A composite binder, negative electrode slurry, negative electrode sheet and lithium ion battery

Abstract

The application relates to a composite binder, a negative electrode slurry, a negative electrode sheet and a lithium ion battery. The composite binder comprises the following raw materials in percentage by weight: 40wt%-60wt% of modified carboxymethyl cellulose, 25wt%-45wt% of polyacrylic acid graft copolymer and 10wt%-20wt% of modified butadiene styrene rubber; the sum of the weight percentages of the raw materials is 100%. In the composite binder, the flexibility, interface compatibility and dispersibility of the binder are optimized through precise molecular structure design, and the problem of coating cracking is solved by combining molecular weight control; no additional additives are needed, and the performance of the battery cell is not affected.

Description

Technical Field

[0001] This article relates to lithium-ion battery technology, particularly a composite binder, negative electrode slurry, negative electrode sheet, and lithium-ion battery. Background Technology

[0002] Cracking of the negative electrode coating is a key issue restricting the production yield and cycle performance of lithium-ion batteries, especially in high-capacity silicon-based negative electrodes (with a volume expansion rate of 200%-300%). Adding additives to the electrode coating can slow down the evaporation rate of moisture, thus preventing cracking during the coating process. For example, patent CN117801173A mentions a solution using polyether ester macromonomers, nonionic modified monoesters, sodium styrene sulfonate, anionic surfactants, hydrophilic acids from polymers, aromatic organic compounds, vinyltrilactate ethyl silane, initiator I, initiator II, and pH adjusters to retain water and prevent cracking. Patent CN118044003A mentions using flexible agents including one or more of diblock copolymers AB and triblock copolymers ABA, where block A includes polyether segments, and block B includes one or more of polyamide segments, polyvinylpyrrolidone segments, and polyacrylonitrile segments. These triblock polymer additives are used to soften the electrode. Currently, the main methods for improving flexibility and preventing cracking are to add additives. However, if too little of these additives is added, they will have no effect, and if too much is added, they will have a huge impact on the battery cell, and will have some effect to varying degrees.

[0003] Meanwhile, existing negative electrode binder systems also have the following limitations: 1. PAA (polyacrylic acid) brittleness problem: Traditional linear PAA molecular chains are rigid and easily break due to stress concentration when the active material expands in volume, leading to coating cracking; 2. Insufficient SBR interfacial compatibility: Conventional SBR consists of non-polar rubber segments, which have weak interfacial interactions with polar active materials (such as oxygen-containing groups on the surface of silicon and graphite), resulting in insufficient adhesion. 3. CMC flexibility defects: Unmodified CMC molecules have dense intramolecular hydrogen bonds and poor chain segment mobility, resulting in high brittleness after drying and film formation, making it difficult to buffer stress during coating and cycling processes; 4. Mismatch between molecular weight distribution and molecular structure: Simply controlling the molecular weight cannot solve the synergistic balance of "rigidity-adhesion-flexibility", and multi-level performance optimization needs to be achieved by combining molecular design.

[0004] Therefore, a new solution is needed to fundamentally solve the problem of electrode coating cracking. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0006] The first aspect of this application provides a composite adhesive comprising, by weight percentage, the following raw materials: Modified carboxymethyl cellulose (CMC) 40 wt%-60 wt% provides a dispersion framework and binds to the base material; Polyacrylic acid (PAA) graft copolymer 25 wt%-45 wt%, enhances interfacial bonding and fatigue resistance; Modified styrene-butadiene rubber (SBR) 10 wt%-20 wt% provides elastic cushioning and polar adsorption; The sum of the weight percentages of the raw materials is 100%.

[0007] In one exemplary embodiment, the composite adhesive is composed of the following raw materials by weight percentage: Modified carboxymethyl cellulose 40wt%-60wt%; 25wt%-45wt% polyacrylic acid graft copolymer; Modified styrene-butadiene rubber 10wt%-20wt%; The sum of the weight percentages of the raw materials is 100%.

[0008] In one exemplary embodiment, the modified carboxymethyl cellulose is obtained by etherification modification to introduce modifying groups.

