Design method and application of pole piece of long-circulation cylindrical battery

Abstract

The invention provides a pole piece design method and application of a long-circulation cylindrical battery, and relates to the technical field of batteries. According to the pole piece design method of the long-circulation cylindrical battery, the pole piece is optimally designed, the surface density and thickness of the pole pieces on the two sides of the negative pole piece are improved to be matched with a gap generated by thinning the edge of the positive pole piece, the edge lithium precipitation phenomenon in the circulation process is improved, the cycle life of the cylindrical battery is prolonged, and the performance stability of the battery is enhanced; and the safety of the cylindrical battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a pole piece design method for a long-cycle cylindrical battery and an application thereof. Background Art

[0002] With the continuous development of lithium battery technology, large cylindrical batteries have penetrated into many aspects of life, especially in the energy storage market, large cylindrical batteries are favored by household storage users. At the same time, the requirements for the cycle life and safety performance of cylindrical batteries are getting higher and higher.

[0003] In the prior art, in order to prevent lithium deposition at the edge of the negative electrode sheet, cylindrical batteries usually thin the edge of the positive electrode sheet, and then match the corresponding negative electrode sheet to wind around the winding needle according to the designed diameter to form a winding core, and then weld, package, and inject liquid to make a battery cell. However, during the cycle of the cylindrical battery, the expansion of the electrode sheet will continue to increase, and the stress of the electrode sheet will also continue to increase. Due to the special cylindrical structure of the winding core, there will be a problem that the stress of the electrode sheet cannot be released, resulting in differences in the expansion of the electrode sheets in different areas, especially the negative electrode sheet. The main reason is that there is thinning on the edges of the positive electrode sheet, resulting in a gap between the negative electrode sheet area corresponding to the positive electrode. After the cycle, the expansion of the two sides of the area corresponding to the negative electrode is greater than the middle area. Since the area in the middle that cannot expand will affect the embedding of lithium ions in the negative electrode, lithium ions are transferred to the large expansion area of ​​the negative electrode, but the amount of negative electrode active material in the large expansion area does not change, resulting in local excessive lithium embedding. After multiple charge and discharge cycles, the battery capacity decays significantly, and at the same time, it triggers the growth of lithium dendrites, piercing the diaphragm, and short-circuiting the battery internally, which seriously affects the safety and cycle life of the battery.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first object of the present invention is to provide a pole piece design method for a long cycle cylindrical battery to solve the above technical problems.

[0006] The second object of the present invention is to provide the application of the above-mentioned pole piece design method in the preparation of cylindrical batteries.

[0007] In order to achieve the above objectives, the following technical solutions are adopted:

[0008] In the first aspect, the present invention provides a method for designing a pole piece of a long-cycle cylindrical battery, wherein the positive pole piece is divided into three coating units in a direction perpendicular to the winding direction, namely, positive pole unit 1, positive pole unit 2 and positive pole unit 3; the three positive pole units have the same compaction density; in the direction from positive pole unit 1 to positive pole unit 3, positive pole unit 1 is divided into four basic units, namely, positive pole unit 1-1, positive pole unit 1-2, positive pole unit 1-3 and positive pole unit 1-4, and positive pole unit 3 is divided into four basic units, namely, positive pole unit 3-4, positive pole unit 3-3, positive pole unit 3-2 and positive pole unit 3-1;

[0009] Then the thickness of the positive electrode unit 2 is:

[0010] H c2 =σ c2 / ρ C +τ c ;

[0011] The thickness of the positive electrode unit 1 is:

[0012] H c1 =(1-0.16*e^(-0.693*X 1 ))σ c2 / ρ C +τ c ;

[0013] The thickness of the positive electrode unit 3 is:

[0014] H c3 =(1-0.16*e^(-0.693*X 3 ))σ c2 / ρ C +τ c ;

