Battery pack

Abstract

The invention provides a battery pack, which is used for providing electric energy for an engine and an ignition device when an automobile is started, and comprises a battery unit and a shell forming a space for accommodating the battery unit, the battery unit comprises n battery monomers, each battery monomer comprises a positive electrode, a positive electrode active material in each positive electrode comprises Li1 + xNiyMzMn2-x-y-zO4-k of a spinel structure, x is greater than or equal to-0.1 and less than or equal to 0.2, y is greater than or equal to 0.4 and less than or equal to 0.6, z is greater than or equal to 0 and less than or equal to 0.2, k is greater than or equal to 0 and less than or equal to 0.8, and M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, T1 and Ti; and the charging cut-off voltage U of the single battery is greater than or equal to 4.8 V. The battery pack prepared by the invention belongs to a high-voltage system, can reduce the number of battery cells connected in series, reduce the complexity and contact internal resistance of connecting pieces, save the overall occupied space of the battery module and reduce the volume and weight of start-stop batteries, and has excellent performance of high and low temperature resistance.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery pack. Background Art

[0002] At present, the commonly used start-stop battery systems on the market are lithium iron phosphate systems and ternary systems. Among them, the lithium iron phosphate system has poor power and low-temperature performance, especially in winter, and the performance is greatly reduced, and the voltage platform is low, and the number of series connections is large. The ternary system has high costs and poor safety performance. Therefore, how to provide a material system that can improve the power, energy density, applicable temperature range and safety of automotive start-stop and mild hybrid system batteries, reduce the number of battery cells in series, and comprehensively improve the overall performance of automotive start-stop batteries has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] Based on this, the present application provides a battery pack to solve the above technical problems.

[0004] The present application provides a battery pack for providing electric energy to an engine and an ignition device when a car is started, comprising a battery unit and a housing forming a space for accommodating the battery unit; the battery unit comprises n battery cells, the battery cell comprises a positive electrode, and the positive electrode active material in the positive electrode comprises a spinel structured Li 1+x Ni y M z Mn 2-x-y-z O 4-k , -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, 0≤k≤0.8, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti; wherein the charging cut-off voltage U of the battery cell is ≥4.8V.

[0005] In some embodiments, the positive electrode active material is a mixture, wherein the spinel structured Li 1+ x Ni y M z Mn 2-x-y-z O 4-k (LNMO) accounts for more than 80% of the total positive electrode active materials.

[0006] In some embodiments, the positive electrode active material is a mixture, wherein the spinel structured Li 1+ x Ni y M z Mn 2-x-y-z O 4-k (LNMO) accounts for more than 90% of the total positive electrode active materials.

[0007] In some embodiments, the battery cells are all-solid-state batteries.

[0008] In some embodiments, the battery cells are semi-solid state batteries.

[0009] In some embodiments, the battery pack has a nominal voltage of 11-13V, the battery unit has three series-connected units, each series-connected unit includes at least one battery cell, and the voltage platform of the battery cell is 4.65-4.75V.

[0010] In some embodiments, the battery pack has a nominal voltage of 22-26V, the battery unit has 4-6 series-connected units, and each series-connected unit includes at least one battery cell.

[0011] In some embodiments, the battery pack has a nominal voltage of 47-49V, the battery unit has 10-12 series-connected units, and each series-connected unit includes at least one battery cell.

[0012] In some embodiments, the cold cranking current of the battery pack is ≧600A.

[0013] In some embodiments, the maximum discharge current of the battery pack is 500-1000A.

[0014] The spinel positive electrode active material used in the present application has a high degree of crystal symmetry and rigidity, which helps to maintain the integrity of the material structure during the charge and discharge process and improves the cycle stability of the material.

[0015] The spinel positive electrode active material used in the present application is resistant to high temperatures and has good thermal stability, which reduces the risk of thermal runaway and improves the safety of the automotive start-stop battery.

