Preparation method of 1.5 V rechargeable battery

Abstract

The invention discloses a preparation method of a 1.5 V rechargeable battery. The method is characterized by comprising the following steps: step 1, preparing a positive active material layer by adopting a multi-component composite positive electrode material to obtain a positive plate; 2, preparing a negative electrode active substance layer by adopting the binary composite negative electrode material to obtain a negative electrode plate; step 3, slitting the positive and negative pole pieces according to size requirements, welding tabs, winding a polyolefin isolating membrane into a columnar roll core, and putting the columnar roll core into a steel shell to complete the assembly of the battery cell; and 4, carrying out vacuum baking on the assembled battery cell, injecting the prepared low-temperature electrolyte, and carrying out a charge-discharge process to prepare the 1.5 V rechargeable battery. The 1.5 V rechargeable battery prepared by the invention has a slowly-dropped voltage platform, the voltage range of the discharge capacity of the battery is 0.8-1.5 V, the normal charge and discharge capacity at the low temperature of-40-60 DEG C can be realized, DCDC voltage reduction is not needed, and meanwhile, the battery is good in safety performance and does not catch fire or explode.

Description

Technical Field

[0001] The present invention relates to a preparation method of a rechargeable battery, and more particularly to a preparation method of a 1.5V rechargeable battery. Background Art

[0002] Currently, with the enhancement of environmental awareness and the popularization of intelligent devices, traditional disposable batteries (such as alkaline batteries) are gradually replaced by rechargeable batteries due to their high pollution, high consumption, and non-reusable disadvantages. The 1.5V rechargeable battery has become an ideal choice for households and electronic devices (such as remote controls, toys, smart door locks, cameras, etc.). Policy promotion has also accelerated this trend. For example, new energy policies encourage resource recycling. The existing 1.5V rechargeable battery system on the market uses an internal DCDC buck circuit to stably reduce the high voltage (3.7V) of a lithium battery to 1.5V, solving the compatibility problem with AA battery devices. At the same time, the following problems are brought: 1. Sudden power-off risk: Since the lithium battery maintains a constant 1.5V voltage output throughout the process, the voltage will drop suddenly when the power is exhausted (such as dropping to 1.1V or 0V), and users cannot predict the remaining power through the voltage drop, which may cause the device to suddenly stop working (such as the smart door lock losing power without warning); 2. Safety hazards: Using lithium batteries in some high-current devices (such as flashlights) may cause safety hazards due to heat generation, and manufacturers clearly recommend using nickel-metal hydride or nickel-zinc batteries; 3. Cost and compatibility issues: Lithium batteries need to be equipped with a buck circuit inside, which leads to high costs due to complex structures and some chargers only support specific brand batteries; 4. Low-temperature performance limitations: The charging efficiency of lithium batteries decreases in low-temperature environments (such as below 0°C), affecting the use of outdoor devices. Summary of the Invention

[0003] In view of the above problems existing in the existing 1.5V rechargeable battery system, the present invention provides a preparation method of a 1.5V rechargeable battery. The 1.5V rechargeable battery prepared by this method has the following three characteristics: (1) It has a characteristic of a gradually decreasing discharge curve, and the discharge capacity is in the voltage range of 0.8V to 1.5V; (2) The battery has an electrochemical characteristic of intrinsic 1.5V and does not require DCDC bucking; (3) The battery can be discharged to 0V without affecting the cycle use of the battery; (4) In a low-temperature environment of -40°C, the battery can be stably charged and discharged; (4) The battery has good safety performance and does not catch fire or explode.

