Patent Application
20250023149
This application relates to the field of electrochemistry, and particularly relates to an electrochemical device and an electronic device.
Currently, batteries are widely applied to electronic products such as unmanned aerial vehicles, mobile phones, tablet computers, notebook computers, etc. In some application scenarios, a single battery cell cannot achieve the desired output power. Therefore, a plurality of battery cells are generally connected in series, in parallel, or in parallel and series, so that the plurality of battery cells cooperate together to achieve the desired output power. However, although the output power can be improved by connecting the plurality of battery cells in series, in parallel, or in parallel and series, the energy density of a whole battery pack is low. Therefore, a design for same pouch series/parallel connected battery is proposed. The same pouch series/parallel connected battery includes a housing and a plurality of electrode assemblies arranged in the same housing. The electrode assemblies connected in series need to be separated by separators to avoid the decomposition of an electrolyte under a high voltage, and the electrode assemblies connected in parallel can avoid mutual interference by being separated by the separators.
The inventors of this application have found through research that, for the same pouch series/parallel connected batteries, the batteries are likely to expand under high-temperature conditions, thereby reducing the safety performance of the batteries.
In view of this, this application provides an electrochemical device and an electronic device, which can improve the safety performance of the electrochemical device.
To solve the above technical problem, a first aspect of this application provides an electrochemical device. The electrochemical device comprises a housing, a first electrode assembly, a second electrode assembly and N separators. The separators are arranged along a first direction, so that the N separators and the housing together define N+1 accommodating cavities arranged along the first direction, wherein the N+1 accommodating cavities comprise a first accommodating cavity and a second accommodating cavity adjacent to each other, wherein N>2. The first electrode assembly is accommodated in the first accommodating cavity, and the second electrode assembly is accommodated in the second accommodating cavity. The second electrode assembly is far from a reference surface relative to the first electrode assembly, wherein the reference surface is a plane that passes through the center of the electrochemical device along the first direction and is perpendicular to the first direction, and the volume V1 of the first accommodating cavity and the volume V2 of the second accommodating cavity satisfy 0.5%≤(V2−V1)/V1≤5%. The inventors of this application have found through research that, in a same pouch series/parallel connected battery, the expansion of the first accommodating cavity located on an inner side will squeeze the second accommodating cavity located on an outer side, and at the moment, the second accommodating cavity may have a risk of excessive expansion due to an excessive internal pressure. Through the above-mentioned solution, on the one hand, when (V2−V1)/V1≥0.5%, the second accommodating cavity has a larger space, so that the expansion generated from the first accommodating cavity located on the inner side can be effectively buffered by the larger second accommodating cavity, thereby inhibiting the occurrence of excessive overall expansion and a packaging failure of the electrochemical device due to the excessive internal pressure of the second accommodating cavity; and on the other hand, when (V2−V1)/V1≤5%, the internal pressure of the first accommodating cavity on the inner side can be inhibited from being too large due to the volume of the first accommodating cavity on the inner side being too small, so that the occurrence of the local excessive expansion of the electrochemical device and a packaging failure of the first accommodating cavity on the inner side is inhibited, thereby improving the safety performance of the electrochemical device.
In some embodiments, 1.5%≤(V2−V1)/V1≤4%. In the above-mentioned solution, the second accommodating cavity can have a relatively larger buffer space, thereby further effectively inhibiting the internal pressure of the second accommodating cavity from being too large, and improving the safety performance of the electrochemical device.
In some embodiments, the volume V1 of the first accommodating cavity, the volume V3 of the first electrode assembly, the volume V2 of the second accommodating cavity and the volume V4 of the second electrode assembly satisfy [(V1−V3)/V3]/[(V2−V4)/V4]≤0.9. In the above-mentioned solution, the sizes of spaces occupied by the electrode assemblies in the accommodating cavities and the relative sizes of remaining spaces are considered, so that the second accommodating cavity can have a larger remaining space to buffer the expansion of the first accommodating cavity, thereby further improving the safety performance of the electrochemical device.
In some embodiments, the electrochemical device satisfies 2.5%≤(V1−V3)/V3≤5.5%. In the above-mentioned solution, the first accommodating cavity has an appropriate remaining space to inhibit self-expansion, thereby reducing squeeze to the second accommodating cavity, and improving the safety performance of the electrochemical device.
