Three-electrode battery and lithium plating and load adjusting method thereof

Abstract

The invention relates to the field of lithium ion batteries, and discloses a three-electrode battery and a lithium plating and load adjusting method thereof. The three-electrode battery comprises a battery shell as well as a laminated pole group, a reference electrode group, a diaphragm and electrolyte which are packaged in the battery shell, the laminated pole group comprises positive electrodes and negative electrodes, the number of layers of the negative electrodes is one more than that of the positive electrodes, and the positive electrodes and the negative electrodes are alternately stacked to form the laminated pole group; the reference electrode group comprises a lithium iron phosphate pole piece, a graphite pole piece and a copper wire; the lithium iron phosphate pole piece and the graphite pole piece are oppositely arranged and located on the outer side of the laminated pole group, and the lithium iron phosphate pole piece is oppositely arranged with a negative electrode in the laminated pole group; the copper wire is positioned between the positive electrode and the negative electrode or between the lithium iron phosphate pole piece and the graphite pole piece. According to the method, the difference between the potential of the reference electrode group and the theoretical potential is greatly reduced, and the accuracy is high; differences between positive and negative parameter potentials and theoretical potentials are greatly reduced, and the accuracy is high; and compared with the prior art, the method is shorter in lithium plating time.

Description

Technical Field

[0001] The invention relates to the field of lithium ion batteries, and in particular to a three-electrode battery and a lithium plating and charge adjustment method thereof. Background Art

[0002] The three-electrode battery is an electrochemical energy storage device consisting of a positive electrode, a negative electrode and a reference electrode. The battery has the advantages of high energy density, long life and low self-discharge rate, and is widely used in mobile communications, digital products, medical equipment and other fields.

[0003] In a three-electrode cell, the positive and negative electrodes are separated by an electrolyte and connected to a common reference electrode. This reference electrode can be a working electrode, used to measure the cell's potential and current, or a reference electrode, used to maintain electrochemical balance within the cell.

[0004] Lithium-ion battery product development requires the provision of lithium plating boundaries for battery cells, and battery parameter testing also requires a stable reference electrode. In three-electrode batteries, using copper wire as a reference electrode can ensure the performance and stability of the battery, while reducing the cost of the battery and facilitating large-scale production and application. Copper wire has good electrical properties and can ensure the current transmission efficiency of the battery. Copper wire has good stability in the chemical reaction of the battery, is not prone to corrosion or oxidation reactions, and ensures the safety and stability of the battery.

[0005] However, the current CuLi reference has the following problems: ① It cannot be stable for a long time and the reference is damaged before the test is completed; ② The Li plating time is long, and the production and testing cycle is long.

[0006] In order to solve this problem, CN118263550A discloses a reference electrode for a lithium-ion battery and a preparation method thereof, wherein the technical solution mainly adopts a method of chemical polishing plus pulse electroplating to improve the reference stability, the lithium plating time is more than one hour, and the stable life of the Li plating layer is only 24-36 hours. Therefore, the time cost is high and the effect is not ideal.

[0007] CN109585907A discloses a three-electrode lithium-ion battery and a method for making the same. In the technical solution, the reference electrode of the three-electrode lithium-ion battery is a lithium iron phosphate electrode. The reference electrode, the positive electrode, the negative electrode, and the copper wire are all immersed in the battery electrolyte. The copper wire and the lithium iron phosphate electrode are spaced apart, and the length of the lithium iron phosphate electrode is 1 / 2 to 2 / 3 of the length of the positive electrode or the negative electrode. However, the reference electrode has a high state of charge, unstable ionization, and is not suitable for testing the charge and discharge potential in dynamic state, and the test accuracy is low. Summary of the invention

[0008] The purpose of the present invention is to overcome the problems of poor static potential stability and long lithium plating and charge adjustment time in the CuLi reference electrode of the prior art.