[0016] The spinel-type positive electrode active material used in the present application provides a three-dimensional lithium ion diffusion channel, which is beneficial to the rapid migration of lithium ions during the charge and discharge process, and increases the diffusion coefficient of lithium ions in the spinel structure, thereby increasing the charge and discharge rate and power density of the battery. The fast ion transfer rate enables the battery to have a higher power output and good rate performance, meeting the needs of the start-stop battery for fast charging and discharging, and frequent starting and stopping.

[0017] The spinel positive electrode active material used in this application can still maintain good electrochemical performance under low temperature conditions, which enables the battery to work normally in a cold environment. At the same time, the material uses abundant manganese elements, which is lower in cost than positive electrode active materials using cobalt or nickel. In addition, the material has a higher operating voltage platform (about 4.7V), which improves the energy density of the battery.

[0018] The automotive start-stop battery prepared in this application can achieve high-rate charge and discharge, can achieve high-rate discharge and charging, and can discharge normally at both low and high temperatures, meeting the current electric vehicle start-stop system's requirements for high battery capacity, high-rate discharge, and high and low temperature resistance. At the same time, due to the high-voltage platform, the use of the start-stop battery provided in this application requires fewer battery cells when used in series, thereby reducing the use of auxiliary materials and structures. Fewer series connections means that the use of connectors, electrical components, and structural parts can be reduced in the battery pack design, thereby reducing overall cost and complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of a battery pack in one embodiment of the present application.

[0020] Description of Reference Numerals

[0021] 101, cover plate; 102, bottom plate; 103, side plate; 110, groove; 120, first end plate; 130, battery cell; 140, pole ear frame plate; 150, series connection row; 160, second end plate; 170, terminal insulator; 180, pole ear. DETAILED DESCRIPTION

[0022] References to embodiments of the present application will now be provided in detail, one or more embodiments of which are described below. Each embodiment is provided as an explanation rather than a limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present application without departing from the scope or spirit of the present application. For example, a feature described or described as part of one embodiment may be used in another embodiment to produce a further embodiment.

[0023] Therefore, it is intended that the present application covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present application are disclosed in or are apparent from the following detailed description. It will be appreciated by those of ordinary skill in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0024] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0025] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0026] In this article, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 100~150 nm means that the units of the left endpoint "100" and the right endpoint "150" are both nm (nanometers).

[0027] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0028] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0029] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, mentioning that the method may also include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0030] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0031] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0032] The present application provides a battery pack for providing electric energy to an engine and an ignition device when a car is started, comprising a battery unit and a housing forming a space for accommodating the battery unit; the battery unit comprises n battery cells, the battery cell comprises a positive electrode, and the positive electrode active material in the positive electrode comprises a spinel structured Li 1+x Ni y M z Mn 2-x-y-z O 4-k , -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, 0≤k≤0.8, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti; wherein the charging cut-off voltage U of the battery cell is ≥4.8V.

[0033] It can be understood that the charging cut-off voltage U of the battery cell is ≥4.8 V. Furthermore, the charging cut-off voltage U of the battery cell is ≥5.0 V.

[0034] In some embodiments, the positive electrode active material is a pure substance, that is, a spinel structured Li 1+x Ni y M z Mn 2-x-y- z O 4-k (LNMO) accounts for 100% of the total amount of all positive electrode active materials.

[0035] In some embodiments, the positive electrode active material is a mixture including other positive electrode active materials in addition to the spinel type positive electrode active material.

[0036] It can be understood that in the present application, there is no particular limitation on the types of other positive electrode active materials. Without affecting the overall inventive concept of the present application, any known positive electrode active material can be applied to the present application. The following is only used as an example. Other positive electrode materials are one or more of lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), lithium manganese oxide (LMO), lithium iron phosphate (LFP), and lithium iron manganese phosphate (LVP).

[0037] The spinel positive electrode active material used in the present application has a high degree of crystal symmetry and rigidity, which helps to maintain the integrity of the material structure during the charge and discharge process and improves the cycle stability of the material.

[0038] The spinel positive electrode active material used in the present application is resistant to high temperatures and has good thermal stability, which reduces the risk of thermal runaway and improves the safety of the automotive start-stop battery.

