A lithium battery with low-temperature self-heating function and working method thereof

Abstract

The present invention relates to a lithium battery with low-temperature self-heating function and a working method thereof. The present invention includes one or two battery cells, wherein the battery cell includes a plurality of positive electrode sheets, a plurality of negative electrode sheets and a plurality of diaphragms that are alternately wound or stacked. When the lithium battery includes one battery cell, a heating electrode sheet is provided on the outside of the battery cell; when the lithium battery includes two battery cells, a heating electrode sheet is provided between the battery cells; a temperature sensor is provided inside the battery cell, the heating electrode sheet is provided with an ear, and the size of the heating electrode sheet is larger than the size of the positive electrode sheet and smaller than the size of the negative electrode sheet, the positive electrode sheet and the heating electrode sheet are connected by a circuit that can be controlled to be disconnected, the heating electrode sheet and the negative electrode sheet are connected by a circuit that can be controlled to be disconnected, and the circuit that can be controlled to be disconnected is connected to a battery management system. The present invention can meet the requirements of low-temperature discharge without sacrificing other performance too much or adding too much extra cost.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, in particular to a lithium battery with low-temperature self-heating function and a working method thereof. Background Art

[0002] Lithium-ion batteries have become the most important chemical energy storage device due to their high voltage platform, high specific energy density, low self-discharge, long cycle life, and environmental protection, and are widely used in various energy storage and new energy electric vehicles. At present, in the field of lithium-ion batteries, due to the limitation of the operating temperature window of lithium batteries, many lithium-battery-powered devices cannot be used normally in cold climates, which greatly affects the promotion of green energy in cold regions.

[0003] The existing technical solutions are generally divided into two types, external heating and internal heating. In the external heating method, a heating device (heating plate or fluid heating) is added to the pack to heat the battery module, such as a heating film containing PTC heating. At low temperatures, the lithium battery is preheated first, and when the temperature of the lithium battery rises to meet the use conditions, it can be used normally. These heating devices add additional structures to the module, increase technical complexity and cost, and the battery itself has difficulty in heat transfer, resulting in low heating efficiency and additional energy waste. Another technology is the internal heating method of the battery, which generally builds a heating plate or heating electrode inside the battery cell, such as aluminum, copper, nickel or a composite metal sheet as a heating electrode, and leads out through the pole ear, on the same side or opposite side as the normal positive and negative pole ears. When working, it is connected to the positive electrode through an external circuit to form a short circuit, thereby heating the inside of the battery. Since the heat is generated inside the battery cell, the heating efficiency is relatively high. However, the heating electrode is generally a metal sheet or wire-like metal that needs to be close to the battery cell electrode. Therefore, the surface requirements are extremely high, that is, it must fit tightly without puncturing the diaphragm to cause a short circuit. Moreover, the surface area of ​​the heating electrode is limited, and short-circuit heating cannot be performed for a long time to avoid harming the electrolyte. Therefore, the effect is limited.

[0004] In summary, in the field of lithium-ion batteries, the operating temperature range has always restricted the use of lithium-ion batteries and the promotion of new energy vehicles, and high and low temperatures cannot be achieved at the same time. Too high or too low temperatures will have a great impact on the service life of lithium batteries, especially at low temperatures, lithium dendrites are prone to occur, which will cause battery short circuits and thermal runaway, leading to safety problems. Therefore, the battery needs to be preheated at low temperatures, and then used normally when the temperature rises to meet the conditions. However, the active materials of some lithium-ion batteries often have excellent low-temperature performance but poor high-temperature performance, so they cannot be used normally, or the batteries that meet low-temperature conditions often have high design requirements, are expensive, and need to sacrifice other aspects of performance, especially high-temperature performance. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a lithium battery with low-temperature self-heating function and a working method thereof.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: a lithium battery with low-temperature self-heating function, including one or two battery cells, the battery cells including a plurality of positive electrode sheets, a plurality of negative electrode sheets and a plurality of separators that are alternately wound or stacked, when the lithium battery includes one battery cell, a heating electrode sheet is provided on the outside of the battery cell; when the lithium battery includes two battery cells, a heating electrode sheet is provided between the battery cells; a temperature sensor is provided inside the battery cell, the heating electrode sheet is provided with an ear, and the size of the heating electrode sheet is larger than the size of the positive electrode sheet and smaller than the size of the negative electrode sheet, the positive electrode sheet and the heating electrode sheet are connected by a circuit that can be controlled to be disconnected, the heating electrode sheet and the negative electrode sheet are connected by a circuit that can be controlled to be disconnected, and the controllable disconnection circuit is connected to a battery management system.

