Flexible lithium battery equalization method based on tiny current converted from ocean current energy

Abstract

The present invention relates to the field of battery management technology, and specifically to a flexible lithium battery balancing method based on a tiny current converted from ocean current energy, comprising an ocean current energy friction nano power generation device and a flexible lithium battery pack carried in an underwater flexible intelligent body; establishing a balancing topology structure, obtaining the voltage of each battery, and selecting the battery with the maximum voltage; discharging to all capacitors through the battery with the maximum voltage, and each capacitor obtains electrical energy; using the capacitor that obtains electrical energy together with the ocean current energy power generation device to discharge to the corresponding battery, so that the voltage of the entire battery pack is balanced. The present invention charges each low-voltage battery through the maximum voltage battery combined with the ocean current energy power generation device to achieve voltage balancing between multiple batteries at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of battery management, and in particular to a flexible lithium battery equalization method based on tiny current converted from ocean current energy. Background Art

[0002] The main ways to group power batteries include series, parallel and hybrid. Different grouping methods can meet different power needs. However, due to the influence of factors such as manufacturing process, there are certain differences in capacity and other aspects when the batteries leave the factory. After being used in groups, the inconsistency of the battery pack is further expanded due to differences in the use environment, application conditions, etc. This inconsistency will increase the probability of hidden dangers in the battery and directly affect the performance and service life of the battery. In order to solve the problem of battery pack inconsistency, battery balancing technology came into being. Realizing rapid balancing of battery packs and reducing energy consumption during the balancing process is one of the main research directions at present.

[0003] The essence of battery balancing is to reduce the energy difference of each battery in the battery pack, so as to maintain a high consistency of the battery pack. Battery pack balancing management is usually divided into two parts: balancing topology design and balancing strategy development. The former forms a current path through component connection, and the latter controls the circuit through an algorithm. The basic topology structure can be divided into passive balancing and active balancing. Passive balancing is energy dissipative balancing, which converts the excess power in a single power battery into heat energy through energy-consuming components. Passive balancing is more suitable for small-scale energy storage devices because of its simple topological structure, easy control and implementation; active balancing is non-dissipative balancing, which means that energy is transferred between batteries through energy storage components, thereby reducing the inconsistency of the battery pack. In theory, it does not consume battery energy. Therefore, active balancing is the key development direction of battery energy balancing.

[0004] According to the different energy transfer elements, active balancing can be divided into four balancing topologies based on capacitors, inductors, transformers and DC / DC converters. Capacitive balancing topologies are divided into single capacitor, switched capacitor and modular switched capacitor structures. Their control strategies are relatively simple and low-cost, but the balancing time is long; inductive balancing topologies use inductors as the main energy storage and buffering elements, which can realize the transmission of electric energy between single batteries or battery packs, but this topology element is expensive and has magnetization losses; transformer balancing topologies are divided into single-winding transformer (switching transformer) and multi-winding transformer. When there are more batteries in series, as the number of transformers increases, the reliability of the system deteriorates and the cost is high; DC / DC converter balancing topologies use DC / DC topologies such as Buck, Boost, Buck-Boost and Cuk to achieve active balancing. This type of topology circuit has good balancing performance, but the structure is complex and the cost is relatively high.

[0005] In addition to the existing balanced topological structures, each of which has its own advantages and disadvantages, the source of electricity that provides power to the battery is also crucial. Energy is an indispensable material resource for human survival. With the development of the economy, the existing energy has been in short supply. In order to alleviate this contradiction, people have set their sights on the ocean. The ocean contains huge energy. Ocean energy mainly exists in the ocean in the form of tidal energy, ocean current energy, and temperature difference energy. Unlike the tides along the coast, the direction and speed of the ocean current are stable all year round. Compared with other renewable energy sources, ocean current energy has the characteristics of high energy flow density and stable energy output characteristics. Summary of the invention

[0006] In order to overcome the deficiencies in the prior art, the present invention mainly solves the problems of short flexible battery life, complex topological structure of flexible battery pack balance, and slow balance speed in the prior art. The present invention provides a flexible lithium battery balance method based on tiny current converted from ocean current energy. The method charges each low-voltage battery through a maximum voltage battery combined with an ocean current power generation device to achieve voltage balance between multiple batteries at the same time.

