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

Abstract

A modified carboxymethyl cellulose salt, a negative electrode dispersant, a negative electrode sheet, a battery cell, a battery, and an electrical device. 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; and the modified carboxymethyl cellulose salt comprises a hemiacetal group. The risk of cracking of the negative electrode film layer in the negative electrode sheet can be reduced.

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. 202410825938.0, filed on June 24, 2024, entitled “Modified carboxymethyl cellulose salt, negative electrode dispersant, negative electrode sheet, battery cell, battery and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present application relates to the technical field of batteries, and more particularly, 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 becoming more and more extensive, the requirements for battery performance are gradually stringent. 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 arranged 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 hemiacetal group.

[0009] Thus, the modified carboxymethyl cellulose salt of the present application comprises a hemiacetal group, which can weaken the interaction between the molecular chains of the modified carboxymethyl cellulose salt, increase the flexibility of the modified carboxymethyl cellulose salt, thereby increasing the flexibility of the negative electrode film layer and reducing the risk of warping and cracking of the negative electrode film layer; and the hemiacetal group makes the dissolution rate of the modified carboxymethyl cellulose salt improved and not easy to form a mass, which can better disperse the negative electrode active material and improve the dispersion performance of the negative electrode slurry;

[0010] Moreover, the main structure of the modified carboxymethyl cellulose salt is still carboxymethyl cellulose salt, so it still has good dispersing effect, can effectively reduce the interfacial tension between the negative active material and the solvent, makes the negative active material uniformly dispersed in the negative electrode slurry, makes the thickness distribution of the negative electrode film layer uniform, and the performance is uniform;

[0011] 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 realize thick coating, and the performance of the negative electrode film layer is uniform and has good flexibility.

[0012] In some embodiments, the hemiacetal group comprises a C1 to C10 aldehyde hemiacetal group, which can be a C1 to C4 aldehyde hemiacetal group. The modified carboxymethyl cellulose salt comprising the above-mentioned hemiacetal group has a faster dissolution rate, and when dissolved in the negative electrode slurry, it can effectively disperse the negative active material; and the interaction between the molecular chains of the above-mentioned modified carboxymethyl cellulose salt is smaller, thereby further reducing the stress generated during drying, so that the negative electrode slurry is not prone to warping during the drying process, and the risk of cracking is reduced.

[0013] In some embodiments, the hemiacetal group comprises one or more of a formaldehyde hemiacetal group, an acetaldehyde hemiacetal group, a propionaldehyde hemiacetal group, a butyraldehyde hemiacetal group, a pentanal hemiacetal group, a hexanal hemiacetal group, a heptanal hemiacetal group, an octanal hemiacetal group, a nonanal hemiacetal group, a decanal hemiacetal group, a glyoxal hemiacetal group, a methylglyoxal hemiacetal group, an ethylglyoxal hemiacetal group, a malonaldehyde hemiacetal group, a succinaldehyde hemiacetal group, a glutaraldehyde hemiacetal group, a heptanedial hemiacetal group, an octanedial hemiacetal group, a nonanedial hemiacetal group, and a decanedial hemiacetal group.

[0014] In some embodiments, the hemiacetal group comprises one or more of a formaldehyde hemiacetal group, an acetaldehyde hemiacetal group, a propionaldehyde hemiacetal group, a butyraldehyde hemiacetal group, a glyoxal hemiacetal group, a malonaldehyde hemiacetal group, and a succinaldehyde hemiacetal group.

[0015] In some embodiments, the modified carboxymethyl cellulose salt further comprises 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.

[0016] Therefore, the flexible group of the embodiments of the present application can reduce the interaction between the polymer molecular chains, thereby reducing the stress generated during drying, reducing the risk of cracking of the negative electrode film layer, and improving the flexibility of the negative electrode film layer.

[0017] In some embodiments, the flexible group comprises 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, a substituted or unsubstituted C3 to C150 ester group.

[0018] Thus, the flexible group of the embodiments of the present application can reduce the interaction between the polymer molecular chains, thereby reducing the stress generated during drying, reducing the risk of cracking of the negative electrode film layer, and improving the flexibility of the negative electrode film layer.

[0019] In some embodiments, the substituted or unsubstituted C3 to C150 ether group comprises a structural formula shown in Formula 1,

[0020] In Formula 1,

[0021] R 11 to R 17 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, a substituted or unsubstituted C2 to C10 alkynyl group;

[0022] m comprises any positive integer from 5 to 60.

[0023] Thus, the ether group of the embodiments of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the longer chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0024] In some embodiments, the substituted or unsubstituted C3 to C150 ether group comprises at least one of a structural formula shown in Formula 1-1 to a structural formula shown in Formula 1-14,

[0025] wherein m1 comprises any positive integer from 1 to 30.

[0026] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group comprises a structural formula shown in Formula 2,

[0027] In Formula 2,

[0028] 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;

[0029] s comprises any positive integer from 5 to 60.

[0030] Thus, the alkyl group of the embodiments of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0031] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group comprises at least one of a structural formula represented by Formula 2-1 to a structural formula represented by Formula 2-11,

[0032] wherein s1 comprises any positive integer of 1 to 30.

[0033] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group comprises a structural formula represented by Formula 3,

[0034] In Formula 3,

[0035] 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;

[0036] R 35 comprises at least one of a hydrogen atom, a halogen atom, and a substituted or unsubstituted C1 to C10 alkyl group;

[0037] p comprises any positive integer of 5 to 60.

[0038] Thus, the polyalkylene group of the embodiments of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0039] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group comprises at least one of a structural formula represented by Formula 3-1 to a structural formula represented by Formula 3-8,

[0040] Formula 3-8,

[0041] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group comprises a structural formula represented by Formula 4,

[0042] In Formula 4,

[0043] R 41 comprises at least one of a single bond and a substituted or unsubstituted C1 to C1 methylene group;

[0044] R 42 to R 46each 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;

[0045] a1 includes any positive integer of 1 to 5.

[0046] Thereby, the amide-based group of the present embodiment can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0047] In some embodiments, R 41 includes a single bond, a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula represented by Formula 4-1,

[0048] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula represented by Formula 4-11 to a structural formula represented by Formula 4-15,

[0049] In some embodiments, R 41 includes a substituted or unsubstituted C1 to C5 methylene group, a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula represented by Formula 4-2,

[0050] a1 includes any positive integer of 1 to 5.

[0051] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula represented by Formula 4-21 to a structural formula represented by Formula 4-24,

[0052] In some embodiments, the substituted or unsubstituted C3 to C150 ester-based group includes a structural formula represented by Formula 5,

[0053] In Formula 5,

[0054] R 51 includes at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0055] R 52 includes a substituted or unsubstituted C1 to C5 alkyl group;

[0056] 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;

[0057] b comprises any positive integer from 1 to 30.

[0058] Thus, the ester group of the modified carboxymethyl cellulose salt in the embodiments of the present application is longer, which can increase the flexibility of the modified carboxymethyl cellulose salt, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0059] In some embodiments, R 51 comprises a single bond, a substituted or unsubstituted C3 to C150 ester group comprising a structural formula shown in formula 5-1,

[0060] In some embodiments, the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula shown in formula 5-11 to a structural formula shown in formula 5-16,

[0061] 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 shown in formula 5-2,

[0062] b1 comprises any positive integer from 1 to 5.

[0063] In some embodiments, the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula shown in formula 5-21 to a structural formula shown in formula 5-28,

[0064] 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.

[0065] In some embodiments, 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 195% to 300%, 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.

[0066] Thus, 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, and the negative electrode dispersant has good flexibility when applied to the negative electrode sheet and is less likely to break.

[0067] In some embodiments, the mass content of the modified carboxymethyl cellulose salt is 0.8% to 1.3%, optionally 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 within the above range, the flexibility of the negative electrode film layer can be effectively improved, the negative electrode active material is uniformly dispersed in the negative electrode film layer, and the performance of the negative electrode film layer is uniform.

[0068] In some embodiments, the coated grammage of the negative electrode film layer is 190 mg / 1540.25 mm 2 to 230 mg / 1540.25 mm 2 ; optionally, the coated grammage of the negative electrode film layer is 210 mg / 1540.25 mm 2 to 230 mg / 1540.25 mm 2 . The coated grammage of the negative electrode film layer is relatively high, which is conducive to achieving thick coating.

[0069] 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 hemiacetal group.

[0070] Thus, the modified carboxymethyl cellulose salt of the embodiments of the present application comprises a hemiacetal group, which can reduce the interaction between the molecular chains of the modified carboxymethyl cellulose salt, increase the flexibility of the modified carboxymethyl cellulose salt, thereby reducing the stress generated during drying, so that the negative electrode film layer is less likely to warp, and the risk of cracking of the negative electrode film layer is reduced.

[0071] Moreover, the hemiacetal group can improve the dissolution rate of the modified carboxymethyl cellulose salt and prevent the formation of agglomerates, thereby better dispersing the negative electrode active material and improving the dispersion performance of the negative electrode slurry. Moreover, the main structure of the modified carboxymethyl cellulose salt is still a carboxymethyl cellulose salt, so it still has good dispersion effect and 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, the thickness distribution of the negative electrode film layer is uniform, and the performance of the negative electrode film layer is uniform.

[0072] Thus, 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 achieve thick coating, and the performance of the negative electrode film layer is uniform and the flexibility is good.

