Battery and electrical device

Abstract

Battery comprising a battery cell and an electrolyte, wherein the battery cell comprises a negative electrode and a separator, the negative electrode comprises a current collector and a layer of negative active material, the layer of negative active material comprises a silicon-based material, and the separator comprises a base film and a coating layer; characterized by the fact that the mass fraction of the element silicon in the layer of negative active material a is; the viscosity of the electrolyte b cP is; the percentage value of the thickness of the coating layer in relation to the thickness of the separator c is and 0.037 ≤ a*b / c ≤ 5.625.

Description

TECHNICAL AREA

[0001] The present invention relates to the field of batteries and in particular to a battery and an electrical device. BACKGROUND

[0002] A lithium battery includes a battery cell consisting of a positive electrode, a negative electrode and a separator, an electrolyte filled into the battery cell, and a battery casing containing the battery cell and the electrolyte; the negative electrode of a conventional battery consists of a current collector and a layer of negative active material applied to the current collector.

[0003] For the negative active material in the negative active material layer, graphite or carbon with a graphite-like structure, etc., is conventionally used. To improve the energy density of a battery, the conventional negative active material layer can be doped with silicon. However, an increased silicon content in the negative electrode leads to increased expansion of the negative electrode, poor electrolyte wetting, and poor fast-charging performance of the battery. SUMMARY

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the disadvantage of the prior art in which an increase in the silicon content in the negative electrode results in poor fast charging performance of the battery, thereby providing a battery and an electrical device with which the above problem is solved.

[0005] To solve the above problem, the present invention provides a battery comprising a battery cell and an electrolyte, wherein the battery cell has a negative electrode and a separator, the negative electrode has a current collector and a layer of negative active material, the layer of negative active material has a silicon-based material, and the separator has a base film and a coating layer; the mass fraction of the element silicon in the layer of negative active material is a; the viscosity of the electrolyte is cP; the percentage of the thickness of the coating layer in relation to the thickness of the separator is c and 0.037 ≤ a*b / c ≤ 5.625.

[0006] The present invention also provides an electrical device which includes the aforementioned battery.

[0007] The advantageous effects of the present invention are as follows: By adjusting the mass fraction a of the element silicon in the layer of the negative active material, the viscosity b cP of the electrolyte and the percentage c of the thickness of the coating layer in relation to the thickness of the separator, by comprehensively controlling the value of a*b / c so that it lies in the range of 0.037 - 5.625, the wetting effect of the electrolyte at the negative electrode and the fast charging performance of the battery can be improved. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0008] The following embodiments are listed for a better, broader understanding of the present invention and are neither limited to the best embodiments described nor do they constitute limitations on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention and that is obtained by anyone through inspiration of the present invention or by combining features of the present invention with other features of the prior art falls within the scope of protection of the present invention.

[0009] For experimental steps or conditions not specified in the embodiments, procedures or conditions may be carried out or set according to conventional experimental steps described in the literature in this field. Reagents or instruments without manufacturer's information are all conventional reagent products that are commercially available.

[0010] The “ranges” disclosed in the present invention are defined by lower and upper limits, wherein a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of a specific range. The ranges defined in this way may or may not include the endpoint values ​​and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 50%–90% and 60%–80% are listed for a specific parameter, it is agreed that ranges of 50%–80% and 60%–90% are also provided.

[0011] A battery comprises a battery cell and an electrolyte; the battery cell comprises a negative electrode and a separator; the negative electrode comprises a current collector and a layer of negative active material; the layer of negative active material comprises a silicon-based material; and the separator comprises a base film and a coating layer; the mass fraction of the element silicon in the layer of negative active material is a; the viscosity of the electrolyte is b cP; the percentage of the thickness of the coating layer relative to the thickness of the separator is c and 0.037 ≤ a*b / c ≤ 5.625. This means that the value of a*b / c can take any value between 0.037 and 5.625, for example: 0.037, 0.05, 0.1, 0.15, 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.625 etc.

