A lithium battery, system and method for identifying the growth position of lithium dendrites

Abstract

The present application provides a lithium battery, a system and a method for identifying the growth position of lithium dendrites. The lithium battery includes a positive electrode, a negative electrode and a separator located between the positive and negative electrodes; the lithium battery further includes a detection layer; the detection layer is located between the separator and the positive electrode; the detection layer includes a polymer layer and an electron-conducting layer; the polymer layer does not conduct electrons; the polymer layer is attached to the positive electrode; the electron-conducting layer includes a plurality of independent detection regions; the plurality of independent detection regions are electrically connected to a plurality of current response devices. Through the detection layer of the lithium battery in the present application, the detection layer contains an electron-conducting layer, and the electron-conducting layer and the negative electrode are jointly connected to the current response device. When the metal dendrite pierces through the first layer of film and contacts the electron-conducting layer, the negative electrode and the electron-conducting layer form a conductive connection through the dendrite, so it can be detected by the current response device. Since there are corresponding current response devices in the detection regions, the regional position of dendrite growth can be detected in real time.

Description

Technical Field

[0001] This application relates to the technical field of lithium batteries, and particularly to a lithium battery, a system, and a method for identifying the growth position of lithium dendrites. Background Art

[0002] The metal negative electrode has an extremely high energy density. Using it as the negative electrode material of the battery can greatly improve the energy density of the battery. Since most metal negative electrodes undergo a metal dissolution-deposition reaction during the battery reaction, the deposited metal will form dendrites under some accidental factors. These dendrites piercing the separator will cause the battery to short-circuit, posing a high safety hazard.

[0003] The soft-pack battery has a large area, while the volume of the dendrites is very small, making it difficult to observe through images. The battery needs to be disassembled to observe the position and growth of the dendrites. At present, Patent CN105226226A discloses a separator, including a first polymer layer, a second polymer layer, and a metal layer located therebetween. By measuring the potential difference between the positive electrode and the negative electrode, and the potential difference between the negative electrode and the metal layer, the occurrence of short circuit can be detected; Patent CN106684298A discloses a battery separator, including a positive electrode insulating layer, a negative electrode insulating layer, and a porous conductive layer. By detecting the change in chemical potential between the porous conductive layer and the negative electrode, the occurrence of short circuit can be detected. However, both of the above patents can only detect the occurrence of lithium dendrites, but cannot detect the position where the lithium dendrites occur, and cannot explore problems such as the probability of lithium dendrites occurring at different positions. Therefore, in order to study the position law of dendrite growth in soft-pack batteries, specific detection devices and methods need to be developed. Summary of the Invention

[0004] In view of the above problems, this application proposes a lithium battery, a system, and a method for identifying the growth position of lithium dendrites; the lithium battery includes a detection layer, and the detection layer contains a conductive electron layer. The conductive electron layer and the negative electrode are jointly connected to a current response device. When the metal dendrite pierces the first layer of film and contacts the conductive electron layer, the negative electrode and the conductive electron layer form a conductive connection through the dendrite, so it can be detected by the current response device. Since there are corresponding current response devices in the detection area, the area position where the dendrites grow can be detected in real time, overcoming the deficiencies and defects mentioned in the background art.

[0005] To achieve the above object, this application adopts the following technical solutions:

[0006] One inventive point of the present application is to provide a lithium battery for identifying the growth position of lithium dendrites, which includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes; the lithium battery further includes a detection layer; the detection layer is located between the separator and the positive electrode; the detection layer includes a polymer layer and an electron-conducting layer; the polymer layer does not conduct electrons; the polymer layer is attached to the positive electrode; the electron-conducting layer includes a plurality of independent detection regions; the plurality of independent detection regions are electrically connected to a plurality of current response devices.

[0007] Optionally, the thickness of the detection layer is 5-15 μm; the porosity of the polymer layer is 30%-70%.

