阅读说明：本技术 四电极锂离子电池及其电位测量方法 (Four-electrode lithium ion battery and potential measuring method thereof ) 是由 王振峰 余仲宝 常嵩 王高峰 范兵 于 2019-10-31 设计创作，主要内容包括：本发明公开了一种四电极锂离子电池及其电位测量方法,包括外壳、电芯和电解液,电芯包括N个层叠设置的电极片；主参比电极位于一个隔膜和主参比电极隔膜之间；辅参比电极位于一个隔膜和辅参比电极隔膜之间；主参比电极和辅参比电极之间设有至少一个电极片,辅参比电极为镀锂电极。这种四电极锂离子电池在进行电位测量时,辅参比电极采用测量准确性较高的镀锂电极,镀锂电极在每次测量时仅需要使用一次用来标定主参比电极的电位,而标定正极片和标定负极片的测量工作均由主参比电极完成,从而大幅延长了镀锂电极的使用寿命,避免了镀锂电极由于多次长期使用而过早的出现锂金属消耗的现象。(The invention discloses a four-electrode lithium ion battery and a potential measuring method thereof, wherein the four-electrode lithium ion battery comprises a shell, a battery cell and electrolyte, wherein the battery cell comprises N electrode plates which are arranged in a stacked mode; the main reference electrode is positioned between one diaphragm and the main reference electrode diaphragm; the auxiliary reference electrode is positioned between one diaphragm and the auxiliary reference electrode diaphragm; at least one electrode slice is arranged between the main reference electrode and the auxiliary reference electrode, and the auxiliary reference electrode is a lithium-plated electrode. When the four-electrode lithium ion battery is used for potential measurement, the auxiliary reference electrode adopts a lithium-plated electrode with higher measurement accuracy, the lithium-plated electrode only needs to be used for calibrating the potential of the main reference electrode once when being measured at each time, and the measurement work of calibrating the positive plate and the negative plate is completed by the main reference electrode, so that the service life of the lithium-plated electrode is greatly prolonged, and the phenomenon that the lithium-plated electrode is too early due to long-term use for many times is avoided.)

1. A four-electrode lithium ion battery comprises a shell, an electric core and electrolyte, wherein the electric core and the electrolyte are contained in the shell, the electric core comprises N electrode plates and (N +1) diaphragms, the N electrode plates are stacked, the (N +1) diaphragms are stacked, one electrode plate is arranged between every two adjacent diaphragms, N is a natural number larger than 2, the N electrode plates are alternately arranged, each positive plate comprises a positive current collector and a positive active layer coated on the positive current collector, and each negative plate comprises a negative current collector and a negative active layer coated on the negative current collector; it is characterized by also comprising a main reference electrode group and an auxiliary reference electrode group;

the main reference electrode group is arranged between one electrode plate and one diaphragm, the main reference electrode group comprises a main reference electrode and a main reference electrode diaphragm which are arranged in a stacked mode, and the main reference electrode is located between one diaphragm and the main reference electrode diaphragm;

the auxiliary reference electrode group is arranged between one electrode plate and one diaphragm, the auxiliary reference electrode group comprises an auxiliary reference electrode and an auxiliary reference electrode diaphragm which are arranged in a stacked mode, the auxiliary reference electrode is located between one diaphragm and the auxiliary reference electrode diaphragm, and the auxiliary reference electrode is used for calibrating the potential of the main reference electrode;

at least one electrode plate is arranged between the main reference electrode and the auxiliary reference electrode, and the auxiliary reference electrode is a lithium-plated electrode.

2. The four-electrode lithium ion battery of claim 1, wherein the secondary reference electrode is a lithium-plated copper wire with a diameter of 40-80 μm.

3. The four-electrode lithium ion battery according to claim 2, wherein the auxiliary reference electrode is provided at a middle of the electrode sheet in a length direction thereof, or the auxiliary reference electrode is provided at a middle of the electrode sheet in a width direction thereof.

