阅读说明：本技术 可充电电池 (Rechargeable battery ) 是由 南映圭 S·荣格 胡启朝 Y·马都列维奇 M·金 Y·索恩 J·弗朗索瓦 杰奎琳·洪 于 2020-03-02 设计创作，主要内容包括：一种可充电电池。公开了采用最小电池单元面压力抑制装置的电池芯组和方法,用于最小化枝晶生长以及增加金属和金属离子电池电池单元的循环寿命。(A rechargeable battery. Battery core packs and methods employing minimum cell face pressure restraint devices are disclosed for minimizing dendrite growth and increasing cycle life of metal and metal-ion battery cells.)

1. A battery core pack, comprising:

a plurality of battery cells forming a battery cell stack, each battery cell comprising at least one negative electrode and at least one positive electrode, wherein metal ions are stripped from the negative electrode during discharge and re-plated on the negative electrode during charge; and

a restraining structure at least partially surrounding the battery cell stack, wherein the restraining structure imparts a substantially uniform surface pressure at a value to the battery cell stack.

2. The battery core pack of claim 1, wherein the substantially uniform surface pressure is at least about 50 psi.

3. The battery core pack of claim 2, wherein the battery cells maintain a discharge capacity greater than 2.5Ah for at least 100 charge/discharge cycles.

4. The battery core pack of claim 3, comprising at least four battery cells having a core pack energy density of at least about 590Wh/L at 30% SoC.

5. The battery core pack of claim 2, wherein the negative electrode comprises lithium metal.

6. The battery core pack of claim 1, wherein the restraining structure comprises a housing into which the stack of battery cells is placed, wherein the housing has openings at both ends.

7. The battery core pack of claim 6, further comprising at least one compliant pad, wherein the at least one compliant pad is disposed between two battery cells, and the thickness of the at least one compliant pad is determined by the degree of expansion of the battery cells and optimized between the variables of allowable battery pack volume and the compliant pad's hardness rating.

8. The battery core pack of claim 7, wherein the compliant gasket comprises a polyurethane sheet material having a shore hardness of between about 40-90 and a shore elasticity of between about 22-40%.

9. The battery core pack of claim 8, further comprising a cooling liner disposed between two battery cells.

10. The battery core pack of claim 2, wherein the restraining structure comprises:

a mounting unit defining a variable space to accommodate the battery cell stack; and

at least one elastic member surrounding the mounting unit to impart the surface pressure to the mounting unit.

11. The battery core pack according to claim 10, wherein the mounting unit comprises:

first and second end plates opposite to each other, each end plate including at least one pair of sliding collars respectively provided at each side portion;

a guide rod inserted into the sliding collar to restrict movement of the battery cell stack due to expansion and contraction during charge and discharge cycles to a single degree of freedom substantially perpendicular to a face of a battery cell, wherein the guide rod is configured to be slidingly received in the sliding collar at each end.

12. The battery core pack of claim 11, comprising four of the guide bars and eight of the sliding collars, wherein each sliding collar is disposed on the end plates approximately adjacent to a corner of the end plates and wherein the guide bars and the sliding collars cooperate to allow expansion and contraction of the battery cell stack in a direction substantially perpendicular to the battery cell face while limiting twisting, skewing, or flexing of the battery cell stack to maintain a substantially uniform minimum pressure on the battery cell face.

13. The battery core pack of claim 12, wherein the at least one resilient member has a spring constant of at least approximately 5.43 lbs/inch.

14. The battery core pack of claim 1, wherein the battery cells comprise lithium ion battery cells.

15. A battery pack, comprising:

a plurality of battery cells forming a battery cell stack, each battery cell comprising at least one negative electrode and at least one positive electrode, wherein metal ions are stripped from the negative electrode during discharge and re-plated on the negative electrode during charge;

a housing containing the stack of battery cells having a preload surface pressure of at least about 50psi, wherein the housing has a stiffness sufficient to maintain the surface pressure over a plurality of charge and discharge cycles of the stack of battery cells; and

at least two compliant pads, wherein each compliant pad is disposed between the battery cells, the compliant pads evenly distribute the battery cell expansion pressure during charging and push back to the battery cells during discharging.

16. The battery core pack of claim 15, wherein the stack of battery cells comprises four battery cells.

17. The battery core pack of claim 16, further comprising cooling liners formed of a high electrical conductivity material disposed between the battery cells of the battery cell stack.