[0008] Optionally, the material of the electron-conducting layer includes a conductive material and a binding material; the binding material bonds the conductive material to the surface of the polymer layer; the region formed by the conductive material is the detection region; the detection region is connected to the current response device through an electrode pin.

[0009] Optionally, the material of the polymer layer includes at least one of polyethylene, polypropylene, aromatic polyamide fiber, polyimide, nanocellulose, and polyethylene terephthalate; the conductive material includes at least one of copper, silver, gold, nickel, and conductive carbon black; the binding material includes at least one of polyvinylidene fluoride, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyurethane, polyvinyl alcohol, and polyvinyl butyral.

[0010] Another inventive point of the present application is to provide a system for identifying the growth position of lithium dendrites, which includes a current response device, a charge-discharge tester, and a lithium battery as described in any one of the above; the charge-discharge tester is respectively connected to the positive and negative electrodes of the lithium battery to charge and discharge the lithium battery; the current response device is respectively connected to the detection layer and the negative electrode of the lithium battery.

[0011] Optionally, each current response device corresponds to each detection region one by one.

[0012] Another inventive point of the present application is to provide a method for identifying the growth position of lithium dendrites. Using the system as described in any one of the above, the lithium battery is subjected to charge-discharge cycles, and the current value of the current response device is detected to identify the growth position of the lithium dendrites.

[0013] Optionally, the method includes: (1) dividing the electron-conducting layer into at least three detection regions, each of the at least three detection regions being connected to a current response device; assembling the positive electrode, the separator, the detection layer, and the negative electrode to obtain a lithium battery; (2) connecting a charge-discharge tester to the positive electrode and the negative electrode of the lithium battery respectively, performing charge-discharge cycles on the lithium battery, and recording the current values of the current response devices; when the current value > 0, lithium dendrites are generated in the detection region connected to the current response device, thereby identifying the growth position of the lithium dendrites.

[0014] Optionally, the method further includes: (3) repeating steps (1) and (2); the number of repetitions is not less than 10 times; (4) counting the detection regions where lithium dendrites are generated, and calculating the probability of lithium dendrites appearing in each detection region.

[0015] Optionally, the method further includes: (5) marking the detection regions in step (4) according to the probability of lithium dendrites appearing, as high-probability regions, medium-probability regions, and low-probability regions; wherein, in the high-probability regions, the probability of lithium dendrites appearing is: > 30%; in the medium-probability regions, the probability of lithium dendrites appearing is: 10% - 30%; in the low-probability regions, the probability of lithium dendrites appearing is: < 10%.

[0016] Optionally, the method further includes: (6) dividing the high-probability regions and the medium-probability regions into multiple secondary detection regions; wherein, each high-probability region includes 2 - 10 secondary detection regions; the medium-probability regions include 2 - 4 secondary detection regions; (7) assembling the lithium battery according to step (1), performing charge-discharge cycles on the lithium battery and recording the current values according to step (2), repeating the number of times not less than 10 times according to step (3), calculating the probability of each detection region according to step (4), marking the secondary high-probability regions, secondary medium-probability regions, and secondary low-probability regions according to step (5), and dividing the secondary high-probability regions and the secondary medium-probability regions into multiple tertiary detection regions according to step (6).

[0017] Optionally, the method further includes: (8) performing multiple cycles according to steps (1) - (7) until one of the following two results appears: i) obvious aggregation behavior appears in the high-frequency regions; ii) the number of detection regions ≥ 24.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] The lithium battery of the present application for identifying the growth position of lithium dendrites contains a detection layer, which can provide conductive connection within the detection area range. When the lithium dendrite penetrates the separator and contacts the detection layer, a conductive contact will be formed, causing the electrons of the negative electrode to pass through the lithium dendrite and the detection layer, then through the external circuit and back to the negative electrode, generating a current path. Through the current response device, the generation of lithium dendrites can be detected based on whether a current is generated. Since the detection layer contains detection areas that are not electrically conductive to each other, when a current record appears in the current response device connected to the detection area, it can be identified that lithium dendrite growth has occurred in the area position. It is also possible to subdivide the defined larger detection area to generate more detection areas, thereby obtaining a more accurate probability distribution of the dendrite growth position; the initial statistical results show that dendrites are more likely to puncture a certain part of the electrode. This part can be divided into more area blocks, more detection areas can be set up, and then through testing - statistical analysis, a more accurate probability distribution relationship of the dendrite growth area can be obtained. Description of the Drawings

