Electrochemical device and electronic equipment

Abstract

The application discloses an electrochemical device and an electronic equipment. The electrochemical device comprises an electrolyte, the electrolyte comprises an additive A and an additive B; the additive A comprises at least one of the additives shown in formula I and formula II; and the additive B comprises at least one of lithium difluorophosphate, lithium difluoro oxalate borate and lithium bisoxalate borate. By adding the additive A and the additive B in the electrolyte, the pressure drop in the high-temperature storage process of the electrochemical device can be improved, and the capacity retention rate in the high-temperature storage process can be improved. When the electrochemical device is in a full charge state, the additive A and the additive B can decompose in the positive electrode interface in sequence, a double-protected inorganic CEI layer is formed, and the voltage stability of the positive electrode interface under a high potential is improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and more particularly to an electrochemical device and electronic device. Background Technology

[0002] Electrochemical devices (such as lithium-ion batteries) have attracted widespread attention due to their high energy density, low maintenance, relatively low self-discharge, long cycle life, no memory effect, stable operating voltage, and environmental friendliness. They are widely used in portable electronic devices (including mobile phones, laptops, cameras, and other electronic products), power tools, and electric vehicles.

[0003] With the development of electrochemical devices, higher requirements are being placed on them, such as high capacity, long battery life, high safety, and wide operating temperature range. Among these requirements, electrochemical devices often suffer from poor voltage stability. For example, when electronic devices are idle for extended periods, especially when fully charged, the open-circuit voltage of the electrochemical device will drop, resulting in a loss of capacity. If the voltage drop is too large, such as from 4.4V to below 3.0V, the device will quickly run out of power, causing it to shut down automatically and inconveniencing the user. Summary of the Invention

[0004] This application provides an electrochemical device and electronic device that can solve the problem of poor voltage stability in electrochemical devices.

[0005] In a first aspect, this application provides an electrochemical device, including an electrolyte, said electrolyte comprising additive A and additive B;

[0006] Wherein, (1) the additive A includes at least one of the additives shown in Formula I and Formula II;

[0007]

[0008] R1 and R2 are each independently selected from any one of fluorine, trimethylsilyl, alkyl, alkenyl, ynyl, and the group shown in formula a;

[0009]

[0010] R3 is selected from any one of fluorine, phenyl, alkyl, and alkenyl groups;

[0011] (2) The additive B includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, and lithium dioxalate borate.

[0012] In some exemplary embodiments, additive A includes at least one of compound 1, compound 2, compound 3, and compound 4:

[0013]

[0014]

[0015] In some exemplary embodiments, the additive A has a mass percentage content of X ppm in the electrolyte, and the additive B has a mass percentage content of Y% in the electrolyte; the electrochemical device satisfies:

[0016] Condition 1: 1.00 × 10 3 ≤X / Y≤1.10×10 6 ;

[0017] The electrochemical device also satisfies at least one of the following conditions:

[0018] Condition 2: 45 ≤ X ≤ 11000;

[0019] Condition 3: 0.005≤Y≤2.1.

[0020] In some exemplary embodiments, the electrochemical device satisfies at least one of the following conditions:

[0021] Condition a: 500≤X≤10000;

[0022] Condition b: 0.01 ≤ Y ≤ 1.5;

[0023] Condition c: 1.00 × 10 3 ≤X / Y≤5×10 5 .

[0024] In some exemplary embodiments, the electrolyte further comprises additive C, which includes at least one of an ester compound and difluoropyridine, and the reduction potential of additive C at 25°C is between 0.8V and 1.3V.

[0025] In some exemplary embodiments, the ester compound includes at least one of fluoroethylene carbonate, vinylene carbonate, triallyl phosphate, and triargyl phosphate.

[0026] In some exemplary embodiments, the additive C has a mass percentage of Z% in the electrolyte, where Z satisfies: 0.01 ≤ Z ≤ 9.

