Battery cell and lithium ion battery

Abstract

A battery cell and a lithium ion battery. The battery cell comprises a jelly roll A and a jelly roll B; the jelly roll A is obtained by sequentially stacking a first positive electrode sheet, a separator, a negative electrode sheet, and the separator; the jelly roll B comprises a first part of lamination and a second part of lamination which are stacked; the first part of lamination is obtained by sequentially stacking the first positive electrode sheet, the separator, the negative electrode sheet, and the separator; and the second part of lamination is obtained by sequentially stacking a ternary positive electrode sheet, the separator, the negative electrode sheet, and the separator, wherein the first positive electrode sheet comprises a first active layer, the first active layer comprises a first active material, and the first active material is selected from any one of lithium iron phosphate and lithium manganese iron phosphate.

Description

Battery cell and lithium-ion battery

[0001] This application claims priority to the Chinese patent applications filed with the China Patent Office on September 7, 2023, with application number 2023224392606, and the Chinese patent application filed with the China Patent Office on September 7, 2023, with application number 2023224359133. The entire contents of the above applications are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of lithium batteries, and in particular to a battery cell and a lithium-ion battery. Background Art

[0003] With the development of new energy technologies, the expansion of new energy market demand has directly driven the increase in market demand for ternary lithium batteries. As a storage device that integrates high energy density and high voltage, ternary lithium-ion batteries have been widely used in mobile and wireless electronic devices, power tools, hybrid and electric vehicles and other fields.

[0004] For ternary lithium batteries, the positive electrode is composed of a combination of manganese, cobalt, and nickel. The proportions of these three transition metal oxides are different. Nickel affects the storage capacity of battery equipment, manganese affects the stability of the battery, and cobalt affects the rate performance of the battery. In addition, the positive electrode materials in ternary lithium batteries also involve lithium iron phosphate components, lithium cobalt oxide components, lithium titanate components, lithium manganate components, etc. Compared with ordinary positive electrode materials, the advantages of various materials can be fully integrated to improve the stability of the positive electrode part. The ternary lithium batteries currently produced have a certain stability during application and a high energy density. They can support high-rate discharge and the cost is relatively moderate. Technical issues

[0005] The use of ternary lithium batteries in new energy vehicles may cause fire accidents, posing a threat to the safety of people around and the safety of the vehicle. The main reasons for spontaneous combustion are extreme collision accidents or battery equipment failures; due to the unstable high-temperature structure of nickel-cobalt-aluminum and nickel-cobalt-manganese materials, high-temperature safety is poor, and when the pH value is too high, the monomers are prone to swelling, which in turn causes danger; the ternary battery cells used in ternary lithium batteries have poor safety and are prone to fire and explosion during puncture, heating and thermal runaway tests; at the same time, after thousands of cycles of charge and discharge, the battery capacity of ternary lithium batteries decays significantly, even decaying to 60% of the rated value. Technical Solutions

[0006] In a first aspect, the present application provides a battery cell, which adopts the following technical solution:

[0007] A battery cell, comprising a core A and a core B; the core B comprises a first portion of laminates and a second portion of laminates, wherein the first portion of laminates is obtained by stacking the first positive electrode sheet, a separator, a negative electrode sheet, and a separator in sequence; and the second portion of laminates is obtained by stacking a ternary positive electrode sheet, a separator, a negative electrode sheet, and a separator in sequence.

[0008] The first positive electrode sheet includes a first active layer, the first active layer includes a first active material, and the first active material is selected from any one of lithium iron phosphate and lithium manganese iron phosphate.

[0009] In a second aspect, the present application provides a battery cell, which adopts the following technical solution:

[0010] A battery cell comprising at least one winding core; the winding core comprising a plurality of first positive electrode sheets, negative electrode sheets, ternary positive electrode sheets and a separator;

[0011] The first positive electrode sheet is provided with a first coating layer formed of the first positive electrode active material, and the thickness of the first coating layer is 40-120 μm; the first positive electrode active material used in the first positive electrode sheet is selected from any one of lithium iron phosphate and lithium manganese iron phosphate;

[0012] The ternary positive electrode sheet is provided with a ternary coating formed of a ternary active material, and the thickness of the ternary coating is 30-100 μm.

