Patent Application
20240047732
The present application relates to the field of batteries, and specifically relates to a lithium-ion battery, a battery module, a battery pack, and an electrical apparatus.
As a secondary battery, a lithium-ion battery works mainly relying on movement of lithium ions between a positive electrode and a negative electrode. During the charge and discharge process, Li+ intercalates and deintercalates back and forth between the two electrodes: during charging, Li+ deintercalates from the positive electrode, intercalates through the electrolyte into the negative electrode, and the negative electrode is in a lithium-rich state; while the opposite is true during discharging.
An electrolyte solution is a carrier of ion transmission in the lithium-ion battery, serves to conduct ions between the positive electrode and the negative electrode of the lithium-ion battery, and is the guarantee for high-voltage, high-specific-energy performance and the like of the lithium-ion battery. The electrolyte solution is generally prepared from a high-purity organic solvent, an electrolyte lithium salt, a necessary additive, and other raw materials under certain conditions and in a certain proportion.
At present, lithium-ion batteries have been widely used in high-tech products such as automobiles and mobile phones. However, with the continuous expansion of the application field of lithium-ion batteries, power performance and cycle life of the batteries still remain to be further improved.
In view of the problems existing in the Background Art, the present application provides a lithium-ion battery, a battery module, a battery pack, and an electrical apparatus.
In a first aspect, the present application provides a lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator between the positive electrode sheet and the negative electrode sheet, and an electrolyte solution. The electrolyte solution comprises an organic solvent, an electrolyte lithium salt dissolved in the organic solvent, and also one or more of additives shown in formula (I),
wherein R is selected from the group consisting of K, Li, Na, Rb, or Cs, R1 is selected from C1-C10 alkyl; and a percentage mass content of the additives shown in formula (I) in the electrolyte solution is denoted as W0%. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, and a specific surface area of a negative electrode active material in the negative electrode active material layer is denoted as X1, in m2/g; satisfying: W0/X1=0.1−10; and optionally, W0/X1=0.2−4.
As researched and validated by the inventor of the present application, the electrolyte solution comprising the additives shown in formula (I) is applied to the lithium-ion battery, and the additives shown in formula (I) are first reduced to a film on a surface of a negative electrode of the lithium-ion battery, forming an interfacial film with low impedance and high ion transmission capacity. This interfacial film serves to protect the negative electrode, and contributes to improving power performance, cycling performance, and service life of the battery. The inventor holds that: within the lithium-ion battery, various reactions occur on surfaces of electrodes, so that physical and chemical properties of a positive electrode active material and the negative electrode active material affect reaction characteristics on a surface of a positive electrode and the surface of the negative electrode within the lithium-ion battery. A ratio of a percentage mass content W0 of the additives shown in formula (I) in the electrolyte solution to a specific surface area X1 of the negative electrode active material is defined within a reasonable range, such that the additives shown in formula (I) form a homogeneous and stable protective film on the surface of the negative electrode of the lithium-ion battery, to guarantee improvement of the cycling performance and power performance of the lithium-ion battery.
In some optional embodiments, in the lithium-ion battery provided in the present application, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, and a specific surface area of the positive electrode active material in the negative electrode active material layer is denoted as X2, m2/g; satisfying: X2/W0=0.4−5; and optionally, X2/W0=0.6−3.
A ratio of the specific surface area X2 of the positive electrode active material to the percentage mass content W0 of the additives shown in formula (I) is defined within a reasonable range, such that reaction and consumption of the additives shown in formula (I) on a surface of a positive electrode of the lithium-ion battery are within a reasonable range, thereby guaranteeing improvement of comprehensive performance of the lithium-ion battery.
In some optional embodiments, the percentage mass content W0% of the additives shown in formula (I) in the electrolyte solution is from 0.1% to 2%, and optionally, W0% is from 0.3% to 1%.
When an addition amount of the additives shown in formula (I) in the electrolyte solution is very small, it is not enough to form a stable interfacial film on the surface of the negative electrode of the lithium-ion battery; and when the addition amount of the additives shown in formula (I) in the electrolyte solution is very large, gas production of the lithium-ion battery can be aggravated. Moreover, the additives shown in formula (I) will also increase viscosity of the electrolyte solution, thereby affecting conductivity of the electrolyte solution. In this regard, the present application further provides a range of the percentage mass content of the additives shown in formula (I) in the electrolyte solution, such that the additives shown in formula (I) are substantially first consumed at the negative electrode of the lithium-ion battery, and are enough to form a homogeneous and stable interfacial film, to protect the negative electrode, fully function to improve low-temperature cycle and power performance of the lithium-ion battery; and weaken adverse effects thereof on the conductivity of the electrolyte solution.