[0073] In some embodiments, the hemiacetal group comprises a C1 to C10 aldehyde hemiacetal group, optionally a C1 to C4 aldehyde hemiacetal group. The modified carboxymethyl cellulose salt comprising the above hemiacetal group has a fast dissolution rate and can effectively disperse the negative electrode active material when dissolved in the negative electrode slurry. Moreover, the interaction between the molecular chains of the above modified carboxymethyl cellulose salt is small, thereby further reducing the stress generated during drying, so that the negative electrode slurry is less likely to warp during the drying process, and the risk of cracking is reduced.

[0074] In some embodiments, the acetal group comprises one or more of a formaldehyde acetal group, an acetaldehyde acetal group, a propionaldehyde acetal group, a butyraldehyde acetal group, a pentanal acetal group, a hexanal acetal group, a heptanal acetal group, an octanal acetal group, a nonanal acetal group, a decanal acetal group, a glycolaldehyde acetal group, a methylglycolaldehyde acetal group, an ethylglycolaldehyde acetal group, a propanedial acetal group, a butanedial acetal group, a pentanedial acetal group, a hexanedial acetal group, a heptanedial acetal group, an octanedial acetal group, a nonanedial acetal group, a decanedial acetal group.

[0075] In some embodiments, the acetal group comprises one or more of a formaldehyde acetal group, an acetaldehyde acetal group, a propionaldehyde acetal group, a butyraldehyde acetal group, a glycolaldehyde acetal group, a propanedial acetal group, a butanedial acetal group.

[0076] In some embodiments, the modified carboxymethylcellulose salt further comprises 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 polyalkene group, a substituted or unsubstituted amide group, a substituted or unsubstituted ester group.

[0077] Thus, the flexible group of the embodiments of the present application is substantially incapable of forming hydrogen bonds or forms hydrogen bonds with weak interactions, thereby reducing the interaction between polymer molecular chains, thus reducing the stress generated during drying, reducing the risk of cracking of the negative electrode film layer, and improving the flexibility of the negative electrode film layer.

[0078] In some embodiments, the flexible group comprises 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.

[0079] Thus, the flexible group of the embodiments of the present application is capable of reducing the interaction between polymer molecular chains, thereby reducing the stress generated during drying, reducing the risk of cracking of the negative electrode film layer, and improving the flexibility of the negative electrode film layer.

[0080] In some embodiments, the substituted or unsubstituted C3 to C150 ether group comprises a structural formula as shown in Formula 1,

[0081] In Formula 1,

[0082] R 11 to R 17each 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;

[0083] m includes any positive integer of 5 to 60.

[0084] Thus, the ether group of the embodiment of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0085] 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,

[0086] wherein m1 includes any positive integer of 1 to 30.

[0087] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes a structural formula of Formula 2,

[0088] In Formula 2,

[0089] 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;

[0090] s includes any positive integer of 5 to 60.

[0091] Thus, the alkyl group of the embodiment of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0092] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes at least one of a structural formula of Formula 2-1 to a structural formula of Formula 2-11,

[0093] wherein s1 includes any positive integer of 1 to 30.

[0094] In some embodiments, the substituted or unsubstituted C3 to C150 polyolefin group includes a structural formula of Formula 3,

[0095] In Formula 3,

[0096] R 31 to R 34each 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;

[0097] R 35 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;

[0098] p includes any positive integer of 5 to 60.

[0099] Thus, the polyolefin group of the embodiments of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0100] In some embodiments, the substituted or unsubstituted C3 to C150 polyolefin group includes at least one of a structural formula represented by Formula 3-1 to

[0101] Formula 3-8,

[0102] In some embodiments, the substituted or unsubstituted C3 to C150 amide group includes a structural formula represented by Formula 4,

[0103] Formula 4,

[0104] R 41 each independently includes at least one of a single bond, a substituted or unsubstituted C1 to C1 methylene group;

[0105] 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;

[0106] a includes any positive integer of 1 to 30.

[0107] Thus, the amide group of the embodiments of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0108] In some embodiments, R 41 each independently includes at least one of a single bond, a substituted or unsubstituted C3 to C150 amide group includes a structural formula represented by Formula 4-1,

[0109] 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 Formula 4-15,

[0110] In some embodiments, R 41 including at least one of a single bond, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C3 to C15 acylamino group including a structural formula of Formula 4-2,

[0111] a1 includes any positive integer of 1 to 5.

[0112] In some embodiments, the substituted or unsubstituted C3 to C15 acylamino group includes at least one of a structural formula of Formula 4-21 to a structural formula of Formula 4-24,

[0113] In some embodiments, the substituted or unsubstituted C3 to C15 ester group includes a structural formula of Formula 5,

[0114] In Formula 5,

[0115] R 51 including at least one of a single bond, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C3 to C15 acylamino group including a structural formula of Formula 4-2,

[0116] R 52 including at least one of a single bond, a substituted or unsubstituted C1 to C5 alkyl group, a substituted or unsubstituted C3 to C15 acylamino group including a structural formula of Formula 4-2,

[0117] 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, a substituted or unsubstituted C2 to C10 alkynyl group;

[0118] b includes any positive integer of 1 to 30.

[0119] Thus, the ester group of the embodiments of the present application can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0120] In some embodiments, R 51 including at least one of a single bond, a substituted or unsubstituted C3 to C15 ester group including a structural formula of Formula 5-1,

[0121] In some embodiments, the substituted or unsubstituted C3 to C15 ester group includes at least one of a structural formula of Formula 5-11 to a structural formula of Formula 5-16,

[0122] In some embodiments, R 51substituted or unsubstituted C1 to C5 methylene group, and a substituted or unsubstituted C3 to C15 ester group includes at least one of structural formulas from formula 5-2 to formula 5-28,

[0123] b1 includes any positive integer from 1 to 5.

[0124] In some embodiments, the substituted or unsubstituted C3 to C15 ester group includes at least one of structural formulas from formula 5-21 to formula 5-28,

[0125] 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.

[0126] In some embodiments, 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 195% to 300%, 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.

[0127] 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, and the negative electrode dispersant has better flexibility and is less likely to break when applied to a negative electrode tab.

[0128] In a third aspect, the present application provides a modified carboxymethyl cellulose salt, wherein the modified carboxymethyl cellulose salt includes a hemiacetal group.

[0129] In some embodiments, the hemiacetal group includes a C1 to C10 aldehyde hemiacetal group.

[0130] In some embodiments, the hemiacetal group includes a C1 to C4 aldehyde hemiacetal group.

[0131] In some embodiments, the hemiacetal group includes one or more of a formaldehyde hemiacetal group, an acetaldehyde hemiacetal group, a propionaldehyde hemiacetal group, a butyraldehyde hemiacetal group, a valeraldehyde hemiacetal group, a caproaldehyde hemiacetal group, a heptaldehyde hemiacetal group, an octaldehyde hemiacetal group, a nonaldehyde hemiacetal group, a decaldehyde hemiacetal group, a glyoxal hemiacetal group, a methylglyoxal hemiacetal group, an ethylglyoxal hemiacetal group, a malonaldehyde hemiacetal group, a succinaldehyde hemiacetal group, a glutaraldehyde hemiacetal group, a pimelic aldehyde hemiacetal group, a suberic aldehyde hemiacetal group, a azelaic aldehyde hemiacetal group, and a sebacic aldehyde hemiacetal group.

[0132] In some embodiments, the hemiacetal group comprises one or more of a formaldehyde hemiacetal group, an acetaldehyde hemiacetal group, a propionaldehyde hemiacetal group, a butyraldehyde hemiacetal group, a glyoxal hemiacetal group, a malondialdehyde hemiacetal group, a succindialdehyde hemiacetal group.

[0133] In some embodiments, the modified carboxymethylcellulose salt further comprises 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 polyalkene group, a substituted or unsubstituted amide group, a substituted or unsubstituted ester group.

[0134] In a fourth aspect, the present application also provides 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 surface of the negative electrode current collector, the negative electrode film layer comprising the negative electrode dispersant according to any one of the embodiments of the second aspect of the present application.

[0135] In a fifth aspect, the embodiments of the present application also provide a battery, the battery comprising the battery cell according to any one of the embodiments of the first aspect of the present application.

[0136] In a sixth aspect, the embodiments of the present application also provide an electric device, the electric device comprising the battery according to any one of the embodiments of the fifth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0137] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some of the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of the drawings.

[0138] FIG. 1 is a schematic diagram of an embodiment of a battery cell of the present application.

[0139] FIG. 2 is an exploded schematic diagram of the embodiment of the battery cell of FIG. 1.

[0140] FIG. 3 is a schematic diagram of an embodiment of a battery module of the present application.

[0141] FIG. 4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0142] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4.

[0143] FIG. 6 is a schematic diagram of an embodiment of an electric device comprising the battery cell of the present application as a power source.

[0144] The drawings are not necessarily drawn to scale.

[0145] The reference signs are explained as follows: 1: battery pack; 2: upper case; 3: lower case; 4: battery module; 5: battery cell; 51: case; 52: electrode assembly; 53: cover plate; 6: electric device. DETAILED DESCRIPTION

[0146] Hereinafter, specific embodiments of the modified carboxymethyl cellulose salt, the negative electrode dispersant, the negative electrode sheet, the battery cell, the battery cell, the battery, and the electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are already well known, repeated description of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description 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.

[0147] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is 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 the present application, unless otherwise stated, a numerical range "a to b" represents a shorthand manner of describing each and every numerical value that is contained in the range between "a" and "b," wherein "a" and "b" are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0" and "5" have been listed herein, and "0 to 5" is merely a shorthand manner of describing each and every numerical value that is contained in the range between "0" and "5." In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0148] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0149] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0150] If not otherwise specified, all steps of the application can be performed in sequence or randomly, preferably in sequence. For example, a method comprising steps a and b means that the method can comprise steps a followed by b or b followed by a. For example, a method can further comprise step c means that step c can be added to the method in any order, for example, the method can comprise steps a, b and c, or steps a, c and b, or steps c, a and b, etc.