[0009] In one exemplary embodiment, the modifying group is hydroxyethyl (-OCH2CH2OH), hydroxypropyl (-OCH2CH(OH)CH3), or methyl; for example, hydroxyethyl.

[0010] In one exemplary embodiment, the etherification modification includes: reacting carboxymethyl cellulose and a substance containing a modifying group (such as propylene oxide (hydroxypropylated), ethylene oxide (hydroxyethylated)), chloromethane, etc.) in an alkaline environment, then adding a long-chain haloalkane (such as hexadecane bromide, octane bromide, etc.), and introducing the modifying group under the catalysis of a phase transfer catalyst and in an alkaline environment to obtain sodium hydroxypropyl carboxymethyl cellulose (HPCMC), sodium hydroxyethyl carboxymethyl cellulose (HECMC), sodium methyl carboxymethyl cellulose (MCMC), hydrophobically modified sodium carboxymethyl cellulose (HM-CMC), etc.

[0011] In one exemplary embodiment, the degree of modification (or degree of substitution DS) of the modified carboxymethyl cellulose is 0.3-0.8, preferably 0.5-0.6; for example, 0.5.

[0012] In one exemplary embodiment, the modified carboxymethyl cellulose has a weight-average molecular weight (Mw) of 500,000 to 900,000 and a PDI (Mw / Mn) ≤ 1.5; for example, a weight-average molecular weight of 650,000 and a PDI of 1.4.

[0013] In one exemplary embodiment, the modified carboxymethyl cellulose has a weight-average molecular weight of 600,000 to 700,000.

[0014] In one exemplary embodiment, the polyacrylic acid graft copolymer is obtained by graft copolymerization of main-chain polyacrylic acid (PAA) and branched polymer.

[0015] In one exemplary embodiment, the grafting rate of the polyacrylic acid graft copolymer is 5%-20%, preferably 10%-15%; for example, 12% or 15%.

[0016] In one exemplary embodiment, the total weight average molecular weight (Mw) of the polyacrylic acid graft copolymer is 1.2 million to 1.8 million; for example, it is 1.4 million.

[0017] In one exemplary embodiment, the weight-average molecular weight (Mw) of the main chain polyacrylic acid in the polyacrylic acid graft copolymer is 1 million to 1.5 million; for example, it is 1.2 million.

[0018] In one exemplary embodiment, the branched polymer in the polyacrylic acid graft copolymer is a flexible segment having terminal hydroxyl groups.

[0019] In one exemplary embodiment, the branched polymer in the polyacrylic acid graft copolymer is selected from one or more of polyethylene glycol (PEG), polypropylene glycol (PPG), and polycaprolactone (PCL).

[0020] In one exemplary embodiment, the weight-average molecular weight of polyethylene glycol is 1,000-5,000; for example, it is 2,000.

[0021] In one exemplary embodiment, the weight-average molecular weight of polypropylene glycol is 2000-8000.

[0022] In one exemplary embodiment, the weight-average molecular weight of polycaprolactone is 3000-10000.

[0023] In one exemplary embodiment, the modified styrene-butadiene rubber has a core-shell structure, with the butadiene-styrene copolymer (BS) as the core layer and polar monomers grafted onto the shell layer, and is prepared by core-shell emulsion polymerization.

[0024] In one exemplary embodiment, the butadiene-styrene copolymer has a particle size of 160-230 nm.

[0025] In one exemplary embodiment, the glass transition temperature (Tg) of the butadiene-styrene copolymer is -30°C to 10°C.

[0026] In one exemplary embodiment, the butadiene-styrene copolymer accounts for 60%-80% by mass in the modified styrene-butadiene rubber; for example, 70%.

[0027] In one exemplary embodiment, the weight-average molecular weight (Mw) of the core layer in the modified styrene-butadiene rubber is 150,000 to 200,000.

[0028] In one exemplary embodiment, the modified styrene-butadiene rubber has a shell layer grafted with 15%-40% of the polar monomer; for example, 15% or 20%.

[0029] In one exemplary embodiment, the total weight-average molecular weight (Mw) of the modified styrene-butadiene rubber is 200,000-250,000, and the PDI (Mw / Mn) is ≤1.3; for example, the weight-average molecular weight is 220,000, and the PDI is 1.2.

