CN115911512A - Lithium ion battery - Google Patents
Lithium ion battery Download PDFInfo
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- CN115911512A CN115911512A CN202211727956.2A CN202211727956A CN115911512A CN 115911512 A CN115911512 A CN 115911512A CN 202211727956 A CN202211727956 A CN 202211727956A CN 115911512 A CN115911512 A CN 115911512A
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a lithium ion battery, which comprises a positive plate and a negative plate, wherein the positive plate comprises a positive current collector, at least one side surface of the positive current collector is provided with a positive active material layer, and the thickness of the positive active material layer is h 0 The surface of the positive electrode active material layer is provided with a first thinning area and a second thinning area, and the thickness of the positive electrode active material layer in the first thinning area is h 1 ，0.55≤h 1 /h 0 ≦ 0.65, and the thickness of the positive electrode active material layer in the second thinning region is h 2 ，h 2 <h 0 (ii) a A positive electrode lug groove is formed in the top surface of the positive electrode active material layer in the first thinning area, and the surface of the positive electrode current collector is exposed out of the positive electrode lug groove; the negative pole piece is connected with a negative pole lug, and the negative pole lug is embedded into the second thinning areaIn (1). The thinning structure of the lithium ion battery provided by the invention can reduce lithium precipitation, so that the battery can normally run under the conditions of low temperature, high multiplying power, low CB value or poor active substance dynamics.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a lithium ion battery.
Background
With the continuous development of society, there is a higher demand for lithium ion batteries with high energy density, high safety and long cycle life, but the current batteries cannot normally operate under the conditions of high rate, low temperature, low CB value or poor active substance dynamics and the like.
CN108091937B discloses a high-rate lithium ion battery pole piece drying method and a high-rate lithium ion battery. And the high-rate lithium ion battery is baked by the pole piece and the winding core respectively to remove water. This technique is effectual gets rid of pole piece and the inside moisture of roll core in the short time, avoids causing diaphragm shrink, pole piece to fall whitewashed scheduling problem because of long-time high temperature toasts to make the battery can move under the high magnification condition.
CN106784846A discloses a high-rate lithium ion battery anode, a preparation method and an application thereof, wherein an anode active substance, a conductive agent, azomethyl pyrrolidone and polyvinylidene fluoride are prepared into anode slurry; preparing a carbon coating slurry from a conductive agent 1, a conductive agent 2 and a binder azomethylpyrrolidone; and sequentially coating the positive electrode slurry and the carbon coating slurry on a positive current collector, drying, rolling a film, cutting to obtain a positive plate with the carbon coated on the surface, assembling the positive plate with a negative plate, a diaphragm and a shell, adding electrolyte, and activating and sorting to obtain the high-rate lithium ion battery. The carbon layer is formed on the surface of the positive electrode, so that the conductivity of the surface of the positive electrode is improved, and the battery can operate under a high-rate condition.
CN113707882A discloses a low-temperature lithium iron phosphate lithium ion power battery and a low-temperature discharging method. The low-temperature lithium iron phosphate lithium ion power battery comprises a positive plate, a negative plate, a diaphragm, electrolyte and a battery shell column, wherein a positive material in the positive plate comprises a positive active substance, a binder, a conductive agent and a positive current collector, the positive active substance adopts a carbon-coated lithium iron phosphate material, the binder adopts polyvinylidene fluoride, the conductive agent adopts one or more of conductive carbon black, conductive graphite, crystalline flake graphite and a carbon nano tube, and the current collector adopts an aluminum foil. The battery can operate in a low-temperature environment by methods such as carbon coating.
The method solves the problem that the lithium ion battery is difficult to operate under the conditions of high multiplying power, low temperature and the like by means of modifying active substances or adjusting preparation parameters of pole pieces and the like. However, the improvement effect of the above means is limited.
