A method for improving the safety of high-energy battery modules by uniform regulation of heat conduction and stress and application thereof

Abstract

The present application belongs to the technical field of high energy density battery, and particularly relates to a method for improving the safety of high energy battery module by uniform regulation of heat conduction and stress. The method fills a heat conduction layer-stress layer composite material between a plurality of groups of lithium metal batteries of the battery module; the heat conduction layer-stress layer composite material method comprises: S1: preparation of a graphene-silicon-based composite material; S2: preparation of a nickel-aluminum-based shape memory alloy; S3: preparation of a heat conduction material and a memory alloy composite material. The method for establishing a graphene-silicon-based composite material and a nickel-aluminum-based shape memory alloy double-layer regulation layer can not only form a nonlinear heat conduction path between battery monomers, and preferentially guide out the heat of the heating area, but also can dynamically balance the stress generated by the expansion / contraction of the battery in the charging and discharging process through preloading force design. The two kinds of materials are loaded between the battery monomers, and the lithium metal battery heat conduction and stress uniform regulation are considered.

Description

A method and application for improving the safety of high-energy battery modules through thermal conductivity and stress uniformity regulation. Technical Field

[0001] This invention belongs to the field of high energy density battery technology, and relates to a method and application for improving the safety of high energy battery modules through thermal conductivity and stress uniformity control. Background Technology

[0002] Lithium metal batteries have an energy density 30%-50% higher than traditional lithium-ion batteries, meeting the high-energy demands of electric vehicles and other applications. They also boast a high operating voltage of over 3.0V, enabling more stable and efficient operation of power tools and other equipment. Furthermore, lithium metal batteries exhibit excellent charge-discharge performance, allowing for rapid charging and discharging with minimal temperature sensitivity. In addition, they are free of harmful heavy metals such as lead, mercury, and cadmium, making them environmentally friendly, and the relatively stable supply of lithium resources facilitates large-scale application.

[0003] High-energy battery modules, such as ternary lithium batteries and solid-state batteries, are prone to localized overheating and thermal runaway risks during charging and discharging due to differences in internal resistance and uneven temperature distribution. Traditional battery modules have defects in mechanical fixation; rigid frames or bolt fixation can lead to stress concentration, which may cause battery deformation or internal short circuits after long-term cycling. Current heat dissipation solutions, such as thermally conductive adhesives and metal heat sinks, struggle to simultaneously achieve thermal uniformity and structural stress control, and their passive heat dissipation efficiency is relatively low. Furthermore, research on thermal conductivity and stress control in lithium metal battery modules is insufficient and urgently needs to be supplemented through experimentation.

[0004] Currently, there is a need to provide a method that actively regulates the heat conduction path and stress distribution to reduce the internal temperature difference of the battery module, alleviate mechanical stress concentration, and thus improve the module's cycle life and safety performance. Summary of the Invention

[0005] The purpose of this invention is to address the problems of large temperature differences and localized overheating in lithium metal batteries, which can easily lead to thermal runaway, and uneven stress that can cause battery deformation or internal short circuits. This invention provides a method for establishing parallel thermo-mechanical regulation using a gradient thermally conductive material layer and a shape memory alloy. The gradient thermally conductive material layer is a graphene-silicon-based composite material that forms nonlinear heat conduction paths between battery cells, preferentially dissipating heat from the heating areas. A shape memory alloy (nickel-aluminum based shape memory alloy) is embedded in the module frame, and through pre-loaded force design, the stress generated by battery expansion / contraction during charging and discharging is dynamically balanced.

[0006] The technical solution adopted in this invention is as follows:

[0007] In a first aspect, the present invention provides a method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity, the specific steps of which are as follows:

[0008] A thermally conductive layer-stress layer composite material is filled between several groups of lithium metal batteries in the battery module;

[0009] The thermally conductive layer-stress layer composite material is a composite material of graphene-silicon-based composite material and nickel-aluminum-based shape memory alloy, and the preparation method is as follows:

[0010] Step S1: Preparation of graphene-silicon composite material:

[0011] The graphene and silicon-based materials are mixed in a mass ratio of 1:3 to 1:9 and then calcined at 700 to 900°C.

[0012] Step S2: Preparation of nickel-aluminum based shape memory alloys:

[0013] S2-1: Mix 1 part by mass of nickel, 5 to 10 parts by mass of aluminum, and 10 to 20 parts by mass of molybdenum thoroughly to obtain a mixed powder;

[0014] S2-2: Press the mixed powder under a pressure of not less than 200MPa to form a green body;

[0015] S2-3: The preform is sintered at 1000-1500℃ in an environment with a vacuum of less than 100Pa, so that atomic diffusion and solid-phase reaction occur between powder particles, thereby achieving particle bonding and densification, and obtaining nickel-aluminum based shape memory alloy.

