Negative electrode composition, negative electrode slurry, negative electrode plate, cylindrical battery roll core and battery

Abstract

The invention relates to the technical field of batteries, in particular to a negative electrode composition, negative electrode slurry, a negative electrode plate, a cylindrical battery roll core and a battery, the negative electrode composition comprises a silicon material, a carbon material, siloxane organic molecules and a binder; wherein based on the total mass of the negative electrode composition, the mass percentage content of the silicon material is 5%-30%; the binder comprises a first binder, and the first binder comprises carboxymethyl cellulose. The pole piece containing the negative electrode composition disclosed by the invention has excellent expansion resistance, structural integrity and adhesive power.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a negative electrode composition, a negative electrode slurry, a negative electrode sheet, a cylindrical battery core, and a battery. Background Technology

[0002] As lithium-ion batteries evolve towards higher energy densities, anode materials are gradually shifting from traditional graphite to high-capacity silicon-based materials. However, silicon materials experience dramatic volume expansion (up to 300%-400%) during lithium insertion and extraction, leading to problems such as electrode structure damage, electrolyte wetting degradation, and electrode detachment, severely impacting cycle life and battery safety. Currently, silicon materials (such as silicon oxide or deposited silicon-carbon) are often combined with carbon materials (such as graphite) to find a balance between capacity and structural stability. On the one hand, a high proportion of silicon materials (such as silicon oxide or deposited silicon-carbon) can cause cumulative micro-expansion in the electrode, affecting its lifespan. On the other hand, traditional CMC / SBR binders have limited dispersion and interfacial synergy with the composite structure of silicon materials (such as silicon oxide or deposited silicon-carbon), making it difficult to alleviate stress concentration and material delamination problems. Summary of the Invention

[0003] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a negative electrode system combining silicon and carbon materials, specifically providing a negative electrode composition, negative electrode slurry, negative electrode sheet, cylindrical battery core, and battery. This negative electrode composition can reduce the interfacial resistance of the electrode sheet, improve adhesion strength, and suppress volume expansion, thereby achieving a balanced performance of lithium-ion batteries under long-life, high-stability cycling conditions.

[0004] As mentioned earlier, silicon materials undergo severe volume expansion (up to 300%-400%) during lithium insertion and extraction, leading to problems such as electrode structure damage, electrolyte wetting degradation, and electrode detachment, seriously affecting cycle life and battery safety. Currently, silicon materials (such as silicon oxide or deposited silicon-carbon) are often combined with carbon materials (such as graphite) to find a balance between capacity and structural stability. This invention has found that the combination of silicon materials (such as silicon oxide or deposited silicon-carbon) and carbon materials (such as graphite) still presents significant challenges in wound cells, especially cylindrical battery structures. Specifically, on the one hand, a high proportion of silicon oxide or deposited silicon-carbon can cause the accumulation of micro-expansion in the electrode under winding stress, resulting in stress concentration in the electrode tab welding area, delamination at the electrode boundary, and nonlinear collapse of the electrode center hole structure, affecting internal resistance, thermal behavior, and life stability. On the other hand, traditional CMC / SBR binders have limited dispersion and interfacial synergy for deposited silicon-carbon or silicon oxide and graphite composite structures, making it difficult to alleviate stress concentration and material delamination problems.

[0005] After in-depth research, the inventors of this invention proposed a structural optimization strategy based on siloxane-based functional additives, thereby providing a negative electrode composition. This composition can increase the electrode's resistance to expansion, structural integrity, and adhesion, and significantly suppress the collapse failure of the central hole in cylindrical cells. The reason for this is that the siloxane-based functional additives can, on the one hand, significantly improve the wetting and dispersibility between silicon materials and binders, constructing a compliant stress buffer network; on the other hand, through in-situ condensation reaction, they form three-dimensional crosslinks with CMC, enhancing the electrode's resistance to expansion, structural integrity, and adhesion, and significantly suppressing the collapse failure of the central hole in cylindrical cells.

[0006] Based on this, a first aspect of the present invention provides a negative electrode composition comprising a silicon material, a carbon material, a siloxane organic molecule, and a binder; wherein, based on the total mass of the negative electrode composition, the silicon material has a mass percentage content of 5%-30%; and the binder comprises a first binder comprising carboxymethyl cellulose.

[0007] A second aspect of the present invention provides a negative electrode slurry comprising a solvent and the negative electrode composition provided in the first aspect of the present invention.

[0008] A third aspect of the present invention provides a negative electrode sheet, comprising a negative electrode current collector and a negative electrode coating; wherein, a negative electrode coating area is provided on the surface of the negative electrode current collector, and the negative electrode coating is disposed on the surface of the negative electrode coating area; the negative electrode coating comprises the negative electrode composition provided in the first aspect of the present invention, or the negative electrode coating is a layer formed after drying the negative electrode slurry provided in the second aspect of the present invention.

[0009] A fourth aspect of the present invention provides a cylindrical battery core, comprising a positive electrode sheet, a separator, a negative electrode sheet, and a separator stacked sequentially in a wound manner to form a battery core; wherein the negative electrode sheet is the negative electrode sheet provided in the aforementioned third aspect of the present invention.

[0010] A fifth aspect of the present invention provides a battery comprising: case; A cylindrical battery core is disposed inside the housing; Electrolyte, wherein the electrolyte is disposed inside the housing; The cylindrical battery core is the cylindrical battery core provided in the fourth aspect of the present invention.

[0011] Through the above technical solution, the content of silicon material in the negative electrode composition of the present invention is first controlled, avoiding the defects of severe volume expansion and stress concentration caused by ultra-high silicon material content, which leads to structural instability. At the same time, the interaction between siloxane organic molecules and carboxymethyl cellulose can significantly improve the wetting and dispersibility between deposited silicon carbon or silicon material and binder, and construct a flexible stress buffer network. This can better increase the anti-expansion ability, structural integrity and adhesion of the electrode containing the negative electrode composition of the present invention. Especially when used in cylindrical battery cores, it can significantly suppress the collapse failure of the central hole of the cylindrical battery core. Attached Figure Description

[0012] Figure 1 The diagram shown is a cross-sectional view of the cylindrical battery core after assembly in some embodiments.

[0013] Figure 2 The diagram shown is a cross-sectional view of the assembled cell after the cylindrical battery core has been circulated 600 times in some embodiments.

[0014] Figure 3 The diagram shown is a schematic diagram of the negative electrode sheet in some embodiments.

[0015] Figure 4 The diagram shown is a schematic diagram of the positive electrode sheet in some embodiments.

[0016] Figure 5 The diagram shown is a three-dimensional schematic of the positive electrode, negative electrode, and separator winding of a cylindrical battery core in some embodiments.

[0017] Figure 6 The diagram shown is a cross-sectional view of the positive electrode, negative electrode, and separator winding of a cylindrical battery core in some embodiments.