[0039] The spinel-type positive electrode active material used in the present application provides a three-dimensional lithium ion diffusion channel, which is beneficial to the rapid migration of lithium ions during the charge and discharge process, and increases the diffusion coefficient of lithium ions in the spinel structure, thereby increasing the charge and discharge rate and power density of the battery. The fast ion transfer rate enables the battery to have a higher power output and good rate performance, meeting the needs of the start-stop battery for fast charging and discharging, and frequent starting and stopping.

[0040] The spinel positive electrode active material used in this application can still maintain good electrochemical performance under low temperature conditions, which enables the battery to work normally in a cold environment. At the same time, the material uses abundant manganese elements, which is lower in cost than positive electrode active materials using cobalt or nickel. In addition, the material has a higher operating voltage platform (about 4.7V), which improves the energy density of the battery.

[0041] In some embodiments, the positive electrode active material is a mixture, wherein the spinel structured Li 1+ x Ni y M z Mn 2-x-y-z O 4-k (LNMO) accounts for more than 80% of the total positive electrode active materials.

[0042] Furthermore, the positive electrode active material is a mixture, wherein the spinel structured Li 1+x Ni y M z Mn 2-x-y-z O 4-k (LNMO) accounts for more than 90% of the total amount of all positive electrode active materials.

[0043] In some embodiments, the particle size D50 of the spinel positive electrode active material is 1 μm to 10 μm, including but not limited to 1 μm, 1.4 μm, 1.8 μm, 2.0 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 4 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 8.3 μm, 9 μm, and 10 μm.

[0044] In some embodiments, the maximum particle size of the spinel-type positive electrode active material is 15 μm or less.

[0045] In some embodiments, the positive electrode layer of the positive electrode further includes a positive electrode binder and a positive electrode conductor.

[0046] It is understood that the positive electrode conductive agent is mainly used to assist and improve the conductivity in lithium-ion batteries. In the present application, the type of conductive agent in the positive electrode layer is not particularly limited, as long as it has conductivity and does not cause chemical changes. The following is only exemplary, the positive electrode conductive agent in the positive electrode layer includes graphite, such as natural graphite or artificial graphite; carbon materials, such as super-P, acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers, such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; metal powders, such as fluorocarbon powders, aluminum powders and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives, etc.

[0047] In some embodiments, the positive electrode conductive agent uses any one or a combination of at least two of VGCF single arm, VGCF double arm, and SP to form a good conductive network.

[0048] In the present application, there is no particular limitation on the specific type of the positive electrode binder in the positive electrode layer, including but not limited to one or more of polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, and lithium alginate.

[0049] In some embodiments, the positive electrode further comprises a solid electrolyte layer. The type of the solid electrolyte layer is not particularly limited in the present application.

[0050] In some embodiments, the battery cell includes a negative electrode, the negative electrode includes a negative electrode layer and a negative electrode current collector, the negative electrode layer includes a negative electrode active material, the negative electrode active material is a double-layer carbon structure, the outer surface of the double-layer carbon structure is a hard carbon material, and the inner core is a soft carbon material.

[0051] In some embodiments, the particle size D50 of the negative electrode active material is 10 μm to 20 μm, including but not limited to 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, and 20 μm.

[0052] In some embodiments, the maximum particle size of the negative electrode active material is 25 μm or less.

[0053] In some embodiments, the mass ratio of the outer surface to the inner core of the negative electrode active material is (5-9): (1-5).

[0054] In some embodiments, the specific surface area of ​​the negative electrode active material is 6 m² / g or less.

[0055] This application uses a double-layer carbon structure as the negative electrode active material. The outer layer material uses a hard carbon material, which has high structural stability and mechanical strength. The hard carbon layer on the outer surface can protect the internal soft carbon layer and resist the volume expansion and contraction force generated during the charge and discharge process. The internal soft carbon material (such as graphite) has a higher theoretical capacity and can store more lithium ions, thereby increasing the energy density of the battery.