[0030] In one exemplary embodiment, the polar monomer in the modified styrene-butadiene rubber is selected from one or more of acrylic acid (AA), methacrylic acid (MAA), and maleic anhydride (MAH); for example, acrylic acid or methacrylic acid.

[0031] In one exemplary embodiment, the composite adhesive comprises, by weight percentage, the following raw materials: Modified carboxymethyl cellulose 50wt%, 35wt% polyacrylic acid graft copolymer 15wt% modified styrene-butadiene rubber.

[0032] In one exemplary embodiment, the composite adhesive comprises, by weight percentage, the following raw materials: Modified carboxymethyl cellulose 45wt%, 40 wt% polyacrylic acid graft copolymer 15wt% modified styrene-butadiene rubber.

[0033] A second aspect of this application provides a negative electrode slurry comprising the aforementioned composite binder.

[0034] A third aspect of this application provides a negative electrode sheet prepared from the aforementioned negative electrode slurry.

[0035] In one exemplary embodiment, the negative electrode sheet is used in a silicon-based negative electrode system.

[0036] The fourth aspect of this application provides a lithium-ion battery, including the aforementioned negative electrode sheet.

[0037] Compared with existing related technologies, this application has the following technical effects: In this composite binder, the flexibility, interfacial compatibility, and dispersibility of the binder are optimized through precise molecular structure design, combined with molecular weight control, to solve the problem of coating cracking; no additional additives are required, and the performance of the battery cell is not affected. Specifically: 1) The cracking rate of the negative electrode sheet in this application is significantly reduced: through molecular design optimization, the cracking rate of graphite negative electrode coating is reduced from 12% in the traditional system to 0.1%, and that of silicon-carbon negative electrode is reduced from more than 20% to 0.5%; 2) Synergistic improvement of interfacial adhesion and flexibility: The peel strength of the negative electrode sheet obtained in this application is increased by 78% (from 1.8N / cm to 3.2N / cm), and the cycle life is extended by more than 80%; 3) Strong process compatibility: No need to modify existing coating equipment, it can be directly applied to various anode systems such as graphite and silicon carbide.

[0038] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application may be realized and obtained by means of the methods described in the description. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0040] In this invention, the “grafting ratio” of the graft copolymer refers to the mass ratio (mass of the branched polymer / mass of the main polymer) of the branched polymer bonded to the main polymer via graft copolymerization, which can be determined according to the methods described in the examples of this specification.

[0041] The degree of modification (or degree of substitution, DS) refers to the average number of hydroxyl groups substituted with methoxy groups on each dehydrated glucose unit.

[0042] The present application will be further described in detail below with reference to specific embodiments, but these embodiments should not be construed as limiting the present application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this invention.

[0043] The raw materials used in this application are all conventional products on the market.

[0044] Unless otherwise specified, all materials and reagents used in the embodiments of this application are commercially available.

[0045] Experimental methods not specified in the examples are generally performed under standard conditions or as recommended by the manufacturer. Example 1

[0046] 1) The raw materials in the composite adhesive of this application are: Hydroxyethyl modified HECMC: degree of substitution DS=0.5, Mw=650,000, PDI=1.4; The specific etherification modification method is as follows: carboxymethyl cellulose is dissolved in an alkaline aqueous solution (pH=9-10), ethylene oxide is added as a hydroxyethylating agent, and the reaction is carried out at 50-60℃ for 2 hours. Then, bromooctane (the phase transfer catalyst is tetrabutylammonium bromide) is added, and the reaction is continued for 1 hour. After cooling to room temperature, the solution is neutralized to pH=7, filtered, and dried to obtain HECMC (see patent CN17229426A). Polyacrylic acid grafted polyethylene glycol (PAA-g-PEG): Main chain Mw=1.2 million, grafted PEG (Mw=2000), grafting rate 12%, total Mw=1.4 million. The specific preparation method is as follows: Free radical graft copolymerization is employed, with grafting achieved through the esterification reaction of the carboxyl groups of the PAA main chain with the terminal hydroxyl groups of the graft polymer. The initiator is ammonium persulfate (see "Poly(acrylic acid) / poly(ethyleneglycol) adduct for attaining multifunctional cellulosic fabrics", NAIbrahim, et al., Carbohydrate Polymers, Volume 89, Issue 2, 20 June 2012, Pages 648-660, https: / / www.sciencedirect.com / science / article / abs / pii / S0144861712002962, or "Preparation of polyethylene glycol / polyacrylamide adduct and utilization in cotton finishing", Z. El-Sayed Mohamed et al., Carbohydrate Polymers Volume 75, Issue 3, 11 February 2009, Pages 648-660). 479-483, https: / / www.sciencedirect.com / science / article / abs / pii / S0144861708003858 / ); The modified styrene-butadiene rubber (i.e., core-shell SBR): core layer BS (70% content, particle size 160-230nm, glass transition temperature -13℃, molecular weight 180,000), shell layer grafted with 15% AA, the total Mw of the core-shell SBR is 220,000, PDI is 1.2. The grafting method for core-shell SBR is the same as that for PAA-g-PEG.