In some embodiments, the electrochemical device satisfies 3%≤(V2−V4)/V4≤9%. In the above-mentioned solution, the second accommodating cavity has a larger remaining space to buffer the expansion of the first accommodating cavity, thereby inhibiting the excessive overall expansion of the electrochemical device, and improving the safety performance of the electrochemical device.
In some embodiments, the electrochemical device further comprises first tabs and second tabs, wherein the first tabs are electrically connected to the first electrode assembly, the second tabs are electrically connected to the second electrode assembly, and both the first tabs and the second tabs are led out from a first side of the housing. A first plane divides the first accommodating cavity into a first space close to the first side and a second space away from the first side; and in a plane perpendicular to the first direction, a projection of the first plane along the first direction forms a first straight line, and a projection of a side edge of the first electrode assembly close to the first side along the first direction forms a first line segment. The first straight line passes through the first line segment. A second plane divides the second accommodating cavity into a third space close to the first side and a fourth space away from the first side; and in the plane perpendicular to the first direction, a projection of the second plane along the first direction forms a second straight line, and a projection of a side edge of the second electrode assembly close to the first side along the first direction forms a second line segment. The second straight line passes through the second line segment. The volume T1 of the first space and the volume T3 of the third space satisfy 5%≤(T3−T1)/T1≤25%. In the above-mentioned solution, considering that head spaces in the accommodating cavities are more prone to expansion, when 5%≤(T3−T1)/T1≤25%, the head space of the larger second accommodating cavity can buffer the expansion of the head of the first accommodating cavity, inhibiting the generation of excessive expansion of the head of the electrochemical device, thereby further improving the safety performance of the electrochemical device.
In some embodiments, the electrochemical device satisfies 10%≤(T3−T1)/T1≤15%. In the above-mentioned solution, the head space in the second accommodating cavity can better buffer the expansion of the head of the first accommodating cavity, thereby inhibiting the generation of excessive expansion of the head of the electrochemical device.
In some embodiments, the electrochemical device satisfies that the second plane is located on one side of the first plane away from the first side. In the above-mentioned solution, after the head space (located on a first side of the first electrode assembly) of the first accommodating cavity expands, a larger buffer space can be provided, thereby improving the safety performance of the electrochemical device.
In some embodiments, the N separators comprise a first separator, wherein the first separator is arranged between the first accommodating cavity and the second accommodating cavity, and the first separator is recessed toward the first accommodating cavity to form a groove.
In some embodiments, the separator comprises a substrate layer and packaging layers located on surfaces of the substrate layer. In the above-mentioned solution, the separator has better isolation and packaging properties.
In some embodiments, the packaging layer comprises a first polymer material.
In some embodiments, a material of the substrate layer comprises at least one of a metal material, a second polymer material or a carbon material.
In some embodiments, the first polymer material comprises at least one of polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymers, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous alpha-olefin copolymers or derivatives of the above-mentioned substances.
In some embodiments, the metal material comprises at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn, stainless steel (SUS) and compositions or alloys thereof.
In some embodiments, the second polymer material comprises at least one of polyethylene glycol terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, sulfide, polyphenylene polyvinyl acetate, polytetrafluoroethylene, polymethyl naphthalene, polyvinylidene difluoride, poly(propylene carbonate), poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), organosilicon, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymers, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenyl ether, polyester, polysulfone, amorphous alpha-olefin copolymers or derivatives of the above-mentioned substances.
In some embodiments, the carbon material comprises at least one of a carbon felt, a carbon film, carbon black, acetylene black, fullerene, a conductive graphite film or a graphene film.
A second aspect of this application further provides an electronic device, comprising the electrochemical device according to any one of the aforementioned embodiments.
