CN117878384A

CN117878384A - Battery cell, battery and electricity utilization device

Info

Publication number: CN117878384A
Application number: CN202410268476.7A
Authority: CN
Inventors: 吴则利; 韩昌隆; 柳娜; 彭淑婷; 郭洁; 吴巧
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2024-03-08
Filing date: 2024-03-08
Publication date: 2024-04-12

Abstract

The application relates to a battery cell, battery and power consumption device, battery cell include positive pole piece and negative pole piece and electrolyte, and positive pole piece includes positive electrode active material layer, and positive electrode active material layer includes the lithium-containing material of olivine structure, and negative pole piece includes negative electrode active material layer, and the size of positive electrode active material layer along the length direction of positive electrode piece is L ₁ mm, positive electrodeThe dimension of the active material layer along the width direction of the positive electrode plate is W ₁ mm, the dimension of the anode active material layer in the length direction is L ₂ mm, the dimension of the anode active material layer in the width direction was W ₂ mm，1＜(L ₂ ‑L ₁ )/(W ₂ ‑W ₁ )≤4，L ₂ /L ₁ ＞1，500≤L ₁ Less than or equal to 600; the electrolyte comprises lithium hexafluorophosphate and lithium difluorosulfonimide, and the ratio of the mass content of the lithium hexafluorophosphate to the mass content of the lithium difluorosulfonimide is more than 1 based on the total mass of the electrolyte. The application can promote the use reliability of the battery monomer.

Description

Battery cell, battery and electricity utilization device

Technical Field

The application relates to a battery cell, a battery and an electric device.

Background

The battery cell has the characteristics of high capacity, long service life and the like, and is widely applied to electronic equipment such as mobile phones, notebook computers, battery cars, electric automobiles, electric airplanes, electric ships, electric toy automobiles, electric toy ships, electric toy airplanes, electric tools and the like. As the battery field has advanced greatly, higher demands are being made on the performance of the battery cells.

However, the reliability of the battery cell is poor at present, and further improvement is still needed.

Disclosure of Invention

The application provides a battery monomer, battery and power consumption device, can promote the single use reliability of battery.

In a first aspect, embodiments of the present application provide a battery cell, where the battery cell includes a positive electrode plate, a negative electrode plate, and an electrolyte, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, the positive electrode active material layer includes a lithium-containing material having an olivine structure, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and a size of the positive electrode active material layer along a length direction of the positive electrode plate is L ₁ mm, the dimension of the positive electrode active material layer along the width direction of the positive electrode plate is W ₁ mm, the dimension of the anode active material layer in the length direction is L ₂ mm, the dimension of the anode active material layer in the width direction was W ₂ mm, where 1 < (L ₂ -L ₁ )/(W ₂ -W ₁ ) Not more than 4, and L ₂ /L ₁ ＞1，500≤L ₁ Less than or equal to 600; the electrolyte comprises lithium hexafluorophosphate and lithium difluorosulfonimide, and the ratio of the mass content of the lithium hexafluorophosphate to the mass content of the lithium difluorosulfonimide is more than 1 based on the total mass of the electrolyte.

Therefore, in the related art, the area of the negative electrode active material layer in the negative electrode plate exceeding the positive electrode active material layer in the positive electrode plate is called an exceeding area, and the amount of receivable active ions increases along with the increase of the exceeding area, but the exceeding area is overlarge, so that the size of the negative electrode plate can be excessively set, the space is wasted, and the energy density of a battery cell is reduced; as the excess area decreases, the risk of precipitation of active ions as metal increases. According to the embodiment of the application, the exceeding area is further designed, so that the exceeding area size of the anode pole piece in the length direction is larger than the exceeding area size in the width direction, the capacity of the anode active material layer for receiving active ions in the length direction is stronger than the capacity of the anode active material layer for receiving active ions in the width direction, the capacity of the anode active material layer for receiving active ions in the area close to the lug can be improved, the capacity of the anode active material layer for integrally receiving active ions is improved, the risk that active ions are separated out into metal is reduced, and the use reliability of a battery cell is improved.

In some embodiments, 1.5.ltoreq.L ₂ -L ₁ )/(W ₂ -W ₁ ) Less than or equal to 2.5. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, 5.ltoreq.L ₂ -L ₁ And is less than or equal to 10. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, 2.ltoreq.W ₂ -W ₁ And is less than or equal to 6. When the battery monomer meets the above range, the battery can be further improvedReliability of use and energy density of the battery cell.

In some embodiments, 500.ltoreq.L ₂ Less than or equal to 600; can be selected to be 540-L ₂ And is less than or equal to 560. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, 500.ltoreq.L ₁ Less than or equal to 600; can be selected to be 540-L ₁ And is less than or equal to 560. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, 100+.W ₂ 155 or less. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, 100+.W ₁ 155 or less. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, the battery cell further comprises a separator disposed between the positive electrode sheet and the negative electrode sheet, the separator having a dimension L in the longitudinal direction ₃ mm，2≤L ₃ -L ₂ And is less than or equal to 5. The length dimension of the isolating film is larger than that of the negative electrode plate, so that the risk of short circuit between the positive electrode plate and the negative electrode plate can be further reduced.

In some embodiments, the battery cell further comprises a separator disposed between the positive electrode sheet and the negative electrode sheet, the separator having a dimension W in the width direction ₃ mm，2≤W ₃ -W ₂ And is less than or equal to 5. The width dimension of the isolating film is larger than that of the negative electrode plate, so that the risk of short circuit between the positive electrode plate and the negative electrode plate can be further reduced.

In some embodiments, 500.ltoreq.L ₃ And is less than or equal to 600. The length dimension of the isolating film is relatively longer, so that the risk of short circuit between the positive pole piece and the negative pole piece can be further reduced.

In some embodiments, 100+.W ₃ And is less than or equal to 160. The width dimension of the isolating film is relatively longer, so that the risk of short circuit between the positive pole piece and the negative pole piece can be further reduced.

In some embodiments, the battery cell further comprises an electrolyte comprising lithium hexafluorophosphate LiPF ₆ And lithium bis (fluorosulfonyl) imide LiFSI, lithium hexafluorophosphate LiPF based on the total mass of the electrolyte ₆ The ratio of the mass content of (2) to the mass content of lithium bis (fluorosulfonyl) imide LiFSI is greater than 1; optionally 1.05 to 1.4, and lithium hexafluorophosphate LiPF ₆ And the total mass content of lithium bis (fluorosulfonyl) imide LiFSI is 10% to 16%; optionally 12% to 16%.

Thus, in embodiments of the present application, lithium hexafluorophosphate LiPF ₆ The lithium bis (fluorosulfonyl) imide LiFSI is combined with the lithium bis (fluorosulfonyl) imide LiSSI, so that the conductivity of the electrolyte can be improved, on one hand, the internal resistance of the battery monomer can be reduced by improving the conductivity, the temperature rise at the joint of the current collector and the tab is reduced, and the temperature rise of the current collector and the tab is more balanced; on the other hand, the improvement of the conductivity of the electrolyte is beneficial to the active ions close to the electrode lugs to be embedded into the anode active material more, the metal precipitation amount on the anode piece in unit time is reduced, and the use reliability of the battery cell is improved.

In some embodiments, lithium hexafluorophosphate LiPF ₆ The mass content of (2) is 6.5% to 9%. Lithium hexafluorophosphate LiPF ₆ When the mass content of (2) is in the above range, the viscosity of the electrolyte can be improved, which is favorable for improving the conductivity of the electrolyte.

In some embodiments, the total mass content of lithium bis-fluorosulfonyl imide LiFSI is 6% to 8%. When the mass content of lithium bis (fluorosulfonyl) imide LiFSI is in the range, the SEI film interface can be effectively repaired, the impedance of the circulation process is reduced, the rapid migration of active ions is facilitated, the active ions can be rapidly embedded into the anode active material, and the risk that the active ions are separated out as metal on the surface of the anode plate is reduced; the lithium bis (fluorosulfonyl) imide LiSSI can also relieve the decomposition of lithium hexafluorophosphate into hydrofluoric acid to a certain extent, can further relieve the side reaction between the hydrofluoric acid and the active material, and can also improve the cycle performance of the battery monomer.

In some embodiments, the electrolyte further comprises an additive comprising at least one of lithium difluorophosphate and lithium fluorosulfonate; alternatively, the mass content of lithium difluorophosphate is 0.05% to 0.2% based on the total mass of the electrolyte; alternatively, the mass content of lithium fluorosulfonate is 0.01% to 0.1% based on the total mass of the electrolyte.

