Electrochemical device and electronic equipment

Abstract

The application discloses an electrochemical device and an electronic equipment, and relates to the technical field of electrochemical energy storage. The electrochemical device comprises a battery shell, a battery cell and a lithium supplement assembly. The battery cell is arranged in the battery shell, and comprises a positive electrode lug and a negative electrode lug. The lithium supplement assembly comprises a lithium supplement electrode, a connecting wire and a first temperature control switch. The two ends of the connecting wire are connected with the negative electrode lug and the lithium supplement electrode. The first temperature control switch is arranged on the connecting wire and is configured to cut off or connect the connecting wire. The first temperature control switch can be closed to connect the negative electrode lug and the lithium supplement electrode. The electrochemical device of the application realizes automatic lithium supplement during the charging and discharging process by arranging the lithium supplement assembly, thereby prolonging the cycle life of the electrochemical device.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to electrochemical devices and electronic equipment. Background Technology

[0002] Lithium-ion batteries have wide applications in energy storage, electric vehicles, and consumer electronics. They mainly rely on the movement of lithium ions between the positive and negative electrodes to function. However, the limited cycle life of lithium-ion batteries restricts their further large-scale application.

[0003] One of the main reasons for the reduced cycle life of lithium-ion batteries is that irreversible lithium loss occurs during use, which reduces battery capacity and consequently affects cycle life. Utility Model Content

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an electrochemical device that automatically replenishes lithium during charging and discharging by incorporating a lithium replenishment component, thereby extending the cycle life of the electrochemical device.

[0005] This application also proposes an electronic device having the above-described electrochemical device.

[0006] An electrochemical device according to a first aspect embodiment of this application includes:

[0007] Battery casing;

[0008] A battery cell, wherein the battery cell is disposed within the battery casing, and the battery cell includes a positive electrode tab and a negative electrode tab;

[0009] A lithium replenishment assembly includes a lithium replenishment electrode, a connecting wire, and a first temperature control switch. The two ends of the connecting wire are connected to the negative electrode and the lithium replenishment electrode. The first temperature control switch is disposed on the connecting wire and is configured to disconnect or connect the connecting wire.

[0010] The first temperature control switch can be closed to connect the negative electrode tab and the lithium replenishment electrode.

[0011] The electrochemical device according to the embodiments of this application has at least the following beneficial effects:

[0012] The electrochemical device of this application can automatically replenish lithium during charging and discharging, thereby delaying lithium ion consumption and extending the cycle life of the electrochemical device. Compared with the single lithium replenishment in the prior art, the lithium replenishment component of this application can achieve multiple, long-term, small-dose lithium replenishment, so as to keep the lithium ion concentration in the electrolyte at a relatively stable state.

[0013] According to some embodiments of this application, the first temperature control switch is disposed inside the battery casing, or the first temperature control switch is disposed outside the battery casing.

[0014] According to some embodiments of this application, the lithium replenishment component further includes a second temperature control switch disposed on the connecting wire, the second temperature control switch being connected in series with the first temperature control switch, the lithium replenishment component having a first state where the first temperature control switch is open and the second temperature control switch is closed, a second state where the first temperature control switch is closed and the second temperature control switch is closed, and a third state where the first temperature control switch is closed and the second temperature control switch is open.

[0015] According to some embodiments of this application, the first temperature control switch is a normally open switch, the second temperature control switch is a normally closed switch, and the opening temperature of the second temperature control switch is greater than the closing temperature of the first temperature control switch.

[0016] According to some embodiments of this application, the first temperature control switch includes a sensing end for measuring the cable temperature of the connecting wire;

[0017] The second temperature control switch is configured to disconnect when the cable temperature exceeds a set value.

[0018] According to some embodiments of this application, the battery cell is formed by stacking multiple electrode sheets, and the lithium replenishment electrode is disposed on one side of the battery cell along the stacking direction of the electrode sheets. The lithium replenishment electrode and the battery cell are separated by a separator.