[0027] In some exemplary embodiments, the additive C has a mass percentage of Z% in the electrolyte, where Z satisfies: 3 ≤ Z ≤ 8.

[0028] In some exemplary embodiments, the electrochemical device further includes a negative electrode sheet, the negative electrode sheet including a negative electrode material layer, the negative electrode material layer including a negative electrode active material;

[0029] The negative electrode active material includes artificial graphite, and the peak intensity ratio (D / G) of the Raman spectrum of the artificial graphite is 0.25 to 0.95.

[0030] In some exemplary embodiments, the electrochemical device further includes a positive electrode sheet, the positive electrode sheet including a positive electrode material layer, the positive electrode material layer including a positive electrode active material, and the positive electrode active material including a ternary material;

[0031] The positive electrode active material further includes at least one of aluminum or zirconium, and the mass percentage of aluminum or zirconium is H% based on the mass of the positive electrode active material, where H satisfies: 0.01 ≤ H ≤ 1.00.

[0032] In some exemplary embodiments, the positive electrode active material includes a ternary material, which includes at least one of nickel-cobalt-aluminum based ternary material or nickel-cobalt-manganese based ternary material;

[0033] Secondly, this application provides an electronic device, including the electrochemical device described above.

[0034] The electrochemical device and electronic device based on the embodiments of this application have at least the following beneficial effects:

[0035] By adding additives A and B to the electrolyte, the voltage drop during high-temperature storage of the electrochemical device can be improved, and the capacity retention rate during high-temperature storage can be enhanced. Specifically, when the electrochemical device is fully charged, the continuous reaction of the electrolyte at the positive electrode interface leads to a decrease in the positive electrode potential, ultimately resulting in a decrease in the open-circuit voltage of the battery. However, when additives A and B are present in the electrolyte, they can undergo decomposition reactions sequentially at the positive electrode interface, forming a dual-protective inorganic CEI layer, thus improving the voltage stability of the positive electrode interface at high potentials.

[0036] When additive C is added to the electrolyte, an effective SEI layer can be formed at the negative electrode interface, ensuring the stability of the negative electrode interface and further improving the voltage drop during storage. Meanwhile, when the D / G value of the graphite in the negative electrode active material is below 0.25, there are too few end edges in the graphite related to lithium ion insertion or detachment, which cannot guarantee the effective reaction of additive C on the graphite. However, when the D / G value of the graphite in the negative electrode active material is above 0.95, it means that there is a large amount of amorphous carbon on the surface of the carbon material, resulting in a large irreversible capacity and affecting the battery capacity. Therefore, the D / G value of the negative electrode active material is controlled within the range of 0.25-0.95.

[0037] Furthermore, the presence of dopants in the positive electrode active material can further enhance the stability of the positive electrode interface. When no dopants are present in the positive electrode active material, severe oxygen release will occur, accelerating the consumption of additives A and B. After doping, the consumption of additives A and B slows down, effectively stabilizing the voltage drop during long-term battery storage. The combined effect of the positive electrode, negative electrode, and electrolyte can effectively improve the battery's voltage drop. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0039] The inventors discovered that the rapid voltage drop in lithium-ion batteries is primarily caused by side reactions at the positive and negative electrode interfaces. Therefore, to mitigate the voltage decrease in lithium-ion batteries, we need to improve the stability of the positive and negative electrode interfaces and reduce electrolyte reactions at these interfaces.

[0040] This application provides an electrochemical device including an electrolyte, which includes additive A and additive B.

[0041] Additive A includes at least one of the additives shown in Formula I and Formula II;

[0042]

[0043] R1 and R2 are each independently selected from any one of fluorine, trimethylsilyl, alkyl, alkenyl, ynyl, and the group shown in formula a;

[0044]

[0045] R3 is selected from any one of fluorine, phenyl, alkyl, and alkenyl groups;

[0046] Additive B includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, and lithium dioxalate borate.

