Pressure activated reserve type lithium battery and preparation method thereof

Abstract

The invention discloses a pressure activation type reserve lithium battery and a preparation method thereof.The lithium battery comprises a battery shell, a battery cover, a low-viscosity solvent packaging module, a pressure trigger activation module and a high-porosity electrode assembly.The low-viscosity solvent packaging module is of an I-shaped cylindrical cavity structure, a first cavity is formed in the upper portion of the low-viscosity solvent packaging module, and a second cavity is formed in the lower portion of the low-viscosity solvent packaging module; the middle part is provided with a second cavity, the lower part is provided with a third cavity, and the three cavities are communicated with one another; a pressure trigger activation module is arranged at the top of the first cavity and is triggered when the acceleration is greater than or equal to 20g, so that the low-viscosity solvent packaging module is promoted to release the low-viscosity mixed solvent; and a high-porosity electrode group is arranged outside the second cavity, and LiFSI, LiPF6 and EC powder are mixed in the second cavity. According to the invention, the acceleration sensor-based pressure-triggered quick activation device is arranged in the battery, so that second-level quick liquid injection activation is realized, and the battery has the characteristics of quick activation, long-term storage stability and extreme environment adaptability.

Description

Technical Field

[0001] The present invention relates to a lithium-ion battery, and particularly to a pressure-activated reserve lithium battery and a preparation method thereof. Background Art

[0002] Traditional high-power reserve batteries have a relatively low specific energy and a short working time, which to a certain extent limits their applications. Lithium-ion batteries have the advantages of high specific energy, good power performance, long endurance time, etc. However, during the long-term storage of a conventional lithium-ion battery in a highly charged state, the electrolyte will continuously react with the electrode material, causing self-discharge and a short storage life, making it difficult to meet the usage requirements. The method of injecting electrolyte to activate the battery is an effective way to improve the battery storage life. However, due to the long time required for the electrolyte to infiltrate the electrode material, the conventional activation method has the problem of a long activation time, often taking up to several hours to achieve the maximum power output, seriously affecting the use. Summary of the Invention

[0003] In order to improve the battery energy density and extend the battery storage life, the present invention provides a pressure-activated reserve lithium battery and a preparation method thereof. For a cylindrical reserve lithium battery, the present invention realizes second-level rapid liquid injection activation by arranging a pressure-triggered rapid activation device based on an acceleration sensor inside the battery, and has the characteristics of rapid activation, long-term storage stability, and extreme environment adaptability.

[0004] The purpose of the present invention is achieved by the following technical solutions:

[0005] A pressure-activated reserve lithium battery, comprising a battery case, a battery cover, a low-viscosity solvent encapsulation module, a pressure-triggered activation module, and a high-porosity electrode group, wherein:

[0006] The inside of the battery case is provided with a low-viscosity solvent encapsulation module, a pressure-triggered activation module, and a high-porosity electrode group, and the top is provided with a battery cover;

[0007] The low-viscosity solvent encapsulation module is in an I-shaped cylindrical cavity structure, with a first cavity in the upper part, a second cavity in the middle part, and a third cavity in the lower part. The three cavities are interconnected, and a low-viscosity mixed solvent is encapsulated inside the cavities;

[0008] The diameter of the first cavity is 17 mm, the height is 10 mm, the diameter of the second cavity is 3 mm, the height is 61 mm, the diameter of the third cavity is 17 mm, and the height is 2 mm;

[0009] Micropores sealed with a film are provided at the lower part of the first cavity, the second cavity, and the upper part of the third cavity, and the pore diameter is 0.1 mm to 5.0 mm;

[0010] The normal temperature viscosity of the low-viscosity mixed solvent is ≤1 mPa·s, and it includes 30-50 vol% of EMC, 10-20 vol% of AN, 10-20 vol% of EA, and 20-30 vol% of DMC;

