CN115719795A - Secondary battery - Google Patents
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- CN115719795A CN115719795A CN202211481382.5A CN202211481382A CN115719795A CN 115719795 A CN115719795 A CN 115719795A CN 202211481382 A CN202211481382 A CN 202211481382A CN 115719795 A CN115719795 A CN 115719795A
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The invention belongs to the technical field of secondary batteries, and particularly relates to a secondary battery which comprises a positive plate and a negative plate, wherein the positive plate comprises a positive current collector and positive coatings arranged on the two side surfaces of the positive current collector, the negative plate comprises a negative current collector and negative coatings arranged on the two side surfaces of the negative current collector, and the pore cross sections and the surface densities of the positive plate and the negative plate meet a correlation formula. According to the secondary battery, the pore section and the surface density of the coating of the positive plate and the negative plate are designed, so that the positive plate and the negative plate are better matched in performance and have better specific discharge capacity and discharge efficiency.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a secondary battery.
Background
With the demand of human science and technology development and a series of energy problems, people put higher demands on portable power sources and energy storage, particularly large-scale energy storage systems and new energy automobiles. The lithium ion battery has the advantages of high energy density, high working voltage, long cycle life, low self-discharge rate and the like, and has strong competitive advantages. Therefore, it is very important to develop a lithium ion battery having excellent overall performance. The negative electrode material is an important part of a lithium ion battery, and the development of a high-performance negative electrode material is one of the prerequisites for producing lithium ions with excellent performance.
The silicon-based oxide (SiOx, x is more than 0 and less than or equal to 2) is used as the negative electrode material of the lithium ion battery, has the advantages of proper lithium intercalation potential, high theoretical specific capacity, environmental protection, no pollution, abundant natural resources and the like, and has wide application prospect in the field of novel lithium ion batteries. At present, in a method for preparing a silicon-containing negative electrode material, for example, a silicon-carbon composite negative electrode material is prepared by compounding a silicon-based oxide and graphite-like carbon, the composite negative electrode material can effectively improve the electrochemical properties of silicon dioxide and silicon, the existence of the graphite-like carbon can also buffer the volume change, and meanwhile, the storage capacity of lithium is also improved.
When a high-performance battery is developed, particularly when a silicon-carbon composite negative electrode material containing silicon-based oxide and graphite is considered, the high-performance battery is different from a single silicon-based negative electrode material, and the pole piece structures prepared from the silicon-based oxide and graphite-carbon composite negative electrode material are definitely different, so that the design requirements are different; the important functions of the anode plate structure include the coating pore section, the surface density and other factors of the anode plate and the cathode plate, and the relationship between the coating pore section and the surface density of the anode plate and the cathode plate, especially the matching degree of the coating pore section and the surface density of the anode plate and the cathode plate, the stability of the coating microscopic structure, the interlayer deformation, the final battery discharge specific capacity, the discharge efficiency and the like is large, so that if a lithium ion battery with good battery performance is designed, how to reasonably match the pore section and the surface density between the coating layers of the anode plate and the cathode plate becomes a key.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the secondary battery is provided, and the pore section and the surface density of the coating of the positive plate and the negative plate are designed, so that the matching performance of the positive plate and the negative plate is better, and the secondary battery has better discharge specific capacity and discharge efficiency.
In order to achieve the purpose, the invention adopts the following technical scheme:
the utility model provides a secondary battery, includes positive plate and negative pole piece, the positive plate includes the anodal mass flow body and sets up in the anodal coating on the anodal mass flow body both sides surface, the negative pole piece include the negative pole mass flow body and set up in the negative coating on the negative pole mass flow body both sides surface, the positive plate with the negative pole piece satisfies following relational expression:
wherein n is the number of layers of the positive plate; m is the number of layers of the negative plate;
wherein S1 is a ratio of void cross-sectional area per unit area of cross-section of the coating layer on the positive electrode sheet in the secondary battery 0% DOD;
wherein S2 is a ratio of void cross-sectional area per unit area of cross-section of the coating layer on the positive electrode sheet in the secondary battery by 100% DOD;
wherein S3 is a ratio of pore cross-sectional area to pore cross-sectional area per unit area of the coating layer cross-section on the negative electrode sheet when the secondary battery is 100% DOD;
wherein S4 is a ratio of pore cross-sectional area to pore cross-sectional area per unit area of the coating layer cross-section on the negative electrode sheet when the secondary battery is 0%;
the surface density of the positive coating is a, the surface density of the negative coating is b, and the positive coating and the negative coating satisfy the following relational expression: 0.52 is less than or equal to ㏒ a/㏒ b is less than or equal to 1.33.
Preferably, the surface density of the positive electrode coating is 0.005-0.032 g/cm 2 。
Preferably, the surface density of the negative electrode coating is 0.002-0.018 g/cm 2 。
Preferably, the positive electrode coating comprises a positive electrode active material, a first conductive agent and a first binder, wherein the weight part ratio of the positive electrode active material to the first conductive agent to the first binder is 85-100: 0.2 to 10:0.1 to 8.
Preferably, the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, and lithium iron phosphate.
Preferably, the negative electrode coating comprises a silicon-carbon composite active material, a second conductive agent and a second binder, and the weight part ratio of the silicon-carbon composite active material to the second conductive agent to the second binder is 85-100: 0.2 to 9:0.1 to 8.