[0012] The present invention allows the wetting effect of the electrolyte at the negative electrode and the fast-charging performance of the battery to be improved by adjusting the silicon content (a), the viscosity (b cP) of the electrolyte, and the percentage (c %) of the coating layer thickness relative to the separator thickness, by comprehensively controlling the value of a*b / c to lie within the range of 0.037 to 5.625. During a battery's charging and discharging process, when the silicon content is high, the volume expansion of the active material layer is significant, causing the internal pores of the electrode to enlarge and requiring electrolyte filling. If the electrolyte viscosity is too high, poor electrode wetting, which is detrimental to lithium ion transport, and reduced fast-charging performance will result.Therefore, a lower viscosity of the electrolyte is required to quickly and completely fill the pores and thus wet the negative electrode; consequently, if the silicon content is high, the viscosity b cP of the electrolyte must not be too high. Furthermore, the separator coating layer exhibits a certain fluid retention capacity; when the electrode expands and compresses the separator, electrolyte is forced out of the separator, and during the expansion of the negative electrode, more pores can absorb the forced-out electrolyte, thus facilitating electrolyte penetration into the electrode. Therefore, the thickness of the coating layer in the separator must not be too small, i.e., the percentage c of the coating layer thickness relative to the thickness of the separator must not be too small. Additionally, the viscosity of the electrolyte must not be too low.The electrolyte contains a solvent and a solute; the higher the viscosity, the stronger the interaction between the solute and the solvent; the lower the viscosity, the weaker the interaction between the solvent and the solute. Therefore, lower viscosity results in inconsistent transport rates between the solute and the solvent, leading to a severe mismatch in these rates and consequently poor electrode wettability. Furthermore, the thickness of the coating layer in the separator must not be too great. Generally, the battery's injection volume is fixed; if the coating layer thickness in the separator is relatively large, the separator absorbs more electrolyte, leaving relatively less electrolyte available for the electrode, and so on.Although some electrolyte may be released from the separator to the negative electrode during subsequent expansion during charging, a smaller initial amount of electrolyte is also achieved on the negative electrode side. In summary, the present invention effectively improves the wetting of the negative electrode, and consequently improves the fast-charging performance of the battery, by comprehensively controlling the mass fraction a of elemental silicon in the layer of negative active material, the viscosity b of the electrolyte, and the percentage c of the coating layer thickness relative to the thickness of the separator such that 0.037 ≤ a*b / c ≤ 5.625.

[0013] Adding silicon to a negative active material can improve the energy density of a battery. The silicon in the negative active material layer can originate from a silicon-carbon material and / or a silicon-oxygen material; "silicon content" refers to the mass fraction *a* of silicon in the negative active material layer, and this content *a* is controlled to be between 0.5% and 30%. For example, *a* is controlled to be 0.5%, 1%, 2%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, etc.

[0014] In a preferred embodiment, the silicon content (a) is controlled to be between 2% and 16%. In particular, it is preferred in the present invention that negative electrodes with a higher silicon content improve the energy density of the battery. However, the silicon content must not be too high, as this would cause increased expansion of the negative electrode, resulting in enlarged electrode pores and an increased need for electrolyte wetting of the electrode. Therefore, in the present invention, the silicon content (a) in the layer of the negative active material is preferably controlled to be between 2% and 16%.

[0015] The viscosity b of the electrolyte influences its wetting effect. In the present invention, the viscosity of the electrolyte is controlled so that it falls within the range of 1.5 to 3.7 cP; for example, b is controlled to be 1.5, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.7, etc.

[0016] In a preferred embodiment, the viscosity of the electrolyte is preferably controlled to be in the range of 2.1–2.8 cP; in particular, electrolytes with a lower viscosity are preferred in the present invention to improve the flowability of the electrolyte and to enhance the wetting effect of the electrolyte on the electrode. However, the viscosity of the electrolyte must not be too low, because an excessively low viscosity causes a severe mismatch between the transport rate of the solvent and the transport rate of the solute in the electrolyte, resulting in poor wettability of the electrode; therefore, the viscosity of the electrolyte is preferably controlled to be in the range of 2.1–2.8 cP, thereby improving the wetting effect of the electrolyte on the electrode.

[0017] The separator comprises a base film and a coating layer, the coating layer being arranged on the surface of the base film; the coating layer generally comprises inorganic and organic components; the coating layer has a porous structure with liquid absorption capacity, and the liquid absorption capacity is related to the thickness of the coating layer; the liquid absorption capacity of the separator can be adjusted by controlling the percentage c of the thickness of the coating layer relative to the thickness of the separator; in the present invention, the percentage c of the thickness of the coating layer relative to the thickness of the separator can be controlled to be between 8% and 50%; for example, c is controlled to be 8%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.

[0018] In a preferred embodiment, the percentage c of the coating layer thickness relative to the separator thickness is preferably controlled to fall within the range of 13% to 32%; in particular, it is preferred in the present invention that a higher percentage c of the coating layer thickness relative to the separator thickness improves the liquid absorption capacity of the coating layer; however, the percentage c of the coating layer thickness relative to the separator thickness must not be too high, because an excessively high percentage results in excessive liquid absorption capacity of the coating layer, and if the amount of injected electrolyte is fixed, most of the electrolyte will be absorbed by the separator, resulting in lower initial electrolyte absorption by the negative electrode, a poor lithium-ion transport rate, and poor fast-charging performance of the battery;Therefore, in the present invention, c is preferably controlled such that it is 13% - 32%, which is more conducive to providing the separator with a more suitable quantity of the electrolyte to be released for wetting the electrode during the subsequent process of electrode expansion.

[0019] Furthermore, the wetting of the negative electrode and the fast charging performance are improved according to the present invention by controlling the value of a*b / c so that it lies within a more preferred range. For example, the value of a*b / c is controlled so that it lies between 0.165 and 2.585.