Therefore, there is a need to develop a lithium ion battery that can reduce lithium deposition, so that the battery can normally operate under conditions of high rate, low temperature, low CB value, or poor active material kinetics.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a lithium ion battery, wherein the thinning structure of the lithium ion battery can reduce lithium precipitation, so that the battery can normally run under the conditions of low temperature, high multiplying power, low CB value or poor active material dynamics.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a lithium ion battery, which includes a positive plate and a negative plate, wherein the positive plate includes a positive current collector, at least one side surface of the positive current collector is provided with a positive active material layer, and the thickness of the positive active material layer is h 0 The surface of the positive electrode active material layer is provided with a first thinning area and a second thinning area, and the thickness of the positive electrode active material layer in the first thinning area is h 1 ，0.55≤h 1 /h 0 ≦ 0.65 (e.g., may be 0.55, 0.56, 0.57, 0.58, 0.59, 0.6, 0.61, 0.62, 0.63, 0.64, or 0.65, etc.), and the thickness of the positive electrode active material layer in the second thinning region is h 2 ，h 2 <h 0 ；
A positive electrode lug groove is formed in the top surface of the positive electrode active material layer in the first thinning area, and the surface of the positive electrode current collector is exposed out of the positive electrode lug groove;
the negative plate is connected with a negative tab, and the negative tab is embedded into the second thinning area.
The invention provides a lithium ion battery, which comprises a positive plate and a negative plate, wherein a tab groove on the surface of the positive plate has higher current density, a thinned positive active material layer is arranged on the periphery of the tab groove, the thinned positive active material layer can reduce the lithium precipitation risk caused by high current density, and meanwhile, a negative tab connected with the negative plate is embedded into a thinning area, so that the local CB value of the negative tab can be improved, and the lithium precipitation risk can be reduced.
The battery structure can widen the temperature window, the multiplying power window, the CB value window and the active substance system of the lithium ion battery, so that the battery can normally run under the conditions of low temperature, high multiplying power, low CB value or poor active substance dynamics, and is difficult to precipitate lithium.
The CB value is a ratio of positive-to-negative electrode capacity to positive electrode capacity.
As a preferred technical solution of the present invention, the top surface of the positive electrode active material layer in the first thinning-out region is parallel to the plane where the positive electrode current collector is located.
As a preferred technical solution of the present invention, the positive electrode active material layer in the first thinning region is an inclined layer, an included angle between a top surface of the inclined layer and a plane where the positive electrode current collector is located is θ, where 0 < θ < 90 °, and may be, for example, 1 °, 2 °, 5 °, 10 °, 15 °, 20 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, or 85 °.
In the invention, the positive electrode active material layer in the first thinning area is an inclined layer, and when the adhesive paper is attached to the surface of the inclined layer, the adhesive paper is not easy to wrinkle.
Preferably, θ = arctan (m/n), where m is a maximum height of the slanted layer and n is a distance of the slanted layer along a length direction of the positive electrode tab.
As a preferred aspect of the present invention, the length of the first thinning-out region is greater than the length of the positive tab slot.
Preferably, the difference between the length of the first thinning area and the length of the positive ear canal is 3-20 mm, and may be 3mm, 5mm, 7mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, or the like, for example.
Preferably, the width of the first thinning-out region is greater than the width of the positive ear groove.
Preferably, the difference between the width of the first thinning area and the width of the positive electrode ear groove is 3-20 mm, such as 3mm, 5mm, 7mm, 10mm, 12mm, 14mm, 16mm, 18mm or 20mm.
In a preferred embodiment of the present invention, the positive tab slot is connected to a positive tab.
Preferably, the surface of the positive lug groove connected with the positive lug is pasted with first gummed paper.
Preferably, the material of the first gummed paper comprises a neoprene rubber-like material.
The neoprene adhesive paper has stronger viscosity, and active substances below the adhesive paper can be difficultly soaked by electrolyte, so that the risk of lithium precipitation is reduced.
As a preferable technical solution of the present invention, the first gummed paper is located between the first thinning area and the positive electrode tab slot.
According to the invention, the edge of the first adhesive tape does not exceed the first thinning area, so that the flatness of the battery cell can be improved, the CB value of the local edge of the adhesive tape can be improved, the risk of lithium precipitation is reduced, and the lithium precipitation is reduced; and the first thinning area is not completely covered due to the existence of errors, and the first gummed paper is difficult to exactly cover the first thinning area.
Preferably, the distance between the long side of the first gummed paper and the long side of the positive electrode tab slot is 2-6 mm, for example, 2mm, 3mm, 4mm, 5mm or 6 mm.
Preferably, the distance between the short side of the first gummed paper and the short side of the positive electrode lug groove is 2-6 mm, for example, 2mm, 3mm, 4mm, 5mm or 6 mm.
Preferably, the distance between the long side of the first gummed paper and the long side of the first thinning zone is 0.5-5 mm, and may be, for example, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, or the like.