[0016] Step S3: Preparation of thermally conductive materials and shape memory alloy composite materials:

[0017] S3-1: Thoroughly mix the graphene-silicon composite material prepared in step S1 with the nickel-aluminum-based shape memory alloy prepared in step S2 at a mass ratio of 1:2 to 2:1;

[0018] S3-2: The mixed powder is hot-pressed to form the desired composite material preform under a pressure of not less than 100 MPa and a temperature of 600 to 1000 °C.

[0019] S3-3: The composite material is heat-treated in an inert atmosphere at a temperature of 800-1200℃ to eliminate internal stress, promote the diffusion and bonding of interfacial atoms, and improve the performance and stability of the composite material.

[0020] Preferably, in step S1, the mixing is carried out by ball milling, with the addition of zirconia balls as the medium, the rotation speed being 400-800 r / min, and the time being 5-20 h.

[0021] Preferably, in step S1, the cooling rate of the composite material after calcination is 2-5 °C / min.

[0022] Preferably, in step S2, the particle size of the nickel powder, aluminum powder, and molybdenum powder is 10 to 100 micrometers.

[0023] Preferably, in steps S2 and S3, mechanical stirring is used for mixing.

[0024] Preferably, in steps S2 and S3, the powder is loaded into a mold and then pressed into pressure by a press.

[0025] Preferably, a muffle furnace is used for calcination in step S1; and a vacuum sintering furnace is used for sintering in step S2.

[0026] In a second aspect, the present invention provides a method for preparing a thermally conductive layer-stress layer composite material, as described in the first aspect.

[0027] Thirdly, the present invention provides a thermally conductive layer-stress layer composite material for filling lithium battery modules, which is prepared by the method described in the second aspect.

[0028] The technical principle of this invention is as follows: A gradient thermally conductive material layer can form a nonlinear thermal conduction path between battery cells, preferentially dissipating heat from the heating area. A shape memory alloy, through a pre-loaded force design, dynamically balances the stress generated by battery expansion / contraction during charging and discharging. The composite loading of these two materials between battery cells achieves both thermal conductivity and uniform stress control in lithium metal batteries.

[0029] The advantages of the resulting structure are as follows: (1) Graphene has ultra-high thermal conductivity, which can quickly dissipate the heat generated by silicon-based materials during operation, greatly improving the heat dissipation performance of composite materials. (2) Under high temperature conditions, graphene can enhance the structural stability of silicon-based materials and suppress the thermal expansion and thermal deformation of silicon-based materials. (3) Under high temperature conditions, nickel-aluminum-based shape memory alloys can still maintain high strength and hardness, have good creep resistance, and can withstand large mechanical and thermal stresses, ensuring the structural integrity and stability of components under high temperature working conditions. (4) Nickel-aluminum-based shape memory alloys themselves have high strength and hardness, can withstand large external forces, and are not prone to plastic deformation. (5) The method is inexpensive and easy to scale up. Therefore, this method has the advantages of being time-saving, simple and effective, with significant improvement effect, and easy to scale up and apply.

[0030] The beneficial effects achieved by this invention are as follows:

[0031] The method established in this invention, which combines a graphene-silicon-based composite material with a nickel-aluminum-based shape memory alloy double-layer control layer, not only creates nonlinear heat conduction paths between battery cells, preferentially dissipating heat from heating regions, but also dynamically balances the stress generated by battery expansion / contraction during charging and discharging through pre-loaded force design. The composite loading of these two materials between battery cells achieves both thermal conductivity and uniform stress control in lithium metal batteries. Attached Figure Description

[0032] Figure 1. Schematic diagram of thermal conductivity and stress uniformity control;

[0033] Figure 2 shows the temperature difference change of the lithium metal battery module before and after regulation;

[0034] Figure 3 shows the stress changes of the lithium metal battery module before and after regulation. Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments.

[0036] Example 1

[0037] Step S1: Preparation of graphene-silicon composite material:

[0038] 1 kg of graphene and 5.7 kg of silicone resin were added to a ball mill jar, along with an equal mass of zirconia balls. The milling speed was 600 r / min for 10 h. The composite material was then calcined in a muffle furnace at 800 °C for 6 h, with a cooling rate of 3 °C / min. After calcination, the material was stored in a glove box for later use.

[0039] Step S2: Preparation of nickel-aluminum based shape memory alloys:

[0040] S2-1: Weigh 0.5 kg of nickel powder (99.5%), 4 kg of aluminum powder (99.9%) and 7 kg of molybdenum powder (99.9%). The powder particle size is 10 micrometers. Mix them thoroughly and evenly using a mechanical mixing method at a speed of 300 r / min for 20 h.

[0041] S2-2: Place the mold containing the powder into a press and press it at room temperature with a pressure of 400MPa to initially form the powder into a blank with a certain shape and strength.