4. The four-electrode lithium ion battery of claim 2, wherein the preparation method of the lithium-plated copper wire is as follows: soaking a copper wire in a lithium plating electrolyte, plating lithium on the copper wire under the current of 5-10 mu A, and preparing the lithium-plated copper wire after 2-6 h, wherein the diameter of the copper wire is 30-60 mu m.

5. The four-electrode lithium ion battery of claim 1, wherein at least an odd number of the electrode tabs are disposed between the primary reference electrode and the secondary reference electrode, and at least an even number of the electrode tabs are disposed between the primary reference electrode and the secondary reference electrode.

6. The four-electrode lithium ion battery of claim 1, wherein the primary reference electrode is in the form of a sheet, strip, or wire;

the material of the main reference electrode is the same as that of the positive plate, the positive current collector, the negative plate or the negative current collector.

7. The four-electrode lithium ion battery of any one of claims 1-6, further comprising a positive electrode tab, a negative electrode tab, a primary reference electrode tab, and an auxiliary reference electrode tab;

the positive electrode tab is electrically connected with the positive plate, the negative electrode tab is electrically connected with the negative plate, the main reference electrode tab is electrically connected with the main reference electrode, and the auxiliary reference electrode tab is electrically connected with the auxiliary reference electrode;

the positive electrode lug and the negative electrode lug are arranged at one side end of the shell, the main reference electrode lug and the auxiliary reference electrode lug are arranged at the other side end of the shell, and the one side end of the shell and the other side end of the shell are oppositely arranged or adjacently arranged.

8. The four-electrode lithium ion battery of claim 7, wherein the positive electrode tab is a blackened aluminum tab, a gray aluminum tab, a yellow aluminum tab or a white aluminum tab;

the negative electrode tab is a nickel tab with black glue, a nickel tab with gray glue, a nickel tab with yellow glue, a nickel tab with white glue or a nickel tab with copper plating;

the main reference electrode tab is a black-glue-containing aluminum tab, a gray-glue-containing aluminum tab, a yellow-glue-containing aluminum tab, a white-glue-containing aluminum tab, a black-glue-containing nickel tab, a gray-glue-containing nickel tab, a yellow-glue-containing nickel tab, a white-glue-containing nickel tab or a copper-nickel-plated tab;

the auxiliary reference electrode tab is a nickel tab with black glue, a nickel tab with gray glue, a nickel tab with yellow glue, a nickel tab with white glue or a nickel tab with copper plating.

9. The four-electrode lithium ion battery according to any one of claims 1 to 6, wherein the material of the shell is an aluminum plastic film;

the material of the positive active layer is lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, a lithium-rich manganese material or a ternary material;

the material of the negative active layer is natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, graphene, silicon carbide, silicon oxide or lithium titanate;

the diaphragm is a PP, PE/PP/PE three-layer diaphragm, an alumina ceramic coating diaphragm, a boehmite coating diaphragm, a cellulose or non-woven fabric diaphragm;

the main reference electrode diaphragm is a PP, PE/PP/PE three-layer diaphragm, an alumina ceramic coating diaphragm, a boehmite coating diaphragm, a cellulose or non-woven fabric diaphragm;

the auxiliary reference electrode diaphragm is a PP, PE/PP/PE three-layer diaphragm, an alumina ceramic coating diaphragm, a boehmite coating diaphragm, a cellulose or non-woven fabric diaphragm.

10. The potential measurement method of the four-electrode lithium ion battery according to any one of claims 1 to 9, characterized by comprising the following steps:

measuring the potential difference of the positive plate as V1 with the main reference electrode, measuring the potential difference of the negative plate as V2 with the main reference electrode, and measuring the potential difference of the main reference electrode calibrated with the auxiliary reference electrode as V3; and

and the potential difference of the positive plate is calibrated by the auxiliary reference electrode is V +, V + is V1+ V3, and the potential difference of the negative plate is calibrated by the auxiliary reference electrode is V-, V-is V2+ V3.

Technical Field

The invention relates to the technical field of secondary batteries, in particular to a four-electrode lithium ion battery and a potential measuring method thereof.

