Electrochemical device and electronic device comprising the same

Abstract

An electrochemical device and an electronic device comprising the electrochemical device, the electrochemical device comprising a negative electrode tab and a positive electrode tab, the negative electrode tab comprising a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, the positive electrode tab comprising a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode active material, the positive electrode active material comprising a lithium manganese oxide; when the SOC of the electrochemical device is 15%, the lattice parameter of the lithium manganese oxide has good high-temperature storage performance and cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to an electrochemical device and an electronic device comprising the same. BACKGROUND

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

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

[0004] The purpose of the present application is to provide an electrochemical device and an electronic device comprising the same to improve the high-temperature storage performance and the high-temperature cycle performance of the electrochemical device.

[0005] The first aspect of the present application provides an electrochemical device comprising a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprising a negative active material layer, the negative active material layer comprising a negative active material, the positive electrode sheet comprising a positive active material layer, the positive active material layer comprising a positive active material, the positive active material comprising lithium manganate; when the SOC (state of charge) of the electrochemical device is 15%, the lattice parameter of the lithium manganate is For example, the lattice parameter a of the lithium manganate is or any value between any two of the above numerical ranges. Without being limited by any theory, when the SOC of the electrochemical device is 15%, the lattice parameter a of the lithium manganate is adjusted within the above range, which can enable the lithium manganate to maintain a stable crystal structure within the entire SOC change range of the electrochemical device (i.e. 0% SOC to 100% SOC range), thereby improving the high-temperature cycle performance of the electrochemical device. At the same time, it can also reduce the structural distortion of the lithium manganate during the charge and discharge cycle of the electrochemical device, inhibit the dissolution of Mn (manganese) ions, make the distribution of negative electrode Mn more uniform, reduce the damage to the SEI (solid electrolyte interface) film on the negative electrode, thereby improving the high-temperature storage performance of the electrochemical device. In addition, it can also improve the lithium precipitation of the negative electrode and improve the safety performance of the electrochemical device.

[0006] In some embodiments of the present application, the lithium manganate comprises Li x Mn 2-yM y O4, wherein 0.9≤x≤1.1, 0≤y≤0.05, M comprises at least one of Al, Mg, Ti, Cr, Cu, Fe, Co, W, Zn, Ga, Zr, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Nb or Gd.

[0007] In some embodiments of the present application, the positive electrode active material further comprises at least one of a lithium transition metal composite oxide or a lithium transition metal phosphate compound.

[0008] In some embodiments of the present application, the lithium transition metal composite oxide comprises Li x1 Ni y1 Co z1 Mn k Z q O 2±a T a , wherein Z comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb or Ce, and T is halogen; wherein 0.2

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

[0010] In some embodiments of the present application, the mass percentage content W1 of Mn in the positive electrode active material is 42% to 47% based on the mass of the positive electrode active material. For example, the mass percentage content of Mn is 42%, 42.3%, 46.9%, 47% or any value within the range between any two of the above values, based on the mass of the positive electrode active material. Without being limited to any theory, the mass percentage content W1 of Mn in the positive electrode active material is adjusted within the above range, the proportion of lithium manganate in the positive electrode active material is appropriate, which can reduce the influence of the poor high-temperature storage performance of the lithium manganate material itself, ensure the improvement effect of other active materials on Mn dissolution, inhibit the dissolution of Mn and its deposition at the negative electrode, thereby improving the high-temperature cycle performance of the electrochemical device; at the same time, it can further improve the low-temperature discharge performance of the electrochemical device.

[0011] In some embodiments of the application, the mass percentage of Mn in the negative active material is less than or equal to 0.1% based on the mass of the negative active material. For example, 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 value between any two of the above-mentioned values, or any value between any two of the above-mentioned ranges. Without being limited by any theory, the mass percentage of Mn in the negative active material being less than or equal to 0.1% can reduce the risk of damaging the stability of the negative SEI film, thereby improving the high-temperature storage performance of the electrochemical device.

[0012] In some embodiments of the application, the negative electrode tab includes a first region, a second region, and a third region between the first region and the second region, the mass percentage of Mn in the first region V1 based on the mass of the negative active material in the first region, the mass percentage of Mn in the second region V2 based on the mass of the negative active material in the second region, the mass percentage of Mn in the third region V3 based on the mass of the negative active material in the third region, the difference between the maximum and minimum of V1, V2, and V3 being ΔV, and the average of V1, V2, and V3 being V, satisfying: ΔV / V≤20%. For example, the value of ΔV / V can 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 value between any two of the above-mentioned values, or any value between any two of the above-mentioned ranges. Without being limited by any theory, the value of ΔV / V being controlled within the above-mentioned range can reduce the difference in the distribution of Mn in the negative electrode tab, and uniform distribution of Mn can result in less difference in negative electrode surface dynamics and stability, reducing the risk of negative electrode side reactions and lithium precipitation, and improving the high-temperature service life and safety reliability of the electrochemical device. The first region includes a region 10 mm away from the first side edge of the negative electrode tab in the width direction, and the first side edge is provided with a tab; the second region includes a region 10 mm away from the second side edge of the negative electrode tab in the width direction, and the second side edge is opposite to the first side edge.

