Aqueous binder composition and preparation method thereof, negative pole piece, lithium ion battery and electric device

Abstract

The invention provides a water-based binder composition and a preparation method thereof, a negative pole piece, a lithium ion battery and an electric device, and relates to the technical field of lithium ion batteries. The aqueous binder composition comprises a phase A and a phase B, the A phase comprises a first polymer, the first polymer comprises a structural unit derived from vinylphosphonic acid or vinylphosphoric acid, and a structural unit derived from 2-hydroxyethyl methacrylate; the phase B comprises a second polymer, and the second polymer comprises a structural unit formed by polydimethylsiloxane glycol, polycarbonate glycol and diisocyanate, and a structural unit formed by diisocyanate and a diamine compound. Multi-point coordination and controllable condensation on the surface of spherical silicon are realized by the phase A to form a phosphorus-rich interface layer, and a buffer network of a microphase period is provided by the phase B, so that the water-based adhesive composition integrates flexibility and swelling resistance, and simultaneous optimization of stripping, electronic path maintenance and expansion inhibition is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a water-based binder composition, a preparation method thereof, a negative electrode sheet, a lithium ion battery and an electric device. BACKGROUND

[0002] When the high-energy-density negative electrode evolves to "graphite + spherical silicon", the increase of the volume fraction of silicon leads to interface debonding, contact degradation and electrode sheet swelling, which become the dominant failure. Currently, the energy density of lithium ion batteries is facing a key bottleneck, and the theoretical capacity (372 mAh / g) of the traditional graphite negative electrode cannot meet the requirements of the next generation of energy storage devices. Therefore, the industry is actively evolving to a "graphite + spherical silicon" composite negative electrode system, among which, nano-silicon-carbon composite material has become the preferred solution due to its relatively moderate volume expansion rate (about 150~200%).

[0003] However, in the process of repeated lithium intercalation (expansion) and lithium extraction (contraction), the silicon particles themselves experience a severe "breathing effect", which will continuously tear and weaken the physical and chemical connections between them and the graphite matrix, conductive agent and binder. Once the interface contact fails, it cannot participate in the subsequent charge and discharge reaction, leading to a sharp rise in active material loss and irreversible capacity. At the same time, the macroscopic swelling problem at the electrode level is highlighted, which will cause significant thickness changes in the entire negative electrode sheet, possibly squeezing the separator channel, increasing the internal resistance and short circuit risk; it will also continuously consume electrolyte and intensify the interface side reaction with the positive electrode. In particular, it will also damage the original dense and stable conductive network, especially the conductive carbon black (such as SuperP) which relies on point contact, which is more likely to fail due to the expansion of particle spacing, even if carbon nanotubes (SWCNT) are mixed, it is also difficult to completely maintain, eventually leading to the contact degradation of the entire electrode structure, manifested as continuous growth of battery internal resistance, decline of rate performance and rapid decay of cycle life.

[0004] Currently, water-based polyacrylic acid (PAA) and its modified systems are widely used as important adhesive materials in the field of battery electrode manufacturing and other fields. However, its inherent technical bottleneck lies in the difficulty in balancing the relationship between acidity, alkalinity, salinization rate and film toughness. At the same time, in order to solve the problem of wet adhesion, biomimetic catechol compounds are introduced in the prior art. This kind of material can significantly improve the adhesion strength of the system on the wet surface, but under strong electrolyte conditions, there are through electron insulating phases and long-term stability fluctuations. On the one hand, the catechol functional group is easy to undergo uncontrollable oxidation or coordination reaction under the action of strong electrolyte, leading to fluctuations and decay of adhesion performance; on the other hand, the insulating quinone structure or complex generated by the reaction may form a continuous through electron insulating phase in the adhesion layer, which seriously hinders the electron conduction inside the electrode, greatly increases the interface impedance, and finally deteriorates the overall electrochemical performance of the battery Therefore, developing novel bonding systems that combine flexibility and swelling resistance, while simultaneously optimizing peeling, electronic pathway retention, and swelling inhibition, has become an urgent research direction in this field.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The present invention aims to provide an aqueous binder composition and its preparation method, a negative electrode sheet, a lithium-ion battery, and an electrical device. The aqueous binder composition utilizes the A phase of a first polymer containing phosphorus coordination sites to achieve multi-point coordination and controllable condensation on a spherical silicon surface, forming a phosphorus-rich interface layer; the B phase of a second polymer with PDMS soft segmentation provides a micro-phase periodic buffer network, balancing flexibility and swelling resistance, thereby simultaneously optimizing exfoliation, electronic pathway maintenance, and expansion suppression.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides an aqueous adhesive composition comprising phase A and phase B; Phase A includes a first polymer, which contains structural units derived from vinylphosphonic acid or vinylphosphonic acid, and structural units derived from 2-hydroxyethyl methacrylate. Phase B includes a second polymer comprising structural units formed of polydimethylsiloxane diol, polycarbonate diol and diisocyanate, as well as structural units formed of diisocyanate and diamine compounds.

[0008] Furthermore, the structural formula of the first polymer is shown in Formula I below:

[0009] Formula I; Wherein, M is selected from any one of H, Li, Na, K, NH4, NR4; R is selected from C1~C4 straight-chain or branched alkyl groups; f is the degree of neutralization, f = 0.2~0.6; x+y=1, x / y = (0.60~0.85):(0.40~0.15).

[0010] Furthermore, M is selected from Li or Na.

[0011] Furthermore, M is Na.

[0012] Furthermore, the raw materials for preparing the first polymer include raw material A and 2-hydroxyethyl methacrylate; wherein, raw material A is vinylphosphonic acid or vinyl phosphoric acid.

[0013] Furthermore, the molar ratio of raw material A to 2-hydroxyethyl methacrylate is (60~85):(40~15).

[0014] Furthermore, the raw materials for preparing the second polymer include polydimethylsiloxane diol, polycarbonate diol, diisocyanate, and diamine compounds.

[0015] Furthermore, the content of the polydimethylsiloxane diol is 15-45% of the total mass of the second polymer.

[0016] Furthermore, the molar amount of -NCO in the diisocyanate and the total molar amount of -OH in polydimethylsiloxane diol and polycarbonate diol is (1.05~1.15):1.

[0017] Furthermore, the number-average molecular weight of the polydimethylsiloxane diol is 1000-3000.

[0018] Furthermore, the number-average molecular weight of the polycarbonate diol is 500-2000.

[0019] Furthermore, the diisocyanate is isophorone diisocyanate.

[0020] Furthermore, the diamine compound is ethylenediamine.

[0021] Furthermore, the molar ratio of residual -NCO in the raw materials for preparing the diamine compound and the second polymer is (1~1.05):1.

[0022] Furthermore, the raw materials for preparing the second polymer also include hydrophilic monomers.

[0023] Further, preferably, the hydrophilic monomer is dimethylolpropionic acid.

[0024] Furthermore, relative to the molar amount of total -NCO or total -OH in the raw materials for preparing the second polymer, the amount of hydrophilic monomer introduced is 1.5~4.0 mol.

[0025] Furthermore, the mass ratio of phase A to phase B is (25~60):(75~40).

[0026] In a second aspect, the present invention provides a method for preparing the aqueous adhesive composition as described in the first aspect, the method comprising: Preparation of phase A: Raw material A, 2-hydroxyethyl methacrylate, initiator and solvent are mixed and subjected to free radical copolymerization reaction. After the reaction is completed, neutralization treatment is performed to obtain the first polymer; wherein, raw material A is vinylphosphonic acid or vinyl phosphoric acid; Preparation of phase B: Polydimethylsiloxane diol, polycarbonate diol and diisocyanate are mixed and subjected to a prepolymerization reaction to obtain a prepolymer; the prepolymer is then subjected to neutralization and emulsification treatments in sequence, and then subjected to a chain extension reaction with a diamine compound to obtain the second polymer; Phase A and Phase B are combined: The first polymer and the second polymer are mixed to obtain the water-based adhesive composition.

