Electrochemical device and electronic device including the same

Abstract

The present application provides an electrochemical device and an electronic device including the electrochemical device. The electrochemical device includes an anode piece and a cathode piece, the anode piece includes an anode active material layer, the anode active material layer includes an anode active material, the cathode piece includes a cathode active material layer, the cathode active material layer includes a cathode active material, and the cathode active material includes a lithium manganese oxide, and when the SOC of the electrochemical device is 15%, the lattice constant a of the lithium manganese oxide satisfies a≦8.2008 Å. The electrochemical device has good high-temperature storage performance and cycle performance. The electronic device including the electrochemical device also has good high-temperature storage performance and cycle performance.

Description

Technical Field

[0001] The present application relates to the field of electrochemistry, and more specifically, to an electrochemical device and an electronic device including the electrochemical device.

Background Art

[0002] Lithium-ion batteries have advantages such as high energy storage density, high open-circuit voltage, low self-discharge rate, long cycle life, and good safety, and are widely used in various fields such as electrical energy storage, portable electronic devices, electric bicycles, electric vehicles, and aerospace devices.

[0003] The performance of lithium-ion batteries mainly depends on the characteristics of the positive electrode sheet, negative electrode sheet, separator, and electrolyte. Generally, the positive electrode active material in the positive electrode sheet is one of the factors affecting the performance of lithium-ion batteries. Here, lithium manganate is a commonly used positive electrode active material and is widely used in the fields of electric bicycles and electric vehicles. However, when lithium manganate is used alone, there are problems such as poor high-temperature storage performance and short service life.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present application is to provide an electrochemical device and an electronic device including the electrochemical device so as to improve the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

Means for Solving the Problems

[0005] As a first aspect of the present application, an electrochemical device is provided. The electrochemical device includes a positive electrode plate and a negative electrode plate. The negative electrode plate includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes lithium manganese oxide, and when the state of charge (SOC) of the electrochemical device is 15%, the lattice constant a of the lithium manganese oxide satisfies a ≤ 8.2008 Å. For example, the lattice constant a of the lithium manganese oxide is 8.1170 Å, 8.1190 Å, 8.1289 Å, 8.1619 Å, 8.1819 Å, 8.1837 Å, 8.1881 Å, 8.1887 Å, 8.1908 Å, 8.1900 Å, 8.1905 Å, 8.1910 Å, 8.1918 Å, 8.1921 Å, 8.2008 Å, or any one numerical value within the range between any two of the above numerical values. Without being limited by any theory, when the SOC of the electrochemical device is 15%, by keeping the lattice constant a of the lithium manganese oxide within the above range, the crystal structure of the lithium manganese oxide can be stably maintained throughout the entire SOC change range of the electrochemical device (i.e., the 0% SOC to 100% SOC range). As a result, the high-temperature cycle performance of the electrochemical device can be improved. At the same time, during the charge-discharge cycle process of the electrochemical device, the strain of the structure of the lithium manganese oxide is reduced, the elution of Mn (manganese) ions is suppressed, the distribution of Mn on the negative electrode is made more uniform, and the destruction of the negative electrode to the SEI (solid electrolyte interface) film can be reduced. Thereby, the high-temperature storage performance of the electrochemical device can be improved. In addition, the lithium precipitation on the negative electrode can be improved, and the safety performance of the electrochemical device can also be enhanced.

[0006] In some embodiments of the present application, the lithium manganese oxide is Li x Mn 2-y M y O4 and includes 0.9 ≤ x ≤ 1.1, 0 ≤ y ≤ 0.05, and M includes at least one selected from the group consisting of Al, Mg, Ti, Cr, Cu, Fe, Co, W, Zn, Ga, Zr, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Nb, and Gd.

[0007] In some embodiments of the present application, the positive electrode active material further includes at least one selected from the group consisting of a lithium transition metal composite oxide and a lithium transition metal phosphate compound.

[0008] In some embodiments of the present application, the lithium transition metal composite oxide is Li x1 Ni y1 Co z1 Mn k Z q O 2±a T a and contains, Z contains at least one selected from the group consisting of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb and Ce, T is a halogen, 0.2 < x1 ≤ 1.2, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1, 0 ≤ k ≤ 1, 0 ≤ q ≤ 1, and y1, z1, k are not simultaneously 0, and 0 ≤ a ≤ 1.

[0009] In some embodiments of the present application, the lithium transition metal phosphate compound is Li x2 R y2 N z2 PO4 and contains, R contains at least one selected from the group consisting of Fe and Mn, N contains at least one selected from the group consisting of Al, Ti, V, Cr, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb and Si, and 0.6 ≤ x2 ≤ 1.2, 0.95 ≤ y2 ≤ 1, 0 ≤ z2 ≤ 0.05.

[0010] In some embodiments of the present application, based on the mass of the positive electrode active material, the mass percentage W1 of Mn in the positive electrode active material is 42% to 47%. For example, based on the mass of the positive electrode active material, the mass percentage of Mn is 42%, 42.3%, 46.9%, 47%, or any one numerical value within the range between any two of the above numerical values. Without being limited by any theory, by keeping the mass percentage W1 of Mn in the positive electrode active material within the above range, the proportion of lithium manganate in the positive electrode active material is appropriate, so that the influence of the poor high-temperature storage performance of the lithium manganate material itself is reduced, the improvement effect on the Mn elution by other active materials is ensured, the elution of Mn and the deposition on the negative electrode can be suppressed, and thereby, the high-temperature cycle performance of the electrochemical device can be enhanced, and the low-temperature discharge performance of the electrochemical device can be further enhanced.

[0011] In some embodiments of the present application, based on the mass of the negative electrode active material, the mass percentage W2 of Mn in the negative electrode active material is 0.1% or less. For example, based on the mass of the negative electrode active material, the mass percentage of Mn is 0.0050%, 0.0100%, 0.0150%, 0.0201%, 0.0230%, 0.0265%, 0.0280%, 0.0294%, 0.0300%, 0.0320%, 0.0340%, 0.0350%, 0.0450%, 0.0550%, 0.0650%, 0.0750%, 0.0850%, 0.0950%, 0.1%, or any one numerical value within the range between any two of the above numerical values. Without being limited by any theory, by keeping the mass percentage W2 of Mn in the negative electrode active material at 0.1% or less, the risk of destroying the stability of the negative electrode SEI film can be reduced, and the high-temperature storage performance of the electrochemical device can be enhanced.

