An electrochemical device, a method for manufacturing the same, and an application thereof

Abstract

The application provides an electrochemical device and a preparation method and application thereof, the electrochemical device comprises a positive electrode, a negative electrode and a separator film and an electrolyte between the positive electrode and the negative electrode, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer which are arranged in a stack, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer which are arranged in a stack, the electrolyte comprises a lithium salt, a non-aqueous solvent and an additive, the positive electrode active material layer comprises a lithium supplement agent, and the additive comprises a sulfonate additive and / or a borate additive. The electrochemical device provided by the application reduces the temperature rise of the battery cell, reduces the gas generation phenomenon, improves the safety and reliability of the battery and is conducive to large-scale popularization and application on the basis of improving the fast charging performance of the battery through the synergistic effect among the lithium supplement agent, the sulfonate additive and the borate additive.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, and relates to an electrochemical device, and more particularly to an electrochemical device, its preparation method and application. Background Technology

[0002] In recent years, the development trend of new energy vehicles has been continuously positive, and electric vehicles have been rapidly popularized. Shipments of lithium iron phosphate batteries and ternary lithium batteries in the power battery field have increased year by year. However, people still experience travel anxiety when it comes to electric vehicles. Therefore, how to improve fast charging technology and save charging time has become a key issue to consider in increasing the adoption rate of electric vehicles.

[0003] To improve the fast-charging performance of batteries, reducing cell impedance is essential. However, existing technologies for reducing cell impedance often lead to a deterioration in safety performance, such as high-temperature swelling. This is because power batteries are prone to generating large amounts of gas under conditions such as overcharging and high temperatures, resulting in decreased battery performance and increased safety risks. In particular, for lithium oxide systems such as LiCoO2 and ternary materials, the collapse of the cathode material structure during overcharging releases active oxygen, oxidizes the electrolyte solvent to produce a large amount of CO2, and releases heat, even triggering thermal runaway, significantly reducing the safety and reliability of the battery.

[0004] Therefore, it is evident that improving battery fast charging performance while reducing cell temperature rise, minimizing gas generation, and enhancing battery safety and reliability has become an urgent problem for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide an electrochemical device, its preparation method, and its application. Through the synergistic effect of lithium replenishing agents, sulfonate additives, and borate additives, the device improves the fast charging performance of the battery, reduces cell temperature rise, reduces gas generation, and enhances battery safety and reliability, which is conducive to large-scale application.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an electrochemical device comprising a positive electrode, a negative electrode, and a separator and an electrolyte located between the positive electrode and the negative electrode. The positive electrode comprises a positive current collector and a positive active material layer stacked together, and the negative electrode comprises a negative current collector and a negative active material layer stacked together. The electrolyte comprises a lithium salt, a non-aqueous solvent, and additives. The positive active material layer contains a lithium replenishing agent, and the additives comprise sulfonate additives and / or borate additives.

[0008] The chemical formula of the lithium supplement is: Li x M y Oz M is selected from any one or at least two of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo or Sn, and 1≤x≤8, y>0, 0<z≤13.

[0009] This invention incorporates specific types of lithium replenishing agents into the positive electrode active material layer, effectively reducing cell impedance and improving fast charging capability. However, because these agents release oxygen along with lithium, and oxygen oxidizes the electrolyte and generates a large amount of gas, especially at high temperatures, side reactions are exacerbated, leading to even more gas production. To address this, sulfonate additives in the electrolyte can react with oxygen, thus reducing gas production. Furthermore, boron in borate additives combines with oxygen, further preventing side reactions between oxygen and the electrolyte. Ultimately, through the synergistic effect between the lithium replenishing agent and the additives, the invention improves battery fast charging performance while reducing cell temperature rise, minimizing gas production, and enhancing battery safety and reliability, facilitating large-scale application.

[0010] Preferably, the total mass of the electrolyte is used as the calculation basis, and the content of the sulfonate additive is defined as a%, then the value range of a is: 0.1≤a≤3.

[0011] Preferably, the total mass of the electrolyte is used as the calculation basis, and the content of the borate additive is defined as b%. Then the value range of b is: 0.01≤b≤1.

[0012] Preferably, the total mass of the positive electrode is used as the calculation basis, and the content of the lithium replenishing agent is defined as c%. Then the value range of c is: 0.2≤c≤3, and more preferably: 0.3≤c≤3.