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

[0014] In some embodiments of the present application, the lithium manganese oxide comprises a doping element M, the doping element M comprises at least one of Nb, Al, Mg, Ti, Cr, Mo, Zr, Y or B, and the mole percentage of the doping element M to Mn in the lithium manganese oxide is 0.01% to 2%. For example, the mole percentage of the doping element M to Mn in the lithium manganese oxide is 0.014%, 0.42%, 0.70%, 1.39%, 1.74% or any value within any two of the above-mentioned value ranges. Without being limited to any theory, when the mole percentage of the doping element M to Mn in the lithium manganese oxide is too large (for example, greater than 2%), the high-temperature cycle performance and the high-temperature storage performance of the electrochemical device can no longer be significantly improved, and there is a risk of reducing the capacity of the electrochemical device; when the mole percentage of the doping element M to Mn in the lithium manganese oxide is too small (for example, less than 0.01%), the improvement effect on the high-temperature cycle performance and the high-temperature storage performance of the electrochemical device can not be obvious. By adjusting the mole percentage of the doping element M to Mn in the lithium manganese oxide within the above-mentioned range, the particle density of the lithium manganese oxide is increased, the ratio of Mn 3+ / Mn 4+ in the lithium manganese oxide is reduced, the structural stability of the lithium manganese oxide is improved, the deposition amount of the negative electrode Mn can be effectively improved, and thus the high-temperature storage performance and the high-temperature cycle performance of the electrochemical device are improved.

[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 value within any two of the above-mentioned value ranges. Without being limited to any theory, by adjusting the value of (Dv90-Dv10) / Dv50 within the above-mentioned range, the particle distribution range of the positive electrode active material is wider, which is more conducive to the reasonable matching of large-particle-size particles and small-particle-size particles. Under the same compaction density, the pressure and the degree of crushing of the positive electrode material particles are reduced, which is more conducive to reducing the Mn elution of the positive electrode, improving the deposition amount of the negative electrode Mn and the uniformity of the negative electrode tab Mn distribution, and thus the high-temperature storage performance and the high-temperature cycle performance of the electrochemical device are further improved.

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

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

[0018] In some embodiments of the present application, the potential of the negative electrode tab against Li is less than 0.6 V when the SOC of the electrochemical device is 0%. Since the potential of the negative electrode tab against Li gradually increases during the discharge process of the electrochemical device, the potential of the negative electrode tab against Li is the highest when the SOC of the electrochemical device is 0%, and the SEI film is unstable at a higher potential and is prone to decomposition and gas generation, increasing the risk of reduced stability of the negative electrode surface. Therefore, the potential of the negative electrode tab against Li is less than 0.6 V when the SOC of the electrochemical device is 0%, reducing the side reactions of the negative electrode interface of the electrochemical device at high temperature, and improving the high-temperature cycle performance and service life of the electrochemical device.

[0019] In some embodiments of the present application, the compaction density of the positive electrode active material layer is 2.8 g / cm 3 to 3.05 g / cm 3 . For example, the compaction 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 value between any two of the above numerical ranges. Without being limited to any theory, the compaction density of the positive electrode active material layer is controlled within the above range, the risk of breakage of the positive electrode active material particles is reduced, the dissolution of Mn is inhibited, and the interface stability of the positive electrode active material layer is improved; at the same time, the contact between the positive electrode active material particles is better, which is conducive to improving the conductivity of the conductive network, better controlling the dissolution of Mn and the interface stability of the positive electrode active material layer, and thus more conducive to improving the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0020] In some embodiments of the present application, the compaction density of the negative electrode active material layer is 1.45 g / cm 3 to 1.65 g / cm 3 . For example, the compaction density of the negative electrode active material layer is 1.45 g / cm 3 , 1.55 g / cm3 1.65 g / cm3 3 or any value within any two of the above-mentioned numerical ranges. Without being limited by any theory, the compaction density of the negative active material layer is regulated within the above-mentioned range, the risk of breakage of the negative active material particles is reduced, and at the same time, it is more beneficial to regulate the amount and uniformity of the deposition of the Mn dissolved from the positive electrode at the negative electrode, thereby more beneficial to improve the high-temperature storage performance and high-temperature cycle performance of the electrochemical device.

[0021] In some embodiments of the present application, the porosity a of the positive active material layer is 15% to 40%. For example, the porosity a is 15%, 20%, 25%, 30%, 35%, 40% or any value within any two of the above-mentioned numerical ranges. Without being limited by any theory, the porosity a is regulated within the above-mentioned range, which can inhibit the contact failure between the positive active material particles during the charge and discharge cycle of the electrochemical device, resulting in the reduction of the cycle performance and energy density of the electrochemical device; at the same time, it can ensure that the positive active material is fully infiltrated by the electrolyte, reduce the transmission distance of lithium ions, and improve the kinetic performance of the electrochemical device.

[0022] In the present application, the porosity a of the positive active material layer refers to the percentage of the volume of the pores between the components in the positive active material layer to the apparent volume of the positive active material layer.

