Battery cell and secondary battery

Abstract

The utility model belongs to the technical field of batteries, and particularly relates to a battery cell and a secondary battery. The battery cell comprises a battery cell body and a plurality of heat conducting rods; a plurality of through holes are formed in the thickness direction of the battery cell body, and the heat conducting rods are mounted in the through holes; the heat conduction rod comprises a heat conduction core layer and an insulating layer wrapping the peripheral surface of the heat conduction core layer. According to the utility model, the heat conduction rods are arranged in the thickness direction of the battery cell, so that the heat transfer of the battery cell in the thickness direction is accelerated, the heat generated in the charging and discharging process of the power battery is quickly diffused outwards, and the risk of thermal runaway of the power battery is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of batteries, and in particular relates to a battery core and a secondary battery. Background Art

[0002] As electric vehicles pursue shorter charging waiting times, more and more electric vehicle manufacturers have put forward fast charging requirements for power batteries; however, during the fast charging process, due to the large charging current, the battery generates significant heat, and excessive heat accumulation can cause thermal runaway of the battery, resulting in property losses. In particular, the structural characteristics of square batteries determine that the thermal conductivity of the battery cell in the thickness direction is poor, and the low thermal conductivity in this direction restricts the heat dissipation capacity of the battery cell. Therefore, it is necessary to provide a battery cell structure that can enhance its heat dissipation in the thickness direction, thereby avoiding safety hazards caused by heat accumulation. Utility Model Content

[0003] The utility model aims to solve the above problems and provides a battery core, which arranges heat-conducting rods in the thickness direction of the battery core and uses them in batteries, so that the heat generated by the battery during charging and discharging can be quickly diffused outward, reducing the risk of thermal runaway.

[0004] According to the technical solution of the utility model, the battery core includes a battery core body and a plurality of heat conducting rods;

[0005] A plurality of through holes are provided in the thickness direction of the battery core body, and the heat conducting rod is installed in the through holes;

[0006] The heat-conducting rod comprises a heat-conducting core layer and an insulating layer coated on the outer peripheral surface of the heat-conducting core layer.

[0007] Specifically, the plurality of through holes are evenly or unevenly distributed on the large surface (flat surface) of the battery cell body, preferably evenly distributed; the direction of the through holes is consistent with the thickness direction of the battery cell body.

[0008] Furthermore, in the thickness direction of the battery cell body, the total area of ​​the plurality of through holes accounts for 5%-20% of the area of ​​the battery cell body.

[0009] Furthermore, the battery cell body includes a positive electrode sheet, a negative electrode sheet and a separator, and the through hole is formed by the positive electrode through hole on the positive electrode sheet, the negative electrode through hole on the negative electrode sheet and the separator through hole in a one-to-one correspondence;

[0010] The aperture of the negative electrode through hole is 3mm-5mm, the aperture of the positive electrode through hole is 0.2mm-0.5mm larger than the aperture of the negative electrode through hole, and the aperture of the diaphragm through hole is consistent with the aperture of the negative electrode through hole;

[0011] The aperture of the through hole is determined by the smaller aperture among the positive electrode through hole, the negative electrode through hole and the diaphragm through hole, and the aperture size is 3mm-5mm.

[0012] Specifically, the battery cell body is formed by winding or stacking a positive electrode sheet, a negative electrode sheet and a separator. Preferably, to facilitate the installation of the heat conducting rod, the battery cell body is formed by stacking a positive electrode sheet, a negative electrode sheet and a separator.

[0013] The positive electrode sheet generally includes a positive electrode current collector and an active material layer located on the surface of the positive electrode current collector. The positive electrode active material in the active material layer is one or more of layered lithium nickel cobalt manganese, transition metal oxides or lithium nickel cobalt aluminum, and composite materials obtained by coating and modification of the above materials, and its chemical formula is: Li x1 Ni (1-y1-z1-a1) Co y1 Mn z1 M1 a1 O2、Li x2 Ni (1-y2-z2-a2) Co y2 Al z2 M2 a2 O2, wherein 0.90≤x1≤1.05, 0<y1≤0.2, 0<z1≤0.2, 0≤a1≤0.05, M1 is selected from one or more of Ti, Al, Zr, Mg, Zn, Ba, Mo, B; 0.90≤x2≤1.05, 0<y2≤0.1, 0<z2≤0.1, 0≤a2≤0.05, M2 is selected from one or more of Ti, Mn, Zr, Mg, Zn, Ba, Mo, B. The positive electrode active material can also be an olivine-type lithium-containing phosphate, whose chemical formula is LiFe 1-x3-y3 Mn x3 M' y3 PO4, wherein 0≤x3≤1, 0≤y3≤0.1, 0≤x3+y3≤1, and M' is selected from one or more of transition metal elements and non-transition metal elements except Fe and Mn.