[0013] Preferably, the content relationship of the sulfonate additive, the borate additive and the lithium supplement is: 0.1≤c / (a+b)≤8.

[0014] Preferably, the lithium supplement includes Li5FeO4, Li5Fe5O8, Li6CoO4, Li2NiO2, Li2O, Li2O2, Li6MnO4, Li6ZnO4, Li2CuO2, Li2CoO2, Li2MnO2, Li2C2O4, and Li2Ni 0.5 Mn 1.5 O4 or Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 1.3 Any one or at least two of O2.

[0015] Preferably, the sulfonate additive is selected from any one or a combination of at least two of the following compounds:

[0016]

[0017] Preferably, the borate additive includes any one or a combination of at least two of lithium tetrafluoroborate (LiBF4), lithium difluorooxalate borate (LiDFOB), or lithium bis(oxalate borate) (LiBOB).

[0018] Preferably, the lithium salt comprises any one or a combination of at least two of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiTFSI), lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(pentafluoroethylsulfonyl)imide, or lithium tri(trifluoromethylsulfonyl)methyl.

[0019] Preferably, the non-aqueous solvent includes any one or a combination of at least two of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), or ethyl propyl carbonate (EPC).

[0020] In a second aspect, the present invention provides a method for preparing the electrochemical device as described in the first aspect, the method comprising the following steps:

[0021] (1) Prepare a positive electrode slurry containing lithium supplementation agent, coat the positive electrode slurry onto the surface of the positive electrode current collector, and then dry and post-process it to obtain the positive electrode;

[0022] (2) Prepare negative electrode slurry, coat the negative electrode slurry onto the surface of the negative electrode current collector, and then dry and post-process it to obtain the negative electrode;

[0023] (3) In a protective gas atmosphere, additives and lithium salts are added to a non-aqueous solvent in sequence, and the mixture is homogeneous to obtain an electrolyte.

[0024] (4) Preparation of the isolation membrane;

[0025] (5) Assemble the positive electrode, negative electrode, separator and battery cell housing, and inject electrolyte after forming to obtain an electrochemical device.

[0026] Steps (1)-(4) are not in any particular order.

[0027] Preferably, the positive current collector in step (1) comprises aluminum foil.

[0028] Preferably, the negative electrode current collector in step (2) comprises copper foil.

[0029] Preferably, the drying temperatures in steps (1) and (2) are 85-120°C.

[0030] Preferably, the post-processing in steps (1) and (2) includes sequential cold pressing, cutting, and slitting.

[0031] Preferably, the protective gas in step (3) includes any one or a combination of at least two of nitrogen, helium, or argon.

[0032] Preferably, the preparation of the isolation membrane in step (4) includes: coating a composite coating on the surface of the substrate.

[0033] Preferably, the substrate comprises a polyethylene film, and the composite coating comprises a polyvinylidene fluoride layer and / or a boehmite ceramic layer.

[0034] Preferably, the assembly of the electrochemical device in step (5) includes: stacking the positive electrode, the separator and the negative electrode in sequence, installing them into the battery cell housing, sealing and shaping the battery cell, injecting electrolyte, and activating the battery cell.

[0035] Thirdly, the present invention provides a vehicle comprising the electrochemical device as described in the first aspect.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention incorporates specific types of lithium replenishing agents into the positive electrode active material layer, effectively reducing cell impedance and improving fast charging capability. However, because these agents release oxygen along with lithium, and oxygen oxidizes the electrolyte and generates a large amount of gas, especially at high temperatures, side reactions are exacerbated, leading to even more gas production. To address this, sulfonate additives in the electrolyte can react with oxygen, thus reducing gas production. Furthermore, boron in borate additives combines with oxygen, further preventing side reactions between oxygen and the electrolyte. Ultimately, through the synergistic effect between the lithium replenishing agent and the additives, the invention improves battery fast charging performance while reducing cell temperature rise, minimizing gas production, and enhancing battery safety and reliability, facilitating large-scale application. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0039] One embodiment of the present invention provides an electrochemical device, including a positive electrode, a negative electrode, and a separator and an electrolyte located between the positive electrode and the negative electrode. The positive electrode includes a positive current collector and a positive active material layer stacked together, and the negative electrode includes a negative current collector and a negative active material layer stacked together. The electrolyte includes a lithium salt, a non-aqueous solvent, and additives. The positive active material layer contains a lithium replenishing agent, and the additives include sulfonate additives and / or borate additives.

