Electrochemical and electronic equipment

Abstract

The present invention provides an electrochemical apparatus and an electronic apparatus, the electrochemical apparatus comprising a negative electrode piece and an electrolyte, the negative electrode piece comprising a negative electrode material layer, the negative electrode material layer comprising silicon, the mass percentage of silicon relative to the total mass of the negative electrode material layer being 20% ​​to 50%, and the electrolyte comprising a compound of formula (I) and ethylene carbonate, the mass percentage of ethylene carbonate relative to the total mass of the electrolyte being 5% to 40%. The negative electrode material layer comprising silicon, the electrolyte comprising a compound of formula (I) and ethylene carbonate, and controlling the mass percentages of silicon and ethylene carbonate within the above ranges is advantageous in improving the ion transport performance and stability of the solid electrolyte interface, thereby improving the charge-discharge efficiency and cycle stability of the electrochemical apparatus. [Formula 1] TIFF2026524580000015.tif44170

Description

[Technical Field]

[0001] This application claims priority to a Chinese patent application filed with the China National Patent Office on June 13, 2024, with application number 202410763808.9, and titled "Electrochemical Apparatus and Electronic Apparatus," the entire contents of which are incorporated herein by reference. The present invention relates to the field of electrochemistry, and more particularly to electrochemical apparatus and electronic apparatus. [Background technology]

[0002] With the rapid development of electronic products, electrochemical devices are widely applied in mobile phones, laptops, tablet computers, drones, electric vehicles, power tools, and power storage systems, due to their advantages such as high energy density and the ability to be miniaturized and lightweight. In particular, in the field of 3C products, users still have a great need to extend the lifespan of electronic products, and therefore place higher demands on the energy density of electrochemical devices. In electrochemical devices, such as lithium-ion batteries, a large amount of solid electrolyte interface (SEI) film is generated on the surface of the negative electrode during the initial charge-discharge process. This formation involves the creation of a single film consisting of stable compounds produced by the decomposition of the electrolyte between the electrolyte and the electrode of the lithium-ion secondary battery. Therefore, the properties of the SEI film depend heavily on the composition of the electrolyte. The SEI film plays a crucial role in lithium-ion batteries, contributing to the protection of electrode materials, stabilization of the electrolyte interface, and regulation of lithium-ion transport. Selecting appropriate electrolyte components to form an SEI film with suitable properties is particularly important for improving the charge-discharge performance and cycle stability of lithium-ion batteries. [Overview of the Initiative]

[0003] The present invention aims to provide electrochemical and electronic devices that improve the charge-discharge efficiency and cycle stability of electrochemical devices.

[0004] A first aspect of the present invention provides an electrochemical apparatus comprising a negative electrode piece and an electrolyte. The negative electrode piece comprises a negative electrode material layer, the negative electrode material layer comprises silicon, the mass percentage of silicon relative to the total mass of the negative electrode material layer is 20% to 50%, and the electrolyte comprises a compound of formula (I) and ethylene carbonate. [ka] Here, R1 is a fluorine atom, a C1-C6 alkyl group at least partially substituted with fluorine, or a C6-C6 alkyl group at least partially substituted with fluorine. 10 aryl group, C1-C6 oxygen-containing alkyl group at least partially substituted with fluorine, C6-C6 at least partially substituted with fluorine 10 Selected from oxygen-containing aryl groups, the O atom in R1 is not directly bonded to the S atom, and R2 and R3 are, independently, unsubstituted or partially fluorinated C1-C5 alkyl groups and unsubstituted or partially fluorinated C6-C5 alkyl groups. 10 Selected from the aryl groups, R2 and R3 may bond to form a ring. The mass percentage of ethylene carbonate relative to the total mass of the electrolyte is 5% to 40%. The negative electrode material layer contains silicon, and the electrolyte contains compound (I) and ethylene carbonate. By controlling the mass percentages of silicon and ethylene carbonate within the above ranges, it is advantageous for forming an SEI film that combines inorganic and organic materials, improving the ion transport performance and stability of the SEI film, thereby improving the charge-discharge efficiency and cycle stability of the electrochemical device.

[0005] In one embodiment of the present invention, the compound of formula (I) comprises at least one compound from among the compounds represented by the following formulas (I-1) to (I-35). [ka] [ka] By selecting the above compounds, improvements in the charge-discharge efficiency and cycle stability of electrochemical devices can be achieved.

[0006] In one embodiment of the present invention, the mass percentage of ethylene carbonate is 10% to 30% of the total mass of the electrolyte. By controlling the mass percentage of ethylene carbonate within the above range, it is possible to improve the cycle stability and charge / discharge efficiency of the electrochemical apparatus.

[0007] In one embodiment of the present invention, the mass percentage of compound (I) is 3% to 50% of the total mass of the electrolyte. By controlling the mass percentage of compound (I) within this range, it is possible to improve the cycle stability and charge / discharge efficiency of the electrochemical apparatus.

[0008] In one embodiment of the present invention, the mass percentage of compound (I) is 10% to 40% of the total mass of the electrolyte. By controlling the mass percentage of compound (I) within the above range, it is possible to further improve the cycle stability and charge / discharge efficiency of the electrochemical apparatus.

[0009] In one embodiment of the present invention, the electrolyte further contains fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate relative to the total mass of the electrolyte is 5% to 30%. By controlling the mass percentage of fluoroethylene carbonate within the above range, it is possible to improve the cycle stability and charge / discharge efficiency of the electrochemical apparatus.

[0010] In one embodiment of the present invention, the electrolyte further contains fluoroethylene carbonate, and the mass percentage of fluoroethylene carbonate is 10% to 30% of the total mass of the electrolyte. By controlling the mass percentage of fluoroethylene carbonate within the above range, it is possible to further improve the cycle stability and charge / discharge efficiency of the electrochemical apparatus.

