Lithium ion battery and temperature adaptive current collector

Abstract

The application discloses a temperature self-adapting current collector, which comprises a base layer and a deformation layer, the base layer is made of metal material, and the deformation layer is made of memory alloy. The first protrusion is arranged on the surface of the deformation layer, which can shorten the electron moving distance and improve the overall charge transmission efficiency. Meanwhile, the deformation layer is made of memory alloy, so that the current collector can make corresponding structural changes according to temperature changes. When the temperature of the battery rises, the contact area automatically increases, and when the temperature decreases, the contact area automatically decreases, so as to ensure that the current collector and the active particles have effective fixed working area. The application further provides a lithium ion battery comprising the temperature self-adapting current collector, and the lithium ion battery further comprises a positive electrode, a diaphragm and a negative electrode which are sequentially arranged. The temperature self-adapting current collector comprises a positive electrode current collector and a negative electrode current collector, so that the conductivity of the lithium ion battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical devices, in particular to a lithium ion battery and a temperature self-adaptive current collector. BACKGROUND

[0002] As a kind of energy storage and conversion device, improving the energy conversion rate of lithium ion battery is the eternal goal of sustainable development. In recent years, in order to obtain sufficient power and energy in a short time, the battery gradually develops towards compactness, high energy density and long cycle life. However, the application of lithium battery in limited space makes it more sensitive to pressure, temperature and vibration, and is prone to internal short circuit, thermal runaway and other phenomena. At the same time, driven by the market, the lithium ion battery with fast charging capacity has become the focus of attention. The essence of improving the fast charging performance of lithium ion battery is to increase the transmission speed of lithium ion in porous medium under high current density, maintain the charge transfer of the interface between the current collector and the electrode, and reduce the internal lithium deposition. However, as the current collector of the battery material, the surface structure of the current collector directly affects the performance of the battery, such as electrical conductivity, discharge-charge capacity and cycle life. The contact between the conventional current collector and the active material is limited, and as the temperature rises, the interface resistance leads to excessive internal resistance of the battery. At the same time, the expansion and shedding of active particles during the cycle process of the battery cause the volume change of the electrode, thereby reducing the capacity and cycle performance of the battery. Therefore, how to realize the charge capacity of lithium ion battery under fast charging condition without being affected has become a difficult problem to be solved.

[0003] In the prior art, the current collector is mostly made of smooth surface and simple structure of rolled aluminum / copper foil or electrolytic aluminum / copper foil, but the resistance increases significantly after a long cycle. Therefore, enhancing the surface function of copper current collector through structural strategy, obtaining rich micro / nano structure can effectively improve the interface combination of active particles and current collector, which is of great significance especially for high-capacity electrode materials. The Chinese patent with publication number CN114908386A proposes an extremely thin multi-layer structure of nanotwin copper foil. The twin layer is obtained by using a first electroplating solution-second electroplating solution-first electroplating solution for three-stage direct current deposition, and a copper foil with fine crystal layer-nanotwin layer-fine crystal layer structure is obtained. The copper foil provided by the present application has higher tensile strength, high elongation, low surface roughness and excellent electrical conductivity, which can meet the application requirements of lithium ion battery current collector. For example, the Chinese patent with publication number CN114214626A proposes a copper foil with a porous surface structure. The copper foil is prepared through a series of steps such as electrochemical zinc plating, heat treatment, wet chemical metallurgical leaching, etc. The prepared copper foil has a porous structure on the surface, the pore size distribution is narrow, the pore density is high, and the surface roughness is low, which is especially suitable for lithium ion batteries.

[0004] Although the prior art reduces the current collector interface resistance to some extent, there are still the following shortcomings: on the one hand, the interface contact problem of the active particle volume change caused by the interface active particle expansion during the battery operation process is not considered; on the other hand, the process during the preparation of the current collector is complex, and the thermal conductivity of the prepared current collector is not ideal, which cannot fully meet the requirements of the current collector under the fast charging condition; more importantly, the electron transmission path between the current collector and the active particle is not fixed, and the conductivity of the battery cannot be guaranteed.