Therefore, in the embodiment of the application, the SEI film with lower impedance can be formed on the surface of the negative electrode plate by matching the lithium difluorophosphate with the lithium fluorosulfonate, so that the transmission capacity of active ions in the negative electrode active material layer is improved, and the risk of metal precipitation of the negative electrode plate near the electrode lug is reduced; lithium difluorophosphate and lithium fluorosulfonate can consume a large amount of electrons in the process of participating in forming an SEI film, can reduce the density of electrons at the tab, and then can reduce the risk that active ions are reduced into metal by electrons, and further improve the use reliability of the battery monomer.

In some embodiments, the electrolyte further comprises an organic solvent, the organic solvent comprising a first solvent and a second solvent, the first solvent comprising dimethyl carbonate and at least one of methyl ethyl carbonate, ethyl acetate, ethylene glycol monopropyl ether, methyl acrylate, and propyl propionate; the second solvent includes at least one of ethylene carbonate and propylene carbonate; alternatively, the total mass content of the first solvent is 55% to 70% based on the total mass of the electrolyte; alternatively, the total mass content of the second solvent is 20% to 35% based on the total mass of the electrolyte. Through the collocation use of the two solvents, the viscosity of the whole electrolyte can be effectively reduced, and the migration rate of active ions in the electrolyte can be improved.

In some embodiments, the olivine structured lithium-containing material includes a lithium iron phosphate-based material; optionally, the lithium iron phosphate-based material includes an element M, and M includes at least one of B, mg, al, ti, V, si, P, S, ca, sc, cr, cu, zn, sr, Y, zr, nb, mo, cd, sn, sb, te, ba, ta, W, yb, la and Ce. The material has higher cycle stability and can effectively improve the cycle performance of the battery monomer.

In some embodiments, M comprises at least one of Mg, al, ti, V and Zn, the mass percent of M element relative to the total mass of the lithium iron phosphate-based material being 100ppm to 1000ppm; alternatively 300ppm to 500ppm. M element can form local fast ion conductor phase in lithium iron phosphate material at least, accelerate the transmission of lithium ion in material, promote the dynamic performance of battery monomer.

In some embodiments, the ratio of the areal density of the single-sided positive electrode active material layer to the areal density of the single-sided negative electrode active material layer is (2.0 to 2.5): 1; alternatively, the areal density of the single-sided positive electrode active material layer is 0.27g/1540.25mm ² To 0.33g/1540.25mm ² The method comprises the steps of carrying out a first treatment on the surface of the Alternatively, the surface density of the single-sided anode active material layer was 0.11g/1540.25mm ² To 0.16g/1540.25mm ² . The negative electrode active material layer and the positive electrode active material layer are matched, so that lithium ions released from the positive electrode active material layer can be quickly embedded into the negative electrode active material layer, and the risk of lithium precipitation at the negative electrode piece is reduced.

In some embodiments, the negative active material layer includes at least one of artificial graphite and natural graphite.

In a second aspect, the present application also proposes a battery comprising a battery cell according to any of the embodiments of the first aspect of the present application.

In a third aspect, the present application further proposes an electrical device comprising a battery according to any of the embodiments of the third aspect of the present application.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic top view of one embodiment of an electrode assembly in a battery cell of the present application.

Fig. 2 is a schematic view of the electrode assembly of fig. 1 at another angle.

Fig. 3 is a schematic diagram of an embodiment of a battery cell of the present application.

Fig. 4 is an exploded schematic view of an embodiment of the battery cell of fig. 3.

Fig. 5 is a schematic view of an embodiment of a battery module of the present application.

Fig. 6 is a schematic diagram of an embodiment of a battery pack of the present application.

Fig. 7 is an exploded schematic view of the embodiment of the battery pack shown in fig. 6.

Fig. 8 is a schematic diagram of an embodiment of an electrical device including a battery cell of the present application as a power source.

The figures are not necessarily to scale.

The reference numerals are explained as follows:

x, width direction; y, length direction; z, thickness direction;

1. a battery pack; 2. an upper case; 3. a lower box body; 4. a battery module;

5. a battery cell; 51. a housing; 52. an electrode assembly; 7. a positive electrode sheet; 71. a positive electrode current collector; 72. a positive electrode active material layer; 8. a negative electrode plate; 81. a negative electrode current collector; 82. a negative electrode active material layer; 9. a separation film;

53. a cover plate;

6. and (5) an electric device.

Detailed Description

Hereinafter, embodiments of a battery cell, a battery, and an electric device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical ranges "a to b" represent a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been listed throughout, and "0 to 5" is only a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method may include steps (a) and (b), and the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may further comprise step (c), meaning that step (c) may be added to the method in any order, e.g. the method may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.

The battery monomer comprises an electrode assembly and electrolyte, the electrode assembly comprises a positive electrode plate, a negative electrode plate and an isolating film, and the isolating film is arranged between the positive electrode plate and the negative electrode plate so as to separate the positive electrode plate and the negative electrode plate and enable active ions to pass through. During the cell charging process, active ions are extracted from the positive electrode active material layer in the positive electrode sheet and migrate into the negative electrode active material in the negative electrode sheet, during which edge precipitation of lithium may occur on the negative electrode sheet.

In order to reduce the risk of lithium precipitation at the edge of the negative electrode plate, the area of the negative electrode plate is generally larger than that of the positive electrode plate in the related technology, so that the negative electrode plate can basically receive active ions from the positive electrode plate, and the risk that the active ions are precipitated as metal at the edge of the negative electrode plate is reduced.

The area of the negative electrode active material layer in the negative electrode plate, which exceeds the positive electrode active material layer in the positive electrode plate, is called an exceeding area, and the quantity of receivable active ions is increased along with the increase of the exceeding area, but the exceeding area is overlarge, so that the size of the negative electrode plate is possibly excessively set, the space is wasted, and the energy density of a battery cell is reduced; as the excess area decreases, the risk of precipitation of active ions as metal increases; therefore, how to set the out-of-range region is related to both improvement in cell use reliability and improvement in energy density.

In view of the above-mentioned problem, this application embodiment provides a battery monomer, and this battery monomer includes anodal pole piece and negative pole piece, and the length of anodal pole piece is less than the length of negative pole piece, and the width of anodal pole piece is less than the width of negative pole piece, and the design of the regional more than the regional design more than the regional design of the regional more than the width of the regional in length direction of negative pole piece for the active ion can all imbed basically in the negative pole active material layer of negative pole piece, promotes the use reliability of battery monomer.

Next, the technical scheme of the embodiment of the present application will be described in detail.

Battery cell

In a first aspect, embodiments of the present application provide a battery cell.

As shown in fig. 1 and 2, the battery cell includes an electrode assembly 52, the electrode assembly 52 includes a positive electrode tab 7 and a negative electrode tab 8, and an electrolyte, the positive electrode tab 7 includes a positive electrode current collector 71 and a positive electrode active material layer 72 disposed on at least one side of the positive electrode current collector 71, the positive electrode active material layer 72 includes a lithium-containing material of an olivine structure, the negative electrode tab 8 includes a negative electrode current collector 81 and a negative electrode active material layer 82 disposed on at least one side of the negative electrode current collector 81,

the positive electrode active material layer 72 has a dimension L in the length direction Y of the positive electrode tab 7 ₁ mm, the size of the positive electrode active material layer 72 in the width direction X of the positive electrode sheet 7 is W ₁ mm, the negative electrode active material layer 82 has a dimension L in the longitudinal direction Y ₂ mm, the negative electrode active material layer 82 has a dimension W in the width direction X ₂ mm，

Wherein 1 < (L) ₂ -L ₁ )/(W ₂ -W ₁ ) Not more than 4, and L ₂ /L ₁ ＞1；

The electrolyte comprises lithium hexafluorophosphate and lithium difluorosulfonimide, and the ratio of the mass content of the lithium hexafluorophosphate to the mass content of the lithium difluorosulfonimide is more than 1 based on the total mass of the electrolyte.

The pole piece in the battery cell is unfolded, the pole piece is of a sheet-shaped structure, the thickness of the pole piece is relatively thin, the face perpendicular to the thickness direction can be regarded as the front face of the pole piece, and the front face is generally in a quadrilateral shape. In order to improve the space utilization rate when the battery cell is assembled into a battery, the battery cell can be arranged into a long battery cell shape, the pole piece can be arranged into a cuboid sheet structure, namely, the front surface of the pole piece is rectangular, the long side dimension of the rectangle is larger than the short side dimension of the rectangle, the long side dimension is the length, the short side dimension is the width, the long side of the rectangle can be considered to be parallel to the length direction Y of the pole piece, and the short side of the rectangle can be considered to be parallel to the width direction X of the pole piece.

