Lithium-ion batteries and power consumption devices

Abstract

The present application discloses a lithium ion battery and a power consumption device, the lithium ion battery including a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, the separator being located between the positive electrode plate and the negative electrode plate, and when the lithium ion battery is charged at 1C until the state of charge reaches 80% SOC, the potential P of the negative electrode is anode is 0.09V (vs. Li + / Li) <P anode <0.15V (vs. Li + / Li).

Description

[Technical Field]

[0001] This disclosure relates to the new energy field, specifically to lithium-ion batteries and power consumption devices. [Background technology]

[0002] Due to their lightweight, small volume, high density, and long lifespan, lithium-ion batteries are widely used in fields such as electric vehicles, 3C digital technology, and energy storage equipment. With the widespread adoption of lithium-ion batteries, the demand for improved input and output characteristics is also increasing. However, relatively high input characteristics can lead to lithium deposition in lithium-ion batteries. Lithium deposition not only significantly reduces the lifespan of lithium-ion batteries but can also lead to relatively serious safety problems. Therefore, improving the input characteristics of lithium-ion batteries while simultaneously reducing the risk of lithium deposition is extremely important.

[0003] Therefore, current lithium-ion batteries and power consumption devices are in need of improvement. [Overview of the project]

[0004] This application is based on the inventor's discovery and recognition of the following facts and problems.

[0005] The inventor discovered that when a lithium-ion battery operates with high input characteristics, the charging current is relatively large, and therefore the rate of decrease in the negative electrode potential is relatively fast. + When the lithium level is reduced to less than 1 / Li, lithium deposition occurs on the negative electrode surface, which significantly reduces the lifespan and safety of the lithium-ion battery.

[0006] According to one aspect of the present application, the present application proposes a lithium-ion battery, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The separator is located between the positive electrode plate and the negative electrode plate. When the lithium-ion battery is charged at 1C until the state of charge reaches 80% SOC, the potential P of the negative electrode anode is 0.09V (vs. Li + / Li) < P anode < 0.15V (vs. Li + / Li). Thereby, the risk of lithium precipitation generated during charging of the lithium-ion battery can be reduced.

[0007] According to an embodiment of the present application, when the lithium-ion battery is charged at 1C until the state of charge reaches 80% SOC, the potential P of the negative electrode anode is 0.09V (vs. Li + / Li) < P anode < 0.13V (vs. Li + / Li). Thereby, the risk of lithium precipitation generated during charging of the lithium-ion battery can be further reduced.

[0008] According to an embodiment of the present application, the CB value of the lithium-ion battery is 1.1 to 1.8, preferably, the CB value of the lithium-ion battery is 1.3 to 1.5. Here, the CB is the negative electrode capacity / positive electrode capacity in the same facing area. The positive electrode capacity and the negative electrode capacity may be obtained by assembling a positive electrode plate and a negative electrode plate of the same area with lithium sheets respectively into a button-type battery and testing the charging capacity using a blue electric tester. The CB value may also be calculated according to the formula CB = negative electrode capacity per unit area / positive electrode capacity per unit area based on the design information of the battery. The negative electrode capacity per unit area = mass of the coating per unit area of the negative electrode plate (CW anode ) × gram capacity of the negative electrode active material (gram capacity anode ) × percentage content of the negative electrode active material in the coating of the negative electrode plate (Loading anode) and the positive electrode capacity per unit area = the mass of the coating per unit area of the positive electrode plate (CW cathode ) × the gram capacity of the positive electrode active material (gram capacity cathode ) × the percentage content of the positive electrode active material in the coating of the positive electrode plate (Loading cathode ). Here, the surface coating of the positive electrode plate is a positive electrode active material layer, and the surface coating of the negative electrode plate is a negative electrode active material layer. Thereby, the stability in the high input-output characteristics of the lithium-ion battery can be improved.

[0009] According to the embodiments of the present application, the electrolyte contains a first lithium salt, the first lithium salt is lithium bis(fluorosulfonyl)imide, and the mass fraction of the first lithium salt in the electrolyte is 5 wt% to 19 wt%. Thereby, the lithium precipitation window during charging of the lithium-ion battery can be improved.