[0011] In one embodiment of the present invention, the electrolyte contains a cyclic compound containing a sulfur-oxygen double bond, and the cyclic compound containing the sulfur-oxygen double bond contains at least one of 1,3-propanesultone, 1,4-butanesultone, and 2,4-butanesultone, and the mass percentage of the cyclic compound containing the sulfur-oxygen double bond relative to the total mass of the electrolyte is 0.1% to 5%. By containing a cyclic compound containing a sulfur-oxygen double bond in the electrolyte and controlling its mass percentage within the above range, good cycle stability can be provided to the electrochemical apparatus.

[0012] In one embodiment of the present invention, the electrochemical apparatus includes a separator and a positive electrode piece. Along the extending direction of the tab of the electrochemical apparatus, the length of the separator beyond the positive electrode piece is a μm, and the thickness of the separator is b μm. Then a and b satisfy 0.0008 ≤ b / a ≤ 0.009 and 1000 ≤ a ≤ 5000. By controlling the values ​​of b and b / a within the above ranges, the electrochemical apparatus can have good cycle stability and charge / discharge efficiency, as well as good safety performance.

[0013] A second aspect of the present invention provides an electronic device including an electrochemical apparatus according to the first aspect of the present invention, wherein the electrochemical apparatus according to the present invention has good charge / discharge efficiency and cycle stability, and therefore the electronic device according to the present invention has good operating performance.

[0014] The present invention provides an electrochemical device and an electronic device. The electrochemical device includes a negative electrode sheet and an electrolytic solution. The negative electrode sheet includes a negative electrode material layer, the negative electrode material layer includes silicon element, and with respect to the total mass of the negative electrode material layer, the mass percentage of the silicon element is 20% to 50%. The electrolytic solution includes a compound of formula (I) and ethylene carbonate (EC), and with respect to the total mass of the electrolytic solution, the mass percentage of ethylene carbonate is 5% to 40%. By causing ethylene carbonate to undergo a reduction reaction on the surface of the negative electrode, an SEI film containing lithium carbonate ions and a large amount of organic substances is formed, and the compound of formula (I) includes a SO2N group and can form an interfacial film containing a large amount of inorganic substances such as Li3N and Li2S. By combining inorganic substances and organic substances, the ion transport performance and stability of the SEI film can be improved, and the charge-discharge efficiency and cycle stability of the electrochemical device can be improved. Of course, when implementing any product or method of the present invention, it is not necessarily required to achieve all the above advantages simultaneously.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by those skilled in the art based on the present invention shall be included within the protection scope of the present invention. In the specific embodiments of the present invention, the lithium-ion battery is used as an example of the electrochemical device to describe the present invention, but the electrochemical device of the present invention is not limited to the lithium-ion battery.

[0016] The present invention provides an electrochemical device including a negative electrode sheet and an electrolytic solution. The negative electrode sheet includes a negative electrode material layer, the negative electrode material layer includes silicon element, and with respect to the total mass of the negative electrode material layer, the mass percentage of the silicon element is 20% to 50%. For example, the mass percentage of the silicon element is 20%, 22%, 25%, 28%, 30%, 35%, 40%, 45%, 48%, 50%, or may be in the range composed of any two of the above values. The electrolytic solution includes a compound of formula (I) and ethylene carbonate. [Chemical] Here, R1 is selected from a fluorine atom, a C1-C6 alkyl group at least partially substituted with fluorine, a C6-C 10 aryl group at least partially substituted with fluorine, a C1-C6 oxygen-containing alkyl group at least partially substituted with fluorine, a C6-C 10 oxygen-containing aryl group at least partially substituted with fluorine. The O atom in R1 is not directly bonded to the S atom. R2 and R3 are each independently selected from an unsubstituted or partially fluorine-substituted C1-C5 alkyl group, an unsubstituted or partially fluorine-substituted C6-C 10 aryl group. R2 and R3 may be linked to form a ring. With respect to the total mass of the electrolytic solution, the mass percentage of ethylene carbonate is 5% - 40%, preferably 10% - 30%. For example, the mass percentage of ethylene carbonate is 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, or may be in the range composed of any two of the above values.

[0017] By controlling the mass percentage of silicon element mass within the above range, the space required for the expansion of nanosilicon particles during the charging and discharging processes of the electrochemical device can be filled. This effectively mitigates phenomena such as material cracking due to the expansion of nanosilicon particles, thereby improving the energy density and cycle characteristics of the electrochemical device. Ethylene carbonate (EC) as a cyclic ester has high dissociation ability of lithium salts and can improve lithium ion transport performance. However, cyclic esters have poor stability and are prone to ring-opening decomposition. If too much is added, it worsens the interfacial impedance and causes deterioration of battery performance. By controlling the mass percentage of EC within the above range, the electrolyte can have good lithium ion transport performance, and the problem of deterioration of the interfacial film due to ring-opening decomposition of EC hindering lithium ion transport and increasing interfacial impedance can be reduced. During the cycle process of a lithium-ion battery, reductive decomposition occurs on the surface of the negative electrode. EC has strong polarity and can form a stable complex with lithium ions. This forms a layer of SEI film containing lithium carbonate and other organic polymers, resulting in a high organic content. This high organic content SEI film has good stability and good ion transport performance. Compound (I) contains an SO2N group, which allows for the formation of an interfacial film containing a high amount of inorganic substances such as Li3N and Li2S. As a result, the electrolyte can contain both compound (I) and ethylene carbonate, forming an SEI film containing both organic and inorganic substances. This improves the stability and ion transport performance of the SEI film, reduces the transport impedance of ions (e.g., lithium ions), and allows for rapid ion release during the charge-discharge process, thereby improving the charge-discharge efficiency and cycle stability of the electrochemical device.