The positive electrode sheet 7 and the negative electrode sheet 8 are stacked, the length direction Y of the positive electrode sheet 7 is parallel to the length direction Y of the negative electrode sheet 8, and the width direction X of the positive electrode sheet 7 is parallel to the width direction X of the negative electrode sheet 8. Fig. 2 shows a schematic lamination view of the electrode assembly 52, in which the positive electrode tab 7, the separator 9, and the negative electrode tab 8 are laminated in this order in the thickness direction Z of the electrode assembly 52.

The pole piece comprises a current collector and pole lugs, the pole lugs are arranged on one side of the current collector, and the pole lugs can be further arranged on at least one side, such as two sides, of the current collector along the length direction Y in order to further improve the energy density of the battery unit. The current collector is provided with an active material layer for removing or inserting active ions such as lithium ions, sodium ions and the like, so as to realize the migration of the active ions; the electrode tab is not provided with an active material layer for electrically connecting the current collector with other parts of the battery cell, such as an electrode terminal, to realize conduction of an external circuit. For example, the positive electrode tab 7 includes a positive electrode current collector 71 and a positive electrode tab provided on at least one side of the positive electrode current collector 71 in the longitudinal direction Y, the positive electrode current collector 71 is provided with a positive electrode active material layer 72, and the positive electrode tab is not provided with the positive electrode active material layer 72. For example, the negative electrode tab 8 includes a negative electrode current collector 81 and a negative electrode tab provided on at least one side of the negative electrode current collector 81 in the length direction Y, a negative electrode active material layer 82 is provided on the negative electrode current collector 81, and a negative electrode active material layer 82 is not provided on the negative electrode tab.

In the related art, although the anode tab is provided with an excess region; however, compared with the current collector, the area of the tab is relatively smaller, the current density at the junction of the current collector and the tab is larger, the temperature rise is higher, the number of active ions which are separated from the positive electrode active material layer close to the tab is more, and the active ions may not be fully embedded into the negative electrode active material layer, so that metal precipitation easily occurs in the region of the negative electrode active material layer close to the tab.

The excess region shown in fig. 1 is a region in which the anode active material layer in the anode tab 8 exceeds the cathode active material layer in the cathode tab 7, and is a rectangular annular region having a dimension L in the length direction Y ₂ -L ₁ The dimension of the region in the width direction X is W ₂ -W ₁ 。

And this application embodiment is through further designing the excess region for the excess region size of negative pole piece 8 on length direction Y is bigger than the excess region size on width direction X, and negative pole active material layer 82 is stronger than the ability of receiving active ion on width direction X in length direction Y, especially can promote the ability of negative pole active material layer 82 to be close to the regional active ion of receiving of utmost point ear, thereby promotes the ability of the whole active ion of receiving of negative pole active material layer 82, reduces the risk that active ion separates out to the metal, improves the service reliability of battery monomer.

Specifically, the dimension of the positive electrode active material layer 72 in the length direction Y may be regarded as the length of the positive electrode active material layer 72, and the dimension of the positive electrode active material layer 72 in the width direction X may be regarded as the width of the positive electrode active material layer 72. The dimension of the anode active material layer 82 in the length direction Y may be regarded as the length of the anode active material layer 82, and the dimension of the anode active material layer 82 in the width direction X may be regarded as the width of the anode active material layer 82.

Length L of anode active material layer 82 ₂ mm minus the length L of the positive electrode active material layer 72 ₁ mm is the excess area length dimension of the anode active material layer 82; width W of anode active material layer 82 ₂ mm minus width W of positive electrode active material layer 72 ₁ mm is the excess area width dimension of the anode active material layer 82; the extent of the excess is greater than the extent of the excess width, i.e. 1 < (L ₂ -L ₁ )/(W ₂ -W ₁ ) The negative electrode active material layer 82 has stronger capability of receiving active ions in the length direction Y, and can effectively receive active ions from the positions close to the tabs, so that active ions extracted from the positive electrode active material can be basically embedded into the negative electrode active material layer 82, the risk of separating out the active ions as metal is reduced, and the use reliability of the battery cell is improved. With the increase of the length dimension of the exceeding area, the amount of receivable active ions increases, but the design of the length dimension of the exceeding area is too large, which may cause the waste of the negative electrode plate 8 and is not beneficial to the improvement of the energy density of the battery unit. Thus, embodiments of the present application further regulate (L ₂ -L ₁ )/(W ₂ -W ₁ ) And the energy density of the battery monomer can be improved while the use reliability of the battery monomer is improved. Especially in the case where the positive electrode active material layer includes a lithium-containing material of an olivine structure and the electrolyte includes lithium hexafluorophosphate and lithium difluorosulfonimide, the embodiment of the present application regulates 1 < (L ₂ -L ₁ )/(W ₂ -W ₁ ) And the energy density of the battery monomer can be improved while the use reliability of the battery monomer is improved.

Embodiments of the present applicationFurther regulate and control the content of L to be less than or equal to 1.25% ₂ -L ₁ )/(W ₂ -W ₁ ) 4 or less, alternatively 1.5 or less (L) ₂ -L ₁ )/(W ₂ -W ₁ ) The use reliability and the energy density of the battery monomer can be further improved by less than or equal to 2.5.

Illustratively, (L) ₂ -L ₁ )/(W ₂ -W ₁ ) May be 1.01, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, 3, 3.2, 3.5, 3.6, 3.8, 4.0 or a range of any two of the above values.

The embodiment of the application can further improve the use reliability and energy density of the battery cell by further controlling the sizes of the anode active material layer 82 and the cathode active material layer 72.

In some embodiments, 5.ltoreq.L ₂ -L ₁ And is less than or equal to 10. Illustratively, L ₂ -L ₁ May be 5, 5.2, 5.5, 5.8, 6, 6.2, 6.5, 7, 7.2, 7.5, 7.8, 8, 8.2, 8.5, 8.8, 9, 9.2, 9.5, 10 or a range of any two of the foregoing values. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, the length L of the anode active material layer 82 ₂ mm may be 500mm to 600mm, and is optionally 540.ltoreq.L ₂ And is less than or equal to 560. For example, the length L of the anode active material layer 82 ₂ The mm may be 500mm, 510mm, 520mm, 530mm, 540mm, 550mm, 560mm, 570mm, 580mm, 590mm, 600mm or a range of any two of the above values. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, the length L of the positive electrode active material layer 72 ₁ mm may be 500mm to 600mm, and is optionally 540.ltoreq.L ₁ And is less than or equal to 560. For example, the length L of the positive electrode active material layer 72 ₁ The mm can be 500mm, 510mm, 520mm, 530mm, 540mm, 550mm, 560mm, 570mm, 580mm, 590mm, 595mm, 600mm or a range of any two values mentioned above. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, 2.ltoreq.W ₂ -W ₁ And is less than or equal to 6. Illustratively W ₂ -W ₁ May be 2, 2.2, 2.5, 2.6, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.6, 4.8, 5, 5.2, 5.5, 5.8, 6 or a range of any two of the foregoing values. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

In some embodiments, the width W of the anode active material layer 82 ₂ The mm may be 100mm to 155mm, alternatively 140mm to 155mm, for example, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, 148mm, 150mm, 155mm or a range of any two of the above values.

In some embodiments, the width W of the positive electrode active material layer 72 ₁ The mm may be 100mm to 155mm, alternatively 140mm to 155mm, for example, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, 148mm, 150mm, 155mm or a range of any two of the above values. When the battery cell satisfies the above range, the use reliability and energy density of the battery cell can be further improved.

The electrode assembly 52 further includes a separator 9, where the separator 9 is disposed between the positive electrode tab 7 and the negative electrode tab 8 to separate the positive electrode tab 7 and the negative electrode tab 8, so that the risk of short-circuiting between the positive electrode tab 7 and the negative electrode tab 8 can be reduced. The area of the isolating membrane 9 can be larger than that of the negative electrode plate 8, so that the risk of short circuit between the positive electrode plate 7 and the negative electrode plate 8 can be further reduced.

In some embodiments, the dimension of the barrier film 9 along the length direction Y is L ₃ mm，2≤L ₃ -L ₂ And is less than or equal to 5. Illustratively, L ₃ -L ₂ May be 2, 2.2, 2.5, 2.6, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.6, 4.8, 5 or a range of any two of the foregoing values. The length dimension of the isolating film is relatively smallerAnd the risk of short circuit between the positive pole piece and the negative pole piece can be further reduced.