[0012] In some embodiments of the present application, the negative electrode sheet includes a first region, a second region, and a third region located between the first region and the second region. Based on the mass of the negative electrode active material in the first region, the mass percentage of Mn in the first region is V1; based on the mass of the negative electrode active material in the second region, the mass percentage of Mn in the second region is V2; based on the mass of the negative electrode active material in the third region, the mass percentage of Mn in the third region is V3. When the difference between the maximum value and the minimum value among V1, V2, and V3 is ΔV, and the average value of V1, V2, and V3 is V, ΔV / V ≤ 20% is satisfied. For example, the value of ΔV / V may be 0%, 1.45%, 3%, 4%, 5%, 7.8%, 9.2%, 10.4%, 10.5%, 10.8%, 11%, 11.5%, 11.8%, 11.9%, 12.1%, 12.3%, 12.4%, 12.5%, 13%, 17%, 19%, 20%, or any one numerical value between any two of the above numerical ranges. Without being limited by any theory, by keeping the value of ΔV / V within the above range, the difference in the Mn distribution in the negative electrode sheet can be reduced. Uniform distribution of Mn can reduce the differences in the negative electrode surface dynamics and stability, lower the risk of negative electrode side reactions and lithium precipitation, and improve the high-temperature service life, safety, and reliability of the electrochemical device. Here, the first region includes the region from the first side edge in the width direction of the negative electrode sheet to a position 10 mm away from the first side edge, and a tab is installed on the first side edge; the second region includes the region from the second side edge in the width direction of the negative electrode sheet to a position 10 mm away from the second side edge, and the second side edge faces the first side edge.

[0013] In the present application, the mass percentage V1 of Mn in the first region, the mass percentage V2 of Mn in the second region, and the mass percentage V3 of Mn in the third region are not particularly limited as long as the object of the present application can be achieved. For example, the mass percentage V1 of Mn in the first region is 0.1020% - 0.1100%. The mass percentage V2 of Mn in the second region is 0.0950% - 0.1000%. The mass percentage V3 of Mn in the third region is 0.1020% - 0.1100%.

[0014] In some embodiments of the present application, the lithium manganese oxide contains a dopant element M, and the dopant element M contains at least one selected from the group consisting of Nb, Al, Mg, Ti, Cr, Mo, Zr, Y, and B. The molar percentages of the dopant element M and Mn in the lithium manganese oxide are 0.01% to 2%. For example, the molar percentages of the dopant element M and Mn in the lithium manganese oxide are 0.014%, 0.42%, 0.70%, 1.39%, 1.74%, or any one numerical value between any two of the above numerical ranges. Without being limited by any theory, if the molar percentages of the dopant element M and Mn in the lithium manganese oxide are too large (for example, greater than 2%), the high-temperature cycle performance and high-temperature storage performance of the electrochemical device may not be significantly improved, and the capacity of the electrochemical device may decrease. If the molar percentages of the dopant element M and Mn in the lithium manganese oxide are too small (for example, less than 0.01%), the improvement effect on the high-temperature cycle performance and high-temperature storage performance of the electrochemical device may not be obvious. By keeping the molar percentages of the dopant element M and Mn in the lithium manganese oxide within the above range, the particle density of the lithium manganese oxide is improved, and the proportion of Mn 3+ / Mn 4+ in the lithium manganese oxide decreases, and the structural stability of the lithium manganese oxide is improved. Therefore, the deposition amount of Mn on the negative electrode can be effectively improved, thereby enhancing the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0015] In some embodiments of the present application, the particle size distribution of the positive electrode active material satisfies 1.2 ≤ (Dv90 - Dv10) / Dv50 ≤ 2.2. For example, the value of (Dv90 - Dv10) / Dv50 is 1.2, 1.32, 1.48, 2.2, or any one value between any two of the above numerical ranges. Without being limited by any theory, by keeping the value of (Dv90 - Dv10) / Dv50 within the above range, the range of the particle distribution of the positive electrode active material becomes wider, which contributes to a reasonable matching between large particle size particles and small particle size particles. When the compression density is the same, the pressure and degree of crushing applied to the positive electrode material particles are reduced, which contributes to the reduction of the elution of Mn in the positive electrode, and can improve the deposition amount of Mn in the negative electrode and the uniformity of the distribution of Mn in the negative electrode sheet. As a result, the high-temperature storage performance and high-temperature cycle performance of the electrochemical device can be further enhanced.

[0016] In the present application, Dv10, Dv50, and Dv90 of the positive electrode active material are not particularly limited as long as the object of the present application can be achieved. For example, Dv10 of the positive electrode active material is 0.9 μm to 6 μm. Dv50 of the positive electrode active material is 9 μm to 18 μm. Dv90 of the positive electrode active material is 19 μm to 35 μm.

[0017] In the present application, Dv10 represents the particle size at which the cumulative volume from the small particle size side is 10% in the volume-based particle size distribution. Dv50 represents the particle size at which the cumulative volume from the small particle size side is 50% in the volume-based particle size distribution. Dv90 represents the particle size at which the cumulative volume from the small particle size side is 90% in the volume-based particle size distribution.

[0018] In some embodiments of the present application, when the SOC of the electrochemical device is 0%, the potential of the negative electrode sheet with respect to Li is less than 0.6V. Since the potential of the negative electrode sheet with respect to Li gradually increases during the discharge process of the electrochemical device, when the SOC of the electrochemical device is 0%, the potential of the negative electrode sheet with respect to Li is the highest, the SEI film becomes unstable at a high potential, decomposition and gas generation are likely to occur, and the stability of the negative electrode surface is likely to decrease. Therefore, when the SOC of the electrochemical device is 0%, the potential of the negative electrode sheet with respect to Li being less than 0.6V can reduce the side reactions at high temperatures at the negative electrode interface of the electrochemical device, and improve the high-temperature cycle performance and service life of the electrochemical device.