[0015] Among them, H c2 is the thickness of the positive electrode unit 2; H c1 is the thickness of the positive electrode unit 1; H c3 is the thickness of the positive electrode unit 3; σ c2 is the surface density of the positive electrode unit 2, ranging from 20 to 42 mg / cm 2 ρ C is the compaction density of the positive electrode, which is 2.0-2.5g / cm 3 ; τ c is the thickness of the positive electrode current collector; X of the positive electrode unit 1-1, the positive electrode unit 1-2, the positive electrode unit 1-3 and the positive electrode unit 1-4 1 The values ​​of are 1, 2, 3, and 4 respectively; the values ​​of X of positive electrode unit 3-4, positive electrode unit 3-3, positive electrode unit 3-2, and positive electrode unit 3-1 3 The values ​​of are 4, 3, 2, and 1 respectively;

[0016] After winding, the areas on the negative electrode sheet corresponding to the positive electrode sheet are recorded as negative electrode unit 1, negative electrode unit 2 and negative electrode unit 3; the compaction density of the three negative electrode units is the same; the negative electrode unit 1 is divided into negative electrode unit 1-1, negative electrode unit 1-2, negative electrode unit 1-3 and negative electrode unit 1-4, which correspond to the positive electrode unit 1-1, positive electrode unit 1-2, positive electrode unit 1-3 and positive electrode unit 1-4 respectively; the negative electrode unit 3 is divided into negative electrode unit 3-1, negative electrode unit 3-2, negative electrode unit 3-3 and negative electrode unit 3-4, which correspond to the positive electrode unit 3-1, positive electrode unit 3-2, positive electrode unit 3-3 and positive electrode unit 3-4 respectively;

[0017] Then the thickness of the negative electrode unit 2 is:

[0018] H a2 =λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0019] The thickness of the negative electrode unit 1 is:

[0020] H a1 =0.16*e^(-0.693*X 1 )*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0021] The thickness of the negative electrode unit 3 is:

[0022] H a3 =0.16*e^(-0.693*X 3 ))σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0023] Among them, H a2 is the thickness of the negative electrode unit 2; H a1 is the thickness of the negative electrode unit 1; H a3is the thickness of the negative electrode unit 3; λ is a constant of 1.15-1.25; α a is the proportion of negative electrode active material; α c C is the proportion of positive electrode active material; a Negative electrode capacity in grams, C c Positive electrode gram capacity; ρ a is the compaction density of the negative electrode sheet, which is 1.3-1.7g / cm 3 ; τ c is the thickness of the negative electrode current collector; X of the negative electrode unit 1-1, the negative electrode unit 1-2, the negative electrode unit 1-3 and the negative electrode unit 1-4 1 The values ​​of are 1, 2, 3, and 4 respectively; the values ​​of X of negative electrode unit 3-4, negative electrode unit 3-3, negative electrode unit 3-2, and negative electrode unit 3-1 3 The values ​​are 4, 3, 2, and 1 respectively.

[0024] As a further technical solution, there is an overhang1 area on the outer side of the negative electrode unit 1;

[0025] The thickness of the pole piece in the overhang1 area is:

[0026] H o1 =0.16*e^(-0.693)*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0027] There is an overhang3 area outside the negative electrode unit 3;

[0028] The thickness of the pole piece in the overhang3 area is:

[0029] H o3 =0.16*e^(-0.693)*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a .

[0030] As a further technical solution, the width of the overhang1 area is 0.5-4 mm;

[0031] The width of the overhang 3 area is 0.5-4 mm.

[0032] As a further technical solution, the width of the positive electrode unit 2 is twice the width of the positive electrode unit 1;

[0033] The width of the positive electrode unit 2 is twice the width of the positive electrode unit 3 .

[0034] As a further technical solution, the thickness of the positive electrode current collector is 13-16 μm;

[0035] The thickness of the negative electrode current collector is 6-7 μm.

[0036] As a further technical solution, the coating formula of the positive electrode sheet includes, by mass percentage, 0.5%-5% positive electrode conductor, 0.5%-5% positive electrode binder, and the remainder is positive electrode active material.

[0037] As a further technical solution, the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate or ternary materials;

[0038] The positive electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube or graphene;

[0039] The positive electrode binder includes PVDF.