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

[0024] In some embodiments of the present application, the electrochemical device further comprises an electrolyte, and the electrolyte comprises a compound containing a sulfur-oxygen double bond; the mass percentage of the compound containing a sulfur-oxygen double bond is 0.01% to 1.00% based on the mass of the electrolyte. For example, the mass percentage of the compound containing a sulfur-oxygen double bond is 0.01%, 0.50%, 1.00% or any value within any two of the above-mentioned numerical ranges. Without being limited by any theory, by regulating the mass percentage of the compound containing a sulfur-oxygen double bond within the above-mentioned range, it is more beneficial to further improve 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 type of the compound containing a sulfur-oxygen double bond is not particularly limited in the present application as long as the purpose of the present application can be achieved. For example, the compound containing a sulfur-oxygen double bond can include at least one of 1,3-propane sultone or ethylene sulfate.

[0026] The electrolyte of the present application further includes a lithium salt and a nonaqueous solvent. The kind of the lithium salt is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the lithium salt can include at least one of lithium hexafluorophosphate (LiPF6), LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, or LiSiF6. Preferably, LiPF6may be included because LiPF6may give a high ionic conductivity and improve the high-temperature cycle performance of a lithium ion battery. The nonaqueous solvent is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the nonaqueous solvent can include at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents. The carbonate compound described above can be at least one of a chain carbonate compound or a cyclic carbonate compound. The chain carbonate compound described above can include at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), or methylethyl carbonate (MEC). The cyclic carbonate compound can include at least one of ethylene carbonate (EC), propylene carbonate (PC), or butylene carbonate (BC). The carboxylate compound described above can include at least one of ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, or propyl propionate. The ether compound described above can include at least one of dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The other organic solvents described above can include at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or a phosphate ester.

[0027] The kind of the negative active material is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the negative active material can include at least one 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 of spinel structure Li4Ti5O 12 , Li-Al alloy, or metallic lithium.

[0028] The negative electrode sheet of the present application further includes a negative current collector. The negative current collector is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the negative current collector can 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, etc. In the present application, the thickness of the negative current collector and the negative active material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the negative current collector is 6 μm to 10 μm, and the thickness of the single-sided negative active material layer is 30 μm to 130 μm. In the present application, the negative active material layer can be disposed on one surface in the thickness direction of the negative current collector, or can be disposed on both surfaces in the thickness direction of the negative current collector. It should be noted that the "surface" herein can be the entire area of the negative current collector, or can be a partial area of the negative current collector, which is not particularly limited in the present application as long as the object of the present application can be achieved. Optionally, the negative electrode sheet can further include a conductive layer between the negative current collector and the negative active material layer. The composition of the conductive layer is not particularly limited in the present application, which can be a commonly used conductive layer in the art. 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 current collector. The positive current collector is not particularly limited in the present application as long as the object of the present application can be achieved. For example, the positive current collector can include an aluminum foil, an aluminum alloy foil, or a composite current collector, etc. In the present application, the thickness of the positive current collector and the positive active material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. The thickness of the single-sided positive active material layer is 30 μm to 120 μm. In the present application, the positive active material layer can be disposed on one surface in the thickness direction of the positive current collector, or can be disposed on both surfaces in the thickness direction of the positive current collector. It should be noted that the "surface" herein can be the entire area of the positive current collector, or can be a partial area of the positive current collector, which is not particularly limited in the present application as long as the object of the present application can be achieved. Optionally, the positive electrode sheet can further include a conductive layer between the positive current collector and the positive active material layer. The composition of the conductive layer is not particularly limited in the present application, which can be a commonly used conductive layer in the art. For example, the conductive layer includes a conductive agent and a binder.

[0030] The conductive agent and the binder are not particularly limited in the present application, as long as the object of the present application can be achieved. For example, the conductive agent can include at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon nanofibers, flake graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, or graphene. For example, the binder can include at least one of polyvinyl alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyimide, polyamide-imide, styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, carboxymethyl cellulose (CMC), or sodium carboxymethyl cellulose (CMC-Na).

[0031] The electrochemical device of the present application also includes a separator to separate the positive electrode sheet and the negative electrode sheet, prevent internal short circuit of the lithium ion battery, allow electrolyte ions to pass freely, and complete the electrochemical charging and discharging process. The separator in the present application is not particularly limited as long as it can achieve the purpose of the present application. For example, at least one of a polyolefin (PO) separator based on polyethylene (PE) or polypropylene (PP), a polyester film (e.g., a polyethylene terephthalate (PET) film), a cellulose film, a polyimide film (PI), a polyamide film (PA), spandex, aramid film, a woven film, a nonwoven film (nonwoven fabric), a microporous film, a composite film, a separator paper, a calendered film, or a spunlaced film. For example, the separator can include a base layer and a surface treatment layer. The base layer can be a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the base layer can include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used. Optionally, a surface treatment layer is provided on at least one surface of the base layer, and the surface treatment layer can be a polymer layer or 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 and can be selected from, for example, at least one 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, or barium sulfate. The binder is not particularly limited and can be selected from, for example, at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene. The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0032] The electrochemical device of the present application is not particularly limited and can include any device in which an electrochemical reaction occurs. In some embodiments, the electrochemical device can 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 preparation process of the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited, for example, can include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding, etc. as needed to obtain a wound electrode assembly, placing the electrode assembly into a packaging shell, injecting an electrolyte into the packaging shell and sealing to obtain an electrochemical device; or stacking the positive electrode sheet, the separator and the negative electrode sheet in order, then fixing the four corners of the entire stack structure with a tape to obtain a stack structure electrode assembly, placing the electrode assembly into a packaging shell, injecting an electrolyte into the packaging shell and sealing to obtain an electrochemical device. In addition, a current protection element, a guide plate, etc. can also be placed in the packaging shell as needed to prevent the pressure inside the electrochemical device from rising, overcharging and discharging.