[0056] The hard carbon layer in the negative electrode active material can improve the structural stability, provide structural support, and reduce the structural damage of the soft carbon layer caused by volume change during the charge and discharge process. Secondly, the hard carbon layer usually has a higher electrical conductivity, which can improve the overall conductivity of the electrode, thereby improving the charge and discharge efficiency of the battery and having a better power density. At the same time, the soft carbon layer has a higher energy density. Therefore, the composite structure of hard carbon and soft carbon overcomes the limitations of a single material and improves the charge and discharge rate of the battery while maintaining a high energy density. The different characteristics of the hard carbon layer and the soft carbon layer enable the composite material to adapt to high-rate charge and discharge, thereby improving the overall performance of the start-stop battery.

[0057] In some embodiments, the negative electrode layer further includes a negative electrode binder and a negative electrode conductor.

[0058] The negative electrode binder includes, but is not limited to, one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM), polycarbonate (PC), polyamide (PA), polyacrylic acid (PAA), acrylic plastics, other polyolefins and copolymers thereof, polysulfone, polyphenylene ether (PPO), styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC).

[0059] In a specific embodiment, the negative electrode binder is a mixture of CMC, PAA and SBR. Among them, the combined use of CMC and SBR provides a good bonding effect. CMC, as a dispersant, improves the bonding force between the negative electrode active material and the negative electrode current collector, and SBR increases the bonding performance of the binder, so that the negative electrode is not easy to fall off under high pressure compaction, and the mechanical stability of the battery is improved. PAA, as a new type of binder, can improve the cohesion of the electrode and the adhesion to the current collector, which helps to extend the service life of the battery. The composite use of this binder solves the shortcomings of a single binder in performance and optimizes the comprehensive performance of electrode materials and batteries. This binder combination helps to reduce the internal resistance of the battery, improve the charge and discharge performance of the battery, and at the same time helps to improve the energy density and cycle stability of the battery, meeting the needs of the start-stop battery pack for automobiles.

[0060] Negative electrode conductive agents include, but are not limited to, carbon-based materials, powdered nickel or other metal particles or conductive polymers. Carbon-based materials may include, for example, particles of carbon black, graphite, super-P, acetylene black (such as KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, and the like.

[0061] In some embodiments, a conductive carbon layer is disposed on a surface of the positive electrode collector close to the positive electrode layer; and / or a conductive carbon layer is disposed on a surface of the negative electrode collector close to the negative electrode layer.

[0062] In some embodiments, the thickness of the conductive carbon layer is 1 μm to 2 μm.

[0063] In this application, a conductive carbon layer of a certain thickness is coated on the surface of the current collector, such as a graphene conductive carbon layer, a carbon nanotube conductive carbon layer, etc. Since the conductive carbon layer has excellent electrical conductivity, coating it on the surface of the current collector can reduce the contact resistance of the electrode and improve the charge and discharge efficiency of the battery. The conductive carbon layer can enhance electron transport and form a continuous conductive network, which helps to quickly transport electrons between the electrode material and the current collector. The conductive carbon layer helps to form a stable solid electrolyte interface (SEI) layer on the electrode surface, improving the cycle stability and safety of the battery. It can also improve the low-temperature performance of the battery, reduce the charge transfer impedance of the electrode material, and improve the charge and discharge performance of the battery under low temperature conditions.

[0064] It is understandable that the present application has no particular limitation on the negative electrode current collector, as long as it has conductivity and does not cause chemical changes in the battery, without violating the inventive concept of the present application.

[0065] Optionally, the shape of the negative electrode current collector includes a foil shape, a plate shape, a grid shape, or the like.

[0066] Optionally, the negative electrode current collector includes any one of aluminum, copper, nickel or zinc.

[0067] Optionally, the negative electrode current collector includes any one of aluminum, copper, nickel or zinc alloy.

[0068] In some embodiments, the battery cell in the present application may be a semi-solid-state battery.