[0009] In order to achieve the above-mentioned object, the first aspect of the present invention provides a three-electrode battery, which includes a battery housing and a laminated electrode group, a reference electrode group, a diaphragm and an electrolyte encapsulated in the battery housing, wherein the laminated electrode group includes a positive electrode and a negative electrode, the number of layers of the negative electrode is one more than the number of layers of the positive electrode, and the positive electrode and the negative electrode are alternately stacked to form the laminated electrode group; the reference electrode group includes a lithium iron phosphate electrode sheet, a graphite electrode sheet and a copper wire;

[0010] The lithium iron phosphate pole piece and the graphite pole piece are arranged opposite to each other and are located outside the laminated pole group, and the lithium iron phosphate pole piece is arranged opposite to the negative pole in the laminated pole group; the copper wire is located between the positive pole and the negative pole, or the copper wire is located between the lithium iron phosphate pole piece and the graphite pole piece;

[0011] Any two of the positive electrode, the negative electrode, the lithium iron phosphate electrode, the graphite electrode and the copper wire are separated by a diaphragm soaked in electrolyte; the effective area of ​​the material particles of the lithium iron phosphate electrode is 10 of the effective area of ​​the material particles of the positive electrode. -6 -1 times.

[0012] A second aspect of the present invention provides a method for lithium plating and charge adjustment of a three-electrode battery, the method comprising the following steps:

[0013] (1) connecting the positive electrode I and the negative electrode I of the external power source to the positive electrode and the negative electrode of the three-electrode battery respectively to perform a first charge adjustment, and controlling the conditions so that the state of charge (SOC) of the positive electrode and the negative electrode is 5-95%;

[0014] The three-electrode battery is the three-electrode battery described in the first aspect;

[0015] (2) plating the copper wire with lithium;

[0016] (3) Connecting the positive electrode I and the negative electrode I of the external power supply to the lithium iron phosphate electrode and the graphite electrode of the three-electrode battery respectively to perform a second charge adjustment to obtain a three-electrode battery I; controlling the conditions so that the state of charge (SOC) of the lithium iron phosphate electrode and the graphite electrode is 5-95%.

[0017] Through the above technical solution, the present invention has at least the following advantages:

[0018] (1) After the three-electrode battery provided by the present invention is subjected to a double charge test, the charge is adjusted to the original SOC, and the potential of the positive electrode and the reference electrode group, and the potential of the negative electrode and the reference electrode group deviate by less than 6 mV compared with those before the double charge test, and the stability is relatively high.

[0019] (2) The lithium plating and charge adjustment method of the three-electrode battery provided by the present invention greatly reduces the difference between the potential of the reference electrode group and its theoretical potential, and preferably the difference is <1 mV, which is greatly reduced compared with the prior art and has high accuracy.

[0020] (3) The lithium plating and charge adjustment method for the three-electrode battery provided by the present invention takes a short time, thus solving the problem of the long preparation time (lithium plating) of the conventional CuLi reference (generally 10 hours). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a three-electrode battery when the copper wire of the present invention is located between the positive electrode and the negative electrode;

[0022] Figure 2 Schematic diagram of a three-electrode battery in which the copper wire of the present invention is located between a lithium iron phosphate pole piece and a graphite pole piece;

[0023] Figure 3 It is a flow chart of the method for lithium plating and charge adjustment of the three-electrode battery of the present invention;

[0024] Figure 4 The relationship curve between the positive parameter potential and time of the three-electrode battery of Example 1 of the present invention at 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C rates in sequence;

[0025] Figure 5 It is the relationship curve between negative parameter potential and time of the three-electrode battery of comparative example 1 of the present invention at a rate of 0.33C;

[0026] Figure 6 This is a negative potential performance test diagram of the three-electrode battery of comparative example 1 of the present invention after being charged at a rate of 0.33C. DETAILED DESCRIPTION

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] In the present invention, the theoretical potential between the positive electrode and the lithium iron phosphate electrode in the reference electrode group is calculated according to the Nernst formula.

[0029] In the present invention, CuLi reference refers to using copper wire as a reference electrode and plating lithium on the copper wire to form CuLi reference.

[0030] In the drawings of the present invention, A represents the positive electrode, B represents the negative electrode, A2 represents the lithium iron phosphate electrode, B2 represents the graphite electrode, and C represents the copper wire.

[0031] As mentioned above, the first aspect of the present invention provides a three-electrode battery, which includes a battery housing and a laminated electrode group, a reference electrode group, a diaphragm and an electrolyte encapsulated in the battery housing, wherein the laminated electrode group includes a positive electrode and a negative electrode, the number of layers of the negative electrode is one more than the number of layers of the positive electrode, and the positive electrode and the negative electrode are alternately stacked to form the laminated electrode group; the reference electrode group includes a lithium iron phosphate electrode sheet, a graphite electrode sheet and a copper wire;

[0032] The lithium iron phosphate pole piece and the graphite pole piece are arranged opposite to each other and are located outside the laminated pole group, and the lithium iron phosphate pole piece is arranged opposite to the negative pole in the laminated pole group; the copper wire is located between the positive pole and the negative pole, or the copper wire is located between the lithium iron phosphate pole piece and the graphite pole piece;

[0033] Any two of the positive electrode, the negative electrode, the lithium iron phosphate electrode, the graphite electrode and the copper wire are separated by a diaphragm soaked in electrolyte; the effective area of ​​the material particles of the lithium iron phosphate electrode is 10 of the effective area of ​​the material particles of the positive electrode. -6 -1 times.