[0047] The electrochemical device also includes a positive electrode. When the battery is fully charged, the substances at the positive electrode interface continuously react with the electrolyte, leading to a decrease in the positive electrode potential and ultimately a decrease in the open-circuit voltage of the electrochemical device. By adding additives A and B to the electrolyte, additives A and B can undergo decomposition reactions at the positive electrode interface sequentially, forming a dual-protected inorganic CEI (solid electrolyte interphase) layer, thereby improving the voltage stability of the positive electrode interface at high potentials.

[0048] Specifically, additive A includes at least one of the following compounds:

[0049]

[0050]

[0051] In some exemplary embodiments, the mass percentage of additive A in the electrolyte is X ppm, and the mass percentage of additive B in the electrolyte is Y%. The electrochemical device satisfies condition 1: 1.00 × 10⁻⁶. 3 ≤X / Y≤1.10×10 6 .

[0052] Optionally, X satisfies condition 2: 45 ≤ X ≤ 11000. For example, X can be 50, 100, 500, 1000, 3000, 5000, 10000, etc. When the mass percentage X of additive A in the electrolyte is less than 50%, the inorganic CEI film formed by additive A at the positive electrode interface has limited effect on improving the stability of the positive electrode interface. The electrolyte also includes lithium salt and non-aqueous organic solvent; lithium salt and additive A are dissolved in the non-aqueous organic solvent. When the content X of additive A in the electrolyte is greater than 10000, the high content of additive A will decompose inside the electrochemical device, generating a large amount of acidic substances, promoting the decomposition and heat generation of lithium salt, and simultaneously corroding the positive electrode active material, weakening the thermal stability of the positive electrode active material, resulting in a generally poor voltage stability effect. Preferably, X satisfies condition a: 500 ≤ X ≤ 10000.

[0053] Optionally, Y satisfies condition 3: 0.005 ≤ Y ≤ 2.1. For example, Y can be 0.01, 0.05, 0.1, 0.3, 0.5, 1.0, 1.5, 1.8, 2.0, etc. The mass percentage of additive B in the electrolyte is between 0.01% and 2%, which can improve the voltage drop of the electrochemical device. Preferably, Y satisfies condition b: 0.01 ≤ Y ≤ 1.5, and X and Y satisfy condition c: 1.00 × 10⁻⁶. 3 ≤X / Y≤5×10 5 .

[0054] In some exemplary embodiments, the electrolyte further comprises additive C, which includes at least one of an ester compound and difluoropyridine, and the reduction potential of additive C at 25°C is between 0.8V and 1.3V. For example, the reduction potential can be 0.8V, 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, etc.

[0055] In some exemplary embodiments, the ester compound includes at least one of fluoroethylene carbonate, vinylene carbonate, triallyl phosphate, and triargyl phosphate.

[0056] In some exemplary embodiments, the mass percentage of additive C in the electrolyte is Z%, where Z satisfies condition 4: 0.01 ≤ Z ≤ 9. Preferably, Z satisfies condition 3 ≤ Z ≤ 8, for example, Z can be 0.05, 0.5, 1, 2, 3, 5, 7, or 8, etc. When additive C is added to the electrolyte, an effective SEI (solide electrolyte interphase) layer can be formed at the negative electrode interface, ensuring the stability of the negative electrode interface and further improving the voltage drop during storage.

[0057] Furthermore, the electrochemical device also satisfies condition 4: 1.11*10 2 ≤X / (Y+Z)≤1.00*10 5 .

[0058] This application does not impose any particular limitation on non-aqueous organic solvents, as long as they can achieve the purpose of this application. For example, non-aqueous organic solvents may include at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. Carbonate compounds may include at least one of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate.

[0059] The electrochemical device further includes a negative electrode, which comprises a negative electrode material layer and a negative electrode current collector, the negative electrode material layer being disposed on the surface of the negative electrode current collector. The negative electrode material layer comprises a negative electrode active material, and in some exemplary embodiments, the negative electrode active material comprises at least one of graphite or silicon-based materials. For example, the silicon-based material may include at least one of silicon, silicon oxides, silicon carbide compounds, and silicon alloys.

