All-solid-state lithium ion battery

Abstract

The invention provides an all-solid-state lithium ion battery, and belongs to the technical field of secondary batteries, the all-solid-state lithium ion battery comprises a solid electrolyte, the solid electrolyte is Li < 2 + a > Zr < 1-a > MaBr < x > I < y > Cl < 6-x-y >, 0 < = a < = 0.5, 0 < = x < = 6, 0 < = y < = 6, and 0 < = x + y < = 6; the M element is selected from at least one of Fe, Co, Ni, Mn, V and Cr. According to the all-solid-state lithium ion battery provided by the invention, a halide solid electrolyte is used for replacing a liquid electrolyte to serve as a conductive material between pole pieces in a bipolar battery, so that the charge-discharge cycle of a multi-battery unit framework in the battery is realized on the premise of reducing the use of a current collector, a tab and a connecting wire in the battery; therefore, the energy density of the battery is increased to the maximum extent and the manufacturing cost of the battery is reduced while the short circuit of the battery liquid caused by leakage of the liquid electrolyte is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to an all-solid-state lithium-ion battery. Background Art

[0002] The current lithium battery devices are limited by the excessive volume and mass of inactive substances, resulting in low battery energy density, and the battery packs are connected in parallel, which will cause the battery voltage to be unadjustable. Due to its structural characteristics, stacked battery packs can reduce the energy density of the battery and achieve high battery voltage. However, for stacked battery packs, when liquid electrolyte is selected as the ion transport medium, very strict sealing devices are required between each battery cell, otherwise the random flow of liquid electrolyte between battery cells will cause liquid short circuit of the battery, and electrolyte leakage will also cause battery performance degradation and even safety accidents.

[0003] Therefore, it is necessary to design an all-solid-state lithium-ion battery to solve the above problems. Summary of the invention

[0004] In view of the above shortcomings of the prior art, the present invention provides an all-solid-state lithium-ion battery for solving the technical problems in the prior art that the battery pack uses liquid electrolyte as a conductive medium, resulting in complex packaging structure, limited energy density and easy liquid short circuit.

[0005] To achieve the above-mentioned object and other related objects, the present invention provides an all-solid-state lithium-ion battery, the all-solid-state lithium-ion battery comprising a solid electrolyte, wherein the solid electrolyte is Li 2+a Zr 1-a M a Br x I y Cl 6-x-y , wherein 0≤a≤0.5, 0≤x≤6, 0≤y≤6, 0≤x+y≤6; and the M element is selected from at least one of Fe, Co, Ni, Mn, V and Cr.

[0006] In an example of the present invention, in the solid electrolyte, the M element is selected from Fe or Co.

[0007] In one example of the present invention, an all-solid-state lithium-ion battery includes a positive electrode active material layer, a negative electrode active material layer and a conductive layer, wherein the conductive layer is located between the positive electrode active material layer and the negative electrode active material layer; and the conductive layer includes the solid electrolyte.

[0008] In an example of the present invention, the positive electrode active material layer includes a positive electrode active material and a composite electrolyte, and the composite electrolyte is made of the same material as the solid electrolyte.

[0009] In one example of the present invention, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese-rich oxide and lithium phosphate.

[0010] In an example of the present invention, the positive electrode active material layer further includes a positive electrode conductive agent, and the mass ratio of the positive electrode active material, the composite electrolyte and the positive electrode conductive agent is (50-75):(20-50):1.

[0011] In an example of the present invention, the conductive agent includes carbon black and carbon nanofibers, wherein the mass ratio of the carbon black to the carbon nanofibers is 1:(0.2-1.5).

[0012] In an example of the present invention, the negative electrode active material layer includes a negative electrode active material and a composite electrolyte, and the composite electrolyte is made of the same material as the solid electrolyte.

[0013] In an example of the present invention, the negative electrode active material layer further includes a negative electrode conductive agent, and the mass ratio of the negative electrode active material, the composite electrolyte and the negative electrode conductive agent is (50-75):(20-50):1.

[0014] In an example of the present invention, the all-solid-state lithium-ion battery further includes a plurality of current collectors, which are stacked; the positive electrode active material layer, the conductive layer and the negative electrode active material layer are disposed between adjacent current collectors.

[0015] The present invention provides an all-solid-state lithium-ion battery. The all-solid-state lithium-ion battery uses a halide solid electrolyte to replace a liquid electrolyte as a conductive material between pole pieces, so as to realize a charge and discharge cycle of a multi-battery unit architecture in the battery while reducing the use of current collectors, pole tabs and connecting wires in the battery. This can avoid liquid electrolyte leakage causing a liquid short circuit in the battery, while maximizing the energy density of the battery and reducing the manufacturing cost of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a schematic diagram of the structure of an all-solid-state lithium-ion battery in one embodiment of the present invention;

[0018] Figure 2Schematic diagram of a process for preparing an electrolyte in one embodiment of the present invention;

[0019] Figure 3 Schematic diagram of the preparation process of an all-solid-state lithium-ion battery in one embodiment of the present invention.