[0011] The film for sealing the micropores is one of PET, LDPE, PP, PI, PDMS, and TPU, with a thickness of 1-20 μm and a pressure tolerance of 0-200 kPa;

[0012] A pressure-trigger activation module is provided at the top of the first cavity. The pressure-trigger activation module is triggered when the acceleration ≥20 g, prompting the low-viscosity solvent encapsulation module to release the low-viscosity mixed solvent, and the release channel is the reserved micropores;

[0013] A high-porosity electrode group is provided outside the second cavity. The porosity of the high-porosity electrode group is 30-70%, and it is internally mixed with LiFSI, LiPF6, and EC powder. The mass ratio of LiFSI, LiPF6, and EC powder is 0.4-0.6:0.1-0.2:0.5-1.0, and the particle size of the powder is ≤5 μm;

[0014] The positive electrode of the high-porosity electrode group uses at least one of delithiated lithium nickel cobalt aluminate, delithiated lithium cobaltate, delithiated lithium nickel cobalt manganate, and delithiated lithium iron phosphate. The negative electrode uses at least one of lithium-inserted graphite, metallic lithium, and lithium-silicon alloy materials. The separator uses a 9-μm aramid solid electrolyte mixed-coated high-porosity separator with a porosity ≥60%. The current collector uses a porous current collector, the micropore diameter is 0.2-1 mm, and the micropore area ratio ≥70%;

[0015] The battery case is vacuum-sealed, and the air pressure inside the case is 1-50 kPa, preferably 2 kPa.

[0016] A preparation method of the above pressure-activated reserve lithium battery includes the following steps:

[0017] Step 1: Prepare the positive and negative electrode sheets respectively according to the conventional method. The positive electrode sheet uses at least one of lithium nickel cobalt aluminate, lithium cobaltate, lithium nickel cobalt manganate, and lithium iron phosphate, and the negative electrode sheet uses at least one of graphite, metallic lithium, and silicon materials;

[0018] Step 2: Perform delithiation of the positive electrode and lithium insertion of the negative electrode (except for metallic lithium) respectively;

[0019] Step 3: In an environment with a temperature lower than 20°C, add LiFSI, LiPF6, and EC powder into the voids in the electrode sheets, and roll the positive and negative electrodes respectively (except for metallic lithium). After rolling, the porosity of the positive electrode is ≥25%, and the porosity of the negative electrode is ≥30%;

[0020] Step 4: Prepare the low-viscosity solvent encapsulation module;

[0021] Step 5, winding the positive and negative electrodes and the separator using the second cavity of the low-viscosity solvent encapsulation module as a reel to form a high-porosity electrode group;

[0022] Step 6, adding a low-viscosity mixed solvent into the low-viscosity solvent packaging module;

[0023] Step 7: prepare a pressure-triggered activation module, and when the acceleration is ≥ 20g, the low-viscosity solvent encapsulation module is linked to release the low-viscosity mixed solvent;

[0024] Step 8, assembling the low-viscosity solvent encapsulation module, the pressure-triggered activation module, and the high-porosity electrode group with the battery shell and the battery cover to form a single battery;

[0025] Step 9: Vacuum seal the battery to ensure that the internal pressure is low;

[0026] Step 10. Activation and use of the battery: When the battery is in use and the acceleration is ≥20g, the pressure triggers the activation module to link the low-viscosity solvent encapsulation module to instantly release the low-viscosity mixed solvent, and the high-porosity electrode group in a vacuum state instantly absorbs the low-viscosity mixed solvent, and the solvent quickly merges with the high-solubility lithium salt and high-dielectric constant EC pre-dispersed inside the electrode to achieve instantaneous high-power output capability.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention can achieve rapid activation in seconds by arranging a rapid activation device inside the battery and adjusting the electrode design.

[0029] 2. The output peak current of the reserve lithium battery of the present invention can reach more than 20A within 5s after activation.