18. The battery core pack of claim 17, wherein the at least one negative electrode comprises lithium metal.

19. A method of controlling dendrite growth on a negative electrode of a metal or metal-ion battery cell, wherein the battery cell comprises at least one planar negative electrode and at least one planar positive electrode and wherein material is stripped from the negative electrode during cell discharge and re-plated on the negative electrode during cell charge, the method comprising:

assembling a plurality of battery cells into a battery cell stack;

positioning the battery cell stack within a restraining structure that at least partially surrounds the battery cell stack; and

applying and maintaining a substantially uniform minimum surface pressure of at least about 50psi on the battery cells of the battery cell stack using the restraining structure.

20. The method of claim 19, wherein the positioning, applying, and holding comprises:

placing a compliant pad in the battery cell stack between at least two pairs of battery cells;

preloading the battery cell stack with the substantially uniform minimum surface pressure; and

placing the battery cell stack within the restraining structure while maintaining the substantially uniform minimum surface pressure, wherein the restraining structure comprises a rigid housing configured and dimensioned to have a stiffness sufficient to maintain the substantially uniform minimum surface pressure over a plurality of charge and discharge cycles of the battery cell stack.

21. The method of claim 19, wherein the positioning, applying, and holding comprises:

placing the stack of battery cells between two substantially rigid end plates;

placing a plurality of elastic members around the battery cell stack and the end plates, the elastic members having a minimum spring constant and being configured and dimensioned to apply the substantially uniform minimum surface pressure to the battery cell stack in an initial unexpanded state; and

restricting skewing or twisting of the end plates relative to each other and the battery cell stack, the end plates and elastic members including the restraining structure.

Technical Field

The present disclosure relates generally to rechargeable batteries. In particular, the present disclosure relates to a battery core pack including a plurality of battery cells.

Background

A typical structure of a lithium metal battery cell includes a lithium metal negative electrode bonded to a copper current collector and a metal oxide positive electrode bonded to an aluminum current collector. Between the negative electrode and the positive electrode is a separator that allows lithium metal ions to reciprocate. Various electrolyte solutions may be used between the positive and negative electrodes. When this type of battery is discharged, lithium metal ions are stripped from the negative electrode and travel through the separator to the positive electrode. During charging, the ion flow is reversed and the metal ions are replated back onto the cathode. However, as is well known in the art, replating is often not uniform, resulting in the formation of dendrites extending from the surface of the negative electrode after many discharge/charge cycles. If not controlled, dendrite growth can puncture the separator and cause shorting of the battery cell after relatively few cycles. The battery is greatly deteriorated when this occurs.

The plating and stripping of the metal ions from the negative electrode also causes the individual battery cells to contract and then expand when the metal ions are stripped and then re-plated. Other battery types, such as lithium ion batteries using graphite or silica ink negative electrodes, also function based on ion exfoliation and replating and therefore can experience significant swelling and problematic dendrite growth upon replating.

Current techniques for controlling dendrite growth, particularly in lithium metal batteries, are less than satisfactory. New solutions are needed to extend battery life cycle.

Disclosure of Invention

In one implementation, the present disclosure is directed to a battery core pack comprising a plurality of battery cells forming a battery cell stack, each battery cell comprising at least one negative electrode and at least one positive electrode, wherein metal ions are stripped from the negative electrode during discharge and re-plated on the negative electrode during charge; and a restraining structure at least partially surrounding the battery cell stack, wherein the restraining structure imparts a substantially uniform surface pressure at a value to the battery cell stack.

In another implementation, the present disclosure is directed to a battery pack comprising a plurality of battery cells forming a battery cell stack, each battery cell comprising at least one negative electrode and at least one positive electrode, wherein metal ions are stripped from the negative electrode during discharge and re-plated on the negative electrode during charge; a housing containing a stack of battery cells having a preload surface pressure of at least about 50psi, wherein the housing has a stiffness sufficient to maintain the surface pressure through a plurality of charge and discharge cycles of the stack of battery cells; and at least two compliant pads, wherein each compliant pad is disposed between the battery cells, the compliant pads evenly distribute battery cell expansion pressure during charging and push back to the battery cells during discharging.

