Positive electrode and electrochemical apparatus containing the same, and electronic apparatus

Abstract

To provide a positive electrode that has both reduced electronic resistance and improved flexibility and prevents brittle fracture of the positive electrode from occurring due to its high compression density, an electrochemical device including the same, and an electronic device.SOLUTION: The positive electrode includes a current collector and a positive electrode active material layer located on the current collector. The positive electrode active material layer includes a positive electrode active material and graphene. A ratio Dv50 / D1 between a particle size Dv50 of the positive electrode active material and a sheet diameter D1 of the graphene is 0.45 to 4.5. The positive electrode has low electronic resistance and improved flexibility. The positive electrode can improve the problem of brittle fracture of the positive electrode occurring at high compression densities.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the field of energy storage, specifically to a positive electrode material, an electrochemical device and an electronic device including the same, and particularly to a secondary lithium battery with a high energy density.

Background Art

[0002] With the development of the lithium-ion battery industry, the market's requirements for the kinetic performance and energy density of lithium-ion batteries are also increasing. Due to the difference in the conductivity of the positive electrode material and the high electronic resistance, the battery resistance becomes slightly larger. At the same time, when the compression density of the positive electrode is high, problems such as brittle fracture when folding in half occur. In the market, there is an urgent need for a new lithium-ion battery to solve this technical problem.

Summary of the Invention

[0003] Embodiments according to the present invention provide a positive electrode, aiming to solve at least some of the problems existing in related fields to some extent. Embodiments according to the present invention further provide an electrochemical device and an electronic device using this positive electrode.

[0004] In one embodiment, the present invention provides a positive electrode including a current collector and a positive electrode active material layer located on the current collector, the positive electrode active material layer including a positive electrode active material and graphene, and the ratio Dv50 / D1 of the particle size Dv50 of the positive electrode active material to the sheet diameter D1 of the graphene being 0.45 to 4.5.

[0005] In some embodiments, the ratio Dv10 / Dv50 of the particle size Dv10 to Dv50 of the positive electrode active material is 0.25 to 0.5.

[0006] In some embodiments, the particle size Dv50 of the positive electrode active material is 0.5 μm to 35 μm.

[0007] In some embodiments, the number of graphene layers is n, where n is 1 to 30, preferably 7 to 20.

[0008] In some embodiments, the positive electrode active material layer further comprises a particulate conductive agent, wherein the particle size D2 of the particulate conductive agent and the particle size Dv50 of the positive electrode active material satisfy D2 / Dv50 < 0.4.

[0009] In some embodiments, the particulate conductive agent comprises at least one of conductive carbon black, Super P, acetylene black, Ketjen black, and graphite.

[0010] In some embodiments, the ratio Dv99 / D1 of the particle size Dv99 of the positive electrode active material to the sheet diameter D1 of the graphene is 3.2 to 4.6.

[0011] In some embodiments, the sheet resistance of the positive electrode active material layer is 0.1 ohm to 550 ohm.

[0012] In some embodiments, the compressed density of the positive electrode active material layer is 3.5 g / cc to 4.5 g / cc.

[0013] In some embodiments, the positive electrode active material comprises at least one of a lithium transition metal composite oxide and a lithium-containing transition metal phosphate compound.

[0014] In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium iron phosphate.

[0015] In some embodiments, the graphene content is 0.1 wt.% to 5 wt.% based on the total weight of the positive electrode active material layer.

[0016] In some embodiments, the coating surface density of the positive electrode active material layer was 200 mg / 1540.25 mm². 2~330mg / 1540.25mm 2 That is the case.

[0017] In another embodiment, the present invention provides an electrochemical apparatus comprising a positive electrode described in an embodiment of the present invention.

[0018] In another embodiment, the present invention provides an electronic device including an electrochemical apparatus described in an embodiment of the present invention.

[0019] The positive electrode provided by the present invention has reduced electronic resistance and improved flexibility, and can overcome the problem of brittle fracture of the positive electrode at high compressive densities.

[0020] Other embodiments and advantages of the embodiments according to the present invention are partially described and shown below, or illustrated by the implementation of the embodiments according to the present invention. [Brief explanation of the drawing]

[0021] In the following, in order to more easily explain embodiments of the present invention, the drawings necessary to explain embodiments of the present invention and the prior art will be briefly described. Clearly, the drawings described below show only a portion of embodiments of the present invention. Those skilled in the art can still obtain drawings of other embodiments from the configurations illustrated in these drawings. [Figure 1] Figure 1 shows a scanning electron microscope (SEM) image of the positive electrode in Example 3 according to the present invention, where the straight line in the figure indicates the length of the graphene sheet diameter. [Figure 2] Figure 2 is an SEM image of the positive electrode in Example 18 according to the present invention, showing that graphene is present around the positive electrode active material particles. [Modes for carrying out the invention]

[0022] Examples of the present invention will be described in detail below. It should be understood that these examples do not limit the scope of the present invention.

[0023] In this specification, quantities, ratios, and other numerical values ​​are expressed in range format. Such range formats should be understood flexibly, including not only the numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges that fall within that range, explicitly specifying each numerical value and subrange.

[0024] In specific embodiments and claims, a list of terms connected to the terms “one of,” “one of,” “a type of,” or other similar terms means any one of the listed terms. For example, if terms A and B are listed, the phrase “one of A and B” means either A or B alone. In other examples, if terms A, B, and C are listed, the phrase “one of A, B, and C” means either A or B alone. Term A may contain one or more elements. Term B may contain one or more elements. Term C may contain one or more elements.

[0025] In specific embodiments and claims, a list of terms connected to the terms “at least one of,” “at least one of,” “at least one type of,” or other similar terms means any combination of the listed terms. For example, if terms A and B are listed, the phrase “one of A and B” means A only or B only. In other examples, if terms A, B and C are listed, the phrase “one of A, B and C” means A only, B only, or C only. Term A may contain one or more elements. Term B may contain one or more elements. Term C may contain one or more elements.

[0026] In one embodiment, the present invention provides an electrochemical apparatus comprising a positive electrode, a negative electrode, a separator, and an electrolyte. I, positive electrode

[0027] In some embodiments, the present invention provides a positive electrode comprising a current collector and a positive electrode active material layer located on the current collector, wherein the positive electrode active material layer comprises a positive electrode active material and graphene, and the ratio Dv50 / D1 of the particle size Dv50 of the positive electrode active material to the sheet diameter D1 of the graphene is 0.45 to 4.5.

[0028] In some embodiments, the positive electrode active material layer is located on one surface of the current collector. In some embodiments, the positive electrode active material layer is located on both surfaces of the current collector.

[0029] In some embodiments, Dv50 / D1 is a range consisting of 0.45, 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8, 3.0, 3.2, 3.5, 3.7, 4.0, 4.2, 4.5, or any two within this range. In some embodiments, Dv50 / D1 is preferably 1.0 to 3.5.

[0030] In some embodiments, the ratio of particle size Dv10 to Dv50 of the positive electrode active material, Dv10 / Dv50, is 0.25 to 0.5. In some embodiments, Dv10 / Dv50 is in the range of 0.25, 0.27, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.48, 0.5, or any two within this range. In some embodiments, Dv10 / Dv50 is preferably 0.33 to 0.45.

[0031] In some embodiments, the particle size Dv50 of the positive electrode active material is 0.5 μm to 35 μm. In some embodiments, the particle size Dv50 of the positive electrode active material is in the range of 0.5 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, or any two within this range. In some embodiments, Dv50 is preferably 10 μm to 25 μm.

[0032] In some embodiments, the number of graphene layers is n, and n is between 1 and 30. In some embodiments, n is in the range of 1, 3, 5, 10, 12, 15, 18, 20, 23, 25, 28, 30, or any two within this range. In some embodiments, n is preferably between 7 and 20.

[0033] In some embodiments, the positive electrode active material layer further comprises a particulate conductive agent, and the particle size D2 of the particulate conductive agent and the particle size Dv50 of the positive electrode active material satisfy D2 / Dv50 < 0.4.

[0034] In some embodiments, D2 / Dv50 is a range consisting of 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, or any two within this range. In some embodiments, D2 / Dv50 is preferably 0.04 to 0.25.

[0035] In some embodiments, the particulate conductive agent comprises at least one of conductive carbon black, Super P, acetylene black, Ketjen black, and graphite.

[0036] In some embodiments, the ratio Dv99 / D1 of the particle size Dv99 of the positive electrode active material to the sheet diameter D1 of the graphene is 3.2 to 4.6.

[0037] In some embodiments, Dv99 / D1 is a range consisting of 3.2, 3.5, 3.8, 4.0, 4.2, 4.4, 4.6, or any two of these values.

[0038] In some embodiments, the sheet resistance of the positive electrode active material layer is 0.1 ohm to 550 ohm. In some embodiments, the sheet resistance of the positive electrode active material layer is in the range of 0.1 ohm, 1 ohm, 3 ohm, 6 ohm, 8 ohm, 10 ohm, 30 ohm, 60 ohm, 90 ohm, 110 ohm, 120 ohm, 150 ohm, 180 ohm, 200 ohm, 220 ohm, 250 ohm, 280 ohm, 300 ohm, 320 ohm, 350 ohm, 380 ohm, 400 ohm, 420 ohm, 450 ohm, 480 ohm, 500 ohm, 530 ohm, 550 ohm, or any two within these ranges. In some embodiments, the sheet resistance of the positive electrode active material layer is preferably 0.1 to 10 ohm.