[0013] A battery cell comprising at least one winding core; the winding core comprising a plurality of first positive electrode sheets, negative electrode sheets, ternary positive electrode sheets and a separator;

[0014] The first positive electrode sheet is provided with a first coating layer formed of the first positive electrode active material, and the thickness of the first coating layer is 40-120 μm; the first positive electrode active material used in the first positive electrode sheet is selected from any one of lithium iron phosphate and lithium manganese iron phosphate;

[0015] The ternary positive electrode sheet is provided with a ternary coating formed of a ternary active material, and the thickness of the ternary coating is 30-100 μm.

[0016] In a third aspect, the present application provides a lithium-ion battery comprising the battery cell described above.

[0017] In a fourth aspect, the present application provides a lithium-ion battery, comprising a battery shell and a battery cell disposed in the battery shell, wherein the battery cell is any of the above-mentioned battery cells; and the number of the winding cores in the battery cell is two. Beneficial effects

[0018] 1. Through the coordination of core A and core B, firstly, the alternating stacking of the first positive electrode sheet and the ternary positive electrode sheet in core B can significantly alleviate the heat transfer between the ternary positive electrode sheets. Through the coordination of core A and core B, the spread of heat in the battery cell can be further isolated, and the sensitivity of the high nickel content in the ternary material to moisture is reduced, thereby achieving the purpose of improving the safety of the battery cell; and, through the coordination of core A and core B, the number of ternary positive electrode sheets in the battery cell is reduced, and the degree of thermal runaway caused by the ternary positive electrode sheets in the battery cell is reduced. Accordingly, the increase in the number of first positive electrode sheets can further significantly alleviate and isolate the spread of heat between the ternary electrode sheets, thereby improving the life and safety of the battery cell.

[0019] 2. By adopting a first positive electrode sheet whose active material is lithium iron phosphate or a first positive electrode sheet whose active material layer is lithium manganese iron phosphate in combination with a ternary positive electrode sheet and controlling the thickness of the first coating and the thickness of the ternary coating, the first coating enables the first positive electrode sheet to effectively isolate or delay the spread of heat between the ternary positive electrode sheets or battery cells, thereby improving the safety performance of the entire battery cell and reducing the probability of explosion in a needle penetration test; secondly, controlling the thickness of the first coating and the thickness of the ternary coating can balance the migration rate of lithium ions between the positive and negative electrodes in the lithium-ion battery, thereby further improving the energy density and cycle life performance of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a schematic structural diagram of a winding core A according to Example 1 of the present application.

[0021] FIG2 is a schematic structural diagram of the winding core B of Example 1 of the present application.

[0022] FIG3 is a schematic structural diagram of a repeating unit in the winding core of the battery cell of Example 2 of the present application.

[0023] FIG4 is a schematic structural diagram of the first repeating set and the second repeating set in the winding core of the battery cell of Example 2 of the present application.

[0024] Description of reference numerals:

[0025] 1. First positive electrode sheet; 2. Separator; 3. Negative electrode sheet; 4. Ternary positive electrode sheet; 5. First portion of laminate; 6. Second portion of laminate; 11. First coating; 31. First graphite coating; 32. Second graphite coating; 41. Ternary coating. Modes for Carrying Out the Invention

[0026] In the description of this application, it should be noted that the terms "upper," "lower," "inner," and "back" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0029] Example 1

[0030] Example 1 of the present application discloses a battery cell, including a core A and a core B; referring to Figures 1 and 2, the core A is obtained by stacking a first positive electrode sheet 1, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 in sequence; wherein, the first positive electrode sheet 1 includes a first active layer, the thickness of the first active layer can be 40μm, 80μm, or 120μm, the first active layer includes a first active material, the particle size D50 of the first active material can be 0.5μm, 0.7μm, or 1μm, and the first active material is selected from any one of lithium iron phosphate and lithium manganese iron phosphate, as long as the particle size of the set first active material and the thickness of the first active layer can have the effect of delaying the heat transfer between the ternary positive electrode sheets 4. In this embodiment, the thickness of the first active layer is 70μm, the particle size D50 of the first active material is 0.8μm, and the first active material is lithium manganese iron phosphate.