[0010] According to the embodiments of the present application, the electrolyte further contains a second lithium salt, and the second lithium salt contains at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium bis(difluorophosphono)imide. Thereby, the lifespan of the lithium-ion battery can be improved.

[0011] According to the embodiments of the present application, the total mass fraction of the first lithium salt and the second lithium salt in the electrolyte is 30 wt% or less. Thereby, the lithium-ion battery can be provided with a relatively high energy density and a relatively low manufacturing cost.

[0012] According to the embodiments of the present application, the molar concentration ratio of the first lithium salt and the second lithium salt in the electrolyte is (3:7) to (the first lithium salt and the second lithium salt in the electrolyte is (3:7) to (9:1). Thereby, the cycle performance and service life of the lithium-ion battery can be further improved.

[0013] According to embodiments of this application, the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium manganese phosphate, lithium iron phosphate, and a lithium-rich manganese solid solution. This allows for various positive electrode applications.

[0014] According to the embodiments of this application, the positive electrode active material layer further contains a conductive agent, and the mass fraction of the conductive agent in the positive electrode active material layer is 0.5 wt% to 6 wt%. This improves the conductivity of the positive electrode.

[0015] According to embodiments of this application, the negative electrode plate includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based material, and tin-based material. This allows for various negative electrode applications.

[0016] According to embodiments of this application, the solvent in the electrolyte comprises at least one of a cyclic carbonate, a linear carbonate, and a linear carboxylic acid ester. This improves the solubility of the lithium salt and the conductivity of the electrolyte.

[0017] According to embodiments of this application, the electrolyte further comprises an additive, the additive comprising at least one of fluorinated ethylene carbonate, cyclic sulfate ester, cyclic sulfonic acid ester, (trimethylsilane) phosphate ester, (trimethylsilane) borate ester, trimethylfluorosilane, lithium difluorophosphate, and lithium difluorobis(oxalato)phosphate, and the mass content of the additive in the electrolyte is 10 ppm or more. This makes it possible to improve the battery life.

[0018] In another aspect of this application, the application proposes a power consumption device comprising the aforementioned lithium-ion battery. Thereafter, this power consumption device has all the features and advantages of the aforementioned lithium-ion battery, which will not be described further here. [Brief explanation of the drawing]

[0019] The above and / or additional aspects and advantages of this application will be made clearer and easier to understand in the description of the embodiments in conjunction with the following drawings, here. [Figure 1] A schematic diagram of the structure of a lithium-ion battery according to one embodiment of this application is shown. [Figure 2] A schematic diagram of the structure of a power consumption device according to one embodiment of this application is shown. [Figure 3] A photograph of a negative electrode plate with no lithium deposition according to one embodiment of this application is shown. [Figure 4] A photograph of a negative electrode plate with a positive lithium deposition level according to one embodiment of this application is shown. [Figure 5] A photograph of a negative electrode plate with a lithium deposition level of ++ according to one embodiment of this application is shown. [Figure 6] A photograph of a negative electrode plate with a lithium deposition level of +++ according to one embodiment of this application is shown. [Figure 7] A photograph of a negative electrode plate with a lithium deposition level of ++++ according to one embodiment of this application is shown. [Figure 8] A photograph of a negative electrode plate with a lithium deposition level of +++++ according to one embodiment of this application is shown. [Modes for carrying out the invention]

[0020] The embodiments of this application are described in detail below, and the examples of such embodiments are shown in the drawings, where the same or similar reference numerals always represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are illustrative and are used solely for the purpose of interpreting this application and should not be understood as limitations thereto.

[0021] In this application's description, "100% SOC" refers to the state when the battery is charged to the maximum design voltage with a constant current of 1C, and then converted to a constant voltage and charged to 0.05C, including the state after standing (generally standing for 10 minutes), and both are considered to be the 100% SOC state, i.e., the fully charged state. "80% SOC" refers to the state when the electrochemical apparatus is charged to an 80% charge state with a constant current, and the battery can be adjusted to an 80% SOC state by referring to the following method, which involves first fully charging the battery and then discharging it with a constant current of 1C for 12 minutes, at which point the battery is in an 80% SOC state and also includes the state after standing (generally standing for 10 minutes).