[0005] Therefore, how to change the present situation that the battery conductivity cannot be guaranteed after reducing the current collector interface resistance in the prior art has become a problem to be solved by those skilled in the art. SUMMARY

[0006] The purpose of the present application is to provide a lithium ion battery and a temperature adaptive current collector to solve the problems existing in the prior art, increase the contact area between the current collector and the active particle, and improve the conductivity of the battery.

[0007] To achieve the above purpose, the present application provides the following scheme: the present application provides a temperature adaptive current collector, comprising:

[0008] a base layer made of metal material;

[0009] a deformation layer made of memory alloy, the deformation layer is connected with the base layer, and the side of the deformation layer away from the base layer has a first protrusion, the first protrusion disappears when the temperature of the deformation layer is not less than the phase transition temperature range of the memory alloy.

[0010] Preferably, the side of the deformation layer away from the base layer has a second protrusion, the first protrusion is arranged on the second protrusion, and a plurality of first protrusions are arranged on each second protrusion.

[0011] Preferably, the first protrusions are arranged in an array.

[0012] Preferably, the number of the second protrusions is multiple, and the second protrusions are arranged at intervals.

[0013] Preferably, the second protrusions are prismatic protrusions.

[0014] Preferably, the first protrusions are block-shaped, strip-shaped or hemispherical structures.

[0015] Preferably, the base layer is bonded with the deformation layer through a conductive adhesive layer.

[0016] Preferably, the base layer and the deformation layer are welded.

[0017] Preferably, the thickness of the deformation layer is 3-7 microns, the height of the second protrusion is 1-2 microns, and the height of the first protrusion is 40-100 nanometers.

[0018] The application also provides a lithium ion battery comprising the temperature-adaptive current collector, and further comprising a positive electrode, a separator and a negative electrode arranged in sequence, wherein the temperature-adaptive current collector comprises a positive electrode current collector and a negative electrode current collector, the positive electrode current collector is arranged on a side of the positive electrode away from the separator, and the deformation layer of the positive electrode current collector is arranged towards the positive electrode; and the negative electrode current collector is arranged on a side of the negative electrode away from the separator, and the deformation layer of the negative electrode current collector is arranged towards the negative electrode.

[0019] The application has the following technical effects relative to the prior art.

[0020] The temperature-adaptive current collector of the application has the deformation layer arranged on the base layer, and the first protrusion arranged on the deformation layer, which can shorten the electron moving distance and improve the overall charge transport efficiency; at the same time, the deformation layer is made of a memory alloy, and when the temperature of the deformation layer is not less than the phase transition temperature range of the memory alloy, the first protrusion disappears, effectively increasing the contact area of the active material and the current collector, so that the current collector of the application can make corresponding structural changes according to the temperature change, the contact area is automatically increased when the battery temperature rises, and the contact area is automatically reduced when the temperature decreases, thereby ensuring the effective fixed working area of the current collector and the active particles.

[0021] The application also provides a lithium ion battery comprising the temperature-adaptive current collector, and further comprising a positive electrode, a separator and a negative electrode arranged in sequence, wherein the temperature-adaptive current collector comprises a positive electrode current collector and a negative electrode current collector, the positive electrode current collector is arranged on a side of the positive electrode away from the separator, and the deformation layer of the positive electrode current collector is arranged towards the positive electrode; and the negative electrode current collector is arranged on a side of the negative electrode away from the separator, and the deformation layer of the negative electrode current collector is arranged towards the negative electrode. The temperature-adaptive current collector can realize self-adaptive change of the contact area with the active particles according to the temperature change of the battery, solve the problem of insufficient interface contact area caused by the volume change of the active particles, and improve the conductivity of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0023] Figure 1 FIG. 1 is a structural schematic diagram of the temperature-adaptive current collector of the application;

[0024] Figure 2 Structure diagram of the first protrusion of the temperature adaptive current collector in the application is a strip-shaped structure;

[0025] Figure 3 Structure diagram of the first protrusion of the temperature adaptive current collector in the application is a hemispherical structure;

[0026] Figure 4 Structure diagram of the second protrusion of the temperature adaptive current collector in the application is a cross section;

[0027] Figure 5 Structure diagram of the lithium ion battery in the application.