[0031] The core B includes a first portion of laminates 5 and a second portion of laminates 6. The first portion of laminates 5 is obtained by stacking the first positive electrode sheet 1, the diaphragm 2, the negative electrode sheet 3, and the diaphragm 2 in sequence, and the second portion of laminates 6 is obtained by stacking the ternary positive electrode sheet 4, the diaphragm 2, the negative electrode sheet 3, and the diaphragm 2 in sequence; the ternary positive electrode sheet 4 of the core B includes a ternary active layer. The thickness of the ternary active layer can be 30μm, 60μm, or 100μm. The ternary active layer includes a ternary material. The particle size D50 of the ternary material can be 3μm, 3.5μm, or 4μm. As long as the particle size of the ternary material and the thickness of the ternary active layer can play a role in not affecting the first positive electrode sheet 1 to delay the heat transfer between the ternary positive electrode sheets 4, in this embodiment, the thickness of the ternary active layer is 60μm, the particle size D50 of the ternary material is 3.5μm, and the ternary material is lithium nickel cobalt manganese oxide.

[0032] A first negative electrode active layer is provided on the surface of the negative electrode sheet 3 near the first positive electrode sheet 1 in the core B. The thickness of the first negative electrode active layer can be 30 μm, 40 μm, or 60 μm. A second negative electrode active layer is provided on the surface of the negative electrode sheet 3 near the ternary positive electrode sheet 4 in the core B. The thickness of the second negative electrode active layer can be 40 μm, 60 μm, or 70 μm, as long as the thickness of the first negative electrode active layer and the second negative electrode active layer can promote the synchronous decay of the negative electrode and the positive electrode in the core B. In the present application, the thickness of the first negative electrode active layer is 35 μm, and the thickness of the second negative electrode active layer is 55 μm. Moreover, the ratio of the number of the first positive electrode sheet 1 to the number of the ternary positive electrode sheet 4 in the core B can be 1:3, 1:2, or 2:3, as long as the set number can delay the spread of heat while maintaining the high rate performance of the battery cell. In this embodiment, the ratio of the number of the first positive electrode sheet 1 to the number of the ternary positive electrode sheet 4 in the core B is 1:2.

[0033] In addition, the ratio of the number of first positive electrode sheets 1 in core A to the number of first positive electrode sheets 1 in core B can be 1:3, 1:2, or 2:3, as long as the set number can make the battery cell have both the excellent performance and safety performance of the ternary battery cell. In this embodiment, the ratio of the number of first positive electrode sheets 1 in core A to the number of first positive electrode sheets 1 in core B is 1:3.

[0034] Accordingly, an embodiment of the present application further provides a lithium-ion battery. The lithium-ion battery includes components contained in a conventional lithium-ion battery, such as a shell, a winding core disposed in the shell, and an electrolyte filled in the shell. Among them, the battery cell of the lithium-ion battery is the battery cell of the lithium-ion battery in the embodiment of the present application described above. Other components, such as the shell and the electrolyte, etc. can be conventional. Since the lithium-ion battery uses the battery cell described above as the battery cell of the lithium-ion battery, it has high safety, thereby effectively improving the safety of the above-mentioned lithium-ion battery application.

[0035] Implementation Method 1

[0036] A battery cell includes a core A and a core B. Core A is formed by stacking a first positive electrode sheet 1, a separator 2, a negative electrode sheet 3, and a separator 2 in this order. The first positive electrode sheet 1 includes a first active layer having a thickness of 70 μm and a first active material having a particle size D50 of 0.8 μm. The first active material is selected from lithium manganese iron phosphate.

[0037] The core B includes a first portion of laminates 5 and a second portion of laminates 6. The first portion of laminates 5 is obtained by stacking a first positive electrode sheet 1, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 in sequence, and the second portion of laminates 6 is obtained by stacking a ternary positive electrode sheet 4, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 in sequence; the ternary positive electrode sheet 4 of the core B includes a ternary active layer, the thickness of the ternary active layer is 60 μm, the ternary active layer includes a ternary material, the particle size D50 of the ternary material can be 3.5 μm, and the ternary material is lithium nickel cobalt manganese oxide; a first negative electrode active layer with a thickness of 35 μm is provided on the surface of the negative electrode sheet 3 close to the first positive electrode sheet 1 in the core B, and a second negative electrode active layer with a thickness of 55 μm is provided on the surface of the negative electrode sheet 3 close to the ternary positive electrode sheet 4 in the core B. Moreover, the ratio of the number of the first positive electrode sheets 1 to the number of the ternary positive electrode sheets 4 in the winding core B is 1:2; the ratio of the number of the first positive electrode sheets 1 in the winding core A to the number of the first positive electrode sheets 1 in the winding core B can be 1:3.