[0034] The second aspect of the present application provides an electronic device comprising the electrochemical device of any one of the preceding aspects 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 is not particularly limited and can include but is not limited to the following types: notebook computers, pen input computers, mobile computers, electronic book players, portable telephones, portable facsimile machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini-disc players, transceivers, electronic organizers, calculators, memory cards, portable audio players, radios, backup power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting appliances, toys, game machines, timepieces, power tools, flashlights, cameras, household large-size storage batteries, and lithium-ion capacitors, etc.

[0036] The present application provides an electrochemical device and an electronic device comprising the same, the electrochemical device comprising a negative electrode sheet and a positive electrode sheet, the negative electrode sheet comprising a negative electrode active material layer, the negative electrode active material layer comprising a negative electrode active material, the positive electrode sheet comprising a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode active material, the positive electrode active material comprising a lithium manganese oxide; when the SOC of the electrochemical device is 15%, the lattice parameter of the lithium manganese oxide is in the range of 4.15-4.20 A. By adjusting the lattice parameter of the lithium manganese oxide in the positive electrode active material to be in the range of 4.15-4.20 A when the electrochemical device is in a 15% SOC state, the lithium manganese oxide can still maintain a relatively stable crystal structure at a suitable SOC, thereby improving the high-temperature cycle performance of the electrochemical device. At the same time, the crystal structure of the lithium manganese oxide is more stable during the charging and discharging cycle, the dissolution of Mn ions is effectively inhibited, and the high-temperature storage performance of the electrochemical device is also effectively improved. DETAILED DESCRIPTION

[0037] ​For purposes of the present application, the following terms have the meanings indicated:

[0038] It should be noted that the specific embodiments of the present application are explained by taking lithium ion batteries as examples of electrochemical devices, but the electrochemical devices of the present application are not limited to lithium ion batteries.

[0039] Embodiments

[0040] The following, taking examples and comparative examples to more specifically explain the embodiments of the present application. Various tests and evaluations are carried out in accordance with the following methods. In addition, unless otherwise specified, the "%" is mass basis.

[0041] Test methods and apparatus:

[0042] Test of the lattice parameter a of lithium manganese oxide:

[0043] The lithium ion battery is left to stand in an environment of 25°C for 30 min, then charged at a constant current to 4.2V at a rate of 0.2C, charged at a constant voltage to 0.05C at 4.2V, left to stand for 30 min, then discharged to 2.8V at a rate of 0.5C, and the discharge capacity at this time is recorded as the actual capacity of the lithium ion battery; then charged at a constant current at 0.1C for 9 min according to the actual capacity, adjusting the SOC of the lithium ion battery to 15%; the positive electrode sheet is obtained by disassembling the lithium ion battery, and is immersed in a DMC (dimethyl carbonate) solution for 24 hours, dried for standby; the prepared electrode sheet is tested using an XRD (X-ray diffractometer) and refined to obtain the lattice parameter a of the lithium manganese oxide.

[0044] Test of the content of each element in the positive electrode active material:

[0045] The lithium ion battery is discharged to 2.8V, the positive electrode sheet is disassembled, and is immersed in a DMC solution for 24h, after drying, the positive electrode active material layer is scraped off from the positive electrode sheet, and after removing the binder and conductive agent by flame calcination, the positive electrode active material powder is obtained for standby. Take 6 parallel samples of the treated positive electrode active material powder, weigh, digest, dilute respectively, then use a ThermoICAP6300 type inductively coupled plasma emission spectrometer to test the mass percentage of different elements, and take the average value, wherein the mass percentage of each element is the mass percentage in the positive electrode active material.

[0046] Test of the content of Mn in the negative electrode active material:

[0047] The lithium ion battery was fully discharged to 2.8 V, and the negative electrode sheet was obtained by disassembly, and then was immersed in a DMC solution for 24 h and dried for standby; the electrode sheet was divided into three regions along the width direction of the electrode sheet, the first region was a region of 10 mm from the edge of the tab to the center of the electrode sheet, the second region was a region of 10 mm from the edge of the non-tab to the center of the electrode sheet, and the third region was the remaining part of the electrode sheet; 6 parallel samples were taken from the first region, the second region and the third region of the treated negative electrode sheet respectively, and then were weighed, digested, diluted, and then the mass percentage content of Mn element was tested by using a Thermo ICAP6300 type inductively coupled plasma emission spectrometer, and the average value was calculated, and the average values of the mass percentage contents of Mn in the first region, the second region and the third region were V1, V2 and V3 respectively. The negative electrode Mn content V was defined as the average value of V1, V2 and V3, and the difference between the maximum value and the minimum value in V1, V2 and V3 was ΔV.

[0048] Test of Dv10, Dv50 and Dv90 of the positive electrode active material:

[0049] The Dv10, Dv50 and Dv90 of the positive electrode active material were tested by using a laser particle size analyzer.

[0050] Test of the potential of the negative electrode sheet to Li:

[0051] The lithium ion battery was fully discharged to 2.8 V, and the potential of the negative electrode sheet to Li in the fully discharged state was tested by using a multi-channel data recorder.

