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

Abstract

A modified carboxymethyl cellulose salt, a negative electrode dispersant, a negative electrode sheet, a battery cell, a battery, and an electric 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, the modified carboxymethyl cellulose salt comprises a conductive group and a flexible group; 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. The negative electrode film layer has good flexibility, is not prone to cracking, and has good electrical conductivity.

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. 202410825817.6, 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 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. The negative electrode sheet of the battery cell described in the present application has good flexibility and is not prone to cracking, and has good conductivity.

[0008] In a first aspect, the present application provides a battery cell, the battery cell comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material and a negative electrode dispersant, the negative electrode dispersant comprising a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprising a conductive group and a flexible group, the flexible group comprising at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, and a substituted or unsubstituted ester group.

[0009] Thus, the negative electrode dispersant in the embodiments of the present application includes a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt includes a flexible group, the flexible group weakens the interaction between the molecular chains of the modified carboxymethyl cellulose salt, improves the flexibility of the polymer molecular chain, can endow the negative electrode film layer with excellent flexibility, reduces the risk of cracking of the negative electrode film layer, especially can reduce the risk of cracking of the thick-coated negative electrode film layer, and improves the energy density of the battery cell; further, the flexible group has excellent flexibility, which can further improve the flexibility of the modified carboxymethyl cellulose salt, and further improve the flexibility of the negative electrode film layer.

[0010] The modified carboxymethyl cellulose salt further includes a conductive group, the conductive group has high electronic conductivity, which can improve the conductivity of the modified carboxymethyl cellulose salt and improve the conductivity of the negative electrode film layer.

[0011] Moreover, the modified carboxymethyl cellulose salt has good dispersion and leveling effects, which can effectively disperse the negative electrode active material, so that the negative electrode active material is uniformly dispersed, and the negative electrode film layer has uniform thickness distribution and uniform performance.

[0012] Thus, when the negative electrode film layer includes the modified carboxymethyl cellulose salt, the flexibility of the negative electrode film layer is improved, the risk of cracking is low, and the negative electrode film layer has uniform thickness and uniform performance.

[0013] In some embodiments, the modified carboxymethyl cellulose salt includes a compound represented by Formula A,

[0014] In Formula A,

[0015] M includes a metal ion or NH4 + ; and at least one of R1 to R5 includes the conductive group, and at least one of R1 to R5 includes the flexible group.

[0016] R1 to R5 each independently include a hydrogen atom, a conductive group or a flexible group, and at least one of R1 to R5 includes the conductive group, and at least one of R1 to R5 includes the flexible group.

[0017] n includes any positive integer from 1500 to 3000.

[0018] Thus, the above-mentioned material has good dispersibility in the embodiments of the present application, and since the modified carboxymethyl cellulose salt further includes a conductive group and a flexible group, the negative electrode film layer has uniform performance, is not prone to cracking, and has excellent conductivity.

[0019] In some embodiments, the conductive group includes one or more of an aromatic polymer group and a polyacetylene group. The above-mentioned groups have excellent conductivity, which can improve the conductivity of the negative electrode film layer.

[0020] In some embodiments, the aromatic polymer group comprises one or more of a five-membered heterocyclic polymer group, an arene derivative polymer group, and a polyindole group.

[0021] In some embodiments, the five-membered heterocyclic polymer group comprises one or more of a polypyrryl group, a polythiophene group, and a polyfuryl group.

[0022] In some embodiments, the arene derivative polymer group comprises one or more of a polyparaphenylene group, a polyphenylene group, a polyphenylenevinylene group, a polyaniline group, and an aniline tetramer group.

[0023] In some embodiments, the polyacetylene group comprises one or more of a polyacetylene group and a polydiacetylene group. The polyacetylene group has good flexibility, which is conducive to further improving the flexibility of the negative electrode dispersing agent; and can improve the electrical conductivity of the negative electrode dispersing agent.

[0024] In some embodiments, the aromatic polymer group has a polymerization degree of 2 to 50.

[0025] In some embodiments, the polyacetylene group has a polymerization degree of 2 to 50.

[0026] 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, and a substituted or unsubstituted C3 to C150 ester group. The above-mentioned groups have excellent flexibility, which can improve the flexibility of the negative electrode film layer.

[0027] In some embodiments, the substituted or unsubstituted C3 to C150 ether group comprises at least one of a structural formula shown in formula 1,

[0028] In formula 1,

[0029] 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, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0030] m comprises any positive integer from 5 to 60.

[0031] Therefore, the ether group in the embodiments of the present application can increase flexibility, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0032] 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,

[0033] wherein m1 includes any positive integer of 1 to 30.

[0034] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes at least one of a structure of Formula 2,

[0035] In Formula 2,

[0036] R 21 to R 27 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0037] s includes any positive integer of 5 to 60.

[0038] Thus, the alkyl group in the embodiments of the present application can increase flexibility, thereby increasing flexibility of the modified carboxymethyl cellulose salt.

[0039] In some embodiments, 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,

[0040] wherein s1 includes any positive integer of 1 to 30.

[0041] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group includes a structure of Formula 3,

[0042] In Formula 3,

[0043] R 31 to R 34 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group;

[0044] R 35 includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0045] p includes any positive integer of 5 to 60.

[0046] Thus, the polyalkylene group in the embodiments of the present application can increase flexibility, thereby increasing flexibility of the modified carboxymethyl cellulose salt.

[0047] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group includes at least one of a structure of Formula 3-1 to a structure of Formula 3-8,

[0048] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes a structural formula of Formula 4,

[0049] In Formula 4,

[0050] R 41 includes at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group, and a substituted or unsubstituted C3 to C150 amide-based group;

[0051] 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;

[0052] a includes any positive integer of 1 to 30.

[0053] Thus, the amide-based group in the embodiments of the present application can increase flexibility, thereby increasing flexibility of the modified carboxymethyl cellulose salt.

[0054] In some embodiments, R 41 includes a single bond, a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula of Formula 4-1,

[0055] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula of Formula 4-11 to a structural formula of Formula 4-15,

[0056] In some embodiments, R 41 includes a substituted or unsubstituted C1 to C5 methylene group, and a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula of Formula 4-2,

[0057] a1 includes any positive integer of 1 to 5.

[0058] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula of Formula 4-21 to a structural formula of Formula 4-24,

[0059] In some embodiments, the substituted or unsubstituted C3 to C150 ester-based group includes a structural formula of Formula 5,

[0060] In formula 5,

[0061] R 51 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0062] R 52 including a substituted or unsubstituted C1 to C5 alkyl group;

[0063] R 53 to R 55 each independently including 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;

[0064] b includes any positive integer from 1 to 30.

[0065] Thus, the ester group in the embodiments of the present application can increase flexibility, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0066] In some embodiments, R 51 including a single bond, a substituted or unsubstituted C3 to C150 ester group including a structural formula represented by formula 5-1,

[0067] In some embodiments, the substituted or unsubstituted C3 to C150 ester group includes at least one of a structural formula represented by formula 5-11 to a structural formula represented by formula 5-16,

[0068] In some embodiments, R 51 including a substituted or unsubstituted C1 to C5 methylene group, and a substituted or unsubstituted C3 to C150 ester group including a structural formula represented by formula 5-2,

[0069] b1 includes any positive integer from 1 to 5.

[0070] In some embodiments, the substituted or unsubstituted C3 to C150 ester group includes at least one of a structural formula represented by formula 5-21 to a structural formula represented by formula 5-28,

[0071] In some embodiments, the weight average molecular weight of the negative electrode dispersant is 40 wDa to 80 wDa. The molecular weight of the grafting group in the negative electrode dispersant is relatively small, which can reduce the hydrogen bonding effect between the molecular chains of the negative electrode dispersant, and at the same time, can make the negative electrode dispersant have good dispersibility.

[0072] In some embodiments, the elongation at break of the reference adhesive film made of sodium carboxymethyl cellulose is 100%, the elongation at break of the adhesive film made of the modified carboxymethyl cellulose salt is 200% to 300%, the width of the adhesive film and the reference adhesive film made of the negative electrode dispersant is 2.5 cm, the length is 5 cm, and the thickness is 1 mm. Thus, the elongation at break of the negative electrode dispersant is higher than that of the conventional sodium carboxymethyl cellulose, so that the flexibility of the negative electrode plate is better and is less likely to break.

[0073] In some embodiments, the mass content of the negative electrode dispersant is 0.8% to 1.3%, or 1.0% to 1.2%, based on the total mass of the negative electrode film layer. When the mass content of the negative electrode dispersant is in the above range, the flexibility of the negative electrode film layer can be effectively improved, the negative electrode active material is uniformly dispersed in the negative electrode film layer, and the performance of the negative electrode film layer is more uniform.

[0074] In some embodiments, the coating grammage of the negative electrode film layer is 190 mg / 1540.25 mm 2 to 235 mg / 1540.25 mm 2 ; or 220 mg / 1540.25 mm 2 to 235 mg / 1540.25 mm 2 . The coating grammage of the negative electrode film layer is relatively high, which is conducive to achieving thick coating.

[0075] In a second aspect, the present application provides a negative electrode dispersant. The modified carboxymethyl cellulose salt includes a conductive group and a flexible group. The flexible group includes at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, and a substituted or unsubstituted ester group.

[0076] Thus, the negative electrode dispersant in the embodiments of the present application includes a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt includes a flexible group, the flexible group weakens the interaction between the molecular chains of the modified carboxymethyl cellulose salt, improves the flexibility of the polymer molecular chain, can endow the negative electrode film layer with excellent flexibility, reduces the risk of cracking of the negative electrode film layer, especially can reduce the risk of cracking of the thick-coated negative electrode film layer, and improves the energy density of the battery cell; further, the flexible group has excellent flexibility, which can further improve the flexibility of the modified carboxymethyl cellulose salt; the modified carboxymethyl cellulose salt also includes a conductive group, the conductive group has high electronic conductivity, which can improve the conductivity of the modified carboxymethyl cellulose salt and improve the conductivity of the negative electrode film layer; and the modified carboxymethyl cellulose salt has good dispersion and leveling effects, which can effectively disperse the negative electrode active material, so that the negative electrode active material is uniformly dispersed, the thickness distribution of the negative electrode film layer is uniform, and the performance of the negative electrode film layer is uniform; thus, when the negative electrode film layer includes the modified carboxymethyl cellulose salt, the flexibility of the negative electrode film layer is improved, the risk of cracking is low, and the thickness of the negative electrode film layer is uniform and the performance is uniform.

[0077] In some embodiments, the modified carboxymethyl cellulose salt includes a compound shown in Formula A,

[0078] In Formula A,

[0079] M includes a metal ion or NH4 + at least one of Li+, Na+, K+, NH4+, and Ca2+;

[0080] R1 to R5 each independently include a hydrogen atom, a conductive group, or a flexible group, and at least one of R1 to R5 includes a conductive group, and at least one other includes a flexible group;

[0081] n includes any positive integer from 1500 to 3000.