[0007] The active material of the positive electrode sheet is ternary NCM, the active material of the negative electrode sheet is graphite, and the separator is a PE film.

[0008] The active material of the heating electrode is lithium titanate, and the conductive agent is carbon nanotubes.

[0009] The electrode lug of the heating electrode sheet is located on the same side or on the opposite side as the electrode lug of the positive electrode sheet and the electrode lug of the negative electrode sheet.

[0010] A method for operating a lithium battery with a low-temperature self-heating function comprises the following steps:

[0011] S1, obtaining the voltage, percentage of the discharge amount to the rated capacity and the internal temperature of the battery cell of the lithium battery through a battery management system;

[0012] S2, determining whether the internal temperature of the lithium battery cell is lower than a preset minimum operating temperature value;

[0013] S3, when the lithium battery needs to be heated, determining whether the percentage of the discharge amount of the lithium battery to the rated capacity is greater than a preset percentage;

[0014] S4, if yes, enable the charging heating mode; otherwise enable the discharging heating mode.

[0015] The discharge heating method is specifically:

[0016] S41, controlling the closing of a controllably disconnectable circuit between the heating electrode and the negative electrode through a battery management system to form a first discharge and heat the lithium battery;

[0017] S42, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, disconnecting the controllable disconnection circuit between the heating electrode and the negative electrode, and controlling the controllable disconnection circuit between the heating electrode and the positive electrode to close through the battery management system, thereby forming a second discharge and heating the lithium battery;

[0018] S43, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, return to step S3 until the percentage of the discharge amount of the lithium battery to the rated capacity is less than or equal to the preset percentage.

[0019] During the first discharge process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the negative electrode is disconnected, the heating is stopped, and the lithium battery starts to work normally;

[0020] During the second discharge process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the positive electrode is disconnected, heating is stopped, and the lithium battery starts to work normally.

[0021] The charging and heating method is specifically as follows:

[0022] S44, controlling the closing of a controllably disconnectable circuit between the heating electrode and the positive electrode through a battery management system to perform a first charge and heat the lithium battery;

[0023] S45, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, disconnecting the controllable disconnection circuit between the heating electrode and the positive electrode, and controlling the controllable disconnection circuit between the heating electrode and the negative electrode to close through the battery management system, thereby forming a second charge and heating the lithium battery;

[0024] S46, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, return to step S3 until the percentage of the discharge amount of the lithium battery to the rated capacity is less than or equal to the preset percentage.

[0025] During the first charging process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the positive electrode is disconnected, the heating is stopped, and the lithium battery starts to work normally;

[0026] During the second charging process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the negative electrode is disconnected, heating is stopped, and the lithium battery starts to work normally.

[0027] The voltage cut-off condition is set according to the positive and negative electrode materials of the battery.

[0028] The present invention has the following advantages and beneficial effects:

[0029] 1. The active material of the intermediate heating electrode of the present invention adopts an active material with excellent low-temperature performance and a potential between the positive and negative electrode active materials, and the pole piece is also designed for low-temperature environments. A conductive agent with excellent conductive properties is used and the dosage is increased, and the compaction density of the pole piece is controlled to ensure that it has excellent low-temperature performance and rate performance, and can be used normally at extremely low temperatures.

[0030] 2. The intermediate heating electrode of the present invention is in a state of lacking lithium ions, so the battery cell can be directly heated by self-discharge without external energy supply, and can be discharged a second time to ensure that the battery cell temperature rises to the use range while still being able to do work externally, thus avoiding energy waste.