[0020] Component number description

[0021] 100, positive electrode plate; 110, positive electrode current collector; 200, negative electrode plate; 210, negative electrode current collector; 300, bipolar electrode plate; 310, bipolar current collector; 400, conductive layer; 500, encapsulation layer; 600, positive electrode active material layer; 700, negative electrode active material layer. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0023] It should be noted that, in the absence of conflict, the features in the following examples and embodiments can be combined with each other. It should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments rather than to limit the scope of the present invention. The test methods in the following examples that do not specify specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0024] For simplicity, only some numerical ranges are explicitly disclosed herein, and each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unspecified range.

[0025] In existing lithium-ion battery systems, each battery cell is individually sealed to prevent the leakage of flowable liquid electrolytes and cause ion short circuits inside the battery pack. Therefore, many inactive materials are used in the battery system, such as current collectors, packaging materials, and tabs and connecting wires for external connections, which limits the energy density of lithium-ion batteries and increases their costs. Therefore, for the further development of lithium-ion battery structures, it is crucial to reduce the use of inactive materials to reduce weight and cost.

[0026] At present, in addition to improving the energy density of batteries by optimizing materials, special structural designs can also provide higher energy density; for example, in the bipolar stacked battery pack configuration, the bipolar stacking architecture forms a connection structure in which multiple battery cells are substantially connected in series by stacking multiple electrode sheets, especially in an example in which multiple bipolar sheets are stacked between the positive electrode sheet and the negative electrode sheet, so that each battery cell composed of the positive electrode and the negative electrode can be connected in series by sharing a current collector. This configuration architecture, on the one hand, allows adjacent positive electrode active material layers and negative electrode active material layers to share a current collector, further reducing the use of inactive materials in the battery and effectively shortening the electronic conduction path between battery cells. On the other hand, all battery cells are packaged in series in one package, greatly reducing the packaging materials used for the battery. Due to the above two reasons, bipolar batteries have higher energy density, lower DC internal resistance, and can provide higher output voltage than traditional batteries, which can support a variety of application scenarios.

[0027] However, in the above-mentioned bipolar battery architecture, if a liquid electrolyte is used as an ion conductor between the pole pieces, the liquid electrolyte is prone to cause ion short circuits inside the battery due to its own better fluidity. There is also a risk of battery packaging leakage leading to liquid short circuits between multiple batteries.

[0028] In order to solve the above technical problems, the present invention provides an all-solid-state lithium-ion battery. The all-solid-state lithium-ion battery adopts a halide solid electrolyte with an LZC structure to replace the liquid electrolyte, so as to realize the charge and discharge cycle of a multi-battery unit architecture in the battery while reducing the use of current collectors, tabs and connecting wires in the battery, thereby avoiding liquid electrolyte leakage and causing liquid short circuit of the battery, while maximizing the energy density of the battery and reducing the manufacturing cost of the battery.

[0029] The all-solid-state lithium-ion battery provided by the present invention comprises a positive electrode sheet, a negative electrode sheet and a conductive layer, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, and the conductive layer is arranged between the positive electrode sheet and the negative electrode sheet. Specifically, the conductive layer is arranged between the positive electrode active material layer and the negative electrode active material layer, and the conductive layer comprises a solid electrolyte.

[0030] The solid electrolyte includes Li 2+a Zr 1-a M a Br x I y Cl 6-x-y , where 0≤a≤0.5, 0≤x≤6, 0≤y≤6, 0≤x+y≤6. The above electrolyte is a halide solid electrolyte, which has a high room temperature ionic conductivity (>1×10 -3 S cm -1), and at the same time has better non-fluidity, and can form a stable ion conductor between the positive electrode active material layer and the negative electrode active material layer.

[0031] In solid electrolyte Li 2+a Zr 1-a M a Br x I y Cl 6-x-y In the embodiment, the M element is selected from at least one of Fe, Co, Ni, Mn, V and Cr. That is, the M element can be any one of the above-listed element types, such as Fe, Co, Ni, Mn, V or Cr, etc.; the M element can also be any two or more combinations of the above-listed element types, for example, the M element can be a combination of Fe and Co, or a combination of Fe and Al, or a combination of Fe and Ni, or a combination of Co and Mn, or a combination of Co and Al, or a combination of Co and Ni, or a combination of Mn and Cr, or a combination of Al and V, or a combination of Cr and V, or a combination of Fe, Co and Al, or a combination of Fe, Co and Ni, or a combination of Fe, Ni, Co and Al, etc., which are not listed here one by one.

[0032] In addition, when the M element is a combination of two or more elements, there is no restriction on the ratio of each element in the combination, and they can be mixed in any ratio, etc. In other embodiments, the M element may also be an element type not listed above.