[0019] In some embodiments of the present application, the compression density of the positive electrode active material layer is 2.8 g / cm 3 ~3.05 g / cm 3 For example, the compression density of the positive electrode active material layer is 2.8 g / cm 3 , 2.95 g / cm 3 , 3.05 g / cm 3 or any one numerical value within any two of the above numerical ranges. Without being limited by any theory, by keeping the compression density of the positive electrode active material layer within the above range, the risk of crushing of the positive electrode active material particles can be reduced, the elution of Mn can be suppressed, and the interfacial stability of the positive electrode active material layer can be improved. Further, by keeping the compression density of the positive electrode active material layer within the above range, the contact between the positive electrode active material particles is better, which contributes to the improvement of the conductivity of the conductive network, better controls the elution of Mn and the interfacial stability of the positive electrode active material layer, and thereby contributes to the improvement of the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0020] In some embodiments of the present application, the compression density of the negative electrode active material layer is 1.45 g / cm 3 ~1.65 g / cm 3 For example, the compression density of the negative electrode active material layer is 1.45 g / cm 3 , 1.55 g / cm 3 , 1.65 g / cm 3Or it is any one numerical value between any two of the above numerical ranges. Without being limited by any theory, by keeping the compression density of the negative electrode active material layer within the above range, the risk of crushing of the negative electrode active material particles is reduced, and it contributes to controlling the deposition amount and distribution uniformity of Mn eluted from the positive electrode on the negative electrode, thereby contributing to the improvement of the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0021] In some embodiments of the present application, the porosity α of the positive electrode active material layer is 15% to 40%. For example, the porosity α is 15%, 20%, 25%, 30%, 35%, 40% or any one numerical value between any two of the above numerical ranges. Without being limited by any theory, by keeping the porosity α within the above range, it is possible to suppress the decrease in the cycle performance and energy density of the electrochemical device due to poor contact between the positive electrode active material particles during the charge-discharge cycle process of the electrochemical device. Also, by keeping the porosity α within the above range, it is ensured that the positive electrode active material is sufficiently infiltrated by the electrolyte, the lithium ion transmission distance is reduced, and the kinetic performance of the electrochemical device can be enhanced.

[0022] In the present application, the porosity α of the positive electrode active material layer is the ratio of the volume of the voids between the components in the positive electrode active material layer to the apparent volume of the positive electrode active material layer.

[0023] In some embodiments of the present application, when the SOC of the electrochemical device is 100%, the starting position of the exothermic peak in the DSC (differential scanning calorimetry) curve of the positive electrode sheet is between 260°C and 280°C. This indicates that the electrochemical device has good thermal stability, and as a result, it has good high-temperature storage performance, high-temperature cycle performance, and safety performance.

[0024] In some embodiments of the present application, the electrochemical device further includes an electrolytic solution, the electrolytic solution contains a compound containing a sulfur-oxygen double bond, and based on the mass of the electrolytic solution, the mass percentage of the compound containing a sulfur-oxygen double bond is 0.01% to 1.00%. For example, the mass percentage of the compound containing a sulfur-oxygen double bond is 0.01%, 0.50%, 1.00% or any one of the numerical values between any two of the above numerical ranges. Without being limited by any theory, by keeping the mass percentage of the compound containing a sulfur-oxygen double bond within the above range, it further contributes to improving the high-temperature storage performance and high-temperature cycle performance of the electrochemical device, thereby further balancing the overall performance of the electrochemical device.

[0025] The present application is not particularly limited to the type of the compound containing a sulfur-oxygen double bond, as long as the object of the present application can be achieved. For example, the compound containing a sulfur-oxygen double bond may include at least one of 1,3-propanesultone and vinyl sulfate.

[0026] The electrolyte of the present application further contains a lithium salt and a non-aqueous solvent. The present application is not particularly limited with respect to the type of lithium salt, as long as the object of the present application can be achieved. For example, the lithium salt may contain at least one selected from the group consisting of lithium hexafluorophosphate (LiPF6), LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, and LiSiF6. Preferably, it may contain LiPF6. This is because LiPF6 can provide high ionic conductivity and improve the high-temperature cycle performance of the lithium-ion battery. The present application is not particularly limited with respect to the non-aqueous solvent, as long as the object of the present application can be achieved. For example, the non-aqueous solvent may contain at least one selected from the group consisting of a carbonic ester compound, a carboxylic acid ester compound, an ether compound, and other organic solvents. The above carbonic ester compound may be at least one selected from the group consisting of a linear carbonic ester compound and a cyclic carbonic ester compound. The above linear carbonic ester compound may contain at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and methyl ethyl carbonate (MEC). The cyclic carbonic ester compound may contain at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). The above carboxylic acid ester compound may contain at least one selected from the group consisting of ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, and propyl propionate. The above ether compound may contain at least one selected from the group consisting of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.The above-mentioned other organic solvents may include at least one selected from the group consisting of dimethyl sulfoxide, 1,2-dioxolane, cyclobutane sulfone, methyl cyclobutane sulfone, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0027] This application is not particularly limited with respect to the type of negative electrode active material, as long as the object of this application can be achieved. For example, the negative electrode active material may include at least one selected from the group consisting of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate Li4Ti5O having a spinel structure 12 and may include at least one selected from the group consisting of Li-Al alloy and metallic lithium.

[0028] The negative electrode sheet of this application further includes a negative electrode current collector. This application is not particularly limited with respect to the negative electrode current collector, as long as the object of this application can be achieved. For example, the negative electrode current collector may include a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, or a composite current collector. This application is not particularly limited with respect to the thicknesses of the negative electrode current collector and the negative electrode active material layer, as long as the object of this application can be achieved. For example, the thickness of the negative electrode current collector is 6 μm to 10 μm, and the thickness of the negative electrode active material layer on one side is 30 μm to 130 μm. In this application, the negative electrode active material layer may be provided on one surface in the thickness direction of the negative electrode current collector, or may be provided on both surfaces in the thickness direction of the negative electrode current collector. Here, the "surface" may be the entire region of the negative electrode current collector or a partial region of the negative electrode current collector, and this application is not particularly limited, as long as the object of this application can be achieved. The negative electrode sheet may optionally further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode active material layer. This application is not particularly limited with respect to the composition of the conductive layer, and it may be a conductive layer generally used in this field. For example, the conductive layer includes a conductive agent and a binder.

[0029] The positive electrode sheet of the present application further includes a positive electrode current collector. The present application is not particularly limited to the positive electrode current collector, as long as the object of the present application can be achieved. For example, the positive electrode current collector may include an aluminum foil, an aluminum alloy foil, a composite current collector, etc. The present application is not particularly limited to the thicknesses of the positive electrode current collector and the positive electrode active material layer, as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. The thickness of the positive electrode active material layer on one side is 30 μm to 120 μm. In the present application, the positive electrode active material layer may be provided on one surface of the positive electrode current collector in the thickness direction, or may be provided on both surfaces of the positive electrode current collector in the thickness direction. Here, the "surface" may be the entire region of the positive electrode current collector or a partial region of the positive electrode current collector. The present application is not particularly limited, as long as the object of the present application can be achieved. The positive electrode sheet may optionally further include a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode active material layer. The present application is not particularly limited to the composition of the conductive layer, and it may be a conductive layer generally used in this field. For example, the conductive layer includes a conductive agent and a binder.

