40 wDa to 80 wDa. When the weight average molecular weight of the modified carboxymethyl cellulose salt is in the above range, the negative electrode dispersant can have excellent dispersing performance.

[0069] In some embodiments, the elongation at break of a reference adhesive film made of sodium carboxymethyl cellulose is 100%, and the elongation at break of an adhesive film made of the modified carboxymethyl cellulose salt is 225% to 400%. The width of the adhesive film and the reference adhesive film is 2.5 cm, the length is 5 cm, and the thickness is 1 mm.

[0070] Therefore, the elongation at break of the negative electrode dispersant in the embodiments of the present application is higher than that of conventional sodium carboxymethyl cellulose. When the negative electrode dispersant is applied to a negative electrode tab, it has good flexibility and is less likely to break.

[0071] In some embodiments, the mass content of the negative electrode dispersant is 0.8% to 1.3%, and can be 1.0% to 1.2%, based on the total mass of the negative electrode film layer. When the mass content of the negative electrode dispersant is in the above range, the flexibility of the negative electrode film layer can be effectively improved, and the negative electrode active material is uniformly dispersed in the negative electrode film layer, and the performance of the negative electrode film layer is more uniform.

[0072] In some embodiments, the coating basis weight of the negative electrode film layer is 200 mg / 1540.25 mm 2 to 280 mg / 1540.25 mm 2 ; and can be 220 mg / 1540.25 mm2 to 280 mg / 1540.25 mm 2 The coating bulk specific gravity of the negative electrode film layer is relatively high, which is conducive to achieving thick coating.

[0073] In a second aspect, the present application provides a negative electrode dispersant, the negative electrode dispersant comprising a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprising a structural unit represented by Formula A,

[0074] In Formula A,

[0075] Q comprises a hydrogen atom or -CH2COOM1, M1 comprises a metal ion or NH4 + at least one of the following:

[0076] R comprises a hydrogen atom or a flexible group, the flexible group comprising at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, and a substituted or unsubstituted ester group.

[0077] Thus, the negative electrode dispersant of the embodiments of the present application comprises a modified carboxymethyl cellulose salt, which comprises the above-mentioned structural unit. The above-mentioned structural unit increases the length of the carbon chain in the main chain of the modified carboxymethyl cellulose salt, increases the rotatability of the main chain, increases the flexibility, and can improve the flexibility of the modified carboxymethyl cellulose salt, thereby improving the flexibility of the negative electrode film layer, reducing the risk of cracking of the negative electrode film layer, especially reducing the risk of cracking of the thick-coated negative electrode film layer, and improving the energy density of the battery cell. Further, the above-mentioned structural unit further comprises a flexible group, which can reduce the interaction between the molecular chains, thereby further improving the flexibility of the modified carboxymethyl cellulose salt, improving the flexibility of the negative electrode film layer, and reducing the risk of cracking of the negative electrode film layer. Moreover, the modified carboxymethyl cellulose salt has good dispersing and leveling effects, can effectively disperse the negative electrode active material, and makes the negative electrode active material disperse uniformly, the thickness distribution of the negative electrode film layer uniform, and the performance uniform. Thus, when the negative electrode film layer comprises the modified carboxymethyl cellulose salt, the flexibility of the negative electrode film layer is improved, the risk of cracking is low, and the thickness of the negative electrode film layer is uniform and the performance is uniform.

[0078] In some embodiments, the structural unit represented by Formula A comprises a structural unit represented by Formula A-1,

[0079] In some embodiments, the structural unit represented by Formula A comprises a structural unit represented by Formula A-2,

[0080] In some embodiments, the negative electrode dispersant further comprises a structural unit represented by Formula B,

[0081] In formula B,

[0082] M2 includes a metal ion or NH4 + at least one.

[0083] In some embodiments, the number of structural units shown in formula A accounts for 0.5% to 20%, optionally 1% to 10%, based on the total number of structural units shown in formula A and formula B.

[0084] Thus, when the number of structural units shown in formula A accounts for the above range in the embodiments of the present application, the modified carboxymethyl cellulose salt has excellent hydrophobic effect, can have excellent dispersion effect on the negative active material such as graphite material, and can effectively improve the flexibility of the carboxymethyl cellulose salt.

[0085] In some embodiments, the flexible group includes at least one of a substituted or unsubstituted C3 to C150 ether group, a substituted or unsubstituted C3 to C150 alkyl group, a substituted or unsubstituted C3 to C150 polyolefin group, a substituted or unsubstituted C3 to C150 amide group, and a substituted or unsubstituted C3 to C150 ester group. The above groups enable the modified carboxymethyl cellulose salt to have excellent flexibility, which can improve the flexibility of the negative electrode film layer.

[0086] In some embodiments, the substituted or unsubstituted C3 to C150 ether group includes a structural formula shown in formula 1,

[0087] In formula 1,

[0088] R 11 to R 17 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0089] m includes any positive integer from 5 to 60.

[0090] In some embodiments, the substituted or unsubstituted C3 to C150 ether group includes at least one of a structural formula shown in formula 1-1 to a structural formula shown in formula 1-14,

[0091] wherein m1 includes any positive integer from 1 to 30.

[0092] Thus, the ether group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0093] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group comprises at least one of a structural formula of Formula 2,

[0094] In Formula 2,

[0095] R 21 to R 27 each independently comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0096] s comprises any positive integer of 5 to 60.

[0097] Thus, the alkyl group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0098] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group comprises at least one of a structural formula of Formula 2-1 to a structural formula of Formula 2-11,

[0099] wherein s1 comprises any positive integer of 1 to 30.

[0100] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group comprises a structural formula of Formula 3,

[0101] In Formula 3,

[0102] R 31 to R 34 each independently comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group;

[0103] R 35 comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0104] p comprises any positive integer of 5 to 60.

[0105] Thus, the polyalkylene group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0106] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group comprises at least one of a structural formula of Formula 3-1 to a structural formula of Formula 3-8,

[0107] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group comprises a structural formula of Formula 4,

[0108] R in Formula 4,

[0109] R 41 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0110] R 42 to R 46 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0111] a includes any positive integer of 1 to 30.

[0112] Thereby, the amide-based group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0113] In some embodiments, R 41 including a single bond, a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula of Formula 4-1,

[0114] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula of Formula 4-11 to a structural formula of Formula 4-15,

[0115] In some embodiments, R 41 including a substituted or unsubstituted C1 to C5 methylene group, a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula of Formula 4-2,

[0116] a1 includes any positive integer of 1 to 5.

[0117] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula of Formula 4-21 to a structural formula of Formula 4-24,

[0118] In some embodiments, the substituted or unsubstituted C3 to C150 ester-based group includes a structural formula of Formula 5,

[0119] R in Formula 5,

[0120] R 51 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0121] R 52 comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0122] R 53 to R 55 comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0123] b comprises any positive integer of 1 to 30.

[0124] Thereby, the ester group can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0125] In some embodiments, R 51 comprises a single bond, and the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula represented by Formula 5-1,

[0126] In some embodiments, the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula represented by Formula 5-11 to a structural formula represented by Formula 5-16,

[0127] In some embodiments, R 51 comprises a substituted or unsubstituted C1 to C5 methylene group, and the substituted or unsubstituted C3 to C150 ester group comprises a structural formula represented by Formula 5-2,

[0128] b1 comprises any positive integer of 1 to 5.

[0129] In some embodiments, the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula represented by Formula 5-21 to a structural formula represented by Formula 5-28,

[0130] In some embodiments, the negative electrode dispersant has a weight average molecular weight of 40 wDa to 80 wDa. When the modified carboxymethyl cellulose salt has a weight average molecular weight in the above range, the negative electrode dispersant can have excellent dispersing properties.

[0131] In some embodiments, a reference adhesive film made of carboxymethyl cellulose sodium has an elongation at break of 100%, an adhesive film made of the modified carboxymethyl cellulose salt has an elongation at break of 225% to 400%, and the adhesive film made of the negative electrode dispersant and the reference adhesive film have a width of 2.5 cm, a length of 5 cm, and a thickness of 1 mm.

[0132] Therefore, the elongation at break of the negative electrode dispersant in the embodiments of the present application is higher than that of the conventional sodium carboxymethyl cellulose, and the negative electrode dispersant has better flexibility when applied to the negative electrode sheet and is less likely to break.

[0133] In a third aspect, the present application further provides a modified carboxymethyl cellulose salt, comprising a structural unit shown in Formula A,

[0134] In Formula A,

[0135] Q comprises a hydrogen atom or -CH2COOM1, M1 comprises a metal ion or NH4 + at least one of them.

[0136] R comprises a hydrogen atom or a flexible group, and the flexible group comprises at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, and a substituted or unsubstituted ester group.

[0137] Therefore, the modified carboxymethyl cellulose salt in the embodiments of the present application comprises the above-mentioned structural unit, which increases the length of the carbon chain in the main chain of the modified carboxymethyl cellulose salt, increases the rotatability of the main chain, increases the flexibility, and can improve the flexibility of the modified carboxymethyl cellulose salt. When applied to the negative electrode film layer, it can improve the flexibility of the negative electrode film layer, reduce the risk of cracking of the negative electrode film layer, especially reduce the risk of cracking of the thick-coated negative electrode film layer, and improve the energy density of the battery cell. Further, the above-mentioned structural unit further comprises a flexible group, which can weaken the hydrogen bond interaction between the molecular chains of the modified carboxymethyl cellulose salt, reduce the interaction force between the molecular chains, thereby further improving the flexibility of the modified carboxymethyl cellulose salt, improving the flexibility of the negative electrode film layer, and reducing the risk of cracking of the negative electrode film layer. Moreover, the modified carboxymethyl cellulose salt has good dispersing and leveling effects, can effectively disperse the negative electrode active material, so that the negative electrode active material is uniformly dispersed, and the thickness distribution of the negative electrode film layer is uniform and the performance is uniform. Therefore, when the negative electrode film layer comprises the modified carboxymethyl cellulose salt, the flexibility of the negative electrode film layer is improved, the risk of cracking is low, and the thickness of the negative electrode film layer is uniform and the performance is uniform.