In some optional embodiments, in the lithium-ion battery provided in the present application, R is K, and R1 is methyl in the structure of formula (I).
In some optional embodiments, in the lithium-ion battery provided in the present application, a percentage mass content of the electrolyte lithium salt in the electrolyte solution is denoted as W1%, satisfying: W1%≥5W0. Optionally, in the lithium-ion battery provided in the present application, the percentage mass content W1% of the electrolyte lithium salt in the electrolyte solution is from 10% to 15%.
The addition of the additives shown in formula (I) increases the viscosity of the electrolyte solution, which is not beneficial for the conductivity of the electrolyte solution, and can further affect dynamic characteristics of the lithium-ion battery. The electrolyte lithium salt in the electrolyte solution can improve the conductivity of the electrolyte solution, and can reduce concentration polarization. Therefore, a reasonable addition amount of the additives shown in formula (I) is also affected by a concentration and a use amount of the lithium salt. In the electrolyte solution provided in the present application, when the percentage mass content of the additives shown in formula (I) is less than or equal to ⅕ percentage mass content of the electrolyte lithium salt, i.e., when W1≥5W0, or W1%=10%−15%, the electrolyte lithium salt can efficiently alleviate deterioration of the viscosity of the electrolyte solution caused by the addition of the additives shown in formula (I), such that the viscosity and conductivity of the electrolyte solution are in a favorable range.
In some optional embodiments, in the lithium-ion battery provided in the present application, the electrolyte solution further comprises a positive electrode sacrificing additive, an oxidation potential of the positive electrode sacrificing additive is lower than 4.5 V; and optionally, the oxidation potential of the positive electrode sacrificing additive is lower than 4.3 V.
As mentioned above, the additives shown in formula (I) can priorly form a film on the surface of the negative electrode of the lithium-ion battery, thereby improving the power performance, cycling performance, and service life of the battery. However, the additives shown in formula (I) have no effects on improving the gas production of the lithium-ion battery, and will also aggravate gas production during storage to a certain extent due to their own poor oxidation resistance. In this regard, the inventor of the present application presents that the positive electrode sacrificing additive is also added in the electrolyte solution provided in the present application. The positive electrode sacrificing additive can priorly form a film on the surface of the positive electrode, thereby improving the gas production of the lithium-ion battery.
Further, the oxidation potential of the positive electrode sacrificing additive added in the electrolyte solution in the present application may be lower than 4.5 V, and optionally lower than 4.3 V. The inventor of the present application finds that the oxidation potential of the additives shown in formula (I) is low, and the additives will, when being oxidized, produce a large amount of gases, which is not beneficial for storage performance of the lithium-ion battery. Further, this situation is obvious when the battery is charged to more than 4.2 V, and is particularly more obvious when the battery is charged to more than 4.4 V. Therefore, when the oxidation potential of the positive electrode sacrificing additive added in the electrolyte situation is lower than 4.5 V, and optionally lower than 4.3 V, the positive electrode sacrificing additive can be guaranteed to form a film prior to the additives shown in formula (I) and the solvent, thereby favorably inhibiting occurrence of the gas production, and improving the storage performance of the lithium-ion battery.
In some optional embodiments, the lithium-ion battery provided in the present application, the positive electrode sacrificing additive is selected from compounds shown in one of formula (II) to formula (IV):
wherein R2 is selected from a carbon atom or alkylene substituted with C1-C9 alkyl.
In some optional embodiments, in the lithium-ion battery provided in the present application, a percentage mass content of the positive electrode sacrificing additive in the electrolyte solution is denoted as W2%, satisfying: 0.5%≤W2≤4%; optionally, W2≤3W0; and further optionally, W2≤2W0.