[0052] Test of the compaction density of the positive electrode active material layer:

[0053] The compaction 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, unit: g; Vc is the volume of the positive electrode active material layer, unit: cm 3 , wherein the volume Vc is the product of the area Sc of the positive electrode active material layer and the thickness of the positive electrode active material layer.

[0054] Test of the compaction density of the negative electrode active material layer:

[0055] The compaction 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, unit: g; Va is the volume of the negative electrode active material layer, unit: cm 3 , wherein the volume Va is the product of the area Sa of the negative electrode active material layer and the thickness of the negative electrode active material layer.

[0056] Test of the porosity a of the positive electrode active material layer:

[0057] The positive electrode tab with a punch radius of d is measured for thickness h1 using a micrometer and loaded into the sample chamber of an AccuPyc 1340 instrument. The positive electrode tab is filled with helium (He) in a closed sample chamber, and the true volume V of the positive electrode tab is measured using Boyle's law PV = nRT. After the test is completed, the positive active material layer on the surface of the positive electrode tab is cleaned, the thickness of the current collector is measured as h2 using a micrometer, and the apparent volume of the positive active material layer is calculated as πd 2 × (h1 - h2). Finally, the porosity of the positive active material layer is obtained as α = 1 - (V - πd 2 × h2) / [πd 2 × (h1 - h2)].

[0058] DSC Test:

[0059] DSC is used to measure the heat flow difference and temperature of the sample and reference. The STA449F3 model synchronous thermal analyzer is used to test the DSC curve, and the method is as follows: adjust the lithium ion battery SOC = 100%, disassemble the lithium ion battery, take out the positive electrode tab, clean it with DMC, cut it into a size of 10 cm x 10 cm, test the temperature range of 150°C to 400°C, the heating rate is 10°C / min, and the DSC curve is obtained.

[0060] High-temperature cycle performance test:

[0061] In an environment of 45°C, the lithium ion battery is subjected to constant current charging at a charging current of 0.5C until the upper limit voltage is 4.2V, and then subjected to constant current discharge at a discharging current of 1C until the final voltage is 2.8V, and the discharge capacity of the first cycle is recorded. Then the same steps are taken for 500 cycles of charging and discharging, and the discharge capacity of the lithium ion battery in the 500th cycle is recorded.

[0062] The cycle capacity retention rate of the lithium ion battery (%) = (discharge capacity in the 500th cycle / discharge capacity in the first cycle) x 100%.

[0063] Each example or comparative example tests 4 samples, and the average value is taken.

[0064] High-temperature storage performance test:

[0065] The lithium ion battery is placed in an environment of 25°C for 30 min, then charged at a constant current of 0.2C to 4.2V, charged at a constant voltage of 4.2V to 0.05C, and then discharged at a constant current of 0.5C to 2.8V. The discharge capacity at this time is recorded as the actual capacity of the lithium ion battery, which is the pre-storage capacity; then the fully charged battery is placed in a 60°C oven for 7 days, and then tested according to the same procedure to obtain the reversible capacity, which is the post-storage capacity.

[0066] High-temperature storage capacity retention rate (%) of lithium ion battery = capacity after storage / capacity before storage x 100%.

[0067] Test of low-temperature performance:

[0068] The lithium ion battery was placed in an environment at 25°C for 30 min, then charged at a constant current to 4.2V at a rate of 0.2C, charged at a constant voltage to 0.05C at 4.2V, placed for 30 min, then discharged to 2.8V at a rate of 0.5C, and the discharge capacity at this time was recorded as the actual capacity C1 of the lithium ion battery at 25°C; then the lithium ion battery was placed in an environment at -10°C for 60 min, then charged at a constant current to 4.2V at a rate of 0.2C, charged at a constant voltage to 0.05C at 4.2V, placed for 30 min, then discharged to 2.8V at a rate of 0.5C, and 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 following formula: discharge capacity retention rate = C2 / C1 x 100%.

[0069] Example 1-1

[0070] Preparation of positive electrode active material

[0071] The raw materials lithium carbonate and manganese dioxide were mixed in a Li:Mn molar ratio of 0.545:1, and a certain amount of niobium pentoxide (Nb2O5) was added as an additive to make the molar percentage of Nb to Mn in the lithium manganese oxide 0.42%, and the lithium manganese oxide was generated by reaction.

[0072] 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 in a mass ratio of 80:20 to obtain the positive electrode active material.

[0073] Preparation of positive electrode tab

[0074] The prepared positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 96.5:2:1.5, NMP (N-methyl pyrrolidone) was added as a solvent, and a slurry with a solid content of 75% was prepared and stirred under the action of a vacuum stirrer until the system became a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm, and dried at 90°C to obtain a positive electrode tab with a single-side coated positive electrode active material layer with a coating thickness of 110 μm. Then, the above steps were repeated on the other surface of the positive electrode tab to obtain a positive electrode tab with a double-side coated positive electrode active material layer. After drying at 90°C, the positive electrode tab was cut into a size of 20 mm x 20 mm to obtain a positive electrode tab with a size of 20 mm x 20 mm x 110 μm. 3The positive electrode active material layer is coated on one surface of the positive current collector copper foil with a thickness of 8 μm, and dried at 90°C to obtain a single-side coated positive electrode active material layer with a coating thickness of 130 μm. After drying at 90°C, the positive electrode active material layer is cold-pressed at a compaction density of 3.5 g / cm