According to the electrochemical device provided by this application, the second electrode assembly is far from the reference surface relative to the first electrode assembly. In other words, the first electrode assembly is closer to a middle position of the electrochemical device along the first direction than the second electrode assembly, and thus the first accommodating cavity is closer to the middle position of the electrochemical device along the first direction than the second accommodating cavity. In this application, the volume V1 of the first accommodating cavity and the volume V2 of the second accommodating cavity satisfy 0.5%≤(V2−V1)/V1≤5%. In other words, the second accommodating cavity is 0.5% to 5% larger than the first accommodating cavity. That is, the accommodating cavity of the electrochemical device closer to the outer side is 0.5% to 5% larger than the adjacent accommodating cavity closer to the inner side. On the one hand, when (V2−V1)/V1≥0.5%, the second accommodating cavity has a larger space, so that the expansion generated from the first accommodating cavity can be effectively buffered by the second accommodating cavity, thereby inhibiting the occurrence of excessive overall expansion and a packaging failure of the electrochemical device due to the excessive internal pressure of the second accommodating cavity; and on the other hand, when (V2−V1)/V1≤5%, the internal pressure of the first accommodating cavity on the inner side can be inhibited from being too large due to the volume of the first accommodating cavity on the inner side being too small, so that the occurrence of the local excessive expansion of the electrochemical device and a packaging failure of the first accommodating cavity on the inner side is inhibited, thereby improving the safety performance of the electrochemical device.
To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings required by the embodiments of this application are introduced briefly below. Apparently, the accompanying drawings depicted below are merely some embodiments of this application, and those of ordinary skill in the art can also obtain other drawings based on the accompanying drawings.
In order to facilitate understanding of this application, this application will be described below in more detail in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as “being fixed to” another element, it may be directly on another element, or there may be one or more intermediate elements therebetween. When an element is described as “being connected to” another element, it may be directly connected to another element, or there may be one or more intermediate elements therebetween. The terms “vertical”, “horizontal”, “left”, “right”, and similar expressions used in this specification are for illustrative purposes only.
Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used in the specification of this application are for the purpose of describing the specific embodiments only and are not intended to limit this application. The term “and/or” as used in this specification includes any combination and all combinations of one or more related listed items.
The inventors of this application have found through research that, in a same pouch series/parallel connected battery, the expansion of a first accommodating cavity located on an inner side will squeeze a second accommodating cavity located on an outer side, and at the moment, the second accommodating cavity may have a risk of excessive expansion due to an excessive internal pressure.
In view of this, referring to
The separators 120 are arranged along a first direction X as shown in
The N+1 accommodating cavities include a first accommodating cavity 170 and a second accommodating cavity 180 adjacent to each other. A first electrode assembly 130 is accommodated in the first accommodating cavity 170, and the second electrode assembly 140 is accommodated in the second accommodating cavity 180. An electrolyte is provided in both the first accommodating cavity 170 and the second accommodating cavity 180, so that independent electrochemical units are formed within both the first accommodating cavity 170 and the second accommodating cavity 180. The electrochemical device 100 may further include other electrode assemblies, such that one electrode assembly is disposed in each of the accommodating cavities except for the first accommodating cavity 170 and the second accommodating cavity 180. In this embodiment, the electrochemical device 100 further includes first tabs 131 and second tabs 141, the two first tabs 131 with opposite polarities are connected to two current collectors with opposite polarities in the first electrode assembly 130 in one-to-one correspondence, and the first tabs extend out of the housing 110 from between the housing 110 and the separator 120; and the two second tabs 141 with opposite polarities are connected to two current collectors with opposite polarities in the second electrode assembly 140 in one-to-one correspondence, and the second tabs extend out of the housing 110 from between the housing 110 and the separator 120.
In some embodiments, the second electrode assembly 140 is far from a reference surface 160 relative to the first electrode assembly 130, wherein the reference surface 160 is a plane that passes through the center of the electrochemical device along the first direction X and is perpendicular to the first direction X. In other words, the first electrode assembly 130 is closer to the thickness center of the electrochemical device 100 along the first direction X than the second electrode assembly 140.
