Electrochemical apparatus and electronic apparatus

Abstract

The present invention provides an electrochemical device and an electronic device for improving the rate characteristics of the electrochemical device. The electrochemical device includes a positive electrode piece and an electrolyte, The positive electrode piece includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes a Mn element and an X element, the X element includes at least one of a Co element and an Al element, and when a molar ratio of the X element to the Mn element is A%, A is 0.1 to 10, and the electrolyte includes a boron-containing lithium salt.

Description

[Technical Field]

[0001] This invention relates to the field of electrochemistry, and more particularly to electrochemical apparatus and electronic apparatus. [Background technology]

[0002] Lithium-ion batteries have advantages such as high energy density, long cycle life, and no memory effect, making them widely applied in fields such as wearable devices, smartphones, drones, electric vehicles, and large-scale energy storage equipment, and they are currently the most promising new type of green chemical power source in the world. However, at the same time, higher performance demands are being placed on lithium-ion batteries. The effective combination of positive electrode active material and electrolyte in lithium-ion batteries significantly impacts their performance. As the number of cycles increases, the protective film on the positive and / or negative electrode surfaces is destroyed, increasing the DC impedance of the lithium-ion battery and degrading its rate characteristics. Therefore, developing a positive electrode active material and electrolyte system that is advantageous in reducing the increase in DC impedance and improving the rate characteristics after cycles is an urgent issue that needs to be addressed. [Overview of the Initiative]

[0003] The present invention aims to provide an electrochemical apparatus and an electronic apparatus for improving the rate characteristics of an electrochemical apparatus.

[0004] A first aspect of the present invention provides an electrochemical apparatus comprising a positive electrode piece and an electrolyte, wherein the positive electrode piece comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, the positive electrode active material comprises Mn and X, the X element comprises at least one of Co and Al, and when the molar ratio of X element to Mn element is A%, A is 0.1 to 10, and the electrolyte comprises a boron-containing lithium salt. The synergistic effect of the positive electrode active material and the electrolyte makes it possible to simultaneously improve the initial rate characteristics and cycle characteristics of the electrochemical apparatus, and simultaneously reduce the DC resistance increase rate.

[0005] In some embodiments of the present invention, the boron-containing lithium salt comprises at least one of lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalate)borate, and lithium tetraborate.

[0006] In some embodiments of the present invention, the mass ratio of the boron-containing lithium salt to the positive electrode active material is 0.0001 to 0.01.

[0007] In some embodiments of the present invention, the mass fraction of the boron-containing lithium salt is 0.01% to 2.2% relative to the mass of the electrolyte.

[0008] In some embodiments of the present invention, the positive electrode active material comprises a lithium manganese oxide containing element X.

[0009] In some embodiments of the present invention, the positive electrode active material further comprises an element M1, wherein the element M1 comprises at least one of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, and Gd, and the molar content of the element M1 (a1%) relative to the number of moles of the element Mn is 0.1% to 2%. The presence of the element M1 in the positive electrode active material and the molar content of the element M1 being within the above range is advantageous in improving the manganese elution phenomenon of the positive electrode piece and improving the cycle characteristics of the electrochemical apparatus.

[0010] In some embodiments of the present invention, the positive electrode active material comprises a lithium manganese oxide containing elements X and M1.

[0011] In some embodiments of the present invention, the electrochemical device satisfies at least one of the following conditions: (i) a1 and A satisfy 0.14 ≦ a1 / A ≦ 0.55; and (ii) the M1 element contains the Nb element, and when the molar content of the Nb element is a2% with respect to the number of moles of the Mn element, a2 and a1 satisfy 0.3 ≦ a2 / a1 ≦ 1. By adjusting the values of a1 / A and / or a2 / a1 within the above ranges, it is advantageous for improving the cycle characteristics and initial rate characteristics of the electrochemical device.

[0012] In some embodiments of the present invention, the positive electrode active material further contains an M2 element, the M2 element contains at least one of Fe, Cu, Cr, and Zn, and the molar content of the M2 element is b1% with respect to the number of moles of the Mn element.

[0013] In some embodiments of the present invention, the positive electrode active material contains the M1 element and the M2 element, and a1 and b1 satisfy 0.1 < a1 + b1 ≦ 2.05. By selecting the M2 element and adjusting the value of the total molar content a1 + b1 of the Mn element and the M2 element within the above range, it is advantageous for improving the cycle characteristics, initial rate characteristics, and reducing the increase rate of the DC resistance of the electrochemical device.

[0014] In some embodiments of the present invention, the positive electrode active material contains a lithium manganese oxide containing an X element and an M2 element.

[0015] In some embodiments of the present invention, the positive electrode active material contains a lithium manganese oxide containing an X element, an M1 element, and an M2 element.

[0016] In some embodiments of the present invention, the positive electrode active material further contains an M3 element, wherein the M3 element contains at least one of F, P, S, and B, and the molar content c1% of the M3 element is 0.1% to 2% relative to the number of moles of the Mn element. By selecting the M3 element, controlling the mass ratio of the boron-containing lithium salt to the positive electrode active material to 0.0001 to 0.01, and adjusting the molar content c1% of the M3 element within the above range, it is advantageous to form a positive electrode active material with a stable structure, to form a protective film on the surface of the positive electrode active material, and to improve the manganese elution phenomenon in the positive electrode piece, thereby improving the cycle characteristics of the electrochemical apparatus.

[0017] In some embodiments of the present invention, the positive electrode active material comprises a lithium manganese oxide containing elements X and M3.

[0018] In some embodiments of the present invention, the positive electrode active material comprises a lithium manganese oxide containing elements X, M1, and M3.

[0019] In some embodiments of the present invention, the positive electrode active material comprises a lithium manganese oxide containing elements X, M2, and M3.

[0020] In some embodiments of the present invention, the positive electrode active material comprises a lithium manganese oxide containing elements X, M1, M2, and M3.

[0021] In some embodiments of the present invention, the positive electrode active material comprises elements M1 and M3, and satisfies at least one of the following: (iii) a1 and c1 satisfy 0.1 ≤ a1 + c1 ≤ 4, and (iv) the M3 element comprises element F, and when the molar content of element F is c2% relative to the number of moles of element Mn, c1 and c2 satisfy 0.05 ≤ c2 / c1 ≤ 0.5. Adjusting the values ​​of a1 + c1 and / or c2 / c1 within the above ranges is advantageous for improving the cycle characteristics of the electrochemical apparatus.

