Negative electrode coating material and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a negative electrode coating material and a lithium ion battery. Wherein the negative electrode coating material comprises a negative electrode active substance and a composite conductive agent, the composite conductive agent comprises oxidized sodium alginate modified carbon nanotubes and nano rare earth metal particles doped in the composite conductive agent, and the rare earth metal particles are loaded on the surfaces of the oxidized sodium alginate modified carbon nanotubes; and in a Fourier transform infrared spectrum of the composite conductive agent, the composite conductive agent has a stretching vibration peak corresponding to an aldehyde group at a transmittance spectrum of 1640 + / -5 cm <-1 >, and has a stretching vibration peak corresponding to a carbonyl group of the carboxylic ester at a transmittance spectrum of 1720 + / -5 cm <-1 >.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to a negative electrode coating material and a lithium-ion battery. Background Technology

[0002] Currently, lithium-ion batteries are widely used in consumer electronics, energy storage, and electric vehicles due to their high energy density and good cycle performance. Traditional graphite anode materials are increasingly unable to meet the demands for high energy density due to capacity limitations (theoretical capacity 372 mAh / g). Deposited silicon-carbon composite materials, as a novel anode coating material, have attracted widespread attention due to their combination of high capacity and low expansion rate.

[0003] In the process of implementing the embodiments of this disclosure, at least the following problems were found in the related art:

[0004] During cycling, silicon materials experience mechanical stress due to volume expansion, leading to particle cracking and subsequent reaction with the electrolyte to form an unstable solid electrolyte interface (SEI) film. This unstable SEI film not only consumes electrolyte and lithium ions but also causes irreversible capacity loss and rapid degradation of cycling performance. Furthermore, because silicon is a semiconductor, its electronic conductivity is relatively low (<10). -3 The low efficiency (S / cm) results in severe polarization at high rates, with a constant current charge ratio of <65%, which severely limits the practical application of silicon-carbon materials in lithium-ion batteries.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of protection of these embodiments, but rather as a prelude to the detailed description that follows.

[0007] This disclosure provides an anode coating material and a lithium-ion battery. By introducing a novel conductive agent into the anode of a deposited silicon-carbon material system to synergize with the silicon substrate, it suppresses interfacial slip during cycling and provides ion jumping sites to reduce concentration polarization. Furthermore, by optimizing parameters such as the conductive agent blending ratio and compaction density, a lithium-ion battery with ultra-high cycling stability is achieved, providing theoretical guidance and practical solutions for the design of high-performance lithium-ion batteries.

[0008] In some embodiments, the negative electrode coating material includes a negative electrode active material and a composite conductive agent, wherein the composite conductive agent includes sodium alginate-modified carbon nanotubes and rare earth metal particles doped in the composite conductive agent, and the rare earth metal particles are loaded on the surface of the sodium alginate-modified carbon nanotubes; and, in the Fourier transform infrared spectrum of the composite conductive agent, the transmittance spectrum is 1640±5 cm⁻¹. -1 It exhibits a stretching vibration peak corresponding to an aldehyde group, and in the transmittance spectrum at 1720±5 cm⁻¹ -1 The peak corresponds to the stretching vibration of the carbonyl group in a carboxylic acid ester.

[0009] Optionally, in the X-ray photoelectron spectrum of the composite conductive agent, there is a characteristic peak corresponding to a Schiff base bond at a binding energy of 399.8 ± 0.3 eV, and a characteristic peak corresponding to an ester bond at a binding energy of 288.6 ± 0.2 eV.

[0010] Optionally, the rare earth metal particles include La2O3 nanoparticles, wherein, in the resolved transmission electron microscope image of the composite conductive agent, the interplanar spacing of the La2O3 nanoparticles is 0.32±0.02nm, and the particle size distribution of the La2O3 nanoparticles is 5nm~10nm, and the standard deviation of the particle size of the La2O3 nanoparticles is less than or equal to 1.5nm.

[0011] Optionally, the sodium alginate-modified carbon nanotubes undergo an esterification reaction assisted by low-temperature plasma to graft sodium alginate onto the surface of the acidified carbon nanotubes to form ester bonds. Simultaneously, the aldehyde groups of sodium alginate form Schiff base bonds with the silanol groups. The aldehyde content in the sodium alginate is greater than or equal to 1.2 mmol / g, and the reaction temperature of the esterification reaction is 40℃~60℃.

[0012] Optionally, in the Raman spectrum of the negative electrode active material, the wavelength of the Raman scattered light is 1350 cm⁻¹. -1 The wavelength of the Raman scattered light in the vicinity is 1580 cm⁻¹ -1 The anode active material has characteristic peaks in the vicinity; and the anode active material comprises silicon-carbon / silicon-oxygen and graphite, wherein the mass percentage of silicon and carbon elements is 5% to 35%.