[0138] In some embodiments, the structural unit shown in Formula A comprises a structural unit shown in Formula A-1,

[0139] In some embodiments, the structural unit shown in Formula A comprises a structural unit shown in Formula A-2,

[0140] In some embodiments, the negative electrode dispersant further comprises a structural unit shown in Formula B,

[0141] In formula B,

[0142] M2 includes metal ions or NH4. + At least one of them.

[0143] In some implementations, based on the total number of structural units shown in Formula A and Formula B, the proportion of structural units shown in Formula A is 0.5% to 20%, and optionally 1% to 10%.

[0144] Therefore, when the proportion of structural units shown in Formula A in the embodiments of this application is within the above range, the modified carboxymethyl cellulose salt has excellent hydrophobic properties, can have excellent dispersion effects on negative electrode active materials such as graphite materials, and can effectively improve the flexibility of carboxymethyl cellulose salt.

[0145] In some embodiments, the flexible group includes at least one of substituted or unsubstituted C3 to C150 ether groups, substituted or unsubstituted C3 to C150 alkyl groups, substituted or unsubstituted C3 to C150 polyolefin groups, substituted or unsubstituted C3 to C150 amide groups, and substituted or unsubstituted C3 to C150 ester groups. These groups endow the modified carboxymethyl cellulose salt with excellent flexibility, thereby improving the flexibility of the negative electrode film.

[0146] Fourthly, this application also proposes a negative electrode sheet, which includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, wherein the negative electrode film layer includes a negative electrode dispersant as described in any embodiment of the second aspect of this application.

[0147] Fifthly, embodiments of this application also propose a battery comprising a battery cell as described in any embodiment of the first aspect of this application.

[0148] In a sixth aspect, embodiments of this application also provide an electrical device including a battery as described in any embodiment of the fifth aspect of this application. Attached Figure Description

[0149] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0150] Figure 1 is a schematic diagram of one embodiment of the battery cell of this application.

[0151] Figure 2 is an exploded view of the embodiment of the battery cell in Figure 1.

[0152] FIG. 3 is a schematic view of an embodiment of a battery module of the present application.

[0153] FIG. 4 is a schematic view of an embodiment of a battery pack of the present application.

[0154] FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4.

[0155] FIG. 6 is a schematic view of an embodiment of an electric device including a battery cell of the present application as a power source.

[0156] The accompanying drawings are merely schematic and are not necessarily drawn to scale.

[0157] The reference signs in the drawings are explained as follows:

[0158] 1: battery pack; 2: upper case; 3: lower case; 4: battery module;

[0159] 5: battery cell; 51: case; 52: electrode assembly; 53: cover plate;

[0160] 6: electric device. DETAILED DESCRIPTION

[0161] Hereinafter, embodiments of the modified carboxymethylcellulose salt, the negative electrode dispersant, the negative electrode sheet, the battery cell, the battery, and the electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed explanations are omitted. For example, there will be cases where detailed explanations of matters that are already well known, repeated explanations of actually identical structures are omitted. This is to avoid the following explanations from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following explanations are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0162] The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges can be "closed" ranges, i.e., the upper and lower limits of the range are included. The ranges can be any combination of open and closed ranges. For example, if a range of 60 to 120 and a range of 80 to 110 are listed, it is understood that a range of 60 to 110 and a range of 80 to 120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, a numerical range "a to b" means any and all subcombinations of the numbers between a and b, inclusive of a and b. For example, the numerical range "0 to 5" means that all real numbers between 0 and 5, inclusive of 0 and 5, have been listed herein. "0 to 5" is merely a shorthand for listing all of the numbers between 0 and 5. Also, when a parameter is stated to be an integer ≥ 2, it is equivalent to state that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0163] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not otherwise specified.

[0164] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if not otherwise specified.

[0165] All steps of the present application can be performed in sequence or randomly, preferably in sequence, if not otherwise specified. For example, a method comprises steps a and b, which means that the method can comprise steps a and b in sequence, or steps b and a in sequence. For example, it is mentioned that the method can further comprise step c, which means that step c can be added to the method in any sequence, for example,

[0166] The method can comprise steps a, b and c, or steps a, c and b, or steps c, a and b, etc.

[0167] "Include" and "contain" mentioned in the present application means open or closed, if not otherwise specified. For example, "include" and "contain" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0168] The term "or" is inclusive in this application, unless otherwise indicated. So, for example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true or present, and B is false or not present; A is false or not present, and B is true or present; or both A and B are true or present.

[0169] Throughout this specification, substituents of compounds are disclosed in groups or in ranges. It is specifically intended that the description include each and every individual subcombination of the members of these groups and ranges. For example, the term "Ci to C8alkyl" is specifically intended to individually disclose C1, C2, C3, C4, C5, C6, C7, C8, Ci to C8, Ci to C7, Ci to C6, Ci to C5, Ci to C4, Ci to C3, Ci to C2, C2 to C8, C2 to C7, C2 to C6, C2 to C5, C2 to C4, C2 to C3, C3 to C8, C3 to C7, C3 to C6, C3 to C5, C3 to C4, C4 to C8, C4 to C7, C4 to C6, C4 to C5, C5 to C8, C5 to C7, C5 to C6, C6 to C8, C6 to C7, and C7 to C8alkyl.

[0170] As other examples, it is expressly intended that the integers in the range of 5 to 40 individually disclose 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40; and it is expressly intended that the integers in the range of 1 to 20 individually disclose 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. In this manner, other groups or ranges can be expressly intended.

[0171] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, and the negative electrode film layer is formed by drying the negative electrode slurry coated on the negative electrode current collector. During the process of forming the negative electrode film layer by the negative electrode slurry, cracking and other phenomena may occur, resulting in that the negative electrode sheet does not meet the production requirements. In order to improve the energy density of the battery monomer, the negative electrode film layer is usually thick coated, and the cracking phenomenon of the negative electrode film layer will be further intensified, so that the negative electrode sheet is difficult to achieve thick coating. In order to improve the cracking phenomenon of the negative electrode film layer, the related technology adds a plasticizer such as butanediol in the negative electrode slurry. The plasticizer is usually a small molecule compound with relatively small molecular weight. The plasticizer can enter between the adhesive polymer molecular chains, reduce the intermolecular stress of the adhesive polymer, and reduce the crystallinity of the polymer molecular chain, thereby improving the plasticity and flexibility of the negative electrode film layer and improving the cracking phenomenon of the negative electrode film layer. However, the residual plasticizer can easily cause the thickness of the negative electrode film layer to be uneven, resulting in interface problems such as dark marks in the negative electrode film layer.

[0172] In view of the above problems, the embodiments of the present application propose a modified carboxymethyl cellulose salt. The modified carboxymethyl cellulose salt is obtained by opening part of the six-membered ring in the carboxymethyl cellulose salt. After opening part of the six-membered ring, the length of the carbon chain segment in the main chain of the modified carboxymethyl cellulose salt increases, the rotatability of the main chain increases, the flexibility increases, and the flexibility of the modified carboxymethyl cellulose salt can be improved. When the modified carboxymethyl cellulose salt is used as a component of a negative electrode dispersant, it can effectively improve the flexibility of the negative electrode film layer and reduce the risk of cracking. In addition, the modified carboxymethyl cellulose salt can also have excellent dispersion effect on the negative electrode active material, which can effectively disperse the negative electrode active material, so that the negative electrode active material is uniformly dispersed, and the thickness distribution of the negative electrode film layer is uniform and the performance is uniform.

[0173] Modified carboxymethyl cellulose salt

[0174] In a first aspect, the embodiments of the present application propose a modified carboxymethyl cellulose salt, which includes a structural unit shown in formula A,

[0175] In formula A,

[0176] Q includes a hydrogen atom or -CH2COOM1, M1 includes a metal ion or NH4 + at least one of them; for example, the metal ion includes at least one of lithium ion, sodium ion, potassium ion;

[0177] R includes a hydrogen atom or a flexible group, and the flexible group includes at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, and a substituted or unsubstituted ester group.

[0178] Carboxymethyl cellulose salt CMC-M is an anionic water-soluble cellulose ether derivative. When it is applied to the negative electrode slurry, it can reduce the interfacial tension between the negative electrode active material and the solvent, and has a good dispersion effect on the negative electrode active material, etc. Under the action of stirring, it is beneficial to the uniform dispersion of the negative electrode active material in the solvent to form a stable slurry system.

[0179] On the one hand, the carboxymethyl cellulose salt is connected by a six-membered heterocyclic ring to form a molecular chain. The six-membered heterocyclic ring is relatively rigid and not easy to rotate, so that the carboxymethyl cellulose salt has relatively large rigidity and poor flexibility. On the other hand, the molecular chain of the carboxymethyl cellulose salt is rich in hydroxyl groups -OH. The presence of hydroxyl groups enables the carboxymethyl cellulose salt to form relatively strong van der Waals forces or hydrogen bonds between its own molecular chains. As a result, the negative electrode slurry has relatively strong drying stress during the drying process and may be warped, and may be cracked during further rolling, causing the negative electrode film layer to crack.

[0180] The negative electrode dispersant of the embodiments of the present application includes a modified carboxymethyl cellulose salt. The modified carboxymethyl cellulose salt is obtained by ring-opening part of the ring structure of the carboxymethyl cellulose salt CMC-M, or further grafting a flexible group after ring-opening, so as to modify the carboxymethyl cellulose salt. After ring-opening of part of the six-membered ring, the length of the carbon chain segment in the main chain of the modified carboxymethyl cellulose salt is increased, the rotatability of the main chain is increased, and the flexibility is increased.