When the percentage mass content W2% of the positive electrode sacrificing additive in the electrolyte solution satisfies 0.5%≤W2≤4%, the positive electrode sacrificing additive can favorably improve the gas production problem of the lithium-ion battery, and improve the gas production of lithium ions. However, the positive electrode sacrificing additive will have adverse effects on both power and service life of the lithium-ion battery. In order to avoid occurrence of the above adverse effects, the percentage mass content of the positive electrode sacrificing additive in the electrolyte solution is most preferably not higher than 3 times as much as the percentage mass content of the additives shown in formula (I) in the electrolyte solution; and further optionally, the percentage mass content of the positive electrode sacrificing additive in the electrolyte solution is most preferably not higher than 2 times as much as the percentage mass content of the additives shown in formula (I) in the electrolyte solution, thereby maintaining favorable power and service life of the lithium-ion battery.
In a second aspect, the present application provides a battery module, comprising the lithium-ion battery in the first aspect of the present application.
In a third aspect, the present application provides a battery pack, comprising the lithium-ion battery in the first aspect of the present application or the battery module in the second aspect of the present application.
In a fourth aspect, the present application provides an electrical apparatus, comprising the lithium-ion battery in the first aspect of the present application, the battery module in the second aspect of the present application, or the battery pack in the third aspect of the present application; where the lithium-ion battery or the battery module or the battery pack serves as a power source or an energy storage unit of the electrical apparatus.
The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are provided merely to illustrate the present application, rather than limiting the scope of the present application.
The first aspect of the present application provides a lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator between the positive electrode sheet and the negative electrode sheet, and an electrolyte solution. The electrolyte solution comprises an organic solvent, an electrolyte lithium salt dissolved in the organic solvent, and one or more of additives shown in formula (I),
where R is selected from the group consisting of K, Li, Na, Rb, or Cs, R1 is selected from C1-C10 alkyl; and a percentage mass content of the additives shown in formula (I) in the electrolyte solution is denoted as W0%, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, and a specific surface area of a negative electrode active material in the negative electrode active material layer is denoted as X1, m2/g; satisfying: W0/X1=0.1−50; and optionally, W0/X1=0.2−10.
The inventor finds that the electrolyte solution comprising the additives shown in formula (I) is applied to the lithium-ion battery, and the additives shown in formula (I) are first reduced to a film on a surface of a negative electrode of the lithium-ion battery, forming an interfacial film with low impedance and high ion transmission capacity. This interfacial film serves to protect the negative electrode, and contributes to improving power performance and cycling performance of the battery.
In addition,
In this regard, the inventor holds that: within the lithium-ion battery, various reactions occur on surfaces of electrodes, so that physical and chemical properties of a positive electrode active material and a negative electrode active material affect reaction characteristics on a surface of the positive electrode and a surface of a negative electrode within the lithium-ion battery. A ratio of a percentage mass content of the additives shown in formula (I) to a specific surface area X1 of the negative electrode active material is defined within a reasonable range, such that the additives shown in formula (I) form a more stable protective film on the surface of the negative electrode of the lithium-ion battery, to better improve power performance and cycling performance of the lithium-ion battery.
Specifically, in an embodiment of the present invention, W0/X1=0.1−50; and optionally, W0/X1=0.2−10. When the ratio of W0/X1 is very large, the content of the additives shown in formula (I) in the electrolyte solution is relatively very high, and a specific surface area of the negative electrode is relatively small, thereby resulting in formation of a very thick protective film on the surface of the negative electrode, causing difficulties in lithium ion transmission, and failing to contribute to improvement of the cycling performance and power performance of the battery. When the ratio of W0/X1 is very small, the content of the additives shown in formula (I) in the electrolyte solution is relatively very low, such that the surface of the negative electrode of the lithium-ion battery is not enough to form a homogeneous and stable interfacial film, the negative electrode is less sufficiently protected, it is difficult to inhibit reduction of the solvent on the surface of the negative electrode, and it is also impossible to effectively improve the cycling performance and power performance of the lithium-ion battery.
In some embodiments, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, a specific surface area of the positive electrode active material in the negative electrode active material layer is denoted as X2, m2/g, and the lithium-ion battery can satisfy: X2/W0=0.1−34; and optionally, X2/W0=0.5−17.