[0013] Optionally, the negative electrode coating material of this application further includes: a negative electrode binder, wherein the negative electrode binder comprises one or more of sodium carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polystyrene-acrylic acid and styrene-butadiene rubber, and the mass percentage of the negative electrode binder is 0.5% to 3%.

[0014] In some embodiments, the lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is composed of a negative current collector and a negative electrode coating material as described in this application coated on at least one surface thereon.

[0015] Optionally, the positive electrode sheet comprises a positive current collector and a positive electrode coating material coated on at least one surface thereon, wherein the positive electrode active material includes lithium nickel cobalt manganese oxide (LiNi). x Co y Mn z M b O2 and lithium iron phosphate, wherein 0.70≤x≤0.95, 0.05≤y<0.45, 0.05≤z<0.45, 0≤b≤0.25, x+y+z+b=1, and element M includes one or more of zirconium, tungsten, titanium, aluminum, strontium, boron and neodymium.

[0016] Optionally, the electrolyte comprises a lithium salt, a solvent, and additives, wherein the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorosulfonylimide, lithium difluorophosphate, lithium difluorooxalate borate, and lithium bis(trifluoromethanesulfonylimide); the solvent comprises one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate; and the additives comprise one or more of fluoroethylene carbonate, difluoroethylene carbonate, ethylene sulfate, ethylene sulfite, ethylene carbonate, and vinyl carbonate.

[0017] Optionally, the apparent compaction density c of the negative electrode sheet satisfies: 1.2 g / cm³ 3 ≤c≤1.7g / cm 3 .

[0018] Optionally, after 1000 cycles at 25°C and 1C, the capacity decay rate of the lithium-ion battery is less than 8.5%, and the expansion rate of the negative electrode is less than 15%; and the ratio N / P of the capacity N of the negative electrode to the capacity P of the positive electrode is between 1.02 and 1.20; and after 1000 cycles at 25°C and 1C, the capacity decay rate of the lithium-ion battery is less than 8.5%, and the expansion rate of the negative electrode is less than 15%.

[0019] In some embodiments, the electrical device includes a lithium-ion battery as described in this application.

[0020] The negative electrode coating material and lithium-ion battery provided in this disclosure can achieve the following technical effects:

[0021] This application modifies carbon nanotubes by doping sodium alginate loaded with nano-rare earth metal particles into the composite conductive agent of the negative electrode coating material. Furthermore, the aldehyde group of sodium alginate can combine with the hydroxyl group on the surface of silicon-based particles to form Schiff base bonds, thereby achieving the combination of high binding energy interfacial bonding and nano-confined ion channels. This significantly improves the rate performance and cycle stability of lithium-ion batteries, suppresses the expansion of silicon-based electrodes, and provides theoretical guidance and practical solutions for the design of fast-charging lithium-ion batteries with high energy density and high cycle stability.

[0022] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0023] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein:

[0024] Figure 1 This is a schematic diagram of the structure of a lithium-ion battery provided in an embodiment of this disclosure;

[0025] Figure 2 This is a schematic diagram of the structure of a battery core provided in an embodiment of this disclosure;

[0026] Figure 3 This is a schematic diagram of the unfolded battery core provided in an embodiment of this disclosure.

[0027] Figure label:

[0028] 1-Positive terminal; 10-Battery core; 11-Positive terminal post; 12-Negative terminal; 2-Shell; 3-Negative electrode sheet; 4-Separator; 5-Positive electrode sheet. Detailed Implementation

[0029] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0030] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0031] In this disclosure, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for better description of the embodiments of this disclosure and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this disclosure according to the specific circumstances.

[0032] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0033] Unless otherwise stated, the term "multiple" means two or more.

[0034] In this embodiment of the disclosure, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0035] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0037] Combination Figure 1 As shown, this embodiment of the present disclosure provides a lithium-ion battery, including a casing 2, which houses a battery core, with a positive terminal 1 at the top and a negative terminal 12 at the bottom, and a positive electrode post 11 disposed on the positive terminal 1. Specifically, Figure 2A schematic diagram of the battery core structure in this application is shown. Figure 3 A schematic diagram of the unfolded battery core in this application is shown. Wherein, as... Figure 3 As shown, the lithium-ion battery also includes a positive electrode 5, a negative electrode 3, a separator 4, and an electrolyte. The positive electrode 5, the negative electrode 3, and the separator 4 are stacked and then wound to form a structure as shown. Figure 2 The cylindrical battery core 10 shown is initially wound at the electrode end along the cylinder axis, and ends at the electrode end on the outer surface of the cylinder after winding.