[0082] Thus, the above-mentioned material has good dispersibility in the embodiments of the present application, and since the modified carboxymethyl cellulose salt also includes a conductive group and a flexible group, when the negative electrode dispersant is applied to the negative electrode film layer, the performance of the negative electrode film layer is uniform, the negative electrode film layer is not prone to cracking, and has excellent conductivity.

[0083] In some embodiments, the conductive group includes one or more of an aromatic polymer group and a polyacetylene group. The above-mentioned groups have excellent conductivity, which can improve the conductivity of the negative electrode film layer.

[0084] In some embodiments, the aromatic polymer group includes one or more of a five-membered heterocyclic polymer group, an aromatic hydrocarbon derivative polymer group, and a polyindole group.

[0085] In some embodiments, the five-membered heterocyclic polymer group comprises one or more of a polypyrrone group, a polythiophene group, and a polyfuran group.

[0086] In some embodiments, the aromatic hydrocarbon derivative polymer group comprises one or more of a polyparabenzene group, a polyparaphenylene group, a polyparaphenylenevinylene group, a polyaniline group, and an aniline tetramer group.

[0087] In some embodiments, the polyacetylene group comprises one or more of a polyacetylene group and a polydiacetylene group. The polyacetylene group has good flexibility, which is conducive to further improving the flexibility of the negative electrode dispersing agent; and can improve the electrical conductivity of the negative electrode dispersing agent.

[0088] In some embodiments, the aromatic polymer group has a degree of polymerization of 2 to 50.

[0089] In some embodiments, the polyacetylene group has a degree of polymerization of 2 to 50.

[0090] 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, and a substituted or unsubstituted C3 to C150 ester group. The above-mentioned groups have excellent flexibility, which can improve the flexibility of the negative electrode film layer.

[0091] In some embodiments, the substituted or unsubstituted C3 to C150 ether group comprises a structural formula shown in formula 1,

[0092] In formula 1,

[0093] 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, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0094] m comprises any positive integer from 5 to 60.

[0095] Thus, the ether group in the embodiments of the present application can increase flexibility, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0096] 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,

[0097] wherein m1 comprises any positive integer from 1 to 30.

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

[0099] In Formula 2,

[0100] 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;

[0101] s comprises any positive integer from 5 to 60.

[0102] Thus, the alkyl group in the embodiments of the present application can increase flexibility, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0103] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group comprises at least one of a structure of Formula 2-1 to a structure of Formula 2-11,

[0104] wherein s1 comprises any positive integer from 1 to 30.

[0105] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group comprises a structure of Formula 3,

[0106] In Formula 3,

[0107] R 31 to R 34 each independently comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group;

[0108] R 35 comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0109] p comprises any positive integer from 5 to 60.

[0110] Thus, the polyalkylene group in the embodiments of the present application can increase flexibility, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0111] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group comprises at least one of a structure of Formula 3-1 to a structure of Formula 3-8,

[0112] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group comprises a structure of Formula 4,

[0113] In Formula 4,

[0114] R 41 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0115] 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;

[0116] a includes any positive integer of 1 to 30.

[0117] Thus, the amide-based group in the embodiments of the present application can increase flexibility, thereby increasing flexibility of the modified carboxymethyl cellulose salt.

[0118] In some embodiments, R 41 including a single bond, a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula of Formula 4-1,

[0119] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula of Formula 4-11 to a structural formula of Formula 4-15,

[0120] In some embodiments, R 41 including a substituted or unsubstituted C1 to C5 methylene group, a substituted or unsubstituted C3 to C150 amide-based group includes a structural formula of Formula 4-2,

[0121] a1 includes any positive integer of 1 to 5.

[0122] In some embodiments, the substituted or unsubstituted C3 to C150 amide-based group includes at least one of a structural formula of Formula 4-21 to a structural formula of Formula 4-24,

[0123] In some embodiments, the substituted or unsubstituted C3 to C150 ester-based group includes a structural formula of Formula 5,

[0124] In Formula 5,

[0125] R 51 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0126] R52 comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0127] R 53 to R 55 comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group;

[0128] b comprises any positive integer from 1 to 30.

[0129] Thus, the ester group in the embodiments of the present application can increase flexibility, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0130] In some embodiments, R 51 comprises a single bond, and the substituted or unsubstituted C3 to C150 ester group comprises a structural formula represented by formula 5-1,

[0131] In some embodiments, the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula represented by formula 5-11 to a structural formula represented by formula 5-16,

[0132] In some embodiments, R 51 comprises a substituted or unsubstituted C1 to C5 methylene group, and the substituted or unsubstituted C3 to C150 ester group comprises a structural formula represented by formula 5-2,

[0133] b1 comprises any positive integer from 1 to 5.

[0134] In some embodiments, the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula represented by formula 5-21 to a structural formula represented by formula 5-28,

[0135] In some embodiments, the weight average molecular weight of the negative electrode dispersant is 40 wDa to 80 wDa. The molecular weight of the grafting group in the negative electrode dispersant is relatively small, which can reduce the hydrogen bonding effect between the molecular chains of the negative electrode dispersant, and at the same time, can make the negative electrode dispersant have better dispersibility.

[0136] In some embodiments, the breaking elongation of the reference adhesive film made of sodium carboxymethyl cellulose is 100%, the breaking elongation of the adhesive film made of the modified carboxymethyl cellulose salt is 200% to 300%, the width of the adhesive film and the reference adhesive film made of the negative electrode dispersant is 2.5 cm, the length is 5 cm, and the thickness is 1 mm. Thus, the breaking elongation of the negative electrode dispersant is higher than that of the conventional sodium carboxymethyl cellulose, and the negative electrode dispersant has better flexibility when applied to the negative electrode sheet and is less likely to break.

[0137] In a third aspect, the present application provides a modified carboxymethyl cellulose salt, which includes a conductive group and a flexible group, and the flexible group includes at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, and a substituted or unsubstituted ester group.

[0138] Thus, the modified carboxymethyl cellulose salt of the embodiments of the present application includes a flexible group, which weakens the interaction between the molecular chains of the modified carboxymethyl cellulose salt, improves the flexibility of the polymer molecular chain, can impart excellent flexibility to the negative electrode film layer, reduce the risk of cracking of the negative electrode film layer, especially reduce the risk of cracking of the thick-coated negative electrode film layer, and improve the energy density of the battery cell. Further, the flexible group has excellent flexibility, which can further improve the flexibility of the modified carboxymethyl cellulose salt. The modified carboxymethyl cellulose salt also includes a conductive group, which has high electronic conductivity and can improve the conductivity of the modified carboxymethyl cellulose salt and the conductivity of the negative electrode film layer. Moreover, the modified carboxymethyl cellulose salt has good dispersing and leveling effects, which can effectively disperse the negative electrode active material, so that the negative electrode active material is uniformly dispersed, the thickness distribution of the negative electrode film layer is uniform, and the performance is uniform. Thus, when the negative electrode film layer includes the modified carboxymethyl cellulose salt, the flexibility of the negative electrode film layer is improved, the risk of cracking is low, and the thickness of the negative electrode film layer is uniform and the performance is uniform.

[0139] In some embodiments, the modified carboxymethyl cellulose salt includes a compound shown in Formula A,

[0140] In Formula A,

[0141] M includes a metal ion or NH4 + at least one of the group consisting of Li+, Na+, K+, NH4+, and Ca2+;

[0142] R1 to R5 each independently include a hydrogen atom, a conductive group, or a flexible group, and at least one of R1 to R5 includes a conductive group and at least one other includes a flexible group;

[0143] n includes any positive integer from 1500 to 3000.

[0144] Therefore, the material has good dispersibility, and the modified carboxymethyl cellulose salt further comprises an electrically conductive group and a flexible group. When the negative electrode dispersant is applied to the negative electrode film layer, the negative electrode film layer has uniform performance, is less likely to crack, and has excellent electrical conductivity.

[0145] In some embodiments, the electrically conductive group comprises one or more of an aromatic polymer group and a polyacetylene group. The above-mentioned groups have excellent electrical conductivity, which can improve the electrical conductivity of the negative electrode film layer.

[0146] In some embodiments, the aromatic polymer group comprises one or more of a five-membered heterocyclic polymer group, an aromatic hydrocarbon derivative polymer group, and a polyindole group.

[0147] In some embodiments, the five-membered heterocyclic polymer group comprises one or more of a polypyrrole group, a polythiophene group, and a polyfuran group.

[0148] In some embodiments, the aromatic hydrocarbon derivative polymer group comprises one or more of a polyparaphenylene group, a polyphenylene group, a polyphenylenevinylene group, a polyaniline group, and an aniline tetramer group.

[0149] In some embodiments, the polyacetylene group comprises one or more of a polyacetylene group and a polydiacetylene group. The above-mentioned polyacetylene group has good flexibility, which is conducive to further improving the flexibility of the negative electrode dispersant; and can improve the electrical conductivity of the negative electrode dispersant.

[0150] In some embodiments, the aromatic polymer group has a degree of polymerization of 2 to 50.

[0151] In some embodiments, the polyacetylene group has a degree of polymerization of 2 to 50.

[0152] 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, and a substituted or unsubstituted C3 to C150 ester group. The above-mentioned groups have excellent flexibility, which can improve the flexibility of the negative electrode film layer.

[0153] In a fourth aspect, the application further provides a negative electrode tab, which comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer comprises the negative electrode dispersant according to any one of the embodiments of the second aspect of the application.

[0154] In a fifth aspect, the application further provides a battery, which comprises the battery cell according to any one of the embodiments of the first aspect of the application.

[0155] In a sixth aspect, the embodiments of the present application further provide a power consuming device including the battery according to any one of the embodiments of the fifth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0156] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. 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.

[0157] FIG. 1 is a schematic diagram of an embodiment of a battery cell of the present application.

[0158] FIG. 2 is an exploded schematic diagram of the embodiment of the battery cell of FIG. 1.

[0159] FIG. 3 is a schematic diagram of an embodiment of a battery module of the present application.

[0160] FIG. 4 is a schematic diagram of an embodiment of a battery pack of the present application.

[0161] FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4.

[0162] FIG. 6 is a schematic diagram of an embodiment of a power consuming device including the battery cell of the present application as a power source.

[0163] The drawings are not necessarily drawn to scale.

[0164] The reference signs are explained as follows:

[0165] 1, battery pack; 2, upper case; 3, lower case; 4, battery module;

[0166] 5, battery cell; 51, housing; 52, electrode assembly; 53, cover plate;

[0167] 6, power consuming device. DETAILED DESCRIPTION

[0168] Hereinafter, the embodiments of the modified carboxymethyl cellulose salt, the negative electrode dispersant, the negative electrode sheet, the battery cell, the battery, and the power consuming device of the present application will be specifically described with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be 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.