[0181] Further, a flexible group can be grafted at the ring-opening position. Such a group can reduce the interaction between polymer molecular chains, thereby reducing the stress generated during drying. Moreover, due to the flexibility of the flexible group, the flexibility of the modified carboxymethyl cellulose salt is improved. When the negative electrode dispersant is applied to the negative electrode slurry, the negative electrode slurry has relatively small drying stress during the drying process, the risk of cracking of the negative electrode film layer is reduced, and the flexibility of the negative electrode film layer is improved. In particular, the risk of cracking of the thickly coated negative electrode film layer is reduced, which is beneficial to improving the energy density of the battery cell.

[0182] Therefore, when the modified carboxymethyl cellulose salt is applied to the negative electrode slurry, the negative electrode film layer formed by drying the negative electrode slurry can be thickly coated, and the performance of the negative electrode film layer is uniform and has good flexibility.

[0183] In some embodiments, the cation in the modified carboxymethyl cellulose salt includes at least one of a metal ion or an ammonium ion NH4 + For example, the metal ion includes at least one of a lithium ion, a sodium ion, or a potassium ion.

[0184] In some embodiments, the modified carboxymethyl cellulose salt includes at least one of a modified carboxymethyl cellulose lithium salt, a modified carboxymethyl cellulose sodium salt, or a modified carboxymethyl cellulose ammonium salt. The above materials have good dispersibility.

[0185] In some embodiments, the modified carboxymethyl cellulose salt further includes a structural unit shown in Formula B,

[0186] In some embodiments, the modified carboxymethyl cellulose salt further includes a structural unit shown in Formula B,

[0187] In Formula B,

[0188] M2 includes at least one of a metal ion or NH4 + For example, the metal ion includes at least one of a lithium ion, a sodium ion, or a potassium ion.

[0189] The modified carboxymethyl cellulose salt is ring-opened and grafted modified on the basis of the carboxymethyl cellulose salt, and the main chain structure of the modified carboxymethyl cellulose salt is still mainly the main chain structure of the carboxymethyl cellulose salt. The main structure of the modified carboxymethyl cellulose salt is still the carboxymethyl cellulose salt, so it still has good dispersion, can effectively reduce the interfacial tension between the negative electrode active material and the solvent, so that the negative electrode active material is uniformly dispersed in the negative electrode slurry, and the modified carboxymethyl cellulose salt makes the thickness distribution of the negative electrode film layer uniform.

[0190] In some embodiments, Q includes a hydrogen atom, and the structural unit shown in Formula A includes a structural unit shown in Formula A-1,

[0191] In some embodiments, the modified carboxymethyl cellulose salt further includes a structural unit shown in Formula C,

[0192] In Formula C,

[0193] M3 includes at least one of a metal ion or NH4 + For example, the metal ion includes at least one of a lithium ion, a sodium ion, or a potassium ion.

[0194] In some embodiments, Q includes -CH2COOM1, and the structural unit shown in Formula A includes a structural unit shown in Formula A-2,

[0195] In some embodiments, the modified carboxymethyl cellulose salt further includes a structural unit shown in Formula D,

[0196] In some embodiments, based on the total number of the structural unit shown in Formula A and the structural unit shown in Formula B, the proportion of the number of the structural unit shown in Formula A is 0.5% to 20%, and optionally 1% to 10%.

[0197] Exemplarily, the number of the structural unit of formula A accounts for 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or a range formed by any two of the above values.

[0198] When the number of the structural unit of formula A accounts for the above range, the modified carboxymethyl cellulose salt has excellent hydrophobic effect, can have excellent dispersion effect on the negative active material such as graphite material, and can effectively improve the flexibility of the carboxymethyl cellulose salt.

[0199] The number of the structural unit can be calculated by detecting the specific group or specific element of the structural unit, and at least one of infrared spectrophotometry IR, nuclear magnetic resonance NMR, pyrolysis-gas chromatography-mass spectrometry, titration and the like can be used for testing.

[0200] In the embodiments of the present application, infrared spectrophotometry IR is used for detection, specifically, the polymer is tested by Thermo Nicolet Nexus 670 attenuated total reflection Fourier transform infrared spectrometer FTIR-ATR, and then tested by referring to the standard GB / T6040-2002, the test range: ATR method 600-4000cm -1 ; repeatability: ±2cm -1 ; resolution: better than 4cm -1 ; transmission depth 0.2-0.6μm.

[0201] In the embodiments of the present application, nuclear magnetic resonance NMR is used for testing, specifically, 1H NMR and 13C NMR are tested on Varian Mercury Plus-400 nuclear magnetic resonance instrument, the test temperature is 20°C, TMS is internal standard, CDCl3 is used as solvent, and the proton resonance frequency is 400MHz.

[0202] In the embodiments of the present application, pyrolysis-gas chromatography-mass spectrometry is used for testing, and the specific testing steps are as follows: 0.5mg of sample is accurately weighed and loaded into a sample cup, fixed on a sample rod, and loaded into a pyrolyzer installed near the GC gas chromatograph inlet, after the pyrolyzer temperature reaches the set temperature, the sample cup is quickly dropped into the pyrolysis furnace core by free fall, the volatile components are instantly gasified in the inert gas N2 atmosphere, carried into the gas chromatography column by the carrier gas, separated, and finally detected by flame ionization detector FID or mass spectrometer MS, so as to obtain the gas chromatogram or total ion current chromatogram.

[0203] In the embodiments of the present application, the number of ring opening can also be calculated by the content of characteristic groups such as aldehyde groups in the intermediates generated in the process of preparing the modified carboxymethyl cellulose salt, and can be detected by a titration method.

[0204] [flexible group]

[0205] In order to further improve the flexibility of the negative electrode dispersant, the flexible group is selected as a long chain structure, such as a long chain structure of C3 to C150. The long chain structure occupies a longer space and has a steric hindrance effect, which can further reduce the interaction between the molecular chains, further reduce the drying stress, and reduce the risk of cracking of the negative electrode film layer; the long chain structure also has excellent flexibility, which can improve the flexibility of the negative electrode film layer, further reduce the risk of cracking of the negative electrode film layer, and make the negative electrode dispersant have good flexibility when applied as a negative electrode slurry.

[0206] In some embodiments, the flexible group includes at least one of a substituted or unsubstituted C3 to C150 ether group, a substituted or unsubstituted C3 to C150 alkyl group, a substituted or unsubstituted C3 to C150 polyolefin group, a substituted or unsubstituted C3 to C150 amide group, and a substituted or unsubstituted C3 to C150 ester group.

[0207] The above-mentioned group is a long chain group, so that the modified carboxymethyl cellulose salt has excellent flexibility, which can improve the flexibility of the negative electrode film layer formed by drying the negative electrode slurry.

[0208] When the above-mentioned group is substituted by a substituent group, the substituent group can include a halogen atom or a heteroatom-containing group, the halogen atom can include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., and the heteroatom can include a nitrogen atom, a sulfur atom, an oxygen atom, etc.

[0209] [ether group]

[0210] In some embodiments, the flexible group includes a substituted or unsubstituted ether group, which can be a substituted or unsubstituted C3 to C150 ether group. The ether group has a long chain, which can increase the flexibility of the flexible group, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0211] In some embodiments, the ether group includes a structural formula as shown in Formula 1,

[0212] In Formula 1,

[0213] R 11 to R 17 Each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group.

[0214] Optionally, when the above-mentioned group is substituted, the substituent group can include a halogen atom, wherein the halogen atom can include at least one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0215] m is the number of repeating structures. m includes any positive integer in the range of 5 to 60. Optionally, m includes any positive integer in the range of 5 to 45. When m is in the above-mentioned range, the dispersing effect of the negative electrode dispersant can be improved while reducing the hydrogen bonding.

[0216] In some embodiments, m can be 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 18, 20, 25, 30, 35, 40, 45, 50, 55, or 60.

[0217] Exemplarily, the ether group includes at least one of the structural formula shown in formula 1-1 to the structural formula shown in formula 1-14,

[0218] In some embodiments, m1 is the number of repeating structures, and m1 includes any positive integer in the range of 1 to 30, which can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.

[0219] In the embodiments of the present application, m-m1 represents the value of m minus m1, and m-m1 includes any positive integer in the range of 1 to 30, which can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.

[0220] [Substituted or unsubstituted alkyl group]

[0221] In some embodiments, the flexible group includes a substituted or unsubstituted alkyl group, which can be a substituted or unsubstituted C3 to C150 alkyl group. The alkyl group can include an unsaturated alkyl group or a saturated alkyl group. The unsaturated alkyl group can be an alkyl group containing a ring structure, such as an alkyl group containing a three-membered ring, a five-membered ring, etc. The alkyl group containing a ring structure can further increase the steric hindrance effect and reduce the drying stress. The saturated alkyl group can include an alkyl group with a branched chain or a straight chain alkyl group. The saturated alkyl group, especially the straight chain alkyl group, can increase the flexibility of the modified carboxymethyl cellulose salt due to the longer chain.

[0222] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes the structural formula shown in formula 2,

[0223] In Formula 2,

[0224] R 21 to R 27 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group.

[0225] Optionally, R 21 to R 27 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 saturated alkyl group.

[0226] Optionally, when the above group is substituted, the substituent can include a halogen atom, wherein the halogen atom can include at least one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0227] s is the number of repeating structures, and s includes any positive integer from 5 to 60. Optionally, s includes any positive integer from 5 to 45. When s is in the above range, the negative electrode dispersant can have a good dispersion effect while reducing hydrogen bonding.

[0228] In some embodiments, s can be 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 18, 20, 25, 30, 35, 40, 45, 50, 55, or 60.

[0229] For example, the substituted or unsubstituted C3 to C150 alkyl group includes at least one of the structural formulae of Formula 2-1 to Formula 2-11,

[0230] In some embodiments, s1 is the number of repeating structures, and s1 includes any positive integer from 1 to 30. s1 can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.

[0231] In the embodiments of the present application, s-s1 represents the value of s minus s1, and s-s1 includes any positive integer from 1 to 30. s-s1 represents 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.