In some embodiments, the dimension of the barrier film 9 along the length direction Y is L ₃ mm, i.e. length L of the barrier film 9 ₃ The mm may be 500mm to 600mm, alternatively 550mm to 560mm; for example, 500mm, 510mm, 520mm, 530mm, 540mm, 550mm, 560mm, 570mm, 580mm, 590mm, 595mm, 600mm, or a range of any two of the above values. The length dimension of the isolating film is relatively longer, so that the risk of short circuit between the positive pole piece and the negative pole piece can be further reduced.

In some embodiments, the dimension of the separator 9 in the width direction X is W ₃ mm，2≤W ₃ -W ₂ And is less than or equal to 5. Illustratively W ₃ -W ₂ May be 2, 2.2, 2.5, 2.6, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.6, 4.8, 5 or a range of any two of the foregoing values. The width dimension of the isolating film is relatively longer, so that the risk of short circuit between the positive pole piece and the negative pole piece can be further reduced.

In some embodiments, the dimension of the separator 9 in the width direction X is W ₃ mm, i.e. width W of the barrier film 9 ₃ The mm may be 100mm to 160mm, alternatively 150mm to 160mm; for example, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, 148mm, 150mm, 155mm, 160mm, or a range of any two of the above values. The width dimension of the isolating film is relatively longer, so that the risk of short circuit between the positive pole piece and the negative pole piece can be further reduced.

In the embodiment of the application, the length and the width of the positive electrode active material layer in the positive electrode plate, the length and the width of the negative electrode active material layer in the negative electrode plate and the length and the width of the isolating film are all in the known meanings in the art, and can be detected by adopting equipment and a method known in the art; taking a positive electrode plate as an example, taking the positive electrode plate as a sample, and taking the length and the width of a positive electrode active material layer in the positive electrode plate by adopting a ten-thousandth ruler. Taking a negative electrode plate as an example, taking the negative electrode plate as a sample, and taking the length and the width of a negative electrode active material layer in the negative electrode plate by adopting a ten-thousandth ruler. Taking an isolating film as an example, taking the isolating film as a sample, and taking the length and the width of the isolating film by adopting a ten-thousandth ruler.

According to the embodiment of the application, the materials and the structure types of the positive electrode plate 7, the negative electrode plate 8 and the isolating film 9 are further improved, so that the use reliability, the energy density and other performances of the battery cell can be further improved.

[ Positive electrode sheet ]

In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposing in the own thickness direction, and the positive electrode active material layer is provided on either or both of the two opposing surfaces of the positive electrode current collector.

The positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a layered structure positive electrode active material (e.g., a material of nickel cobalt lithium manganate, nickel acid lithium/sodium, cobalt acid lithium/sodium, lithium manganate/sodium, lithium rich/sodium layered, and rock salt phase layered, etc.), an olivine structure lithium-containing material (e.g., including a lithium iron phosphate-based material, a lithium manganese phosphate-based material, etc.), a spinel structure positive electrode active material (e.g., spinel lithium manganate, spinel nickel lithium manganate, lithium rich spinel lithium manganate, nickel lithium manganate, etc.).

In some embodiments, the lithium iron phosphate-based material includes an element M; m comprises at least one of B, mg, al, ti, V, si, P, S, ca, sc, cr, cu, zn, sr, Y, zr, nb, mo, cd, sn, sb, te, ba, ta, W, yb, la, ce; the material is stable, and the cycle life of the battery system can be effectively prolonged. The M element can be arranged on the surface of the lithium iron phosphate material to play a role in coating, so that the structural stability of the lithium iron phosphate material is improved; or is positioned in the crystal phase of the lithium iron phosphate material to stabilize the lattice structure; it can also be located on the surface of the lithium iron phosphate material and in the crystal phase of the lithium iron phosphate material. When the lithium iron phosphate material is detected, the M element can be detected, namely, the lithium iron phosphate material is considered to comprise the M element.

In some embodiments, M comprises at least one of Mg, al, ti, V and Zn, optionally Al. The mass content of the M element relative to the total mass of the lithium iron phosphate material is 100ppm to 2000ppm; alternatively 300ppm to 500ppm. The lithium iron phosphate material contains the M element with the content, and the M element can at least form a local fast ion conductor phase in the lithium iron phosphate material, so that the transmission of lithium ions in the material is accelerated, and the dynamic performance of the battery monomer is improved.

For example, the lithium iron phosphate material may include at least one of Mg, al, ti, V and Zn, and the M element may be disposed on the surface of the lithium iron phosphate material, so as to perform a coating function and improve structural stability of the lithium iron phosphate material; or is positioned in the crystal phase of the lithium iron phosphate material to stabilize the lattice structure; it can also be located on the surface of the lithium iron phosphate material and in the crystal phase of the lithium iron phosphate material.

Illustratively, the mass content of the M element may be 100ppm, 200ppm, 300ppm, 400ppm, 450ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, or a range of any two of the foregoing numerical compositions.

In some embodiments, the lithium iron phosphate-based material includes a core including lithium iron phosphate particles and a carbon coating disposed on at least a portion of an outer surface of the core; the electrolyte further includes an organic solvent including a first solvent having a viscosity of not more than 0.8 Pa-s.

The lithium iron phosphate material is subjected to coating modification through the carbon coating layer, so that the conductivity of the lithium iron phosphate material can be improved, and the cycle performance in a working state is improved; however, due to the dense coating of the carbon coating layer, the electrolyte may infiltrate poorly into the core of the lithium iron phosphate material, and DCR growth in a state of standing and storage may be deteriorated; the embodiment of the application is matched with a low-viscosity organic solvent system, so that the wettability of electrolyte to the lithium iron phosphate material can be improved, and the DCR growth in a standing storage state can be reduced.

In some embodiments, the mass content of the carbon coating layer is 1.0% to 1.5% based on the total mass of the lithium iron phosphate-based material; the mass content of the organic solvent is more than or equal to 45 percent based on the total mass of the electrolyte; optionally 60% to 91%. When the mass content of the carbon coating layer and the mass content of the organic solvent are in the above ranges, both improvement of the cycle performance of the battery cell in the operating state and DCR growth in the stationary storage state can be achieved.

Illustratively, the carbon coating may be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% by mass or a range of any two values recited above; the organic solvent may be present in an amount of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 36.4%, 37%, 38%, 39%, 40%, 40.4%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 50.4%, 51%, 52%, 52.5%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91% or in a range comprised of any two of the foregoing values.

In embodiments of the present application, the content of the element in the positive electrode active material is in the meaning well known in the art, and may be detected using equipment and methods well known in the art, for example, by inductively coupled plasma atomic emission spectrometry testing with reference to EPA 6010D-2014, and measuring using plasma atomic emission (ICP-OES, instrument model: thermo ICAP 7400). First, 0.4. 0.4 g of the positive electrode active material was weighed, and 10ml (50% strength) of aqua regia was added thereto. Then placed on a 180℃plate for 30min. After digestion on the plate, the volume was fixed to 100% mL and quantitative testing was performed using standard curve method.

In some embodiments, the lithium iron phosphate-based material has a mass content of 85% or more and less than 100% based on the total mass of the positive electrode active material layer. For example, the mass content of the lithium iron phosphate material may be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or a range of any two of the above values.

In some embodiments, the positive electrode active material layer may further optionally include a positive electrode conductive agent. The present embodiment is not particularly limited in the kind of the positive electrode conductive agent, and the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, as an example. In some embodiments, the mass percent of the positive electrode conductive agent is less than or equal to 5% based on the total mass of the positive electrode active material layer.

In some embodiments, the positive electrode active material layer further optionally includes a positive electrode binder. The embodiment of the present application is not particularly limited in kind of the positive electrode binder, and the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate-based resin, as an example. In some embodiments, the mass percent of the positive electrode binder is less than or equal to 5% based on the total mass of the positive electrode active material layer.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel alloy, titanium alloy, silver, and silver alloy. As an example, the polymeric material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).

The positive electrode active material layer is usually formed by coating a positive electrode slurry on a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.