[0018] Explanation of reference numerals in the attached figures Detailed Implementation The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0019] [Negative Electrode Composition] In a first aspect, in some embodiments, the present invention provides a negative electrode composition comprising a silicon material, a carbon material, a siloxane organic molecule, and a binder; wherein, based on the total mass of the negative electrode composition, the mass percentage of the silicon material is 5%-30%, for example, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, or any two of the above values; the binder comprises a first binder, the first binder comprising carboxymethyl cellulose.

[0020] In particular, the negative electrode composition of the present invention can be applied to lithium-ion cylindrical secondary batteries.

[0021] The negative electrode composition of this invention first controls the content of silicon material to avoid the defects of drastic volume expansion and stress concentration caused by excessively high silicon content, which leads to structural instability. Further research found that in the negative electrode composition of this invention, when the content of silicon material is too low, although the interface structure is relatively stable in the early stage, the electrode material has a weak response to charge and discharge capacity due to insufficient active material, resulting in a low capacity retention rate. The peel strength is also reduced due to the bonding and support capacity of the active material.

[0022] Furthermore, in this invention, through the synergistic interaction of carboxymethyl cellulose and siloxane organic molecules, and in combination with a specific amount of silicon material, the negative electrode composition, when applied to batteries, especially lithium-ion cylindrical secondary batteries, can effectively construct a silicon-based negative electrode system with good interfacial stability and cycle toughness. The specific amount of silicon material can form a relatively uniform network distribution in the negative electrode sheet and has a certain buffer porosity, which helps to alleviate stress concentration during lithiation / delithiation processes, while significantly improving the reversible capacity of the negative electrode sheet, thereby providing good lithium storage capacity and structural stability. The synergistic effect between particles and the synergistic composite with the binder helps to form a stable electron / ion transport network and flexible skeleton structure, which can improve the integrity of interfacial contact and cycle durability, thereby significantly reducing the interfacial resistance of the negative electrode sheet containing the negative electrode composition of this invention, improving adhesion strength, suppressing volume expansion and the degree of collapse of the central hole of the cylindrical cell, thereby achieving a balanced performance of lithium-ion batteries under long-life and high-stability cycling conditions.

[0023] Siloxane organic molecules In some embodiments, the siloxane organic molecules include at least one of trisiloxane alkoxylates (collectively referred to as TSA), hydroxyl-terminated polydimethylsiloxane, 3-aminopropyltriethoxysilane, and hexamethylcyclotrisiloxane, with trisiloxane alkoxylates being preferred.

[0024] In this invention, the aforementioned siloxane organic molecules, especially trisiloxane alkoxylates, can effectively improve the wetting and dispersibility between silicon materials and binders, construct a compliant stress buffer network, and thus significantly reduce the interfacial resistance of the negative electrode sheet containing the negative electrode composition of this invention, improve adhesion strength, suppress volume expansion and the degree of collapse of the central hole of the cylindrical cell, thereby achieving a balanced performance of lithium-ion batteries under long-life and high-stability cycling conditions.

[0025] In some embodiments, the trisiloxane alkoxylate includes at least one of heptamethyltrisiloxane propoxyethanol, trisiloxane ethoxylate, and tetrasiloxane ethoxylate, preferably heptamethyltrisiloxane propoxyethanol, wherein the structure of heptamethyltrisiloxane propoxyethanol is as follows: .

[0026] Further research in this invention has revealed that the use of trisiloxane alkoxylates, especially heptamethyltrisiloxane propoxyethanol, in synergy with other components in the negative electrode composition can better enhance the anti-expansion ability, structural integrity, and adhesion of the negative electrode sheet, and significantly suppress the collapse failure of the central hole of the cylindrical cell. The reason for this is that trisiloxane alkoxylates (TSA) have superwetting polyether side chains and trifunctional silicon oxide backbones, which can better improve the wetting and dispersibility between silicon materials and binders, construct a flexible stress buffer network, and can also form three-dimensional crosslinks with carboxymethyl cellulose (CMC) through in-situ condensation reaction.

[0027] The specific content of siloxane organic molecules in this invention is not particularly limited, as long as the purpose of this invention can be achieved. In some embodiments, based on the total mass of the negative electrode composition, the mass content of the siloxane organic molecules is 0.3%-2.1%, for example, 0.3%, 0.6%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.1%, or any two of the above ratios.

[0028] In this invention, controlling the content of siloxane-based organic molecules in the negative electrode composition within a suitable range can better achieve the optimal synergy of interfacial stability, mechanical support capability, and ion transport performance, thereby ensuring a comprehensive balance between cycle stability and structural safety. Siloxane-based organic molecules can effectively crosslink the silicon-oxygen structural units in the negative electrode sheet, forming a local three-dimensional framework through the network polymerization behavior of silicon-oxygen-silicon bonds. This framework can more uniformly fill the nano- and micro-pores between silicon material particles and construct auxiliary stress-bearing channels in the binder system. This synergistic network effectively improves the toughness and structural integrity of the electrode sheet, enhances the adhesion and traction between silicon material particles, binder, and current collector, and significantly reduces the shedding of active material during repeated cycling. Simultaneously, siloxane-based organic molecules can induce the formation of a more stable SEI film rich in organosilicon groups during the initial cycle, reducing side reactions, thereby lowering interfacial impedance and electrochemical polarization, and improving peel strength and capacity retention.

[0029] Furthermore, when the content of siloxane-based organic molecules is too low, the concentration of these molecules in the electrode is insufficient to form a continuous stress buffer network. Their intermolecular cross-linking density is low, and they mainly exist in a dispersed state within the gaps between a few particles. This makes it difficult to achieve effective stress dispersion and interface filling at the microscopic level, resulting in the negative electrode still being exposed to high volume expansion stress, leading to high interface resistance and unsatisfactory control of electrode expansion rate. When the content of siloxane-based organic molecules is too high, these molecules cannot be completely and uniformly dispersed, potentially forming partially enriched regions. These enriched regions typically have low electronic and ionic conductivity, introducing inactive barriers and hindering the uniform migration path of lithium ions within the electrode. Consequently, the overall mechanical and cycle performance may slightly decrease.

[0030] Silicon materials Silicon materials can improve battery energy density. In this invention, by controlling the component system of a specific negative electrode composition, the capacity and structural stability can be better balanced. As long as the purpose of this invention can be achieved, there are no special restrictions on the type of silicon material. In some embodiments, the silicon material includes at least one of deposited silicon carbon, silicon oxide, and pure silicon, preferably deposited silicon carbon.

[0031] The deposited silicon-carbon in this invention is achieved by combining silicon and carbon at the atomic / molecular level through chemical vapor deposition or similar physical vapor deposition (PVD) technology. The deposited silicon-carbon can be any known type of deposited silicon-carbon in the art, and this invention does not impose any special restrictions on it, so it will not be described in detail.

[0032] In this invention, the use of the aforementioned silicon material, especially deposited silicon-carbon, can better balance the capacity and structural stability of the battery containing the negative electrode composition of this invention.

[0033] carbon materials Carbon materials, as the main active material, can provide capacity and also provide a conductive network. In this invention, the carbon material can be any known carbon material in the art, as long as it can achieve the purpose of this invention. In some embodiments, the carbon material includes at least one of natural graphite, artificial graphite, soft carbon, and hard carbon.

