CN206401458U - A wound lithium ion battery composite cell and a wound lithium ion battery - Google Patents

Abstract

The utility model is related to a kind of coiled lithium ion battery composite battery core and coiled lithium ion battery, belongs to technical field of lithium ion.Coiled lithium ion battery composite battery core includes pole piece, the pole piece includes positive plate, barrier film, negative plate, the pole piece also includes lithium paper tinsel, and the positive plate, barrier film, negative plate and lithium paper tinsel are stacked and together with winding successively according to the order of " negative plate lithium paper tinsel barrier film positive plate barrier film "；The pole piece winding center is provided with the lithium piece extended along pole piece axis direction or lithium rod.Coiled lithium ion battery composite battery core of the present utility model inside the battery core of coiled battery by adding lithium piece or lithium rod, on the one hand in the centrally disposed supporter of battery core, is conducive to anode ring forming, on the other hand also can carry out benefit lithium to battery core inside.Lithium paper tinsel is set in battery core, the lithium ion of abundance can be provided for the different interlayers inside battery core.

Description

A wound lithium ion battery composite cell and a wound lithium ion battery

technical field

The utility model relates to a winding type lithium ion battery composite electric core and a winding type lithium ion battery, belonging to the technical field of lithium ion batteries.

Background technique

Lithium-ion batteries are widely used in the fields of digital electronics and electric vehicles due to their high energy density, good cycle life, and environmental friendliness. With the development of the market, higher requirements are placed on the energy density of lithium-ion batteries. The main methods to improve the energy density of lithium-ion batteries are: using high-capacity, high-pressure positive and negative electrode materials, using high-voltage electrolytes and optimizing battery design. The study found that improving the first-time efficiency of lithium-ion batteries and thus increasing the gram capacity of positive electrode materials is an effective way to increase the energy density of lithium-ion batteries, and supplementing lithium to the negative electrode is an effective measure to improve the first-time efficiency of lithium-ion batteries.

Invention patent (CN104993098A) discloses a lithium-ion battery, including a positive electrode sheet, a negative electrode sheet, and a separator. The negative electrode sheet includes a negative electrode current collector. The surface of the negative electrode current collector is provided with a negative electrode material coating, and the negative electrode material coating surface is coated with a lithium powder layer. , so as to improve the first-time efficiency of lithium-ion batteries, but the consistency of lithium supplementation with lithium powder is poor, and lithium powder splashes cause safety hazards. Injection is more difficult. Lithium supplementation with lithium strips or sheets is relatively easy to operate. However, in the prior art, the use of lithium sheets for lithium supplementation is mostly aimed at stacked lithium batteries, and it is difficult to achieve uniform lithium supplementation due to the winding structure of wound lithium batteries.

Utility model content

The utility model provides a wound-type lithium-ion battery composite cell capable of realizing uniform lithium supplementation, and a wound-type lithium-ion battery using the above-mentioned composite cell.

The technical solution adopted by the utility model to solve the problems of the technologies described above is as follows:

A wound type lithium-ion battery composite cell, comprising a pole core, the pole core includes a positive electrode sheet, a diaphragm, and a negative electrode sheet, and the polar core also includes a lithium foil, and the positive electrode sheet, the diaphragm, the negative electrode sheet and the lithium foil Stack and wind together in the order of "negative electrode sheet-lithium foil-separator-positive electrode sheet-separator";

A lithium sheet or a lithium rod extending along the axis of the pole core is arranged at the center of the pole core winding.

The length of the lithium sheet or lithium rod is less than the axial length of the pole core.

The width of the lithium foil is smaller than the width of the positive electrode sheet, the width of the positive electrode sheet is smaller than the width of the negative electrode sheet, and the width of the negative electrode sheet is smaller than the width of the diaphragm.

The wound lithium ion battery cell also includes a positive pole tab and a negative pole tab respectively arranged at both ends of the pole core.

The positive electrode sheet includes a positive electrode collector, and the positive electrode lug is welded to the positive electrode collector.