[0039] In some embodiments, the compressed density of the positive electrode active material layer is 3.5 g / cc to 4.5 g / cc. In some embodiments, the compressed density of the positive electrode active material layer is in the range of 3.5 g / cc, 3.7 g / cc, 3.9 g / cc, 4.0 g / cc, 4.2 g / cc, 4.4 g / cc, 4.5 g / cc, or any two within this range. In some embodiments, the compressed density of the positive electrode active material layer is preferably 4.0 g / cc to 4.5 g / cc.

[0040] In this invention, the definitions of the compressible density and critical compressible density of the positive electrode active material layer are: Compressible density of the positive electrode active material layer = Mass of the positive electrode active material layer per unit area (g / cm³) 2 This is the thickness (cm) of the positive electrode active material layer. The mass of the positive electrode active material layer per unit area can be weighed using a balance, and the thickness of the positive electrode active material layer can be measured using a micrometer.

[0041] The critical compressibility density of the positive electrode active material layer refers to the compressibility density of the positive electrode active material layer when the positive electrode is subjected to the maximum reduction amount.

[0042] In some embodiments, the positive electrode active material comprises at least one of a lithium transition metal composite oxide and a lithium-containing transition metal phosphate compound.

[0043] In some embodiments, the positive electrode active material includes at least one of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium iron phosphate.

[0044] In some embodiments, based on the total weight of the positive electrode active material layer, the content of the graphene is 0.1 wt.% to 5 wt.%. In some embodiments, based on the total weight of the positive electrode active material layer, the content of the graphene is 0.1 wt.%, 0.6 wt.%, 1 wt.%, 1.2 wt.%, 1.5 wt.%, 1.8 wt.%, 2.0 wt.%, 2.2 wt.%, 2.5 wt.%, 2.8 wt.%, 3.0 wt.%, 3.2 wt.%, 3.5 wt.%, 3.8 wt.%, 4.0 wt.%, 4.2 wt.%, 4.5 wt.%, 4.8 wt.%, 5 wt.%, or a range consisting of any two within these values. In some embodiments, the content of the graphene is preferably 0.2 wt.% to 1.00 wt.%.

[0045] In some embodiments, the coating surface density of the positive electrode active material layer is 200 mg / 1540.25 mm 2 ~330 mg / 1540.25 mm 2 is the case. In some embodiments, the coating surface density C of the positive electrode active material layer is 200 mg / 1540.25 mm 2 , 230 mg / 1540.25 mm 2 , 260 mg / 1540.25 mm 2 , 280 mg / 1540.25 mm 2 , 300 mg / 1540.25 mm 2 , 330 mg / 1540.25 mm 2 or a range consisting of any two within these values.

[0046] In some embodiments, the positive electrode active material layer may consist of one or more layers, for example, two, three, four, five layers, or any two of these values. In some embodiments, each layer in the multiple positive electrode active material layer may contain the same or different positive electrode active material.

[0047] The electrodes (positive or negative electrodes) of an electrochemical device (e.g., a lithium-ion battery) are generally manufactured by mixing an active material, a conductive agent, a thickener, a binder, and a solvent, and then applying the resulting slurry to a current collector. Furthermore, the theoretical capacity of an electrochemical device varies depending on the type of active material. Generally, electrochemical devices experience a decrease in charge and discharge capacity as the cycle progresses. This is because, during charging and / or discharging, changes in the electrode interface prevent the electrode active material from performing its function.

[0048] The inventors of this invention have unexpectedly discovered the following: By controlling the ratio Dv50 / D1 of the positive electrode active material to the graphene sheet diameter D1 within a predetermined range, the electronic resistance of the positive electrode can be improved, and the flexibility of the positive electrode can be enhanced, thereby avoiding the problem of brittle fracture of the positive electrode at high compressive densities. (1) Positive electrode active material

[0049] The type of positive electrode active material in the present invention is not particularly limited, and it is sufficient if it can electrochemically intercept and release metal ions (e.g., lithium ions). In some embodiments, the positive electrode active material is a substance containing lithium and at least one transition metal. In some embodiments, the positive electrode active material may include, for example, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds, but is not limited to these.

[0050] In some examples, the transition metal in lithium transition metal composite oxides includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some examples, the lithium transition metal composite oxide is lithium cobalt composite oxide such as LiCoO2, lithium nickel composite oxide such as LiNiO2, lithium manganese composite oxide such as LiMnO2, LiMn2O4, Li2MnO4, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2, LiLiLi 0.5 Mn 0.3 Co 0.2 This includes lithium nickel manganese cobalt composite oxides such as O2. In these, some of the transition metal atoms that make up the lithium transition metal composite oxides are substituted with other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, and W. Examples of lithium transition metal composite oxides include LiNi. 0.5 Mn 0.5 O2, LiLiLi 0.85 Co 0.10 Al 0.05 O2, LiLiLi 0.33 Co 0.33 Mn 0.33 O2, LiLiLi 0.45 Co 0.10 Al 0.45 O2, LiMn 1.8 Al 0.2 O4 and LiMn 1.5 Ni 0.5 It may include, but is not limited to, O4, etc. Examples of lithium transition metal composite oxide combinations include, but are not limited to, a combination of LiCoO2 and LiMn2O4, and some of the Mn in LiMn2O4 may be substituted with a transition metal (e.g., LiNi 0.33 Co 0.33 Mn 0.33 In O2, some of the Co in LiCoO2 may be replaced with a transition metal.

[0051] In some embodiments, the transition metals in the lithium-containing transition metal phosphate compound include V, Ti, Cr, Mn, Fe, Co, Ni, Cu, etc. In some embodiments, the lithium-containing transition metal phosphate compound includes iron phosphates such as LiFePO4, Li3Fe2(PO4)3, LiFeP2O7, and cobalt phosphates such as LiCoPO4. However, some of the transition metal atoms that are the main components of these lithium transition metal phosphate compounds are substituted with other elements such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si, etc.

[0052] In some embodiments, the powdered material of the lithium transition metal oxide Li a M b O2 is used, where 0.9 < a < 1.1 and 0.9 < b < 1.1, and M is a transition metal mainly selected from Mn, Co, and Ni, and the composition M varies according to the particle size.

[0053] In some embodiments, in the powdered electrode active material of the lithium transition metal oxide Li a M b O2, M = A Z A' Z' M' 1-Z-Z' where M' = Mn x Ni y Co 1-x-y and 0 ≤ y ≤ 1, 0 ≤ x ≤ 1, 0 ≤ Z + Z' < 0.1, Z' < 0.02, A is at least one selected from the elements Al, Mg, Ti, Cr, and A' is at least one selected from the elements F, Cl, S, Zr, Ba, Y, Ca, B, Be, Sn, Sb, Na, Zn.

[0054] In some embodiments, the average composition of the transition metal is M = Mn x Ni y Co 1-x-y and 0.03 < x < 0.35.

[0055] In some embodiments, the average composition of the transition metal is M = Mn x Ni y Co 1-x-yAnd, 0.03 <xであり、x+y<0.7である。

[0056] In some examples, the composition is related to size Li a M b In powdered electrode active materials containing O2, basically all parts of the particles have a layered crystalline structure, and the larger particles are Li a M b It has the composition of O2, and M=Mn x Ni y Co 1-x-y , x+y<0.35, and the small particles are Li a M b It has the composition of O2, and M=Mn x' Ni y' Co 1-x'-y' The small particles have at least 10% and lower Co, (1-x'-y') < 0.9 × (1-xy), and at least 5% and higher Mn, x'-x > 0.05. This allows for obtaining a powder whose composition is size-dependent. That is, components with larger particles (e.g., those concentrated in the ≥ 20 μm area) can diffuse rapidly in the bulk phase. Another component has smaller particles (e.g., those distributed around 5 μm), and this component can be made safe. This provides an electrode active material that combines high cycle stability and high safety with high volumetric energy density and high gravimetric energy density.

[0057] In some embodiments, a single particle is essentially a lithium transition metal oxide and contains Co, the content of which increases continuously with increasing particle size.

[0058] In some examples, a single particle further contains Mn in a transition metal, and the Mn content decreases continuously with increasing particle size.

[0059] In some embodiments, large particles have a composition close to LiCoO2, which allows for a high Li diffusion constant, thus enabling sufficient rate performance. Large particles occupy only a small portion of the total surface area of ​​the positive electrode. Therefore, the amount of heat released by reaction with the electrolyte on the surface or outer portion is limited, resulting in fewer large particles and thus poor safety. Small particles, having a composition with less Co, provide improved safety. A low lithium diffusion constant is acceptable for small particles due to the short length of the solid diffusion path, eliminating a significant loss of rate performance.

[0060] In some examples, the preferred composition of small particles contains less Co and more stable elements, such as Mn. Slow bulk Li diffusion is acceptable, but surface stability is high. In the cathode active material powder of the present invention, the preferred composition of large particles contains more Co and less Mn because fast bulk lithium diffusion is required, and therefore slightly lower surface stability is acceptable.

[0061] In some examples, the composition is Li x Within a single MO2 particle, preferably, at least 80 w% of M is cobalt or nickel. In some examples, the inner portion of the particle has a composition close to LiCoO2, while the outer portion is lithium manganese nickel cobalt oxide.