[0019] According to some embodiments of this application, the battery cell is formed by winding a positive electrode and a negative electrode, the lithium replenishment electrode is disposed on the opposite outer side of the battery cell, and the lithium replenishment electrode and the battery cell are separated by a separator.

[0020] According to some embodiments of this application, the battery casing defines a rectangular receiving cavity, the battery cell is placed in the receiving cavity, the outer peripheral surface of the battery cell and the corner of the receiving cavity define an encapsulation gap, and the lithium replenishment electrode is disposed in the encapsulation gap.

[0021] According to some embodiments of this application, the battery housing includes a top cover with a positive electrode post and a negative electrode post, the lithium replenishment electrode is disposed inside the top cover, and the lithium replenishment electrode is provided with a relief groove to avoid the positive electrode post and the negative electrode post.

[0022] An electronic device according to a second aspect of this application includes the electrochemical device mentioned in any of the foregoing embodiments.

[0023] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0024] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0025] Figure 1 This is a schematic diagram of the lithium replenishment circuit according to an embodiment of this application;

[0026] Figure 2 This is a schematic diagram of a lithium replenishment circuit according to another embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the structure of the stacked battery cell according to an embodiment of this application;

[0028] Figure 4 This is a schematic diagram of the structure of the wound cell and the lithium replenishment electrode assembled in the battery casing according to an embodiment of this application.

[0029] Figure label:

[0030] Battery casing 100;

[0031] Cell 200; Positive electrode 210; Positive electrode tab 211; Negative electrode 220; Negative electrode tab 221; Separator 230;

[0032] Lithium replenishment component 300; lithium replenishment electrode 310; connecting wire 320; first temperature control switch 330; second temperature control switch 340; Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The embodiments of this application may omit unnecessary detailed descriptions. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0034] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0035] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate small variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely and examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the terms may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the difference between two values ​​is less than or equal to ±10% of the average of the values ​​(e.g., less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%), then the two values ​​can be considered "substantially" the same.

[0036] Furthermore, for ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0037] Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format in this document. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only the numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0038] In the detailed description and claims, a list of items connected by the terms "one of," "among," "a kind of," or other similar terms may mean any of the listed items. For example, if items A and B are listed, then the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, then the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0039] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0040] In the following description, all figures disclosed in this application are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit (RL) and an upper limit (RU) is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within that range are specifically disclosed: R = RL + k * (RU - RL), where k is a variable with a 1% increment from 1% to 100%, i.e., k is 1%, 2%, 3%, 4%, 5%, ... 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any range of values ​​defined by the two R values ​​as defined above are also specifically disclosed.

[0041] Throughout this specification, references to “implementation,” “partial implementation,” “one implementation,” “another approach,” “specific approach,” or “partial approach” mean that at least one implementation or embodiment in this application includes the specific features, structures, materials, or characteristics described in that implementation or embodiment.

[0042] In this application, numerical ranges are involved. Unless otherwise specified, the numerical ranges mentioned above are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form a range not explicitly stated.

[0043] Lithium-ion batteries have wide applications in energy storage, electric vehicles, and consumer electronics. They mainly rely on the movement of lithium ions between the positive and negative electrodes to function. However, the limited cycle life of lithium-ion batteries restricts their further large-scale application.

[0044] One of the main reasons for the reduced cycle life of lithium-ion batteries is that irreversible lithium loss occurs during use, which reduces battery capacity and consequently affects cycle life.

[0045] More specifically, the commonly used methods for replenishing lithium on the negative electrode are contact lithium replenishment, electrochemical lithium replenishment, etc., all of which are one-time lithium replenishment at the initial stage of cycling. Current lithium replenishment methods can improve the battery's negative electrode capacity and cycle performance, but after a certain number of cycles, the two tend to be the same, indicating that the current lithium replenishment methods have limited lithium replenishment capacity. They can only make up for the loss of active lithium in the early stage of cycling and cannot continuously replenish the loss of active lithium to improve the cycle performance of lithium-ion batteries. Therefore, the degree of improvement in cycle life is limited.