A ratio of the specific surface area X2 of the positive electrode active material to the percentage mass content of the additives shown in formula (I) is defined within a reasonable range, such that consumption of the additives shown in formula (I) on the surface of the positive electrode of the lithium-ion battery is within a reasonable range. Specifically, when X2/W0 is very large, there is a relatively large amount of the positive electrode active material, and the content of the additives shown in formula (I) is relatively low. In this case, a reaction interface of the positive electrode is large, and the consumption of the additives shown in formula (I) is large, such that too many additives shown in formula (I) are consumed on the surface of the positive electrode, which is not beneficial for a film-forming reaction of the additives shown in formula (I) at the negative electrode. When X2/W0 is very small, there is a relatively small amount of the positive electrode active material, and the content of the additives shown in formula (I) is relatively high. Since the additives shown in formula (I) themselves are not resistant to oxidation, excessive additives shown in formula (I) will have adverse effects on viscosity and conductivity of the electrolyte solution, as well as storage performance of the lithium-ion battery.
In some embodiments, the percentage mass content W0% of the additives shown in formula (I) in the electrolyte solution is from 0.1% to 2%; and further optionally, W0% is from 0.3% to 1%.
When an addition amount of the additives shown in formula (I) in the electrolyte solution is very small, it is not enough to form a stable interfacial film on the surface of the negative electrode of the lithium-ion battery; and when the addition amount of the additives shown in formula (I) in the electrolyte solution is very large, the gas production of the lithium-ion battery can be aggravated to a certain extent. Moreover, the additives shown in formula (I) will also increase viscosity of the electrolyte solution, thereby affecting conductivity of the electrolyte solution. In this regard, the present application further provides a range of the percentage mass content of the additives shown in formula (I) in the electrolyte solution, such that the additives shown in formula (I) are substantially first consumed at the negative electrode of the lithium-ion battery, and are enough to form a homogeneous and stable interfacial film, to protect the negative electrode, fully function to improve the cycling performance and power performance of the lithium-ion battery; and weaken adverse effects thereof on the conductivity of the electrolyte solution.
In some embodiments, the additives shown in formula (I) may be selected from, but are not limited to, structures shown in formulas (I-1) to (I-8):
In some embodiments, R is K and R1 is methyl in the structure of formula (I); and the additives have the structure shown in formula (I-1):
In some embodiments, a percentage mass content of an electrolyte lithium salt in the electrolyte solution is denoted as W1%, and the lithium-ion battery can satisfy: W1%≥5W0.
The addition of the additives shown in formula (I) somewhat increases the viscosity of the electrolyte solution, which is not beneficial for the conductivity of the electrolyte solution, and can further affect dynamic characteristics of the lithium-ion battery. The electrolyte lithium salt in the electrolyte solution can improve the conductivity of the electrolyte solution, and can reduce concentration polarization. Therefore, a reasonable addition amount of the additives shown in formula (I) is also affected by a concentration and a use amount of the lithium salt. In some embodiments of the present application, when the percentage mass content of the additives shown in formula (I) is less than or equal to ⅕ percentage mass content of the electrolyte lithium salt, i.e., when W1≥5W0, the electrolyte lithium salt can efficiently alleviate deterioration of the viscosity of the electrolyte solution caused by the addition of the additives shown in formula (I), such that the viscosity and conductivity of the electrolyte solution are in a favorable range.
In some embodiments, the percentage mass content W1% of the electrolyte lithium salt in the electrolyte solution is from 10% to 15%. When W1 and W0 satisfy W1≥5W0, and W1%=10%−15%, the lithium-ion battery has favorable dynamic characteristics.
In some embodiments, the electrolyte solution of the lithium-ion battery further comprises a positive electrode sacrificing additive, an oxidation potential of the positive electrode sacrificing additive is lower than 4.5 V; and optionally, the oxidation potential of the positive electrode sacrificing additive is lower than 4.3 V.
The additives shown in formula (I) can priorly form a film on the surface of the negative electrode of the lithium-ion battery, thereby improving the power performance, cycling performance, and service life of the battery. However, the additives shown in formula (I) have no effects on improving the gas production of the lithium-ion battery, and will also aggravate gas production during storage to a certain extent due to their own poor oxidation resistance. In some embodiments of the present application, the positive electrode sacrificing additive is also added in the electrolyte solution. The positive electrode sacrificing additive can priorly form a film on the surface of the positive electrode, thereby avoiding adverse effects of the additives shown in formula (I) on the gas production during storage of the lithium-ion battery.