[0022] In some embodiments of the present invention, the positive electrode active material includes secondary particles. When the average particle diameter of the primary particles in the secondary particles is D1, the positive electrode active material satisfies at least one of the following: (1) the Dv50 of the positive electrode active material is 4 μm to 15 μm; (2) the average particle diameter D1 of the primary particles is 200 nm to 2 μm; and (3) 4 ≤ Dv50 / D1 ≤ 50, where Dv50 is the particle diameter of 50% cumulative in the volume-based distribution of the positive electrode active material obtained by measurement using a laser scattering particle size distribution analyzer. By adjusting the values of Dv50, D1, and Dv50 / D1 within the above ranges, it is advantageous for improving the initial rate characteristics and cycle characteristics of the electrochemical device.

[0023] In some embodiments of the present invention, the electrolyte further includes a compound containing a sulfur-oxygen double bond. The compound containing a sulfur-oxygen double bond includes at least one of 1,3-propanesultone, propenyl-1,3-sultone, and vinyl sulfate. The mass fraction of the compound containing a sulfur-oxygen double bond with respect to the mass of the electrolyte is 0.01% to 2%. By selecting the compound containing a sulfur-oxygen double bond and adjusting its mass fraction within the above range, the initial rate characteristics and cycle characteristics of the electrochemical device can be improved, and the increase rate of the DC resistance can be reduced.

[0024] A second aspect of the present invention provides an electronic device including the electrochemical device according to any embodiment of the present invention.

[0025] A first aspect of the present invention provides an electrochemical device including a positive electrode plate and an electrolytic solution, wherein the positive electrode plate includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes Mn element and X element, X element includes at least one of Co element and Al element, when the molar ratio of X element to Mn element is A%, A is 0.1 to 10, preferably 1 to 5, the electrolytic solution includes a boron-containing lithium salt, and the mass ratio of the boron-containing lithium salt to the positive electrode active material is 0.0001 to 0.01. Due to the synergistic effect between the positive electrode active material and the electrolytic solution, it contributes to forming a protective film on the negative electrode at the initial stage of charge and discharge of the electrochemical device, repairing the protective film of the negative electrode during the cycle process of the electrochemical device, reducing the increase in interfacial impedance during the cycle process of the electrochemical device, contributing to improving the problem of deterioration of rate characteristics during the cycle process of the electrochemical device, and enhancing the structural stability of the positive electrode active material, thereby simultaneously enhancing the initial rate characteristics and cycle characteristics of the electrochemical device and reducing the DC resistance increase rate.

Embodiments for Carrying out the Invention

[0026] In order to make the objectives, technical solutions, and advantages of the present invention clearer, examples are given below to explain the present invention in more detail. Obviously, the described embodiments are only a part of the embodiments of the present invention and not all of the embodiments. For the examples in the present invention, all other examples obtained by those skilled in the art belong to the protection scope of the present invention. In the specific embodiments of the present invention, the lithium-ion battery is used as an example of the electrochemical device to explain the present invention, but the electrochemical device of the present invention is not limited to the lithium-ion battery.

[0027] A first aspect of the present invention provides an electrochemical device including a positive electrode plate and an electrolytic solution, wherein the positive electrode plate includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes Mn element and X element, X element includes at least one of Co element and Al element, when the molar ratio of X element to Mn element is A%, A is 0.1 to 10, preferably 1 to 5, and the electrolytic solution includes a boron-containing lithium salt.

[0028] In some embodiments of the present invention, the boron-containing lithium salt comprises at least one of lithium tetrafluoroborate (LiBF4), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalate)borate (LiBOB), and lithium tetraborate (Li2B4O7).

[0029] In some embodiments of the present invention, the mass ratio of the boron-containing lithium salt to the positive electrode active material is 0.0001 to 0.01. For example, the molar ratio A of element X to element Mn may be 0.1, 0.5, 1, 3, 5, 7, or 10, or within the range of any two of these values, and the mass ratio of the boron-containing lithium salt to the positive electrode active material may be 0.0001, 0.001, 0.005, or 0.01, or within the range of any two of these values.

[0030] Without being limited by any theory, the inventors have found that when the molar ratio of element X to element Mn in the positive electrode active material is A%, and A is between 0.1 and 10, and the electrolyte contains a boron-containing lithium salt, and the mass ratio of the boron-containing lithium salt to the positive electrode active material is between 0.0001 and 0.01, the synergistic effect of the positive electrode active material and the electrolyte contributes to the formation of a protective film on the negative electrode during the initial stages of charging and discharging of the electrochemical apparatus, repairs the protective film on the negative electrode during the cycle process of the electrochemical apparatus, and mitigates the increase in interfacial impedance during the cycle process of the electrochemical apparatus. This improves the problem of rate characteristic degradation during the cycle process of the electrochemical apparatus, and enhances the structural stability of the positive electrode active material, thereby simultaneously improving the initial rate characteristics and cycle characteristics of the electrochemical apparatus. In electrochemical devices, such as lithium-ion batteries, the mass of boron-containing lithium salt in the electrolyte can be measured by the following method: The lithium-ion battery is weighed and its mass is determined as m0. The lithium-ion battery is disassembled, centrifuged, immersed in a dimethyl carbonate solution for 10 hours and dried, and then weighed to determine its mass as m1. The total mass of the electrolyte is then determined as m0-m1. The electrolyte obtained by centrifugation is measured by gas chromatography and ion chromatography to obtain the proportion of each substance contained in the electrolyte. Mass of boron-containing lithium salt = Total mass of electrolyte × Proportion of boron-containing lithium salt content.

[0031] In some embodiments of the present invention, the positive electrode active material comprises at least one of lithium manganese oxide containing element X and lithium iron manganese phosphate containing element X.

[0032] In some embodiments of the present invention, the positive electrode active material comprises lithium manganate containing element X.