[0034] In some embodiments, the carbon material has a mass percentage of 65%-90% based on the total mass of the negative electrode composition, for example, 65%, 70%, 75%, 80%, 85%, 90%, or any two of the above values.

[0035] In this invention, controlling the carbon material content within the above-mentioned range can, to a certain extent, provide mechanical support and expansion space for the silicon particles with huge volume expansion, and prevent the electrode structure from breaking.

[0036] adhesive In some embodiments, the adhesive further includes a second adhesive, the second adhesive comprising at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), and polymethacrylic acid (PMAA); preferably, the second adhesive comprises styrene-butadiene rubber (SBR).

[0037] In this invention, the negative electrode composition includes the above-mentioned binder, which is applied to the negative electrode slurry. The resulting negative electrode sheet has good conductivity and cycle stability, thus giving it excellent electrochemical performance when used in lithium-ion cylindrical secondary batteries.

[0038] In some embodiments, the mass ratio of the first adhesive to the second adhesive is 1:(0.6-2.5), for example, 1:0.6, 1:0.8, 1:1, 1:1.3, 1:1.5, 1:2, 1:2.5, or any range of two of the above ratios.

[0039] In this invention, the mass ratio of the first binder to the second binder is controlled within a suitable range so that when the negative electrode composition is applied to the negative electrode slurry, the prepared negative electrode sheet can have good conductivity and cycle stability, thereby giving it excellent electrochemical performance when used in lithium-ion cylindrical secondary batteries.

[0040] In some embodiments, the binder has a mass percentage of 1.4%-3.3% based on the total mass of the negative electrode composition, for example, 1.4%, 1.7%, 2%, 2.3%, 2.5%, 2.7%, 2.9%, 3.2%, 3.3%, or any range of two of the above values.

[0041] conductive agent In some embodiments, the negative electrode composition further includes a conductive agent.

[0042] In this invention, the negative electrode composition includes the above-mentioned conductive agent, so that when applied to the negative electrode slurry, the prepared negative electrode sheet can have good conductivity and cycle stability.

[0043] The aforementioned conductive agent may be any known conductive agent in the art, including but not limited to at least one of conductive carbon black (SuperP), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes, and acetylene black.

[0044] In some embodiments, the mass percentage of the conductive agent is 0.5%-2% based on the total mass of the negative electrode composition, for example, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, or 2%, and the specific content is not limited.

[0045] [Negative Electrode Slurry] According to a second aspect of the present invention, in some embodiments, the present invention also provides a negative electrode slurry, comprising a solvent and the negative electrode composition provided in the first aspect of the present invention.

[0046] The negative electrode slurry of this application includes the corresponding components of the negative electrode composition described above according to the present invention. Therefore, the slurry coating formed by coating it onto the negative electrode current collector has excellent adhesion, and the prepared negative electrode sheet has good capacity and cycle stability. When applied to secondary batteries, it can improve the cycle performance of secondary batteries.

[0047] Furthermore, the above-mentioned negative electrode slurry has excellent stability, which makes it easy to control the uniformity of the negative electrode slurry. In some embodiments, the viscosity change rate Δη of the negative electrode slurry does not exceed ±30% within 12 hours of standing.

[0048] In some embodiments, the solvent includes water, specifically, the solvent may include deionized water.

[0049] In some embodiments, the solid content of the negative electrode slurry is 45wt%-55wt%, for example, 45wt%, 50wt%, or 55wt%, and the specific content is not limited.

[0050] In this invention, controlling the solid content of the negative electrode slurry within a suitable range facilitates the control of the coating weight of the negative electrode slurry and the thickness of the negative electrode coating area, thereby enabling the negative electrode sheet to have a high capacity.

[0051] [Preparation method of negative electrode slurry] In some embodiments, the present invention also provides a method for preparing a negative electrode slurry, comprising: mixing the above-mentioned negative electrode composition with a solvent uniformly to obtain a negative electrode slurry.

[0052] The above mixing method is not particularly limited, as long as each component in the negative electrode composition can be mixed evenly with the solvent.

[0053] [Negative electrode plate] According to the invention, a third aspect, such as Figure 3 As shown, in some embodiments, the present invention also provides a negative electrode sheet 1, including a negative electrode current collector 11 and a negative electrode coating 111; wherein, a negative electrode coating area is provided on the surface of the negative electrode current collector 11, and the negative electrode coating 111 is disposed on the surface of the negative electrode coating area; the negative electrode coating 111 includes the negative electrode composition provided in the first aspect of the present invention, or the negative electrode coating 111 is a layer formed after drying the negative electrode slurry provided in the second aspect of the present invention.

[0054] In this invention, the negative electrode sheet 1 and the negative electrode coating 111 include the negative electrode composition of this invention, or are formed by drying the negative electrode slurry of this invention, and have an excellent bonding network, so that the negative electrode sheet 1 of this invention has comprehensive performance advantages such as low impedance, high adhesion, and low expansion, and is suitable for engineering applications of high energy density cylindrical cells.

[0055] Furthermore, the negative electrode 1 has excellent affinity and wettability with the electrolyte, which can better increase the initial formation efficiency, rate performance, cycle life and safety of the battery containing the negative electrode 1. In some embodiments, the initial contact angle between the negative electrode 1 and the electrolyte (EC / DME, v / v=1 / 1) is ≤30° and the complete diffusion time is ≤2s.

[0056] According to the present invention, the negative electrode coating area can be disposed on one surface or on both surfaces of the negative electrode current collector 11. As an example, the negative electrode coating area is disposed on opposite sides of the negative electrode current collector 11 along the thickness direction. Preferably, the two surfaces are disposed opposite each other and have the same size and other characteristics.

[0057] In this invention, both surfaces of the negative electrode current collector 11 can be entirely or partially configured as negative electrode coating areas. Preferably, both surfaces of the negative electrode current collector 11 are partially configured as negative electrode coating areas. That is, in some embodiments, a negative electrode uncoated area 112 is also provided on the surface of the negative electrode current collector 11. The negative electrode coating area is located on one long side of the negative electrode current collector 11 along the winding direction, and the negative electrode uncoated area 112 is located in the area outside the negative electrode coating area. The negative electrode uncoated area 112 is used to form a negative electrode tab after being cut, folded, or flattened. In other words, the negative electrode coating area is located on one long side of the negative electrode current collector 11 along the winding direction, and the negative electrode uncoated area 112 is located on the other long side of the negative electrode current collector 11 along the winding direction. The negative electrode coating area is used to coat the negative electrode coating 111, and the negative electrode uncoated area 112 is used to form a negative electrode tab after being cut, folded, or flattened.

[0058] According to the present invention, it can be understood that "along the winding direction" refers to the winding direction of the negative electrode sheet 1 when used in a lithium-ion cylindrical secondary battery; "negative electrode uncoated area 112" refers to the exposed negative electrode current collector 11, which is not provided with a negative electrode coating area.

[0059] In this invention, the size of the negative electrode coating area is not particularly limited and can be set according to the radial cross-sectional area of ​​the core of the subsequently prepared lithium-ion cylindrical secondary battery.