[0034] According to a preferred embodiment, the effective area of ​​the material particles of the lithium iron phosphate electrode is 10 times the effective area of ​​the material particles of the positive electrode. -5 -10 -1 times, for example, 10 -4 times, 10 -3 times, 10 -2 times.

[0035] Particularly preferably, the effective area of ​​the material particles of the lithium iron phosphate electrode is 10 of the effective area of ​​the material particles of the positive electrode. -3 -10 -1 In this preferred case, the shielding effect of the capacitance of the lithium iron phosphate electrode on the high-frequency signal can be further reduced.

[0036] The present invention Figure 1 A schematic diagram of a three-electrode battery when the copper wire is located between the positive electrode and the negative electrode is provided.

[0037] The present invention Figure 2 A schematic diagram of a three-electrode battery is provided when the copper wire is located between the lithium iron phosphate pole piece and the graphite pole piece.

[0038] It should be noted that the calculation formula for the effective area of ​​the lithium iron phosphate electrode and the positive electrode material particles is:

[0039] S=6ρ 面 × loading × L × W / (ρ 真 ×D 50 ) Formula (I)

[0040] In formula (I), S is the effective area of ​​the material particles of the pole piece;

[0041] ρ 面 is the surface cross-section of the electrode, in g / cm 2 ;

[0042] Loading is the mass ratio of active material (lithium iron phosphate) on the electrode, ranging from 0 to 100%;

[0043] L is the length of the pole piece, in cm;

[0044] W is the width of the pole piece, in cm;

[0045] ρ 真 is the true density of the electrode, which is 3.6 g / cm 3 ;

[0046] D 50 It is the particle size corresponding to when the cumulative particle size distribution number of the active material (lithium iron phosphate) on the electrode reaches 50%, measured by using a Mastersizer 3000 laser particle size analyzer; the unit is cm.

[0047] According to a preferred embodiment, the copper wire is located between the lithium iron phosphate pole piece and the graphite pole piece. In this preferred embodiment, the CuLi reference treatment Li formed by the lithium plating of the copper wire can be minimized. + The diffusion migration provides a reliable potential verification for the lithium iron phosphate pole piece and the graphite pole piece.

[0048] According to a preferred specific implementation manner, the copper wire is located between the positive electrode and the negative electrode, and the length of the copper wire inserted into the three-electrode battery relative to the negative electrode is half of that of the negative electrode.

[0049] “The length of the copper wire extending into the three-electrode battery relative to the negative electrode” refers to the length of the lower end of the copper wire relative to the upper end of the negative electrode in the three-electrode battery.

[0050] According to another preferred specific embodiment, the copper wire is located between the lithium iron phosphate pole piece and the graphite pole piece, and the length of the copper wire extending deep into the three-electrode battery relative to the graphite pole piece is half of that of the graphite pole piece.

[0051] “The length of the copper wire extending into the three-electrode battery relative to the graphite pole piece” refers to the length of the lower end of the copper wire relative to the upper end of the graphite pole piece in the three-electrode battery.

[0052] Preferably, the thickness of the separator is 8-12 μm.

[0053] Preferably, the copper wire has a diameter of 10-100 μm.

[0054] Preferably, the length of the positive electrode is 2-12 cm and the area is 3-120 cm 2 .

[0055] Preferably, the length of the negative electrode is 2.4-12.5 cm and the area is 4.8-145 cm 2 .

[0056] Preferably, the positive electrode has 1-50 layers, preferably 5-20 layers.

[0057] More preferably, the number of layers of the positive electrode is 7, and the number of layers of the negative electrode is 8. The preferred condition is to meet the minimum number of layers under the minimum thickness of the punching machine. In this preferred case, the maximum current requirement of the charging and discharging device is low.

[0058] The present invention has no particular limitation on the number of layers of the separator between the lithium iron phosphate electrode and the negative electrode, and those skilled in the art can select it according to technical means known in the art, for example, it can be 1 layer, 2 layers or 3 layers.