[0033] In some embodiments of the present invention, the mass fraction of the boron-containing lithium salt relative to the mass of the electrolyte is 0.01% to 2.2%. For example, the mass fraction of the boron-containing lithium salt may be 0.01%, 0.02%, 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1.2%, 1.5%, 2.0%, or 2.2%, or may be in the range of any two of these values. Without being limited by any theory, the inventors have found that when the content of the boron-containing lithium salt is 0.01% to 2.2%, and particularly when the content is 0.05% to 0.9%, the electrochemical apparatus has excellent initial rate characteristics and cycle characteristics, and at the same time, the rate of increase in DC impedance is low.

[0034] In some embodiments of the present invention, the positive electrode active material further comprises an element M1, wherein the element M1 comprises at least one of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, and Gd, and the molar content a1% of the element M1 relative to the number of moles of the element Mn is 0.1% to 2%. For example, the molar content a1% of the element M1 may be 0.1%, 0.5%, 1%, 1.5%, or 2%, or may be in the range of any two of these values. Without regard to any theory, the inventors have found that if the molar content of element M1 a1% is too low (e.g., less than 0.1%), there is no significant improvement in the performance of the electrochemical apparatus; as the molar content of element M1 a1% increases, the synergistic effect of the positive electrode active material and electrolyte is advantageous for forming a structurally stable protective film that improves the manganese elution phenomenon in the positive electrode piece; and if the molar content of element M1 a1% is too high (e.g., more than 2%), it affects the initial rate characteristics and capacity per gram of the electrochemical apparatus. It is advantageous for the positive electrode active material to contain the element M1 and for the molar content of element M1 to be within the aforementioned range to improve the manganese elution phenomenon in the positive electrode piece and improve the cycle characteristics of the electrochemical apparatus.

[0035] In some embodiments of the present invention, the electrochemical apparatus satisfies at least one of the following conditions: (i) 0.14 ≤ a1 / A ≤ 0.55, and (ii) element M1 includes element Nb, and when a2 is the molar content of element Nb relative to the number of moles of element Mn, a2 and a1 satisfy 0.3 ≤ a2 / a1 ≤ 1. For example, the value of a1 / A may be 0.14, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or 0.55, or within the range of any two of these values. For example, the value of a2 / a1 may be 0.3, 0.4, 0.54, 0.6, 0.7, 0.8, 0.9, or 1, or within the range of any two of these values. Without regard to any theory, the inventors have found that if the value of a1 / A is too small (e.g., less than 0.14), the improvement in the cycle characteristics of the electrochemical apparatus is not significant, and if the value of a1 / A is too large (e.g., greater than 0.55), it affects the specific capacity of the electrochemical apparatus. Adjusting the value of a1 / A within the above range is advantageous in improving the cycle characteristics and specific capacity of the electrochemical apparatus. Adjusting the value of a2 / a1 within the above range is also advantageous in improving the cycle characteristics and specific capacity of the electrochemical apparatus. The present invention does not have any particular restrictions on the value of a2%, as long as the objective of the present invention is achieved, for example, a2% is between 0.03% and 2%.

[0036] In some embodiments of the present invention, the positive electrode active material further contains an M2 element, the M2 element contains at least one of Fe, Cu, Cr, and Zn, and when the molar content of the M2 element is b1% with respect to the number of moles of the Mn element, a1 and b1 satisfy 0.1 < a1 + b1 ≤ 2.05. For example, the value of a1 + b1 is 0.11, 0.5, 1, 1.5, 2, or 2.05, or may be in a range consisting of any two of these numerical values. Without being limited to any theory, the inventor of the present invention has found that if the value of a1 + b1 is too large (for example, exceeding 2.05), the content of the M2 element also increases, which affects the thermal stability of the positive electrode active material, thereby affecting the initial rate characteristics and cycle characteristics of the electrochemical device. By selecting the M2 element and adjusting the value of the total molar content a1 + b1 of the M1 element and the M2 element within the above range, it is advantageous to improve the cycle characteristics and initial rate characteristics of the electrochemical device. The present invention has no particular limitation on the value of b1, and it is only necessary to achieve the object of the present invention. For example, b1 satisfies 0 < b1 ≤ 0.05.

[0037] In some embodiments of the present invention, the positive electrode active material further contains an M3 element, the M3 element contains at least one of F, P, S, and B, and the molar content c1% of the M3 element is 0.1% to 2% with respect to the number of moles of the Mn element. For example, the molar content c1% of the M3 element is 0.1%, 0.5%, 1%, 1.5%, or 2%, or may be in a range consisting of any two of these numerical values. Without being limited to any theory, the inventor of the present invention has found that by selecting the M3 element, controlling the mass ratio of the boron-containing lithium salt to the positive electrode active material to be 0.0001 to 0.01, and adjusting the molar content c1% of the M3 element within the above range, it is advantageous for the formation of a protective film with a stable structure, can improve the manganese dissolution phenomenon in the positive electrode sheet, and thereby can enhance the cycle characteristics of the electrochemical device.

[0038] In some embodiments of the present invention, the electrochemical apparatus satisfies (iii) a1 and c1 ≤ 0.1 ≤ a1 + c1 ≤ 4, and (iv) when the element M3 contains element F, and the molar content of element F is c2% relative to the number of moles of element Mn, then c1 and c2 satisfy 0.05 ≤ c2 / c1 ≤ 0.5. For example, the value of a1 + c1 may be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4, or within a range of any two of these values. For example, the value of c2 / c1 may be 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, or within a range of any two of these values. Without being limited by any theory, the inventors have found that adjusting the values ​​of a1 + c1 and / or c2 / c1 within the above ranges is advantageous in improving the cycle characteristics of the electrochemical apparatus. The present invention does not have any particular restrictions on the value of c2%, as long as the objective of the present invention is achieved. For example, c2 satisfies 0.1 ≤ c2 ≤ 1.

[0039] In some embodiments of the present invention, the positive electrode active material includes secondary particles, and D1 is the average particle diameter of the primary particles in the secondary particles. In some embodiments of the present invention, the Dv50 of the positive electrode active material is 4 μm to 15 μm. For example, the Dv50 of the positive electrode active material may be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm, or may be in a range consisting of any two of these values.

[0040] In some embodiments of the present invention, the average particle size D1 of the primary particles is 0.2 μm to 2 μm. For example, the average particle size D1 of the primary particles may be 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, or 2 μm, or may be in the range of any two of these values. Without being limited by any theory, the inventors have found that adjusting the average particle size D1 of the primary particles within the above range is advantageous in improving the rate characteristics and cycle characteristics of the electrochemical apparatus.