[0027] Furthermore, in the preparation of phase A, the molar ratio of raw material A and 2-hydroxyethyl methacrylate is (60~85):(40~15).

[0028] Furthermore, in the preparation of phase A, the initiator is azobisisobutyronitrile.

[0029] Furthermore, during the preparation of phase A, the initiator has a mass fraction of 0.2~1.0 wt% of the total monomers.

[0030] Furthermore, during the preparation of phase A, the temperature of the free radical copolymerization reaction is 65~80℃, and the time of the free radical copolymerization reaction is 3~8 h.

[0031] Furthermore, during the preparation of phase A, the neutralization treatment is carried out using an alkali metal hydroxide, and the degree of neutralization of the first polymer is 20-60%.

[0032] Furthermore, during the preparation of phase B, the content of polydimethylsiloxane diol is 15-45% of the total mass of the second polymer.

[0033] Furthermore, during the preparation of phase B, the number-average molecular weight of the polydimethylsiloxane diol is 1000~3000.

[0034] Furthermore, during the preparation of phase B, the number-average molecular weight of the polycarbonate diol is 500-2000.

[0035] Furthermore, in the preparation of phase B, the diisocyanate is isophorone diisocyanate.

[0036] Furthermore, in the preparation of phase B, the prepolymerization reaction is carried out by feeding materials at an equivalence ratio of -NCO / -OH (1.05~1.15):1.

[0037] Furthermore, during the preparation of phase B, hydrophilic monomers need to be mixed during the prepolymerization reaction.

[0038] Furthermore, in the preparation of phase B, the hydrophilic monomer is dimethylolpropionic acid.

[0039] Furthermore, during the preparation of phase B, the amount of hydrophilic monomer introduced is 1.5~4.0 mol relative to the total -NCO or total -OH equivalent.

[0040] Furthermore, during the preparation of phase B, the temperature of the prepolymerization reaction is 70~80℃, and the time of the prepolymerization reaction is 0.5~3 h.

[0041] Furthermore, in the preparation of phase B, the neutralization treatment is performed using triethylamine; and / or, the molar ratio of triethylamine to -COOH in the prepolymer is (1~1.05):1.

[0042] Furthermore, in the preparation of phase B, the diamine compound is ethylenediamine; and / or, the molar ratio of the diamine compound to the residual -NCO in the prepolymer is (1~1.05):1.

[0043] Thirdly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a current collector and a negative electrode active material layer disposed on at least one side of the current collector; wherein the negative electrode active material layer comprises an aqueous binder composition as described in the first aspect.

[0044] Furthermore, the aqueous binder composition accounts for 1.2 to 3.0 wt% of the mass of the negative electrode active material layer.

[0045] Furthermore, the current collector is a copper current collector.

[0046] Furthermore, the negative electrode active material layer also includes graphite, spherical silicon-containing active material, and conductive agent.

[0047] Furthermore, the spherical silicon-containing active material includes any one or a combination of at least two of spherical silicon nanoparticles, spherical silicon-oxygen particles, and spherical silicon-carbon particles.

[0048] Furthermore, the spherical silicon-carbon particles include a silicon core and a carbon coating layer covering the surface of the silicon core.

[0049] Furthermore, the particle size D50 of the spherical silicon-carbon particles is 2~8 μm, and the thickness of the carbon coating layer is 3~10 nm.

[0050] Furthermore, the spherical silicon-carbon particles include a silicon core and a carbon coating layer covering the surface of the silicon core; wherein the particle size D50 of the spherical silicon-carbon particles is 2~8 μm, and the thickness of the carbon coating layer is 3~10 nm.

[0051] Furthermore, the conductive agent includes conductive carbon black and / or single-walled carbon nanotubes.

[0052] Furthermore, the mass ratio of the graphite to the spherical silicon-containing active material is (70~95):(30~5).

[0053] Furthermore, the content of the conductive agent accounts for 0.5 to 3.0% of the mass of the negative electrode active material layer.

[0054] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a negative electrode, a positive electrode, and an electrolyte as described in the third aspect.

[0055] Furthermore, the ratio N / P of the capacity N of the negative electrode to the capacity P of the positive electrode is (1.02~1.20):1.

[0056] Furthermore, the positive electrode includes a current collector and a positive active material layer disposed on at least one side of the current collector.

[0057] Furthermore, the positive electrode active material layer includes a positive electrode active material.

[0058] Furthermore, the chemical formula of the positive electrode active material is Li a Ni x Co y Mn z M b O2; Wherein, 0.9 < a ​​< 1.2, 0.8 ≤ x ≤ 0.93, 0.1 ≤ y < 0.4, 0.05 ≤ z < 0.4, 0 ≤ b ≤ 0.1, and M represents at least one element among Zr, W, Ti, Al, Sr, La, B, and Nd.

[0059] Furthermore, the electrolyte includes lithium salt, solvent, and additives.

[0060] Furthermore, the lithium salt includes any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluorooxalate borate, and lithium bis(trifluoromethanesulfonyl)imide.

[0061] Furthermore, the solvent includes any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate.

[0062] Furthermore, the additive includes any one or a combination of at least two of the following: fluoroethylene carbonate, difluoroethylene carbonate, ethylene sulfate, ethylene sulfite, ethylene carbonate, and vinyl carbonate.

[0063] Fifthly, the present invention provides an electrical device comprising a lithium-ion cylindrical battery as described in the fourth aspect.

[0064] Compared with the prior art, the present invention has the following beneficial effects: The aqueous binder composition of the present invention can achieve a synergistic effect of high peel strength, low electronic resistance degradation and low expansion; and the aqueous binder composition of the present invention is water-based and process-friendly, and the interface "phosphorus-rich layer + microphase buffer" solves the problem of few binding sites between spherical silicon-carbon interface and binder. Detailed Implementation

[0065] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0066] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0068] In a first aspect, the present invention provides an aqueous adhesive composition comprising phase A and phase B; Phase A includes a first polymer, which contains structural units derived from vinylphosphonic acid or vinylphosphonic acid, and structural units derived from 2-hydroxyethyl methacrylate. Phase B includes a second polymer comprising structural units formed of polydimethylsiloxane diol, polycarbonate diol and diisocyanate, as well as structural units formed of diisocyanate and diamine compounds.

[0069] In this invention, the first polymer in phase A is a copolymer containing phosphoric acid / phosphonic acid coordination groups. Its main chain contains structural units derived from vinylphosphonic acid (VPA) or vinyl phosphoric acid (VPA*) (wherein, phosphonic acid contains =PC bonds, which are resistant to hydrolysis and have strong coordination; while phosphoric acid contains =POC bonds, which are more hydrophilic), and structural units derived from 2-hydroxyethyl methacrylate (HEMA). The first polymer (phase A) containing phosphorus coordination sites achieves multi-point coordination and controllable condensation on the spherical silicon surface, forming a 2-20 nm phosphorus-rich interface layer. The first polymer in phase B is a segmented waterborne polyurethane containing polydimethylsiloxane diol (PDMS-diol) soft segments and urea / urethane hard segments. The phase B with PDMS soft segments provides a buffer network with a 10-35 nm microphase period, which takes into account both flexibility and anti-swelling. Under the synergistic effect of phases A and B, the waterborne binder combination achieves the purpose of simultaneously optimizing peeling, electronic pathway maintenance and expansion inhibition.

[0070] As an optional implementation, the acid group neutralization degree of phase A is 20-60% based on the neutralization count of alkali metal hydroxides (such as lithium hydroxide monohydrate or sodium hydroxide), for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0071] As an optional implementation, the structural formula of the first polymer is shown in Formula I below:

[0072] Formula I; Wherein, M is selected from any one of H, Li, Na, K, NH4, NR4; R is selected from C1~C4 straight-chain or branched alkyl groups; f is the degree of neutralization, f = 0.2~0.6; x+y=1, x / y = (0.60~0.85):(0.40~0.15).