[0018] The negative electrode material layer of the present invention contains silicon, which is introduced from a silicon-based material, and the silicon-based material may be at least one selected from silicon-carbon composite materials, silicon-oxygen composite materials, micron silicon, Si-Sn alloys, Si-Mg alloys, Si-Ge alloys, and Si-Zn alloys. In some embodiments, the silicon-carbon composite material may be silicon supported in carbon nanopores.

[0019] In one embodiment of the present invention, the compound of formula (I) comprises at least one compound from among the compounds represented by the following formulas (I-1) to (I-35). [ka] [ka] By selecting the above compound, the inorganic content in the SEI film is increased, which contributes to further improving the ion transport performance of the SEI film. This improves the release efficiency during the lithium ion charge and discharge process, and further enhances the charge and discharge efficiency and cycle stability of the electrochemical device.

[0020] In one embodiment of the present invention, the mass percentage of compound (I) relative to the total mass of the electrolyte is 3% to 50%, preferably 10% to 40%. For example, the mass percentage of compound (I) may be 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 48%, 50%, or within a range composed of any two of the above values. The present invention makes it possible to improve lithium ion transport performance by forming an SEI film combining inorganic and organic materials at the negative electrode interface by combining compound (I) and EC. By controlling the mass percentage of compound (I) within the above range, the SEI film has good toughness, reducing the risk of rupture, reducing the problem of ion transport inhibition due to an excessively thick interfacial film, and improving the cycle stability and charge / discharge efficiency of the electrochemical apparatus.

[0021] In one embodiment of the present invention, the electrolyte further contains fluoroethylene carbonate (FEC), wherein the mass percentage of fluoroethylene carbonate is 5% to 30%, preferably 10% to 30%, relative to the total mass of the electrolyte. For example, the mass percentage of fluoroethylene carbonate may be 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 27%, 30%, or within a range composed of any two of the above values. FEC is a good additive to lithium-ion battery electrolytes, and by adding FEC to the electrolyte, a crosslinked, highly tough polymer protective layer can be formed at the electrode interface, reducing side reactions between silicon-based materials and the electrolyte. By controlling the mass percentage of fluoroethylene carbonate within the above range, it is advantageous to further reduce the reaction between silicon-based materials and the electrolyte, thereby further improving the cycle stability of the electrochemical device and mitigating the problem of lithium ion transport inhibition caused by an excessively thick polymer protective layer, thereby improving the charge and discharge efficiency of the electrochemical device.

[0022] In one embodiment of the present invention, the electrolyte contains a cyclic compound containing a sulfur-oxygen double bond, the cyclic compound containing the sulfur-oxygen double bond containing at least one of 1,3-propanesultone, 1,4-butanesultone, and 2,4-butanesultone, and the mass percentage of the cyclic compound containing the sulfur-oxygen double bond relative to the total mass of the electrolyte is 0.1% to 5%. For example, the mass percentage of the cyclic compound containing the sulfur-oxygen double bond may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or within a range composed of any two of the above values. By controlling the mass percentage of the cyclic compound containing the sulfur-oxygen double bond within the above range, the sulfur-oxygen double bond-containing compound and the compound of formula (I) can act synergistically in the film formation process, which is advantageous for forming a more stable interfacial film on the surface of the negative electrode and reduces side reactions between the silicon-based material and the electrolyte, thus the electrochemical apparatus has good cycle stability.

[0023] In the present invention, the electrolyte further comprises a lithium salt and a base solvent. The present invention does not particularly limit the type of lithium salt, and lithium salts known in the art can be used. Exemplarily, the lithium salt may include, but is not limited to, at least one of LiBF4, LiPF6, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, and LiPO2F2. The present invention does not particularly limit the base solvent as long as the object of the present invention is achieved. For example, it may include, but is not limited to, at least one of carbonate compounds, carboxylate compounds, ether compounds, and other organic solvents. The carbonate compound may include, but is not limited to, linear carbonate compounds or other cyclic carbonate compounds. The above-mentioned linear carbonate compound may include, but is not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and ethyl methyl carbonate (EMC). The above-mentioned other cyclic carbonate compound may include, but is not limited to, at least one of propylene carbonate (PC), butylene carbonate (BC), and vinyl ethylene carbonate (VEC). The above-mentioned carboxylate compound may include, but is not limited to, at least one of ethyl acetate, propyl acetate, propyl propionate, and ethyl propionate. The above-mentioned ether compound may include, but is not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran.The other organic solvents listed above may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters.

[0024] The present invention does not particularly limit the mass percentages of the lithium salt and base solvent in the electrolyte, as long as the objective of the present invention can be achieved. For example, the mass percentage of the lithium salt relative to the total mass of the electrolyte is 8% to 20%, and for example, the mass percentage of the lithium salt may be 8%, 10%, 13%, 15%, 18%, 20%, or within a range composed of any two of the above values. The mass percentage of the base solvent is 0% to 84%, for example, 0%, 3%, 5%, 8%, 10%, 13%, 15%, 18%, 20%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 53%, 55%, 57%, 60%, 63%, 65%, 67%, 70%, 73%, 75%, 78%, 80%, 84%, or it may be within the range of any two of the above values. In the present invention, the characteristics of different components contained in the electrolyte can be combined, and any embodiment included in the above combination falls within the scope of protection of the present invention.