In some embodiments, the volume V1 of the first accommodating cavity 170 and the volume V2 of the second accommodating cavity 180 satisfy V2>V1. At the time, because the second accommodating cavity 180 that is far from the thickness center of the electrochemical device 100 along the first direction X has a larger space, so that the expansion generated from the first accommodating cavity 170 on the inner side can be effectively buffered by the larger second accommodating cavity 180, inhibiting the occurrence of the excessive overall expansion and a packaging failure of the electrochemical device 100 caused by the internal pressure of the second accommodating cavity 180 being too large. In some embodiments, the volume V1 of the first accommodating cavity 170 and the volume V2 of the second accommodating cavity 180 satisfy 0.5%≤(V2−V1)/V1≤5%. As an example, (V2−V1)/V1 may be 0.5%, 1%, 2%, 3%, 4% or 5%, etc. In other words, the second accommodating cavity 180 is 0.5% to 5% larger than the first accommodating cavity 170. That is, the accommodating cavity of the electrochemical device 100 closer to the outer side is 0.5% to 5% larger than the adjacent accommodating cavity closer to the inner side. At the moment, when (V2−V1)/V1≤5%, the internal pressure of the first accommodating cavity 170 on the inner side can be inhibited from being too large due to the volume of the first accommodating cavity 170 on the inner side being too small, so that the occurrence of local excessive expansion of the electrochemical device 100 and a packaging failure of the first accommodating cavity 170 on the inner side is inhibited, thereby improving the safety performance of the electrochemical device 100. The volume V1 of the first accommodating cavity 170 and the volume V2 of the second accommodating cavity 180 can be measured by dismantling the electrochemical device and can also be measured in situ using a three-dimensional CT scanning technology.
The first accommodating cavity 170 and the second accommodating cavity 180 may be any two adjacent accommodating cavities within the housing 110, where distances between the two accommodating cavities and the reference surface 160 are unequal. For example, when N is 4, the housing 110 is internally provided with 5 accommodating cavities. For the convenience of description, the thicknesses of the accommodating cavities along the first direction X are the same, and along the first direction X, the accommodating cavities are sequentially numbered as an accommodating cavity I, an accommodating cavity II, an accommodating cavity III, an accommodating cavity IV and an accommodating cavity V. When the thicknesses of the accommodating cavities along the first direction X are the same, the accommodating cavity III is closest to the thickness center of the electrochemical device 100 along the first direction X. The second accommodating cavity 180 may be the accommodating cavity I, and at the moment, the first accommodating cavity 170 is the accommodating cavity
II; the second accommodating cavity 180 may also be the accommodating cavity II, and then the first accommodating cavity 170 is the accommodating cavity III; the second accommodating cavity 180 may also be the accommodating cavity IV, and then the first accommodating cavity 170 is the accommodating cavity III; and the second accommodating cavity 180 may also be the accommodating cavity V, and then the first accommodating cavity 170 is the accommodating cavity IV. When the number of the accommodating cavities of the electrochemical device 100 is another number, the configuration follows the rule.
Specifically, in the electrochemical device 100, only the first accommodating cavity 170 and the second accommodating cavity 180 may satisfy a spatial size relationship of 0.5%≤(V2−V1)/V1≤5%. Also, all the adjacent accommodating cavities may satisfy the above relationship. As an example, in the foregoing embodiment when N is 4, it is possible to simultaneously satisfy the space of the accommodating cavity I being 0.5% to 5% larger than that of the accommodating cavity II, the space of the accommodating cavity II being 0.5% to 5% larger than that of the accommodating cavity III, the space of the accommodating cavity IV is 0.5% to 5% larger than that of the accommodating cavity III, and the space of the accommodating cavity Vis 0.5% to 5% larger than that of the accommodating cavity IV. When the number of the accommodating cavities of the electrochemical device 100 is another number, the configuration follows the rule.
In some embodiments, 1.5%≤(V2−V1)/V1≤5%. As an example, (V2−V1)/V1 may be 1.5%, 2%, 2.5%, 3%, 4% or 5%, etc. In the above-mentioned solution, the second accommodating cavity 180 can have a relatively larger buffer space, thereby further effectively inhibiting excessive internal pressure of the second accommodating cavity 180, and improving the safety performance of the electrochemical device 100.