[0069] In some embodiments, the battery cell includes a diaphragm, and the diaphragm is a PI-based diaphragm or a PI / PE-based diaphragm. The binder on the diaphragm is PAA. PAA contains a large number of carboxyl groups, and these polar functional groups can form strong hydrogen bonds with the active material and the surface of the current collector, thereby providing better adhesion and mechanical properties. PAA has good electrochemical stability over a wide voltage range, which is crucial for maintaining the long-term cycle stability of the battery. PAA has low swelling in the electrolyte, which helps to maintain the structural stability of the electrode sheet during the charge and discharge process, thereby improving the cycle life of the battery. PAA can promote the migration of lithium ions in the electrode, thereby obtaining a higher lithium ion transfer rate, which helps to improve the charge and discharge performance of the battery. As a binder, PAA can better withstand the stress generated by the volume expansion of the active material, thereby improving the cycle stability of the battery. PAA forms a more or less coating on the surface of the active material, which acts as an artificial SEI (solid electrolyte interface) and helps to improve the electrical performance of the battery.

[0070] The use of PAA can maintain the long-term cycle stability of the battery, keep the electrode sheet structurally stable during the charge and discharge process, and improve the cycle life of the battery. PAA can also promote the migration of lithium ions within the electrode, thereby obtaining a higher lithium ion transfer rate, which helps to improve the battery's charge and discharge performance and improve the overall performance of the vehicle's start-stop power supply.

[0071] In some embodiments, the battery cell has an electrolyte therein, and the electrolyte includes an organic solvent and a lithium salt.

[0072] It is understood that an electrolyte that can match a high voltage system battery is used in the present application. The electrolyte should be able to remain stable at high voltage and reduce the oxidative decomposition of the electrolyte. Including solvents with high oxidation potential and wide electrochemical window, specifically, as solvents, sulfone solvents such as sulfolane; nitrile solvents such as R-CN; fluorinated solvents such as fluoroethylene carbonate (FEC) can be used.

[0073] It is also understandable that any lithium salt in the electrolyte matching the high voltage system battery needs to have high conductivity, good chemical stability and film-forming properties, and provide the required lithium ions for the lithium secondary battery. Specifically, lithium bis(oxalatoborate) (LiBOB), lithium bis(fluorooxalatoborate) (LiDFOB), lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI), etc. can be used as lithium salts.

[0074] In some embodiments, the electrolyte further includes other additives. The type of additives is not particularly limited in this application, and any known electrolyte additives can be applied to this application without violating the overall inventive concept of this application.

[0075] In some embodiments, the battery cell in the present application may also be an all-solid-state battery, in which case the battery cell further includes a solid electrolyte membrane disposed between the positive electrode and the negative electrode.

[0076] In some embodiments, the solid electrolyte membrane includes any one or a combination of at least two of a sulfide solid electrolyte, a halide solid electrolyte, and an oxide solid electrolyte. The above are all common solid electrolytes in the art and are only examples and not limitations.

[0077] In some embodiments, the battery pack has a nominal voltage of 11-13V, the battery unit has three series-connected units, each series-connected unit includes at least one battery cell, and the voltage platform of the battery cell is 4.65-4.75V.

[0078] In some embodiments, the battery pack has a nominal voltage of 22-26V, the battery unit has 4-6 series-connected units, and each series-connected unit includes at least one battery cell.

[0079] In some embodiments, the battery pack has a nominal voltage of 47-49V, the battery unit has 10-12 series-connected units, and each series-connected unit includes at least one battery cell.

[0080] In some embodiments, the cold cranking current of the battery pack is ≧600A.

[0081] In some embodiments, the maximum discharge current of the battery pack is 500-1000A.

[0082] like Figure 1 It should be noted that this section is only a schematic illustration of the structure of the start-stop power supply, and is not a limitation on the scope of protection. Based on the actual battery arrangement and installation requirements, conventional improvements to the start-stop battery related structure should still be considered within the scope of protection of this application.

[0083] The battery pack is used to provide electric energy for starting and stopping the car. Its structure includes a bottom plate 102, a cover plate 101, a side plate 103 and a battery module. The cover plate 101 is connected to the bottom plate 102, and a storage space is formed between the cover plate 101, the side plate 103 and the bottom plate 102. The battery module is installed inside the storage space, and the bottom plate 102, the cover plate 101 and the side plate 103 provide a bearing function for the battery module, and can provide a stable working place for the module assembly.