Preferably, the silicon-carbon composite active substance comprises silicon-based oxide SiOx (0 < x ≦ 2) particles and carbon and graphite particles coated on the surfaces of the SiOx particles.
Preferably, the silicon content in the silicon-carbon composite active substance is 0.2-55%.
Preferably, the particle size of the silicon-based oxide and the graphite particles satisfies the following relationship: silicon-based oxide particle size D of 0.3 mu m 50 < particle diameter D of graphite particles 50 ＜30.5μm。
Preferably, the particle size of the silicon-based oxide and the graphite particles satisfies the following relationship: 2.2 mu m < silicon-based oxide particle diameter D 50 < particle diameter D of graphite particles 50 ＜12.4μm。
Compared with the prior art, the invention has the beneficial effects that: according to the secondary battery, the pore section and the surface density of the coating of the positive plate and the negative plate are designed, so that the positive plate and the negative plate are better matched in performance and have better specific discharge capacity and discharge efficiency.
Drawings
FIG. 1 is a schematic view of a cross-sectional area of a coating layer projected onto a two-dimensional plane.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the present invention is not limited thereto.
The utility model provides a secondary battery, includes positive plate and negative pole piece, the positive plate includes the anodal mass flow body and sets up in the anodal coating on the anodal mass flow body both sides surface, the negative pole piece include the negative pole mass flow body and set up in the negative coating on the negative pole mass flow body both sides surface, the positive plate with the negative pole piece satisfies following relational expression:
wherein n is the number of layers of the positive plate; m is the number of layers of the negative plate;
wherein S1 is the ratio of pore cross-sectional area per unit area of the cross-section of the coating layer on the positive electrode sheet when the secondary battery is subjected to 0% DOD;
wherein S2 is the ratio of pore cross-sectional area per unit area of the cross-section of the coating layer on the positive electrode sheet at the time of 100% DOD of the secondary battery;
wherein S3 is the ratio of pore cross-sectional area per unit area of the cross-section of the coating layer on the negative electrode sheet when the secondary battery is 100% DOD;
wherein S4 is the ratio of pore cross-sectional area per unit area of the cross-section of the coating layer on the negative electrode sheet when the secondary battery is subjected to 0% DOD;
the surface density of the positive coating is a, the surface density of the negative coating is b, and the positive coating and the negative coating satisfy the following relational expression: 0.52 is less than or equal to ㏒ a/㏒ b is less than or equal to 1.33.
According to the secondary battery, the pore section and the surface density of the coating of the positive plate and the negative plate are designed, so that the positive plate and the negative plate are better matched in performance and have better specific discharge capacity and discharge efficiency.
The positive current collector is at least one of aluminum foil, carbon-coated aluminum foil, nickel-plated aluminum foil, foamed aluminum foil, zinc-plated aluminum foil, nickel, molybdenum, titanium, niobium and iron alloy aluminum foil.
The negative current collector is at least one of copper foil, porous copper foil, foamed copper foil, tin-zinc-plated copper foil, carbon-coated copper foil, nickel foil, titanium foil and polymer composite current collector.
The S1 and S4 may be obtained by: placing a silicon-containing lithium ion battery with 0 percent DOD into an explosion-proof box filled with inert gas, disassembling the battery by using a manipulator, taking out disassembled positive and negative plates, cleaning the positive and negative plates by using DMC solution, removing residual electrolyte salt to obtain the positive and negative plates, drying the positive and negative plates to constant weight at 40-80 ℃, selecting coating layers on the positive and negative plates to obtain small coating layers with the thickness of 2mm and 2mm, removing impurities, vacuumizing and soaking by using epoxy resin, embedding, curing and trimming the coating layers, conveniently slicing, cutting the coating layers by using an ultrathin slicer to obtain sections with the thickness of 0.05-10 mu m, randomly selecting 10 coating layer 50 mu m area regions on the cross section of one surface of the coating layer section by using an electron microscope, wherein the cross section of the coating layer section is an electron microscope photograph, adjusting the color difference between the particles of the electron microscope photograph and the pores, the cross section of the particles shows a bright white part, the cross section of the pores shows a shadow part (the pore size is 0.08 mu m and is under the magnification of 2000-10000 times), the total area f calculated by using area software, and when the selected positive plate is 25000, the total area of the positive plate is 25000; when the negative plate is selected, S4= f/25000. FIG. 1 is a schematic view of a cross-sectional area of a coating layer projected onto a two-dimensional plane.
Further, the S2 and S3 can be obtained by: placing a silicon-containing lithium ion battery with 100DOD into an explosion-proof box filled with inert gas, disassembling the battery by using a mechanical arm, taking out disassembled positive and negative plates, cleaning the positive and negative plates by using DMC solution, removing residual electrolyte salt to obtain the positive and negative plates, drying the positive and negative plates to constant weight at 40-80 ℃, selecting coating layers on the positive and negative plates to obtain small coating layers with the thickness of 2mm, removing impurities, carrying out vacuumizing impregnation by using epoxy resin, embedding, curing and trimming, conveniently slicing, cutting and cutting the coating layers by using an ultrathin slicing machine to obtain coating layer slices with the thickness of 0.05-10 mu m, randomly selecting 10 coating layer slices with the area of 50 mu m and 50 mu m on the cross section of one surface of each coating layer slice (20-30 area areas can be obtained, the result is more accurate when the area is larger), wherein the cross section of each coating layer slice is an electron microscope, adjusting the color difference between particles of an electron microscope photo, the cross section of each electron microscope picture is displayed as a bright white part, the cross section of each pore is displayed as a shadow part (the pore size is not less than 0.08 mu m and is more than 2000-10000 times larger than the size), calculating the total area of the positive plate, and the area is calculated as 25000 when the total area of the positive plate is 2502 e/e; when the negative plate is selected, S3= e/25000.