[0041] In some embodiments of the present invention, Dv50 and D1 satisfy 4 ≤ Dv50 / D1 ≤ 50. The value of Dv50 / D1 may be 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50, or within the range of any two of these values. Without being limited by any theory, the inventors have found that adjusting the Dv50 and Dv50 / D1 of the positive electrode active material within the above range is advantageous in improving the rate characteristics and cycle characteristics of the electrochemical apparatus. In the present invention, secondary particles refer to particles formed by the aggregation of primary particles.

[0042] In the present invention, the Dv50 of the positive electrode active material can be obtained by measuring it using a laser particle size analyzer, and the average particle diameter of the primary particles can be obtained by measuring it using a scanning electron microscope.

[0043] In some embodiments of the present invention, the electrolyte further comprises a compound containing a sulfur-oxygen double bond, wherein the sulfur-oxygen double bond-containing compound comprises at least one of 1,3-propanesultone (PS), 1-propene-1,3-sultone (PTS), and vinyl sulfate (DTD), and the mass fraction of the sulfur-oxygen double bond-containing compound is 0.01% to 2% of the mass of the electrolyte. For example, the mass fraction of the sulfur-oxygen double bond-containing compound may be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, or 2%, or may be in the range of any two of these values. Without being limited by any theory, the inventors have found that the presence of a sulfur-oxygen double bond-containing compound can mitigate the increase in interfacial impedance during the cycle process of an electrochemical apparatus and improve the problem of degraded rate characteristics during the cycle process of an electrochemical apparatus. However, if the mass fraction of the sulfur-oxygen double bond-containing compound is too high (e.g., more than 2%), a thick protective film may form on the negative electrode, potentially causing problems such as lithium deposition during high-rate charging. By selecting a compound containing the aforementioned sulfur-oxygen double bond and adjusting its mass fraction within the above range, the initial rate characteristics and cycle characteristics of the electrochemical apparatus can be improved, and the rate of increase in DC resistance can be reduced, thereby improving the problem of degraded rate characteristics during the cycle process.

[0044] The present invention does not have any particular limitations on the method for preparing the positive electrode active material, as long as the objective of the present invention is achieved. For example, the method for preparing the positive electrode active material involves uniformly mixing the raw materials, firing them under constant heating rate conditions while controlling the amount of air permeation, and the firing temperature is T x The baking time is t' y The present invention may also include, but is not limited to, a step of controlling the cooling rate thereafter to obtain a positive electrode active material. x and firing time t' y There are no particular restrictions on this, as long as the objective of the present invention is achieved. For example, the heating rate is 5°C / min and the firing temperature is T x The temperature is 800℃~900℃, and the firing time t' yThe incubation period is 15 to 50 hours, and the cooling rate is 3°C / min. The present invention does not have any particular limitations on the raw materials, as long as the objective of the present invention can be achieved. For example, the raw materials may include, but are not limited to, at least one of MnO2, Li2CO3, Al2O3, and Co2O3.

[0045] The heating rate, cooling rate, firing time, and firing temperature typically affect factors such as the particle size of the positive electrode active material, the phase uniformity of metal and oxygen ions, and the oxygen vacancy content, and further affect the physical and chemical properties of the positive electrode active material. For example, a decrease in firing temperature and / or a reduction in firing time reduces the particle size of the positive electrode active material; an increase in firing temperature and / or an increase in firing time increases the particle size of the positive electrode active material.

[0046] In the present invention, the method for introducing elements M1, M2, and M3 into the positive electrode active material is not particularly limited, as long as the objective of the present invention is achieved. For example, a compound containing M1, M2, and M3 may be selectively added during the preparation process of the positive electrode active material. The present invention is not particularly limited to the compound containing M1, as long as the objective of the present invention is achieved. For example, it may contain at least one of Nb2O5, MgO, TiO2, WO3, Ga2O3, ZrO2, Y2O3, V2O5, SrO2, MoO3, RuO2, AgO, SnO2, Au2O3, La2O3, CeO2, Pr2O3, Nd2O3, Sm2O3, and Gd2O3, but is not limited to these. The present invention is not particularly limited to the compound containing M2, as long as the objective of the present invention is achieved. For example, the compound containing M2 may contain at least one of Fe2O3, CuO2, CrO3, and ZnO2, but is not limited to these. The present invention is not particularly limited to compounds containing M3, as long as it can achieve the objectives of the present invention. For example, a compound containing M3 may contain, but is not limited to, at least one of LiF, HBO3, Li3PO4, and Li2SO4.

[0047] In this invention, the molar ratio of different elements in the positive electrode active material is obtained by disassembling an electrochemical apparatus containing the positive electrode active material in a 0% charged state to obtain a positive electrode sheet, and then measuring and calculating the content of the different elements.

[0048] The positive electrode piece typically includes a positive electrode current collector. In the present invention, the positive electrode current collector is not particularly limited and only needs to achieve the objectives of the present invention. For example, it may include, but is not limited to, aluminum foil, aluminum alloy foil, or a composite current collector. In the present invention, the thickness of the positive electrode current collector is not particularly limited and only needs to achieve the objectives of the present invention. For example, it is 8 μm to 12 μm. In the present invention, the positive electrode material layer may be provided on one surface in the thickness direction of the positive electrode current collector, or on both surfaces in the thickness direction of the positive electrode current collector. Here, "surface" may refer to the entire area of ​​the positive electrode current collector, or to a part of the area of ​​the positive electrode current collector. It is not particularly limited to the present invention and only needs to achieve the objectives of the present invention.

[0049] In the present invention, the positive electrode material layer comprises the positive electrode active material of any of the above embodiments of the present invention, and the positive electrode material layer may further comprise a binder. The present invention does not particularly limit the binder, as long as it can achieve the objectives of the present invention. For example, the binder may comprise, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethylcellulose, sodium carboxymethylcellulose, polyimide, polyamide-imide, styrene-butadiene rubber, and polyvinylidene fluoride.