[0169] The ranges disclosed herein are intended to be "open" ranges, i.e., the end values are not included in the range. The ranges are intended to be "inclusive," i.e., the end values are included in the range. The ranges are intended to be combinable, i.e., any of the lower limits can be combined with any of the upper limits to form a range. For example, if a range is listed as 60 to 120 and 80 to 110, it is intended to be understood that the ranges 60 to 110 and 80 to 120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, a numerical range "a to b" means any and all subcombinations of the numbers between a and b, inclusive of a and b. For example, the numerical range "0 to 5" means that all of the numbers between 0 and 5, inclusive of 0 and 5, have been listed herein. In other words, "0 to 5" is a shorthand for listing all of the numbers between 0 and 5, inclusive of 0 and 5. Also, when a parameter is stated to be an integer ≥ 2, it is equivalent to state that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0170] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not otherwise specified.

[0171] All technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if not otherwise specified.

[0172] All steps of the present application can be performed in sequence or randomly, preferably in sequence, if not otherwise specified. For example, a method comprises steps a and b, which means that the method can comprise steps a and b in sequence, or steps b and a in sequence. For example, it is mentioned that the method can further comprise step c, which means that step c can be added to the method in any sequence, for example,

[0173] The method can comprise steps a, b and c, or steps a, c and b, or steps c, a and b, etc.

[0174] "Include" and "contain" mentioned in the present application means open or closed, if not otherwise specified. For example, "include" and "contain" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0175] The term "or" is inclusive in this application, unless otherwise indicated. So, for example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true or present, and B is false or not present; A is false or not present, and B is true or present; or both A and B are true or present.

[0176] Throughout this specification, substituents of compounds are disclosed in groups or in ranges. It is specifically intended that the description include each and every individual subcombination of the members of these groups and ranges. For example, the term "Ci to C8alkyl" is specifically intended to individually disclose C1, C2, C3, C4, C5, C6, C7, C8, Ci to C8, Ci to C7, Ci to C6, Ci to C5, Ci to C4, Ci to C3, Ci to C2, C2 to C8, C2 to C7, C2 to C6, C2 to C5, C2 to C4, C2 to C3, C3 to C8, C3 to C7, C3 to C6, C3 to C5, C3 to C4, C4 to C8, C4 to C7, C4 to C6, C4 to C5, C5 to C8, C5 to C7, C5 to C6, C6 to C8, C6 to C7, and C7 to C8alkyl.

[0177] As other examples, it is expressly intended that the integers in the range of 5 to 40 individually disclose 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, and 40; and it is expressly intended that the integers in the range of 1 to 20 individually disclose 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20. In this manner, other groups or ranges are expressly intended.

[0178] The negative electrode sheet includes 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 is formed by coating the negative electrode slurry onto the negative current collector and drying it. During the formation of the negative electrode film layer, cracking may occur, causing the negative electrode sheet to fail to meet production requirements. In order to improve the energy density of the battery cell, the negative electrode film layer is usually thickly coated, which further aggravates the cracking phenomenon, making it difficult to achieve thick coating of the negative electrode sheet. In order to improve the cracking phenomenon of the negative electrode film layer, related technologies add plasticizers such as butanediol to the negative electrode slurry. Plasticizers are usually small molecule compounds with relatively small molecular weights. Plasticizers can enter between the polymer molecular chains of the binder, reduce the intermolecular stress of the binder polymer, and reduce the crystallinity of the polymer molecular chains, thereby improving the shaping ability and flexibility of the negative electrode film layer and improving the cracking phenomenon. However, residual plasticizers can easily lead to uneven thickness of the negative electrode film layer, resulting in interface problems such as dark marks in the negative electrode film layer.

[0179] Furthermore, since battery cells have high energy density requirements, additives such as conductive agents in the negative electrode film layer will reduce the amount of negative electrode active material added, and the addition of additives will reduce energy density; if the amount of additives is reduced, the fast charging performance of the battery cell may be affected; therefore, in related technologies, it is difficult to balance energy density and fast charging performance.

[0180] In view of the above problems, this application proposes a negative electrode dispersant comprising modified carboxymethyl cellulose salt. The carboxymethyl cellulose salt is grafted and modified with conductive and flexible groups. The conductive groups can improve the electronic conductivity of the modified carboxymethyl cellulose salt and enhance its electrical conductivity; the flexible groups can reduce the interaction forces between molecular chains. When applied to negative electrode slurry, it can play an excellent dispersing role for negative electrode active materials, improve the flexibility of the negative electrode film, and improve the cracking phenomenon of the negative electrode film, thereby improving the energy density and fast charging performance of the battery cell.

[0181] Modified carboxymethyl cellulose salt

[0182] In a first aspect, embodiments of this application provide a modified carboxymethyl cellulose salt, which includes a conductive group and a flexible group. The flexible group includes 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.

[0183] Carboxymethyl cellulose salt (CMC-M) is a type of anionic, water-soluble cellulose etherified derivative. When applied to negative electrode slurry, it can reduce the interfacial tension between the negative electrode active material and the solvent, thus providing good dispersion for the negative electrode active material. Under stirring, it helps the negative electrode active material to be uniformly dispersed in the solvent to form a stable slurry system.

[0184] The molecular chain of the carboxymethyl cellulose salt is rich in hydroxyl groups -OH, and the presence of the hydroxyl groups enables the formation of strong van der Waals forces or hydrogen bonds between the molecular chains of the carboxymethyl cellulose salt itself, so that the negative electrode slurry has strong drying stress during the drying process and is prone to warping and cracking during further rolling, causing the negative electrode film layer to crack.

[0185] The negative electrode dispersant of the embodiments of the present application includes a modified carboxymethyl cellulose salt, which is obtained by grafting modification of the side chain of the carboxymethyl cellulose salt CMC-M. The repeating units included in the modified carboxymethyl cellulose salt can be one or more. The side chain of the carboxymethyl cellulose salt is grafted by a grafting group, which replaces the hydrogen atoms in the hydroxyl groups, destroys the hydroxyl structure in the carboxymethyl cellulose salt, and thus destroys the regular hydrogen bond structure and reduces the number of hydrogen bonds.

[0186] The modified carboxymethyl cellulose salt is a carboxymethyl cellulose salt in which at least one hydrogen atom of a hydroxyl group is replaced by a flexible group. Such a group can reduce the interaction between polymer molecular chains, thereby reducing the stress generated during drying. Moreover, due to the flexibility of the flexible group, the flexibility of the modified carboxymethyl cellulose salt is improved. When the negative electrode dispersant is applied to the negative electrode slurry, the drying stress of the negative electrode slurry during the drying process is small, the risk of cracking of the negative electrode film layer is reduced, the interface performance of the negative electrode film layer is improved, and the flexibility of the negative electrode film layer is improved. In particular, it can reduce the risk of cracking of the thickly coated negative electrode film layer, which is conducive to improving the energy density of the battery cell.

[0187] The modified carboxymethyl cellulose salt is a carboxymethyl cellulose salt in which at least one hydrogen atom of a hydroxyl group is replaced by a flexible group. Such a group can reduce the interaction between polymer molecular chains, thereby reducing the stress generated during drying. Moreover, due to the flexibility of the flexible group, the flexibility of the modified carboxymethyl cellulose salt is improved. When the negative electrode dispersant is applied to the negative electrode slurry, the drying stress of the negative electrode slurry during the drying process is small, the risk of cracking of the negative electrode film layer is reduced, the interface performance of the negative electrode film layer is improved, and the flexibility of the negative electrode film layer is improved. In particular, it can reduce the risk of cracking of the thickly coated negative electrode film layer, which is conducive to improving the energy density of the battery cell.

[0188] Moreover, the main structure of the modified carboxymethyl cellulose salt is still that of the carboxymethyl cellulose salt, so it still has good dispersing 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, so that the thickness distribution of the negative electrode film layer is uniform and the performance is uniform.

[0189] 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 conductivity.

[0190] In some embodiments, the cations in the modified carboxymethyl cellulose salt include metal ions or ammonium ions NH4 +at least one of lithium ion, sodium ion, potassium ion, and the like.

[0191] 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.

[0192] In other embodiments, the modified carboxymethyl cellulose salt can further include a modified carboxymethyl cellulose potassium salt, and the like.

[0193] In some embodiments, the modified carboxymethyl cellulose salt includes a compound represented by Formula A,

[0194] In Formula A,

[0195] M includes a metal ion or NH4 + at least one of lithium ion, sodium ion, potassium ion, and the like;

[0196] R1to R5each independently include a hydrogen atom, a conductive group, or a flexible group, and at least one of R1to R5includes a conductive group, and at least another includes a flexible group;

[0197] n represents a degree of polymerization of the modified carboxymethyl cellulose salt, and n can also be considered as a number of repeating structures.

[0198] The above materials have good dispersibility, and since the modified carboxymethyl cellulose salt further includes a conductive group and a flexible group, when the negative electrode dispersant is applied to the negative electrode film layer, the negative electrode film layer has uniform performance, the negative electrode film layer is less likely to crack, and has excellent conductivity.

[0199] Optionally, n includes any positive integer between 1500 and 3000. Illustratively, n can be 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, or 3000.

[0200] The repeating unit in the modified carboxymethyl cellulose salt can include one or more.

[0201] The negative electrode dispersant can include one or more modified carboxymethyl cellulose salts.

[0202] At least two of R1 to R5 replace the hydrogen atom in the hydroxyl group, at least one of R1 to R5 includes a conductive group, which can be understood as that the hydrogen atom in at least one of the hydroxyl groups in the carboxymethyl cellulose salt is replaced by a conductive group, at least one of R1 to R5 includes a flexible group, which can be understood as that the hydrogen atom in at least one of the hydroxyl groups in the carboxymethyl cellulose salt is replaced by a flexible group, that is, at least two of R1 to R5 are not hydrogen atoms, for example, three of R1 to R5 are hydrogen atoms, or two of R1 to R5 are hydrogen atoms, or one of R1 to R5 is a hydrogen atom, or even R1 to R5 can all be non-hydrogen atoms.

[0203] The conductive group can replace the hydrogen atoms in at least two of the hydroxyl groups, so that the electronic conductivity of the modified carboxymethyl cellulose salt is further improved.

[0204] The flexible group can replace the hydrogen atoms in at least two of the hydroxyl groups.

[0205] As the number of hydrogen atoms decreases, 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 carboxymethyl cellulose salt molecular chains, the smaller the drying stress of the negative electrode slurry, and the negative electrode film layer is not prone to cracking and other phenomena, and the interface performance is improved. In the case where R1 to R5 can all be non-hydrogen atoms, the carboxymethyl cellulose salt basically does not contain hydroxyl groups, the number of hydrogen bonds contained in the carboxymethyl cellulose salt is small, the interaction between the carboxymethyl cellulose salt molecular chains is small, the drying stress is significantly reduced, and the negative electrode film layer is not prone to cracking and other phenomena, and the interface performance is improved.

[0206] [Conductive group]

[0207] In some embodiments, the conductive group can include a conductive polymer, which is a polymer with a highly π-π conjugated polymer chain. Specifically, the conductive polymer contains alternating single and double bonds on the main chain, has a conjugated long chain structure, and the delocalized π electrons on the double bond can migrate on the molecular chain to form an electric current, so that the high molecular structure itself inherently has conductivity.

[0208] In some embodiments, the conductive group includes a C2 to C150 conductive group.