In some embodiments, the oxidation potential of the positive electrode sacrificing additive added in the electrolyte solution is lower than 4.5 V, and optionally lower than 4.3 V. The oxidation potential of the additives shown in formula (I) is low, and the additives will, when being oxidized, produce a large amount of gases, which is not beneficial for the storage performance. Further, this situation is obvious when the battery is charged to more than 4.2 V, and is particularly more obvious when the battery is charged to more than 4.4 V. Therefore, when the oxidation potential of the positive electrode sacrificing additive added in the electrolyte situation is lower than 4.5 V, and optionally lower than 4.3 V, the positive electrode sacrificing additive can be guaranteed to form a film prior to the additives shown in formula (I) and the solvent, thereby favorably inhibiting occurrence of the gas production, and improving the storage performance of lithium-ion battery.
In some embodiments, the positive electrode sacrificing additive is selected from compounds shown in one of formula (II) to formula (IV):
wherein R2 is selected from a carbon atom or alkylene substituted with C1-C9 alkyl.
In some embodiments, in the positive electrode sacrificing molecular formula, R2 is optionally methylene.
In some embodiments, a percentage mass content of the positive electrode sacrificing additive in the electrolyte solution is denoted as W2%, and the lithium-ion battery can satisfy: 0.5%≤W2≤4%; optionally, W2≤3W0; and further optionally, W2≤2W0.
When the percentage mass content W2% of the positive electrode sacrificing additive in the electrolyte solution satisfies 0.5%≤W2≤4%, the positive electrode sacrificing additive can favorably improve the gas production problem of the lithium-ion battery. However, the positive electrode sacrificing additive will have adverse effects on both power and service life of the lithium-ion battery. In order to avoid occurrence of the above adverse effects, the percentage mass content of the positive electrode sacrificing additive in the electrolyte solution is most preferably not higher than 3 times as much as the percentage mass content of the additives shown in formula (I) in the electrolyte solution. Further optionally, the percentage mass content of the positive electrode sacrificing additive in the electrolyte solution is most preferably not higher than 2 times as much as the percentage mass content of the additives shown in formula (I) in the electrolyte solution, thereby maintaining favorable power and service life of the lithium-ion battery.
In addition, in an embodiment of the present application, the negative electrode active material of the lithium-ion battery may be various materials suitable for negative electrode active materials of lithium-ion batteries in the art, for example, may include, but is not limited to, a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbead, silicon-based material, tin-based material, lithium titanate, or other metals that can be alloyed with lithium. The graphite may be selected from a combination of one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material may be selected from a combination of one or more of elementary silicon, silicon-oxygen compound, silicon-carbon composite, and silicon alloy; and the tin-based material may be selected from a combination of one or more of elementary tin, tin-oxygen compound, and tin alloy.
The negative electrode current collector is usually a structure or part collecting current. The negative electrode current collector may be various materials suitable for use as negative electrode current collectors of lithium-ion batteries in the art. For example, the negative electrode current collector may include, but is not limited to, a metal foil, and more specifically, may include, but is not limited to, a copper foil. In addition, the negative electrode sheet may also be a lithium sheet.
The specific type of the positive electrode active material is not particularly limited, as long as the positive electrode active material can satisfy intercalation and deintercalation of lithium ions. The positive electrode active material may be either a material with a layered structure, such that lithium ions diffuse in a two-dimensional space, or a material with a spinel structure, such that lithium ions diffuse in a three-dimensional space. Optionally, the positive electrode active material may be selected from one or more of a lithium transition metal oxide or a compound obtained from doping a lithium transition metal oxide with other transition metals or non-transition metals or non-metals. Specifically, the positive electrode active material may be selected from one or more of a lithium-cobalt oxide, a lithium-nickel oxide, a lithium-manganese oxide, a lithium-nickel-manganese oxide, a lithium-nickel-cobalt-manganese oxide, a lithium-nickel-cobalt-aluminum oxide, or a lithium-containing phosphate of olivine structure. For example, the positive electrode active material may be LiqNixMnyCoiMpO2, where x+y+i+p=1, q value ranges from 0.8 to 1.2, and M may be selected from one or more of Al, Mo, Cr, Ti, Ru, or Zr.
The type of the positive electrode current collector is not specifically limited, and may be selected according to actual requirements. The positive electrode current collector can usually be a layered body, and the positive electrode current collector is usually a structure or part capable of collecting current. The positive electrode current collector may be various materials suitable for use as positive electrode current collectors of electrochemical energy storage apparatuses in the art. For example, the positive electrode current collector may include, but is not limited to, a metal foil, and more specifically, may include, but is not limited to, a nickel foil and an aluminum foil.