[0073] As an optional implementation, M is selected from Li or Na.

[0074] In a preferred embodiment, M is Na.

[0075] As an optional embodiment, the raw materials for preparing the first polymer include raw material A and 2-hydroxyethyl methacrylate; wherein, raw material A is vinylphosphonic acid or vinyl phosphoric acid.

[0076] As an optional implementation, the molar ratio of raw material A to 2-hydroxyethyl methacrylate is (60~85):(40~15), for example, it can be 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, etc.

[0077] As an optional implementation, the raw materials for preparing the second polymer include polydimethylsiloxane diol, polycarbonate diol, diisocyanate, and diamine compounds.

[0078] As an optional implementation, the content of the polydimethylsiloxane diol is 15-45% of the total mass of the second polymer, for example, it can be 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0079] As an optional implementation, the molar ratio of -NCO in the diisocyanate to the total molar ratio of -OH in polydimethylsiloxane diol and polycarbonate diol is (1.05~1.15):1, for example, it can be 1.05:1, 1.06:1, 1.05:1, 1.1:1, 1.12:1, 1.14:1, 1.15:1, etc.

[0080] As an optional implementation, the number average molecular weight of the polydimethylsiloxane diol (PDMS-diol) is 1000~3000, for example, it can be 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 3000, etc.

[0081] As an optional implementation, the number average molecular weight of the polycarbonate diol (PCDL) is 500 to 2000, for example, it can be 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1800, 2000, etc.

[0082] As an optional embodiment, the diisocyanate is isophorone diisocyanate (IPDI).

[0083] As an optional implementation, the diamine compound is ethylenediamine.

[0084] As an optional implementation, the molar ratio of residual -NCO in the raw materials for preparing the diamine compound and the second polymer is (1~1.05):1, for example, it can be 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, etc.

[0085] As an optional implementation, the raw materials for preparing the second polymer also include hydrophilic monomers.

[0086] As an optional implementation, the hydrophilic monomer is dimethylolpropionic acid.

[0087] As an optional implementation, the amount of hydrophilic monomer introduced is 1.5 to 4.0 mol% relative to the molar amount of total -NCO or total -OH in the raw materials for preparing the second polymer. For example, it can be 1.5 mol%, 1.6 mol%, 1.8 mol%, 2.0 mol%, 2.2 mol%, 2.4 mol%, 2.6 mol%, 2.8 mol%, 3.0 mol%, 3.2 mol%, 3.4 mol%, 3.6 mol%, 3.8 mol%, 4.0 mol%, etc.

[0088] It should be noted that the second polymer comprises structural units formed from polydimethylsiloxane diol, polycarbonate diol, and diisocyanate; these structural units comprise the following three types of segments: ; In PDMS-IPDI-PDMS, m is the number of repetitions of the PDMS soft segment unit, m = 15~45, preferably 20~40; and a is the number of repetitions of the PDMS-IPDI-PDMS unit, a = 8~120, preferably 10~60.

[0089] ; In PCDL-IPDI-PCDL, p is the number of repetitions of the PCDL unit, p = 3~20, preferably 4~12; and b is the number of repetitions of the PCDL-IPDI-PCDL unit, b = 8~120, preferably 10~60.

[0090] ; In PCDL-IPDI-PDMS, p is the number of repetitions of the PCDL unit, p = 3~20; m is the number of repetitions of the PDMS soft segment unit, m = 15~45, preferably 20~40; and c is the number of repetitions of the PCDL-IPDI-PDMS unit, c = 8~120, preferably 10~60.

[0091] It should be noted that the second polymer comprises a structural unit formed by a diisocyanate (with residues -NCO) and a diamine compound; this structural unit comprises the following structural segments: ; In EDA-IPDI, d is the number of repetitions of the EDA-IPDI unit, where d = 3~60, preferably 5~30.

[0092] It should be noted that the second polymer is also grafted with units derived from dimethylolpropionic acid, and the grafting methods include the following three: (a) Insertion between hard segments: ; (ii) Insertion between hard segments and PMDS: ; (iii) Insertion between hard segments and PCDL: .

[0093] As an optional implementation, the mass ratio of phase A to phase B is (25~60):(75~40), for example, it can be 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, etc.

[0094] As an optional implementation, phase A includes poly(vinylphosphonic acid-co-2-hydroxyethyl methacrylate) or poly(vinyl phosphate-co-hydroxy acrylate).

[0095] As an optional implementation, the mass fraction of phosphorus element in phase A, calculated as XPS or ICP, is 4.0~12.0 wt%, for example, it can be 4.0 wt%, 5.0 wt%, 6.0 wt%, 7.0 wt%, 8.0 wt%, 9.0 wt%, 10.0 wt%, 11.0 wt%, 12.0 wt%, etc.

[0096] In a second aspect, the present invention provides a method for preparing the aqueous adhesive composition as described in the first aspect, the method comprising: Preparation of phase A: Raw material A, 2-hydroxyethyl methacrylate, initiator and solvent are mixed and subjected to free radical copolymerization reaction. After the reaction is completed, neutralization treatment is performed to obtain the first polymer; wherein, raw material A is vinylphosphonic acid or vinyl phosphoric acid; Preparation of phase B: Polydimethylsiloxane diol, polycarbonate diol and diisocyanate are mixed and subjected to a prepolymerization reaction to obtain a prepolymer; the prepolymer is then subjected to neutralization and emulsification treatments in sequence, and then subjected to a chain extension reaction with a diamine compound to obtain the second polymer; Phase A and Phase B are combined: The first polymer and the second polymer are mixed to obtain the aqueous adhesive composition.

[0097] As an optional implementation, in the preparation of phase A, the molar ratio of raw material A and 2-hydroxyethyl methacrylate is (60~85):(40~15), for example, it can be 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, etc.

[0098] As an optional implementation, the initiator in the preparation of phase A is azobisisobutyronitrile.

[0099] As an optional implementation, during the preparation of phase A, the initiator has a mass fraction of 0.2 to 1.0 wt% of the total monomers, for example, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, etc.

[0100] As an optional implementation, during the preparation of phase A, the temperature of the free radical copolymerization reaction is 65~80℃, for example, 65℃, 68℃, 70℃, 72℃, 75℃, 78℃, 80℃, etc., and the time of the free radical copolymerization reaction is 3~8 h, for example, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, etc.

[0101] As an optional implementation, during the preparation of phase A, the neutralization treatment is carried out by neutralization with an alkali metal hydroxide, and the degree of neutralization of the first polymer is 20-60%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0102] As an optional implementation, during the preparation of phase B, the content of polydimethylsiloxane diol is 15-45% of the total mass of the second polymer, for example, it can be 15%, 20%, 25%, 30%, 35%, 40%, etc.

[0103] As an optional implementation, during the preparation of phase B, the number average molecular weight of the polydimethylsiloxane diol (PDMS-diol) is 1000~3000, for example, it can be 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 3000, etc.

[0104] As an optional implementation, during the preparation of phase B, the number average molecular weight of the polycarbonate diol (PCDL) is 500~2000, for example, it can be 500, 600, 700, 800, 900, 1000, 1200, 1400, 1600, 1800, 2000, etc.

[0105] As an optional implementation, in the preparation of phase B, the mass ratio of polydimethylsiloxane diol to polycarbonate diol is (20~45):(80~55), for example, it can be 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, etc.

[0106] As an optional implementation, in the preparation of phase B, the diisocyanate is isophorone diisocyanate (IPDI).

[0107] As an optional implementation, during the preparation of phase B, the prepolymerization reaction is carried out at an equivalent ratio of -NCO / -OH (1.05~1.15):1, for example, it can be 1.05:1, 1.06:1, 1.05:1, 1.1:1, 1.12:1, 1.14:1, 1.15:1, etc.

[0108] As an optional implementation, during the preparation of phase B, hydrophilic monomers also need to be mixed during the prepolymerization reaction.

[0109] As an optional implementation, in the preparation of phase B, the hydrophilic monomer is dimethylolpropionic acid (DMPA).