[0060] When the negative electrode active material includes silicon-based material, the silicon content in the silicon-based material is M%, where M is 1≤M≤100. For example, M can be 1%, 5%, 7%, 10%, 30%, 50%, 70%, 100%, etc.

[0061] When the negative electrode active material includes artificial graphite, the peak intensity ratio of the D band to the G band in the Raman spectrum of artificial graphite, i.e., the D / G value, is 0.25–0.95. For example, D / G can be 0.3, 0.35, 0.4, 0.5, 0.6, 0.7, 0.85, 0.9, etc. By controlling the D / G value within the range of 0.25–0.95, it helps the additive C to form a more stable polymer SEI layer at the negative electrode interface, resulting in better voltage stability of the lithium-ion battery.

[0062] The negative electrode active material layer may further include a negative electrode conductive agent and / or a negative electrode binder. This application embodiment does not particularly limit the negative electrode conductive agent, as long as it achieves the purpose of this application. For example, the negative electrode conductive agent may include at least one of carbon black, acetylene black, Ketjen black, sheet graphite, graphene, carbon nanotubes, carbon fibers, or carbon nanowires. This application embodiment also does not particularly limit the negative electrode binder, as long as it achieves the purpose of this application. For example, the negative electrode binder may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyacrylate, polyacrylate, polyvinylpyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0063] The embodiments of this application do not have any particular limitations on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, the negative electrode current collector may include at least one of copper foil, nickel foil or carbon-based current collector.

[0064] The positive electrode sheet includes a positive electrode material layer and a positive electrode current collector, with the positive electrode material layer disposed on the surface of the positive electrode current collector. The positive electrode material layer includes a positive electrode active material. In some exemplary embodiments, the positive electrode active material includes a ternary material, which includes at least one of nickel-cobalt-aluminum based ternary materials or nickel-cobalt-manganese based ternary materials. For example, the positive electrode active material may include at least one of lithium nickel cobalt-manganese oxide and lithium nickel cobalt-aluminum oxide. In some exemplary embodiments, the positive electrode active material may also include at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium nickel manganese oxide.

[0065] In some exemplary embodiments, the positive electrode active material contains a dopant element, including at least one of aluminum or zirconium, which can result in a smaller voltage drop in the electrochemical device and a stronger stabilizing effect on the positive electrode interface.

[0066] The positive electrode material layer also includes a positive electrode conductive agent and / or a positive electrode binder. This application embodiment does not particularly limit the positive electrode conductive agent, as long as it achieves the purpose of this application. For example, the positive electrode conductive agent may include at least one of conductive carbon black, acetylene black, Ketjen black, sheet graphite, graphene, carbon nanotubes, or carbon fibers. This application embodiment also does not particularly limit the positive electrode binder, as long as it achieves the purpose of this application. For example, the positive electrode binder may include at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, or polymethyl methacrylate.

[0067] There are no particular limitations on the positive current collector in this application. The positive current collector can be any positive current collector known in the art, such as aluminum foil, aluminum alloy foil, or composite current collector.

[0068] The electrochemical device also includes a separator membrane positioned between the positive and negative electrodes to prevent short circuits. The separator membrane may be a polyethylene (PE) film or a polypropylene (PP) film. The electrochemical device also includes a positive electrode tab, a negative electrode tab, and an outer packaging. The positive electrode, separator membrane, and negative electrode are stacked sequentially or stacked on one side and wound together. The positive electrode is connected to the positive electrode tab, and the negative electrode is connected to the negative electrode tab, forming an electrode assembly. The electrode assembly is placed inside the outer packaging, and the positive and negative electrode tabs are led out from the inner space of the outer packaging to the outer space so that they can be electrically connected to an external circuit. Then, electrolyte is injected into the inner space of the outer packaging, and the outer packaging is sealed to obtain the electrochemical device. The outer packaging may be an aluminum-plastic film bag or an aluminum foil bag.