[0151] If not otherwise specified, "comprising" and "including" as used in the present application means "open" and can also mean "closed". For example, "comprising" and "including" can mean that further components, which are not listed, can also be included or can mean that only the listed components are included.

[0152] If not otherwise specified, the term "or" in the present application is inclusive. 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.

[0153] Throughout the specification, substituents of compounds are disclosed in groups or in ranges. It is specifically intended that where a group or range of substituents is disclosed, each and every individual subcombination of that group or range is also disclosed. For example, it is specifically intended that "Ci to C8 alkyl" individually discloses Ci, 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 C8 alkyl.

[0154] As further examples, it is specifically intended that an integer in the range of 5 to 40 individually discloses 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 specifically intended that an integer in the range of 1 to 20 individually discloses 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 are specifically intended.

[0155] The negative pole piece includes a negative pole current collector and a negative pole film layer arranged on at least one side of the negative pole current collector, and the negative pole film layer is formed by drying the negative pole slurry coated on the negative pole current collector. During the process of forming the negative pole film layer by the negative pole slurry, cracking and other phenomena may occur, resulting in that the negative pole piece does not meet the production requirements. In order to improve the energy density of the battery monomer, the negative pole film layer is usually thickly coated, and the cracking phenomenon of the negative pole film layer will be further intensified, so that the negative pole piece is difficult to realize thick coating. In order to improve the cracking phenomenon of the negative pole film layer, the related technology adds a plasticizer such as butanediol in the negative pole slurry. The plasticizer is usually a small molecular 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 plastic shaping ability and flexibility of the negative pole film layer and improving the cracking phenomenon of the negative pole film layer. However, the residual plasticizer is easy to cause the thickness of the negative pole film layer to be uneven, so that the negative pole film layer has interface problems such as dark marks.

[0156] In view of the above problems, the embodiments of the present application propose a negative pole dispersant, which includes a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt includes a hemiacetal group, so that the dissolution rate of the modified carboxymethyl cellulose salt is improved, and it is not easy to form a group, which can better disperse the negative pole active material and improve the dispersion performance of the negative pole slurry. In addition, the hemiacetal group can destroy the original regular hydrogen bond structure of the carboxymethyl cellulose salt, so that the interaction between the molecular chains of the modified carboxymethyl cellulose salt is small, the flexibility of the modified carboxymethyl cellulose salt is increased, thereby the stress generated during drying can be reduced, so that the negative pole slurry is not easy to warp during the drying process, and the risk of cracking is reduced.

[0157] Modified carboxymethyl cellulose salt

[0158] In the first aspect, the embodiments of the present application propose a modified carboxymethyl cellulose salt, which includes a hemiacetal group.

[0159] The carboxymethyl cellulose salt CMC-M is an anionic water-soluble cellulose ether derivative. When it is applied to the negative pole slurry, it can reduce the interfacial tension between the negative pole active material and the solvent, and has a good dispersion effect on the negative pole active material. Under the action of stirring, it is beneficial to uniformly disperse the negative pole active material in the solvent to form a stable slurry system.

[0160] The molecular chain of the carboxymethyl cellulose salt is rich in hydroxyl groups -OH. The presence of the hydroxyl groups enables the carboxymethyl cellulose salt itself to form strong van der Waals forces or hydrogen bonds between the molecular chains, so that the negative electrode slurry has strong drying stress during the drying process and warps, and may crack during further rolling, so that the negative electrode film layer cracks. In the present application, the electrode sheet may have a certain degree of concave-convex phenomenon during the rolling of the electrode sheet, and the edge thickness of the electrode sheet is thicker than the middle part. The above phenomenon is the warping phenomenon.

[0161] The modified carboxymethyl cellulose salt of the embodiments of the present application is obtained by modifying the carboxymethyl cellulose salt. Specifically, a hemiacetal group is formed by the addition reaction of an aldehyde group and a hydroxyl group in the carboxymethyl cellulose salt. The hemiacetal group improves the dissolution rate of the modified carboxymethyl cellulose salt and makes it less likely to form clumps, so that it can better disperse the negative electrode active material and improve the dispersion performance of the negative electrode slurry. The hemiacetal group can also make the interaction between the molecular chains of the modified carboxymethyl cellulose salt smaller, increase the flexibility of the modified carboxymethyl cellulose salt, and thus reduce the stress generated during drying, so that the negative electrode slurry is less likely to warp during the drying process to form a negative electrode film layer, and the risk of cracking of the negative electrode film layer is reduced.

[0162] Moreover, the main structure of the modified carboxymethyl cellulose salt is still that of the carboxymethyl cellulose salt, so it still has good dispersion effect and 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, the thickness distribution of the negative electrode film layer is uniform, and the performance is uniform.

[0163] 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.

[0164] In some embodiments, the hemiacetal group includes a C1 to C10 aldehyde hemiacetal group. The modified carboxymethyl cellulose salt containing the above hemiacetal group has a fast dissolution rate and can effectively disperse the negative electrode active material when dissolved in the negative electrode slurry. Moreover, the interaction between the molecular chains of the above modified carboxymethyl cellulose salt is small, so that the stress generated during drying can be further reduced, the negative electrode slurry is less likely to warp during the drying process, and the risk of cracking is reduced.

[0165] Alternatively, the hemiacetal group includes a C1 to C4 aldehyde hemiacetal group. The relatively short aldehyde group is more likely to react with the carboxymethyl cellulose salt to form a hemiacetal group.

[0166] Exemplarily, the semi-acetal group includes one or more of a formaldehyde semi-acetal group, an acetaldehyde semi-acetal group, a propionaldehyde semi-acetal group, a butyraldehyde semi-acetal group, a pentanal semi-acetal group, a hexanal semi-acetal group, a heptanal semi-acetal group, an octanal semi-acetal group, a nonanal semi-acetal group, a decanal semi-acetal group, a glyoxal semi-acetal group, a methylglyoxal semi-acetal group, an ethylglyoxal semi-acetal group, a malonaldehyde semi-acetal group, a succinaldehyde semi-acetal group, a glutaraldehyde semi-acetal group, a adipaldehyde semi-acetal group, a pimelic aldehyde semi-acetal group, a suberic aldehyde semi-acetal group, a azelaic aldehyde semi-acetal group.

[0167] Optionally, the semi-acetal group includes one or more of a formaldehyde semi-acetal group, an acetaldehyde semi-acetal group, a propionaldehyde semi-acetal group, a butyraldehyde semi-acetal group, a glyoxal semi-acetal group, a malonaldehyde semi-acetal group, a succinaldehyde semi-acetal group.

[0168] In some embodiments, the modified carboxymethyl cellulose salt includes a semi-acetal group and a flexible group, the modified carboxymethyl cellulose salt is a carboxymethyl cellulose salt in which at least one hydroxyl group and an aldehyde group are added to form a semi-acetal group, and at least one hydrogen atom of another hydroxyl group is replaced by 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 polyolefin group, a substituted or unsubstituted amide group, a substituted or unsubstituted ester group.

[0169] The group replacing the hydrogen atom in the hydroxyl group includes a flexible group, which can reduce the interaction between polymer molecular chains, thereby reducing the stress generated during drying; and because the flexible group has a certain flexibility, it can improve the flexibility of the modified carboxymethyl cellulose salt, so that the anode slurry has less drying stress during the drying process when the modified carboxymethyl cellulose salt is applied to the anode slurry, reducing the risk of cracking of the anode film layer and improving the flexibility of the anode film layer.

[0170] The flexible group can replace the hydrogen atoms of at least two hydroxyl groups.

[0171] With the decrease in the number of hydrogen atoms, it means that the number of replaced hydroxyl groups in the carboxymethyl cellulose salt increases, the more the number of replaced hydroxyl groups, the smaller the interaction between the molecular chains of the carboxymethyl cellulose salt, the smaller the drying stress of the anode slurry, and the anode film layer is not prone to cracking and other phenomena, and the interface performance is improved.

[0172] 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, a potassium ion.

[0173] 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.

[0174] In other embodiments, the modified carboxymethyl cellulose salt can also include a modified carboxymethyl cellulose potassium salt, etc.

[0175] [flexible group]

[0176] In order to further reduce the interaction between the molecular chains of the modified carboxymethyl cellulose salt, it is considered to select the substituent group as a long chain structure, such as a long chain structure of C3 to C150. If a part of the hydroxyl groups in the modified carboxymethyl cellulose salt are not substituted and another part of the hydroxyl groups are substituted by a long chain structure, 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, reduce the risk of cracking of the negative electrode film layer, and improve the interface performance of the negative electrode film layer; the long chain structure 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 and dispersibility when applied as a negative electrode slurry.

[0177] 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, or a substituted or unsubstituted C3 to C150 ester group.

[0178] The above 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.

[0179] When the above 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, or an iodine atom, etc., and the heteroatom can include a nitrogen atom, a sulfur atom, or an oxygen atom, etc.

[0180] [ether group]

[0181] In some embodiments, the substituted or unsubstituted ether group includes a substituted or unsubstituted C3 to C150 ether group. The ether group has a long chain, which can increase the flexibility of the modified carboxymethyl cellulose salt, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0182] In some embodiments, the ether group includes a structural formula as shown in Formula 1,

[0183] In Formula 1,

[0184] 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.

[0185] 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.

[0186] m is the number of repeating structures. m includes any positive integer of 5 to 60. Optionally, m includes any positive integer of 5 to 45. When m is in the above range, the interaction between the modified carboxymethyl cellulose salt molecules can be reduced, so that the modified carboxymethyl cellulose salt has excellent flexibility.