[0040] As a further technical solution, the coating formula of the negative electrode sheet includes, by mass percentage, 0.5%-4% negative electrode conductive agent, 0.5%-4% negative electrode binder, and the remainder is negative electrode active material.

[0041] As a further technical solution, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, graphene or silicon negative electrode materials;

[0042] The negative electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube or graphene;

[0043] The negative electrode binder includes at least one of styrene-butadiene rubber, polyacrylic acid, sodium alginate or sodium carboxymethyl cellulose.

[0044] In a second aspect, the present invention provides the application of the above-mentioned pole piece design method in the preparation of cylindrical batteries.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The pole piece design method for a long cycle cylindrical battery provided by the present invention optimizes the pole piece design, improves the pole piece surface density and thickness on both sides of the negative pole piece to match the gap generated by the thinning of the positive pole piece edge, improves the edge lithium deposition phenomenon during the cycle process, extends the cycle life of the cylindrical battery, enhances the performance stability of the battery, and improves the safety of the cylindrical battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 Schematic diagram of the coating distribution of the positive electrode sheet;

[0049] Figure 2 Schematic diagram of negative electrode coating distribution. DETAILED DESCRIPTION

[0050] The embodiments of the present invention will be described in detail below in conjunction with the embodiments and examples, but it will be appreciated by those skilled in the art that the following embodiments and examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified, proceed according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0051] In the first aspect, the present invention provides a method for designing a pole piece of a long-cycle cylindrical battery, wherein the positive pole piece is divided into three coating units in a direction perpendicular to the winding direction, namely, positive pole unit 1, positive pole unit 2 and positive pole unit 3; the three positive pole units have the same compaction density; in the direction from positive pole unit 1 to positive pole unit 3, positive pole unit 1 is divided into four basic units, namely, positive pole unit 1-1, positive pole unit 1-2, positive pole unit 1-3 and positive pole unit 1-4, and positive pole unit 3 is divided into four basic units, namely, positive pole unit 3-4, positive pole unit 3-3, positive pole unit 3-2 and positive pole unit 3-1;

[0052] Then the thickness of the positive electrode unit 2 is:

[0053] H c2 =σ c2 / ρ C +τ c ;

[0054] The thickness of the positive electrode unit 1 is:

[0055] H c1 =(1-0.16*e^(-0.693*X 1 ))σ c2 / ρ C +τ c ;

[0056] The thickness of the positive electrode unit 3 is:

[0057] H c3 =(1-0.16*e^(-0.693*X 3 ))σ c2 / ρ C +τ c ;

[0058] Among them, H c2 is the thickness of the positive electrode unit 2; H c1 is the thickness of the positive electrode unit 1; H c3 is the thickness of the positive electrode unit 3; σ c2 is the surface density of the positive electrode unit 2, ranging from 20 to 42 mg / cm 2 ρ C is the compaction density of the positive electrode, which is 2.0-2.5g / cm 3 ; τ c is the thickness of the positive electrode current collector; X of the positive electrode unit 1-1, the positive electrode unit 1-2, the positive electrode unit 1-3 and the positive electrode unit 1-4 1 The values ​​of are 1, 2, 3, and 4 respectively; the values ​​of X of positive electrode unit 3-4, positive electrode unit 3-3, positive electrode unit 3-2, and positive electrode unit 3-1 3 The values ​​of are 4, 3, 2, and 1 respectively;

[0059] After winding, the areas on the negative electrode sheet corresponding to the positive electrode sheet are recorded as negative electrode unit 1, negative electrode unit 2 and negative electrode unit 3; the compaction density of the three negative electrode units is the same; the negative electrode unit 1 is divided into negative electrode unit 1-1, negative electrode unit 1-2, negative electrode unit 1-3 and negative electrode unit 1-4, which correspond to the positive electrode unit 1-1, positive electrode unit 1-2, positive electrode unit 1-3 and positive electrode unit 1-4 respectively; the negative electrode unit 3 is divided into negative electrode unit 3-1, negative electrode unit 3-2, negative electrode unit 3-3 and negative electrode unit 3-4, which correspond to the positive electrode unit 3-1, positive electrode unit 3-2, positive electrode unit 3-3 and positive electrode unit 3-4 respectively;