[0060] According to the present invention, the negative electrode current collector 11 can be any type in the art, such as a metal foil or a composite current collector (a composite current collector can be formed by setting a metal material on a polymer substrate). As an example, the negative electrode current collector 11 can be a copper foil.

[0061] In some embodiments, the compaction density of the negative electrode coating 111 is 1.35 g / cm³. 3 -1.75g / cm 3 For example, 1.35 g / cm³ 3 1.45g / cm 3 1.55g / cm 3 1.65g / cm 3 1.75g / cm 3 , or a range consisting of any two of the above values.

[0062] In this invention, controlling the compaction density of the negative electrode coating 111 within a suitable range can improve the stacking efficiency of the negative electrode active material and the compactness of the electron / ion conduction network, thereby optimizing the interface contact quality and electrode reaction kinetics.

[0063] Furthermore, when the compaction density is too low, the porosity of the negative electrode coating 111 is high, and the electron and ion migration paths are discontinuous, resulting in greater interfacial contact resistance, lower peel strength, and a tendency for structural loosening and active material shedding during cycling. Ultimately, this leads to an increase in the expansion rate of the negative electrode 1 and a lower capacity retention rate of the battery containing the negative electrode 1. While a high compaction density increases the volumetric energy density, the mechanical deformation of particles and uneven distribution of the binder during compaction cause an increase in internal stress in the negative electrode 1, leading to a rebound in interfacial resistance and a decrease in peel strength. Simultaneously, after long cycling, a higher electrode expansion rate and a greater degree of central pore collapse are observed, reflecting insufficient flexibility and reduced buffering capacity of the electrode structure.

[0064] The negative electrode coating 111 in this invention has a good conductive network, thereby having a low interface resistance. In some embodiments, the interface resistance R of the negative electrode 1 is low. α 3mΩ·cm 2 -11mΩ·cm 2 .

[0065] The negative electrode 1 in this invention has excellent structural integrity and adhesion. In some embodiments, the peel strength of the negative electrode 1 is 10 N / m-23.4 N / m.

[0066] It should be noted that the various parameter tests for the negative electrode coating 111 or the negative electrode sheet 1 mentioned above can be performed by sampling during the battery manufacturing process or by sampling from the manufactured battery.

[0067] [Cylindrical battery core] According to the present invention, such as Figures 5-6 As shown, in a fourth aspect, in some embodiments, the present invention also provides a cylindrical battery core, comprising a battery core formed by sequentially stacking a positive electrode 2, a separator 3, a negative electrode 1, and a separator 3 in a wound manner.

[0068] The cylindrical battery core of the present invention includes the aforementioned negative electrode sheet 1, which can significantly suppress the collapse failure of the center hole of the cylindrical battery core. For example, in some embodiments, after the cylindrical battery core is charged and discharged at 25°C for 600 cycles at a 1C rate, the degree of collapse of its center hole is <12%.

[0069] Negative electrode sheet The negative electrode 1 mentioned above in this invention is the negative electrode 1 provided in the third aspect of this invention.

[0070] In this invention, the cylindrical battery core includes the negative electrode sheet 1 mentioned above, which gives the cylindrical battery core comprehensive performance advantages such as low impedance, high adhesion, and low expansion. In cyclic use, it can reduce the defect of the central hole collapse failure of the cylindrical battery core.

[0071] In some embodiments, the surface of the negative electrode current collector 11 is provided with a negative electrode coated area and a negative electrode uncoated area 112. The negative electrode coated area is disposed on one long side of the negative electrode current collector 11 along the winding direction, and the negative electrode uncoated area 112 is disposed in the area outside the negative electrode coated area. The negative electrode uncoated area 112 is used to form a negative electrode tab after being cut, stacked or flattened. The radial cross-sectional area of ​​the cylindrical battery core is denoted as S1, and the area of ​​the negative electrode coated area on one surface of the negative electrode current collector 11 is denoted as S2. Wherein, S1 and S2 satisfy the following relationship: 0.3%≤S1 / S2*100%≤0.5%.

[0072] In this invention, controlling the ratio of S1 to S2 within a suitable range enables a more balanced distribution of internal forces in the core structure, which is beneficial for forming a strong interfacial bonding force and a stable electrode structure, reducing interfacial resistance, improving adhesion and cycle stability, and mitigating volume expansion and structural collapse.

[0073] Furthermore, when the ratio of S1 to S2 is too low, the area of ​​the negative electrode coating 111 is relatively large, resulting in a smaller gap in the center of the cell. This restricts stress release and electrolyte diffusion, easily leading to defects such as expansion stress concentration, interface detachment, increased resistance, and decreased peel strength in the negative electrode sheet 1. When the ratio of S1 to S2 is too high, the effective radial active area of ​​the core decreases, the electrode load decreases, and the energy density is limited. At the same time, insufficient negative electrode coating 111 leads to a local increase in current density, which in turn causes uneven electrode load, "over-lithiation" or peel failure in some areas, resulting in cycle life degradation. The cell is also more prone to loosening due to insufficient structural support, causing slight deformation of the central hole.

[0074] Positive electrode sheet like Figure 4 As shown, in some embodiments, the positive electrode sheet 2 includes a positive current collector 21 and a positive electrode coating 211 including a positive electrode active material. The surface of the positive current collector 21 is provided with a positive electrode coated area and a positive electrode uncoated area 212. The positive electrode coating 211 is disposed on the surface of the positive electrode coated area. The positive electrode coated area is disposed on one long side of the positive current collector 21 along the winding direction. The positive electrode uncoated area 212 is disposed in the area outside the positive electrode coated area. The positive electrode uncoated area 212 is formed into a positive electrode tab after being cut, stacked or flattened.

[0075] According to the present invention, it can be understood that "positive electrode uncoated area 212" refers to the exposed positive electrode current collector 21, which is not provided with a positive electrode coating area.

[0076] In some embodiments, the area of ​​the positive electrode coating region on one surface of the positive electrode current collector 21 is denoted as S3, and S2 and S3 satisfy the following relationship: 1 < S2 / S3 ≤ 1.07, for example, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, or a range of any two of the above values, preferably 1.02-1.04.

[0077] In this invention, controlling the ratio of S2 / S3 within the above range ensures that the negative electrode 1 wraps around the positive electrode 2 to prevent lithium plating, thereby better increasing the cycle stability and other performance of the battery core.

[0078] According to the present invention, the positive electrode coating area can be disposed on one surface or on both surfaces of the positive electrode current collector 21. As an example, the positive electrode coating area is disposed on opposite sides of the positive electrode current collector 21 along the thickness direction. Preferably, the two surfaces are disposed opposite each other and have the same size and other characteristics.