[0187] 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.

[0188] Exemplarily, the ether group includes at least one of the structural formulae shown in formula 1-1 to formula 1-14,

[0189] In some embodiments, m1 is the number of repeating structures, m1 includes any positive integer of 1 to 30, and 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.

[0190] In the embodiments of the present application, m-m1 represents the value of m minus m1, m-m1 includes any positive integer of 1 to 30, and 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.

[0191] [Substituted or unsubstituted alkyl]

[0192] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes a substituted or unsubstituted C3 to C150 alkyl group having a ring structure. The substituted or unsubstituted C3 to C150 alkyl group having a ring structure can further increase steric hindrance and reduce drying stress.

[0193] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes a substituted or unsubstituted C3 to C150 alkyl group having a ring structure, and the substituted or unsubstituted C3 to C150 alkyl group having a ring structure includes at least one of a structure of Formula 2,

[0194] In Formula 2,

[0195] 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 saturated alkyl group.

[0196] Optionally, 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 saturated alkyl group.

[0197] Optionally, when the above group is substituted, the substituent can include a halogen atom, and the halogen atom can include at least one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0198] s is a number of repeating structures, and s includes any positive integer of 5 to 60. Optionally, s includes any positive integer of 5 to 45. When s is in the above range, the modified carboxymethyl cellulose salt can have excellent flexibility due to a reduction in an interaction between molecular chains of the modified carboxymethyl cellulose salt.

[0199] 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.

[0200] For example, the substituted or unsubstituted C3 to C150 alkyl group includes at least one of a structure of Formula 2-1 to a structure of Formula 2-11,

[0201] In some embodiments, s1 is a number of repeating structures, 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.

[0202] In embodiments of the present application, s-s1 represents a value of s minus s1, 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.

[0203] [Substituted or unsubstituted polyolefin group]

[0204] In some embodiments, the substituted or unsubstituted polyolefin group includes a substituted or unsubstituted C3 to C150 polyolefin group. The polyolefin group can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain.

[0205] In some embodiments, the substituted or unsubstituted C3 to C150 polyolefin group includes a structural formula represented by Formula 3,

[0206] In Formula 3,

[0207] 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, and a substituted or unsubstituted C2 to C10 alkenyl group;

[0208] R 35 includes at least one of a hydrogen atom, a halogen atom, and a substituted or unsubstituted C1 to C10 alkyl group.

[0209] Optionally, when the above 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.

[0210] p is a number of repeating structures, p includes any positive integer from 5 to 60. Optionally, p includes any positive integer from 5 to 45. When p is in the above range, the interaction between the molecular chains of the modified carboxymethyl cellulose salt can be reduced, so that the modified carboxymethyl cellulose salt has excellent flexibility.

[0211] 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.

[0212] Exemplarily, the substituted or unsubstituted C3 to C150 polyolefin group includes at least one of structural formulae shown in formula 3-1 to formula 3-8,

[0213] 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 also improve the voltage resistance of the negative electrode dispersant and improve the stability of the negative electrode film layer.

[0214] [Substituted or unsubstituted amide-based group]

[0215] In some embodiments, the substituted or unsubstituted amide-based group includes a substituted or unsubstituted C3 to C150 amide-based group.

[0216] The amide-based group can include a monomolecular amide-based group or a polyamide-based group, and the amide-based group includes a strong electronegative element nitrogen element. After the amide-based group is grafted to the side chain of the carboxymethyl cellulose salt, the hydrogen atom at the original hydroxyl position can be replaced, thereby destroying the regular O-H-O hydrogen bond structure of the carboxymethyl cellulose salt and forming a new N-H-O hydrogen bond structure. The N-H-O hydrogen bond structure is weaker than the O-H-O hydrogen bond, so that the intermolecular force of the carboxymethyl cellulose salt after grafting and modification is weakened, the flexibility is increased, and the interface performance of the negative electrode film layer is improved. In addition, the strong electronegative element nitrogen element can form a complexation effect 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 cell.

[0217] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes a structural formula shown in formula 4,

[0218] In formula 4,

[0219] R 41 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0220] 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;

[0221] a is the number of repeating structures, 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.

[0222] 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.

[0223] Both ends of the amide group in Formula 4 can be connected to an oxygen atom in a hydroxyl group in the 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 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.

[0224] 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,

[0225] For example, the structural formula represented by Formula 4-1 includes at least one of a structural formula represented by Formula 4-11 to a structural formula represented by Formula 4-15,

[0226] 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,

[0227] a1 is the number of repeating structures, a1 includes any positive integer from 1 to 5. For example, a1 can be 1, 2, 3, 4, or 5.

[0228] In some embodiments, the structural formula represented by Formula 4-2 includes at least one of a structural formula represented by Formula 4-21 to a structural formula represented by Formula 4-24,

[0229] [Substituted or unsubstituted ester group]

[0230] In some embodiments, R1 to R5 each independently include a substituted or unsubstituted ester group, which can be a substituted or unsubstituted C3 to C150 ester group.

[0231] Ester groups can include mono-molecule ester groups or polyester groups. When ester groups are grafted onto the side chains of carboxymethyl cellulose salts, they can replace the original hydroxyl positions, thereby disrupting the regular OHO hydrogen bond structure of the carboxymethyl cellulose salt and weakening its own hydrogen bonding. This results in reduced intermolecular forces and increased flexibility in the grafted and modified carboxymethyl cellulose salt, improving the interfacial properties of the negative electrode film. Furthermore, it can enhance the migration rate of active ions such as lithium ions. The ester groups themselves possess good flexibility, and replacing the hydroxyl positions further improves the flexibility of the carboxymethyl cellulose salt, thus enhancing the interfacial properties of the negative electrode film.

[0232] In some embodiments, the substituted or unsubstituted C3 to C150 ester groups include the structural formula shown in Formula 5.

[0233] In Equation 5,

[0234] R 51 Including at least one of the C1 to C5 methylene groups, whether single-bonded, substituted, or unsubstituted;

[0235] R 52 Including substituted or unsubstituted C1 to C5 alkyl groups;

[0236] 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, or a substituted or unsubstituted C2 to C10 alkynyl group;

[0237] b is the number of repeating structures, and b includes any positive integer from 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.

[0238] In Formula 5, both ends of the ester group can be connected to the oxygen atom in the hydroxyl group of the carboxymethyl cellulose salt, for example, the left end group can be connected to an oxygen atom, or the right end group can be connected to an oxygen atom. The end groups of the ester group in Formula 5 that are not connected to oxygen atoms can include hydrogen atoms or C1 to C3 alkyl groups.

[0239] In some implementations, R 51 Ester groups, including single bonds, substituted or unsubstituted C3 to C150 ester groups, include the structures shown in Formula 5-1.

[0240] For example, the structural formula shown in Equation 5-1 includes at least one of the structural formulas shown in Equations 5-11 to 5-16.

[0241] In some implementations, R 51 Includes substituted or unsubstituted C1 to C5 methylene groups, and substituted or unsubstituted C3 to C150 ester groups including the structures shown in Formula 5-2.

[0242] b1 is the number of repeating structures. b1 includes any positive integer from 1 to 5. For example, b1 can be 1, 2, 3, 4 or 5.

[0243] For example, the structural formula shown in Equation 5-2 includes at least one of the structural formulas shown in Equations 5-21 to 5-28.

[0244] In the above embodiments, the halogen atom may include at least one of fluorine, chlorine, and bromine atoms. These atoms can improve the voltage resistance of the polymer.

[0245] By way of example, the substituted or unsubstituted C3 to C150 ester groups include at least one of the structural formulas shown in Formulas 5-21 to 5-28.

[0246] In the above embodiments, the weight-average molecular weight of the flexible groups is between 100 Da and 5000 Da. When the molecular weight of the grafted groups in the modified carboxymethyl cellulose salt is within the above range, the interaction forces between the molecular chains of the modified carboxymethyl cellulose salt can be reduced, giving the modified carboxymethyl cellulose salt excellent flexibility.

[0247] For example, the weight-average molecular weight of the flexible group can be 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. The range is 1900Da, 1950Da, 2000Da, 2050Da, 2100Da, 2150Da, 2200Da, 2250Da, 2300Da, 2350Da, 2400Da, 2450Da, 2500Da, 3000Da, 3100Da, 3200Da, 3300Da, 3400Da, 3500Da, 3600Da, 3700Da, 3800Da, 3900Da, 4000Da, 4100Da, 4200Da, 4300Da, 4400Da, 4500Da, 4600Da, 4700Da, 4800Da, 4900Da, 5000Da, or any two of the above values.

[0248] In some embodiments, the modified carboxymethyl cellulose salt has a weight-average molecular weight of 40 wDa to 80 wDa. When the weight-average molecular weight of the modified carboxymethyl cellulose salt is within the above range, the negative electrode dispersant can exhibit excellent dispersing properties.

[0249] 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 any range of two of the above values.

[0250] In this application, the weight-average molecular weight of the polymer can be tested using methods known in the art, such as gel chromatography, or using a Waters 2695 Isocratic HPLC gel chromatograph with a differential refractive index detector 2141.

[0251] Conventional sodium carboxymethyl cellulose (CMC) is a solid polymer at room temperature. Dissolving CMC in water (1% by mass) and stirring at 1200 rpm for 2 hours, followed by drying in an oven at 40°C for at least 24 hours, yields a reference film with a width of 2.5 cm, a length of 5 cm, and a thickness of 1 mm. The elongation at break of the reference film is measured, and this elongation is defined as 100%. It should be noted that conventional CMC refers to sodium carboxymethyl cellulose where the side chains are not substituted with other groups, particularly the hydrogen atoms at the hydroxyl positions.