[0046] To address the aforementioned problems, this application proposes an electrochemical device, such as... Figures 1 to 4 As shown, the electrochemical device includes a battery casing 100 and a battery cell 200. The battery casing 100 can be a steel casing, an aluminum casing, or a pouch casing. The battery cell 200 is encapsulated within the battery casing 100. The battery cell 200 includes a positive electrode 210, a negative electrode 220, and a separator 230 located between them. The positive electrode 210 has a positive electrode tab 211, and the negative electrode 220 has a negative electrode tab 221. The positive electrode tab 211 and the negative electrode tab 221 are led out from both sides or the same side of the battery cell 200 and electrically connected to the positive and negative terminals on the battery casing 100.

[0047] To address lithium replenishment and mitigate lithium loss during cycling, the electrochemical device of this application further includes a lithium replenishment component 300, such as... Figure 1 As shown, the lithium replenishment assembly 300 includes a lithium replenishment electrode 310, a connecting wire 320, and a first temperature control switch 330. The lithium replenishment electrode 310 is disposed within the battery casing 100 and separated from the positive and negative electrode sheets by a separator 230. The lithium replenishment electrode 310 is at least one of a lithium metal sheet, a metal sheet with a lithium metal plating layer, and an insulating sheet with a lithium metal plating layer; wherein the lithium metal content of the lithium replenishment electrode 310 is from 0.0026 g / Ah to 0.52 g / Ah, preferably from 0.052 g / Ah to 0.079 g / Ah. The two ends of the connecting wire 320 are respectively connected to the negative electrode tab 221 and the lithium replenishment electrode 310, forming an electrical connection path between the lithium replenishment electrode 310 and the negative electrode. The first temperature control switch 330 is disposed on the connecting wire 320 in series in the electrical connection path. The first temperature control switch 330 is configured to be able to disconnect or connect the connecting wire 320.

[0048] It should be noted that the first temperature control switch 330 can change its on / off state according to temperature changes. The temperature control switch is a conventional temperature control element. Those skilled in the art can select the specific type of temperature control switch and set the temperature threshold according to actual needs, which will not be described in detail here.

[0049] It is understandable that the first temperature control switch 330 automatically closes when the ambient temperature of the electrochemical device reaches the first set threshold, so as to connect the negative electrode tab 221 and the lithium replenishment electrode 310. At this time, the lithium in the lithium replenishment electrode 310 is replenished to the negative electrode through the connecting wire 320, thereby compensating for the lithium loss during the cycle and improving the cycle life of the electrochemical device.

[0050] It should be noted that during the charging and discharging process of the electrochemical device, as the electrochemical reaction proceeds, the internal temperature of the electrochemical device will gradually rise, which will be reflected in the temperature change of the external part of the electrochemical device. The first temperature control switch 330 can switch the on / off state of the connecting wire 320 under the influence of temperature changes, so as to replenish lithium during the charging and discharging process of the electrochemical device.

[0051] More specifically, based on the foregoing, since the temperatures of both the inside and outside of the electrochemical device change, the first temperature control switch 330 can be located either inside or outside the battery housing 100. If the first temperature control switch 330 is located inside the battery housing 100, it directly senses temperature changes near the battery cell 200, such as monitoring the temperature of the electrolyte or the gas temperature inside the battery housing 100, resulting in a faster and more accurate response. If the first temperature control switch 330 is located outside the battery housing 100, it indirectly determines the internal temperature by detecting temperature changes on the outer wall of the battery housing 100, facilitating installation and maintenance.

[0052] In summary, the electrochemical device of this application can automatically replenish lithium during charging and discharging, thereby delaying lithium ion consumption and extending the cycle life of the electrochemical device. Compared with the single lithium replenishment in the prior art, the lithium replenishment component 300 of this application can achieve multiple, long-term, small-dose lithium replenishment, so as to keep the lithium ion concentration in the electrolyte at a relatively stable state.