[0025] In one embodiment of the present invention, the electrolyte may comprise a compound of formula (I), EC, a lithium salt, and a base solvent. The mass percentages of the compound of formula (I), EC, and lithium salt are as described above, and the mass percentage of the base solvent relative to the total mass of the electrolyte is 0% to 84%. The electrochemical apparatus comprising the electrolyte having the above characteristics is advantageous for improving charge-discharge efficiency and cycle stability.

[0026] In one embodiment of the present invention, the electrolyte may comprise a compound of formula (I), EC, FEC, a lithium salt, and a base solvent. The mass percentages of the compound of formula (I), EC, FEC, and lithium salt are as described above, and the mass percentage of the base solvent relative to the total mass of the electrolyte is 0% to 79%. The electrochemical apparatus comprising an electrolyte having the above characteristics is advantageous in further improving charge-discharge efficiency and cycle stability.

[0027] In one embodiment of the present invention, the electrolyte may include a compound of formula (I), EC, a lithium salt, a base solvent, and a cyclic compound containing a sulfur-oxygen double bond. The mass percentages of the compound of formula (I), EC, a lithium salt, and the cyclic compound containing a sulfur-oxygen double bond are as described above, and the mass percentage of the base solvent relative to the total mass of the electrolyte is 0% to 83%. The electrochemical apparatus containing the electrolyte having the above characteristics is advantageous in further improving charge-discharge efficiency and cycle stability.

[0028] In one embodiment of the present invention, the electrolyte may comprise a compound of formula (I), EC, FEC, a cyclic compound containing a sulfur-oxygen double bond, a lithium salt, and a base solvent. The mass percentages of the compound of formula (I), EC, FEC, the cyclic compound containing a sulfur-oxygen double bond, and the lithium salt are as described above, and the mass percentage of the base solvent relative to the total mass of the electrolyte is 0% to 78%. The electrochemical apparatus comprising the electrolyte having the above characteristics is advantageous in further improving charge-discharge efficiency and cycle stability.

[0029] In one embodiment of the present invention, the electrochemical apparatus includes a separator and a positive electrode piece, and along the extending direction of the tab of the electrochemical apparatus, the length of the separator beyond the positive electrode piece is a μm, and the thickness of the separator is b μm, such that a and b satisfy 0.0008 ≤ b / a ≤ 0.009 and 1000 ≤ a ≤ 5000. For example, the value of b / a may be 0.0008, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, or within the range of any two of the above values, and the value of a may be 1000, 1300, 1500, 1800, 2000, 2300, 2500, 2800, 3000, 3300, 3500, 3800, 4000, 4300, 4500, 4800, 5000, or within the range of any two of the above values. In the present invention, the extension direction of the tab of the electrochemical apparatus is the width direction of the positive electrode piece. By controlling the values ​​of b / a and a within the above range, the risk of short-circuiting between the positive and negative electrodes can be reduced, and there is no loss of mass energy density of the electrochemical apparatus due to wasted space in the electrochemical apparatus, resulting in a high energy density for the electrochemical apparatus. Furthermore, the addition of compound (I) improves the thermal shock resistance of the separator, and the addition of FEC compound further improves the thermal shock resistance of the separator. By satisfying the above characteristics of the separator, the temperature rise inside the electrochemical apparatus under thermal disturbance can be further reduced, and the thermal contraction of the separator can be reduced, resulting in the electrochemical apparatus having good cycle stability and charge / discharge efficiency, as well as further improving safety performance. In the present invention, the thickness b of the separator may be 4 μm to 18 μm. For example, the value of b may be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or within the range composed of any two of the above values.

[0030] The material of the separator of the present invention is not particularly limited, as long as the objectives of the present invention are achieved. For example, the separator may contain at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, and aramid. For example, polyethylene may contain at least one of high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. The surface of the separator of the present invention may include a porous layer. The porous layer on the surface of the separator of the present invention is not particularly limited, as long as the objectives of the present invention are achieved. For example, the porous layer may be provided on at least one surface of the separator, and the porous layer may contain at least one of inorganic particles and a binder, and the porous layer can improve the heat resistance, oxidation resistance, and electrolyte wettability of the separator, and improve the adhesion between the separator and the electrode piece. The size of the pore diameter is not particularly limited, as long as the objectives of the present invention are achieved, for example, the size of the pore diameter may be 0.01 μm to 1 μm. For example, the inorganic particles may include at least one of the following: alumina (Al2O3), silica (SiO), magnesia (MgO), titania (TiO2), hafnium dioxide (HfO2), tin oxide (SnO2), cerium dioxide (CeO2), nickel oxide (NiO), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO2), yttrium oxide (Y2O3), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. For example, the binder of the porous layer may contain at least one of the following: polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0031] The negative electrode sheet of the present invention further includes a negative electrode current collector. The negative electrode current collector of the present invention is not particularly limited as long as the object of the present invention can be achieved. For example, the negative electrode current collector may include, but is not limited to, copper foil, aluminum foil, nickel foil, or a carbon-based current collector. For example, the thickness of the negative electrode current collector is 4 μm to 10 μm. The thickness of the negative electrode material layer of the present invention is not particularly limited as long as the object of the present invention can be achieved. For example, the thickness of the negative electrode material layer is 30 μm to 150 μm. The thickness of the negative electrode sheet of the present invention is not particularly limited as long as the object of the present invention can be achieved. For example, the thickness of the negative electrode sheet is 50 μm to 350 μm. In the present invention, the negative electrode material layer may be provided on one surface in the thickness direction of the negative electrode current collector, or may be provided on two surfaces in the thickness direction of the negative electrode current collector. Note that the above "surface" may be all regions of the negative electrode current collector, or may be a part of the regions of the negative electrode current collector. The present invention only needs to achieve the object of the present invention and is not particularly limited. The negative electrode material layer of the present invention may further include a conductive agent and a binder.