[0031] 3. The present invention can meet the requirements of low-temperature discharge without sacrificing other performances or increasing too much extra cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a structural diagram of a lithium battery of the present invention;

[0033] Figure 2 It is a schematic diagram of the assembly of the lithium battery of the present invention;

[0034] Figure 3 It is a schematic diagram of a heating control circuit of the present invention;

[0035] Figure 4 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] like Figure 1-3As shown, a lithium battery with low-temperature self-heating function includes one or two cells, and the cell includes a plurality of positive plates 1, a plurality of negative plates 2, and a plurality of separators 4 that are alternately wound or stacked. When the lithium battery includes one cell, a heating plate 3 is provided on the outside of the cell; when the lithium battery includes two cells, a heating plate 3 is provided between the cells; a temperature sensor 5 is provided inside the cell, and the heating plate 3 is provided with a tab 31, and the size of the heating plate 3 is larger than the size of the positive plate 1 and smaller than the size of the negative plate 2. The positive plate 1 and the heating plate 3 are connected by a circuit that can be controlled to be disconnected, and the heating plate 3 and the negative plate 2 are connected by a circuit that can be controlled to be disconnected, and the circuit that can be controlled to be disconnected is connected to a battery management system. The positive plate 1 is provided with a positive tab 11, and the negative plate 2 is provided with a negative tab 21. The tab 31 of the heating plate 3 is located on the same side or the opposite side as the positive tab 11 and the negative tab 21. The active material of the positive electrode 1 is ternary NCM, the active material of the negative electrode 2 is graphite, the separator 4 is a PE film, and the packaging is an aluminum-plastic film packaging. The active material of the heating electrode 3 is lithium titanate, and the conductive agent is carbon nanotubes.

[0038] The manufacturing method of the lithium battery of the present invention is as follows:

[0039] 1) First, the positive electrode sheet and the negative electrode sheet are made, and then the positive and negative electrode sheets are made through the processes of batching, coating, rolling and cutting.

[0040] 2) Make an intermediate heating electrode. The potential of the active material selected for the intermediate heating electrode is between the potentials of the above-mentioned positive and negative electrode active materials, and the active material has excellent low-temperature performance and rate performance, and is not prone to lithium dendrites. The size of the intermediate heating electrode should be larger than the single-sided sheet of the positive electrode and smaller than the single-sided sheet of the negative electrode. The intermediate heating electrode is in a lithium ion-deficient state, that is, external lithium ions can be embedded in it. If the intermediate heating electrode is initially in a full lithium ion state, it can be discharged using an external device.

[0041] 3) The positive and negative electrodes and separators are wound or stacked to form a battery cell.

[0042] 4) Place the middle heating electrode into the prepared diaphragm bag.

[0043] 5) Place the independent middle heating electrode on the outside of the battery cell and firmly stick it with tape. If the battery has a dual-cell structure, place the middle heating electrode in the middle of the two cells.

[0044] 6) A temperature sensor resistant to electrolyte corrosion is placed inside the battery cell to monitor the temperature inside the battery cell.

[0045] 7) Weld the positive and negative electrodes and the middle heating electrode with pole ears, and separate the three pole ears, with the pole ears located on the same side or opposite sides.

[0046] 8) The welded composite battery cell is packaged, injected, aged, formed, aged, and divided into different capacities to obtain a heatable battery.

[0047] 9) The batteries are assembled into a battery pack, and the positive electrode and the intermediate heating electrode, as well as the negative electrode and the intermediate heating electrode are connected through a circuit that can be controlled to be disconnected.

[0048] like Figure 4 As shown, a working method of a lithium battery with low-temperature self-heating function comprises the following steps:

[0049] S1, obtaining the voltage, percentage of the discharge amount to the rated capacity and the internal temperature of the battery cell of the lithium battery through a battery management system;

[0050] S2, determining whether the internal temperature of the lithium battery cell is lower than a preset minimum operating temperature value, where the preset minimum operating temperature value may be set to 0° C.;

[0051] S3, when the lithium battery needs to be heated, determining whether the percentage of the discharge amount of the lithium battery to the rated capacity is greater than a preset percentage; the preset percentage may be a typical value, or may be selected between 80% and 100% according to the battery design;

[0052] S4, if yes, enable the charging heating mode; otherwise enable the discharging heating mode.