[0030] The present application is not particularly limited with respect to the above conductive agent and binder, as long as the object of the present application can be achieved. For example, the conductive agent may include at least one selected from the group consisting of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, flaky graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, and graphene. For example, the binder may include at least one selected from the group consisting of polypropylene alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyimide, polyamideimide, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), aqueous acrylic resin, carboxymethyl cellulose (CMC), and sodium carboxymethyl cellulose (CMC-Na).

[0031] The electrochemical device of the present application further includes a separator, which separates the positive electrode sheet and the negative electrode sheet, prevents internal short circuit of the lithium-ion battery, allows electrolyte ions to pass freely, and plays a role in completing the electrochemical charge and discharge process. The present application is not particularly limited to the separator, as long as the object of the present application can be achieved. For example, the separator is at least one selected from the group consisting of polyvinyl (PE), polyolefin (PO)-based separators mainly composed of polypropylene (PP), polyester films (e.g., polyethylene terephthalate (PET) films), cellulose films, polyimide films (PI), polyamide films (PA), spandex, aramid films, woven fabric films, non-woven fabric films (non-woven fabrics), microporous membranes, composite films, separator papers, rolled films, and spun films. For example, the separator may include a base material layer and a surface treatment layer. The base material layer may be a non-woven fabric, film, or composite film having a porous structure, and the material of the base material layer may include at least one selected from the group consisting of polyvinyl, polypropylene, polyethylene terephthalate, and polyimide. Optionally, a polypropylene porous membrane, polyvinyl porous membrane, polypropylene non-woven fabric, polyvinyl non-woven fabric, or polypropylene-polyvinyl-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the base material layer. The surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder, and the inorganic particles are not particularly limited. For example, they may be at least one selected from the group consisting of aluminum oxide, 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 binder is not particularly limited and may be, for example, at least one selected from the group consisting of polyvinylidene fluoride, a copolymer of vinylidene fluoride - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer contains at least one selected from the group consisting of polyamide, polyacrylonitrile, a polymer of acrylic acid ester, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride - hexafluoropropylene).

[0032] The electrochemical device of the present application is not particularly limited and may include any device in which an electrochemical reaction occurs. In some embodiments, the electrochemical device 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, etc.

[0033] The manufacturing process of the electrochemical device is generally known to those skilled in the art and is not particularly limited in the present application. For example, the electrochemical device can be manufactured by laminating a positive electrode sheet, a separator, and a negative electrode sheet in this order, and obtaining an electrode assembly with a winding structure by operations such as winding or folding as necessary, putting the electrode assembly into a packaging case, injecting an electrolyte into the packaging case, and sealing it. Or, the electrochemical device can be manufactured by laminating a positive electrode sheet, a separator, and a negative electrode sheet in this order, fixing the four corners of the entire laminated structure with a tape to obtain an electrode assembly with a laminated structure, putting the electrode assembly into a packaging case, injecting an electrolyte into the packaging case, and sealing it. Also, in order to prevent an increase in pressure and overcharge - discharge inside the electrochemical device, an over - current prevention element, a lead plate, etc. may be put into the packaging case as necessary.

[0034] As a second aspect of the present application, there is provided an electronic device including the electrochemical device described in any one of the technical solutions of the present application. The electronic device has good high-temperature storage performance and high-temperature cycle performance.

[0035] The electronic device of the present application 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 machine, a portable copier, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini CD, a transceiver, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power source, a motor, an automobile, a motorcycle, an auxiliary bicycle, a bicycle, a lighting fixture, a toy, a game machine, a watch, a power tool, a flash, a camera, a large household storage battery, and a lithium-ion capacitor.

Advantages of the Invention

[0036] The present application provides an electrochemical device and an electronic device including the electrochemical device. The electrochemical device includes a negative electrode plate and a positive electrode plate. The negative electrode plate includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes lithium manganese oxide, and when the SOC of the electrochemical device is 15%, the lattice constant a of lithium manganese oxide satisfies a ≤ 8.2008 Å. When the electrochemical device is in a state of 15% SOC, by keeping the lattice constant a of lithium manganese oxide in the positive electrode active material within the range of a ≤ 8.2008 Å, lithium manganese oxide can maintain a relatively stable crystal structure even at an appropriate SOC, thereby improving the high-temperature cycle performance of the electrochemical device. Further, when the electrochemical device is in a state of 15% SOC, by keeping the lattice constant a of lithium manganese oxide in the positive electrode active material within the range of a ≤ 8.2008 Å, the crystal structure of lithium manganese oxide is more stable during charge and discharge cycles, the elution of Mn ions is effectively suppressed, and furthermore, the high-temperature storage performance of the electrochemical device can be effectively enhanced.

Best Mode for Carrying Out the Invention

[0037] To more clearly explain the object, technical solution, and advantages of the present application, the present application will be further described in detail below with reference to examples. Of course, the described examples are merely some examples of the present invention and not all examples. All other examples that can be conceived by those skilled in the art based on the examples of the present application belong to the protection scope of the present application.

[0038] In the specific embodiments of the present application, the lithium-ion battery is used as an example of the electrochemical device to describe the present application. However, the electrochemical device of the present application is not limited to only lithium-ion batteries.

[0039] Examples Hereinafter, the embodiments of the present application will be described more specifically with reference to examples and comparative examples. Each test and evaluation is carried out according to the methods described below. Note that “%” is based on mass unless otherwise specified.

[0040] Measurement method and device: Measurement of the lattice constant a of lithium manganese oxide: The lithium-ion battery was left standing in an atmosphere of 25°C for 30 minutes, then charged at a constant current of 0.2C until it reached 4.2V, charged at a constant voltage of 4.2V until it reached 0.05C, left standing for 30 minutes, and then discharged at 0.5C until it reached 2.8V. The discharge capacity at this time was recorded as the actual capacity of the lithium-ion battery. Then, according to the actual capacity, it was charged at a constant current of 0.1C for 9 minutes and adjusted until the SOC of the lithium-ion battery reached 15%. The lithium-ion battery was disassembled to obtain a positive electrode sheet. The positive electrode sheet was immersed in a DMC (dimethyl carbonate) solution for 24 hours, dried, and set aside for later use. The prepared electrode sheet was measured and corrected using an XRD (X-ray diffractometer) to obtain the lattice constant a of lithium manganese oxide.