[0209] As the length of the molecular chain increases, the number of π electrons increases, the electronic activation energy is lower, the electrons are more easily delocalized, and the conductivity is better; and as the length of the molecular chain increases, the flexibility of the molecular chain increases, which can further improve the flexibility of the modified carboxymethyl cellulose.

[0210] In some embodiments, the conductive group includes one or more of an aromatic polymer group and a polyacetylene group.

[0211] In some embodiments, the aromatic polymer group comprises one or more of a five-membered heterocyclic polymer group, an arene derivative polymer group, and a polyindole group; the aromatic polymer group has steric hindrance effect, which can increase the distance between molecular chains, further weaken the interaction between the chains, further reduce the stress generated during drying, and reduce the risk of cracking of the negative electrode film layer; and can improve the conductivity of the negative electrode dispersant.

[0212] For example, the five-membered heterocyclic polymer group comprises one or more of a polypyrrole group, a polythiophene group, and a polyfuran group.

[0213] For example, the arene derivative polymer group comprises one or more of a polyparaphenylene group, a polyphenylenevinylene group, a polyaniline group, and an aniline tetramer group.

[0214] In some embodiments, the polyacetylene group comprises one or more of a polyacetylene group and a polydiacetylene group. The polyacetylene group has good flexibility, which is conducive to further improving the flexibility of the negative electrode dispersant; and can improve the conductivity of the negative electrode dispersant.

[0215] In some embodiments, the aromatic polymer group has a degree of polymerization of 2 to 50, which can be 2 to 20, for example, 2, 3, 4, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50, or a range formed by any two of the above values.

[0216] In some embodiments, the polyacetylene group has a degree of polymerization of 2 to 50, which can be 2 to 20, for example, 2, 3, 4, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 48, 50, or a range formed by any two of the above values.

[0217] [flexible group]

[0218] In order to further reduce the effect of hydrogen bonds in the negative electrode dispersant, the substituent group is selected 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 the other part of the hydroxyl groups are substituted by a long chain structure, the long chain structure occupies a long space and has steric hindrance effect, which can further weaken the hydrogen bond effect formed by the unsubstituted hydroxyl groups, thereby reducing the interaction between the molecular chains, further reducing the drying stress, reducing the risk of cracking of the negative electrode film layer, and improving the interfacial 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 used as a negative electrode slurry.

[0219] 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.

[0220] The above-mentioned groups are long chain groups, so that the modified carboxymethyl cellulose salt has excellent flexibility, and the flexibility of the negative electrode film layer formed by drying the negative electrode slurry can be improved.

[0221] When the above-mentioned groups are substituted, the substituent group can include a halogen atom or a heteroatom-containing group, the halogen atom can include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or the like, and the heteroatom can include a nitrogen atom, a sulfur atom, an oxygen atom, or the like.

[0222] [ether group]

[0223] In some embodiments, R1 to R5 each independently include a substituted or unsubstituted ether group, which can be a substituted or unsubstituted C3 to C150 ether group. The ether group has a long chain, so that the flexibility can be increased, thereby increasing the flexibility of the modified carboxymethyl cellulose salt.

[0224] In some embodiments, the ether group includes a structural formula as shown in Formula 1,

[0225] In Formula 1,

[0226] R 11 to R 17 each independently include 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.

[0227] Optionally, when the above-mentioned groups are 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, or an iodine atom.

[0228] m is the number of repeating structures. m includes any positive integer from 5 to 60. Optionally, m includes any positive integer from 5 to 45. When m is in the above-mentioned range, the dispersion effect of the negative electrode dispersant can be good on the basis of reducing the hydrogen bonding.

[0229] 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.

[0230] Exemplarily, the ether group includes at least one of the structural formulae shown in formula 1-1 to formula 1-14,

[0231] In some embodiments, m1 is the number of repeating structures, m1 includes any positive integer from 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.

[0232] In the embodiments of the present application, m-m1 represents the value of m minus m1, m-m1 includes any positive integer from 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.

[0233] [Substituted or unsubstituted alkyl group]

[0234] In some embodiments, R1 to R5 each independently include a substituted or unsubstituted alkyl group, which can be a substituted or unsubstituted C3 to C150 alkyl group. The alkyl group can include an unsaturated alkyl group or a saturated alkyl group, and the unsaturated alkyl group can be an alkyl group containing a ring structure, such as an alkyl group containing a three-membered ring, a five-membered ring, etc. The alkyl group containing a ring structure can further increase steric hindrance and reduce drying stress. The saturated alkyl group can include an alkyl group having a branched chain or a straight chain, and the saturated alkyl group, especially the straight chain alkyl group, can increase the flexibility of the modified carboxymethyl cellulose salt due to the longer chain.

[0235] In some embodiments, the substituted or unsubstituted C3 to C150 alkyl group includes a structural formula shown in formula 2,

[0236] In formula 2,

[0237] R 21 to R 27 each independently include at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group.

[0238] Optionally, R 21 to R 27 each independently include at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 saturated alkyl group.

[0239] Optionally, when the above-mentioned group is substituted, the substituent group can include a halogen atom, wherein the halogen atom can include at least one of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0240] s is the number of repeating structures, s includes any positive integer from 5 to 60. Alternatively, s includes any positive integer from 5 to 45. When s is in the above range, the negative electrode dispersant can have good dispersing effect on the basis of reducing hydrogen bonding.

[0241] 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.

[0242] Exemplarily, the substituted or unsubstituted C3 to C150 alkyl group includes at least one of the structural formulae shown in formula 2-1 to formula 2-11,

[0243] In some embodiments, s1 is the 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.

[0244] In the embodiments of the present application, s-s1 represents the 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.

[0245] [Substituted or unsubstituted polyalkylene group]

[0246] In some embodiments, R1 to R5 each independently include a substituted or unsubstituted polyalkylene group, which can be a substituted or unsubstituted C3 to C150 polyalkylene group. The polyalkylene group can increase the flexibility of the modified carboxymethyl cellulose salt due to the long chain.

[0247] In some embodiments, the substituted or unsubstituted C3 to C150 polyalkylene group includes the structural formula shown in formula 3,

[0248] In formula 3,

[0249] R 31 to R 34 each independently include 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;

[0250] R 35 comprises at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group.

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

[0252] p is the number of repeating structures, and p comprises any positive integer from 5 to 60. Optionally, p comprises any positive integer from 5 to 45. When p is in the above-mentioned range, the dispersion performance of the negative electrode dispersant can be improved while reducing the hydrogen bonding.

[0253] 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.

[0254] Exemplarily, the substituted or unsubstituted C3 to C150 polyalkylene group comprises at least one of the structural formulae shown in formula 3-1 to formula 3-8,

[0255] In each of the above-mentioned embodiments, the halogen atom can comprise at least one of a fluorine atom, a chlorine atom, and a bromine atom. The above-mentioned atom can also improve the voltage resistance of the negative electrode dispersant and improve the stability of the negative electrode film layer.

[0256] [Substituted or unsubstituted amide group]

[0257] In some embodiments, R1 to R5 each independently comprises a substituted or unsubstituted amide group, which can be a substituted or unsubstituted C3 to C150 amide group.

[0258] The amide group can comprise a monomolecular amide group or a polyamide group, and the amide group comprises a strong electronegative element nitrogen element. After the amide 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 bonding structure of the carboxymethyl cellulose salt and forming a new N-H-O hydrogen bonding structure. The N-H-O hydrogen bonding structure is weaker than the O-H-O hydrogen bonding, so that the intermolecular force of the grafted and modified carboxymethyl cellulose salt 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.

[0259] In some embodiments, the substituted or unsubstituted C3 to C150 amide group comprises the structural formula shown in formula 4,

[0260] In Formula 4,

[0261] R 41 including at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0262] 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;

[0263] a is the number of repeating structures, and a includes any positive integer of 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.

[0264] Optionally, when the above 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.

[0265] Either end of the amide group in Formula 4 can be connected to an oxygen atom in a hydroxyl group of a carboxymethyl cellulose salt, for example, the left end group is connected to the oxygen atom, or the right end group is connected to the oxygen atom. The end group of the amide group in Formula 4, which is not connected to the oxygen atom, can include a hydrogen atom or a C1 to C3 alkyl group.

[0266] In some embodiments, R 41 including a single bond, a substituted or unsubstituted C3 to C150 amide group includes a structural formula represented by Formula 4-1,

[0267] 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,

[0268] In some embodiments, R 41 including a substituted or unsubstituted C1 to C5 methylene group, a substituted or unsubstituted C3 to C150 amide group includes a structural formula represented by Formula 4-2,

[0269] a1 is the number of repeating structures, and a1 includes any positive integer of 1 to 5. For example, a1 can be 1, 2, 3, 4, or 5.

[0270] In some embodiments, the structural formula shown in Formula 4-2 includes at least one of a structural formula shown in Formula 4-21 to a structural formula shown in Formula 4-24,

[0271] [Substituted or unsubstituted ester group]

[0272] In some embodiments, R1to R5each independently include a substituted or unsubstituted ester group, which can be a substituted or unsubstituted C3to C150ester group.

[0273] The ester group can include a monomolecular ester group or a polymeric ester group. After the ester group is grafted to the side chain of the carboxymethyl cellulose salt, the ester group can replace the original hydroxyl position and further destroy the regular O-H-O hydrogen bond structure of the carboxymethyl cellulose salt, weaken the hydrogen bond effect of the carboxymethyl cellulose salt itself, so that the intermolecular force of the carboxymethyl cellulose salt after grafting modification is weakened, the flexibility is increased, and the interface performance of the negative electrode film layer is improved; and the migration rate of active ions such as lithium ions can be improved. And the ester group itself has good flexibility, which can further improve the flexibility of the carboxymethyl cellulose salt after replacing the hydroxyl position, thereby improving the interface performance of the negative electrode film layer.

[0274] In some embodiments, the substituted or unsubstituted C3to C150ester group includes a structural formula shown in Formula 5,

[0275] In Formula 5,

[0276] R 51 including at least one of a single bond, a substituted or unsubstituted C1to C5alkylene group;

[0277] R 52 including a substituted or unsubstituted C1to C5alkyl group;

[0278] R 53 to R 55 each independently include at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1to C10alkyl group, a substituted or unsubstituted C2to C10alkenyl group, and a substituted or unsubstituted C2to C10alkynyl group;

[0279] 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.

[0280] Either of the two ends of the ester group in Formula 5 can be connected to the oxygen atom in the hydroxyl group in the carboxymethyl cellulose salt, for example, the left end group is connected to the oxygen atom, or the right end group is connected to the oxygen atom. The end group of the ester group in Formula 5 that is not connected to the oxygen atom can include a hydrogen atom or a C1 to C3 alkyl group.

[0281] In some embodiments, R 51 comprising a single bond, the substituted or unsubstituted C3 to C150 ester group comprises a structural formula represented by Formula 5-1,

[0282] For example, the structural formula represented by Formula 5-1 comprises at least one of a structural formula represented by Formula 5-11 to a structural formula represented by Formula 5-16,

[0283] In some embodiments, R 51 comprising a substituted or unsubstituted C1 to C5 methylene group, the substituted or unsubstituted C3 to C150 ester group comprises a structural formula represented by Formula 5-2,

[0284] b1 is the number of repeating structures, b1 comprises any positive integer from 1 to 5, for example, b1 can be 1, 2, 3, 4, or 5.