[0022] According to one aspect of this application, the present application proposes a lithium-ion battery, referring to Figure 1, comprising a positive electrode plate (the positive electrode plate may include a positive electrode current collector 11 and a positive electrode active material layer 12 located on at least one surface of the positive electrode current collector 11), a negative electrode plate (the negative electrode plate may include a negative electrode current collector 21 and a negative electrode active material layer 22 located on at least one surface of the negative electrode current collector 21), a separator 30, and an electrolyte 40, wherein the separator 30 is located between the positive electrode plate and the negative electrode plate, and when the lithium-ion battery is charged at 1C until the charge state reaches 80% SOC, the potential P of the negative electrode anode This is 0.09V (vs.Li + / Li) <P anode <0.15V(vs.Li + The negative electrode potential of the lithium-ion battery satisfies 0V (vs.Li). When a lithium-ion battery operates with high input characteristics, for example, when charging using 3C, 5C and higher charge multipliers, the charging current is relatively large and the rate of decrease in negative electrode potential is relatively fast, so the negative electrode potential of the lithium-ion battery is 0V (vs.Li). +When reduced to less than / Li, Li that is not embedded in the negative electrode + This can only obtain electrons on the negative electrode surface, thereby forming a silvery-white metallic lithium element. Lithium deposition not only significantly reduces battery performance and drastically shortens cycle life, but can also cause battery short circuits, potentially leading to serious consequences such as battery combustion and explosion. In this application, the inventors have found that when a lithium-ion battery is charged at a 1C multiplier and charged to 80% SOC (State of Charge, also called battery charge state or remaining energy), the negative electrode potential P anode 0.09V (vs.Li + / Li) <P anode <0.15V(vs.Li + We discovered that by satisfying the condition ( / Li), the negative electrode potential can be raised higher than the potential plateau where lithium deposition is likely to occur in this state, significantly improving the lithium deposition window of the battery, reducing the risk of lithium deposition during high-magnification charging, and improving the capacity retention rate during high-power charging and discharging.

[0023] According to some embodiments of this application, in order to further improve the charging efficiency of the battery, when a lithium-ion battery is charged at 1C until the charge state reaches 80% SOC, the potential P of the negative electrode anode 0.09V (vs.Li + / Li) <P anode <0.13V(vs.Li + By satisfying the (Li) condition, the charging speed can be improved while simultaneously further reducing the risk of lithium deposition that occurs during the charging of lithium-ion batteries.

[0024] According to some embodiments of this application, the CB value of a lithium-ion battery is not particularly limited, and for example, the CB value of a lithium-ion battery may be 1.1 to 1.8, where CB = negative electrode capacity / positive electrode capacity per unit area, and the positive electrode capacity and negative electrode capacity are obtained by assembling positive and negative electrode plates of the same area with lithium sheets to form a button cell and testing the charging capacity using a blue electrical tester. The CB value may also be obtained by calculating the formula CB = negative electrode capacity per unit area / positive electrode capacity per unit area based on the battery design information, where negative electrode capacity per unit area = mass of coating per unit area of ​​the negative electrode plate (CW anode ) × Gram capacity of negative electrode active material (gram capacity anode ) × Percentage content of negative electrode active material in the coating of the negative electrode plate (Loading anode ) and the positive electrode capacity per unit area = the mass of the coating per unit area of ​​the positive electrode plate (CW cathode ) × Gram capacity of positive electrode active material (gram capacity) cathode ) × Percentage content of positive electrode active material in the coating of the positive electrode plate (Loading cathode ) where the surface coating of the positive electrode plate is the positive electrode active material layer, and the surface coating of the negative electrode plate is the negative electrode active material layer. When the CB value is within the above range, the negative electrode potential P when the lithium-ion battery is charged at 1C until the charge state reaches 80% SOC is anode 0.09V (vs.Li + / Li) and 0.15V (vs.Li + By controlling the relationship between / Li and the battery, it effectively reduces the occurrence of lithium deposition during high-magnification charging of lithium-ion batteries, enabling lithium-ion batteries to possess relatively high energy density and relatively high charging power density, thus helping to achieve high-magnification charging and discharging.