[0252] In some embodiments, a modified carboxymethyl cellulose salt is prepared into a film by dissolving the modified carboxymethyl cellulose salt in water at a mass content of 1%, stirring at 1200 rpm for 2 hours, and then drying in an oven at, for example, 40°C for at least 24 hours to obtain a film with a width of 2.5 cm, a length of 5 cm, and a thickness of 1 mm. The elongation at break of the film is calculated using a 100% reference test, and the elongation at break of the film is between 195% and 300%, optionally between 205% and 300%. During the preparation of the film, the thickness deviation can be controlled within 0.5%.

[0253] Therefore, the elongation at break of the negative electrode dispersant is higher than that of conventional sodium carboxymethyl cellulose. When the negative electrode dispersant is applied to the negative electrode sheet, it has better flexibility and is less prone to breakage.

[0254] For example, the elongation at break of the film can be 195%, 200%, 210%, 220%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, 300%, or a range of any two of the above values.

[0255] In this application, the elongation at break of the film has a meaning known in the art and can be tested using equipment and methods known in the art, specifically referring to the standard GB / T36363-2018.

[0256] Unmodified carboxymethyl cellulose salt was added to deionized water to prepare a 1% (w / w) gel solution. The stirrer speed was 500 r / min, and the time required for the carboxymethyl cellulose salt to completely dissolve was recorded as 30 min.

[0257] Modified carboxymethyl cellulose salt was added to deionized water to prepare a 1% (w / w) gel solution. The stirrer was set at 500 rpm, and the time required for the modified carboxymethyl cellulose salt to completely dissolve was recorded as the dissolution time. In some embodiments, the dissolution time of the modified carboxymethyl cellulose salt was less than 30 minutes. The relatively short dissolution time and fast dissolution rate of the modified carboxymethyl cellulose salt, along with its resistance to clumping, are more conducive to its dispersing effect, resulting in more stable performance of the negative electrode slurry.

[0258] In the case where the modified carboxymethyl cellulose salt includes a hemiacetal group, the modified carboxymethyl cellulose salt is obtained by addition of at least one hydroxyl group and a hemiacetal group in the carboxymethyl cellulose salt.

[0259] The preparation method includes step S100, an addition treatment.

[0260] The addition treatment includes: providing carboxymethyl cellulose salt and aldehyde compounds, and carrying out an addition reaction between the two in a catalytic system to obtain a modified carboxymethyl cellulose salt containing a hemiacetal group.

[0261] Hydrogen chloride and other substances can be used as catalysts for catalysis.

[0262] Carboxymethyl cellulose salts include compounds represented by formula C.

[0263] In formula C, M includes metal ions or NH4+. + At least one of them.

[0264] Taking formaldehyde as an example of an aldehyde compound, the catalytic reaction is explained. Formaldehyde and carboxymethyl cellulose salt undergo a catalytic reaction, where the aldehyde group in formaldehyde can undergo an addition reaction with one of the hydroxyl groups in the carboxymethyl cellulose salt, forming the following products.

[0265] Of course, multiple formaldehyde molecules can react with multiple hydroxyl groups in carboxymethyl cellulose salt.

[0266] The preparation method for a modified carboxymethyl cellulose salt, wherein at least one hydrogen atom in one of the hydroxyl groups is replaced by a flexible group, includes:

[0267] The method includes step S210 alkalization treatment and step S220 substitution treatment.

[0268] In step S210, the alkalization treatment specifically includes: providing carboxymethyl cellulose salt, and alkalizing the carboxymethyl cellulose salt with an alkali to activate the hydroxyl sites of the carboxymethyl cellulose salt and form active reaction sites.

[0269] Carboxymethyl cellulose salts include compounds represented by formula C.

[0270] In formula C, M includes metal ions or NH4+. + At least one of them.

[0271] After alkalization treatment of carboxymethyl cellulose salt, the hydrogen atoms at the hydroxyl positions are activated, for example, by using sodium hydroxide (NaOH) or potassium hydroxide (KOH). At least one hydrogen atom at the hydroxyl position in the carboxymethyl cellulose salt is replaced by a sodium (Na) atom. For example, all hydrogen atoms at the hydroxyl positions in the carboxymethyl cellulose salt are replaced by Na. The resulting intermediate product is a compound as shown in formula D.

[0272] In step S220, the substitution treatment specifically includes: adding a substituted compound to the system to carry out a substitution reaction. The substituted compound will replace the sodium (Na) atom located at the hydroxyl position, and the product after substitution is the modified carboxymethyl cellulose salt, as shown in Formula A.

[0273] In formula (A),

[0274] M includes metal ions or NH4. + At least one of them;

[0275] R1 to R5 each independently include a hydrogen atom or a flexible group, and at least one of R1 to R5 includes a flexible group, while at least one of R1 to R5 is not a flexible group, serving as an addition site for aldehyde compounds.

[0276] n represents the degree of polymerization of the modified carboxymethyl cellulose salt, or it can be considered as the number of repeating structures.

[0277] Optionally, n includes any positive integer from 1500 to 3000. For example, n can be 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, or 3000.

[0278] The repeating units in the modified carboxymethyl cellulose salt may include one or more.

[0279] In some embodiments, the substituted compound includes substituted or unsubstituted ether compounds, optionally C3 to C150 ether compounds.

[0280] For example, substituted or unsubstituted C3 to C150 ether compounds include compounds shown in Formula 11.

[0281] In Equation 11,

[0282] R 11To 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, or a substituted or unsubstituted C2 to C10 alkynyl group.

[0283] m includes any positive integer from 5 to 60.

[0284] In some embodiments, the substituted compound includes substituted or unsubstituted alkanes, optionally C3 to C150 alkanes.

[0285] By way of example, substituted or unsubstituted C3 to C150 alkanes include compounds of formula 21.

[0286] In Equation 21,

[0287] R 21 To R 27 Each independently comprises at least one of a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1 to C10 alkyl group;

[0288] s includes any positive integer from 5 to 60.

[0289] In some embodiments, the substituted compound includes substituted or unsubstituted polyolefins, optionally C3 to C150 polyolefins.

[0290] By way of example, substituted or unsubstituted C3 to C150 polyolefins include compounds of formula 31.

[0291] In Equation 31,

[0292] 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, or a substituted or unsubstituted C2 to C10 alkenyl group;

[0293] R 35 Including at least one of hydrogen atoms, halogen atoms, substituted or unsubstituted C1 to C10 alkyl groups;

[0294] p includes any positive integer from 5 to 60.

[0295] In some embodiments, the substituted compound includes substituted or unsubstituted amide compounds, optionally substituted or unsubstituted C3 to C150 amide compounds, and may be C3 to C150 amide polymers.

[0296] Exemplarily, substituted or unsubstituted C3 to C150 amide polymers include compounds shown in Formula 41.

[0297] In Equation 41,

[0298] R 41 Including at least one of the C1 to C5 methylene groups, whether single-bonded, substituted, or unsubstituted;

[0299] 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, or a substituted or unsubstituted C2 to C10 alkynyl group;

[0300] R 47 and R 48 Each independently comprises a hydrogen atom or a C1 to C3 alkyl group.

[0301] a includes any positive integer from 1 to 30.

[0302] In some embodiments, the substituted compound includes substituted or unsubstituted ester compounds, optionally substituted or unsubstituted C3 to C150 ester compounds, which may be C3 to C150 ester polymers.

[0303] Exemplary examples include substituted or unsubstituted C3 to C150 ester polymer compounds, comprising compounds of formula 51.

[0304] In Equation 5,

[0305] R 51 Including at least one of the C1 to C5 methylene groups, whether single-bonded, substituted, or unsubstituted;

[0306] R 52 Including substituted or unsubstituted C1 to C5 alkyl groups;

[0307] 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, or a substituted or unsubstituted C2 to C10 alkynyl group;

[0308] R 56 and R 57 Each independently comprises a hydrogen atom or a C1 to C3 alkyl group;

[0309] b includes any positive integer from 1 to 30.

[0310] In the preparation of modified carboxymethyl cellulose salt, the reaction can be carried out under reaction conditions commonly used in the field, and the mass ratio of each raw material can also be selected according to the mass ratio commonly used in the field.

[0311] In some embodiments, an aldehyde compound can be added first for substitution, and an addition reaction can be carried out at some hydroxyl positions to form a hemiacetal group; then a flexible compound can be added for substitution, and substitution can be carried out at the hydroxyl positions that have not been added by the hemiacetal group, replacing the hydrogen atoms on the hydroxyl group with flexible groups.

[0312] In other embodiments, a flexible compound can be added first for substitution, substituting at some hydroxyl positions to replace the hydrogen atoms on the hydroxyl groups with flexible groups; then an aldehyde compound is added for addition reaction, forming hemiacetal groups at the hydroxyl positions that have not been substituted by the flexible groups.

[0313] Negative electrode dispersant

[0314] Secondly, embodiments of this application provide a negative electrode dispersant, which includes the modified carboxymethyl cellulose salt of any embodiment of the first aspect of this application.

[0315] In some embodiments, the negative electrode dispersant may also include carboxymethyl cellulose salt.

[0316] In some embodiments, the ratio of the mass content of carboxymethyl cellulose salt to the mass content of modified carboxymethyl cellulose salt can be from 0.5 to 2. When the mass content ratio of carboxymethyl cellulose salt to modified carboxymethyl cellulose salt is within the above range, it can work together with the modified carboxymethyl cellulose salt to improve the flexibility of the formed film and reduce the risk of cracking of the negative electrode film.