[0007] The purpose of the present invention is to provide a flexible lithium battery balancing method based on a tiny current converted from ocean current energy, comprising an ocean current energy friction nano power generation device and a flexible lithium battery pack carried in an underwater flexible intelligent body;

[0008] The flexible lithium battery pack includes a plurality of flexible lithium batteries;

[0009] Establish a balanced topology structure, including capacitors and ocean current energy friction nano-power generation devices connected in parallel to each battery; each battery can be independently connected in series with a voltage collection device through switch control; each battery can be connected in parallel with multiple capacitors through switch control;

[0010] Based on the balanced topology, the voltage of each battery is obtained and the battery with the maximum voltage is selected;

[0011] All capacitors are discharged through the battery with the highest voltage, and each capacitor obtains electrical energy;

[0012] The capacitor for obtaining electric energy is used together with the ocean current power generation device to discharge to the corresponding battery, so that the voltage of the entire battery group is balanced; wherein the capacitor corresponding to the battery with the maximum voltage is not discharged.

[0013] Preferably, when acquiring the voltage of each battery, the switch is controlled so that the voltage acquisition device is connected in parallel with each battery in turn to measure its voltage value.

[0014] Preferably, the voltage balancing process of the entire battery pack includes multiple balancing cycles, each cycle includes transferring excess energy from the battery with the maximum voltage in the battery pack to the battery with a voltage lower than the maximum voltage, and combining it with the ocean current energy friction nano power generation device.

[0015] Preferably, when the battery with the maximum voltage discharges to all capacitors, the discharge power calculation formula of the battery with the maximum voltage is:

[0016]

[0017] In the formula, is the discharge power of the battery with maximum voltage; The voltage value of the battery with the maximum voltage;

[0018] For battery The effective value of the outgoing balancing current is calculated as follows:

[0019]

[0020] In the formula, is an equilibrium cycle; The battery at time t The discharge current, t The value of t 0 ~ t 1 .

[0021] Preferably, each capacitor obtains the voltage of electric energy, and the calculation formula is:

[0022]

[0023] In the formula, For each capacitor, t The voltage of the electrical energy is obtained at all times; The voltage value of the battery with the maximum voltage; is the internal resistance of the battery at maximum voltage; is the equivalent resistance of each capacitor; For The initial voltage of each capacitor at time t; for t Moment Battery The discharge current; is the capacitance of the capacitor; is the number of cells in the battery pack.

[0024] Preferably, the ocean current energy friction nano power generation device includes a dielectric film and a flexible electrode. Based on the flow-induced vibration phenomenon, it converts the kinetic energy of the ocean current into the mechanical energy of the vibration of the ocean current energy friction nano power generation device. This process causes the dielectric film and the flexible electrode inside the device to produce relative displacement, resulting in a change in the interface electric field, thereby generating a displacement current.

[0025] Preferably, the ocean current energy friction nano power generation device is a multi-layer stacked film structure, wherein a first flexible electrode, a dielectric film and a second flexible electrode are sequentially stacked from top to bottom;

[0026] A certain gap is set between the first flexible electrode and the dielectric film, and between the dielectric film and the second flexible electrode.

[0027] Preferably, the first flexible electrode comprises a first PET film, and a first conductive ink is applied on a side of the first PET film facing the dielectric film;

[0028] The second flexible electrode includes a second PET film, and a second conductive ink is applied on a side of the second PET film facing the dielectric film;

[0029] The dielectric film is a polytetrafluoroethylene film.

[0030] Preferably, the thickness of the first PET film and the second PET film are both 20-30 mm. ;

[0031] The thickness of the dielectric film is 40 to 60 .

[0032] Preferably, the flexible lithium battery comprises a flexible organic positive electrode sheet and a flexible carbon-based negative electrode sheet which are stacked, and a double-layer composite material separator is arranged between the flexible organic positive electrode sheet and the flexible carbon-based negative electrode sheet; the flexible lithium battery is encapsulated by an aluminum-plastic film, and an electrolyte is also injected into the flexible lithium battery.

[0033] The present invention has at least the following beneficial effects:

[0034] The present invention provides a flexible lithium battery equalization method based on tiny current converted from ocean current energy. The present invention performs battery equalization on the self-developed flexible lithium battery by constructing an equalization topology structure between multiple batteries. The working process of the equalization topology structure is divided into two stages, namely, the detection stage and the equalization stage. The detection stage is the preparation stage of the equalization stage. In this stage, the voltage monitoring device detects the voltage of all batteries, and the microcontroller selects the battery with the maximum voltage. In the equalization stage, the equalization topology transfers the excess energy in the battery with the maximum voltage to the battery with the small voltage.