[0020] Figure 1 It is a distribution diagram of a detection area provided by an embodiment of the present application;

[0021] Figure 2 It is another distribution diagram of a detection area provided by an embodiment of the present application;

[0022] Figure 3 It is another distribution diagram of a detection area provided by an embodiment of the present application;

[0023] Figure 4 It is another distribution diagram of a detection area provided by an embodiment of the present application;

[0024] Figure 5 It is another distribution diagram of a detection area provided by an embodiment of the present application;

[0025] Figure 6 It is a distribution schematic diagram of the detection area provided by Test Example 1 of the present application;

[0026] Figure 7 It is a schematic diagram of the system provided by Test Example 1 of the present application;

[0027] Figure 8 It is a distribution schematic diagram of the further divided detection area provided by Test Example 1 of the present application;

[0028] Figure 9 It is a probability distribution schematic diagram of the further divided detection area provided by Test Example 1 of the present application;

[0029] Figure 10 It is a distribution schematic diagram of the detection area provided by Test Example 2 of the present application;

[0030] Figure 11 Schematic diagram of the distribution of the further divided detection areas provided for Test Example 2 of this application. Detailed implementation mode

[0031] To make the purpose, technical solution and advantages of this application clearer, the following further details this application. However, it should be understood that the description here is only used to explain this application and is not used to limit the scope of this application.

[0032] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of this application in this article are only for the purpose of describing specific embodiments and are not intended to limit this application. The reagents and instruments used herein are all commercially available, and the characterization means involved can refer to the relevant descriptions in the prior art, which will not be elaborated herein.

[0033] To further understand this application, the following further details this application in combination with the best embodiments.

[0034] Embodiment 1

[0035] This embodiment provides a lithium battery for identifying the growth position of lithium dendrites, including a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes; the lithium battery further includes a detection layer; the detection layer is located between the separator and the positive electrode; the detection layer includes a polymer layer and an electron-conducting layer; the polymer layer does not conduct electrons; the polymer layer is attached to the positive electrode; the electron-conducting layer includes a plurality of independent detection areas; a plurality of independent detection areas are electrically connected to a plurality of current response devices.

[0036] Among them, the polymer layer can pass ions but does not conduct electrons; it is convenient for lithium ions, etc. to pass through and avoids affecting the electrical performance of the battery. The porosity of the polymer layer is 30% - 70%, which belongs to the current porosity range value of the separator and can play the role of the separator. It can not only prevent electrode particles from directly passing through, but also not prevent positive and negative ions from freely passing through, which is a further protection for the battery. When the battery is in operation, lithium dendrites will irreversibly deposit on the surface of the negative electrode. As lithium continues to deposit, the lithium dendrites will also grow, and eventually pierce the first layer structure of the separator; usually, the separator of a general battery has only one layer. When it is pierced, it causes a short circuit inside the lithium-ion battery, resulting in thermal runaway of the battery and triggering combustion and explosion. When the lithium dendrites penetrate the separator, this polymer layer can play the role of a second separator, avoiding battery scrapping and reducing potential safety hazards.

[0037] The electron-conducting layer includes a plurality of independent detection areas, that is, each detection area is independent of each other and does not affect each other.

[0038] The thickness of the detection layer is 5 to 15 μm, and it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm. When the detection layer is too thick, it will seriously affect the electrical performance of the battery itself and affect the use of the battery; when the detection layer is too thin, it will cause the thickness of the polymer layer and the electron-conducting layer to be further reduced, which not only makes the operation difficult, is easy to break, but also is easily pierced by lithium dendrites, causing damage to the battery.