[0025] According to some embodiments of this application, the positive electrode capacity per unit area and the negative electrode capacity per unit area in CB calculations can be determined by referring to the following test method.

[0026] First, a button battery is manufactured. A positive or negative electrode plate is cut into a wafer with a diameter of Φ=14 mm to serve as the working electrode, a lithium sheet with a diameter of Φ=18 mm is used as the counter electrode, and the two are separated by a polyethylene (PE) separator with a diameter of Φ=20 mm. An appropriate amount of electrolyte is added, and the assembly is completed to obtain a button battery.

[0027] Step 2: Test the electrode capacities. Take assembled button batteries with normal open-circuit voltages and perform capacity tests, with at least four parallel samples per group. The positive electrode capacity test flow is as follows: Set the button battery charge / discharge voltage window to 2.8V to the upper limit voltage (maximum design voltage), first let it stand for 5 minutes, then charge it to the upper limit voltage with a constant current of 0.1C, then convert it to a constant voltage and charge it to 50μA, then let it stand for 5 minutes, and discharge it to 2.8V with a constant current of 0.1C. Repeat this flow three times, and take the discharge capacity of the third cycle as the positive electrode capacity. The negative electrode capacity test flow is as follows: The button battery charge / discharge voltage window is set to 2V to 0.005V. First, it is left standing for 5 minutes, then discharged to 0.005V with a constant current of 0.05C, converted to a constant current of 50μA and discharged to 0.005V, left standing for 5 minutes, discharged to 0.005V with a constant current of 10μA, left standing for 5 minutes, and then charged to 2V with a constant current of 0.1C. This flow is repeated three times, and the charge capacity of the third cycle is taken as the capacity of the negative electrode plate. For the above capacity test, button cell data with a normal curve and relatively good agreement with parallel samples is selected.

[0028] Finally, Tring cathode Loading anode This is the mass percentage content of the positive electrode active material or negative electrode active material in the positive electrode plate or negative electrode plate coating, which is determined during the electrode plate design. CW cathode and CW anode This involves coating the positive and negative electrode plates, drying them, and then placing them on a small wafer (e.g., 1540.25 mm) on a flat positive and negative electrode plate. 2 The area (of which) is driven in, and then 1540.25 mm 2The weight of the positive electrode active material layer (obtained by the weight of a small wafer plate minus the weight of empty aluminum foil) and the weight of the negative electrode active material layer (obtained by the weight of a small wafer plate minus the weight of empty aluminum foil) over the area may be weighed. Gram capacity cathode and gram capacity anode Test method: gram capacity cathode and gram capacity anode This is obtained by testing the electrode plate capacitance using the method described above for testing the positive electrode plate capacitance and negative electrode plate capacitance, and then dividing the obtained capacitance by the mass of the positive electrode or negative electrode active material in the electrode plate.