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

[0005] A preparation method of a 1.5V rechargeable battery includes the following steps:

[0006] Step 1. Prepare the positive electrode active material layer using a multi-component composite cathode material to obtain a positive electrode sheet: Stir and mix the multi-component composite cathode material, binder, and composite conductive paste in proportion, and coat it on an aluminum current collector to obtain a positive electrode sheet that meets the process standards. Among them: The mass ratio of the multi-component composite cathode material, binder, and composite conductive paste is 1: 0.02 - 0.06: 0.008 - 0.015; The multi-component composite cathode material is obtained by mixing lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP in a mass ratio of 0.5 - 1: 0.1 - 0.5: 0.1 - 0.5; The composite conductive paste is obtained by mixing graphene and carbon nanotubes in a mass ratio of 0.1 - 0.5: 0.5 - 1; The binder includes but is not limited to one of PAA-Li (lithium polyacrylate), PVDF (polyvinylidene fluoride), and PTFE (polytetrafluoroethylene);

[0007] Step 2. Prepare the negative electrode active material layer using a binary composite anode material to obtain a negative electrode sheet: Stir and mix the binary composite anode material, binder, and composite conductive paste in proportion, and coat it on an aluminum current collector to obtain a negative electrode sheet that meets the process standards. Among them: The mass ratio of the binary composite anode material, binder, and composite conductive paste is 1: 0.02 - 0.06: 0.008 - 0.015; The binary composite anode material is obtained by mixing lithium titanium phosphate LTP and lithium titanate LTO in a mass ratio of 0.5 - 1: 0.1 - 0.5; The composite conductive paste is obtained by mixing graphene and carbon nanotubes in a mass ratio of 0.1 - 0.5: 0.5 - 1; The binder includes but is not limited to one of PAA-Li (lithium polyacrylate), PVDF (polyvinylidene fluoride), and PTFE (polytetrafluoroethylene);

[0008] Step 3. After cutting the positive and negative electrode sheets to the required size and welding the electrode tabs, wind them with a polyolefin separator into a cylindrical core, and put them into a steel shell to complete the assembly of the battery cell. Among them: The volume density of the positive electrode active material layer is controlled at 3.3 - 4.0 g / cm 3 and the volume density of the negative electrode active material layer is controlled at 1.8 - 2.5 g / cm 3 , and the thickness of the separator is 9 - 14 μm;

[0009] Step 4. Preparation of the low-temperature electrolyte: Prepare the solvent, lithium salt, and additive according to the following mass percentages: Lithium hexafluorophosphate LiPF6 accounts for 8 - 12%, lithium difluorooxalate borate LiDFOB accounts for 2 - 4%, ethylene carbonate EC accounts for 20 - 25%, propylene carbonate PC accounts for 15 - 25%, ethyl methyl carbonate EMC accounts for 30 - 40%, dimethyl carbonate DMC accounts for 10 - 15%, fluoroethylene carbonate FEC accounts for 5 - 15%, and tris(trimethylsilyl) phosphate TMSP accounts for 2 - 3%.

[0010] Step 5: After the assembly is completed, the battery cells are baked in vacuum, and the prepared low-temperature electrolyte is injected. After the charge-discharge process, a 1.5V rechargeable battery is made. Among them: the baking temperature is 80 - 100°C; the charge-discharge process includes the following sequence: (1) After the battery is filled with liquid and sealed, it is left standing at 45°C for 18 - 24h; (2) The battery is charged to 1.8 - 2.5V at 0.1C and charged at a constant voltage for 2h; (3) The battery is left standing at 45°C for 7 days; (4) The battery is charged at a constant voltage to 1.7 - 2.0V at 0.05C, and the charging time is 2h.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] 1. The 1.5V rechargeable battery prepared by the present invention has a voltage platform with a slow decline. The voltage range of the battery discharge capacity is 0.8V - 1.5V, which ideally matches the scenario requirements at this voltage.

[0013] 2. The 1.5V rechargeable battery prepared by the present invention can achieve normal charge-discharge ability at low temperatures of -40°C to 60°C, and has a long cycle life, meeting the use requirements in extremely cold and low temperatures.

[0014] 3. The 1.5V rechargeable battery prepared by the present invention can be stored for a long time, has a high charge retention rate, meets the state of being charged at any time, and is convenient to use.