[0041] Measurement of the content of each element in the positive electrode active material: The lithium-ion battery was fully discharged until it reached 2.8 V, disassembled to obtain the positive electrode sheet, the positive electrode sheet was immersed in DMC solution for 24 hours, dried, and then the positive electrode active material layer was scraped off from the positive electrode sheet, and the binder and conductive agent were removed by flame burning to obtain the positive electrode active material powder, which was set aside for later use. Six samples of the same specification were taken from the processed positive electrode active material powder, weighed, dissolved, diluted respectively, and the mass percentage of each element was measured by an inductively coupled plasma optical emission spectrometer of model Thermo ICAP6300, and the average value was calculated. Here, the mass percentage of each element was the mass percentage in the positive electrode active material.

[0042] Measurement of the Mn content in the negative electrode active material: The lithium-ion battery was fully discharged until it reached 2.8 V, disassembled to obtain the negative electrode sheet, the negative electrode sheet was immersed in DMC solution for 24 hours, dried, and set aside for later use. The electrode sheet was divided into three regions along the width direction of the electrode sheet. The first region was a region 10 mm from the tab side edge towards the center of the electrode sheet, the second region was a region 10 mm from the non-tab side edge towards the center of the electrode sheet, and the third region was the remaining part of the electrode sheet. Six samples of the same specification were taken from each of the first region, the second region, and the third region of the processed negative electrode sheet, weighed, dissolved, diluted respectively, and the mass percentage of Mn element was measured by an inductively coupled plasma optical emission spectrometer of model Thermo ICAP6300, and the average value was calculated. The average values of the measured mass percentages of Mn in the first region, the second region, and the third region were denoted as V1, V2, and V3 respectively. The average value of V1, V2, and V3 was defined as the Mn content V of the negative electrode, and the difference value between the maximum value and the minimum value among V1, V2, and V3 was defined as ΔV.

[0043] Measurement of Dv10, Dv50, and Dv90 of the positive electrode active material: Dv10, Dv50, and Dv90 of the positive electrode active material were measured by a laser particle size analyzer.

[0044] Measurement of the potential of the negative electrode sheet with respect to Li: The potential of the negative electrode sheet with respect to Li was measured by a multi-channel data recorder after completely discharging the lithium-ion battery until it reached 2.8 V.

[0045] Measurement of the compression density of the positive electrode active material layer: The compression density Pc of the positive electrode active material layer was calculated by the formula Pc = mc / Vc. In the formula, mc is the mass of the positive electrode active material layer, and its unit is g. Vc is the volume of the positive electrode active material layer, and its unit is cm 3 was. Here, the volume Vc was the product of the area Sc of the positive electrode active material layer and the thickness of the positive electrode active material layer.

[0046] Measurement of the compression density of the negative electrode active material layer: The compression density Pa of the negative electrode active material layer was calculated by the formula Pa = ma / Va. In the formula, ma is the mass of the negative electrode active material layer, and its unit is g. Va is the volume of the negative electrode active material layer, and its unit is cm 3 was. Here, the volume Va was the product of the area Sa of the negative electrode active material layer and the thickness of the negative electrode active material layer.

[0047] Measurement of the porosity α of the positive electrode active material layer: A positive electrode sheet with a radius of d was punched out, the thickness h1 of the positive electrode sheet was measured with a micrometer, and it was placed in the sample chamber of AccuPyc 1340. The sample chamber was sealed, and the polar sheet was filled with helium gas (He). The true volume V of the positive electrode sheet was measured by Boyle's law PV = nRT. After the measurement was completed, the positive electrode active material layer on the surface of the positive electrode sheet was washed, the thickness h2 of the current collector was measured with a micrometer, and the apparent volume πd of the positive electrode active material layer 2 × (h1 - h2) was calculated. Finally, the porosity α of the positive electrode active material layer was calculated by the formula α = 1 - (V - πd 2 × h2) / [πd 2 × (h1 - h2)].

[0048] Measurement of DSC: The DSC is used to measure the relationship between the heat flow difference and temperature between the sample and the reference. The DSC curve was measured by a simultaneous thermal analyzer of model STA449F3 in the following manner. The state of charge (SOC) of the lithium-ion battery was adjusted to 100%, the lithium-ion battery was disassembled, the positive electrode sheet was taken out, cleaned with DMC, cut to a specification of 10 cm × 10 cm, and measured at a measurement temperature range of 150 °C to 400 °C and a heating rate of 10 °C / min to obtain the DSC curve.

[0049] Measurement of high-temperature cycle performance: In an atmosphere of 45 °C, the lithium-ion battery was charged at a constant current of 0.5 C until the upper limit voltage reached 4.2 V, and then discharged at a constant current of 1 C until the final voltage reached 2.8 V. The discharge capacity of the first cycle was recorded. Then, charge-discharge cycles were performed 500 times in the same steps, and the discharge capacity of the lithium-ion battery in the 500th cycle was recorded. Cycle capacity retention rate of lithium-ion battery (%) = (discharge capacity of the 500th cycle / discharge capacity of the first cycle) × 100% For each example or comparative ratio, four samples were measured respectively, and the average value was calculated.

[0050] Measurement of high-temperature storage performance: The lithium-ion battery was left standing in an atmosphere of 25 °C for 30 minutes, charged at a constant current of 0.2 C until it reached 4.2 V, charged at a constant voltage of 4.2 V until it reached 0.05 C, left standing for 30 minutes, and then discharged at a constant current of 0.5 C until it reached 2.8 V. The discharge capacity at this time was recorded as the actual capacity of the lithium-ion battery. This capacity was the capacity before storage. Then, the fully charged battery was stored in an oven at 60 °C for 7 days, and its reversible capacity was measured in the same steps. This capacity was the capacity after storage. High-temperature storage capacity retention rate of lithium-ion battery (%) = capacity after storage / capacity before storage × 100%

[0051] Measurement of low-temperature performance: The lithium-ion battery was left standing in an atmosphere of 25°C for 30 minutes, then charged at a constant current of 0.2C until it reached 4.2V, charged at a constant voltage of 4.2V until it reached 0.05C, left standing for 30 minutes, and discharged at 0.5C until it reached 2.8V. The discharge capacity at this time was recorded as the actual capacity C1 of the lithium-ion battery at 25°C. Then, after the lithium-ion battery was left standing in an atmosphere of -10°C for 60 minutes, it was charged at a constant current of 0.2C until it reached 4.2V, charged at a constant voltage of 4.2V until it reached 0.05C, left standing for 30 minutes, and discharged at 0.5C until it reached 2.8V. The discharge capacity at this time was recorded as the actual capacity C2 of the lithium-ion battery at -10°C. The discharge capacity retention rate at -10°C was calculated by the formula: discharge capacity retention rate = C2 / C1 × 100%.