The inventors of this application have further studied and found that a better effect can be achieved by controlling relative relations between the remaining spaces within the first accommodating cavity 170 and the second accommodating cavity 180 and spaces occupied by the electrode assemblies. Thus, in some embodiments, the volume V1 of the first accommodating cavity 170, the volume V3 of the first electrode assembly 130, the volume V2 of the second accommodating cavity 180 and the volume V4 of the second electrode assembly 140 are configured to satisfy [(V1−V3)/V3]/[(V2−V4)/V4]≤0.9. As an example, [(V1−V3)/V3]/[(V2−V4)/V4] may be 0.5, 0.6, 0.7, 0.8 or 0.9, etc. (V1−V3)/V3 is a ratio of the remaining space within the first accommodating cavity 170 except for the space occupied by the first electrode assembly 130 to the space occupied by the first electrode assembly 130. (V2−V4)/V4 is a ratio of the remaining space within the second accommodating cavity 180 except for the space occupied by the second electrode assembly 140 to the space occupied by the second electrode assembly 140. In this embodiment, the sizes of the spaces occupied by the electrode assemblies in the accommodating cavities and the relative sizes of the remaining spaces are considered comprehensively, so that the second accommodating cavity 180 can have a larger remaining space to buffer the expansion of the first accommodating cavity 170, thereby further inhibiting excessive expansion of the electrochemical device 100, and improving the safety performance of the electrochemical device 100.
In some embodiments, the electrochemical device satisfies 2.5%≤(V1−V3)/V3≤5.5%. In the above-mentioned solution, the first accommodating cavity 170 has an appropriate remaining space to inhibit self-expansion, thereby reducing squeeze to the second accommodating cavity 180, and improving the safety performance of the electrochemical device 100.
In some embodiments, the electrochemical device satisfies 3%≤(V2−V4)/V4≤9%. In the above-mentioned solution, the second accommodating cavity 180 has a larger remaining space to buffer the expansion of the first accommodating cavity 170, thereby inhibiting the excessive overall expansion of the electrochemical device 100 and improving the safety performance of the electrochemical device 100.
As shown in
A first plane 150 divides the first accommodating cavity 170 into a first space 171 close to the first side and a second space away from the first side, and in a plane perpendicular to the first direction X, a projection of the first plane 150 along the first direction X forms a first straight line, and a projection of a side edge of the first electrode assembly 130 close to the first side along the first direction X forms a first line segment. The first straight line passes through the first line segment. In other words, the first plane 150 is attached to an end portion of the first electrode assembly 130 close to the first side. Specifically, when an end portion of an anode electrode plate of the first electrode assembly 130 close to the first side covers an end portion of a cathode electrode plate close to the first side, the first plane 150 is attached to the end portion of the anode electrode plate close to the first side. The first space 171 is a space of the first accommodating cavity 170 located on the first side of the electrode assembly.
A second plane divides the second accommodating cavity 180 into a third space 181 close to the first side and a fourth space away from the first side. In the plane perpendicular to the first direction X, a projection of the second plane along the first direction X forms a second straight line, and a projection of a side edge of the second electrode assembly 140 close to the first side along the first direction X forms a second line segment. The second straight line passes through the second line segment. In other words, the second plane is attached to an end portion of the second electrode assembly 140 close to the first side. Specifically, when an end portion of an anode electrode plate of the second electrode assembly 140 close to the first side covers an end portion of a cathode electrode plate close to the first side, the second plane is attached to the end portion of the anode electrode plate close to the second side. The third space 181 is a space of the second accommodating cavity 180 located on the first side of the electrode assembly.
The inventors of this application considered that volume expansion in each accommodating cavity of the electrochemical device 100 more easily occurs in the head space (namely, the space of the electrode assembly close to the tabs, i.e., the aforementioned first space 171 or the aforementioned third space 181). In view of this, in some embodiments, the volume T1 of the first space 171 and the volume T3 of the third space 181 are configured to satisfy 5%≤(T3−T1)/T1≤25%. As an example, (T3—T1)/T1 may be 5%, 10%, 15%, 20% or 25%, etc. In this solution, considering that the head spaces in the accommodating cavities are more prone to expansion, when 5%≤(T3−T1)/T1≤25%, the head space of the larger second accommodating cavity 180 can buffer the expansion of the head of the first accommodating cavity 170, inhibiting the excessive expansion of the head of the electrochemical device 100, thereby further improving the safety performance of the electrochemical device 100. Preferably, 10%≤(T3−T1)/T1≤25%.
In some embodiments, the second plane is configured to be located on one side of the first plane 150 away from the first side. After the head space (located on the first side of the first electrode assembly 130) of the first accommodating cavity 170 expands, a larger buffer space can be provided, thereby improving the overall safety performance of the electrochemical device 100.