[0038] Furthermore, the positive electrode 5 of this application is composed of a positive current collector and a positive electrode coating material coated on at least one surface thereon, wherein the positive electrode active material includes lithium nickel cobalt manganese oxide (LiNi). x Co y Mn z M b O2 and lithium iron phosphate, wherein 0.70≤x≤0.95, 0.05≤y<0.45, 0.05≤z<0.45, 0.0≤b≤0.25, x+y+z+b=1, and element M includes one or more of zirconium, tungsten, titanium, aluminum, strontium, boron and neodymium.

[0039] Meanwhile, the negative electrode 3 of this application is composed of a negative electrode current collector and a negative electrode coating material coated on at least one of its surfaces. The negative electrode coating material includes a negative electrode active material and a composite conductive agent. The composite conductive agent includes sodium alginate oxide (OSA) modified carbon nanotubes (CNTs) and nano-rare earth metal particles doped in the composite conductive agent, with the rare earth metal particles loaded on the surface of the OSA modified carbon nanotubes. In the X-ray photoelectron spectroscopy (XPS) of the composite conductive agent, a characteristic peak corresponding to a Schiff base bond (-C=N-) is observed at a binding energy of 399.8 ± 0.3 eV, and a characteristic peak corresponding to an ester bond (-COO-) is observed at a binding energy of 288.6 ± 0.2 eV.

[0040] Furthermore, in the Fourier transform infrared (FT-IR) spectrum of the composite conductive agent, the transmittance spectrum is at 1640±5 cm⁻¹. -1 It exhibits a stretching vibration peak corresponding to the aldehyde group (-CHO), and in the transmittance spectrum at 1720±5 cm⁻¹ -1 The stretching vibration peak corresponds to the carbonyl group (C=O) of the carboxylic acid ester (-COOR).

[0041] In the embodiments of this application, the nano-rare earth metal particles include La2O3 nanoparticles. In the resolved transmission electron microscope (TEM) image of the composite conductive agent, the interplanar spacing of the La2O3 nanoparticles is 0.32 ± 0.02 nm (corresponding to the {101} crystal plane), and the particle size distribution of the La2O3 nanoparticles is 5 nm to 10 nm, with a particle size standard deviation less than or equal to 1.5 nm. Selected area electron diffraction (SAED) detected diffraction rings corresponding to the {101}, {110}, and {202} crystal planes of La2O3, with a lattice constant a of 0.394 ± 0.005 nm and a lattice constant c of 0.613 ± 0.005 nm.

[0042] In the embodiments of this application, the sodium alginate-modified carbon nanotubes of this application undergo an esterification reaction assisted by low-temperature plasma. Sodium alginate is grafted onto the surface of the acidified carbon nanotubes to form ester bonds. Simultaneously, the aldehyde groups of sodium alginate form Schiff base bonds (-C=N-) with the silanol groups. The aldehyde content in the sodium alginate is greater than or equal to 1.2 mmol / g, and the esterification reaction temperature is 40℃~60℃. The specific chemical reaction process is as follows:

[0043] 1. Amination pretreatment (silanol group → silanoyl group):

[0044] ≡Si-OH+H2N-R'→≡Si-NH-R'+H2O;

[0045] Wherein, R' is the organic chain of an amination reagent (e.g., a silane coupling agent).

[0046] 2. Schiff base bond formation (aldehyde + amino):

[0047] OSA-CHO+H2N-≡Si→OSA-CH=N-≡Si+H2O;

[0048] Product structure: Schiff base bond: -CH=N － (Imine bond).

[0049] In the embodiments of this application, in the Raman spectrum corresponding to the negative electrode active material of this application, the wavelength of the Raman scattered light is 1350 cm⁻¹. -1 The wavelength of the Raman scattered light in the vicinity is 1580 cm⁻¹ -1 There are characteristic peaks in the vicinity.

[0050] In the embodiments of this application, the negative electrode active material of this application includes silicon-carbon / silicon-oxygen and graphite, wherein the mass percentage of silicon and carbon elements is 5% to 35%.

[0051] In the embodiments of this application, the negative electrode coating material further includes a negative electrode binder, which includes one or more of sodium carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polystyrene-acrylic acid and styrene-butadiene rubber, and the mass percentage of the negative electrode binder is 0.5% to 3%.

[0052] In the embodiments of this application, the electrolyte of this application includes lithium salt, solvent, and additives, wherein the lithium salt includes one or more combinations of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorosulfonylimide, lithium difluorophosphate, lithium difluorooxalate borate, and lithium bis(trifluoromethanesulfonylimide); the solvent includes one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate; and the additives include one or more of fluoroethylene carbonate, difluoroethylene carbonate, ethylene sulfate, ethylene sulfite, ethylene carbonate, and vinyl carbonate.

