Battery pack grouping mode of soft-package metal lithium battery

Abstract

The invention relates to a metal lithium battery pack grouping mode which comprises two clamping pieces, each clamping piece is provided with at least one plane, the planes of the two clamping pieces are parallel to each other and are oppositely arranged, one or more than two stacked soft package single batteries are arranged between the oppositely arranged planes of the two clamping pieces, and the soft package single batteries are connected with the clamping pieces. The two clamping pieces are bundled and fixed through one or more than two hook-and-loop fasteners, the hook faces and the loop faces of the hook-and-loop fasteners are bundled in a buckled mode by winding the hook-and-loop fasteners on the outer sides of the clamping pieces, and the winding length of each hook-and-loop fastener is 1.2-2 times of the perimeter length of a circle (forming a closed loop) where the hook-and-loop fastener is wound. According to the invention, the stability of internal contact of the battery can be maintained in the battery charging process.

Description

Technical Field

[0001] The invention belongs to the field of lithium batteries and is a method for assembling a metal lithium battery. Background Art

[0002] Lithium-ion batteries have had a profound impact on modern society. Over the past 25 years, the specific energy of lithium-ion batteries has steadily increased while the cost has dropped significantly. However, the electric vehicle energy storage market requires higher specific energy, exceeding 500Wh / kg at the battery level, and lower costs. Currently, many scientists are developing the next generation of high energy density batteries, such as lithium-air batteries and lithium-sulfur batteries. All-solid-state batteries have also attracted widespread attention due to their inherent high safety characteristics. Among many methods, lithium metal is considered to be a key component to achieve higher specific energy. Lithium metal batteries are the key system that can achieve battery energy density of 350Wh / kg-500Wh / kg. To date, most research has focused on the material level. Although there have been some proposals for new battery structures with improved performance and soft-pack battery characteristics, there are not many technologies on how to achieve practical use of lithium metal batteries because there are still many problems with lithium metal batteries.

[0003] First, lithium metal is a highly active substance, so lithium metal batteries have certain safety issues; second, the thickness of the negative electrode lithium metal increases during the charging process, and decreases during the discharging process, which results in a dynamic change in the battery thickness during the charging and discharging process. If the binding force of the battery on the soft-pack battery during the charging and discharging process cannot change according to the change in battery thickness, the internal resistance of the battery during the charging and discharging process will increase, resulting in a simultaneous decrease in the charging and discharging capacity; third, in addition to the dynamic thickness change of the pole piece during the cycle, the overall thickness of the battery will also gradually increase, resulting in poor cycle life and other problems. After the batteries are grouped, the above problems will become more serious due to the superposition effect.

[0004] In many practical applications, multiple single batteries need to be connected in series and parallel to form a module or battery pack. After forming a group, the safety and cycle life of the battery system are affected not only by the battery operating environment, but also by another major influencing factor: the force applied to the battery during use and whether the support force on the battery pack can change dynamically with charging and discharging.

[0005] There is currently no good solution to the above problems in the industry. Summary of the invention

[0006] In view of the above problems, the present invention provides a metal lithium battery grouping method, which can dynamically adjust the restraining force during the charging and discharging process of the battery pack, ensure normal charging and discharging of the battery pack, and improve the safety and cycle life of the battery system.

[0007] The present invention protects a method for assembling a metal lithium battery group, including two parallel clamping members, each of which has a plane, the planes of the two clamping members are arranged opposite to each other, a soft-pack battery is arranged between the two clamping members, and the two clamping members are bundled and fixed by nylon Velcro, the nylon Velcro is wound around the outside of the supporting member, each circle of the Velcro does not cross, the number of winding circles is between 1.2 circles and 2 circles, and the soft-pack battery is a metal lithium battery.

[0008] Furthermore, the clamping member is an end plate.

[0009] Furthermore, the Velcro has a certain elasticity.

[0010] In the prior art, the end plate is mainly fixed by welding. After welding, the size is fixed and there is no rebound space. The present invention reserves rebound space for the battery pack by combining the end plate with Velcro, and can ensure the binding force of the battery pack during use. The end plate and the mold Velcro are assembled in a way that the Velcro is parallel to the length direction or the width direction of the end plate, and the bundling Velcro is fixed in circles, and the ends of each circle of Velcro are not connected.

[0011] Beneficial effects:

[0012] The present invention realizes the grouping of soft-pack lithium metal batteries by setting Velcro and clamping parts. It is important to adjust the dynamic expansion force of the battery pack during the charging and discharging process. As the battery is charged, the thickness of the negative electrode plate of the battery, that is, the thickness of the metal lithium, will increase, causing the overall thickness of the battery to increase. Since most battery packs are assembled by welding end plates, the internal expansion force of the battery pack cannot be released, and as the number of battery uses increases, the expansion force will gradually increase, affecting the battery safety and cycle life. As the battery discharges, the thickness of the negative metal lithium decreases, the binding force of the battery pack decreases, and gaps appear between the positive electrode, the diaphragm and the negative electrode inside the battery, causing the internal resistance of the battery to increase and the battery capacity to decrease. Through the method of the present invention, the battery charging process can dynamically release the expansion force that gradually increases during the use of the battery pack because the nylon Velcro has elasticity. After the expansion force is released, the service life of the battery pack can be improved and the safety of the battery pack can be improved. During the battery discharge process, the Velcro binding force will gradually compress the distance between the positive and negative electrodes and the diaphragm inside the battery as the battery thickness changes, so as to keep the stability of the battery contact inside. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a front view of the lithium metal battery pack of Example 1 of the present invention.