[0035] The balancing topology structure adopted by the present invention only requires one voltage acquisition device corresponding to n batteries to complete voltage detection of all batteries, and can realize voltage balancing among multiple batteries at the same time, and the energy of the high-voltage battery is directly transferred to the low-voltage battery, thereby improving the energy transfer efficiency.

[0036] Based on the principle of friction nanogenerator and flow-induced vibration, the present invention proposes a current energy friction nanogenerator to charge the voltage in the equalization circuit. The current has the characteristics of strong regularity, predictable energy density, and relatively stable power generation in different periods. This device uses a front blunt body to enhance the vibration amplitude and frequency of the current energy friction nanogenerator, so as to better collect the current energy. The current has the characteristics of strong regularity, predictable energy density, and relatively stable power generation in different periods.

[0037] The present invention uses a self-made flexible lithium battery that is resistant to long-term bending. The battery adopts a wave stress-resistant structure and can achieve high-frequency bending. Compared with traditional lithium batteries, the battery's service life and specific energy are greatly improved.

[0038] The present invention uses an ocean current power generation device in combination with a high-voltage capacitor to charge a low-voltage battery, thereby greatly improving the balancing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention provides a flow chart of a flexible lithium battery equalization method based on tiny current converted from ocean current energy.

[0040] Figure 2 It is a battery balancing topology.

[0041] Figure 3 This is a schematic diagram of the battery voltage detection stage.

[0042] Figure 4 Schematic diagram of charging the capacitor from the maximum voltage battery during the balancing phase.

[0043] Figure 5 Schematic diagram of charging a low-voltage battery during the equalization phase.

[0044] Figure 6 Schematic diagram of the working principle of independent layer friction nanopower generation.

[0045] Figure 7 The vibration model.

[0046] Figure 8 is the kinematic coordinate system.

[0047] Fig. 9 Schematic diagram of the working principle of the ocean current energy friction nano power generation device.

[0048] Fig.10Schematic diagram of the structure of the ocean current energy friction nano power generation device.

[0049] Fig.11 Schematic diagram of the ocean current friction nano-power generation device simulating power generation in ocean waves in a circulating water pool. DETAILED DESCRIPTION

[0050] In order to illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description in conjunction with embodiments.

[0051] The underwater flexible intelligent body adopted by the present invention is a manta ray-like submersible. The present invention carries a sea current energy friction nano-power generation device and a flexible lithium battery pack in the flapping wing space of the manta ray-like submersible.

[0052] See also Figure 1 As shown, the present invention provides a flexible lithium battery balancing method based on a tiny current converted from ocean current energy, comprising an ocean current energy friction nano power generation device and a flexible lithium battery pack carried in an underwater flexible intelligent body; the flexible lithium battery pack comprises a plurality of flexible lithium batteries, and the balancing method specifically comprises:

[0053] S1. Establish a balanced topology structure, including capacitors and ocean current energy friction nano-power generation devices connected in parallel to each battery; each battery can be independently connected in series with a voltage collection device through switch control; each battery can be connected in parallel with multiple capacitors through switch control;

[0054] In this embodiment, see Figure 2 As shown in the battery balancing topology, each battery B j By switching S ja , S jd The corresponding capacitor C j In parallel with capacitor C 1， C 2 , ..., C n By switching S jb With S jc Connected in parallel, each battery B j By switching S j Connected in parallel with the ocean current power generation device, each battery B j By switching S ja , S jd , S jb With S jc Connected in series with the voltage acquisition device, the value range of number j is 1 to n.

[0055] It should be noted that when the balancing topology is working, n batteries only need to correspond to one voltage acquisition device to complete the voltage detection, and then a pair of complementary PWM signals (PWM 1 and PWM2) controlled by the microcontroller unit (MCU) drive the MOSFET switch to control the battery with the largest voltage in the battery pack to discharge to the remaining small batteries. Since the energy transmission between batteries is transmitted through the switching capacitor as the transmission path, this increases the voltage difference between the battery and the capacitor, increases the charge and discharge current, and improves the balancing speed. At the same time, it also realizes voltage balancing between multiple batteries at the same time, and the energy of the large-capacity battery is directly transferred to the small-capacity battery, and the energy transfer efficiency is high.

[0056] Among them, MOSFET is a semiconductor field effect transistor, which is a commonly used switching device in switched capacitor converters. The power losses on MOSFET are conduction loss, switching loss and drive loss. The conduction loss is mainly determined by the on-resistance and the on-current flowing through the MOSFET, and its calculation formula is:

[0057]

[0058] In the formula, is the conduction loss, is the average drain current when the MOSFET is turned on, and D is the duty cycle; is the on-resistance.