[0032] The negative electrode material layer of the present invention may further include a carbon material, and the carbon material may be at least one selected from natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, and soft carbon. The content range of the carbon material may be 10% to 70% based on the total mass of the negative electrode material layer. The negative electrode material layer of the present invention may further include a binder and a conductive agent.

[0033] The positive electrode sheet of the present invention is not particularly limited as long as the object of the present invention can be achieved. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The positive electrode current collector of the present invention is not particularly limited as long as the object of the present invention can be achieved. For example, the positive electrode current collector may include, but is not limited to, aluminum foil or aluminum alloy foil. The positive electrode material layer of the present invention includes a positive electrode active material. The type of the positive electrode active material of the present invention is not particularly limited as long as the object of the present invention can be achieved. For example, the positive electrode active material is LiCo 1-y M y O2, LiNi 1-y M y O2, LiMn 2-y M yO4, LiSa x Co y Mn z M 1-x-y-z The positive electrode active material may contain at least one of the following: O2, etc., and M contains at least one of the following: Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Ti, etc., and 0≦y≦1, 0≦x≦1, 0≦z≦1, x+y+z≦1. For example, the positive electrode active material may contain at least one of the following: lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), lithium iron phosphate (LiFePO4), lithium iron manganese phosphate, etc., and the positive electrode active material may be doped and / or coated. The thickness of the positive electrode current collector of the present invention is not particularly limited, as long as the objective of the present invention is achieved. For example, the thickness of the positive electrode current collector is 4μm to 12μm. The thickness of the positive electrode material layer of the present invention is not particularly limited, as long as the objective of the present invention is achieved. For example, the thickness of the positive electrode material layer is 30μm to 120μm. The thickness of the positive electrode piece of the present invention is not particularly limited, as long as the objective of the present invention is achieved. For example, the thickness of the positive electrode piece is 50 μm to 250 μm. The positive electrode material layer of the present invention may further contain a conductive agent and a binder.

[0034] The conductive agent and binder described above are not particularly limited, as long as they can achieve the objectives of the present invention. For example, the conductive agent may include at least one of conductive carbon black, acetylene black, Ketjenblack, layered graphite, graphene, carbon nanotubes, carbon nanowires, and carbon fibers. The binder may include at least one of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate salt, sodium carboxymethylcellulose (CMC-Na), polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), polyaniline, polyimide, polyamide-imide, polysiloxane, epoxy resin, polyester resin, and polyurethane resin.

[0035] In some embodiments of the present invention, the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer may be (70-98):(0.5-15):(1-15) in terms of positive electrode active material:conductive agent:binder.

[0036] The preparation process for electrochemical apparatuses is well known to those skilled in the art, and the present invention is not particularly limited. For example, the present invention may include the steps of sequentially stacking positive electrode pieces, separators, and negative electrode pieces, performing operations such as winding and folding as necessary to obtain a wound electrode assembly, placing the electrode assembly in an outer bag, injecting electrolyte into the outer bag and sealing it to obtain an electrochemical apparatus. Alternatively, the present invention may include the steps of sequentially stacking positive electrode pieces, separators, and negative electrode pieces, then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly, placing the electrode assembly in an outer bag, injecting electrolyte into the outer bag and sealing it to obtain an electrochemical apparatus. Furthermore, in order to prevent pressure rise inside the electrochemical apparatus, overcharging and over-discharging, etc., overcurrent prevention elements, lead plates, etc. may be placed in the outer bag as necessary. The present invention does not limit the outer bag, and those skilled in the art can select it as needed as long as the objective of the present invention is achieved. For example, an aluminum plastic film outer bag can be used.

[0037] A second aspect of the present invention provides an electronic device including an electrochemical apparatus according to the first aspect of the present invention, wherein the electrochemical apparatus according to the present invention has good charge / discharge efficiency and cycle stability, and therefore the electronic device according to the present invention has good operating performance.

[0038] The electronic devices of the present invention are not particularly limited and may be any known electronic devices used in the prior art. In some embodiments, the electronic devices include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, portable facsimile machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable cleaners, portable CD players, MiniDiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, or lithium-ion capacitors.

[0039] Examples The embodiments of the present invention will be described in more detail below with reference to examples and comparative examples. Various tests and evaluations will be carried out as follows. Unless otherwise specified, "parts" and "%" are based on mass.

[0040] Measurement method and apparatus: Measurement of the length of the separator that exceeds the positive electrode piece: The lithium-ion battery was disassembled, the electrode assembly was removed from the outer bag, and the stacked negative electrode, separator, and positive electrode were obtained in order. The length of the portion of the separator that extends beyond the edge of the positive electrode was measured in a μm along the extending direction of the tab of the electrochemical apparatus, i.e., along the width direction of the positive electrode. In the case of a wound electrode assembly, after unfolding the electrode assembly, the stacked negative electrode, separator, and positive electrode were obtained in order, and the length a of the portion of the separator that extends beyond the edge of the positive electrode was measured.

[0041] Measurement of charge and discharge efficiency: The charge-discharge efficiency of lithium-ion batteries was evaluated based on the initial efficiency. In the initial charge-discharge process of the lithium-ion battery, it was charged to 4.45V with a constant current of 0.5C, then charged to 0.025C with a constant voltage of 4.45V, and the resulting charge capacity was defined as C0. After standing for 5 minutes, it was discharged to 3.0V at 0.5C to obtain the discharge capacity D0. The initial efficiency of the full cell = D0 / C0.