[0039] The material of the electron-conducting layer includes a conductive material and a binding material; the binding material bonds the conductive material to the surface of the polymer layer; the region formed by the conductive material is the detection region; the detection region is connected to the current response device through an electrode pin.

[0040] The polymer is divided to form different partitions, and then the conductive material is bonded to the surface of the polymer layer through the binding material. This method can be used to form the required detection region pattern in the substrate by means such as coating, screen printing, inkjet printing, etc., so as to form the detection region. Each detection region has an electrode pin connected to the current response device outside, which is used to form a current path.

[0041] The material of the polymer layer can be the material of a common separator, for example, it can be at least one of polyethylene, polypropylene, aromatic polyamide fiber, polyimide, nanocellulose, polyethylene terephthalate.

[0042] The conditions that the conductive material should meet are having good electron conductivity and chemical stability, including at least one of copper, silver, gold, nickel, conductive carbon black; while conductive materials such as iron, aluminum, and tin are not conducive to detecting the existence of lithium dendrites because they are prone to alloying reactions with lithium.

[0043] The binding material can stably exist in the lithium battery electrolyte and has a binding effect, including at least one of polyvinylidene fluoride, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyurethane, polyvinyl alcohol, polyvinyl butyral.

[0044] Example 2

[0045] This example provides a system for identifying the growth position of lithium dendrites, including a current response device, a charge and discharge tester, and the lithium battery as described above; the charge and discharge tester is respectively connected to the positive electrode and the negative electrode of the lithium battery to charge and discharge the lithium battery; the current response device is respectively connected to the detection layer and the negative electrode of the lithium battery.

[0046] When the battery is working normally, lithium dendrites generated will grow on the negative electrode. When the dendrite growth pierces through the separator and contacts the electron-conducting layer, it will form an electron path with the negative electrode and the current response device, thus generating current. Therefore, the current response device will generate a response. Since the electron-conducting layer is arranged throughout the entire area of the polymer layer, the position where lithium dendrites exist can be observed more significantly; and because the polymer layer also has the property of a separator, it can also immediately pause the battery when lithium dendrites occur, avoiding the subsequent short circuit of the battery and resulting in scrapping.

[0047] Among them, each current response device is connected to a corresponding detection area one by one, for identifying the generation situation of lithium dendrites in each detection area.

[0048] The charge and discharge tester can perform charge and discharge cycles on the lithium battery to enable the lithium battery to be normally charged. The current response device is simultaneously connected to the detection layer and the negative electrode. When the lithium dendrite contacts the detection area, a conductive path will be formed, and the current response device will generate current, thereby enabling the growth position of the lithium dendrite to be judged.

[0049] Embodiment 3

[0050] This embodiment provides a method for identifying the growth position of lithium dendrites. By using the system described above in any one of the previous paragraphs, performing charge and discharge cycles on the lithium battery, and detecting the current value of the current response device, the growth position of the lithium dendrite can be identified.

[0051] The method includes: (1) Dividing the electron-conducting layer into at least three detection areas, and at least three detection areas are respectively connected to the current response device; assembling the positive electrode, separator, detection layer, and negative electrode to obtain a lithium battery.

[0052] The more the number of detection areas, the more accurate the detection; however, the more the number of detection areas, the more the workload will increase, and there will also be a large amount of waste of manpower and resources. Therefore, at least three are preferably selected.

[0053] Among them, the area of the polymer layer is not less than that of the negative electrode, that is, it can correspond to each site of the negative electrode.

[0054] (2) Connect the charge and discharge tester to the positive electrode and the negative electrode of the lithium battery respectively, perform charge and discharge cycles on the lithium battery, and record the current value of the current response device; when the current value > 0, lithium dendrites are generated in the detection area connected to the current response device, thereby identifying the growth position of the lithium dendrites.