[0029] According to some embodiments of this application, the composition of the electrolyte is not particularly limited. For example, the electrolyte may contain a first lithium salt, the first lithium salt being lithium bis(fluorosulfonyl)imide (LiFSI). By adding lithium bis(fluorosulfonyl)imide as a lithium salt to the electrolyte, the conductivity of the electrolyte is improved, and the impedance of lithium ion transport in the liquid phase is reduced, thereby reducing overpotential due to ohmic impedance during high-magnification charging of the battery, and thereby improving the lithium deposition window of the battery. On the other hand, lithium bis(fluorosulfonyl)imide has relatively high chemical stability, effectively reducing the occurrence of side reactions during the storage process of lithium-ion batteries, improving the increase in DCR (DC impedance) during the storage process of batteries, and improving overpotential due to interfacial impedance when charging with high magnification during the long-term use of lithium-ion batteries, further effectively mitigating the deterioration process of the lithium deposition window during the use of lithium-ion batteries. By combining the aforementioned negative electrode potential range for charging the lithium-ion battery to 80% SOC with the use of lithium bis(fluorosulfonyl)imide as the lithium salt in the electrolyte, a synergistic effect is achieved, significantly reducing the risk of lithium deposition during high-magnification charging of the battery. According to some other embodiments of this application, when the first lithium salt is lithium bis(fluorosulfonyl)imide, the mass fraction of the first lithium salt in the electrolyte may be 5 wt% to 19 wt%. When the mass fraction of the first lithium salt in the electrolyte is within the above range, the electrolyte has relatively high ionic conductivity, and the ionic conductivity σ at 25°C is 10 mS / cm or more, which helps to realize rapid transport of lithium ions. When the content of the first lithium salt in the electrolyte is too high, the viscosity of the electrolyte increases, which reduces the conductivity of the electrolyte and increases the impedance of liquid phase transport. Conversely, when the content of the first lithium salt in the electrolyte is too low, the degree of improvement in the ionic conductivity of the electrolyte is relatively small, and the effect of the lithium deposition window cannot be systematically improved.

[0030] In this application, whether or not words such as "approximately" or "about" are used, all figures disclosed herein are approximations. The numerical values ​​of each figure may vary by 10% or less, or by a reasonable variation as a person skilled in the art would consider, e.g., 1%, 2%, 3%, 4%, or 5%.

[0031] According to some embodiments of this application, the composition of the electrolyte is not particularly limited. For example, the electrolyte may further contain a second lithium salt, the second lithium salt may contain at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate, and lithium bis(difluorophosphono)imide. By employing an electrolyte containing both a first and a second lithium salt, the service life of the lithium-ion battery can be effectively improved. If the electrolyte contains only the first lithium salt, the slight corrosive effect of the first lithium salt on the cathode current collector can be mitigated. According to some other embodiments of this application, when the electrolyte contains both a first and a second lithium salt, the total mass fraction of the first and second lithium salts in the electrolyte may be 30 wt% or less, and the mass fraction of the first lithium salt in the electrolyte may be 5 wt% to 19 wt%, thereby providing a relatively good improvement effect on the lithium-ion battery and relatively low manufacturing costs. According to some other embodiments of this application, the molar concentration ratio of the first lithium salt to the second lithium salt in the electrolyte may be (3:7) to (9:1), thereby further improving the cycle performance and service life of the lithium-ion battery.

[0032] In the description of this application, “first feature” and “second feature” may include one or more of these features.

[0033] According to some embodiments of this application, the composition of the electrolyte is not particularly limited, and for example, the electrolyte may further contain additives, and the mass content of the additives in the electrolyte may be 10 ppm or more. The additives may include at least one of fluorinated ethylene carbonate, cyclic sulfate esters, cyclic sulfonic acid esters, (trimethylsilane) phosphate esters, (trimethylsilane) borate esters, trimethylfluorosilane, lithium difluorophosphate, and lithium difluorobis(oxalato)phosphate, and the addition of additives can effectively improve the battery life.

[0034] According to some embodiments of this application, the composition of the electrolyte is not particularly limited, and the solvent in the electrolyte may include at least one of a cyclic carbonate, a linear carbonate, and a linear carboxylic acid ester, thereby improving the solubility of the lithium salt and the conductivity of the electrolyte.

[0035] According to some embodiments of this application, referring to Figure 1, the positive electrode may include a positive electrode current collector 11 and a positive electrode active material layer 12 located on at least one surface of the positive electrode current collector 11, the positive electrode current collector 11 may include aluminum foil, and the positive electrode active material layer 12 may include a positive electrode active material, the positive electrode active material may include at least one of lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese oxide lithium, nickel cobalt aluminate lithium, lithium manganese phosphate, lithium iron phosphate, and a lithium-rich manganese solid solution. Preferably, the positive electrode active material may include nickel cobalt manganese oxide lithium and / or nickel cobalt aluminate lithium, the nickel cobalt manganese oxide lithium is NCM111(LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), NCM523 (LiNi 0.5 Co 0.2 Mn 0.3 O2), NCM622 (LiNi 0.6 Co 0.2 Mn 0.2 O2), NCM811 (LiNi0.8 Co 0.1 Mn 0.1 It may contain at least one of the positive electrode active materials such as O2.