[0059] Switching loss is the loss caused by hard switching when the MOSFET is turned on and off. The switching loss of the MOSFET can be obtained by the following formula:

[0060]

[0061] In the formula, is the switching loss; is the drain-source voltage of MOSFET during the switching transition phase; is the drain current when the MOSFET is on; and They are the turn-on and turn-off transition times of the MOSFET respectively; is the operating frequency.

[0062] During the turn-on process of the MOSFET, the drain current Before rising from 0, there is a period of time when the MOSFET is not turned on, and there is neither switching loss nor conduction loss, but during this period of time, the driving signal As the voltage increases, the driver chip charges the gate of the MOSFET, so this is also a form of loss, namely, drive loss. The formula for drive loss is as follows:

[0063]

[0064] In the formula, is the driving loss; is the gate-source voltage; depending on the type of original The value will change and can be checked in the component datasheet; is the operating frequency.

[0065] In this embodiment, based on the constructed balancing topology, the parameters of the capacitor balancing circuit used therein are designed, as follows:

[0066] In the constructed topology circuit, if the capacitance value is too large, the charging and discharging time of the capacitor will increase, thereby reducing the high-frequency performance of the capacitor, and there will be a larger parasitic inductance; if the capacitance value is too small, the energy storage on the capacitor will easily reach saturation, and the energy transferred in a single working cycle will be less, which will make the time for the balancing circuit to reach equilibrium longer, and the switching will increase the number of times the switch is turned on, which will increase the switching loss of the circuit. Therefore, the capacitance value of the capacitor needs to be designed according to the actual circuit. The energy transferred by the capacitor in a charging working cycle or a discharging working cycle is:

[0067]

[0068] In the formula, and Refers to the maximum voltage and minimum voltage that the capacitor can withstand when working in a balanced manner; Refers to the energy absorbed by the capacitor in one working cycle; is the capacitance value.

[0069] It should be noted that if the capacitance value is too large, the charging and discharging time of the capacitor will be longer. Increasing the capacitance value C will cause the time constant to Increase, so that the capacitor needs more time to charge and discharge, the balancing circuit needs a longer working cycle, so that the time required for the battery pack to reach balance becomes longer.

[0070] Taking the capacitor charging cycle as an example, the capacitor is between 0 and 3 The charging can be basically completed in 3 hours. to 5 time to complete the discharge. Assume that the charging time is , the discharge time is , the switching cycle of the balancing circuit is T , then:

[0071] , , , ;

[0072] To avoid the capacitor value being too small and thus prolonging the time required for the battery pack to reach the final balance, , then: ;

[0073] In the formula, R is the total resistance of the balancing loop. R and equilibrium cycle T Setting the Capacitor Value .

[0074] In this embodiment, in order to ensure the voltage balance of the entire battery pack, the detection phase interval is set, specifically including:

[0075] The voltage detection phase and the battery balancing process are performed independently. In order to prevent the balancing process from frequently entering the detection phase, an appropriate detection interval time needs to be set.

[0076] When the battery voltage difference is large, the maximum voltage battery When the battery voltage is still at a high level, the detection interval is set to more than 6s; on the contrary, when the battery voltage difference is small, the battery When the voltage is at a lower level, the interval of the detection phase is set to 2s or even 1s, so as to ensure that the balancing topology always works with the maximum voltage battery. Continuously discharging.

[0077] S2. Based on the balanced topology, obtain the voltage of each battery and select the battery with the maximum voltage;

[0078] When acquiring the voltage of each battery, the switch is controlled so that the voltage acquisition device is connected in parallel with each battery in turn to measure its voltage value.

[0079] In this embodiment, a voltage acquisition device, i.e., a voltage sensor, is used to measure the voltage of the battery, thereby selecting the battery with the maximum voltage. According to the current battery balancing speed, detection is performed every several switching cycles to ensure that the balancing topology always keeps the battery with the maximum voltage for discharge.

[0080] join Figure 3 As shown, before battery balancing begins, it is necessary to enter the detection phase and turn on the switches in sequence. , , , ( j =1, 2, …, n ), and measure the voltage of each battery through the auxiliary voltage acquisition device. When the detection device completes the detection and obtains the voltage of all batteries, the microcontroller unit , ,……, Find the battery with the highest voltage. Assume that the battery The battery with the highest voltage value is selected for the controller.

