Lithium-ion batteries and power-consuming 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] The present disclosure relates to the field of new energy, and more particularly to lithium-ion batteries and power-consuming devices. [Background technology]

[0002] Due to their light weight, small volume, high density, and long life, lithium-ion batteries are widely used in fields such as electric vehicles, 3C digital devices, and energy storage devices. As lithium-ion batteries become more widely used, the demand for their input and output characteristics is also increasing. However, relatively high input power can lead to lithium precipitation in lithium-ion batteries. This not only significantly shortens the battery's lifespan, but can also pose serious safety issues. Therefore, how to improve the input power characteristics of lithium-ion batteries while simultaneously reducing the risk of lithium precipitation is becoming increasingly important.

[0003] As a result, current lithium-ion batteries and power-consuming devices are in need of improvement. Summary of the Invention

[0004] The present application has been made based on the inventor's discovery and recognition of the following facts and problems.

[0005] The inventors have discovered that when a lithium-ion battery operates at a high input voltage, the charging current is relatively large, and therefore the rate at which the negative electrode potential decreases is relatively fast. + / Li), lithium deposition occurs on the surface of the negative electrode, which significantly reduces the life and safety of the lithium ion battery.

[0006] According to one aspect of the present application, the present application proposes a lithium ion battery, 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 1 C until the state of charge of the lithium ion battery 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), thereby reducing the risk of lithium deposition occurring during charging of lithium-ion batteries.

[0007] According to the 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 anode is 0.09V (vs. Li + / Li) <P anode <0.13V (vs. Li + / Li), which further reduces the risk of lithium deposition occurring during charging of lithium-ion batteries.

[0008] According to the embodiment of the present application, the CB value of the lithium ion battery is 1.1 to 1.8, and preferably 1.3 to 1.5, where CB is the negative electrode capacity / positive electrode capacity in the same opposing 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 a lithium sheet, respectively, to form a button battery, and testing the charging capacity using a blue electrical tester. The CB value may be calculated based on the design information of the battery according to the formula: CB = negative electrode capacity per unit area / positive electrode capacity per unit area, where negative electrode capacity per unit area = mass of coating (CW) per unit area of ​​the negative electrode plate. anode ) × gram capacity of negative electrode active material (gram capacity anode ) × percentage content of negative active material in coating of negative electrode plate (Loading anode) and the positive electrode capacity per unit area = the mass of coating per unit area of ​​the positive electrode plate (CW cathode ) × gram capacity of 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 ), where 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 improving the stability of the lithium ion battery at high input and output.

[0009] According to an embodiment of the present application, the electrolyte solution contains a first lithium salt, which is lithium bis(fluorosulfonyl)imide, and the mass fraction of the first lithium salt in the electrolyte solution is 5 wt% to 19 wt%, thereby improving the lithium deposition window during charging of the lithium-ion battery.

[0010] According to an embodiment of the present application, the electrolyte solution further includes a second lithium salt, which includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium bis(difluorophosphono)imide, thereby improving the life of the lithium-ion battery.

[0011] According to an embodiment 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, which allows the lithium ion battery to have a relatively high energy density and a relatively low manufacturing cost.

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

[0013] According to an embodiment of the present application, the positive electrode plate includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron phosphate, and a lithium-rich manganese-based solid solution, thereby meeting various positive electrode uses.

[0014] According to an embodiment of the present 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%, thereby improving the conductivity of the positive electrode.

[0015] According to an embodiment of the present application, the negative electrode plate includes a negative electrode active material layer, and the negative electrode active material layer includes 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, thereby meeting various negative electrode uses.

[0016] According to an embodiment of the present application, the solvent in the electrolyte solution includes at least one of a cyclic carbonate, a chain carbonate, and a chain carboxylic acid ester, thereby improving the solubility of the lithium salt and the conductivity of the electrolyte solution.