[0050] In the present invention, the positive electrode material layer may further contain a conductive agent, and the present invention is not particularly limited to the conductive agent, as long as it can achieve the objectives of the present invention. For example, the conductive agent may contain, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjenblack, graphene, metallic materials, and conductive polymers. The carbon nanotubes may contain, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The carbon fibers may contain, but are not limited to, vapor-grown carbon fibers (VGCF) and / or nanocarbon fibers. The metallic materials may contain, but are not limited to, metal powders and / or metal fibers. Specifically, the metal may contain, but is not limited to, at least one of copper, nickel, aluminum, and silver. The conductive polymer may contain, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, and polypyrrole.

[0051] In the present invention, the electrochemical apparatus further includes a negative electrode piece, and the present invention is not particularly limited to the negative electrode piece as long as it can achieve the objectives of the present invention. For example, the negative electrode piece usually includes a negative electrode current collector and a negative electrode material layer. In the present invention, the negative electrode material layer may be provided on one surface in the thickness direction of the negative electrode current collector, or on both surfaces in the thickness direction of the negative electrode current collector. The term "surface" here may refer to the entire area of ​​the negative electrode current collector, or to a part of the area of ​​the negative electrode current collector, and is not particularly limited to the present invention as long as it can achieve the objectives of the present invention.

[0052] In the present invention, the negative electrode current collector is not particularly limited and should be able to achieve the objectives of the present invention. For example, it may include, but is not limited to, copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, and composite current collectors. In the present invention, the thickness of the negative electrode current collector is not particularly limited and should be able to achieve the objectives of the present invention. For example, the thickness is 4 μm to 12 μm.

[0053] In the present invention, the negative electrode material layer includes a negative electrode active material, where the negative electrode active material is not particularly limited and only needs to be able to achieve the objectives of the present invention. For example, it may include, but is not limited to, at least one of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, silicon-carbon composites, and silicon oxides.

[0054] In the present invention, the negative electrode material layer may further contain a conductive agent, and the present invention is not particularly limited to the conductive agent, as long as it can achieve the objective of the present invention. For example, it may contain at least one of the aforementioned conductive agents, but is not limited to these. In the present invention, the negative electrode material layer may further contain a binder, and the present invention is not particularly limited to the binder, as long as it can achieve the objective of the present invention. For example, it may contain at least one of the aforementioned binders, but is not limited to these.

[0055] Optionally, the negative electrode piece may further include a conductive layer, the conductive layer located between the negative electrode current collector and the negative electrode material layer. The present invention does not have any particular limitations on the composition of the conductive layer, and may include any conductive layer commonly used in the art. For example, the conductive layer may include the above-mentioned conductive agent and the above-mentioned binder, but is not limited to these.

[0056] The present invention does not particularly limit the separator, as long as it can achieve the objectives of the present invention. For example, the separator may include at least one of polyethylene (PE), polypropylene (PP), polyolefin (PO) separators mainly composed of polytetrafluoroethylene, polyester film (e.g., polyethylene terephthalate (PET) film), cellulose film, polyimide film (PI), polyamide film (PA), spandex, aramid film, woven film, nonwoven film (nonwoven fabric), microporous film, composite film, separator paper, laminate film, and spun film, but is not limited to these, and is preferably PP. The separator of the present invention may have a porous structure, and the size of the pores is not particularly limited, as long as it can achieve the objectives of the present invention. For example, the size of the pores may be 0.01 μm to 1 μm.

[0057] For example, the separator may include a base layer and a surface treatment layer. The base layer may be a nonwoven fabric, film, or composite film having a porous structure. The material of the base layer may include, but is not limited to, at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Optionally, a polypropylene porous film, polyethylene porous film, polypropylene nonwoven fabric, polyethylene nonwoven fabric, or polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the base layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials.

[0058] The inorganic layer may, but is not limited to, inorganic particles and an inorganic layer binder. The present invention is not particularly limited to inorganic particles; for example, the inorganic particles may, but are not limited to, at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The present invention is not particularly limited to the inorganic layer binder; for example, the inorganic layer binder may, but is not limited to, at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer. The polymer material may include, but is not limited to, at least one of the following: polyamide, polyacrylonitrile, acrylic acid ester polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0059] In the present invention, the electrolyte may further contain a lithium salt. The present invention is not particularly limited to the lithium salt, as long as it can achieve the objectives of the present invention. For example, the lithium salt may contain, but is not limited to, at least one of LiPF6, LiClO4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, and LiC(SO2CF3)3. The lithium salt preferably contains LiPF6.

[0060] In the present invention, the electrolyte may further contain a non-aqueous solvent. The present invention is not particularly limited to the non-aqueous solvent, as long as it can achieve the objectives of the present invention. For example, the non-aqueous solvent may contain, but is not limited to, at least one of carbonate ester compounds and carboxylic acid ester compounds. The carbonate ester compound may contain, but is not limited to, at least one of linear carbonate ester compounds, cyclic carbonate ester compounds, and fluorocarbonate ester compounds. The linear carbonate ester compound may contain, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), and methyl ethyl carbonate (MEC). The cyclic carbonate ester compound may contain, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and vinylethylene carbonate (VEC). The fluorocarbonate ester compound may contain, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate. The carboxylic acid ester compound may contain, but is not limited to, at least one of ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, and γ-butyrolactone.

[0061] The electrochemical apparatus of the present invention is not particularly limited and may include any apparatus for causing an electrochemical reaction. In some embodiments, the electrochemical apparatus may include, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0062] The manufacturing process of electrochemical devices is well known to those skilled in the art, and the present invention is not particularly limited. For example, it may include, but is not limited to, the steps of: stacking positive electrode pieces, separators and negative electrode pieces in order, performing operations such as winding and folding as necessary to obtain a wound electrode group, placing the electrode assembly in a packaging bag, injecting electrolyte into the packaging bag and sealing it, thereby obtaining an electrochemical device; or stacking positive electrode pieces, separators and negative electrode pieces in order, then placing the entire stacked electrode assembly in a packaging bag, injecting electrolyte into the packaging bag and sealing it, thereby obtaining an electrochemical device. Furthermore, an overcurrent prevention element, lead plates, etc., may be provided in the packaging bag as needed to prevent pressure rise, overcharging, and over-discharging inside the electrochemical device.