[0232] [Substituted or unsubstituted polyolefin group]

[0233] In some embodiments, the flexible group comprises a substituted or unsubstituted polyalkylene group, optionally a substituted or unsubstituted C3 to C150 polyalkylene group. The polyalkylene group is able to increase the flexibility of the modified carboxymethyl cellulose salt due to the longer chain.

[0234] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group comprises a structural formula as shown in Formula 3,

[0235] In Formula 3,

[0236] R 31 to R 34 each independently comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, and a substituted or unsubstituted C2 to C10 alkenyl group;

[0237] R 35 comprises at least one of a hydrogen atom, a halogen atom, and a substituted or unsubstituted C1 to C10 alkyl group.

[0238] Optionally, when the above-mentioned group is substituted, the substituent group can comprise a halogen atom, wherein the halogen atom can comprise at least one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0239] p is a number of repeating structures, and p comprises any positive integer from 5 to 60. Optionally, p comprises any positive integer from 5 to 45. When p is within the above-mentioned range, the negative electrode dispersant is able to have good dispersing performance while reducing the hydrogen bonding.

[0240] In some embodiments, p can be 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 18, 20, 25, 30, 35, 40, 45, 50, 55, or 60.

[0241] Exemplarily, the substituted or unsubstituted C3 to C150 polyalkylene group comprises at least one of a structural formula as shown in Formula 3-1 to a structural formula as shown in Formula 3-8,

[0242] In each of the above-mentioned embodiments, the halogen atom can comprise at least one of a fluorine atom, a chlorine atom, and a bromine atom. The above-mentioned atom is also able to improve the voltage resistance of the negative electrode dispersant and improve the stability of the negative electrode film layer.

[0243] [Substituted or unsubstituted amide-based group]

[0244] In some embodiments, the flexible group comprises a substituted or unsubstituted amide-based group, optionally a substituted or unsubstituted C3 to C150 amide-based group.

[0245] The amide group can include a single molecule amide group or a polyamide group, and the amide group includes a strong electronegative element nitrogen element, which can destroy the regular O-H-O hydrogen bond structure of the carboxymethyl cellulose salt after the amide group is grafted to the side chain of the carboxymethyl cellulose salt, and form a new N-H-O hydrogen bond structure, and the N-H-O hydrogen bond structure is weaker than the O-H-O hydrogen bond, so that the intermolecular force of the modified carboxymethyl cellulose salt is weakened, the flexibility is increased, and the flexibility of the negative electrode film layer is improved. And the strong electronegative element nitrogen element can form a complex with active ions such as lithium ions or sodium ions in the battery system, accelerate the transmission rate of the active ions, and improve the kinetic performance of the battery monomer.

[0246] In some embodiments, the substituted or unsubstituted C3 to C150 amide group includes a structural formula shown in formula 4,

[0247] In formula 4,

[0248] R 41 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0249] R 42 to R 46 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0250] a is the number of repeating structures, and a includes any positive integer from 1 to 30. a can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.

[0251] Optionally, when the above-mentioned group is substituted, the substituent group can include at least one of a halogen atom, a hydroxyl group, and a carboxyl group, wherein the halogen atom can include at least one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0252] Either end of the amide group in formula 4 can be connected to the oxygen atom in the modified carboxymethyl cellulose salt, for example, the left end group is connected to the oxygen atom, or the right end group is connected to the oxygen atom. The end group of the amide group in formula 4 which is not connected to the oxygen atom can include a hydrogen atom or a C1 to C3 alkyl group.

[0253] In some embodiments, R 41 including a single bond, a substituted or unsubstituted C3 to C150 amide group includes a structural formula shown in formula 4-1,

[0254] Exemplarily, the structural formula shown in formula 4-1 includes at least one of the structural formula shown in formula 4-11 to the structural formula shown in formula 4-15,

[0255] In some embodiments, R 41 including substituted or unsubstituted C1 to C5 methylene, the substituted or unsubstituted C3 to C15 amide group includes the structural formula shown in formula 4-2,

[0256] a1 is the number of repeating structures, a1 includes any positive integer from 1 to 5. Exemplarily, a1 can be 1, 2, 3, 4 or 5.

[0257] In some embodiments, the structural formula shown in formula 4-2 includes at least one of the structural formula shown in formula 4-21 to the structural formula shown in formula 4-24,

[0258] [Substituted or unsubstituted ester group]

[0259] In some embodiments, the flexible group includes a substituted or unsubstituted ester group, which can be a substituted or unsubstituted C3 to C15 ester group.

[0260] The ester group can include a monomolecular ester group or a polyester group. After the ester group is grafted to the side chain of the carboxymethyl cellulose salt, it can destroy the regular O-H-O hydrogen bond structure of the carboxymethyl cellulose salt, weaken the hydrogen bond interaction of the carboxymethyl cellulose salt itself, so that the intermolecular force of the carboxymethyl cellulose salt after grafting modification is weakened, the flexibility is increased, and the flexibility of the negative electrode film layer is improved; and it can improve the migration rate of active ions such as lithium ions. And the ester group itself has good flexibility, which can further improve the flexibility of the carboxymethyl cellulose salt after substituting the hydroxyl position, thereby improving the flexibility of the negative electrode film layer.

[0261] In some embodiments, the substituted or unsubstituted C3 to C15 ester group includes the structural formula shown in formula 5,

[0262] In formula 5,

[0263] R 51 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene;

[0264] R 52 including a substituted or unsubstituted C1 to C5 alkyl group;

[0265] R 53 to R 55each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0266] b is the number of repeating structures, and b includes any positive integer of 1 to 30. b can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30.

[0267] Either end of the ester group in Formula 5 can be connected to the oxygen atom in the modified carboxymethyl cellulose salt, for example, the left end group can be connected to the oxygen atom, or the right end group can be connected to the oxygen atom. The end group of the ester group in Formula 5, which is not connected to the oxygen atom, can include a hydrogen atom or a C1 to C3 alkyl group.

[0268] In some embodiments, R 51 includes a single bond, and the substituted or unsubstituted C3 to C150 ester group includes a structural formula represented by Formula 5-1,

[0269] For example, the structural formula represented by Formula 5-1 includes at least one of a structural formula represented by Formula 5-11 to a structural formula represented by Formula 5-16,

[0270] In some embodiments, R 51 includes a substituted or unsubstituted C1 to C5 methylene group, and the substituted or unsubstituted C3 to C150 ester group includes a structural formula represented by Formula 5-2,

[0271] b1 is the number of repeating structures, and b1 includes any positive integer of 1 to 5, for example, b1 can be 1, 2, 3, 4, or 5.

[0272] For example, the structural formula represented by Formula 5-2 includes at least one of a structural formula represented by Formula 5-21 to a structural formula represented by Formula 5-28,

[0273] In each of the above embodiments, the halogen atom can include at least one of a fluorine atom, a chlorine atom, and a bromine atom. The above atom can improve the voltage resistance of the polymer.

[0274] For example, the substituted or unsubstituted C3 to C150 ester group includes at least one of a structural formula represented by Formula 5-21 to a structural formula represented by Formula 5-28,

[0275] In each of the above embodiments, the weight average molecular weight of the flexible group is 78 Da to 5000 Da. The molecular weight of the grafted group in the negative electrode dispersant is relatively small, which can reduce the hydrogen bonding effect between the molecular chains of the negative electrode dispersant, and at the same time, can make the negative electrode dispersant have good dispersibility.

[0276] For example, the weight average molecular weight of the flexible group can be 78 Da, 80 Da, 85 Da, 88 Da, 90 Da, 92 Da, 95 Da, 98 Da, 100 Da, 120 Da, 150 Da, 200 Da, 250 Da, 300 Da, 350 Da, 400 Da, 450 Da, 500 Da, 550 Da, 600 Da, 650 Da, 700 Da, 750 Da, 800 Da, 850 Da, 900 Da, 950 Da, 1000 Da, 1050 Da, 1100 Da, 1150 Da, 1200 Da, 1250 Da, 1300 Da, 1350 Da, 1400 Da, 1450 Da, 1500 Da, 1550 Da, 1600 Da, 1650 Da, 1700 Da, 1750 Da, 1800 Da, 1850 Da, 1900 Da, 1950 Da, 2000 Da, 2050 Da, 2100 Da, 2150 Da, 2200 Da, 2250 Da, 2300 Da, 2350 Da, 2400 Da, 2450 Da, 2500 Da, 3000 Da, 3100 Da, 3200 Da, 3300 Da, 3400 Da, 3500 Da, 3600 Da, 3700 Da, 3800 Da, 3900 Da, 4000 Da, 4100 Da, 4200 Da, 4300 Da, 4400 Da, 4500 Da, 4600 Da, 4700 Da, 4800 Da, 4900 Da, 5000 Da, or a range between any two of the above values.

[0277] In some embodiments, the weight average molecular weight of the modified carboxymethyl cellulose salt is 40 wDa to 80 wDa. When the weight average molecular weight of the modified carboxymethyl cellulose salt is in the above range, the negative electrode dispersant can have excellent dispersing performance.

[0278] For example, the weight average molecular weight of the modified carboxymethyl cellulose salt can be 40 wDa, 42 wDa, 45 wDa, 46 wDa, 48 wDa, 50 wDa, 52 wDa, 55 wDa, 58 wDa, 60 wDa, 62 wDa, 65 wDa, 68 wDa, 70 wDa, 72 wDa, 75 wDa, 78 wDa, 80 wDa, or a range between any two of the above values.

[0279] In the present application, the weight average molecular weight of the polymer can be tested by a method known in the art, for example, by using a gel chromatography, such as a Waters 2695 Isocratic HPLC type gel chromatograph with a differential refractometer detector 2141.