[0040] The chemical formula of the lithium supplement is: Li x M y O z M is selected from any one or at least two combinations of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, or Sn. Typical but non-limiting combinations include combinations of Fe and Ni, Ni and Mn, Mn and Cu, Cu and Zn, Zn and Co, Co and Cr, Cr and Zr, Zr and Sb, Sb and Ti, Ti and V, V and Mo, or Mo and Sn.

[0041] In some embodiments, 1≤x≤8, for example, x = 1, 2, 3, 4, 5, 6, 7 or 8; y>0, for example, y = 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5; 0<z≤13, for example, z = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13, but not limited to the listed values, other unlisted values ​​within this range also apply.

[0042] This invention incorporates specific types of lithium replenishing agents into the positive electrode active material layer, effectively reducing cell impedance and improving fast charging capability. However, because these agents release oxygen along with lithium, and oxygen oxidizes the electrolyte and generates a large amount of gas, especially at high temperatures, side reactions are exacerbated, leading to even more gas production. To address this, sulfonate additives in the electrolyte can react with oxygen, thus reducing gas production. Furthermore, boron in borate additives combines with oxygen, further preventing side reactions between oxygen and the electrolyte. Ultimately, through the synergistic effect between the lithium replenishing agent and the additives, the invention improves battery fast charging performance while reducing cell temperature rise, minimizing gas production, and enhancing battery safety and reliability, facilitating large-scale application.

[0043] In some embodiments, the total mass of the electrolyte is used as the calculation basis, and the content of the sulfonate additive is defined as a%. Then the value range of a is: 0.1≤a≤3. For example, a can be 0.1, 0.5, 1, 1.5, 2, 2.5 or 3, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] In some embodiments, the total mass of the electrolyte is used as the calculation basis, and the content of the borate additive is defined as b%. Then the value of b is in the range of 0.01≤b≤1. For example, b can be 0.01, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] In some embodiments, the total mass of the positive electrode is used as the calculation basis, and the content of the lithium replenishing agent is defined as c%. Then the value range of c is: 0.2≤c≤3, for example, c = 0.2, 0.5, 1, 1.5, 2, 2.5 or 3, and more preferably: 0.3≤c≤3, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] In some embodiments, the content relationship of the sulfonate additive, borate additive and lithium supplement is: 0.1≤c / (a+b)≤8, for example, c / (a+b)=0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 or 8, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0047] This invention limits the content relationship of sulfonate additives, borate additives, and lithium replenishing agents within the aforementioned range, which helps to fully leverage the synergistic effect between lithium replenishing agents and additives, finding a suitable balance between improving fast-charging performance and controlling gas production. If the above ratio is too large, i.e., the lithium replenishing agent content is too high, it leads to excessive oxygen release, while the additive content is too low, which is insufficient to suppress these side reactions; if the above ratio is too small, i.e., the lithium replenishing agent content is too low and the additive content is too high, the film formed by the additive at the interface is too thick, resulting in a significant limitation on the impedance reduction effect.

[0048] In some embodiments, the lithium supplement includes Li5FeO4, Li5Fe5O8, Li6CoO4, Li2NiO2, Li2O, Li2O2, Li6MnO4, Li6ZnO4, Li2CuO2, Li2CoO2, Li2MnO2, Li2C2O4, and Li2Ni 0.5 Mn 1.5 O4 or Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 1.3Any combination of one or at least two of the following: Li5FeO4 and Li5Fe5O8; Li5Fe5O8 and Li6CoO4; Li6CoO4 and Li2NiO2; Li2NiO2 and Li2O; Li2O and Li2O2; Li2O2 and Li6MnO4; Li6MnO4 and Li6ZnO4; Li6ZnO4 and Li2CuO2; Li2CuO2 and Li2CoO2; Li2CoO2 and Li2MnO2; Li2MnO2 and Li2C2O4; Li2C2O4 and Li2NiO2. 0.5 Mn 1.5 Combinations of O4, or Li2Ni 0.5 Mn 1.5 O4 and Li(Ni 0.8 Co 0.1 Mn 0.1 ) 1.3 The combination of O2.