[0020] If the silicon-based material comprises a silicon-carbon material, the silicon-carbon material has a porous carbon matrix and silicon particles, wherein the silicon particles are pure silicon crystals embedded in the porous carbon matrix, and the pores of the porous carbon itself can serve to reduce expansion, thereby reducing the expansion of the electrolyte, enabling a suitable increase in the viscosity of the electrolyte and a suitable reduction in the amount of electrolyte absorbed by the separator; therefore, the value of a*b / c is preferably 0.431 - 1.05.

[0021] The energy density of the battery is related to the degree of compaction of the negative electrode. By appropriately increasing the degree of compaction, the contact between particles can be improved, thereby increasing the electron conductivity of the negative electrode, which is beneficial for improving the energy density of the battery; in the present invention, the degree of compaction of the negative electrode is 1.25–1.8 g / cm³. 3 ; for example: 1.25 g / cm³ 3 , 1.3 g / cm³ 3 , 1.4 g / cm³ 3 , 1.5 g / cm³ 3 , 1.6 g / cm³ 3 , 1.7 g / cm³ 3 , 1.8 g / cm³ 3 , etc.

[0022] An increased degree of compaction is beneficial for improving the battery's energy density; however, at a higher degree of compaction, the electrode pores become smaller, and the initial amount of electrolyte that can be absorbed by the electrode decreases. The viscosity b of the electrolyte can be reduced, and the range of a*b / c can be further controlled to ensure complete wetting of the pores with the electrolyte. Furthermore, the percentage c of the coating layer thickness relative to the separator thickness can be advantageously increased to enhance the separator's fluid retention, thereby facilitating the rewetting of the electrode after subsequent electrolyte removal from the separator. In particular, the value of a*b / c is 1.45–1.8 g / cm³ when the degree of compaction of the negative electrode is 1.45–1.8 g / cm³. 3preferably 0.333 - 0.820, which improves the wetting of the negative electrode and the fast charging performance.

[0023] The electrolyte contains a solvent and a lithium salt; The solvent is selected from carbonate esters, carboxylic acid esters, ethers, sulfones, nitriles, phosphate esters or fluorides of the above solvents; The lithium salt is selected from lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonate, lithium bis(fluoromethane)sulfonylimide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorobis(oxalato)phosphate and lithium tetrafluoro(oxalato)phosphate.

[0024] To reduce the viscosity of the electrolyte, the solvent contains at least 10% - 60% carbonate ester solvent and 0% - 50% carboxylic acid ester solvent; and / or the concentration of the lithium salt in the electrolyte is 0.8 - 2.5 M; for example: 0.8 M, 0.9 M, 1.0 M, 1.2 M, 1.5 M, 1.8 M, 2.0 M, 2.3 M, 2.5 M.

[0025] With regard to the separator, the coating layer contains inorganic components with good liquid retention capacity. The thickness of the coating layer must not be too great, because excessive thickness leads to high electrolyte absorption by the separator, with most of the electrolyte being absorbed by the separator and thus reducing the amount of electrolyte available to the negative electrode. Furthermore, the thickness of the coating layer must not be too small, because the coating layer possesses a certain liquid retention capacity that can be used to effectively supplement the negative electrode with electrolyte during the subsequent long cycling process. Therefore, the thickness of the coating layer is preferably 1–7 µm; for example: 1 µm, 2 µm, 3 µm, 4 µm, 5 µm, 6 µm, 7 µm, etc.

[0026] The inorganic component contained in the coating layer is selected from aluminium oxide, boehmite, silicon dioxide, zirconium oxide, titanium dioxide, cerium oxide and magnesium aluminate, etc.

[0027] An electrical device comprises the above battery; and the battery has a positive electrode, and the positive active material in the positive electrode comprises LiNi. x Co y Mn z O2, where 1 > x ≥ 0.5, x+y+z= 1.

[0028] The following is a detailed description of the embodiments of the battery and the electrical device disclosed in the present invention. However, unnecessarily detailed descriptions may be omitted. For example, detailed descriptions of well-known substances and repeated descriptions of essentially identical structures may be left out. This is to avoid unnecessary length in the following description and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand the present application and is not intended to limit the subject matter specified in the claims. [Battery]

[0029] The battery of the present invention is a secondary battery, also known as a rechargeable battery or accumulator, which refers to a battery that can be reused after a discharge by reactivating the active materials through charging.

[0030] A typical battery consists of a battery cell, an electrolyte, and an outer casing; the battery cell has a positive electrode, a negative electrode, and a separator. During charging and discharging, active ions (such as lithium ions) move back and forth between the positive and negative electrodes through insertion and extraction. The separator is positioned between the positive and negative electrodes, primarily serving to prevent a short circuit between them while allowing the passage of active ions. The electrolyte between the positive and negative electrodes primarily serves to conduct the active ions.