[0063] A second aspect of the present invention provides an electronic device including an electrochemical apparatus in any of the above-described embodiments of the present invention. The electrochemical apparatus provided by the present invention has good cycle characteristics and rate characteristics, thereby providing an electronic device with a long lifespan and good performance.

[0064] The electronic device of the present invention is not particularly limited and may be any known electronic device used in the prior art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile, a portable copier, a portable printer, a stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a MiniDisc, a transceiver, an electronic organizer, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric assist bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, or a large household storage battery.

[0065] Examples Measurement methods and devices: Measurement of rate characteristics: In a 25°C environment, a lithium-ion battery was charged with a constant current at a rate of 0.5C to a voltage of 4.22V, then charged with a constant voltage of 0.02C, left to stand for 60 minutes, then discharged with a constant current at a rate of 0.2C to a voltage of 2.8V, recording the discharge capacity D0, left to stand for 5 minutes, then charged again with a constant current at a rate of 0.5C to a voltage of 4.22V, then charged with a constant voltage of 0.02C, left to stand for 60 minutes, then discharged with a constant current at a rate of 5C to a voltage of 2.8V, recording the discharge capacity D'. Capacity retention rate = D' / D0 × 100%. The initial rate characteristics of the lithium-ion battery are data of the rate characteristics measured when the number of cycles of the lithium-ion battery is less than 10 cycles.

[0066] Measurement of cycle characteristics: In a 25°C environment, a lithium-ion battery was charged at a rate of 1C to a voltage of 4.22V, then charged at a constant voltage of 0.02C, left standing for 60 minutes, and then discharged at a rate of 1C to a voltage of 2.8V. The discharge capacity D3 was recorded, and after 500 cycles, the discharge capacity D4 was recorded. Cycle capacity retention rate = D4 / D3 × 100%.

[0067] Measurement of DC resistance (Rcc): The lithium-ion battery was left standing in a 25°C environment for 5 minutes, then charged with a constant current at a rate of 0.5C up to a voltage of 4.2V, then charged with a constant voltage at 4.2V down to a current of 0.025C, left standing for 5 minutes, and then discharged at a rate of 0.2C up to a voltage of 2.8V. The discharge capacity at this time was recorded as the actual capacity of the lithium-ion battery, and the rate was calculated using this actual capacity after measurement as follows. The lithium-ion battery was left standing at 25°C for 5 minutes, then charged with a constant current of 0.5C to a voltage of 4.2V, then charged with a constant voltage of 0.025C at 4.2V, and left standing for 120 minutes. The lithium-ion battery was charged to 100%. Next, it was discharged at a rate of 0.1C for 10 seconds, and the discharge current I1 and the voltage V1 after discharge were recorded, with a sampling interval of 100 milliseconds for voltage, current, and time. Then, the lithium-ion battery was discharged at a rate of 1C for 360 seconds, and the discharge current I2 and the voltage V2 at 1 second of discharge were recorded, with a sampling interval of 100 milliseconds for voltage, current, and time. The DC resistance of the lithium-ion battery was calculated using the following formula: R = (V1 - V2) / (I2 - I1). Let R1 be the DC resistance measured when the battery is charged to 50% before the cycle, and let R2 be the DC resistance measured when the battery is charged to 50% after 500 cycles. DC resistance increase rate = R2 / R1 × 100%.

[0068] Particle size measurement: 0.02 g of the material to be measured was added to a 50 mL washed beaker, followed by 20 mL of deionized water, and then a few drops of 1% sodium hexametaphosphate (a surfactant) were added to completely disperse the powder in the water. The mixture was then ultrasonically treated for 5 minutes in a 120 W ultrasonic cleaner, and the particle size distribution was measured using a MasterSizer 2000. Dv50 is the particle size of the 50% cumulative volume-based distribution measured using a laser scattering particle size analyzer. The average particle size D1 of the primary particles was obtained by measuring with a scanning electron microscope.

[0069] Example 1-1 <Preparation of positive electrode active material> Mix MnO2, Li2CO3, Al2O3 and Co3O4 as raw materials in a molar ratio of Li, Mn, Al, Co elements of 1:1.96:0.03:0.01, and the firing temperature T x is set at 830 °C, and the firing time t' y is set at 35 h to obtain a cathode active material containing secondary particles in which primary particles are aggregated, namely LiMn 1.96 Al 0.03 Co 0.01 O4. Among them, the Dv50 of MnO2 secondary particles is 11.8 μm, the Dv50 of the cathode active material is 12.4 μm, and the average particle diameter D1 of the primary particles is 0.6 μm.

[0070] <Preparation of Cathode Plate> Mix the cathode active material prepared as above, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder in a mass ratio of 96.5:2:1.5, add N-methylpyrrolidone (NMP), and stir with a vacuum stirrer until the system becomes a uniform cathode slurry. Among them, the solid content of the cathode slurry is 70%. The cathode slurry is uniformly coated on one surface of an aluminum foil as a cathode current collector with a thickness of 12 μm, and the aluminum foil is dried at 120 °C for 1 h to obtain a cathode plate with a cathode material layer coated on one side. By repeating the above steps on the other surface of the aluminum foil, a cathode plate with cathode material layers coated on both sides is obtained. The coating mass on one side of the cathode material layer is 20 mg / cm 2 . Then, after cold rolling, cutting, slitting, and tab welding, it is dried under vacuum conditions at 120 °C for 1 h to obtain a cathode plate with a specification of 74 mm × 867 mm.

[0071] <Preparation of Anode Plate> Artificial graphite, styrene-butadiene rubber (SBR), and sodium carboxymethylcellulose (CMC) were mixed in a mass ratio of 96:2:2 as negative electrode active materials, deionized water was added, and a negative electrode slurry was obtained by vacuum stirring. The solid content of the negative electrode slurry was 75%. The negative electrode slurry was uniformly applied to one surface of a 12 μm thick copper foil used as a negative electrode current collector, and the copper foil was dried at 120°C to obtain a negative electrode piece with a coating layer thickness of 130 μm and a negative electrode material layer applied to one side. By repeating the above steps on the other surface of the copper foil, a negative electrode piece with negative electrode material layers applied to both sides was obtained. The coating mass on one side of the negative electrode material layer was 6.5 mg / cm². 2 Subsequently, after cold rolling, cutting, slitting, and tab welding, the material was dried for 1 hour under vacuum conditions at 120°C to obtain a negative electrode piece with specifications of 78 mm × 875 mm.