Background

With the application of lithium ion batteries, the research on the material, performance and safety problems of the lithium ion batteries is more and more, and in order to better research the positive and negative electrode performances of the lithium ion batteries, a reference electrode is often introduced, and the potential of the positive electrode or the negative electrode with respect to the reference electrode is respectively tested by taking the reference electrode as a standard. Therefore, the performances of battery cycle, high and low temperature charge and discharge, rate charge and discharge and the like can be researched from the internal reaction mechanism of the battery. The method has very important guiding significance in battery structure design, pole piece design, anode-cathode ratio, material collocation, electrolyte component optimization and the like.

At present, a better measurement method is mainly characterized in that a lithium-plated metal sheet (wire) is arranged between membranes and serves as a reference electrode to be used as a three-electrode system for extracting the potential of the positive electrode and the negative electrode of the battery and comparing the potential with the potential of the reference electrode, so that the potential change of the positive electrode and the negative electrode in the electrochemical reaction process is obtained. The lithium-plated metal sheet (wire) is used as a reference electrode and has high measurement accuracy, however, the lithium metal is consumed and dissolved under the long-time work of the lithium metal as the reference electrode, so that the measurement service life of a measurement system using the reference electrode is short.

Disclosure of Invention

Based on this, it is necessary to provide a four-electrode lithium ion battery with long service life.

In addition, it is necessary to provide a potential measuring method of the four-electrode lithium ion battery.

A four-electrode lithium ion battery comprises a shell, an electric core and electrolyte, wherein the electric core and the electrolyte are contained in the shell, the electric core comprises N electrode plates and (N +1) diaphragms, the N electrode plates are stacked, the (N +1) diaphragms are stacked, one electrode plate is arranged between every two adjacent diaphragms, N is a natural number larger than 2, the N electrode plates are alternately arranged, each positive plate comprises a positive current collector and a positive active layer coated on the positive current collector, and each negative plate comprises a negative current collector and a negative active layer coated on the negative current collector; the device also comprises a main reference electrode group and an auxiliary reference electrode group;

the main reference electrode group is arranged between one electrode plate and one diaphragm, the main reference electrode group comprises a main reference electrode and a main reference electrode diaphragm which are arranged in a stacked mode, and the main reference electrode is located between one diaphragm and the main reference electrode diaphragm;

the auxiliary reference electrode group is arranged between one electrode plate and one diaphragm, the auxiliary reference electrode group comprises an auxiliary reference electrode and an auxiliary reference electrode diaphragm which are arranged in a stacked mode, the auxiliary reference electrode is located between one diaphragm and the auxiliary reference electrode diaphragm, and the auxiliary reference electrode is used for calibrating the potential of the main reference electrode;

at least one electrode plate is arranged between the main reference electrode and the auxiliary reference electrode, and the auxiliary reference electrode is a lithium-plated electrode.

The potential measuring method of the four-electrode lithium ion battery comprises the following steps:

measuring the potential difference of the positive plate as V1 with the main reference electrode, measuring the potential difference of the negative plate as V2 with the main reference electrode, and measuring the potential difference of the main reference electrode calibrated with the auxiliary reference electrode as V3; and

and the potential difference of the positive plate is calibrated by the auxiliary reference electrode is V +, V + is V1+ V3, and the potential difference of the negative plate is calibrated by the auxiliary reference electrode is V-, V-is V2+ V3.

When the four-electrode lithium ion battery is used for potential measurement, the auxiliary reference electrode adopts a lithium-plated electrode with higher measurement accuracy, the lithium-plated electrode only needs to be used for calibrating the potential of the main reference electrode once when being measured at each time, and the measurement work of calibrating the positive plate and the negative plate is completed by the main reference electrode, so that the service life of the lithium-plated electrode is greatly prolonged, and the phenomenon that the lithium-plated electrode is too early due to long-term use for many times is avoided. Compared with the traditional three-electrode system which takes a lithium-plated metal sheet (wire) as a reference electrode, the four-electrode lithium ion battery has longer measuring service life.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Wherein:

fig. 1 is a schematic structural diagram of a four-electrode lithium ion battery according to an embodiment.