[0049] In some embodiments, the sulfonate additive is selected from any one or a combination of at least two of the following compounds:

[0050]

[0051] In some embodiments, the borate additive includes any one or a combination of at least two of lithium tetrafluoroborate, lithium difluorooxalate borate, or lithium bis(oxalate borate). Typical but non-limiting combinations include combinations of lithium tetrafluoroborate and lithium difluorooxalate borate, combinations of lithium difluorooxalate borate and lithium bis(oxalate borate), combinations of lithium tetrafluoroborate and lithium bis(oxalate borate), or combinations of lithium tetrafluoroborate, lithium difluorooxalate borate, and lithium bis(oxalate borate).

[0052] In some embodiments, the lithium salt comprises any one or a combination of at least two of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(pentafluoroethylsulfonyl)imide, or lithium tri(trifluoromethanesulfonyl)methyl. Typical but non-limiting combinations include combinations of lithium hexafluorophosphate and lithium difluorophosphate, and combinations of lithium difluorophosphate and lithium difluorooxalate borate. Combinations of lithium difluorooxalate borate and lithium difluorosulfonyl imide, combinations of lithium difluorosulfonyl imide and lithium difluoromethanesulfonyl imide, combinations of lithium difluoromethanesulfonyl imide and lithium tetrafluoroborate, combinations of lithium tetrafluoroborate and lithium difluorooxalate borate, combinations of lithium difluorooxalate borate and lithium hexafluoroantimonylate, combinations of lithium hexafluoroantimonylate and lithium hexafluoroarsenate, combinations of lithium hexafluoroarsenate and lithium di(pentafluoroethylsulfonyl)imide, or combinations of lithium di(pentafluoroethylsulfonyl)imide and lithium tri(trifluoromethanesulfonyl)methyl lithium.

[0053] In some embodiments, the non-aqueous solvent includes any one or a combination of at least two of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or ethyl propyl carbonate. Typical but non-limiting combinations include combinations of ethylene carbonate and propylene carbonate, propylene carbonate and methyl ethyl carbonate, methyl ethyl carbonate and diethyl carbonate, diethyl carbonate and dimethyl carbonate, dimethyl carbonate and dipropyl carbonate, dipropyl carbonate and methyl propyl carbonate, or methyl propyl carbonate and ethyl propyl carbonate.

[0054] One embodiment of the present invention provides a method for preparing the above-mentioned electrochemical device, the method comprising the following steps:

[0055] (1) Prepare a positive electrode slurry containing lithium supplementation agent, coat the positive electrode slurry onto the surface of the positive electrode current collector, and then dry and post-process it to obtain the positive electrode;

[0056] (2) Prepare negative electrode slurry, coat the negative electrode slurry onto the surface of the negative electrode current collector, and then dry and post-process it to obtain the negative electrode;

[0057] (3) In a protective gas atmosphere, additives and lithium salts are added to a non-aqueous solvent in sequence, and the mixture is homogeneous to obtain an electrolyte.

[0058] (4) Preparation of the isolation membrane;

[0059] (5) Assemble the positive electrode, negative electrode, separator and battery cell housing, and inject electrolyte after forming to obtain an electrochemical device.

[0060] Steps (1)-(4) are not in any particular order.

[0061] In some embodiments, the positive current collector in step (1) comprises aluminum foil.

[0062] In some embodiments, the negative current collector in step (2) comprises copper foil.

[0063] In some embodiments, the drying temperatures in steps (1) and (2) are 85-120°C, for example, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] In some embodiments, the post-processing described in steps (1) and (2) includes sequential cold pressing, cutting, and slitting.

[0065] In some embodiments, the protective gas in step (3) includes any one or a combination of at least two of nitrogen, helium, or argon. Typical but non-limiting combinations include a combination of nitrogen and helium, a combination of helium and argon, a combination of nitrogen and argon, or a combination of nitrogen, helium, and argon.

[0066] In some embodiments, the preparation of the isolation membrane in step (4) includes coating a composite coating on the surface of a substrate.

[0067] In some embodiments, the substrate comprises a polyethylene film, and the composite coating comprises a polyvinylidene fluoride layer and / or a boehmite ceramic layer.