[0047] The composite binder formulation is as follows (by weight percentage): modified CMC 50wt%, PAA-g-PEG 35wt%, and core-shell SBR 15wt%.

[0048] In this embodiment, the composite adhesive is added step by step during the mixing process using a known method.

[0049] 2) Preparation of negative electrode slurry and negative electrode sheet: The active materials of the negative electrode slurry in this embodiment are: artificial graphite (96 parts) and conductive carbon black (1 part). First, mix the graphite and conductive carbon black well, then add 1.05 parts of grafted PAA and continue stirring and mixing. Then add 1.5 parts of modified CMC and deionized water to adjust the solid content to about 51% and stir evenly. Finally, add 0.45 parts of core-shell SBR emulsion, continue stirring, and add water to adjust the solid content to 50%.

[0050] The resulting negative electrode slurry has a solid content of 50% and a viscosity of 3000 mPa·S.

[0051] The negative electrode slurry was coated onto a 6μm thick copper foil serving as the current collector, resulting in a coating thickness of 60μm. After drying at a temperature gradient of 50℃→90℃→70℃ for 10 minutes, the foil was rolled to achieve a rolling density of 1.7g / cm³. 3 The negative electrode is obtained and a half cell is formed.

[0052] 3) Electrode and battery performance testing: 3.1 Basic Performance: Coating cracking rate: 0.1% (observed by optical microscope, 100 samples). Peel strength: 3.2 N / cm (ASTM D903 standard); Normal temperature cycling (25℃, 1C): 90% capacity retention after 1500 cycles.

[0053] 3.2 Flexibility test (GB / T1040.3-2006): Using the cylindrical bending method, the electrode sheet did not crack after being bent 180° on a cylinder with a radius of 5mm; Folding test: The coating did not peel off after being folded 100 times (180° folding angle), while the traditional system could only withstand 20 times.

[0054] 3.3 High-Temperature Electrical Performance Test (45℃, 1C Charge / Discharge): Capacitance retention rate of 85% after 500 cycles, impedance increase of <30%; High temperature storage (60℃, 7 days of full charge storage): capacity loss rate <5%, gas expansion <2% (volume ratio).

[0055] 3.4x performance: 0.2C capacity: 365mAh / g; 1C capacity retention: 95% (relative to 0.2C); 5C capacity retention: 82% (compared to 0.2C), while the traditional system's 5C capacity retention is only 60%.

[0056] Example 2 (Silicon-carbon anode, silicon content 20 wt%) 1) The composite adhesive formulation in this embodiment: Modified CMC 45wt%, same as in Example 1; PAA-g-PPG 40wt%, of which grafted PPG (Mw=4000), grafting rate 15%, total Mw=1.45 million, other contents are the same as in Example 1; The core-shell SBR is 15wt%, wherein after grafting 20% ​​MAA onto the shell, the total Mw of the core-shell SBR is 240,000, PDI is 1.2, and other parameters are the same as in Example 1.

[0057] 2) Adjustment of the preparation process of negative electrode slurry and negative electrode sheet: The solid content of the negative electrode slurry is 45%, the viscosity is 6000-9000 mP·S, and the rolling density is 1.4 g / cm³. 3 Other aspects are the same as in Example 1.