[0060] Then the thickness of the negative electrode unit 2 is:

[0061] H a2 =λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0062] The thickness of the negative electrode unit 1 is:

[0063] H a1 =0.16*e^(-0.693*X 1 )*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0064] The thickness of the negative electrode unit 3 is:

[0065] H a3 =0.16*e^(-0.693*X 3 ))σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0066] Among them, H a2 is the thickness of the negative electrode unit 2; H a1 is the thickness of the negative electrode unit 1; H a3 is the thickness of the negative electrode unit 3; λ is a constant of 1.15-1.25; α a is the proportion of negative electrode active material; α c C is the proportion of positive electrode active material; a Negative electrode capacity in grams, C c Positive electrode gram capacity; ρ a is the compaction density of the negative electrode sheet, which is 1.3-1.7g / cm 3 ; τ c is the thickness of the negative electrode current collector; X of the negative electrode unit 1-1, the negative electrode unit 1-2, the negative electrode unit 1-3 and the negative electrode unit 1-4 1 The values ​​of are 1, 2, 3, and 4 respectively; the values ​​of X of negative electrode unit 3-4, negative electrode unit 3-3, negative electrode unit 3-2, and negative electrode unit 3-1 3 The values ​​are 4, 3, 2, and 1 respectively.

[0067] The pole piece design method for a long cycle cylindrical battery provided by the present invention optimizes the pole piece design, improves the pole piece surface density and thickness on both sides of the negative pole piece to match the gap generated by the thinning of the positive pole piece edge, improves the edge lithium deposition phenomenon during the cycle process, extends the cycle life of the cylindrical battery, enhances the performance stability of the battery, and improves the safety of the cylindrical battery.

[0068] In some optional embodiments, there is an overhang1 area outside the negative electrode unit 1;

[0069] The pole sheet surface density in the overhang1 region is:

[0070] σ o1 =0.16*e^(-0.693)*σ c2 / ρ C *ρ a +λ*C c *σ c2 *α c / (C a *α a ) ；

[0071] The thickness of the pole piece in the overhang1 area is:

[0072] H o1 =0.16*e^(-0.693)*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0073] There is an overhang3 area outside the negative electrode unit 3;

[0074] The pole sheet surface density in the overhang3 region is:

[0075] σ o3 =0.16*e^(-0.693)*σ c2 / ρ C *ρ a +λ*C c *σ c2 *α c / (C a *α a ) ；

[0076] The thickness of the pole piece in the overhang3 area is:

[0077] H o3 =0.16*e^(-0.693)*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a .

[0078] In some optional embodiments, the width of the overhang1 area may be, for example, but not limited to, 0.5 mm, 1 mm, 2 mm or 4 mm;

[0079] The width of the overhang 3 area may be, for example, but not limited to, 0.5 mm, 1 mm, 2 mm or 4 mm.

[0080] In some optional embodiments, the width of the positive electrode unit 2 is twice the width of the positive electrode unit 1;

[0081] The width of the positive electrode unit 2 is twice the width of the positive electrode unit 3 .

[0082] In some optional embodiments, the thickness of the positive electrode current collector may be, for example, but not limited to, 13 μm, 14 μm or 16 μm;

[0083] The thickness of the negative electrode current collector may be, for example, but not limited to, 6 μm, 6.5 μm or 7 μm.

[0084] In some optional embodiments, the coating formula of the positive electrode sheet includes 0.5%-5% positive electrode conductor, 0.5%-5% positive electrode binder and positive electrode active material.

[0085] The mass percentage of the positive electrode conductive agent may be, for example, but not limited to, 0.5%, 1% or 5%;

[0086] The mass percentage of the positive electrode binder may be, for example, but not limited to, 0.5%, 1% or 5%.