[0033] In some embodiments, the M element includes at least Fe or Co. For example, the electrolyte may be Li 2.1 Zr 0.9 Fe 0.1 Cl6、Li 2.3 Zr 0.7 Fe 0.3 Cl6、Li 2.5 Zr 0.5 Fe 0.5 Cl6、Li 2.1 Zr 0.9 Co 0.1 Cl6、Li 2.3 Zr 0.7 Co 0.3 Cl6、Li 2.5 Zr 0.5 Co 0.5 Cl6、Li 2.1 Zr 0.9 Fe 0.1 I 0.3 Br 3.9 Cl 2.1 , Li 2.3 Zr 0.7 Fe0.3 I 0.9 Br 2.8 Cl 2.3 , Li 2.5 Zr 0.5 Fe 0.5 I 1.5 Br2Cl 2.5 , Li 2.1 Zr 0.9 Co 0.1 I 0.3 Br 3.9 Cl 2.1 , Li 2.3 Zr 0.7 Co 0.3 I 0.9 Br 2.8 Cl 2.3 or Li 2.5 Zr 0.5 Co 0.5 I 1.5 Br2Cl 2.5 .

[0034] In some embodiments, the positive electrode active material layer includes a positive electrode active material, a composite electrolyte and a positive electrode conductive agent. The mass ratio of the positive electrode active material, the composite electrolyte and the positive electrode conductive agent is (50-75): (20-50): 1. Among them, the composite electrolyte is made of the same material as the solid electrolyte. The positive electrode active material includes one or more of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium-rich manganese-based oxide (LRMO) and lithium-containing phosphate. The positive electrode conductive agent includes one of carbon black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, etc. or a combination of two or more mixed in any proportion. In one example, the positive electrode conductive agent includes carbon black and carbon nanofibers, and the mass ratio of carbon black to carbon nanofibers is 1: (0.2-1.5).

[0035] In some embodiments, the negative electrode active material layer includes a negative electrode active material, a composite electrolyte and a negative electrode conductive agent. The mass ratio of the negative electrode active material, the composite electrolyte and the negative electrode conductive agent is (50-75): (20-50): 1. Among them, the composite electrolyte is made of the same material as the solid electrolyte. The negative electrode active material is selected from one or more of artificial graphite (single crystal graphite, polycrystalline graphite, pyrolytic graphite, graphite fiber, etc.), natural graphite (block graphite, flake graphite, earthy graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon or organic silicon), silicon oxide compounds, and silicon carbon compounds. The negative electrode conductive agent is selected from one of carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers, or a combination of two or more of the above in any proportion. The negative electrode binder is selected from any one of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), and styrene-butadiene rubber (SBR), or a combination of several of the above in any proportion.

[0036] See also Figure 2 The present invention provides a method for preparing the solid electrolyte described in any one of the above embodiments, the preparation method comprising the following steps:

[0037] S101, uniformly mixing LiX, ZrX4 and MX3 to obtain a mixture;

[0038] S102, ball milling the mixture;

[0039] S103, calcining the mixture to obtain an electrolyte;

[0040] The M element is at least one selected from Fe, Co, Ni, Mn, V and Cr; the X element is at least one halogen element; further, the X element is at least one selected from Br, I and Cl.

[0041] In some embodiments, in step S101, the molar ratio of mixed LiX, ZrX4 and MX3 is (2+a):(1-a):a, wherein 0≤a≤0.5; that is, the molar ratio of LiX, ZrX4 and MX3 is (2-2.5):(0.5-1):(0-0.5), for example, the molar ratio of LiX, ZrX4 and MX3 can be 2.1:0.9:0.1, 2.3:0.7:0.3 or 2.5:0.5:0.5.

[0042] In step S102, the mixed material may be ball-milled using equipment and methods known in the art. For example, the mixed material and ball milling beads are mixed and placed in a ball milling device for rotational ball milling to obtain a powder with uniform particle size.

[0043] In some embodiments, the ball-to-material ratio of the ball milling beads and the mixed material placed in the ball milling equipment is (10-40):1. For example, the ball-to-material ratio of the ball milling beads and the mixed material can be 40:1, 35:1, 30:1, 25:1, 20:1, 15:1 or 10:1. Optionally, the ball-to-material ratio can be 10:1.

[0044] In some embodiments, in step S102, the ball milling speed of the mixture is 300 to 1200 rpm. For example, the ball milling speed may be 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm or 1200 rpm. Optionally, the ball milling speed may be 500 rpm.

[0045] In some embodiments, in step S102, the ball milling time for the mixture is 10 to 30 hours, for example, the ball milling time may be 10 hours, 15 hours, 20 hours, 25 hours or 30 hours, and optionally, the ball milling time may be 10 hours.

[0046] In step S102, the mixed material is ball-milled at the ball-milling speed and time in the above-mentioned embodiment, so that the raw materials LiX, ZrX4 and MX3 can be fully ground and powders with uniform particle sizes can be obtained. If the ball-milling speed is not enough and the time is short, the powders after ball-milling will have different particle sizes and large particle size differences, resulting in unstable performance and low ion conductivity of the halide solid electrolyte material obtained by calcination; if the ball-milling speed is too high and the time is too long, the ball-milling beads will be damaged, which will easily cause the components containing ball-milling beads in the original formula to be damaged.