[0317] For example, the ratio of the mass content of carboxymethyl cellulose salt to the mass content of 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 any range of two of the above values.

[0318] Negative electrode sheet

[0319] Thirdly, embodiments of this application provide 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 includes a negative electrode dispersant as described in any embodiment of the second aspect of this application. The negative electrode dispersant can be used as a dispersant in the negative electrode film layer, enabling the negative electrode active material to be uniformly dispersed in the negative electrode film layer, resulting in uniform performance of the negative electrode film layer. Furthermore, the dispersant can improve the flexibility of the negative electrode film layer and reduce the risk of cracking. For example, the negative electrode current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0320] In some embodiments, the mass content of modified carboxymethyl cellulose salt is 0.8% to 1.3% based on the total mass of the negative electrode film, optionally 1.0% to 1.3%, and further optionally 1.0% to 1.2%. When the mass content of modified carboxymethyl cellulose salt is within the above range, it can effectively reduce the risk of cracking in the negative electrode film and effectively improve the performance uniformity and flexibility of the negative electrode film. Furthermore, its relatively low proportion has virtually no impact on the proportion of the negative electrode active material, thereby enabling the battery cell to have a high energy density. Moreover, since modified carboxymethyl cellulose salt can significantly improve the flexibility of the negative electrode film, plasticizers and other additives do not need to be added to the negative electrode slurry, thus reducing the adverse effects of introducing plasticizers.

[0321] For example, the mass content of 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 of any two of the above values.

[0322] In some embodiments, the negative electrode dispersant in the negative electrode film layer may also include carboxymethyl cellulose salt, such as at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, lithium carboxymethyl cellulose, etc. The difference between this type of carboxymethyl cellulose salt and the above-mentioned modified carboxymethyl cellulose salt is that the hydroxyl groups in this type of carboxymethyl cellulose salt are not replaced. The carboxymethyl cellulose salt can work together with the above-mentioned modified carboxymethyl cellulose salt to play a dispersing role. On this basis, the modified carboxymethyl cellulose salt can also further improve the flexibility of the negative electrode film layer.

[0323] In some embodiments, the mass content of carboxymethyl cellulose salt can be from 0.05% to 1.0% based on the total mass of the negative electrode film; optionally, it can be from 0.05% to 0.3%. When the mass content of carboxymethyl cellulose salt is within the above range, it can work together with the modified carboxymethyl cellulose salt to improve the uniformity and flexibility of the negative electrode film.

[0324] For example, the mass content of 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% of the total mass. %, 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 consisting of any two of the above values.

[0325] In some embodiments, the ratio of the mass content of carboxymethyl cellulose salt to the mass content of modified carboxymethyl cellulose salt can be from 0.5 to 2. When the mass content ratio of carboxymethyl cellulose salt to modified carboxymethyl cellulose salt is within the above range, it can work together with the modified carboxymethyl cellulose salt to improve the uniformity and flexibility of the negative electrode film.

[0326] For example, the ratio of the mass content of carboxymethyl cellulose salt to the mass content of 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 any range of two of the above values.

[0327] In some embodiments, the basis weight of the negative electrode film coating is 190 mg / 1540.25 mm. 2 Up to 230mg / 1540.25mm 2 ; 210mg / 1540.25mm is optional. 2 Up to 230mg / 1540.25mm 2 The relatively high basis weight of the negative electrode film layer is beneficial for achieving thick coating.

[0328] For example, the coating basis weight of the negative electrode film can be 190 mg / 1540.25 mm. 2 200mg / 1540.25mm 2210mg / 1540.25mm 2 220mg / 1540.25mm 2 230mg / 1540.25mm 2 Or a range consisting of any two of the above values.

[0329] The negative electrode active material may be any negative electrode active material known in the art for use in battery cells. As an example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0330] In some embodiments, the negative electrode active material may include, but is not limited to, at least one of natural graphite and artificial graphite, and the negative electrode dispersant can effectively disperse the above-mentioned negative electrode active material and improve the dispersion uniformity of the negative electrode active material in the negative electrode film layer.

[0331] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0332] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose particular limitations on the type of negative electrode binder. As an example, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, and waterborne acrylic resins such as polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder is ≤5% based on the total weight of the negative electrode film layer.

[0333] In some embodiments, the negative electrode film layer may optionally include other additives. As an example, other additives may include thickeners, such as PTC thermistor materials. In some embodiments, the mass percentage of other additives is ≤2% based on the total weight of the negative electrode film layer.

[0334] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0335] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode dispersant, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0336] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer sandwiched between the negative electrode current collector and the negative electrode film layer, and disposed on the surface of the negative electrode current collector, for example, composed of a conductive agent and an adhesive. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0337] battery cell

[0338] Fourthly, this application proposes a battery cell including a negative electrode sheet. The negative electrode sheet includes the negative electrode sheet of any embodiment of the third aspect of this application. Due to the use of this negative electrode sheet, the thickness of the negative electrode sheet is uniform and the performance is consistent, which is beneficial for uniform charging and discharging throughout the negative electrode sheet during the cyclic charging and discharging process of the battery cell.

[0339] [Positive electrode plate]

[0340] In some implementations, the battery cell also includes a positive electrode.

[0341] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0342] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0343] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy on a polymer substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0344] In some embodiments, the positive electrode active material may include, but is not limited to, at least one of lithium transition metal oxides, lithium phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their respective modified compounds. Examples of lithium phosphates may include, but are not limited to, at least one of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds.

[0345] The positive electrode film layer includes a positive electrode active material, which may be a positive electrode active material known in the art for use in battery cells. As an example, the positive electrode active material may include at least one of the following materials: layered positive electrode active materials such as ternary, lithium nickel oxide / sodium, lithium cobalt oxide / sodium, lithium manganese oxide / sodium, lithium-rich / sodium layered, and rock salt phase layered materials; olivine-type phosphate active materials; and spinel-structured positive electrode active materials such as spinel lithium manganese oxide, spinel lithium nickel manganese oxide, lithium-rich spinel lithium manganese oxide, and lithium nickel manganese oxide.

[0346] For example, the general formula for layered positive electrode active materials is: Li x A y Ni a Co b Mn c M 1-a-b-c Y zWherein, 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, and 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, and Ce; Y is selected from one or more of O and F. Optionally, y=0. Specifically, the layered structure positive electrode active material may include lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), and 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 One or more of O2 (NCM523).

[0347] For example, the general formula of olivine-type phosphate active materials is: Li x A y Me a M b P 1-c X c Y z Wherein, 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, and Mg; Me is selected from one or more of Mn, Fe, Co, and 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, and Ce; X is selected from one or more of S, Si, Cl, B, C, and N; Y is selected from one or more of O and F. Specifically, olivine-type phosphate active materials include one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0348] For example, the general formula of a spinel-structured positive electrode active material is: Li x A y Mn a M 2-a Y zWherein, 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, and 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, and Ce; Y is selected from one or more of O and F. Specifically, spinel-structured positive electrode active materials include LiMn2O4 and 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 One or more of Mn2O4.

[0349] In this application, the modified compounds of the above-mentioned positive electrode active materials may be those that have undergone doping modification and / or surface coating modification of the positive electrode active materials.

[0350] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the binder is ≤5% based on the total weight of the positive electrode film layer.

[0351] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, 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.

[0352] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, optional conductive agent, optional binder and any other components, in a solvent such as N-methylpyrrolidone to form a positive electrode slurry; coating the positive electrode slurry onto a positive current collector, and obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0353] Electrolyte

[0354] In some implementations, the battery cell also includes an electrolyte.

[0355] During the charging and discharging process of a single battery cell, active ions repeatedly insert and extract between the positive and negative electrode plates, while the electrolyte acts as a conductor for these active ions. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to actual needs.

[0356] Electrolytes consist of electrolyte salts and solvents. The types of electrolyte salts and solvents are not specifically limited and can be selected according to actual needs.

[0357] As an example, the electrolyte salt may include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0358] As an example, the solvent may 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.

[0359] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0360] [Isolation membrane]

[0361] In some implementations, the battery cell also includes a separator.

[0362] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0363] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0364] In some implementations, the positive electrode, separator, and negative electrode can be fabricated into an electrode assembly using a winding process and / or a stacking process.

[0365] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0366] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0367] This application does not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 shows a square battery cell 5 as an example.

[0368] In some embodiments, as shown in FIG2, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing 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 close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly 52 by a winding process and / or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted as needed.

[0369] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0370] In some embodiments of this application, the battery cells according to this application can be assembled into a battery module. 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.

[0371] Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0372] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0373] In some embodiments, the battery modules described above 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.

[0374] Figures 4 and 5 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3. The upper box 2 covers the lower box 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0375] The battery in the embodiments of this application may include one or more battery cells. When the battery includes multiple battery cells, the battery may include a battery module or a battery pack.

[0376] Electrical appliances

[0377] Fifthly, embodiments of this application provide an electrical device, which includes at least one of the battery cell, battery module, or battery pack described in this application. The battery cell, battery module, or battery pack can be used as the power source for the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices such as mobile phones and laptops, electric vehicles such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric trains, ships and satellites, energy storage systems, etc.

[0378] Electrical devices can be equipped with individual battery cells, battery modules, or battery packs depending on their usage requirements.

[0379] Figure 6 is a schematic diagram of an example electrical device 6. This electrical device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device 6, a battery pack 1 or a battery module can be used.

[0380] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0381] Example

[0382] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. 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 by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0383] Example 1: Preparation of Lithium-ion Batteries

[0384] 1. Preparation of positive electrode sheet

[0385] Aluminum foil is used as the positive current collector.