[0285] For example, the structural formula represented by Formula 5-2 comprises at least one of a structural formula represented by Formula 5-21 to a structural formula represented by Formula 5-28,

[0286] 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 atoms can improve the voltage resistance of the polymer.

[0287] For example, the substituted or unsubstituted C3 to C150 ester group comprises at least one of a structural formula represented by Formula 5-21 to a structural formula represented by Formula 5-28,

[0288] In each of the above embodiments, the weight average molecular weight of the flexible group is 15 Da to 5000 Da. The molecular weight of the grafting group in the negative electrode dispersant is relatively small, which reduces the hydrogen bonding effect between the molecular chains of the negative electrode dispersant, while the flexibility is good, and the negative electrode dispersant has good dispersibility.

[0289] Exemplarily, the weight average molecular weight of the flexible group can be 15 Da, 20 Da, 25 Da, 30 Da, 35 Da, 40 Da, 45 Da, 50 Da, 55 Da, 60 Da, 65 Da, 70 Da, 75 Da, 80 Da, 85 Da, 90 Da, 95 Da, 100 Da, 120 Da, 150 Da, 200 Da, 250 Da, 300 Da, 350 Da, 400 Da, 450 Da, 500 Da, 550 Da, 600 Da, 650 Da, 700 Da, 750 Da, 800 Da, 850 Da, 900 Da, 950 Da, 1000 Da, 1050 Da, 1100 Da, 1150 Da, 1200 Da, 1250 Da, 1300 Da, 1350 Da, 1400 Da, 1450 Da, 1500 Da, 1550 Da, 1600 Da, 1650 Da, 1700 Da, 1750 Da, 1800 Da, 1850 Da, 1900 Da, 1950 Da, 2000 Da, 2050 Da, 2100 Da, 2150 Da, 2200 Da, 2250 Da, 2300 Da, 2350 Da, 2400 Da, 2450 Da, 2500 Da, 3000 Da, 3100 Da, 3200 Da, 3300 Da, 3400 Da, 3500 Da, 3600 Da, 3700 Da, 3800 Da, 3900 Da, 4000 Da, 4100 Da, 4200 Da, 4300 Da, 4400 Da, 4500 Da, 4600 Da, 4700 Da, 4800 Da, 4900 Da, 5000 Da, or a range between any two of the above values.

[0290] In some embodiments, the weight average molecular weight of the modified carboxymethyl cellulose salt is 40 wDa to 80 wDa. When the weight average molecular weight of the modified carboxymethyl cellulose salt is in the above range, the negative electrode dispersant can have excellent dispersing performance.

[0291] Exemplarily, the weight average molecular weight of the modified carboxymethyl cellulose salt can be 40 wDa, 42 wDa, 45 wDa, 46 wDa, 48 wDa, 50 wDa, 52 wDa, 55 wDa, 58 wDa, 60 wDa, 62 wDa, 65 wDa, 68 wDa, 70 wDa, 72 wDa, 75 wDa, 78 wDa, 80 wDa, or a range between any two of the above values.

[0292] In the present application, the weight average molecular weight of the polymer can be tested by a method known in the art, for example, by using gel chromatography, such as Waters 2695 Isocratic HPLC type gel chromatograph with a differential refractive index detector 2141.

[0293] The conventional sodium carboxymethyl cellulose is a solid polymer at room temperature. The sodium carboxymethyl cellulose is dissolved in solvent water, the mass content of the sodium carboxymethyl cellulose is 1%, and after stirring at 1200 rpm for 2 h, the reference adhesive film is obtained by drying in an oven, for example, at 40℃ for more than 24 h. The width of the reference adhesive film is 2.5 cm, the length is 5 cm, and the thickness is 1 mm. The breaking elongation of the reference adhesive film is tested, and the breaking elongation of the reference adhesive film is defined as 100%. It should be noted that the conventional sodium carboxymethyl cellulose refers to the side chain of the sodium carboxymethyl cellulose which is not substituted by other groups, and in particular, the hydrogen atom at the hydroxyl position is not substituted.

[0294] In some embodiments, the modified carboxymethyl cellulose salt is prepared into an adhesive film. The modified carboxymethyl cellulose salt is dissolved in solvent water, the mass content of the modified carboxymethyl cellulose salt is 1%, and after stirring at 1200 rpm for 2 h, the adhesive film is obtained by drying in an oven, for example, at 40℃ for more than 24 h. The width of the adhesive film is 2.5 cm, the length is 5 cm, and the thickness is 1 mm. The breaking elongation of the adhesive film is tested and calculated based on the breaking elongation of the reference adhesive film of 100%, and the breaking elongation of the adhesive film is 200% to 300%, which can be optionally 219% to 300%. When the adhesive film is prepared, the thickness deviation of the adhesive film can be controlled within 0.5%.

[0295] Therefore, the breaking elongation of the negative electrode dispersant is higher than that of the conventional sodium carboxymethyl cellulose, and the negative electrode dispersant has better flexibility when applied to the negative electrode sheet and is less likely to break.

[0296] For example, the breaking elongation of the adhesive film can be 200%, 210%, 220%, 230%, 240%, 250%, 260%, 270%, 280%, 290%, 300%, or a range formed by any two of the above values.

[0297] In this application, the breaking elongation of the adhesive film has the meaning known in the art and can be tested by using the equipment and method known in the art. Specifically, the test can be performed according to the standard GB / T36363-2018.

[0298] The modified carboxymethyl cellulose salt can be prepared by the following method:

[0299] In some embodiments, the method comprises the step S100 of alkalization treatment and the step S200 of substitution treatment.

[0300] In step S100, the alkalization treatment specifically comprises: providing a carboxymethyl cellulose salt, and alkalizing the carboxymethyl cellulose salt by an alkali to activate the hydroxyl sites of the carboxymethyl cellulose salt and form active reaction sites.

[0301] The carboxymethyl cellulose salt includes a compound shown in formula C,

[0302] In formula C, M includes a metal ion or NH4 +

[0303] After the base treatment of the carboxymethyl cellulose salt, the hydrogen atoms at the hydroxyl positions are activated, for example, the base treatment is performed by using sodium hydroxide NaOH or potassium hydroxide KOH, and the hydrogen atoms at at least one of the hydroxyl positions in the carboxymethyl cellulose salt are replaced by sodium Na atoms, for example, all the hydrogen atoms at the hydroxyl positions in the carboxymethyl cellulose salt are replaced by Na, and the intermediate product after the replacement is a compound shown in formula D,

[0304] In some embodiments, the activated hydroxyl positions account for 0.05% to 20% of the total number of hydroxyl positions, and optionally 1% to 5%. The grafting rate of the flexible group and the conductive group is 0.05% to 20%, and optionally 1% to 5%.

[0305] Specifically, the activated hydroxyl positions account for the total number of hydroxyl positions, representing the proportion of the replaced hydroxyl positions, and the grafting rate of the flexible group and the conductive group can be detected by using methods and devices known in the art, for example, the grafting rate of each group can be calculated according to the feeding ratio of the carboxymethyl cellulose salt and the base, and then according to the feeding ratio of the flexible compound and the conductive compound.

[0306] In some embodiments, the grafting rate of the conductive group in the modified carboxymethyl cellulose salt is 0.05% to 20%, and optionally 0.5% to 5%. When the grafting rate of the conductive group is in the above range, the conductive performance of the modified carboxymethyl cellulose salt is further improved.

[0307] In some embodiments, the grafting rate of the flexible group in the modified carboxymethyl cellulose salt is 0.05% to 20%, and optionally 0.5% to 5%. When the grafting rate of the flexible group is in the above range, the flexibility of the modified carboxymethyl cellulose salt is further improved, thereby improving the flexibility of the negative electrode film layer and reducing the risk of cracking.

[0308] In step S200, the substitution treatment specifically includes: adding a substitution compound into the system to perform a substitution reaction. The substitution compound will replace the sodium Na atoms at the hydroxyl positions, and the product after the substitution is the modified carboxymethyl cellulose salt, which is shown in formula A.

[0309] The substitution compound includes a conductive compound and a flexible compound.

[0310] ​In some embodiments, in step S200, the conductive compound can be added first to substitute at a portion of the hydroxyl groups, replacing the hydrogen atoms on the hydroxyl groups with conductive groups; and then the flexible compound can be added to substitute at the hydroxyl groups that are not substituted by the conductive groups, replacing the hydrogen atoms on the hydroxyl groups with flexible groups.

[0311] In some other embodiments, in step S200, the flexible compound can be added first to substitute at a portion of the hydroxyl groups, replacing the hydrogen atoms on the hydroxyl groups with flexible groups; and then the conductive compound can be added to substitute at the hydroxyl groups that are not substituted by the flexible groups, replacing the hydrogen atoms on the hydroxyl groups with conductive groups.

[0312] In some embodiments, the conductive compound includes C2 to C150 conductive compounds.

[0313] In some embodiments, the conductive compound includes one or more of aromatic polymers and polyacetylenes.

[0314] In some embodiments, the aromatic polymers include one or more of five-membered heterocyclic polymers, arene derivative polymers, and polyindoles.

[0315] Illustratively, the five-membered heterocyclic polymers include one or more of polypyrrroles, polythiophenes, and polyfurans. For example, the polythiophenes include one or more of polythiophene and polyethylene dioxythiophene.

[0316] Illustratively, the arene derivative polymers include one or more of polyacenes, polyphenylenes, polyphenylene vinylene, polyaniline, and aniline tetramer.

[0317] In some embodiments, the polyacetylenes include one or more of polyacetylene and polydiacetylene.

[0318] In some embodiments, the substituting compound includes substituted or unsubstituted ethers, which can optionally be substituted or unsubstituted C3 to C150 ethers.

[0319] Illustratively, the substituted or unsubstituted C3 to C150 ethers include compounds as shown in Formula 11,

[0320] In Formula 11,

[0321] R 11 to R 17 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group, and a substituted or unsubstituted C2 to C10 alkynyl group.

[0322] m includes any positive integer from 5 to 60.

[0323] In some embodiments, the substituted compound includes a substituted or unsubstituted alkane, optionally a substituted or unsubstituted C3 to C150 alkane.

[0324] Exemplarily, the substituted or unsubstituted C3 to C150 alkane includes a compound as shown in formula 21,

[0325] In formula 21,

[0326] R 21 to R 27 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0327] s includes any positive integer from 5 to 60.

[0328] In some embodiments, the substituted compound includes a substituted or unsubstituted polyalkene, optionally a substituted or unsubstituted C3 to C150 polyalkene.

[0329] Exemplarily, the substituted or unsubstituted C3 to C150 polyalkene includes a compound as shown in formula 31,

[0330] In formula 31,

[0331] R 31 to R 34 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C2 to C10 alkenyl group;

[0332] R 35 includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl group;

[0333] p includes any positive integer from 5 to 60.