[0280] The conventional sodium carboxymethyl cellulose is a solid polymer at room temperature. The sodium carboxymethyl cellulose is dissolved in solvent water, the mass content of the sodium carboxymethyl cellulose is 1%, and after stirring at 1200 rpm for 2 h, the reference adhesive film is obtained by drying in an oven, for example, at 40℃ for more than 24 h. The reference adhesive film has a width of 2.5 cm, a length of 5 cm, and a thickness of 1 mm. The breaking elongation of the reference adhesive film is tested, and the breaking elongation of the reference adhesive film is defined as 100%. It should be noted that the conventional sodium carboxymethyl cellulose refers to the side chain of the sodium carboxymethyl cellulose which is not substituted by other groups, and in particular, the hydrogen atom at the hydroxyl position is not substituted.

[0281] In some embodiments, the modified carboxymethyl cellulose salt is prepared into an adhesive film. The modified carboxymethyl cellulose salt is dissolved in solvent water, the mass content of the modified carboxymethyl cellulose salt is 1%, and after stirring at 1200 rpm for 2 h, the adhesive film is obtained by drying in an oven, for example, at 40℃ for more than 24 h. The adhesive film has a width of 2.5 cm, a length of 5 cm, and a thickness of 1 mm. The breaking elongation of the adhesive film is tested, and the breaking elongation of the adhesive film is calculated based on the breaking elongation of the reference adhesive film of 100%, and the breaking elongation of the adhesive film is 225% to 400%. When the adhesive film is prepared, the thickness deviation of the adhesive film can be controlled within 0.5%.

[0282] Therefore, the breaking elongation of the negative electrode dispersant is higher than that of the conventional sodium carboxymethyl cellulose, and the negative electrode dispersant has better flexibility when applied to the negative electrode sheet and is less likely to break.

[0283] For example, the breaking elongation of the adhesive film can be 225%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, 300%, 320%, 350%, 380%, 400%, or a range formed by any two of the above values.

[0284] In the present application, the breaking elongation of the adhesive film has the meaning known in the art and can be tested by using the equipment and method known in the art. Specifically, the test can be performed according to the standard GB / T36363-2018.

[0285] The modified carboxymethyl cellulose salt can be prepared by the following method:

[0286] In some embodiments, the method comprises the step S100 of performing an epoxy ring-opening reaction treatment.

[0287] In step S100, the epoxy ring-opening reaction treatment specifically includes: providing a carboxymethyl cellulose salt, mixing a ring-opening agent with the carboxymethyl cellulose salt, and then performing a ring-opening treatment to open two adjacent hydroxyl positions of the carboxymethyl cellulose salt.

[0288] In some embodiments, the ring-opening agent includes at least one of sodium tert-butoxide or potassium tert-butoxide.

[0289] In some embodiments, the method includes the step S100 of the epoxy ring-opening reaction treatment and the step S200 of the substitution treatment.

[0290] In step S100, the epoxy ring-opening reaction treatment specifically includes: providing a carboxymethyl cellulose salt, mixing a ring-opening agent with the carboxymethyl cellulose salt, and then performing a ring-opening treatment to open two adjacent hydroxyl positions of the carboxymethyl cellulose salt. Optionally, after the ring-opening treatment, an acidic catalyst is added to activate the hydroxyl groups at the ring-opening positions to aldehyde groups.

[0291] In some embodiments, the ring-opening agent includes at least one of sodium tert-butoxide or potassium tert-butoxide.

[0292] In some embodiments, the acidic catalyst includes phosphoric acid or the like.

[0293] In step S200, the substitution treatment specifically includes: adding a substitution compound to the system to perform a substitution reaction, the substitution compound substitutes the aldehyde groups, and the product after substitution is the modified carboxymethyl cellulose salt. Optionally, after substitution, the aldehyde groups are reduced to hydroxyl groups, and the reducing agent can include at least one of sodium borohydride or lithium aluminum hydride.

[0294] The substitution compound includes a flexible compound.

[0295] In some embodiments, the substitution compound includes a substituted or unsubstituted ether, which can be a substituted or unsubstituted C3 to C150 ether.

[0296] For example, the substituted or unsubstituted C3 to C150 ether includes a compound shown in formula 11,

[0297] In formula 11,

[0298] R 11 to R 17 Each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C2 to C10 alkenyl, or a substituted or unsubstituted C2 to C10 alkynyl.

[0299] m includes any positive integer from 5 to 60.

[0300] In some embodiments, the substituted compound includes a substituted or unsubstituted alkane, optionally a substituted or unsubstituted C3 to C150 alkane.

[0301] Exemplarily, the substituted or unsubstituted C3 to C150 alkane includes a compound as shown in Formula 21,

[0302] In Formula 21,

[0303] R 21 to R 27 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0304] s includes any positive integer from 5 to 60.

[0305] In some embodiments, the substituted compound includes a substituted or unsubstituted polyalkene, optionally a substituted or unsubstituted C3 to C150 polyalkene.

[0306] Exemplarily, the substituted or unsubstituted C3 to C150 polyalkene includes a compound as shown in Formula 31,

[0307] In Formula 31,

[0308] R 31 to R 34 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group;

[0309] R 35 includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0310] p includes any positive integer from 5 to 60.

[0311] In some embodiments, the substituted compound includes a substituted or unsubstituted amide compound, optionally a substituted or unsubstituted C3 to C150 amide compound, which can be a C3 to C150 amide polymer.

[0312] Exemplarily, the substituted or unsubstituted C3 to C150 amide polymer includes a compound as shown in Formula 41,

[0313] In Formula 41,

[0314] R 41 includes at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0315] R 42 to R46 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C2 to C10 alkenyl, and a substituted or unsubstituted C2 to C10 alkynyl;

[0316] R 47 and R 48 each independently includes a hydrogen atom or a C1 to C3 alkyl.

[0317] a includes any positive integer from 1 to 30.

[0318] In some embodiments, the substituted compound includes a substituted or unsubstituted ester compound, optionally a substituted or unsubstituted C3 to C150 ester compound, optionally a C3 to C150 ester polymer.

[0319] Exemplarily, the substituted or unsubstituted C3 to C150 ester polymer includes a compound shown in formula 51,

[0320] In formula 5,

[0321] R 51 includes at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene;

[0322] R 52 includes a substituted or unsubstituted C1 to C5 alkyl;

[0323] R 53 to R 55 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C2 to C10 alkenyl, and a substituted or unsubstituted C2 to C10 alkynyl;

[0324] R 56 and R 57 each independently includes a hydrogen atom or a C1 to C3 alkyl.

[0325] b includes any positive integer from 1 to 30.

[0326] In the preparation of the modified carboxymethyl cellulose salt, the reaction can be carried out under the reaction conditions commonly used in the art, and the mass ratio of each raw material can also be selected according to the mass ratio commonly used in the art. The ring-opening rate of the modified carboxymethyl cellulose salt can be calculated according to the feeding ratio.

[0327] Negative electrode dispersant

[0328] In a second aspect, the embodiments of the present application provide a negative electrode dispersant, the negative electrode dispersant including the modified carboxymethyl cellulose salt of any of the embodiments of the first aspect of the present application.

[0329] In some embodiments, the negative electrode dispersant can further include a carboxymethyl cellulose salt.

[0330] In some embodiments, the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt can be 0.5 to 2. When the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt is in the above range, the modified carboxymethyl cellulose salt can work together with the carboxymethyl cellulose salt to improve the flexibility of the gel film formed by the carboxymethyl cellulose salt and reduce the risk of cracking of the negative electrode film layer.

[0331] For example, the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range defined by any two of the above values.

[0332] Negative electrode tab

[0333] In a third aspect, the embodiments of the present application provide a negative electrode tab. The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes the negative electrode dispersant according to any one of the embodiments of the second aspect of the present application. The negative electrode dispersant can be used as a dispersant in the negative electrode film layer, which can uniformly disperse the negative electrode active material in the negative electrode film layer, so that the performance of the negative electrode film layer is uniform. In addition, the dispersant can also improve the flexibility of the negative electrode film layer and reduce the risk of cracking of the negative electrode film layer.

[0334] For example, the negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0335] In some embodiments, the mass content of the modified carboxymethyl cellulose salt is 0.8% to 1.3%, optionally 1.0% to 1.3%, and further optionally 1.0% to 1.2%, based on the total mass of the negative electrode film layer. When the mass content of the modified carboxymethyl cellulose salt is in the above range, the risk of cracking of the negative electrode film layer can be effectively reduced, and the performance uniformity and flexibility of the negative electrode film layer can be effectively improved. In addition, the proportion of the modified carboxymethyl cellulose salt is relatively low, which basically does not affect the proportion of the negative electrode active material, so that the battery cell has a higher energy density. Moreover, since the modified carboxymethyl cellulose salt can significantly improve the flexibility of the negative electrode film layer, etc., the negative electrode slurry can not add plasticizers and other auxiliary agents, thereby reducing the adverse effects caused by the introduction of plasticizers.

[0336] Exemplarily, the mass content of the modified carboxymethyl cellulose salt can be 0.80%, 0.85%, 0.90%, 0.95%, 1.00%, 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.10%, 1.11%, 1.12%, 1.13%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, 1.2%, 1.3%, or a range between any two of the above values.

[0337] In some embodiments, the negative electrode dispersant in the negative electrode film layer can further include a carboxymethyl cellulose salt, such as at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, lithium carboxymethyl cellulose, and the like. The carboxymethyl cellulose salt is different from the modified carboxymethyl cellulose salt in that the hydroxyl groups in the carboxymethyl cellulose salt are not substituted. The carboxymethyl cellulose salt and the modified carboxymethyl cellulose salt can jointly play a dispersing role, and on this basis, the modified carboxymethyl cellulose salt can additionally improve the flexibility of the negative electrode film layer.

[0338] In some embodiments, the mass content of the carboxymethyl cellulose salt can be 0.05% to 1.0%, or optionally 0.05% to 0.3%, based on the total mass of the negative electrode film layer. When the mass content of the carboxymethyl cellulose salt is within the above range, the carboxymethyl cellulose salt and the modified carboxymethyl cellulose salt can jointly improve the performance uniformity and flexibility of the negative electrode film layer.

