CN108539124A - With the secondary cell and preparation method thereof for mending lithium electrode - Google Patents

Abstract

The present invention relates to the secondary cell and preparation method thereof for mending lithium electrode.According to an exemplary embodiment, a kind of secondary cell may include：Positive plate and negative plate, are isolated from each other by diaphragm；And at least one benefit pole piece comprising lithium active layer, at least one benefit pole piece are kept apart also by diaphragm and the positive plate and negative plate.The secondary cell of the present invention can realize high capacity, and with pole piece is mended so as to supplement elemental lithium to negative plate or positive plate for the first time or in cyclic process, to realize high coulombic efficiency, and improve cycle characteristics.

Description

Secondary battery with lithium-supplementing electrode and preparation method thereof

technical field

The present invention generally relates to the field of new energy, and more particularly, relates to a secondary battery with a lithium-supplementing electrode, which can supplement lithium elements to the negative electrode sheet or the positive electrode sheet of the secondary battery during the first or cycle process, and also relates to A method of making such a secondary battery with a lithium-replenishing electrode.

Background technique

In recent years, the rapidly developing electric vehicle and energy storage industries have put forward higher requirements for the energy density, cost, cycle and safety of secondary batteries represented by lithium-ion batteries and sodium-ion batteries. Taking lithium-ion batteries as an example, conventional lithium-ion batteries mainly use graphite negative electrodes, and the theoretical capacity of graphite negative electrodes is 372mAh/g. The capacity of g is close to the limit of theoretical capacity. In order to achieve higher energy density and power density, people began to pay attention to new negative electrode materials, such as non-graphitizable carbon materials, silicon negative electrodes, silicon-carbon composite negative electrodes, silicon oxide negative electrodes, and silicon oxide silicon carbon composite negative electrodes. However, these materials have serious problems such as high irreversible capacity and low initial Coulombic efficiency, which easily lead to a significant decline in the capacity of lithium-ion batteries.

At present, in order to solve the problem of low coulombic efficiency of lithium-ion battery anode materials for the first time, researchers have proposed chemical reduction methods, artificial SEI (Solid Electrolyte Interface, solid electrolyte interface) membrane methods, and electrochemical pre-lithiation methods. The pre-lithiation method is the most direct method to solve the problem of low initial coulombic efficiency of lithium-ion battery anode materials.

In Chinese patent application No. 200480021793.X, a method of directly contacting lithium powder with electrode materials, and then realizing pre-lithiation of electrode materials through galvanic reaction is disclosed. However, this method is prone to produce "dead lithium", and the reaction is violent, which easily leads to the destruction of the structure of the electrode material, and it is difficult to form a dense and stable SEI film, which ultimately reduces the cycle performance of the electrode material. In addition, lithium powder is a relatively dangerous material and is easy to burn. Therefore, the process conditions for implementing the pre-lithiation method are relatively harsh, resulting in an increase in cost.

In Chinese Patent Application No. 201210573270.2, in view of the problem of large lithiation current, a low-temperature liquid injection method is disclosed, which allows the primary battery reaction to be carried out at a lower temperature to control the lithium intercalation speed of the material, thereby improving the first time of the material. While improving Coulombic efficiency and capacity, the cycle performance of the material is improved. However, this method requires low-temperature operation, the process is relatively complicated, and the cost is high. Moreover, the viscosity of the electrolyte at low temperature increases, and the liquid injection operation is difficult.

In Chinese patent application No. 201410839836.0, metal lithium is coated on the positive and negative electrodes, and then coated with a solid electrolyte to reduce the reaction speed, but the manufacturing process is complicated and it is not easy for large-scale industrial production.

Nano-silicon and carbon composite negative electrodes or silicon oxide and carbon composite negative electrodes are considered to be the third-generation negative electrodes, and the theoretical capacity can reach 4200mAh/g. Using this type of negative electrode can increase the energy density of the battery to 300wh/kg, but the first cycle and cycle efficiency of this type of negative electrode are lower than that of the positive electrode. To achieve a long cycle, the battery still needs to be replenished with lithium.

Contents of the invention

One aspect of the present invention is to provide a novel secondary battery, which can achieve high capacity, and has a lithium supplementary pole piece so that it can replenish lithium elements to the negative pole piece or positive pole piece of the secondary battery during the first or cycle process, to achieve high Coulombic efficiency.