[0081] When the battery with the maximum voltage discharges to all capacitors, the discharge power calculation formula of the battery with the maximum voltage is:

[0082]

[0083] In the formula, is the discharge power of the battery with maximum voltage; The voltage value of the battery with the maximum voltage;

[0084] For battery The effective value of the outgoing balancing current is calculated as follows:

[0085]

[0086] In the formula, is an equilibrium cycle; The battery at time t The discharge current, t The value of t 0 ~ t 1 .

[0087] S3, discharging to all capacitors through the battery with the maximum voltage, and each capacitor obtains electrical energy;

[0088] In this embodiment, see Figure 4 As shown, the maximum battery voltage Corresponding switch , , , ( j =1, 2, …, n ) is closed, and the other switches are open. At this time, the maximum voltage battery In parallel with each capacitor, at this stage, the battery Discharge all capacitors, the maximum voltage battery The excess energy in the battery is transferred to the capacitors, so at the end of this period, the voltage on each capacitor will be equal to the battery voltage. The voltages are the same, both are maximum voltages.

[0089] Regulation: ; ; In the formula, for The corresponding parallel capacitance value is, for The equivalent series resistance.

[0090] In the process of the maximum voltage battery charging the capacitor, ignoring the MOSFET loss and only considering the equivalent resistance of the battery and capacitor, the relationship between the battery voltage and the capacitor voltage is:

[0091]

[0092] In the formula, is the charging current flowing through each capacitor branch, n is the sum of the capacitors; Is the maximum voltage battery Voltage value;

[0093] When the maximum battery voltage The capacity is much larger than the capacitor When the maximum battery voltage is The voltage can be regarded as a constant;

[0094] For Moment capacitor The initial voltage of j The value range is from 1 to n ; is the internal resistance of the battery with maximum voltage; For capacitors The equivalent resistance of for The initial voltage value of the nth capacitor at time s; s is the complex frequency variable in the Laplace transform; C is the capacitance value of the capacitor;

[0095] For the flow through ( n -1) Charging current of the capacitor branch.

[0096] Solving the relationship between battery voltage and capacitor voltage, we can get: s The charging current on the capacitor in the domain for:

[0097]

[0098] in,

[0099] ;

[0100] .

[0101] According to Kirchhoff's current law, the maximum voltage battery The discharge current is:

[0102]

[0103] Each capacitor obtains the voltage of electrical energy, that is, the capacitor The voltage on can be expressed as:

[0104]

[0105] In the formula, For each capacitor, t The voltage of the electrical energy is obtained at all times; The voltage value of the battery with the maximum voltage; is the internal resistance of the battery at maximum voltage; is the equivalent resistance of each capacitor; For The initial voltage of each capacitor at time t; For battery The discharge current at this stage; is the capacitance value; is the number of capacitors.

[0106] S4. Use the capacitor for obtaining electric energy together with the ocean current power generation device to discharge to the corresponding battery, so that the voltage of the entire battery group is balanced; wherein the capacitor corresponding to the battery with the maximum voltage is not discharged.

[0107] The process of voltage balancing of the entire battery pack includes multiple balancing cycles, each cycle includes transferring excess energy from the battery with the maximum voltage in the battery pack to the battery with a voltage lower than the maximum voltage, and combining the ocean current energy friction nano power generation device.

[0108] In this embodiment, when charging a low voltage battery, refer to Figure 5 As shown in the figure, when the maximum voltage battery has fully charged each capacitor, each capacitor has the maximum voltage, and the switch , , ( j =1, 2, …, n , except x) is closed, other switches are disconnected. At this time, the ocean current energy power generation device is connected in parallel with the capacitors with the maximum voltage and the corresponding small voltage batteries. The voltage on each capacitor is greater than the voltage of the battery in parallel. Therefore, each capacitor and the ocean current energy power generation device discharges to each small voltage battery together, and part of the energy stored in the capacitor is transferred to each small voltage battery. Each small voltage battery is charged and the voltage increases.

[0109] Each battery flows into The charging power is calculated as follows:

[0110]

[0111] The value range of j is 1 to n except x. For the battery The effective value of the balancing current is calculated as follows:

[0112]

[0113] Therefore, the instantaneous efficiency calculation formula of the multi-battery battery balancing topology during the balancing period is:

[0114]

[0115] To this end, the highest voltage battery in the battery pack is achieved The excess energy in the battery is transferred to each low-voltage battery, and combined with the ocean current power generation device, the voltage of the high-voltage battery is reduced and the voltage of the low-voltage battery is increased. Finally, after multiple balancing cycles, the voltage of the entire battery group can be balanced.