[0068] In some embodiments, the thickness of the polyethylene film is 6-8 μm, for example, it can be 6 μm, 6.2 μm, 6.4 μm, 6.6 μm, 6.8 μm, 7 μm, 7.2 μm, 7.4 μm, 7.6 μm, 7.8 μm or 8 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0069] In some embodiments, the thickness of the polyvinylidene fluoride layer is 4-6 μm, for example, it can be 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, 5.2 μm, 5.4 μm, 5.6 μm, 5.8 μm or 6 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0070] In some embodiments, the thickness of the boehmite ceramic layer is 2-4 μm, for example, it can be 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm or 4 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0071] In some embodiments, the assembly of the electrochemical device in step (5) includes: stacking the positive electrode, the separator and the negative electrode in sequence, installing them into the battery cell housing, sealing and shaping the battery cell, injecting electrolyte, and activating the battery cell.

[0072] One embodiment of the present invention provides a vehicle that includes the above-described electrochemical device.

[0073] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0074] Examples 1-22

[0075] This set of embodiments provides a lithium-ion battery and its preparation method. The lithium-ion battery includes a positive electrode, a negative electrode, and a separator and electrolyte located between the positive electrode and the negative electrode. The positive electrode includes a positive current collector (aluminum foil) and a positive active material layer stacked together. The negative electrode includes a negative current collector (copper foil) and a negative active material layer stacked together. The electrolyte includes lithium salt, a non-aqueous solvent, and additives. The positive active material layer contains a lithium replenishing agent. The additives include sulfonate additives and / or borate additives.

[0076] In this set of embodiments, the lithium salt is LiPF6, and the non-aqueous solvent is a mixture of EC, EMC and DMC; the specific types and contents of lithium supplementing agents, sulfonate additives and borate additives in each embodiment are shown in Table 1 below.

[0077] Table 1

[0078]

[0079]

[0080] The chemical structural formulas of compounds 1-6 in Table 1 above are shown in Table 2 below.

[0081] Table 2

[0082]

[0083] The lithium-ion batteries provided in this set of embodiments are prepared according to the following method:

[0084] (1) Preparation of positive electrode: Active material (lithium iron phosphate LiFePO4 + lithium supplement), conductive carbon (SP), carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) are mixed in N-methylpyrrolidone solvent at a mass ratio of 96.3:0.7:1:2 and stirred evenly to obtain positive electrode slurry; aluminum foil is used as positive electrode current collector, and the positive electrode current collector coated with positive electrode slurry is baked at 85°C for 1 hour, and then cold-pressed, cut and slit in sequence to obtain positive electrode.

[0085] (2) Anode preparation: Artificial graphite, conductive carbon, sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are mixed in deionized water at a mass ratio of 96.4:1:1.2:1.4 and stirred evenly to obtain anode slurry; copper foil is used as anode current collector, and the anode current collector coated with anode slurry is baked at 120°C for 1 hour, and then cold-pressed, cut and slit in sequence to obtain anode.

[0086] (3) Electrolyte preparation: EC, EMC and DMC are mixed in an argon atmosphere at a volume ratio of 3:2:5 to obtain an anhydrous solvent; then sulfonate additives and / or borate additives are added to the anhydrous solvent according to the conditions in Table 1 above, and then LiPF6 is added, with the total mass of the electrolyte as the calculation basis, and the content of LiPF6 is 12.5%.

[0087] (4) Preparation of the isolation membrane: A polyethylene film with a thickness of 7 μm is used as the substrate, and a PVDF coating with a thickness of 5 μm is applied to both sides of the film, and then a boehm ceramic layer with a thickness of 3 μm is applied.

[0088] (5) Battery assembly: The positive electrode, separator and negative electrode are stacked in sequence, with the separator in the middle of the positive and negative electrodes to play a role in isolation. The side coated with boehm ceramic layer is aligned with the positive electrode. Then the cells are stacked and placed in an aluminum-plastic film. After drying at 80°C, the obtained electrolyte is injected. The cells are then subjected to vacuum sealing, standing, formation and shaping processes to complete the preparation of the silicon-based lithium-ion battery.

[0089] Comparative Example 1

[0090] This comparative example provides a lithium-ion battery and its preparation method. Except for the absence of a lithium replenishing agent in the preparation of the positive electrode, the other steps and conditions are the same as in Example 1, and therefore will not be described in detail here.