[0062] A powdered electrode active material whose composition is related to size can be produced by depositing a precipitate containing at least one transition metal onto seed crystal particles having a different transition metal composition than the precipitate, adding a predetermined amount of lithium source, and performing at least one type of heat treatment, thereby essentially ensuring that all resulting particles contain a core derived from the seed crystal, which is completely covered by the precipitate layer. (2) Positive electrode current collector

[0063] The type of positive electrode current collector is not particularly limited and may be any material suitable for any known positive electrode current collector. Examples of positive electrode current collectors may include, but are not limited to, metallic materials such as aluminum, stainless steel, nickel-plated layers, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is made of a metallic material. In some embodiments, the positive electrode current collector is made of aluminum.

[0064] The form of the positive electrode current collector is not particularly limited. When the positive electrode current collector is made of a metallic material, the form of the positive electrode current collector may include, but is not limited to, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal film, a metal plate mesh, stamped metal, foamed metal, etc. When the positive electrode current collector is made of a carbon material, the form of the positive electrode current collector may include, but is not limited to, a carbon plate, a carbon film, a carbon cylinder, etc. In some embodiments, the positive electrode current collector is a metal film. In some embodiments, the metal film is mesh-like. The thickness of the metal film is not particularly limited. In some embodiments, the thickness of the metal film is greater than 1 μm, greater than 3 μm, or greater than 5 μm. In some embodiments, the thickness of the metal film is less than 1 mm, less than 100 μm, or less than 50 μm. In some embodiments, the thickness of the metal film is within the range of any two of the above values.

[0065] To reduce the electronic contact resistance of the positive electrode current collector and the positive electrode active material layer, a conductive additive may be included on the surface of the positive electrode current collector. Examples of conductive additives include, but are not limited to, carbon and precious metals such as gold, platinum, and silver.

[0066] The ratio of the thickness of the positive electrode current collector to the thickness of the positive electrode active material layer is the ratio of the thickness of the positive electrode active material layer on one side before the electrolyte is injected to the thickness of the positive electrode current collector, and this value is not particularly limited. In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the positive electrode active material layer is less than 20, less than 15, or less than 10. In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the positive electrode active material layer is greater than 0.5, greater than 0.8, or greater than 1. In some embodiments, the ratio of the thickness of the positive electrode current collector to the thickness of the positive electrode active material layer is within the range of any two of the above values. When the ratio of the thickness of the positive electrode current collector to the thickness of the positive electrode active material layer is within the above range, heat dissipation of the positive electrode current collector during charging and discharging at high current density can be suppressed, and the capacity of the electrochemical device can be secured. II, negative electrode

[0067] The negative electrode includes a negative electrode current collector and a negative electrode active material layer located on one or both sides of the negative electrode current collector. Negative electrode active material layer

[0068] The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer may consist of one or more layers, and in a multi-layer negative electrode active material layer, each layer may contain the same or different negative electrode active material. The negative electrode active material is any material capable of reversibly intercalating and releasing metal ions such as lithium ions. In some embodiments, the rechargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintended deposition of lithium metal on the negative electrode during charging. (1) Carbon materials

[0069] In some embodiments, the negative electrode active material layer includes a carbon material.

[0070] In some embodiments, the negative electrode active material layer comprises at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, and amorphous carbon.

[0071] In some embodiments, amorphous carbon is present on the surface of the carbonaceous material.

[0072] In some embodiments, the shape of the carbonaceous material may include, but is not limited to, fibrous, spherical, particulate, and flaky forms.

[0073] In some embodiments, the carbon material has at least one of the following characteristics. (a) 5m 2 Specific surface area (BET) less than / g, and (b) Median diameter (Dv50) of 5 μm to 30 μm. Specific surface area (BET)

[0074] In some embodiments, the carbon material is 5m 2 It has a specific surface area of ​​less than / g. In some examples, the carbon material is 3m 2 It has a specific surface area of ​​less than / g. In some examples, the carbon material is 1m 2 It has a specific surface area of ​​less than / g. In some examples, the carbon material is 0.1m 2 It has a specific surface area greater than / g. In some examples, the carbon material is 0.7m 2 It has a specific surface area of ​​less than / g. In some examples, the carbon material is 0.5m 2 It has a specific surface area of ​​less than / g. In some embodiments, the specific surface area of ​​the carbon material is within the range of any two of the above values. When the specific surface area of ​​the carbon material is within the above range, the deposition of lithium on the surface of the electrode can be suppressed, and the generation of gas due to the reaction between the negative electrode and the electrolyte can be suppressed.

[0075] The porosity of the negative electrode active material layer can be measured using the AccuPyc II 1340 true density analyzer. Each sample is measured at least three times, and at least three data points are selected and averaged to calculate the porosity of the negative electrode active material layer based on the following formula: Porosity = (V1 - V2) / V1 × 100%, where V1 is the apparent volume, V1 = surface area of ​​the sample × thickness of the sample × number of samples, and V2 is the true volume. Median diameter (Dv50)

[0076] The median diameter (Dv50) of the carbon material refers to the volume-based average particle diameter obtained by laser diffraction / scattering. In some examples, the median diameter (Dv50) of the carbon material is 5 μm to 30 μm. In some examples, the median diameter (Dv50) of the carbon material is 10 μm to 25 μm. In some examples, the median diameter (Dv50) of the carbon material is 15 μm to 20 μm. In some examples, the median diameter (Dv50) of the carbon material is in the range of 1 μm, 3 μm, 5 μm, 7 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any two of these values. When the median diameter of the carbon material is within the above range, the irreversible capacitance of the electrochemical apparatus is small, and the negative electrode is easily coated uniformly.

[0077] The median diameter (Dv50) of the carbon material can be measured by dispersing the carbon material in a 0.2 wt% aqueous solution (10 mL) of polyoxyethylene (20) sorbitan monolaurate and using a laser diffraction / scattering particle size analyzer (LA-700, Horiba, Ltd.). (2) (Other ingredients) Materials containing silicon and / or tin

[0078] In some embodiments, the negative electrode active material layer further comprises at least one of silicon-containing materials, tin-containing materials, and alloy materials. In some embodiments, the negative electrode active material layer further comprises at least one of silicon-containing materials and tin-containing materials. In some embodiments, the negative electrode active material layer further comprises one or more of silicon-containing materials, silicon-carbon composite materials, silicon oxide materials, alloy materials, and lithium-containing metal composite oxide materials. In some embodiments, the negative electrode active material layer further comprises other types of negative electrode active materials, for example, one or more materials containing metallic elements and metalloid elements that can form alloys with lithium. In some embodiments, examples of the metallic elements and metalloid elements may include, but are not limited to, Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd, and Pt. In some embodiments, examples of the metallic elements and metalloid elements include Si, Sn, or combinations thereof. Si and Sn have excellent lithium-ion release capabilities, which can result in high energy density in lithium-ion batteries. In some examples, other types of negative electrode active materials may further include one or more of metal oxides and polymer compounds. In some examples, the metal oxides may include, but are not limited to, iron oxide, ruthenium oxide, and molybdenum oxide. In some examples, the polymer compounds may include, but are not limited to, polyacetylene, polyaniline, and polypyrrole. Negative electrode conductive material

[0079] In some embodiments, the negative electrode active material layer further comprises a negative electrode conductive material, which may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. Negative electrode binder

[0080] In some embodiments, the negative electrode active material layer further comprises a negative electrode binder. The negative electrode binder can improve the bonding between negative electrode active material particles and the bonding between the negative electrode active material and the current collector. The type of negative electrode binder is not particularly limited as long as it is a material that is stable in the electrolyte or solvent used when preparing the electrode.

[0081] Examples of negative electrode binders include resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamides, polyimides, cellulose, and nitrocellulose; rubbery polymers such as styrene-butadiene rubber (SBR), isoprene rubber, polybutadiene rubber, fluororubber, acrylonitrile-butadiene rubber (NBR), and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers or their hydrogenated versions; ethylene-propylene-diene ternary copolymer (EPDM); and styrene-ethylene-butadiene-styrene copolymers. The negative electrode binder may include, but is not limited to, thermoplastic elastomer polymers such as composites, styrene-isoprene-styrene block copolymers or their hydrogenated products, soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions having ion-transporting properties for alkali metal ions (e.g., lithium ions). The negative electrode binder may be used alone or in any combination.

[0082] In some embodiments, the content of the negative electrode binder is greater than 0.1 wt%, greater than 0.5 wt%, or greater than 0.6 wt%, based on the total weight of the negative electrode active material layer. In some embodiments, the content of the negative electrode binder is less than 20 wt%, less than 15 wt%, less than 10 wt%, or less than 8 wt%, based on the total weight of the negative electrode active material layer. In some embodiments, the content of the negative electrode binder is within the range of any two of the above values. When the content of the negative electrode binder is within the above range, the capacity of the electrochemical apparatus and the strength of the negative electrode can be sufficiently ensured.