Preferably, the distance between the short side of the first adhesive paper and the short side of the first thinning zone is 0.5-5 mm, and may be, for example, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, or the like.
Preferably, the thickness of the first gummed paper is less than or equal to the depth of the first thinning area.
In the present invention, the first thinning-out region has a depth h 3 ，h 3 ＝h 0 -h 1 。
In a preferred embodiment of the present invention, the average particle diameter of the active material in the positive electrode active material layer is d, and the thickness h of the positive electrode active material layer in the second thinning-out region is 2 Satisfies the following conditions:
1.5×d≤h 2 /h 0 ≤2/π。
d is a numerical value of the average particle diameter of the active material in the positive electrode active material layer, and the unit of the average particle diameter is μm.
In the present invention, h 2 /h 0 When the thickness is too high, the risk of lithium precipitation is increased, and the aim of improving the CB value cannot be achieved due to lower thinning degree; h is a total of 2 /h 0 When the current collector is too low, the positive plate can be exposed out of the current collector, so that safety risk exists, and the battery cannot be used.
As a preferable aspect of the present invention, a second adhesive tape is attached to a top surface of the positive electrode active material layer in the second thinning-out region.
Preferably, the material of the second gummed paper comprises a neoprene-like material.
The neoprene adhesive paper has stronger viscosity, and active substances below the adhesive paper can be difficultly soaked by electrolyte, so that the risk of lithium precipitation is reduced.
In a preferred embodiment of the present invention, an area of the second adhesive sheet is smaller than an area of a top surface of the positive electrode active material layer in the second thinning-out region.
Preferably, the length of the second gummed paper is smaller than the length of the second thinning zone.
Preferably, the width of the second gummed paper is smaller than the width of the second thinning section.
Preferably, the distance between the long side of the second gummed paper and the long side of the second thinning zone is 0.5-5 mm, for example, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, or 5mm, etc.
Preferably, the distance between the short side of the second gummed paper and the short side of the second thinning zone is 0.5-5 mm, for example, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm or 5mm, etc.
Preferably, the thickness of the second gummed paper is less than or equal to the depth of the second thinning area.
In the present invention, the depth of the first thinning-out region is h 4 ，h 4 ＝h 0 -h 2 。
As a preferable technical scheme of the invention, the surface of the negative electrode tab is coated with weld toe glue.
Preferably, the length of the second gummed paper is longer than the length of the area where the toe welding glue is located.
Preferably, the difference between the length of the second gummed paper and the length of the area where the weld toe glue is located is 0.1-10 mm, for example, 0.1mm, 0.2mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm.
Preferably, the width of the second gummed paper is larger than the width of the area where the toe welding glue is located.
In the invention, the length and the width of the second gummed paper on the positive pole piece are respectively greater than the length and the width of the area where the corresponding negative pole weld toe glue is positioned, so as to prevent lithium precipitation of the corresponding negative pole.
Preferably, the difference between the width of the second gummed paper and the width of the area where the weld toe glue is located is 0.1-10 mm, for example, 0.1mm, 0.2mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, etc.
The recitation of numerical ranges herein includes not only the above-recited values, but also any values between any of the above-recited numerical ranges not recited, and for brevity and clarity, is not intended to be exhaustive of the specific values encompassed within the range.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention provides a lithium ion battery, which comprises a positive plate and a negative plate, wherein a tab groove on the surface of the positive plate has higher current density, the periphery of the tab groove is provided with a thinned positive active material layer, the thinned positive active material layer can reduce the lithium precipitation risk caused by high current density, and meanwhile, a negative tab connected with the negative plate is embedded into a thinning area, so that the CB value of a negative tab local area can be improved, and the lithium precipitation risk can be reduced.
(2) The battery structure can widen the temperature window, the multiplying power window, the CB value window and an active substance system of the lithium ion battery, so that the battery can normally run under the conditions of low temperature, high multiplying power, low CB value or poor active substance dynamics, and is difficult to separate lithium.