[0055] The current response device is connected to the detection layer and the negative electrode. When the lithium dendrite grows on the negative electrode and grows to a certain extent, pierces through the separator, and contacts the detection layer, the current response device, the detection layer, and the negative electrode will form a path, so that the current value of the current response device > 0, and it can be judged whether lithium dendrites occur in the corresponding detection area.

[0056] The method further includes: (3) repeating step (1) and step (2); the number of repetitions is not less than 10 times; (4) statistically analyzing the detection regions where lithium dendrites are generated, and calculating the probability of lithium dendrites appearing in each detection region.

[0057] By performing multiple charge and discharge cycles on the battery, the positions of lithium dendrite growth can be obtained multiple times; then, by statistically analyzing these positions, the probability of lithium dendrites appearing in each detection region can be obtained, so as to better improve the lithium battery targeted.

[0058] The method further includes: (5) marking the detection regions in step (4) according to the probability of lithium dendrites appearing, and marking them as high-probability regions, medium-probability regions, and low-probability regions; among them, in the high-probability region, the probability of lithium dendrites appearing is: > 30%; in the medium-probability region, the probability of lithium dendrites appearing is: 10% - 30%; in the low-probability region, the probability of lithium dendrites appearing is: < 10%.

[0059] By marking the detection regions where lithium dendrites appear, a general range of lithium dendrite appearance can be obtained, which is convenient for further dividing the detection regions subsequently.

[0060] The method further includes: (6) dividing the high-probability regions and medium-probability regions into multiple secondary detection regions; among them, each high-probability region includes 2 - 10 secondary detection regions; the medium-probability region includes 2 - 4 secondary detection regions; (7) assembling the lithium battery according to step (1), performing charge and discharge cycles on the lithium battery according to step (2) and recording the current values, repeating the number of times in step (3) not less than 10 times, calculating the probability of each detection region according to step (4), marking the secondary high-probability regions, secondary medium-probability regions, and secondary low-probability regions according to step (5), and dividing the secondary high-probability regions and secondary medium-probability regions into multiple tertiary detection regions according to step (6).

[0061] This step (6) and step (7) are to further divide the high-probability regions and medium-probability regions on the basis of the previous ones, and then perform detection again, so as to obtain a more accurate judgment of the position where lithium dendrites occur. This process is similar to steps (1) - (5), except that the detection regions increase, and at the same time, the required current response devices also increase accordingly.

[0062] After obtaining the preliminary statistical results of the growth positions of lithium dendrites, specific regions can be further subdivided to generate more detection regions, thereby obtaining a more accurate probability distribution of the dendrite growth positions. For example, if the initial statistical results show that dendrites are more likely to penetrate the central part of the electrode, the central region can be divided into more sub-regions, more detection areas can be set up, and then testing-statistical analysis can be carried out to obtain a more accurate probability distribution relationship of the dendrite growth regions.

[0063] The method further includes: (8) performing multiple cycles according to steps (1) to (7) until one of the following two results appears: i) obvious aggregation behavior appears in the high-frequency region; ii) the number of detection regions ≥ 24.

[0064] According to the actual situation, the detection regions can be further subdivided to make the growth positions of lithium dendrites more accurate. However, since the area of the negative electrode is not large, the corresponding area of the detection regions is also very limited. When the number of detection regions ≥ 24, the requirements can already be met; or if the probability of lithium dendrites in a certain detection region is particularly high, the growth positions of lithium dendrites can be basically determined.

[0065] The detection regions can be evenly distributed on the surface of the polymer layer, such as Figure 1 shown, forming squares with a certain interval to cover the entire region, and any position where lithium dendrites occur can be detected. The number of detection regions is not limited and can be adjusted according to different situations; generally, it is not less than three.