[0052] Example 1-1 <Preparation of the positive electrode active material> Lithium carbonate and manganese dioxide as raw materials were mixed at a molar ratio of Li:Mn of 0.545:1, and a certain amount of niobium pentoxide (Nb2O5) was added as an additive to react and produce lithium manganese oxide so that the molar percentages of Nb and Mn in the lithium manganese oxide became 0.42%. The above lithium manganese oxide and layered lithium nickel cobalt manganese oxide Li(Ni 0.55 Co 0.15 Mn 0.30 )O2 were mixed at a mass ratio of 80:20 to obtain the positive electrode active material.

[0053] <Preparation of the positive electrode sheet> The obtained cathode active material, acetylene black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were mixed at a weight ratio of 96.5:2:1.5, and NMP (N-methylpyrrolidone) was added as a solvent to prepare a slurry with a solid content of 75%. The cathode slurry was stirred with a vacuum stirrer until it became uniform. The cathode slurry was uniformly coated on the surface of one side of an aluminum foil, which is a cathode current collector with a thickness of 10 μm, and dried at 90°C to obtain a cathode sheet with a cathode active material layer coated on one side with a coating layer thickness of 110 μm. Then, by repeating the above steps for the other surface of the cathode sheet, a cathode sheet with cathode active material layers coated on both sides was obtained. After drying at 90°C and cold pressing at a compression density of 2.95 g / cm 3 , it was cut and tabs were welded to obtain a cathode sheet.

[0054] <Preparation of Anode Sheet> Artificial graphite as an anode active material, acetylene black as a conductive agent, SBR as a binder, and sodium carboxymethyl cellulose as a thickener were mixed at a weight ratio of 95:2:2:1, and deionized water was added to prepare an anode slurry with a solid content of 70%. The anode slurry was stirred with a vacuum stirrer until it became uniform. The anode slurry was uniformly coated on the surface of one side of a copper foil, which is an anode current collector with a thickness of 8 μm, and dried at 90°C to obtain an anode sheet with an anode active material layer coated on one side with a coating layer thickness of 130 μm. Then, by repeating the above steps for the other surface of the anode, an anode sheet with anode active material layers coated on both sides was obtained. After drying at 90°C and cold pressing at a compression density of 1.55 g / cm 3 , it was cut and tabs were welded to obtain an anode sheet.

[0055] <Preparation of Separator> A PE porous polymer film with a thickness of 14 μm was used.

[0056] <Preparation of Electrolyte> In a glove box with an argon atmosphere having a water content of less than 10 ppm, propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) were uniformly mixed at a mass ratio of 1:1:1 to obtain an organic solvent. Lithium salt LiPF6 was added and uniformly mixed to obtain a base electrolyte. Here, the mass concentration of LiPF6 was 12.5%.

[0057] <Preparation of Lithium Ion Battery> The prepared positive electrode sheet, separator, and negative electrode sheet were laminated and wound in this order so that the separator was interposed between the positive electrode sheet and the negative electrode sheet to play a role of isolation, obtaining an electrode assembly. The electrode assembly was dried in a vacuum oven at 85 °C for 12 hours in an aluminum-plastic composite film packaging case to remove moisture, the prepared electrolyte was injected, and a lithium ion battery was obtained by performing processes such as vacuum sealing, standing, formation, degassing, and shaping.

[0058] In Example 1-2, except that the molar ratio Li:Mn of lithium carbonate and manganese dioxide as raw materials was 0.560:1 during the preparation of lithium manganese oxide, it was the same as Example 1-1.

[0059] In Example 1-3, except that lithium manganese oxide, lithium iron phosphate LiFePO4, and lithium nickel cobalt manganese oxide Li(Ni 0.55 Co 0.15 Mn 0.30 )O2 were mixed at a mass ratio of 80:15:5 as the positive electrode active material, it was the same as Example 1-2.

[0060] In Example 1-4, except that lithium manganese oxide, lithium iron phosphate LiFePO4, and lithium nickel cobalt manganese oxide Li(Ni 0.55 Co 0.15 Mn 0.30 )O2 were mixed at a mass ratio of 80:10:10 as the positive electrode active material, it was the same as Example 1-3.

[0061] In Examples 1-5, the procedure was the same as in Examples 1-4, except that during the preparation of lithium manganese oxide, the molar ratio of lithium carbonate to manganese dioxide as raw materials, Li:Mn, was 0.575:1.

[0062] In Examples 1-6, the procedure was the same as in Example 1-1, except that during the preparation of lithium manganese oxide, the molar ratio of lithium carbonate to manganese dioxide as raw materials, Li:Mn, was 0.575:1.

[0063] In Examples 1-7, the procedure was the same as in Example 1-1, except that during the preparation of lithium manganese oxide, the molar ratio of lithium carbonate to manganese dioxide as raw materials, Li:Mn, was 0.580:1.

[0064] In Examples 1-8, the procedure was the same as in Example 1-5, except that during the preparation of lithium manganese oxide, the molar ratio of lithium carbonate to manganese dioxide as raw materials, Li:Mn, was 0.580:1.

[0065] In Examples 2-1, the procedure was the same as in Example 1-2, except that during the preparation of lithium manganese oxide, niobium pentoxide as an additive was not used.

[0066] In Examples 2-2, the procedure was the same as in Example 1-2, except that magnesium oxide (MgO) was used as an additive during the preparation of lithium manganese oxide, and the molar percentages of Mg and Mn in lithium manganese oxide were 0.42%.

[0067] In Examples 2-3, the procedure was the same as in Example 1-2, except that aluminum oxide (Al2O3) was used as an additive during the preparation of lithium manganese oxide, and the molar percentages of Al and Mn in lithium manganese oxide were 0.42%.