[0083] When the negative electrode active material layer contains a rubbery polymer (e.g., SBR), in some examples, the content of the negative electrode binder is greater than 0.1 wt%, greater than 0.5 wt%, or greater than 0.6 wt%, based on the total weight of the negative electrode active material layer. In some examples, the content of the negative electrode binder is less than 5 wt%, less than 3 wt%, or less than 2 wt%, based on the total weight of the negative electrode active material layer. In some examples, the content of the negative electrode binder is within the range of any two of the above values, based on the total weight of the negative electrode active material layer.

[0084] When the negative electrode active material layer contains a fluorine-based polymer (e.g., polyvinylidene fluoride), in some examples, the content of the negative electrode binder is greater than 1 wt%, greater than 2 wt%, or greater than 3 wt%, based on the total weight of the negative electrode active material layer. In some examples, the content of the negative electrode binder is less than 15 wt%, less than 10 wt%, or less than 8 wt%, based on the total weight of the negative electrode active material layer. Based on the total weight of the negative electrode active material layer, the content of the negative electrode binder is within the range of any two of the above values. solvent

[0085] The type of solvent used to form the negative electrode slurry is not particularly limited, as long as it can dissolve or disperse the negative electrode active material, negative electrode binder, and, if necessary, the thickener and conductive material. In some examples, the solvent used to form the negative electrode slurry can be either an aqueous solvent or an organic solvent. Examples of aqueous solvents include, but are not limited to, water and alcohol. Examples of organic solvents include, but are not limited to, N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, tetrahydrofuran (THF), toluene, acetone, diethyl ether, hexamethylphosphoamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, and the like. The solvents can be used alone or in any combination. Thickening agent

[0086] Thickening agents are typically used to adjust the viscosity of the negative electrode slurry. The types of thickening agents are not limited and may include, for example, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, starch oxide, starch phosphorylated, casein, and their salts. These thickening agents may be used individually or in any combination.

[0087] In some examples, the content of the thickener is greater than 0.1 wt%, greater than 0.5 wt%, or greater than 0.6 wt%, based on the total weight of the negative electrode active material layer. In some examples, the content of the thickener is less than 5 wt%, less than 3 wt%, or less than 2 wt%, based on the total weight of the negative electrode active material layer. When the content of the thickener is within the above range, it is possible to suppress a decrease in the capacity and an increase in resistance of the electrochemical apparatus, and to ensure that the negative electrode slurry has good coatability. Surface coating

[0088] In some embodiments, substances with a different composition can be attached to the surface of the negative electrode active material layer. Examples of substances attached to the surface of the negative electrode active material layer include, but are not limited to, oxides such as aluminum oxide, silicon dioxide, titanium dioxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, and bismuth oxide; sulfates such as lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, and aluminum sulfate; and carbonates such as lithium carbonate, calcium carbonate, and magnesium carbonate. (3) Content of negative electrode active material

[0089] In some embodiments, the content of the negative electrode active material is greater than 80 wt%, greater than 82 wt%, or greater than 84 wt%, based on the total weight of the negative electrode active material layer. In some embodiments, the content of the negative electrode active material is less than 99 wt%, or less than 98 wt%, based on the total weight of the negative electrode active material layer. In some embodiments, the content of the negative electrode active material is within the range of either of the above numbers, based on the total weight of the negative electrode active material layer. (4) Thickness of the negative electrode active material layer

[0090] The thickness of the negative electrode active material layer refers to the thickness of the negative electrode active material layer on any side of the negative electrode current collector. In some embodiments, the thickness of the negative electrode active material layer is greater than 15 μm, greater than 20 μm, or greater than 30 μm. In some embodiments, the thickness of the negative electrode active material layer is less than 300 μm, less than 280 μm, or less than 250 μm. In some embodiments, the thickness of the negative electrode active material layer is within the range of any two of the above values. (5) Density of the negative electrode active material

[0091] In some embodiments, the density of the negative electrode active material in the negative electrode active material layer is 1 g / cm³. 3 Super, 1.2g / cm 3 More than 1.3 g / cm³ 3 It is extremely high. In some examples, the density of the negative electrode active material in the negative electrode active material layer is 2.2 g / cm³. 3 Less than 2.1 g / cm³ 3Less than 2.0 g / cm³ 3 Less than 1.9 g / cm³ 3 It is less than. In some embodiments, the density of the negative electrode active material in the negative electrode active material layer is within the range of any two of the above values. When the density of the negative electrode active material is within the aforementioned range, the destruction of the negative electrode active material particles can be prevented, the increase in the initial irreversible capacity of the electrochemical apparatus or the deterioration of high-current-density charge-discharge characteristics due to a decrease in the permeability of the electrolyte around the negative electrode current collector / negative electrode active material interface can be suppressed, and furthermore, the decrease in the capacity and increase in resistance of the electrochemical apparatus can be suppressed. Negative electrode current collector

[0092] Any known conventional current collector can be used as the current collector holding the negative electrode active material. Examples of negative electrode current collectors may include, but are not limited to, metallic materials such as aluminum, copper, nickel, stainless steel, and nickel-plated steel. In some embodiments, the negative electrode current collector is copper.

[0093] When the negative electrode current collector is made of a metallic material, the form of the negative electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal plate mesh, stamped metal, foamed metal, etc. In some embodiments, the negative electrode current collector is a metal film. In some embodiments, the negative electrode current collector is copper foil. In some embodiments, the negative electrode current collector is rolled copper foil produced by a rolling method or electrolytic copper foil produced by an electrolytic method.

[0094] In some embodiments, the thickness of the negative electrode current collector is greater than 1 μm or greater than 5 μm. In some embodiments, the thickness of the negative electrode current collector is less than 100 μm or less than 50 μm. In some embodiments, the thickness of the negative electrode current collector is within the range of any two of the above values.

[0095] The ratio of the thickness of the negative electrode current collector to the thickness of the negative electrode active material layer is the ratio of the thickness of the negative electrode active material layer on one side to the thickness of the negative electrode current collector before the electrolyte is injected, and this value is not particularly limited. In some embodiments, the ratio of the thickness of the negative electrode current collector to the thickness of the negative electrode active material layer is less than 150, less than 20, or less than 10. In some embodiments, the ratio of the thickness of the negative electrode current collector to the thickness of the negative electrode active material layer is greater than 0.1, greater than 0.4, or greater than 1. In some embodiments, the ratio of the thickness of the negative electrode current collector to the thickness of the negative electrode active material layer is within the range of any two of the above values. When the ratio of the thickness of the negative electrode current collector to the thickness of the negative electrode active material layer is within the above range, the capacity of the electrochemical device can be secured, and heat dissipation of the negative electrode current collector can be suppressed when charging and discharging at high current densities. III, electrolyte

[0096] The electrolyte used in the electrochemical apparatus of the present invention comprises an electrolyte and a solvent for dissolving the electrolyte. In some examples, the electrolyte used in the electrochemical apparatus of the present invention further comprises an additive.

[0097] In some embodiments, the electrolyte further comprises a non-aqueous solvent used as a solvent for any electrolyte known in the prior art.

[0098] In some examples, the non-aqueous solvent may include, but is not limited to, one or more of the following: cyclic carbonates, linear carbonates, cyclic carboxylic acid esters, linear carboxylic acid esters, cyclic ethers, linear ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0099] In some examples, the cyclic carbonate may include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some examples, the cyclic carbonate has 3 to 6 carbon atoms.

[0100] In some examples, the chain-like carbonate may include, but is not limited to, one or more chain-like carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate. Examples of fluorine-substituted chain-like carbonates may include, but is not limited to, one or more chain-like carbonates such as bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethylmethyl carbonate, 2,2-difluoroethylmethyl carbonate, and 2,2,2-trifluoroethylmethyl carbonate.

[0101] In some examples, the cyclic carboxylic acid ester may include, but is not limited to, one or more of γ-butyrolactone and γ-valerolactone. In some examples, some hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.

[0102] In some examples, the linear carboxylic acid ester may include, but is not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate. In some examples, some hydrogen atoms of the linear carboxylic acid ester may be substituted with fluorine. In some examples, the fluorine-substituted linear carboxylic acid ester may include, but is not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate.

[0103] In some embodiments, the cyclic ether may include, but is not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0104] In some embodiments, the chain ether may include, but is not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane.

[0105] In some examples, the phosphorus-containing organic solvent may include, but is not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethylethyl phosphate, methyldiethyl phosphate, ethylenemethyl phosphate, ethyleneethyl phosphate, triphenyl phosphate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,3,3,3-pentafluoropropyl) phosphate.

[0106] In some examples, the sulfur-containing organic solvent may include, but is not limited to, one or more of the following: sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In some examples, some hydrogen atoms in the sulfur-containing organic solvent may be substituted with fluorine.

[0107] In some examples, the aromatic fluorine-containing solvent may include, but is not limited to, one or more of fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0108] In some examples, the solvent used in the electrolyte of the present invention includes cyclic carbonates, linear carbonates, cyclic carboxylic acid esters, linear carboxylic acid esters, and combinations thereof. In some examples, the solvent used in the electrolyte of the present invention includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, or ethyl acetate. In some examples, the solvent used in the electrolyte of the present invention includes ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, and combinations thereof.