[0075] <Manufacture of negative electrode sheet>

[0076] The negative electrode active material artificial graphite, conductive agent acetylene black, binder SBR, and thickening agent sodium carboxymethyl cellulose are mixed in a mass ratio of 95:2:2:1, and then deionized water is added to prepare a negative electrode slurry with a solid content of 70%. The negative electrode slurry is stirred in a vacuum stirrer until the system becomes a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on one surface of a negative current collector copper foil with a thickness of 8 μm, and dried at 90°C to obtain a single-side coated negative electrode active material layer with a coating thickness of 130 μm. After drying at 90°C, the negative electrode active material layer is cold-pressed at a compaction density of 3.5 g / cm 3

[0077] <Manufacture of separator>

[0078] A PE porous polymer film with a thickness of 14 μm is used.

[0079] <Manufacture of electrolyte>

[0080] In an argon atmosphere glove box with a water content of less than 10 ppm, propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) are uniformly mixed in a mass ratio of 1:1:1 to obtain an organic solvent. Lithium salt LiPF6 is added and uniformly mixed to obtain a base electrolyte. The mass concentration of LiPF6 is 12.5%.

[0081] <Manufacture of lithium ion battery>

[0082] The positive electrode sheet, the separator, and the negative electrode sheet prepared above are stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a role of isolation, and then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum plastic film packaging shell, dried in a vacuum oven at 85°C for 12 h to remove water, and then injected with the electrolyte prepared above. The lithium ion battery is obtained after vacuum packaging, standing, formation, degassing, and shaping.

[0083] In Example 1-2, the Li:Mn molar ratio of raw materials lithium carbonate and manganese dioxide in the preparation process of lithium manganese oxide is 0.560:1, and the rest is the same as Example 1-1.

[0084] In Example 1-3, except that the lithium manganese oxide, lithium iron phosphate LiFePO4, and lithium nickel cobalt manganese phosphate Li(Ni 0.55 Co 0.15 Mn​0.30 )O2 as a positive active material in a mass ratio of 80:15:5, and the rest is the same as Example 1-2.

[0085] In Example 1-4, except for lithium manganese oxide, lithium iron phosphate LiFePO4, and layered lithium nickel cobalt manganese oxide Li(Ni 0.55 Co 0.15 Mn 0.30 )O2 as a positive active material in a mass ratio of 80:10:10, and the rest is the same as Example 1-3.

[0086] In Example 1-5, except that the Li:Mn molar ratio of raw materials lithium carbonate and manganese dioxide is 0.575:1 during the preparation of lithium manganese oxide, and the rest is the same as Example 1-4.

[0087] In Example 1-6, except that the Li:Mn molar ratio of raw materials lithium carbonate and manganese dioxide is 0.575:1 during the preparation of lithium manganese oxide, and the rest is the same as Example 1-1.

[0088] In Example 1-7, except that the Li:Mn molar ratio of raw materials lithium carbonate and manganese dioxide is 0.580:1 during the preparation of lithium manganese oxide, and the rest is the same as Example 1-1.

[0089] In Example 1-8, except that the Li:Mn molar ratio of raw materials lithium carbonate and manganese dioxide is 0.580:1 during the preparation of lithium manganese oxide, and the rest is the same as Example 1-5.

[0090] In Example 2-1, except that no niobium pentoxide additive is added during the preparation of lithium manganese oxide, and the rest is the same as Example 1-2.

[0091] In Example 2-2, except that magnesium oxide (MgO) is used as an additive during the preparation of lithium manganese oxide, so that the molar percentage of Mg to Mn in lithium manganese oxide is 0.42%, and the rest is the same as Example 1-2.

[0092] In Example 2-3, except that aluminum oxide (Al2O3) is used as an additive during the preparation of lithium manganese oxide, so that the molar percentage of Al to Mn in lithium manganese oxide is 0.42%, and the rest is the same as Example 1-2.

[0093] In Example 2-4, except that titanium dioxide (TiO2) is used as an additive during the preparation of lithium manganese oxide, so that the molar percentage of Ti to Mn in lithium manganese oxide is 0.42%, and the rest is the same as Example 1-2.

[0094] In Example 2-5, except that the molar percentage of Nb to Mn in the lithium manganese oxide is 0.014% in the preparation of the lithium manganese oxide, the rest is the same as Example 1-2.

[0095] In Example 2-6, except that the molar percentage of Nb to Mn in the lithium manganese oxide is 0.70% in the preparation of the lithium manganese oxide, the rest is the same as Example 1-2.

[0096] In Example 2-7, except that the molar percentage of Nb to Mn in the lithium manganese oxide is 1.39% in the preparation of the lithium manganese oxide, the rest is the same as Example 1-2.

[0097] In Example 2-8, except that the molar percentage of Nb to Mn in the lithium manganese oxide is 1.74% in the preparation of the lithium manganese oxide, the rest is the same as Example 1-2.

[0098] In Example 3-1 to Example 3-5, except that (Dv90-Dv10) / Dv50 is adjusted according to Table 3, the rest is the same as Example 1-2.