[0053] The discharge heating method is specifically:

[0054] S41, controlling the controllable disconnection circuit between the heating electrode and the negative electrode to close through the battery management system, forming the first discharge to heat the lithium battery; during the first discharge process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, disconnecting the controllable disconnection circuit between the heating electrode and the negative electrode, stopping heating, and the lithium battery starts to work normally.

[0055] S42, when the cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature, the controllable disconnection circuit between the heating electrode and the negative electrode is disconnected, and the controllable disconnection circuit between the heating electrode and the positive electrode is closed by the battery management system to form a second discharge to heat the lithium battery; during the second discharge process, when the internal temperature of the battery cell reaches the preset minimum operating temperature, the controllable disconnection circuit between the heating electrode and the positive electrode is disconnected, heating is stopped, and the lithium battery starts to work normally.

[0056] S43, when the cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, return to step S3 until the percentage of the discharge amount of the lithium battery to the rated capacity is less than or equal to 90%.

[0057] The self-discharge condition of the internal temperature of the battery cell is greater than 0°C. The voltage cut-off condition is set according to the positive and negative electrode materials of the battery. The charging cut-off voltage of the positive electrode and the heating electrode is: 2.75V; the discharge cut-off voltage is: 1.25V (the positive electrode is ternary NMC) (LFP range is 1V~2.5V); the charging cut-off voltage of the negative electrode and the heating electrode is: 2.0V, and the discharge cut-off voltage is: 1.0V (the negative electrode is graphite).

[0058] The charging and heating method is the opposite of the discharging and heating method. The positive electrode and the middle heating electrode are connected first, and charging and heating are performed first. Specifically, 1. The controllable opening and closing circuit between the heating electrode and the positive electrode is controlled by the battery management system to form the first charging to heat the lithium battery; 2. When the cut-off condition is reached and the internal temperature of the battery cell does not meet the self-discharge condition, the controllable opening and closing circuit between the heating electrode and the positive electrode is disconnected, and the controllable opening and closing circuit between the heating electrode and the negative electrode is controlled by the battery management system to form the second charging to heat the lithium battery; 3. When the cut-off condition is reached and the internal temperature of the battery cell does not meet the self-discharge condition, return to step 1 until the percentage of the discharge amount of the lithium battery to the rated capacity is less than or equal to 90%. During the first charging process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the positive electrode is disconnected, heating is stopped, and the lithium battery starts to work normally; during the second charging process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the negative electrode is disconnected, heating is stopped, and the lithium battery starts to work normally.

[0059] When the battery pack is working and needs to be heated, the battery management system first determines the battery DOD state. When DOD < 90%, the discharge heating program is enabled, otherwise the charge heating program is enabled. When the discharge heating program is enabled, the circuit between the negative electrode and the intermediate heating electrode is first controlled to be connected to form the first discharge and heat the battery. When the battery temperature meets the self-discharge condition (the working condition is met when the preset T is > 0°C), the connection between the negative electrode and the intermediate heating electrode is disconnected, the heating is stopped, and normal operation begins; when the cut-off condition is reached and the internal temperature of the battery still does not meet the battery self-discharge condition, the connection between the negative electrode and the intermediate heating electrode is disconnected, and the connection between the intermediate heating electrode and the positive electrode is connected to form the second discharge and heat the battery. When the internal temperature of the battery rises above 0°C, the connection of the heating electrode is disconnected, and the battery works normally. When the voltage cut-off condition is reached and the internal temperature of the battery cell still does not meet the working conditions, the connection between the positive electrode and the intermediate heating electrode is disconnected, and the negative electrode and the intermediate heating electrode are connected. The above steps are continued until DOD > 90%, and the charge heating mode is enabled. The charge heating mode is opposite to the discharge heating process. The positive electrode and the intermediate heating electrode are connected first, and the charge heating is performed first. In addition to heating the battery, the power of the secondary discharge can also be used by external low-power loads, avoiding energy waste.