[0068] In Example 2-4, except that titanium dioxide (TiO2) was used as an additive during the preparation of lithium manganese oxide and the molar percentages of Ti and Mn in the lithium manganese oxide were 0.42%, it was carried out in the same manner as in Example 1-2.

[0069] In Example 2-5, except that the molar percentages of Nb and Mn in the lithium manganese oxide were 0.014% during the preparation of lithium manganese oxide, it was carried out in the same manner as in Example 1-2.

[0070] In Example 2-6, except that the molar percentages of Nb and Mn in the lithium manganese oxide were 0.70% during the preparation of lithium manganese oxide, it was carried out in the same manner as in Example 1-2.

[0071] In Example 2-7, except that the molar percentages of Nb and Mn in the lithium manganese oxide were 1.39% during the preparation of lithium manganese oxide, it was carried out in the same manner as in Example 1-2.

[0072] In Example 2-8, except that the molar percentages of Nb and Mn in the lithium manganese oxide were 1.74% during the preparation of lithium manganese oxide, it was carried out in the same manner as in Example 1-2.

[0073] In Examples 3-1 to 3-5, except that (Dv90 - Dv10) / Dv50 was adjusted as shown in Table 3, it was carried out in the same manner as in Example 1-2.

[0074] In Examples 4-1 to 4-3, except that the compression density of the positive electrode sheet was adjusted as shown in Table 3, it was carried out in the same manner as in Example 1-2.

[0075] In Examples 4-4 to 4-5, except that the compression density of the negative electrode sheet was adjusted as shown in Table 3, it was carried out in the same manner as in Example 1-2.

[0076] In Examples 5-1 to 5-2, except that the potential of the negative electrode sheet with respect to Li when the state of charge of the prepared lithium ion battery was 0% SOC was adjusted by matching the initial efficiency of the positive electrode sheet and the negative electrode sheet, the procedure was the same as in Example 1-2.

[0077] In Examples 6-1 to 6-4, except that 1,3-propanesultone, a compound containing a sulfur-oxygen double bond, was added to <the preparation of the electrolyte solution> and the mass percentage of the compound containing a sulfur-oxygen double bond was adjusted as shown in Table 5 based on the mass of the electrolyte solution, the procedure was the same as in Example 1-2.

[0078] In Comparative Example 1-1, except that the ratio of lithium carbonate and manganese dioxide as raw materials was 0.540:1 during the preparation of lithium manganese oxide, the procedure was the same as in Example 1-1.

[0079] The performance parameters of Examples 1-1 to 1-8 and Comparative Example 1-1 are shown in Table 1. The performance parameters of Examples 2-1 to 2-8 are shown in Table 2. The performance parameters of Examples 3-1 to 3-5 and Examples 4-1 to 4-5 are shown in Table 3. The performance parameters of Examples 5-1 to 5-2 are shown in Table 4. The performance parameters of Examples 6-1 to 6-4 are shown in Table 5.

[0080]

Table 1

[0081] As can be seen from Examples 1-1 to 1-8 and Comparative Example 1-1, with the change in the lattice constant a of lithium manganese oxide when SOC = 15%, the high-temperature storage performance and high-temperature cycle performance of the lithium-ion battery change. When the SOC of the lithium-ion battery is 15%, Examples 1-1 to 1-8 in which the lattice constant a of lithium manganese oxide satisfies a ≤ 8.2008 Å have better high-temperature storage performance and high-temperature cycle performance. Especially for the high-temperature cycle performance, it is significantly improved compared with Comparative Example 1-1 in which the lattice constant a of lithium manganese oxide does not satisfy a ≤ 8.2008 Å. Without being limited by any theory, the possible reasons are as follows. When the SOC of the lithium-ion battery is 15%, if the lattice constant a of lithium manganese oxide is within the above range, the amount of lithium desorption of lithium manganese oxide at this SOC is more appropriate, the change in the crystal structure itself is smaller, the rapid storage decay of lithium manganese oxide at low SOC can be suppressed, and it contributes to maintaining the lithium manganese oxide in a stable crystal structure during the lithium-ion battery cycling process (i.e., within the change range of 0% SOC to 100% SOC), thereby improving the high-temperature cycle performance of the electrochemical device. Also, when the SOC of the lithium-ion battery is 15%, if the lattice constant a of lithium manganese oxide is within the above range, the strain of the structure of lithium manganese oxide can be reduced during the charge and discharge cycle process of the lithium-ion battery, the elution of Mn (manganese) ions can be suppressed, the distribution of Mn at the negative electrode can be made more uniform, and the destruction of the SEI (solid electrolyte interface) film at the negative electrode can be reduced, thereby improving the high-temperature storage performance of the lithium-ion battery.

[0082]

Table 2

[0083] The types of dopant elements in lithium manganese oxide and the molar percentages of dopant elements M and Mn generally affect the high-temperature storage performance and high-temperature cycle performance of an electrochemical device. As can be seen from Examples 1-2 and Examples 2-1 to 2-8, compared with the non-doping technical solution of Example 2-1, by doping Nb, Mg, Al, and Ti elements, the density of the positive electrode active material particles is increased, and the ratio of Mn 3+ / Mn 4+ is reduced, the structural stability is improved, the deposition amount of Mn on the negative electrode is improved, and thereby, the high-temperature storage performance and high-temperature cycle performance of the battery are significantly improved. By comparing Examples 1-2 and Examples 2-5 to 2-8, it can be seen that with the increase in the doping amount, the improvement of the high-temperature performance is more significant, and the low-temperature performance becomes slightly lower.

[0084]

Table 3

[0085] As can be seen from Examples 1-2 and Examples 3-1 to 3-5, within a certain range, with the increase in (Dv90 - Dv10) / Dv50, the range of particle distribution becomes wider, which is contributed by the reasonable matching of large-particle-size particles and small-particle-size particles. When the compression density is the same, the pressure applied to the particles and the degree of crushing are reduced, which contributes to the reduction of the elution of Mn at the positive electrode, and improves the deposition amount of Mn on the negative electrode and the uniformity of the distribution of Mn on the negative electrode sheet. Thereby, the high-temperature storage performance and high-temperature cycle performance are further enhanced. However, if the particle distribution is too wide or too narrow, it will have an adverse effect. For example, in Example 3-4, since (Dv90 - Dv10) / Dv50 is relatively low, the matching of large-particle-size particles and small-particle-size particles becomes inappropriate, and during the cold pressing of the electrode sheet, there are more gaps between some particles, or some particles are cracked due to overpressure, thereby increasing the elution of Mn and reducing the high-temperature performance. For example, in Example 3-5, since (Dv90 - Dv10) / Dv50 is relatively high, the matching of large-particle-size particles and small-particle-size particles also becomes inappropriate, and the high-temperature storage performance and high-temperature cycle performance are reduced.