[0066] The distribution of the detection regions can also be evenly or unevenly distributed outward from the center of the polymer layer to form an annular structure; for example, as Figure 2 shown, there are four detection regions, namely detection regions 1 to 4. Among them, detection region 1 exists at the center, and there are three concentric annular structures outside detection region 1, which are detection region 2, detection region 3, and detection region 4 from the inside to the outside in turn; the widths of detection region 2, detection region 3, and detection region 4 can be the same or set differently according to the actual situation. Or, as Figure 3 shown, detection region 1 is a circular structure located at the center and diffuses outward in turn to form concentric ring detection regions 1 to 6.

[0067] The distribution of the detection regions can also be evenly or unevenly distributed outward from the edge position of the polymer layer to form a diffusion structure. For example, as Figure 4 shown, it diffuses according to one corner to form a concentric arc structure; or as Figure 5 shown, it diffuses from the center of one side to also form a semi-circular structure. Figure 4 and Figure 5 The numbers in only represent the numbers of the detection regions. For example,Figure 4 In this, 1 represents detection area 1, 13 represents detection area 13, and the same applies to other numbers.

[0068] Figures 1 to 5 The number of detection areas herein is only for illustration and does not limit the number of detection areas.

[0069] By setting up the detection layer, the degree of lithium dendrite formation can be explored. Combining with the position of lithium dendrites, it is possible to better judge the impact of lithium dendrites on the battery and find methods to prevent or eliminate lithium dendrites.

[0070] Example 4

[0071] According to the content of this application, the lithium battery of Example 1, the system of Example 2, and the method of Example 3 are specifically described as follows:

[0072] Test Example 1

[0073] (1) The conductive material of the electron-conducting layer is metallic copper, and the binding material is PVDF (polyvinylidene fluoride). The polymer layer uses a PP (polypropylene) microporous membrane with a thickness of 8 μm and a porosity of 48%.

[0074] In this embodiment, the electron-conducting layer is fixed on the polymer layer by screen printing, which specifically includes: First, copper powder and PVDF are added to NMP (N-methylpyrrolidone) in a mass ratio of 4:1 and stirred evenly to form a conductive paste. A four-equal-part pattern is formed in a 300-mesh stainless-steel wire screen. A PP microporous membrane with an appropriate area is cut, placed at the bottom of the wire screen, and then the conductive paste is evenly coated on the upper part of the wire screen. After drying, it is the detection layer with a thickness of 11 μm.

[0075] Figure 6 It is a schematic diagram of the detection area. The substrate is a polymer membrane that can transport ions. The substrate area is equivalent to that of the negative electrode, and an electron-conducting layer is provided on its surface. The electron-conducting layer is divided into four equal parts, namely the detection areas. Each detection area is provided with a separate electrode pin to connect the circuit to the outside of the battery.

[0076] By connecting ultra-thin conductive sheets to each detection area of the detection layer, the detection areas can be associated with the external circuit. During the process of assembling the battery, the detection layer is located between the separator and the positive electrode, and at the same time, the conductive layer of the detection layer faces the negative electrode side.

[0077] (2) The positive electrode tab and the negative electrode tab of the lithium battery are respectively connected to the positive electrode and the negative electrode in the external field power supply for charge and discharge tests. Each electrode pin is equipped with a current response device and connected to the negative electrode, as Figure 7As shown in the figure. When lithium dendrites grow on the negative electrode and pierce the separator, the dendrites will come into contact with the corresponding detection area in the detection layer. Then, a current path for current to pass through is formed from the negative electrode - dendrite - detection area - current response device - negative electrode. The corresponding current response device issues a current warning and stops the battery test. By marking the detection area corresponding to the current response device, the location where the current occurs can be identified.

[0078] (3) The growth of lithium dendrites is comprehensively affected by factors such as the electrolyte environment, electrode structure, SEI film structure, and current density distribution. Using statistical methods to study its regularity can obtain more reliable results. In this embodiment, the detection layer is divided into four equal detection areas. Multiple identical lithium batteries are tested, and 30 batteries that have short - circuited and failed are selected for identifying the dendrite growth position (using multiple batteries containing the detection layer for cyclic testing. Each battery is an independent sample, and the test is carried out until the battery short - circuits. Randomly select 30 of the short - circuited batteries for identifying the dendrite growth position). The statistical results are shown in Table 1.