[0036] According to some embodiments of this application, the positive electrode active material layer further contains a conductive agent, and the mass fraction of the conductive agent in the positive electrode active material layer is 0.5 wt% to 6 wt%. This improves the conductivity of the positive electrode.

[0037] According to some embodiments of this application, referring to Figure 1, there is a negative electrode which may include a negative electrode current collector 21 and a negative electrode active material layer 22 located on at least one surface of the negative electrode current collector 21, the negative electrode current collector 21 may include copper foil, and the negative electrode active material layer 22 may include a negative electrode active material which includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based material, and tin-based material.

[0038] According to some embodiments of this application, the type of separator is not particularly limited, and any known porous structure separator with good chemical and mechanical stability may be selected. Specifically, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. If the separator is a multi-layer composite film, the materials of each layer may be the same or different, and a person skilled in the art can select them according to the actual situation.

[0039] According to some embodiments of this application, the structure of the lithium-ion battery is not particularly limited, and for example, the positive electrode, negative electrode and separator can be manufactured into an electrode assembly by a winding process or a lamination process.

[0040] In another aspect of this application, the application proposes a power consumption device comprising the aforementioned lithium-ion battery. Thereafter, this power consumption device has all the features and advantages of the aforementioned lithium-ion battery, which will not be described further here.

[0041] According to some embodiments of this application, lithium-ion batteries may be used as a power source for power consumption devices or as energy storage units for power consumption devices. Power consumption devices may include mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, and the like.

[0042] According to some embodiments of this application, referring to Figure 2, the power consumption device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements for the lithium-ion battery of this power consumption device, a battery pack or battery module can be employed. Specifically, the lithium-ion battery may be assembled into a battery module, and the number of lithium-ion batteries contained in the battery module may be one or more, which can be selected by those skilled in the art depending on the application and capacity of the battery module. The above battery module may be further assembled into a battery pack, and the number of battery modules contained in the battery pack may be one or more, the specific number can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0043] Examples The present invention will be explained below with specific examples, but it should be noted that the following examples are used solely to illustrate this invention and should not be considered to limit the scope of this invention. Where specific techniques or conditions are not specified in the examples, they will be carried out in accordance with techniques or conditions described in literature within the art or in accordance with product descriptions. Where the manufacturer of the reagents or instruments used is not specified, they are all commonly available commercial products.

[0044] See the table below for details. Here, the positive electrode active material is the ternary material NCM111(LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 The positive electrode current collector is aluminum foil, the negative electrode active material is graphite, and the negative electrode current collector is copper foil. The electrolyte contains a solvent, a lithium salt, and an additive. The solvent contains ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), with a mass fraction ratio of EC, DMC, and EMC being 2:3:5. The electrolyte additive is 1 wt% vinylene carbonate (VC). The first lithium salt is lithium bis(fluorosulfonyl)imide (LIFSI), and the second lithium salt is lithium hexafluorophosphate (LiPF6). See Table 1 for the specific content of the first and second lithium salts.

[0045] [Table 1A] [Table 1B]

[0046] The method for testing the negative electrode potential during the battery charging process involves taking the positive and negative electrode plates of a lithium-ion battery, fabricating a three-electrode battery with a reference electrode according to a method for manufacturing a three-electrode battery, and further monitoring the anode potential during overcharging of the battery charge and discharge using the reference electrode, and measuring the negative electrode potential when charging to 80% SOC at 1C. The method for manufacturing a three-electrode battery is as follows: a positive electrode plate, a negative electrode plate, and a separator are taken and punch-cut according to the required size, with the positive electrode plate size being 42mm*49mm, the negative electrode plate size being 44mm*51mm, and the separator size being 46mm*53mm. The positive electrode plate, separator, and negative electrode plate are then stacked in that order, with a single copper wire with a diameter of 200 microns placed between the positive and negative electrode plates during the stacking process. This copper wire is pulled out from the electrodes, a nickel sheet is welded to it, and it becomes a third electrode (reference electrode). After the stacking is complete, the stacked structure is placed in an aluminum plastic film bag, a certain amount of the electrolyte is injected and packaged, and after standing, chemical formation, and aging, a three-electrode battery is obtained.