[0087] In some optional embodiments, the positive electrode active material includes but is not limited to lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate or ternary material, or other positive electrode active materials known to those skilled in the art;

[0088] The positive electrode conductive agent includes but is not limited to carbon black, conductive graphite, carbon fiber, carbon nanotube or graphene, or other positive electrode conductive agents known to those skilled in the art;

[0089] The positive electrode binder includes but is not limited to PVDF, or other positive electrode binders well known to those skilled in the art.

[0090] In some optional embodiments, the coating formula of the negative electrode sheet includes 0.5%-4% negative electrode conductive agent, 0.5%-4% negative electrode binder, and the balance is negative electrode active material.

[0091] The mass percentage of the negative electrode conductive agent may be, for example, but not limited to, 0.5%, 1% or 4%;

[0092] The mass percentage of the negative electrode binder may be, for example, but not limited to, 0.5%, 1% or 4%.

[0093] In some optional embodiments, the negative electrode active material includes but is not limited to graphite, hard carbon, soft carbon, graphene or silicon negative electrode material, or other negative electrode active materials known to those skilled in the art;

[0094] The negative electrode conductive agent includes but is not limited to carbon black, conductive graphite, carbon fiber, carbon nanotube or graphene, or other negative electrode conductive agents known to those skilled in the art;

[0095] The negative electrode binder includes, but is not limited to, styrene-butadiene rubber, polyacrylic acid, sodium alginate or sodium carboxymethyl cellulose, or other negative electrode binders known to those skilled in the art.

[0096] In some optional embodiments, the pole piece tabs of the cylindrical battery are two-way tabs, and the tabs may be in the form of full tabs or multiple tabs.

[0097] In a second aspect, the present invention provides the application of the above-mentioned pole piece design method in the preparation of cylindrical batteries.

[0098] By using gaskets of corresponding shapes and sizes on a spray coating machine, the positive and negative electrode current collectors of the battery can be coated separately, and then a cylindrical battery can be prepared through winding and other processes.

[0099] The present invention is further described below by means of specific examples and comparative examples. However, it should be understood that these examples are only used for more detailed description and should not be construed as limiting the present invention in any form.

[0100] Example 1

[0101] A method for designing a pole piece of a long-cycle cylindrical battery, wherein the positive pole piece is divided into 20 basic length units in a direction perpendicular to the winding direction, with a total of 3 coating units, which are positive pole unit 1 (4 basic units, which are positive pole unit 1-1, positive pole unit 1-2, positive pole unit 1-3 and positive pole unit 1-4), positive pole unit 2 (12 basic units) and positive pole unit 3 (4 basic units, which are positive pole unit 3-4, positive pole unit 3-3, positive pole unit 3-2 and positive pole unit 3-1); the compaction density of the three positive pole units is the same;

[0102] Then the thickness of the positive electrode unit 2 is:

[0103] H c2 =σ c2 / ρ C +τ c ;

[0104] The thickness of the positive electrode unit 1 is:

[0105] H c1 =(1-0.16*e^(-0.693*X 1 ))σ c2 / ρ C +τ c ;

[0106] The thickness of the positive electrode unit 3 is:

[0107] H c3 =(1-0.16*e^(-0.693*X 3 ))σ c2 / ρ C +τ c ;

[0108] Among them, H c2 is the thickness of the positive electrode unit 2; H c1 is the thickness of the positive electrode unit 1; H c3 is the thickness of the positive electrode unit 3; σ c2 is the surface density of the positive electrode unit 2, ranging from 20 to 42 mg / cm 2 ρ C is the compaction density of the positive electrode, which is 2.0-2.5g / cm 3 ; τ c is the thickness of the positive electrode current collector; X of the positive electrode unit 1-1, the positive electrode unit 1-2, the positive electrode unit 1-3 and the positive electrode unit 1-4 1 The values ​​of are 1, 2, 3, and 4 respectively; the values ​​of X of positive electrode unit 3-4, positive electrode unit 3-3, positive electrode unit 3-2, and positive electrode unit 3-1 3 The values ​​of are 4, 3, 2, and 1 respectively;