[0084] As a way to fix the battery module, a groove 110 is provided on the bottom plate 102, the battery module is placed inside the groove 110, and the bottom of the battery module is bonded to the bottom wall of the groove 110. The groove 110 provided on the bottom plate 102 is adapted to the battery module, and the battery module is fixedly connected by bonding the bottom to the bottom wall of the groove 110, which can improve the installation stability of the battery module.

[0085] The battery modules are stacked on the base plate 102 and connected in series with each other, and multiple battery modules are used to provide current. The submodule includes multiple battery cells 130 arranged in parallel, and the multiple battery cells 130 are stacked and bonded to each other. Among them, a submodule can be formed by connecting multiple battery cells 130 in parallel, and the output current of each submodule can be increased. Among them, by stacking multiple battery cells 130, the space utilization rate can be improved, and at the same time, the energy density of the battery cell 130 itself is greater than that of the square aluminum shell module in the prior art, thereby achieving the purpose of increasing the energy density of each submodule, so as to achieve the purpose of increasing the energy density of the overall battery.

[0086] The battery module further includes a tab support plate 140 , wherein the tab support plate 140 is mounted on the tabs 180 of the battery cells 130 , and the tabs 180 of the battery cells 130 pass through the tab support plate 140 .

[0087] The battery module further includes a plurality of series connection bars 150, which are welded on the tab frame plate 140, and a plurality of submodules are connected in series to form a loop through the plurality of series connection bars 150. Two series connection bars 150 are welded on each submodule, so that a plurality of battery cells 130 in the submodule can be arranged in parallel, and a plurality of submodules can be connected in series by connecting a plurality of series connection bars 150 in series.

[0088] The module assembly also includes a first end plate 120, a second end plate 160, a total positive copper bar (not shown), and a total negative copper bar (not shown). The second end plate 160 is buckled on the pole ear frame plate 140. The total positive copper bar and the total negative copper bar are arranged at intervals on the second end plate 160, and cooperate with the series connection bar 150 to form a loop, wherein the total positive copper bar and the total negative copper bar are used to lead out the positive and negative electrodes of multiple sub-modules connected in series, so that multiple sub-modules connected in series can output electrical energy to the outside. The side plate 103 is buckled on the second end plate 160.

[0089] Two terminal insulators 170 are provided on the side plate 103, which are respectively the positive output terminal and the negative output terminal, and the positive output terminal and the negative output terminal are respectively connected to the positive and negative poles of multiple sub-modules arranged in series, so that current can be output to the outside through the two terminal insulators 170, thereby achieving the purpose of the start-stop battery outputting current to the outside.

[0090] This application uses a high-voltage spinel nickel-manganese-oxide lithium battery pack as a car start-stop battery. Through the high operating voltage characteristics of its single cell, the number of batteries connected in series can be reduced, greatly optimizing the integration efficiency of the car start-stop battery module. For example, in a 12v system start-stop battery, theoretically only three battery sub-modules need to be connected in series to achieve the car start-stop function. Compared with other low-voltage car start-stop batteries, the number of battery sub-modules connected in series is reduced, the complexity of the connectors and the contact internal resistance are reduced, and the overall space occupied by the battery module is saved, reducing the volume and weight of the start-stop battery.

[0091] Under the same energy demand, the 12v nickel manganese oxide start-stop battery pack in this application is compared with the 12v lithium iron phosphate start-stop battery. The 12v lithium iron phosphate start-stop battery has 4 battery sub-modules connected in series, while the 12v nickel manganese oxide start-stop battery only needs to connect three battery sub-modules in series. The nickel manganese oxide solution reduces 1 battery sub-module, achieving a module space saving rate of about 25%, while reducing the complexity of connectors and contact internal resistance. In the 24V start-stop battery system, the lithium iron phosphate system requires 8 battery cells in series (3.2V×8=25.6V), while the nickel manganese oxide system only requires 5 battery cells in series (4.8V×5=24.0V, matched with the 24V system through BMS voltage window adjustment). This solution reduces 3 battery sub-modules, saves 37.5% of the module space, and significantly improves the volume energy density (increases by about 18-22%). In addition, in the 48v start-stop battery system, the 48v lithium nickel manganese oxide start-stop battery only needs to connect 10 battery sub-modules in series, while the 48v lithium iron phosphate start-stop battery needs at least 15 battery sub-modules in series. This configuration reduces 5 battery sub-modules, saves 30% of the module space, and reduces the system weight by about 28-32%.