[0099] In Example 4-1 to Example 4-3, except that the compaction density of the positive electrode sheet is adjusted according to Table 3, the rest is the same as Example 1-2.

[0100] In Example 4-4 to Example 4-5, except that the compaction density of the negative electrode sheet is adjusted according to Table 3, the rest is the same as Example 1-2.

[0101] In Example 5-1 to Example 5-2, except that the potential of the negative electrode sheet against Li when the state of charge of the lithium ion battery prepared by matching the first efficiency of the positive electrode sheet and the negative electrode sheet is 0% SOC state, the rest is the same as Example 1-2.

[0102] In Example 6-1 to Example 6-4, except that the compound containing a sulfur-oxygen double bond 1,3-propane sultone is added in the preparation of the electrolyte, and the mass percentage of the compound containing a sulfur-oxygen double bond is adjusted according to Table 5 based on the mass of the electrolyte, the rest is the same as Example 1-2.

[0103] In Comparative Example 1-1, except that the ratio of raw material lithium carbonate and manganese dioxide is 0.540:1 in the preparation of the lithium manganese oxide, the rest is the same as Example 1-1.

[0104] The performance parameters of Examples 1-1 to 1-8, 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, 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, and the performance parameters of Examples 6-1 to 6-4 are shown in Table 5:

[0105] Table 1

[0106]

[0107]

[0108] As can be seen from Examples 1-1 to 1-8 and Comparative Example 1-1, the high-temperature storage performance and the high-temperature cycle performance of the lithium ion battery vary with the change of the lattice parameter a of the lithium-manganese oxide when the SOC = 15%. When the SOC = 15% of the lithium ion battery, the lattice parameter a of the lithium-manganese oxide Examples 1-1 to 1-8 have better high-temperature storage performance and high-temperature cycle performance, especially high-temperature cycle performance, compared with Comparative Example 1-1 in which the lattice parameter a of the lithium-manganese oxide is not within the range, without being limited to any theory, and the possible reason is that when the SOC = 15% of the lithium ion battery, the lattice parameter a of the lithium-manganese oxide is adjusted within the above range, then at this SOC, the amount of delithiation of the lithium-manganese oxide is moderate, and the change of the crystal structure thereof is relatively small, which can inhibit the too fast storage decay of the lithium-manganese oxide at a low SOC, is conducive to the maintenance of a stable crystal structure of the lithium-manganese oxide during the cycle of the lithium ion battery (i.e. within the change range of 0% SOC to 100% SOC), and thus improves the high-temperature cycle performance of the electrochemical device. At the same time, it can also reduce the structural distortion of the lithium-manganese oxide during the charge-discharge cycle of the lithium ion battery, inhibit the dissolution of Mn (manganese) ions, make the distribution of the negative electrode Mn more uniform, reduce the damage to the SEI (solid electrolyte interface) film on the negative electrode, and thus improve the high-temperature storage performance of the lithium ion battery.

[0109] Table 2

[0110]

[0111]

[0112] The type of doping elements and the molar percentage of doping elements M and Mn in lithium manganese oxide will also generally affect the high-temperature storage performance and high-temperature cycle performance of the electrochemical device. As can be seen from Examples 1-2, Examples 2-1 to Examples 2-8, compared with the design scheme without doping of Example 2-1, doping Nb, Mg, Al, Ti elements can improve the density of positive active material particles, reduce the Mn 3+ / Mn 4+ ratio, improve the structural stability, improve the Mn deposition amount of the negative electrode, and significantly improve the high-temperature storage and high-temperature cycle performance of the battery. Comparing Examples 1-2, Examples 2-5 to Examples 2-8, with the increase of the doping amount, the improvement of the high-temperature performance is more significant, and the low-temperature performance is slightly reduced.

[0113] Table 3

[0114]

[0115] As can be seen from Examples 1-2, Examples 3-1 to Examples 3-5, within a certain range, with the increase of (Dv90-Dv10) / Dv50, the particle distribution range is wider, which is more conducive to the matching of large and small particles, the pressure and crushing degree of particles are reduced under the same compaction density, which is conducive to reducing the Mn dissolution of the positive electrode, improving the Mn deposition amount of the negative electrode and the Mn distribution uniformity of the negative electrode sheet, and obtaining better high-temperature storage performance and high-temperature cycle performance. However, too wide or too narrow particle distribution will have adverse effects, such as Example 3-4, low (Dv99-Dv10) / Dv50 will lead to unreasonable matching of large and small particles, and there will be more gaps between some particles or some particles will be crushed due to overpressure during the cold pressing process of the electrode sheet, thereby increasing the Mn dissolution and reducing the high-temperature performance, such as Example 3-5, high (Dv99-Dv10) / Dv50 will also lead to unreasonable matching of large and small particles, and reduce the high-temperature storage and cycle performance.

[0116] As can be seen from Examples 1-2, Examples 4-1 to Examples 4-5, within a certain range, with the increase of the compaction density of the positive electrode sheet, the contact between the material particles is better, which is conducive to improving the conductive network, but will increase the particle crushing, thereby increasing the Mn dissolution and reducing the stability of the material surface, leading to the decrease of the high-temperature storage and high-temperature cycle performance. In addition, with the increase of the compaction density of the negative electrode sheet, it may cause the deposition and uneven distribution of Mn in the negative electrode, causing side reactions such as lithium precipitation in some areas, affecting the battery interface, and thus reducing the cycle life.