The positive electrode current collector includes a positive electrode central current collector having a network structure and a positive electrode annular current collector which is arranged around the positive electrode central current collector and extends outward along the extension direction of the positive electrode central current collector.

The negative electrode sheet includes a negative electrode collector, and the negative electrode tab is welded to the negative electrode collector.

The negative electrode current collector includes a negative electrode central current collector with a network structure and a negative electrode annular current collector which is arranged around the negative electrode central current collector and extends outward along the extension direction of the negative electrode central current collector.

A winding lithium-ion battery includes a battery case and a cell arranged in the battery case, and the cell is any one of the above-mentioned wound lithium-ion battery composite cells.

The winding-type lithium-ion battery composite battery core of the utility model adds lithium sheets or lithium rods inside the battery core of the winding-type battery. It can replenish lithium inside the cell during charging and discharging. At the same time, combined with the lithium foil on the surface of the negative electrode sheet, the uniformity of lithium supplementation is greatly improved, thereby improving the first-time efficiency of the lithium-ion battery and the uniformity of the lithium ion concentration inside the lithium-ion battery. Setting the lithium foil in the battery can provide sufficient lithium ions for the different layers inside the battery, promote the formation of the SEI film, and improve the cycle performance and rate performance of the battery.

Further, the positive electrode current collector and the negative electrode current collector of the present application adopt a current collector with a network structure in the center, which can shorten the transmission distance of lithium ions between layers and improve its rate performance without reducing the dynamic strength of the current collector.

Description of drawings

Fig. 1 is the structural representation of the winding type lithium-ion battery composite electric core of the present utility model;

Fig. 2 is the side view structure schematic diagram of the winding type lithium-ion battery composite electric core of the present invention;

FIG. 3 is a schematic structural view of the positive current collector of the wound lithium-ion battery composite cell of the present invention.

detailed description

In order to make the technical problems, technical solutions and beneficial effects solved by the utility model easier to understand, the utility model will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

As shown in FIGS. 1-3 , the wound lithium ion battery of the present invention includes a battery case, and the battery case is provided with different battery cases according to different types of batteries. The wound lithium ion battery may be a square wound battery or a cylindrical wound battery. The square wound battery can be a flat pouch battery or a square cylindrical battery. In this embodiment, the battery is a soft-pack battery, and the battery case is packaged with aluminum-plastic film. A wound lithium-ion battery composite cell is packaged in the battery case. The composite battery core is a flat square cylindrical winding battery core, and the radial section of the battery core is rectangular.

The wound-type lithium-ion battery composite cell includes a pole core and tabs arranged at both ends of the pole core. The pole core includes a winding body with a square cylindrical shape and a winding core arranged at the winding center of the winding body. The radial section of the wound body is rectangular, and the winding core is a rectangular lithium sheet 1 . The positive electrode sheet 5, the diaphragm 4, the negative electrode sheet 2, and the lithium foil 3 are stacked and wound together in the order of "negative electrode sheet-lithium foil-separator-positive electrode sheet-separator" from the inside to the outside to form a wound body. The lithium sheet 1 is arranged in the center of the wound body, and the innermost layer of the wound body is the negative electrode sheet 2. Therefore, the lithium sheet 1 and the innermost negative electrode sheet 2 are fully bonded to facilitate lithium supplementation to the negative electrode sheet. The outermost layer of the wound body is a separator, and the positive electrode sheet 5 attached to the inner surface of the outermost separator is prevented from contacting the battery case.

The positive electrode sheet 5, the separator 4, the negative electrode sheet 2, and the lithium foil 3 are all elongated, and their lengths are approximately equal. In terms of width, the order of separator, negative electrode sheet, positive electrode sheet, and lithium foil decreases in descending order. The width of the lithium sheet 1 is substantially consistent with the width of the winding center space formed in the center of the winding body. The length of the lithium sheet 1 is slightly smaller than the axial length of the wound body.