[0038] Implementation Method 2

[0039] A battery cell includes a core A and a core B, with core A disposed above core B. Core A is formed by stacking a first positive electrode sheet 1, a separator 2, a negative electrode sheet 3, and a separator 2 in this order. The first positive electrode sheet 1 includes a first active layer having a thickness of 40 μm and a first active material having a particle size D50 of 0.5 μm. The first active material is selected from lithium iron phosphate.

[0040] The core B includes a first portion of laminates 5 and a second portion of laminates 6. The first portion of laminates 5 is obtained by stacking a first positive electrode sheet 1, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 in sequence, and the second portion of laminates 6 is obtained by stacking a ternary positive electrode sheet 4, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 in sequence; the ternary positive electrode sheet 4 of the core B includes a ternary active layer, the thickness of the ternary active layer is 30 μm, the ternary active layer includes a ternary material, the particle size D50 of the ternary material can be 3 μm, and the ternary material is lithium nickel cobalt manganese oxide; a first negative electrode active layer with a thickness of 32 μm is provided on the surface of the negative electrode sheet 3 close to the first positive electrode sheet 1 in the core B, and a second negative electrode active layer with a thickness of 45 μm is provided on the surface of the negative electrode sheet 3 close to the ternary positive electrode sheet 4 in the core B. Moreover, the ratio of the number of the first positive electrode sheets 1 to the number of the ternary positive electrode sheets 4 in the winding core B is 1:3; the ratio of the number of the first positive electrode sheets 1 in the winding core A to the number of the first positive electrode sheets 1 in the winding core B can be 2:3.

[0041] Implementation 3

[0042] A battery cell includes a core A and a core B, with core A disposed above core B. Core A is formed by stacking a first positive electrode sheet 1, a separator 2, a negative electrode sheet 3, and a separator 2 in this order. The first positive electrode sheet 1 includes a first active layer having a thickness of 120 μm and a first active material having a particle size D50 of 1 μm. The first active material is selected from lithium manganese iron phosphate.

[0043] The core B includes a first portion of laminates 5 and a second portion of laminates 6. The first portion of laminates 5 is obtained by stacking a first positive electrode sheet 1, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 in sequence, and the second portion of laminates 6 is obtained by stacking a ternary positive electrode sheet 4, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 in sequence; the ternary positive electrode sheet 4 of the core B includes a ternary active layer, the thickness of the ternary active layer is 100 μm, the ternary active layer includes a ternary material, the particle size D50 of the ternary material can be 3.9 μm, and the ternary material is lithium nickel cobalt manganese oxide; a first negative electrode active layer with a thickness of 55 μm is provided on the surface of the negative electrode sheet 3 close to the first positive electrode sheet 1 in the core B, and a second negative electrode active layer with a thickness of 70 μm is provided on the surface of the negative electrode sheet 3 close to the ternary positive electrode sheet 4 in the core B. Moreover, the ratio of the number of the first positive electrode sheets 1 to the number of the ternary positive electrode sheets 4 in the winding core B is 2:3; the ratio of the number of the first positive electrode sheets 1 in the winding core A to the number of the first positive electrode sheets 1 in the winding core B can be 1:2.

[0044] A needle puncture safety test was conducted on embodiments 1-3 and conventional ternary lithium batteries in the art. The lithium-ion batteries tested differed from conventional lithium-ion batteries in terms of their cell structure, while all other components of the two types of lithium-ion batteries were identical. The results of the needle puncture safety test and the cycling performance test are shown in Table 1 below.