[0109] After winding, the areas on the negative electrode sheet corresponding to the positive electrode sheet are recorded as negative electrode unit 1, negative electrode unit 2 and negative electrode unit 3; the compaction density of the three negative electrode units is the same; the negative electrode unit 1 is divided into negative electrode unit 1-1, negative electrode unit 1-2, negative electrode unit 1-3 and negative electrode unit 1-4, which correspond to the positive electrode unit 1-1, positive electrode unit 1-2, positive electrode unit 1-3 and positive electrode unit 1-4 respectively; the negative electrode unit 3 is divided into negative electrode unit 3-1, negative electrode unit 3-2, negative electrode unit 3-3 and negative electrode unit 3-4, which correspond to the positive electrode unit 3-1, positive electrode unit 3-2, positive electrode unit 3-3 and positive electrode unit 3-4 respectively;

[0110] Then the thickness of the negative electrode unit 2 is:

[0111] H a2 =λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0112] The thickness of the negative electrode unit 1 is:

[0113] H a1 =0.16*e^(-0.693*X 1 )*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0114] The thickness of the negative electrode unit 3 is:

[0115] H a3 =0.16*e^(-0.693*X 3 ))σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0116] There is an overhang1 area with a width of 2 mm on the outside of the negative electrode unit 1;

[0117] The thickness of the pole piece in the overhang1 area is:

[0118] H o1 =0.16*e^(-0.693)*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a ;

[0119] There is an overhang3 area with a width of 2 mm on the outside of the negative electrode unit 3;

[0120] The thickness of the pole piece in the overhang3 area is:

[0121] H o3 =0.16*e^(-0.693)*σ c2 / ρ C +λ*C c *σ c2 *α c / (C a *α a ) / ρ a +τ a .

[0122] Among them, H a2 is the thickness of the negative electrode unit 2; H a1 is the thickness of the negative electrode unit 1; H a3 is the thickness of the negative electrode unit 3; λ is a constant of 1.15-1.25; α a is the proportion of negative electrode active material; α c C is the proportion of positive electrode active material; a Negative electrode capacity in grams, C c Positive electrode gram capacity; ρ a is the compaction density of the negative electrode sheet, which is 1.3-1.7g / cm 3 ; τ c is the thickness of the negative electrode current collector; X of the negative electrode unit 1-1, the negative electrode unit 1-2, the negative electrode unit 1-3 and the negative electrode unit 1-4 1 The values ​​of are 1, 2, 3, and 4 respectively; the values ​​of X of negative electrode unit 3-4, negative electrode unit 3-3, negative electrode unit 3-2, and negative electrode unit 3-1 3 The values ​​are 4, 3, 2, and 1 respectively.

[0123] Test Example 1

[0124] The electrodes were designed and prepared by the design method of Example 1 to obtain batteries 1-3. Figure 1 and Figure 2 As shown, Figure 1 In the figure, from left to right are: coating unit 3, coating unit 2, coating unit 1 and pole ear; Figure 2 In the figure, from left to right are the tab, overhang 3 area, coating unit 3, coating unit 2, coating unit 1 and overhang 1 area.

[0125] Battery 1: The coating formula of the positive electrode sheet is: positive electrode active material (lithium iron phosphate): conductive agent: binder = 96.7:1.5:1.8; the coating formula of the negative electrode sheet is: negative electrode active material (artificial graphite): conductive agent: binder = 95:2:3; the design parameters of the positive electrode sheet and the negative electrode sheet are shown in Table 1; the separator is: 14μmPP separator; the electrolyte formula is: solvent + 1.2M LiPF 6 + Additives, wherein the solvent is: EC, DMC and DEC in a volume ratio of 1:1:1, and the additives are: 1% VC+1% FEC+0.5% DTD.