In some embodiments, the areal density of the single-sided positive electrode active material layer is 0.27g/1540.25mm ² To 0.33g/1540.25mm ² For example, 0.270g/1540.25mm ² 、0.275g/1540.25mm ² 、0.280g/1540.25mm ² 、0.285g/1540.25mm ² 、0.290g/1540.25mm ² 、0.30g/1540.25mm ² 、0.31g/1540.25mm ² 、0.32g/1540.25mm ² 、0.33g/1540.25mm ² Or a range of any two values recited above. When the surface density of the positive electrode active material layer meets the above range, the porosity and thickness of the positive electrode active material layer can be considered under the condition of meeting certain gram capacity of the positive electrode plate, so that the migration rate and migration path of lithium ions in the positive electrode active material layer are considered, and the quick charging performance of the battery cell is improved.

The surface density of the single-side negative electrode active material layer was 0.11g/1540.25mm in combination with the surface density of the positive electrode active material layer ² To 0.15g/1540.25mm ² For example 0.11g/1540.25mm ² 、0.12g/1540.25mm ² 、0.13g/1540.25mm ² 、0.14g/1540.25mm ² 、0.15g/1540.25mm ² Or a range of any two values recited above. When the surface density of the anode active material layer meets the above range, the porosity and the thickness of the anode active material layer can be considered under the condition of meeting a certain gram capacity of the anode piece, so that the migration rate and the migration path of lithium ions in the anode active material layer are considered; and the anode active material layer is matched with the cathode active material layer, so that lithium ions released from the cathode active material layer can be quickly embedded into the anode active material layer, and the risk of lithium precipitation at the anode piece is reduced.

In the present embodiment, the areal density of the single-sided positive electrode active material layer is a meaning well known in the art, and may be tested using methods known in the art. Areal density = single-sided positive electrode active material layer weight/single-sided positive electrode active material layer area, wherein single-sided positive electrode active material layer weight = (average weight of pole piece-average weight of current collector)/2, since both sides of the positive electrode current collector may have positive electrode active material layers. The specific test process is as follows: taking a single-sided coated and cold-pressed positive electrode plate (if the positive electrode plate is coated on two sides, the positive electrode film on one side can be wiped off firstly), punching into a small wafer with the area of S1, weighing the small wafer, and recording as M1. Then, the positive electrode active material layer of the positive electrode sheet after weighing is wiped off, the weight of the positive electrode current collector is weighed and recorded as M0, and the surface density of the positive electrode active material layer= (the weight of the positive electrode sheet M1-the weight of the positive electrode current collector M0)/S1. The surface density testing process of the single-sided anode active material layer is, for example, the surface density testing process of the single-sided cathode active material layer, and will not be described herein.

The "average" here may be an average value taken after 5 parallel tests.

[ negative electrode sheet ]

In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the anode current collector has two surfaces opposing in the own thickness direction, and the anode active material layer is provided on either or both of the two opposing surfaces of the anode current collector.

The negative electrode active material may employ a negative electrode active material for a battery cell, which is well known in the art. As an example, the anode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy material.

In some embodiments, the negative electrode active material in the negative electrode active material layer includes at least one of artificial graphite and natural graphite; alternatively, the negative active material includes artificial graphite, and the structural stability of the artificial graphite is relatively high.

The qualitative and quantitative properties of each substance or each element in the application can be detected by using proper equipment and methods known to those skilled in the art, the related detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards and the like, and those skilled in the art can adaptively change certain detection steps/instrument parameters and the like from the aspect of detection accuracy so as to obtain more accurate detection results. One detection method may be used qualitatively or quantitatively, or several detection methods may be used in combination for qualitative or quantitative determination.

For example, the graphite material in the present application can be subjected to an X-ray powder diffraction test and qualitative analysis on a negative electrode sheet or a negative electrode active material in combination with JIS/K0131-1996X ray diffraction analysis method general rule.

In some embodiments, the total mass content of the artificial graphite and the natural graphite is 85% or more and less than 100% based on the total mass of the anode active material layer. For example, the mass content of the artificial graphite may be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or a range of any two of the above values.

In some embodiments, the anode active material layer further optionally includes an anode conductive agent. The present embodiment is not particularly limited in kind of the anode conductive agent, and the anode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, as an example. In some embodiments, the negative electrode conductive agent is present in an amount of 5% by mass or less, based on the total weight of the negative electrode active material layer.

In some embodiments, the anode active material layer further optionally includes an anode binder. The present embodiment is not particularly limited in kind of the anode binder, and the anode binder may include at least one of styrene-butadiene rubber (SBR), a water-soluble unsaturated resin SR-1B, an aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), and carboxymethyl chitosan (CMCS), as an example. In some embodiments, the mass percent of the anode binder is less than or equal to 5%, based on the total weight of the anode active material layer.

In some embodiments, the anode active material layer may further optionally include other adjuvants. As an example, other adjuvants may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, and the like. In some embodiments, the other auxiliary agent is present in an amount of 2% by mass or less, based on the total weight of the anode active material layer.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. As an example of the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As an example, the metallic material may include at least one of copper, copper alloy, nickel alloy, titanium alloy, silver, and silver alloy. As an example, the polymeric material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).

The negative electrode active material layer is usually formed by applying a negative electrode slurry to a negative electrode current collector, drying and cold-pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional auxiliaries in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

The negative electrode tab does not exclude other additional functional layers than the negative electrode active material layer. For example, in some embodiments, the negative electrode tab of an embodiment of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on a surface of the negative electrode current collector, sandwiched between the negative electrode current collector and the negative electrode active material layer. In other embodiments, the negative electrode tab of embodiments of the present application further includes a protective layer covering the surface of the negative electrode active material layer.

[ isolation Membrane ]

The type of the separator according to the embodiment of the present invention is not particularly limited, and any known porous separator having good chemical stability and mechanical stability may be used.

In some embodiments, the material of the isolation film may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the separator, and the negative electrode tab may be manufactured into an electrode assembly through a winding process and/or a lamination process.

In some embodiments, the battery cell may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte as described above.

In some embodiments, the exterior packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the battery cell may also be a pouch, such as a pouch-type pouch. The soft bag can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[ electrolyte ]

In some embodiments, the battery cell further comprises an electrolyte, and active ions are inserted and removed back and forth between the positive electrode plate and the negative electrode plate in the charging and discharging process of the battery cell, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

In some embodiments, the electrolyte includes a lithium salt, which may include lithium hexafluorophosphate LiPF ₆ And lithium bis-fluorosulfonimide LiFeSI, optionally, the lithium salt may include lithium hexafluorophosphate LiPF ₆ And lithium bis (fluorosulfonyl) imide LiFSI, lithium hexafluorophosphate LiPF based on the total mass of the electrolyte ₆ The ratio of the mass content of (2) to the mass content of lithium bis (fluorosulfonyl) imide LiSSI is greater than 1, and the lithium hexafluorophosphate LiPF ₆ And the total mass content of lithium bis (fluorosulfonyl) imide LiFSI is 10% to 16%.

Lithium hexafluorophosphate LiPF ₆ The lithium bis (fluorosulfonyl) imide LiFSI is combined with the lithium bis (fluorosulfonyl) imide LiSSI, so that the conductivity of the electrolyte can be improved, on one hand, the internal resistance of the battery monomer can be reduced by improving the conductivity, the temperature rise at the joint of the current collector and the tab is reduced, and the temperature rise of the current collector and the tab is more balanced; on the other hand, the electrolyte is electrically chargedThe improvement of the conductivity is beneficial to the active ions close to the lug to be embedded into the negative electrode active material more, the metal precipitation amount on the negative electrode plate in unit time is reduced, and the use reliability of the battery cell is improved. Embodiments of the present application further regulate lithium hexafluorophosphate LiPF ₆ The ratio of the mass content of the lithium bis (fluorosulfonyl) imide to the mass content of LiFSI is 1.05 to 1.4, and the use reliability of the battery cell can be further improved.

Exemplary lithium hexafluorophosphate LiPF ₆ The ratio of the mass content of (3) to the mass content of lithium bis (fluorosulfonyl) imide LiFSI may be 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.12, 1.13, 1.15, 1.16, 1.18, 1.19, 1.2, 1.22, 1.24, 1.25, 1.28, 1.30, 1.32, 1.33, 1.35, 1.38, 1.40 or a range consisting of any two of the above values.

Exemplary lithium hexafluorophosphate LiPF ₆ The mass content of (c) is 6.5% to 9%, for example 6.5%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.5%, 7.6%, 7.8%, 7.9%, 8.0%, 8.2%, 8.5%, 8.8%, 9% or a range of any two of the above values. Lithium hexafluorophosphate LiPF ₆ When the mass content of (2) is in the above range, the viscosity of the electrolyte can be improved, which is favorable for improving the conductivity of the electrolyte.