[0047] In step S103, the ball-milled mixture is calcined twice under a vacuum environment. Specifically, step S103 includes the following steps:

[0048] S201, placing the mixed material at a first temperature for calcination;

[0049] S202, placing the mixture after the primary calcination at a second temperature for secondary calcination;

[0050] The first temperature of the first calcination of the mixture is greater than the second temperature of the second calcination. The two calcinations can fully react the raw materials LiX, ZrX4 and MX3, and the crystal water produced by the reaction can be removed during the calcination process to obtain an electrolyte with higher purity.

[0051] In some embodiments, the first temperature for calcining the mixture is 150°C to 300°C, for example, 150°C, 180°C, 210°C, 240°C, 270°C or 300°C; the second temperature for calcining the mixture is 200°C to 400°C, for example, 200°C, 250°C, 300°C, 350°C or 400°C.

[0052] like Figure 1 As shown, in some embodiments, the all-solid-state lithium-ion battery is a bipolar battery, the bipolar battery adopts a bipolar stacking architecture, and the bipolar battery includes a positive electrode active material layer, a negative electrode active material layer, a conductive layer and a plurality of current collectors. A plurality of current collectors are stacked, and the positive electrode active material layer, the conductive layer and the negative electrode active material layer are arranged between adjacent current collectors to form a battery unit with the current collectors on both sides, and the positive electrode active material layer, the conductive layer and the negative electrode active material layer in the battery unit are stacked in a set order. The plurality of battery cells formed in the bipolar battery are stacked in series to form a stacked electrode body.

[0053] In the stacked electrode body, the positive active material layer and the negative active material layer between adjacent current collectors are arranged relatively, and the conductive layer can be used as a conductor to transfer lithium ions between the positive active material layer and the negative active material layer of adjacent current collectors to help lithium ions to be embedded and removed back and forth between the positive and negative active materials, thereby forming a battery cell that realizes energy storage and release. At the same time, due to the structure of multiple current collectors stacked, adjacent battery cells in the stacked electrode body can be connected in series through current collectors or conductive layers, which makes the bipolar battery essentially form an electrochemical device with multiple battery cells connected in series.

[0054] like Figure 1 As shown, in some embodiments, the bipolar battery includes a positive electrode sheet 100, a negative electrode sheet 200, and at least one bipolar electrode sheet 300, wherein the positive electrode sheet 100 is configured as one side of the stacked electrode body along the stacking direction, and the negative electrode sheet 200 is configured as the other side of the stacked electrode body along the stacking direction, and at least one bipolar electrode sheet 300 is stacked and configured between the positive electrode sheet 100 and the negative electrode sheet 200. The conductive layer 400 is configured between adjacent bipolar electrode sheets 300, and between the bipolar electrode sheet 300 and the positive electrode sheet 100 and the negative electrode sheet 200. Among them, the positive electrode sheet 100 includes a positive electrode collector 110 and a positive electrode active material layer 600 arranged on one side of the positive electrode collector 110; the negative electrode sheet 200 includes a negative electrode collector 210 and a negative electrode active material layer 700 arranged on one side of the negative electrode collector 210; the bipolar electrode sheet 300 includes a bipolar current collector 310, a positive electrode active material layer 600 arranged on one side of the bipolar current collector 310, and a negative electrode active material layer 700 arranged on the other side of the bipolar current collector 310.

[0055] like Figure 1As shown, in the stacked electrode body, the positive electrode active material layer 600 and the negative electrode active material layer 700 between adjacent stacked current collectors are arranged relative to each other and electrically connected in series through the conductive layer 400, and the electrons are received or derived by the adjacent current collectors, thereby forming a battery unit; for example, the positive electrode active material layer 600 between the bipolar pole pieces 300 is arranged relative to the negative electrode active material layer 700 of the negative pole piece 200 and electrically connected through the conductive layer 400, the positive electrode active material layer 600 of the bipolar pole piece 300 is arranged relative to the negative electrode active material layer 700 of the negative pole piece 200 and electrically connected through the conductive layer 400, and the negative electrode active material layer 700 of the bipolar pole piece 300 is arranged relative to the positive electrode active material layer 600 of the positive pole piece 100 and electrically connected through the conductive layer 400. At the same time, under the structure of stacking the bipolar pole pieces 300, the adjacent battery units in the stacked electrode body are electrically connected in series by sharing the bipolar current collector 310.

[0056] In addition, in the bipolar battery, the conductive layer 400 includes the electrolyte described in any of the above embodiments. The electrolyte, as a solid electrolyte of the LZC architecture, can be stably configured in a non-fluid solid form between the positive electrode active material layer 600 and the negative electrode active material layer 700 of adjacent current collectors, thereby helping the bipolar battery to achieve charge and discharge cycles of multiple battery cells connected in series.