[0117] Table 4

[0118]

[0119] The potential of the negative electrode sheet to Li also generally affects the high-temperature storage performance and high-temperature cycle performance of the electrochemical device. As can be seen from Examples 1-2, 5-1 to 5-2, the Examples 1-2 and 5-2 with the potential of the negative electrode sheet to Li ≤ 0.56 V have more excellent high-temperature cycle performance, because the negative electrode potential gradually increases during discharging, the lithium ion battery has the highest negative electrode potential at the full discharge state of 0% SOC, the SEI is unstable and prone to decomposition and gas generation at a higher potential, thereby reducing the high-temperature cycle performance.

[0120] Table 5

[0121]

[0122] As can be seen from Examples 1-2, 6-1 to 6-4, when the content of the compound containing a sulfoxide double bond, 1,3-propane sultone, is 0.01% to 1.00% based on the mass of the electrolyte, 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-propane sultone in the electrolyte is too high (Example 6-4), there is no further significant improvement in the high-temperature storage and cycle performance, and instead the low-temperature performance is reduced.

[0123] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device, comprising a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprising a negative electrode active material layer including a negative electrode active material, the positive electrode sheet comprising a positive electrode active material layer including a positive electrode active material, the positive electrode active material including a lithium manganese oxide having a spinel structure, the positive electrode active material further including at least one of a layered lithium transition metal complex oxide or a lithium transition metal phosphoric compound; The lattice parameter a of the lithium manganese oxide satisfies: a mass percentage content of Mn in the positive electrode active material W1 is 42% to 47% based on the mass of the positive electrode active material, the lithium manganese oxide including a doping element M, the doping element M including at least one of Nb, Al, Mg, Ti, Cr, Mo, Zr, Y or B, a mole percentage of the doping element M to Mn in the lithium manganese oxide is 0.01% to 2%; a potential of the negative electrode sheet to Li is less than or equal to 0.56V when SOC of the electrochemical device is 0%; a starting position of an exothermic peak on a DSC curve of the positive electrode sheet is between 260℃ and 280℃ when SOC of the electrochemical device is 100%.

2. The electrochemical device of claim 1, wherein, The electrochemical device satisfies at least one of the following characteristics: (b) a mass percentage content of Mn in the negative electrode active material W2 is less than or equal to 0.1% based on the mass of the negative electrode active material; (c) the negative electrode sheet includes a first region, a second region, and a third region between the first region and the second region, a mass percentage content of Mn in the first region V1 based on the mass of the negative electrode active material in the first region, a mass percentage content of Mn in the second region V2 based on the mass of the negative electrode active material in the second region, a mass percentage content of Mn in the third region V3 based on the mass of the negative electrode active material in the third region, a difference between the maximum value and the minimum value of V1, V2 and V3 is ΔV, and an average value of V1, V2 and V3 is V, satisfying: ΔV / V≤20%; the first region includes a region of the negative electrode sheet in a width direction from a first side edge to a distance of 10mm from the first side edge, and a tab is provided on the first side edge; the second region includes a region of the negative electrode sheet in a width direction from a second side edge to a distance of 10mm from the second side edge, and the second side edge is opposite to the first side edge.

3. The electrochemical device of claim 1, wherein, The particle size distribution of the positive electrode active material satisfies: 1.2≤(Dv90-Dv10) / Dv50≤2.

2.

4. The electrochemical device of claim 1, wherein, The electrochemical device satisfies at least one of the following characteristics: (d) the positive electrode active material layer has a compaction density of 2.8 g / cm 3 to 3.05 g / cm 3 ; (e) the compacted density of the negative electrode active material layer is 1.45 g / cm 3 to 1.65 g / cm 3 .

5. The electrochemical device of claim 1, wherein, a porosity α of the positive electrode sheet is 15% to 40%.

6. The electrochemical device of claim 1, wherein, The electrochemical device further includes an electrolyte, and the electrolyte includes a compound containing a sulfur-oxygen double bond.

7. The electrochemical device of claim 6, wherein, A mass percentage content of the compound containing a sulfur-oxygen double bond is 0.01% to 1.00% based on the mass of the electrolyte.

8. The electrochemical device of claim 1, wherein, The lithium manganese oxide includes Li x Mn 2-y M y O4, wherein 0.9≤x≤1.1, 0≤y≤0.05, and M includes at least one of Al, Mg, Ti, Cr, Cu, Fe, Co, W, Zn, Ga, Zr, Ru, Ag, Sn, Au, La, Ce, Pr, Nd, Sm, Nb, or Gd.

9. The electrochemical device of claim 1, wherein, The electrochemical device satisfies at least one of the following characteristics: (h) the lithium transition metal complex oxide comprises Li x1 Ni y1 Co z1 Mn k Z q O 2±a T a wherein Z comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, or Ce, and T is a halogen; wherein 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. (i) the lithium transition metal phospho compound comprises Li x2 R y2 N z2 PO4, wherein R comprises at least one of Fe or Mn; N comprises at least one of Al, Ti, V, Cr, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si; wherein 0.6≤x2≤1.2, 0.95≤y2≤1, 0≤z2≤0.

05. 10.An electronic device comprising the electrochemical device according to any one of claims 1 to 9.

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