There are various methods for realizing that the space volume of the first accommodating cavity 170 is less than that of the second accommodating cavity 180. In one embodiment, it can be because the size of the first accommodating cavity 170 along the first direction X is less than that of the second accommodating cavity 180 along the first direction X, thereby enabling the space volume of the first accommodating cavity 170 to be less than that of the second accommodating cavity 180. In another embodiment, as shown in
In yet another embodiment, as shown in
Likewise, in order to adjust volume ratios between all adjacent accommodating cavities, one groove 122 can be stamped on each of the separators 120.
The groove 122 may be disposed in any position of the first separator 121. In one embodiment, as shown in
As shown in
In some embodiments, the first polymer material includes at least one of polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymers, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous alpha-olefin copolymers or derivatives of the above-mentioned substances.
The metal material includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn, stainless steel (SUS) and compositions or alloys thereof.
The second polymer material includes at least one of polyethylene glycol terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethyl naphthalene, polyvinylidene difluoride, poly(propylene carbonate), poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), organosilicon, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymers, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenyl ether, polyester, polysulfone, amorphous alpha-olefin copolymers or derivatives of the above-mentioned substances.
The carbon material includes at least one of a carbon felt, a carbon film, carbon black, acetylene black, fullerene, a conductive graphite film or a graphene film.
The electrode assembly of this application is not particularly limited, and may be any electrode assembly of the prior art as long as the object of this application can be achieved, for example, a stacked electrode assembly or a wound electrode assembly may be used. The electrode assembly generally includes a positive electrode plate, a negative electrode plate and a separator film.
The negative electrode plate in this application is not particularly limited as long as the object of this application can be achieved. For example, the negative electrode plate generally includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is not particularly limited, and may be any negative electrode current collector known in the field, such as a copper foil, an aluminum foil, an aluminum alloy foil and a composite current collector, etc. The negative electrode active material layer includes a negative electrode active material. The negative electrode active material is not particularly limited, and may be any negative electrode active material known in the field. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon, silicon-carbon, lithium titanate, etc.
The positive electrode plate in this application is not particularly limited as long as the object of this application can be achieved. For example, the positive electrode plate generally includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is not particularly limited, and may be any positive electrode current collector known in the field, such as aluminum foil, aluminum alloy foil or a composite current collector, etc. The positive electrode active material layer includes a positive electrode active material. The positive electrode active material is not particularly limited and may be any positive electrode active material of the prior art, for example, may include at least one of lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide or lithium manganese iron phosphate.
The electrolyte in this application is not particularly limited and may be any electrolyte known in the field, for example, may be any one of a gel electrolyte, a solid electrolyte or a liquid electrolyte. For example, the liquid electrolyte may include a lithium salt and a non-aqueous solvent.
The lithium salt is not particularly limited, and may be any lithium salt known in the field as long as the object of this application can be achieved. For example, the lithium salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulphonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalate)borate LiB(C2O4)2 (LiBOB) or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB). For example, the lithium salt may be LiPF6.
The non-aqueous solvent is not particularly limited as long as the object of this application can be achieved. For example, the non-aqueous solvent may include at least one of a carbonate compound, a carboxylic ester compound, an ether compound, a nitrile compound or other organic solvents.
For example, the carbonate compound may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1, 1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate or trifluoromethyl ethylene carbonate.
The separator film in this application is not particularly limited, for example, the separator film includes a polymer or an inorganic substance, etc. formed from a material that is stable to the electrolyte in this application. The separator film generally should have ionic conductivity and electronic insulation.
For example, the separator film may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a film or a composite film with a porous structure. A material of the substrate layer may be selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used.
Optionally, the surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic substance layer, and may also be a layer formed by mixing a polymer or an inorganic substance.
For example, the inorganic substance layer includes inorganic particles and a binder. The inorganic particles are not particularly limited, and for example, may include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is not particularly limited, and for example, may include a combination of one or more of polyvinylidene difluoride, a vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, sodium polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, poly(methyl methacrylate), polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer includes a polymer. A material of the polymer includes at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, sodium polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, polyvinylidene difluoride or poly (vinylidene fluoride-hexafluoropropylene).
A second aspect of this application further provides an electronic device, including the electrochemical device according to any one of the aforementioned embodiments.