The separator of the lithium-ion battery may be various materials suitable for separators of lithium-ion batteries in the art, for example, may include, but is not limited to, a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fiber.
The method for preparing the lithium-ion battery should be known to those skilled in the art. For example, the positive electrode sheet, the separator, and the negative electrode sheet may each be a layered body, such that they may be cut to a target size and then sequentially stacked, or may also be winded to the target size to form a battery cell, and may be further combined with the electrolyte solution to form the lithium-ion battery.
It should be noted that the battery cell 5 shown in
The second aspect of the present application provides a battery module, comprising the lithium-ion battery described in the first aspect of the present application. In some embodiments, the lithium-ion batteries may be assembled into a battery module, the number of lithium-ion batteries comprised in the battery module may be a plural number, and the specific number may be adjusted based on the application and capacity of the battery module.
The third aspect of the present application provides a battery pack, comprising the battery module in the second aspect of the present application. In some embodiments, the battery module may be assembled into a battery pack, and the number of battery modules comprised in the battery pack may be adjusted based on the application and capacity of the battery pack.
The fourth aspect of the present application provides an electrical apparatus, comprising the lithium-ion battery in the first aspect of the present application, or the battery module in the second aspect of the present application, or the battery pack in the third aspect of the present application. The lithium-ion battery, or the battery module, or the battery pack may be used as a power source of the electrical apparatus, or an energy storage unit of the electrical apparatus. The electrical apparatus may be, but is not limited to, a mobile device (such as a mobile phone or a laptop), an electric vehicle (such as an all-electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck), an electric train, a ship, a satellite, an energy storage system, etc.
The lithium-ion battery, the battery module, or the battery pack may be selected for the electrical apparatus according to use demand thereof.
As another example, the electrical apparatus may be a mobile phone, a tablet, a laptop, etc. The electrical apparatus is generally required to be thin and light, and may be powered by the lithium-ion battery in the present application.
The present application will be further described below with reference to specific Embodiments. It should be understood that the illustrative Embodiments below are merely provided for exemplification, and do not constitute any limitation to the present application. Unless otherwise stated, all reagents used in the Embodiments are commercially available or can be obtained by synthesis according to conventional methods, and can be directly used without further treatment. The experimental conditions unspecified in the Embodiments are conventional conditions or conditions recommended by material suppliers or equipment suppliers.
Preparations in Embodiments 1-25 of the present application follow the following methods and the specific parameters in Table 1.
(1) Preparation of an Electrolyte Solution
An organic solvent was prepared in a drying room, and then an electrolyte lithium salt, an additive shown in formula (I-1), and a positive electrode sacrificing additive were added into the organic solvent. The mixture was sufficiently mixed to obtain the electrolyte solution.
(2) Preparation of a Positive Electrode Sheet
A positive electrode active material (LiNi0.5Co0.2Mn0.3O2 (NCM523)), a conductive agent (carbon black (Super P)), and a binder (polyvinylidene fluoride (PVDF)) at a mass ratio of 96.2:2.7:1.1 were sufficiently mixed in an appropriate amount of a solvent (N-methyl pyrrolidone (NMP)), to obtain a positive electrode slurry. The positive electrode slurry was coated on a positive electrode current collector (aluminum foil), dried, cold pressed, striped, and cut, to obtain the positive electrode sheet.
(3) Preparation of a Negative Electrode Sheet
A negative electrode active material (artificial graphite), a conductive agent (carbon black (Super P)), a binder (styrene butadiene rubber (SBR)), and sodium carboxymethyl cellulose (CMC-Na) at a mass ratio of 96.4:0.7:1.8:1.1 were sufficiently mixed in an appropriate amount of a solvent (deionized water), to obtain a negative electrode slurry. The negative electrode slurry was coated on a negative electrode current collector (copper foil), dried, cold pressed, striped, and cut, to obtain the negative electrode sheet.
(4) Separator
A PP separator of 12 μm was used.