[0045] Table 1

[0046] No. Needle puncture pass rate / % Heavy object impact pass rate / % Cycle life / times Implementation method 191863150 Implementation method 289843000 Implementation method 388823005 Conventional ternary lithium battery in this field 51482020

[0047] As can be seen from Table 1, the core in the present application can significantly improve the safety performance and cycle life of the lithium battery; this is because, by using the combination of core A and core B, the first positive electrode sheet 1 can significantly alleviate the heat release rate generated by the ternary positive electrode sheet 4 in the needle penetration test, avoid the occurrence of local excessive temperature in the core, and reduce the sensitivity of the high nickel content in the ternary material to moisture, thereby significantly improving the safety of the battery cell; and, by arranging the first negative electrode active layer and the second negative electrode active layer corresponding to the first active layer and the ternary active layer on the surface of the negative electrode sheet 3, the positive and negative electrode sheets in the lithium-ion battery can achieve synchronous attenuation, thereby further improving the cycle life of the battery cell.

[0048] Example 2

[0049] Implementation 4

[0050] The embodiment of the present application discloses a battery cell, comprising at least one roll core, the number of which can be one, three, or five. In the present application, the number of roll cores is two. Referring to Figure 3, a roll core comprises a plurality of repeating units stacked in sequence. The number of repeating units can be two, ten, or thirty, as long as the number is sufficient for the application of the battery cell in a lithium battery. In the present embodiment, the number of repeating units is eight; in a repeating unit, a first positive electrode sheet 1, a diaphragm 2, a negative electrode sheet 3, a diaphragm 2, a ternary positive electrode sheet 4, a diaphragm 2, a negative electrode sheet 3, and a diaphragm 2 are stacked in sequence; the diaphragm 2 used in the roll core can be a polyethylene diaphragm or a polypropylene diaphragm. In the present embodiment, the diaphragm 2 uses a polyethylene diaphragm.

[0051] The positive electrode active material used in the first positive electrode sheet 1 can be lithium iron phosphate or lithium iron manganese phosphate. In this embodiment, the positive electrode active material is lithium iron manganese phosphate. The first positive electrode sheet 1 is provided with a first coating 11 formed of lithium iron manganese phosphate slurry. The thickness of the first coating 11 can be 40μm, 80μm, or 120μm. The positive electrode active material used in the ternary positive electrode sheet 4 can be lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide. In this embodiment, the active material on the surface of the ternary positive electrode sheet 4 is lithium nickel cobalt manganese oxide. The ternary positive electrode sheet 4 is provided with a ternary coating 41 formed of lithium nickel cobalt manganese oxide slurry. The thickness of the ternary coating 41 can be 30μm, 60μm, or 100μm. In addition, the positive electrode current collectors used in the first positive electrode sheet 1 and the ternary positive electrode sheet 4 are both carbon-coated aluminum foil. By controlling the thickness of the first coating 11 and the ternary coating 41 , the spread of heat between the ternary positive electrode sheets 4 can be effectively delayed or even isolated, thereby improving the safety and cycle life of the lithium battery.

[0052] Referring to Figure 3 , a first graphite coating 31 formed of graphite slurry is provided on the surface of the negative electrode sheet 3 near the first positive electrode sheet 1. The thickness of the first graphite coating 31 can be 40 μm, 60 μm, or 80 μm. A second graphite coating 32 formed of graphite slurry is provided on the surface of the negative electrode sheet 3 near the ternary positive electrode sheet 4. The thickness of the second graphite coating 32 can be 50 μm, 70 μm, or 100 μm. The first graphite coating 31 on the first positive electrode sheet 1 corresponds to the first graphite coating 31 on the negative electrode sheet 3, and the second graphite coating 32 on the ternary positive electrode sheet 4 corresponds to the second graphite coating 32 on the negative electrode sheet 3, further improving the cycle life of the lithium battery.

[0053] Accordingly, an embodiment of the present application also provides a lithium-ion battery. The lithium-ion battery includes components contained in a conventional lithium-ion battery, such as a shell, a winding core disposed in the shell, and an electrolyte filled in the shell. Among them, the winding core of the lithium-ion battery is the lithium-ion battery cell in the above embodiment. Other components, such as the shell and the electrolyte, can be conventional. Since the lithium-ion battery uses the lithium-ion battery winding core described above as the winding core of the battery, it has high safety, thereby effectively improving the safety of the above-mentioned lithium-ion battery application.