[0059] Preferably, the positive electrode, the negative electrode, the lithium iron phosphate electrode sheet, the graphite electrode sheet and the copper wire respectively form a positive electrode tab, a negative electrode tab, a first reference tab, a second reference tab and a third reference tab outside the battery casing.

[0060] As mentioned above, the second aspect of the present invention provides a method for lithium plating and charge adjustment of a three-electrode battery, the method comprising the following steps:

[0061] (1) connecting the positive electrode I and the negative electrode I of the external power source to the positive electrode and the negative electrode of the three-electrode battery respectively to perform a first charge adjustment, and controlling the conditions so that the state of charge (SOC) of the positive electrode and the negative electrode is 5-95%;

[0062] The three-electrode battery is the three-electrode battery described in the first aspect;

[0063] (2) plating the copper wire with lithium;

[0064] (3) Connecting the positive electrode I and the negative electrode I of the external power supply to the lithium iron phosphate electrode and the graphite electrode of the three-electrode battery respectively to perform a second charge adjustment to obtain a three-electrode battery I; controlling the conditions so that the state of charge (SOC) of the lithium iron phosphate electrode and the graphite electrode is 5-95%.

[0065] Preferably, the present invention Figure 3 A flow chart of a method for lithium plating and charge adjustment of the above three-electrode battery is provided, and the method comprises the following steps:

[0066] (1) connecting the positive electrode I and the negative electrode I of the external power source to the positive electrode and the negative electrode of the three-electrode battery respectively to perform a first charge adjustment, and controlling the conditions so that the state of charge (SOC) of the positive electrode and the negative electrode is 5-95%;

[0067] The three-electrode battery is the three-electrode battery described in the first aspect;

[0068] (2) plating the copper wire with lithium;

[0069] (3) Connecting the positive electrode I and the negative electrode I of the external power supply to the lithium iron phosphate electrode and the graphite electrode of the three-electrode battery respectively to perform a second charge adjustment to obtain a three-electrode battery I; controlling the conditions so that the state of charge (SOC) of the lithium iron phosphate electrode and the graphite electrode is 5-95%.

[0070] Preferably, in step (1), the conditions are controlled so that the state of charge (SOC) of the positive electrode and the negative electrode is 30-50%.

[0071] Preferably, in step (3), the conditions are controlled so that the state of charge (SOC) of the positive electrode and the negative electrode is 30-50%.

[0072] Preferably, in step (2), the lithium plating treatment is performed by constant current lithium plating, and the conditions of the lithium plating treatment include: a current intensity of 50-100 μA and a time of 40-80 min.

[0073] In step (2), the present invention has no particular restrictions on the method of lithium plating, as long as it can ensure that the copper wire is completely coated with lithium metal. Exemplarily, the method of lithium plating includes: connecting the negative electrode I of the external power supply to the copper wire, and connecting the positive electrode I of the external power supply to the positive electrode, the negative electrode and the lithium iron phosphate electrode in sequence, and performing DC charging. The charging process step is preferably continuous lithium plating, and the positive plating is maintained for 20-35 minutes and the negative plating is maintained for 20-35 minutes.

[0074] Preferably, the method further comprises: connecting the positive electrode I and the negative electrode I of the external power supply to the lithium iron phosphate electrode sheet and the negative electrode in the three-electrode battery I respectively to perform a third charge adjustment to obtain a three-electrode battery II; and controlling the conditions so that the state of charge SOC of the lithium iron phosphate electrode sheet and the negative electrode is 5-95%, preferably 30-50%. The inventors have found that in this preferred case, the stability of the static potential of the reference electrode group can be further improved.

[0075] Preferably, the conditions of the first load adjustment, the second load adjustment and the third load adjustment each independently include: a ratio of 0.02-1.5C, and a time of 10-180 minutes.

[0076] Preferably, during testing, the conventional CuLi three-electrode can be used by connecting the wire originally connected to the CuLi reference to the lithium iron phosphate electrode; the copper wire is used to verify the accuracy of the new reference, and lithium is plated as it is used.

[0077] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the normal temperature refers to a temperature of 23±2°C.

[0078] In the following examples, the potential parameters were measured by a battery testing system of a Biologé electrochemical workstation from France.

[0079] Positive electrode: Lithium iron phosphate electrode, length 11cm, area 8cm 2 .