[0334] In some embodiments, the substituted compound includes a substituted or unsubstituted amide compound, optionally a substituted or unsubstituted C3 to C150 amide compound, which can be a C3 to C150 amide polymer.

[0335] Exemplarily, the substituted or unsubstituted C3 to C150 amide compound includes a compound as shown in formula 41,

[0336] In formula 41,

[0337] R 41 includes at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene group;

[0338] R42 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, and a substituted or unsubstituted C2 to C10 alkynyl;

[0339] R 47 and R 48 each independently includes a hydrogen atom or a C1 to C3 alkyl.

[0340] a includes any positive integer from 1 to 30.

[0341] In some embodiments, the substituted compound includes a substituted or unsubstituted ester compound, which can be a substituted or unsubstituted C3 to C150 ester compound, and specifically can be a C3 to C150 ester polymer.

[0342] Exemplarily, the substituted or unsubstituted C3 to C150 ester compound includes a compound shown in formula 51,

[0343] In formula 5,

[0344] R 51 includes at least one of a single bond, a substituted or unsubstituted C1 to C5 methylene;

[0345] R 52 includes a substituted or unsubstituted C1 to C5 alkyl;

[0346] R 53 to R 55 each independently includes at least one of a hydrogen atom, a halogen atom, a substituted or unsubstituted C1 to C10 alkyl, a substituted or unsubstituted C2 to C10 alkenyl, and a substituted or unsubstituted C2 to C10 alkynyl;

[0347] R 56 and R 57 each independently includes a hydrogen atom or a C1 to C3 alkyl.

[0348] b includes any positive integer from 1 to 30.

[0349] In the preparation of the negative electrode dispersant, the reaction can be carried out under the reaction conditions commonly used in the art, and the molar ratio of each raw material can also be selected according to the molar ratio commonly used in the art.

[0350] The negative electrode dispersant

[0351] In a second aspect, the embodiments of the present application provide a negative electrode dispersant, which includes the modified carboxymethyl cellulose salt of any of the embodiments of the first aspect of the present application.

[0352] In some embodiments, the negative electrode dispersant can further include a carboxymethyl cellulose salt.

[0353] In some embodiments, the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt can be 0.5 to 2. When the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt is in the above range, the modified carboxymethyl cellulose salt can work together with the carboxymethyl cellulose salt to improve the flexibility of the gel film formed by the carboxymethyl cellulose salt and reduce the risk of cracking of the negative electrode film layer.

[0354] For example, the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range defined by any two of the above values.

[0355] Negative electrode tab

[0356] In a third aspect, the embodiments of the present application provide a negative electrode tab. The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes the negative electrode dispersant according to any one of the embodiments of the second aspect of the present application. The negative electrode dispersant can be used as a dispersant in the negative electrode film layer, which can uniformly disperse the negative electrode active material in the negative electrode film layer, make the performance of the negative electrode film layer uniform, and improve the flexibility of the negative electrode film layer and reduce the risk of cracking of the negative electrode film layer. In addition, the negative electrode dispersant has excellent electrical conductivity, which can improve the electrical conductivity of the negative electrode film layer. For example, the negative electrode current collector has two opposite surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0357] In some embodiments, the mass content of the modified carboxymethyl cellulose salt is 0.8% to 1.3%, optionally 1.0% to 1.3%, and further optionally 1.0% to 1.2%, based on the total mass of the negative electrode film layer. When the mass content of the modified carboxymethyl cellulose salt is in the above range, the risk of cracking of the negative electrode film layer can be effectively reduced, and the performance uniformity and flexibility of the negative electrode film layer can be effectively improved. In addition, the proportion of the modified carboxymethyl cellulose salt is relatively low, which basically does not affect the proportion of the negative electrode active material, so that the battery cell has a higher energy density. Moreover, since the modified carboxymethyl cellulose salt can significantly improve the flexibility of the negative electrode film layer, etc., the negative electrode slurry can not add plasticizers and other auxiliary agents, thereby reducing the adverse effects caused by the introduction of plasticizers.

[0358] Exemplarily, the mass content of the modified carboxymethyl cellulose salt can be 0.80%, 0.85%, 0.90%, 0.95%, 1.00%, 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.10%, 1.11%, 1.12%, 1.13%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, 1.2%, 1.3%, or a range between any two of the above values.

[0359] In some embodiments, the negative electrode dispersant in the negative electrode film layer can further include a carboxymethyl cellulose salt, such as at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, lithium carboxymethyl cellulose, and the like. The carboxymethyl cellulose salt is different from the modified carboxymethyl cellulose salt in that the hydroxyl groups in the carboxymethyl cellulose salt are not substituted. The carboxymethyl cellulose salt and the modified carboxymethyl cellulose salt can jointly play a dispersing role, and on this basis, the modified carboxymethyl cellulose salt can additionally improve the flexibility of the negative electrode film layer.

[0360] In some embodiments, the mass content of the carboxymethyl cellulose salt can be 0.05% to 1.0%, or optionally 0.05% to 0.3%, based on the total mass of the negative electrode film layer. When the mass content of the carboxymethyl cellulose salt is within the above range, the carboxymethyl cellulose salt and the modified carboxymethyl cellulose salt can jointly improve the performance uniformity and flexibility of the negative electrode film layer.

[0361] Exemplarily, the mass content of the carboxymethyl cellulose salt can be 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.3%, 0.35%, 0.4%, 0.42%, 0.45%, 0.46%, 0.48%, 0.50%, 0.52%, 0.55%, 0.56%, 0.58%, 0.60%, 0.62%, 0.65%, 0.66%, 0.68%, 0.70%, 0.72%, 0.75%, 0.78%, 0.80%, 0.82%, 0.85%, 0.86%, 0.88%, 0.9%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1.00%, or a range between any two of the above values.

[0362] In some embodiments, the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt can be 0.5 to 2. When the ratio of the mass content of the carboxymethyl cellulose salt to the mass content of the modified carboxymethyl cellulose salt is within the above range, the carboxymethyl cellulose salt and the modified carboxymethyl cellulose salt can jointly improve the performance uniformity and flexibility of the negative electrode film layer.

[0363] For example, the ratio of the mass content of the carboxymethyl cellulose salt and the mass content of the modified carboxymethyl cellulose salt can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a range defined by any two of the aforementioned values.

[0364] In some embodiments, the coating basis weight of the negative electrode film layer can be 190 mg / 1540.25 mm 2 to 235 mg / 1540.25 mm 2 ; optionally 220 mg / 1540.25 mm 2 to 235 mg / 1540.25 mm 2 . The coating basis weight of the negative electrode film layer is relatively high, which is conducive to achieving thick coating.

[0365] For example, the coating basis weight of the negative electrode film layer can be 190 mg / 1540.25 mm 2 , 200 mg / 1540.25 mm 2 , 210 mg / 1540.25 mm 2 , 220 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 235 mg / 1540.25 mm 2 or a range defined by any two of the aforementioned values.

[0366] The negative electrode active material can be any known in the art for use in battery cells. For example, the negative electrode active material can include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material can include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material can include at least one of elemental tin, tin oxide, and tin alloy material.

[0367] In some embodiments, the negative electrode active material can include, but is not limited to, at least one of natural graphite and artificial graphite, and the negative electrode dispersant is capable of effectively dispersing the aforementioned negative electrode active material, thereby improving the dispersion uniformity of the negative electrode active material in the negative electrode film layer.

[0368] In some embodiments, the negative electrode film layer can optionally further include a negative electrode conductive agent. The present embodiments do not have particular limitations on the type of the negative electrode conductive agent, which may, for example, include at least one of super conductive carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is ≤ 5% based on the total weight of the negative electrode film layer. Since the modified carboxymethyl cellulose salt has conductivity, it can be used as an auxiliary conductive agent to reduce the amount of the negative electrode conductive agent, which is conducive to increasing the amount of the negative electrode active material and improving the energy density of the battery cell.

[0369] In some embodiments, the negative electrode film layer can optionally further include a negative electrode binder. The present embodiments do not have particular limitations on the type of the negative electrode binder, which may, for example, include at least one of styrene butadiene rubber SBR, water-soluble unsaturated resin SR-1B, water-based acrylic resin, for example, polyacrylic acid PAA, polymethyl acrylic 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.

[0370] In some embodiments, the negative electrode film layer can optionally further include other auxiliary agents. For example, the other auxiliary agents may, for example, include thickening agents, for example, PTC thermistor materials, and the like. In some embodiments, the mass percentage of the other auxiliary agents is ≤ 2% based on the total weight of the negative electrode film layer.

[0371] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be a copper foil. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. For example, the metal material can include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. For example, the polymer material base layer can include at least one of polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, and polyethylene PE.

[0372] The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, a negative electrode dispersant, an optional conductive agent, an optional binder, and other optional auxiliary agents in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone NMP or deionized water, but is not limited thereto.

[0373] The negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the embodiments of the present application further includes a conductive primer layer composed of a conductive agent and a binder, which is interposed between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode sheet of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0374] Battery cell

[0375] In a fourth aspect, the embodiments of the present application provide a battery cell including a negative electrode sheet. The negative electrode sheet includes any of the negative electrode sheets of the embodiments of the third aspect of the present application. The use of the negative electrode sheet can improve the kinetic performance of the battery cell.

[0376] [Positive electrode sheet]

[0377] In some embodiments, the battery cell further includes a positive electrode sheet.

[0378] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material.

[0379] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0380] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material such as aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, or the like on a base material such as a polypropylene (PP) base material, a polyethylene terephthalate (PET) base material, a polybutylene terephthalate (PBT) base material, a polystyrene (PS) base material, a polyethylene (PE) base material, or the like.

[0381] In some embodiments, the positive electrode active material can include, but is not limited to, at least one of a lithium-containing transition metal oxide, a lithium-containing phosphate, and a modified compound of each thereof. Examples of the lithium-containing transition metal oxide can include, but are not limited to, at least one of a lithium cobalt oxide, a lithium nickel oxide, a lithium manganese oxide, a lithium nickel cobalt oxide, a lithium manganese cobalt oxide, a lithium nickel manganese oxide, a lithium nickel cobalt manganese oxide, a lithium nickel cobalt aluminum oxide, and a modified compound of each thereof. Examples of the lithium-containing phosphate can include, but are not limited to, at least one of a lithium iron phosphate, a composite of a lithium iron phosphate and carbon, a lithium manganese phosphate, a composite of a lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a composite of a lithium manganese iron phosphate and carbon, and a modified compound of each thereof.

[0382] The positive electrode film layer includes a positive electrode active material, which can employ a positive electrode active material known in the art for use in battery cells. As an example, the positive electrode active material can include at least one of the following materials: layered structure positive electrode active materials such as ternary, lithium / sodium nickelate, lithium / sodium cobaltate, lithium / sodium manganate, lithium / sodium-rich layered, and rock-salt phase layered materials, olivine-type phosphate active materials, spinel structure positive electrode active materials such as spinel lithium manganate, spinel lithium nickel manganate, lithium-rich spinel lithium manganate, and lithium nickel manganate, etc.