[0053] It is understood that in the above embodiments, the on / off control of the connecting wire 320 can be achieved by a single first temperature control switch 330. When the ambient temperature of the first temperature control switch 330 is greater than the operating temperature of the first temperature control switch 330, the first temperature control switch 330 closes, allowing lithium ions in the lithium replenishment electrode 310 to flow through the electrolyte to the negative electrode of the electrochemical device, thus replenishing lithium at the negative electrode. When the potential of the negative electrode is equal to the potential of the lithium replenishment electrode 310, the potential difference of the lithium replenishment driving force is zero, and the lithium replenishment ends. In other embodiments, the lithium replenishment duration can also be controlled by preset closing time of the first temperature control switch 330, for example, the closing time of the first temperature control switch 330 can be controlled to be 1 second to 2 hours, preferably 10 minutes to 30 minutes.

[0054] In addition, to avoid frequent opening and closing of the first temperature control switch 330, a delay circuit or delay module can be set on the first temperature control switch 330. The delay circuit or time delay module controls the interval of the first temperature control switch 330's reactivation after reset (i.e., closing again after opening) to be set to about 100 cycles of the battery cell 200 (1 cycle is 1 charge and discharge cycle), so as to avoid frequent lithium replenishment when the ambient temperature is high.

[0055] In other embodiments, such as Figure 2 As shown, the lithium replenishment assembly 300 also includes a second temperature control switch 340 disposed on the connecting wire 320. It should be noted that the second temperature control switch 340 is connected in series with the first temperature control switch 330. That is, the connecting wire 320 is only fully conductive when both the first temperature control switch 330 and the second temperature control switch 340 are closed, allowing for an effective electrical connection between the lithium replenishment electrode 310 and the negative electrode tab 221. If either the first temperature control switch 330 or the second temperature control switch 340 is disconnected, the connecting wire 320 is cut off, and the lithium replenishment process stops. Therefore, depending on the switching states of the dual temperature control switches, the lithium replenishment component 300 has three operating states: In the first state, the first temperature control switch 330 is open and the second temperature control switch 340 is closed. At this time, the connecting wire 320 is disconnected, no current flows between the lithium replenishment electrode 310 and the negative electrode tab 221, and the lithium replenishment process does not occur; In the second state, the first temperature control switch 330 is closed and the second temperature control switch 340 is closed. At this time, the connecting wire 320 is conductive, a complete circuit is formed between the lithium replenishment electrode 310 and the negative electrode tab 221, and lithium ions migrate from the lithium replenishment electrode 310 to the negative electrode to achieve lithium replenishment; In the third state, the first temperature control switch 330 is closed and the second temperature control switch 340 is open. The connecting wire 320 is also in the open state, and the lithium replenishment process does not occur.

[0056] Understandably, the dual-temperature-controlled switch design enhances the controllability and safety of the lithium replenishment process, avoiding the risk of false triggering or continuous lithium replenishment due to the failure of a single temperature control switch. By reasonably setting the operating temperature thresholds of the two temperature control switches, a phased response to the thermal state of the electrochemical device can be achieved, ensuring that the lithium replenishment mechanism is activated only within a suitable temperature range, thereby improving the cycle stability and safety of the electrochemical device.

[0057] More specifically, the first temperature control switch 330 is a normally open switch, meaning it remains open at room temperature or low temperature, and automatically closes only when the temperature of the electrochemical device rises to a first set threshold. The second temperature control switch 340 is a normally closed switch, meaning it remains open at room temperature or low temperature, and automatically closes when the temperature of the electrochemical device exceeds a second set threshold. The opening temperature of the second temperature control switch 340 is higher than the closing temperature of the first temperature control switch 330, thus ensuring that during the heating process of the electrochemical device, the first temperature control switch 330 is triggered to open first, and then the second temperature control switch 340 remains open, establishing the lithium replenishment circuit. When the temperature continues to rise above the second set threshold, the second temperature control switch 340 opens, cutting off the lithium replenishment path and preventing excessive lithium replenishment.