(5) Preparation of a Lithium-Ion Battery
The positive electrode sheet, the separator, and the negative electrode sheet were sequentially stacked, such that the separator was located between the positive electrode sheet and the negative electrode sheet to function for separation, and then winded to obtain an electrode assembly. The electrode assembly was placed in an outer package, and the above prepared electrolyte solution was injected into a dried battery. The lithium-ion battery was obtained through the processes, such as vacuum encapsulation, standing, formation, and shaping.
The difference between Comparative Embodiments 1 and 2 and Embodiment 3 only lies in that a ratio of a percentage mass content of additives shown in formula (I) added in the electrolyte solution to a specific surface area of the negative electrode active material in Embodiment 1 is different. Embodiments 1-25 were referred to for preparation steps in Comparative Embodiments 1-2.
(1) Testing of Low-Temperature Cycling Performance of the Lithium-Ion Battery
At 10° C., the battery was charged to 4.25 V at a constant current of 0.3 C, then charged to a current of 0.05 C at a constant voltage of 4.25 V, laid aside for 5 min, and then discharged to 2.5 V at a constant current of 0.5 C. The resulting capacity was denoted as an initial capacity C0. The above steps were repeated for the same battery mentioned above, and counting was started simultaneously. A discharge capacity C300 of the battery was recorded after 300 cycles, and a cycling capacity retention rate of the battery after 300 cycles=C300/C0*100%.
(2) Testing of High-Temperature Cycling Performance of the Lithium-Ion Battery
At 60° C., the battery was charged to 4.25 V at a constant current of 1 C, then charged to a current of 0.05 C at a constant voltage of 4.25 V, laid aside for 5 min, and then discharged to 2.5 V at a constant current of 1 C. The resulting capacity was denoted as an initial capacity Co0. The above steps were repeated for the same battery mentioned above, and counting was started simultaneously. A discharge capacity C300 of the battery was recorded after 300 cycles, and a cycling capacity retention rate of the battery after 300 cycles=C300/C0*100%.
(3) Storage Test of a Lithium-Ion Secondary Battery at 60° C.
At 60° C., the lithium-ion secondary battery was charged to 4.35 V at a constant current of 0.5 C, then charged to a current of 0.05 C at a constant voltage. In this case, thickness of the lithium-ion secondary battery was tested and denoted as h0; then, the lithium-ion secondary battery was put into a thermostat at 60° C., and taken out after 30 days of storage. The thickness of the lithium-ion secondary battery was tested, and was denoted as h1. After 30 days of storage, thickness expansion rate of the lithium-ion secondary battery=[(h1−h0)/h0]×100%.
(4) Power Test of the Lithium-Ion Battery
At 25° C., the above lithium-ion battery was charged to 4.25 V at a charging rate of 1 C, then charged to a current of less than 0.05 C at a constant voltage, and then discharged at a discharging rate of 1 C for 30 min. In this case, a SOC of the battery was 50%, and in this case, the voltage was denoted as V1. Then, the battery was discharged at a discharging rate of 4 C (corresponding current at 4 C was I) for 30 sec. In this case, the voltage was denoted as V2. An initial discharge DCR (Direct Current Resistance) of the lithium-ion battery was computed following DC=(V1−V2)/I.
Composition parameters and detection results of the electrolyte solution and the lithium-ion battery in Embodiments 1-25 and Comparative Embodiments 1-2 are shown in Table 1.
Embodiments 1-5 and Comparative Embodiments 1-2 show the effects of the ratio of the percentage mass content of the additives of formula (I) to the specific surface area of the negative electrode active material on the performance of the lithium-ion battery. When the ratio of W0/X1 is very large, the content of the additives of formula (I) in the electrolyte solution is relatively very high, and a specific surface area of the negative electrode is relatively small, thereby resulting in formation of a very thick protective film on a surface of the negative electrode, causing difficulties in lithium ion transmission, and failing to contribute to improvement of power performance and cycling performance of the battery. When the ratio of W0/X1 is very small, the content of the additives of formula (I) in the electrolyte solution is very low, such that the surface of the negative electrode of the lithium-ion battery is not enough to form a homogeneous and stable interfacial film, the negative electrode is less sufficiently protected, it is difficult to inhibit reduction of the solvent on the surface of the negative electrode, and it is also impossible to effectively improve the power performance and cycling performance of the lithium-ion battery.