According to an exemplary embodiment, a secondary battery may include: a positive electrode sheet and a negative electrode sheet separated from each other by a separator; and at least one lithium-replenishing electrode sheet including a lithium active layer, the at least one lithium-replenishing electrode sheet Also separated from the positive and negative electrode sheets by a separator.

In some examples, the lithium active layer includes one or more of pure metal lithium, lithium-silicon alloy, lithium-aluminum alloy, lithium-boron alloy, and lithium-magnesium alloy.

In some examples, the secondary battery further includes: a casing for accommodating the positive electrode sheet, negative electrode sheet, lithium supplementary electrode sheet, and separator; a positive electrode tab connected to the positive electrode sheet and extending out of the casing a negative electrode tab connected to the negative electrode piece and extending out of the casing; and a lithium-supplementing tab connected to the lithium-supplementing pole piece and extending out of the casing. The lithium-supplementing tab may include nickel or aluminum.

In some examples, a plurality of positive electrode sheets, separators, and negative electrode sheets are stacked to form a stack, and the at least one lithium-supplementing electrode sheet is disposed on one of the left, right, front, rear, and bottom sides of the stack or more, the positive tab, the negative tab and the lithium-supplementing tab are disposed at the top side of the stack.

In some examples, when the positive tab is electrically connected to the lithium-supplementing tab, the lithium-supplementing pole piece replenishes lithium to the positive pole piece.

In some examples, when the negative electrode tab is electrically connected to the lithium-replenishing tab, the lithium-replenishing pole piece can replenish lithium to the negative pole piece.

In some examples, the lithium-supplementing pole piece further includes a current collector, and the lithium active layer is disposed on the current collector. The current collector may include one or more of copper foil, nickel foil, steel foil, and carbon film.

In some examples, the secondary battery includes a liquid lithium ion battery, a solid lithium ion battery, a liquid metal lithium battery, a solid metal lithium battery, or a sol lithium ion battery.

In some examples, the secondary battery is a sodium ion or metal sodium battery, and the lithium-supplementing pole piece is a sodium-supplementing pole piece.

According to another exemplary embodiment, a method for preparing a secondary battery may include: preparing a positive electrode sheet, a negative electrode sheet, and a separator; preparing a lithium supplementary electrode sheet including a lithium active layer; The pole piece and the diaphragm are assembled into an electric core, wherein the positive pole piece, the negative pole piece and the lithium-supplementing pole piece are separated from each other by the diaphragm; and the electric core is packaged into a casing.

In some examples, the method further includes: welding the positive tab, the negative tab, and the lithium-replenishing tab to the positive electrode piece, the negative electrode piece, and the lithium-filling electrode piece respectively. Wherein, after the packaging step, the positive tab, the negative tab and the lithium-supplementing tab respectively extend from the battery core to the outside of the housing.

In some examples, the method further includes: performing a formation step of a secondary battery; and electrically connecting the positive tab or the negative tab to the lithium-supplementing tab so as to charge the positive or negative tab through a discharge process. Lithium supplementation.

Other features and advantages of the invention will become apparent from the following description of exemplary embodiments.

Description of drawings

The drawings schematically show exemplary embodiments of the invention. It should be understood that the drawings are not drawn to scale.

FIG. 1 shows a schematic structural diagram of a secondary battery in the prior art.

FIG. 2 shows a schematic structural view of a secondary battery according to an exemplary embodiment of the present invention.

FIG. 3 shows a schematic structural view of the lithium-supplementing pole piece included in the secondary battery of FIG. 2 .

FIG. 4 illustrates a flowchart of a method of manufacturing a secondary battery according to an exemplary embodiment of the present invention.

Detailed ways

FIG. 1 shows a schematic structural diagram of a secondary battery 100 in the prior art. As shown in FIG. 1 , the secondary battery 100 includes a case 110 and cells 120 accommodated in the case. The cell 120 includes a stack of a positive electrode sheet 122 , a separator 121 and a negative electrode sheet 124 , wherein the positive electrode sheet 122 and the negative electrode sheet 124 are separated from each other by the separator 121 . The stack can have various configurations, such as multiple sheet-like layers stacked one on top of the other, or multiple layers bent or rolled into a cylindrical or flat shape, and the like. The positive tab 122 extends out of the housing 110 through the positive tab 132 , and the negative tab 124 extends out of the housing 110 through the negative tab 134 , so as to perform charging and discharging operations. The case 110 may also have an opening (not shown) for injecting electrolyte. It should be understood that various structures, materials, etc. of the secondary battery 100 in the prior art are known in the art, so they are only briefly described here and will not be described in detail one by one.

