WO2025002607A1

WO2025002607A1 - Battery pack and electric vehicle including the same

Info

Publication number: WO2025002607A1
Application number: PCT/EP2024/058571
Authority: WO
Inventors: Tobias Glossmann; Eleni TEMECHE
Original assignee: Mercedes Benz Group AG
Current assignee: Mercedes Benz Group AG
Priority date: 2023-06-24
Filing date: 2024-03-28
Publication date: 2025-01-02
Anticipated expiration: 2025-12-24

Abstract

A battery pack includes at least one first-type battery cell and a plurality of second-type battery cells surrounding the at least one first-type battery cell. The plurality of second-type battery cells are connected to the at least one first-type battery cell. An energy density of the at least one first-type battery cell is higher than an energy density of each of the plurality of second-type battery cells.

Description

BATTERY PACK AND ELECTRIC VEHICLE INCLUDING THE SAME

FIELD OF THE TECHNOLOGY

[0001] This application relates to the field of electric vehicle technology and, more particularly, to a battery pack and an electric vehicle including the battery pack.

BACKGROUND OF THE DISCLOSURE

[0002] Lithium-ion battery (LIB) cells with higher energy density, e.g., battery cells using Ni-rich cathode materials, compared to LIB cells with lower energy density, e.g., battery cells using lithium iron phosphate (LFP) cathode materials, may have lower thermal stability and overall faster performance degradation. The performance degradation is mainly attributed to thermodynamic instability of the cathode material. Safety concerns may arise during occurrence of abuse conditions, e.g., overheating, overcharging, electric shorting, etc. On the contrary, LIB cells with lower energy density generally have better thermal stability and higher capacity retention. It is challenging to find an LIB that can deliver both high electrochemical performance and desirable safety simultaneously.

SUMMARY

[0003] In accordance with various embodiments of the present disclosure, there is provided a battery pack. The battery pack includes at least one first-type battery cell and a plurality of second-type battery cells surrounding the at least one first-type battery cell. The plurality of second-type battery cells are connected to the at least one first-type battery cell. An energy density of the at least one first-type battery cell is higher than an energy density of each of the plurality of second-type battery cells. [0004] Also in accordance with various embodiments of the present disclosure, there is provided an electric vehicle. The electric vehicle includes vehicle body, a drivetrain system arranged at the vehicle body and configured to drive a movement of the vehicle body, and a battery assembly configured to provide power to the drivetrain system. The battery assembly includes a controller and a battery pack. The battery pack includes at least one first-type battery cell and a plurality of second-type battery cells surrounding the at least one first-type battery cell. The plurality of second-type battery cells are connected to the at least one first-type battery cell. An energy density of the at least one first-type battery cell is higher than an energy density of each of the plurality of second-type battery cells.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a schematic diagram illustrating an example of an electric vehicle according to some embodiments of the present disclosure.

[0006] FIG. 2 is a schematic diagram illustrating an example of a battery pack according to some embodiments of the present disclosure.

[0007] FIG. 3 is a schematic diagram illustrating another example of a battery pack according to some embodiments of the present disclosure.

[0008] FIGs. 4A-4B are schematic diagrams illustrating examples of calculating the packing density of a battery pack according to some embodiments of the present disclosure. [0009] FIGs. 5A-5C are schematic diagrams illustrating examples of a battery pack according to some embodiments of the present disclosure.

[0010] FIG. 6 is a schematic diagram illustrating an example of an electric vehicle according to some embodiments of the present disclosure. [0011] FIG. 7 is a schematic diagram illustrating an example of an electric vehicle according to some embodiments of the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0012] The following describes the technical solutions in the embodiments of the present disclosure with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. The described embodiments are merely some but not all of the embodiments of the present disclosure. Other embodiments obtained by a person skilled in the art based on the embodiments of the present disclosure without creative efforts shall fall within the scope of the present disclosure.

[0013] References in the specification to “one embodiment,” “an embodiment,” “an exemplary embodiment,” “some embodiments,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment.

[0014] Further, when a particular feature, structure or characteristic is described in connection with an embodiment, it would be within the knowledge of a person skilled in the art to effect such feature, structure or characteristic in connection with other embodiments whether or not explicitly described. A person of ordinary skill in the art can make modifications to the described embodiments according to the principle of the present disclosure. For example, one or more components of the disclosed device can be omitted, or one or more components not explicitly described above can be added to the device. Similarly, one or more steps in the disclosed method can be omitted or one or more steps not explicitly described above can be included in the method. [0015] Unless otherwise specified, all technical and scientific terms used in this disclosure have the same or similar meanings as generally understood by those having ordinary skill in the art. As described herein, the terms used in the specification of the present disclosure are intended to describe example embodiments, instead of limiting the present disclosure. In general, terminology may be understood at least in part from usage in context. For example, the term “one or more” as used herein, depending at least in part upon context, may be used to describe any feature, structure, or characteristic in a singular sense or may be used to describe combinations of features, structures, or characteristics in a plural sense. Similarly, terms, such as “a,” “an,” or “the,” may be understood to convey a singular usage or to convey a plural usage, depending at least in part upon context.

[0016] As used herein, when a first component is referred to as “fixed to” a second component, it is intended that the first component may be directly attached to the second component or may be indirectly attached to the second component via another component. When a first component is referred to as “connecting” to a second component, it is intended that the first component may be directly connected to the second component or may be indirectly connected to the second component via a third component between them. The term “and/or” used herein includes any suitable combination of one or more related items listed.

[0017] As used herein, unless otherwise specified, a value or a range of values may refer to a desired, target, or nominal value or range of values and can include slight variations. The term “about” or “approximately” associated with a value can allow a variation within, for example, 10% of the value, such as ±2%, ±5%, or ±10% of the value, or another proper variation as appreciated by those having ordinary skill in the art. The term “about” or “approximately” associated with a state can allow a slight deviation from the state. For example, a first component being approximately perpendicular to a second component can indicate that the first component is either exactly perpendicular to the second component or slightly deviates from being perpendicular to the second component, and an angle between the first and second components can be within a range from, e.g., 80° to 100°, or another proper range as appreciated by those having ordinary skill in the art.