[0079] Table 1

[0080] Detection area identifier Short-circuit occurrence frequency Short-circuit occurrence probability A 19 63.3％ B 9 30％ C 1 3.3％ D 1 3.3％

[0081] (4) From the statistical results in Table 1, it can be found that detection areas A and B belong to the high - frequency areas, and detection areas C and D belong to the low - frequency areas. Among them, the probability of detection area A is much greater than that of detection area B.

[0082] (5) To further understand the location where the short - circuit occurs, new detection areas are designed. Detection area A is divided into 6 equal areas, and detection area B is also divided into 6 equal areas. Figure 8 is a diagram of the further - divided detection layer. Test again, select 30 batteries that have short - circuited and failed for identifying the dendrite growth position. The statistical results are shown in Table 2.

[0083] Table 2

[0084] Detection area identifier Short-circuit occurrence frequency Short-circuit occurrence probability A1 6 20％ A2 5 16.6％ A3 4 13.3％ A4 3 10％ A5 1 3.3％ A6 1 3.3％ B1 3 10％ B2 2 6.6％ B3 2 6.6％ B4 1 3.3％ B5 1 3.3％ B6 0 0 C 1 3.3％ D 1 3.3％

[0085] Mark the statistical results in the detection layer, as Figure 9 shown. It can be identified that the areas where lithium dendrite punctures occur are concentrated at the negative electrode tab, and the probability of lithium dendrite puncture is higher in the areas closer to the tab. Since the dendrite growth position shows obvious regularity, the detection is terminated. Therefore, through this method, it can be concluded that lithium dendrites tend to generate in the tab area.

[0086] Experimental Example 2

[0087] Carry out according to the steps of Experimental Example 1, except that the detection areas in step (1) are changed to three, specifically as Figure 10As shown, it is divided into three equal detection regions for identifying the relationship between the growth position of lithium dendrites and the electrode in the vertical direction. Other steps are the same as those in Test Example 1.

[0088] Table 3

[0089] Detection area identifier Short-circuit occurrence frequency Short-circuit occurrence probability A 23 76.6％ B 5 16.7％ C 2 6.7％

[0090] As can be seen from Table 3, the short - circuit occurrence positions in Test Example 2 are concentrated in Region A, that is, the part of the battery near the tab. In the next test, focus on monitoring the positions in Region A where short - circuits are likely to occur. Region A is divided into 8 non - electrically - connected regions. At this time, the structure of Region A in the detection layer is similar to the structure at the same position in Test Example 1, while Detection Region B can be divided into 2 equal regions, and Detection Region C does not need to be detected anymore. Therefore, 10 monitoring regions are generated, as Figure 11 shown. Compared with Example 1, the region division can be reduced, thus reducing the number of electrode pins in the detection layer. Table 4 is the probability distribution diagram of Test Example 2. The growth positions of dendrites show obvious regularity, so the detection is terminated. It can be seen that the structural planning of the detection region can improve the detection efficiency. When dealing with lithium - metal batteries of different systems, detection layers with different structures can be adopted to obtain more accurate monitoring results.

[0091] Table 4

[0092]

[0093]

[0094] Comparative Example 1

[0095] The separator containing an electron - conducting layer is prepared in a similar way to Test Example 1. The difference is that the electron - conducting layer in Comparative Example 1 completely covers the electrode region without any region division, and only one electrode pin is set for electrical connection with the external circuit.

[0096] Since the electron - conducting layer is a completely integrated region, even if a current signal of lithium dendrite contact appears, the growth position of the dendrite cannot be judged, and it cannot be used to study the law of the dendrite growth region.