[0014] The negative electrode sheet generally includes a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector. The negative electrode active material layer generally contains a negative electrode active material. The negative electrode active material can be selected from one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres and silicon-based materials. The graphite includes but is not limited to natural graphite, artificial graphite, various coated / modified natural graphite or artificial graphite.

[0015] The separator is a conventional separator for secondary batteries, such as a polypropylene film.

[0016] Furthermore, the diameter of the heat conducting rod is consistent with the aperture of the through hole, or the heat conducting rod and the through hole are interference fit.

[0017] Furthermore, both ends of the heat conductive rod extend out of the through hole to play a certain supporting role; preferably, its length can be consistent with the internal width of the shell in which the battery cell body is installed, so that the two ends of the heat conductive rod are in contact with the shell after the battery cell is installed.

[0018] Furthermore, in the cross section of the heat-conducting rod, the area ratio of the insulating layer to the heat-conducting core layer is 10%-50%, that is, the cross-sectional area of ​​the insulating layer is 10%-50% of the cross-sectional area of ​​the heat-conducting core layer.

[0019] Furthermore, the insulating layer plays the role of insulation and liquid retention, and its material is elastic material, which further plays a shock-absorbing role.

[0020] Furthermore, the insulating layer is made of foam, for example, PE (polyethylene) foam, polyether foam, chloroprene rubber foam, nitrile rubber foam, etc., and the preferred material is PE foam.

[0021] Furthermore, the thickness of the insulating layer (under natural state) is 0.5 mm-1.0 mm.

[0022] Furthermore, the thermally conductive core layer is a porous structure with a pore size of 100 μm-500 μm, preferably a pore size of 300 μm.

[0023] Furthermore, the thermally conductive core layer is made of a material with high thermal conductivity, such as a ceramic material with high thermal conductivity, specifically Si / C ceramic, Si3N4 ceramic, AlN ceramic, etc.

[0024] A second aspect of the utility model provides a secondary battery, comprising the above-mentioned battery cell.

[0025] Furthermore, the secondary battery also includes a top cover and a shell, the battery cell is installed in the shell, and the top cover is buckled at the opening of the shell; preferably, when the battery cell is installed in the shell, both ends of the thermal conductive rod are in contact with the shell.

[0026] Compared with the prior art, the technical solution of the utility model has the following advantages:

[0027] The utility model arranges heat conducting rods in the thickness direction of the battery cell to accelerate the heat transfer in the thickness direction of the battery cell, so that the heat generated by the power battery during the charging and discharging process can be quickly diffused outward, thereby reducing the risk of thermal runaway of the power battery.

[0028] The heat-conducting rod of the utility model comprises a heat-conducting core layer and an insulating layer, wherein the insulating layer avoids its influence on the performance of the battery core; the heat-conducting core layer gives the heat-conducting rod a higher heat-conducting performance, and can quickly conduct heat out from the thickness direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the utility model in which the battery cell is installed in the shell.

[0030] Figure 2 It is a structural schematic diagram of the heat conducting rod of the utility model.

[0031] Explanation of the accompanying drawings: 1-battery cell body, 2-thermal conductive rod, 2.1-thermal conductive core layer, 2.2-insulating layer, 3-through hole, 4-shell. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0033] The utility model provides a battery cell, comprising a battery cell body 1 and a plurality of heat conducting rods 2. A plurality of through holes 3 are provided in the thickness direction of the battery cell body 1 (a direction perpendicular to the large surface of the battery cell body 1), and a heat conducting rod 2 ( Figure 1 In order to clearly show the through holes 3, only the heat conducting rods 2 in the first row of through holes 3 are drawn).

[0034] It is conceivable that a plurality of through holes 3 are distributed on the large surface of the battery cell body 1 in a uniform or non-uniform manner, preferably uniformly distributed; the direction of the through hole 3 is consistent with the thickness direction of the battery cell body 1; the shape of the through hole 3 can be circular or other shapes, and the cross-sectional shape of the thermal conductive rod 2 is consistent with the through hole 3. For ease of processing, the through hole 3 is circular by default.