[0030] 3. The pressure-activated reserve lithium battery of the present invention can significantly improve the storage life of the battery, and the solution can be extended to batteries of various sizes without restrictions on the size and model of the battery. It can be widely used in unmanned systems, electronic equipment, instrumentation, aerospace and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural diagram of a pressure-activated reserve lithium battery, 11 is a high-porosity electrode group; 12 is a low-viscosity solvent packaging module; 13 is a pressure-triggered activation module; 14 is a battery shell; 15 is a battery cover;

[0032] Figure 2 121 is a schematic diagram of a low-viscosity solvent packaging module, and 122 is a low-viscosity mixed solvent. DETAILED DESCRIPTION

[0033] The technical solutions of the present invention will be further described below in conjunction with embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0034] Embodiment 1

[0035] This embodiment provides a pressure-activated reserve lithium battery. As Figure 1 shown, the lithium battery includes a high-porosity electrode group 11, a low-viscosity solvent encapsulation module 12, a pressure-trigger activation module 13, a battery case 14, and a battery cover 15, wherein: the low-viscosity solvent encapsulation module 12, the pressure-trigger activation module 13, and the high-porosity electrode group 11 are arranged inside the battery case 14, and the battery cover 15 is arranged on the top; the low-viscosity solvent encapsulation module 12 is of an I-shaped cylindrical cavity structure, with a first cavity in the upper part, a second cavity in the middle part, and a third cavity in the lower part. The three cavities are interconnected, and a low-viscosity mixed solvent is encapsulated inside the cavities; micropores sealed by a film are provided in the lower part of the first cavity, the second cavity, and the upper part of the third cavity; the pressure-trigger activation module 13 is arranged on the top of the first cavity and is triggered when the acceleration ≥ 20g, prompting the low-viscosity solvent encapsulation module 12 to release the low-viscosity mixed solvent; the high-porosity electrode group 11 is arranged outside the second cavity. The specific preparation steps are as follows:

[0036] Step S1: Prepare the positive and negative electrode sheets respectively according to the conventional method. The positive electrode uses lithium nickel cobalt aluminate, the negative electrode uses graphite, the current collector uses a porous current collector, the micropore diameter is 0.5 mm, and the micropore area ratio is 70%;

[0037] Step S2: Perform de-lithiation of the positive electrode and lithium intercalation of the negative electrode respectively. After de-lithiation of the positive electrode, the open-circuit voltage is 4.25 V (Vs Li + / Li), and after lithium intercalation of the negative electrode, the open-circuit voltage is 0.05 V (Vs Li + / Li). After de-lithiation and lithium intercalation, remove the residual electrolyte components on the positive and negative electrodes;

[0038] Step S3: In an environment with a temperature lower than 20 °C, add LiFSI, LiPF6, and EC powder into the voids in the electrode sheets. The content of LiFSI is 0.5 g, the content of LiPF6 is 0.2 g, and the content of EC is 0.6 g. Roll the positive and negative electrodes respectively. After rolling, the porosity of the positive electrode is 30%, and the porosity of the negative electrode is 35%;

[0039] Step S4: Prepare the low-viscosity solvent encapsulation module. Micropores sealed by a film are provided in the lower part of the first cavity, the second cavity, and the upper part of the third cavity of the low-viscosity solvent encapsulation module. The film material is LDPE, with a thickness of 10 μm and a pore diameter of 2.0 mm;

[0040] Step S5: Wind the positive and negative electrodes and the separator around a reel in the second cavity of the low-viscosity solvent encapsulation module to form a pole piece group. The separator uses a 9-μm aramid-coated high-porosity separator with a porosity of 70%, and the porosity of the pole piece group is 45%.

[0041] Step S6: Add a low-viscosity mixed solvent inside the low-viscosity solvent encapsulation module: 40 vol% EMC, 10 vol% AN, 20 vol% EA, 30 vol% DMC, and the normal temperature viscosity is about 0.55 mPa·s.