[0080] Negative electrode: graphite electrode, length 11.5cm, area 8.5cm 2 .

[0081] Diaphragm: Conventional lithium battery diaphragm, made of polypropylene (PP), 20μm thick, model 7X+3AL+2P.

[0082] Electrolyte: The main component is lithium salt LiPF 6 , solvent (ethylene carbonate EC, dimethyl carbonate DMC and ethyl methyl carbonate EMC in a volume ratio of 1:1:1), and 1wt% of vinylene carbonate VC.

[0083] Copper wire: diameter 50μm.

[0084] In the following examples, A represents the positive electrode, B represents the negative electrode, A2 represents the lithium iron phosphate electrode, B2 represents the graphite electrode, and C represents the copper wire.

[0085] Example 1

[0086] This embodiment is used to illustrate a method for lithium plating and charge adjustment of a three-electrode battery, which method includes the following steps:

[0087] (1) Connecting the positive electrode I and the negative electrode I of the external power source to the positive electrode and the negative electrode of the three-electrode battery respectively to perform the first charge adjustment, and adjusting the charge to 40% SOC at a rate of 0.33C (time is 73 minutes);

[0088] The aforementioned three-electrode battery comprises a battery housing and a laminated electrode group, a reference electrode group, a diaphragm and an electrolyte encapsulated inside the battery housing, the laminated electrode group comprises a positive electrode and a negative electrode, the number of layers of the negative electrode is 8 layers, the number of layers of the positive electrode is 7 layers, and the positive electrode and the negative electrode are alternately stacked to form a laminated electrode group; the reference electrode group comprises a lithium iron phosphate electrode sheet, a graphite electrode sheet and a copper wire;

[0089] The lithium iron phosphate pole piece and the graphite pole piece are arranged opposite to each other and are located outside the laminated pole piece group, and the lithium iron phosphate pole piece is arranged opposite to the negative electrode in the laminated pole piece group; the copper wire is located between the lithium iron phosphate pole piece and the graphite pole piece, and the length of the copper wire penetrating into the three-electrode battery relative to the graphite pole piece is half of the length of the graphite pole piece;

[0090] Any two of the positive electrode, negative electrode, lithium iron phosphate electrode, graphite electrode and copper wire are separated by a diaphragm soaked in electrolyte; the effective area of ​​the positive electrode material particles is 34cm 2 The effective area of ​​the lithium iron phosphate plate material particles is 10 of the effective area of ​​the positive electrode material particles. -3 times;

[0091] The number of layers of the separator between the lithium iron phosphate electrode and the negative electrode is 1;

[0092] The positive electrode, the negative electrode, the lithium iron phosphate electrode sheet, the graphite electrode sheet and the copper wire respectively form a positive electrode tab, a negative electrode tab, a first reference tab, a second reference tab and a third reference tab outside the battery housing;

[0093] The capacity of the three-electrode battery is about 3Ah.

[0094] (2) The copper wire is plated with lithium by constant current lithium plating (current intensity is 80 μA, time is 60 min), the specific method is as follows:

[0095] The negative electrode I of the external power supply is connected to the copper wire, and the positive electrode I of the external power supply is connected to the positive electrode, the negative electrode and the lithium iron phosphate electrode in sequence for DC charging. The charging process steps are continuous lithium plating, and the positive plating is maintained for 20 minutes and the negative plating is maintained for 20 minutes.

[0096] (3) The positive electrode I and the negative electrode I of the external power supply are connected to the lithium iron phosphate electrode and the graphite electrode of the three-electrode battery respectively, and the charge is adjusted to 40% SOC at a rate of 0.33C (time is 73 minutes) to obtain a three-electrode battery I.

[0097] (4) The positive electrode I and the negative electrode I of the external power supply are connected to the lithium iron phosphate electrode and the negative electrode in the three-electrode battery I, respectively, and the charge is adjusted to 40% SOC (time is 73 minutes) at a rate of 0.33C to obtain a three-electrode battery II.

[0098] The total time of lithium plating and charge adjustment in Example 1 is 4.65 hours, which is shorter than the lithium plating time (10 hours) of conventional lithium plating on both sides, and the preparation time is shorter. Therefore, this method is time-saving and more efficient.

[0099] Moreover, the reference potential of the lithium iron phosphate electrode of the reference electrode group obtained by this method is stable. After battery AB is charged at 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C in sequence (about 100h), the charge of battery AB is adjusted to 40% SOC. The voltage of AA2 changes from about -1mV before the test to about 4mV, with a change range of less than 6mV, and the stability is much higher than that of the conventional CuLi reference.