[0031] For example, the process for manufacturing a battery is as follows: The positive electrode, the separator, and the negative electrode are layered on top of each other in that order, with the separator located between the positive and negative electrodes for insulation; this is then wound up, resulting in an unencapsulated battery cell; the unencapsulated battery cell is arranged in the outer packaging shell, dried, and the electrolyte is injected, followed by vacuum packaging, standing, formation, shaping, and other processes, resulting in a secondary battery. [Positive electrode]

[0032] The positive electrode typically comprises a positive current collector and a positive film layer arranged on at least one side of the positive current collector. The positive film layer includes a positive active material, a conductive agent, and a binder, with any conventional positive material being suitable for use as the positive active material.

[0033] The process for manufacturing the above positive electrode is as follows: the positive active material, the conductive agent, the binder, and any other components are dispersed in a solvent, stirred in a vacuum mixer until the system becomes homogeneous, thereby obtaining a positive slurry; the positive slurry is applied homogeneously to both surfaces of the aluminum foil of the positive current collector, dried in air at room temperature, then transferred to an oven for further drying, followed by cold pressing and cutting, thereby obtaining the positive electrode.

[0034] In the present invention, the positive active material is a conventional positive active material in the field of batteries, for example: a ternary positive material LiNi. x Co y Mn z O2 etc., where 1 > x ≥ 0.5, x + y + z = 1.

[0035] The conductive medium serves to improve the conductivity between particles of the positive active material. In the present invention, the conductive medium can be conventional options in the field of batteries, for example: carbon nanotubes, carbon black, or graphene, etc.

[0036] The binder serves to improve the adhesion between particles of the positive active material and between the positive active material and the current collector. In the present invention, the binder can be a conventional option in the field of batteries. For example, the binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin, sodium carboxymethylcellulose (CMC), and / or sodium alginate.

[0037] In the present invention, the solvent is used to achieve a uniform dispersion of the positive active material, the conductive agent and the binder, and can be conventional solvent types in the field of batteries, for example: N,N-dimethylacetamide, dimethyl sulfoxide, trimethyl phosphate, dimethyl carbonate, N,N-dimethylformamide, etc.

[0038] The present invention is not subject to any specific limitation with respect to the positive current collector, as long as it has conductivity and does not cause adverse chemical changes in the battery, and for this purpose, for example, the following can be used: stainless steel, aluminum, nickel, titanium, burnt carbon or aluminum or stainless steel that has been subjected to a surface treatment with carbon, nickel, titanium or silver, etc. [Negative electrode]

[0039] The negative electrode comprises a negative current collector and a layer of negative active material arranged on at least one side of the negative current collector. The layer of negative active material includes conventional silicon-based materials used in batteries, as well as other negative active materials; the silicon-based material includes silicon-carbon and / or silicon-oxygen materials; other negative active materials include synthetic graphite, natural graphite, etc.

[0040] The present application does not restrict the method for producing a silicon-carbon material. In particular, it can be produced by a vapor deposition (CVD) process; specifically, a silane gradually decomposes by the adsorption capacity of porous carbon at 450–500 °C, forming the element silicon, which is deposited in the carbon framework; an acetylene-carbon coating (500–550 °C) forms a stable carbon coating layer on the silicon-carbon surface, ultimately yielding a silicon-carbon material, which is not described further here. In the present invention, the number of silicon particles deposited in porous carbon can be controlled by controlling the silane flow rate and the deposition time.

[0041] In some embodiments, the conductive agent serves to improve the conductivity between particles of the negative active material. The layer of the negative active material may optionally comprise a conductive agent, which in the present invention may be conventional options in the field of batteries; for example, the conductive agent may be selected from carbon nanotubes, carbon black, or graphene.

[0042] The binder serves to improve the adhesion between particles of the negative active material and between the negative active material and the current collector. In the present invention, the binder can be a conventional option in the field of batteries. For example, the binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin, sodium carboxymethylcellulose (CMC), and / or sodium alginate.

[0043] In some embodiments, the negative current collector is, for example, a copper foil.

[0044] In some embodiments, the negative electrode can be produced by the following process: the above components for producing the negative electrode, such as the negative active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (such as water), forming a negative slurry; the negative slurry is applied to the negative current collector, followed by drying, rolling, cutting, and other operations, thereby obtaining the negative electrode. [Electrolyte]

[0045] The electrolyte serves to conduct ions between the positive electrode and the negative electrode.

[0046] The electrolyte comprises a solvent and a solute. In the present invention, the type of solute in the electrolyte, which can be selected according to requirements, is not subject to any specific limitation. For example, the electrolyte in the present invention can be various electrolytes applicable to electrochemical energy storage devices in this field. The solute typically comprises a lithium salt, and the solvent is an organic solvent.