[0116] The ocean current energy friction nano power generation device adopted in the present invention includes a dielectric film and a flexible electrode. Based on the flow-induced vibration phenomenon, it converts the kinetic energy of the ocean current into the mechanical energy of the vibration of the ocean current energy friction nano power generation device. This process causes the dielectric film and the flexible electrode inside the device to produce relative displacement, resulting in a change in the interface electric field, thereby generating a displacement current.

[0117] The ocean current energy friction nano power generation device is a multi-layer stacked film structure, with a first flexible electrode, a dielectric film and a second flexible electrode stacked in sequence from top to bottom;

[0118] A certain gap is set between the first flexible electrode and the dielectric film, and between the dielectric film and the second flexible electrode.

[0119] Wherein, the first flexible electrode comprises a first PET film, and a first conductive ink is applied on a side of the first PET film facing the dielectric film;

[0120] The second flexible electrode includes a second PET film, and a second conductive ink is applied on a side of the second PET film facing the dielectric film;

[0121] The dielectric film is a polytetrafluoroethylene film.

[0122] Specifically, the thickness of the first PET film and the second PET film is 20-30 mm. ;

[0123] The thickness of the dielectric film is 40 to 60 .

[0124] The ocean current energy friction nano power generation device is packaged by polytetrafluoroethylene tape.

[0125] See also Figure 6 As shown, the working principle of the independent layer friction nanogenerator is as follows:

[0126] like Figure 6 As shown in (i), at the initial position, due to the large electronegativity difference between the dielectric film and the electrode, when the dielectric film contacts the electrode, due to the combined effect of electrostatic induction and contact electrification, equal amounts of positive and negative charges will be generated on the surface of the electrode and the dielectric film. PLA is polylactic acid;

[0127] Under the action of the fluid, the dielectric film separates from the bottom electrode and moves upward. At this time, electrons are transferred from the top electrode to the bottom electrode through the external circuit, thereby forming a transient current, such as Figure 6 As shown in (ii) in .

[0128] When the film is in full contact with the top electrode, e.g. Figure 6 As shown in (iii) in Figure 1, all the positive charges appear on the top electrode, achieving conservation with the negative charges on the dielectric film.

[0129] The subsequent reverse motion of the dielectric film results in the reverse transfer of electrons through the external circuit, e.g. Figure 6 As shown in (iv) in .

[0130] At this point, a complete power generation process is completed, realizing the conversion of flow energy to mechanical energy and then to electrical energy.

[0131] See also Figure 7 As shown, the vibration model of the flag-shaped ocean current energy friction nano-power generation device established by the present invention; the X-axis represents the position coordinate along the length direction of the cantilever beam, and the Y-axis represents the lateral displacement of the beam. is the gap height.

[0132] According to the Euler-Bernoulli beam formula, its dynamic characteristics can be described as:

[0133]

[0134] In the formula, represents the inertial force of the film, represents the damping characteristics of the film, Indicates the density of the film.

[0135] In this embodiment, the ocean current energy friction nano power generation device generates electricity based on the independent layer principle, and its kinematic coordinate system is as follows: Figure 8As shown; y represents the change in position of the object under the action of external force, y (t) represents the height of the gap, x represents the position along the length direction of the vibrating object, d represents the thickness of the electrode, is the charge density. According to the kinematic coordinate system, its control equation can be described as:

[0136]

[0137] In the formula, represents the open circuit voltage; C, Q represent the power generation unit capacitance and the transferred charge respectively; They represent the thickness of the electrode, the height of the gap, the dielectric constant, the contact area between the electrode and the dielectric material, and the charge density, respectively.

[0138] The working principle of the ocean current energy friction nano power generation device used in the present invention is as follows: Fig. 9 As shown, the power generation process of the friction nanogenerator, Fig. 9 As shown in (a), the dielectric film is in contact with the bottom flexible electrode, and equal amounts of positive and negative charges are generated on the bottom flexible electrode and the dielectric film; Fig. 9 As shown in (b), when the dielectric film is separated from the bottom flexible electrode, electrons flow from the top flexible electrode to the bottom flexible electrode through the external circuit to generate instantaneous current; Fig. 9 As shown in (c), the dielectric film is in contact with the top flexible electrode, and all positive charges appear on the top flexible electrode; Fig. 9 As shown in (d), the dielectric film is separated from the top flexible electrode, and electrons are transferred through the external circuit, generating instantaneous current.