[0042] Measurement of cycle stability: The cycle stability of lithium-ion batteries was evaluated by the cycle capacity retention rate. The lithium-ion batteries were placed in a constant temperature test chamber at 25°C and left standing for 30 minutes to allow the batteries to reach a constant temperature. They were charged to 4.45V with a constant current of 0.5C, then charged at a constant voltage until the current reached 0.025C, left standing for 5 minutes, and discharged at a constant current of 0.5C to 3.0V, recording the initial discharge capacity C1. This step was repeated 200 times, and the discharge capacity C2 after 200 cycles was recorded. The cycle capacity retention rate of the lithium-ion battery was then calculated. Cycle capacity retention rate (%) = C2 / C1 × 100%.

[0043] Measurement of the mass percentage of the element silicon: A lithium-ion battery discharged to 3.0V at 0.5C was disassembled, the negative electrode piece was removed, immersed in dimethyl carbonate (DMC) for 20 minutes, and then washed once each with DMC and acetone. The negative electrode piece was then placed in an oven and baked at 80°C for 12 hours to obtain the negative electrode piece. The negative electrode piece was dried in a vacuum oven at 100°C for 24 hours, and a 1g powder sample of the negative electrode material layer on the negative electrode piece was scraped off with a blade. The mass percentage of silicon element in the negative electrode material layer was then measured using an ICP (Inductively Coupled Plasma) analyzer.

[0044] Thermal shock test: A lithium-ion battery was placed in a constant temperature test chamber at 25°C and left undisturbed for 30 minutes to allow the lithium-ion battery to reach a constant temperature. It was then charged to 4.45V with a constant current of 0.5C, and further charged with a constant voltage until the current reached 0.025C. The lithium-ion battery to be measured was placed vertically inside the chamber and heated to T=100°C at a heating rate of 5±2°C and held for 100 minutes. If the lithium-ion battery passed the test, it was heated to T+1°C and kept constant for 100 minutes. The test was stopped when the lithium-ion battery failed the test using a gradient heating method that increased by 1°C each time, and this temperature was recorded as the thermal shock temperature of the lithium-ion battery. The criteria for determining whether a test is pass or fail is that the lithium-ion battery being measured does not ignite or explode during a 100-minute constant temperature period. Three batteries were measured in each group, and a test was deemed pass if all three batteries passed. A test was deemed fail if any one of the batteries ignited or exploded.

[0045] Example 1-1 <Preparation of positive electrode piece> Lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride (PVDF), which are the positive electrode active materials, were mixed in a mass ratio of 95:2.5:2.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75%, which was then uniformly stirred. The slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil positive electrode current collector and dried at 90°C to obtain a positive electrode piece with a coating layer thickness of 110 μm. After the above steps were completed, one side of the positive electrode piece was coated. Then, the above steps were repeated on the other surface of the positive electrode piece to obtain a positive electrode piece with positive electrode active material coated on both sides. After the coating was completed, the positive electrode piece was cut to a size of 74 mm × 867 mm, tabs were welded on, and it was prepared for the next step. After cold pressing, the thickness of the positive electrode material layer on one side was 75 μm, and the compressed density of the positive electrode material layer was 4 g / cm³. 3 That was the case.

[0046] <Preparation of the negative electrode piece> A silicon-carbon composite material (silicon supported in carbon nanopores, with a silicon content of 50% relative to the total mass of the silicon-carbon composite material), artificial graphite, sodium carboxymethylcellulose (CMC-Na) as a negative electrode binder, and styrene-butadiene rubber as a negative electrode binder were mixed in a mass ratio of silicon-carbon composite material:artificial graphite:CMC-Na:styrene-butadiene rubber of 70:20:2:8. Deionized water was added, and the mixture was uniformly mixed under the action of a vacuum stirrer to obtain a negative electrode slurry with a solid content of 30 wt%. A negative electrode slurry was uniformly applied to one surface of a copper foil negative electrode current collector with a thickness of 12 μm, and dried under conditions of 120°C to obtain a negative electrode piece with a coating layer thickness of 143 μm and a negative electrode material layer applied to one side. The above steps were repeated on the other surface of the copper foil to obtain a negative electrode piece with negative electrode material layers applied to both sides, and after cold pressing and cutting, a negative electrode piece with dimensions of 78 mm × 875 mm was obtained. Here, the mass percentage of silicon element relative to the total mass of the negative electrode material layer was 35%. After cold pressing, the thickness of the negative electrode material layer on one side was 80 μm, and the compressed density of the negative electrode material layer was 1 g / cm³. 3 That was the case.

[0047] <Preparation of Electrolyte> In a glove box under an argon gas atmosphere with a water content of <10 ppm, propylene carbonate (PC) and diethyl carbonate (DEC) were mixed in a mass ratio of PC:DEC = 2:8 to obtain a base solvent. Then, lithium hexafluorophosphate (LiPF6), an ethylene carbonate, and the compound of formula (I-1) were added and mixed uniformly to obtain an electrolyte. In this solution, the mass percentage of lithium hexafluorophosphate was 12.5% ​​of the total mass of the electrolyte, the mass percentage of ethylene carbonate was 25%, the mass percentage of the compound of formula (I-1) was 50%, and the remainder was the base solvent.

[0048] <Preparation of the separator> A polyethylene (PE) film with a thickness of b = 15 μm (manufactured by Celgard) was used.

[0049] <Preparation of Lithium-ion Batteries> The prepared positive electrode piece, separator, and negative electrode piece were stacked in order, with the separator positioned midway between the positive and negative electrodes to act as a separator. Along the extending direction of the tab of the electrochemical apparatus, the length a of the portion of the separator that extends beyond the edge of the positive electrode was 5000 μm, and the assembly was wound to obtain the electrode assembly. The electrode assembly was placed in an aluminum plastic film outer bag, dried, and then the electrolyte was injected. A lithium-ion battery was obtained through processes such as vacuum sealing, standing, formation (charging to 4.45V with a constant current of 0.1C, then charging with a constant voltage until the current drops to 0.02C), degassing, and trimming.