[0110] As an optional implementation, during the preparation of phase B, the amount of the hydrophilic monomer introduced relative to the total -NCO or total -OH equivalent is 1.5~4.0 mol%, for example, it can be 1.5 mol%, 1.6 mol%, 1.8 mol%, 2.0 mol%, 2.2 mol%, 2.4 mol%, 2.6 mol%, 2.8 mol%, 3.0 mol%, 3.2 mol%, 3.4 mol%, 3.6 mol%, 3.8 mol%, 4.0 mol%, etc.

[0111] As an optional implementation, during the preparation of phase B, the temperature of the prepolymerization reaction is 70~85℃, for example, it can be 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 85℃, etc., and the time of the prepolymerization reaction is 0.5~3 h, for example, it can be 0.5 h, 0.6 h, 0.8 h, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, etc.

[0112] As an optional implementation, in the preparation of phase B, the neutralization treatment is carried out using triethylamine.

[0113] As an optional implementation, the molar ratio of -COOH in the triethylamine and the prepolymer is (1~1.05):1.

[0114] As an optional implementation, in the preparation of phase B, the emulsification treatment is carried out by emulsification with water at 20~35°C; wherein the amount of water added is 2~6 times the mass of the prepolymer.

[0115] As an optional implementation, the diamine compound used in the preparation of phase B is ethylenediamine.

[0116] As an optional implementation, the molar ratio of the diamine compound to the residual -NCO in the prepolymer is (1~1.05):1.

[0117] As an optional implementation, the method for preparing the aqueous adhesive composition specifically includes the following steps: S1 free radical copolymerization (phase A): In water and / or alcohol solvents, vinylphosphonic acid or vinyl phosphoric acid is copolymerized with 2-hydroxyethyl methacrylate at a molar ratio of 60:40 to 85:15 (azobisisobutyronitrile initiator is 0.2 to 1.0 wt% relative to the total monomers; reaction temperature is 65 to 80 °C, time is 3 to 8 h) to obtain phase A mother liquor; subsequently, it is neutralized to 20 to 60% neutralization degree with lithium hydroxide monohydrate or sodium hydroxide, and the solid content is adjusted to 10 to 30 wt%. S2, Prepolymerization-Emulsification-Chain Extension (Phase B): A prepolymer was obtained by reacting polydimethylsiloxane diol and polycarbonate diol with isophorone diisocyanate at a mass ratio of 20:80 to 45:55, with an -NCO / -OH equivalent ratio of 1.05 to 1.15, at 70 to 85 °C. Dimethylolpropionic acid (1.5 to 4.0 mol%) was introduced and neutralized with triethylamine at an isomolar ratio. The mixture was then emulsified with water at 20 to 35 °C (the amount of water added was 2 to 6 times the mass of the prepolymer). The remaining -NCO was then extended with ethylenediamine at an isomolar ratio to obtain a B-phase dispersion with a solid content of 25 to 40 wt%, wherein the PDMS soft segments accounted for 15 to 45 wt% of the B-phase solids. S3, A / B combination: The water-based adhesive composition is obtained by mixing A:B at a ratio of 25:75 to 60:40 (solid content by mass).

[0118] Thirdly, the present invention provides a negative electrode sheet, the negative electrode sheet comprising a current collector and a negative electrode active material layer disposed on at least one side of the current collector; wherein the negative electrode active material layer comprises an aqueous binder composition as described in the first aspect.

[0119] As an optional embodiment, the aqueous binder composition accounts for 1.2 to 3.0 wt% of the mass of the negative electrode active material layer, for example, it can be 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, etc.

[0120] As an optional implementation, the current collector is a copper current collector.

[0121] As an optional implementation, the negative electrode active material layer further includes graphite, spherical silicon-containing active material, and conductive agent.

[0122] As an optional implementation, the spherical silicon-containing active material includes any one or a combination of at least two of spherical silicon nanoparticles, spherical silicon-oxygen particles, and spherical silicon-carbon particles.

[0123] As an optional implementation, the spherical silicon-carbon particles include a silicon core and a carbon coating layer covering the surface of the silicon core.

[0124] As an optional implementation, the particle size D50 of the spherical silicon-carbon particles is 2~8 μm, for example, it can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, etc., and the thickness of the carbon coating layer is 3~10 nm, for example, it can be 345678910.

[0125] As an optional implementation, the conductive agent includes conductive carbon black and / or single-walled carbon nanotubes.

[0126] As an optional implementation, the mass ratio of graphite to spherical silicon-containing active material is (70~95):(30~5), for example, it can be 70:30, 75:25, 80:20, 85:15, 90:10, 95:5, etc.

[0127] As an optional implementation, the content of the conductive agent accounts for 0.5 to 3.0% of the mass of the negative electrode active material layer, for example, it can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, etc.

[0128] As an optional implementation, the negative electrode sheet is prepared by the following steps: (A) Slurry preparation and coating: Graphite, spherical silicon-containing active material, conductive agent and the aqueous binder composition described in the first aspect are mixed, and the mass fraction of the aqueous binder composition in the dry electrode is adjusted to 1.2~3.0 wt% and the slurry solid content is 40–55 wt%, and then coated on the surface of a current collector (such as copper foil); (B) Drying and post-curing: The negative electrode sheet is obtained by sequentially performing two-stage medium-temperature drying (80~110℃, 15~30 min) and short-time post-curing (100~120℃, 10~20 min).

[0129] As an optional implementation, the compaction density of the negative electrode sheet is 1.2~1.7 g / cm³. 3 For example, it could be 1.2 g / cm³. 3 1.3, 1.4, 1.5, 1.6, 1.7, etc.

[0130] As an optional implementation, the negative electrode sheet shall at least satisfy any one of the conditions (a) to (c): (a) XPS: The P / Si atomic ratio measured on the surface of spherical silicon-containing active materials is 0.03 to 0.12, and the P2p binding energy is in the range of about 133 to 135 eV; (b) FTIR: Characteristic absorption peaks of P–O–Si bonds appear, located at approximately 1040–1070 cm⁻¹. -1 ; (c) TEM-EDS: A continuous phosphorus-rich interface layer with a thickness of 2~20 nm is visible on the outside of the spherical silicon-containing active material.

[0131] As an optional implementation, the negative electrode sheet, after standing at 25°C and 60%RH for 24 hours, has a swelling rate of ≤30% when immersed in an electrolyte (EC / EMC / DEC=1:1:1, containing 5% FEC). For example, this can be 30%, 28%, 25%, 24%, 20%, 18%, 15%, 14%, 10%, 9%, 8%, 7%, 6%, 5%, 1%, etc.; and has a 180° peel strength ≥1.5 N·cm. -1 For example, it could be 1.5 N·cm -1 1.6 N·cm -1 1.7 N·cm -1 1.8 N·cm -1 1.9 N·cm -1 2.0 N·cm -1 wait.

[0132] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a negative electrode, a positive electrode, and an electrolyte as described in the third aspect.

[0133] As an optional implementation, the ratio N / P of the capacity N of the negative electrode to the capacity P of the positive electrode is (1.02~1.20):1.

[0134] As an optional implementation, the positive electrode includes a current collector and a positive active material layer disposed on at least one side of the current collector.

[0135] As an optional implementation, the positive electrode active material layer includes a positive electrode active material.

[0136] As an optional implementation, the chemical formula of the positive electrode active material is Li. a Ni x Co y Mn z M b O2; Wherein, 0.9 < a ​​< 1.2, 0.8 ≤ x ≤ 0.93, 0.1 ≤ y < 0.4, 0.05 ≤ z < 0.4, 0 ≤ b ≤ 0.1, and M represents at least one element among Zr, W, Ti, Al, Sr, La, B, and Nd.

[0137] As an optional implementation, the electrolyte includes lithium salt, solvent, and additives.

[0138] As an optional implementation, the lithium salt includes any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluorooxalate borate, and lithium bis(trifluoromethanesulfonyl)imide.