[0054] Implementation 5

[0055] Referring to Figure 4, a battery cell, in which the stacking structure between the first positive electrode sheet 1, the separator 2, the negative electrode sheet 3, and the ternary positive electrode sheet 4 in the winding core is different from that in embodiment 4. In this embodiment, a winding core includes a stacked first repeating set and a second repeating set; the first repeating set is obtained by stacking the first positive electrode sheet 1, the separator 2, the negative electrode sheet 3, and the separator 2 in sequence, and the second repeating set is obtained by stacking the ternary positive electrode sheet 4, the separator 2, the negative electrode sheet 3, and the separator 2 in sequence. The number of first positive electrode sheets 1 in the first repeating set can be one, ten, or twenty, as long as the number of the first positive electrode sheets 1 and the number of the ternary positive electrode sheets 4 provided can have the effect of improving the safety of the ternary battery cell. In this embodiment, the number of the first positive electrode sheets 1 is the same as the number of the ternary positive electrode sheets 4, and the number of the first positive electrode sheets 1 is ten, and the number of the ternary positive electrode sheets 4 is ten.

[0056] Accordingly, an embodiment of the present application also provides a lithium-ion battery. The lithium-ion battery includes components contained in a conventional lithium-ion battery, such as a shell, a winding core disposed in the shell, and an electrolyte filled in the shell. Among them, the winding core of the lithium-ion battery is the lithium-ion battery cell in the above embodiment. Other components, such as the shell and the electrolyte, can be conventional. Since the lithium-ion battery uses the lithium-ion battery winding core described above as the winding core of the battery, it has high safety, thereby effectively improving the safety of the above-mentioned lithium-ion battery application.

[0057] Embodiment 6 A battery cell includes two winding cores with the same structure, one winding core includes ten repeating units stacked in sequence, and one repeating unit is stacked in sequence in the order of a first positive electrode sheet 1, a separator 2, a negative electrode sheet 3, a separator 2, a ternary positive electrode sheet 4, a separator 2, a negative electrode sheet 3, and a separator 2; the positive electrode collectors used in the first positive electrode sheet 1 and the ternary positive electrode sheet 4 are both carbon-coated aluminum foil, and the separator 2 is a polyethylene separator.

[0058] The positive electrode active material used in the first positive electrode sheet 1 is lithium iron manganese phosphate, and the thickness of the first coating 11 formed by lithium iron manganese phosphate on the first positive electrode sheet 1 is 80 μm; the positive electrode active material used in the ternary positive electrode sheet 4 is lithium nickel cobalt manganese oxide, and the thickness of the ternary coating 41 formed by lithium nickel cobalt manganese oxide slurry on the ternary positive electrode sheet 4 is 60 μm; a first graphite coating 31 with a thickness of 60 μm formed by graphite slurry is provided on the surface of the negative electrode sheet 3 close to the first positive electrode sheet 1; a second graphite coating 32 with a thickness of 70 μm formed by graphite slurry is provided on the surface of the negative electrode sheet 3 close to the ternary positive electrode sheet 4.

[0059] A lithium-ion battery comprises a shell, two winding cores arranged in the shell, and an electrolyte filled in the shell.

[0060] Implementation 7

[0061] A battery cell includes two winding cores with the same structure, one winding core includes five repeating units stacked in sequence, and a repeating unit is stacked in sequence in the order of a first positive electrode sheet 1, a separator 2, a negative electrode sheet 3, a separator 2, a ternary positive electrode sheet 4, a separator 2, a negative electrode sheet 3, and a separator 2; the positive electrode current collectors used in the first positive electrode sheet 1 and the ternary positive electrode sheet 4 are both carbon-coated aluminum foil, and the separator 2 is a polypropylene separator.

[0062] The positive electrode active material used in the first positive electrode sheet 1 is lithium iron manganese phosphate, and the thickness of the first coating 11 formed by lithium iron manganese phosphate on the first positive electrode sheet 1 is 40 μm; the positive electrode active material used in the ternary positive electrode sheet 4 is lithium nickel cobalt manganese oxide, and the thickness of the ternary coating 41 formed by lithium nickel cobalt manganese oxide slurry on the ternary positive electrode sheet 4 is 30 μm; the surface of the negative electrode sheet 3 close to the first positive electrode sheet 1 is provided with a first graphite coating 31 with a thickness of 40 μm formed by graphite slurry; the surface of the negative electrode sheet 3 close to the ternary positive electrode sheet 4 is provided with a second graphite coating 32 with a thickness of 50 μm formed by silicon graphite slurry.