[0047] The battery capacity retention test method involves, after the battery is manufactured as described above, following these steps under 25°C conditions: 1) leaving it undisturbed for 5 minutes, 2) discharging it to 2.8V with a constant current of 1C, 3) leaving it undisturbed for 5 minutes, 4) charging it to the upper limit voltage with a constant current of 1C, then converting it to a constant voltage and charging it to 0.05C until fully charged, 5) leaving it undisturbed for 5 minutes, and 6) discharging it to 2.7V with a constant current of 1C. The discharge capacity in step 6 is taken as the battery's discharge capacity.

[0048] The cycle performance test method involves first adjusting the battery to an 80% SOC state under 25°C conditions, then 1) leaving it still for 5 minutes, 2) charging it to the upper limit voltage with a constant current of 1C, then converting it to a constant voltage and charging it to 0.05C until fully charged, 3) leaving it still for 5 minutes, and 4) discharging it with a constant current of 1C for 12 minutes. During this time, the battery reaches the 80% SOC state, and the corresponding battery voltage is recorded as V1, corresponding to the 80% SOC state. The battery is then left at a temperature of -10°C to start the cycle flow, 1) leaving it still for 2 hours, 2) charging it with a constant current of 15C for 5 seconds, 3) resting for 10 minutes, 4) discharging it with a constant current of 15C for 5 seconds, and 5) leaving it still for 10 minutes. Steps 2 through 5 of the cycle flow are repeated for a total of 1000 cycles. The method for calculating the battery capacity retention rate is as follows. A capacity test flow was used before and after the battery cycle to test the capacity of the battery at -10°C, 80% SOC, 15C / 15C, and 5s. The capacity before the cycle was designated as Cap1, and the capacity after the cycle as Cap2. The capacity retention rate at -10°C, 80% SOC, 15C / 15C, 5s, and 1000cls was calculated as Cap2 / Cap1.

[0049] The test method for the degree of lithium deposition at the battery interface includes subjecting the batteries of the above examples and comparative examples to 1000 cycles of -10°C 15C / 15C for 5 seconds, fully charging the batteries, then disassembling the fully charged batteries, and using the resulting negative electrode plate as the sample to be tested.

[0050] According to the test results, when the batteries in Examples 1 to 10 were charged to 80% SOC at 1C, the negative electrode potential was between 0.09 and 0.15V in all cases. The capacity retention rate after 5s 1000cls charge / discharge at -10℃ and 5C / 5C was greater than 90% in all cases, indicating a relatively low degree of lithium deposition at the interface, and the negative electrode active material layer on the surface of the negative electrode plate remained its original color after decomposition. When the batteries in Comparative Examples 1 to 6 were charged to 80% SOC at 1C, the negative electrode potential was less than 0.09V in all cases. The capacity retention rate after 5s 1000cls charge / discharge at -10℃ and 5C / 5C was less than 90% in all cases, indicating clear interfacial lithium deposition. Both safety and cycle life were relatively poor, and as the lithium deposition level increased, a large amount of silvery deposits were clearly observed on the surface of the cathode plate, and the entire negative electrode active material layer on the surface of the negative electrode plate appeared silvery.

[0051] In the description of this application, "A and / or B" may include A alone, B alone, or A and B, where A and B are merely illustrative examples and may be any technical features connected in this application using "and / or".