[0057] like Figure 1 As shown, in some embodiments, the bipolar battery further includes a packaging layer 500, which is packaged on the outside of the stacked electrode body. For example, the packaging layer 500 is packaged on at least two side end faces of the stacked electrode body along the stacking direction. Specifically, the packaging layer 500 is packaged on the side of the positive electrode collector 110 in the positive electrode sheet 100 that is away from the positive electrode active material layer 600, and the packaging layer 500 is packaged on the side of the negative electrode collector 210 in the negative electrode sheet 200 that is away from the negative electrode active material layer 700.

[0058] See also Figure 1 and Figure 3 , the composition and preparation method of the bipolar battery are described in detail below:

[0059] The positive electrode sheet 100 in the bipolar battery includes a positive electrode collector 110 and a positive electrode active material layer 600 disposed on one surface of the positive electrode collector 110. Among them, the positive electrode collector 110 can be made of a material with good conductivity and mechanical strength, such as aluminum foil. The positive electrode collector 110 has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer 600 is disposed on any one of the two opposite surfaces of the positive electrode collector 110. The positive electrode active material layer 600 includes a positive electrode active material, a positive electrode conductive agent, a positive electrode binder and a composite electrolyte. The composite electrolyte and the halide solid electrolyte are made of the same material. The specific types of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder are not specifically limited here. Materials known in the art that can be used in lithium-ion batteries can be used, and those skilled in the art can choose according to actual needs.

[0060] The positive electrode active material may be selected from the positive electrode active material including one or more of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium-rich manganese-based oxide (LRMO) and lithium-containing phosphate; lithium-containing phosphate includes but is not limited to lithium iron manganese phosphate, lithium iron phosphate, lithium manganese phosphate, etc. The positive electrode binder is selected from polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), etc. The positive electrode conductive agent is selected from one of carbon black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, etc., or a combination of two or more of the above in any proportion.

[0061] The positive electrode sheet can be prepared according to methods known in the art. For example, the positive electrode active material, the positive electrode conductive agent, the positive electrode binder and the composite electrolyte are dispersed in a solvent (such as N-methylpyrrolidone, referred to as NMP) at a mass ratio of 75:1:1:23 to form a uniform positive electrode slurry: the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, a positive electrode active material layer is formed on the positive electrode collector to obtain a positive electrode sheet. The ratio between the components in the positive electrode slurry can be set with reference to the conventional ratio, and is not limited here.

[0062] The negative electrode sheet 200 in the bipolar battery includes a negative electrode current collector 210 and a negative electrode active material layer 700 disposed on one surface of the negative electrode current collector 210. The negative electrode current collector 210 can be made of a material with good conductivity and mechanical strength, such as copper foil. The negative electrode current collector 210 has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer 700 is disposed on any one or both of the two opposite surfaces of the negative electrode current collector 210. The negative electrode active material layer 700 includes a negative electrode active material, a negative electrode conductive agent, a negative electrode binder and a composite electrolyte. The composite electrolyte and the halide solid electrolyte are made of the same material. The specific types of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder are not specifically limited here. Materials known in the art that can be used in lithium-ion batteries can be used, and those skilled in the art can choose according to actual needs.

[0063] The negative electrode active material is selected from one or more of artificial graphite, natural graphite, soft carbon, hard carbon, pure silicon, silicon oxide compounds, and silicon carbon compounds. The negative electrode conductive agent is selected from one of carbon black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, etc., or a combination of two or more of them mixed in any proportion. The negative electrode binder is selected from any one of polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), or a combination of several of them mixed in any proportion.

[0064] The negative electrode sheet can be prepared according to methods known in the art. For example, the negative electrode active material, the negative electrode binder, the negative electrode conductive agent and the composite electrolyte are dispersed in a solvent (such as N-methylpyrrolidone, referred to as NMP) at a mass ratio of 75:1:1:23 to form a uniform negative electrode slurry: the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, a negative electrode active material layer is formed on the negative electrode current collector to obtain a negative electrode sheet. Among them, the ratio between the components in the negative electrode slurry can be set with reference to the conventional ratio, and is not limited here.

[0065] The bipolar pole piece 300 in the bipolar battery includes a bipolar current collector 310, a positive electrode active material layer 600 disposed on one side of the bipolar current collector 310, and a negative electrode active material layer 700 disposed on the other side of the bipolar current collector 310. Among them, the bipolar pole piece 300 can be composed of metal foil, metal mesh, etc. From the perspective of excellent operability, the bipolar pole piece 300 can also be made of metal foil. The bipolar pole piece 300 can also be composed of multiple metal foils. As metals constituting the bipolar pole piece 300, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. can be listed.

[0066] The bipolar plate can be prepared according to methods known in the art. For example, the positive electrode slurry and the negative electrode slurry are prepared according to the above preparation method, and the positive electrode slurry and the negative electrode slurry are sequentially coated on both sides of the bipolar current collector, and after drying, cold pressing and other processes, the positive electrode active material layer and the negative electrode active material layer are formed on both sides of the bipolar current collector to obtain the bipolar plate.