[0028] Wherein, 1 is the base layer, 2 is the deformation layer, 3 is the first protrusion, 4 is the second protrusion, 5 is the positive current collector, 6 is the positive electrode, 7 is the separator, 8 is the negative electrode, and 9 is the negative current collector. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0030] The purpose of the application is to provide a lithium ion battery and a temperature adaptive current collector to solve the problems in the prior art, increase the contact area of the current collector and active particles, and improve the conductivity of the battery.

[0031] In order to make the above-mentioned purposes, characteristics and advantages of the application more obvious and easy to understand, the application will be further described in detail below with reference to the drawings and specific embodiments.

[0032] The application provides a temperature adaptive current collector, which comprises a base layer 1 and a deformation layer 2, the base layer 1 is made of metal material; the deformation layer 2 is made of memory alloy, the deformation layer 2 is connected with the base layer 1, and the deformation layer 2 has a first protrusion 3 on the side away from the base layer 1; when the temperature of the deformation layer 2 is not less than the phase transition temperature range of the memory alloy, the first protrusion 3 disappears.

[0033] The temperature self-adapting current collector of the present application is provided with a deformation layer 2 on the base layer 1, and the deformation layer 2 is provided with first protrusions 3, which can shorten the electron moving distance and improve the overall charge transmission efficiency; at the same time, the deformation layer 2 is made of a memory alloy, and when the temperature of the deformation layer 2 is not less than the phase transition temperature range of the memory alloy, the first protrusions 3 disappear, effectively increasing the contact area of the active material and the current collector, so that the current collector can make corresponding structural changes according to the temperature change, the battery temperature rises, the contact area automatically increases, the temperature decreases, the contact area automatically decreases, and the effective fixed working area of the current collector and the active particles is ensured. It should be emphasized that the temperature self-adapting current collector of the present application simultaneously includes the base layer 1 and the deformation layer 2, compared with only providing the deformation layer 2, the production cost is saved, the weight of the temperature self-adapting current collector is reduced, and the lightweight of the battery is beneficial to be realized.

[0034] In the specific embodiment, the side of the deformation layer 2 away from the base layer 1 has second protrusions 4, which form channels on the surface of the current collector, promote the regularization of the electron transmission path, and the first protrusions 3 are arranged on the second protrusions 4, and a plurality of first protrusions 3 are arranged on each second protrusion 4. First, the second protrusions 4 are arranged on the deformation layer 2, which is beneficial to increase the surface area of the deformation layer 2 and improve the heat conduction performance of the current collector, and the size of the second protrusions 4 is larger, and the first protrusions 3 are arranged on the second protrusions 4, which can increase the number of the first protrusions 3, so as to further realize the controllability of the contact area of the current collector and the active particles.

[0035] In actual application, the number of the first protrusions 3 is multiple, and the first protrusions 3 are arranged in an array, and the array mode can be selected according to the specific specifications of the current collector. The first protrusions 3 arranged in an array also achieve the purpose of increasing micro-channels on the surface of the current collector, and further promote the regularity of the electron transmission path.

[0036] Among them, the number of the second protrusions 4 is multiple, and the second protrusions 4 are arranged at intervals, and the second protrusions 4 can be arranged at equal intervals to ensure the uniformity of the contact between the current collector and the active material, and at the same time, the processing and manufacturing difficulty is reduced.

[0037] In the specific embodiment, the second protrusions 4 are prismatic protrusions, and the cross-sectional shape of the second protrusions 4 can be selected as a triangle or a quadrilateral, that is, the second protrusions 4 are in a triangular prism or quadrangular prism structure. In actual application, the second protrusions 4 with appropriate shapes can also be arranged according to the actual working conditions, so as to improve the flexible adaptability of the current collector.