[0072] <Preparation of Electrolyte> In a glove box under a dry argon atmosphere, PC, EC, and DEC were mixed in a mass ratio of 1:1:1. Then, lithium salt LiPF6 and boron-containing lithium salt LiBF4 were added to an organic solvent and dissolved, and the mixture was homogeneously prepared to obtain an electrolyte. Of the total mass of the electrolyte, the content of LiPF6 was 12.5%. The ratio of the mass of LiBF4 to the mass of the positive electrode active material is shown in the table below.

[0073] <Preparation of the separator> A 7μm thick porous PE film (manufactured by Celgard) was used.

[0074] <Preparation of Lithium-ion Batteries> The positive electrode piece, separator, and negative electrode piece prepared as described above were stacked in order, with the separator interposed between the positive and negative electrode pieces to provide isolation. The assembly was then wound up to obtain an electrode assembly. The electrode assembly was placed in an aluminum plastic film packaging bag, dried, and then injected with electrolyte. A lithium-ion battery was obtained through processes such as vacuum packaging, standing, chemical formation, formation, and cutting. The amount of electrolyte injected was controlled to 4.2 g / Ah, and the mass ratio of boron-containing lithium salt to positive electrode active material was controlled to 0.002. The upper limit voltage for formation was 4.15 V, the formation temperature was 70 °C, and the formation standing time was 2 h.

[0075] Examples 1-2 to 1-10, Example 1-19 The procedure was the same as in Example 1-1, except that the relevant manufacturing parameters were adjusted according to Table 1.

[0076] Examples 1-11 to 1-18 In the preparation of the positive electrode active material, the process was the same as in Example 1-1, except that the molar ratio of the raw materials was adjusted relative to the molar ratio of different elements in the positive electrode active material, and the mass fraction of the boron-containing lithium salt and the mass ratio of the boron-containing lithium salt to the positive electrode active material were adjusted as shown in Table 1.

[0077] Examples 2-1 to 2-7 In the production of the positive electrode active material, the procedure was the same as in Examples 1-5, except that the M1-containing compound was added as a raw material according to Table 2, and the molar ratio of the raw materials was adjusted according to the molar ratio of different elements in the positive electrode active material.

[0078] Examples 2-8 and 2-9 In the production of the positive electrode active material, the process was the same as in Examples 1-5, except that M1-containing compounds and M2-containing compounds were added as raw materials according to Table 2, and the molar ratio of the raw materials was adjusted according to the molar ratio of different elements in the positive electrode active material.

[0079] Examples 2-10 and 2-11 In the production of the positive electrode active material, the procedure was the same as in Examples 1-5, except that the M3-containing compound was added as a raw material according to Table 3, and the molar ratio of the raw materials was adjusted according to the molar ratio of different elements in the positive electrode active material.

[0080] Examples 2-12 to 2-15 In the production of the positive electrode active material, the procedure was the same as in Example 2-1, except that the M3-containing compound was added as a raw material according to Table 3, and the molar ratio of the raw materials was adjusted according to the molar ratio of different elements in the positive electrode active material.

[0081] Example 2-16 In the production of the positive electrode active material, the process was the same as in Example 2-1, except that M2-containing compounds and M3-containing compounds were added as raw materials according to Table 3, and the molar ratio of the raw materials was adjusted according to the molar ratio of different elements in the positive electrode active material.

[0082] Examples 3-1 to 3-5 were the same as in Examples 1-5, except that the relevant preparation parameters were adjusted according to Table 4.

[0083] Examples 4-1 to 4-6 were the same as in Examples 1-5, except that a compound containing a sulfur-oxygen double bond was added to the electrolyte preparation and the relevant preparation parameters were adjusted according to Table 5.

[0084] Comparative Examples 1-1 to 1-4 were the same as in Example 1-1, except that the relevant preparation parameters were adjusted according to Table 1, or the molar ratio of the raw materials was adjusted according to the molar ratio of different elements in the positive electrode active material.

[0085] The preparation parameters and performance of each example and comparative example are shown in Tables 1 to 5.

[0086] [Table 1]

[0087] Note: In Table 1, " / " indicates that the corresponding preparation parameter or substance does not exist.

[0088] As can be seen from Examples 1-1 to 1-18 and Comparative Examples 1-1 to 1-4, when the molar ratio A of element X to element Mn and the mass ratio of boron-containing lithium salt to positive electrode active material are both within the range of the present invention, the resulting electrochemical apparatus simultaneously exhibits good initial rate characteristics and cycle characteristics, as well as a low Rcc increase rate. As can be seen from Examples 1-1 to 1-19, when the mass fraction of the boron-containing lithium salt is within the range of the present invention, the resulting electrochemical apparatus exhibits better overall performance. Therefore, the electrochemical apparatus provided by the present invention can simultaneously improve the rate characteristics and cycle characteristics of the electrochemical apparatus and reduce the Rcc increase rate through the synergistic effect of the positive electrode active material and electrolyte.

[0089] [Table 2]

[0090] Note: In Table 2, " / " indicates that the corresponding preparation parameter or substance does not exist.

[0091] Introducing elements M1 and / or M2 into the positive electrode active material typically affects the performance of the electrochemical apparatus, such as rate characteristics, cycle characteristics, and Rcc growth rate. As can be seen from Examples 1-5 and 2-1 to 2-7, introducing element M1 into the positive electrode active material can further improve the initial rate characteristics and cycle characteristics of the electrochemical apparatus and reduce the Rcc growth rate. As can be seen from Examples 2-1 to 2-7, when the values ​​of a1, a2 / a1, a1 / A are within the range of the present invention, the resulting electrochemical apparatus has better initial rate characteristics and cycle characteristics and a lower Rcc growth rate. As can be seen from Examples 1-5, 2-8, and 2-9, simultaneously introducing elements M1 and M2 into the positive electrode active material can further improve the initial rate characteristics and cycle characteristics of the electrochemical apparatus and reduce the Rcc growth rate. As can be seen from Examples 2-8 and 2-9, when the value of a1+b1 is within the range of the present invention, the resulting electrochemical apparatus has good initial rate characteristics and cycle characteristics, and a lower Rcc growth rate.