[0109] After adding linear carboxylic acid esters and / or cyclic carboxylic acid esters to the electrolyte, the linear carboxylic acid esters and / or cyclic carboxylic acid esters form a passivation film on the electrode surface, thereby improving the capacity retention rate after intermittent charging cycles of the electrochemical apparatus. In some examples, the electrolyte contains 1% to 60% of linear carboxylic acid esters, cyclic carboxylic acid esters, and combinations thereof. In some examples, the electrolyte contains ethyl propionate, propyl propionate, γ-butyrolactone, and combinations thereof, with the content of these combinations being 1% to 60%, 10% to 60%, 10% to 50%, or 20% to 50% based on the total weight of the electrolyte. In some examples, based on the total weight of the electrolyte, the electrolyte contains 1% to 60%, 10% to 60%, 20% to 50%, 20% to 40%, or 30% of propyl propionate.

[0110] In some embodiments, the additive may include, but is not limited to, one or more of the following: fluorocarbonates, ethylene carbonates having carbon-carbon double bonds, compounds containing sulfur-oxygen double bonds, and acid anhydrides.

[0111] In some embodiments, the content of the additive is 0.01% to 15%, 0.1% to 10%, or 1% to 5% based on the total weight of the electrolyte.

[0112] According to the embodiment of the present invention, based on the total weight of the electrolyte, the content of the propionic acid ester is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times the amount of the additive.

[0113] In some embodiments, the additive comprises one or more types of fluorocarbonates. Fluoroethylene carbonate, when the lithium-ion battery is charged and discharged, acts together with propionic acid ester to form a stable protective film on the surface of the negative electrode, thereby suppressing the decomposition reaction of the electrolyte.

[0114] In some embodiments, the fluorocarbonate has the structure of formula C=O(OR1)(OR2), where R1 and R2 are each selected from alkyl groups or halogenated alkyl groups having 1 to 6 carbon atoms, but at least one of R1 and R2 is selected from fluoroalkyl groups having 1 to 6 carbon atoms, and optionally, R1 and R2, together with the atoms connected to them, form a 5- to 7-membered ring.

[0115] In some examples, the fluorocarbonate may include, but is not limited to, one or more of the following: fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4,4-difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, trifluoromethylmethyl carbonate, trifluoroethylmethyl carbonate, and ethyltrifluoroethyl carbonate.

[0116] In some examples, the additive includes one or more ethylene carbonates having carbon-carbon double bonds. Examples of the ethylene carbonates having carbon-carbon double bonds include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, fluoro vinylene carbonate, trifluoromethyl vinylene carbonate; vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, 1-n-propyl-2-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1,1-divinylethylene carbonate, 1,2-divinylethylene carbonate, 1,1-dimethyl-2-methyleneethylene carbonate, and 1,1-diethyl-2-methyleneethylene carbonate. In some examples, the ethylene carbonate having a carbon-carbon double bond includes vinylene carbonate, which is readily available and can achieve better results.

[0117] In some embodiments, the additive includes one or more compounds containing sulfur-oxygen double bonds. Examples of the compounds containing sulfur-oxygen double bonds include, but are not limited to, one or more of cyclic sulfate esters, linear sulfate esters, linear sulfonic acid esters, cyclic sulfonic acid esters, linear sulfites, and cyclic sulfites.

[0118] Examples of the cyclic sulfate ester include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1,2-butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1,4-pentanediol sulfate, and 1,5-pentanediol sulfate.

[0119] Examples of the aforementioned chain-like sulfate esters may include, but are not limited to, one or more of the following: dimethyl sulfate, ethylmethyl sulfate, and diethyl sulfate.

[0120] Examples of the chain-like sulfonic acid ester include, but are not limited to, one or more of the following: fluorosulfonic acid esters such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl dimethanesulfonate, methyl 2-(methanesulfonyloxy)propionate, and ethyl 2-(methanesulfonyloxy)propionate.

[0121] Examples of cyclic sulfonic acid esters include 1,3-propanesultone, 1-fluoro-1,3-propanesultone, 2-fluoro-1,3-propanesultone, 3-fluoro-1,3-propanesultone, 1-methyl-1,3-propanesultone, 2-methyl-1,3-propanesultone, 3-methyl-1,3-propanesultone, 1-propylene-1,3-sultone, 2-propylene-1,3-sultone, 1-fluoro-1-propylene-1,3-sultone, 2-fluoro-1-propylene-1,3-sultone, 3-fluoro-1-propylene-1,3-sultone, 1-fluoro-2-propylene-1,3-sultone It may contain, but is not limited to, one or more of the following: lutone, 2-fluoro-2-propylene-1,3-sultone, 3-fluoro-2-propylene-1,3-sultone, 1-methyl-1-propylene-1,3-sultone, 2-methyl-1-propylene-1,3-sultone, 3-methyl-1-propylene-1,3-sultone, 1-methyl-2-propylene-1,3-sultone, 2-methyl-2-propylene-1,3-sultone, 3-methyl-2-propylene-1,3-sultone, 1,4-butanesultone, 1,5-pentanesultone, methylene methanedisulfonate, ethylene methanedisulfonate, etc.

[0122] Examples of the aforementioned chain-like sulfite esters may include, but are not limited to, one or more of the following: dimethyl sulfite, ethyl sulfite, and diethyl sulfite.

[0123] Examples of the cyclic sulfite ester include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfite, 1,2-propylene glycol sulfite, 1,3-propylene glycol sulfite, 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite, 1,4-pentanediol sulfite, and 1,5-pentanediol sulfite.

[0124] In some embodiments, the additive comprises one or more acid anhydrides. Examples of the acid anhydrides include, but are not limited to, one or more of cyclic phosphoric acid anhydrides, carboxylic acid anhydrides, disulfonic acid anhydrides, and carboxylic acid sulfonic acid anhydrides. Examples of the cyclic phosphoric acid anhydrides include, but are not limited to, one or more of trimethyl cyclic phosphoric acid anhydrides, triethyl cyclic phosphoric acid anhydrides, and tripropyl cyclic phosphoric acid anhydrides. Examples of the carboxylic acid anhydrides include, but are not limited to, one or more of succinic anhydride, glutaric acid anhydride, and maleic anhydride. Examples of the disulfonic acid anhydrides include, but are not limited to, ethane disulfonic acid anhydrides and propane disulfonic acid anhydrides. Examples of the carboxylic acid sulfonic acid anhydrides include, but are not limited to, one or more of sulfobenzoic acid anhydrides, sulfopropionic acid anhydrides, and sulfobutyric acid anhydrides.

[0125] In some examples, the additive is a combination of fluorocarbonate and ethylene carbonate having a carbon-carbon double bond. In some examples, the additive is a combination of fluorocarbonate and a compound having a sulfur-oxygen double bond. In some examples, the additive is a combination of fluorocarbonate and a compound having 2 to 4 cyano groups. In some examples, the additive is a combination of fluorocarbonate and a cyclic carboxylic acid ester. In some examples, the additive is a combination of fluorocarbonate and cyclic phosphoric acid anhydride. In some examples, the additive is a combination of fluorocarbonate and carboxylic acid anhydride. In some examples, the additive is a combination of fluorocarbonate and sulfonic acid anhydride. In some examples, the additive is a combination of fluorocarbonate and carboxylic acid sulfonic acid anhydride.

[0126] The electrolyte is not particularly restricted, and any known electrolyte can be used. In the case of lithium secondary batteries, lithium salts are generally used.Examples of electrolytes include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAlF4, LiSbF6, LiTaF6, and LiWF7; lithium tungstates such as LiWOF5; lithium carboxylate salts such as HCO2Li, CH3CO2Li, CH2FCO2Li, CHF2CO2Li, CF3CO2Li, CF3CH2CO2Li, CF3CF2CO2Li, CF3CF2CF2CO2Li, and CF3CF2CF2CF2CO2Li; and FSO3Li, CH3SO3Li, CH2FSO3Li, CHF2SO3Li, and CF3SO3Li. Lithium sulfonate salts such as CF3CF2SO3Li, CF3CF2CF2SO3Li, CF3CF2CF2CF2SO3Li; Limidolithium salts such as LiN(FCO)2, LiN(FCO)(FSO2), LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanebissulfonyliimide lithium, cyclic 1,3-perfluoropropanedisulfonyliimide lithium, LiN(CF3SO2)(C4F9SO2); LiC(FSO2)3, LiC Methylated lithium salts such as (CF3SO2)3 and LiC(C2F5SO2)3; lithium borate salts such as bis(malonic acid route) lithium borate and difluoro(malonic acid route) lithium borate; lithium phosphate salts such as tris(malonic acid route) lithium phosphate, difluorobis(malonic acid route) lithium phosphate, and tetrafluoro(malonic acid route) lithium phosphate; and LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, L This may include, but is not limited to, fluorine-containing organolithium salts such as iBF3CF3, LiBF3C2F5, LiBF3C3F7, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, and LiBF2(C2F5SO2)2; lithium oxalatoborate salts such as lithium difluorooxalate borate and lithium bis(malonato)borate; and lithium malonatophosphate salts such as lithium tetrafluorooxalate phosphate, lithium difluorobis(malonato)phosphate, and lithium tris(malonato)phosphate.

[0127] In some examples, the electrolyte is selected from LiPF6, LiSbF6, LiTaF6, FSO3Li, CF3SO3Li, LiN(FSO2)2, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanebissulfonyliimide lithium, cyclic 1,3-perfluoropropanedisulfonyliimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, LiPF3(C2F5)3, difluorooxalate borate lithium, bis(malonato)borate lithium, or difluorobis(malonato)phosphate lithium. These contribute to improvements in the output power characteristics, high-rate charge / discharge characteristics, high-temperature storage characteristics, and cycle characteristics of electrochemical devices.