The positive electrode sheet 5 includes a positive electrode collector and positive electrode material layers disposed on both surfaces of the positive electrode collector. The positive electrode material layer can be made of positive electrode materials in the prior art, such as lithium iron phosphate, conductive agent, and binder. The positive current collector is square and made of aluminum. The positive electrode current collector includes a positive electrode central current collector 51 with a network structure, and a positive electrode annular current collector 52 is provided around the positive electrode central current collector. The positive electrode central current collector and the positive electrode annular current collector are on the same plane, that is, the extension directions of the two are the same. The positive electrode annular current collector is integrated with the positive electrode central current collector. During processing, a piece of aluminum sheet can be used to process uniformly distributed mesh holes in its set central area.

The negative electrode sheet 2 includes a negative electrode current collector and negative electrode material layers arranged on both surfaces of the negative electrode current collector. The negative electrode material layer can be made of negative and positive electrode materials in the prior art, such as graphite, conductive agent, and binder. The negative current collector is square and made of copper material. The negative electrode current collector includes a negative electrode central current collector with a network structure, and a negative electrode annular current collector is provided around the negative electrode central current collector. The negative electrode central current collector and the negative electrode annular current collector are on the same plane, that is, the extension directions of the two are consistent. The negative electrode annular current collector is integrated with the negative electrode central current collector. During processing, a copper sheet can be used to process evenly distributed mesh holes in its set central area.

Both ends of the pole core are respectively provided with a positive pole tab 61 and a negative pole tab 62 . The positive tab 61 is welded to the positive current collector of the positive sheet 5 . The negative electrode tab 62 is welded to the negative electrode current collector of the negative electrode sheet 2 . The positive pole tab 61 is an aluminum tab, and the negative pole tab 62 is a nickel tab.

When the winding type lithium-ion battery of the utility model is produced, the lithium sheet is placed on the winding needle of the winding machine, and the electrodes stacked in sequence according to the order of "negative electrode sheet-lithium foil-diaphragm-positive electrode sheet-diaphragm" The layered body formed by the sheet, separator and lithium foil is wound on the needle and the lithium sheet, and the negative electrode sheet is on the innermost side and is in contact with the lithium sheet. The number of winding turns can be determined according to the set capacity of the battery, generally 2-20 turns. After the winding is completed, the winding body and the lithium sheet in the center are removed together to obtain the pole core, and the high-temperature tape is wound and pasted on the outer peripheral surface of the pole core. Scrape the positive pole tab welding area on the positive pole piece at one end of the pole core, and scrape the negative pole tab welding area on the negative pole piece at the other end of the pole core. The positive tab is welded in the positive tab welding area by an ultrasonic welding machine or a laser welding machine, and the negative tab is welded in the negative tab welding area to obtain a wound lithium-ion battery composite cell. The battery cell is dried, put into the shell, injected with liquid, packaged, formed, and constant volume to obtain a wound lithium-ion battery.

A soft-packed lithium-ion battery without lithium sheet and lithium foil in the battery cell was used as a comparative example, and the current collector was a solid current collector, and the others were the same as those in the above-mentioned embodiments. The electrochemical performances of the lithium ion batteries in the above examples and the lithium ion batteries in the comparative example were tested, and the test results are shown in the table below.

Table 1

Battery capacity (Ah) first time efficiency Internal resistance (mΩ) Positive electrode gram capacity (mAh/g) Example 6.2 95.3% 5.2 143.6 comparative example 5.1 88.9% 7.8 135.7

It can be seen from Table 1 that by adding lithium sheets and lithium foils to the cells, the initial efficiency and internal resistance of lithium-ion batteries are significantly improved. The reason may be that lithium sheets and lithium foils provide sufficient lithium for the charging and discharging process. Ions also provide sufficient lithium ions for the formation of SEI, thereby improving its first-time efficiency, reducing its internal resistance, and promoting the gram capacity of its positive electrode material.

In other embodiments of the present utility model, the lithium ion battery is a cylindrical wound lithium ion battery. The battery cell is a cylindrical winding battery cell, and the battery case includes a cylindrical case and a circular cover. The shell and cover are made of stainless steel. At this time, the lithium sheets in the wound lithium-ion composite batteries are replaced with lithium rods. The positive pole lug is welded to the inner wall of the cover, and the negative pole lug is welded to the bottom wall of the battery case. In this way, the battery cover and the battery case form the positive and negative poles of the battery, respectively.