[0047] In particular, the concentration of the lithium salt in the electrolyte is 0.8 - 2.5 M, and the lithium salt is selected from lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(oxalato)borate (LiBOB), lithium difluorobis(oxalato)phosphate (LiDFOP), lithium trifluoromethanesulfonate (LiTFS), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB) and / or lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0048] In particular, the solvent is selected from carbonate esters, carboxylic acid esters, ethers, sulfones, nitriles, phosphate esters, or fluorides of the solvents listed above; the solvent contains at least 10% to 60% carbonate ester solvent and 0% to 50% carboxylic acid ester solvent. For example, the solvent contains fluoroethylene carbonate (FEC), propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propionate (EP), ethyl acetate (EA), acetonitrile (AN), and / or trifluoroethanol (TFEA). [Separator]

[0049] In the present invention, a separator with a base film and a coating layer is used.

[0050] In the present invention there is no specific restriction with regard to the type of base film, and any known base film with a porous structure with good chemical resistance and mechanical resistance can be used; in some embodiments, the base film is, for example, PP or PE.

[0051] The coating layer in the present invention comprises an inorganic component; the inorganic component is selected from aluminum oxide, boehmite, silicon dioxide, zirconium oxide, titanium dioxide, cerium oxide and magnesium aluminate, etc.; in some embodiments, the coating layer also comprises an organic component, and the organic component is selected from polyvinylidene fluoride, polymethyl methacrylate, aramid, etc. Example 1

[0052] A battery comprising a battery cell and an electrolyte, wherein the battery cell has a negative electrode and a separator, the negative electrode has a current collector and a layer of negative active material, the layer of negative active material has a negative active material, the negative active material has a silicon-based material, the silicon-based material is a silicon-carbon material, and the separator has a base film and a coating layer. 1. Production of the positive electrode

[0053] The specific process for manufacturing the positive electrode is as follows: the positive active material LiNi x Co y Mn zO2 (x = 0.92, y = 0.05, z = 0.03), the conductive agent acetylene carbon black and the binder PVDF are mixed in a mass ratio of 92:4:4, the solvent NMP is added, the mixture is stirred in a vacuum mixer until the system becomes homogeneous, resulting in a positive slurry; the positive slurry is applied evenly to both surfaces of the aluminum foil of the positive current collector, dried in air at room temperature, then transferred to an oven for further drying, followed by cold pressing and cutting, resulting in the positive electrode. 2. Production of the negative electrode

[0054] The specific manufacturing process is as follows: a negative active material, the conductive agent carbon black, the thickening agent CMC, and the binder SBR are mixed in a mass ratio of 96.4:1:1.2:1.4; deionized water is added as a solvent; the mixture is stirred in a vacuum mixer until homogeneous, resulting in a negative slurry; the negative slurry is applied uniformly to both surfaces of copper foil, the negative current collector; it is air-dried at room temperature, then transferred to an oven for further drying, followed by cold pressing and cutting to obtain the negative electrode; the density of the negative electrode obtained after cold pressing is listed in Table 1, and the density of the negative electrode in this embodiment is 1.6 g / cm³ 3 amounts.

[0055] In the present invention, the negative active material is obtained by mixing artificial graphite and a silicon-carbon material with a mass ratio of (40-99):(1-60), wherein the artificial graphite and the silicon-carbon material in this embodiment are mixed with a mass ratio of 65.2:34.8, as shown in Table 1; the silicon-carbon material is produced by a gaseous vapor deposition (CVD) process, in particular by means of the adsorption capacity of porous carbon at a deposition temperature of 450 °C, wherein a silane decomposes at the high temperature to form gaseous silicon and hydrogen, with gaseous silicon being deposited in the carbon matrix, i.e.The carbon framework is gradually infiltrated by gaseous silicon under these conditions. After the deposition of the silicon matrix is ​​complete, a carbon coating layer must be created to prevent exposure of pure silicon to air. This is achieved by depositing acetylene carbon onto the silicon-carbon surface at a carbon coating temperature of 550 °C, thereby forming a stable silicon-carbon material. In the production of a silicon-carbon material according to the present invention, the decomposition of silane and the simultaneous deposition process take place at a high temperature, with the silane flow rate controlled to be 18 l / min and the deposition time being 15 h, thus producing a silicon-carbon material with a silicon content of 50%. 3. Procurement of the separator

[0056] The separator in this embodiment is a commercial product comprising a base film and a coating layer, with the separator parameters shown in Table 1. In this embodiment, the base film material is PP, the thickness of the base film is 12 mm, the inorganic component in the coating layer is aluminum oxide, and the thickness of the coating layer is 1.5 mm. 4. Preparation of an electrolyte

[0057] The specific manufacturing process is as follows: various solvents are mixed in an argon-filled glovebox to obtain an organic solvent. In this embodiment, fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and propylene carbonate (PC) are mixed in a mass ratio of 15:20:60:5. Then, thoroughly dried lithium salt (LiPF6) is dissolved in the organic solvent mixture, followed by the addition of 0.5% 1,3-propanesultone, 0.5% tris(trimethylsilyl) phosphate, and 1% vinyl sulfate, based on the electrolyte. The mixture is stirred until complete dissolution, producing an electrolyte with a lithium salt concentration of 2.5 M, as shown in Table 1. 5. Battery installation