[0139] In this embodiment, the preparation process of the ocean current energy friction nano power generation device includes:

[0140] First, the conductive ink is evenly printed on a PET film with a thickness of 25 μm and slowly dried in a drying oven to obtain a flexible electrode;

[0141] Secondly, the bottom flexible electrode and the PTFE dielectric film with a thickness of 50μm are cut to size and bonded with double-sided tape. After bonding, an air layer that can be contacted and separated is formed between the dielectric material and the flexible electrode. Then, the top flexible electrode is cut to size so that it is 1mm larger than the middle PTFE dielectric film and is also bonded with double-sided tape. After the friction layer materials are bonded one by one, a piece of PTFE tape that is 1mm larger than the top flexible electrode is used to fit the entire friction layer to achieve a sealing effect.

[0142] See also Fig.10As shown, the ocean current energy friction nano power generation device used in the present invention is a multi-layer stacked film structure, which is encapsulated inside the flapping space of the manta ray-like submersible. The multi-layer stacked film structure mainly includes two PET films brushed with conductive ink, a PTFE film and a sealing tape. Fig.11 As shown, the ocean current energy friction nano power generation device is placed in a circulating water pool. The water flow simulates ocean waves, and the continuous kinetic energy of the water is converted into mechanical energy for the flag to swing.

[0143] It should be noted that the PET film is a thermoplastic polyester film; the dielectric film is a polytetrafluoroethylene film (PTFE film).

[0144] The flexible lithium battery used in the present invention comprises a flexible organic positive electrode sheet and a flexible carbon-based negative electrode sheet which are stacked, and a double-layer composite material separator is arranged between the flexible organic positive electrode sheet and the flexible carbon-based negative electrode sheet; the flexible lithium battery is packaged by an aluminum-plastic film, and an electrolyte is also injected into the flexible lithium battery.

[0145] In this embodiment, a wave stress-resistant structure is adopted, and a flexible lithium battery is manufactured using a flexible electrode material that is resistant to long-term high-frequency bending, so as to improve the battery's anti-bending ability.

[0146] In the process of making flexible lithium batteries, the organic positive electrode mixed slurry is first coated on aluminum foil, repeatedly rolled to prepare a flexible organic positive electrode sheet that is resistant to long-term and high-frequency bending and cut, and then the carbon-based negative electrode mixed slurry is coated on copper foil, repeatedly rolled to prepare a flexible carbon-based negative electrode sheet that is resistant to long-term and high-frequency bending and cut into appropriate sizes and shapes, the diaphragm and aluminum-plastic film are cut into appropriate sizes and shapes, and the tabs are fixed to the positive and negative electrodes using an ultrasonic welding machine. The aluminum-plastic film is punched to form a wavy groove, and then the various components of the flexible lithium battery are assembled, punched into a wavy structure and placed in the groove, the flexible lithium battery is hot-pressed and packaged using a heat sealer, and then the electrolyte is injected into a vacuum glove box, and the flexible lithium battery is completely sealed using a vacuum pre-sealer, and the flexible lithium battery is placed in a constant temperature box and left to stand for a period of time before being taken out, the internal resistance of the flexible lithium battery is detected and recorded, and the flexible lithium battery is activated using a hot pressing formation machine, and the internal resistance of the flexible lithium battery after activation is measured again, compared with the previous measurement value and the battery state is judged, and then the formed flexible lithium battery is placed in a secondary vacuum final sealing machine, the gas and excess electrolyte are discharged and re-sealed, and the excess aluminum-plastic film is cut to complete the preparation of the wavy stress-resistant structure flexible lithium battery.

[0147] The wave-resistant stress-resistant structure flexible lithium battery can be bent to a large extent. Compared with the existing technology, the wave-resistant stress-resistant structure adopted has more superior material properties than the existing flexible lithium battery, which is prone to rapid decline in performance and life due to structural deformation under repeated bending. The flexible organic positive electrode that can resist long-term and high-frequency bending can still maintain good electrical conductivity and specific energy under high-frequency bending due to the intervention of carbon-based negative electrode materials.

[0148] In summary, in order to meet the requirements of fast balancing speed and high system efficiency, the present invention proposes a flexible lithium battery balancing method based on tiny currents converted from ocean current energy. A multi-battery fast balancing topology circuit topology is proposed to balance the self-developed flexible lithium batteries. The working process of the balancing topology is divided into two stages, namely the detection stage and the balancing stage. The detection stage is the preparation stage for the balancing stage. In this stage, the voltage monitoring device detects the voltages of all batteries, and the microcontroller selects the battery with the maximum voltage. In the balancing stage, the balancing topology transfers the excess energy in the battery with the maximum voltage to the battery with the low voltage.