[0069] This application also provides an electronic device, including the electrochemical device described above.

[0070] The electronic devices described in this application are not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic devices include, but are not limited to: laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0071] The following will use an electrochemical device, specifically a lithium-ion battery, as an example to provide a more detailed description of this application.

[0072] I. Pressure Drop Test Method

[0073] The battery was charged to 4.45V at a constant current of 0.5C at 25℃, and the constant voltage (CV) was cut off when the current reached 0.025C. The fully charged battery was then placed in a 60℃ oven for high-temperature storage. After 30 days, the battery was removed and its open-circuit voltage was tested when the battery temperature dropped to room temperature. Three batteries were tested in each group, and the average value of the three tests was taken as the voltage value of the group.

[0074] II. Preparation methods of lithium-ion batteries

[0075] 1. Preparation of positive electrode sheet

[0076] A positive electrode slurry was prepared by dissolving lithium cobalt oxide (positive electrode active material), polyvinylidene fluoride (PVDF) (positive electrode binder), and conductive carbon black (Super-P) (positive electrode conductive agent) in N-methylpyrrolidone (NMP) at a mass ratio of 96:2:2. The positive electrode slurry was then uniformly coated onto a 12 μm thick aluminum foil for the positive electrode current collector and baked at 120 °C for 1 hour. After compaction and slitting, the positive electrode sheet was obtained.

[0077] In each embodiment and comparative example, aluminum and / or zirconium elements are added to the positive electrode active material and stirred evenly. The material is then coated normally according to the above steps to obtain a positive electrode sheet with added aluminum and / or zirconium elements.

[0078] 2. Preparation of negative electrode sheet

[0079] Artificial graphite (anode active material), sodium carboxymethyl cellulose (CMC) (anode binder), and styrene-butadiene rubber (anode binder) were dissolved in water at a mass ratio of 85:2:13 and thoroughly mixed to obtain anode slurry. The anode slurry was then uniformly coated onto a 12μm thick copper foil (220) anode current collector and baked at 120℃ for 1 hour to obtain anode sheet. After compaction and slitting, the anode sheet was obtained.

[0080] 3. Preparation of electrolyte

[0081] Ethylene carbonate and diethyl carbonate were mixed in a mass ratio of 3:7 to obtain a non-aqueous organic solvent. Simultaneously, 1M lithium salt LiPF6 was added to the non-aqueous organic solvent to obtain an electrolyte base material.

[0082] In each embodiment and comparative example, additives A, B, and C were added to the electrolyte base material to obtain the electrolyte.

[0083] 4. Preparation of lithium-ion batteries

[0084] Polypropylene film is used as the separator. The positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to isolate them. They are then wound, with the positive tab connected to the positive electrode and the negative tab connected to the negative electrode, thus obtaining the electrode assembly. The electrode assembly is placed inside an aluminum foil bag, with the positive and negative tabs extended from the inside to the outside of the outer packaging. After baking at 80°C to remove moisture, electrolyte is injected into the inner space of the outer packaging. Following vacuum sealing, settling, formation, and shaping processes, a lithium-ion battery is obtained.

[0085] The lithium-ion batteries of the examples and comparative examples were prepared according to the above method and then tested.

[0086] In Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-22 of Table 1, the positive electrode active material used was lithium cobalt oxide (LiCoO2), and the negative electrode active material was artificial graphite with a D / G value of 0.25.