[0058] The specific process is as follows: The above positive electrode, separator, and negative electrode are layered on top of each other in this order, with the separator located between the positive and negative electrodes for insulation; this is then wound up, resulting in an unencapsulated battery cell; the unencapsulated battery cell is placed in the outer packaging shell, dried, and the electrolyte is injected, followed by vacuum packaging, standing, capacity adjustment, and other procedures, resulting in a lithium-ion battery. Examples 2-12 and comparative examples 1-2

[0059] A secondary battery that differs from Example 1 in that the parameter conditions for the manufacture of the negative electrode, the acquisition of the separator and the manufacture of the electrolyte are different, with different parameters shown in Table 1 below and others being completely identical to Example 1. Table 1 Artificial graphite: Silicon-based material Type of material: silicon-based Thickness of the base film Type of base foil Thickness of the coating layer Type of coating layer Solvent composition Type of lithium salts Concentration of lithium salts degree of compaction Example 1 65,2:34,8 SiC 12 PP 1,5 Aluminum oxide FEC:EMC:DMC:PC = 15:20:60:5 LiPF6 2,5 M 1,6 Example 2 99:1 SiC 8 PP 3 Aluminum oxide FEC:EMC:TFEA = 20:20:60 LiFSI 0,8 M 1,6 Example 3 74,2:25,8 SiC 10 PE 1,5 Boehomite FEC:EMC:TFEA = 20:20:60 LiPF6 1,2 M 1,6 Example 4 95,6:4,4 SiC 7 PP 3 Aluminum oxide FEC:EMC:DMC:AN=15:20:60:5 LiPF6 1,1 M 1,6 Example 5 77:23 SiC 7 PP 3 Aluminum oxide FEC:EMC:TFEA = 20:20:60 LiPF6 0,8 M 1,6 Example 6 94,8:5,2 SiC 9 PP 1,5 Aluminum oxide FEC:EMC:DMC:AN=15:20:60:5 LiPF6 1,1 M 1,6 Example 7 77:23 SiC 8,5 PP 3 Aluminum oxide FEC:EMC:TFEA = 20:20:60 LiPF6 0,8 M 1,6 Example 8 66,8:33,2 SiO 9 PP 1,5 Aluminum oxide FEC:EMC:TFEA = 20:20:60 LiPF6 1,2 M 1,4 Example 9 95,2:4,8 SiC 7 PP 3 Aluminum oxide FEC:EMC:TFEA = 20:20:60 LiPF6 0,8 M 1,6 Example 10 95,6:4,4 SiC 12 PP 1,5 Aluminum oxide FEC:EMC:EA = 20:10:70 LiPF6 0,8 M 1,6 Example 11 68,8:31,2 SiO 7 PP 4,5 Aluminum oxide EC:EMC:DEC:FEMC20:30:30:20 LiPF6 1,1 M 1,4 Example 56,4:43,6 SiC 11 PP 7 Aluminum FEC:EMC: LiFSI 0,6 M 1,6 12 moxid EA = 20:10:70 Comparison example 1 37,8:62,2 SiC 12 PP 1,5 Aluminum oxide EC:EMC:DEC:FEMC20:30:30:20 LiPF6 1,0 M 1,6 Comparison example 2 98,8:1,2 SiC 7 PP 5 Aluminum oxide FEC:EMC:EA = 20:10:70 LiPF6 0,7 M 1,6

[0060] Determination of a, b and c for the batteries of the above examples and comparison examples.

[0061] Determination of a: Determination of the mass fraction a of the element silicon in the layer of negative active material, wherein the determination method is as follows: Pretreatment: The negative electrode is washed with the solvent DMC, dried at 60 °C, and powder is scraped off.

[0062] The sample is weighed, placed in a nickel crucible previously filled with potassium hydroxide, and the sample surface is covered with a small amount of potassium hydroxide. Two drops of ethanol are added, and the mixture is heated in an electric furnace until the potassium hydroxide melts and dehydrates. It is then transferred to a muffle furnace at 1100 °C, where the melting temperature is maintained for 8 hours. The nickel crucible is removed, and the mixture is allowed to cool slightly. The crucible is placed in a 300 mL plastic beaker, and hot water is added for extraction. After the reaction, the crucible is removed, and the beaker is acidified with HCl. Hydrogen peroxide is added, and after cooling, other impurities are filtered off. The filtered solution is transferred to a 100 mL volumetric flask, filled to volume, and shaken well.After standing, a portion of the solution is transferred to another 100 mL volumetric flask, filled to volume, shaken well, and allowed to settle until clear and ready for testing. A blank solution is also prepared, corresponding to a solution obtained by following the above steps without the addition of a sample. Then, suitable operating conditions for the ICP instrument are set, including a gas flow rate of 0.5 l / min, a power of 1150 W, and a wavelength of 288.158 nm for determining silicon, depending on the sample characteristics and the elements to be detected; the silicon content is then tested by ICP.