[0128] The electrolyte content is not particularly limited as long as it does not impair the effects of the present invention. In some examples, the total molar concentration of lithium in the electrolyte is greater than 0.3 mol / L, greater than 0.4 mol / L, or greater than 0.5 mol / L. In some examples, the total molar concentration of lithium in the electrolyte is less than 3 mol / L, less than 2.5 mol / L, or less than 2.0 mol / L. In some examples, the total molar concentration of lithium in the electrolyte is within the range of any two of the above values. When the electrolyte concentration is within the above range, there is not too little lithium as charged particles, and the viscosity can be kept within an appropriate range, making it easier to ensure good conductivity.

[0129] When two or more electrolytes are used, the electrolyte includes at least one salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates. In some examples, the electrolyte includes a salt selected from the group consisting of monofluorophosphates, oxalates, and fluorosulfonates. In some examples, the electrolyte includes a lithium salt. In some examples, based on the total weight of the electrolyte, the content of the salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is greater than 0.01% or greater than 0.1%. In some examples, based on the total weight of the electrolyte, the content of the salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is less than 20% or less than 10%. In some examples, the content of the salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is within the range of any two of the above values.

[0130] In some examples, the electrolyte includes one or more substances selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfons, and one or more other salts. Other salts include the lithium salts exemplified above, but in some examples, these include LiPF6, LiN(FSO2)(CF3SO2), LiN(CF3SO2)2, LiN(C2F5SO2)2, cyclic 1,2-perfluoroethanebissulfonyliimide lithium, cyclic 1,3-perfluoropropanedisulfonyliimide lithium, LiC(FSO2)3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiBF3CF3, LiBF3C2F5, LiPF3(CF3)3, and LiPF3(C2F5)3. In some examples, the other salt is LiPF6.

[0131] In some examples, the content of other salts is greater than 0.01% or greater than 0.1% based on the total weight of the electrolyte. In some examples, the content of other salts is less than 20%, less than 15%, or less than 10% based on the total weight of the electrolyte. In some examples, the content of other salts is within the range of any two of the above values. Other salts having the above content contribute to the balance between the conductivity and viscosity of the electrolyte.

[0132] In addition to the solvent, additives, and electrolyte salts, the electrolyte may optionally contain additional additives such as negative electrode film-forming agents, positive electrode protective agents, and overcharge prevention agents. Generally, additives used in non-aqueous electrolyte secondary batteries can be used, and examples include, but are not limited to, ethylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluoroanisole, propanesultone, and propylenesultone. These additives can be used individually or in any combination. Furthermore, the content of these additives in the electrolyte is not particularly limited and should be appropriately set according to the type of additive, etc. In some examples, the additive content, based on the total weight of the electrolyte, is less than 5%, in the range of 0.01% to 5%, or in the range of 0.2% to 5%. IV, Separator

[0133] To prevent short circuits, a separator is usually installed between the positive and negative electrodes. In this case, the electrolyte of the present invention is generally used by permeating the separator.

[0134] The material and shape of the separator are not particularly limited as long as they do not impair the effects of the present invention. The separator may be a resin, glass fiber, inorganic material, or the like, made of a material stable in the electrolyte of the present invention. In some embodiments, the separator includes a porous sheet or nonwoven fabric-like substance with excellent liquid retention properties. Examples of materials for resin or glass fiber separators include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, and glass filters. In some embodiments, the material of the separator is a glass filter. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The materials of the separator can be used individually or in any combination.

[0135] The separator may further consist of laminated materials, and may include, for example, a three-layer separator laminated in the order of polypropylene, polyethylene, and polypropylene, but is not limited to these.

[0136] Examples of inorganic materials may include, but are not limited to, oxides such as aluminum oxide and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates (e.g., barium sulfate, calcium sulfate, etc.). The inorganic material may be in particulate or fibrous form, but is not limited to these.

[0137] The separator may be in the form of a film, and may include, but is not limited to, nonwoven fabrics, woven fabrics, microporous membranes, etc. In the form of a film, the pore size of the separator is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In addition to the independent film-like separator, the following separator can also be used: a separator formed by forming a composite porous layer containing the inorganic particles on the surfaces of the positive and / or negative electrodes using a resin-based binder. For example, a separator in which a porous layer is formed on both sides of the positive electrode using a fluororesin as a binder, with aluminum oxide particles having a 90% particle size of less than 1 μm.

[0138] The thickness of the separator is arbitrary. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. In some embodiments, the thickness of the separator is within the range of any two of the above values. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, as well as the rate characteristics and energy density of the electrochemical apparatus.

[0139] When a porous material such as a porous sheet or nonwoven fabric is used as a separator, the porosity of the separator is arbitrary. In some embodiments, the porosity of the separator is greater than 20%, greater than 35%, or greater than 45%. In some embodiments, the porosity of the separator is less than 90%, less than 85%, or less than 75%. In some embodiments, the porosity of the separator is within the range of any two of the above values. When the porosity of the separator is within the above range, insulation and mechanical strength can be ensured, and film resistance can be suppressed, resulting in good rate characteristics for electrochemical devices.

[0140] The average pore diameter of the separator is also arbitrary. In some embodiments, the average pore diameter of the separator is less than 0.5 μm or less than 0.2 μm. In some embodiments, the average pore diameter of the separator is greater than 0.05 μm. In some embodiments, the average pore diameter of the separator is within the range of any two of the above values. If the average pore diameter of the separator exceeds the above range, short circuits are more likely to occur. When the average pore diameter of the separator is within the above range, short circuits can be prevented and film resistance can be suppressed, thus providing the electrochemical apparatus with good rate characteristics. V, Electrochemical apparatus components

[0141] The electrochemical apparatus components include an electrode group, a current collection structure, an outer casing, and a protective element. electrode group

[0142] The electrode group may be either a laminated structure in which the positive electrode and negative electrode are stacked via the separator, or a structure in which the positive electrode and negative electrode are wound in a spiral shape via the separator. In some embodiments, the ratio of the mass of the electrode group to the internal volume of the battery (electrode group occupancy rate) is greater than 40% or greater than 50%. In some embodiments, the electrode group occupancy rate is less than 90% or less than 80%. In some embodiments, the electrode group occupancy rate is within the range of any two of the above values. When the electrode group occupancy rate is within the above range, the capacity of the electrochemical device can be secured, the deterioration of characteristics such as repeated charge-discharge performance and high-temperature storage due to the rise in internal pressure can be suppressed, and the operation of the gas release valve can be prevented. Current collection structure

[0143] The current collection structure is not particularly limited. In some embodiments, the current collection structure is a structure that reduces the resistance of the wiring and connection parts. When the electrode group has the laminated structure, a structure is applied in which the metal core portions of each electrode layer are bundled together and welded to the terminals. This is also applied when the internal resistance increases as the electrode area increases, by installing two or more terminals inside the electrode to reduce resistance. When the electrode group has the wound structure, the internal resistance can be reduced by installing two or more lead wire structures for both the positive and negative electrodes and bundling them together to the terminals. Outer case

[0144] The material of the outer casing is not particularly limited, as long as it is a stable substance in the electrolyte used. The outer casing may be made of metals such as nickel-plated steel, stainless steel, aluminum or aluminum alloy, magnesium alloy, or a laminated film of resin and aluminum foil, but is not limited to these. In some embodiments, the outer casing is made of aluminum or an aluminum alloy metal or a laminated film.

[0145] The metal outer casing may include, but is not limited to, a package sealing structure formed by welding metals together by laser welding, resistance welding, or ultrasonic welding, or a rivet joint structure using the metals via a resin gasket. The outer casing using the laminated film may include, but is not limited to, a package sealing structure formed by heat bonding resin layers together. To improve airtightness, a resin different from the resin used in the laminated film can be sandwiched between the resin layers. When forming a sealing structure by heat bonding the resin layers with a current collector terminal, a resin having polar groups or a modified resin with polar groups introduced is used as the sandwiched resin because there is a bond between the metal and the resin. The shape of the outer casing is also arbitrary and may be cylindrical, rectangular, laminated, button-shaped, pouch-shaped, etc. protective element

[0146] The protective elements can include a positive temperature coefficient (PTC) that increases electrical resistance when abnormal heat is generated or an excessive current flows, a thermal fuse, a thermistor, or a valve (current interruption valve) that interrupts the current flowing through the circuit by rapidly increasing the internal pressure or temperature of the battery when abnormal heat is generated. The protective elements can be those that do not operate under normal high-current usage, and the system can be designed to prevent abnormal heat generation or thermal runaway even without protective elements. VI. Applications

[0147] The electrochemical apparatus of the present invention includes any apparatus that generates an electrochemical reaction, and specific examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, this electrochemical apparatus is a lithium secondary battery, including lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.

[0148] The present invention provides another electronic device, including the electrochemical device described in the present invention.

[0149] The applications of the electrochemical apparatus of the present invention are not particularly limited and can be used in any electronic device known in the prior art. In some embodiments, the electrochemical apparatus of the present invention is used in, but is not limited to, laptop computers, pen-input computers, mobile computers, e-book players, mobile phones, portable fax machines, portable printers, stereo headsets, video recorders, LCD televisions, portable cleaners, portable CD players, MiniDiscs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashes, cameras, large household storage batteries or lithium-ion capacitors, etc.