In other embodiments of the present invention, one or both of the positive electrode current collector and the negative electrode current collector use a solid current collector in the prior art.

In other embodiments of the present utility model, the lithium sheet is not provided, and only the lithium foil is reserved.

In other embodiments of the present utility model, the inner edge of the positive electrode annular collector is welded and fixedly connected to the outer edge of the positive electrode central collector.

In other embodiments of the present utility model, the length of the lithium sheet or lithium rod is equal to the axial length of the pole core.

In other embodiments of the present invention, the width of the lithium foil, the width of the positive electrode sheet, the width of the negative electrode sheet and the width of the diaphragm are all equal.

In other embodiments of the present utility model, both the positive pole lug and the negative pole lug are arranged at the same end of the pole core.

In other embodiments of the present utility model, the positive electrode lug and the positive electrode current collector are integrally arranged, and are obtained by cutting during preparation. The same negative electrode tab and the negative electrode current collector can also be integrally arranged.

The embodiment of the winding type lithium ion battery composite cell of the present invention has the same structure as the aforementioned winding type lithium ion battery composite cell. The above-mentioned alternative forms of the structure of the wound lithium-ion battery composite cell are also applicable to the embodiments of the wound lithium-ion battery composite cell.

Claims (9)

1. A wound-type lithium-ion battery composite cell, comprising a pole core, the pole core includes a positive pole piece (5), a separator (4), and a negative pole piece (2), characterized in that the pole core also includes The lithium foil (3), the positive electrode sheet (5), the diaphragm (4), the negative electrode sheet (2) and the lithium foil (3) are stacked sequentially in the order of "negative electrode sheet-lithium foil-diaphragm-positive electrode sheet-diaphragm" and coiled together; A lithium sheet or a lithium rod extending along the axis of the pole core is arranged at the center of the pole core winding. 2 . The wound lithium ion battery composite battery cell according to claim 1 , wherein the length of the lithium sheet or lithium rod is smaller than the axial length of the pole core. 3 . 3. The wound lithium-ion battery composite battery cell according to claim 1, characterized in that, the width of the lithium foil (3) is smaller than the width of the positive electrode sheet (5), and the width of the positive electrode sheet (5) is smaller than that of the negative electrode The width of the sheet (2), the width of the negative electrode sheet (2) is smaller than the width of the diaphragm (4). 4. The wound-type lithium-ion battery composite battery cell according to claim 1, characterized in that, the wound-type lithium-ion composite battery cell also includes positive pole lugs (61) and negative poles respectively arranged at both ends of the pole core. ear (62). 5 . The wound lithium-ion battery composite cell according to claim 4 , wherein the positive electrode sheet ( 5 ) includes a positive electrode current collector, and the positive electrode tab ( 61 ) is welded to the positive electrode current collector. 6. The wound lithium-ion battery composite cell according to claim 5, characterized in that, the positive electrode current collector includes a positive electrode central collector (51) with a network structure and a ring arranged on the positive electrode central collector. A positive electrode annular current collector (52) surrounding the fluid and extending outward along the extension direction of the positive electrode central current collector. 7. The wound lithium-ion battery composite cell according to claim 4, characterized in that, the negative electrode sheet (2) includes a negative electrode current collector, and the negative electrode tab (62) is welded to the negative electrode current collector. 8. The winding type lithium-ion battery composite electric core as claimed in claim 7, wherein the negative electrode current collector comprises a negative electrode central current collector with a mesh structure and is arranged around the negative electrode central current collector and A negative electrode annular current collector extending outward along the extension direction of the negative electrode central current collector. 9. A winding lithium ion battery, comprising a battery case and an electric core arranged in the battery case, characterized in that, the electric core is the winding lithium ion battery according to any one of claims 1-8. Composite batteries.