[0063] A lithium-ion battery comprises a shell, two winding cores arranged in the shell, and an electrolyte filled in the shell.

[0064] Implementation 8

[0065] A battery cell includes two winding cores with the same structure, one winding core includes twenty repeating units stacked in sequence, and one repeating unit is stacked in sequence in the order of a first positive electrode sheet 1, a separator 2, a negative electrode sheet 3, a separator 2, a ternary positive electrode sheet 4, a separator 2, a negative electrode sheet 3, and a separator 2; the positive electrode current collectors used in the first positive electrode sheet 1 and the ternary positive electrode sheet 4 are both carbon-coated aluminum foil, and the separator 2 is a polyethylene separator.

[0066] The positive electrode active material used in the first positive electrode sheet 1 is lithium iron manganese phosphate material, and the thickness of the first coating 11 formed by lithium iron manganese phosphate on the first positive electrode sheet 1 is 120 μm; the positive electrode active material used in the ternary positive electrode sheet 4 is lithium nickel cobalt manganese oxide, and the thickness of the ternary coating 41 formed by lithium nickel cobalt manganese oxide slurry on the ternary positive electrode sheet 4 is 100 μm; the surface of the negative electrode sheet 3 close to the first positive electrode sheet 1 is provided with a first graphite coating layer formed by graphite slurry with a thickness of 80 μm; the surface of the negative electrode sheet 3 close to the ternary positive electrode sheet 4 is coated with a second graphite coating layer 32 formed by graphite slurry with a thickness of 100 μm.

[0067] A lithium-ion battery comprises a shell, two winding cores arranged in the shell, and an electrolyte filled in the shell.

[0068] Implementation Method 9

[0069] The difference between this embodiment 9 and embodiment 6 is that a roll core includes a stacked first repeating set and a second repeating set, the first repeating set is obtained by stacking the first positive electrode sheet 1, the diaphragm 2, the negative electrode sheet 3, and the diaphragm 2 in sequence, and the second repeating set is obtained by stacking the ternary positive electrode sheet 4, the diaphragm 2, the negative electrode sheet 3, and the diaphragm 2 in sequence, and the number of first positive electrode sheets 1 in the first repeating set is equal to the number of ternary positive electrode sheets 4 in the second repeating set, both of which are ten; the rest are consistent with the application embodiment 6.

[0070] A needle puncture safety test was conducted on embodiments 6-9 and conventional ternary lithium batteries in the art. The tested batteries differed in the battery cells of the lithium-ion batteries of the present application and the conventional lithium-ion batteries, while all other components of the two types of lithium-ion batteries were identical. The results of the needle puncture safety test are shown in Table 2 below.

[0071] Table 2

[0072] Implementation method needle puncture pass rate / % Implementation method 686% Implementation method 790% Implementation method 889% Implementation method 988% Conventional ternary lithium battery in this field 50%

[0073] As can be seen from Table 2, the winding core in the present application can significantly improve the safety performance of the lithium battery; this is because, by controlling the thickness of the first coating 11 and the ternary coating 41, the first positive electrode sheet 1 can significantly alleviate the heat release rate generated by the ternary positive electrode sheet 4 in the needle penetration test, avoiding the occurrence of local excessive temperature in the winding core, thereby significantly improving the safety of the battery cell; and, by arranging the first graphite coating 31 and the second graphite coating 32 with a thickness corresponding to the first coating 11 and the ternary coating 41 on the surface of the negative electrode sheet 3, the transmission efficiency and transfer balance of lithium ions between the negative electrode sheet 3 and different positive electrode sheets are further improved, thereby further improving the safety and cycle life of the battery cell.

Claims

1. A battery cell, comprising a winding core A and a winding core B; the winding core A is obtained by stacking a first positive electrode sheet (1), a separator (2), a negative electrode sheet (3), and a separator (2) in sequence; the winding core B comprises a first portion of stacked sheets (5) and a second portion of stacked sheets (6); the first portion of stacked sheets (5) is obtained by stacking the first positive electrode sheet (1), the separator (2), the negative electrode sheet (3), and the separator (2) in sequence; the second portion of stacked sheets (6) is obtained by stacking a ternary positive electrode sheet (4), the separator (2), the negative electrode sheet (3), and the separator (2) in sequence; in, The first positive electrode sheet (1) comprises a first active layer, the first active layer comprises a first active material, and the first active material is selected from any one of lithium iron phosphate and lithium manganese iron phosphate materials.