[0339] Exemplarily, the mass content of the carboxymethyl cellulose salt can be 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.3%, 0.35%, 0.4%, 0.42%, 0.45%, 0.46%, 0.48%, 0.50%, 0.52%, 0.55%, 0.56%, 0.58%, 0.60%, 0.62%, 0.65%, 0.66%, 0.68%, 0.70%, 0.72%, 0.75%, 0.78%, 0.80%, 0.82%, 0.85%, 0.86%, 0.88%, 0.9%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1.00%, or a range between any two of the above values.

[0340] In some embodiments, the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt can be 0.5 to 2. When the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt is within the above range, the carboxymethyl cellulose salt and the modified carboxymethyl cellulose salt can jointly improve the performance uniformity and flexibility of the negative electrode film layer.

[0341] For example, the ratio of the mass content of the carboxymethyl cellulose salt and the mass content of the modified carboxymethyl cellulose salt can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range defined by any two of the aforementioned values.

[0342] In some embodiments, the coating basis weight of the negative electrode film layer can be 200 mg / 1540.25 mm 2 to 280 mg / 1540.25 mm 2 ; optionally 220 mg / 1540.25 mm 2 to 280 mg / 1540.25 mm 2 The coating basis weight of the negative electrode film layer is relatively high, which is conducive to achieving thick coating.

[0343] For example, the coating basis weight of the negative electrode film layer can be 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 240 mg / 1540.25 mm 2 , 250 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 270 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , or a range defined by any two of the aforementioned values.

[0344] The negative electrode active material can be any known in the art for use in battery cells. For example, the negative electrode active material can include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0345] In some embodiments, the negative electrode active material can include, but is not limited to, at least one of natural graphite and artificial graphite, and the negative electrode dispersant can effectively disperse the aforementioned negative electrode active material, thereby improving the dispersion uniformity of the negative electrode active material in the negative electrode film layer.

[0346] In some embodiments, the negative electrode film layer can optionally further include a negative electrode conductive agent. The present embodiments do not have particular limitations on the type of negative electrode conductive agent, and as an example, the negative electrode conductive agent can include at least one of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0347] In some embodiments, the negative electrode film layer can optionally further include a negative electrode binder. The present embodiments do not have particular limitations on the type of negative electrode binder, and as an example, the negative electrode binder can include at least one of styrene butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, for example, polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS, polyacrylamide PAM, polyvinyl alcohol PVA, sodium alginate SA, and carboxymethyl chitosan CMCS. In some embodiments, the mass percentage content of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0348] In some embodiments, the negative electrode film layer can optionally further include other auxiliary agents. As an example, the other auxiliary agents can include thickening agents, for example, PTC thermistor materials, etc. In some embodiments, the mass percentage content of the other auxiliary agents is ≤2% based on the total weight of the negative electrode film layer.

[0349] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include at least one of polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, and polyethylene PE.

[0350] The negative electrode film layer is generally formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a negative electrode dispersant, an optional conductive agent, an optional binder, and other optional auxiliary agents in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone NMP or deionized water, but is not limited thereto.

[0351] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab of the present embodiments further includes a conductive primer layer composed of a conductive agent and a binder, which is disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some other embodiments, the negative electrode tab of the present embodiments further includes a protective layer covering the surface of the negative electrode film layer.

[0352] Battery cell

[0353] In a fourth aspect, the embodiments of the present application provide a battery cell. The battery cell comprises a negative electrode tab. The negative electrode tab comprises any of the negative electrode tabs according to the third aspect of the present application. Due to the use of the negative electrode tab, the thickness of the negative electrode tab is uniform, and the performance of the negative electrode tab is uniform. During the cycle charging and discharging of the battery cell, the uniform charging and discharging of the negative electrode tab at all places is beneficial.

[0354] [Positive electrode tab]

[0355] In some embodiments, the battery cell further comprises a positive electrode tab.

[0356] The positive electrode tab comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises a positive electrode active material.

[0357] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0358] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can comprise a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. on a base material such as a polypropylene (PP) base material, a polyethylene terephthalate (PET) base material, a polybutylene terephthalate (PBT) base material, a polystyrene (PS) base material, a polyethylene (PE) base material, etc.

[0359] In some embodiments, the positive electrode active material can include, but is not limited to, at least one of a lithium-containing transition metal oxide, a lithium-containing phosphate, and a modified compound of each of them. Examples of the lithium-containing transition metal oxide can include, but are not limited to, at least one of a lithium cobalt oxide, a lithium nickel oxide, a lithium manganese oxide, a lithium nickel cobalt oxide, a lithium manganese cobalt oxide, a lithium nickel manganese oxide, a lithium nickel cobalt manganese oxide, a lithium nickel cobalt aluminum oxide, and a modified compound of each of them. Examples of the lithium-containing phosphate can include, but are not limited to, at least one of a lithium iron phosphate, a composite of lithium iron phosphate and carbon, a lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and a modified compound of each of them.

[0360] The positive electrode film layer includes a positive electrode active material, which can employ a positive electrode active material known in the art for use in battery cells. As an example, the positive electrode active material can include at least one of the following materials: layered structure positive electrode active materials such as ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium / sodium-rich layered, and rock-salt phase layered materials, olivine-type phosphate active materials, spinel structure positive electrode active materials such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel lithium manganate, and lithium nickel manganate, etc.

[0361] As an example, the layered structure positive electrode active material has a general formula of: Li x A y Ni a Co b Mn c M 1-a-b-c Y z wherein 0≤x≤2.1, 0≤y≤2.1, and 0.9≤x+y≤2.1; 0≤a≤1, 0≤b≤1, 0≤c≤1, and 0.1≤a+b+c≤1; 1.8≤z≤3.5; A is selected from one or more of Na, K, Mg; M is selected from one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y is selected from one or more of O, F. Optionally, y=0. Specifically, the layered structure positive electrode active material can include one or more of lithium cobaltate LCO, lithium nickelate LNO, lithium manganate LMO, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), and LiNi 0.5 Co0 .2 Mn 0.3 O2(NCM523).

[0362] As an example, the olivine-type phosphate active material has a general formula of: Li x A y Me a M b P 1-c X c Y zwherein 0≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A is selected from one or more of Na, K, Mg; Me is selected from one or more of Mn, Fe, Co, Ni; M is selected from one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X is selected from one or more of S, Si, Cl, B, C, N; Y is selected from one or more of O, F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0363] Exemplarily, the general formula of the spinel-structured positive electrode active material is: Li x A y Mn a M 2-a Y z wherein 0≤x≤2, 0≤y≤1, and 0.9≤x+y≤2; 0.5≤a≤2; 3≤z≤5; A is selected from one or more of Na, K, Mg; M is selected from one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y is selected from one or more of O, F. Specifically, the spinel-structured positive electrode active material includes one or more of LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiCr 0.3 Mn 1.7 O4, Li 1.1 Al 0.1 Mn 1.9 O4, Li2Mn2O4, and Li 1.5 Mn2O4.

[0364] In the present application, the modified compound of each of the above positive electrode active materials can be a doping modification and / or a surface coating modification to the positive electrode active material.

[0365] In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene-fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene-fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass percentage of the binder is ≤ 5% based on the total weight of the positive electrode film layer.

[0366] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the conductive agent is ≤ 5% based on the total weight of the positive electrode film layer.

[0367] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the optional conductive agent, the optional binder, and any other components, in a solvent, such as N-methylpyrrolidone, to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing, etc., obtaining the positive electrode tab.

[0368] [Electrolyte]

[0369] In some embodiments, the battery cell further includes an electrolyte.

[0370] During the charging and discharging of the battery cell, active ions are embedded and extracted back and forth between the positive electrode tab and the negative electrode tab, and the electrolyte plays a role in conducting the active ions between the positive electrode tab and the negative electrode tab. The type of electrolyte is not particularly limited in the present application and can be selected according to actual needs.

[0371] The electrolyte includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0372] As an example, the electrolyte salt can include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-phosphate (LiPO2F2), lithium difluoro-di-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0373] As an example, the solvent can include, but is not limited to, at least one of ethylene carbonate EC, propylene carbonate PC, ethyl methyl carbonate EMC, diethyl carbonate DEC, dimethyl carbonate DMC, dipropyl carbonate DPC, methyl propyl carbonate MPC, ethyl propyl carbonate EPC, butylene carbonate BC, fluoroethylene carbonate FEC, methyl formate MF, methyl acetate MA, ethyl acetate EA, propyl acetate PA, methyl propionate MP, ethyl propionate EP, propyl propionate PP, methyl butyrate MB, ethyl butyrate EB, 1,4-butyrolactone GBL, sulfolane SF, dimethyl sulfone MSM, methyl ethyl sulfone EMS, and diethyl sulfone ESE.

[0374] In some embodiments, the electrolyte solution can further include an additive. For example, the additive can include a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, etc.

[0375] [Separator]

[0376] In some embodiments, the battery cell can further include a separator.

[0377] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0378] In some embodiments, the material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0379] In some embodiments, the positive electrode tab, the separator, and the negative electrode tab can be made into an electrode assembly through a winding process and / or a stacking process.

[0380] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte solution described above.

[0381] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as at least one of polypropylene PP, polybutylene terephthalate PBT, and polybutylene succinate PBS.

[0382] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. FIG. 1 is a battery cell 5 having a square structure as an example.

[0383] In some embodiments, as shown in FIG. 2, the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to requirements.

[0384] The preparation method of the battery cell of the present application is known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly is placed in an outer package, the electrolyte is injected after drying, and the battery cell is obtained after processes such as vacuum packaging, standing, formation, and shaping.