In the above relation, the inventor considers that the proportion of the cross section area of the pores on the section of the coating layer is in positive correlation with the porosity, when the proportion of the cross section area of the pores is higher, the porosity of the coating layer is also higher, and the porosity of the coating layer is in close relation with the discharge specific capacity, the discharge efficiency, the internal resistance and the cycle performance of the battery, so that when the proportion of the cross section area of the positive and negative coating layers is too high or too low in unit area, the porosity of the cross section of the positive and negative coating layers is too high or too low to match with the positive and negative coating layers, lithium ions cannot be inserted or extracted favorably, and the stability, the interlayer deformation and the electrical performance of the battery are influenced. In either 0% DOD or 100% DOD, the percentage of the pore cross-sectional area of the upper section of the positive coating layer and the percentage of the pore cross-sectional area of the upper section of the negative coating layer are designed reasonably, so that the discharge capacity of the battery can be increased, the polarization loss can be reduced, the cycle life of the battery can be prolonged, and the utilization rate of the lithium ion battery can be improved.
The size of the layer density of the coating on the pole piece is directly related to the discharge capacity of the battery. The larger the surface density is, the more compact the coating layer is, the more active substances contained in the pole piece are, the higher the capacity of the battery is, the smaller the gap is, the contact probability and the contact area among the particles are increased, but the electrolyte is not easy to permeate into the electrode, so that the migration path of lithium ions in the charging and discharging process is lengthened, the charging and discharging performance under large current is not facilitated, and when the surface density is larger, the difference between the surface density of the positive pole piece and the surface density of the negative pole piece is larger and unreasonable; when the surface density is small, the pole piece is not in close contact with the current collector, the surface of the pole piece is rough, more gaps exist in the pole piece, the active substances contained in the pole piece are smaller, the capacity of the lithium ion battery is reduced, errors in the pole piece quality weighing and electrochemical performance testing process are larger, and when the surface density is small, the difference between the surface density of the positive pole piece and the surface density of the negative pole piece is larger and unreasonable. The inventor finds out through experiments that when the density a and the value b of the coating layer surfaces on the positive and negative current collectors are designed to meet the condition that the density a and the value b are not less than 0.52 and not more than ㏒ a/㏒ b and not more than 1.33, reasonable active substances of the coating layer are ensured, the transfer path is moderate in the lithium ion charging and discharging process, and the electrochemical performance is good.
In some embodiments, the areal density of the positive electrode coating is from 0.005 to 0.032g/cm 2 . The surface density of the positive electrode coating is 0.005g/cm 2 、0.009g/cm 2 、0.011g/cm 2 、0.018g/cm 2 、0.022g/cm 2 、0.024g/cm 2 、0.028g/cm 2 、0.030g/cm 2 、0.032g/cm 2 。
In some embodiments, the negative electrode coating has an areal density of 0.002 to 0.018g/cm 2 . The surface density of the negative electrode coating is 0.005g/cm 2 、0.009g/cm 2 、0.011g/cm 2 、0.013g/cm 2 、0.016g/cm 2 、0.017g/cm 2 、0.018g/cm 2 。
In some embodiments, the positive electrode coating includes a positive electrode active material, a first conductive agent, and a first binder, and the weight ratio of the positive electrode active material, the first conductive agent, and the first binder is 85-100: 0.2 to 10:0.1 to 8. The weight part ratio of the positive active substance to the first conductive agent to the first binder is 85-87: 0.2 to 1.5: 0.1-0.5, 85-87: 0.5 to 1.5: 0.1-0.5, 85-87: 0.5 to 2: 0.2-1, 85-87: 1 to 3: 0.5-1.5, 87-89: 1 to 3: 1.5-3, 89-90: 1.5 to 3:1 to 3, 90 to 92:1.5 to 3: 1.5-3, 92-93: 2 to 3: 1.5-3, 92-93: 1 to 4:1 to 3, 93 to 95:1.5 to 4: 1.5-3, 93-95: 2 to 5: 2-5, 94-95: 1 to 5: 2-5, 94-95: 2 to 5: 1.5-5, 94-95: 2.5-5: 1.5-5, 94-96: 1.5 to 6: 1.5-5, 94-96: 2 to 6: 2-5, 94-96: 2.5 to 6: 2-5, 95-97: 3 to 7: 3-6, 95-98: 4 to 8:4 to 8, 97 to 100:5 to 8: 6-8, 99-100: 7 to 9: 7-8, 99-100: 8-10: 7-8, 85-90: 0.2 to 5: 0.1-8, 85-92: 4 to 6: 0.1-8, 88-95: 5 to 8: 0.1-8, 90-100: 0.2 to 3: 0.1-8, 90-95: 0.2 to 4: 0.1-8, 89-100: 0.2 to 5: 0.1-8, 89-95: 0.2 to 7:0.1 to 8. The weight part ratio of the positive active material to the first conductive agent to the first binder is 85:0.2:0.1, 85:0.8:0.8, 85:0.7:0.9, 85:8: 2. 85:10: 3. 85:7: 4. 85:6:0.1, 85:0.2: 5. 85:4: 6. 85:0.2: 7. 85:2: 8. 85:1:9.
further, the positive electrode active material contains one or more of oxides, nitrates and carbonates of at least one element of Mg, al, ti, fe, cd, zr, mo, zn, B, cu, V and Ag; further, the positive electrode active material contains an oxide, nitrate, phosphate, carbonate of one or more elements selected from Al, ba, zn, ti, co, W, Y, si, sn, B, and P.