Claims

1. A lithium battery with low-temperature self-heating function, comprising one or two battery cells, wherein the battery cells comprise a plurality of positive electrode sheets, a plurality of negative electrode sheets and a plurality of separators that are alternately wound or stacked, characterized in that: When the lithium battery includes one battery cell, a heating electrode is provided on the outside of the battery cell; when the lithium battery includes two battery cells, a heating electrode is provided between the battery cells; a temperature sensor is provided inside the battery cell, the heating electrode is provided with an electrode ear, and the size of the heating electrode is larger than the size of the positive electrode and smaller than the size of the negative electrode, the positive electrode and the heating electrode are connected by a circuit that can be controlled to be disconnected, the heating electrode and the negative electrode are connected by a circuit that can be controlled to be disconnected, and the controllable disconnection circuit is connected to a battery management system; the active material of the heating electrode is lithium titanate, and the conductive agent is carbon nanotubes.

2. A lithium battery with low temperature self-heating function according to claim 1, characterized in that: The active material of the positive electrode sheet is ternary NCM, the active material of the negative electrode sheet is graphite, and the separator is a PE film.

3. A lithium battery with low temperature self-heating function according to claim 1, characterized in that: The electrode lug of the heating electrode sheet is located on the same side or on the opposite side as the electrode lug of the positive electrode sheet and the electrode lug of the negative electrode sheet.

4. A method for operating a lithium battery with low-temperature self-heating function according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, obtaining the voltage, percentage of the discharge amount to the rated capacity and the internal temperature of the battery cell of the lithium battery through a battery management system; S2, determining whether the internal temperature of the lithium battery cell is lower than a preset minimum operating temperature value; S3, when the lithium battery needs to be heated, determining whether the percentage of the discharge amount of the lithium battery to the rated capacity is greater than a preset percentage; S4, if yes, enable the charging heating mode; otherwise enable the discharging heating mode.

5. The operating method of a lithium battery with low-temperature self-heating function according to claim 4, characterized in that: The discharge heating method is specifically: S41, controlling the closing of a controllably disconnectable circuit between the heating electrode and the negative electrode through a battery management system to form a first discharge and heat the lithium battery; S42, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, disconnecting the controllable disconnection circuit between the heating electrode and the negative electrode, and controlling the controllable disconnection circuit between the heating electrode and the positive electrode to close through the battery management system, thereby forming a second discharge and heating the lithium battery; S43, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, return to step S3 until the percentage of the discharge amount of the lithium battery to the rated capacity is less than or equal to the preset percentage.

6. The operating method of a lithium battery with low-temperature self-heating function according to claim 5, characterized in that: During the first discharge process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the negative electrode is disconnected, the heating is stopped, and the lithium battery starts to work normally; During the second discharge process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the positive electrode is disconnected, heating is stopped, and the lithium battery starts to work normally.

7. The operating method of a lithium battery with low temperature self-heating function according to claim 4, characterized in that: The charging and heating method is specifically as follows: S44, controlling the closing of a controllably disconnectable circuit between the heating electrode and the positive electrode through a battery management system to perform a first charge and heat the lithium battery; S45, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, disconnecting the controllable disconnection circuit between the heating electrode and the positive electrode, and controlling the controllable disconnection circuit between the heating electrode and the negative electrode to close through the battery management system, thereby forming a second charge and heating the lithium battery; S46, when the voltage cut-off condition is reached and the internal temperature of the battery cell has not reached the preset minimum operating temperature value, return to step S3 until the percentage of the discharge amount of the lithium battery to the rated capacity is less than or equal to the preset percentage.

8. The operating method of a lithium battery with low-temperature self-heating function according to claim 7, characterized in that: During the first charging process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the positive electrode is disconnected, the heating is stopped, and the lithium battery starts to work normally; During the second charging process, when the internal temperature of the battery cell reaches the preset minimum operating temperature value, the controllable disconnection circuit between the heating electrode and the negative electrode is disconnected, heating is stopped, and the lithium battery starts to work normally.

9. A method for operating a lithium battery with low-temperature self-heating function according to claim 5 or 7, characterized in that: The voltage cut-off condition is set according to the positive and negative electrode materials of the battery.

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