[0035] Since the larger the area occupied by the through hole 3, the lower the energy density of the battery cell, in some preferred embodiments, the total area of ​​several through holes 3 accounts for 5%-20% of the area of ​​the battery cell body 1 (large surface), for example, it can be 5%, 7%, 10%, 14%, 17%, 20%, etc., preferably 10%.

[0036] The battery cell body 1 includes a positive electrode sheet, a negative electrode sheet and a separator. The through hole 3 is formed by the positive electrode through hole on the positive electrode sheet, the negative electrode through hole on the negative electrode sheet and the separator through hole in a one-to-one correspondence. The size of the through hole 3 is determined by the smaller of the positive electrode through hole, the negative electrode through hole and the separator through hole, that is, the size of the through hole 3 is consistent with the smaller of the positive electrode through hole, the negative electrode through hole and the separator through hole.

[0037] Specifically, the battery cell body 1 is formed by winding or stacking the positive electrode sheet, the negative electrode sheet and the separator. Preferably, in order to facilitate the installation of the heat conducting rod, the battery cell body 1 is formed by stacking the positive electrode sheet, the negative electrode sheet and the separator (such as Figure 1 shown).

[0038] In some preferred embodiments, the diameter of the negative electrode through hole is 3mm-5mm, the diameter of the positive electrode through hole is 0.2mm-0.5mm larger than that of the negative electrode through hole, and the diameter of the diaphragm through hole is consistent with that of the negative electrode through hole. Among them, the diameter of the positive electrode through hole is larger than that of the negative electrode through hole, ensuring that the negative electrode sheet at the through hole covers the positive electrode sheet to prevent lithium deposition.

[0039] Based on the apertures of the positive electrode through hole, the negative electrode through hole and the diaphragm through hole, the aperture of the through hole 3 is 3mm-5mm, which is consistent with the negative electrode through hole and the diaphragm through hole. The heat conducting rod 2 is installed in the through hole 3. To ensure the stability of the installation, its diameter is consistent with the aperture of the through hole 3 or slightly larger than the aperture of the through hole 3 (that is, the heat conducting rod 2 and the through hole 3 are interference fit).

[0040] Since the larger the contact area between the heat conducting rod 2 and the electrode, the better the heat conduction effect, however, the smaller the diameter of the through hole 3, the less electrolyte can be stored, and the support effect of the heat conducting rod 2 in the thickness direction is weaker. Taking the above factors into consideration, the preferred diameter of the negative electrode through hole is 3 mm.

[0041] In some preferred embodiments, both ends of the heat conducting rod 2 extend out of the through hole 3, that is, the length of the heat conducting rod 2 is greater than the thickness of the battery cell body 1, and its length may be consistent with the internal width of the shell 4 in which the battery cell body 1 is installed. When the battery cell body 1 is installed in the shell 4, both ends of the heat conducting rod 2 are in contact with the shell 4 (for example, an aluminum shell). On the one hand, the heat conducting rod 2 provides support for the shell 4, and on the other hand, the contact between the heat conducting rod 2 and the shell 4 is more conducive to heat dissipation.

[0042] like Figure 2 As shown, the heat-conducting rod 2 includes an internal heat-conducting core layer 2.1 and an external insulating layer 2.2, wherein the heat-conducting core layer 2.1 can play a supporting and heat-conducting role, and the insulating layer 2.2 can insulate the heat-conducting core layer 2.1 and the battery body 1 and play a role in retaining liquid.

[0043] In some preferred embodiments, in the cross section of the heat-conducting rod 2, the area ratio of the insulating layer 2.2 to the heat-conducting core layer 2.1 is 10%-50%, for example, 10%, 20%, 30%, 40%, 50%, etc., so as to ensure the insulation and liquid-retaining function of the insulating layer 2.2 and the support and heat-conducting function of the heat-conducting core layer 2.1.

[0044] In some preferred embodiments, the insulating layer 2.2 is made of elastic material, has a shock-absorbing effect, and can improve the toughness of the insulating layer 2.2. The thickness of the insulating layer (under natural state) is 0.5mm-1.0mm, for example, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, etc.

[0045] In some preferred embodiments, the insulating layer 2.2 is made of foam, such as PE (polyethylene) foam, polyether foam, chloroprene rubber foam, nitrile rubber foam, etc. The preferred material is PE foam. Since there are a large number of pores in the foam, the electrolyte can enter and exit according to the capillary phenomenon.