Embodiments 3 and 6-9 show the effects of the ratio of the specific surface area of the positive electrode active material of the lithium-ion battery to the percentage mass content of the additives in formula (I) on the performance of the lithium-ion battery. When X2/W0 is very large, there is a relatively large amount of the positive electrode active material, and the content of the additives of formula (I) is relatively low. In this case, a reaction interface of the positive electrode is large, and consumption of the additives of formula (I) is large, such that too many additives of formula (I) are consumed on a surface of the positive electrode, which is not beneficial for a film-forming reaction of the additives at the negative electrode. When X2/W0 is very small, there is a relatively small amount of the positive electrode active material, and the content of the additives of formula (I) is relatively high. Since the additives of formula (I) themselves are weakly resistant to oxidation, excessive additives of formula (I) will have adverse effects on viscosity and conductivity of the electrolyte solution, as well as storage performance and power performance of the lithium-ion battery.
Embodiments 3 and 10-13 show the effects of the percentage mass content of the additives of formula (I) on the performance of the lithium-ion battery. When an addition amount of the additives shown in formula (I) in the electrolyte solution is very small, it is not enough to form a stable interfacial film on the surface of the negative electrode of the lithium-ion battery; when the addition amount of the additives shown in formula (I) in the electrolyte solution is very large, gas production of the lithium-ion battery can be aggravated to a certain extent; and moreover, the additives shown in formula (I) will also increase the viscosity of the electrolyte solution, thereby affecting the conductivity of the electrolyte solution. When the percentage mass content W0% of the additives shown in formula (I) in the electrolyte solution is from 0.1% to 2%, and optionally, when W0% is from 0.3% to 1%, the additives are substantially first consumed at the negative electrode of the lithium-ion battery, and are enough to form a homogeneous and stable interfacial film, to protect the negative electrode, fully function to improve the cycling performance and power performance of the lithium-ion battery; and have no obvious adverse effects on the conductivity of the electrolyte solution.
Embodiments 3 and 14-17 show the effects of the percentage mass content of the electrolyte lithium salt in the electrolyte solution on the performance of the lithium-ion battery. The addition of the additives of formula (I) somewhat increases the viscosity of the electrolyte solution, which is not beneficial for the conductivity of the electrolyte solution, and can further affect dynamic characteristics of the lithium-ion battery. The electrolyte lithium salt in the electrolyte solution can improve the conductivity of the electrolyte solution, and can reduce concentration polarization. The percentage mass content of the electrolyte lithium salt in the electrolyte solution in Embodiments 3 and 16-17 is within a reasonable range, such that the power performance and cycling performance of the lithium-ion battery are also favorable.
Embodiments 18-22 show the effects of the percentage mass content of the positive electrode sacrificing additive in the electrode solution on the performance of the lithium-ion battery. The additives of formula (I) can priorly form a film on the surface of the negative electrode of the lithium-ion battery, thereby improving the power performance, cycling performance, and service life of the battery. However, the additives will aggravate gas production during storage to a certain extent. The addition of the positive electrode sacrificing additive can just make up for the above defects of the additives of formula (I) by priorly forming a film on the surface of the positive electrode, thereby improving the gas production during storage of the lithium-ion battery. The content of the positive electrode sacrificing additive in Embodiments 19-29 in a favorable range can guarantee favorable cycling performance, power performance and storage performance of the lithium-ion battery.
Embodiments 23-25 show examples of using the additives of formula (I) with different specific structures and the positive electrode sacrificing additive within the scope provided in the present application. These examples show that these additives of formula (I) with different specific structures and the positive electrode sacrificing additive can achieve technical effects of the present application.
According to the disclosure and teachings in the above specification, those skilled in the art can further make alterations and modifications to the above embodiments. Therefore, the present application is not limited to the specific embodiments disclosed and described above, and some modifications and alterations to the present application should also be encompassed within the scope of protection of the claims of the present application. In addition, although some specific terms are used in the present specification, these terms are provided merely for ease of description, and do not constitute any limitation to the present application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202111159457.3 | Sep 2021 | CN | national |
The present application is a continuation of International Application PCT/CN2022/094119, filed on May 20, 2022, which claims the priority of Chinese Patent Application No. 202111159457.3 filed on 30 Sep. 2021 and titled “LITHIUM-ION BATTERY, BATTERY MODULE, BATTERY PACK, AND ELECTRICAL APPARATUS,” the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2022/094119 | May 2022 | US |
| Child | 18482881 | US |