[0092] The present application will be further described below with reference to specific embodiments and comparative examples.

[0093] Example 1

[0094] This embodiment provides a battery cell, including a positive electrode, a negative electrode, an electrolyte and a separator, and its specific composition is as follows:

[0095] The positive electrode includes a positive electrode layer and a positive electrode current collector, wherein the positive electrode layer includes a positive electrode active material LiNi 0.5 Mn 1.5 O4, the positive electrode binder is PVDF and the positive electrode conductor is single-arm VGCF, double-arm VGCF and Super-P, and the mass ratio of the positive electrode active material, the positive electrode binder and the positive electrode conductor (the mass ratio of single-arm VGCF, double-arm VGCF and Super-P is 1:1:3) is 91:4:5. A solid electrolyte layer LLZO is coated on the positive electrode layer of the positive electrode. The positive electrode current collector is aluminum foil.

[0096] The negative electrode includes a negative electrode layer and a negative electrode current collector, wherein the negative electrode layer includes graphite, a negative electrode active material, CMC, PAA and SBR as negative electrode binders, and Super-P as negative electrode conductive agent, and the mass ratio of the negative electrode active material, the negative electrode binder (the mass ratio of CMC, PAA and SBR is 1:1:1) and the negative electrode conductive agent is 95:3:2. The negative electrode current collector is copper foil.

[0097] The positive electrode and the negative electrode are cut separately and then stacked and assembled with the separator to obtain a semi-finished battery cell; wherein the separator is a PI-based separator.

[0098] 82wt% organic solvent (Sulfolane: FEC = 1:1), 10wt% LiPF6, 4wt% LiTFSI electrolyte, 3wt% LiBOB and 1wt% tris(trimethylsilyl) borate (TMSB) were prepared into an ionic liquid electrolyte, and the electrolyte was injected into the semi-finished battery cell; after the injection, the battery cell was formed and sealed to form a battery cell. The charging cut-off voltage of the battery cell is 4.8V, and the size is 9.1mm*148mm*142.5mm in thickness*width*height.

[0099] Example 2

[0100] This embodiment uses the battery cells prepared in Example 1 to form a battery pack, which is further assembled into a start-stop power supply: the battery pack in this embodiment has a nominal voltage of 12V and includes a total of 3 battery cells. 0.5 Mn 1.5 O4, the positive electrode binder is PVDF and the positive electrode conductive agent is single-arm VGCF, double-arm VGCF and Super-P, and the mass ratio of positive electrode active material, positive electrode binder and positive electrode conductive agent (the mass ratio of single-arm VGCF, double-arm VGCF and Super-P is 1:1:3) is 91:4:5. Under certain low temperature conditions (-18℃), when the terminal voltage of a fully charged 12V lithium nickel manganese oxide battery pack drops to 7.2V within 30s, the minimum current that the start-stop battery can supply is 600A.

[0101] Example 3

[0102] This embodiment uses the battery cells prepared in Example 1 to form a battery pack, which is further assembled into a start-stop power supply: the battery pack in this embodiment has a nominal voltage of 48V and includes a total of 10 battery cells. 0.5 Mn 1.5O4, the positive electrode binder is PVDF and the positive electrode conductive agent is single-arm VGCF, double-arm VGCF and Super-P, and the mass ratio of positive electrode active material, positive electrode binder and positive electrode conductive agent (the mass ratio of single-arm VGCF, double-arm VGCF and Super-P is 1:1:3) is 91:4:5. Under certain low temperature conditions (-18℃), when the terminal voltage of a fully charged 48V lithium nickel manganese oxide start-stop battery pack drops to 7.2V within 30s, the minimum current that the battery can supply is 700A.