[0053] Optionally, the apparent compaction density c of the negative electrode sheet of this application satisfies: 1.2 g / cm³ 3 ≤c≤1.7g / cm 3 .

[0054] Optionally, after cycling 1000 times at 25°C and 1C, the capacity decay rate of the lithium-ion battery of this application is less than 8.5%, and the expansion rate of the negative electrode sheet of this application is less than 15%.

[0055] Optionally, the ratio N / P of the capacity N of the negative electrode to the capacity P of the positive electrode in this application is between 1.02 and 1.20.

[0056] Optionally, the lithium-ion battery of this application is assembled in the form of a 21700 cylindrical battery unit with a capacity of 5Ah.

[0057] Furthermore, embodiments of this disclosure also provide an electrical device, including a lithium-ion battery as described in this application.

[0058] The present invention provides a lithium-ion battery by doping sodium alginate modified carbon nanotubes loaded with nano-rare earth metal particles into the composite conductive agent of the negative electrode coating material. The aldehyde group of sodium alginate can combine with the hydroxyl group on the surface of silicon-based particles to form Schiff base bonds, thereby achieving the combination of high binding energy interfacial bonding and nano-confined ion channels. This significantly improves the rate performance and cycle stability of the lithium-ion battery, suppresses the expansion of silicon-based electrodes, and provides theoretical guidance and practical solutions for the design of fast-charging lithium-ion batteries with high energy density and high cycle stability.

[0059] The technical solution of this application will be further described below with reference to specific embodiments.

[0060] The battery fabrication method is tested, taking Example 1 as an example:

[0061] 1. Method for manufacturing positive electrode plates:

[0062] Take positive electrode active material (LiNi) 0.8 Co 0.1 Mn 0.1 O2, at this time LiNi x Co y Mn z M b The positive electrode coating material is obtained by thoroughly mixing conductive carbon black, carbon nanotubes and polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone solvent system at a mass ratio of 96:1:1:2. The positive electrode coating material is then coated onto a 12.0 μm thick aluminum foil, dried and cold-pressed to obtain the positive electrode sheet.

[0063] 2. Negative electrode manufacturing method:

[0064] The negative electrode sheet comprises a negative current collector copper foil and a negative electrode coating material coated on both sides of the copper foil. By mass percentage, the negative electrode coating material comprises 10.0% deposited silicon carbon, 76.0% graphite, 0.75% of the aforementioned conductive agent, 0.75% conductive carbon black, 1.0% thickener sodium carboxymethyl cellulose (CMC), 0.75% binder polyacrylic acid (PAA), and 0.75% binder styrene-butadiene rubber (SBR). These 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 onto both sides of the negative current collector (copper foil), dried, and cold-pressed to form the negative electrode sheet with a compaction density of 1.5 g / cm³. 3 ;

[0065] The preparation method of the composite conductive agent of sodium alginate (OSA) modified CNT and rare earth metal doped:

[0066] 10 g of single-walled carbon nanotubes (diameter 8 nm–15 nm, length 10 μm–20 μm) were added to 500 mL of concentrated nitric acid (65 wt%) and refluxed at 110 °C for 12 h. The mixture was centrifuged and washed until neutral, then vacuum dried at 80 °C (carboxyl density 0.15 ± 0.02 mmol / g, titrated). 5 g of OSA was dissolved in pH 5 buffer, and 0.1 M NaIO4 (molar ratio 1:1.2) was added. The mixture was reacted at 40 °C for 20 min, yielding an aldehyde content of 1.5 mmol / g (titrated).

[0067] Acidified CNTs and OSA were dispersed in deionized water at a mass ratio of 1:0.6, with a solid content of 10 wt%. The mixture was then transferred to a plasma reactor with an argon flow rate of 50 sccm, a power of 150 W, and a temperature of 60 °C for 60 min to obtain OSA-CNT powder.

[0068] OSA-CNTs were impregnated in 0.2 M La(NO3)3 / citric acid solution (where the molar ratio of La(NO3)3 / citric acid was 1:2) and calcined at 600 °C for 2 h to obtain La2O3 nanoparticle-supported CNTs with a La2O3 content of 3 wt%.

[0069] 3. Preparation of electrolyte:

[0070] An electrolyte was prepared by mixing lithium salt lithium hexafluorophosphate (LiPF6), organic solvents 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.

[0071] 4. Diaphragm:

[0072] 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.