[0015] 4. The 1.5V rechargeable battery prepared by the present invention has an electrochemical characteristic of an intrinsic 1.5V, does not require DCDC step-down, and at the same time, the battery has good safety performance and does not catch fire or explode. Description of the Drawings

[0016] Figure 1 It is the charge-discharge curve graph of the 1.5V rechargeable battery obtained in Example 1.

[0017] Figure 2 It is the discharge curve graph at -40°C of the 1.5V rechargeable battery obtained in Example 1. Detailed Embodiments

[0018] The technical solutions of the present invention will be further described below in conjunction with the 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.

[0019] Example 1:

[0020] Step 1: Weigh lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP respectively according to the mass ratio of 0.5:0.1:0.4, and mix them in a mixer for 1 h to obtain a multi-component composite cathode material; add the multi-component composite cathode material, binder PVDF, and composite conductive paste (graphene: carbon nanotube = 0.3:0.7) to a vacuum high-speed mixer according to the mass ratio of 1:0.03:0.008 for mixing and slurrying, coat it on a 12-μm aluminum foil, and the volume density after rolling is 3.35 g / cm 3 , and obtain a positive electrode sheet.

[0021] Step 2: Weigh lithium titanium phosphate LTP and lithium titanate LTO respectively according to the mass ratio of 0.5:0.5, and mix them in a mixer for 1 h to obtain a binary composite anode material; add the binary composite anode material, binder PVDF, and composite conductive paste (graphene: carbon nanotube = 0.3:0.7) to a vacuum high-speed mixer according to the mass ratio of 1:0.04:0.01 for mixing and slurrying, coat it on a 12-μm aluminum foil, and the volume density after rolling is 2.05 g / cm 3 , and obtain a negative electrode sheet.

[0022] Step 3: Cut the positive and negative electrode sheets to the required size, weld the tab, and wind them into a cylindrical core with a 12-μm separator, put them into a steel shell, bake in vacuum at 80 °C for 16 h, inject the prepared low-temperature electrolyte, and assemble it into a 1.5-V rechargeable battery. The formula of the low-temperature electrolyte is as follows: the proportion of lithium hexafluorophosphate LiPF6 is 8%, the proportion of lithium difluorooxalate borate LiDFOB is 2%, the proportion of ethylene carbonate EC is 20%, the proportion of propylene carbonate PC is 20%, the proportion of ethyl methyl carbonate EMC is 30%, the proportion of dimethyl carbonate DMC is 10%, the proportion of fluoroethylene carbonate FEC is 8%, and the proportion of tris(trimethylsilyl) phosphate TMSP is 2%.

[0023] Step 4: Charge and discharge in the following order: (1) Let the battery stand at 45 °C for 18 h after injecting the electrolyte and sealing; (2) Charge the battery to 2.2 V at 0.1 C and charge at constant voltage for 2 h; (3) Let the battery stand at 45 °C for 7 days; (4) Charge the battery to 1.9 V at constant voltage at 0.05 C, and the charging time is 2 h.

[0024] The 1.5-V rechargeable battery prepared in this example has 100% SOC, can be stored for a long time, and the charge-discharge curve is as Figure 1 shown, and the discharge curve at low temperature of -40 °C is as Figure 2 shown. As Figure 1 can be seen, the battery has a gradually decreasing voltage platform, and the voltage range of most of the discharge capacity of the battery is between 0.8 V and 1.5 V. As Figure 2 can be seen, the battery has good low-temperature discharge performance, and the voltage range of most of the discharge capacity of the battery is between 0.8 V and 1.5 V at low temperature.

[0025] Example 2:

[0026] Step 1: Weigh lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP at a mass ratio of 0.5:0.2:0.3 respectively, and mix them in a mixer for 1 h to obtain a multi-component composite cathode material; add the multi-component composite cathode material, binder PVDF, and composite conductive paste (graphene:carbon nanotube = 0.2:0.8) to a vacuum high-speed mixer for stirring and slurrying at a mass ratio of 1:0.03:0.01, coat it on a 12-μm aluminum foil, and after rolling, the bulk density is 3.4 g / cm 3 , to obtain a positive electrode sheet.