[0042] Step S7: Prepare a pressure-trigger activation module containing an acceleration sensor. When the acceleration ≥ 20 g, the low-viscosity solvent encapsulation module is linked to release the low-viscosity mixed solvent.

[0043] Step S8: Assemble the low-viscosity solvent encapsulation module, the pressure-trigger activation module, and the high-porosity electrode group with the battery case and the battery cover to form a single cell.

[0044] Step S9: Vacuum-pack the battery to ensure that the inside is in a low-pressure state, and the internal pressure of the housing is 2 kPa.

[0045] Step S10: Activation and use of the battery: When the battery is in use and the acceleration ≥ 20 g, the pressure-trigger activation module links the low-viscosity solvent encapsulation module to instantly release the low-viscosity mixed solvent. The high-porosity electrode group in the vacuum state instantly adsorbs the low-viscosity mixed solvent, and the solvent quickly fuses with the highly soluble lithium salt and the high-dielectric-constant EC pre-dispersed inside the electrode, achieving the instantaneous high-power output ability.

[0046] Example 2

[0047] The difference between this example and Example 1 is that the negative electrode uses metallic lithium, and there is no lithium insertion process and no rolling process. The thickness of the metallic lithium is 30 μm, the metallic lithium is coated on the copper foil, and both the metallic lithium and the copper foil are provided with micropores with a pore diameter of 0.5 mm, and the micropore area accounts for 70%.

[0048] Example 3

[0049] The difference between this example and Example 1 is that the negative electrode uses a silicon-based material, and a lithium-silicon alloy is formed through lithium insertion treatment.

[0050] Comparative Example 1

[0051] The positive electrode uses lithium nickel cobalt aluminate, the negative electrode uses graphite, and a cylindrical lithium-ion battery is prepared by a conventional method, and normal liquid injection is carried out. Correspondingly, there is no need to activate the lithium-ion battery.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Comparative Example 1 is as follows: the positive electrode is subjected to de-lithiation treatment, the negative electrode is subjected to lithiation treatment, an electrolyte storage tank is provided, and the electrolyte is injected during use to activate the battery, corresponding to a reserve battery with conventional slow activation.

[0054] The batteries developed in the above Examples 1 to 3 and Comparative Examples 1 and 2 were stored for 1 year, then activated for use, and the 20A high-current discharge capacity 5s after battery activation was measured. At the same time, the discharge capacity at a cut-off voltage of 2.5V was recorded, as shown in Table 1.

[0055] Table 1

[0056] Scheme Name Rated Capacity / Ah Whether 20A Output is Achieved after 5s Activation Discharge Capacity / Ah Capacity Retention Rate Example 1 2.6 Yes 2.424 93.2％ Example 2 2.8 Yes 2.435 87.0％ Example 3 2.7 Yes 2.415 89.4％ Comparative Example 1 2.6 Yes 2.216 85.2％ Comparative Example 2 2.6 No 0.205 7.9％

[0057] As can be seen from Table 1, due to the use of the same positive electrode and negative electrodes with different capacities, their design capacities are different. The capacity is the lowest when using graphite as the negative electrode, with a battery design capacity of 2.6Ah. The capacity is the highest when using metallic lithium as the negative electrode, with a design capacity of up to 2.8Ah. The capacity of the silicon-based negative electrode is the second, with a design capacity of 2.7Ah.

[0058] Comparative Example 1 is a conventional battery design. The battery is stored in a high state of charge and can respond immediately without activation, with a relatively large power output capacity. However, its self-discharge rate is also the largest. After being stored for 1 year, the discharge capacity is only 2.216Ah, and the retention rate is 85.2%. Comparative Example 2 is a conventional activation method for reserve lithium-ion batteries, that is, activation is achieved by immediately injecting the electrolyte. However, due to factors such as high electrolyte viscosity, low electrode porosity, few infiltration channels, and difficulty in discharging the gas inside the electrode group, the activation time is extremely long, usually taking dozens of minutes or even hours to achieve the maximum power output. Therefore, it does not have the 20A high-current output capacity in a short time, and the discharge capacity is also the lowest, only 0.205Ah, and it can hardly discharge.