[0073] 5. Assembly of lithium-ion batteries:

[0074] 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.

[0075] Example 2

[0076] The difference between this embodiment and Embodiment 1 is that, before plasma treatment, OSA is oxidized with NaIO4, and the oxidation time is shortened to make the OSA aldehyde content 1.2 mmol / g (the subsequent aldehyde content scheme is also adjusted in this way). Everything else is the same as in Embodiment 1.

[0077] Example 3

[0078] The difference between this embodiment and Example 1 is that the OSA aldehyde content is 2 mmol / g, while all other aspects are the same as in Example 1.

[0079] Example 4

[0080] The difference between this embodiment and Example 1 is that the molar ratio of La(NO3)3 / citric acid is 1:2.5, resulting in a La2O3 particle size of 12nm. All other aspects are the same as in Example 1.

[0081] Example 5

[0082] The difference between this embodiment and Example 1 is that the molar ratio of La(NO3)3 / citric acid is 1:1.5, resulting in a La2O3 particle size of 5nm. All other aspects are the same as in Example 1.

[0083] Example 6

[0084] The difference between this embodiment and Embodiment 1 is that the mass ratio of acidified CNT to OSA is 1:0.3, while all other aspects are the same as in Embodiment 1.

[0085] Example 7

[0086] The difference between this embodiment and Embodiment 1 is that the mass ratio of acidified CNT to OSA is 1:1, while all other aspects are the same as in Embodiment 1.

[0087] Example 8

[0088] The difference between this embodiment and Example 1 is that OSA-CNT is impregnated with 0.1 MLa(NO3)3 / citric acid, so that the content of La2O3 nanoparticles in CNT is 2 wt%, while all other aspects are the same as in Example 1.

[0089] Example 9

[0090] OSA-CNTs were impregnated with 0.3 M La(NO3)3 / citric acid, resulting in a La2O3 nanoparticle content of 6 wt% in the CNTs. All other aspects were the same as in Example 1.

[0091] Example 10

[0092] The difference between this embodiment and Embodiment 1 is that the mass percentage of the conductive agent in the negative electrode coating material is 0.25%, and the mass percentage of the conductive carbon black is 1.25%. All other aspects are the same as in Embodiment 1.

[0093] Example 11

[0094] The difference between this embodiment and Embodiment 1 is that the mass percentage of the conductive agent in the negative electrode coating material is 0.5%, and the mass percentage of the conductive carbon black is 1.0%, while all other aspects are the same as in Embodiment 1.

[0095] Example 12

[0096] The difference between this embodiment and Embodiment 1 is that the mass percentage of the conductive agent in the negative electrode coating material is 1.25%, and the mass percentage of the conductive carbon black is 0.5%. All other aspects are the same as in Embodiment 1.

[0097] Example 13

[0098] The difference between this embodiment and Embodiment 1 is that the compaction of the negative electrode sheet is 1.35 g / cm³. 3 Everything else is the same as in Example 1.

[0099] Example 14

[0100] The difference between this embodiment and Embodiment 1 is that the compaction of the negative electrode sheet is 1.65 g / cm³. 3 Everything else is the same as in Example 1.

[0101] Comparative Example 1

[0102] The difference between this comparative example and Example 1 is that the OSA aldehyde content is 0.8 mmol / g, while all other aspects are the same as in Example 1.

[0103] Comparative Example 2

[0104] The difference between this comparative example and Example 1 is that the molar ratio of La(NO3)3 / citric acid is 1:3.5, resulting in a La2O3 particle size of 15nm. All other aspects are the same as in Example 1.

[0105] Comparative Example 3

[0106] The difference between this comparative example and Example 1 is that the mass ratio of acidified CNT to OSA is 1:0.5, while all other aspects are the same as in Example 1.

[0107] Comparative Example 4

[0108] The difference between this comparative example and Example 1 is that OSA-CNTs are impregnated with 0.4 MLa(NO3)3 / citric acid, so that the content of La2O3 nanoparticles in CNTs is 7 wt%. All other aspects are the same as in Example 1.

[0109] Comparative Example 5

[0110] The difference between this comparative example and Example 1 is that the compaction of the negative electrode sheet is 1.75 g / cm³. 3 Everything else is the same as in Example 1.