[0014] Figure 2 for Figure 1 Side view of.

[0015] In the figure, 1. Metal lithium battery; 2. Clamping part: end plate; 3. Velcro. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention protects a soft-pack metal lithium battery assembly method, including two parallelly arranged clamping parts, the clamping parts are flat end plates, the two end plates are relatively parallelly arranged in a plane, a metal lithium soft-pack single battery is arranged between the two end plates, the two end plates are bundled and fixed by Velcro, the Velcro fixes the holding part by winding, the winding direction is parallel to the length or width direction of the single battery, more than two Velcros are fixed in circles respectively, and the more than two Velcros are parallel to each other and do not intersect; each Velcro is wound 1.5 times, and each Velcro is overlapped and buckled with its hand and tail, with an overlap of 0.5 turns.

[0018] The following are specific embodiments.

[0019] Example 1 (first embodiment)

[0020] This embodiment adopts the above-mentioned method to assemble a battery pack, and the battery pack is a 7-series battery pack. The mechanical components of the battery pack include a soft-pack single battery 1, an end plate 2, and a Velcro 3. The single battery uses a 5Ah metal lithium soft-pack battery, and the battery size is 94mm (length: excluding the pole ear) * 35mm (width) * 7mm (thickness). The positive electrode active material of the metal lithium soft-pack battery is nickel cobalt manganese oxide lithium NCM811 material, and the positive electrode formula is 95% NCM811 + 2% polyvinylidene fluoride (PVDF) + 3% conductive carbon black (SP). The positive electrode is prepared into a positive electrode sheet by slurry stirring, coating the slurry on the surface of aluminum foil, rolling and die cutting, etc., wherein the positive electrode coating surface density is 25mg / cm 2 The thickness of the positive electrode after rolling is 110μm±2μm, the size of the positive electrode of the battery after die cutting is 31mm*85mm (width*length), the negative electrode of the battery is a 50μm metal lithium lithium strip, the width of the metal lithium is 87mm, the battery separator is a 12μm thick PE separator, the separator width is 89mm, the outer packaging material of the battery is aluminum-plastic film, the end plate 2 is an aluminum end plate, a total of two pieces, the size is 98mm (length) * 38mm (width) * 2mm (thickness), the Velcro width is 10mm, a total of 10 strips, each length is 261mm, such as Figure 1 &2, Figure 1 This is the main view of the battery pack after assembly. Figure 2This is a side view of the battery pack after grouping. The positive electrode and the negative electrode are separated by a diaphragm. Seven soft-pack batteries are grouped by stacking. Two end plates are located on the upper and lower sides of the stacked battery pack. Velcro fixes the end plates and soft-pack batteries by winding.

[0021] The charge-discharge and cycle performance data of the battery packs in the above embodiments were tested, and a comparative group was designed at the same time. The design of the battery pack in the comparative group was designed according to the structure of Embodiment 1, and the end plate and Velcro in Embodiment 1 were removed. The change in the capacity retention rate of the battery pack during the battery cycle and the percentage increase in the thickness of the battery pack after discharge were tested. The capacity retention rate was the battery discharge capacity divided by the initial capacity of the battery multiplied by 100% and rounded, and the percentage increase in the thickness of the battery pack was the thickness value after the battery pack cycle divided by the initial discharge state thickness value multiplied by 100% and rounded. The test results are as follows:

[0022] Implementation method cycle 30 times

[0023]

[0024] The cycle capacity retention rate of the battery pack in Example 1 is greater than the capacity retention rate of the battery pack in the comparative example, and the percentage increase in the thickness of the battery pack is less than the percentage increase in the thickness of the battery pack in the comparative example, indicating that the charge and discharge performance of the battery in Example 1 is normal, the internal resistance of the battery has not changed significantly, and the volume change during the charge and discharge of the battery has no effect on the charge and discharge of the battery. In addition, as the cycle proceeds, the expansion force of the battery pack assembled in the embodiment is effectively restrained, and the dynamic change of the expansion force improves the cycle performance of the battery pack.

[0025] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for assembling a metal lithium battery assembly, comprising two clamping members, each of which has at least one plane, the planes of the two clamping members are parallel to each other and arranged opposite to each other, and one or more stacked soft-packed single batteries are arranged between the planes of the two clamping members arranged opposite to each other, The two clamping parts are tied and fixed by one or more Velcro strips, and the Velcro strips are tied and interlocked by winding them around the outside of the supporting part, and the winding length of each Velcro strip is 1.2 times to 2 times (preferably 1.4 times to 1.6 times, i.e. the number of winding circles) of the circumference of one circle (forming a closed loop) where it is wound, that is, the hook side and the hair side of each Velcro strip start to interlock after one circle of winding, and the interlocking length of the hook side and the hair side is 0.2 times to 1 times (preferably 0.4 times to 0.6 times) of the length of one circle of winding.

2. The grouping method according to claim 1, characterized in that: The two clamping pieces are tied and fixed by two or more Velcro strips, which are wound along planes of different parallel circles, and two adjacent wound Velcro strips are spaced from each other, that is, the Velcro strips in each circle do not cross each other.

3. The grouping method according to claim 1, characterized in that: The soft-pack battery is a rectangular metal lithium battery; the clamping piece is a rectangular end plate; The Velcro is wrapped along any two parallel sides of the rectangle, that is, the two sides of the Velcro in the width direction are parallel to the two sides of the rectangle.

4. The grouping method according to claim 1, 2 or 3, characterized in that: The Velcro is made of nylon.

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