[0100] Example 2

[0101] A three-electrode battery I is obtained by using a lithium plating and charge adjustment method for a three-electrode battery similar to that of Example 1, except that step (4) is not performed in this example and the rest are the same.

[0102] The potential stability of the stable reference electrode A2 obtained in this embodiment is reduced, but it is still better than the conventional CuLi reference. The stable reference system obtained by this method is subjected to 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C charging tests in sequence, and the charge of the AB battery is adjusted to 40% SOC. The voltage of AA2 changes from about 40 to 70 mV before the test to about 20 to 60 mV, and the change range is less than 40 mV.

[0103] This shows that the static potential stability of this method is still higher than that of the conventional CuLi reference, and it can be used for short-term monitoring of the positive and negative electrode potentials in situations where efficiency needs to be improved.

[0104] Comparative Example 1

[0105] A lithium plating and charge adjustment method for a three-electrode battery is similar to that of Example 1, except that the effective area of ​​the material particles of the positive electrode is kept unchanged, and the effective area of ​​the material particles of the lithium iron phosphate electrode is adjusted to be the same as the effective area of ​​the material particles of the positive electrode.

[0106] The rest are the same, and a three-electrode battery II is obtained.

[0107] The stable reference system obtained by this comparative example was tested with 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C charging, and the charge of the AB battery was adjusted to 40% SOC. The AA2 voltage changed from about -1mV before the test to about 5mV, with a change of less than 6mV. This shows that the static potential stability of this method is much higher than that of the conventional CuLi reference, but the charge and discharge potential fluctuates to a certain extent during the test. It can be used in situations where the potential of the positive and negative electrodes of a battery needs to be monitored for a long time at various SOCs.

[0108] Comparative Example 2

[0109] The experiment was conducted using the CuLi reference of the prior art. The specific structure of the three-electrode battery and the lithium plating method are as follows:

[0110] (1) The structure of the three-electrode battery is as follows:

[0111] The three-electrode battery comprises a battery housing and a laminated electrode group, a copper wire, a diaphragm and an electrolyte encapsulated in the battery housing, the laminated electrode group comprises a positive electrode and a negative electrode, the number of layers of the negative electrode is 8, the number of layers of the positive electrode is 7, and the positive electrode and the negative electrode are alternately stacked to form the laminated electrode group;

[0112] The copper wire is located between the positive electrode and the negative electrode. Any two of the positive electrode, the negative electrode and the copper wire are separated by a diaphragm soaked in electrolyte. The effective area of ​​the material particles of the positive electrode is 34cm 2 ;

[0113] The positive electrode, the negative electrode and the copper wire form a positive electrode tab, a negative electrode tab and a reference tab outside the battery shell respectively;

[0114] The capacity of the two-electrode battery is about 3Ah; the diameter of the copper wire is 50μm.

[0115] (2) The copper wire is plated with lithium by constant current lithium plating (current intensity is 80 μA, time is 60 min), the specific method is as follows:

[0116] The negative electrode I of the external power source is connected to the copper wire, and the positive electrode I of the external power source is connected to the positive electrode and the negative electrode in sequence, and DC charging is performed. The charging process steps are continuous lithium plating, and the positive plating is maintained for 10 minutes and the negative plating is maintained for 10 minutes. A three-electrode battery is obtained.

[0117] After the three-electrode battery obtained in this comparative example was fixed in capacity, it was tested at 0.33C charging. The negative electrode potential shifted by more than 50mV, and some even shifted by more than 50mV during the fixed capacity process, indicating poor stability.

[0118] The present invention Figure 4The relationship between the positive potential and time of the three-electrode battery of Example 1 of the present invention is provided in the following example at 0.05 / 0.1 / 0.33 / 0.5 / 1 / 1.5C rates. Figure 4 It can be seen that the static positive parameter potential of the three-electrode battery of Example 1 has a small change range and high stability.

[0119] The present invention Figure 5 The negative parameter potential and time curve of the three-electrode battery of Comparative Example 1 of the present invention at a rate of 0.33C is exemplarily provided; Figure 5 In the graph, the horizontal axis represents voltage (in mV), the vertical axis represents time (in s), the yellow line represents the negative electrode potential, and the blue line represents the full battery voltage. Figure 5 It can be seen that the static negative parameter potential of the three-electrode battery in comparative example 1 varies greatly and has poor stability.