[0126] Battery 2: The coating formula of the positive electrode sheet is: positive electrode active material: conductive agent: binder = 96.7:1.5:1.8; the coating formula of the negative electrode sheet is: negative electrode active material: conductive agent: binder = 95:2:3; the design parameters of the positive electrode sheet and the negative electrode sheet are shown in Table 2; the separator is: 14μmPP separator; the electrolyte formula is: solvent + LiPF 6 + additives, wherein the solvent is: EC, DMC and DEC in a volume ratio of 1:1:1, and the additives are: 1% VC+1% FEC+0.5% DTD.

[0127] Battery 3: The coating formula of the positive electrode sheet is: positive electrode active material: conductive agent: binder = 96.7:1.5:1.8; the coating formula of the negative electrode sheet is: negative electrode active material: conductive agent: binder = 95:2:3; the design parameters of the positive electrode sheet and the negative electrode sheet are shown in Table 3; the separator is: 14μmPP separator; the electrolyte formula is: solvent + LiPF 6 + additives, wherein the solvent is: EC, DMC and DEC in a volume ratio of 1:1:1, and the additives are: 1% VC+1% FEC+0.5% DTD.

[0128] At the same time, corresponding control groups 1-3 are set up for battery 1, battery 2 and battery 3 respectively. The difference between control group 1 and battery 1 is that the design parameters are shown in Table 1; the difference between control group 2 and battery 2 is that the design parameters are shown in Table 2; the difference between control group 3 and battery 3 is that the design parameters are shown in Table 3.

[0129] The above batteries were tested and the results are shown in Tables 1-3.

[0130] Table 1

[0131]

[0132] Note: The thickness of the pole piece in the table is the average thickness. The same applies to Table 2-Table 3.

[0133] Table 2

[0134]

[0135]

[0136] Table 3

[0137]

[0138]

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing a pole piece for a long-cycle cylindrical battery, characterized in that: In the direction perpendicular to the winding direction, the positive electrode sheet is divided into three coating units, namely positive electrode unit 1, positive electrode unit 2 and positive electrode unit 3; the compaction density of the three positive electrode units is the same; in the direction from positive electrode unit 1 to positive electrode unit 3, positive electrode unit 1 is divided into four basic units, namely positive electrode unit 1-1, positive electrode unit 1-2, positive electrode unit 1-3 and positive electrode unit 1-4, and positive electrode unit 3 is divided into four basic units, namely positive electrode unit 3-4, positive electrode unit 3-3, positive electrode unit 3-2 and positive electrode unit 3-1; Then the thickness of the positive electrode unit 2 is: H c2 =s c2 / r C +t c ; The thickness of the positive electrode unit 1 is: H c1 =(1-0.16*e^(-0.693*X1))σ c2 / r C +t c ; The thickness of the positive electrode unit 3 is: H c3 =(1-0.16*e^(-0.693*X3))σ c2 / r C +t c ; Among them, H c2 is the thickness of the positive electrode unit 2; H c1 is the thickness of the positive electrode unit 1; H c3 is the thickness of the positive electrode unit 3; σ c2 is the surface density of the positive electrode unit 2, ranging from 20 to 42 mg / cm 2 ρ C is the compaction density of the positive electrode, which is 2.0-2.5g / cm 3 ; τ c is the thickness of the positive electrode current collector; the values ​​of X1 of the positive electrode unit 1-1, the positive electrode unit 1-2, the positive electrode unit 1-3 and the positive electrode unit 1-4 are 1, 2, 3, 4, respectively; the values ​​of X3 of the positive electrode unit 3-4, the positive electrode unit 3-3, the positive electrode unit 3-2 and the positive electrode unit 3-1 are 4, 3, 2, 1, respectively; After winding, the areas on the negative electrode sheet corresponding to the positive electrode sheet are recorded as negative electrode unit 1, negative electrode unit 2 and negative electrode unit 3; the compaction density of the three negative electrode units is the same; the negative electrode unit 1 is divided into negative electrode unit 1-1, negative electrode unit 1-2, negative electrode unit 1-3 and negative electrode unit 1-4, which correspond to the positive electrode unit 1-1, positive electrode unit 1-2, positive electrode unit 1-3 and positive electrode unit 1-4 respectively; the negative electrode unit 3 is divided into negative electrode unit 3-1, negative electrode unit 3-2, negative electrode unit 3-3 and negative electrode unit 3-4, which correspond to the positive electrode unit 3-1, positive electrode unit 3-2, positive electrode unit 3-3 and positive electrode unit 3-4 respectively; Then the thickness of the negative electrode unit 2 is: H a2 =λ*C c *s c2 *a c / (C a *a a ) / p a +t a ; The thickness of the negative electrode unit 1 is: H a1 =0.16*e^(-0.693*X1)*σ c2 / r C +λ*C c *s c2 *a c / (C a *a a ) / p a +t a ; The thickness of the negative electrode unit 3 is: H a3 =0.16*e^(-0.693*X3))σ c2 / r C +λ*C c *s c2 *a c / (C a *a a ) / p a +t a ; Among them, H a2 is the thickness of the negative electrode unit 2; H a1 is the thickness of the negative electrode unit 1; H a3 is the thickness of the negative electrode unit 3; λ is a constant of 1.15-1.25; α a is the proportion of negative electrode active material; α c C is the proportion of positive electrode active material; a Negative electrode capacity in grams, C c Positive electrode gram capacity; ρ a is the compaction density of the negative electrode sheet, which is 1.3-1.7g / cm 3 ; τ c is the thickness of the negative electrode current collector; the values ​​of X1 of the negative electrode unit 1-1, the negative electrode unit 1-2, the negative electrode unit 1-3 and the negative electrode unit 1-4 are 1, 2, 3, 4 respectively; the values ​​of X3 of the negative electrode unit 3-4, the negative electrode unit 3-3, the negative electrode unit 3-2 and the negative electrode unit 3-1 are 4, 3, 2, 1 respectively.