[0087] Table 1

[0088]

[0089]

[0090] In Comparative Examples 1-1 to 1-3 of Table 1, the addition of only additive A, additive B, or neither to the electrolyte resulted in significant voltage drop in the lithium-ion batteries after storage. In Examples 1-1 to 1-22 of Table 1, the addition of additive A and additive B, with additive A at a concentration of 45 ppm to 11000 ppm and additive B at a concentration of 0.005% to 2.1% in the electrolyte, all resulted in varying degrees of improvement in the voltage drop of the lithium-ion batteries. According to Examples 1-1 to 1-7, preferably, the concentration of additive A in the electrolyte is 500 ppm to 10000 ppm; and according to Examples 1-8 to 1-15, preferably, the concentration of additive B in the electrolyte is 0.01% to 1.5%, resulting in even better improvement in the voltage drop of the lithium-ion batteries.

[0091] In Examples 2-1 to 2-12 of Table 2, the positive electrode active material used was LiCoO2, the negative electrode active material was graphite, the D / G value of the artificial graphite was 0.25, and 1000 ppm of compound 1, 0.5% of lithium difluorophosphate and additive C were added to the electrolyte.

[0092] Table 2

[0093]

[0094]

[0095] In Table 2, for Examples 2-1 to 2-12, the mass percentage (Z%) of additive C in the electrolyte ranges from 0.01% to 9%, which improves the voltage of the lithium-ion battery. Preferably, when the mass percentage (Z%) of additive C in the electrolyte ranges from 3% to 8%, the voltage of the lithium-ion battery also increases with the increase of additive C content in the electrolyte. The addition of additive C can form an effective polymer SEI layer at the negative electrode interface, mitigating side reactions at the negative electrode interface, effectively suppressing the increase in negative electrode voltage, and achieving the goal of stabilizing the lithium-ion battery voltage.

[0096] In Examples 3-1 to 3-6 of Table 3, the positive electrode active material used was LiCoO2, the negative electrode active material was artificial graphite, and 1000 ppm of Compound 1, 0.5% of lithium difluorophosphate, and 1% of additive C were added to the electrolyte.

[0097] Table 3

[0098] Additive C Z(％) D / G Voltage after storage (V) Examples 2-4 Fluoroethylene carbonate 1 0.25 4.15 Example 3-1 Fluoroethylene carbonate 1 0.30 4.15 Example 3-2 Fluoroethylene carbonate 1 0.40 4.17 Example 3-3 Fluoroethylene carbonate 1 0.55 4.18 Examples 3-4 Fluoroethylene carbonate 1 0.70 4.19 Examples 3-5 Fluoroethylene carbonate 1 0.90 4.20 Examples 3-6 Fluoroethylene carbonate 1 0.95 4.20 Examples 3-7 Fluoroethylene carbonate 5 0.70 4.22

[0099] In Table 3, Examples 2-4 and Examples 3-1 to 3-7 show that adjusting the D / G value of the negative electrode active material graphite between 0.25 and 0.95 improves the voltage drop of lithium-ion batteries to varying degrees. According to Examples 3-1 to 3-5, when the D / G value of the negative electrode active material artificial graphite is between 0.40 and 0.90, it helps additive C form a more stable polymer SEI layer at the negative electrode interface, resulting in better voltage stability of the lithium-ion battery. When the D / G value of artificial graphite is below 0.25, there are too few end edges in the artificial graphite related to lithium-ion insertion or detachment, which cannot guarantee the effective reaction of additive C on the artificial graphite; however, when the D / G value of artificial graphite is above 0.95, it means that there is a large amount of amorphous carbon on the surface of the artificial graphite, resulting in a large irreversible capacity, which affects the battery capacity. Therefore, the D / G value of artificial graphite is controlled within the range of 0.25-0.95.

[0100] In Examples 4-1 to 4-3 of Table 4, the positive electrode active material used was LiCoO2, the negative electrode active material was artificial graphite, the artificial graphite D / G value was 0.4, and 1000 ppm of Compound 1, 0.5% of lithium difluorophosphate, and 5% of fluoroethylene carbonate were added to the electrolyte.