[0059] Examples 1 to 3 adopt a low-viscosity solvent encapsulation module, a pressure-triggered activation module, and a high-porosity electrode group. By combining the pre-dispersion of highly soluble lithium salts and ultra-low-viscosity mixed solvent components, and vacuum encapsulating the high-porosity electrode group, the rapid penetration of the electrolyte is realized, thus achieving the rapid activation of the battery. In addition, EC with high viscosity and high dielectric constant is pre-dispersed in the electrode in the form of powder, which solves the problems of high viscosity of the solvent component, slow infiltration, and at the same time solves the problem of lithium salt dissociation.

[0060] Example 1: The positive electrode uses lithium nickel cobalt aluminate, and the negative electrode uses graphite. The formation of the electrode sheet is achieved by deintercalating lithium from the positive electrode and intercalating lithium into the negative electrode. Through the design of a high-porosity current collector, electrode sheet, and separator, the preparation of a high-porosity electrode group is realized. Combining the pre-dispersed lithium salt, EC, ultra-low viscosity mixed solvent components, and vacuum packaging process, the pressure-trigger activation module is used to drive the low-viscosity solvent packaging module by utilizing the change in the external pressure of the battery. Through the reserved channels, the rapid injection of the solvent is completed, and the lithium salt is quickly dissolved to establish a voltage difference, thereby realizing the rapid activation of the battery. It has the ability to output a large current, with a discharge capacity of up to 2.424 Ah and a retention rate of 93.2%, far exceeding 85.2% of Comparative Example 1. As the storage time extends, the gap will become more obvious. Before battery activation, vacuum dry storage is adopted, and almost no side reactions occur inside. The long-term storage has a minimal impact on the capacity loss of the battery, and it can ensure a storage life of more than 15 years.

[0061] In Examples 2 and 3, different types of negative electrodes were replaced, and similar results could be achieved. Among them, in Example 2, metallic lithium was selected as the negative electrode, and its designed capacity was up to 2.8 Ah. Due to the relatively small specific surface area of the metallic lithium strip, its rate performance was poor. By compounding metallic lithium with a copper current collector and reserving a large number of micropores, both the electrolyte diffusion channels were increased and the electrode reaction surface area was improved, enhancing the reaction rate, thereby improving the rate performance. However, its rate performance was still inferior to that of the graphite negative electrode, and the discharge capacity was slightly lower, at 2.435 Ah, with a retention rate of 87.0%. In Example 3, a lithium-silicon alloy was selected as the negative electrode. The silicon negative electrode is usually wrapped in carbon spheres in the form of nanoscale particles as a buffer for conductivity and volume expansion. The lithiation process of silicon will form a lithium-silicon alloy, which has a higher capacity and requires less usage compared to the graphite negative electrode. Therefore, the specific energy of the battery will be higher, and the designed capacity can reach 2.7 Ah. Its activation effect is the same as that of Example 1, and both can achieve high-power output ability after activation, with a discharge capacity of 2.415 Ah and a retention rate of 89.4%, higher than the metallic lithium negative electrode in Example 2.

Claims

1. A pressure-activated reserve lithium battery, characterized in that The lithium battery includes a battery case, a battery cover, a low-viscosity solvent encapsulation module, a pressure-trigger activation module, and a high-porosity electrode group, where: The low-viscosity solvent encapsulation module is in the shape of an I-shaped cylindrical cavity structure, with a first cavity at the upper part, a second cavity in the middle, and a third cavity at the lower part. The three cavities are interconnected, and a low-viscosity mixed solvent is encapsulated inside the cavities. Micropores sealed with a film are provided at the lower part of the first cavity, the second cavity, and the upper part of the third cavity. A pressure-trigger activation module is arranged at the top of the first cavity. The pressure-trigger activation module is triggered when the acceleration ≥ 20g, prompting the low-viscosity solvent encapsulation module to release the low-viscosity mixed solvent. A high-porosity electrode group is arranged outside the second cavity, and LiFSI, LiPF6, and EC powder are mixed inside the high-porosity electrode group.