Fig. 2 is a schematic diagram of a structure and an agilent monitoring potential connection when the inside of a battery cell of the four-electrode lithium ion battery shown in fig. 1 is unfolded.

Fig. 3 is a schematic diagram of a potential measurement method of the four-electrode lithium ion battery shown in fig. 1.

Fig. 4 is a charge-discharge curve of the positive electrode-auxiliary reference electrode and the negative electrode-auxiliary reference electrode of the four-electrode lithium ion battery prepared in example 1;

fig. 5 is a charge-discharge curve of the positive electrode-main reference electrode and the negative electrode-main reference electrode of the four-electrode lithium ion battery prepared in example 1;

fig. 6 is a fitted charge-discharge curve of the positive electrode, negative electrode, full cell of the four-electrode lithium ion battery prepared in example 1.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

With reference to fig. 1 and 2, a four-electrode lithium ion battery according to an embodiment includes a housing 10, a battery cell, an electrolyte, a main reference electrode group, and an auxiliary reference electrode group, where the battery cell and the electrolyte are all accommodated in the housing 10, the battery cell includes N electrode sheets and (N +1) separators 20, the (N +1) separators 20 are stacked, the N electrode sheets are stacked, and one electrode sheet is disposed between every two adjacent separators 20.

In general, the (N +1) membranes 20 may be continuous zigzag membranes. In some embodiments, (N +1) membranes 20 may also be cut (N +1) membranes 20.

The N electrode plates are the negative electrode plates 40 and the positive electrode plates 30 which are alternately arranged.

In general, the outermost layer of the negative electrode tabs 40 and the positive electrode tabs 30 that are alternately arranged is preferably the negative electrode tab 40. That is, the negative electrode tabs 40 and the positive electrode tabs 30 alternately arranged may be the negative electrode tabs 40, the positive electrode tabs 30, and the negative electrode tabs 40 sequentially stacked.

The positive electrode sheet 30 includes a positive electrode collector and a positive electrode active layer coated on the positive electrode collector, the negative electrode sheet 40 includes a negative electrode collector and a negative electrode active layer coated on the negative electrode collector, and a separator 20 is disposed between every two adjacent electrode sheets.

N is a natural number greater than 2. Specifically, the specific value of N may be set as desired.

The primary reference electrode set is disposed between one electrode pad and one separator 20, the primary reference electrode set includes a primary reference electrode 52 and a primary reference electrode separator 54 that are stacked, the primary reference electrode 52 being disposed between one separator 20 and the primary reference electrode separator 54.

The auxiliary reference electrode group is arranged between one electrode sheet and one diaphragm 20, the auxiliary reference electrode group comprises an auxiliary reference electrode 62 and an auxiliary reference electrode diaphragm 64 which are arranged in a stacked mode, the auxiliary reference electrode 62 is located between one diaphragm 20 and the auxiliary reference electrode diaphragm 64, and the auxiliary reference electrode 62 is used for calibrating the potential of the main reference electrode 52.

At least one electrode pad is provided between the primary reference electrode 52 and the secondary reference electrode 62, and the secondary reference electrode 62 is a lithium-plated electrode.

When the four-electrode lithium ion battery is used for potential measurement, the auxiliary reference electrode 62 adopts a lithium-plated electrode with higher measurement accuracy, the lithium-plated electrode only needs to be used for calibrating the potential of the main reference electrode 52 once during each measurement, and the measurement work of the calibration positive plate 30 and the calibration negative plate 40 is completed by the main reference electrode 52, so that the service life of the lithium-plated electrode is greatly prolonged, and the phenomenon that the lithium-plated electrode is prematurely consumed due to multiple long-term use is avoided. Compared with the traditional three-electrode system which takes a lithium-plated metal sheet (wire) as a reference electrode, the four-electrode lithium ion battery has longer measuring service life.

In the present embodiment, the auxiliary reference electrode 62 is a lithium-plated copper wire, and the diameter of the lithium-plated copper wire is preferably 40 μm to 80 μm.