[0018] The present disclosure provides a battery pack and an electric vehicle. For example, a battery pack may utilize a dual chemistry pack design including at least two different types of battery cells. In one embodiment, the battery pack may be lithium-ion battery pack, which provides high electrochemical performance and high safety simultaneously.

[0019] For example, FIG. 1 illustrates an example of a battery pack 100 according to some embodiments of the present disclosure. The battery pack 100 includes at least one first- type battery cell 110 and a plurality of second-type battery cells 120, and the plurality of second- type battery cells 120 are electrically and/or physically connected to the at least one first-type battery cell 110. The plurality of second-type battery cells 120 are arranged to surround the at least one first-type battery cell 110. A quantity of the first-type battery cell 110 in the battery pack 100 may be 1 , 2, 3, ... , or any other suitable number. A quantity of the plurality of second- type battery cells 120 in the battery pack 100 may be 2, 3, ... , or any other suitable number. A ratio of a number of the at least one first-type battery cell 110 versus a number of the second- type battery cells 120 can be any suitable ratio, e.g., 1 :1, 1 :2, 1 :3 ... etc. The ratio may be determined based on actual application requirements for, e.g., longer range, longer cycle life, faster charging, etc. For example, as illustrated in FIG. 1 , the ratio of a number of the at least one first-type battery cell 110 versus the number of the second -type battery cells 120 is 1 :4. [0020] The at least one first-type battery cell 110 has different characteristics from the plurality of second-type battery cells 120. In some embodiments, an energy density of the at least one first-type battery cell 110 is different from an energy density of the plurality of second- type battery cells 120. The energy density may be measured as a volumetric energy density and may use a unit Wh/L. The volumetric energy density of a battery cell refers to the amount of energy that can be contained within a given volume of the battery cell. The energy density may also be measured as a gravimetric energy density and may use a unit Wh/kg. The gravimetric energy density of a battery cell refers to the amount of energy that can be contained within a given mass of the battery cell. For example, a lithium iron phosphate (LFP) battery cell may have a gravimetric energy density ranging from 90 to 130 Wh/kg, and a lithium nickel manganese cobalt oxides (NMC) battery cell may have a gravimetric energy density ranging from 190 to 260Wh/kg, where these gravimetric energy density values vary depending on the cell design.

[0021] In some embodiments, an energy density of the at least one first-type battery cell 110 is higher than an average energy density of the plurality of second-type battery cells 120. The average energy density of the plurality of second -type battery cells 120 refers to an average value of the energy densities among the plurality of second-type battery cells 120. In one example, one or more of the plurality of second -type battery cells 120 may have lower energy density than the at least one first-type battery cell 110, one or more of the plurality of second- type battery cells 120 may have higher energy density than the at least one first-type battery cell 110, and the average energy density of overall of the plurality of second -type battery cells 120 is lower than the energy density of the at least one first-type battery cell 110. In another example, one or more of the plurality of second-type battery cells 120 may have lower energy density than the at least one first-type battery cell 110, one or more of the plurality of second-type battery cells 120 may have same energy density as the at least one first-type battery cell 110, and the average energy density of overall of the plurality of second -type battery cells 120 is lower than the energy density of the at least one first-type battery cell 110. In further another example, one or more of the plurality of second-type battery cells 120 may have lower energy density than the at least one first-type battery cell 110, one or more of the plurality of second-type battery cells 120 may have higher energy density than the at least one first-type battery cell 110, one or more of the plurality of second -type battery cells 120 may have same energy density as the at least one first-type battery cell 110, and the average energy density of overall of the plurality of second- type battery cells 120 is lower than the energy density of the at least one first-type battery cell 110.

[0022] In some other embodiments, the energy density of the at least one first-type battery cell 110 is higher than an energy density of each of the plurality of second-type battery cells 120.

[0023] In some embodiments, a thermal stability of the at least one first-type battery cell 110 is different from a thermal stability of the plurality of second-type battery cells 120. The thermal stability of a battery cell can be determined by measuring the stability of the battery cell at different temperatures. Higher thermal stability of a battery cell indicates higher temperature the battery cell can sustain before the battery cell become unstable. At certain temperature, when a battery cell become unstable due to heat, the battery cell may decompose and fail, and a thermal runaway may happen, causing adjacent battery cells to become unstable. [0024] In some embodiments, the thermal stability of the at least one first-type battery cell 110 is lower than the thermal stability of each of the plurality of second -type battery cells 120.

[0025] In some embodiments, the battery pack 100 may be a lithium-ion battery (LIB) pack or any other battery pack can implement the design provided by the present disclosure. For example, the battery pack may be an M-ion-battery, where M may be one of sodium, lithium, aluminum, calcium, and magnesium.

[0026] In some embodiments, compared to the second-type battery cell 120, the first-type battery cell 110 may have higher energy density and lower thermal stability. The first-type battery cell 110 may include a lithium nickel manganese cobalt oxides (NMC) battery cell, lithium nickel cobalt aluminum oxide (NCA) battery cell, metal-based rechargeable battery cell (e.g., lithium metal battery cell), solid-state battery cell, and/or any other suitable battery cell (e.g., an organic battery cell). For example, the first-type battery cell 110 may rely on nickel rich cathode materials, e.g., LiNio.8Mno.1Coo.1O2 and LiNi_xCo_yAl_zO2. Compared to the first-type battery cell 110, the second-type battery cell 120 may have higher thermal stability and lower energy density. For example, the second-type battery cell 120 may include a lithium iron phosphate (LFP) battery cell, and/or any other suitable battery cell. In some embodiments, the first-type battery cell and second -type battery cell pair (i.e., first-type battery cell/second-type battery cell) may include NMC battery cell/LFP battery cell, NCA battery cell/LFP battery cell, lithium nickel manganese cobalt aluminum oxides (NMCA) battery cell/lithium manganese iron phosphate (LMFP) battery cell, (lithium nickel oxide) LNO battery cell/LFP battery cell, LNO battery cell/LMFP battery cell, etc. For example, the second-type battery cell 120 could be phosphate cathode-based LFP cells, and the first-type battery cell in 110 may have NMC as the cathode and have any suitable material (e.g., Li-metal or its alloys, silicon-based materials, or graphite) as the anode.