[0058] Furthermore, unlike the first temperature control switch 330 which is used to measure the ambient temperature inside or outside the electrochemical device, the sensing end of the second temperature control switch 340 is used to measure the cable temperature of the connecting wire 320. That is, the second temperature control switch 340 directly detects the heat generated by the current passing through the connecting wire 320. After the lithium replenishment circuit is connected, the temperature of the connecting wire 320 gradually increases as the current continues to pass through. When the temperature reaches the action threshold of the second temperature control switch 340, it automatically disconnects, thereby cutting off the lithium replenishment circuit. On the one hand, this can avoid the risk of lithium plating caused by excessive lithium embedding in the negative electrode due to prolonged lithium replenishment, and on the other hand, it can also avoid the safety hazards caused by overheating of the wire.

[0059] The specific embodiments are illustrated below, such as Figure 2 As shown, the closing temperature of the first temperature control switch 330 is 40°C, and the opening temperature of the second temperature control switch 340 is 70°C. It can be understood that the reset temperature of the temperature control switch is usually 5°C to 25°C lower than the operating temperature. For example, the reset temperature of the first temperature control switch 330 is 30°C, and the reset temperature of the second temperature control switch 340 is 50°C. When the ambient temperature of the electrochemical device rises to 40°C, the first temperature control switch 330 closes, and the second temperature control switch 340 remains closed, thus connecting the lithium replenishment circuit and allowing lithium ions to migrate. As the connecting wire 320 gradually heats up, when its temperature reaches 70°C, the second temperature control switch 340 opens, cutting off the lithium replenishment circuit. As a result, the temperature of the connecting wire 320 gradually decreases. When the temperature drops below 50°C, the second temperature control switch 340 closes again to reset. However, if the ambient temperature of the electrochemical device is still above 40°C, the first temperature control switch 330 remains closed, and the lithium replenishment circuit will be connected again. When the electrochemical device stops charging and discharging and its ambient temperature drops below 30°C, the first temperature control switch 330 opens to reset, and the lithium replenishment circuit is completely cut off.

[0060] It should be noted that, in order to avoid frequent lithium replenishment caused by frequent switching of the second temperature control switch 340, a delayed action design can be made for the second temperature control switch 340. The interval between the reset time of the second temperature control switch 340 or the time after the switch is reset and then restarted can be set to about 100 cycles of the battery cell 200 (1 cycle is 1 charge and discharge cycle), so as to avoid frequent lithium replenishment when the ambient temperature is high.

[0061] In some embodiments, the battery cell 200 is a laminated battery cell 200. For example... Figure 3 As shown, the battery cell 200 is formed by stacking multiple electrode sheets, with a separator 230 separating adjacent electrode sheets. The lithium replenishment electrode 310 is disposed on one side of the battery cell 200 along the stacking direction of the electrode sheets, and the lithium replenishment electrode 310 and the battery cell 200 are separated by the separator 230.

[0062] In other embodiments, the battery cell 200 is a wound battery cell 200. The battery cell 200 is formed by winding a positive electrode 210 and a negative electrode 220, and a lithium replenishment electrode 310 is disposed on the opposite outer side of the battery cell 200. The lithium replenishment electrode 310 and the battery cell 200 are separated by a separator 230.

[0063] It is understandable that, for the wound cell 200, the cell 200 includes two end faces arranged opposite each other along the winding axis and an outer peripheral surface located between the two end faces. If the battery casing 100 defines a rectangular receiving cavity, such as a steel-cased battery or a pouch battery, then after the cell 200 is placed in the receiving cavity, as... Figure 4 As shown, the outer peripheral surface of the battery cell 200 and the four corners of the receiving cavity define four encapsulation gaps, and the lithium replenishment electrode 310 is disposed in at least one of these encapsulation gaps. Placing the lithium replenishment electrode 310 in the encapsulation gaps makes full use of the redundant space inside the electrochemical device and avoids the placement of the lithium replenishment electrode 310 from affecting the energy density of the electrochemical device.