FIG. 2 shows a schematic structural diagram of a secondary battery 200 according to an embodiment of the present invention. As shown in FIG. 2 , the battery 200 also includes a casing 210 and a cell 220 housed in the casing 210 . The shell 210 can be a flexible shell, for example made of plastic film, etc., or a rigid shell, for example made of metal or alloy such as aluminum and steel. The housing 210 can be insulating or conductive. When the housing 210 is conductive, the pole piece should be isolated from the housing by a diaphragm. In some embodiments, one of the positive electrode sheet, the negative electrode sheet and the lithium supplementary electrode sheet described below can also be electrically connected to the conductive casing 210, so that the conductive casing 210 can be used as a connection terminal thereof, as is often the case in the prior art Use the battery case as the negative terminal. At this time, one tab described below may be omitted. The housing 210 may have various shapes, such as a cylindrical shape, a flat shape, a cubic shape, etc., to suit the outline of a battery compartment of an electronic device to which it is applied.

The cell 220 may include a stack of a positive electrode sheet 222 , a negative electrode sheet 224 and a separator 221 , wherein the positive electrode sheet 222 and the negative electrode sheet 224 are separated from each other by the separator 221 . The positive electrode sheet 222, the negative electrode sheet 224 and the separator 221 may be the same as those in the prior art. The difference from the secondary battery in the prior art is that the battery cell 220 also includes a lithium-supplementing pole piece 226 . The lithium-supplementing pole piece 226 can be flexibly arranged in the casing 210 . For example, the lithium-supplementing pole piece 226 may be disposed on one or more sides of the stack formed by the positive pole piece, the negative pole piece and the separator, such as the left side, the right side, the front side, the rear side and the bottom side. For another example, the lithium-supplementing electrode sheet 226 may also be disposed in a stack formed by the positive electrode sheet, the negative electrode sheet, and the separator. That is to say, the lithium-supplementing electrode sheet 226 can be stacked or wound together with the positive electrode sheet, the negative electrode sheet and the separator. In the example of FIG. 2 , two lithium-replenishing pole pieces 226 are respectively arranged on the left and right sides of the stack formed by the positive pole piece, the negative pole piece and the separator. The lithium-supplementing pole piece 226 can also be separated from the positive pole piece 222 and the negative pole piece 224 through the diaphragm 221 , and can also be separated from the casing 210 through the diaphragm 221 . Although not shown, it should be understood that a plurality of positive electrode sheets 222 may be integrated, or electrically connected to each other through a connecting circuit; a plurality of negative electrode sheets 224 may be integrated, or electrically connected to each other through a connecting circuit; Sheets 226 may also be integral, or electrically connected to each other by connecting circuits.

The positive electrode sheet 222 and the negative electrode sheet 224 may be the same as those used in the prior art. For example, the positive electrode sheet 222 may include lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium-rich layered oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate , lithium nickel phosphate, lithium iron manganese phosphate, iron phosphate, manganese phosphate, cobalt phosphate, nickel phosphate, lithium iron silicate, lithium manganese silicate, lithium cobalt silicate, lithium nickel silicate, iron silicate, manganese silicate, Cobalt silicate, nickel silicate, and any combination thereof. In some other embodiments, the material forming the positive plate 222 may also be selected from manganese dioxide, iron sulfide, manganese sulfide, cobalt sulfide, nickel sulfide, titanium sulfide, iron sulfate, iron phosphate, sulfur carbon and vanadium oxide, and any combination of them. Examples of materials that can be used to form the negative electrode sheet 224 include, but are not limited to, natural graphite, artificial graphite, soft carbon, hard carbon, materials containing silicon, tin, germanium, zinc, aluminum, boron, magnesium, transition metal oxides, Transition metal sulfide, transition metal fluoride, transition metal nitride, transition metal phosphide, wherein the transition metal can be selected from one of Cr, Cu, Fe, Co, Ni, Nb, V, Mo, W and Ru one or more species.