Drawings
Fig. 1 is a schematic diagram of a pole piece structure of a lithium ion battery provided in embodiment 1;
fig. 2 is a schematic view of the positive electrode sheet provided in embodiment 1 pasted with a first adhesive paper;
fig. 3 is a schematic view of an area where a toe glue is located on a negative electrode sheet provided in example 1;
fig. 4 is a schematic winding diagram of the positive electrode sheet and the negative electrode sheet provided in example 1;
fig. 5 is a schematic structural view of a first thinning-out region provided in embodiment 2;
fig. 6 is a schematic structural view of a conventional positive electrode sheet provided in comparative example 3;
wherein, 1-a first thinning zone; 2-positive ear grooves; 3-a second thinning zone; 4-first gummed paper; 5-second gummed paper; 6-negative electrode tab.
Detailed Description
It is to be understood that in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be taken as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature.
It should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "disposed," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The technical solution of the present invention is further explained by the following embodiments.
Example 1
This embodiment provides a lithium ion battery, lithium ion battery includes positive plate and negative plate, as shown in fig. 1, positive plate includes the anodal mass flow body, the both sides surface of anodal mass flow body is provided with anodal active material layer, is anodal A face and anodal B face respectively, the thickness h on anodal active material layer 0 The thickness h of the positive electrode active material layer in the first thinning area 1 is 50 mu m, the active material in the positive electrode active material layer is lithium cobaltate, the average particle diameter d of the active material is 10 mu m, the surface of the positive electrode active material layer is provided with a first thinning area 1 and a second thinning area 3 1 Is 27.5 μm, h 1 /h 0 =0.55, thickness h of positive electrode active material layer in the second thinning-out region 3 2 27.5 μm;
the first top surface that reduces the anodal active material layer in the thin district 1 is parallel with the plane at anodal mass flow body place, anodal ear groove 2 has been seted up to the first top surface that reduces the anodal active material layer in the thin district 1, and first length that reduces thin district 1 is greater than the length of anodal ear groove 2, and the difference is 5mm, and first width that reduces thin district 1 is greater than the width of anodal ear groove 2, and the difference is 5mm, anodal ear groove 2 exposes the surface of anodal mass flow body, and anodal ear groove 2 is connected with anodal ear, and 2 surface subsides of anodal ear groove that are connected with anodal ear have first adhesive tape 4, and its material is the chloroprene rubber class, and viscosity is 1.8, and first adhesive tape 4 is located between first thin district 1 and anodal ear groove 2, as shown in fig. 2, and the distance between the long limit of first adhesive tape 4 and the long limit of anodal ear groove 2 is 3mm, the distance between the short side of first adhesive tape 4 and the short limit of anodal ear groove 2 is 3mm, the first adhesive tape 4 is the first short side and is the first short side of the first adhesive tape 4, and the first short side of the first adhesive tape 4 is the first distance between the long limit of the first adhesive tape 4 is 22 mm, and the first short side of the first adhesive tape 4 is the short side of the first short side of the thin district 22 mm, and is the first short side of the distance of the short side of the thin district 2 is the short side of the first adhesive tape 4, and is the short side of the first adhesive tape 4 is 22 mm.
The negative plate is divided into a negative electrode A surface and a negative electrode B surface, wherein a negative electrode active substance is graphite (K58T type), the designed CB value is 1.07, negative electrode lug grooves are formed in two surfaces of the negative plate, the negative electrode lug grooves are connected with negative electrode lugs 6, the negative electrode lugs 6 are embedded into the second thinning area 3, a second adhesive tape 5 is pasted and covered on the top surface of a positive electrode active substance layer in the second thinning area 3 and is made of chloroprene rubber, the viscosity of the second adhesive tape is 1.8, the length of the second adhesive tape 5 is smaller than that of the second thinning area 3, the width of the second adhesive tape 5 is smaller than that of the second thinning area 3, the distance between the long edge of the second adhesive tape 5 and the long edge of the second thinning area 3 is 0.5mm, the distance between the short edge of the second adhesive tape 5 and the short edge of the second thinning area 3 is 0.5mm, and the thickness of the second adhesive tape 5 is 22 mu m; as shown in fig. 3, the length of the area where the weld toe glue is located is a, the width of the area is b, the length of the second adhesive paper 5 is greater than a, the difference between the length of the second adhesive paper 5 and a is 1mm, the width of the second adhesive paper 5 is greater than b, and the difference between the width of the second adhesive paper 5 and b is 1mm;
the positive electrode sheet and the negative electrode sheet are stacked together and wound to assemble the lithium ion battery as shown in fig. 4.