Illustratively, the mass content of lithium bis-fluorosulfonimide LiFSI is 6% to 8%, e.g., 6%, 6.5%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.5%, 7.6%, 7.8%, 7.9%, 8.0%, or a range of any two of the foregoing values. When the mass content of the lithium bis (fluorosulfonyl) imide LiFSI is in the range, the lithium bis (fluorosulfonyl) imide LiSSI can form a solid electrolyte interface (Solid Electrolyte Interphase, SEI) film rich in fluorine elements on the surface of the anode active material, can effectively repair the SEI film interface, reduce the impedance of a circulation process, is beneficial to the rapid migration of active ions, can enable the active ions to be rapidly embedded into the anode active material, and reduces the risk that the active ions are separated out as metal on the surface of the anode piece; the lithium bis (fluorosulfonyl) imide LiSSI can also relieve the decomposition of lithium hexafluorophosphate into hydrofluoric acid to a certain extent, can further relieve the side reaction between the hydrofluoric acid and the active material, and can also improve the cycle performance of the battery monomer.

In some embodiments, the electrolyte further comprises an additive comprising at least one of lithium difluorophosphate and lithium fluorosulfonate, optionally the additive comprises lithium difluorophosphate and lithium fluorosulfonate.

On the one hand, the cooperation of the lithium difluorophosphate and the lithium fluorosulfonate can enable the surface of the negative electrode plate to form an SEI film with lower impedance, improve the transmission capacity of active ions in the negative electrode active material layer and reduce the risk of metal precipitation of the negative electrode plate near the tab; on the other hand, lithium difluorophosphate and lithium fluorosulfonate can consume a large amount of electrons in the process of participating in forming an SEI film, can reduce the density of electrons at the electrode lug, further can reduce the risk that active ions are reduced into metal by electrons, and further improves the use reliability of the battery monomer.

Illustratively, the lithium difluorophosphate is present in an amount of from 0.05% to 0.2%, such as 0.05%, 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2% or in a range of any two values recited above, based on the total mass of the electrolyte.

Illustratively, the lithium fluorosulfonate is present in an amount of 0.01% to 0.1%, such as 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.08%, 0.10%, 0.11%, or in a range of any two of the foregoing values, based on the total mass of the electrolyte.

In some embodiments, the electrolyte further comprises an organic solvent comprising a first solvent and a second solvent, the first solvent having a viscosity that is less than the viscosity of the second solvent. Through the collocation use of the two solvents, the viscosity of the whole electrolyte can be effectively reduced, and the migration rate of active ions in the electrolyte can be improved. Optionally, the viscosity of the first solvent is not more than 0.8pa·s.

In some embodiments, the first solvent may include dimethyl carbonate DMC and at least one of methyl ethyl carbonate EMC, ethyl acetate, ethylene glycol monopropyl ether EP, methyl acrylate MA, and propyl propionate PP; the second solvent may include at least one of ethylene carbonate EC and propylene carbonate PC. The viscosity of the first solvent is relatively small, so that the overall viscosity of the electrolyte can be reduced; the second solvent has relatively strong dissociation capability to lithium salt, and is beneficial to improving the migration rate of lithium ions. By adopting the solvent system, the viscosity of the electrolyte is relatively small, active ions such as lithium ions are more easily balanced in the battery cell, and the risk of lithium separation caused by local excessive density of the lithium ions in the battery cell can be reduced; and the solvent system and the lithium salt are used together, so that the conductivity of the electrolyte is relatively high, and the migration rate of lithium ions is improved, thereby improving the dynamic performance of the battery monomer.

In some embodiments, the total mass content of the first solvent is 55% to 70%, such as 55%, 56%, 57%, 58%, 59%, 60%, 62%, 63%, 65%, 68%, 70%, or a range of any two of the above numerical compositions, based on the total mass of the electrolyte. When the total mass content of the first solvent is in the range, the overall viscosity of the electrolyte can be reduced, the uniformity of lithium ion transmission is improved, the lithium precipitation risk is reduced, and the use reliability of the battery monomer is improved.

In some embodiments, the total mass content of the second solvent is 20% to 35%, such as 20%, 21%, 22%, 23%, 24%, 25%, 26%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or a range of any two of the above values, based on the total mass of the electrolyte. When the total mass content of the second solvent is in the range, the dissociation capability of lithium salt can be improved, the rapid migration of lithium ions is facilitated, and the dynamic performance of the battery monomer can be further improved.

In the embodiment of the present application, the type and content of the inorganic component/lithium salt concentration in the electrolyte are the meanings known in the art, and can be detected by using the equipment and method known in the art, for example, the inorganic component/lithium salt concentration in the electrolyte can be qualitatively or quantitatively analyzed by the ion chromatography method with reference to the standard JY/T020-1996 general rule of ion chromatography method. In the embodiment of the application, the newly prepared electrolyte can be taken as a sample, or the battery which has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) is reversely disassembled, and the free electrolyte obtained from the battery is taken as the sample and detected by adopting an ion chromatography analysis method.

In the embodiments of the present application, the types and contents of the organic components in the electrolyte are in the meaning known in the art, and may be detected by using devices and methods known in the art, for example, qualitative and quantitative analysis of the organic components in the electrolyte may be performed by gas chromatography with reference to GB/T9722-2006 general rules for chemical gas chromatography. In the embodiment of the application, the newly prepared electrolyte can be taken as a sample, or the battery which has been discharged (discharged to the lower limit cutoff voltage so that the charged state of the battery is about 0% SOC) is reversely disassembled, and the free electrolyte obtained from the battery is taken as the sample and detected by adopting an ion chromatography analysis method.

For another example, taking liquid-phase Nuclear Magnetic Resonance (NMR) to test the components of a certain additive in the electrolyte, taking lithium difluorophosphate and lithium hexafluorophosphate as examples, preparing 1 7ml glass bottle in a nitrogen glove box, adding 5ml nuclear magnetic reagent premix into the glass bottle, and standing at room temperature of 20-25 ℃ for 24 hours in the nitrogen glove box, so that the electrolyte in the pole piece and the isolating film is diffused into the nuclear magnetic premix, thereby obtaining a nuclear magnetic measurement sample. The nuclear magnetic premix comprises 100ml of deuterated acetonitrile and 3ml of trifluoromethyl benzene, and the nuclear magnetic reagent premix is pre-dried by using a molecular sieve 4A in advance (15 g of newly opened 4A molecular sieve is added into 100ml of nuclear magnetic reagent premix and dried for more than 30 days in a nitrogen glove box at the temperature of 20-25 ℃). The 19F NMR measurement (nuclear magnetic resonance (NMR): bruker Avance 400 HD) was used.

In order to identify and quantify the individual species, the following settings were employed in terms of flip angle and scan time.

Fluorine spectrum test pulse sequence: 2gfhigqn.2;

delay time: 1 second;

number of scans: 16 times.

Based on trifluoromethylbenzene and LiPF in F-NMR ₆ The relative content of the two substances is calculated by the integral intensity of the signal peaks, and the calculation method comprises the following steps:

PF ₆ ^- relative content= (I) _PF6 ^- ×M _PF6 ^- /6)/(I _CF3ph ×M _CF3ph And 3), wherein I is the corresponding nuclear magnetic peak area, M is the corresponding relative molecular mass, and then the molar ratio relation of the hexafluorophosphate radical and lithium ions is used for calculating the content of lithium hexafluorophosphate in the electrolyte.

Based on trifluoromethyl benzene and PO in F-NMR ₂ F ₂ ^- The relative content of the two substances is calculated by the integral intensity of the signal peaks, and the calculation method comprises the following steps:

PO ₂ F ₂ ^- relative content= (I) _PO2F2- ×M _PO2F2- /2)/(I _CF3ph ×M _CF3ph And 3), wherein I is the corresponding nuclear magnetic peak area, M is the corresponding relative molecular mass, and then the molar ratio relation of the difluorophosphate radical and lithium ions is used for calculating the content of the lithium difluorophosphate in the electrolyte.

In some embodiments, various types of solutes or solvents in the electrolytes referred to herein include both substances that are actively added in preparing the electrolyte and substances that are derived from substances already present in some electrolyte(s) during storage or use, either during electrolyte preparation or during battery preparation from the electrolyte or from a battery containing the electrolyte.

The shape of the battery cell according to the embodiment of the present application is not particularly limited, and may be cylindrical, square, or any other shape. Fig. 3 shows a square-structured battery cell 5 as an example.