[0067] In addition, the present invention also provides a method for preparing the above-mentioned bipolar battery, which comprises: stacking a plurality of electrode sheets, and arranging the positive electrode active material layer and the negative electrode active material layer of adjacent electrode sheets relatively to each other in the process of stacking the plurality of electrode sheets in sequence along the stacking direction; configuring a conductive layer between adjacent stacked electrode sheets, and configuring the conductive layer between the positive electrode active material layer and the negative electrode active material layer of adjacent electrode sheets to complete the series electrical connection of the plurality of electrode sheets.

[0068] The technical scheme of the present invention is described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available.

[0069] Example 1

[0070] This embodiment provides a solid electrolyte, which is Li 2.1 Zr 0.9 Fe 0.1 Cl6. The preparation method of the electrolyte comprises:

[0071] S101, mixing LiCl, ZrCl4, and FeCl3 in a molar ratio of 2.1:0.9:0.1 to obtain a mixture;

[0072] S102, placing the mixed material and ball milling beads in a ball milling jar at a ball-to-material ratio of 10:1, and then ball milling at a speed of 500 rpm for 10 hours;

[0073] S103. Place the mixture in a vacuum environment, heat it at 180° C. for 4 h, and then heat it at 200° C. for 3 h to obtain an electrolyte.

[0074] Example 2

[0075] This embodiment provides a solid electrolyte, which is Li 2.3 Zr 0.7 Fe 0.3 The electrolyte preparation process in this embodiment is different from that in embodiment 1 in that: in step S101, LiCl, ZrCl4, and FeCl3 are mixed in a molar ratio of 2.3:0.7:0.3 to obtain a mixture.

[0076] Example 3

[0077] This embodiment provides a solid electrolyte, which is Li 2.5 Zr 0.5 Fe 0.5 The electrolyte preparation process in this embodiment is different from that in embodiment 1 in that: in step S101, LiCl, ZrCl4, and FeCl3 are mixed in a molar ratio of 2.5:0.5:0.5 to obtain a mixture.

[0078] Example 4

[0079] This embodiment provides a solid electrolyte, which is Li 2.5 Zr 0.5 Fe 0.5 I 1.5 Br2Cl 2.5 The electrolyte preparation process in this embodiment is different from that in Embodiment 1 in that: in step S101, LiCl, ZrBr4, and FeI3 are mixed in a molar ratio of 2.5:0.5:0.5 to obtain a mixture.

[0080] Example 5

[0081] This embodiment provides a solid electrolyte, which is Li 2.5 Zr 0.5 Co 0.5 I 1.5 Br2Cl 2.5 The electrolyte preparation process in this embodiment is different from that in Embodiment 1 in that: in step S101, LiCl, ZrBr4, and FeI3 are mixed in a molar ratio of 2.5:0.5:0.5 to obtain a mixture.

[0082] Comparative Example 1

[0083] Comparative Example 1 provides a liquid electrolyte, in which the solute is LiPF6, and the solvent is ethylene carbonate (EC) and diethyl carbonate (DEC), wherein the usage ratio of EC and DEC in the solvent can be 3:7, and the LiPF6 concentration in the electrolyte is 1 mol / L.

[0084] The electrolyte preparation method includes: uniformly mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 3:7 to prepare an organic solvent; dissolving fully dried lithium salt LiPF6 in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0085] Comparative Example 2

[0086] Comparative Example 2 provides a liquid electrolyte, in which the solute is LiPF6, the solvent is ethylene carbonate (EC) and diethyl carbonate (DEC), and the additive is fluoroethylene carbonate; wherein the usage ratio of EC and DEC in the solvent can be 5:5, and the LiPF6 concentration in the electrolyte is 1 mol / L.

[0087] The electrolyte preparation method includes: uniformly mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 5:5 to prepare an organic solvent; adding fluoroethylene carbonate accounting for 5% of the mass content of the prepared electrolyte to the organic solvent; dissolving fully dried lithium salt LiPF6 in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0088] Comparative Example 3

[0089] Comparative Example 3 provides a liquid electrolyte, in which the solute is LiPF6, the solvent is ethylene carbonate (EC) and propylene carbonate (PC), and the additive is fluoroethylene carbonate; wherein the usage ratio of EC and PC in the solvent can be 5:5, and the LiPF6 concentration in the electrolyte is 1 mol / L.

[0090] The electrolyte preparation method includes: uniformly mixing ethylene carbonate (EC) and propylene carbonate (PC) in a mass ratio of 5:5 to prepare an organic solvent; adding fluoroethylene carbonate accounting for 5% of the mass content of the prepared electrolyte to the organic solvent; dissolving fully dried lithium salt LiPF6 in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0091] The solid electrolytes provided in Examples 1 to 5 and the liquid electrolytes provided in Comparative Examples 1 to 3 were respectively used in bipolar batteries to verify the efficacy of the present invention.