Example 2
This embodiment provides a lithium ion battery, lithium ion battery includes positive plate and negative pole piece, positive plate includes the anodal mass flow body, the both sides surface of anodal mass flow body is provided with anodal active material layer, is anodal A face and anodal B face respectively, the thickness h on anodal active material layer 0 30 μm, and the active material in the positive electrode active material layer is nickel cobalt lithium manganate (LiNi) 0.8 Co 0.1 Mn 0.1 O 2 Simple and easyCalled NCM 811), the average particle diameter d of the active material is 5 μm, a first thinning area and a second thinning area are arranged on the surface of the positive electrode active material layer, and the thickness h of the positive electrode active material layer in the first thinning area 1 Is 18 μm, h 1 /h 0 =0.6, thickness h of positive electrode active material layer in the second thinning-out region 2 Is 18 μm;
anodal ear groove has been seted up to the top surface on the anodal active material layer in the first district that thins, and the first remaining anodal active material layer that thins is the slope layer in the district, the top surface on slope layer and the planar contained angle theta at anodal mass flow body place are 30, as shown in figure 5, and the length in first district that thins is greater than the length in anodal ear groove, and the difference is 11mm, and the first width that thins the district is greater than the width in anodal ear groove, and the difference is 11mm, anodal ear groove exposes the surface of anodal mass flow body, anodal ear groove are connected with anodal ear, and the anodal ear groove surface subsides that are connected with anodal ear have first adhesive tape, and its material is the chloroprene rubber class, and viscosity is 1.8, and first adhesive tape is located between first district and the anodal ear groove, and the distance between the long limit of first adhesive tape and the long limit in anodal ear groove is 6mm, the distance between the short edge of first adhesive tape and the short side of anodal ear groove is 6mm, the first short side is the distance between the first short side of first adhesive tape and the first short side is the distance between the short side of 5mm, and the first short side is the distance between the first short side of the first adhesive tape, and the thickness is the first short side distance between the area, and the thickness is 15 mm.
The negative plate is divided into a negative A surface and a negative B surface, wherein a negative active material is graphite (K58T type), the designed CB value is 1.07, negative lug grooves are formed in both surfaces of the negative plate, the negative lug grooves are connected with negative lugs, the negative lugs are embedded into the second thinning area, second gummed paper is pasted on the top surface of the positive active material layer in the second thinning area and is made of chloroprene rubber, the viscosity of the second gummed paper is 1.8, the length of the second gummed paper is smaller than that of the second thinning area, the width of the second gummed paper is smaller than that of the second thinning area, the distance between the long edge of the second gummed paper and the long edge of the second thinning area is 5mm, the distance between the short edge of the second gummed paper and the short edge of the second thinning area is 5mm, and the thickness of the second gummed paper is 15 mu m; the surfaces of the negative electrode lugs are coated with weld toe glue, the length of the second gummed paper is greater than the length of the area where the weld toe glue is located, the difference of the lengths is 5mm, the width of the second gummed paper is greater than the width of the area where the weld toe glue is located, and the difference of the widths is 5mm;
and the positive plate and the negative plate are overlapped together and wound to assemble the lithium ion battery.
Example 3
This embodiment provides a lithium ion battery, lithium ion battery includes positive plate and negative pole piece, positive plate includes the anodal mass flow body, the both sides surface of anodal mass flow body is provided with anodal active material layer, is anodal A face and anodal B face respectively, the thickness h on anodal active material layer 0 The thickness h of the positive electrode active material layer in the first thinning area is 20 micrometers, the active material in the positive electrode active material layer is lithium iron phosphate, the average particle size d of the active material is 0.3 micrometers, the surface of the positive electrode active material layer is provided with a first thinning area and a second thinning area, and the thickness h of the positive electrode active material layer in the first thinning area 1 Is 13 μm, h 1 /h 0 =0.65, thickness h of positive electrode active material layer in the second thinning-out region 2 Is 13 μm;
anodal ear groove has been seted up to the top surface on the anodal active material layer in the first thinning zone, and remaining anodal active material layer is the slope layer in the first thinning zone, the top surface on slope layer and the planar contained angle theta at anodal mass flow body place are 45, and the length in first thinning zone is greater than the length in anodal ear groove, and the difference is 6mm, and the width in first thinning zone is greater than the width in anodal ear groove, and the difference is 6mm, anodal ear groove exposes the surface of anodal mass flow body, anodal ear groove are connected with anodal ear, and the anodal ear groove surface subsides that are connected with anodal ear have first adhesive tape, and its material is the chloroprene rubber class, and viscosity is 1.8, and first adhesive tape is located between first thinning zone and the anodal ear groove, and the distance between the long limit of first adhesive tape and the long limit in anodal ear groove is 5mm, the distance between the minor face of first adhesive tape and the minor face in anodal ear groove is 5mm, the first adhesive tape and the first minor face are 1mm between the first short side of thinning zone, and the minor side of first adhesive tape are the distance between the minor side of first adhesive tape, and the minor side is the thickness of first adhesive tape is 1mm, and the minor side is the thickness of first adhesive tape between the minor side of first adhesive tape is 10mm.