[0079] In some embodiments, a positive electrode uncoated region 212 is further provided on the surface of the positive electrode current collector 21. The positive electrode coated region is located on one long side of the positive electrode current collector 21 along the winding direction, and the positive electrode uncoated region 212 is located in the area outside the positive electrode coated region. The positive electrode uncoated region 212 is used to form a negative electrode tab after being cut, stacked, or flattened. That is, the positive electrode coated region is located on one long side of the positive electrode current collector 21 along the winding direction, and the positive electrode uncoated region 212 is located on the other long side of the positive electrode current collector 21 along the winding direction. The positive electrode coated region is used to coat the positive electrode coating 211, and the positive electrode uncoated region 212 is used to form a positive electrode tab after being cut, stacked, or flattened.

[0080] In the battery of the present invention, the positive electrode active material may be a known positive electrode active material for batteries, such as lithium nickel cobalt manganese oxide (LiNiO2). x Co y Mn z M b O2), where x+y+z+b=1, and element M includes one or more of zirconium (Zr), tungsten (W), titanium (Ti), aluminum (Al), strontium (Sr), boron (B), and neodymium (Nd). This invention is not limited to the above-mentioned positive electrode active material; other conventionally known materials that can be used as positive electrode active materials in batteries can also be used.

[0081] In the battery of the present invention, the positive electrode coating 211 typically comprises a positive electrode active material, as well as an optional positive electrode binder and an optional positive electrode conductive agent.

[0082] As an example, positive electrode conductive agents include, but are not limited to, conductive carbon black and / or carbon nanotubes.

[0083] As an example, positive electrode binders include, but are not limited to, polyvinylidene fluoride (PVDF) or its derivatives.

[0084] In this invention, the specific amounts of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent can be the amounts conventional in the art. As an example, the mass ratio of the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent is 96:2:2.

[0085] According to the present invention, the positive electrode coating 211 is typically formed by coating a positive electrode slurry onto the positive electrode coating area of ​​the positive electrode current collector 21, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional positive electrode binder, and an optional positive electrode conductive agent in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. The positive electrode current collector 21 may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used.

[0086] diaphragm The membrane primarily serves to prevent short circuits between the positive and negative electrodes, while also allowing active ions to pass through. As long as the purpose of this invention is achieved, there are no special limitations; any known porous membrane with good chemical and mechanical stability can be selected. Generally, a membrane with high porosity (typically 40%-60%) can be used.

[0087] As an example, the diaphragm has: a base membrane of polyethylene (PE) with a thickness of 9.0 μm, and a porous coating structure with a ceramic coating and a polyvinylidene fluoride (PVDF) coating sequentially disposed on both sides of the base membrane; the ceramic coating has a thickness of 1.0 μm and the polyvinylidene fluoride (PVDF) coating has a thickness of 1.0 μm.

[0088] [Battery] According to a fifth aspect of the present invention, in some embodiments, the present invention also provides a battery comprising: case; A cylindrical battery core is disposed inside the housing; Electrolyte, wherein the electrolyte is disposed inside the housing; The cylindrical battery core is the cylindrical battery core provided in the fourth aspect of the present invention.

[0089] The preferred lithium-ion cylindrical secondary battery provided in this invention comprises the cylindrical battery core provided in the fourth aspect of this invention, thereby enabling the battery to have excellent interface stability and cycle life. Specifically, in some embodiments, the battery retains no less than 85% of its capacity after 600 charge-discharge cycles at 25°C and a 1C rate.

[0090] In this invention, the battery can be assembled according to conventional methods in the art. For example, the prefabricated connecting piece of the cylindrical battery core is fixed by welding and installed into the casing. After completing key processes such as electrolyte injection, sealing and formation, the battery is obtained. The prefabricated connecting piece can be prepared according to methods known in the art. As an example, specifically, the prefabricated connecting piece can be a nickel-steel composite material. The connection method is as follows: one end is fixed to the positive electrode tab / negative electrode tab of the core by laser welding, and the other end is fixed to the top electrode cap (positive electrode) of the battery by laser welding.

[0091] electrolyte According to the present invention, as long as the purpose of the present invention can be achieved, the present invention does not have a special limitation on the specific type of electrolyte. In some embodiments, the electrolyte is a lithium-ion electrolyte.

[0092] As an example, a lithium-ion electrolyte includes a lithium salt, a solvent, and additives. The lithium salt includes, but is not limited to, 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, but is not limited to, one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate; the additives include, but are not limited to, one or more of fluoroethylene carbonate, difluoroethylene carbonate, ethylene sulfate, ethylene sulfite, vinylene carbonate, and vinyl carbonate.

[0093] As an example, the electrolyte may be ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), lithium hexafluorophosphate, vinylene carbonate (VC), and fluoroethylene carbonate (FEC) in a mass ratio of 25:25:25:14.5:6:4.5.

[0094] The preparation method of the electrolyte is not particularly limited in this invention, as long as the components in the electrolyte are mixed evenly. Optionally, the components can be filtered after mixing to remove trace particulate impurities.

[0095] As an example, the preparation of the electrolyte includes: first, stirring the solvent at 200 rpm-400 rpm for 20-60 minutes in an argon glove box to form a homogeneous solvent system; then, slowly dissolving the lithium salt at a controlled temperature of <10℃ to avoid local overheating and decomposition of the lithium salt; after complete dissolution, adding the additives one by one, increasing the stirring rate to 500 rpm-800 rpm for 1-5 hours to ensure molecular-level dispersion of the additives; finally, removing trace particulate impurities by pressure filtration through a 0.2 μm PTFE filter membrane, thus obtaining an electrolyte with high stability and synergistic film-forming effect.

[0096] The casing in this invention can be a hard casing or a soft casing. Optionally, the casing is a hard casing, specifically a metal battery casing.

[0097] In the context of this specification, including the following embodiments and comparative examples, tests were conducted as follows: 1. Method for measuring electrode contact angle: The electrolyte (EC / DME, volume ratio 1:1) was added dropwise at 10 μL to the surface of the negative electrode, and the contact angle between the droplet and the electrode surface was recorded using a contact angle meter. The complete diffusion time was monitored using a high-resolution camera to determine the time required for the droplet to spread and fully wet the electrode surface, and it was required to be no more than 2 seconds to ensure good wettability and rapid wetting ability of the electrode surface to the electrolyte.

[0098] 2. Test method for compacted density of negative electrode sheet: 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 negative electrode coating (negative electrode coated area) on both sides of three of these square samples was removed, rinsed with ethanol, dried, weighed, and the average mass M1 was calculated. Simultaneously, the average thickness L1 of the sample was measured using a micrometer. Then, the mass of the remaining three square samples was weighed, and the average mass M2 was calculated. The average thickness L2 of the sample 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 .

[0099] 3. Method for testing the interface resistance of the negative electrode: The film resistance of the negative electrode was determined using the 46-probe method (45 probes arranged in a square matrix, with one probe serving as a ground probe) of the RM2610 resistance testing system. The sample was placed on the testing apparatus, and the pressure applied to the probes was adjusted using a pressure gauge to ensure good contact between the probes and the sample, with a contact area of ​​0.01 cm². 2 During the test, a constant current was applied to the 20 peripheral probes, allowing the current to flow through the surface, interface, and current collector of the negative electrode. Simultaneously, the 25 central probes measured the voltage change in real time. Finally, the membrane resistance was calculated using Ohm's law and fitting analysis. Nine square grids were randomly selected from the front, middle, and rear sections of the electrode for membrane resistance measurement, and the obtained values ​​were recorded as R1, R2, R3, R4, R5, R6, R7, R8, and R9, respectively. Finally, the arithmetic mean of these values ​​was calculated to obtain the average membrane resistance R of the actual tested negative electrode (R = (R1 + R2 + R3 + R4 + R5 + R6 + R7 + R8 + R9) / 9).