In some embodiments, the positive active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron phosphate.
In some embodiments, the negative electrode coating comprises a silicon-carbon composite active material, a second conductive agent and a second binder, and the weight part ratio of the silicon-carbon composite active material to the second conductive agent to the second binder is 85-100: 0.2 to 9:0.1 to 8. The weight part ratio of the silicon-carbon composite active substance to the second conductive agent to the second binder is 85-90: 0.2 to 4: 0.1-4, 85-90: 0.2 to 2: 0.1-3, 85-90: 0.2 to 2: 0.1-4, 85-90: 0.2 to 2: 0.1-3, 85-90: 0.2 to 2: 0.1-2, 85-90: 0.2 to 3: 0.1-5, 85-90: 0.2 to 3: 4-8, 85-90: 0.2 to 3: 4-8, 85-90: 3 to 4: 3-8, 85-90: 3 to 4:4 to 8, 85 to 87:0.5 to 1.5: 0.5-1, 85-87: 0.5 to 2:1 to 1.5, 85 to 87:1 to 3: 1-2, 87-89: 1 to 3: 1.5-3, 89-90: 1.5 to 3:1 to 3, 90 to 92:1.5 to 3: 1.5-3, 92-93: 2 to 3: 1.5-3, 92-93: 1 to 4:1 to 3, 93 to 95:1.5 to 4: 1.5-3, 93-95: 2 to 5: 2-5, 94-95: 1 to 5: 2-5, 94-95: 2 to 5: 1.5-5, 94-95: 2.5-5: 1.5-5, 94-96: 1.5 to 6: 1.5-5, 94-96: 2 to 6: 2-5, 94-96: 2.5-6: 2-5, 95-97: 3 to 7: 3-6, 95-98: 4 to 8:4 to 8, 97 to 100:5 to 8: 6-8, 99-100: 7 to 9:7 to 8. Specifically, the weight part ratio of the silicon-carbon composite active substance to the second conductive agent to the second binder is 85:0.2:0.1, 85:0.2:0.4, 85:0.2:0.6, 86:0.2:0.5, 88:0.2:0.7, 89:0.2:0.8, 90:0.2:0.9, 92:0.2: 1. 98:0.2: 4. 95:0.2: 5. 100:0.2: 6. 85:0.2: 7. 85:0.2: 8. 85:4:7.
in some embodiments, the silicon-carbon composite active material includes silicon-based oxide SiOx (0 < x.ltoreq.2) particles and carbon and graphite particles coated on the surfaces of the SiOx particles. The coating of the silicon-based oxide is beneficial to improving the electrochemical performance and the cycle efficiency.
In some embodiments, the silicon content in the silicon-carbon composite active material is 0.2-55%. The silicon-carbon composite active substance has a certain silicon content, so that the performance of the silicon-carbon composite active substance can be improved, and the cycle performance and the safety are improved.
In some embodiments, the silicon-based oxide and the graphite particles have a particle size that satisfies the following relationship: silicon-based oxide particle size D of 0.3 mu m 50 < particle diameter D of graphite particles 50 Less than 30.5 μm. The silicon-carbon composite active substance is obtained by embedding silicon-based oxide particles with a low particle size D50 into graphite particles with a high particle size D50 and mixing; the graphite particles are at least one of modified natural graphite particles, artificial graphite particles, porous graphite and graphitized carbon particles;
in some embodiments, the silicon-based oxide and the graphite particles have a particle size that satisfies the following relationship: 2.2 mu m < silicon-based oxide particle diameter D 50 < particle diameter D of graphite particles 50 ＜12.4μm。
The first conductive agent and the second conductive agent are at least one of Ketjen black, carbon nano tubes, acetylene black, conductive graphite, conductive carbon black, conductive graphene, a metal-carbon fiber conductive agent and a metal-carbon composite powder conductive agent; the first binder and the second binder are at least one of monomers and polymers such as guar gum, sodium alginate, acrylic acid, styrene butadiene rubber, vinyl alcohol, aniline, benzimidazole, arabic gum, xanthan gum, carrageenan, lithium carboxymethyl cellulose, vinylidene fluoride, sodium carboxymethyl cellulose, vinylidene fluoride, tetrafluoroethylene and the like.
The isolating membrane is made of main materials such as polyethylene, polypropylene, polyacrylonitrile, polyamide acid, polyamide, polyarylethersulfone, polyvinylidene fluoride, polyethylene terephthalate, polyester cellulose, non-woven fabrics, cellulose paper or/and a coating which is one or more of single-layer, double-layer or multi-layer composite membranes made of high polymers such as aluminum oxide, zirconium oxide, silicon oxide, titanium oxide and ceramic particles.