The diaphragm 221 may include a polymer film. Examples of polymeric materials used to form the diaphragm 221 include, but are not limited to, polypropylene, polyethylene, ethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethylmethacrylate ester, polyacrylonitrile, polyimide, polyetherimide, polycarbonate, polyaramid, cellulose, and any combination thereof. In some embodiments, the thickness of the membrane 221 may be in the range of 6-60 μm, preferably in the range of 6-25 μm. In some embodiments, the separator 221 may be porous to facilitate the circulation of the electrolyte, for example, the separator 221 may have a porosity of 30%-90%.

During the charging and discharging process of the secondary battery 200 , an electron channel is formed between the positive electrode sheet 222 and the negative electrode sheet 224 , and the lithium element transfers back and forth between the positive electrode sheet 222 and the negative electrode sheet 224 . Since "dead lithium" may be formed during the cycle, the capacity of the secondary battery 200 decreases. The present invention can supplement lithium element to the positive electrode sheet 222 and the negative electrode sheet 224 by providing the lithium replenishing electrode sheet 226 . FIG. 3 shows a schematic structural diagram of the lithium-supplementing pole piece 226 . As shown in FIG. 3 , the lithium supplementary pole piece 226 may include a current collector 227 and a lithium active layer 228 formed on the current collector 227 . The current collector 227 can be one or more of copper foil, nickel foil, steel foil, and carbon film, and its thickness can be, for example, 1 μm˜20 mm, preferably 2˜8 μm. Current collector 227 may be a porous or dense foil. The lithium active layer 228 may include metal lithium, lithium-silicon alloy, lithium-aluminum alloy, lithium-boron alloy, lithium-magnesium alloy and other materials, which may be formed on the current collector 227 in the form of strips, strips, rings or dots. The thickness of the lithium active layer 228 may be, for example, 20 μm˜1 mm, preferably 20˜700 μm. In some embodiments, if the lithium active layer 228 has sufficient mechanical strength, the current collector 227 may also be omitted.

Although FIG. 3 shows that a lithium active layer 228 is formed on one surface of the current collector 227, it will be understood that in other embodiments, a lithium active layer may also be formed on both upper and lower surfaces of the current collector 227. 228.

Continuing to refer to FIG. 2 , the secondary battery 200 also includes a positive tab 232, a negative tab 234, and a lithium-filling tab 236, which are respectively connected to the positive pole piece 222, the negative pole piece 224, and the lithium-filling pole piece 236, and extend to the casing 210, so as to perform charging and discharging and lithium replenishment operations on the secondary battery 200, which will be described in detail later. The positive tab 232 and the negative tab 234 may be the same as those in the prior art. The lithium-supplemented tab 236 may include nickel or aluminum tab, for example.

The secondary battery 200 shown in FIG. 2 may be various secondary batteries, such as a liquid lithium ion battery, a solid lithium ion battery, a liquid metal lithium battery, a solid metal lithium battery, or a sol lithium ion battery. When the secondary battery 200 is a liquid battery, the casing 210 may further include an electrolyte solution to infiltrate the positive electrode sheet 222 , the negative electrode sheet 224 and the lithium supplementary electrode sheet 226 .

The operation of the secondary battery 200 is described below. Like the prior art secondary battery, by connecting the positive tab 232 and the negative tab 234 to an external device, charging and discharging operations can be performed, which will not be described in detail here. Connect the lithium-replenishing tab 236 to the positive tab 232 or the negative tab 234, and then the lithium-filling operation can be performed on the positive tab 222 or the negative tab 224. For example, when the lithium supplementary tab 236 is connected to the positive tab 232 , a lithium ion path is formed between the positive pole piece 222 and the lithium supplementary pole piece 226 . Through the discharge reaction, the lithium metal on the lithium supplementary electrode sheet 226 loses electrons, becomes lithium ions, and migrates to the positive electrode sheet 222 to form a lithium compound. When the lithium supplementary tab 236 is connected to the negative tab 234 , a lithium ion path is formed between the negative pole piece 224 and the lithium supplementary pole piece 226 . Through the discharge reaction, the lithium metal on the lithium supplementary electrode sheet 226 loses electrons, becomes lithium ions, and migrates to the negative electrode sheet 224 to form lithium compounds such as LixC ₆ (in the case of a commonly used graphite negative electrode).