[0100] 4. Test method for peel strength of negative electrode sheet: First, use double-sided tape to fix the strip sample onto a flat, thin steel plate, ensuring the tape is centered on the plate. Then, peel off the protective layer of the double-sided tape and attach the strip sample of the negative electrode to be tested onto the tape. Use a pressure roller to evenly press the strip sample to ensure good adhesion. Next, tear off the unattached end, bend the torn negative electrode sheet upwards, and clamp it in the upper fixture of a tensile testing machine for a 180° peel test. Record the tensile force curve. The segment where the tensile force changes by no more than 10% is selected as the stable peel segment. Finally, divide the average tensile force of this segment by the width of the strip sample electrode to calculate the peel strength of the negative electrode. Peel force tests are conducted on the front, middle, and back segments of the electrode, and the obtained values ​​are recorded as N1, N2, and N3, respectively. Finally, the arithmetic mean of these values ​​is calculated to obtain the average peel force N of the actual tested negative electrode (N = (N1 + N2 + N3) / 3).

[0101] 5. Cyclic performance testing method: Place the battery in a 25°C constant temperature chamber for 6 hours and test it according to the following steps: (1) 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.

[0102] (2) Let it stand for 30 minutes after charging is complete.

[0103] (3) Perform constant current discharge, and discharge to 2.5V at a rate of 0.1C.

[0104] (4) Cyclic charge and discharge process: Charge at a constant current rate of 1C to 4.2V. Let stand for 30 minutes again. Discharge at a constant current rate of 1C to 2.5V.

[0105] (5) Repeat the above charging and discharging process for a total of 600 cycles.

[0106] Statistical analysis of the battery discharge capacity Q1 and Q after 1 cycle and 600 cycles. 600 Calculate the battery capacity decay rate: (Q1-Q 600 ) / Q1×100%.

[0107] 6. Method for determining the expansion rate of the negative electrode after 600 cycles: Take the battery that has undergone 600 cycles and obtain a dry and clean negative electrode sheet according to the pretreatment steps. Measure the thickness of the electrode sheet at nine points using a micrometer and take the average value, i.e., T. 600 Electrode expansion rate = (T) 600 -T0) / T 600 ×100%, where T0 is the initial thickness of the dried electrode before cycling, T600 The thickness of the electrode after 600 cycles of washing and drying with dimethyl carbonate.

[0108] The pretreatment steps are as follows: 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. Inside a glove box (protected by argon or other inert atmosphere), the battery is carefully disassembled, and the positive electrode of the cylindrical cell is removed. The negative electrode is peeled off using tweezers or a suitable tool, taking care not to damage the negative electrode coating. Next, the removed negative electrode is cut to an appropriate size and immersed in anhydrous dimethyl carbonate (DMC) solution for 30 minutes to dissolve and remove residual electrolyte and possible byproducts. After removing the negative electrode, the surface is gently wiped with lint-free paper, and then the DMC solution is replaced. This immersion-wiping process is repeated three times to ensure no residual contaminants remain on the electrode surface. Subsequently, the electrode is rinsed with anhydrous ethanol and wiped again to further remove solvent and impurities. After cleaning, the electrode is placed in a glove box and left to stand for 48 hours to ensure it is completely dry, preventing interference from residual solvent in subsequent testing.

[0109] 7. Method for determining the degree of collapse of the center hole of a cylindrical battery core after 600 cycles: After the cylindrical battery core was assembled, its initial outer diameter radius and the inner diameter radius of the central hole were measured using X-ray CT technology. Subsequently, the cylindrical battery core was charged and discharged at 25°C at a 1C rate for 600 cycles, and the outer and inner diameter radii were measured again after 600 cycles. The degree of central hole collapse = | |×100%, T=initial outer radius - initial inner radius, T =Outer radius after cycling - Inner radius after cycling. A schematic diagram of the cross-section of the assembled cylindrical battery core is shown below. Figure 1 As shown, the cross-sectional structure of the cylindrical battery core after 600 cycles and subsequent assembly is illustrated in the diagram. Figure 2 As shown.

[0110] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0111] Example 1 1. Method for manufacturing positive electrode sheets: like Figure 4 As shown, the positive electrode 2 includes a positive current collector 21 (aluminum foil) and a positive electrode coating 211 coated on both sides of the aluminum foil, wherein, A positive electrode coating area 211 is provided on one long side of the positive electrode current collector 21 along the winding direction, and a positive electrode uncoated area 212 is provided on the other long side of the positive electrode current collector 21 along the winding direction. The positive electrode uncoated area 212 is located in the area outside the positive electrode coating area. The area of ​​the positive electrode coating area on one surface of the positive electrode current collector 21 is denoted as S3. Take positive electrode active material (LiNi) 0.8 Co 0.1 Mn 0.1 O2), 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 211 material. The positive electrode coating 211 material was then coated onto a 12.0 μm thick aluminum foil, and after drying and cold pressing, a positive electrode sheet 2 with positive electrode coating 211 was obtained.

[0112] 2. Method for manufacturing negative electrode plate 1: like Figure 3 As shown, the negative electrode sheet 1 includes a negative current collector 11 (copper foil) and a negative electrode coating 111 coated on both sides of the copper foil. The negative current collector 11 has a negative electrode coated area with the negative electrode coating 111 on one long side along the winding direction, and a negative electrode uncoated area 112 on the other long side along the winding direction. The negative electrode uncoated area 112 is located in the area outside the negative electrode coated area. The area of ​​the negative electrode coated area on one surface of the negative current collector 11 is denoted as S2. The negative electrode coating 111 material, calculated by mass percentage, comprises 15.0% deposited silicon carbon, 80.0% artificial graphite, 0.75% SWCNT, 0.75% Super P, 1.0% sodium carboxymethyl cellulose (CMC), 1.3% styrene-butadiene rubber (SBR), and 1.2% heptamethyltrisiloxane propoxyethanol. These substances are added to deionized water and stirred to form a negative electrode slurry with a solid content of 50 wt%. This slurry is then coated on both sides of the negative electrode current collector (copper foil). After drying and rolling, negative electrode sheet 1 is prepared with a compaction density of 1.55 g / cm³. 3 .