[0385] In some embodiments of the present application, the battery cell according to the present application can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0386] FIG. 3 is a schematic view of a battery module 4 as an example. As shown in FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0387] Optionally, the battery module 4 can further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0388] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0389] FIGS. 4 and 5 are schematic views of a battery pack 1 as an example. As shown in FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0390] The battery of the embodiments of the present application can include one battery cell or a plurality of battery cells, and in the case of including a plurality of battery cells, the battery can include a battery module or a battery pack.

[0391] Electric device

[0392] In a fifth aspect, the embodiments of the present application provide an electric device comprising at least one of the battery cell, the battery module or the battery pack of the present application. The battery cell, the battery module or the battery pack can be used as a power source of the electric device, or can be used as an energy storage unit of the electric device. The electric device can be, but is not limited to, a mobile device such as a mobile phone, a notebook computer, etc., an electric vehicle such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., an electric train, a ship and a satellite, an energy storage system, etc.

[0393] The electric device can select the battery cell, the battery module or the battery pack according to its use requirement.

[0394] FIG. 6 is a schematic diagram of an electric device 6 as an example. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the electric device 6, the battery pack 1 or the battery module can be used.

[0395] The electric device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The electric device usually requires thin and light, and the battery cell can be used as a power source.

[0396] Embodiments

[0397] The embodiments described below are merely illustrative of the present application and are not intended to limit the scope of the present application, since various modifications and changes can be made to the embodiments within the scope of the present application, which will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the embodiments are commercially available.

[0398] Preparation of lithium ion battery

[0399] 1. Preparation of positive electrode sheet

[0400] An aluminum foil is used as the positive current collector.

[0401] The positive active material lithium cobalt oxide LiCoO2, the conductive agent acetylene black, and the binder polyvinylidene fluoride PVDF are mixed uniformly in a proper amount of solvent N-methyl pyrrolidone NMP at a mass ratio of 95:2:3 to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive current collector aluminum foil, and through processes such as drying, cold pressing, slitting and cutting, a positive electrode sheet is obtained.

[0402] 2. Preparation of the negative electrode sheet

[0403] The copper foil is used as the negative current collector.

[0404] The artificial graphite as the negative active material, the conductive agent conductive carbon, the binder phenolic emulsion, and the negative dispersant are mixed uniformly in deionized water to prepare the negative electrode slurry. The mass ratio of the artificial graphite, the conductive agent conductive carbon, the binder phenolic emulsion, and the negative dispersant in the solid components of the negative electrode slurry is 96.7:0.7:1.5:1.1, and the negative dispersant comprises modified CMC-Na. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C, and then cold-pressed to obtain the negative electrode sheet containing the negative active material layer.

[0405] 3. Preparation of the electrolyte

[0406] The organic solvents ethylene carbonate EC, methyl ethyl carbonate EMC, and diethyl carbonate DEC are mixed in a volume ratio of 1:1:1 to obtain the electrolyte solvent in an environment with a water content of less than 10 ppm, and then the lithium salt lithium hexafluorophosphate is mixed with the mixed solvent, and the lithium salt is 1 mol / L.

[0407] 4. Preparation of the lithium ion battery

[0408] The positive electrode sheet, the polyethylene PE separator, and the negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with the electrolyte, and then subjected to vacuum packaging, standing, formation, shaping, and other processes to obtain the lithium ion battery.

[0409] Examples 2-1 to 2-5

[0410] Different from Example 1, the types of flexible groups in the negative dispersant in the negative electrode slurry are different, wherein, in Example 2-5, only ring opening is performed without grafting flexible groups after ring opening.

[0411] Example 3

[0412] Different from Example 1, the number of repetitions of the flexible groups in the negative dispersant in the negative electrode slurry is different, and the feeding ratio is also different.

[0413] Comparative Example 1

[0414] Different from Example 1, the negative dispersant is added to the negative electrode slurry, and the negative dispersant is replaced by sodium carboxymethyl cellulose CMC-Na, and the mass ratio of the artificial graphite, the conductive agent conductive carbon, the binder phenolic emulsion, and the negative dispersant CMC-Na in the solid components of the negative electrode slurry is 96.7:0.7:1.5:1.1.

[0415] Comparative Example 2

[0416] Different from example 1, the negative electrode dispersant is added in the negative electrode slurry, the negative electrode dispersant is replaced by sodium carboxymethyl cellulose, and a plasticizer is added in the negative electrode slurry, and the mass ratio of artificial graphite, conductive agent conductive carbon, adhesive phenylpropyl emulsion, negative electrode dispersant CMC-Na, plasticizer butanediol in the solid content of the negative electrode slurry is 96.55:0.7:1.5:1.1:0.15.

[0417] The relevant parameters of the examples and comparative examples are shown in Table 1.

[0418] Test section

[0419] 1. Negative electrode slurry filtration test:

[0420] Filter screen 150 mesh, cut the filter screen into 25 cm*25 cm with scissors.

[0421] Fold the 150 mesh filter screen into a fan shape and hang it on the mouth of a clean beaker, pour 500 mL of negative electrode slurry from above the filter screen at one time, the negative electrode slurry flows out from the tip of the filter screen, and the time is recorded. Record the filtration time of 300 mL.

[0422] 2. Negative electrode slurry gel and sedimentation state:

[0423] Take 500 ml of negative electrode slurry and place it for different times to observe whether the negative electrode slurry appears jelly gel state, and test the slurry viscosity, if the upper layer slurry viscosity of the test beaker decreases and the lower layer slurry becomes thick, it indicates that the slurry sedimentation occurs.

[0424] 3. Coating weight of negative electrode film layer:

[0425] The coating window measures the approximate critical range of the quality stability of the coating product, and exceeding this range will result in cracking and other defects. Using an extrusion coater and coating at a speed of 50 m / min, as the coating quality of the negative electrode sheet of the comparative examples and examples gradually increases, observe whether the film layer cracks, if not, continue to increase the weight until the surface film layer of the electrode sheet cracks, record the non-cracking coating weight of the negative electrode film layer, which is the coating weight of the negative electrode film layer in Table 1.

[0426] Test results

[0427] The test results are shown in Table 1.

[0428] Table 1

[0429] The weight average molecular weight of the negative electrode dispersant in the examples and comparative examples is 60 wDa.

[0430] The number of repeating structures in the flexible group refers to the number of continuously repeating groups in the flexible group, such as the value of m in formula 1-1, the value of s in formula 2-1, the value of p in formula 3-7, the value of a in formula 4-11, and the value of b in formula 5-11.

[0431] The mass ratio of the flexible compound to the carboxymethyl cellulose salt CMC-M can be used to characterize the proportion of the number of flexible groups after ring opening and side chain grafting; specifically, it refers to the mass ratio of the flexible compound to the carboxymethyl cellulose salt CMC-M in the raw materials for preparing the modified CMC-M, which is calculated based on 100 g of carboxymethyl cellulose salt.

[0432] The proportion of formula A in Table 1 refers to the sum of the proportions of the structural units represented by formula A-1 and the structural units represented by formula A-2.

[0433] The above examples and comparative examples have been tested by gel and sedimentation, and the negative electrode slurry has no sedimentation and no gel, and the state of the negative electrode slurry is relatively stable.

[0434] As can be seen from Table 1, Comparative Example 1 adds a dispersant sodium carboxymethyl cellulose CMC-Na in the negative electrode slurry. The sodium carboxymethyl cellulose has not been modified by side chain, which is beneficial to improve the dispersion performance of the negative electrode active material in the negative electrode slurry. However, due to the hydrogen bonding effect of the sodium carboxymethyl cellulose itself, the interaction between the molecular chains is strong, the drying stress is large during the drying process, the brittleness is strong, and the negative electrode film layer is prone to cracking, which is not conducive to thick coating of the negative electrode slurry, and the coating bulk density is small.

[0435] Compared with Comparative Example 1, Comparative Example 2 further adds a plasticizer in the negative electrode slurry. The plasticizer can effectively improve the plasticizing ability and flexibility of the negative electrode film layer, which is beneficial to thick coating of the negative electrode slurry, the coating bulk density is improved, and the cracking phenomenon of the negative electrode film layer is improved. However, it is found through testing that the thickness of the negative electrode film layer with the plasticizer is not uniform, resulting in uneven performance of the negative electrode film layer.

[0436] However, the plasticizer is not added in the negative electrode slurry of the present application, the negative electrode dispersant sodium carboxymethyl cellulose is partially ring-opened, and can be further modified by side chain grafting, which can reduce the hydrogen bonding effect of the dispersant, weaken the interaction between the molecular chains of the dispersant, enhance the flexibility of the negative electrode dispersant, improve the flexibility of the negative electrode film layer, reduce the risk of cracking of the negative electrode film layer, especially reduce the risk of cracking of the thick coated negative electrode film layer, and improve the energy density of the battery cell. Moreover, the modified carboxymethyl cellulose salt has good dispersing and leveling effects, can effectively disperse the negative electrode active material, and make the negative electrode active material disperse uniformly, the thickness distribution of the negative electrode film layer is uniform, and the performance is uniform.

[0437] The adjustment of the ring-opening rate in the embodiment of the present application can make the proportion of the structural unit shown in formula A be 0.5% to 20%, and optionally 1% to 10%, so as to effectively improve the flexibility of the negative electrode film layer, and make the thickness distribution of the negative electrode film layer uniform and the performance uniform.

[0438] In the embodiment of the present application, at least one of ether groups, alkyl groups, alkenyl groups, amide groups or ester groups can be used for graft modification when graft modification is performed on the side chain, which can effectively improve the flexibility of the modified carboxymethyl cellulose salt, and can improve the flexibility of the negative electrode film layer, so that the thickness distribution of the negative electrode film layer is uniform and the performance is uniform.

[0439] Moreover, when the repeating number of the structural unit of the flexible group is adjusted, for example, the repeating number is 1 to 60, the flexibility of the negative electrode film layer can still be improved, so that the thickness distribution of the negative electrode film layer is uniform and the performance is uniform.