[0139] As an optional implementation, the solvent includes any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate.

[0140] As an optional implementation, the additive includes any one or a combination of at least two of fluoroethylene carbonate, difluoroethylene carbonate, ethylene sulfate, ethylene sulfite, ethylene carbonate, and vinyl carbonate.

[0141] Fifthly, the present invention provides an electrical device comprising a lithium-ion cylindrical battery as described in the fourth aspect.

[0142] The present invention will be further illustrated below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0143] Example 1 This embodiment provides an aqueous binder composition, and in particular, a negative electrode sheet and a lithium-ion battery prepared from it.

[0144] (1) Preparation of water-based adhesive composition (1-1) Preparation of phase A: Preparation of the first polymer (PVPA-co-HEMA copolymer): The formulation composition of the raw materials for the preparation of phase A is shown in Table 1 below: Table 1

[0145] The A phase is prepared by the following steps: S1 (free radical copolymerization): In a 500 mL four-necked flask, add water / ethanol to dissolve VPA and HEMA; purge with nitrogen for 30 min, add AIBN, and stir magnetically (300 rpm) in a 70 °C oil bath for 6 h. After the reaction is complete, cool to 25 °C.

[0146] S2 (40% neutralization): Prepare a 10 wt% LiOH·H2O aqueous solution, add it dropwise to the polymerization solution under ice bath conditions, and monitor the pH (7.5~8.2). S3: Concentrate by rotary evaporation to 20 wt% solids content, denoted as A-20, total amount 200 g.

[0147] (1-2) Preparation of phase B: Preparation of the second polymer (PDMS-WPU dispersion): The formulation composition of the raw materials for the preparation of phase B is shown in Table 1 below: Table 2

[0148] The B phase is prepared by the following steps: S4 (Prepolymer Synthesis): In a 500 mL dry three-necked flask, PDMS-diol and PCDL were added and the mixture was heated under vacuum (-0.08 MPa) at 80°C for 30 min; then the temperature was lowered to 70°C, nitrogen gas was introduced, and 20.8 g of IPDI was added dropwise, and the mixture was stirred (400 rpm) for 1 h; subsequently, 0.70 g of DMPA was added, and the reaction was maintained at 75~80°C for 1 h to obtain the prepolymer (theoretical NCO%≈3.5~4.0).

[0149] S5 (Emulsification and Chain Extension): Cool the prepolymer to 45-50°C, add 0.50 g of TEA to neutralize (pH = 7.5-8.0); slowly add 250 g of deionized water at 800 rpm for high-speed emulsification to obtain a milky white dispersion; prepare an EDA aqueous solution (10 wt%), add it dropwise, and complete the chain extension with -NCO / -NH = 1.00 (maintain <30°C to prevent side reactions); the finished product is designated as B-30 (30 wt%), where PDMS soft segments = 30 wt% (measured against total solids of B).

[0150] (1-3) A phase and B phase composite: Based on a 100 g electrode coating layer, A-20 solution and B-30 dispersion (calculated according to the solid mass ratio of 4:6, i.e., A:B=40:60 solid content ratio) were stirred at low speed for 30 min, with pH 7.5~8.5, to obtain the water-based binder composition.

[0151] (2) Method for manufacturing negative electrode plates: The negative electrode sheet includes a negative current collector copper foil and a negative electrode coating material coated on both sides of the copper foil. Calculated by mass percentage, it includes 98% active material (where the graphite:spherical silicon carbon mass ratio is 9:1), 1% SP, 1% SWCNT, and the aqueous binder composition prepared in step (1) with a mass ratio of 0.2:1 to the total mass of the aforementioned solid powder. The above substances are added to deionized water and stirred to form the negative electrode coating material, with a solid content of 42%. The negative electrode coating material is then coated on both sides of the negative current collector (copper foil). It is then subjected to segmented drying at 90℃×20 min and 110℃×10 min, followed by curing and drying at 110℃×15 min, and then cold-pressed to form the negative electrode sheet with a compaction density of 1.5 g / cm³. 3 The negative electrode sheet is obtained.

[0152] Key reactions / interface chemistry (occurring in parallel during slide preparation): (i) The PVPA site condenses / coordinates with Si-OH (interfacial anchoring), and the specific reaction formula is as follows: Si-OH + HO-P(=O)(OH)-(PVPA)- Si-OP(=O)(OH)-(PVPA)+H2O; (ii) Strong coordination of salinization sites: Si-O - -Li + --OP(=O)-(PVPA); (iii) PDMS-WPU microphase formation: During drying / post-curing, PDMS soft segments and urea / urethane hard segments form a microphase region of 10~35nm.

[0153] (3) Method for manufacturing positive electrode plates: Take the positive electrode active material (Li1Ni0) .8 Co 0.1 Mn 0.1 O2 (NCM811), conductive carbon black, carbon nanotubes, and polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 96:1:1:2 to obtain a positive electrode coating material. The positive electrode coating material was then coated onto a 12.0 μm thick aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0154] (4) Preparation of electrolyte: An electrolyte was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and vinylene carbonate (VC) in a mass percentage ratio of 10.0: 22.0: 53.0: 3.0: 7.0: 5.0.

[0155] (5) Diaphragm: A high-porosity membrane was selected, in which the thickness of the PE base membrane was 9 μm, the thickness of the ceramic coating on both sides of the base membrane was 1.0 μm, and the thickness of the PVDF coating was 1.0 μm.

[0156] (6) Assembly of lithium-ion batteries: After the positive and negative electrode sheets are rolled and slit, they are wound together with the separator according to a set process to form a 21700 cylindrical battery core. Subsequently, the battery core is fixed to a pre-made connecting piece by welding and then installed into a metal battery casing. After completing key processes such as electrolyte injection, sealing, and formation, the lithium-ion battery described in Example 1 is obtained. This lithium-ion battery uses a cylindrical casing with an external dimension of 21.0 mm in diameter and 70.0 mm in length, conforming to the 21700 standard specification.

[0157] Example 2 This embodiment provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the composition. The only difference from Example 1 is that in the preparation process of phase A, 5.54 g of LiOH·H2O is added in step S2 to neutralize the VPA dicarboxylic acid to a degree of 30%. All other aspects are the same as in Example 1.

[0158] Example 3 This embodiment provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the composition. The only difference from Example 1 is that in the preparation process of phase A, 10.15g of LiOH·H2O is added in step S2 to neutralize the VPA dicarboxylic acid to a degree of 55%. All other aspects are the same as in Example 1.

[0159] Example 4 This embodiment provides an aqueous binder composition, a negative electrode active material layer comprising the composition, a negative electrode sheet, and a lithium-ion battery; the only difference from Example 1 is that, in the preparation process of the B phase, the PDMS-diol prepolymer formulation is changed from 30 g to 20 g, and the PCDL is changed from 70 g to 80 g, thus reducing the PDMS content from 30%. 20%, and everything else is the same as in Example 1.

[0160] Example 5 This embodiment provides an aqueous binder composition, a negative electrode active material layer comprising the composition, a negative electrode sheet, and a lithium-ion battery; the only difference from Example 1 is that the B-phase prepolymer formulation is modified by changing PDMS-diol from 30 g to 40 g and PCDL from 70 g to 60 g, thus reducing PDMS content from 30%. 40%, and everything else is the same as in Example 1.

[0161] Example 6 This embodiment provides an aqueous binder composition, a negative electrode active material layer comprising the composition, a negative electrode sheet, and a lithium-ion battery; the only difference from Embodiment 1 is the adjustment of the AB mixture solid content ratio, with the A phase quantity increased from 40%. 35%, i.e., A:B=35:65 solid content ratio, and everything else is the same as in Example 1.

[0162] Example 7 This embodiment provides an aqueous binder composition, a negative electrode active material layer comprising the composition, a negative electrode sheet, and a lithium-ion battery; the only difference from Embodiment 1 is the adjustment of the AB mixture solid content ratio, with the A phase quantity increased from 40%. 50%, that is, A:B=50:50 solid content ratio, and everything else is the same as in Example 1.