[0058] 3) Electrode and battery performance testing: 3.1 Basic Performance: Coating cracking rate: 0.5%; Peel strength: 3.0 N / cm; Room temperature cycling (25℃, 0.5C): 82% capacity retention after 1000 cycles.

[0059] 3.2 Flexibility Test: No cracking occurred when the bending radius was 8mm, and the coating remained intact after 50 folds.

[0060] 3.3 High-temperature electrical performance test (45℃, 0.5C): Capacitance retention of 75% after 500 cycles, impedance growth <40%.

[0061] 3.4x performance: 0.2C capacity: 660mAh / g; 2C capacity retention: 78% (relative to 0.2C).

[0062] Comparative Example 1 (Traditional System) 1) The process uses unmodified CMC (Mw=500,000) + linear PAA (Mw=1,000,000) + conventional SBR (Mw=200,000) in a mass ratio of 50:35:15, and other processes are the same as in Example 1.

[0063] 2) Electrode and battery performance testing: 2.1 Basic Performance: Coating cracking rate: 12%; Peel strength: 1.8 N / cm; Normal temperature cycling (25℃, 1C): 65% capacity retention after 800 cycles.

[0064] 2.2 Flexibility Test: Cracks will appear when the bending radius is greater than 15mm; Folding test: The coating peeled off noticeably after 20 folds.

[0065] 2.3 High-Temperature Electrical Performance Test (45℃, 1C): Capacitance retention rate of 58% after 500 cycles, impedance growth rate >80%; High-temperature storage (60℃, 7 days): capacity loss rate >15%, gas expansion >8%.

[0066] 2.4x performance: 0.2C capacity: 360mAh / g; 1C capacity retention: 82%; 5C capacity retention: 60%.

[0067] In summary, the composite adhesive of this application optimizes the adhesive's flexibility, interfacial compatibility, and dispersibility through precise molecular structure design, and solves the problem of coating cracking by controlling molecular weight; specifically: 1) Grafting flexible segments onto the PAA main chain improves the fatigue resistance and flexibility of PAA: The flexible segments act as "molecular springs", buffering the volume expansion stress through segment curling and stretching, while retaining the chemical bonding ability of the PAA main chain carboxyl groups with active substances (-COOH forms coordination bonds with Si-OH and C-OH). 2) The core-shell structure and polar segment modification of SBR enhance the interfacial compatibility between SBR and active materials: The core layer uses butadiene-styrene copolymer (BS) as the core, retaining the high elasticity of SBR and buffering volume expansion; the shell layer is modified with polar monomers, and the polar groups (-COOH, -COO-) can form hydrogen bonds or coordination bonds with the hydroxyl groups on the surface of the active material, improving the interfacial adhesion; the core-shell ratio ensures the balance between elasticity and polarity. 3) Synergistic modification of CMC's dispersibility and flexibility, enhancing its dispersion, suspension, and film-forming flexibility: Introducing hydroxyethyl (-OCH2CH2OH) or hydroxypropyl (-OCH2CH(OH)CH3) groups, breaking the dense hydrogen bonds within the CMC molecule through etherification; the degree of modification is controlled at 0.3-0.8, retaining the carboxymethyl (-CH2COO) group. - The electrostatic repulsion of the hydroxyalkyl group (ensuring dispersibility) is reduced, while the chain mobility is increased through the hydroxyalkyl group (enhancing flexibility). The molecular weight distribution is controlled by the fractional precipitation method, with the polydispersity index (PDI=Mw / Mn) ≤1.5, to avoid excessively high slurry viscosity caused by high molecular weight components.

[0068] Meanwhile, this application requires no additional additives and does not affect the performance of the battery cell.

[0069] As can be seen from the embodiments and comparative examples of this application, the cracking rate of the negative electrode sheet of this application is significantly reduced: through molecular design optimization, the cracking rate of graphite negative electrode coating is reduced from 12% in the traditional system to 0.1%, and that of silicon-carbon negative electrode is reduced from more than 20% to 0.5%; the interfacial adhesion and flexibility are synergistically improved: the peel strength of the negative electrode sheet obtained by this application is increased by 78% (from 1.8N / cm to 3.2N / cm), and the cycle life is extended by more than 80%; the process compatibility is strong: no modification to existing coating equipment is required, and it can be directly applied to various negative electrode systems such as graphite and silicon-carbon.