[0050] Examples 1-2 to 1-10 In the preparation of the electrolyte, the parameters for the mass percentages of compound (I) and ethylene carbonate were adjusted according to Table 1, the mass percentage of the base solvent was changed accordingly, and the mass percentage of LiPF6 was not changed; otherwise, it was the same as in Example 1-1.

[0051] Examples 1-11 to 1-17 In the preparation of the electrolyte, the procedure was the same as in Examples 1-3, except that the type of compound of formula (I) was adjusted according to Table 1.

[0052] Examples 1-18 to 1-19 In the preparation of the negative electrode piece, the process was the same as in Examples 1-3, except that the mass percentage of silicon element was changed as shown in Table 1 by adjusting the mass percentage of silicon-carbon composite material in the negative electrode material layer, and the mass percentage of artificial graphite also changed accordingly.

[0053] Comparative Examples 1-1 to 1-8 In the preparation of the electrolyte, the parameters related to the content of compound (I) and ethylene carbonate were adjusted according to Table 1, the mass percentage of the base solvent was changed accordingly, and the mass percentage of LiPF6 was not changed; otherwise, it was the same as in Examples 1-3.

[0054] Examples 2-1 to 2-15 In the preparation of the electrolyte, the procedure was the same as in Examples 1-3, except that a cyclic compound containing a sulfur-oxygen double bond and / or fluoroethylene carbonate were added according to Table 2, their mass percentage and the type of cyclic compound containing a sulfur-oxygen double bond were adjusted, the mass percentage of the base solvent was changed accordingly, and the mass percentage of LiPF6 was not changed.

[0055] Examples 3-1 to 3-5 In the <Separator Preparation>, the procedure was the same as in Examples 1-3, except that separators with different parameters were selected so that the values ​​of a, b, and b / a were as shown in Table 3. The preparation parameters and performance parameters for each example and comparative example are shown in Tables 1 to 3.

[0056] [Table 1]

[0057] As can be seen from Examples 1-1 to 1-19 and Comparative Examples 1-1 to 1-8, the examples selected the type of compound of formula (I) within the scope of the present invention and controlled the mass percentage of ethylene carbonate and the mass percentage of silicon element, but the comparative examples did not simultaneously satisfy the above characteristics. Compared with the comparative examples above, the lithium-ion batteries in the examples of the present invention have a higher capacity retention rate and initial efficiency. This indicates that the lithium-ion batteries have better cycle stability and charge / discharge efficiency.

[0058] In the electrolyte, the mass percentage of compound (I) typically affects the charge-discharge efficiency and cycle stability of the lithium-ion battery. As can be seen from Examples 1-1 to 1-5 and Comparative Examples 1-2 to 1-5, when the mass percentage of compound (I) is too high, for example in Comparative Example 1-4, the capacity retention rate and initial efficiency of the lithium-ion battery are low; when the mass percentage of compound (I) is too low, for example in Comparative Example 1-2, the capacity retention rate and initial efficiency of the lithium-ion battery are low; and when compound (I) is not included, for example in Comparative Example 1-5, the capacity retention rate and initial efficiency of the lithium-ion battery are low.

[0059] This indicates that the cycle stability and charge / discharge efficiency of lithium-ion batteries cannot be improved if the mass percentage of compound (I) is too high or too low. By controlling the mass percentage of compound (I) within the range of the present invention, an interfacial film containing a large amount of inorganic material is formed, further improving the ion transport performance of the SEI film and reducing the lithium-ion transport impedance, thereby improving the capacity retention rate and initial efficiency of lithium-ion batteries. This indicates that lithium-ion batteries have better cycle stability and charge / discharge efficiency.

[0060] The presence of EC in the electrolyte and the mass percentage of EC typically affect the charge-discharge efficiency and cycle stability of lithium-ion batteries. As can be seen from Examples 1-3, 1-6 to 1-10, and Comparative Examples 1-1 to 1-4, when the mass percentage of EC is too low, for example in Comparative Example 1-2, the capacity retention rate and initial efficiency of the lithium-ion battery are low; when the mass percentage of EC is too high, for example in Comparative Example 1-3, the capacity retention rate and initial efficiency of the lithium-ion battery are low; and when the electrolyte does not contain EC, for example in Comparative Example 1-1, the capacity retention rate and initial efficiency of the lithium-ion battery are low. This indicates that when the electrolyte does not contain EC, or when the mass percentage of EC is too high or too low, the cycle stability and charge-discharge efficiency of the lithium-ion battery cannot be improved. By controlling the mass percentage of EC within the range of the present invention, the transport performance of lithium ions can be improved, and the lithium-ion battery can have a higher capacity retention rate and initial efficiency. This indicates that the lithium-ion battery has better cycle stability and charge-discharge efficiency.

[0061] The type of compound of formula (I) typically affects the charge-discharge efficiency and cycle stability of lithium-ion batteries. As can be seen from Examples 1-3 and Examples 1-11 to 1-17, by selecting a compound of formula (I) within the scope of the present invention, lithium-ion batteries can have high capacity retention and initial efficiency. This indicates that lithium-ion batteries have good cycle stability and charge-discharge efficiency.

[0062] In the negative electrode material layer, the mass percentage of silicon typically affects the charge-discharge efficiency and cycle stability of lithium-ion batteries. As can be seen from Examples 1-3 and 1-18 to 1-19, by controlling the mass percentage of silicon within the range of the present invention, lithium-ion batteries can have high capacity retention and initial efficiency. This indicates that lithium-ion batteries have good cycle stability and charge-discharge efficiency.