[0064] In some embodiments (not shown in the figures), the battery casing 100 includes a top cover with a positive electrode post and a negative electrode post, which extend into the interior of the battery casing 100 for connection to the positive electrode tab 211 and the negative electrode tab 221, respectively. Therefore, a certain space needs to be reserved between the main structure of the battery cell 200 and the top cover for the connection between the tabs and the electrode posts. Thus, after the battery cell 200 is installed in the casing, this reserved space can be used to install a lithium replenishment electrode 310. The lithium replenishment electrode 310 is located inside the top cover and has a clearance groove. The positive electrode post and the negative electrode post can pass through the clearance groove and connect to the positive electrode tab 211 and the negative electrode tab 221, respectively. Therefore, the lithium replenishment electrode 310 achieves the lithium replenishment function without affecting the normal connection between the tabs and the electrode posts, and does not require additional space in the main body of the battery cell 200, further improving the utilization rate of the internal space of the electrochemical device.

[0065] It should also be noted that the electrochemical device of this application includes any device that undergoes an electrochemical reaction to convert chemical energy into electrical energy, and specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0066] The present application and its beneficial effects will be further described in detail below with reference to specific embodiments, but the implementation of the present application is not limited thereto:

[0067] Example 1: A battery is manufactured by the following steps:

[0068] (1) Preparation of negative electrode 220: Graphite, silicon carbide (SiC), conductive carbon nanotubes (CNT), binder polyacrylic acid (PAA), and sodium carboxymethyl cellulose (CMC) were thoroughly mixed in deionized water solvent at a mass ratio of graphite:SiC:CNT:PAA:CMC = 85:12:1:1.2:0.8 to obtain a negative electrode slurry with a solid content of 40%. The negative electrode slurry was coated on a current collector copper foil, dried at 85°C, and then cold-pressed to form a negative electrode active material layer. Then, the edges were cut, slits were made, and electrode tabs were welded to obtain negative electrode 220.

[0069] (2) Preparation of positive electrode 210: The positive electrode active material LiCoO2, conductive agent Super P and binder polyvinylidene fluoride (PVDF) are mixed evenly in N-methylpyrrolidone solvent (NMP) at a mass ratio of 97:2:1 to obtain a positive electrode slurry with a solid content of 70%; the positive electrode slurry is coated on the current collector aluminum foil, dried at 85°C and then cold-pressed, then trimmed and slit, and then the tabs are welded to obtain positive electrode 210;

[0070] (3) Preparation of lithium replenishment electrode 310: A lithium copper composite strip with a lithium content of 0.065 g / Ah is prepared by rolling or vapor deposition, and after being cut, the electrode tabs are welded to obtain the lithium replenishment electrode 310.

[0071] (4) Preparation of electrolyte: Lithium hexafluorophosphate (LiPF6) with a concentration of 1 mol / L was dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (the mass ratio of DMC, EC and EMC is 3:5:2) to obtain the electrolyte.

[0072] (5) Separator 230: PE separator 230 with a thickness of 9μm is selected;

[0073] (6) Assembly of the secondary battery: The prepared positive electrode 210, separator 230, and negative electrode 220 are stacked in sequence, with the separator 230 positioned between the positive electrode 210 and the negative electrode 220, and wound to obtain the battery cell 200. After baking the battery cell 200 in an 85°C vacuum oven for 48 hours, the lithium replenishing electrode 310 is placed on the outermost layer of the battery cell 200. After fixing the lithium replenishing electrode 310, the battery cell 200 is placed in an aluminum-plastic film outer packaging for sealing. Electrolyte is injected into the dried battery, and the battery is sealed, allowed to stand, formed, shaped, and capacity tested, and then resealed to obtain the secondary battery. A normally open temperature switch with an operating temperature of 50°C and a normally closed temperature switch with an operating temperature of 80°C are selected, and the first temperature control switch 330 and the second temperature control switch 340, connected in series, are connected between the negative electrode tab 221 and the lithium replenishing electrode tab.