[0046] In some preferred embodiments, the thermal conductive core layer 2.1 is a porous structure (similar to the porous structure of a sponge), which is conducive to storing electrolyte. When the free electrolyte in the battery core dries up, it precipitates, thereby improving the cycle storage performance of the battery core. To facilitate the absorption and discharge of the electrolyte, the pore size distribution is 100μm-500μm, for example, it can be 100μm, 200μm, 300μm, 400μm, 500μm, etc., and the preferred pore size is 300μm.

[0047] In some preferred embodiments, the thermally conductive core layer 2.1 is made of a material with high thermal conductivity, such as a ceramic material with high thermal conductivity, specifically Si / C ceramic, Si3N4 ceramic, AlN ceramic, etc.

[0048] Taking the preparation of the battery body by lamination as an example, the preparation method of the above battery cell can be as follows:

[0049] The positive and negative electrode sheets and separators that have been rolled are cut into the designed size, and then punched at the designed positions on the positive and negative electrode sheets and separators to form positive electrode through holes, negative electrode through holes and separator through holes respectively. The punched positive and negative electrode sheets and separators are stacked so that the punching positions correspond one to one to form through holes 3, and the battery body 1 is obtained. After the battery body 1 is fixed with glue, the heat conducting rods 2 are inserted into the through holes 3 one by one.

[0050] The battery cell can be used to prepare a secondary battery and further used in electrical equipment.

[0051] Example 1

[0052] This embodiment provides a battery cell with a battery cell model of 4430095 size, and a positive electrode active material of layered lithium nickel cobalt manganese transition metal oxide (NCM), whose chemical formula is LiNi 0.6 Co 0.2 Mn 0.2 O2; active material: binder: conductive agent = 97.7%: 1.4%: 0.9%; positive electrode single surface density is 248mg / 1540.25mm 2 The negative electrode active material is artificial graphite, where active material: binder: conductive agent = 96.4%: 2.8%: 0.8%; the single surface density of the negative electrode is 152mg / 1540.25mm 2 The battery cell body 1 is prepared by lamination, and the specific preparation method is as above.

[0053] (1) The diameters of through hole 3, negative electrode through hole, and diaphragm through hole are 3.2 mm, and the diameter of positive electrode through hole is 3.5 mm;

[0054] (2) The total area of ​​all through holes 3 accounts for 10% of the area of ​​the battery cell body 1;

[0055] (3) The main material of the thermal conductive core layer 2.1 is Si / C ceramic with a solid porous structure. The pore size of the porous structure is 300 μm. The diameter of the thermal conductive core layer 2.1 is 2.7 mm. The insulating layer 2.2 is PE foam with a thickness of 0.5 mm.

[0056] Example 2

[0057] This embodiment provides a battery cell, which is different from the embodiment 1 in that the number of through holes 3 is reduced so that the total area of ​​all through holes 3 accounts for 5% of the area of ​​the battery cell body 1 .

[0058] Example 3

[0059] This embodiment provides a battery cell, which is different from the embodiment 1 in that the number of through holes 3 is reduced, so that the total area of ​​all through holes 3 accounts for 8% of the area of ​​the battery cell body 1 .

[0060] Example 4

[0061] This embodiment provides a battery cell, which is different from the embodiment 1 in that the number of through holes 3 is increased so that the total area of ​​all through holes 3 accounts for 15% of the area of ​​the battery cell body 1 .

[0062] Example 5

[0063] This embodiment provides a battery core, which is different from Embodiment 1 in that the main material of the heat-conducting core layer 2.1 is adjusted to be AlN ceramic with a solid porous structure.

[0064] Example 6

[0065] This embodiment provides a battery core, which is different from Embodiment 1 in that the main material of the heat-conducting core layer 2.1 is adjusted to be Si3N4 ceramic with a solid porous structure.

[0066] Example 7

[0067] This embodiment provides a battery cell, which is different from Embodiment 2 in that the positive electrode active material is LFP (lithium iron phosphate).

[0068] Example 8

[0069] This embodiment provides a battery cell, which is different from Embodiment 3 in that the positive electrode active material is LFP.

[0070] Example 9

[0071] This embodiment provides a battery cell, which is different from the embodiment 1 in that the positive electrode active material is LFP.