[0063] Determination of b: Determination of the viscosity b of the electrolyte, wherein the determination method is as follows: The battery was fully charged, disassembled, and the battery cell removed. The battery cell was sealed in an aluminum-plastic bag and compressed using a press to extract the remaining electrolyte. A syringe was used to pierce the bag and isolate the electrolyte. The extracted electrolyte was then tested using a Cambridge viscometer. The Cambridge viscometer's design principle is based primarily on a technology for determining viscosity by electromagnetic oscillations, employing a magnetically suspended probe to measure the viscosity. Specifically, the electrolyte was placed in a beaker, and the sample temperature was maintained at 25 °C for testing. The reading was recorded after the displayed value had stabilized. The viscosity b of the electrolyte in this embodiment is listed in Table 2.

[0064] Determination of c: Tests of the percentage value c of the thickness of the coating layer in relation to the thickness of the separator, wherein two test procedures included the following: a. The thickness of the separator H1 is measured with a micrometer; the coating layer is removed from the surface of the separator with a tape, and the thickness of the base film H2 is measured with the micrometer; thus, the thickness of the coating layer is (H2-H1) / n, where n = 1 or 2; b. Obtaining the cross-section of the separator using SEM, where the thickness of the coating layer and the thickness of the base film are measured with a scanning electron microscope.

[0065] In this embodiment, the scanning electron microscope is used to measure the thickness of the coating layer and the thickness of the base film, with the resulting percentage value c of the thickness of the coating layer relative to the thickness of the separator being shown in Table 2.

[0066] Test 1 - Fast charging capability at a SOC of 10 - 80%: a. A battery was charged with a constant current of 0.33 C up to an upper voltage limit of 4.25 V, then discharged with a constant voltage until the forward current was less than or equal to 0.05 C; The above steps were repeated 3 times, with the third discharge capacity being used as the battery's discharge capacity; b: Based on the battery capacity in a, the battery was charged at 0.33 C up to a 10% SOC; this was recorded as T0 and c: Then, charging was carried out at 4C, 3.5C, 3.0C, 2.75C, 2.5C, 2.25C, 2.0C, 1.75C, 1.5C, 1.25C, 1C and 0.33C up to discharge cut-off voltages of 3.95V, 3.97V, 3.985V, 3.996V, 4.005V, 4.015V, 4.025V, 4.045V, 4.067V, 4.091V, 4.11V and 4.25V respectively, with the time T1 for charging the battery to an 80% SOC being recorded and T1 - T0 being the fast charging duration in units of minutes.

[0067] Test 2 - Energy density test: a: The battery was charged with a constant current of 0.33 C up to an upper voltage limit of 4.25 V, then discharged with a constant voltage until the forward current was less than or equal to 0.05 C; The above steps were repeated 3 times, with the third discharge energy being used as the battery's discharge energy E; b: The weight M of the battery was measured using an electronic scale and c: Calculation of gravimetric energy density: E / M in units of Wh / kg.

[0068] Test 3 - Cycle lifetime test at 25 °C: The lithium-ion battery was held at 25°C for 120 minutes, charged at a constant current of 0.5C to a discharge cut-off voltage of 4.25V, and then charged at a constant voltage until the forward current reached ≤0.05C. It was left to stand for 10 minutes and then discharged at a constant current of 0.5C to 2.5V. The above steps constitute one cycle. These steps were repeated until the state of health (SOH) reached 80%, and the number of cycles was recorded.

[0069] The test results above are shown in Table 2, Table 3 and Table 4 below. Table 2 / a b c ABC Fast charging capability Energy density Cycle duration r Example 1 16,80 % 3,68 11,11% 5,564 22,5 346,6 706 Example 3 12,40 % 2,69 13,04% 2,557 17,0 340,3 1008 Example 5 11,10 % 2,21 30,00% 0,818 14,8 334,4 1232 Example 7 11,10 % 2,19 23,20% 1,048 16,8 335,0 1115 Example 8 16,00 % 2,69 14,29% 3,013 19,0 341,0 780 Example 11 15,00 % 3,21 39,13% 1,231 17,0 338,0 916 Example 12 21,00 % 1,51 38,89% 0,815 15,4 342,6 864 Comparative example 1 30,00 % 2,39 11,11% 6,453 25,0 352,1 415 Table 3 / a b c ABC Test 1 Test 2 Test 3 Example 2 0,50% 2,08 27,27% 0,038 20,8 279,7 2180 Comparative example 2 0,60% 1,71 41,67% 0,025 22,6 257,8 1650 Table 4 / a b c ABC Test 1 Test 2 Test 3 Example 4 2,10 % 2,51 30,00 % 0,176 19 298,6 2145 Example 6 2,50 % 2,51 14,29 % 0,439 18 301,7 2230 Example 9 2,30 % 2,21 30,00 % 0,169 16 300,4 1984 Example 10 2,10 % 1,79 11,11 % 0,338 21 301,1 1600