[0074] Example 2: A battery was made using the same steps as in Example 1, wherein the lithium content of the lithium-copper composite strip was adjusted to 0.055 g / Ah.

[0075] Example 3: A battery was made using the same steps as in Example 1, wherein the lithium content of the lithium-copper composite strip was adjusted to 0.060 g / Ah.

[0076] Example 4: A battery was made using the same steps as in Example 1, wherein the lithium content of the lithium-copper composite strip was adjusted to 0.075 g / Ah.

[0077] Example 5: The battery is manufactured using the same steps as in Example 1, wherein the operating temperature of the first temperature control switch 330 is adjusted to 50°C and the operating temperature of the second temperature control switch 340 is adjusted to 70°C.

[0078] Example 6: The battery is manufactured using the same steps as in Example 1, wherein the operating temperature of the first temperature control switch 330 is adjusted to 50°C and the operating temperature of the second temperature control switch 340 is adjusted to 90°C.

[0079] Example 7: The battery is manufactured using the same steps as in Example 1, wherein the operating temperature of the first temperature control switch 330 is adjusted to 40°C and the operating temperature of the second temperature control switch 340 is adjusted to 80°C.

[0080] Example 8: The battery is made using the same steps as in Example 1, wherein a first temperature control switch 330 with an operating temperature of 50°C is used. When the negative electrode potential is equal to the lithium replenishment electrode 310 potential, the lithium replenishment driving force potential difference is zero, and the lithium replenishment ends.

[0081] Example 9: A battery is manufactured using the same steps as in Example 1, wherein a first temperature control switch 330 with an operating temperature of 50°C is used, and a delay circuit or time delay module controls the closing time of the first temperature control switch 330 to be 20 minutes to control the amount of lithium replenishment and avoid excessive lithium replenishment.

[0082] Comparative Example 1: A standard 200 cell was used without any lithium replenishment method.

[0083] The coulombic efficiency, energy density, and capacity retention of Examples 1 to 9 and Comparative Example 1 were measured for the first time. The measurement methods for each parameter are as follows:

[0084] Initial coulombic efficiency = initial discharge capacity / initial charge capacity. Here, the initial charge and discharge capacity refers to the charge and discharge capacity during battery formation and capacity grading, where the initial discharge capacity during capacity grading is the battery capacity.

[0085] Energy density: Discharge capacity (Ah) is obtained by discharging at a constant current of 0.2C to a cutoff voltage of 3.0V; the energy density calculation formula is: Energy density = Discharge capacity × Operating voltage / Battery volume;

[0086] Capacity: Under 25°C conditions, the batteries in the examples or comparative examples were charged and discharged for the first time. They were charged at a constant current of 2C to the cutoff voltage of 4.53V, and then charged at a constant voltage of 4.53V until the current was less than 0.025C. After resting for 5 minutes, they were discharged at a constant current of 0.5C to the cutoff voltage of 3.0V. The discharge capacity of the battery was measured as A. Then, in an environment of 45°C, 1500 charge and discharge cycles were performed according to the above steps. The discharge capacity of the secondary battery after the 1500th cycle was measured as B. The cycle capacity retention rate was calculated as B / A.