Specifically, the lithium-plated copper wire is preferably obtained by lithium-plating an oxygen-free copper wire having a diameter of 30 to 60 μm. More preferably, the diameter of the oxygen-free copper wire is 50 μm or 60 μm.

Generally, the preparation method of the lithium-plated copper wire is as follows: soaking a copper wire (preferably an oxygen-free copper wire) in a lithium plating electrolyte, plating lithium on the copper wire under a current of 5-10 muA, and obtaining the lithium-plated copper wire after 2-6 h.

The lithium plating electrolyte is typically a non-aqueous organic solution of a lithium salt, which also contains small amounts of additives.

The lithium salt is selected from LiPF₆、LiBF₄、LiBOB、LiDFOB、LiCF₃SO₃、LiC(CF₃SO₂)₃At least one of LTFSI and LiFSI. The concentration of the lithium salt is 0.9mol/L to 1.5 mol/L.

The non-aqueous organic solvent is a cyclic carbonate or a chain carbonate, and preferably is at least one of Ethylene Carbonate (EC), Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Acetate (EA), Propyl Acetate (PA), Methyl Propionate (MP), and Ethyl Propionate (EP).

The additive is at least one of negative electrode film forming agents such as Vinylene Carbonate (VC), ethylene vinyl carbonate (VEC) or fluoroethylene carbonate (FEC), and the mass of the additive accounts for 0.1-2% of the total mass of the electrolyte. In other embodiments, other additives with similar functions are also suitable.

Compared with pure lithium metal as a reference electrode, the lithium-plated copper wire does not need an oxygen-free environment (a glove box filled with inert gas and an ultralow-temperature drying box) during preparation, so that the manufacturing cost and the difficulty are greatly reduced.

In other embodiments, the secondary reference electrode 62 may also be other wires plated with lithium, or the secondary reference electrode 62 may also be a sheet of lithium-plated metal, a strip of lithium-plated metal, or the like.

With reference to fig. 1, in the present embodiment, it is preferable that the auxiliary reference electrode 62 be provided at the middle (1/2) in the width direction of the electrode sheet, so that the measurement accuracy of the auxiliary reference electrode 62 can be improved.

The auxiliary reference electrode 62 may be disposed at the middle of the electrode sheet in the length direction, depending on the shape of the battery cell and the battery.

Preferably, at least an odd number of electrode pads are provided between the primary reference electrode 52 and the secondary reference electrode 62. Referring to fig. 2, in the present embodiment, 1 electrode tab is provided between the main reference electrode 52 and the auxiliary reference electrode 62.

In other embodiments, at least an even number of electrode pads may be provided between primary reference electrode 52 and secondary reference electrode 62.

In general, the primary reference electrode 52 may be in the form of a sheet, strip, or wire. Preferably, in the present embodiment, the main reference electrode 52 is in the form of a sheet.

Preferably, the material of the main reference electrode 52 is the same as the positive electrode tab 30, the positive electrode collector, the negative electrode tab 40, or the negative electrode collector. Such an arrangement may avoid changes in the composition of the electrolyte due to partial dissolution of other electrodes of the primary reference electrode 52 during operation.

Returning to fig. 1, the four-electrode lithium ion battery further includes a positive electrode tab 72, a negative electrode tab 74, a primary reference electrode tab 76, and a secondary reference electrode tab 78.

The positive electrode tab 72 is electrically connected with the positive plate 30, the negative electrode tab 74 is electrically connected with the negative plate 40, the main reference electrode tab 76 is electrically connected with the main reference electrode 52, and the auxiliary reference electrode tab 78 is electrically connected with the auxiliary reference electrode 62.

A positive electrode tab 72 and a negative electrode tab 74 are provided at one side end of the case 10, and a primary reference electrode tab 76 and a secondary reference electrode tab 78 are provided at the other side end of the case 10.

In the present embodiment, one side end of the case 10 and the other side end of the case 10 are disposed opposite to each other, that is, the positive electrode tab 72 (and/or the negative electrode tab 74) is disposed opposite to the primary reference electrode tab 76 (and/or the secondary reference electrode tab 78).