[0111] Test method:

[0112] First, discharge the lithium-ion battery to a constant current of 2.5V to ensure it is in a safe state, reducing the risk of short circuits or thermal runaway during disassembly. Carefully disassemble the battery within a glove box (protected by argon or other inert atmosphere) and remove the negative electrode from the cylindrical cell. Use plastic tweezers to peel off the electrode, avoiding damage to the active material layer. Next, cut the removed negative electrode to an appropriate size and soak it in anhydrous dimethyl carbonate (DMC) solution for 30 minutes to dissolve and remove residual electrolyte and possible byproducts. After removing the electrode, gently wipe the surface with lint-free paper, then replace with fresh DMC solution, repeating the soaking-wiping process three times to ensure no residual contaminants remain on the electrode surface. Subsequently, rinse the electrode with anhydrous ethanol and wipe it again to further remove solvent and impurities. After cleaning, place the electrode in a glove box and let it stand for 48 hours to ensure it is completely dry, preventing interference from residual solvent in subsequent tests. After drying, the negative electrode active material layer is gently scraped off using a plastic scraper to ensure the collected powder is uncontaminated. The scraped powder is transferred to a centrifuge tube containing anhydrous ethanol and ultrasonically dispersed for 30 minutes in an ultrasonic cleaner to further remove any possible residual electrolyte, binder, and impurities. After ultrasonic treatment, the sample is centrifuged (at 5000 rpm for 2 minutes), the supernatant is discarded, and the powder is redispersed with anhydrous ethanol, ultrasonicated again for 10 minutes, and then centrifuged again. This process is repeated three times to ensure the purity of the powder sample. Finally, the precipitate is collected and transferred to a vacuum drying oven and dried at 80°C for 12 hours to ensure complete removal of residual solvents. The dried powder is placed in a sealed bag or sealed sample box, immediately removed from the glove box, and the sample is quickly subjected to XRD, XPS, Raman, and HRTEM tests.

[0113] Specific XRD measurement method: A copper target X-ray diffractometer (Cu-Kα radiation) was used. With a tube voltage of 40kV and a tube current of 40mA, the sample was uniformly dispersed on a silicon substrate, and XRD patterns were acquired at a scan rate of 2° / min within the range of 2θ = 15° to 70°.

[0114] The specific method for determining the intensity (height) of elemental characteristic peaks in XPS spectra: XPS testing was performed using a PHI-5000 VersaProbe instrument, with AlKα (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.

[0115] Raman spectral analysis: A 532 nm laser was used as the excitation source, with the laser power set to 1–5 mW to avoid sample ablation. The sample was uniformly dispersed on a silicon substrate. The sample was measured at 500–1700 cm⁻¹. -1 ~1700cm - Raman spectra were collected within a range of 1 cm⁻¹, with the spectral resolution set to 1 cm⁻¹. - 1. Perform 3-5 scans to improve the signal-to-noise ratio. The instrument uses an XYZ automatic displacement platform for precise focusing, and the silicon wafer (520.7cm²) is scanned before testing. - 1) Calibration to ensure data accuracy.

[0116] The determination methods of HRTEM and HRTEM-EDS are as follows: The powder sample is ultrasonically dispersed in ethanol, and the suspension is dropped onto a copper microgrid (diameter 3 mm) and dried. In a 200 kV transmission electron microscope, the high-resolution mode is selected, and the TiN layer (interplanar spacing ~0.21 nm) is determined by selected area electron diffraction (SAED) and fast Fourier transform (FFT), and the thickness of the layer is measured. At the same time, the EDS spectrometer is turned on, the acquisition time is set to ≥30 seconds / point, and the beam current is ≤1 nA. Elemental surface scanning or line scanning is performed to determine the distribution of Ti, N, Si and C.

[0117] Test method for compaction density of negative electrode sheet:

[0118] First, the negative 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 compacted density of the electrode sheet was also calculated (in g / cm³). 3 :

[0119]

[0120] Performance testing methods:

[0121] Place the battery in a 25°C constant temperature chamber for 6 hours and test it according to the following steps:

[0122] First round of constant current and constant voltage charging: Charge at a constant current of 0.1C to 4.2V, then switch to constant voltage charging until the current drops to 0.01C.

[0123] Let it stand for 30 minutes after charging is complete.

[0124] Perform constant current discharge, discharging to 2.5V at a rate of 0.1C.

[0125] Cyclic charge and discharge process: constant current charging at a rate of 3C to 4.2V, then switching to constant voltage charging until the current drops to 0.1C.

[0126] Let it stand for another 30 minutes.

[0127] Discharge at a constant current rate of 3C to 2.5V.

[0128] Let it stand for another 30 minutes.

[0129] Repeat the above (4)-(7) charging and discharging process for a total of 500 cycles.

[0130] The percentage of the constant current segment: The capacity of the battery charged when the constant current is charged to 4.2V in step (4) above is recorded as C0; the total capacity of the battery charged when the constant voltage is charged until the current drops to 0.1C is recorded as C1, and the percentage of the constant current segment = C0 / C1*100%.