[0163] Example 8 This embodiment provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the same composition. The only difference from Example 1 is that the mass ratio of binder to solid powder is adjusted to 0.15:1 when preparing the negative electrode slurry. All other aspects are the same as in Example 1.

[0164] Example 9 This embodiment provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the same composition. The only difference from Example 1 is that the mass ratio of binder to solid powder is adjusted to 0.25:1 when preparing the negative electrode slurry. All other aspects are the same as in Example 1.

[0165] Example 10 This embodiment provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the composition; the only difference from Example 1 is that the drying oven setting is sequentially reduced to 80°C / 100°C, and the post-curing process is cancelled, while all other aspects are the same as in Example 1.

[0166] Example 11 This embodiment provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the composition. The only difference from Example 1 is that the composition is subjected to segmented drying at 110°C for 20 min and 120°C for 10 min in sequence, followed by curing and drying at 120°C for 10 min. All other aspects are the same as in Example 1.

[0167] Comparative Example 1 This comparative example provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the same composition. The only difference from Example 1 is that LiOH·H2O is not added in step S2 during the preparation of phase A. All other aspects are the same as in Example 1.

[0168] Comparative Example 2 This comparative example provides an aqueous binder composition, a negative electrode active material layer comprising the same, a negative electrode sheet, and a lithium-ion battery; the only difference from Example 1 is that in the preparation process of phase A, the prepolymer formulation of phase B is changed from 30 g to 50 g of PDMS-diol and from 70 g to 50 g of PCDL, thus reducing the PDMS content from 30%. 50%, and everything else is the same as in Example 1.

[0169] Comparative Example 3 This comparative example provides an aqueous binder composition, a negative electrode active material layer comprising the same, a negative electrode sheet, and a lithium-ion battery; the only difference from Example 1 is the adjustment of the AB mixture solid content ratio, with the A phase quantity increased from 40%. 70%, i.e., A:B=70:30 solid content ratio, all other aspects are the same as in Example 1.

[0170] Comparative Example 4 This comparative example provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the same. The only difference from Example 1 is that the mass ratio of binder to solid powder is adjusted to 0.08:1 when preparing the negative electrode slurry; all other aspects are the same as in Example 1.

[0171] Comparative Example 5 This comparative example provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the same composition. The only difference from Example 1 is that the drying process is performed by setting the oven to a single stage of 130 °C for 30 min; there is no post-curing. All other aspects are the same as in Example 1.

[0172] Comparative Example 6 This comparative example provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the same. The only difference from Example 1 is that the aqueous binder composition does not contain component A, and the missing part is made up with component B. The total amount of binder is the same as in Example 1, and everything else is the same as in Example 1.

[0173] Comparative Example 7 This comparative example provides an aqueous binder composition, as well as a negative electrode active material layer, a negative electrode sheet, and a lithium-ion battery containing the same. The only difference from Example 1 is that the aqueous binder composition does not contain component B, and the missing part is made up with component A. The total amount of binder is the same as in Example 1, and everything else is the same as in Example 1.

[0174] The parameter variations for the above embodiments and comparative examples are shown in Table 3 below: Table 3

[0175] Test Example 1 Test method: First, the lithium-ion battery is discharged at a constant current to 2.5V to ensure it is in a safe state, reducing the risk of short circuits or thermal runaway during disassembly. The battery is carefully disassembled inside a glove box (protected by argon or other inert atmosphere), and the electrodes of the cylindrical cell are removed. The electrodes are peeled off using plastic tweezers, taking care not to damage the active material layer. Next, the removed electrodes are cut to appropriate sizes and immersed in anhydrous dimethyl carbonate (DMC) solution for 30 minutes to dissolve and remove residual electrolyte and possible byproducts. After removing the electrodes, the surface is gently wiped with lint-free paper, and then the immersion-wiping process is repeated three times with fresh DMC solution to ensure no residual contaminants remain on the electrode surface. Subsequently, the electrodes are rinsed with anhydrous ethanol and wiped again to further remove solvent and impurities. After cleaning, the electrodes are placed in a glove box and left to stand for 48 hours to ensure they are completely dry, preventing interference from residual solvents in subsequent testing. After drying, the active material layer is gently scraped off using a plastic scraper, ensuring the collected powder is not contaminated. The scraped powder was transferred to centrifuge tubes containing anhydrous ethanol and ultrasonically dispersed for 30 minutes in an ultrasonic cleaner to further remove any possible residual electrolyte and impurities. After ultrasonic treatment, the sample was centrifuged (at 5000 rpm for 2 minutes), the supernatant was discarded, and the powder was redispersed with anhydrous ethanol, ultrasonicated again for 10 minutes, and then centrifuged again. This process was repeated three times to ensure the purity of the powder sample. Finally, the precipitate was collected and transferred to a vacuum drying oven and dried at 80°C for 12 hours to ensure complete removal of residual solvent. The dried powder was placed in a sealed bag or sealed sample box, immediately removed from the glove box, and the sample was quickly subjected to XRD, XPS, Raman, and HRTEM tests.

[0176] (1) Specific XRD measurement method: A copper target X-ray diffractometer (Cu-Kα radiation, 1.54 Å, tube voltage 40kV, tube current 40mA) was used to uniformly disperse the sample on the silicon substrate and obtain the XRD spectrum at a scanning rate of 2° / min in the range of 2θ=15°~70°.

[0177] (2) Specific method for determining the intensity (height) of elemental characteristic peaks in XPS spectra: XPS testing was performed using a PHI-5000 Versa Probe device, with Al Kα (1486.6 eV) as the X-ray source and a power of 150 W (15 kV × 10 mA). The test included full-spectrum scanning (0~1100 eV, step size 1 eV), background subtraction was performed using Shirley background correction, and C1s (284.8 eV) was used as an internal standard for data normalization and elemental quantitative analysis.

[0178] (3) Raman measurement method: A 532 nm laser was used as the excitation source, and the laser power was set to 1~5 mW to avoid sample ablation. The sample was uniformly dispersed on a silicon substrate. The laser power was set at 500~1700 cm⁻¹. -1 Raman spectra were collected within the range, with a spectral resolution set to 1 cm⁻¹. -1 The instrument performs 3-5 scans to improve the signal-to-noise ratio. It uses an XYZ automatic displacement platform for precise focusing and performs pre-scanning on a silicon wafer (520.7 cm²). -1 Calibration is performed to ensure data accuracy. (4) Determination methods of HRTEM and HRTEM-EDS: The powder sample was ultrasonically dispersed in ethanol, the suspension was dropped onto a copper microgrid (3 mm in diameter) and dried. The high-resolution mode was selected in the 200 kV transmission electron microscope. Selected area electron diffraction (SAED) and fast Fourier transform (FFT) were used to determine the coating layer and measure the thickness of the layer. The EDS spectrometer was turned on at the same time. The acquisition time was set to ≥30 seconds / point and the beam current was ≤1 nA. The distribution of Fe, N, B and C was determined by elemental surface scanning or line scanning.

[0179] (5) Test method for electrode compaction density: First, the positive electrode sheet, after being washed with dimethyl carbonate and vacuum dried, was cut into six standard-sized square samples (2.0cm × 2.0cm). Next, the active material on both sides of three of these square samples was removed, and they were rinsed with ethanol, dried, weighed, and their average mass M1 was calculated. Simultaneously, the average thickness L1 of the samples was measured using a micrometer. Then, the mass of the remaining three square samples was weighed, and their average mass M2 was calculated. The average thickness L2 of these samples was also measured. The electrode sheet thickness was calculated as L2 - L1 (in cm). The compaction density of the electrode sheet was also calculated. Unit: g / cm 3 .

[0180] (6) Performance testing methods: Place the battery in a 45°C constant temperature chamber for 6 hours and test it according to the following steps: (a) First round of constant current and constant voltage charging: Charge at a constant current of 0.1 C to 4.25 V, then switch to constant voltage charging until the current drops to 0.01 C.