[0027] In some other embodiments, compared to the second-type battery cell 120, the first-type battery cell 110 may have higher energy density and higher thermal stability. Compared to the first-type battery cell 110, the second-type battery cell 120 may lower thermal stability and lower energy density. For example, the first-type battery cell 110 and the second- type battery cell 120 can include any suitable solid-state batteries.

[0028] In some other embodiments, compared to the second-type battery cell 120, the first-type battery cell 110 may have higher energy density. Compared to the first-type battery cell 110, the second-type battery cell 120 may have lower energy density. The first-type battery cell 110 has the same or similar thermal stability as the second -type battery cell 120. In some embodiments, the first-type battery cell and second-type battery cell pair (i.e., first-type battery cell/ second-type battery cell) may include (lithium nickel manganese oxide) LNMO battery cell/LFP battery cell, or any other suitable pair of battery cells.

[0029] As illustrated in FIG. 1 , the at least one first-type battery cell 110 and the plurality of second-type battery cells 120 may be arranged in a manner that the at least one first-type battery cell 110 is surrounded by the plurality of second-type battery cells 120. FIGs. 2 and 3 illustrate some examples of a battery pack 100 according to some embodiments of the present disclosure.

[0030] In some embodiments, as illustrated in FIG. 2, the at least one first-type battery cell 110 includes a plurality of first-type battery cells 110 arranged at an inner core of the battery pack 100, and the plurality of second-type battery cells 120 are arranged at a peripheral of the plurality of first-type battery cells 110. A cross-sectional dimension of each of the first battery cells 110 may be same as or different from a cross-sectional dimension of each of the second battery cells 120. As illustrated in FIG. 2, the first battery cells 110 and the second battery cells 120 are cylindrical battery cells, and the cross-sectional dimension of the first battery cell 110 is same as the cross-sectional dimension of the second battery cell 120. For example, a radius of cross-section of the first battery cell 110 is same as a radius of the cross-section of the second battery cell 120.

[0031] In some other embodiments, as illustrated in FIG. 3, the at least one first-type battery cell 110 includes a plurality of first-type battery cells 110 spaced with each other by one of the plurality of second-type battery cells 120. A cross-sectional dimension of each of the first battery cells 110 may be different from a cross-sectional dimension of each of the second battery cells 120. As illustrated in FIG. 2, the first battery cells 110 and the second battery cells 120 are cylindrical battery cells, and the cross-sectional dimension of the first battery cell 110 is smaller than the cross-sectional dimension of the second battery cell 120. For example, a radius of crosssection of the first battery cell 110 is smaller than a radius of the cross-section of the second battery cell 120. The plurality of first-type battery cells 110 fill the gaps among the plurality of second-type battery cells 120.

[0032] In the packing patterns illustrated in FIGs. 2 and 3, at least one of the first-type battery cells 110 are tangent with one or more of the second-type battery cells 120. In some embodiments, the battery cells may or may not be in contact with each other. For example, the battery cells may be separated with each other with an isolation structure.

[0033] The at least one first-type battery cell 110 is connected to the plurality of second- type battery cells 120. For example, the battery pack 100 may include a plurality of battery groups and each of the battery groups may include a plurality of battery cells. The plurality of batery groups may be connected with each other in parallel and the battery cells in a same batery group may be connected with each other in series. For example, the connections may be achieved through bus bar with bolts. The connection may be flexible and easy to replace.

[0034] Different packing patterns of the first batery cell and the second battery cell can result in different packing densities. Dependent on actual applications, a higher packing density may be desirable when there is a limited available space for the batery pack to occupy and/or when it is required to achieve a more compact effect. The battery pack 100 illustrated in FIG. 3 has a higher packing density than the batery pack illustrated in FIG. 2. For example, FIGs. 4A- 4B illustrate examples of calculating the packing density of a batery pack according to some embodiments of the present disclosure.

[0035] For illustration purpose, the batery pack in FIG. 4 A includes nine battery cells and has a similar packing pattern as the battery pack 100 illustrated in FIG. 2. In real application, the battery pack may include any suitable numbers of battery cells. The battery cells in FIG. 4A are cylindrical batery cells and a cross-section of each of the cylindrical batery cells has a radius r₁₅ and a rectangle box indicates the boundaries of the battery pack. Assuming that the batery cells are tangent with each other and the boundaries of the battery pack are tangent with the most outer layer of batery cells, based on the geometry relations, the length a and the length b of the box are correlated to the radius r_x of the cylindrical batery cells. For example, based on the geometry relations, a =

+ 2)r₁₅ and b = 7T . The packing density equals to a ratio of a total cross-sectional area of the nine batery cells versus a cross-sectional area of the batery pack. That is, the packing density

= _{7r (2}^₊₂y_r ~ 0- 4.

[0036] For illustration purposes, the battery pack in FIG. 4B includes nine larger battery cells and four smaller battery cells filling the gaps among the nine larger batery cells. The packing pattern in FIG. 4B is similar as the packing pattern of the battery pack 100 illustrated in

FIG. 3. In real application, the battery pack may include any suitable numbers of battery cells. The nine larger battery cells illustrated in FIG. 4B have same dimension as the nine battery cells illustrated in FIG. 4A. Both of the larger battery cells and smaller battery cells in FIG. 4B are cylindrical battery cells. A cross-section of each of the larger cylindrical battery cells has a radius r₁₅ a cross-section of each of the smaller cylindrical battery cells has a radius r₂, and a rectangle box indicates the boundaries of the battery pack. Assuming that each of the smaller cylindrical battery cells is tangent to 4 adjacent larger cylindrical battery cells and the boundaries of the battery pack are tangent with the most outer layer of battery cells, based on the geometry relations, the length a and the length b of the battery pack and the radius r₂ of the smaller cylindrical battery cells are correlated to the radius r_x of the larger cylindrical battery cells. For example, based on the geometry relations, a = 6r₁₅ b = 6r₁₅ and r₂ = ( 2 — l)ri. The packing density equals to a ratio of a total sum of cross-sectional area of the nine larger cylindrical battery cells and four smaller cylindrical battery cells versus a cross-sectional area of the battery

1 1, i ■ J ' -, 9TT k. That is, the packing density = -_ri ² +4TTr — -₂ ² 9Trr = -₁ ²+4TT(V2-l) pac ; — -²r₁ ² « 0.85.