It can be understood that the lithium replenishment operation to any one of the positive electrode sheet 222 and the negative electrode sheet 224 can be carried out at any time, for example, when the secondary battery 200 is cycled for the first time, or during the cycle; when charging, or when discharging ,and many more. Preferably, for example, when the charging of the secondary battery 200 is completed, lithium elements are intercalated in the negative electrode. At this time, lithium ions embedded in the negative electrode may be insufficient due to the consumption of lithium elements or the formation of “dead lithium”, and lithium ions may be added to the negative electrode sheet 224 at this time. For another example, when the discharge of the secondary battery 200 is completed, all lithium elements migrate to the positive electrode side. At this time, the lithium ions migrating to the positive electrode may not be sufficient, and lithium ions can be supplemented to the positive electrode sheet 222 . Certainly, as mentioned above, it is also possible to replenish lithium to the positive electrode sheet 222 during charging, or to replenish lithium to the negative electrode sheet 224 during discharging. In the above process of lithium supplementation, in order to control the speed of lithium supplementation, the discharge process can be controlled, and lithium supplementation with constant current or constant voltage can be used.

The amount of lithium supplementation can be determined through experiments in advance. For example, the Coulombic efficiency of the positive half-cell can be measured to calculate the amount of lithium deactivated per cycle, and the Coulombic efficiency of the negative half-cell can be measured to calculate the amount of lithium deactivated per cycle, the difference between the two is The theoretical value of the amount of lithium that needs to be replenished per cycle. Considering the actual efficiency in the process of lithium supplementation, the actual amount of lithium supplemented may be greater than the theoretical value. On the other hand, when too much lithium is added, lithium precipitation may occur, causing safety problems, so the actual amount of lithium added is preferably less than the theoretical value. In some embodiments, the amount of lithium actually supplemented may be in the range of 0.5-5 times of the theoretical value. The present inventors have found that, considering safety issues such as lithium supplementation efficiency and lithium precipitation, preferably, the amount of lithium actually supplemented can be in the range of 0.6 to 2.5 times the theoretical value, so as to achieve good battery performance and ensure safety.

FIG. 4 shows a flowchart of a method 300 of manufacturing a secondary battery according to an exemplary embodiment of the present invention. As shown in FIG. 4 , the method 300 may start at step S310 , preparing a positive electrode sheet, a negative electrode sheet and a separator. As mentioned above, these elements can be the same as those in the prior art, so the preparation process thereof will not be described again here. Then in step S320, the lithium-supplementing pole piece of the present invention can be prepared. The process of preparing the lithium-replenishing pole piece may include forming a lithium active layer on the current collector by coating, rolling, etc. to form a pole piece, and then cutting the pole piece into a lithium-supplementing pole piece of a desired shape and size, and A baking process may also be included to obtain dry pole pieces. Then in step S330, the positive electrode sheet, the negative electrode sheet, the lithium supplementary electrode sheet and the separator can be assembled into a battery cell. The assembly process may include sequentially stacking the positive electrode sheet, the negative electrode sheet, the lithium supplementary electrode sheet, and the separator to form a stacked structure, and may also include winding each electrode sheet and separator into a desired shape. As mentioned above, the lithium-supplementing electrode sheet can be located outside the stack of the positive electrode sheet, negative electrode sheet, and separator, or it can be located in the stack. In step S340, the tabs may be welded to the battery core. Specifically, the positive tab is welded to the positive pole piece, the negative pole tab is welded to the negative pole piece, and the lithium-supplementing tab is welded to the lithium-supplementing pole piece. In this step, if the cell includes a plurality of individual positive electrodes, a plurality of individual negative electrodes, and a plurality of individual lithium supplementary electrodes, it may also include welding together a plurality of individual positive electrodes through a connecting circuit , welding together a plurality of individual negative electrode pieces, and welding together a plurality of individual lithium-supplementing electrode pieces.

Next, in step S350, the battery cells may be packaged into the casing to form a secondary battery, and the tabs extend out of the casing to facilitate connection to external devices. In this step, if the secondary battery is a liquid battery, injecting electrolyte solution into the casing is also included. In this way, the assembly of the secondary battery is basically completed, but in order to make the manufactured secondary battery work normally, it needs to be formed in step S360. The formation step S360 can be the same as the formation step of the prior art, and part of the lithium may be consumed in this step, so the lithium replenishment step S370 can also be included to replenish lithium to the positive and/or negative electrodes of the secondary battery, as described above like that. In this way, the manufacture of the secondary battery is completed, and the formed secondary battery can be directly used by users.