[0383] As an example, the layered structure positive electrode active material has a general formula of: Li x A y Ni a Co b Mn c M 1-a-b-c Y z wherein 0≤x≤2.1, 0≤y≤2.1, and 0.9≤x+y≤2.1; 0≤a≤1, 0≤b≤1, 0≤c≤1, and 0.1≤a+b+c≤1; 1.8≤z≤3.5; A is selected from one or more of Na, K, Mg; M is selected from one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y is selected from one or more of O, F. Optionally, y=0. Specifically, the layered structure positive electrode active material can include one or more of lithium cobaltate LCO, lithium nickelate LNO, lithium manganate LMO, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), and LiNi 0.5 Co0 .2 Mn 0.3 O2(NCM523).

[0384] As an example, the olivine-type phosphate active material has a general formula of: Li x A y Me a M b P 1-c X c Y zwherein 0≤x≤1.3, 0≤y≤1.3, and 0.9≤x+y≤1.3; 0.9≤a≤1.5, 0≤b≤0.5, and 0.9≤a+b≤1.5; 0≤c≤0.5; 3≤z≤5; A is selected from one or more of Na, K, Mg; Me is selected from one or more of Mn, Fe, Co, Ni; M is selected from one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X is selected from one or more of S, Si, Cl, B, C, N; Y is selected from one or more of O, F. Specifically, the olivine-type phosphate active material includes one or more of LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0385] Exemplarily, the general formula of the spinel-structured positive electrode active material is: Li x A y Mn a M 2-a Y z wherein 0≤x≤2, 0≤y≤1, and 0.9≤x+y≤2; 0.5≤a≤2; 3≤z≤5; A is selected from one or more of Na, K, Mg; M is selected from one or more of Ni, Co, B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; Y is selected from one or more of O, F. Specifically, the spinel-structured positive electrode active material includes one or more of LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiCr 0.3 Mn 1.7 O4, Li 1.1 Al 0.1 Mn 1.9 O4, Li2Mn2O4, and Li 1.5 Mn2O4.

[0386] In the present application, the modified compound of each of the above positive electrode active materials can be a doping modification and / or a surface coating modification to the positive electrode active material.

[0387] In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene-fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene-fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass percentage of the binder is ≤ 5% based on the total weight of the positive electrode film layer.

[0388] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the conductive agent is ≤ 5% based on the total weight of the positive electrode film layer.

[0389] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the optional conductive agent, the optional binder, and any other components, in a solvent, such as N-methylpyrrolidone, to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing, etc., obtaining the positive electrode tab.

[0390] [Electrolyte]

[0391] In some embodiments, the battery cell further includes an electrolyte.

[0392] During the charging and discharging of the battery cell, active ions are embedded and extracted back and forth between the positive electrode tab and the negative electrode tab, and the electrolyte plays a role in conducting the active ions between the positive electrode tab and the negative electrode tab. The type of electrolyte is not particularly limited in the present application and can be selected according to actual needs.

[0393] The electrolyte includes an electrolyte salt and a solvent. The types of the electrolyte salt and the solvent are not particularly limited and can be selected according to actual needs.

[0394] As an example, the electrolyte salt can include, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro-oxalato-borate (LiDFOB), lithium bis-oxalato-borate (LiBOB), lithium difluoro-phosphate (LiPO2F2), lithium difluoro-di-oxalato-phosphate (LiDFOP), and lithium tetrafluoro-oxalato-phosphate (LiTFOP).

[0395] As an example, the solvent can include, but is not limited to, at least one of ethylene carbonate EC, propylene carbonate PC, ethyl methyl carbonate EMC, diethyl carbonate DEC, dimethyl carbonate DMC, dipropyl carbonate DPC, methyl propyl carbonate MPC, ethyl propyl carbonate EPC, butylene carbonate BC, fluoroethylene carbonate FEC, methyl formate MF, methyl acetate MA, ethyl acetate EA, propyl acetate PA, methyl propionate MP, ethyl propionate EP, propyl propionate PP, methyl butyrate MB, ethyl butyrate EB, 1,4-butyrolactone GBL, sulfolane SF, dimethyl sulfone MSM, methyl ethyl sulfone EMS, and diethyl sulfone ESE.

[0396] In some embodiments, the electrolyte solution can further include an additive. For example, the additive can include a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature performance of the battery, an additive capable of improving low-temperature power performance of the battery, etc.

[0397] [Separator]

[0398] In some embodiments, the battery cell can further include a separator.

[0399] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0400] In some embodiments, the material of the separator can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0401] In some embodiments, the positive electrode tab, the separator, and the negative electrode tab can be made into an electrode assembly through a winding process and / or a stacking process.

[0402] In some embodiments, the battery cell can include an outer package. The outer package can be used to package the electrode assembly and the electrolyte solution described above.

[0403] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as at least one of polypropylene PP, polybutylene terephthalate PBT, and polybutylene succinate PBS.

[0404] The shape of the battery cell is not particularly limited in the present application, and can be cylindrical, square, or any other shape. FIG. 1 is a battery cell 5 having a square structure as an example.

[0405] In some embodiments, as shown in FIG. 2, the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and side plates connected to the bottom plate, which enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process and / or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to requirements.

[0406] The preparation method of the battery cell of the present application is known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly is placed in an outer package, the electrolyte is injected after drying, and the battery cell is obtained after processes such as vacuum packaging, standing, formation, and shaping.

[0407] In some embodiments of the present application, the battery cell according to the present application can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0408] FIG. 3 is a schematic view of a battery module 4 as an example. As shown in FIG. 3, in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0409] Optionally, the battery module 4 can further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0410] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0411] FIGS. 4 and 5 are schematic views of a battery pack 1 as an example. As shown in FIGS. 4 and 5, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0412] The battery of the embodiments of the present application can include one battery cell or a plurality of battery cells, and in the case of including a plurality of battery cells, the battery can include a battery module or a battery pack.

[0413] power device

[0414] In a fifth aspect, the embodiments of the present application provide a power device, which comprises at least one of the battery cell, the battery module or the battery pack of the present application. The battery cell, the battery module or the battery pack can be used as a power source of the power device, or can be used as an energy storage unit of the power device. The power device can be, but is not limited to, a mobile device such as a mobile phone, a notebook computer, etc., an electric vehicle such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., an electric train, a ship and a satellite, an energy storage system, etc.

[0415] The power device can select the battery cell, the battery module or the battery pack according to its use requirement.

[0416] FIG. 6 is a schematic diagram of a power device 6 as an example. The power device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the power device 6, the battery pack 1 or the battery module can be used.

[0417] The power device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power device usually requires thin and light, and the battery cell can be used as a power source.

[0418] Embodiments

[0419] The embodiments described below are merely illustrative of the present application and various modifications and changes can be made within the scope of the present 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 according to conventional methods and can be used directly without further treatment, and the instruments used in the embodiments are commercially available.

[0420] Preparation of lithium ion battery

[0421] 1. Preparation of positive electrode sheet

[0422] An aluminum foil is used as the positive current collector.

[0423] The positive active material lithium cobalt oxide LiCoO2, the conductive agent acetylene black, and the binder polyvinylidene fluoride PVDF are mixed in a mass ratio of 95:2:3 in an appropriate amount of solvent N-methyl pyrrolidone NMP to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive current collector aluminum foil, and through processes such as drying, cold pressing, slitting and cutting, a positive electrode sheet is obtained.

[0424] 2. Preparation of the negative electrode sheet

[0425] Copper foil is used as the negative current collector.

[0426] The artificial graphite as the negative active material, the conductive agent conductive carbon, the binder phenylpropyl emulsion, and the negative dispersant are mixed uniformly in deionized water to prepare a negative electrode slurry. The mass ratio of the artificial graphite, the conductive agent conductive carbon, the binder phenylpropyl emulsion, and the negative dispersant in the solid components of the negative electrode slurry is 96.7:0.7:1.5:1.1, and the negative dispersant includes modified CMC-Na. The negative electrode slurry is coated on the current collector copper foil and dried at 85°C, and then cold-pressed to obtain a negative electrode sheet containing a negative active material layer.

[0427] 3. Preparation of the electrolyte

[0428] The organic solvents ethylene carbonate EC, methyl ethyl carbonate EMC, and diethyl carbonate DEC are mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent in an environment with a water content of less than 10 ppm, and then the lithium salt lithium hexafluorophosphate is mixed with the mixed solvent, and the lithium salt is 1 mol / L.

[0429] 4. Preparation of the lithium ion battery

[0430] The positive electrode sheet, the polyethylene PE separator, and the negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with an electrolyte, and then subjected to vacuum packaging, standing, formation, shaping, and other processes to obtain a lithium ion battery.

[0431] Examples 2-1 to 2-4

[0432] Unlike Example 1, the type of flexible group in the negative dispersant in the negative electrode slurry is different.

[0433] Examples 3-1 to 3-3

[0434] Unlike Example 1, the type of conductive group in the negative dispersant in the negative electrode slurry is different.

[0435] Examples 4-1 and 4-2

[0436] Unlike Example 1, the number of repeating structures of the flexible group in Example 4-1 is different.

[0437] Unlike Example 1, the number of repeating structures of the conductive group in Example 4-2 is different.

[0438] Comparative Example 1

[0439] Different from example 1, the negative electrode dispersant is added in the negative electrode slurry, the negative electrode dispersant is replaced by sodium carboxymethyl cellulose CMC-Na, and the mass ratio of artificial graphite, conductive agent conductive carbon, adhesive styrene-acrylic emulsion, negative electrode dispersant CMC-Na in the solid components of the negative electrode slurry is 96.7:0.7:1.5:1.1.

[0440] Comparative example 2

[0441] Different from example 1, the negative electrode dispersant is added in the negative electrode slurry, the negative electrode dispersant is replaced by sodium carboxymethyl cellulose CMC-Na, and the plasticizer is added in the negative electrode slurry, and the mass ratio of artificial graphite, conductive agent conductive carbon, adhesive styrene-acrylic emulsion, negative electrode dispersant CMC-Na, plasticizer butanediol in the solid components of the negative electrode slurry is 96.55:0.7:1.5:1.1:0.15.

[0442] The relevant parameters of the examples and comparative examples are shown in Table 1.

[0443] Test part

[0444] 1. Negative electrode slurry filtration test:

[0445] Filter screen 150 mesh, cut the filter screen into 25cm*25cm with scissors. Fold the 150 mesh filter screen into a fan shape and fix it in the air above the clean beaker. Pour 500mL of negative electrode slurry from above the filter screen at one time, and record the time from the beginning of the negative electrode slurry flowing out from the tip of the filter screen. Record the filtration time of 300mL.

[0446] 2. Negative electrode slurry gel and sedimentation state:

[0447] Take 500ml of negative electrode slurry and place it for different times to observe whether the negative electrode slurry appears in a jelly gel state, and test its slurry viscosity. If the viscosity of the upper layer of the test beaker decreases and the lower layer of the slurry becomes thick, it indicates that the slurry has settled.