[0131] 500-cycle capacity retention: Statistical analysis of battery discharge capacities Q1 and Q2 after 1 and 500 cycles. 1000 Calculate the battery capacity decay rate: (Q1-Q 1000 ) / Q1×100.

[0132] Electrode expansion rate: After 500 cycles, the battery is removed using the method described above, and the expansion rate of the electrode is calculated by comparing it with the initial electrode thickness.

[0133] Table 1: Parameter Variation Table

[0134]

[0135] Table 2: Performance Comparison Table

[0136]

[0137] As shown in Table 2, comparing Examples 1-3 with Comparative Example 1, it can be seen that as the aldehyde content of OSA increases, the capacity retention rate shows an upward trend. However, the expansion rate also increases when the aldehyde content reaches 2 mmol / g. This is because the aldehyde group forms a Schiff base bond (-C=N-) with the silanol group. When the aldehyde content increases, the density of the Schiff base bond increases, and the anchoring force between the aldehyde and silicon particles increases, which can effectively suppress volume expansion. However, excessive aldehyde content will lead to an increase in the rigidity of the OSA molecular chain, resulting in increased interfacial brittleness, which is not conducive to cycling and expansion suppression.

[0138] Examples 4-5 and Comparative Example 2 show that when the La2O3 particle size ≈ Li +When the solvation shell diameter is 0.8 nm, the ion diffusion barrier can be lowered, which is beneficial to reduce polarization and improve the cross-current ratio. However, when the La2O3 particle size is >10 nm, it will lead to an increase in the tortuosity of the ion channel and the tortuosity coefficient of ion transport, resulting in a sharp drop in fast charging capability and hindering performance release. At the same time, the ultra-small La2O3 particle size (<5 nm) will partially penetrate the SEI film, causing side reactions and thus affecting the cycle capacity retention rate.

[0139] Examples 6-7 and Comparative Example 3 show that when the CNT / OSA mass ratio is at its optimal level, the CNT surface is uniformly coated with OSA, achieving a balance between electron and ion channels, which is beneficial for the battery's high performance. However, when the CNT / OSA mass ratio is <1:1, insufficient CNTs lead to discontinuous conductive networks, increased electronic impedance, and increased battery polarization. When the CNT content is too low, silicon particles, as poor electronic conductors, significantly increase battery polarization and significantly decrease the current ratio. When the CNT / OSA mass ratio is >1:1.5, OSA agglomeration leads to increased interfacial impedance, similarly affecting the battery's high-rate charge / discharge capability.

[0140] Examples 8-9 and Comparative Example 4 show that when the La2O3 loading increases within a certain range, both the fast-charging capability (cross-current ratio) and cycle performance improve. This is because the increased La2O3 loading leads to an increase in the oxygen vacancy concentration in the negative electrode, thereby increasing the Li... + The mobility increases; however, when the content of La2O3 is greater than 5 wt%, excessive addition will lead to agglomeration, which will block the electron channel, reduce the cross-sectional area of ​​the electron channel, and increase the electron transition barrier, resulting in a sharp deterioration in performance.

[0141] Examples 10-12 show that the capacity retention initially increases and then stabilizes with increasing SWCNT / Super P ratio. This phenomenon stems from the optimization of the conductive network: pure Super P (0D carbon black) constructs a conductive framework only through point contacts, easily forming isolated conductive "islands," thus limiting electron transport efficiency; while the introduction of an appropriate amount of SWCNT (1D carbon nanotubes) can form a three-dimensional interconnected conductive network, significantly improving electronic conductivity and optimizing Li... +Transport path. However, when the SWCNT content is high, the conductive network has reached the percolation threshold, and further increasing the SWCNT content cannot further reduce the interfacial impedance; instead, it will reduce the cost-effectiveness due to increased material costs. Therefore, a 0.75 / 0.75 blending ratio of SWCNT / Super P achieves the best balance between performance and cost. In addition, the introduction of SWCNT also has a certain inhibitory effect on electrode expansion. Comparing Comparative Example 5 and Examples 13-14, it can be seen that as the compaction gradually increases, the kinetic performance of the lithium battery also shows a trend of first increasing and then decreasing. This is attributed to the need for the compaction density of the negative electrode to balance between enhanced electron conduction and hindered ion transport. Furthermore, excessive compaction may damage the active material interface, exposing more active specific surface area, leading to increased SE I during charging and discharging, and aggravated electrode expansion.

[0142] In summary, by synergistically optimizing the aldehyde content of OSA, the particle size of La2O3, the CNT / OSA mass ratio, the proportion of conductive agent, and the compaction density, the rate performance and cycle stability of lithium-ion batteries can be significantly improved.