[0113] 3. Preparation of electrolyte: In an argon-filled glove box, high-purity ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were first mixed at a mass ratio of 25.0%:25.0%:25.0% and stirred at 300 rpm for 30 minutes to form a homogeneous solvent system. Then, 14.5 wt% of LiPF6 was slowly added under controlled temperature conditions (<10℃) to avoid local overheating and decomposition of the lithium salt. After complete dissolution, 6.0 wt% of vinylene carbonate (VC) and 4.5 wt% of fluoroethylene carbonate (FEC) were added sequentially, and the stirring rate was increased to 600 rpm and maintained for 2 hours to ensure molecular-level dispersion of the additives. Finally, the electrolyte was filtered under pressure through a 0.2 μm PTFE membrane to remove trace particulate impurities, thus obtaining an electrolyte with high stability and synergistic film-forming effect.

[0114] 4. Diaphragm: The base film is made of polyethylene (PE) with a thickness of 9.0 μm. A porous coating structure is formed on both sides of the base film, consisting of a ceramic coating and a polyvinylidene fluoride (PVDF) coating. The ceramic coating has a thickness of 1.0 μm and the polyvinylidene fluoride (PVDF) coating has a thickness of 1.0 μm.

[0115] 5. Battery assembly: After the positive electrode 2 and negative electrode 1 are respectively rolled and slit, they are wound together with the separator 3 according to the set process. Specifically, the positive electrode 2, separator 3, negative electrode 1, and separator 2 are sequentially stacked and wound to form a 21700 cylindrical battery core. The winding structure diagram is shown below. Figure 5 and Figure 6 As shown; where S1 / S2*100% is set to 0.4%, S2 / S3 to 1.03, and S1 is the radial cross-sectional area of ​​the 21700 cylindrical battery core. Subsequently, the cylindrical battery core is fixed to the pre-fabricated connecting piece by welding and then installed into a metal battery casing. After completing key processes such as electrolyte injection, sealing, and formation, the battery described in Example 1 is obtained. This 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.

[0116] The results of the electrode interface resistance, electrode peel strength, expansion rate of negative electrode 1 after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and cycle performance of the battery are shown in Table 1.

[0117] Example 2 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of heptamethyltrisiloxane propoxyethanol in the negative electrode coating material is 0.3 wt%, and the content of sodium carboxymethyl cellulose (CMC) is 1.9 wt%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0118] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0119] Example 3 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of heptamethyltrisiloxane propoxyethanol in the negative electrode coating material is 0.6 wt%, and the content of sodium carboxymethyl cellulose (CMC) is 1.6 wt%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0120] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0121] Example 4 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of heptamethyltrisiloxane propoxyethanol in the negative electrode coating material is 1.8 wt%, and the content of sodium carboxymethyl cellulose (CMC) is 0.4 wt%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0122] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0123] Example 5 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of heptamethyltrisiloxane propoxyethanol in the negative electrode coating material is 2.1 wt%, the content of sodium carboxymethyl cellulose (CMC) is 0.4 wt%, and the content of styrene-butadiene rubber (SBR) is 1.0 wt%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0124] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0125] Example 6 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of deposited silicon carbon in the negative electrode coating material is 5 wt%, and the content of artificial graphite is 90%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0126] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0127] Example 7 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of deposited silicon carbon in the negative electrode coating material is 10 wt%, and the content of artificial graphite is 85%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0128] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0129] Example 8 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of deposited silicon carbon in the negative electrode coating material is 20 wt%, and the content of artificial graphite is 75%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0130] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0131] Example 9 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of deposited silicon carbon in the negative electrode coating material is 25 wt%, and the content of artificial graphite is 70%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0132] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0133] Example 10 Following the method of Example 1, the difference between this example and Example 1 is that the compaction density of the negative electrode sheet is 1.35 g / cm³. 3 ; Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0134] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0135] Example 11 Following the method of Example 1, the difference between this example and Example 1 is that the compaction density of the negative electrode sheet is 1.45 g / cm³. 3 ; Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0136] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0137] Example 12 Following the method of Example 1, the difference between this example and Example 1 is that the compaction density of the negative electrode sheet is 1.65 g / cm³. 3 ; Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0138] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0139] Example 13 Following the method of Example 1, the difference between this example and Example 1 is that the compaction density of the negative electrode sheet is 1.75 g / cm³. 3 ; Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0140] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0141] Example 14 The difference between this embodiment and Embodiment 1 is that S1 / S2*100% is set to 0.3% to form a 21700 cylindrical battery core; Everything else was the same as in Example 1, and the battery was finally prepared.

[0142] The results of the negative electrode sheet expansion rate, the degree of collapse of the central hole of the cylindrical battery core, and the cycle performance of the battery after 600 cycles are shown in Table 1.

[0143] Example 15 The difference between this embodiment and Embodiment 1 is that S1 / S2*100% is set to 0.35% to form a 21700 cylindrical battery core. Everything else was the same as in Example 1, and the battery was finally prepared.

[0144] The results of the negative electrode sheet expansion rate, the degree of collapse of the central hole of the cylindrical battery core, and the cycle performance of the battery after 600 cycles are shown in Table 1.

[0145] Example 16 The difference between this embodiment and Embodiment 1 is that S1 / S2*100% is set to 0.45% to form a 21700 cylindrical battery core. Everything else was the same as in Example 1, and the battery was finally prepared.

[0146] The results of the negative electrode sheet expansion rate, the degree of collapse of the central hole of the cylindrical battery core, and the cycle performance of the battery after 600 cycles are shown in Table 1.

[0147] Example 17 The difference between this embodiment and Embodiment 1 is that S1 / S2*100% is set to 0.5% to form a 21700 cylindrical battery core; Everything else was the same as in Example 1, and the battery was finally prepared.

[0148] The results of the negative electrode sheet expansion rate, the degree of collapse of the central hole of the cylindrical battery core, and the cycle performance of the battery after 600 cycles are shown in Table 1.

[0149] Example 18 The difference between this embodiment and Embodiment 1 is that S2 / S3 is set to 1.02 to form a 21700 cylindrical battery core, following the method of Embodiment 1. Everything else was the same as in Example 1, and the battery was finally prepared.

[0150] The results of the negative electrode sheet expansion rate, the degree of collapse of the central hole of the cylindrical battery core, and the cycle performance of the battery after 600 cycles are shown in Table 1.

[0151] Example 19 The difference between this embodiment and Embodiment 1 is that S2 / S3 is set to 1.04 to form a 21700 cylindrical battery core; Everything else was the same as in Example 1, and the battery was finally prepared.

[0152] The results of the negative electrode sheet expansion rate, the degree of collapse of the central hole of the cylindrical battery core, and the cycle performance of the battery after 600 cycles are shown in Table 1.

[0153] Example 20 The method of Example 1 is followed, but the difference between this example and Example 1 is that heptamethyltrisiloxane propoxyethanol is replaced with hydroxyl-terminated polydimethylsiloxane. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0154] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0155] Example 21 The method of Example 1 is followed, but the difference between this example and Example 1 is that heptamethyltrisiloxanepropoxyethanol is replaced with hexamethylcyclotrisiloxane. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0156] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0157] Comparative Example 1 The method of Example 1 is followed, but the difference between this example and Example 1 is that 1.2 wt% of heptamethyltrisiloxane propoxyethanol in the negative electrode coating material is replaced with 1.2 wt% styrene-butadiene rubber (SBR), that is, 2.5% styrene-butadiene rubber (SBR) is added.