[0149] This balancing topology can realize the maximum voltage battery combined with the ocean current energy power generation device to charge the low voltage batteries, which increases the voltage difference between the battery and the capacitor, which is one of the factors affecting the charging and discharging current. The charging and discharging current increases, the balancing speed is accelerated, and at the same time, the energy flows directly from the high voltage battery to the low voltage battery, which improves the balancing efficiency.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A flexible lithium battery equalization method based on tiny current converted from ocean current energy, characterized in that: It includes a sea current energy friction nano power generation device and a flexible lithium battery pack carried in an underwater flexible intelligent body; The flexible lithium battery pack includes a plurality of flexible lithium batteries; Establish a balanced topology structure, including capacitors and ocean current energy friction nano-power generation devices connected in parallel to each battery; each battery can be independently connected in series with a voltage collection device through switch control; each battery can be connected in parallel with multiple capacitors through switch control; Based on the balanced topology, the voltage of each battery is obtained and the battery with the maximum voltage is selected; All capacitors are discharged through the battery with the highest voltage, and each capacitor obtains electrical energy; The capacitor for obtaining electric energy is used together with the ocean current energy power generation device to discharge to the corresponding parallel batteries, so that the voltage of the entire battery group is balanced; wherein the capacitor corresponding to the battery with the maximum voltage is not discharged.

2. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 1, characterized in that: When obtaining the voltage of each battery, the switch is controlled so that the voltage acquisition device is connected in parallel with each battery in turn to measure its voltage value.

3. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 1, characterized in that: The process of voltage balancing of the entire battery pack includes multiple balancing cycles, each cycle includes transferring excess energy from the battery with the maximum voltage in the battery pack to the battery with a voltage lower than the maximum voltage, and combining the ocean current energy friction nano power generation device.

4. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 1, characterized in that: When the battery with the maximum voltage discharges to all capacitors, the discharge power calculation formula of the battery with the maximum voltage is: P BOUT =V Bmax ×I Bx Where P BOUT is the discharge power of the maximum voltage battery; V Bmax The voltage value of the battery with the maximum voltage; I Bx For battery B x The effective value of the outgoing balancing current is calculated as follows: Where, T s is an equilibrium period; i Bx (t) is battery B at time t x The discharge current of t is t0~t1.

5. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 1, characterized in that: Each capacitor obtains the voltage of electrical energy, which is calculated as: In the formula, v cj (t) is the voltage of each capacitor at time t when it obtains electrical energy; V Bmax is the voltage value of the battery with the maximum voltage; R Bx is the internal resistance of the battery at maximum voltage; R ESR is the equivalent resistance of each capacitor; v Ck (t0) is the initial voltage of each capacitor at time t0; i Bx (t) is battery B at time t x The discharge current; C is the capacitance of the capacitor; n is the number of batteries in the battery pack.

6. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 1, characterized in that: The ocean current energy friction nano power generation device includes a dielectric film and a flexible electrode. Based on the flow-induced vibration phenomenon, it converts the kinetic energy of the ocean current into the mechanical energy of the vibration of the ocean current energy friction nano power generation device. This process causes the dielectric film and the flexible electrode inside the device to produce relative displacement, resulting in changes in the interface electric field, and then generating displacement current.

7. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 1, characterized in that: The ocean current energy friction nano power generation device is a multi-layer stacked film structure, with a first flexible electrode, a dielectric film and a second flexible electrode stacked in sequence from top to bottom; A certain gap is set between the first flexible electrode and the dielectric film, and between the dielectric film and the second flexible electrode.

8. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 7, characterized in that: The first flexible electrode includes a first PET film, and a first conductive ink is applied on a side of the first PET film facing the dielectric film; The second flexible electrode includes a second PET film, and a second conductive ink is applied on a side of the second PET film facing the dielectric film; The dielectric film is a polytetrafluoroethylene film.

9. The flexible lithium battery equalization method based on micro-current converted from ocean current energy according to claim 8, characterized in that: The thickness of the first PET film and the second PET film are both 20-30 μm; The thickness of the dielectric film is 40-60 μm.

10. The flexible lithium battery equalization method based on micro current converted from ocean current energy according to claim 1, characterized in that: The flexible lithium battery comprises a flexible organic positive electrode sheet and a flexible carbon-based negative electrode sheet which are stacked, and a double-layer composite material separator is arranged between the flexible organic positive electrode sheet and the flexible carbon-based negative electrode sheet; the flexible lithium battery is encapsulated by an aluminum-plastic film, and an electrolyte is also injected into the flexible lithium battery.

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