[0037] Comparing the packing density of the battery pack illustrated in FIG. 4A and the battery pack illustrated in FIG. 4B, a battery pack includes battery cells of at least two different sizes may help to increase the packing density. The ratio, dimension, and packing pattern of the battery cells of at least two different sizes may be adjusted based on actual applications.

[0038] For simplification purpose, in the packing patterns illustrated in FIGs. 4A and 4B, the battery cells are tangent with each other. In some embodiments, the battery cells may or may not be in contact with each other. For example, the battery cells may be separated with each other with an isolation structure. [0039] In some embodiments, e.g., as illustrated in FIGs. 2-4B, the battery cells in the battery pack are cylindrical battery cells. In some other embodiments, the battery cells in the battery pack may include a prismatic battery cell or a pouch cell. FIGs. 5A-5C illustrate examples of a battery pack 100 according to some embodiments of the present disclosure.

[0040] As illustrated in FIG. 5 A, the battery pack 100 includes a first-type battery cell 110 and a plurality of second-type battery cells 120. The first-type battery cell 110 is a prismatic battery cell or a pouch cell. The first-type battery cell 110 includes a cell stack pressure apparatus 111 configured to ensure high strength of the first-type battery cell 110. The cell stack pressure apparatus 111 may include a low weight band with plates and or springs. The plurality of second-type battery cells 120 surrounds the first-type battery cell 110.

[0041] As illustrated in FIG. 5B, the battery pack 100 includes a first-type battery cell 110 and a plurality of second-type battery cells 120 having different sizes. The first-type battery cell 110 is a prismatic battery cell or a pouch cell. The first-type battery cell 110 includes a cell stack pressure apparatus 111 configured to ensure high strength of the first-type battery cell 110. The plurality of second -type battery cells 120 surrounds the first-type battery cell 110. The plurality of second-type battery cells 120 includes a plurality of battery cells 120-1 having a first size, and a plurality of battery cells 120-2 having a second size different from (e.g., smaller than) the first size, where the plurality of battery cells 120-2 fills the gap among the plurality of battery cells 120-1.

[0042] As illustrated in FIG. 5C, the battery pack 100 includes a first-type battery cell 110 and a plurality of second-type battery cells 120 having different sizes. The first-type battery cell 110 is a prismatic battery cell or a pouch cell. The first-type battery cell 110 includes a cell stack pressure apparatus 111 configured to ensure high strength of the first-type battery cell 110. The plurality of second -type battery cells 120 surrounds the first-type battery cell 110. The plurality of second-type battery cells 120 includes a plurality of battery cells 120-1 having a first size, and a plurality of battery cells 120-2 having a second size different from (e.g., smaller than) the first size, where the plurality of battery cells 120-2 are arranged between the plurality of battery cells 120-1 and the first-type battery cell 110.

[0043] In some embodiments, the plurality of second -type battery cells 120 may be connected with each other with an adhesive to form a protection wall of the at least one first-type battery cell 110. The adhesive may be any suitable material, e.g., any suitable glue, to connect the plurality of second-type battery cells 120 to form one or more stiff blocks and the stiff block protect the at least one first-type battery cells 110 surrounded by the one or more stiff blocks. [0044] According to the embodiments of the present disclosure, the plurality of second- type battery cells 120 provide mechanical support for the battery pack 100 and help to protect the at least one first-type battery cell 110. In some embodiments, the plurality of first-type battery cells 110 may include at least one of a cylindrical battery cell, a prismatic battery cell, or a pouch battery cell, and the second-type battery cell 120 may include at least one of a cylindrical battery cell, a prismatic battery cell, or a pouch battery cell. In one example, the first-type battery cell 110 may be a cylindrical battery cell, and the second-type battery cell 120 may be a cylindrical battery cell. In another example, the first-type battery cell 110 may be a prismatic battery cell, and the second-type battery cell 120 may be a cylindrical battery cell. In further another example, the first-type battery cell 110 may be a pouch battery cell, and the second -type battery cell 120 may be a cylindrical battery cell. In further another example, the first-type battery cell 110 may be a pouch battery cell, and the second-type battery cell 120 may be a prismatic battery cell. In some embodiments, the second-type battery cell 120 may be a pouch battery cell. [0045] Further, the second -type battery cell 120 may have relatively lower energy density and higher thermal stability, and the first-type battery cell 110 may have relatively higher energy density and lower thermal stability. The plurality of second-type battery cells 120 may be arranged around crash zones of a crash accident or may be arranged around areas susceptible to abusive conditions, and the at least one first-type battery cell 110 may be packed more effectively, e.g., surrounded by the plurality of second-type battery cells 120. As such, the at least one first-type battery cell 110 may be protected by the plurality of second-type battery cells 120.

[0046] During deformation of the battery pack 100 caused by accidents, e.g., a crash of the electric vehicle 1, the plurality of second-type battery cells 120 are more thermally stable than the first-type battery cell 110 and may not release much energy, and the plurality of second- type battery cells 120 near the crush zone can mitigate potential thermal runaway during the accidents, thereby making the deformation less dangerous. It is also possible to minimize the costs associated with a thermal level system equipment such as cooling systems dependent on battery chemistry.