[0092] The preparation method of the solid electrolyte assembled bipolar battery in the above embodiments 1 to 5 is as follows:

[0093] Positive electrode sheet preparation: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent carbon black, binder polyvinylidene fluoride, and the solid electrolyte provided in the embodiment are dissolved in N-methylpyrrolidone (NMP) in a mass ratio of 75:1:1:23 and mixed to obtain a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil serving as a positive electrode current collector, and the positive electrode sheet is obtained after drying, cold pressing, and cutting.

[0094] Preparation of negative electrode sheet: The negative electrode active material graphite, the conductive agent carbon black, the binder polyvinylidene fluoride and the solid electrolyte provided in the embodiment are dissolved in N-methylpyrrolidone (NMP) in a mass ratio of 75:1:1:23, mixed and homogenized to obtain a negative electrode slurry, and the negative electrode slurry is coated on a copper foil serving as a negative electrode current collector, and the negative electrode sheet is obtained after drying, cold pressing and cutting.

[0095] Bipolar electrode preparation: LiNi positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive agent carbon black, binder polyvinylidene fluoride, and the solid electrolyte provided in the embodiment are dissolved in N-methylpyrrolidone (NMP) in a mass ratio of 75:1:1:23 and mixed to obtain a positive electrode slurry, and the positive electrode slurry is coated on one side of the bipolar current collector, and the positive electrode side of the bipolar pole piece is made after drying and cold pressing; the negative electrode active material graphite, conductive agent carbon black, binder polyvinylidene fluoride, and the solid electrolyte provided in the embodiment are dissolved in N-methylpyrrolidone (NMP) in a mass ratio of 75:1:1:23 and mixed to obtain a negative electrode slurry, and the negative electrode slurry is coated on the other side of the bipolar current collector, and the negative electrode side of the bipolar pole piece is made after drying and cold pressing; finally, the bipolar pole piece is die-cut.

[0096] like Figure 3 As shown, bipolar battery assembly includes the following steps:

[0097] S301, assembling the encapsulation layer 500 onto the side of the negative electrode current collector 210 in the negative electrode sheet 200 that is away from the negative electrode active material layer;

[0098] S302, assembling the solid electrolyte provided in the embodiment as the conductive layer 400 onto the negative electrode active material layer of the negative electrode sheet 200;

[0099] S303, disposing the bipolar pole piece 300 on the conductive layer 400;

[0100] S304, configuring a conductive layer 400 on the bipolar pole piece 300;

[0101] S305, repeating steps S303 to S304 nine times to reach the preset required number of battery cells;

[0102] S306, assembling the encapsulation layer 500 onto the side of the positive electrode current collector 110 in the positive electrode sheet 100 away from the positive electrode active material layer, and assembling the positive electrode sheet 100 onto the conductive layer 400 away from the negative electrode sheet 200;

[0103] S307, heat-packaging the assembled battery cells, and then going through the processes of standing, hot and cold pressing, forming, clamping, and capacity division to obtain a bipolar battery.

[0104] The preparation method of the liquid electrolyte assembled bipolar battery in the above comparative examples 1 to 3 is as follows:

[0105] Positive electrode sheet preparation: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent carbon black, and binder polyvinylidene fluoride are dissolved in N-methylpyrrolidone (NMP) in a mass ratio of 98:1:1 and mixed to obtain a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil serving as a positive electrode current collector, and the positive electrode sheet is obtained after drying, cold pressing, and cutting.

[0106] Preparation of negative electrode sheet: negative electrode active material graphite, conductive agent carbon black, binder polyvinylidene fluoride and conductive agent Li 2.5 Zr 0.5 Fe 0.5 Cl6 was dissolved in N-methylpyrrolidone (NMP) in a mass ratio of 88:1:1:10 and mixed to obtain a negative electrode slurry. The negative electrode slurry was coated on a copper foil serving as a negative electrode current collector, and the negative electrode sheet was obtained after drying, cold pressing and cutting.

[0107] Bipolar electrode preparation: LiNi positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive agent carbon black, and binder polyvinylidene fluoride are dissolved in N-methylpyrrolidone (NMP) in a mass ratio of 98:1:1 and mixed to obtain a positive electrode slurry. The positive electrode slurry is coated on one side of the bipolar current collector, and the positive electrode side of the bipolar pole piece is prepared after drying and cold pressing. The negative electrode active material graphite, conductive agent carbon black, binder polyvinylidene fluoride and conductive agent Li 2.5 Zr 0.5 Fe 0.5 Cl6 was dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 88:1:1:10 and mixed to obtain a negative electrode slurry, which was coated on the other side of the bipolar current collector, dried, and cold pressed to form the negative electrode side of the bipolar pole piece; finally, the bipolar pole piece was die-cut.

[0108] Preparation of the diaphragm: A polyethylene with a thickness of 9 μm was used as a base film, and a nano-aluminum oxide coating with a thickness of 3 μm was coated on the base film to obtain a diaphragm.