[0052] Unless otherwise specified, all technical terms used in this application have the same meaning as those generally understood by technicians in the art to which this application pertains. All patents and disclosure publications relating to this application are incorporated into this application by reference as a whole. The terms “incorporate” or “include” are open expressions, meaning they include the content shown in this application but do not exclude content in other embodiments.

[0053] In this specification, the reference terms "one embodiment," "another embodiment," etc., mean that the specific features, structures, materials, or characteristics described in association with this embodiment are included in at least one embodiment of this application. In this specification, the general expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples. A person skilled in the art may combine different embodiments or examples and features of different embodiments or examples described herein, provided that they do not contradict each other. It should also be noted that in this specification, the terms "first" and "second" are for descriptive purposes only and should not be understood as indicating or implying relative importance or the number of technical features being referred to.

[0054] As has been shown and described above, the embodiments described herein are illustrative and should not be understood as limitations to this application. Those skilled in the art can modify, alter, replace, and transform the embodiments within the scope of this application. [Explanation of symbols]

[0055] 11: Positive electrode current collector 12: Positive electrode active material layer 21: Negative electrode current collector 22: Negative electrode active material layer 30: Separator 40: Electrolyte

Claims

1. A lithium-ion battery comprising a positive electrode plate, a negative electrode plate, a separator, and an electrolyte, wherein the separator is located between the positive electrode plate and the negative electrode plate. When the lithium-ion battery is charged at 1C until its charge state reaches 80% SOC, the potential P of the negative electrode ａｎｏｄｅ is 0.09V (vs. Li ＋ / Li) <P ａｎｏｄｅ <0.15V (vs. Li ＋ Satisfying / Li), A lithium-ion battery wherein the electrolyte contains a first lithium salt, the first lithium salt being lithium bis(fluorosulfonyl)imide, and the mass fraction of the first lithium salt in the electrolyte is 5 wt% to 19 wt%.

2. When the lithium-ion battery is charged at 1C until its charge state reaches 80% SOC, the potential P of the negative electrode ａｎｏｄｅ is 0.09V (vs. Li ＋ / Li) <P ａｎｏｄｅ <0.13V (vs. Li ＋ A lithium-ion battery according to claim 1, satisfying the condition / Li.

3. The lithium-ion battery according to claim 1, wherein the CB value of the lithium-ion battery is 1.1 to 1.8, where CB = negative electrode capacity / positive electrode capacity in the same opposing area.

4. The lithium-ion battery according to claim 1, wherein the electrolyte further comprises a second lithium salt, the second lithium salt comprising at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium bis(difluorophosphono)imide.

5. The lithium-ion battery according to claim 4, wherein the total mass fraction of the first lithium salt and the second lithium salt in the electrolyte is 30 wt% or less.

6. The lithium-ion battery according to claim 4, wherein the molar concentration ratio of the first lithium salt to the second lithium salt in the electrolyte is (3:7) to (9:1).

7. The lithium-ion battery according to claim 1, wherein the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese oxide, nickel cobalt aluminate, lithium manganese phosphate, lithium iron phosphate, and a lithium-rich manganese solid solution.

8. The lithium-ion battery according to claim 7, wherein the positive electrode active material layer further contains a conductive agent, and the mass fraction of the conductive agent in the positive electrode active material layer is 0.5 wt% to 6 wt%.

9. The lithium-ion battery according to claim 1, wherein the negative electrode plate includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based material, and tin-based material.

10. The lithium-ion battery according to claim 1, wherein the solvent in the electrolyte comprises at least one of a cyclic carbonate, a linear carbonate, and a linear carboxylic acid ester.

11. The lithium-ion battery according to claim 1, wherein the electrolyte further comprises an additive, the additive comprising at least one of fluorinated ethylene carbonate, cyclic sulfate ester, cyclic sulfonic acid ester, (trimethylsilane) phosphate ester, (trimethylsilane) borate ester, trimethylfluorosilane, lithium difluorophosphate, and lithium difluorobis(oxalato) phosphate, and the mass content of the additive in the electrolyte is 10 ppm or more.

12. A power consumption device comprising a lithium-ion battery according to any one of claims 1 to 11.

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