[0027] Step 2: Weigh lithium titanium phosphate LTP and lithium titanate LTO at a mass ratio of 0.5:0.5 respectively, and mix them in a mixer for 1 h to obtain a binary composite anode material; add the binary composite anode material, binder PVDF, and composite conductive paste (graphene:carbon nanotube = 0.2:0.8) to a vacuum high-speed mixer for stirring and slurrying at a mass ratio of 1:0.04:0.01, coat it on a 12-μm aluminum foil, and after rolling, the bulk density is 2.2 g / cm 3 , to obtain a negative electrode sheet.

[0028] Step 3: Cut the positive and negative electrode sheets to the required size, weld the tabs, and then wind them into a cylindrical core with a 12-μm separator, put it into a steel shell, bake it in vacuum at 80 °C for 16 h, inject the prepared low-temperature electrolyte, and assemble it into a 1.5-V rechargeable battery. The formula of the low-temperature electrolyte is as follows: lithium hexafluorophosphate LiPF6 accounts for 8%, lithium difluorooxalate borate LiDFOB accounts for 2%, ethylene carbonate EC accounts for 20%, propylene carbonate PC accounts for 20%, ethyl methyl carbonate EMC accounts for 30%, dimethyl carbonate DMC accounts for 10%, fluoroethylene carbonate FEC accounts for 8%, and tris(trimethylsilyl) phosphate TMSP accounts for 2%.

[0029] Step 4: Charge and discharge in the following order: (1) Let the battery stand at 45 °C for 18 h after injecting the electrolyte and sealing; (2) Charge the battery to 2.1 V at 0.1 C and carry out constant-voltage charging for 2 h; (3) Let the battery stand at 45 °C for 7 days; (4) Charge the battery to 1.9 V at 0.05 C with constant voltage, and the charging time is 2 h.

[0030] The 1.5-V rechargeable battery prepared in this example has 100% SOC and can be stored for a long time.

[0031] Example 3:

[0032] Step 1: Weigh lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP according to the mass ratio of 0.6:0.2:0.2, and mix them in a mixer for 1 h to obtain a multi-component composite cathode material; add the multi-component composite cathode material, binder PAA-Li, and composite conductive paste (graphene:carbon nanotube = 0.4:0.6) to a vacuum high-speed mixer according to the mass ratio of 1:0.03:0.008, stir and mix the slurry, coat it on a 12-μm aluminum foil, and the volume density after rolling is 3.6 g / cm 3 , to obtain a positive electrode sheet.

[0033] Step 2: Weigh lithium titanium phosphate LTP and lithium titanate LTO according to the mass ratio of 0.7:0.3, and mix them in a mixer for 1 h to obtain a binary composite anode material; add the binary composite anode material, binder PAA-Li, and composite conductive paste (graphene:carbon nanotube = 0.4:0.6) to a vacuum high-speed mixer according to the mass ratio of 1:0.05:0.01, stir and mix the slurry, coat it on a 12-μm aluminum foil, and the volume density after rolling is 2.05 g / cm 3 , to obtain a negative electrode sheet.

[0034] Step 3: Cut the positive and negative electrode sheets to the required size, weld the electrode tabs, and then wind them into a cylindrical core with a 14-μm separator membrane, put them into a steel shell, bake them in a vacuum at 80 °C for 16 h, inject the prepared low-temperature electrolyte, and assemble them into a 1.5-V rechargeable battery. The formula of the low-temperature electrolyte is as follows: lithium hexafluorophosphate LiPF6 accounts for 9%, lithium difluoro(oxalato)borate LiDFOB accounts for 3%, ethylene carbonate EC accounts for 20%, propylene carbonate PC accounts for 15%, ethyl methyl carbonate EMC accounts for 30%, dimethyl carbonate DMC accounts for 13%, fluoroethylene carbonate FEC accounts for 8%, and tris(trimethylsilyl) phosphate TMSP accounts for 2%.