[0158] Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0159] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0160] Comparative Example 2 The method of Example 1 is followed, but the difference between this example and Example 1 is that the content of deposited silicon carbon in the negative electrode coating material is 50 wt%, and the content of artificial graphite is 45%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0161] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0162] Comparative Example 3 The method of Example 1 is followed, but the difference between this example and Example 1 is that 1.0 wt% of sodium carboxymethyl cellulose (CMC) in the negative electrode coating material is replaced with 1.0 wt% of styrene-butadiene rubber (SBR), that is, no CMC is added, and the amount of styrene-butadiene rubber (SBR) added is 2.3%. Everything else is the same as in Example 1, and the negative electrode sheet and the corresponding battery are finally prepared.

[0163] The results of the negative electrode interface resistance, electrode peel strength, negative electrode expansion rate after 600 cycles, degree of collapse of the central hole of the cylindrical battery core after 600 cycles, and battery cycle performance are shown in Table 1.

[0164] Table 1. Test results from the examples and comparative examples. The results from the examples and comparative examples show that, through the synergistic effect of siloxane-based organic molecules and CMC, and by precisely controlling the silicon material content, the present invention can effectively suppress the volume expansion of the silicon anode and improve interface stability and cycle life. Specifically, in Comparative Example 1, without the addition of siloxane-based organic molecules, the electrode expansion rate and the degree of central pore collapse increased significantly after cycling, resulting in a final interface resistance as high as 9.5 mΩ·cm. 2The capacity retention rate was only 55.4%, reflecting severe active particle detachment and a loose structure. The reason for this was the lack of added siloxane organic molecules, resulting in the electrode lacking an effective structural buffer and interface stabilization mechanism. Comparative Example 2 used an abnormally high content (50wt%) of deposited silicon-carbon material, which caused severe volume expansion and stress concentration, leading to structural instability. After 600 cycles, the capacity retention rate further decreased to 53.2%, the expansion rate reached 24.5%, and the pore collapse was the most severe (25.9%), making it difficult to meet the high reliability cycling requirements. Although Comparative Example 3 added siloxane organic molecules, it did not use CMC, and the binder used was entirely SBR. After cycling, the electrode expansion rate and the degree of central pore collapse increased significantly, and the final interface resistance reached as high as 12.3 mΩ·cm. 2 The capacity retention rate was only 50.1%.

[0165] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A negative electrode composition, characterized in that, The composition includes silicon material, carbon material, siloxane organic molecules, and binder; wherein, based on the total mass of the negative electrode composition, the mass percentage of silicon material is 5%-30%; the binder includes a first binder, which includes carboxymethyl cellulose.

2. The negative electrode composition according to claim 1, wherein, The siloxane organic molecules include at least one of trisiloxane alkoxylates, hydroxyl-terminated polydimethylsiloxanes, 3-aminopropyltriethoxysilanes, and hexamethylcyclotrisiloxanes. And / or, the silicon material includes at least one of deposited silicon carbon, silicon oxide, and pure silicon; And / or, the carbon material includes at least one of natural graphite, artificial graphite, soft carbon, and hard carbon; And / or, the adhesive further includes a second adhesive, the second adhesive comprising at least one of styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, and polymethacrylic acid; And / or, the negative electrode composition further includes a conductive agent; And / or, based on the total mass of the negative electrode composition, the mass content of the siloxane organic molecules is 0.3%-2.1%; And / or, based on the total mass of the negative electrode composition, the carbon material has a mass percentage of 65%-90%; And / or, based on the total mass of the negative electrode composition, the binder has a mass percentage content of 1.4%-3.3%.

3. The negative electrode composition according to claim 2, wherein, The trisiloxane alkoxylates include at least one of heptamethyltrisiloxane propoxyethanol, trisiloxane ethoxylate, and tetrasiloxane ethoxylate; And / or, the mass ratio of the first adhesive to the second adhesive is 1:(0.6-2.5); And / or, the conductive agent includes at least one of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, and acetylene black; And / or, based on the total mass of the negative electrode composition, the mass percentage of the conductive agent is 0.5%-2%.

4. A negative electrode slurry, characterized in that, Includes solvent and negative electrode composition; The solvent includes water, and the negative electrode composition includes the negative electrode composition according to any one of claims 1-3.

5. A negative electrode sheet, characterized in that, Including negative electrode current collector and negative electrode coating; The surface of the negative electrode current collector is provided with a negative electrode coating area, and the negative electrode coating is disposed on the surface of the negative electrode coating area; The negative electrode coating comprises the negative electrode composition according to any one of claims 1-3, or the negative electrode coating is a layer formed after drying the negative electrode slurry according to claim 4.

6. The negative electrode sheet according to claim 5, wherein, The surface of the negative electrode current collector is also provided with a negative electrode uncoated area. The negative electrode coated area is provided on one long side of the negative electrode current collector along the winding direction. The negative electrode uncoated area is provided in the area outside the negative electrode coated area. The negative electrode uncoated area is used to form a negative electrode tab after being cut, stacked or flattened. And / or, the compaction density of the negative electrode coating is 1.35 g / cm³. 3 -1.75g / cm 3 .

7. A cylindrical battery core, characterized in that, The battery cell is formed by sequentially stacking positive electrode plates, separators, negative electrode plates, and separators in a wound manner. The negative electrode sheet includes the negative electrode sheet as described in claim 5 or 6.

8. The cylindrical battery core according to claim 7, wherein, The surface of the negative electrode current collector is provided with a negative electrode coated area and a negative electrode uncoated area. The negative electrode coated area is located on one long side of the negative electrode current collector along the winding direction, and the negative electrode uncoated area is located in the area outside the negative electrode coated area. The negative electrode uncoated area is used to form a negative electrode tab after being cut, stacked or flattened. The radial cross-sectional area of ​​the cylindrical battery core is denoted as S1, and the area of ​​the negative electrode coated area on one surface of the negative electrode current collector is denoted as S2. Wherein, S1 and S2 satisfy the following relationship: 0.3%≤S1 / S2*100%≤0.5%.

9. The cylindrical battery core according to claim 8, wherein, The positive electrode sheet includes a positive current collector and a positive electrode coating including a positive active material. The surface of the positive current collector is provided with a positive electrode coated area and a positive electrode uncoated area. The positive electrode coating is disposed on the surface of the positive electrode coated area. The positive electrode coating area is located on one long side of the positive electrode current collector along the winding direction, and the positive electrode uncoated area is located in the area outside the positive electrode coating area. The positive electrode uncoated area is formed into a positive electrode tab after being cut, stacked or flattened. Let S3 be the area of ​​the positive electrode coating region on one surface of the positive electrode current collector. S2 and S3 satisfy the following relationship: 1 < S2 / S3 ≤ 1.

07.

10. A battery, characterized in that, include: case; A cylindrical battery core is disposed inside the housing; Electrolyte, wherein the electrolyte is disposed inside the housing; Wherein, the cylindrical battery core is the cylindrical battery core as described in claim 8 or 9.

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