In some embodiments, as shown in fig. 4, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate coupled to the bottom plate, the bottom plate and the side plate enclosing to form a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 is used to cover the opening to close the accommodation chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 52 through a winding process and/or a lamination process. The electrode assembly 52 is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of the electrode assemblies 52 included in the battery cell 5 may be one or more, and may be adjusted according to the need.

Methods of preparing the battery cells of the embodiments of the present application are well known. In some embodiments, the positive electrode tab, separator, negative electrode tab, and electrolyte may be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet may be wound and/or laminated to form an electrode assembly, the electrode assembly is placed in an outer package, dried and then injected with an electrolyte, and the battery cell is obtained through vacuum packaging, standing, formation, shaping and other steps.

In some examples of embodiments of the present application, the battery cells according to embodiments of the present application may be assembled into a battery module, and the number of battery cells included in the battery module may be plural, and the specific number may be adjusted according to the application and capacity of the battery module.

Fig. 5 is a schematic view of the battery module 4 as an example. As shown in fig. 5, in the battery module 4, a plurality of battery cells 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of battery cells 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a housing having an accommodating space in which the plurality of battery cells 5 are accommodated.

In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

Fig. 6 and 7 are schematic views of the battery pack 1 as an example. As shown in fig. 6 and 7, a battery box and a plurality of battery modules 4 provided in the battery box may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used for covering the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

Power utilization device

A second aspect of the embodiments provides an electrical device comprising at least one of the battery cells, battery modules, or battery packs of the embodiments. The battery cell, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The electric device may be, but is not limited to, a mobile device (e.g., a cellular phone, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

The power utilization device can select a battery cell, a battery module or a battery pack according to the use requirement.

Fig. 8 is a schematic diagram of the power consumption device 6 as an example. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. To meet the high power and high energy density requirements of the power consumer 6, a battery pack or battery module may be employed.

As another example, the power consumption device may be a mobile phone, a tablet computer, a notebook computer, or the like. The power utilization device is required to be light and thin, and a battery unit can be used as a power supply.

Examples

The following examples more particularly describe the disclosure of embodiments of the present application, which examples are intended as illustrative only, since numerous modifications and variations within the scope of the disclosure of embodiments of the present application will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages and ratios reported in the examples below are on a mass basis, and all reagents used in the examples are commercially available or were obtained synthetically according to conventional methods and can be used directly without further treatment, as well as the instruments used in the examples.

Example 1

1. Preparation of positive electrode plate

The positive pole piece comprises a positive current collector aluminum foil and a positive active material layer, wherein the positive active material layer comprises a film layer formed by uniformly coating positive slurry (N-methylpyrrolidone NMP as a solvent) on the surface of the positive current collector aluminum foil, drying and cold pressing, and the positive active material layer comprises the following components in percentage by weight: 1.4:1.1, a positive electrode active material, a conductive agent carbon black, and a binder polyvinylidene fluoride (PVDF).

The positive electrode active material includes a lithium iron phosphate-based material. The surface density of the positive electrode active material layer was 0.3g/1540.25mm ² 。

2. Preparation of negative electrode plate

The negative electrode plate comprises a negative electrode current collector copper foil and a negative electrode active material layer, wherein the negative electrode active material layer comprises a film layer formed by uniformly coating negative electrode slurry (deionized water serving as a solvent) on the surface of the negative electrode current collector copper foil, drying and cold pressing, and the negative electrode active material layer comprises the following components in percentage by weight: 1.8:1.2:0.8 of a negative electrode active material, a binder styrene-butadiene rubber (SBR), a thickener sodium carboxymethylcellulose (CMC-Na) and a conductive agent carbon black (Super P).

The negative active material includes artificial graphite. Negative electrodeThe surface density of the active material layer was 0.15g/1540.25mm ² . The ratio of the areal density of the single-sided positive electrode active material layer to the areal density of the single-sided negative electrode active material layer was 2:1.

3. Isolation film

The isolating film is porous polypropylene film.

4. Preparation of electrolyte

The electrolyte comprises an organic solvent, lithium salt and an additive.

5. Preparation of a Battery

The lithium ion battery comprises an outer packaging shell, an electrode assembly and electrolyte, wherein the electrode assembly and the electrolyte are arranged in the outer packaging shell, the electrode assembly comprises a positive electrode plate, a negative electrode plate and an isolating film, the electrode assembly is a winding type electrode assembly, and the isolating film is arranged between the positive electrode plate and the negative electrode plate.

Comparative example 1 and comparative example 2

A lithium ion battery was fabricated by a method similar to example 1, except that the length of the positive electrode active material layer in the positive electrode sheet was adjusted, unlike example 1.

Examples 2-1 to 2-5

A lithium ion battery was fabricated by a method similar to example 1, except that at least one of the width and length of the anode active material layer in the anode tab was adjusted, unlike example 1.

Examples 3-1 and 3-2

A lithium ion battery was produced by a method similar to example 1, except that at least one of the width and the length of the separator was adjusted, unlike example 1.

Examples 4-1 and 4-2

A lithium ion battery was fabricated by a method similar to example 1, except that the areal density of the anode active material layer was adjusted, unlike example 1.

Wherein,

the surface density of the anode active material layer in example 4-1 was 0.13g/1540.25mm ² The ratio of the areal density of the single-sided positive electrode active material layer to the areal density of the single-sided negative electrode active material layer was 2.3:1.

Negative electrode active material in example 4-2The surface density of the sexual material layer was 0.16g/1540.25mm ² The ratio of the areal density of the single-sided positive electrode active material layer to the areal density of the single-sided negative electrode active material layer was 1.875:1.

Example 5

A lithium ion battery was produced in a similar manner to example 1, except that the material of the positive electrode active material including a lithium iron phosphate-based material including aluminum element in an amount of 400ppm was adjusted as in example 1.

The relevant parameters of examples 1 to 5, comparative example 1 and comparative example 2 are shown in table 1.

The electrolyte compositions of the above examples and comparative examples are the same as those of example 1, as shown in table 2.

Performance testing

1. Lithium ion battery lithium evolution test

And (3) fully charging the lithium ion batteries prepared in the examples and the comparative examples to 3.6V at 4C, fully discharging the lithium ion batteries to 2.0V at 1C at 25 ℃, repeating the steps for 10 times, fully charging the lithium ion batteries at 4C, then disassembling the negative electrode plate, and observing the lithium precipitation condition on the surface of the negative electrode plate.

Test results

The test results are shown in Table 1.

TABLE 1

As a result of the test, it was found that,

the area of the lithium-separating region on the surface of the negative electrode less than 5% is regarded as slight lithium separation,

the area of the lithium-separating area on the surface of the negative electrode is 5 to 40 percent, which is regarded as moderate lithium separation,

the area of the lithium-separating region on the surface of the negative electrode greater than 40% is considered to be severely lithium-separating.

The area of the lithium-eluting region on the surface of the negative electrode of comparative example 1 was 49%, which is a serious lithium-eluting region.

In table 1, based on comparative example 1, the lithium precipitation condition was defined as 100%, and the percentage of the lithium precipitation area of other examples and comparative examples was calculated to occupy the lithium precipitation area of comparative example 1, and the lithium precipitation condition was intermediate lithium precipitation when the lithium precipitation condition was 10% to 82%; when the lithium precipitation condition is less than 10%, slightly precipitating lithium; when the lithium precipitation is more than 82%, the lithium is severely precipitated.

The excess area is smaller in comparative example 1, and there is a risk of lithium precipitation; compared with comparative example 1, the embodiment adjusts the size of the exceeding area, the design of the exceeding area of the negative electrode plate in the length direction is larger than the design of the exceeding area in the width direction, so that active ions can be basically embedded into the negative electrode active material layer of the negative electrode plate, the lithium precipitation degree is reduced, and the use reliability of the battery cell is improved. However, with further increase of the excess area, the energy density may be reduced, for example, the excess area in the longitudinal direction in comparative example 2 is designed too large, and the energy density may be reduced.

As can be seen from a combination of examples 1 to 2-5, 1 < (L ₂ -L ₁ )/(W ₂ -W ₁ ) 4 or less, in particular 1.5 or less (L) ₂ -L ₁ )/(W ₂ -W ₁ ) When the lithium precipitation degree of the battery is less than or equal to 2.5, the lithium precipitation degree of the battery is lower, and the use reliability of the battery is further improved.

Examples 3-1 and 3-2 can further adjust the lithium precipitation degree of the battery by adjusting the size of the separator, so that the use reliability of the battery is further improved.

Examples 4-1 and 4-2 can further adjust the capacity of the anode active material layer to receive active ions by adjusting the areal density of the anode active material layer, thereby adjusting the lithium precipitation degree of the battery, and further improving the use reliability of the battery.