[0072] Example 10

[0073] This embodiment provides a battery cell, which is different from Embodiment 4 in that the positive electrode active material is LFP.

[0074] Comparative Example 1

[0075] This comparative example provides a battery cell, which is different from Example 1 in that no through hole 3 is provided and no heat conducting rod 2 is provided.

[0076] Comparative Example 2

[0077] This comparative example provides a battery cell, which is different from Example 7 in that no through hole 3 is provided and no heat conducting rod 2 is provided.

[0078] Results Analysis

[0079] The internal temperatures of the battery cells of the above embodiment and comparative example were tested, and the results are shown in Table 1.

[0080] The test method is as follows: (1) a thermocouple is placed inside the battery cell, and the other end of the thermocouple is connected to a display to monitor the temperature change inside the battery cell during the charge and discharge process, and record the highest temperature during the charge and discharge process; this experiment uses the highest charge and discharge temperature of the embodiment with a through-hole area of ​​zero as a reference, and the temperature drop inside the battery cell is the difference between the highest charge and discharge temperature of embodiment 1 and the highest charge and discharge temperature of other embodiments;

[0081] (2) Charge the battery cell at a constant current and constant voltage of 1 / 3C to the cut-off voltage, leave it for 30 minutes, and then discharge it at a current of 2C to the cut-off voltage.

[0082] Table 1

[0083] Serial number Positive active material Thermal core material Total through hole area ratio Temperature drop inside the battery cell Example 1 NCM Si / C 10％ 5.6℃ Example 2 NCM Si / C 5％ 2.2℃ Example 3 NCM Si / C 8％ 3.4℃ Example 4 NCM Si / C 15％ 6.4℃ Example 5 NCM AlN 10％ 4.8℃ Example 6 NCM <![CDATA[Si3N4]]> 10％ 4.2℃ Example 7 LFP Si / C 5％ 1.7℃ Example 8 LFP Si / C 8％ 2.4℃ Example 9 LFP Si / C 10％ 4.3℃ Example 10 LFP Si / C 15％ 5.2℃ Comparative Example 1 NCM / 0 0℃ Comparative Example 2 LFP / 0 0℃

[0084] The results show that as the total area ratio of the through-holes increases, the temperature drop inside the battery cell gradually increases; at the same time, the temperature drop inside the battery cell is affected by the positive electrode active material and the thermal conductive core layer material.

[0085] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention of the utility model.

Claims

1. A battery cell, characterized in that: It includes a battery cell body and a number of heat conducting rods; A plurality of through holes are provided in the thickness direction of the battery core body, and the heat conducting rod is installed in the through holes; The heat-conducting rod comprises a heat-conducting core layer and an insulating layer coated on the outer peripheral surface of the heat-conducting core layer.

2. The battery cell according to claim 1, characterized in that: In the thickness direction of the battery core body, the total area of ​​the plurality of through holes accounts for 5%-20% of the area of ​​the battery core body.

3. The battery cell according to claim 1, characterized in that: The battery cell body comprises a positive electrode sheet, a negative electrode sheet and a diaphragm, and the through holes are formed by the positive electrode through holes on the positive electrode sheet, the negative electrode through holes on the negative electrode sheet and the diaphragm through holes in a one-to-one correspondence; The aperture of the negative electrode through hole is 3mm-5mm, the aperture of the positive electrode through hole is 0.2mm-0.5mm larger than that of the negative electrode through hole, and the aperture of the diaphragm through hole is consistent with that of the negative electrode through hole.

4. The battery cell according to claim 1, characterized in that: The diameter of the heat conducting rod is consistent with the aperture of the through hole, or the heat conducting rod and the through hole are interference fit.

5. The battery cell according to claim 1 or 4, characterized in that: Two ends of the heat conducting rod extend out of the through hole.

6. The battery cell according to claim 1, characterized in that: In the cross section of the heat-conducting rod, the area ratio of the insulating layer to the heat-conducting core layer is 10%-50%.

7. The battery cell according to claim 1, characterized in that: The insulating layer is made of elastic material.

8. The battery cell according to claim 1 or 7, characterized in that: The thickness of the insulating layer is 0.5 mm-1.0 mm.

9. The battery cell according to claim 1, characterized in that: The heat-conducting core layer is a porous structure with a pore size of 100 μm-500 μm.

10. A secondary battery, characterized in that: A battery cell comprising any one of claims 1 to 9.

Images