[0120] The present invention Figure 6 The negative potential performance test diagram of the three-electrode battery of Comparative Example 1 of the present invention after being charged at a rate of 0.33C is provided as an example. Figure 6 It can be seen that the reference electrode of the three-electrode battery of Comparative Example 1 was damaged during the second discharge cycle.

[0121] It can be seen from the above results that the lithium plating and charge adjustment method of a three-electrode battery provided by the present invention is short in time and improves the stability of the static potential and the dynamic potential; and this method greatly reduces the difference between the potential of the reference electrode group and its theoretical potential, and in the preferred case, the difference is <1mV.

[0122] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A three-electrode battery, comprising a battery housing and a laminate electrode group, a reference electrode group, a diaphragm and an electrolyte encapsulated in the battery housing, characterized in that: The laminated electrode group includes a positive electrode and a negative electrode, the number of layers of the negative electrode is one more than the number of layers of the positive electrode, and the positive electrode and the negative electrode are alternately stacked to form the laminated electrode group; the reference electrode group includes a lithium iron phosphate electrode sheet, a graphite electrode sheet and a copper wire; The lithium iron phosphate pole piece and the graphite pole piece are arranged opposite to each other and are located outside the laminated pole group, and the lithium iron phosphate pole piece is arranged opposite to the negative pole in the laminated pole group; the copper wire is located between the positive pole and the negative pole, or the copper wire is located between the lithium iron phosphate pole piece and the graphite pole piece; Any two of the positive electrode, the negative electrode, the lithium iron phosphate electrode, the graphite electrode and the copper wire are separated by a diaphragm soaked in electrolyte; the effective area of ​​the material particles of the lithium iron phosphate electrode is 10 of the effective area of ​​the material particles of the positive electrode. -6 -1 times.

2. The three-electrode battery according to claim 1, wherein: The thickness of the diaphragm is 8-12 μm; And / or, the copper wire has a diameter of 10-100 μm.

3. The three-electrode battery according to claim 1 or 2, wherein: The positive electrode has a length of 2-12 cm and an area of ​​3-120 cm 2 .

4. The three-electrode battery according to any one of claims 1 to 3, wherein: The number of layers of the positive electrode is 1-50.

5. The three-electrode battery according to any one of claims 1 to 4, wherein: The negative electrode has a length of 2.4-12.5 cm and an area of ​​4.8-145 cm 2 .

6. The three-electrode battery according to any one of claims 1 to 5, wherein: The positive electrode, the negative electrode, the lithium iron phosphate electrode sheet, the graphite electrode sheet and the copper wire respectively form a positive electrode tab, a negative electrode tab, a first reference tab, a second reference tab and a third reference tab outside the battery housing.

7. A method for lithium plating and charge adjustment of a three-electrode battery, characterized in that: The method comprises the following steps: (1) connecting the positive electrode I and the negative electrode I of the external power source to the positive electrode and the negative electrode of the three-electrode battery respectively to perform a first charge adjustment, and controlling the conditions so that the state of charge (SOC) of the positive electrode and the negative electrode is 5-95%; The three-electrode battery is a three-electrode battery according to any one of claims 1 to 6; (2) plating the copper wire with lithium; (3) Connecting the positive electrode I and the negative electrode I of the external power supply to the lithium iron phosphate electrode and the graphite electrode of the three-electrode battery respectively to perform a second charge adjustment to obtain a three-electrode battery I; controlling the conditions so that the state of charge (SOC) of the lithium iron phosphate electrode and the graphite electrode is 5-95%.

8. The method according to claim 7, wherein: In step (2), the lithium plating treatment is performed by constant current lithium plating, and the conditions of the lithium plating treatment include: current intensity of 50-100 μA, and time of 40-80 min.

9. The method according to claim 7 or 8, wherein: The method also includes: connecting the positive electrode I and the negative electrode I of the external power supply to the lithium iron phosphate electrode and the negative electrode in the three-electrode battery I respectively to perform a third charge adjustment to obtain a three-electrode battery II; controlling the conditions so that the charge state SOC of the lithium iron phosphate electrode and the negative electrode is 5-95%.

10. The method according to claim 9, wherein: The conditions of the first load adjustment, the second load adjustment and the third load adjustment each independently include: a ratio of 0.02-1.5C, and a time of 10-180 minutes.

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