Example 5 further improvement in battery performance was facilitated by disposing an aluminum element in the positive electrode active material.

Examples 6-1 to 6-5

A lithium ion battery was produced in a similar manner to example 1, except that lithium hexafluorophosphate LiPF in an electrolyte was adjusted in accordance with example 1 ₆ And lithium bis (fluorosulfonyl) imide LiFSI.

Examples 7-1 to 7-5

A lithium ion battery was produced in a similar manner to example 1, except that the content of at least one of lithium difluorophosphate and lithium fluorosulfonate in the electrolyte was adjusted, unlike example 1.

Examples 8-1 and 8-2

A lithium ion battery was produced in a similar manner to example 1, except that the content of the organic solvent in the electrolytic solution was adjusted, unlike example 1.

Comparative example 3

A lithium ion battery was produced in a similar manner to example 1, except that the kind and content of lithium salt in the electrolyte were adjusted, unlike example 1.

TABLE 2

In the table 2 of the description of the present invention,

the first solvent comprises dimethyl carbonate DMC and ethylmethyl carbonate EMC in a mass ratio of 1:1.

The second solvent comprises ethylene carbonate EC and propylene carbonate PC in a mass ratio of 1:1, the mass content of the second solvent = 100% of the total mass of the electrolyte- (lithium salt + additive + first solvent) total mass content. For example, the mass content of the second solvent in example 1 was 29.85%, the mass content of the second solvent in example 8-1 was 24.85%, and the mass content of the second solvent in example 8-2 was 34.85%.

As is clear from Table 2, in comparative example 3, only lithium hexafluorophosphate LiPF was added to the electrolyte ₆ As a lithium salt, the mass content thereof is 15.00%, the viscosity in the system is high, migration of lithium ions is not facilitated, and the risk of lithium precipitation may be increased.

The electrolyte is added with lithium hexafluorophosphate and lithium difluorosulfonimide LiFSI, in particular lithium hexafluorophosphate LiPF in example 1, example 6-1 to example 6-5 ₆ The ratio of the mass content of (2) to the mass content of lithium bis (fluorosulfonyl) imide LiFeSI is 1.05 to 1.4 by lithium hexafluorophosphate LiPF ₆ And lithium bis (fluorosulfonyl) imide LiFSI, can improve electricityThe conductivity of the electrolyte reduces the internal resistance of the battery monomer, is beneficial to the active ions near the lug to be embedded into the negative electrode active material more, reduces the metal precipitation amount on the negative electrode plate in unit time, and is beneficial to improving the use reliability of the battery monomer.

In examples 7-1 and 7-2, the mass content of lithium difluorophosphate and lithium fluorosulfonate is controlled to be 0.05% to 0.2%, and/or the mass content of lithium fluorosulfonate is controlled to be 0.01% to 0.1%, so that the transmission capacity of active ions in the anode active material layer can be improved, and the risk of metal precipitation of the anode tab near the tab can be reduced.

In examples 8-1 and 8-2, the migration rate of active ions in the electrolyte can be increased and the lithium precipitation degree of the battery cell can be improved by adjusting the mass content of the low-viscosity solvent.

Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the application and that changes, substitutions and alterations of the embodiments may be made without departing from the spirit, principles and scope of the application.

Claims

1. The battery cell is characterized by comprising a positive electrode plate, a negative electrode plate and electrolyte, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, the positive electrode active material layer comprises a lithium-containing material with an olivine structure, the negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector,

the size of the positive electrode active material layer along the length direction of the positive electrode plate is L ₁ mm, the dimension of the positive electrode active material layer along the width direction of the positive electrode plate is W ₁ mm, the dimension of the anode active material layer along the length direction is L ₂ mm, the dimension of the anode active material layer in the width direction is W ₂ mm，

Wherein 1 < (L) ₂ -L ₁ )/(W ₂ -W ₁ )≤4, and L ₂ /L ₁ ＞1，500≤L ₁ ≤600；

The electrolyte comprises lithium hexafluorophosphate LiPF ₆ And lithium bis (fluorosulfonyl) imide LiFeSI, based on the total mass of the electrolyte, the lithium hexafluorophosphate LiPF ₆ The ratio of the mass content of (2) to the mass content of lithium bis (fluorosulfonyl) imide LiSSI is greater than 1.

2. The battery cell of claim 1, wherein 1.5 +. ₂ -L ₁ )/(W ₂ -W ₁ )≤2.5。

3. The battery cell of claim 1, wherein 5.ltoreq.l ₂ -L ₁ Less than or equal to 10; or 2 is less than or equal to W ₂ -W ₁ ≤6。

4. The battery cell of claim 1, wherein 500L ₂ ≤600。

5. The battery cell of claim 1, wherein 100 +.w ₂ 155 or less; or 100.ltoreq.W ₁ ≤155。

6. The battery cell of claim 1, further comprising a separator disposed between the positive electrode tab and the negative electrode tab, the separator having a dimension L along the length direction ₃ mm, a dimension W in the width direction ₃ mm，2≤L ₃ -L ₂ Less than or equal to 5; and/or 2.ltoreq.W ₃ -W ₂ ≤5。

7. The battery cell of claim 6, wherein 500.ltoreq.L ₃ Less than or equal to 600; and/or 100.ltoreq.W ₃ ≤160。

8. The battery cell of claim 1, wherein the lithium hexafluorophosphate LiPF ₆ And bis-fluorosulfonylThe total mass content of the lithium imide LiFSI is 10 to 16 percent.

9. The battery cell of claim 8, wherein the lithium hexafluorophosphate LiPF based on the total mass of the electrolyte ₆ The ratio of the mass content of (2) to the mass content of lithium bis (fluorosulfonyl) imide LiSSI is 1.05 to 1.4.

10. The battery cell of claim 8, wherein the lithium hexafluorophosphate LiPF based on the total mass of the electrolyte ₆ Is 6.5 to 9% by mass; or (b)

The total mass content of the lithium bis (fluorosulfonyl) imide LiFSI is 6% to 8% based on the total mass of the electrolyte.

11. The battery cell of any one of claims 1 to 10, wherein the electrolyte further comprises an additive comprising at least one of lithium difluorophosphate and lithium fluorosulfonate.

12. The battery cell according to claim 11, wherein the mass content of the lithium difluorophosphate is 0.05% to 0.2% based on the total mass of the electrolyte; and/or

The lithium fluorosulfonate is present in an amount of 0.01% to 0.1% by mass based on the total mass of the electrolyte.

13. The battery cell of any one of claims 1 to 10, wherein the electrolyte further comprises an organic solvent comprising:

a first solvent comprising at least one of dimethyl carbonate and methyl ethyl carbonate, ethyl acetate, ethylene glycol monopropyl ether, methyl acrylate and propyl propionate; and

and a second solvent including at least one of ethylene carbonate and propylene carbonate.

14. The battery cell of claim 13, wherein the total mass content of the first solvent is 55% to 70% based on the total mass of the electrolyte; and/or

The second solvent has a total mass content of 20% to 35% based on the total mass of the electrolyte.

15. The battery cell of any one of claims 1 to 10, wherein the olivine structured lithium-containing material comprises a lithium iron phosphate-based material.

16. The battery cell of claim 15, wherein the lithium iron phosphate-based material comprises an element M, M comprising at least one of B, mg, al, ti, V, si, P, S, ca, sc, cr, cu, zn, sr, Y, zr, nb, mo, cd, sn, sb, te, ba, ta, W, yb, la and Ce.

17. The battery cell of claim 16, wherein M comprises at least one of Mg, al, ti, V and Zn, and wherein the mass percentage of M element relative to the total mass of the lithium iron phosphate-based material is 100ppm to 1000ppm.

18. The battery cell according to any one of claims 1 to 10, wherein a ratio of an areal density of the positive electrode active material layer on one side to an areal density of the negative electrode active material layer on one side is (2.0 to 2.5): 1.

19. The battery cell according to claim 18, wherein the positive electrode active material layer on one side has an areal density of 0.27g/1540.25mm ² To 0.33g/1540.25mm ² The method comprises the steps of carrying out a first treatment on the surface of the And/or

The surface density of the negative electrode active material layer on one side is 0.11g/1540.25mm ² To 0.16g/1540.25mm ² 。

20. The battery cell of claim 18, wherein the negative active material layer comprises at least one of artificial graphite and natural graphite.

21. A battery comprising a cell according to any one of claims 1 to 20.

22. An electrical device comprising the battery of claim 21.