[0017] According to an embodiment of the present application, the electrolyte solution further contains an additive, which includes at least one of fluorinated ethylene carbonate, cyclic sulfate ester, cyclic sulfonate 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 solution is 10 ppm or more, thereby improving the battery life.

[0018] According to another aspect of the present application, the present application proposes a power consuming device, said power consuming device comprising a lithium ion battery as described above, whereby said power consuming device has all the features and advantages of said lithium ion battery, which will not be further described herein. [Brief explanation of the drawings]

[0019] The above and / or additional aspects and advantages of the present application will become more apparent and easier to understand in the following description of the embodiments taken in conjunction with the drawings, in which: [Figure 1] 1 shows a schematic structural diagram of a lithium ion battery according to one embodiment of the present application. [Figure 2] 1 shows a structural schematic diagram of a power consumption device according to one embodiment of the present application; [Figure 3] 1 shows a photograph of a negative electrode plate with a lithium deposition level of no lithium deposition according to one embodiment of the present application. [Figure 4] 1 shows a photograph of a negative electrode plate with a positive lithium deposition level according to one embodiment of the present application. [Figure 5] 1 shows a photograph of a negative electrode plate with a lithium deposition level of ++ according to one embodiment of the present application. [Figure 6] A photograph of a negative electrode plate with a lithium deposition level of +++ according to one embodiment of the present application is shown. [Figure 7] A photograph of a negative electrode plate with a lithium deposition level of ++++ according to one embodiment of the present application is shown. [Figure 8] A photograph of a negative electrode plate with a lithium deposition level of +++++ according to one embodiment of the present application is shown. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, the embodiments of the present application will be described in detail, and examples of the 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 only used to interpret the present application, and should not be understood as limitations on the present application.

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

[0022] According to one aspect of the present application, the present application proposes a lithium-ion battery, and referring to FIG. 1 , the battery includes 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, the separator 30 being located between the positive electrode plate and the negative electrode plate, and when the lithium-ion battery is charged at 1 C until the state of charge reaches 80% SOC, the potential P anode is 0.09V (vs. Li + / Li) <P anode <0.15V (vs. Li + When a lithium-ion battery operates at a high input voltage, for example, when it is charged at 3C, 5C, or a higher charging rate, the charging current is relatively large and the rate at which the negative electrode potential decreases is relatively fast, so that the negative electrode potential of the lithium-ion battery does not reach 0V (vs. Li + / Li), the Li that is not embedded in the negative electrode + can only obtain electrons on the surface of the negative electrode, thereby forming silver-white metallic lithium element. Lithium deposition not only obviously reduces battery performance and significantly shortens cycle life, but may also cause battery short circuit, resulting in serious consequences such as battery combustion and explosion. In this application, the inventors have shown that when a lithium-ion battery is charged at 1C and charged to 80% SOC (State of Charge, also known as battery state of charge or remaining energy), the negative electrode potential P anode is 0.09V (vs. Li + / Li) <P anode <0.15V (vs. Li + / Li), the lithium deposition window of the battery can be significantly improved by raising the negative electrode potential above the potential plateau where lithium deposition is likely to occur under this condition, reducing the risk of lithium deposition during high-power charging, and improving the capacity retention rate during high-power charging and discharging.

[0023] According to some embodiments of the present application, in order to further improve the charging efficiency of the battery, when the lithium ion battery is charged at 1C until the state of charge reaches 80% SOC, the potential P anode is 0.09V (vs. Li + / Li) <P anode <0.13V (vs. Li + / Li), it is possible to improve the charging speed and further reduce the risk of lithium deposition that occurs when charging a lithium-ion battery.