[0087] In summary, the data is shown in the table below:

[0088] Example 1 92.8 829 87.1 Example 2 92.4 820 86.1 Example 3 92.6 824 86.5 Example 4 93.1 834 87.3 Example 5 92.8 829 86.3 Example 6 92.8 829 87.4 Example 7 92.8 829 87.2 Example 8 92.8 829 85.2 Example 9 92.8 829 86.4 Comparative Example 1 86.1 750 68.0

[0089] The data in the table shows that when the lithium metal content of the lithium replenishment electrode 310 and the operating temperatures of the first temperature control switch 330 and the second temperature control switch 340 are within a reasonable range, the cycle capacity retention rate of the electrochemical device at higher temperatures can be significantly improved. The higher the lithium metal content of the lithium replenishment electrode 310, the greater the initial coulombic efficiency and energy density of the electrochemical device, and the higher the cycle capacity retention rate can still be maintained even with a large number of cycles. The greater the difference between the operating temperatures of the first temperature control switch 330 and the second temperature control switch 340, the longer the lithium replenishment time and the greater the amount of lithium replenished. However, it is necessary to control the difference in operating temperatures within a certain range to avoid excessive lithium replenishment that could lead to lithium plating.

[0090] A second aspect of this application also provides an electronic device including the electrochemical device described above. The electronic device described in this application is not particularly limited and can be used with any electronic device known in the prior art. The electrochemical device described in this application is not particularly limited in its use and can be used with any electronic device known in the prior art. According to some embodiments of this application, the electronic device includes, but is not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robot dogs, industrial robots, and android robots.

[0091] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. An electrochemical device, characterized in that, include: Battery casing; A battery cell, wherein the battery cell is disposed within the battery casing, and the battery cell includes a positive electrode tab and a negative electrode tab; A lithium replenishment assembly includes a lithium replenishment electrode, a connecting wire, and a first temperature control switch. The two ends of the connecting wire are connected to the negative electrode and the lithium replenishment electrode. The first temperature control switch is disposed on the connecting wire and is configured to disconnect or connect the connecting wire. The first temperature control switch can be closed to connect the negative electrode tab and the lithium replenishment electrode.

2. The electrochemical device according to claim 1, characterized in that, The first temperature control switch is located inside the battery casing, or the first temperature control switch is located outside the battery casing.

3. The electrochemical device according to claim 1, characterized in that, The lithium replenishment component also includes a second temperature control switch disposed on the connecting wire. The second temperature control switch is connected in series with the first temperature control switch. The lithium replenishment component has a first state in which the first temperature control switch is open and the second temperature control switch is closed, a second state in which the first temperature control switch is closed and the second temperature control switch is closed, and a third state in which the first temperature control switch is closed and the second temperature control switch is open.

4. The electrochemical device according to claim 3, characterized in that, The first temperature control switch is a normally open switch, the second temperature control switch is a normally closed switch, and the opening temperature of the second temperature control switch is greater than the closing temperature of the first temperature control switch.

5. The electrochemical device according to claim 4, characterized in that, The first temperature control switch includes a sensing end for measuring the temperature of the cable of the connecting wire; The second temperature control switch is configured to disconnect when the cable temperature exceeds a set value.

6. The electrochemical device according to claim 1, characterized in that, The battery cell is formed by stacking multiple electrode sheets, and the lithium replenishment electrode is disposed on one side of the battery cell along the stacking direction of the electrode sheets. The lithium replenishment electrode and the battery cell are separated by a separator.

7. The electrochemical device according to claim 1, characterized in that, The battery cell is formed by winding a positive electrode and a negative electrode. The lithium replenishment electrode is disposed on the opposite outer side of the battery cell, and the lithium replenishment electrode and the battery cell are separated by a separator.

8. The electrochemical device according to claim 7, characterized in that, The battery casing defines a rectangular receiving cavity, the battery cell is placed in the receiving cavity, the outer peripheral surface of the battery cell and the corner of the receiving cavity define a packaging gap, and the lithium replenishment electrode is disposed in the packaging gap.

9. The electrochemical device according to claim 1, characterized in that, The battery casing includes a top cover with a positive electrode post and a negative electrode post, and the lithium replenishment electrode is disposed inside the top cover. The lithium replenishment electrode has a relief groove to avoid the positive electrode post and the negative electrode post.

10. An electronic device, characterized in that, Includes the electrochemical device as described in any one of claims 1 to 9.

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