[0181] (b) Let it stand for 30 minutes after charging is complete.

[0182] (c) Perform constant current discharge at a rate of 0.1 C to 2.5 V.

[0183] (d) Cyclic charge and discharge process: constant current charging at a rate of 1 C to 4.25 V, then constant voltage charging until the current drops to 0.1 C.

[0184] (e) Let it stand for another 30 minutes.

[0185] (f) Discharge at a constant current rate of 1C to 2.5 V.

[0186] (g) Let stand for another 30 minutes.

[0187] (h) Repeat the above (4)-(7) charging and discharging process for a total of 200 cycles.

[0188] 200-cycle capacity retention: Statistical analysis of battery discharge capacities Q1 and Q2 after 1 and 200 cycles. 200 Statistical analysis of battery capacity retention rate: Q 200 / Q1×100%.

[0189] (7) Test method for film resistance of negative electrode: The film resistance of each negative electrode is measured using the 46-probe method of the RM2610 resistance test system (45 probes are arranged in a square matrix, with 1 probe serving as a ground probe). The specific process is as follows: (7-1) First, the negative electrode sheet, which has been washed with dimethyl carbonate and vacuum dried at 60°C for 6 hours, is divided into 40 square grid samples of 1.0cm×1.0cm to ensure that the sample surface is flat. (7-2) Next, place the sample on the test device and use a pressure gauge to adjust the pressure applied by the probe to ensure good contact between the probe and the sample. The contact area is 0.01 cm². During the test, the 20 outer probes apply a constant current so that the current flows through the surface, interface and current collector of the negative electrode. At the same time, the 25 middle probes measure the voltage change in real time. Since the surface, interface and current collector of the electrode have significantly different resistances, the measured voltage will reflect these differences. (7-3) Finally, the film resistance R1 is calculated according to Ohm's law and fitting analysis method. Then, the same method is used to randomly select another 9 square grids on the above electrode to measure the film resistance. The obtained values ​​are recorded as R2, R3, R4, R5, R6, R7, R8, R9, and R10, respectively. Finally, by calculating the arithmetic mean of these values, the average film resistance Rβ of the actual tested negative electrode is obtained (Rβ=(R1+R2+R3+R4+R5+R6+R7+R8+R9+R10) / 10) in order to comprehensively evaluate the conductivity and uniformity of the negative electrode.

[0190] Using the above method, the film resistance of a fresh electrode and an electrode after 200 cycles can be measured, and the rate of increase in film resistance can be calculated.

[0191] (8) Test method for peeling force of negative electrode sheet: (8-1) First, the negative electrode sheet that has been washed with dimethyl carbonate and vacuum dried is cut into strips of standard size (2.0cm×10.0cm); (8-2) Next, use double-sided tape to fix the strip sample onto a flat thin steel plate, ensuring that the tape is stuck in the center of the steel plate. Then peel off the protective layer of the double-sided tape, stick the strip sample of the electrode to be tested onto the double-sided tape, and use a pressure roller to evenly roll the strip sample to ensure good adhesion. (8-3) Next, tear off the unattached end, bend the natural end of the torn electrode upward, and clamp it in the upper fixture of the tensile testing machine to perform a 180° peel test. Record the tensile force curve. Select the stage where the tensile force changes by no more than 10% as the stable peeling section. Finally, divide the average tensile force of the section by the width of the long sample electrode to calculate the peel strength of the negative electrode.

[0192] Electrode expansion rate (%) after 1C×200 cycles The initial thickness t0 after rolling is the same as the electrode thickness t after 1C×200 charge-discharge cycles as described above. 200 (The average of three values ​​taken at the same point) Δ t200 =100%×(t200 t0) / t0 The specific test results are shown in Table 4 below: Table 4

[0193] As shown in Table 4, comparing Examples 1-3 with Comparative Example 1, it can be seen that insufficient neutralization leads to weak interfacial anchoring, as well as pH imbalance and abnormal ionic strength within the binder. This results in deterioration of polyelectrolyte chain curling, making it difficult for phosphorus-rich sites to form stable P–O–Si bonds with the silicon surface. Consequently, contact point degradation occurs more rapidly after cycling, manifested as a significant increase in the rate of increase in electronic resistance and an increase in expansion rate. On the other hand, excessive neutralization leads to over-salinization of acidic sites, reducing the opportunities for condensation and multidentate coordination, decreasing the interfacial chemical anchoring density, and causing a simultaneous decrease in peel strength and long-cycle contact stability.

[0194] Comparing Examples 4, 1, and 5 with Comparative Example 2, it can be seen that when PDMS is too low, the soft phase continuity is insufficient, the dry film modulus is too high, and stress concentration makes microcracks and local debonding more likely to occur, and peeling and expansion are significantly worsened. When PDMS is moderate, nanoscale microphase separation is formed, and the soft and hard phases work together to slow down the volume change, maintaining interface adhesion while avoiding excessive insulation, and the rate of increase in electronic resistance is at a low level. When PDMS continues to rise to the high and extremely high range, the probability of the insulating soft phase penetration increases, the effective contact area of ​​the conductive channel decreases, and the electronic resistance deterioration intensifies after cycling. Although the expansion suppression is improved, the overall situation still presents a dual risk of maintaining conductivity and mechanical strength.

[0195] Comparing Examples 6, 1, and 7 with Comparative Example 3, it can be seen that when the proportion of Phase A is low, the interfacial chemical anchoring points are sparse, and the contact surface is prone to loosening after long cycles, resulting in suboptimal peeling and resistance. When Phase A and Phase B are close to equilibrium, the density of phosphorus-rich sites and the continuity of the soft phase compensate for each other, simultaneously ensuring interfacial adhesion and strain mitigation, while maintaining a relatively optimal resistance increase rate and expansion rate. When the proportion of Phase A is too high, the dry film tends to harden, its energy dissipation capacity weakens, crack propagation and stress transfer become more direct, leading to unfavorable evolution of the electronic contact surface and a decline in peeling strength. This indicates that variables need to be controlled within a narrow range to avoid deviations that could cause an imbalance between chemical anchoring and mechanical buffering.

[0196] Comparing Examples 8, 1, and 9 with Comparative Example 4, it can be seen that when the binder concentration is too low, the electrode pores and particle gaps are not fully filled, resulting in insufficient bridging between particles and between particles and the current collector. After cycling, contact point breakage and hole expansion occur, the electronic resistance rise rate increases significantly, peel strength decreases markedly, and the expansion rate increases simultaneously. When the binder concentration is moderate, a continuous adhesive network can be formed without excessively increasing the insulation volume fraction, resulting in better overall performance. When the binder concentration is too high, although peeling and expansion are improved, the increased insulation phase ratio and ion channel tortuosity lead to a larger electronic resistance rise rate after cycling. Therefore, the total amount needs to be precisely controlled, striking a balance between complete filling and maintaining conductivity.

[0197] Comparing Examples 10, 1, and 11 with Comparative Example 5, it can be seen that when the drying temperature is too low and post-curing is lacking, the residual solvent and water content are high, microphase separation is insufficient, and interfacial energy and local internal stress are difficult to release, resulting in significant contact degradation after cycling, and simultaneous deterioration of the electronic resistance increase rate and expansion rate. Medium-temperature two-stage drying combined with short-term post-curing can complete phase rearrangement and moderate dehydration condensation, forming a uniform and stable interfacial structure with the best overall performance. Excessively high temperatures or the use of only single-stage drying easily lead to a dense surface and internal retention state, with internal and external gradients causing hidden cracks and uneven pores, accelerating contact decay in subsequent cycles, and simultaneously impairing electronic resistance and peeling performance. Therefore, the thermal history determines the balance between phase morphology and residues, and is a key process factor for long-term stability.