[0035] Step 4: Charge and discharge in the following order: (1) Let the battery stand at 45 °C for 18 h after injecting the electrolyte and sealing; (2) Charge the battery to 2.3 V at 0.1 C and carry out constant-voltage charging for 2 h; (3) Let the battery stand at 45 °C for 7 days; (4) Charge the battery to 2.0 V at a constant voltage of 0.05 C, and the charging time is 2 h.

[0036] The 1.5-V rechargeable battery prepared in this example has 100% SOC and can be stored for a long time.

[0037] Example 4:

[0038] Step 1: Weigh lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP according to the mass ratio of 0.7:0.2:0.1 respectively, and mix them in a mixer for 1 h to obtain a multi-component composite cathode material; add the multi-component composite cathode material, binder PAA-Li, and composite conductive paste (graphene:carbon nanotube = 0.5:0.5) to a vacuum high-speed mixer according to the mass ratio of 1:0.03:0.008 to stir and mix the slurry, coat it on a 12-μm aluminum foil, and the volume density after rolling is 3.7 g / cm 3 , to obtain a positive electrode sheet.

[0039] Step 2: Weigh lithium titanium phosphate LTP and lithium titanate LTO according to the mass ratio of 0.7:0.3 respectively, and mix them in a mixer for 1 h to obtain a binary composite anode material; add the binary composite anode material, binder PAA-Li, and composite conductive paste (graphene:carbon nanotube = 0.5:0.5) to a vacuum high-speed mixer according to the mass ratio of 1:0.04:0.01 to stir and mix the slurry, coat it on a 12-μm aluminum foil, and the volume density after rolling is 1.9 g / cm 3 , to obtain a negative electrode sheet.

[0040] Step 3: Cut the positive and negative electrode sheets into required sizes according to the size requirements, weld the electrode tabs, and then wind them into a cylindrical core with a 14-μm separator, put them into a steel shell, bake them in a vacuum at 80 °C for 16 h, inject the prepared low-temperature electrolyte, and assemble them into a 1.5-V rechargeable battery. The formula of the low-temperature electrolyte is as follows: lithium hexafluorophosphate LiPF6 accounts for 9%, lithium difluoro(oxalato)borate LiDFOB accounts for 3%, ethylene carbonate EC accounts for 20%, propylene carbonate PC accounts for 15%, ethyl methyl carbonate EMC accounts for 30%, dimethyl carbonate DMC accounts for 13%, fluoroethylene carbonate FEC accounts for 8%, and tris(trimethylsilyl) phosphate TMSP accounts for 2%.

[0041] Step 4: Charge and discharge in the following order: (1) Let the battery stand at 45 °C for 18 h after injecting the electrolyte and sealing; (2) Charge the battery to 2.2 V at 0.1 C and perform constant-voltage charging for 2 h; (3) Let the battery stand at 45 °C for 7 days; (4) Charge the battery to 1.9 V at a constant voltage of 0.05 C, and the charging time is 2 h.

[0042] The 1.5-V rechargeable battery prepared in this example has 100% SOC and can be stored for a long time.

[0043] Example 5:

[0044] Step 1: Weigh lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP according to the mass ratio of 0.5:0.2:0.3 respectively, and mix them in a mixer for 1 h to obtain a multi-component composite cathode material; according to the mass ratio of 1:0.03:0.01, add the multi-component composite cathode material, binder PAA-Li, and composite conductive paste (graphene:carbon nanotube = 0.1:0.9) to a vacuum high-speed mixer to stir and mix the slurry, coat it on a 12-μm aluminum foil, and the volume density after rolling is 3.4 g / cm 3 , and obtain a positive electrode sheet.