[0038] Specifically, the first protrusion 3 is in a block, strip or semi-spherical structure, and the specific structure of the first protrusion 3 can be flexibly selected or combined according to the actual working condition to adapt to different specifications of the battery. It should be noted that the first protrusion 3 can be processed by micro-nano machining technology. After the first protrusion 3 is processed, the first protrusion 3 temporarily disappears through a hot-pressing and cooling setting process, the temperature critical point of the structure transformation is determined, and thus the structure of the deformation layer 2 can be self-adapted according to the temperature of the battery. In the embodiment, the deformation layer 2 is made of single-path TiNi shape memory alloy. The shape memory alloy can realize the lattice structure transformation between austenite and martensite according to the temperature change, and has self-recovery ability at different temperatures, so that the current collector has temperature self-adaptability. In the embodiment, the phase transition point temperature of the TiNi shape memory alloy is 20-40°C. When the thermal response reaches this temperature range, the first protrusion 3 disappears, and the contact surface between the active particles and the current collector is expanded. The deformation layer 2 has self-resetting ability. When the temperature of the battery exceeds the optimal working temperature, the first protrusion 3 disappears. When the temperature of the battery decreases, the first protrusion 3 appears. In other embodiments of the present application, the type of shape memory alloy can also be selected according to the specific working condition.

[0039] More specifically, the base layer 1 is connected to the deformation layer 2 by a conductive adhesive layer, which is reliable and convenient to operate. The conductive adhesive has good adhesion and conductivity, which ensures the normal operation of the current collector. In practical applications, the conductive adhesive layer can be selected from carbon black conductive adhesive, silver paste conductive adhesive, copper paste conductive adhesive, conductive adhesive, or other types of conductive adhesive according to the specific public selection. The thickness of the conductive adhesive layer is 1-2 μm, which can also be adjusted according to the actual connection requirements. In addition, the base layer 1 can be welded to the deformation layer 2. The welded connection is firm and can effectively enhance the structural integrity of the current collector. At the same time, the welded connection is convenient to operate. In practical applications, methods such as hot-pressing welding, laser welding or ultrasonic welding can be selected. When hot-pressing welding is used, the shape memory alloy and the base layer 1 (copper / aluminum foil layer) are placed in the clamp of the hot-pressing welding machine, and a certain pressure and temperature are applied to make the surfaces melt and fuse together. When laser welding is used, the interface part of the shape memory alloy and the base layer 1 (copper / aluminum foil layer) is heated and melted by a laser beam, and then quickly cooled to realize the connection of the two. When ultrasonic welding is used, the interface part of the shape memory alloy and the base layer 1 (copper / aluminum foil layer) is heated by ultrasonic vibration to make the surfaces melt and fuse together.

[0040] In addition, the thickness of the deformation layer 2 is 3-7 μm, and the preferred thickness range is 4-6 μm. The height of the second protrusion 4 is 1-2 μm, and the height of the first protrusion 3 is 40-100 nm.

[0041] The application further provides a lithium ion battery comprising the temperature self-adapting current collector, and further comprising a positive electrode 6, a diaphragm 7 and a negative electrode 8 arranged in sequence, wherein the temperature self-adapting current collector comprises a positive electrode current collector 5 and a negative electrode current collector 9, the positive electrode current collector 5 is arranged on the side of the positive electrode 6 away from the diaphragm 7, and the deformation layer 2 of the positive electrode current collector 5 is arranged towards the positive electrode 6, and the negative electrode current collector 9 is arranged on the side of the negative electrode 8 away from the diaphragm 7, and the deformation layer 2 of the negative electrode current collector 9 is arranged towards the negative electrode 8. The positive electrode current collector 5 and the negative electrode current collector 9 can change the contact area with the active particles according to the change of the battery temperature, solve the problem of insufficient interface contact area caused by the change of the volume of the active particles, and improve the conductivity of the lithium ion battery. It should be noted that in the specific embodiment, the base layer 1 of the positive electrode current collector 5 is an aluminum foil layer, the thickness of the positive electrode current collector 5 is 10-15 μm, the base layer 1 of the negative electrode current collector 9 is a copper foil layer, the thickness of the negative electrode current collector 9 is 5-10 μm, and the preferred thickness of the positive electrode current collector 5 and the negative electrode current collector 9 is the same, i.e. 10 μm. In actual application, the positive electrode current collector 5 and the negative electrode current collector 9 can also select other types of metal materials as the base layer 1 according to the actual needs of the battery. In addition, it should be explained that the working process of the lithium ion battery is known to those skilled in the art, and will not be described here.