[0063] [Table 2]

[0064] The mass percentage of FEC typically affects the cycle stability and charge / discharge efficiency of lithium-ion batteries. By further adding FEC to the electrolyte and having the mass percentage of FEC within the range of the present invention, the lithium-ion batteries, for example in Examples 2-1 to 2-4, exhibit higher cycle capacity retention and initial efficiency. FEC is a good electrolyte additive for lithium-ion batteries, and by adding FEC to the electrolyte, a crosslinked, highly tough polymer protective layer can be formed at the electrode interface, reducing side reactions between silicon-based materials and the electrolyte. This indicates that the cycle stability and charge / discharge efficiency of lithium-ion batteries are further improved.

[0065] The type and mass percentage of cyclic compounds containing sulfur-oxygen double bonds typically affect the cycle stability and charge-discharge efficiency of lithium-ion batteries. By further adding cyclic compounds containing sulfur-oxygen double bonds to the electrolyte, and by having the type and mass percentage of these compounds fall within the range of the present invention, lithium-ion batteries exhibit higher cycle capacity retention and initial efficiency, as seen in Examples 2-5 to 2-7 and 2-15. The sulfur-oxygen double-bond-containing compounds and the compound of formula (I) can work synergistically during the film formation process, which is advantageous for forming a SEI film on the negative electrode surface with better stability and ion transport performance. This indicates that the cycle stability and charge-discharge efficiency of lithium-ion batteries are further improved.

[0066] As can be seen from Examples 1-3 and 2-8 to 2-13, when the electrolyte contains both FEC and a cyclic compound containing a sulfur-oxygen double bond, the FEC and the compound containing the sulfur-oxygen double bond, along with the compound of formula (I), work synergistically during the film formation process, allowing the lithium-ion battery to have a high capacity retention rate and initial efficiency. This indicates that the lithium-ion battery has good cycle stability and charge-discharge efficiency.

[0067] [Table 3]

[0068] The length of the separator beyond the positive electrode and the thickness of the separator typically affect the cycle stability, charge / discharge efficiency, and thermal shock performance of lithium-ion batteries. As can be seen from Examples 1-3 and 3-1 to 3-5, when the values ​​of a and b / a are within the range of the present invention, lithium-ion batteries have high cycle capacity retention, initial efficiency, and thermal shock temperature. This indicates that lithium-ion batteries have good cycle stability and charge / discharge efficiency, as well as good thermal shock performance.

[0069] The above describes only preferred embodiments of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. An electrochemical apparatus comprising a negative electrode piece and an electrolyte, The aforementioned negative electrode piece includes a negative electrode material layer, The aforementioned negative electrode material layer contains silicon, The mass percentage of the silicon element relative to the total mass of the negative electrode material layer is 20% to 50%. The electrolyte comprises a compound of formula (I) and ethylene carbonate. 【Chemistry 1】 R １ is selected from a fluorine atom, a C １ -C ６ alkyl group that is at least partially substituted with fluorine, a C ６ -C １０ aryl group that is at least partially substituted with fluorine, a C １ -C ６ oxygen-containing alkyl group that is at least partially substituted with fluorine, a C ６ -C １０ oxygen-containing aryl group, and in the said R １ the O atom is not directly bonded to the S atom. R ２ and R ３ Each of these is independently an unsubstituted or partially fluorinated C １ ~C ５ alkyl groups, unsubstituted or partially fluorinated C ６ ~C １０ Selected from the aryl groups, R ２ and R ３ They may be connected to form a ring. An electrochemical apparatus in which the mass percentage of ethylene carbonate relative to the total mass of the electrolyte is 5% to 40%.

2. The compound of formula (I) is represented by the following formulas (I-1) to (I-35): 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 The electrochemical apparatus according to claim 1, comprising at least one compound from among the compounds represented by .

3. The electrochemical apparatus according to claim 1, wherein the mass percentage of ethylene carbonate is 10% to 30% of the total mass of the electrolyte.

4. The electrochemical apparatus according to claim 1, wherein the mass percentage of the compound of formula (I) is 3% to 50% of the total mass of the electrolyte.

5. The electrochemical apparatus according to claim 1, wherein the mass percentage of the compound of formula (I) is 10% to 40% of the total mass of the electrolyte.

6. The electrochemical apparatus according to claim 1, wherein the electrolyte further contains fluoroethylene carbonate, and the mass percentage of the fluoroethylene carbonate is 5% to 30% of the total mass of the electrolyte.

7. The electrochemical apparatus according to claim 1, wherein the electrolyte further contains fluoroethylene carbonate, and the mass percentage of the fluoroethylene carbonate is 10% to 30% of the total mass of the electrolyte.

8. The electrolyte contains a cyclic compound containing a sulfur-oxygen double bond, and the cyclic compound containing a sulfur-oxygen double bond contains at least one of 1,3-propanesultone, 1,4-butanesultone, and 2,4-butanesultone. The electrochemical apparatus according to claim 1, wherein the mass percentage of the cyclic compound containing the sulfur-oxygen double bond is 0.1% to 5% with respect to the total mass of the electrolyte.

9. The electrochemical apparatus includes a separator and a positive electrode piece. The electrochemical apparatus according to any one of claims 1 to 8, wherein, along the extending direction of the tab in the electrochemical apparatus, the length of the separator beyond the positive electrode piece is a μm, and the thickness of the separator is b μm, such that a and b satisfy 0.0008 ≤ b / a ≤ 0.009 and 1000 ≤ a ≤ 5000.

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

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