The electrolyte contains one or more of lithium hexafluorophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, lithium tetrafluoroborate, lithium dioxalate borate, lithium trifluoromethanesulfonate, lithium oxalyldifluoroborate, lithium difluorophosphate, 4,5-dicyano-2-trifluoromethylimidazole lithium difluorobis (oxalyl) phosphate and lithium tetrafluorooxalyl phosphate.
Further, the electrolyte contains an organic solvent, and the organic solvent can be cyclic carbonate including PC, EC and FEC; or chain carbonates, including DEC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc.
Further, the electrolyte contains one or more additives of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, methylene methanedisulfonate and tris (trimethylsilane) boron/phosphate, wherein the additives include but are not limited to film forming additives, conductive additives, flame retardant additives, anti-overcharge additives, and control of H in the electrolyte 2 At least one of additives of O and HF content, additives for improving high temperature performance, and multifunctional additives.
A method for manufacturing a secondary battery, comprising the steps of:
step A1, preparing positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain a positive plate;
step A2, preparing negative electrode composite slurry, coating the silicon-carbon composite slurry on a negative electrode current collector to form a coating layer, tabletting, and drying to obtain a negative electrode plate;
and A3, matching the prepared positive plate and the prepared negative plate with an isolating membrane, closely arranging the positive plate, the isolating membrane and the negative plate to obtain a battery cell, injecting electrolyte, and packaging the battery cell to obtain the silicon-containing lithium ion battery.
Wherein, in the silicon-containing lithium ion battery, the change of the thickness of the coating layer on the negative electrode sheet is 0.12 to 0.65, preferably 0.20 to 0.46 in a 0% DOD state.
Further, the thickness change amount = (battery 0%.
The silicon-containing lithium ion battery in the step A3 comprises n layers of positive plates and coating layers on two sides of the n layers of positive plates; comprises m layers of negative plates and coating layers on two sides of the m layers of negative plates (n and m are natural numbers, n is more than or equal to 1, and m is more than or equal to 1).
Example 1
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.6 Co 0.3 Mn 0.1 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional use of D 50 SiO particles of 3.6 μm and D 50 The artificial graphite particles with the particle size of 7.3 mu m are prepared from the following components in a mass ratio of 2: and 8, mechanically mixing, embedding small-particle-size SiO particles into large-particle-size artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon composite slurry, coating the silicon-carbon composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: and (2) matching the 3 layers of positive plates and 4 layers of negative plates with the polyethylene/polypropylene composite isolating film, closely arranging the negative plates, the isolating film and the positive plates to obtain a battery cell, injecting electrolyte containing 1mol/L of lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Example 2
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.6 Co 0.3 Mn 0.1 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional D 50 SiO particles of 3.6 μm and D 50 The artificial graphite particles with the particle size of 7.3 mu m are prepared from the following components in a mass ratio of 2: and 8, mechanically mixing, embedding small-particle-size SiO particles into large-particle-size artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon composite slurry, coating the silicon-carbon composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: and (2) matching the 3 layers of positive plates and 4 layers of negative plates with the polyethylene/polypropylene composite isolating film, closely arranging the negative plates, the isolating film and the positive plates to obtain a battery cell, injecting electrolyte containing 1M lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Example 3
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.6 Co 0.3 Mn 0.1 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), and adding solvent N-methyl pyrrolidoneAnd (3) NMP, stirring, preparing positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting and drying to obtain the positive plate.
A2: optional use of D 50 SiO particles of 3.6 μm and D 50 The artificial graphite particles with the particle size of 7.3 mu m are prepared from the following components in a mass ratio of 2: and 8, mechanically mixing, embedding small-particle-size SiO particles into large-particle-size artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon composite slurry, coating the silicon-carbon composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: and (2) matching the 3 layers of positive plates and 4 layers of negative plates with the polyethylene/polypropylene composite isolating film, closely arranging the negative plates, the isolating film and the positive plates to obtain a battery cell, injecting electrolyte containing 1M lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Example 4
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.6 Co 0.3 Mn 0.1 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional use of D 50 SiO particles of 3.6 μm and D 50 The artificial graphite particles with the particle size of 7.3 mu m are prepared from the following components in a mass ratio of 2: and 8, mechanically mixing, embedding small-particle-size SiO particles into large-particle-size artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon composite slurry, coating the silicon-carbon composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: the preparation method comprises the following steps of preparing 3 layers of positive plates, 4 layers of negative plates and a polyethylene/polypropylene composite isolating membrane, closely arranging the negative plates, the isolating membrane and the positive plates to obtain a battery cell, injecting electrolyte containing 1mol/L lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Example 5
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.15 Mn 0.05 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional D 50 SiO particles of 4.3 μm and D 50 The artificial graphite particles with the particle size of 9.7 mu m are mixed according to the mass ratio of 2.5:7.5 mechanically mixing, embedding small-granularity SiO particles into large-granularity artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon composite slurry, coating the silicon-carbon composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: and (2) matching the 7-layer positive plate and the 8-layer negative plate with the polyethylene/polypropylene composite isolating film, closely arranging the negative plate, the isolating film and the positive plate to obtain a battery cell, injecting electrolyte containing 1M lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Example 6
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.15 Mn 0.05 O 2 ) Conductive additionMixing the agent and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive electrode plate.