[0045] Step 2: Weigh lithium titanium phosphate LTP and lithium titanate LTO according to the mass ratio of 0.6:0.4 respectively, and mix them in a mixer for 1 h to obtain a binary composite anode material; according to the mass ratio of 1:0.04:0.01, add the binary composite anode material, binder PAA-Li, and composite conductive paste (graphene:carbon nanotube = 0.1:0.9) to a vacuum high-speed mixer to stir and mix the slurry, coat it on a 12-μm aluminum foil, and the volume density after rolling is 1.8 g / cm 3 , and obtain a negative electrode sheet.

[0046] Step 3: Cut the positive and negative electrode sheets according to the size requirements, weld the electrode tabs, and then wind them into a cylindrical core with a 10-μm separator, put them into a steel shell, bake them in vacuum at 80 °C for 16 h, inject the prepared low-temperature electrolyte, and assemble them into a 1.5-V rechargeable battery. The formula of the low-temperature electrolyte is as follows: lithium hexafluorophosphate LiPF6 accounts for 10%, lithium difluoro(oxalato)borate LiDFOB accounts for 2%, ethylene carbonate EC accounts for 20%, propylene carbonate PC accounts for 18%, ethyl methyl carbonate EMC accounts for 30%, dimethyl carbonate DMC accounts for 10%, fluoroethylene carbonate FEC accounts for 7%, and tris(trimethylsilyl) phosphate TMSP accounts for 3%.

[0047] Step 4: Charge and discharge in the following order: (1) Let the battery stand at 45 °C for 18 h after injecting the electrolyte and sealing; (2) Charge the battery at 0.1C to 2.3V and carry out constant-voltage charging for 2 h; (3) Let the battery stand at 45 °C for 7 days; (4) Charge the battery at 0.05C with constant voltage to 1.9V, and the charging time is 2 h.

[0048] The 1.5-V rechargeable battery prepared in this example has 100% SOC and can be placed for a long time.

[0049] Example 6:

[0050] Step 1: Weigh lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP respectively according to the mass ratio of 0.6:0.1:0.3, and mix them in a mixer for 1 h to obtain a multi-component composite cathode material; add the multi-component composite cathode material, binder PVDF, and composite conductive paste (graphene:carbon nanotube = 0.3:0.7) to a vacuum high-speed mixer according to the mass ratio of 1:0.03:0.012 for stirring and slurrying, coat it on a 12-μm aluminum foil, and the volume density after rolling is 3.5 g / cm 3 , and obtain a positive electrode sheet.

[0051] Step 2: Weigh lithium titanium phosphate LTP and lithium titanate LTO respectively according to the mass ratio of 0.6:0.4, and mix them in a mixer for 1 h to obtain a binary composite anode material; add the binary composite anode material, binder PVDF, and composite conductive paste (graphene:carbon nanotube = 0.3:0.7) to a vacuum high-speed mixer according to the mass ratio of 1:0.04:0.015 for stirring and slurrying, coat it on a 12-μm aluminum foil, and the volume density after rolling is 1.8 g / cm 3 , and obtain a negative electrode sheet.

[0052] Step 3: Cut the positive and negative electrode sheets into required sizes according to the size requirements, weld the tab ears, then wind them into a cylindrical core with a 10-μm separator, put them into a steel shell, bake them in a vacuum at 100 °C for 16 h, inject the prepared low-temperature electrolyte, and assemble them into a 1.5-V rechargeable battery. The formula of the low-temperature electrolyte is as follows: lithium hexafluorophosphate LiPF6 accounts for 10%, lithium difluoro(oxalato)borate LiDFOB accounts for 2%, ethylene carbonate EC accounts for 20%, propylene carbonate PC accounts for 18%, ethyl methyl carbonate EMC accounts for 30%, dimethyl carbonate DMC accounts for 10%, fluoroethylene carbonate FEC accounts for 7%, and tris(trimethylsilyl) phosphate TMSP accounts for 3%.