2. A method for preparing a battery cell according to claim 1, wherein: The thickness of the first active layer is 40-120 μm.

3. A battery cell according to any one of claims 1 or 2, wherein: The said The particle size D50 of an active material is 0.5-1 μm.

4. A method for preparing a battery cell according to claim 1, wherein: The three The positive electrode sheet (4) comprises a ternary active layer, and the thickness of the ternary active layer is 30-100 μm.

5. A battery cell according to claim 4, wherein: The ternary active layer comprises The invention relates to a ternary material, wherein the particle size D50 of the ternary material is 3-4 μm.

6. A battery cell according to claim 1, wherein: In the winding core B, a first negative electrode active layer with a thickness of 30-60 μm is provided on the surface of the negative electrode sheet (3) close to the first positive electrode sheet (1); and a second negative electrode active layer with a thickness of 40-70 μm is provided on the surface of the negative electrode sheet (3) close to the ternary positive electrode sheet (4).

7. A battery cell according to claim 1, wherein: In the winding core B, The ratio of the number of the first positive electrode sheets (1) to the number of the ternary positive electrode sheets (4) is (1-2):

3.

8. A battery cell according to claim 7, wherein: In the winding core B, the ratio of the number of the first positive electrode sheets (1) to the number of the ternary positive electrode sheets (4) is 1:

2.

9. A battery cell according to claim 1, wherein: The ratio of the number of the first positive electrode sheets (1) in the winding core A to the number of the first positive electrode sheets (1) in the winding core B is (1-2):

3.

10. A lithium ion battery, comprising a battery cell, wherein the battery cell is the battery cell according to any one of claims 1 to 9.

11. A battery cell, comprising at least one winding core; the winding core comprising a plurality of first positive electrode sheets (1), negative electrode sheets (3), ternary positive electrode sheets (4) and a separator (2); The first positive electrode sheet (1) is provided with a first coating (11) formed of the first positive electrode active material, and the thickness of the first coating (11) is 40-120 μm; the first positive electrode active material is selected from any one of lithium iron phosphate and lithium manganese iron phosphate materials; The ternary positive electrode sheet (4) is provided with a ternary coating (41) formed of a ternary active material, and the thickness of the ternary coating (41) is 30-100 μm.

12. A battery cell according to claim 11, wherein: One of the winding cores comprises a plurality of repeating units stacked in sequence; one of the repeating units is stacked in sequence in the manner of the first positive electrode sheet (1), the separator (2), the negative electrode sheet (3), the separator (2), the ternary positive electrode sheet (4), the separator (2), the negative electrode sheet (3), and the separator (2).

13. A battery cell according to claim 12, wherein: The number of the repeating units in one core is 2-30.

14. A battery cell according to claim 11, wherein: The winding core comprises a first repeating set and a second repeating set which are stacked; the first repeating set is obtained by stacking the first positive electrode sheet (1), the separator (2), the negative electrode sheet (3), and the separator (2) in sequence, and the second repeating set is obtained by stacking the ternary positive electrode sheet (4), the separator (2), the negative electrode sheet (3), and the separator (2) in sequence.

15. A battery cell according to claim 14, wherein: The number of the first positive electrode sheets (1) in the first repetitive set is the same as the number of the ternary positive electrode sheets (4) in the second repetitive set.

16. A battery cell according to any one of claims 11 to 15, wherein: A first graphite coating (31) is provided on the surface of the negative electrode sheet (3) close to the first positive electrode sheet (1).

17. A battery cell according to claim 16, wherein: The thickness of the first graphite coating (31) is 40-80 μm.

18. A battery cell according to claim 16, wherein: A second graphite coating (32) is provided on the surface of the negative electrode sheet (3) close to the ternary positive electrode sheet (4).

19. A battery cell according to claim 18, wherein: The thickness of the second graphite coating (32) is 50-100 μm.

20. A lithium-ion battery, comprising a battery shell and a battery cell disposed in the battery shell, wherein the battery cell is the battery cell according to any one of claims 11 to 19, and the number of the winding cores in the battery cell is two.

Images