[0024] According to some embodiments of the present application, the CB value of the lithium ion battery is not particularly limited. For example, the CB value of the lithium ion battery may be 1.1 to 1.8, where CB = negative electrode capacity / positive electrode capacity in the same opposing area. The positive electrode capacity and negative electrode capacity are obtained by assembling positive electrode plates and negative electrode plates of the same area with lithium sheets, respectively, to form button batteries, and testing the charging capacity using a blue electrical tester. The CB value may be calculated based on the battery design information using the formula: CB = negative electrode capacity per unit area / positive electrode capacity per unit area, and the negative electrode capacity per unit area = the mass of coating (CW) per unit area of ​​the negative electrode plate. anode ) × gram capacity of negative electrode active material (gram capacity anode ) × percentage content of negative active material in coating of negative electrode plate (Loading anode ) and the positive electrode capacity per unit area = the mass of coating per unit area of ​​the positive electrode plate (CW cathode ) × gram capacity of 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 ) where 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. 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 state of charge reaches 80% SOC anode to 0.09V (vs. Li + / Li) and 0.15V (vs. Li + / Li), which effectively reduces the occurrence of lithium deposition during high-rate charging of lithium-ion batteries, allowing the lithium-ion batteries to combine relatively high energy density with relatively high charging power density, and helping to achieve high-rate charging and discharging.

[0025] According to some embodiments of the present application, the positive electrode capacity per unit area and the negative electrode capacity per unit area in the CB calculation can be determined with reference to the following test method.

[0026] First, a button battery is fabricated by cutting the positive or negative electrode plate into wafers with a diameter of 14 mm to form the working electrode, and a lithium sheet with a diameter of 18 mm to form the counter electrode.The two electrodes are separated by a polyethylene (PE) separator with a diameter of 20 mm, and an appropriate amount of electrolyte is added.Then, the button battery is assembled.

[0027] Step 2: Test the plate capacity. Test the capacity of the assembled button batteries with normal open-circuit voltage, with at least four parallel samples per group. The positive plate capacity test procedure is to set the charge / discharge voltage window of the button battery to 2.8V to the upper voltage (maximum design voltage), let it rest for 5 minutes, then charge it to the upper voltage with a constant current of 0.1C, then charge it at a constant voltage of 50μA, let it rest for 5 minutes, and discharge it to 2.8V with a constant current of 0.1C. This procedure is repeated three times, and the discharge capacity of the third cycle is taken as the positive plate capacity. The negative plate capacity test procedure is as follows: The voltage window for charging and discharging a button battery is set to 2V~0.005V. First, let it rest for 5 minutes, then discharge it to 0.005V at a constant current of 0.05C. Then change to a constant current of 50μA and discharge it to 0.005V. Let it rest for 5 minutes, then discharge it to 0.005V at a constant current of 10μA. Let it rest for 5 minutes, and then charge it to 2V at a constant current of 0.1C. This process 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, select the button cell data whose curve is normal and has a relatively good agreement with the parallel sample.

[0028] Finally, Loading cathode and Loading anode is the mass percentage content of the positive or negative active material in the positive or negative electrode plate coating, determined when the electrode plate is designed. cathode and C.W. anode After coating and drying the positive and negative electrodes, small wafers (e.g., 1540.25 mm) are applied to the flat positive and negative electrodes, respectively. 2 (area) and 1540.25mm 2The weight of the positive electrode active material layer (obtained by subtracting the weight of the empty aluminum foil from the weight of the small wafer electrode plate) and the weight of the negative electrode active material layer (obtained by subtracting the weight of the empty aluminum foil from the weight of the small wafer electrode plate) may be weighed. cathode and gram capacity anode Test Method: Gram Capacity cathode and gram capacity anode is obtained by testing the plate capacity using the above-mentioned method for testing the positive and negative plate capacities, and then dividing the obtained capacity by the mass of the positive or negative active material in the plate.