The negative plate is divided into a negative A surface and a negative B surface, wherein a negative active material is graphite (K58T type), the designed CB value is 1.07, negative lug grooves are formed in both surfaces of the negative plate, the negative lug grooves are connected with negative lugs, the negative lugs are embedded into the second thinning area, second gummed paper is pasted on the top surface of the positive active material layer in the second thinning area and is made of chloroprene rubber, the viscosity of the second gummed paper is 1.8, the length of the second gummed paper is smaller than that of the second thinning area, the width of the second gummed paper is smaller than that of the second thinning area, the distance between the long edge of the second gummed paper and the long edge of the second thinning area is 3mm, the distance between the short edge of the second gummed paper and the short edge of the second thinning area is 3mm, and the thickness of the second gummed paper is 10 mu m; the surfaces of the negative electrode lugs are coated with weld toe glue, the length of the second gummed paper is larger than the length of an area where the weld toe glue is located, the difference of the lengths is 8mm, the width of the second gummed paper is larger than the width of the area where the weld toe glue is located, and the difference of the widths is 8mm;
and the positive plate and the negative plate are overlapped together and wound to assemble the lithium ion battery.
Example 4
This example provides a lithium ion battery, which is different from example 1 in that the thickness h of the positive electrode active material layer in the second thinning-out region 2 Thickness h of positive electrode active material layer 0 Is adjusted to h 2 /h 0 =0.9, and the rest is exactly the same as in example 1.
Example 5
This embodiment provides a lithium ion battery, which is different from embodiment 1 in that the thickness h of the positive electrode active material layer in the second thinned region 2 Thickness h of positive electrode active material layer 0 Is adjusted to h 2 /h 0 =0.1, and the rest is exactly the same as in example 1.
Example 6
This example provides a lithium ion battery, which is different from example 1 in that the active material layer in the first thinning region is an inclined layer, the included angle θ between the top surface of the inclined layer and the plane where the positive electrode current collector is located is 30 °, and the rest is exactly the same as example 1.
Comparative example 1
This comparative example provides a lithium ion battery, which differs from example 1 in that the thickness h of the positive electrode active material layer in the first thinning-out region 1 Thickness h of positive electrode active material layer 0 Is adjusted to h 1 /h 0 =0.67, all the other examples are exactly the same as in example 1.
Comparative example 2
This comparative example provides a lithium ion battery, which differs from example 1 in that the thickness h of the positive electrode active material layer in the first thinning-out region 1 Thickness h of positive electrode active material layer 0 Is adjusted to h 1 /h 0 =0.5, and the rest is exactly the same as in example 1.
Comparative example 3
This comparative example provides a lithium ion battery, which is different from example 1 in that the first and second thinning regions are not provided on the positive electrode sheet as shown in fig. 6, and is otherwise identical to example 1.
Comparative example 4
This comparative example provides a lithium ion battery, which is different from example 1 in that the first and second thinning regions are not provided on the positive electrode sheet, the CB value is adjusted to 1.15, and the rest is completely the same as example 1.
Comparative example 5
This comparative example provides a lithium ion battery, which is different from example 1 in that the first and second thinning regions are not provided on the positive electrode sheet, the thickness of the first adhesive paper is adjusted to 12 μm, the viscosity of the first adhesive paper is adjusted to 3.2, and the rest is completely the same as example 1.
Comparative example 6
This comparative example provides a lithium ion battery, which is different from example 1 in that the positive electrode sheet is not provided with the first thinning region and the second thinning region, and the negative electrode active material is adjusted to graphite (SK 3-Y type) having better kinetics, and the rest is completely the same as example 1.