[0097] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A lithium battery for identifying the growth position of lithium dendrites, comprising a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, characterized in that, The lithium battery further includes a detection layer; the detection layer is located between the separator and the positive electrode; The detection layer includes a polymer layer and an electron-conducting layer; The polymer layer does not conduct electrons; the polymer layer is attached to the positive electrode; The electron-conducting layer includes a plurality of independent detection regions; a plurality of independent detection regions are electrically connected to a plurality of current response devices; The thickness of the detection layer is 5-15 μm; The porosity of the polymer layer is 30%-70%; The material of the electron-conducting layer includes a conductive material and a binding material; the binding material bonds the conductive material to the surface of the polymer layer; the region formed by the conductive material is the detection region; The detection region is connected to the current response device through an electrode pin; the conductive material includes at least one of copper, silver, gold, nickel, and conductive carbon black; the binding material includes at least one of polyvinylidene fluoride, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyurethane, polyvinyl alcohol, and polyvinyl butyral.

2. The lithium battery according to claim 1, characterized in that, The material of the polymer layer includes at least one of polyethylene, polypropylene, aromatic polyamide fiber, polyimide, nanocellulose, and polyethylene terephthalate.

3. A system for identifying the growth position of lithium dendrites, characterized in that, Including a current response device, a charge and discharge tester, and a lithium battery as described in any one of claims 1-2; The charge and discharge tester is respectively connected to the positive electrode and the negative electrode of the lithium battery to charge and discharge the lithium battery; The current response device is respectively connected to the detection layer and the negative electrode of the lithium battery.

4. The system according to claim 3, characterized in that, Each current response device corresponds to each detection region one by one.

5. A method for identifying the growth position of lithium dendrites, characterized in that, Using the system of claim 3 or 4, the lithium battery is subjected to charge and discharge cycles, and the current value of the current response device is detected to identify the growth position of lithium dendrites.

6. The method according to claim 5, characterized in that, The method includes: (1) Divide the electron-conducting layer into at least three detection regions, and at least three detection regions are respectively connected to current response devices; assemble the positive electrode, the separator, the detection layer, and the negative electrode to obtain a lithium battery; (2) Connect the charge and discharge tester to the positive electrode and the negative electrode of the lithium battery respectively, and perform charge and discharge cycles on the lithium battery, and record the current value of the current response device; When the current value > 0, lithium dendrites are generated in the detection region connected to the current response device, so as to identify the growth position of lithium dendrites.

7. The method according to claim 6, characterized in that, The method further includes: (3) Repeat steps (1) and (2); the number of repetitions is not less than 10 times; (4) Statistically analyze the detection regions where lithium dendrites are generated, and calculate the probability of lithium dendrites appearing in each detection region.

8. The method according to claim 7, characterized in that, The method further includes: (5) Mark the detection regions in step (4) according to the probability of lithium dendrite appearance, and mark them as high-probability regions, medium-probability regions, and low-probability regions; Among them, in the high-probability region, the probability of lithium dendrite appearance is: > 30%; in the medium-probability region, the probability of lithium dendrite appearance is: 10%-30%; in the low-probability region, the probability of lithium dendrite appearance is: < 10%.

9. The method according to claim 8, characterized in that, The method further includes: (6) Divide the high-probability region and the medium-probability region into a plurality of secondary detection regions; among them, each high-probability region includes 2-10 secondary detection regions; the medium-probability region includes 2-4 secondary detection regions; (7) Assemble the lithium battery according to step (1), charge and discharge the lithium battery in cycles according to step (2), record the current value, repeat the number of times not less than 10 times according to step (3), calculate the probability of each detection area according to step (4), mark the secondary high-probability area, secondary medium-probability area and secondary low-probability area according to step (5), and divide the secondary high-probability area and secondary medium-probability area into multiple tertiary detection areas according to step (6).

10. The method according to claim 9, characterized in that, The method further includes: (8) Perform multiple cycles according to steps (1) to (7) until one of the following two results appears: i) Obvious aggregation behavior appears in the high-frequency area; ii) The number of detection areas ≥ 24.

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