Compared with the prior art, the secondary battery of the present invention has many advantages. For example, compared with the prior art, the secondary battery of the present invention has fewer structural changes, and only adds lithium-supplementing pole pieces and lithium-supplementing tabs. By properly setting the lithium-supplementing tabs, the secondary battery of the present invention can be fully compatible with existing electronic equipment. However, by appropriately improving the charging equipment, for example, providing a circuit connected to the lithium-supplementing tab, lithium can be easily supplemented to improve the performance of the secondary battery. The process of manufacturing a secondary battery only needs to ensure that the lithium-supplemented pole piece does not react with the environment, which is achieved by keeping the dew point of the environment below -40 degrees. Other aspects are the same as the preparation of existing lithium-ion batteries. Therefore, this can greatly reduce the manufacturing cost.

In existing secondary batteries, if lithium sheets are directly bonded on the surface of the negative electrode, or lithium powder is mixed in the negative electrode, when the electrolyte is added, the in-situ discharge chemical reaction is very strong, which will lead to the formation of SEI on the surface of the negative electrode. It is uncontrollable and directly affects the cycle characteristics of the battery. However, in the secondary battery of the present invention, the formation process in the first week after the electrolyte is injected is the same as the formation process without metal lithium, and the formation of SEI is controllable, which is beneficial to improve the cycle characteristics of the battery. Lithium supplementation is performed after formation, and the lithium supplementation process can be controlled by controlling the current or voltage, which is conducive to further improving the cycle characteristics of the battery.

The invention also has the advantage that the lithium is stored on the lithium-supplementing pole piece and does not participate in the normal charging and discharging process of the battery. In each cycle, only a small amount of lithium needs to be supplemented, and such lithium supplementation can reduce the probability of lithium precipitation at the negative electrode. Moreover, the lithium on the lithium-replenishing pole piece only comes out, and no lithium dendrites will appear on the lithium-supplementing pole piece, which greatly improves the safety of the battery.

Some examples of the present invention are described below, and compared with comparative examples to illustrate some effects of the present invention.

Example 1

A 1Ah lithium cobaltate/graphite soft-packed battery cell is prepared by stirring, coating, rolling, pole piece cutting, baking pole piece, and lamination. The capacity ratio N/P of the negative electrode material and the positive electrode material is about 1. After winding a layer of separator, place a lithium supplementary pole piece on the left side of the dry cell to make a lithium supplementary dry battery cell. The lithium supplementary pole piece includes a copper foil current collector and a metal lithium layer formed on the current collector. The tabs are welded for lithium-supplementing dry cells, wherein the tabs for lithium-supplementing are nickel tabs, then packaged and injected with electrolyte to form a secondary battery. Cycling at 0.5°C, replenishing lithium with a capacity of 0.03Ah to the positive electrode after charging in the first week, the efficiency in the first week is 95%. After subsequent weekly charging, lithium with a capacity of 0.001425 Ah was added to the graphite negative electrode. After 20 weeks of cycling, the Coulombic efficiency is 99.95%, and the capacity retention rate is 94%.

Example 2

A 1Ah lithium cobaltate/silicon negative electrode soft-packed battery is prepared by stirring, coating, rolling, pole piece cutting, baking pole piece, and lamination. The N/P ratio is about 1.1. After winding a layer of separator, On the left side of the dry cell, a lithium-aluminum alloy strip pole piece with a steel mesh current collector nickel tab is placed to make a lithium-supplemented dry cell. The tabs are welded for lithium-supplementing dry cells, and packaged into a casing to form a secondary battery. Cycling was performed at 0.5°C, and 0.1Ah of lithium was added to the negative electrode after the first week of charging. After subsequent weekly charging, 0.14Ah capacity lithium was added to the silicon negative electrode. After 20 weeks of cycling, the Coulombic efficiency is 99.87%, and the capacity retention rate is 87.5%.