[0109] Bipolar battery assembly includes the following steps:

[0110] S401, assembling a separator on the negative electrode plate;

[0111] S402, assembling a bipolar pole piece on the diaphragm;

[0112] S403, assembling a diaphragm on a bipolar pole piece;

[0113] S404, repeating steps S303 to S304 nine times to reach the preset required number of battery cells;

[0114] S405, assembling the positive electrode sheet on the separator on the side away from the negative electrode sheet;

[0115] S406, the assembled battery unit is loaded into an aluminum-plastic film, and then baked at 80°C to remove water, and then the electrolyte provided in the comparative example is injected and sealed, and then the bipolar battery is obtained through the processes of standing, hot and cold pressing, formation, clamping, and capacity division.

[0116] The bipolar batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to cycle performance tests. The test results are shown in Table 1. The test method is as follows:

[0117] Under 25℃ environment, with a charge and discharge rate of 1C, in the test voltage range of 28V (discharge cut-off voltage) to 43.5V (charge cut-off voltage), the bipolar battery was subjected to multiple charge and discharge cycle tests. The battery capacity CN after each charge and discharge test was recorded, and the corresponding battery capacity retention rate CN / C1 was calculated. When the battery capacity retention rate decayed to 80%, the number of cycles N was recorded.

[0118] Table 1: Performance parameters of bipolar batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3

[0119]

[0120] By comparing the test results of Examples 1 to 5 and Comparative Examples 1 to 3, it can be seen that the bipolar battery equipped with a liquid electrolyte cannot perform normal charge and discharge cycles and cannot be used in practical applications; while the bipolar battery equipped with a solid electrolyte can perform stable charge and discharge cycles and can be actually used in electrical devices.

[0121] By comparing the test results of Examples 1 to 3, it can be seen that in the halide electrolyte of the LZC architecture, doping a suitable amount (molar content of 10% to 30%) of transition metal elements can improve the cycle performance of the bipolar battery. For example, when the component of Fe in the LZC halide is 0.1 to 0.3, the cycle performance of the bipolar battery will increase with the increase of the Fe content; and when the component of Fe in the LZC halide is greater than 0.3, the cycle performance of the bipolar battery will decay with the increase of the Fe content.

[0122] By comparing the test results of Examples 3 to 5, it can be seen that in the halide electrolyte of the LZC architecture, doping with multiple halogen elements can effectively improve the cycle performance of the bipolar battery without affecting the battery energy density.

[0123] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An all-solid-state lithium-ion battery, characterized in that: A solid electrolyte is included, wherein the solid electrolyte is Li 2+a Zr 1- a M a Br x I y Cl 6-x-y , wherein 0≤a≤0.5, 0≤x≤6, 0≤y≤6, 0≤x+y≤6; and the M element is selected from at least one of Fe, Co, Ni, Mn, V and Cr.

2. The all-solid-state lithium-ion battery according to claim 1, characterized in that: In the solid electrolyte, the M element is selected from Fe or Co.

3. The all-solid-state lithium-ion battery according to claim 1 or 2, characterized in that: include: A positive electrode active material layer, a negative electrode active material layer and a conductive layer, wherein the conductive layer is located between the positive electrode active material layer and the negative electrode active material layer; Wherein, the conductive layer includes the solid electrolyte.

4. The all-solid-state lithium-ion battery according to claim 3, characterized in that: The positive electrode active material layer includes a positive electrode active material and a composite electrolyte, and the composite electrolyte is made of the same material as the solid electrolyte.

5. The all-solid-state lithium-ion battery according to claim 4, characterized in that: The positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-rich manganese-based oxide and lithium-containing phosphate.

6. The all-solid-state lithium-ion battery according to claim 4, characterized in that: The positive electrode active material layer also includes a positive electrode conductive agent, and the mass ratio of the positive electrode active material, the composite electrolyte and the positive electrode conductive agent is (50-75):(20-50):

1.

7. The all-solid-state lithium-ion battery according to claim 6, characterized in that: The conductive agent includes carbon black and carbon nanofibers, wherein the mass ratio of the carbon black to the carbon nanofibers is 1:(0.2-1.5).

8. The all-solid-state lithium-ion battery according to claim 3, characterized in that: The negative electrode active material layer includes a negative electrode active material and a composite electrolyte, and the composite electrolyte is made of the same material as the solid electrolyte.

9. The all-solid-state lithium-ion battery according to claim 8, characterized in that: The negative electrode active material layer further includes a negative electrode conductive agent, and the mass ratio of the negative electrode active material, the composite electrolyte and the negative electrode conductive agent is (50-75):(20-50):

1.

10. The all-solid-state lithium-ion battery according to claim 3, characterized in that: Also includes: A plurality of current collectors, wherein the plurality of current collectors are stacked; The positive electrode active material layer, the conductive layer, and the negative electrode active material layer are disposed between adjacent current collectors.

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