[0029] According to some embodiments of the present application, the composition of the electrolyte is not particularly limited, and for example, the electrolyte may include a first lithium salt, and the first lithium salt may be lithium bis(fluorosulfonyl)imide (LiFSI). Adding lithium bis(fluorosulfonyl)imide to the electrolyte as a lithium salt improves the conductivity of the electrolyte and reduces the impedance of liquid-phase transport of lithium ions, thereby reducing the overpotential caused by ohmic impedance during high-rate charging of the battery and thereby improving the lithium deposition window of the battery. Meanwhile, lithium bis(fluorosulfonyl)imide has relatively high chemical stability, which can effectively reduce the occurrence of side reactions during storage of lithium-ion batteries and improve the increase in DCR (direct current impedance) during battery storage. It also has an effect of improving the overpotential caused by interfacial impedance during high-rate charging during long-term use of lithium-ion batteries, further effectively alleviating the deterioration process of the lithium deposition window during use of lithium-ion batteries. By combining the negative electrode potential range for charging the lithium-ion battery to 80% SOC described above with the use of lithium bis(fluorosulfonyl)imide as the lithium salt in the electrolyte, a synergistic effect can be achieved, significantly reducing the risk of lithium precipitation during high-power charging of the battery. According to some other embodiments of the present 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, with an ionic conductivity σ of 10 mS / cm or more at 25°C, which helps to realize rapid transport of lithium ions. If the content of the first lithium salt in the electrolyte is too high, the viscosity of the electrolyte will increase, thereby reducing the conductivity of the electrolyte and increasing the impedance of liquid phase transport. If the content of the first lithium salt in the electrolyte is too low, the improvement in the ionic conductivity of the electrolyte will be relatively small, and the effect of the lithium deposition window will not be systematically improved.

[0030] In this application, regardless of whether words such as "approximately" or "about" are used, all numbers disclosed herein are approximate values. The numerical values ​​of each number may vary by up to 10%, or by a reasonable variation that would be considered by one of ordinary skill in the art, such as 1%, 2%, 3%, 4%, or 5%.

[0031] According to some embodiments of the present application, the composition of the electrolyte is not particularly limited. For example, the electrolyte may further contain a second lithium salt, which may include at least one of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate, and lithium bis(difluorophosphono)imide. The use of an electrolyte containing a first lithium salt and a second lithium salt effectively improves the service life of a lithium-ion battery. When the electrolyte contains only the first lithium salt, the slight corrosion of the first lithium salt on the cathode current collector can be mitigated. According to some other embodiments of the present application, when the electrolyte simultaneously contains the first lithium salt and the second lithium salt, the total mass fraction of the first lithium salt and the second lithium salt in the electrolyte may be 30 wt% or less. Here, the mass fraction of the first lithium salt in the electrolyte may be 5 wt% to 19 wt%, thereby achieving both a relatively good improvement effect and a relatively low manufacturing cost for the lithium-ion battery. According to some other embodiments of the present 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), which can further improve the cycle performance and service life of the lithium ion battery.

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

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

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

[0035] According to some embodiments of the present application, referring to FIG. 1 , a 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, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron phosphate, and a lithium-rich manganese-based solid solution. Preferably, the positive electrode active material may include lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide. The lithium nickel cobalt manganese oxide may be 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 O2).

[0036] According to some embodiments of the present 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%, thereby improving the conductivity of the positive electrode.

[0037] According to some embodiments of the present application, referring to FIG. 1 , a negative electrode 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, where 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, where the negative electrode active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, a silicon-based material, and a tin-based material.

[0038] According to some embodiments of the present application, the type of separator is not particularly limited, and any known porous separator with good chemical and mechanical stability may be selected. Specifically, the separator material 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. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and those skilled in the art can select the material according to the actual situation.

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

[0040] According to another aspect of the present application, the present application proposes a power consuming device, which comprises a lithium ion battery as described above, whereby the power consuming device has all the features and advantages of the lithium ion battery as described above, which will not be further described herein.

[0041] According to some embodiments of the present application, lithium-ion batteries may be used as a power source for power consuming devices or as an energy storage unit for power consuming devices, which 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, etc.