[0143] The foregoing description and accompanying drawings fully illustrate embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included or substituted for parts and features of other embodiments. Embodiments of the present disclosure are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from its scope. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A negative electrode coating material, characterized in that, It includes a negative electrode active material and a composite conductive agent, wherein the composite conductive agent includes sodium alginate-modified carbon nanotubes and nano-rare earth metal particles doped in the composite conductive agent, and the rare earth metal particles are loaded on the surface of the sodium alginate-modified carbon nanotubes. Furthermore, in the Fourier transform infrared spectrum of the composite conductive agent, the transmittance spectrum is 1640±5 cm⁻¹. -1 It exhibits a stretching vibration peak corresponding to an aldehyde group, and in the transmittance spectrum at 1720±5 cm⁻¹ -1 The peak corresponds to the stretching vibration of the carbonyl group in a carboxylic acid ester.

2. The negative electrode coating material according to claim 1, characterized in that, In the X-ray photoelectron spectrum of the composite conductive agent, there is a characteristic peak corresponding to a Schiff base bond at a binding energy of 399.8 ± 0.3 eV, and a characteristic peak corresponding to an ester bond at a binding energy of 288.6 ± 0.2 eV.

3. The negative electrode coating material according to claim 1, characterized in that, The rare earth metal nanoparticles include La2O3 nanoparticles. In the resolved transmission electron microscope image of the composite conductive agent, the interplanar spacing of the La2O3 nanoparticles is 0.32±0.02nm, and the particle size distribution of the La2O3 nanoparticles is 5nm~10nm, with a particle size standard deviation of less than or equal to 1.5nm.

4. The negative electrode coating material according to claim 1, characterized in that, The sodium alginate-modified carbon nanotubes undergo esterification via low-temperature plasma-assisted esterification, grafting sodium alginate onto the surface of the acidified carbon nanotubes to form ester bonds. Simultaneously, the aldehyde groups of sodium alginate and silanol groups form Schiff base bonds. The aldehyde content in sodium oxidized alginate is greater than or equal to 1.2 mmol / g, and the reaction temperature of the esterification reaction is 40℃~60℃.

5. The negative electrode coating material according to claim 1, characterized in that, In the Raman spectrum of the negative electrode active material, the wavelength of the Raman scattered light is 1350 cm⁻¹. -1 The wavelength of the Raman scattered light in the vicinity is 1580 cm⁻¹ -1 It has a characteristic peak in the vicinity; Furthermore, the negative electrode active material comprises silicon-carbon / silicon-oxygen and graphite, wherein the mass percentage of silicon and carbon elements is 5% to 35%.

6. The negative electrode coating material according to any one of claims 1 to 5, characterized in that, Also includes: The negative electrode binder comprises one or more of sodium carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polystyrene-acrylic acid, and styrene-butadiene rubber, wherein the mass percentage of the negative electrode binder is 0.5% to 3%.

7. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The negative electrode sheet is composed of a negative current collector and a negative electrode coating material as described in any one of claims 1 to 6 coated on at least one surface thereon.

8. The lithium-ion battery according to claim 7, characterized in that, The positive electrode sheet comprises a positive current collector and a positive electrode coating material coated on at least one surface thereon, wherein the positive electrode active material includes lithium nickel cobalt manganese oxide (LiNi). x Co y Mn z M b O2 and lithium iron phosphate, wherein 0.70≤x≤0.95, 0.05≤y<0.45, 0.05≤z<0.45, 0.0≤b≤0.25, x+y+z+b=1, and element M includes one or more of zirconium, tungsten, titanium, aluminum, strontium, boron and neodymium.

9. The lithium-ion battery according to claim 7, characterized in that, The electrolyte comprises a lithium salt, a solvent, and additives, wherein the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorosulfonylimide, lithium difluorophosphate, lithium difluorooxalate borate, and lithium bis(trifluoromethanesulfonylimide); the solvent comprises one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate; and the additives comprise one or more of fluoroethylene carbonate, difluoroethylene carbonate, ethylene sulfate, ethylene sulfite, ethylene carbonate, and vinyl carbonate.

10. The lithium-ion battery according to any one of claims 7 to 9, characterized in that, The apparent compaction density c of the negative electrode sheet satisfies: 1.2 g / cm³ 3 ≤c≤1.7g / cm 3 ; Furthermore, the ratio N / P of the capacity N of the negative electrode to the capacity P of the positive electrode is between 1.02 and 1.20; Furthermore, after 1000 cycles at 25°C and a 1C rate, the capacity decay rate of the lithium-ion battery is less than 8.5%, and the expansion rate of the negative electrode is less than 15%.

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