Performance testing
The lithium ion batteries provided in examples 1 to 6 and comparative examples 1 to 6 were subjected to charge and discharge tests.
(1) Cycle performance testing at different temperatures
The lithium ion battery is subjected to cycle test at the temperature of 10 ℃, 25 ℃ and 45 ℃, the charging and discharging conditions in the test are all 1.5C/1.5C, the lithium precipitation condition is observed, and the capacity retention rate of part of the battery is recorded.
(2) Charge and discharge test under different multiplying power
At the temperature of 10 ℃, the lithium ion battery is subjected to a charge-discharge test for 20 weeks under the charge-discharge conditions of 1C/1C, 2C/2C and 3C/3C respectively, and the lithium separation condition is observed.
The test results are shown in table 1, where the positive electrode sheets provided in example 5 and comparative example 2 both had exposed foil, and were at risk of safety, and the batteries could not be assembled for the above-described charge and discharge tests.
TABLE 1
And (3) analysis:
from the results of example 1, it is known that the battery employing the thinning structure can normally operate at low and high temperatures, exhibits excellent cycle performance, and does not undergo lithium deposition under high rate conditions, and thus, the thinning structure of the present invention can effectively widen the temperature window and rate window.
From the results of example 1, example 4 and example 5, it can be seen that when h is satisfied 2 /h 0 When the second thinning layer is too thick, lithium precipitation occurs in the lithium ion battery, because a higher CB value is needed to prevent lithium precipitation under the condition of insufficient dynamics, and the CB value cannot reach a proper range when the thinning degree is insufficient; when h is generated 2 /h 0 When the thickness of the second thinning layer is too low, the positive plate is exposed out of the current collector, so that safety risk exists and the battery cannot be used.
From the results of example 1 and example 6, it is understood that when the active material layer in the first thinning layer is an inclined layer, the cycle and the lithium deposition are not significantly affected, but the incorporation of the inclined layer improves the yield of the adhesive.
From the results of example 1, comparative example 1 and comparative example 2, it can be seen that when h is reached 1 /h 0 When the thickness of the first thinning layer is too high, lithium is separated from the lithium ion battery, because a higher CB value is needed to prevent lithium separation under the condition of insufficient dynamics, and the CB value does not reach a reasonable range when the thinning degree is not enough; when h is generated 2 /h 0 Too low, i.e., too thin of the first thinning layer, may result in the foil being exposed in the thinning region, making subsequent processes impossible and making it impossible to assemble the battery for testing.
From the results of example 1 and comparative example 3, it is clear that the conventional battery structure is liable to undergo lithium deposition, whereas the battery structure of the present invention can greatly reduce the risk of lithium deposition.
As can be seen from the results of example 1 and comparative example 4, the structure of comparative example 4 is a conventional structure, but has a high CB value, and the battery with a high CB value tends to have a lower risk of lithium precipitation. The battery of the present invention also had excellent performance at a lower CB value, was less prone to lithium precipitation, and had a higher capacity retention rate than the battery of comparative example 4.
From the results of example 1 and comparative example 5, it can be seen that the structure of comparative example 5 is a conventional structure, and thinner and more viscous gummed paper is used, which can reduce the risk of lithium evolution, but under the high rate condition of 3C, the battery undergoes lithium evolution. Compared with the battery of comparative example 5, the battery of the present invention using the common adhesive paper also exhibited excellent performance, was not easily precipitated lithium, did not precipitate lithium even under the high rate condition of 3C, and had a higher capacity retention rate.
From the results of example 1 and comparative example 6, it is clear that the structure of comparative example 6 is a conventional structure, and a negative electrode having better kinetic properties is used, which also reduces the risk of lithium deposition. Compared with the battery of comparative example 6, the battery of the present invention also exhibits excellent performance using a negative electrode having a general kinetic performance, is less prone to lithium precipitation, and has a higher capacity retention rate.
In conclusion, the thinning structure of the invention not only can widen the temperature window and the multiplying power window of the lithium ion battery, but also can widen the CB value window, the gummed paper system and the active substance system.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein fall within the scope and disclosure of the present invention.