2. The pole piece design method according to claim 1, characterized in that: An overhang1 region exists on the outer side of the negative electrode unit 1; The thickness of the pole piece in the overhang1 area is: H o1 =0.16*e^(-0.693)*σ c2 / r C +λ*C c *s c2 *a c / (C a *a a ) / p a +t a ; There is an overhang3 area outside the negative electrode unit 3; The thickness of the pole piece in the overhang3 area is: H o3 =0.16*e^(-0.693)*σ c2 / r C +λ*C c *s c2 *a c / (C a *a a ) / p a +t a 。 3. The pole piece design method according to claim 2, characterized in that: The width of the overhang1 area is 0.5-4 mm; The width of the overhang 3 area is 0.5-4 mm.

4. The pole piece design method according to claim 1, characterized in that: The width of the positive electrode unit 2 is twice the width of the positive electrode unit 1; The width of the positive electrode unit 2 is twice the width of the positive electrode unit 3 .

5. The pole piece design method according to claim 1, characterized in that: The thickness of the positive electrode current collector is 13-16 μm; The thickness of the negative electrode current collector is 6-7 μm.

6. The pole piece design method according to claim 1, characterized in that: Calculated by mass percentage, the coating formula of the positive electrode sheet includes 0.5%-5% positive electrode conductor, 0.5%-5% positive electrode binder, and the balance is positive electrode active material.

7. The pole piece design method according to claim 6, characterized in that: The positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate or ternary materials; The positive electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube or graphene; The positive electrode binder includes PVDF.

8. The pole piece design method according to claim 1, characterized in that: Calculated by mass percentage, the coating formula of the negative electrode sheet includes 0.5%-4% of negative electrode conductive agent, 0.5%-4% of negative electrode binder, and the balance is negative electrode active material.

9. The pole piece design method according to claim 8, characterized in that: The negative electrode active material includes at least one of graphite, hard carbon, soft carbon, graphene or silicon negative electrode material; The negative electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube or graphene; The negative electrode binder includes at least one of styrene-butadiene rubber, polyacrylic acid, sodium alginate or sodium carboxymethyl cellulose.

10. Application of the pole piece design method according to any one of claims 1 to 9 in the preparation of cylindrical batteries.

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