[0047] In addition, the first-type battery cell 110 having higher energy density usually cost more than the second-type battery cells 120. The protection of the plurality of second -type battery cells 120 may help to lower the repair cost of the first-type battery cell 110, and may also increase the possibility of recycling or reusing the first-type battery cell 110 when the battery pack 100 is damaged or crashed. In case the long lasting second-type battery cells 120 (e.g., LFP battery cells) outlast the at least one first-type battery cell 110 (e.g., NMC battery cell), it is possible to only replace the at least one first-type battery cell 110.

[0048] Furthermore, the battery pack 100 provided by the present disclosure can maximize the energy density by using different types of battery cells and also accounts for expansion in different battery cells. The battery pack 100 provided by the present disclosure can use Ni-rich cathode material for the first-type battery cell, and minimize the Co content, thus lowering cost while improving overall stability of the battery pack 100 by the combination of the at least two different types of battery cells.

[0049] The battery pack 100 may be divided into a plurality of groups or modules, and one or more of the plurality of groups or modules may include different types of battery cells. For example, the plurality of groups includes a first group and a second group, where the first group may include a first combined structure of at least one first-type battery cell and at least one second-type battery cell, and the second group may include a second combined structure of at least one third-type battery cell and at least one fourth-type battery cell. In some embodiments, the first combined structure in the first group may be similar to or same as the second combined structure in the second group. In some embodiments, the first combined structure may be different from the second combined structure. The first combined structure or the second combined structure refers to how the different types of battery cells are arranged (e.g., FIGs. 2, 3, and 5A-5C).

[0050] Another aspect of the present disclosure provides an electric vehicle. FIGs. 6 and 7 illustrate an example of an electric vehicle 1 according to some embodiments of the present disclosure. As illustrated in FIG. 6, the electric vehicle 1 includes vehicle body 20, a drivetrain system 30 arranged at the vehicle body 20 and configured to drive a movement of the vehicle body 20, and a battery assembly 10 configured to provide power to the drivetrain system 30.

The drivetrain system 30 may include one or more electric motors, drive shafts, transmission mechanisms, etc., for delivering the electric power provided by the battery assembly 10 to the wheels of the electric vehicle 1 , to cause the electric vehicle 1 to move.

[0051] The battery assembly 10 includes a battery pack 100 and a controller 200 configured to control the battery pack 100. The controller 200 may include, may be a part of, or may be connected to a battery management system that controls charging and discharging of the battery pack 100 in different levels, e.g., in the level of battery groups each comprising a plurality of battery cells, and/or in the level of battery cells among the same battery group or across different battery groups. The controller 200 may control charging and discharging parameters of battery pack 100 based on different application requirements. The controller 200 may include one or more processors and a storage medium including instructions that enable the one or more processors to perform control operation of the battery pack 100. The storage medium can be any medium that can store program codes, for example, a USB disk, a mobile hard disk, a read-only memory (ROM), a random-access memory (RAM), a magnetic disk, or an optical disk.

[0052] The battery pack 100 includes at least one first-type battery cell 110 and a plurality of second-type battery cells 120, and the plurality of second-type battery cells 120 are electrically and/or physically connected to the at least one first-type battery cell 110. The plurality of second-type battery cells 120 are arranged to surround the at least one first-type battery cell 110. A quantity of the first-type battery cell 110 in the battery pack 100 may be 1, 2, 3, ... , or any other suitable number. A quantity of the plurality of second-type battery cells 120 in the battery pack 100 may be 2, 3, ... , or any other suitable number. A ratio of a number of the at least one first-type battery cell 110 versus a number of the second -type battery cells 120 can be any suitable ratio, e.g., 1 :1, 1 :2, 1 :3 ... etc. The ratio may be determined based on actual application requirements for, e.g., longer range, longer cycle life, faster charging, etc. For example, as illustrated in FIG. 6, the ratio of a number of the at least one first-type battery cell 110 versus the number of the second-type battery cells 120 is 1 :4.

[0053] The at least one first-type battery cell 110 has different characteristics from the plurality of second-type battery cells 120. In some embodiments, an energy density of the at least one first-type battery cell 110 is different from an energy density of the plurality of second- type battery cells 120. The energy density may be measured as a volumetric energy density and may use a unit Wh/L. The volumetric energy density of a battery cell refers to the amount of energy that can be contained within a given volume of the battery cell. The energy density may also be measured as a gravimetric energy density and may use a unit Wh/kg. The gravimetric energy density of a battery cell refers to the amount of energy that can be contained within a given mass of the battery cell. For example, a LFP battery cell may have a gravimetric energy density ranging from 90 to 130 Wh/kg, and a NMC battery cell may have a gravimetric energy density ranging from 190 to 260 Wh/kg, where these gravimetric energy density values vary depending on the cell design.

[0054] In some embodiments, an energy density of the at least one first-type battery cell 110 is higher than an average energy density of the plurality of second-type battery cells 120. The average energy density of the plurality of second -type battery cells 120 refers to an average value of the energy densities among the plurality of second-type battery cells 120. In one example, one or more of the plurality of second -type battery cells 120 may have lower energy density than the at least one first-type battery cell 110, one or more of the plurality of second- type battery cells 120 may have higher energy density than the at least one first-type battery cell

110, and the average energy density of overall of the plurality of second -type battery cells 120 is lower than the energy density of the at least one first-type battery cell 110. In another example, one or more of the plurality of second-type battery cells 120 may have lower energy density than the at least one first-type battery cell 110, one or more of the plurality of second-type battery cells 120 may have same energy density as the at least one first-type battery cell 110, and the average energy density of overall of the plurality of second -type battery cells 120 is lower than the energy density of the at least one first-type battery cell 110. In further another example, one or more of the plurality of second-type battery cells 120 may have lower energy density than the at least one first-type battery cell 110, one or more of the plurality of second-type battery cells 120 may have higher energy density than the at least one first-type battery cell 110, one or more of the plurality of second -type battery cells 120 may have same energy density as the at least one first-type battery cell 110, and the average energy density of overall of the plurality of second- type battery cells 120 is lower than the energy density of the at least one first-type battery cell 110.

[0055] In some other embodiments, the energy density of the at least one first-type battery cell 110 is higher than an energy density of each of the plurality of second-type battery cells 120.