[0042] S2-3: The preform is smoothly placed into a sintering furnace, vacuumed, and sintered at high temperature to allow atomic diffusion and solid-phase reactions to occur between powder particles, achieving particle bonding and densification. The sintering temperature is 1300℃, and the time is 2 hours. After cooling, it is removed for later use at a cooling rate of 3℃ / min.

[0043] Step S3: Preparation of thermally conductive materials and shape memory alloy composite materials:

[0044] S3-1: Weigh 4 kg of the prepared graphene-silicon composite material and 6 kg of nickel-aluminum-based shape memory alloy and add them to a ball mill. The speed is 200 r / min and the time is 10 h to ensure that the two are fully mixed.

[0045] S3-2: The mixed powder is placed into a mold and the desired composite material preform is produced by hot pressing at 150MPa and 800℃.

[0046] S3-3: The composite material is heat-treated at 1000℃ in an argon atmosphere to eliminate internal stress, promote the diffusion and bonding of interfacial atoms, and improve the performance and stability of the composite material.

[0047] Test Results

[0048] Battery module preparation:

[0049] S4-1: Purchase ten lithium metal pouch batteries with a capacity of 10Ah from Yiwei Lithium Energy Company; stack the ten batteries on top of each other and place them in a room temperature chamber; attach a temperature and pressure sensor to the top and bottom surfaces of each battery; place graphene-silicone resin (1x63x92mm) and nickel-aluminum-molybdenum shape memory alloy composite material (1x63x92mm) between the lithium metal pouch batteries;

[0050] S4-2: Ten lithium metal batteries were charged and discharged at a rate of 0.1C at room temperature, with a test voltage of 3.0-4.3V; after three activation cycles, the batteries were charged and discharged for a long period of time at a current density of 1C.

[0051] A schematic diagram of the prepared thermal conductivity and stress uniformity is shown in Figure 1; Figure 2 clearly shows that the thermal conductivity of the battery module is low and stable after passing through the graphene-silicon composite material. In addition, the stress variation of the battery module is even lower, as shown in Figure 3.

Claims

1. A method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity, characterized in that, The specific steps are as follows: A thermally conductive layer-stress layer composite material is filled between several groups of lithium metal batteries in the battery module; the thermally conductive layer-stress layer composite material is a composite material of graphene-silicon-based composite material and nickel-aluminum-based shape memory alloy, and the preparation method is as follows: Step S1: Preparation of graphene-silicon-based composite material: Graphene and silicon-based materials are mixed at a mass ratio of 1:3 to 1:9 and then calcined at 700 to 900°C; Step S2: Preparation of nickel-aluminum-based shape memory alloy: S2-1: 1 part by mass of nickel, 5 to 10 parts by mass of aluminum, and 10 to 20 parts by mass of molybdenum are thoroughly mixed to obtain a mixed powder; S2-2: The mixed powder is pressed under a pressure of not less than 200 MPa. S2-3: The blank is sintered at 1000-1500℃ in an environment with a vacuum of less than 100Pa to obtain a nickel-aluminum based shape memory alloy; Step S3 Preparation of thermally conductive material and shape memory alloy composite material: S3-1: The graphene-silicon based composite material prepared in step S1 is fully mixed with the nickel-aluminum based shape memory alloy prepared in step S2 at a mass ratio of 1:2 to 2:1; S3-2: The mixed powder is hot-pressed to form the required composite material blank at a pressure of not less than 100MPa and a temperature of 600-1000℃; S3-3: The composite material is heat-treated in an inert atmosphere at a temperature of 800-1200℃.

2. The method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity according to claim 1, characterized in that, In step S1, the mixing is carried out by ball milling, with the addition of zirconia balls as the medium, at a speed of 400-800 r / min, for a time of 5-20 h.

3. The method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity according to claim 1, characterized in that, In step S1, the cooling rate of the composite material after calcination is 2-5℃ / min.

4. The method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity according to claim 1, characterized in that, In step S2, the particle size of the nickel powder, aluminum powder, and molybdenum powder is 10 to 100 micrometers.

5. The method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity according to claim 1, characterized in that, In steps S2 and S3, mechanical stirring is used for mixing.

6. The method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity according to claim 1, characterized in that, In steps S2 and S3, the powder is loaded into the mold and then pressed into pressure by a press.

7. The method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity according to claim 1, characterized in that, In step S1, a muffle furnace is used for calcination; in step S2, a sintering furnace is used for vacuum sintering.

8. The method for improving the safety of high-energy battery modules by regulating thermal conductivity and stress uniformity according to claim 1, characterized in that, The area of ​​the thermally conductive layer-stress layer composite material filling the lithium metal battery is not less than the cross-section of the lithium metal battery, and the thickness is not less than 1 / 5 of the thickness of the lithium metal battery.

9. A method for preparing a thermally conductive layer-stress layer composite material, as described in any one of steps S1 to S3 of claims 1 to 8.

10. A thermally conductive layer-stress layer composite material for filling lithium battery modules, prepared by the method described in claim 9.

Images