[0086] As can be seen from Examples 1-2 and Examples 4-1 to 4-5, within a certain range, as the compression density of the positive electrode sheet increases, the contact between material particles becomes better, contributing to the improvement of the conductive network. However, since the crushing of particles increases, the Mn elution increases, the stability of the material surface decreases, and thereby the high-temperature storage performance and high-temperature cycle performance decrease. In addition, as the compression density of the negative electrode sheet increases, the deposition and uneven distribution of Mn on the negative electrode occur, and side reactions such as lithium precipitation occur in some regions, affecting the battery interface, and thereby the cycle life may be shortened.

[0087]

Table 4

[0088] The potential of the negative electrode sheet with respect to Li generally affects the high-temperature storage performance and high-temperature cycle performance of the electrochemical device. As can be seen from Examples 1-2 and Examples 5-1 to 5-2, Examples 1-2 and 5-2 in which the potential of the negative electrode sheet with respect to Li is 0.56 V or less have better high-temperature cycle performance. This is because the negative electrode potential gradually increases during the discharge process, and the lithium-ion battery has the highest negative electrode potential in the fully discharged state of 0% SOC. The SEI becomes unstable at a high potential, and decomposition and gas generation are likely to occur, thereby reducing the high-temperature cycle performance.

[0089]

Table 5

[0090] As can be seen from Example 1-2 and Examples 6-1 to 6-4, based on the mass of the electrolyte, when the content of 1,3-propanesultone containing a sulfur-oxygen double bond is 0.01% to 1.00%, the high-temperature storage performance and high-temperature cycle performance of the lithium-ion battery can be further improved, thereby further balancing the overall performance of the lithium-ion battery. When the content of 1,3-propanesultone in the electrolyte is too high (Example 6-4), the high-temperature storage performance and high-temperature cycle performance are not further significantly improved, and on the contrary, the low-temperature performance deteriorates.

[0091] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and principles of the present invention all belong to the protection scope of the present invention.

Claims

1. An electrochemical device including a positive electrode plate and a negative electrode plate, wherein the negative electrode plate includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes lithium manganese oxide having a spinel structure, when the SOC of the electrochemical device is 15%, the lattice constant a of the lithium manganese oxide satisfies a ≦ 8.1908 Å, the lithium manganese oxide includes a dopant element M, the dopant element M includes at least one selected from the group consisting of Nb, Al, Mg, Ti, Cr, Mo, Zr, Y, and B, the molar percentages of the dopant element M and Mn in the lithium manganese oxide are 0.01% to 2%, the positive electrode active material further includes at least one selected from the group consisting of a layered lithium transition metal composite oxide and a lithium transition metal phosphate compound, An electrochemical device.

2. The electrochemical device (a) based on the mass of the positive electrode active material, the mass percentage W1 of Mn in the positive electrode active material is 42% to 47%, (b) based on the mass of the negative electrode active material, the mass percentage W2 of Mn in the negative electrode active material is 0.1% or less, (c) the negative electrode plate includes a first region, a second region, and a third region located between the first region and the second region. Based on the mass of the negative electrode active material in the first region, the mass percentage of Mn in the first region is V1. Based on the mass of the negative electrode active material in the second region, the mass percentage of Mn in the second region is V2. Based on the mass of the negative electrode active material in the third region, the mass percentage of Mn in the third region is V3. When the difference between the maximum value and the minimum value among V1, V2, and V3 is ΔV and the average value of V1, V2, and V3 is V, ΔV / V ≦ 20% is satisfied, satisfies at least one of the above, the first region includes the region from the first side edge in the width direction of the negative electrode plate to a point 10 mm away from the first side edge. A tab is installed on the first side edge, the second region includes the region from the second side edge in the width direction of the negative electrode plate to a point 10 mm away from the second side edge. The second side edge faces the first side edge, The electrochemical device according to Claim 1.

3. The particle size distribution of the positive electrode active material satisfies 1.2 ≦ (Dv90 - Dv10) / Dv50 ≦ 2.2, The electrochemical device according to claim 1.

4. When the SOC of the electrochemical device is 0%, the potential of the negative electrode sheet is less than 0.6 V. The electrochemical device according to claim 1.

5. (d) The compression density of the positive electrode active material layer is 2.8 g / cm ３ to 3.05 g / cm ３ and (e) The compression density of the negative electrode active material layer is 1.45 g / cm ３ to 1.65 g / cm ３ and satisfies at least one of the following: The electrochemical device according to claim 1.

6. The porosity α of the positive electrode sheet is 15% to 40%. The electrochemical device according to claim 1.

7. When the SOC of the electrochemical device is 100%, the starting position of the exothermic peak in the DSC curve of the positive electrode sheet is between 260°C and 280°C. The electrochemical device according to claim 1.

8. further includes an electrolytic solution, the electrolytic solution contains a compound containing a sulfur-oxygen double bond. The electrochemical device according to claim 1.

9. Based on the mass of the electrolytic solution, the mass percentage of the compound containing the sulfur-oxygen double bond is 0.01% to 1.00%. The electrochemical device according to claim 8.

10. (h) The lithium transition metal composite oxide contains Li ｘ１ Ni ｙ１ Co ｚ１ Mn ｋ Z ｑ O ２±ａ T ａ and Z contains at least one selected from the group consisting of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, and Ce, T is a halogen, 0.2 < x1 ≤ 1.2, 0 ≤ y1 ≤ 1, 0 ≤ z1 ≤ 1, 0 ≤ k ≤ 1, 0 ≤ q ≤ 1, and y1, z1, k are not simultaneously 0, and 0 ≤ a ≤ 1, and (i) The lithium transition metal phosphate compound contains Li ｘ２ R ｙ２ N ｚ２ PO ４ and R contains at least one selected from the group consisting of Fe and Mn, N contains at least one selected from the group consisting of Al, Ti, V, Cr, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, and Si, and 0.6 ≦ x2 ≦ 1.2, 0.95 ≦ y2 ≦ 1, 0 ≦ z2 ≦ 0.05, and satisfies at least one of the following: The electrochemical device according to claim 1.

11. An electronic device including the electrochemical device according to any one of claims 1 to 10. Electronic device.

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