Claims (10)
1. The lithium ion battery is characterized by comprising a positive plate and a negative plate, wherein the positive plate comprises a positive current collector, at least one side surface of the positive current collector is provided with a positive active material layer, and the thickness of the positive active material layer is h 0 The surface of the positive electrode active material layer is provided with a first thinning area and a second thinning area, and the thickness of the positive electrode active material layer in the first thinning area is h 1 ，0.55≤h 1 /h 0 ≦ 0.65, and the thickness of the positive electrode active material layer in the second thinning region is h 2 ，h 2 <h 0 ；
A positive electrode lug groove is formed in the top surface of the positive electrode active material layer in the first thinning area, and the surface of the positive electrode current collector is exposed out of the positive electrode lug groove;
the negative plate is connected with a negative tab, and the negative tab is embedded into the second thinning area.
2. The lithium ion battery of claim 1, wherein a top surface of the positive electrode active material layer in the first thinning region is parallel to a plane of the positive electrode current collector.
3. The lithium ion battery of claim 1, wherein the positive electrode active material layer in the first thinning area is an inclined layer, and an included angle between the top surface of the inclined layer and a plane where the positive electrode current collector is located is theta, and 0 < theta < 90 degrees.
4. The lithium ion battery of any of claims 1-3, wherein the first thinned region has a length greater than a length of the positive ear well;
preferably, the difference between the length of the first thinning area and the length of the positive electrode ear groove is 3-20 mm;
preferably, the width of the first thinning-out region is greater than the width of the positive ear groove;
preferably, the difference between the width of the first thinning area and the width of the positive electrode ear slot is 3-20 mm.
5. The lithium ion battery according to any one of claims 1 to 4, wherein a positive tab is connected to the positive tab slot;
preferably, the surface of the positive lug groove connected with the positive lug is pasted with first gummed paper;
preferably, the material of the first gummed paper comprises a neoprene rubber-like material.
6. The lithium ion battery of any of claims 1-5, wherein the first adhesive tape is positioned between the first thinning region and the positive tab slot;
preferably, the distance between the long edge of the first gummed paper and the long edge of the positive electrode lug groove is 2-6 mm;
preferably, the distance between the short edge of the first gummed paper and the short edge of the positive electrode lug groove is 2-6 mm;
preferably, the distance between the long edge of the first gummed paper and the long edge of the first thinning area is 0.5-5 mm;
preferably, the distance between the short edge of the first gummed paper and the short edge of the first thinning area is 0.5-5 mm;
preferably, the thickness of the first gummed paper is less than or equal to the depth of the first thinning area.
7. The lithium ion battery according to any one of claims 1 to 6, wherein the average particle diameter of the active material in the positive electrode active material layer is d, and the thickness h of the positive electrode active material layer in the second thinning region is 2 Satisfies the following conditions:
1.5×d≤h 2 /h 0 ≤2/π。
8. the lithium ion battery of any one of claims 1-7, wherein a second gummed paper is pasted on the top surface of the positive electrode active material layer in the second thinning region;
preferably, the material of the second gummed paper comprises a neoprene-like material.
9. The lithium ion battery of any one of claims 1-8, wherein the second gummed paper has an area smaller than the top surface area of the positive electrode active material layer in the second thinned region;
preferably, the length of the second gummed paper is less than the length of the second thinning zone;
preferably, the width of the second gummed paper is smaller than the width of the second thinning area;
preferably, the distance between the long edge of the second gummed paper and the long edge of the second thinning area is 0.5-5 mm;
preferably, the distance between the short edge of the second gummed paper and the short edge of the second thinning area is 0.5-5 mm;
preferably, the thickness of the second gummed paper is less than or equal to the depth of the second thinning area.
10. The lithium ion battery according to any one of claims 1-9, wherein the surface of the negative tab is coated with a weld toe glue;
preferably, the length of the second gummed paper is greater than that of the area where the toe welding glue is located;
preferably, the difference between the length of the second gummed paper and the length of the area where the toe welding glue is located is 0.1-10 mm;
preferably, the width of the second gummed paper is larger than the width of the area where the toe welding glue is located;
preferably, the difference between the width of the second gummed paper and the width of the area where the toe welding glue is located is 0.1-10 mm.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117790684A (en) * | 2024-02-27 | 2024-03-29 | 武汉星纪魅族科技有限公司 | Lithium ion battery and preparation method thereof, and preparation method of electrode plate |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117790684A (en) * | 2024-02-27 | 2024-03-29 | 武汉星纪魅族科技有限公司 | Lithium ion battery and preparation method thereof, and preparation method of electrode plate |
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