[0150] The following describes the fabrication of a lithium-ion battery, using lithium-ion batteries as an example and referring to specific embodiments. It should be understood that the preparation methods described in this invention are merely illustrative, and any other suitable preparation methods are within the scope of this invention. [Examples]

[0151] Examples and comparative examples of lithium-ion batteries according to the present invention are described below, and their performance was evaluated. 1. Manufacturing of lithium-ion batteries 1. Preparation of the positive electrode

[0152] (1) Preparation of positive electrodes in Examples 1-28, Examples 35-39, and Comparative Examples 1-13

[0153] A latex solution (7% solids) was prepared by adding polyvinylidene fluoride (PVDF), a binder, to N-methylpyrrolidone (NMP). After mixing was complete, lithium cobalt oxide (LCO), the positive electrode active material, was added and stirred for a predetermined time. Then, a graphene slurry (a graphene sheet layer was uniformly dispersed in N-methylpyrrolidone with a solids content of 5% to obtain the graphene slurry) was added, and the mixture was stirred continuously with a vacuum stirrer until the system was homogeneous, obtaining a positive electrode slurry with a solids content of 75%. The mass ratio of each component was LCO:binder = 96:2. This positive electrode slurry was applied to 12 μm aluminum foil, dried, and cold-pressed to obtain a positive electrode active material layer. This layer was then cut and tabs were welded to obtain the positive electrode. Based on the total weight of the positive electrode active material layer, the graphene content was W.

[0154] The positive electrode is installed according to the conditions of the examples and comparative examples in the table below, so that the positive electrode has the corresponding configuration and parameters. (2) Preparation of the positive electrode in Examples 29 and 34 Aside from the fact that the latex solution was prepared by adding polyvinylidene fluoride (PVDF), a binder, and Super P, a particulate conductive agent, together to N-methylpyrrolidone, the preparation of the positive electrode in Examples 29-34 was similar to the preparation of the positive electrode in Example 5. 2. Fabrication of the negative electrode

[0155] Artificial graphite, styrene-butadiene rubber, and sodium carboxymethylcellulose were mixed with deionized water in a mass ratio of 96%:2%:2% and uniformly stirred to obtain a negative electrode slurry. This negative electrode slurry was coated onto a 12 μm copper foil. After drying, cold pressing, cutting, and welding tabs, a negative electrode was obtained. 3. Preparation of the electrolyte

[0156] In a dry argon gas atmosphere, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) (weight ratio 1:1:1) are mixed, and LiPF6 is added. 、 The mixture was uniformly combined to form an electrolyte with a LiPF6 concentration of 1.15 mol / L. 4. Fabrication of the separator

[0157] A porous polyethylene (PE) polymer film was used as the separator. 5. Manufacturing of lithium-ion batteries

[0158] The obtained positive electrode, separator, and negative electrode were sequentially stacked, wound, and placed on an outer foil, leaving an injection port. Electrolyte was injected through the injection port, and the lithium-ion battery was fabricated through processes such as packaging, formation, and grading. 2.Measurement method

[0159] 1. Measurement methods for Dv10, Dv50, and Dv99 (1) Starting up the device: First, the sample injection system, optical path system, and computer of the device were turned on, and the device was preheated for 30 minutes; (2) Cleaning of the sample injection system: Fill the sample injector with water, adjust the rotation speed to maximum and wash for 5 seconds, then adjust the rotation speed to 0. Repeat the washing process three times to ensure that the sample injector is clean. (3) Enter the "Manual Measurement" interface and sequentially set the material name, refractive index, material type, measurement time, and number of measurements; (4) Click "start" to perform light collimation and background light measurements, and (5) The positive electrode active material was dispersed in an aqueous solution (10 mL) and measured using a laser diffraction / scattering particle size analyzer (Master Sizer 3000). The sample was added to the sample pool, and the degree of light shielding increased with the amount of sample added. When the degree of light shielding increased to 8% to 12%, the addition of the sample was stopped, and after waiting until the degree of light shielding stabilized (generally remaining stable after 30 seconds), "start" was clicked to begin the particle size measurement. Upon completion of the measurement, Dv10, Dv50, and Dv99 were obtained. Each example and comparative example required the measurement of three parallel samples. The average values ​​of Dv10, Dv50, and Dv99 for the three parallel samples were calculated, and these average values ​​were taken as the Dv10, Dv50, and Dv99 values ​​for the positive electrode active material. Dv10 means that particles smaller than the specified particle size account for 10% of the total volume of particles, Dv50 means that particles smaller than the specified particle size account for 50% of the total volume of particles, and Dv99 means that particles smaller than the specified particle size account for 99% of the total volume of particles.

[0160] 2. Method for measuring graphene (GN) sheet diameter The positive electrode was laid out on a sample measuring stage, and a scanning electron microscope (SEM) image of the sample was taken. Using image analysis software, SEM images were taken at three different locations on the positive electrode in each example or comparative example, resulting in three SEM images. Ten graphene samples were randomly selected from each SEM image, and the longest diameter of each graphene sample was determined as its sheet diameter using a scale. The average of the sheet diameters of the 30 graphene samples in the three SEM images was calculated and defined as the graphene sheet diameter D1. Figure 1 shows a scanning electron microscope (SEM) image of the positive electrode in Example 3 according to the present invention, where the straight line in the figure represents the length of the graphene sheet diameter. Figure 2 is an SEM image of the positive electrode in Example 18 according to the present invention, showing that graphene is present around the positive electrode active material particles.

[0161] 3. Method for measuring the particle size of particulate conductive agents The positive electrode was laid out on a sample measuring stage, and a scanning electron microscope (SEM) was used to take a photograph of the sample. Three SEM images were obtained by taking SEM images at three different locations on the positive electrode in each example or comparative example. Using image analysis software, ten particulate conductive particles were randomly selected from each SEM image, and the area of ​​each of these particulate conductive particles was determined. Assuming that the particulate conductive particles were spherical, the particle size R (diameter) of each particulate conductive particle was calculated using the following formula. R = 2 × (S / π) 1 / 2 Here, S is the area of ​​the particulate conductive material. The average particle size D2 of the particulate conductive agent was determined by taking the arithmetic mean of the particle sizes of 30 (10 × 3) particulate conductive agents in the three SEM images mentioned above.

[0162] 4. Method for measuring sheet resistance (1) Sheet resistance was measured using a sheet resistance meter manufactured by Yuanneng Technology; (2) The power supply to the device was maintained at 220V, and the atmospheric pressure was above 0.7MPa; (3) With the battery fully charged, the positive electrode was removed and the cut positive electrode (60 x 80 mm) was placed flat on the sample stand; (4) After that, the sample stand was placed in the measurement chamber of the apparatus and measurement was started; (5) The atmospheric pressure was set to "0" throughout the entire measurement process.

[0163] 5. Method for measuring adhesive strength (1) Remove the dried positive electrode and cut out a sample measuring 30 mm wide x 100-160 mm long using a blade; (2) Special double-sided tape was attached to the steel plate, with a tape width of 20 mm and a length of 90 to 150 mm; (3) Attach the positive electrode sample cut out in step (1) to double-sided tape and position the measuring surface downwards; (4) A piece of paper tape, whose width was equal to the width of the positive electrode and whose length was 80-200 mm longer than the length of the sample, was inserted below the positive electrode and secured with wrinkle tape; (5) The power to the SASTEST tensioning machine was turned on, the indicator light illuminated, and the limiting block was adjusted to the appropriate position; (6) The sample prepared in step (4) was fixed to the measuring stage, the speed was set to 10 mm / min, the measuring range was 0-40 mm, and the paper sheet was pulled at a 90° angle until the measurement was complete; and (7) Save the measurement data according to the instructions in the software, remove the electrode after the measurement is complete, and turn off the device.

[0164] 6. Method for measuring the state of brittle fracture The positive electrodes prepared in the examples and comparative examples were cold-pressed at 25°C and 40% RH to a predetermined compression density. Next, the positive electrodes were cut into 20 mm × 100 mm pieces, folded in half, and pressed once onto the folded positive electrodes using a 2 kg roller. The positive electrodes were unfolded and observed under lamp light. If light transmission or fracture was observed in an area of ​​10% or more of the width, it was considered that the brittleness did not meet the processing requirements, and this was defined as serious brittle fracture. If light transmission or fracture was observed in an area of ​​less than 10% of the width, it was defined as slight brittle fracture. If no light transmission or fracture was observed, it was defined as no brittle fracture. 3. Measurement results

[0165] Tables 1-1 and 1-2 show the composition, parameters, and measurement results of the positive electrodes for the examples and comparative examples. Dv50 is the DV50 of the positive electrode active material. The percentage reduction in sheet resistance in Table 1-2 refers to the percentage reduction in resistance in the examples compared to the comparative examples, where the only difference from the examples is the absence of graphene.