[0056] In some embodiments, a thermal stability of the at least one first-type battery cell 110 is different from a thermal stability of the plurality of second-type battery cells 120. The thermal stability of a battery cell can be determined by measuring the stability of the battery cell at different temperatures. Higher thermal stability of a battery cell indicates higher temperature the battery cell can sustain before the battery cell become unstable. At certain temperature, when a battery cell become unstable due to heat, the battery cell may decompose and fail, and a thermal runaway may happen, causing adjacent battery cells to become unstable. [0057] In some embodiments, the thermal stability of the at least one first-type battery cell 110 is lower than the thermal stability of each of the plurality of second -type battery cells 120.

[0058] In some embodiments, the battery pack 100 may be a lithium-ion battery (LIB) pack or any other battery pack can implement the design provided by the present disclosure. For example, the battery pack may be an M-ion-battery, where M may be one of sodium, lithium, aluminum, calcium, and magnesium.

[0059] In some embodiments, compared to the second-type battery cell 120, the first-type battery cell 110 may have higher energy density and lower thermal stability. The first-type battery cell 110 may include a lithium nickel manganese cobalt oxides (NMC) battery cell, lithium nickel cobalt aluminum oxide (NCA) battery cell, metal-based rechargeable battery cell (e.g., lithium metal battery cell), solid-state battery cell, and/or any other suitable battery cell (e.g., an organic battery cell) . For example, the first-type battery cell 110 may rely on nickel rich cathode materials, e.g., LiNio.8Mno.1Coo.1O2 and LiNi_xCo_yAl_zO2. Compared to the first-type battery cell 110, the second-type battery cell 120 may have higher thermal stability and lower energy density. For example, the second-type battery cell 120 may include a lithium iron phosphate (LFP) battery cell, and/or any other suitable battery cell. In some embodiments, the first-type battery cell and second -type battery cell pair (i.e., first-type battery cell/second-type battery cell) may include NMC battery cell/LFP battery cell, NCA battery cell/LFP battery cell, NMCA battery cell/LMFP battery cell, LNO battery cell/LFP battery cell, LNO battery cell/LMFP battery cell, etc. For example, the second-type battery cell 120 could be phosphate cathode-based LFP cells, and the first-type battery cell in 110 may have NMC as the cathode and have any suitable material (e.g., Li-metal or its alloys, silicon-based materials, or graphite) as the anode.

[0060] In some other embodiments, compared to the second-type battery cell 120, the first-type battery cell 110 may have higher energy density and higher thermal stability. Compared to the first-type battery cell 110, the second-type battery cell 120 may lower thermal stability and lower energy density. For example, the first-type battery cell 110 and the second- type battery cell 120 can include any suitable solid-state batteries.

[0061] In some other embodiments, compared to the second-type battery cell 120, the first-type battery cell 110 may have higher energy density. Compared to the first-type battery cell 110, the second-type battery cell 120 may have lower energy density. The first-type battery cell 110 has the same or similar thermal stability as the second -type battery cell 120. In some embodiments, the first-type battery cell and second-type battery cell pair (i.e., first-type battery cell/ second-type battery cell) may include LNMO battery cell/LFP battery cell, or any other suitable pair of battery cells.

[0062] As illustrated in FIG. 6, the at least one first-type battery cell 110 and the plurality of second-type battery cells 120 may be arranged in a manner that the at least one first-type battery cell 110 is surrounded by the plurality of second-type battery cells 120. Some examples of a battery pack 100 according to some embodiments of the present disclosure may be referred to FIGs. 2 and 3.

[0063] As illustrated in FIG. 2, the at least one first-type battery cell 110 includes a plurality of first-type battery cells 110 arranged at an inner core of the battery pack 100, and the plurality of second-type battery cells 120 are arranged at a peripheral of the plurality of first-type battery cells 110. A cross-sectional dimension of each of the first battery cells 110 may be same as or different from a cross-sectional dimension of each of the second battery cells 120. As illustrated in FIG. 2, the first battery cells 110 and the second battery cells 120 are cylindrical battery cells, and the cross-sectional dimension of the first battery cell 110 is same as the cross- sectional dimension of the second battery cell 120. For example, a radius of cross-section of the first battery cell 110 is same as a radius of the cross-section of the second battery cell 120. [0064] As illustrated in FIG. 3, the at least one first-type battery cell 110 includes a plurality of first-type battery cells 110 spaced with each other by one of the plurality of second- type battery cells 120. A cross-sectional dimension of each of the first battery cells 110 may be different from a cross-sectional dimension of each of the second battery cells 120. As illustrated in FIG. 2, the first battery cells 110 and the second battery cells 120 are cylindrical battery cells, and the cross-sectional dimension of the first battery cell 110 is smaller than the cross-sectional dimension of the second battery cell 120. For example, a radius of cross-section of the first battery cell 110 is smaller than a radius of the cross-section of the second battery cell 120. The plurality of first-type battery cells 110 fill the gaps among the plurality of second-type battery cells 120.

[0065] In the packing patterns illustrated in FIGs. 2 and 3, at least one of the first-type battery cells 110 are tangent with one or more of the second-type battery cells 120. In some embodiments, the battery cells may or may not be in contact with each other. For example, the battery cells may be separated with each other with an isolation structure.

[0066] The at least one first-type battery cell 110 is connected to the plurality of second- type battery cells 120. For example, the battery pack 100 may include a plurality of battery groups and each of the battery groups may include a plurality of battery cells. The plurality of battery groups may be connected with each other in parallel and the battery cells in a same batery group may be connected with each other in series. For example, the connections may be achieved through bus bar with bolts. The connection may be flexible and easy to replace.

[0067] Different packing patterns of the first batery cell and the second battery cell can result in different packing densities. Dependent on actual applications, a higher packing density may be desirable when there is a limited available space for the batery pack to occupy and/or when it is required to achieve a more compact effect. The battery pack 100 illustrated in FIG. 3 has a higher packing density than the batery pack illustrated in FIG. 2. For example, some examples of calculating the packing density of a batery pack according to some embodiments of the present disclosure may be referred to FIGs. 4A-4B. Comparing the packing density of the batery pack illustrated in FIG. 4A and the batery pack illustrated in FIG. 4B, a battery pack includes battery cells of at least two different sizes may help to increase the packing density.