A2: optional use of D 50 SiO particles of 4.3 μm and D 50 The artificial graphite particles with the particle size of 9.7 mu m are mixed according to the mass ratio of 2.5:7.5 mechanically mixing, embedding small-granularity SiO particles into large-granularity artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon composite slurry, coating the silicon-carbon composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: the 7-layer positive plate and the 8-layer negative plate which are prepared are matched with the polyethylene/polypropylene composite isolating film, the battery cell is obtained by closely arranging the negative plate, the isolating film and the positive plate, electrolyte containing 1mol/L lithium tetrafluoroborate is injected (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Example 7
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.15 Mn 0.05 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional D 50 SiO particles of 4.3 μm and D 50 The artificial graphite particles with the particle size of 9.7 mu m are mixed according to the mass ratio of 2.5:7.5 mechanical mixing, embedding the small-granularity SiO particles into the large-granularity artificial graphite particles to obtain the silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, the conductive additive and the binder according to a certain mass ratio (shown in Table 1), adding deionized water, stirring to prepare silicon-carbon composite slurry, and mixing the silicon-carbon composite slurryCoating the solution on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: and (2) matching the 7-layer positive plate and the 8-layer negative plate with the polyethylene/polypropylene composite isolating film, closely arranging the negative plate, the isolating film and the positive plate to obtain a battery cell, injecting electrolyte containing 1M lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Example 8
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.15 Mn 0.05 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional use of D 50 SiO particles of 4.3 μm and D 50 The artificial graphite particles with the particle size of 9.7 mu m are mixed according to the mass ratio of 2.5:7.5 mechanically mixing, embedding small-granularity SiO particles into large-granularity artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon composite slurry, coating the silicon-carbon composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: the 7-layer positive plate and the 8-layer negative plate which are prepared are matched with the polyethylene/polypropylene composite isolating film, the battery cell is obtained by closely arranging the negative plate, the isolating film and the positive plate, electrolyte containing 1mol/L lithium tetrafluoroborate is injected (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Comparative example 1
The preparation method of the positive plate, the negative plate and the lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxygenCompound (LiNi) 0.6 Co 0.3 Mn 0.1 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional use of D 50 The silicon-containing active substance is obtained by SiO particles with the particle size of 3.6 mu m, the silicon-containing active substance, the conductive additive and the binder are mixed according to a certain mass ratio (shown in table 1), deionized water is added, stirring is carried out, silicon-containing composite slurry is prepared, the silicon-containing composite slurry is coated on a negative current collector to form a coating layer, and the negative plate is obtained by tabletting and drying.
A3: and (2) matching the 3 layers of positive plates and 4 layers of negative plates with the polyethylene/polypropylene composite isolating film, closely arranging the negative plates, the isolating film and the positive plates to obtain a battery cell, injecting electrolyte containing 1mol/L of lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Comparative example 2
The preparation method of the positive plate, the negative plate and the lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.15 Mn 0.05 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional use of D 50 The active material containing silicon, the conductive additive and the binder are mixed according to a certain mass ratio (shown in table 1), deionized water is added, stirring is carried out, the composite slurry containing silicon is prepared, the composite slurry containing silicon is coated on a negative current collector to form a coating layer, and the coating layer is pressed and dried to obtain the negative plate.
A3: the preparation method comprises the following steps of preparing 7 layers of positive plates, 8 layers of negative plates, matching a polyethylene/polypropylene composite isolating membrane, tightly arranging the negative plates, the isolating membrane and the positive plates to obtain a battery cell, injecting electrolyte containing 1M lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to a ratio of 1.
Comparative example 3
The preparation method of the positive plate, the negative plate and the lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.15 Mn 0.05 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional use of D 50 SiO particles of 4.3 μm and D 50 The artificial graphite particles with the particle size of 3.5 mu m are prepared from the following components in a mass ratio of 2: and 8, mechanically mixing, embedding small-particle-size SiO particles into large-particle-size artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon-containing composite slurry, coating the silicon-containing composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: and (2) matching the 7-layer positive plate and the 8-layer negative plate with the polyethylene/polypropylene composite isolating film, closely arranging the negative plate, the isolating film and the positive plate to obtain a battery cell, injecting electrolyte containing 1M lithium tetrafluoroborate (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Comparative example 4
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.6 Co 0.3 Mn 0.1 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding N-methylpyrrolidone NMP serving as a solvent, stirring to prepare positive composite slurry, and coating the positive composite slurry on the positive composite slurryAnd forming a coating layer on the positive current collector, tabletting and drying to obtain the positive plate.
A2: optional use of D 50 SiO particles of 4.3 μm and D 50 The artificial graphite particles with the particle size of 3.5 mu m are prepared from the following components in a mass ratio of 2: and 8, mechanically mixing, embedding small-particle-size SiO particles into large-particle-size artificial graphite particles to obtain a silicon-carbon composite active substance, mixing the silicon-carbon composite active substance, a conductive additive and a binder according to a certain mass ratio (shown in table 1), adding deionized water, stirring, preparing silicon-carbon-containing composite slurry, coating the silicon-containing composite slurry on a negative current collector to form a coating layer, tabletting and drying to obtain the negative plate.