[0103] Comparative Example 1

[0104] The nominal voltage of the automotive start-stop battery in this comparative example is 12V, the positive electrode active material of the battery cell is lithium iron phosphate, the battery cell voltage is 3.2V, the battery cell size is 9.1mm*148mm*142.5mm in thickness*width*height, and there are 4 battery cells in total. Under certain low temperature conditions (-18℃), when the terminal voltage of a fully charged 12V lithium iron phosphate start-stop battery drops to 7.2V within 30s, the minimum current that the battery can supply is 500A.

[0105] Comparative Example 2

[0106] The nominal voltage of the start-stop battery in this comparative example is 48V, the positive electrode active material of the battery cell is lithium iron phosphate, the battery cell voltage is 3.2V, the battery cell size is 9.1mm*148mm*142.5mm in thickness*width*height, and there are 15 battery cells in total. Under certain low temperature conditions (-18℃), when the terminal voltage of a fully charged 48V battery drops to 7.2V within 30s, the minimum current that the battery can supply is 550A.

[0107] Compared with comparative example 1, the space utilization rate of embodiment 2 is improved by 25%, the cold starting current is significantly increased, and the low temperature performance of the automobile start-stop battery in embodiment 1 is significantly better than that of the automobile start-stop battery in comparative example 1.

[0108] Compared with comparative example 2, the space utilization rate of embodiment 3 is improved by 30%, the cold starting current is significantly increased, and the low temperature performance of the automobile start-stop battery in embodiment 3 is significantly better than that of the automobile start-stop battery in comparative example 2.

[0109] The automotive start-stop battery prepared in this application can achieve high-rate charge and discharge, can achieve 30C discharge and 20C charging, and can discharge normally at low temperature (-30°C) and high temperature (60°C), meeting the current electric vehicle start-stop system's requirements for high battery capacity, high-rate discharge, and high and low temperature resistance. At the same time, due to the high-voltage platform, the start-stop battery provided in this application requires fewer battery cells when used in series, thereby reducing the use of auxiliary materials and structures. Fewer series connections means that the use of connectors, electrical components, and structural parts can be reduced in the battery pack design, thereby reducing overall cost and complexity.

[0110] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A battery pack used to provide power to the engine and ignition device when starting a car, characterized in that: The invention comprises a battery unit and a housing forming a space for accommodating the battery unit; the battery unit comprises n battery cells, the battery cells comprise a positive electrode, and the positive electrode active material in the positive electrode comprises a spinel structured Li 1+x Ni y M z Mn 2-x-y-z O 4-k , -0.1≤x≤0.2, 0.4≤y≤0.6, 0≤z≤0.2, 0≤k≤0.8, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti; wherein the charging cut-off voltage U of the battery cell is ≥4.8V.

2. The battery pack according to claim 1, wherein: The positive electrode active material is a mixture, wherein the spinel structured Li 1+x Ni y M z Mn 2-x-y-z O 4-k It accounts for more than 80% of the total positive electrode active materials.

3. The battery pack according to claim 1, wherein: The positive electrode active material is a mixture, wherein the spinel structured Li 1+x Ni y M z Mn 2-x-y-z O 4-k It accounts for more than 90% of the total positive electrode active materials.

4. The battery pack according to claim 1, wherein: The battery cell is an all-solid-state battery.

5. The battery pack according to claim 1, wherein: The battery cell is a semi-solid battery.

6. The battery pack according to claim 1, wherein: The battery pack has a nominal voltage of 11-13V, the battery unit has three series-connected units, each series-connected unit includes at least one battery cell, and the voltage platform of the battery cell is 4.65-4.75V.

7. The battery pack according to claim 1, wherein: The battery pack has a nominal voltage of 22-26V, the battery unit has 4-6 series-connected units, and each series-connected unit includes at least one battery cell.

8. The battery pack according to claim 1, wherein: The battery pack has a nominal voltage of 47-49V, and the battery unit has 10-12 series-connected units, each of which includes at least one battery cell.

9. The battery pack according to claim 1, wherein: The cold starting current of the battery pack is ≧600A.

10. The battery pack according to claim 1, wherein: The maximum discharge current of the battery pack is 500-1000A.

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