[0091] Comparative Example 2

[0092] This comparative example provides a lithium-ion battery and its preparation method. Except for the absence of sulfonate ester additives and borate additives in the preparation of the electrolyte, the other steps and conditions are the same as in Example 1, and therefore will not be described in detail here.

[0093] Comparative Example 3

[0094] This comparative example provides a lithium-ion battery and its preparation method. Except that no lithium replenishing agent is added during the preparation of the positive electrode, and no sulfonate ester additives and borate additives are added during the preparation of the electrolyte, the other steps and conditions are the same as in Example 1, so they will not be described in detail here.

[0095] Performance testing

[0096] (1) Internal resistance test: At 25℃, the lithium-ion battery was fully discharged at 1C and then tested. The specific test process is as follows: First, the lithium-ion battery was charged at a constant current of 0.33C to a voltage of 3.8V, and then charged at a constant voltage of 3.8V to a current of 0.05C. After standing for 5 minutes, it was left to stand at 60℃ for 2 days. Then, the cell was placed in a 25℃ oven and discharged at a constant current of 0.33C for 1.5 hours. After standing for 5 minutes, the voltage U1 was recorded. Then, it was discharged at 3C (the current is recorded as I) for 10 seconds and the voltage U2 was recorded. After standing for 0.5 hours, the sampling time interval was 0.1 seconds. The internal resistance DCR=(U1-U2) / I was calculated.

[0097] (2) High-temperature gas generation test: The lithium-ion battery was placed in a constant temperature chamber at 25°C and left to stand for 30 minutes. The volume V0 of each battery was measured by Archimedes' displacement method. Then, the battery was charged at a constant current of 0.33C to 3.8V and then charged at a constant voltage of 0.05C. The battery was then placed in a constant temperature chamber at 70°C for thermal storage. After 30 days, the battery was taken out and the volume was measured by Archimedes' displacement method to be V30. The volume growth rate of the battery was calculated as (V30-V0) / V0×100%.

[0098] The results of internal resistance testing and high-temperature gas generation testing of the lithium-ion batteries obtained in Examples 1-22 and Comparative Examples 1-3 are shown in Table 3 below.

[0099] Table 3

[0100]

[0101]

[0102] As shown in Table 3:

[0103] (1) In Examples 1-14, a specific type of lithium replenishing agent was added to the positive electrode active material layer, and sulfonate ester additives and borate additives were added to the electrolyte. The resulting lithium-ion battery maintained a high level of fast charging performance and safety.

[0104] (2) Based on Example 1, no sulfonate additives were added to the electrolyte in Example 15 and no borate additives were added to the electrolyte in Example 16. All other conditions remained unchanged. The fast charging performance and safety of the resulting lithium-ion batteries were reduced to varying degrees. This is because: the sulfonate additives in the electrolyte can react with oxygen, thereby reducing gas production, and the boron in the borate additives will combine with oxygen, further avoiding side reactions between oxygen and the electrolyte.

[0105] (3) Based on Example 1, Examples 17-22 respectively adjusted the content of lithium replenishing agent, sulfonate additive and borate additive to outside the specified range, which ultimately led to different degrees of adverse effects on the fast charging performance and safety of the obtained lithium-ion battery.

[0106] (4) Based on Example 1, no lithium replenishing agent was added to Comparative Example 1, no sulfonate additives and borate additives were added to Comparative Example 2, and no lithium replenishing agent, sulfonate additives and borate additives were added to Comparative Example 3. Ultimately, the fast charging performance and safety of the resulting lithium-ion batteries were significantly adversely affected.

[0107] Therefore, this invention effectively reduces cell impedance and improves fast charging capability by adding specific types of lithium replenishing agents to the positive electrode active material layer. However, because it releases oxygen along with lithium, and oxygen oxidizes the electrolyte and generates a large amount of gas, especially under high temperature conditions, it exacerbates side reactions and generates even more gas. To address this, sulfonate additives in the electrolyte can react with oxygen, thereby reducing gas production. Furthermore, boron in borate additives combines with oxygen, further preventing side reactions between oxygen and the electrolyte. Ultimately, through the synergistic effect between the lithium replenishing agent and the additives, the invention improves battery fast charging performance while reducing cell temperature rise, decreasing gas production, and enhancing battery safety and reliability, which is beneficial for large-scale application.