A3: the 7-layer positive plate and the 8-layer negative plate which are prepared are matched with the polyethylene/polypropylene composite isolating film, the negative plate, the isolating film and the positive plate are tightly arranged to obtain a battery cell, electrolyte containing 1mol/L lithium tetrafluoroborate is injected (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Comparative example 5
The preparation method of the positive plate, the negative plate and the silicon-containing lithium ion battery comprises the following steps:
a1: lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.15 Mn 0.05 O 2 ) Mixing the conductive additive and the binder according to a certain mass ratio (shown in table 1), adding a solvent N-methylpyrrolidone NMP, stirring, preparing a positive electrode composite slurry, coating the positive electrode composite slurry on a positive electrode current collector to form a coating layer, tabletting, and drying to obtain the positive plate.
A2: optional use of D 50 The active material containing silicon, the conductive additive and the binder are mixed according to a certain mass ratio (shown in table 1), deionized water is added, stirring is carried out, the composite slurry containing silicon is prepared, the composite slurry containing silicon is coated on a negative current collector to form a coating layer, and the coating layer is pressed and dried to obtain the negative plate.
A3: the 7-layer positive plate and the 8-layer negative plate which are prepared are matched with the polyethylene/polypropylene composite isolating film, the battery cell is obtained by closely arranging the negative plate, the isolating film and the positive plate, electrolyte containing 1mol/L lithium tetrafluoroborate is injected (the lithium tetrafluoroborate is dissolved in EC, DMC and EMC and mixed according to 1.
Examples, comparative examples test
1. And (3) testing S1, S2, S3 and S4:
charging gave 3 0-% DOD silicon-containing lithium ion batteries, discharging gave 3 100-% DOD silicon-containing lithium ion batteries, and measuring S1, S4 of 0-DOD silicon-containing lithium ion Chi Geceng and S2, S3 of 100DOD% silicon-containing lithium ion Chi Geceng:
s1, S4: placing a silicon-containing lithium ion battery with 0DOD into an explosion-proof box filled with inert gas, disassembling the battery by using a manipulator, taking out disassembled positive and negative plates, cleaning the positive and negative plates by using DMC solution, removing residual electrolyte salt to obtain the positive and negative plates, drying the positive and negative plates to constant weight at 40-80 ℃, selecting coating layers on the positive and negative plates to obtain small coating layers with the thickness of 2mm and 2mm, removing impurities, vacuumizing and soaking by using epoxy resin, embedding, curing and trimming the coating layers, conveniently slicing, cutting the coating layers by using an ultrathin slicer to obtain sections with the thickness of 0.05-10 mu m, observing by using an electron microscope, randomly selecting 10 coating layer area areas with the area of 50 mu m on the cross section of one surface of the coating layer section, wherein the cross section of the coating layer section is an electron microscope photo, adjusting the color difference between the electron microscope photo particles and pores, wherein the cross section of the particles shows a bright white part, the cross section of the pores shows a shadow part (the pore size is not less than 0.08 mu m), calculating the total area of the shadow part as f by using area calculation software, and when the selected positive plate is the positive plate, S1 f = 00; when the negative plate is selected, S4= f/25000. S2, S3: placing a silicon-containing lithium ion battery with 100DOD into an explosion-proof box filled with inert gas, disassembling the battery by using a mechanical arm, taking out disassembled positive and negative plates, cleaning the positive and negative plates by using DMC solution, removing residual electrolyte salt to obtain the positive and negative plates, drying the positive and negative plates to constant weight at 40-80 ℃, selecting coating layers on the positive and negative plates to obtain small coating layers with the thickness of 2mm, removing impurities, carrying out vacuumizing and soaking, embedding, curing and trimming by using epoxy resin, conveniently slicing, cutting and cutting a plane vertical to the coating layers by using an ultrathin slicing machine to obtain coating layer slices with the thickness of 0.05-10 mu m, observing by using an electron microscope, randomly selecting 10 areas with the area of 50 mu m and 50 mu m on the cross section of one surface of each coating layer slice, wherein the cross section of each coating layer slice is an electron microscope photo, adjusting the color difference between the electron microscope photo particles and pores, the cross section of the particles is displayed as a bright white part, the cross section of the pores is displayed as a shadow part (the pore size is not less than 0.08 mu m), calculating the total area of the shadow part as e by using area calculation software, and when the selected positive plate is the positive plate, S2E = 25000; when the negative plate is selected, S3= e/25000.
Calculation, (examples 1 to 4, comparative examples 1, 3,n =3, m =4; examples 5 to 8, comparative examples 2, 4,n =7, m =8,) and an average value was taken.
2. Thickness variation amount:
the lithium ion batteries of 4 examples and comparative examples were selected and tested for the amount of change in thickness of the coating layer on the negative electrode sheet at 0% dod, averaged, and calculated as thickness change = (volume of coating layer at 0% dod for battery-volume of coating layer at 100% dod for battery)/volume of coating layer at 100% dod for battery.
3. Coating layer density:
in each example and each comparative example, the values of the densities a and b of the coating layer surfaces after tabletting and drying in the preparation of the positive plate and the negative plate are calculated to obtain ㏒ a and ㏒ b.
4. Testing the compressive strength of the silicon-carbon composite active substance and the silicon-containing active substance:
selecting the silicon-carbon composite active substance and the silicon-containing active substance in the examples and the comparative examples, and measuring the compressive strength; placing a sample to be detected on an objective table; the pressure head approaches the coating layer downwards at a constant speed until the pressure head can contact the coating layer; the pressure and the displacement of the pressure head are recorded at the moment of contact; the downward pressing of the pellets at a constant speed is continued until the pellets break.