Comparative example 1

A 1Ah lithium cobaltate/silicon carbon soft-packed battery cell was prepared by stirring, coating, rolling, pole piece cutting, baking pole piece, and lamination, with an N/P ratio of 1, and assembled into a secondary battery. Cycling was performed at 0.5°C. The efficiency in the first week was 82.31%, the Coulombic efficiency was 99.38% after 20 cycles, and the capacity retention rate was 67.24%.

By comparing the above examples 1-2 and comparative example 1, it can be seen that the secondary battery of the present invention has better coulombic efficiency and cycle characteristics than the secondary battery of the prior art.

Several embodiments of the invention are described above in relation to lithium ion/lithium metal batteries, but it should be understood that the principles of the invention are also applicable to sodium ion/sodium metal batteries, which are similar in all respects to lithium batteries. At this time, the lithium-supplementing pole piece may be called a sodium-supplementing pole piece, which includes a sodium active layer. Since the deposition potential of metal sodium is higher than that of lithium, the current collector of aluminum material, such as aluminum foil, aluminum strip, aluminum mesh, etc., can be used for sodium supplementation pole piece. Aluminum tabs can also be used for sodium supplementation tabs. In other words, it should be understood that throughout this specification, when lithium is mentioned, examples of sodium should also be covered.

The present invention is described above with reference to the exemplary embodiments, but the present invention is not limited thereto. It will be apparent to those skilled in the art that various changes and modifications in form and details can be made without departing from the scope and spirit of the invention. The scope of the present invention is defined only by the appended claims and their equivalents.

Claims (11)

1. a kind of secondary cell, including：

Positive plate and negative plate, are isolated from each other by diaphragm；And

At least one benefit pole piece comprising lithium active layer, at least one benefit pole piece is also by diaphragm and the anode Piece and negative plate are kept apart.

2. secondary cell as described in claim 1, wherein the lithium active layer includes pure metal lithium, Li-Si alloy, the conjunction of lithium aluminium It is one or more in gold, lithium boron alloy and lithium magnesium alloy.

3. secondary cell as described in claim 1, further includes：

Shell, for accommodating the positive plate, negative plate, mending pole piece and diaphragm；

Anode ear is connected to the positive plate and extends to outside the shell；

Negative electrode lug is connected to the negative plate and extends to outside the shell；And

Lithium electrode ear is mended, the benefit pole piece is connected to and extends to outside the shell.

4. secondary cell as claimed in claim 3, wherein multiple positive plates, diaphragm and negative plate are stacked to a stacking, described One or more of the left side in the stacking, right side, front side, rear side and bottom side place, institute is arranged at least one benefit pole piece It states anode ear, negative electrode lug and mends lithium electrode ear and top sides in the stacking are set.

5. secondary cell as claimed in claim 3, wherein described when the anode ear is electrically connected to the benefit lithium electrode ear It mends pole piece and benefit lithium is carried out to the positive plate, and

When the negative electrode lug is electrically connected to the benefit lithium electrode ear, the benefit pole piece carries out benefit lithium to the negative plate.

6. secondary cell as described in claim 1, wherein the benefit pole piece further includes collector, and the lithium active layer is set It sets on the collector.

7. secondary cell as described in claim 1, wherein the secondary cell include liquid lithium ionic cell, solid-state lithium from Sub- battery, liquid metal lithium battery, solid metallic lithium battery or colloidal sol lithium ion battery.

8. secondary cell as described in claim 1, wherein the secondary cell is sodium ion or metal sode cell, the benefit Pole piece is to mend sodium pole piece.

9. a kind of method preparing secondary cell, including：

Prepare positive plate, negative plate and diaphragm；

Prepare to mend pole piece, the benefit pole piece includes lithium active layer；

The positive plate, negative plate, benefit pole piece and diaphragm are assembled into battery core, wherein the positive plate, negative plate and benefit lithium Pole piece is isolated from each other by the diaphragm；And

The battery core is encapsulated into shell.

10. method as claimed in claim 9, further includes：

Anode ear, negative electrode lug and benefit lithium electrode ear are welded to the positive plate, negative plate and mended in pole piece, wherein in institute After stating encapsulation step, the anode ear, negative electrode lug and benefit lithium electrode ear are extended to from the battery core except the shell respectively.

11. method as claimed in claim 10, further includes：

Execute the chemical conversion step of secondary cell；And

The anode ear or negative electrode lug are electrically connected to the benefit lithium electrode ear, with by discharge process to the positive plate or cathode Piece supplements elemental lithium.