[0053] Step 4: Charge and discharge in the following order: (1) Leave the battery at 45 °C for 18 h after injecting the electrolyte and sealing; (2) Charge the battery at 0.1C to 2.4 V and carry out constant-voltage charging for 2 h; (3) Leave the battery at 45 °C for 7 days; (4) Charge the battery at 0.05C with constant voltage to 1.8 V, and the charging time is 2 h.

[0054] The 1.5-V rechargeable battery prepared in this example has 100% SOC and can be stored for a long time.

Claims

1. A method for preparing a 1.5V rechargeable battery, characterized in that The method includes the following steps: Step 1: Stir and mix a multi-component composite cathode material, a binder, and a composite conductive paste in proportion, and coat them on an aluminum current collector to obtain a positive electrode sheet, where: the mass ratio of the multi-component composite cathode material, the binder, and the composite conductive paste is 1: 0.02 - 0.06: 0.008 - 0.015; Step 2: Stir and mix a binary composite anode material, a binder, and a composite conductive paste in proportion, and coat them on an aluminum current collector to obtain a negative electrode sheet, where: the mass ratio of the binary composite anode material, the binder, and the composite conductive paste is 1: 0.02 - 0.06: 0.008 - 0.015; Step 3: Cut the positive and negative electrode sheets to the required size, weld the tabs, and wind them into a cylindrical core with a polyolefin separator, and put them into a steel shell to complete the assembly of the battery cell; Step 4: After the assembly is completed, the battery cell is vacuum baked, injected with the prepared low-temperature electrolyte, and after the charge and discharge process, a 1.5V rechargeable battery is made.

2. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the said Step 1, the multi-component composite cathode material is obtained by mixing lithium nickel cobalt manganese oxide NCM, lithium manganese iron phosphate LMFP, and lithium iron phosphate LFP in a mass ratio of 0.5 - 1: 0.1 - 0.5: 0.1 - 0.

5.

3. The preparation method of the 1.5V rechargeable battery according to claim 1, wherein In the said Step 2, the binary composite anode material is obtained by mixing lithium titanium phosphate LTP and lithium titanate LTO in a mass ratio of 0.5 - 1: 0.1 - 0.

5.

4. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the said Step 1 and Step 2, the composite conductive paste is obtained by mixing graphene and carbon nanotubes in a mass ratio of 0.1 - 0.5: 0.5 - 1.

5. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the said Step 1 and Step 2, the binder is one of PAA-Li, PVDF, and PTFE.

6. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the third step, the volume density of the positive active material layer is controlled to be 3.3 - 4.0 g / cm 3 , and the volume density of the negative active material layer is controlled to be 1.8 - 2.5 g / cm 3 .

7. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the said Step 3, the thickness of the separator is 9 - 14μm.

8. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the said Step 4, by mass percentage, the low-temperature electrolyte is prepared from the following components: lithium hexafluorophosphate LiPF6 accounts for 8 - 12%, lithium difluoro(oxalato)borate LiDFOB accounts for 2 - 4%, ethylene carbonate EC accounts for 20 - 25%, propylene carbonate PC accounts for 15 - 25%, ethyl methyl carbonate EMC accounts for 30 - 40%, dimethyl carbonate DMC accounts for 10 - 15%, fluoroethylene carbonate FEC accounts for 5 - 15%, and tris(trimethylsilyl) phosphate TMSP accounts for 2 - 3%.

9. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the said Step 4, the baking temperature is 80 - 100°C.

10. The preparation method of the 1.5V rechargeable battery according to claim 1, characterized in that In the said Step 4, the charge and discharge process includes the following sequence: (1) The battery is left standing at 45°C for 18 - 24h after the electrolyte is injected and the battery is sealed; (2) The battery is charged to 1.8 - 2.5V at 0.1C and charged at a constant voltage for 2h; (3) The battery is left standing at 45°C for 7 days; (4) The battery is charged at a constant voltage of 0.05C to 1.7 - 2.0V, and the charging time is 2h.

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