[0092] [Table 3]

[0093] Note: In Table 3, " / " indicates that the corresponding preparation parameter or substance does not exist.

[0094] Introducing at least one of the elements M1, M2, or M3 into the positive electrode active material typically affects the performance of the electrochemical apparatus, such as initial rate characteristics, cycle characteristics, and Rcc growth rate. As can be seen from Examples 1-5, 2-10, and 2-11, introducing the element M3 into the positive electrode active material can further improve the initial rate characteristics and cycle characteristics of the electrochemical apparatus and reduce the Rcc growth rate. As can be seen from Examples 1-5 and 2-12 to 2-15, introducing both the elements M1 and M3 into the positive electrode active material can further improve the initial rate characteristics and cycle characteristics of the electrochemical apparatus and reduce the Rcc growth rate. As can be seen from Examples 2-10 to 2-15, when at least one of the values ​​of c1, c2 / c1, or a1+c1 is within the range of the present invention, the resulting electrochemical apparatus has good initial rate characteristics and cycle characteristics and a lower Rcc growth rate. As can be seen from Examples 1-5 and 2-16, simultaneously introducing elements M1, M2, and M3 into the positive electrode active material can further improve the initial rate characteristics and cycle characteristics of the electrochemical apparatus and reduce the Rcc increase rate.

[0095] [Table 4]

[0096] The particle sizes of the primary particles and the positive electrode active material typically affect the performance of the electrochemical apparatus, such as rate characteristics, cycle characteristics, and Rcc increase rate. As can be seen from Examples 1-5 and 3-1 to 3-5, when the particle sizes of the primary particles and the positive electrode active material are within the range of the present invention, i.e., when the average particle size D1 of the primary particles and the values ​​of Dv50 and Dv50 / D1 of the positive electrode active material are within the range of the present invention, the resulting electrochemical apparatus has good overall performance.

[0097] [Table 5]

[0098] Note: In Table 5, " / " indicates that the corresponding preparation parameter or substance does not exist.

[0099] Adding compounds containing sulfur-oxygen double bonds to the electrolyte typically affects the performance of an electrochemical apparatus, such as rate characteristics, cycle characteristics, and Rcc growth rate. As can be seen from Examples 1-5 and 4-1 to 4-6, adding compounds containing sulfur-oxygen double bonds to the electrolyte can further improve the rate characteristics and cycle characteristics of the electrochemical apparatus and reduce the Rcc growth rate. When the mass fraction of the sulfur-oxygen double bond-containing compound is within the range of the present invention, the resulting electrochemical apparatus has good rate characteristics and cycle characteristics, and a lower Rcc growth rate. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention are also included within the scope of the protection of the present invention.

Claims

1. An electrochemical apparatus comprising a positive electrode piece and an electrolyte, The positive electrode piece includes a positive electrode material layer, The positive electrode material layer includes a positive electrode active material, The positive electrode active material is lithium manganese oxide containing Mn and X elements. The aforementioned element X includes at least one of the elements Co and Al. When the molar ratio of element X to element Mn is A%, A is between 0.1 and 10. The electrolyte contains a boron-containing lithium salt, The ratio of the mass of the boron-containing lithium salt to the mass of the positive electrode active material is 0.0001 to 0.

01. The boron-containing lithium salt comprises at least one of lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalate)borate, and lithium tetraborate. The mass fraction of the boron-containing lithium salt relative to the mass of the electrolyte is 0.01% to 2.2%. The positive electrode active material further contains element M1, The aforementioned M1 element includes at least one of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, and Gd. An electrochemical apparatus in which the molar content a1% of the M1 element is 0.1% to 2% relative to the number of moles of the Mn element.

2. The electrochemical apparatus is, (i) a1 and A satisfy 0.14 ≤ a1 / A ≤ 0.55, (ii) The element M1 includes the element Nb, and when the molar content of the element Nb is a2% relative to the number of moles of the element Mn, a2 and a1 satisfy 0.3 ≤ a2 / a1 ≤ 1. An electrochemical apparatus according to claim 1, satisfying at least one of the following:

3. The positive electrode active material further contains element M2, The electrochemical apparatus according to claim 1, wherein the M2 element comprises at least one of Fe, Cu, Cr, and Zn.

4. The electrochemical apparatus according to claim 3, wherein, with respect to the number of moles of the Mn element, the molar content of the M1 element is a1% and the molar content of the M2 element is b1%, and a1 and b1 satisfy 0.1 < a1 + b1 ≤ 2.

05.

5. The positive electrode active material further contains the element M3, The aforementioned M3 element includes at least one of F, P, S, and B. The electrochemical apparatus according to claim 1, wherein the molar content c1% of the M3 element is 0.1% to 2% with respect to the number of moles of the Mn element.

6. (iii) a1 and c1 satisfy 0.1 ≤ a1 + c1 ≤ 4, (iv) The M3 element contains the F element, and when the molar content of the F element is c2% relative to the number of moles of the Mn element, c1 and c2 satisfy 0.05 ≤ c2 / c1 ≤ 0.

5. The electrochemical apparatus according to claim 5, satisfying at least one of the following conditions.

7. The positive electrode active material includes secondary particles, When D1 is the average particle diameter of the primary particles in the aforementioned secondary particles, (1) The Dv50 of the positive electrode active material is 4 μm to 15 μm, (2) The average particle diameter D1 of the primary particles is 0.2 μm to 2 μm, (3) Dv50 and D1 satisfy 4 ≤ Dv50 / D1 ≤ 50, and Dv50 is the particle size of 50% of the cumulative volume reference distribution of the positive electrode active material obtained by measurement with a laser scattering particle size analyzer. An electrochemical apparatus according to claim 1, satisfying at least one of the following:

8. The electrolyte further comprises a compound containing a sulfur-oxygen double bond, The compound containing the sulfur-oxygen double bond comprises at least one of 1,3-propanesultone, 1-propene-1,3-sultone, and vinyl sulfate. The electrochemical apparatus according to claim 1, wherein the mass fraction of the compound containing the sulfur-oxygen double bond is 0.01% to 2% with respect to the mass of the electrolyte.

9. An electronic apparatus comprising an electrochemical apparatus as described in any one of claims 1 to 8.

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