The ratio, dimension, and packing pattern of the batery cells of at least two different sizes may be adjusted based on actual applications.

[0068] In some embodiments, e.g., as illustrated in FIGs. 2-4B, the batery cells in the batery pack are cylindrical battery cells. In some other embodiments, the battery cells in the batery pack may include a prismatic batery cell or a pouch cell (e.g., FIGs. 5A-5C).

[0069] As illustrated in FIG. 5 A, the batery pack 100 includes a first-type batery cell 110 and a plurality of second-type battery cells 120. The first-type batery cell 110 is a prismatic batery cell or a pouch cell. The first-type battery cell 110 includes a cell stack pressure apparatus 111 configured to ensure high strength of the first-type batery cell 110. The cell stack pressure apparatus 111 may include a low weight band with plates and or springs. The plurality of second-type batery cells 120 surrounds the first-type batery cell 110. [0070] As illustrated in FIG. 5B, the battery pack 100 includes a first-type battery cell 110 and a plurality of second-type battery cells 120 having different sizes. The first-type battery cell 110 is a prismatic battery cell or a pouch cell. The first-type battery cell 110 includes a cell stack pressure apparatus 111 configured to ensure high strength of the first-type battery cell 110. The plurality of second -type battery cells 120 surrounds the first-type battery cell 110. The plurality of second-type battery cells 120 includes a plurality of battery cells 120-1 having a first size, and a plurality of battery cells 120-2 having a second size different from (e.g., smaller than) the first size, where the plurality of battery cells 120-2 fills the gap among the plurality of battery cells 120-1.

[0071] As illustrated in FIG. 5C, the battery pack 100 includes a first-type battery cell 110 and a plurality of second-type battery cells 120 having different sizes. The first-type battery cell 110 is a prismatic battery cell or a pouch cell. The first-type battery cell 110 includes a cell stack pressure apparatus 111 configured to ensure high strength of the first-type battery cell 110. The plurality of second -type battery cells 120 surrounds the first-type battery cell 110. The plurality of second-type battery cells 120 includes a plurality of battery cells 120-1 having a first size, and a plurality of battery cells 120-2 having a second size different from (e.g., smaller than) the first size, where the plurality of battery cells 120-2 are arranged between the plurality of battery cells 120-1 and the first-type battery cell 110.

[0072] In some embodiments, the plurality of second -type battery cells 120 may be connected with each other with an adhesive to form a protection wall of the at least one first-type battery cell 110. The adhesive may be any suitable material, e.g., any suitable glue, to connect the plurality of second-type battery cells 120 to form one or more stiff blocks and the stiff block protect the at least one first-type battery cells 110 surrounded by the one or more stiff blocks. [0073] According to the embodiments of the present disclosure, the plurality of second- type battery cells 120 provide mechanical support for the battery pack 100 and help to protect the first-type battery cell 110. In some embodiments, the plurality of first-type battery cells 110 may include at least one of a cylindrical battery cell, a prismatic battery cell, or a pouch battery cell, and the second-type battery cell 120 may include at least one of a cylindrical battery cell, a prismatic battery cell, or a pouch battery cell. In one example, the first-type battery cell 110 may be a cylindrical battery cell, and the second-type battery cell 120 may be a cylindrical battery cell. In another example, the first-type battery cell 110 may be a prismatic battery cell, and the second-type battery cell 120 may be a cylindrical battery cell. In further another example, the first-type battery cell 110 may be a pouch battery cell, and the second-type battery cell 120 may be a cylindrical battery cell. In further another example, the first-type battery cell 110 may be a pouch battery cell, and the second-type battery cell 120 may be a prismatic battery cell. In some embodiments, the second-type battery cell 120 may be a pouch battery cell.

[0074] Further, the second -type battery cell 120 may have relatively lower energy density but higher thermal stability, and the first-type battery cell 110 may have relatively higher energy density but lower thermal stability. The plurality of second-type battery cells 120 may be arranged around crash zones of a crash accident or may be arranged around areas susceptible to abusive conditions, and the at least one first-type battery cell 110 may be packed more effectively in the electric vehicle 1, e.g., surrounded by the plurality of second-type battery cells 120. As such, the at least one first-type battery cell 110 may be protected by the plurality of second-type battery cells 120.

[0075] During deformation of the battery pack 100 caused by accidents, e.g., a crash of the electric vehicle 1, the plurality of second-type battery cells 120 are more thermally stable than the first-type battery cell 110 and may not release much energy, and the plurality of second- type battery cells 120 near the crush zone can mitigate potential thermal runaway during the accidents, thereby making the deformation less dangerous. It is also possible to minimize the costs associated with a thermal level system equipment such as cooling systems dependent on battery chemistry.

[0076] In addition, the first-type battery cell 110 having higher energy density usually cost more than the second-type battery cells 120. The protection of the plurality of second -type battery cells 120 may help to lower the repair cost of the first-type battery cell 110, and may also increase the possibility of recycling or reusing the first-type battery cell 110 when the battery pack 100 is damaged or crashed. In case the long lasting second-type battery cells 120 (e.g., LFP battery cells) outlast the at least one first-type battery cell 110 (e.g., NMC battery cell), it is possible to only replace the at least one first-type battery cell 110.

[0077] Furthermore, the battery pack 100 provided by the present disclosure can maximize the energy density by using different types of battery cells and also accounts for expansion in different battery cells. The battery pack 100 provided by the present disclosure can use Ni-rich cathode material for the first-type battery cell, and minimize the Co content, thus lowering cost while improving overall stability of the battery pack 100 by the combination of the at least two different types of battery cells.