The embodiments of this application will be described below more specifically by providing embodiments and comparative examples. Various tests and evaluations are conducted according to the following methods, and “parts” and “percent” are based on weight unless otherwise specified.
A preparation process of a lithium-ion battery in the embodiments and the comparative examples is as follows:
Corresponding specific structure size parameters of lithium-ion batteries are adjusted according to Table 1, and other parameters are the same as those in Embodiment 1.
In an environment of 25±3° C., the lithium-ion battery is charged at a constant current rate of 0.05 C to a fully-charged design voltage of 4.3×n V (where n is the number of electrode assemblies), then charged at a fully-charged design voltage of 4.3×n V until a cut-off current is 0.025 C, so that the lithium-ion battery reaches a fully-charged state; the thickness of the lithium-ion battery at this time is measured as H0, and the lithium-ion battery is placed in a constant-temperature chamber at 60° C. for 24 h; and after being taken out, the lithium-ion battery is cooled to 25±3° C., a maximum thickness of the lithium-ion battery at this moment is measured as H1, and the high-temperature storage expansion rate=(H1−H0)/H0×100%. At the same time, whether leakage exists in a packaging part of the lithium-ion battery is observed.
Table 1 shows the structural size parameters and performance of lithium-ion batteries in the embodiments and the comparative examples.
It can be seen from the comparison between Embodiments 1-15 and Comparative Examples 1-2 in Table 1, that the lithium-ion batteries in Embodiments 1-15 satisfy 0.5%≤(V2−V1)/V1≤5% have significantly reduced high-temperature storage expansion rates and better packaging stability. This is because, on the one hand, when (V2−V1)/V1≥0.5%, the accommodating cavity located on the outer side has a larger space, so that the expansion generated from the accommodating cavity located on the inner side can be effectively buffered by the larger accommodating cavity on the outer side, thereby inhibiting the occurrence of excessive overall expansion and a packaging failure of the lithium-ion battery due to the excessive internal pressure of the accommodating cavity on the outer side, thereby improving the safety performance of the lithium-ion battery; and on the other hand, when (V2−V1)/V1≤5%, the internal pressure of the accommodating cavity on the inner side can be inhibited from being too large due to the volume of the accommodating cavity on the inner side being too small, so that the occurrence of local excessive expansion and leakage of the accommodating cavity on the inner side is inhibited, thereby further improving the safety performance of the battery.
Further, it can be seen from the comparison between Embodiments 4 and 11 that Embodiment 4 that further satisfies [(V1−V3)/V3]/[(V2−V4)/V4]≤0.9 can have a low high-temperature storage expansion rate. This is because the sizes of the spaces occupied by the electrode assemblies in the accommodating cavities and the relative sizes of the remaining spaces are considered comprehensively, so that the accommodating cavity on the outer side can have a larger remaining space to buffer the expansion of the accommodating cavity on the inner side, thereby further inhibiting high-temperature storage expansion of the lithium-ion battery.
In addition, it can be seen from the comparison between Embodiments 1-9 and Embodiments 12-15 that Embodiments that satisfy 10%≤(T3−T1)/T1≤15% can have a low high-temperature storage expansion rate. This is because, considering that the head space in the accommodating cavity is more prone to expansion, when 10%≤(T3−T1)/T1≤15%, the head space of the larger accommodating cavity on the outer side can buffer the expansion of the head of the accommodating cavity on the inner side, inhibiting the excessive expansion of the head of the lithium-ion battery, thereby further reducing the high-temperature storage expansion rate of the lithium-ion battery.
It should be noted that preferred embodiments of this application are provided in the specification of this application and the accompanying drawings thereof. However, this application may be implemented in various forms and is not limited to the embodiments described in this specification. These embodiments are not intended to limit the content of this application additionally, and the purpose of providing these embodiments is to make a more comprehensive understanding of the disclosed content of this application. Furthermore, the described technical features are continuously combined to form various embodiments not listed above, and all these embodiments are considered to be within the scope depicted in the description of this application. Further, those of ordinary skill in the art may make improvements or modifications according to the above description, and all these improvements and modifications shall belong to the scope of protection of the appended claims of this application.
This application is a continuation application of PCT International Application No. PCT/CN2022/084557, filed on Mar. 31, 2022, the contents of which are incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2022/084557 | Mar 2022 | WO |
| Child | 18901584 | US |