[0042] It should be further explained that in actual application, a conductive coating can be coated on the surface of the deformation layer 2 in contact with the positive electrode 6 and the negative electrode 8. The conductive coating can reduce the air thermal resistance and offset the impedance caused by the contact resistance. The thickness of the conductive coating is 1-2 μm, and can also be adjusted according to the actual working condition.

[0043] The temperature self-adapting current collector of the application simultaneously arranges the base layer 1 and the deformation layer 2. The deformation layer 2 can automatically control the contact area with the active material according to the change of the battery temperature, solve the problem of insufficient interface contact area caused by the change of the volume of the active particles, automatically increase the contact area when the battery temperature rises, and automatically reduce the contact area when the temperature decreases, thereby ensuring the effective fixed working area of the current collector and the active particles. Meanwhile, the first protrusion 3 and the second protrusion 4 can form micro-channels, regularize the electron transmission path, shorten the electron moving distance, and improve the overall charge transmission efficiency. In addition, the temperature self-adapting current collector of the application simultaneously comprises the base layer 1 and the deformation layer 2, which can save the production cost, reduce the weight of the current collector, and be conducive to realizing the lightweight of the battery, compared with arranging only the deformation layer 2.

[0044] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used for helping to understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, according to the idea of the present application, the specific implementation manners and application ranges will be changed. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A temperature-adaptive current collector, characterized in that: include: A base layer, wherein the base layer is made of a metal material; a deformation layer, the deformation layer being made of a memory alloy, the deformation layer being connected to the base layer, the deformation layer having a first protrusion on a side away from the base layer, and the first protrusion disappearing when the temperature of the deformation layer is not less than the phase transition temperature of the memory alloy; The deformable layer has a second protrusion on a side away from the base layer. The first protrusion is arranged on the second protrusion, and each of the second protrusions is provided with a plurality of the first protrusions.

2. The temperature-adaptive current collector according to claim 1, characterized in that: The first protrusions are arranged in an array.

3. The temperature-adaptive current collector according to claim 1, characterized in that: There are multiple second protrusions, and the second protrusions are arranged at intervals.

4. The temperature-adaptive current collector according to claim 1, characterized in that: The second protrusion is a prismatic protrusion.

5. The temperature-adaptive current collector according to any one of claims 1 to 4, characterized in that: The first protrusion is a block-shaped, strip-shaped or hemispherical structure.

6. The temperature-adaptive current collector according to any one of claims 1 to 4, characterized in that: The base layer is bonded to the deformable layer via a conductive adhesive layer.

7. The temperature-adaptive current collector according to any one of claims 1 to 4, characterized in that: The base layer is connected to the deformation layer by welding.

8. The temperature-adaptive current collector according to claim 1, characterized in that: The thickness of the deformable layer is 3 μm to 7 μm, the height of the second protrusion is 1 μm to 2 μm, and the height of the first protrusion is 40 nm to 100 nm.

9. A lithium-ion battery comprising the temperature-adaptive current collector according to any one of claims 1 to 8, characterized in that: It also includes a positive electrode, a diaphragm and a negative electrode arranged in sequence, the temperature adaptive current collector includes a positive current collector and a negative current collector, the positive current collector is arranged on the side of the positive electrode away from the diaphragm, and the deformation layer of the positive current collector is arranged toward the positive electrode, the negative current collector is arranged on the side of the negative electrode away from the diaphragm, and the deformation layer of the negative current collector is arranged toward the negative electrode.

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