[0070] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A composite adhesive, comprising, by weight percentage, the following raw materials: Modified carboxymethyl cellulose 40wt%-60wt%, 25wt%-45wt% of polyacrylic acid graft copolymer Modified styrene-butadiene rubber 10wt%-20wt%; The sum of the weight percentages of the raw materials is 100%.

2. The composite adhesive according to claim 1, wherein, The composite adhesive comprises, by weight percentage, the following raw materials: Modified carboxymethyl cellulose 50wt%, 35wt% polyacrylic acid graft copolymer Modified styrene-butadiene rubber 15wt%; or By weight percentage, it includes the following raw materials: Modified carboxymethyl cellulose 45wt%, 40 wt% polyacrylic acid graft copolymer 15wt% modified styrene-butadiene rubber.

3. The composite adhesive according to claim 1 or 2, wherein, The modified carboxymethyl cellulose was obtained by introducing modifying groups through etherification modification; Optionally, in the modified carboxymethyl cellulose, the modifying group is hydroxyethyl, hydroxypropyl, or methyl; Optionally, the degree of modification of the modified carboxymethyl cellulose is 0.3-0.8; Optionally, the modified carboxymethyl cellulose has a weight-average molecular weight of 500,000 to 900,000 and a PDI ≤ 1.

5.

4. The composite adhesive according to claim 1 or 2, wherein, The polyacrylic acid graft copolymer is obtained by graft copolymerization of main-chain polyacrylic acid and branched polymer. Optionally, the grafting rate of the polyacrylic acid graft copolymer is 5%-20%; Optionally, the total weight average molecular weight of the polyacrylic acid graft copolymer is 1.2 million to 1.8 million. Optionally, the weight-average molecular weight of the main-chain polyacrylic acid is 1 million to 1.5 million. Optionally, the branched polymer is a flexible segment having terminal hydroxyl groups.

5. The composite adhesive according to claim 4, wherein, In the polyacrylic acid graft copolymer, the branched polymer is selected from one or more of polyethylene glycol, polypropylene glycol, and polycaprolactone.

6. The composite adhesive according to claim 5, wherein, The polyethylene glycol has a weight-average molecular weight of 1000-5000; and / or The polypropylene glycol has a weight-average molecular weight of 2000-8000; and / or The weight-average molecular weight of the polycaprolactone is 3000-10000.

7. The composite adhesive according to claim 1 or 2, wherein, The modified styrene-butadiene rubber has a core-shell structure, with the butadiene-styrene copolymer as the core layer and polar monomers grafted onto the shell layer, and is prepared by core-shell emulsion polymerization; Optionally, in the modified styrene-butadiene rubber, the mass percentage of butadiene-styrene copolymer is 60%-80%; and / or Optionally, in the modified styrene-butadiene rubber, the particle size of the butadiene-styrene copolymer is 160-230 nm; Optionally, in the modified styrene-butadiene rubber, the glass transition temperature Tg of the butadiene-styrene copolymer is -30°C to 10°C; Optionally, in the modified styrene-butadiene rubber, the weight-average molecular weight of the core layer is 150,000 to 200,000; Optionally, in the modified styrene-butadiene rubber, the shell layer is grafted with 15%-40% of the polar monomer; Optionally, the modified styrene-butadiene rubber has a total weight average molecular weight of 200,000-250,000 and a PDI ≤ 1.3; Optionally, in the modified styrene-butadiene rubber, the polar monomer is selected from one or more of acrylic acid, methacrylic acid, and maleic anhydride.

8. A negative electrode slurry, said negative electrode slurry comprising the composite binder according to any one of claims 1 to 7.

9. A negative electrode sheet prepared from the negative electrode slurry according to claim 8; Optionally, the negative electrode is used in a silicon-based negative electrode system.

10. A lithium-ion battery comprising the negative electrode sheet as described in claim 9.