In other embodiments, one side end of the housing 10 and the other side end of the housing 10 may be disposed adjacently.

Specifically, the positive tab 72 may be a black gel aluminum tab, a gray gel aluminum tab, a yellow gel aluminum tab, or a white gel aluminum tab.

Specifically, the negative electrode tab 74 may be a black gel nickel tab, a gray gel nickel tab, a yellow gel nickel tab, a white gel nickel tab, or a copper nickel tab.

Specifically, the main reference electrode tab 76 is a black-gel aluminum tab, a gray-gel aluminum tab, a yellow-gel aluminum tab, a white-gel aluminum tab, a black-gel nickel tab, a gray-gel nickel tab, a yellow-gel nickel tab, a white-gel nickel tab, or a copper-nickel plated tab.

Specifically, the auxiliary reference electrode tab 78 may be a black gel nickel tab, a gray gel nickel tab, a yellow gel nickel tab, a white gel nickel tab, or a copper nickel tab.

Specifically, the material of the housing 10 may be an aluminum plastic film.

Specifically, the material of the positive electrode active layer may be lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium manganese phosphate, a lithium manganese rich material, or a ternary material.

Specifically, the material of the negative active layer may be natural graphite, artificial graphite, soft carbon, hard carbon, mesocarbon microbeads, graphene, silicon carbide, silicon oxide, or lithium titanate.

Specifically, the separator 20 may be a PP, PE/PP/PE three-layer separator, an alumina ceramic-coated separator, a boehmite-coated separator, a cellulose or non-woven fabric separator.

Specifically, the primary reference electrode separator 54 may be a PP, PE/PP/PE three-layer separator, an alumina ceramic coated separator, a boehmite coated separator, a cellulose or non-woven fabric separator.

Specifically, the secondary reference electrode membrane 64 may be a PP, PE/PP/PE three-layer membrane, an alumina ceramic coated membrane, a boehmite coated membrane, a cellulose or non-woven fabric membrane.

The invention also discloses a potential measuring method of the four-electrode lithium ion battery, which comprises the following steps:

measuring the potential difference of the positive plate 30 by using the main reference electrode 52 as V1, measuring the potential difference of the negative plate 40 by using the main reference electrode 52 as V2, and measuring the potential difference of the main reference electrode 52 calibrated by using the auxiliary reference electrode 62 as V3; and

the potential difference of the positive plate 30 marked by the auxiliary reference electrode 62 is V +, V + is V1+ V3, and the potential difference of the negative plate 40 marked by the auxiliary reference electrode 62 is V-, V-is V2+ V3.

With reference to fig. 3, the potential measuring method for the four-electrode lithium ion battery can obtain the potentials of the positive plate 30 and the negative plate 40 marked by the auxiliary reference electrode 62 by calibrating the potential difference V3 of the main reference electrode 52 with the auxiliary reference electrode 62, respectively measuring the potential difference V1 of the positive plate 30 by adding the main reference electrode 52, and measuring the potential difference V2 of the negative plate 40 by the main reference electrode 52.

When the main reference electrode 52 and the auxiliary reference electrode 62 are used together, the accurate potential of the main reference electrode 52 can be obtained in real time, and then the potentials of the positive plate 30 and the negative plate 40 are accurately measured through the main reference electrode 52, so that the accurate positive electrode potential and the accurate negative electrode potential can be obtained.

In the potential measurement method of the four-electrode lithium ion battery, the auxiliary reference electrode 62 adopts a lithium-plated electrode with high measurement accuracy, the lithium-plated electrode only needs to be used for calibrating the potential of the main reference electrode 52 once during each measurement, and the measurement work of the calibration positive plate 30 and the calibration negative plate 40 is completed by the main reference electrode 52, so that the service life of the lithium-plated electrode is greatly prolonged, and the phenomenon that the lithium-plated electrode is prematurely consumed due to multiple long-term use is avoided. Compared with the traditional three-electrode system which takes a lithium-plated metal sheet (wire) as a reference electrode, the four-electrode lithium ion battery has longer measuring service life.