[0108] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode, and a separating membrane and an electrolyte located between the positive and negative electrodes, wherein the positive electrode comprises a positive current collector and a positive active material layer stacked thereon, the negative electrode comprises a negative current collector and a negative active material layer stacked thereon, and the electrolyte comprises a lithium salt, a non-aqueous solvent, and an additive, characterized in that, The positive electrode active material layer contains a lithium supplement, and the additives include sulfonate additives and / or borate additives; The chemical formula of the lithium supplement is: Li x M y O z Wherein, M is selected from any one or at least two of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo or Sn, and 1≤x≤8, y>0, 0<z≤13.

2. The electrochemical device according to claim 1, characterized in that, Using the total mass of the electrolyte as the calculation basis, the content of the sulfonate additive is defined as a%, then the range of a is: 0.1≤a≤3; And / or, using the total mass of the electrolyte as the calculation basis, the content of the borate additive is defined as b%, then the range of b is: 0.01≤b≤1; And / or, using the total mass of the positive electrode as the calculation basis, the content of the lithium replenishing agent is defined as c%, then the range of c is: 0.2≤c≤3.

3. The electrochemical device according to claim 2, characterized in that, The content relationship of the sulfonate additive, the borate additive and the lithium supplement is: 0.1≤c / (a+b)≤8.

4. The electrochemical device according to any one of claims 1-3, characterized in that, The lithium supplements include Li5FeO4, Li5Fe5O8, Li6CoO4, Li2NiO2, Li2O, Li2O2, Li6MnO4, Li6ZnO4, Li2CuO2, Li2CoO2, Li2MnO2, Li2C2O4, and Li2Ni 0.5 Mn 1.5 O4 or Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 1.3 Any one or at least two of O2; And / or, the sulfonate additive is selected from any one or a combination of at least two of the following compounds: And / or, the borate additives include any one or a combination of at least two of lithium tetrafluoroborate, lithium difluorooxalate borate, or lithium bis(oxalate borate).

5. The electrochemical device according to any one of claims 1-4, characterized in that, The lithium salt includes any one or a combination of at least two of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorooxalate borate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(pentafluoroethylsulfonyl)imide, or lithium tri(trifluoromethylsulfonyl)methyl. And / or, the non-aqueous solvent includes any one or a combination of at least two of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, or ethyl propyl carbonate.

6. A method for preparing an electrochemical device as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: (1) Prepare a positive electrode slurry containing lithium supplementation agent, coat the positive electrode slurry onto the surface of the positive electrode current collector, and then dry and post-process it to obtain the positive electrode; (2) Prepare negative electrode slurry, coat the negative electrode slurry onto the surface of the negative electrode current collector, and then dry and post-process it to obtain the negative electrode; (3) In a protective gas atmosphere, additives and lithium salts are added to a non-aqueous solvent in sequence, and the mixture is homogeneous to obtain an electrolyte. (4) Preparation of the isolation membrane; (5) Assemble the positive electrode, negative electrode, separator and battery cell housing, and inject electrolyte after molding to obtain an electrochemical device; Steps (1)-(4) are not in any particular order.

7. The preparation method according to claim 6, characterized in that, The positive current collector in step (1) includes aluminum foil; And / or, the negative current collector in step (2) includes copper foil.

8. The preparation method according to claim 6 or 7, characterized in that, The drying temperatures described in steps (1) and (2) are 85-120℃, respectively; And / or, the post-processing described in steps (1) and (2) respectively includes cold pressing, cutting and slitting performed sequentially.

9. The preparation method according to any one of claims 6-8, characterized in that, The protective gas in step (3) includes any one or a combination of at least two of nitrogen, helium, or argon; And / or, the preparation of the isolation membrane in step (4) includes: coating a composite coating on the surface of a substrate; And / or, the substrate comprises a polyethylene film, and the composite coating comprises a polyvinylidene fluoride layer and / or a boehmite ceramic layer; And / or, the assembly of the electrochemical device in step (5) includes: stacking the positive electrode, the separator and the negative electrode in sequence, installing them into the battery cell housing, sealing and shaping them, injecting electrolyte, and activating the battery cell.

10. A vehicle, characterized in that, The vehicle contains the electrochemical device as described in any one of claims 1-5.

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