[0386] The positive electrode active material lithium cobalt oxide (LiCoO2), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are mixed evenly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 to obtain a positive electrode slurry. The positive electrode slurry is coated onto the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through processes such as drying, cold pressing, slitting, and cutting.

[0387] 2. Preparation of negative electrode sheet

[0388] Copper foil is used as the negative electrode current collector.

[0389] Artificial graphite (as the negative electrode active material), conductive carbon (as a conductive agent), styrene-acrylic emulsion (as a binder), and a negative electrode dispersant are mixed evenly in deionized water to prepare a negative electrode slurry. The mass ratio of artificial graphite, conductive carbon, styrene-acrylic emulsion, and negative electrode dispersant in the solid components of the negative electrode slurry is 96.7:0.7:1.5:1.1, and the negative electrode dispersant includes modified CMC-Na. The negative electrode slurry is coated onto a current collector copper foil, dried at 85°C, and cold-pressed to obtain a negative electrode sheet containing a negative electrode film.

[0390] 3. Preparation of electrolyte

[0391] In an environment with a water content of less than 10 ppm, the organic solvents ethylene carbonate EC, ethyl methyl carbonate EMC, and diethyl carbonate DEC are mixed in a volume ratio of 1:1:1 to obtain the electrolyte solvent. Then, lithium hexafluorophosphate is mixed with the mixed solvent, and the lithium salt concentration is 1 mol / L.

[0392] 4. Preparation of lithium-ion batteries

[0393] The positive electrode sheet, polyethylene (PE) separator, and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0394] Examples 2-1 to 2-5

[0395] Unlike Example 1, the type of flexible groups in the negative electrode dispersant in the negative electrode slurry is different.

[0396] Examples 3-1 to 3-3

[0397] Unlike Example 1, the type of semi-condensation structure in the negative electrode dispersant in the negative electrode slurry is different.

[0398] Example 4

[0399] Unlike Example 1, the flexible groups and hemiacetal groups in the negative electrode dispersant of the negative electrode slurry have different molecular weights.

[0400] Example 5

[0401] Unlike Example 1, the negative electrode dispersant in the negative electrode slurry does not contain grafted flexible groups, but only includes semi-condensation groups.

[0402] Comparative Example 1

[0403] Unlike Example 1, a negative electrode dispersant was added to the negative electrode slurry. The negative electrode dispersant was replaced with sodium carboxymethyl cellulose (CMC-Na). The mass ratio of artificial graphite, conductive carbon, styrene-acrylic emulsion binder, and CMC-Na dispersant in the solid components of the negative electrode slurry was 96.7:0.7:1.5:1.1.

[0404] Comparative Example 2

[0405] Unlike Example 1, a negative electrode dispersant is added to the negative electrode slurry, and the negative electrode dispersant is replaced with sodium carboxymethyl cellulose. A plasticizer is also added to the negative electrode slurry. The mass ratio of artificial graphite, conductive carbon, styrene-acrylic emulsion, CMC-Na negative electrode dispersant, and butanediol plasticizer in the solid components of the negative electrode slurry is 96.55:0.7:1.5:1.1:0.15.

[0406] The relevant parameters for the embodiments and comparative examples are shown in Table 1.

[0407] Test section

[0408] 1. Negative electrode slurry filterability test:

[0409] Use a 150-mesh filter and cut it into 25cm x 25cm pieces.

[0410] Fold a 150-mesh filter into a fan shape and suspend it above the mouth of a clean beaker. Pour 500 mL of negative electrode slurry all at once over the filter. The slurry will start to flow out from the tip of the filter. Start recording the time. Record the filtration time for 300 mL.

[0411] 2. Gel and sedimentation state of the negative electrode slurry:

[0412] Take 500ml of negative electrode slurry and observe whether the negative electrode slurry forms a jelly-like gel state after different time periods. Also test the viscosity of the slurry. If the viscosity of the upper layer of slurry in the test beaker decreases and the lower layer of slurry thickens, it indicates that slurry sedimentation has occurred.

[0413] 3. Basis weight of negative electrode film coating:

[0414] The coating window measures the approximate critical range of the quality stability of the coated product; exceeding this range leads to defects such as cracking. An extrusion coater was used at a speed of 50 m / min. As the coating quality of the negative electrode sheets in the comparative and example examples gradually improved, the presence of cracks in the film layer was observed. If no cracks appeared, the weight was increased until cracks appeared on the surface of the electrode sheet. The weight of the negative electrode film layer that could withstand without cracking was recorded, which is the coating weight of the negative electrode film layer in Table 1.

[0415] 4. DC impedance test of lithium-ion batteries

[0416] The DC resistance test procedure for the battery is as follows: At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were charged to 4.2V at a constant current of 1 / 3C, and then charged to a current of 0.05C at a constant voltage of 4.2V. After resting for 5 minutes, the voltage V1 was recorded. Then, the batteries were discharged at 1 / 3C for 30 seconds, and the voltage V2 was recorded. The internal resistance DCR of the lithium-ion battery was obtained by subtracting V1 from V2 and then 1 / 3C.

[0417] 5. Dissolution time of dispersant

[0418] The dispersant was added to deionized water to prepare a 1% (w / w) gel solution. The stirrer was set to 500 rpm, and the time required for the dispersant to completely dissolve was recorded.

[0419] Completely dissolved: There are basically no flocculent substances in the system, and it appears as a transparent gel.

[0420] Test Results

[0421] The test results are shown in Table 1.

[0422] Table 1

[0423] In the examples and comparative examples, the weight-average molecular weight of the negative electrode dispersant was 60 wDa.

[0424] The number of repeating structures in a flexible group refers to the number of groups that repeat continuously in the flexible group, such as the value of m in Formula 1-1, the value of m in Formula 1-10, the value of s in Formula 2-1, the value of p in Formula 3-1, the value of a in Formula 4-24, and the value of b in Formula 5-21.

[0425] According to the gelation and sedimentation tests conducted in the above embodiments and comparative examples, the negative electrode slurry showed no sedimentation or gelation, and its state was relatively stable.

[0426] As shown in Table 1, Comparative Example 1 added sodium carboxymethyl cellulose (CMC-Na) as a dispersant to the negative electrode slurry. This sodium carboxymethyl cellulose was not modified by side chains. It is beneficial to improve the dispersion performance of the negative electrode active material in the negative electrode slurry. However, due to the hydrogen bonding of sodium carboxymethyl cellulose itself, the forces between molecular chains are strong, resulting in greater drying stress and brittleness during the drying process. This can easily lead to cracking of the negative electrode film, which is not conducive to the thick coating of the negative electrode slurry and results in a smaller coating weight.

[0427] Compared to Comparative Example 1, Comparative Example 2 added a plasticizer to the negative electrode slurry. The plasticizer effectively improves the shaping ability and flexibility of the negative electrode film, which is beneficial for thick coating of the negative electrode slurry, increasing its coating weight and improving the cracking phenomenon of the negative electrode film. However, tests revealed that the negative electrode film with added plasticizer had uneven thickness, resulting in inconsistent performance. Furthermore, both Comparative Example 1 and Comparative Example 2 had longer dissolution times.

[0428] In this embodiment, no plasticizer is added to the negative electrode slurry. Instead, an aldehyde addition reaction is performed on the negative electrode dispersant sodium carboxymethyl cellulose to form a modified carboxymethyl cellulose salt. This greatly increases the dissolution rate of the modified carboxymethyl cellulose salt, effectively shortening the preparation time of the negative electrode slurry and improving the dispersion performance of the negative electrode active material. It also breaks the original regular hydrogen bond of the carboxymethyl cellulose salt, weakening the interaction between the dispersant molecular chains and enhancing the flexibility of the negative electrode dispersant. This improves the flexibility of the negative electrode film and reduces the risk of cracking of the negative electrode film.

[0429] Furthermore, flexible groups can be grafted onto the modified carboxymethyl cellulose salt side to reduce the hydrogen bonding effect of the dispersant, thereby weakening the interaction between dispersant molecular chains and enhancing the flexibility of the negative electrode dispersant. This improves the flexibility of the negative electrode film, reduces the risk of cracking, especially for thick-coated negative electrode films, and increases the energy density of the battery cell. Moreover, the modified carboxymethyl cellulose salt has good dispersing and leveling effects, effectively dispersing the negative electrode active material, resulting in uniform dispersion of the negative electrode active material, uniform thickness distribution of the negative electrode film, and consistent performance.

[0430] In the embodiments of this application, when grafting modification of the side chain, at least one of ether groups, alkyl groups, alkenyl groups, amide groups or ester groups can be used for grafting modification. All of these can effectively improve the flexibility of the modified carboxymethyl cellulose salt and improve the flexibility of the negative electrode film, so that the thickness distribution of the negative electrode film is uniform and the performance is consistent.

[0431] The embodiments of this application regulate the amount of dispersant added in the negative electrode slurry, which can effectively adjust the thickness of the negative electrode slurry coating and improve the flexibility of the negative electrode film.

[0432] This application uses the method of Example 1 to prepare 10 lithium-ion batteries. The average thickness of the negative electrode film layer of each lithium-ion battery is measured. Specifically, the elemental analysis (CP) of the cross-section of the ion polished surface is performed in accordance with GB / T 17359-2012. The thickness of the negative electrode film layer at 10 locations in the negative electrode sheet is measured, and the average value is calculated as the average thickness of the lithium-ion battery. The thickness deviation of the negative electrode film layer of the 10 lithium-ion batteries is controlled within 0.5%.

[0433] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting this application, and that the embodiments can be changed, substituted and modified without departing from the spirit, principles and scope of this application.