[0198] Meanwhile, the adhesives provided in Examples 1 to 11 above all meet the following characteristics: (a) XPS: The P / Si atomic ratio measured on the surface of spherical silicon-containing active materials is 0.01 to 0.12, and the P2p binding energy is in the range of about 133 to 135 eV; (b) FTIR: Characteristic absorption peaks of P–O–Si bonds appear, located at approximately 1040–1070 cm⁻¹. -1 ; (c) TEM-EDS: A continuous phosphorus-rich interface layer is visible on the outside of the spherical silicon-containing active material, and the thickness of the phosphorus-rich interface layer is 2~20 nm.

[0199] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-based adhesive composition, characterized in that, The aqueous adhesive composition comprises phase A and phase B; Phase A includes a first polymer, which contains structural units derived from vinylphosphonic acid or vinylphosphonic acid, and structural units derived from 2-hydroxyethyl methacrylate. Phase B includes a second polymer comprising structural units formed of polydimethylsiloxane diol, polycarbonate diol and diisocyanate, as well as structural units formed of diisocyanate and diamine compounds.

2. The aqueous adhesive composition according to claim 1, characterized in that, The structural formula of the first polymer is shown in Formula I below: Formula I; Wherein, M is selected from any one of H, Li, Na, K, NH4, NR4; R is selected from C1~C4 straight-chain or branched alkyl groups; f is the degree of neutralization, f = 0.2~0.6; x+y=1, x / y = (0.60~0.85):(0.40~0.15); Preferably, M is selected from Li or Na, and more preferably Na; Preferably, the raw materials for preparing the first polymer include raw material A and 2-hydroxyethyl methacrylate; wherein, raw material A is vinylphosphonic acid or vinyl phosphoric acid; Preferably, the molar ratio of raw material A to 2-hydroxyethyl methacrylate is (60~85):(40~15).

3. The aqueous adhesive composition according to claim 1, characterized in that, The raw materials for preparing the second polymer include polydimethylsiloxane diol, polycarbonate diol, diisocyanate, and diamine compounds; Preferably, the content of the polydimethylsiloxane diol is 15-45% of the total mass of the second polymer; Preferably, the molar amount of -NCO in the diisocyanate and the molar amount of total -OH in polydimethylsiloxane diol and polycarbonate diol is (1.05~1.15):1; Preferably, the number-average molecular weight of the polydimethylsiloxane diol is 1000-3000; Preferably, the number-average molecular weight of the polycarbonate diol is 500-2000; Preferably, the diisocyanate is isophorone diisocyanate; Preferably, the diamine compound is ethylenediamine; Preferably, the molar ratio of residual -NCO in the raw materials for preparing the diamine compound and the second polymer is (1~1.05):

1.

4. The aqueous adhesive composition according to claim 1 or 3, characterized in that, The raw materials for preparing the second polymer also include hydrophilic monomers; Preferably, the hydrophilic monomer is dimethylolpropionic acid; Preferably, the amount of the hydrophilic monomer introduced is 1.5 to 4.0 mol relative to the molar amount of total -NCO or total -OH in the raw materials for preparing the second polymer.

5. A method for preparing an aqueous adhesive composition according to any one of claims 1 to 4, characterized in that, The preparation method includes: Preparation of phase A: Raw material A, 2-hydroxyethyl methacrylate, initiator and solvent are mixed and subjected to free radical copolymerization reaction. After the reaction is completed, neutralization treatment is performed to obtain the first polymer; wherein, raw material A is vinylphosphonic acid or vinyl phosphoric acid; Preparation of phase B: Polydimethylsiloxane diol, polycarbonate diol and diisocyanate are mixed and subjected to a prepolymerization reaction to obtain a prepolymer; the prepolymer is then subjected to neutralization and emulsification treatments in sequence, and then subjected to a chain extension reaction with a diamine compound to obtain the second polymer; Phase A and Phase B are combined: The first polymer and the second polymer are mixed to obtain the water-based adhesive composition.

6. The method for preparing the aqueous adhesive composition according to claim 5, characterized in that, In the preparation of phase A, the molar ratio of raw material A to 2-hydroxyethyl methacrylate is (60~85):(40~15); Preferably, in the preparation of phase A, the initiator is azobisisobutyronitrile; Preferably, during the preparation of phase A, the initiator has a mass fraction of 0.2~1.0 wt% of the total monomers. Preferably, during the preparation of phase A, the temperature of the free radical copolymerization reaction is 65~80℃, and the time of the free radical copolymerization reaction is 3~8 h; Preferably, during the preparation of phase A, the neutralization treatment is performed using an alkali metal hydroxide, and the degree of neutralization of the first polymer is 20-60%.

7. The method for preparing the aqueous adhesive composition according to claim 5, characterized in that, In the preparation of phase B, the content of polydimethylsiloxane diol is 15-45% of the total mass of the second polymer; Preferably, the prepolymerization reaction is carried out at an equivalence ratio of -NCO / -OH of (1.05~1.15):1; Preferably, during the prepolymerization reaction, hydrophilic monomers are also mixed. Preferably, the amount of the hydrophilic monomer introduced is 1.5~4.0 mol% relative to the total -NCO or total -OH equivalent. Preferably, the temperature of the prepolymerization reaction is 70~80℃, and the time of the prepolymerization reaction is 0.5~3 h; Preferably, the neutralization treatment is performed using triethylamine; and / or, the molar ratio of triethylamine to -COOH in the prepolymer is (1~1.05):1; Preferably, the diamine compound is ethylenediamine; and / or, the molar ratio of the diamine compound to the residual -NCO in the prepolymer is (1~1.05):

1.

8. A negative electrode sheet, characterized in that, The negative electrode sheet includes a current collector and a negative electrode active material layer disposed on at least one side of the current collector; The negative electrode active material layer comprises the aqueous binder composition as described in any one of claims 1 to 4; Preferably, the aqueous binder composition accounts for 1.2 to 3.0 wt% of the mass of the negative electrode active material layer. Preferably, the current collector is a copper current collector; Preferably, the negative electrode active material layer further includes graphite, spherical silicon-containing active material, and conductive agent; Preferably, the spherical silicon-containing active material includes any one or a combination of at least two of spherical silicon nanoparticles, spherical silicon-oxygen particles, and spherical silicon-carbon particles; Preferably, the spherical silicon-carbon particles comprise a silicon core and a carbon coating layer covering the surface of the silicon core; wherein the particle size D50 of the spherical silicon-carbon particles is 2~8 μm, and the thickness of the carbon coating layer is 3~10 nm; Preferably, the conductive agent comprises conductive carbon black and / or single-walled carbon nanotubes; Preferably, the mass ratio of graphite to spherical silicon-containing active material is (70~95):(30~5); the content of the conductive agent accounts for 0.5~3.0% of the mass of the negative electrode active material layer.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode, the positive electrode, and the electrolyte as described in claim 8; Preferably, the ratio N / P of the capacity N of the negative electrode to the capacity P of the positive electrode is (1.02~1.20):1; Preferably, the positive electrode includes a current collector and a positive active material layer disposed on at least one side of the current collector; and / or, the positive active material layer includes a positive active material Li. a Ni x Co y Mn z M b O2; where 0.9 < a ​​< 1.2, 0.8 ≤ x ≤ 0.93, 0.1 ≤ y < 0.4, 0.05 ≤ z < 0.4, 0 ≤ b ≤ 0.1, and M represents at least one element among Zr, W, Ti, Al, Sr, La, B, and Nd; Preferably, the electrolyte comprises a lithium salt, a solvent, and additives; Preferably, the lithium salt comprises any one or a combination of at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium difluorooxalate borate, and lithium bis(trifluoromethanesulfonyl)imide. Preferably, the solvent includes any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate; Preferably, the additive includes any one or a combination of at least two of the following: fluoroethylene carbonate, difluoroethylene carbonate, ethylene sulfate, ethylene sulfite, ethylene carbonate, and vinyl carbonate.

10. An electrical device, characterized in that, The electrical device includes the lithium-ion cylindrical battery as described in claim 9.

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