5. And (3) electrical property detection:
charging to 4.2V at initial and cut-off voltages of 2.8V and 4.2V at the temperature of 25 ℃, charging to 0.05C at a constant voltage of 4.2V, discharging to 2.8V at 0.2C, and recording the first coulombic efficiency and capacity retention rate.
6. Appearance of coating layer
And observing the appearance of the membrane after the battery circulates for 400 th circle by using a scanning electron microscope.
TABLE 1 quality ratio (%)
Table 2 examples and comparative examples test data
Table 3 test of electrical properties of examples and comparative examples
As can be seen from tables 1 to 3, the secondary batteries manufactured in examples 1 to 8 according to the present invention have better electrochemical properties than the secondary batteries of comparative examples 1 to 5, the first coulombic efficiency was as high as 92.64%, the capacity retention rate at the 50 th cycle was as high as 96.15%, the capacity retention rate at the 400 th cycle was as high as 89.69%, the compressive strength was as high as 81.7Mpa, and the coating layers had less fine cracks, no cracks, and good appearance. The first coulombic efficiency of the secondary battery of the comparison document is only 82.5%, the capacity retention rate of the 50 th circle is as high as 84.88%, the capacity retention rate of the 400 th circle is as high as 82.95%, the extrusion strength is as high as 76.6Mpa, cracks of different degrees appear on the appearance of the coating layer, and meanwhile, the coating layer is obviously cracked, and the situation is not good.
The invention is characterized in that the ratio of the pore cross-sectional areas of the upper section of the coating layer on the positive and negative pole pieces is S1 and S4 when the DOD is designed to be 0 percent, the ratio of the pore cross-sectional areas of the upper section of the coating layer on the positive and negative pole pieces when the DOD is 100 percent, and the surface densities a and b of the coating layers on the positive and negative current collectors are 0.52- ㏒ a/㏒ b-1.33, so that the obtained coating layers on the positive and negative pole pieces have reasonable pores, the stability of the fine structure of the coating layers and good interlayer deformation, and the silicon-carbon composite active substance, the conductive additive and the binder on the negative pole pieces and the positive active substance, the conductive additive and the binder on the positive pole piece coating layers can be fully contacted.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. The utility model provides a secondary battery, its characterized in that, includes positive plate and negative plate, positive plate includes the anodal mass flow body and sets up in the anodal positive coating on the anodal mass flow body both sides surface, negative plate include the negative current collection body and set up in the negative coating on the negative current collection body both sides surface, positive plate with the negative plate satisfies following relational expression:
wherein n is the number of layers of the positive plate; m is the number of layers of the negative plate;
wherein S1 is the ratio of pore cross-sectional area per unit area of the cross-section of the coating layer on the positive electrode sheet when the secondary battery is subjected to 0% DOD;
wherein S2 is a ratio of void cross-sectional area per unit area of cross-section of the coating layer on the positive electrode sheet in the secondary battery by 100% DOD;
wherein S3 is a ratio of pore cross-sectional area to pore cross-sectional area per unit area of the coating layer cross-section on the negative electrode sheet when the secondary battery is 100% DOD;
wherein S4 is the ratio of pore cross-sectional area per unit area of the cross-section of the coating layer on the negative electrode sheet when the secondary battery is subjected to 0% DOD;
the surface density of the positive coating is a, the surface density of the negative coating is b, and the positive coating and the negative coating satisfy the following relational expression: 0.52 is less than or equal to ㏒ a/㏒ b is less than or equal to 1.33.
2. The secondary battery according to claim 1, wherein the surface density of the positive electrode coating layer is 0.005 to 0.032g/cm 2 。
3. The secondary battery according to claim 1, wherein the negative electrode coating has an areal density of 0.002 to 0.018g/cm 2 。
4. The secondary battery according to claim 1, wherein the positive electrode coating layer comprises a positive electrode active material, a first conductive agent and a first binder, and the weight part ratio of the positive electrode active material to the first conductive agent to the first binder is 85-100: 0.2 to 10:0.1 to 8.
5. The secondary battery according to claim 4, wherein the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, and lithium iron phosphate.
6. The secondary battery of claim 1, wherein the negative electrode coating comprises a silicon-carbon composite active material, a second conductive agent and a second binder, and the weight part ratio of the silicon-carbon composite active material to the second conductive agent to the second binder is 85-100: 0.2 to 9:0.1 to 8.
7. The secondary battery according to claim 6, wherein the silicon-carbon composite active material includes silicon-based oxide SiOx (0 < x.ltoreq.2) particles and carbon and graphite particles coated on the surfaces of the SiOx particles.
8. The secondary battery according to claim 6, wherein the silicon content in the silicon-carbon composite active material is 0.2 to 55%.
9. The secondary battery according to claim 7, wherein the particle diameters of the silicon-based oxide and the graphite particles satisfy the following relationship: silicon-based oxide particle size D of 0.3 mu m 50 < particle diameter D of graphite particles 50 ＜30.5μm。
10. The secondary battery according to claim 9, wherein the particle diameters of the silicon-based oxide and the graphite particles satisfy the following relationship: 2.2 mu m < silicon-based oxide particle diameter D 50 < particle diameter D of graphite particles 50 ＜12.4μm。
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