Claims

1. A battery cell, comprising a negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer comprising a negative electrode active material and a negative electrode dispersant, the negative electrode dispersant comprising modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprising a hemiacetal group.

2. The battery cell according to claim 1, wherein, The hemiacetal group includes C1 to C10 aldehyde hemiacetal groups.

3. The battery cell according to claim 2, wherein, The hemiacetal group includes C1 to C4 aldehyde hemiacetal groups.

4. The battery cell according to any one of claims 1 to 3, wherein, The hemiacetal group includes one or more of the following: formaldehyde hemiacetal group, acetaldehyde hemiacetal group, propionaldehyde hemiacetal group, butyraldehyde hemiacetal group, pentanaldehyde hemiacetal group, hexanal hemiacetal group, heptanaldehyde hemiacetal group, octanaldehyde hemiacetal group, nonanaldehyde hemiacetal group, decanaldehyde hemiacetal group, glyoxal hemiacetal group, methylglyoxal hemiacetal group, ethylglyoxal hemiacetal group, malondialdehyde hemiacetal group, succinaldehyde hemiacetal group, glutaraldehyde hemiacetal group, hexanal hemiacetal group, heptanaldehyde hemiacetal group, octanaldehyde hemiacetal group, nonanaldehyde hemiacetal group, and decanaldehyde hemiacetal group.

5. The battery cell according to claim 4, wherein, The hemiacetal group includes one or more of the following: formaldehyde hemiacetal group, acetaldehyde hemiacetal group, propionaldehyde hemiacetal group, butyraldehyde hemiacetal group, glyoxal hemiacetal group, malondialdehyde hemiacetal group, and succinaldehyde hemiacetal group.

6. The battery cell according to any one of claims 1 to 5, wherein, The modified carboxymethyl cellulose salt further includes flexible groups, which include at least one of substituted or unsubstituted ether groups, substituted or unsubstituted alkyl groups, substituted or unsubstituted polyolefin groups, substituted or unsubstituted amide groups, and substituted or unsubstituted ester groups.

7. The battery cell according to claim 6, wherein, The flexible group includes at least one of the following: 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.

8. The battery cell according to claim 7, wherein, The substituted or unsubstituted C3 to C150 ether groups include the structural formula shown in Formula 1. In Equation 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 group, a substituted or unsubstituted C2 to C10 alkenyl group, or a substituted or unsubstituted C2 to C10 alkynyl group; m includes any positive integer from 5 to 60.

9. The battery cell according to claim 7 or 8, wherein, The substituted or unsubstituted C3 to C150 ether groups include at least one of the structural formulas shown in Formula 1-1 to Formula 1-14. Where m1 includes any positive integer from 1 to 30.

10. The battery cell according to any one of claims 7 to 9, wherein, The substituted or unsubstituted C3 to C150 alkyl groups include the structures shown in Formula 2. In Equation 2, R 21 To R 27 Each independently comprises at least one of a hydrogen atom, a halogen atom, or a substituted or unsubstituted C1 to C10 alkyl group; s includes any positive integer from 5 to 60.

11. The battery cell according to claim 10, wherein, The substituted or unsubstituted C3 to C150 alkyl group includes at least one of the structural formulas shown in Formula 2-1 to Formula 2-11. Where s1 includes any positive integer from 1 to 30.

12. The battery cell according to any one of claims 7 to 11, wherein, The substituted or unsubstituted C3 to C150 polyolefin groups include the structural formula shown in Formula 3. In Equation 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 group, or a substituted or unsubstituted C2 to C10 alkenyl group; R 35 Including at least one of hydrogen atoms, halogen atoms, substituted or unsubstituted C1 to C10 alkyl groups; p includes any positive integer from 5 to 60.

13. The battery cell according to claim 12, wherein, The substituted or unsubstituted C3 to C150 polyolefin groups include at least one of the structural formulas shown in Formula 3-1 to Formula 3-8.

14. The battery cell according to any one of claims 7 to 13, wherein, The substituted or unsubstituted C3 to C150 amide groups include the structural formula shown in Formula 4. In Equation 4, R 41 Including at least one of C1 to C1 methylene groups, including single bonds, substituted or unsubstituted groups; 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, or a substituted or unsubstituted C2 to C10 alkynyl group; a includes any positive integer from 1 to 30.

15. The battery cell according to claim 14, wherein, R 41 Including single bonds, the substituted or unsubstituted C3 to C150 amide groups include the structural formula shown in Formula 4-1.

16. The battery cell according to claim 15, wherein, The substituted or unsubstituted C3 to C150 amide groups include at least one of the structural formulas shown in Formulas 4-11 to 4-15.

17. The battery cell according to claim 14, wherein, R 41 Includes substituted or unsubstituted C1 to C5 methylene groups, wherein the substituted or unsubstituted C3 to C150 amide groups include the structures shown in Formula 4-2. a1 includes any positive integer from 1 to 5.

18. The battery cell according to claim 17, wherein, The substituted or unsubstituted C3 to C150 amide groups include at least one of the structural formulas shown in Formulas 4-21 to 4-24.

19. The battery cell according to any one of claims 7 to 18, wherein, The substituted or unsubstituted C3 to C150 ester groups include the structural formula shown in Formula 5. In Equation 5, R 51 Including at least one of the C1 to C5 methylene groups, whether single-bonded, substituted, or unsubstituted; R 52 Including substituted or unsubstituted C1 to C5 alkyl groups; 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, or a substituted or unsubstituted C2 to C10 alkynyl group; b includes any positive integer from 1 to 30.

20. The battery cell according to claim 19, wherein, R 51 Including single bonds, the substituted or unsubstituted C3 to C150 ester groups include the structural formula shown in Formula 5-1.

21. The battery cell according to claim 20, wherein, The substituted or unsubstituted C3 to C150 ester groups include at least one of the structural formulas shown in Formulas 5-11 to 5-16.

22. The battery cell according to claim 19, wherein, R 51 Includes substituted or unsubstituted C1 to C5 methylene groups, wherein the substituted or unsubstituted C3 to C150 ester groups include the structural formula shown in Formula 5-2. b1 includes any positive integer from 1 to 5.

23. The battery cell according to claim 22, wherein, The substituted or unsubstituted C3 to C150 ester groups include at least one of the structural formulas shown in Formulas 5-21 to 5-28.

24. The battery cell according to any one of claims 1 to 23, wherein, The weight-average molecular weight of the negative electrode dispersant is 40 wDa to 80 wDa.

25. The battery cell according to any one of claims 1 to 24, wherein, The reference film made of sodium carboxymethyl cellulose has an elongation at break of 100%, the film made of the modified carboxymethyl cellulose salt has an elongation at break of 195% to 300%, and the film made of the negative electrode dispersant and the reference film have a width of 2.5 cm, a length of 5 cm, and a thickness of 1 mm.

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

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

28. The battery cell according to any one of claims 1 to 27, wherein, The coating basis weight of the negative electrode film is 190 mg / 1540.25 mm. 2 Up to 230mg / 1540.25mm 2 .

29. The battery cell according to claim 28, wherein, The coating basis weight of the negative electrode film is 210 mg / 1540.25 mm. 2 Up to 230mg / 1540.25mm 2 .

30. A negative electrode dispersant comprising a modified carboxymethyl cellulose salt, said modified carboxymethyl cellulose salt comprising a hemiacetal group.

31. The negative electrode dispersant according to claim 30, wherein, The hemiacetal group includes C1 to C10 aldehyde hemiacetal groups.

32. The negative electrode dispersant according to claim 31, wherein, The hemiacetal group includes C1 to C4 aldehyde hemiacetal groups.

33. The negative electrode dispersant according to any one of claims 30 to 32, wherein, The hemiacetal group includes one or more of the following: formaldehyde hemiacetal group, acetaldehyde hemiacetal group, propionaldehyde hemiacetal group, butyraldehyde hemiacetal group, pentanaldehyde hemiacetal group, hexanal hemiacetal group, heptanaldehyde hemiacetal group, octanaldehyde hemiacetal group, nonanaldehyde hemiacetal group, decanaldehyde hemiacetal group, glyoxal hemiacetal group, methylglyoxal hemiacetal group, ethylglyoxal hemiacetal group, malondialdehyde hemiacetal group, succinaldehyde hemiacetal group, glutaraldehyde hemiacetal group, hexanal hemiacetal group, heptanaldehyde hemiacetal group, octanaldehyde hemiacetal group, nonanaldehyde hemiacetal group, and decanaldehyde hemiacetal group.

34. The negative electrode dispersant according to claim 33, wherein, The hemiacetal group includes one or more of the following: formaldehyde hemiacetal group, acetaldehyde hemiacetal group, propionaldehyde hemiacetal group, butyraldehyde hemiacetal group, glyoxal hemiacetal group, malondialdehyde hemiacetal group, and succinaldehyde hemiacetal group.

35. The negative electrode dispersant according to any one of claims 30 to 34, wherein, The modified carboxymethyl cellulose salt further includes flexible groups, which include at least one of substituted or unsubstituted ether groups, substituted or unsubstituted alkyl groups, substituted or unsubstituted polyolefin groups, substituted or unsubstituted amide groups, and substituted or unsubstituted ester groups.

36. A modified carboxymethyl cellulose salt, said modified carboxymethyl cellulose salt comprising a hemiacetal group.

37. A negative electrode sheet, comprising a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer comprising a negative electrode dispersant as described in any one of claims 30 to 35.

38. A battery comprising a battery cell as described in any one of claims 1 to 29.

39. An electrical device comprising the battery as claimed in claim 38.

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