[0078] As illustrated in FIG. 7, the battery assembly 10 is arranged at the vehicle body 20. For example, battery assembly 10 may be arranged around a center of the vehicle body 20 or any other suitable position. The battery assembly 10 may be fixed to or mounted at the vehicle body 20 by a support structure 110. [0079] The battery assembly 10 usually has a heavy weight, such that the electric vehicle 1 may experience lateral acceleration during different driving scenarios. The first-type battery cell 110, e.g., a NMC battery cell, may include a relatively lighter cell with higher energy density. The plurality of second-type battery cells 120, e.g., LFP battery cells, may include relatively heavier cells with lower energy density. The gravity center 12 may be adjusted by adjusting a ratio, packing pattern, and/or positions of the first-type battery cell 110 and the plurality of second-type battery cells 120. In one example, the gravity center 12 may be lowered, thereby reducing the rollover risk for the electric vehicle 1. In another example, the gravity center 12 may be adjusted along the front-rear direction of the electric vehicle 1 or along a direction approximately perpendicular to the front-rear direction of the electric vehicle 1. The structure of the battery pack 100 may be modified and improved to hold the overall mass that may be dispersed in different configurations. The rotation inertia of the electric vehicle 1 may be optimized by strategically placing the first-type battery cell 110 and the plurality of second-type battery cells 120.

[0080] Another aspect of the present disclosure provides a method for fabricating a battery pack. The method includes providing at least one first-type battery cell in the battery pack, and a plurality of second-type battery cells in the battery pack, where the plurality of second-type battery cells surround the at least one first-type battery cell and are connected to the at least one first-type battery cell, and an energy density of the at least one first-type battery cell is higher than an energy density of each of the plurality of second-type battery cells.

[0081] For simplification purposes, detailed descriptions of the method may be omitted, and references can be made to the descriptions of the battery pack and the electric vehicle.

[0082] A method consistent with the disclosure can be implemented in the form of computer program stored in a non-transitory computer-readable storage medium, which can be sold or used as a standalone product. The computer program can include instructions that enable a computer device, such as a personal computer, a server, or a network device, to perform part or all of a method consistent with the disclosure, such as one of the example methods described above. The storage medium can be any medium that can store program codes, for example, a USB disk, a mobile hard disk, a read-only memory (ROM), a random-access memory (RAM), a magnetic disk, or an optical disk.

[0083] The above detailed descriptions only illustrate certain exemplary embodiments of the present disclosure, and are not intended to limit the scope of the present disclosure. Those skilled in the art can understand the specification as whole and technical features in the various embodiments can be combined into other embodiments understandable to those persons of ordinary skill in the art. Any equivalent or modification thereof, without departing from the spirit and principle of the present disclosure, falls within the true scope of the present disclosure.

Claims

CLAIMS What is claimed is:

1. A battery pack comprising: at least one first-type battery cell; and a plurality of second-type battery cells surrounding the at least one first-type battery cell and connected to the at least one first-type battery cell, an energy density of the at least one first- type battery cell being higher than an energy density of each of the plurality of second-type battery cells.

2. The battery pack of claim 1 , wherein a thermal stability of the at least one first- type battery cell is lower than a thermal stability of each of the plurality of second-type battery cells.

3. The battery pack of claim 1, wherein a cross-sectional dimension of the at least one first-type battery cell is smaller than a cross-sectional dimension of each of the plurality of second-type battery cells.

4. The battery pack of claim 1 , wherein the at least one first-type battery cell comprises at least one of a prismatic battery cell, a cylindrical battery cell, or a pouch battery cell.

5. The battery pack of claim 1 , wherein each of the plurality of second-type battery cells comprises at least one of a cylindrical battery cell, a prismatic battery cell, or a pouch battery cell.

6. The battery pack of claim 1 , wherein the at least one first-type battery cell comprises a solid-state battery cell.

7. The battery pack of claim 1 , wherein the at least one first-type battery cell is arranged at an inner core of the battery pack.

8. The battery pack of claim 1 , wherein the at least one first-type battery cell comprises a plurality of first-type battery cells spaced with each other by one of the plurality of second-type battery cells.

9. The battery pack of claim 8, wherein the plurality of first-type battery cells fill the gaps among the plurality of second-type battery cells.

10. The battery pack of claim 1, wherein the plurality of second-type battery cells are connected with each other with an adhesive to form a protection wall of the at least one first-type battery cell.

11. An electric vehicle comprising: a vehicle body; a drivetrain system arranged at the vehicle body and configured to drive a movement of the vehicle body; and a battery assembly configured to provide power to the drivetrain system, the battery assembly including: a controller; and a battery pack including: at least one first-type battery cell; and a plurality of second-type battery cells surrounding the at least one first- type battery cell and connected to the at least one first-type battery cell, an energy density of the at least one first-type battery cell being higher than an energy density of the plurality of second-type battery cells.

12. The electric vehicle of claim 11 , wherein a thermal stability of the at least one first-type battery cell is lower than a thermal stability of each of the plurality of second-type battery cells.

13. The electric vehicle of claim 11, wherein a cross-sectional dimension of the at least one first-type battery cell is smaller than a cross-sectional dimension of each of the plurality of second-type battery cells.

14. The electric vehicle of claim 11, wherein the at least one first-type battery cell comprises at least one of a prismatic battery cell, a cylindrical battery cell, or a pouch battery cell.

15. The electric vehicle of claim 11, wherein each of the plurality of second -type battery cells comprises at least one of a cylindrical battery cell, a prismatic battery cell, or a pouch battery cell.

16. The electric vehicle of claim 11, wherein the at least one first-type battery cell comprises a solid-state battery cell.

17. The electric vehicle of claim 11, wherein the at least one first-type battery cell is arranged at an inner core of the battery pack.

18. The electric vehicle of claim 11 , wherein the at least one first-type battery cell comprises a plurality of first-type battery cells spaced with each other by one of the plurality of second-type battery cells.

19. The electric vehicle of claim 18, wherein the plurality of first-type battery cells fill the gaps among the plurality of second-type battery cells.

20. The electric vehicle of claim 11 , wherein the plurality of second-type battery cells are connected with each other with an adhesive to form a protection wall of the at least one first- type battery cell.