[0101] Table 4

[0102] element H(％) Voltage after storage (V) Examples 3-7 No aluminum or zirconium / 4.22 Example 4-1 Aluminum 0.45 4.27 Example 4-2 Zirconium 0.18 4.25 Example 4-3 Aluminum + Zirconium 0.30+0.15 4.26

[0103] In Table 4, according to Examples 3-2, 4-1 to 4-3, the positive electrode active material contains at least one of aluminum and zirconium. Based on the mass of the positive electrode active material, the mass percentage of aluminum or zirconium is H%. When H satisfies 0.01≤H≤1.00, the battery voltage drop is smaller and the stabilizing effect on the electrode interface is stronger.

[0104] Adding aluminum or zirconium to the positive electrode active material helps stabilize the positive electrode interface, reduces the consumption of additives A and B, and ultimately improves the battery voltage drop. When the positive electrode active material does not contain aluminum or zirconium, severe oxygen release will occur at the positive electrode, which will accelerate the consumption of additives A and B. After doping, the consumption of additives A and B slows down, effectively stabilizing the voltage drop during long-term battery storage.

[0105] In the description of this application, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0106] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrochemical device comprising an electrolyte, characterized in that, The electrolyte includes additive A, additive B, and additive C; Wherein, (1) the additive A includes at least one of the additives shown in Formula I and Formula II; Formula I Formula II R1 and R2 are each independently selected from any one of fluorine, trimethylsilyl, alkyl, alkenyl, ynyl, and the group shown in formula a; Formula a R3 is selected from any one of fluorine, phenyl, alkyl, and alkenyl groups; (2) The additive B includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, and lithium dioxalate borate; (3) The additive C includes at least one of ester compounds and difluoropyridine; The additive A has a mass percentage content of X ppm in the electrolyte, the additive B has a mass percentage content of Y %, and the additive C has a mass percentage content of Z %, with 45≤X≤11000, 0.005≤Y≤2.1, and 3≤Z≤9. The electrochemical device further includes a negative electrode sheet, which includes a negative electrode material layer and a negative electrode active material. The negative electrode active material includes artificial graphite, and the peak intensity ratio (D / G) of the Raman spectrum of the artificial graphite is 0.25 to 0.

95.

2. The electrochemical device according to claim 1, characterized in that, Additive A includes at least one of compound 1, compound 2, compound 3, and compound 4: Compound 1 Compound 2 Compound 3 Compound 4.

3. The electrochemical device according to claim 1, characterized in that, The additive A has a mass percentage content of X ppm in the electrolyte, and the additive B has a mass percentage content of Y % in the electrolyte; the electrochemical device satisfies: Condition 1: 1.00 × 10 3 ≤X / Y≤1.10×10 6 .

4. The electrochemical device according to claim 3, characterized in that, The electrochemical device satisfies at least one of the following conditions: Condition a: 500≤X≤10000; Condition b: 0.01 ≤ Y ≤ 1.5; Condition c: 1.00 × 10 3 ≤X / Y≤5×10 5 .

5. The electrochemical device according to claim 1, characterized in that, The reduction potential of the additive C at 25°C is between 0.8V and 1.3V.

6. The electrochemical device according to claim 1, characterized in that, The ester compounds include at least one of fluoroethylene carbonate, vinylene carbonate, triallyl phosphate, and triargyl phosphate.

7. The electrochemical device according to claim 1, characterized in that, The additive C has a mass percentage of Z% in the electrolyte, where Z satisfies: 3 ≤ Z ≤ 8.

8. The electrochemical device according to claim 1, characterized in that, The electrochemical device further includes a positive electrode sheet, the positive electrode sheet includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes a ternary material; The positive electrode active material further comprises at least one of aluminum or zirconium, and the mass percentage of aluminum or zirconium is H% based on the mass of the positive electrode active material, where H satisfies: 0.01 ≤ H ≤ 1.

00.

9. An electronic device, characterized in that, The electrochemical device includes any one of claims 1-8 above.

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