[0042] According to some embodiments of the present application, referring to FIG. 2 , the power consumption device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like. To meet the demand for high power output and high energy density from the lithium-ion batteries of this power consumption device, a battery pack or battery module may be adopted. Specifically, the lithium-ion batteries 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 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, which can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0043] Example The present invention will be described below by way of specific examples. However, it should be noted that the following examples are used only to illustrate the present invention and should not be construed as limiting the scope of the present invention. If specific techniques or conditions are not specified in the examples, they will be carried out in accordance with the techniques or conditions described in literature in the art or in accordance with the product instructions. If the manufacturer of the reagents or instruments used is not specified, they are all ordinary products that are commercially available.

[0044] Specifically, see the table below. Here, the positive electrode active material is the ternary material NCM111 (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), the positive electrode current collectors were all aluminum foil, the negative electrode active material was all graphite, and the negative electrode current collectors were all copper foil. The electrolyte included a solvent, a lithium salt, and an additive. The solvent included ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC), and the mass fraction ratio of the EC, DMC, and EMC solvents was 2:3:5. The electrolyte additive was 1 wt% vinylene carbonate (VC). The first lithium salt was lithium bis(fluorosulfonyl)imide (LIFSI), and the second lithium salt was lithium hexafluorophosphate (LiPF6). The specific contents of the first lithium salt and the second lithium salt are shown in Table 1.

[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, respectively, and fabricating a three-electrode battery with a reference electrode according to the three-electrode battery fabrication method. Furthermore, the reference electrode is used to monitor the positive electrode potential during overcharging during battery charging and discharging, and measuring the negative electrode potential when charging to 80% SOC at 1C. The three-electrode battery is fabricated as follows: a positive electrode plate, a negative electrode plate, and a separator are taken and punched according to size requirements, 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 this order. During the stacking process, a copper wire with a diameter of 200 microns is placed between the positive and negative electrodes. This copper wire is pulled out from the electrode and welded to a nickel sheet to form the third electrode (reference electrode). After the stacking is complete, the stacked structure is placed in an aluminum plastic film bag, and a certain amount of the electrolyte is injected and packaged. After standing, formation, and aging, the three-electrode battery is obtained.

[0047] The test method for battery capacity retention rate includes the following steps after the completion of the fabrication of the above-mentioned battery: 1) let it stand for 5 minutes under conditions of 25°C; 2) discharge to 2.8V at a constant current of 1C; 3) let it stand for 5 minutes; 4) charge to the upper limit voltage at a constant current of 1C, then convert to a constant voltage and charge to 0.05C until fully charged; 5) let it stand for 5 minutes; and 6) discharge to 2.7V at a constant current of 1C. The discharge capacity in step 6 is the discharge capacity of the battery.

[0048] The cycle performance test method initially included adjusting the battery to 80% SOC at 25°C, then 1) letting it rest for 5 minutes, 2) charging it to the upper limit voltage at a constant current of 1C, then converting to a constant voltage and charging it at 0.05C until it reached full charge, 3) letting it rest for 5 minutes, and 4) discharging it at a constant current of 1C for 12 minutes. At this point, the battery reached 80% SOC, and the corresponding battery voltage was recorded as V1, corresponding to the 80% SOC state. The battery was then left at -10°C to begin the cycle flow: 1) letting it rest for 2 hours, 2) charging it at a constant current of 15C for 5 seconds, 3) resting for 10 minutes, 4) discharging it at a constant current of 15C for 5 seconds, 5) letting it rest for 10 minutes, and finally cycling it through steps 2 through 5 of the cycle flow for a total of 1000 cycles. The battery capacity retention was calculated as follows: Using the capacity test flow before and after the battery cycle, the capacity of the battery before and after the cycle was cycle tested at -10℃, 80% SOC, 15C / 15C, 5s. The capacity before the cycle was Cap1, and the capacity after the cycle was Cap2. The capacity retention rate at -10℃, 80% SOC, 15C / 15C, 5s, 1000cls = Cap2 / Cap1.