2. The pressure-activated reserve lithium battery according to claim 1, wherein The diameter of the first cavity is 17 mm, and the height is 10 mm. The diameter of the second cavity is 3 mm, and the height is 61 mm. The diameter of the third cavity is 17 mm, and the height is 2 mm.

3. The pressure-activated reserve lithium battery according to claim 1, characterized in that The film is one of PET, LDPE, PP, PI, PDMS, and TPU, with a thickness of 1 - 20 μm and a pressure tolerance of 0 - 200 kPa. The pore diameter of the micropores is 0.1 mm - 5.0 mm.

4. The pressure-activated reserve lithium battery according to claim 1, wherein The pore diameter of the micropores is 0.1 mm - 5.0 mm.

5. The pressure-activated reserve lithium battery according to claim 1, characterized in that The low-viscosity mixed solvent includes 30 - 50 vol% of EMC, 10 - 20 vol% of AN, 10 - 20 vol% of EA, and 20 - 30 vol% of DMC, and the normal-temperature viscosity ≤ 1 mPa·s.

6. The pressure-activated reserve lithium battery according to claim 1, wherein The porosity of the high-porosity electrode group is 30 - 70%, and the mass ratio of LiFSI, LiPF6, and EC powder is 0.4 - 0.6:0.1 - 0.2:0.5 - 1.0, and the particle size of the powder ≤ 5 μm.

7. The pressure-activated reserve lithium battery according to claim 1, wherein The positive electrode of the high-porosity electrode group adopts at least one of delithiated lithium nickel cobalt aluminate, delithiated lithium cobaltate, delithiated lithium nickel cobalt manganate, and delithiated lithium iron phosphate. The negative electrode adopts at least one of lithium-inserted graphite, metallic lithium, and lithium-silicon alloy materials. The separator adopts a 9-μm aramid solid electrolyte mixed-coated high-porosity separator with a porosity ≥ 60%. The current collector adopts a porous current collector with a micropore diameter of 0.2 - 1 mm and a micropore area ratio ≥ 70%.

8. The pressure-activated reserve lithium battery according to claim 1, wherein The battery case is vacuum-sealed, and the air pressure inside the case is 1 - 50 kPa.

9. The pressure-activated reserve lithium battery according to claim 8, wherein The air pressure inside the case is 2 kPa.

10. A method for preparing a pressure-activated reserve lithium battery according to any one of claims 1-9, characterized in that The method includes the following steps: Step 1: Prepare the positive and negative electrode sheets respectively. Step 2: Perform delithiation of the positive electrode and lithium insertion of the negative electrode respectively. Step 3: Add LiFSI, LiPF6, and EC powder into the voids in the electrode sheets in an environment where the temperature is lower than 20°C. Step 4: Prepare the low-viscosity solvent encapsulation module. Step 5: Wind the positive and negative electrodes and the separator around the second cavity of the low-viscosity solvent encapsulation module as a reel to form a high-porosity electrode group. Step 6: Add the low-viscosity mixed solvent into the low-viscosity solvent encapsulation module. Step 7: Prepare the pressure-trigger activation module, and when the acceleration ≥ 20g, link the low-viscosity solvent encapsulation module to release the low-viscosity mixed solvent. Step 8: Assemble the low-viscosity solvent encapsulation module, the pressure-trigger activation module, and the high-porosity electrode group with the battery case and the battery cover to fabricate a single cell; Step 9: Vacuum-pack the battery to ensure a low-pressure state inside.

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