[0440] The embodiment of the present application controls the addition amount of the dispersant in the negative electrode slurry, which can effectively adjust the thick coating degree of the negative electrode slurry, and improve the flexibility of the negative electrode film layer and the like.

[0441] The negative electrode sheet in embodiment 1 is detected in multiple places in the present application, for example, 10 places of the negative electrode sheet are taken to perform ion polishing section element analysis CP according to GB / T 17359-2012, to confirm the thickness of the negative electrode film layer in the negative electrode sheet, and the thickness deviation of the negative electrode film layer obtained by 10 tests is controlled within 0.5%, so that the thickness of the negative electrode film layer in the negative electrode sheet is considered to be uniform, and the thickness consistency is high.

[0442] The method of embodiment 1 is used to prepare 10 lithium ion batteries in the present application, the average thickness of the negative electrode film layer of each lithium ion battery is measured, that is, ion polishing section element analysis CP is performed according to GB / T 17359-2012, the thickness of the negative electrode film layer at 10 places of the negative electrode sheet is measured, and the average value is calculated as the average thickness of the lithium ion battery, and the thickness deviation of the negative electrode film layer of the 10 lithium ion batteries is controlled within 0.5%.

[0443] Although the illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments cannot be interpreted as a limitation of the present application, and the embodiments can be changed, replaced and modified without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material and a negative electrode dispersant, the negative electrode dispersant comprising a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprising a structural unit represented by Formula A, Formula A In formula A, Q comprises a hydrogen atom or -CH2COOM1, M1comprises a metal ion or NH4 + at least one of the group consisting of R includes a hydrogen atom or a flexible group, the flexible group including at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyalkene group, a substituted or unsubstituted amide group, a substituted or unsubstituted ester group.

2. The battery cell of claim 1, wherein, The structural unit of formula A includes a structural unit of formula A-1, 3. The battery cell of claim 1, wherein, The structural units of the formula A include structural units of the formula A-2, 4. The battery cell of any one of claims 1 to 3, the negative electrode dispersant further comprising a structural unit represented by Formula B, In formula B, M2includes at least one of a metal ion or NH4 + .

5. The battery cell of any one of claims 1 to 4, wherein, The number ratio of the structural unit shown in formula A to the total number of the structural unit shown in formula A and the structural unit shown in formula B is 0.5% to 20%.

6. The battery cell of claim 5, wherein, The number ratio of the structural unit shown in formula A to the total number of the structural unit shown in formula A and the structural unit shown in formula B is 1% to 10%.

7. The battery cell of any one of claims 1 to 6, wherein, The flexible group includes at least one of a substituted or unsubstituted C3 to C150 ether group, a substituted or unsubstituted C3 to C150 alkyl group, a substituted or unsubstituted C3 to C150 polyalkene group, a substituted or unsubstituted C3 to C150 amide group, a substituted or unsubstituted C3 to C150 ester group.

8. The battery cell of claim 7, wherein, The substituted or unsubstituted C3to C150ether group includes a structural formula represented by Formula 1, In Formula 1, R 11 to R 17 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C2 to C10 alkenyl, and a substituted or unsubstituted C2 to C10 alkynyl; m includes any positive integer from 5 to 60.

9. The battery cell of claim 7 or 8, wherein, The substituted or unsubstituted C3to C150ether group includes at least one of the structural formulas from Formula 1-1 to Formula 1-14, m1 includes any positive integer from 1 to 30.

10. The battery cell of any one of claims 7-9, wherein, The substituted or unsubstituted C3to C150alkyl group includes a structural formula represented by Formula 2, In Formula 2, R 21 to R 27 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group; s includes any positive integer from 5 to 60.

11. The battery cell of any one of claims 7-10, wherein, The substituted or unsubstituted C3 to C150 alkyl includes at least one of structural formulas from Formula 2-1 to Formula 2-11, s1 includes any positive integer from 1 to 30.

12. The battery cell of any one of claims 7-11, wherein, The substituted or unsubstituted C3to C150polyalkylene group includes a structural formula represented by Formula 3, In Formula 3, R 31 to R 34 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, and a substituted or unsubstituted C2 to C10 alkenyl. R 35 at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group; p includes any positive integer from 5 to 60.

13. The battery cell of any one of claims 7-11, wherein, The substituted or unsubstituted C3to C150polyalkene group includes at least one of the structural formulae shown in Formula 3-1 through Formula 3-8, 14. The battery cell of any one of claims 7-13, wherein, The substituted or unsubstituted C3to C150amide group includes a structural formula shown in Formula 4, In Formula 4, R 41 at least one of a single bond, substituted or unsubstituted C1to C5alkylene; R 42 to R 46 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C2 to C10 alkenyl, a substituted or unsubstituted C2 to C10 alkynyl; a includes any positive integer from 1 to 30.

15. The battery cell of claim 14, wherein, R 41 including a single bond, said substituted or unsubstituted C3to C15amide-based group includes a structural formula represented by Formula 4-1, 16. The battery cell of claim 15, wherein, The substituted or unsubstituted C3to C150amide group includes at least one of the structural formulas from Formula 4-11 to Formula 4-15, 17. The battery cell of claim 14, wherein, R 41 substituted or unsubstituted C1to C5alkylene, the substituted or unsubstituted C3to C15amide group includes a structural formula as shown in Formula 4-2, a1 includes any positive integer from 1 to 5.

18. The battery cell of claim 17, wherein, The substituted or unsubstituted C3to C150amide group includes at least one of the structural formulae from Formula 4-21 to Formula 4-24, 19. The battery cell of any one of claims 7-18, wherein, The substituted or unsubstituted C3to C150ester group includes a structural formula represented by Formula 5, In Formula 5, R 51 at least one of a single bond, substituted or unsubstituted C1to C5alkylene; R 52 including substituted or unsubstituted C1to C5alkyl; R 53 to R 55 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C2 to C10 alkenyl, a substituted or unsubstituted C2 to C10 alkynyl; b includes any positive integer from 1 to 30.

20. The battery cell of claim 19, wherein, R 51 including a single bond, said substituted or unsubstituted C3to C15aliphatic group including a structural formula represented by Formula 5-1, 21. The battery cell of claim 20, wherein, The substituted or unsubstituted C3to C150ester group includes at least one of the structural formulas from Formula 5-11 to Formula 5-16, 22. The battery cell of claim 19, wherein, R 51 substituted or unsubstituted C1to C5alkylene, the substituted or unsubstituted C3to C15ester group includes a structural formula as shown in formula 5-2, b1 includes any positive integer from 1 to 5.

23. The battery cell of claim 22, wherein, The substituted or unsubstituted C3to C150ester group includes at least one of the structural formulas from Formula 5-21 to Formula 5-28, 24. The battery cell of any one of claims 1-23, wherein, The weight average molecular weight of the negative electrode dispersant is 40 wDa to 80 wDa.

25. The battery cell of any one of claims 1-24, wherein, The elongation at break of a reference adhesive film made of sodium carboxymethyl cellulose is 100%, the elongation at break of an adhesive film made of the modified carboxymethyl cellulose salt is 225% to 400%, the width of the adhesive film and the reference adhesive film is 2.5 cm, the length is 5 cm, and the thickness is 1 mm.

26. The battery cell of any one of claims 1-25, wherein, The mass content of the modified carboxymethyl cellulose salt is 0.8% to 1.3% based on the total mass of the negative electrode film layer.

27. The battery cell of claim 26, wherein, The mass content of the modified carboxymethyl cellulose salt is 1.0% to 1.2% based on the total mass of the negative electrode film layer.

28. The battery cell of any one of claims 1-27, wherein, The coating mass of the negative electrode film layer is 200 mg / 1540.25 mm 2 to 280 mg / 1540.25 mm 2 .

29. The battery cell of claim 28, wherein, The coating mass of the negative electrode film layer is 220 mg / 1540.25 mm 2 to 280 mg / 1540.25 mm 2 .

30. A negative electrode dispersant comprising a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprising structural units represented by Formula A, ###00001### Formula A In formula A, Q includes a hydrogen atom or -CH2COOM1, M1 includes a metal ion or NH4 + at least one of the following: R includes a hydrogen atom or a flexible group, the flexible group including at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyalkene group, a substituted or unsubstituted amide group, a substituted or unsubstituted ester group.

31. The negative dispersant of claim 30, wherein, The structural unit of formula A includes a structural unit of formula A-1, 32. The negative dispersant of claim 30 or 31, wherein, The structural units of the formula A include structural units of the formula A-2, 33. The negative dispersant of any one of claims 30-32, further comprising a structural unit represented by Formula B, In formula B, M2includes at least one of a metal ion or NH4 + .

34. The negative dispersant of any one of claims 30-33, wherein, The number ratio of the structural unit shown in formula A to the total number of the structural unit shown in formula A and the structural unit shown in formula B is 0.5% to 20%.

35. The negative dispersant of claim 34, wherein, The number ratio of the structural unit shown in formula A to the total number of the structural unit shown in formula A and the structural unit shown in formula B is 1% to 10%.

36. The negative dispersant of any one of claims 30-35, wherein, The flexible group includes at least one of a substituted or unsubstituted C3 to C150 ether group, a substituted or unsubstituted C3 to C150 alkyl group, a substituted or unsubstituted C3 to C150 polyalkene group, a substituted or unsubstituted C3 to C150 amide group, a substituted or unsubstituted C3 to C150 ester group.

37. A modified carboxymethylcellulose salt comprising structural units represented by Formula A, ###00015### Formula A In formula A, Q includes a hydrogen atom or -CH2COOM1, M1 includes a metal ion or NH4 + at least one of the group consisting of R comprises a hydrogen atom or a flexible group comprising at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, a substituted or unsubstituted ester group.

38. A negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer comprising the negative electrode dispersant of any one of claims 30-36.

39. A battery comprising the battery cell of any one of claims 1-29.

40. An electrically powered device comprising the battery of claim 39.

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