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

[0050] Test results showed that the negative electrode potentials of the batteries in Examples 1 to 10, when charged at 1C to 80% SOC, were all between 0.09 and 0.15V. After charging and discharging at -10°C for 1000 cls at 5C / 5C for 5 seconds, were all greater than 90%. The degree of interfacial lithium deposition was relatively low, and the negative electrode active material layer on the surface of the negative electrode plate after disassembly remained the original color. The negative electrode potentials of the batteries in Comparative Examples 1 to 6, when charged at 1C to 80% SOC, were all less than 0.09V. After charging and discharging at -10°C for 1000 cls at 5C / 5C for 5 seconds, were all less than 90%. The interfacial lithium deposition was evident, and safety and cycle life were both relatively poor. Furthermore, as the level of lithium deposition increased, a large amount of silvery deposits were clearly visible on the surface of the negative electrode 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 any one of the cases of A alone, B alone, and A and B, where A and B are merely examples, and they may be any technical features connected with "and / or" in this application.

[0052] Unless otherwise explained, all technical terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. All patents and publications related to this application are incorporated by reference in their entirety into this application. The terms "comprise" or "include" are open-ended, i.e., include the content set forth in this application but do not exclude the content of other aspects.

[0053] In the description of this specification, the reference terms "one embodiment," "another embodiment," and the like mean that the specific features, structures, materials, or characteristics described in connection with this embodiment are included in at least one embodiment of the present application. In this specification, general expressions using 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 any appropriate manner in any one or more embodiments or examples. Furthermore, if not mutually inconsistent, a person skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification. It should also be noted that the terms "first" and "second" used in this specification are for descriptive purposes only and cannot be understood as indicating or implying relative importance or the number of technical features indicated.

[0054] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are illustrative and should not be construed as limitations on the present application, and that those skilled in the art may make changes, modifications, substitutions and variations to the above embodiments within the scope of the present 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, the separator being 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 ＋ A lithium-ion battery that satisfies the following criteria:

2. 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 ＋ 2. The lithium ion battery according to claim 1, wherein:

3. The lithium ion battery according to claim 1 or 2, wherein the CB value of the lithium ion battery is 1.1 to 1.8, and optionally the CB value of the lithium ion battery is 1.3 to 1.5, wherein the CB = negative electrode capacity / positive electrode capacity in the same opposing area.

4. 4. The lithium ion battery according to claim 1, wherein the electrolyte solution contains a first lithium salt, the first lithium salt is lithium bis(fluorosulfonyl)imide, and a mass fraction of the first lithium salt in the electrolyte solution is 5 wt % to 19 wt %.

5. 5. The lithium-ion battery of claim 4, 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.

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

7. 7. The lithium ion battery according to claim 5, wherein the molar concentration ratio of the first lithium salt to the second lithium salt in the electrolytic solution is from (3:7) to (9:1).

8. 8. 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 including a positive electrode active material, the positive electrode active material including at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate, lithium iron phosphate, and a lithium-rich manganese-based solid solution.

9. 9. The lithium ion battery according to claim 8, 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 %.

10. 10. 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 including 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, a silicon-based material, and a tin-based material.

11. 11. The lithium ion battery according to claim 1, wherein the solvent in the electrolytic solution contains at least one of a cyclic carbonate, a chain carbonate, and a chain carboxylic acid ester.

12. 12. The lithium ion battery according to claim 1, wherein the electrolyte solution further contains an additive, the additive including at least one of fluorinated ethylene carbonate, a cyclic sulfate ester, a cyclic sulfonate ester, a (trimethylsilane)phosphate ester, a (trimethylsilane)borate ester, trimethylfluorosilane, lithium difluorophosphate, and lithium difluorobis(oxalato)phosphate, and the mass content of the additive in the electrolyte solution is 10 ppm or more.

13. 13. A power consuming device comprising a lithium ion battery according to any one of claims 1 to 12.

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