[0070] From the data in Tables 2-4 it is evident that: in the present application, by comprehensively adjusting the content a of the element silicon, the viscosity b of the electrolyte and the percentage c of the thickness of the coating layer in relation to the thickness of the base film by controlling the value of a*b / c so that it falls within the range of 0.037 - 5.625, the wetting of the negative electrode can be effectively improved and thus the fast charging performance can be improved, while maintaining a good energy density of the battery.From a comparison of the data in Tables 2-4, in particular from a comparison of examples 1 and 8 with other examples in Table 2 and of example 10 with other examples in Table 4, it is evident that: if the value of a*b / c is further optimized so that it is 0.165-2.585, a greater improvement in fast charging performance and cycle performance is achieved, while maintaining the energy density of the battery.

[0071] If the value of a is further optimized to be 2% - 16%, b is further optimized to be 2.1 - 2.8, and c is further optimized to be 13% - 32%, not only can the fast charging performance be effectively improved, but the cycle performance can also be significantly improved, with the number of cycles reaching more than 1000.

[0072] If a, b, c are all within preferred ranges and the value of a*b / c is in the preferred range of 0.165 - 2.585, then, if the silicon-based material is a silicon-carbon material, the value of a*b / c is further optimized to be 0.431 - 1.05 when the density of the negative electrode is 1.45 - 1.8 g / cm³ 3 The value of a*b / c is further optimized to be 0.333 - 0.82; if the above conditions for the preferred settings are met simultaneously, referring to examples 5 and 7 in Table 2 and example 6 in Table 4, the cycle performance is significantly improved compared to data in other examples, with fast charging performance being improved.

[0073] It is clear that the embodiments described above are merely examples for illustrative purposes and do not constitute limitations on the modes of implementation. For the average person skilled in the art, other, different forms of modification or variations may be conceived based on the above description. An enumeration of all possible implementation modes is neither necessary nor possible here. Any obvious modifications or variations derived therefrom are nevertheless within the scope of protection of this application.

Claims

[1] Battery comprising a battery cell and an electrolyte, wherein the battery cell comprises a negative electrode and a separator, the negative electrode comprises a current collector and a layer of negative active material, the layer of negative active material comprises a silicon-based material, and the separator comprises a base film and a coating layer; characterized by , that the mass fraction of the element silicon in the layer of negative active material a is; the viscosity of the electrolyte b cP is; the percentage value of the thickness of the coating layer in relation to the thickness of the separator c is and 0.037 ≤ a*b / c ≤ 5.

625. [2] Battery according to claim 1, characterized by , that a is 0.5% - 30% and / or b 1.5 - 3.7 and / or c 8% - 50%. [3] Battery according to claim 2, characterized by , that a is 2% - 16% and / or b 2.1 - 2.8 and / or c 13% - 32%. [4] Battery according to one of claims 1-3, characterized by , that the value of a*b / c is 0.165 - 2.585; if the silicon-based material is a silicon-carbon material, the value of a*b / c is 0.431 - 1.

05. [5] Battery according to any one of the preceding claims, characterized by , that the degree of compaction of the negative electrode is 1.25 - 1.8 g / cm³ 3 amounts. [6] Battery according to claim 5, characterized by , that if the density of the negative electrode is 1.45 - 1.8 g / cm³ 3 The value of a*b / c is 0.333 - 0.

82. [7] Battery according to any of the preceding claims, characterized by that the electrolyte contains a solvent and a lithium salt; the solvent is selected from carbonate esters, carboxylic acid esters, ethers, sulfones, nitriles, phosphate esters or fluorides of the above solvents and The lithium salt is selected from lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium difluorobis(oxalato)phosphate and lithium tetrafluoro(oxalato)phosphate. [8] Battery according to claim 7, characterized by that the solvent contains at least 10 wt.% - 60 wt.% carbonate ester solvent, 0 wt.% - 50 wt.% carboxylic acid ester solvent and / or that the concentration of the lithium salt in the electrolyte is 0.8 - 2.5 M. [9] Battery according to any of the preceding claims, characterized by, that the coating layer has an inorganic component, wherein the inorganic component contained in the coating layer is selected from aluminium oxide, boehmite, silicon dioxide, zirconium oxide, titanium dioxide, cerium oxide and magnesium aluminate, and the thickness of the coating layer is 1-7 µm. [10] Electrical device, characterized by that it comprises the battery according to one of claims 1-9; wherein the battery has a positive electrode and the positive active material in the positive electrode is LiNi x Co y Mn z O2 has, where 1 > x ≥ 0.5, x + y + z = 1.