[0166] [Table 1-1]

[0167] [Table 1-2]

[0168] As can be seen from the measurement results in Tables 1-2, Compared to the comparative examples, the positive electrodes in Examples 1-19 exhibited significantly reduced sheet resistance (reduction > 50%) and high compressive density (compression > 3.5 g / cc), with no or minimal brittle fracture. A good conductive network distribution was formed between graphene and the positive electrode active material, improving the electrode's electrical conductivity. Furthermore, by controlling the ratio Dv50 / D1 of the positive electrode active material to graphene within a predetermined range, better particle and sheet layer deposition could be achieved, improving particle slip, increasing the limiting compressive density of the positive electrode, and improving the flexibility of the positive electrode, thus avoiding the problem of severe brittle fracture in the positive electrode under high compression.

[0169] As can be seen from Examples 1-3, 9, 11-13, and 16-19, when the graphene sheet diameter D1 is 10 μm in all cases, and Dv50 / D1 is between 0.45 and 4.5, the positive electrode has the advantage of a sheet resistance reduction of more than 50%, a high compressive density of more than 3.5 g / cc, and no brittle fracture, compared to Comparative Example 1 where no graphene was added. In contrast, as can be seen from Examples 20-21, when Dv50 / D1 < 0.45, the reduction in the positive electrode's sheet resistance is < 50%, and there is a problem of severe brittle fracture. Firstly, if the graphene sheet diameter is too large compared to the particle size of the active material, the active material particles aggregate with each other, resulting in many interfaces and less graphene between the interfaces, which prevents a significant reduction in sheet resistance. Furthermore, because graphene is absent between most of the active material particles and the sheet diameter is large, the graphene sheet layer cannot bend well along the gaps between the active material particles, thus preventing slip action and resulting in brittle fracture problems at high compressive densities.

[0170] As can be seen from Example 12, when Dv50 / D1 increases to 4.22, the average particle size D50 of the active material is large and the sheet diameter D1 of the graphene is small, resulting in poor deposition of positive electrode active material particles. This makes it difficult for graphene to pass through the gaps between active material particles and form a good conductive network. At the same time, the porosity of the electrode increases, affecting ion and electron transmission, and thus reducing the reduction in sheet resistance. Furthermore, graphene with a small sheet diameter aggregates in the pores between active material particles, and there is less graphene sandwiched at the particle contact interface. This prevents slip action during compression, increasing the risk of brittle fracture.

[0171] When the positive electrode's Dv50 / D1 is within the range of 1.0 to 3.5, it achieves both a significantly reduced sheet resistance (reduction > 65%) and high compressive density, thus eliminating the problem of brittle fracture. Furthermore, when the average particle size D50 of the positive electrode active material is 10 μm to 25 μm, the sheet resistance is further reduced to 0.2 to 10 ohms. As can be seen from Examples 3 to 8, the cathodes in Examples 3 to 4 and 6 to 7, which have 7 to 20 GN sheet layers, exhibit superior workability compared to Examples 5 and 8, which have 3 or 30 GN sheet layers. This is because fewer GN sheet layers result in weaker slip action, while too many sheet layers reduce flexibility, which is unfavorable for bending the film.

[0172] Examples 14-15 increased the amount of graphene used compared to Example 3. The sheet resistance of the positive electrode in Examples 14-15 was further reduced significantly, with a reduction of over 90%, resulting in a high critical compressive density and no brittle fracture problems. Table 2 shows the effect of the ratio of positive electrode active material particle size Dv10 / Dv50 on the positive electrode critical compressibility and workability.

[0173] [Table 2]

[0174] As can be seen from the results above, the positive electrode exhibits high critical compressibility and flexibility when Dv10 / Dv50 is between 0.33 and 0.45. On the other hand, during compression of the positive electrode, appropriately sized small active material particles contribute to filling the voids of the large active material, thereby promoting slip between active material particles and further improving the critical compressibility. Meanwhile, some of the small active material particles fill the gaps between the large active material and graphene, increasing the contact area between the active material and graphene, contributing to the full exertion of the slip effect of graphene and further improving the flexibility of the positive electrode. Table 3 shows the effect of the relationship between the particle size D2 of the particulate conductive agent (Super P) and the positive electrode active material Dv50 on the critical compressive density and workability of the positive electrode. The Super P content was calculated from the total weight of the positive electrode active material layer.

[0175] [Table 3]

[0176] As can be seen from the above results, if the particle size D2 of the particulate conductive agent and the particle size Dv50 of the positive electrode active material satisfy D2 / D50 < 0.4 during the fabrication of the positive electrode, the workability brittleness of the positive electrode can be significantly improved. This is because graphene exists only on the surface of the active material particles, and can only exert a slip effect when the active material particles are in direct contact with each other. In contrast, the added particulate conductive agent can be dispersed in the gaps between the active material particles, so the conductive agent particles can directly promote the slip of the active material particles that come into contact with them during compression, thereby improving the compressive density and improving workability brittleness. In particular, as can be seen from Examples 30 to 32, when D2 / D50 = 0.04 to 0.25, the positive electrode has an even more significantly improved limiting compressive density. This is because if the conductive agent particles are too small, the filling effect in the gaps is low, making it difficult to improve the compressive density. In contrast, if the conductive particles are too large, they fill the gaps between the active material particles, weakening their effect in promoting slip, and their own density is lower than that of the active material, resulting in a decrease in compressible density.

[0177] Table 4 shows the effect of the ratio Dv99 / D1, which is the ratio of graphene sheet diameter D1 to positive electrode active material particle size Dv99, on the improvement of positive electrode conductivity. The percentage reduction in sheet resistance is the percentage reduction in sheet resistance for Examples 35 to 39 compared to the sheet resistance of Comparative Examples 10 to 14.

[0178] [Table 4]

[0179] As can be seen from the above results, when the relationship between the GN sheet diameter D1 and the active material particle size Dv99 satisfies Dv99 / D1 = 3.2 to 4.6, the reduction in positive electrode sheet resistance was more than 75%. This is because graphene exists only on the surface of the active material particles, allowing for the construction of a conductive network between particles when the active material particles and the graphene sheet layer are in direct contact, thereby achieving the effect of conducting electrons. Compared to the example where D1 / Dv99 is less than 1 / 4.6, when D1 / Dv99 is between 1 / 3.2 and 1 / 4.6, the graphene sheet diameter is relatively larger, ensuring that the graphene extends from the deposition region of the small-particle active material. In contrast, the specific surface area of ​​the large-particle active material is smaller, making it easier to connect to the graphene on its surface and constructing an even better conductive network, thus significantly improving the positive electrode sheet resistance.

[0180] Throughout the specification, any reference using “Example,” “Partial Example,” “One Example,” “Another Example,” “Example,” “Specific Example,” or “Partial Example” means that at least one example or example of the present invention includes the specific features, structures, materials, or properties described in that example or example. Therefore, for example, any “In some examples,” “In an example,” “In one example,” “In another example,” “In one example,” “In a particular example,” or “In an example” found anywhere in the specification does not necessarily refer to the same example or example of the present invention. Furthermore, the specific features, structures, materials, or properties described herein can be combined in any preferred manner in one or more examples or examples.

[0181] While exemplary embodiments have been disclosed and described, those skilled in the art should understand that such embodiments are not intended to limit the invention and that modifications, substitutions, and changes to the embodiments are permitted as long as they do not depart from the technical spirit, principles, and scope of the invention.

Claims

1. The current collector comprises a positive electrode active material layer located on the current collector, The positive electrode active material layer comprises a positive electrode active material and graphene. The positive electrode has a ratio Dv99 / D1 of the particle size Dv99 of the positive electrode active material to the sheet diameter D1 of the graphene, which is 3.2 to 4.

6.

2. The positive electrode according to claim 1, wherein the ratio of particle size Dv10 to Dv50 of the positive electrode active material, Dv10 / Dv50, is 0.25 to 0.

5.

3. The positive electrode according to claim 1, wherein the particle size Dv50 of the positive electrode active material is 0.5 μm to 35 μm.

4. The positive electrode according to claim 1, wherein the number of graphene layers is n, and n is 1 to 30.

5. The positive electrode according to claim 1, wherein the number of graphene layers is n, and n is 7 to 20.

6. The positive electrode active material layer further comprises a particulate conductive agent, The positive electrode according to claim 1, wherein the particle size D2 of the particulate conductive agent and the particle size Dv50 of the positive electrode active material satisfy D2 / Dv50 < 0.

4.

7. The positive electrode according to claim 6, wherein the particulate conductive agent comprises at least one of conductive carbon black and graphite.

8. The positive electrode according to claim 1, wherein the sheet resistance of the positive electrode active material layer is 0.1 ohm to 550 ohm.

9. The positive electrode according to claim 1, wherein the compressed density of the positive electrode active material layer is 3.5 g / cc to 4.5 g / cc.

10. The positive electrode according to claim 1, wherein the positive electrode active material comprises at least one of a lithium transition metal composite oxide and a lithium-containing transition metal phosphate compound.

11. The positive electrode according to claim 1, wherein the positive electrode active material comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium iron phosphate.

12. The positive electrode according to claim 1, wherein the graphene content is 0.1 wt.% to 5 wt.% based on the total weight of the positive electrode active material layer.

13. The positive electrode according to claim 1, wherein the coating surface density of the positive electrode active material layer is 200 mg / 1540.25 mm² to 330 mg / 1540.25 mm².

14. An electrochemical apparatus comprising a positive electrode according to any one of claims 1 to 13.

15. An electronic apparatus including the electrochemical apparatus described in claim 14.

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