[0448] 3. Coating weight of negative electrode film layer:

[0449] The coating window measures the approximate critical range of the quality stability of the coating product. Exceeding this range will result in defects such as cracking. Using an extrusion coater and coating at a speed of 50m / min, observe whether the film layer cracks as the quality of the negative electrode sheet of the comparative examples and examples gradually increases. If there is no cracking, continue to increase the weight until the surface film layer of the electrode sheet cracks, and record the non-cracking coating weight of the negative electrode film layer, which is the coating weight of the negative electrode film layer in Table 1.

[0450] 4. DC impedance test of lithium ion battery

[0451] The battery direct current impedance test process is as follows: at 25℃, the lithium ion battery prepared by the examples and the comparative examples is charged at 1 / 3C constant current to 4.2V, and then charged at 4.2V constant voltage to the current of 0.05C, and after 5min, the voltage V1 is recorded. Then discharged at 1 / 3C for 30s, the voltage V2 is recorded, then V2-V1 / 1 / 3C, the internal resistance DCR of the lithium ion battery is obtained.

[0452] Test results

[0453] The test results are shown in Table 1

[0454] Table 1

[0455] The weight average molecular weight of the negative electrode dispersant in the examples and the comparative examples is 60wDa.

[0456] The number of repeating structures in the flexible group refers to the number of continuously repeating groups in the flexible group, such as the value of m in formula 1-1, the value of s in formula 2-10, the value of p in formula 3-1, the value of a in formula 4-11, and the value of b in formula 5-16. The number of repeating structures in the conductive group refers to the degree of polymerization of the conductive group.

[0457] Each of the above examples and the comparative examples is subjected to gel and sedimentation test, and the negative electrode slurry has no sedimentation and no gel, and the state of the negative electrode slurry is relatively stable.

[0458] As can be seen from Table 1, the comparative example 1 adds the dispersant sodium carboxymethyl cellulose CMC-Na in the negative electrode slurry, and the sodium carboxymethyl cellulose is not subjected to side chain modification, which is beneficial to improve the dispersion performance of the negative electrode active material in the negative electrode slurry. However, due to the hydrogen bond effect of the sodium carboxymethyl cellulose itself, the negative electrode slurry is prone to cracking and other problems during the process of drying the negative electrode slurry into a negative electrode film layer, which is not conducive to thick coating of the negative electrode slurry, and the coating bulk density is small.

[0459] Compared with the comparative example 1, the comparative example 2 further adds a plasticizer in the negative electrode slurry, and the plasticizer can effectively improve the plasticizing ability and flexibility of the negative electrode film layer, which is beneficial to thick coating of the negative electrode slurry, the coating bulk density is improved, and the cracking phenomenon of the negative electrode film layer is improved. However, it is found through test that the negative electrode film layer added with the plasticizer has uneven thickness, and the impedance of the negative electrode film layer is high.

[0460] The application embodiment does not add a plasticizer in the negative electrode slurry, and side chain graft modification is performed on a dispersant sodium carboxymethyl cellulose, so that the hydrogen bond action of the dispersant is reduced, the force between the molecular chains of the dispersant is weakened, the flexibility of the negative electrode dispersant is enhanced, the flexibility of the negative electrode film layer is improved, the risk of cracking of the negative electrode film layer is reduced, especially the risk of cracking of the thick-coated negative electrode film layer is reduced, and the energy density of the battery cell is improved; moreover, the modified carboxymethyl cellulose salt has good dispersion and leveling effects, can effectively disperse the negative electrode active material, so that the negative electrode active material is uniformly dispersed, the thickness distribution of the negative electrode film layer is uniform, and the performance is uniform; and the impedance of the negative electrode film layer is further reduced, and the impedance range is 450 mΩ to 510 mΩ, so that the kinetic performance of the lithium ion battery is improved.

[0461] In the side chain graft modification, at least one of an ether group, an alkyl group, an alkenyl group, an amide group or an ester group can be used for graft modification, which can effectively improve the flexibility of the modified carboxymethyl cellulose salt, and can improve the flexibility of the negative electrode film layer, so that the thickness distribution of the negative electrode film layer is uniform, and the performance is uniform.

[0462] The application embodiment is suitable for one or more of a variety of conductive groups, such as an aromatic polymer group and a polyacetylene group, which can effectively improve the flexibility of the negative electrode film layer, and can reduce the impedance of the negative electrode film layer.

[0463] The application embodiment can effectively increase the flexibility of the negative electrode film layer by adjusting the number of repeating units, and can also improve the conductivity of the negative electrode film layer to a certain extent.

[0464] The application embodiment adjusts the addition amount of the dispersant in the negative electrode slurry, which can effectively adjust the thick-coating degree of the negative electrode slurry, improve the flexibility of the negative electrode film layer, reduce the impedance of the negative electrode film layer, and the like.

[0465] The application detects the negative electrode sheet in example 1 at multiple places, for example, 10 places of the negative electrode sheet are taken to perform ion polishing section element analysis CP according to GB / T 17359-2012, the thickness of the negative electrode film layer in the negative electrode sheet is confirmed, and the thickness deviation of the negative electrode film layer obtained by 10 tests is controlled within 0.5%, so that it can be considered that the thickness of the negative electrode film layer in the negative electrode sheet is uniform, and the thickness consistency is high.

[0466] The application uses the method of example 1 to prepare 10 lithium ion batteries, measures the average thickness of the negative electrode film layer of each lithium ion battery, that is, ion polishing section element analysis CP is performed according to GB / T 17359-2012, the thickness of the negative electrode film layer at 10 places of the negative electrode sheet is measured, and the average value is calculated as the average thickness of the lithium ion battery, and the thickness deviation of the negative electrode film layer of the 10 lithium ion batteries is controlled within 0.5%.

[0467] While the illustrative implementations have been demonstrated and described, it will be understood by those skilled in the art that the implementations described above are not to be interpreted in a limiting sense but are intended merely to illustrate various implementations of the application. Changes and modifications to the implementations described can be made without departing from the spirit, nature or scope of the application.

Claims

A battery cell includes a negative electrode sheet, the negative electrode sheet including 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 including a negative electrode active material and a negative electrode dispersant, the negative electrode dispersant including modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt including conductive groups and flexible groups, the flexible groups including 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. According to claim 1, the battery cell, wherein, The modified carboxymethyl cellulose salt includes the compound shown in Formula A. In formula A, M includes metal ions or NH4. + At least one of them; R1 to R5 each independently include a hydrogen atom, a conductive group or a flexible group, and at least one of R1 to R5 includes a conductive group and at least another includes a flexible group; n includes any positive integer from 1500 to 3000. The battery cell according to claim 1 or 2, wherein, The conductive group includes one or more of aromatic polymer groups and polyacetylenic groups. According to claim 3, the battery cell, wherein, The aromatic polymer group includes one or more of five-membered heterocyclic polymer groups, aromatic hydrocarbon derivative polymer groups, and polyindole groups; and / or The polyacetylenic group includes one or more of polyacetylenic and polydiacetylenic groups. According to claim 4, the battery cell, wherein, The five-membered heterocyclic polymer group includes one or more of polypyrrole, polythiophene, and polyfuran groups; and / or The aromatic derivative polymer groups include one or more of polyphenylene, polyphenylene, polyphenylene ethylene, polyaniline, and aniline tetramer. The battery cell according to any one of claims 3 to 5, wherein, The degree of polymerization of the aromatic polymer group is 2 to 50; and / or the degree of polymerization of the polyacetylene group is 2 to 50. The battery cell according to any one of claims 1 to 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. According to claim 7, the battery cell, 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. 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. 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. The battery cell according to any one of claims 7 to 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. 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. The battery cell according to any one of claims 7 to 11, 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. 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 the C1 to C5 methylene groups, whether single-bonded, substituted, or unsubstituted; R 42 To R 46 Each independently includes hydrogen atoms, halogen atoms, substituted or unsubstituted C1 to C10 alkyl groups, and substituted... Or at least one of unsubstituted C2 to C10 alkenyl groups, substituted or unsubstituted C2 to C10 alkynyl groups; a includes any positive integer from 1 to 30. According to claim 14, the battery cell, wherein, R 41 Including single bonds, the substituted or unsubstituted C3 to C150 amide groups include the structural formula shown in Formula 4-1. According to claim 15, the battery cell, 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. According to claim 14, the battery cell, 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. According to claim 17, the battery cell, 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. 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. According to claim 19, the battery cell, wherein, R 51 Including single bonds, the substituted or unsubstituted C3 to C150 ester groups include the structural formula shown in Formula 5-1. According to claim 20, the battery cell, 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. According to claim 19, the battery cell, wherein, R 51 Including substituted or unsubstituted C1 to C5 methylene groups, The substituted or unsubstituted C3 to C150 ester groups include the structures shown in Formula 5-2. b1 includes any positive integer from 1 to 5. According to claim 22, the battery cell, 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. 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. 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 200% 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. 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%. According to claim 26, the battery cell, 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%. 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 235mg / 1540.25mm 2 . According to claim 28, the battery cell, wherein, The coating basis weight of the negative electrode film is 220 mg / 1540.25 mm. 2 Up to 235mg / 1540.25mm 2 . A negative electrode dispersant comprising a modified carboxymethyl cellulose salt, the modified carboxymethyl cellulose salt comprising a conductive group and a flexible group, the flexible group comprising at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, or a substituted or unsubstituted ester group. According to claim 30, the negative electrode dispersant, wherein, The modified carboxymethyl cellulose salt includes the compound shown in Formula A. In formula A, M includes metal ions or NH4. + At least one of them; R1 to R5 each independently include a hydrogen atom, a conductive group or a flexible group, and at least one of R1 to R5 includes a conductive group and at least another includes a flexible group; n includes any positive integer from 1500 to 3000. The negative electrode dispersant according to claim 30 or 31, wherein, The conductive group includes one or more of aromatic polymer groups and polyacetylenic groups. According to claim 32, the negative electrode dispersant, wherein, The aromatic polymer group includes one or more of five-membered heterocyclic polymer groups, aromatic hydrocarbon derivative polymer groups, and polyindole groups; and / or The polyacetylenic group includes one or more of polyacetylenic and polydiacetylenic groups. According to claim 33, the negative electrode dispersant, wherein, The five-membered heterocyclic polymer group includes one or more of polypyrrole, polythiophene, and polyfuran groups; and / or The aromatic derivative polymer groups include one or more of polyphenylene, polyphenylene, polyphenylene ethylene, polyaniline, and aniline tetramer. The negative electrode dispersant according to any one of claims 32 to 34, wherein, The degree of polymerization of the aromatic polymer groups is 2 to 50; and / or The degree of polymerization of the polyacetylenic group is 2 to 50. The negative electrode dispersant according to any one of claims 30 to 35, 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. A modified carboxymethyl cellulose salt includes a conductive group and a flexible group, wherein the flexible group includes at least one of a substituted or unsubstituted ether group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted polyolefin group, a substituted or unsubstituted amide group, or a substituted or unsubstituted ester group. A negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode dispersant as described in any one of claims 30 to 36. A battery comprising a battery cell as described in any one of claims 1 to 29. An electrical device comprising the battery as described in claim 39.

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