In yet another implementation, the present disclosure is directed to a method of controlling dendrite growth on a negative electrode of a metal or metal-ion battery cell, wherein the battery cell comprises at least one planar negative electrode and at least one planar positive electrode and wherein material is stripped from the negative electrode during discharge of the battery cell and re-plated on the negative electrode during charge of the battery cell. The method includes assembling a plurality of battery cells into a battery cell stack; positioning the battery cell stack within a restraining structure, the restraining structure at least partially surrounding the battery cell stack; and applying and maintaining a substantially uniform minimum surface pressure of at least about 50psi over the cells of the cell stack using the restraining structure.

Drawings

For the purpose of illustrating the disclosure, the drawings show aspects of one or more embodiments. It should be understood, however, that the present disclosure is not limited to the precise methods and apparatuses illustrated in the drawings, wherein:

FIG. 1 is a plot of battery cycle life versus cell face pressure for embodiments of the present disclosure;

fig. 2 is a perspective view of an embodiment of a battery core pack as disclosed herein;

FIG. 3 is a cross-sectional view of the embodiment of FIG. 2, as viewed through section line A-A in FIG. 2;

FIG. 4 is a cross-sectional view of the embodiment of FIG. 2, as viewed through section line B-B in FIG. 2;

FIG. 5 is a cross-sectional view of an alternative embodiment of the present disclosure, as viewed through section line A-A of FIG. 2;

FIG. 6 is a perspective view of another alternative embodiment of the present disclosure;

FIG. 7 is an exploded perspective view of the embodiment of FIG. 6;

FIG. 8 is a longitudinal cross-sectional view of the embodiment shown in FIGS. 6 and 7;

FIG. 9 is an exploded schematic view showing an assembly process for the embodiment of FIG. 6;

fig. 10 is a schematic side view of an apparatus for testing the pressure of a surface of a battery cell;

fig. 11 is a cross-sectional view of a typical battery cell as may be used with embodiments of the present disclosure.

Detailed Description

Lithium dendrite growth on the surface of a lithium metal negative electrode in a lithium metal battery has been known to cause short circuits and general degradation of cell performance. These negative effects can occur after relatively few discharge/charge cycles. The present disclosure proposes, among other things, cell face pressure control techniques that provide more uniform lithium plating and stripping and inhibit lithium dendrite growth to extend the life of the battery. In one embodiment, a mechanically constrained constant volume pack for a plurality of battery cells in a module or battery pack is provided. In another embodiment, a mechanically constrained system of substantially "constant" pressure for a plurality of battery cells in a module or battery pack is provided. While the present disclosure is exemplified using a lithium metal battery cell, as those skilled in the art will appreciate, the teachings contained herein for techniques for facilitating more uniform plating and stripping and inhibiting dendritic negative electrode surface growth are also applicable to other metal and metal-ion battery types (a representation of a lithium metal battery cell suitable for use with the embodiments disclosed herein is shown in fig. 11).

Fig. 1 shows the cycle life of a battery cell when the battery cell is under different pressures. Pressure is uniformly applied to both surfaces of the battery cell. The results show that when the applied pressure is above 50psi, dendrite growth is well constrained and the number of cycle lives varies slightly. Thus, to obtain a greater number of cycle lives, a pressure of greater than 50psi applied to the surface of each cell is the critical pressure to control dendrite growth. As shown in fig. 1, at pressures below this critical pressure, the number of cycle lives drops significantly, while at pressures above the critical pressure the number is maintained at about 120. In the case where the substantially uniform pressure applied to both surfaces of the battery cell is at or above the critical pressure, the cycle life of the battery cell is improved, indicating that the dendrite growth is effectively suppressed by the substantially uniform pressure.

Fig. 2-5 illustrate a constant volume approach in order to keep the surface pressure above a critical level, and fig. 6-9 illustrate a "constant pressure" approach.

Fig. 2 is a perspective view of a battery pack according to one embodiment of the present disclosure. The battery pack 110 includes a hollow case 112 having two openings 117 (fig. 3) in a longitudinal direction and enclosing a constant volume. The housing 112 may house a plurality of battery cells 114, each having a negative electrode 113 and a positive electrode 115. In the present embodiment, four battery cells 114 are shown in fig. 3 and 4, and the battery pack 110 including four battery cells has a capacity of 3 Ah. A practical limit to the number of cells in a constant volume embodiment is the adaptation of the force generated by the natural cell expansion when the metal ions are replated to the negative electrode. As the number of cells increases, the overall dendrite growth increases, resulting in increased force applied to the battery pack. The shell 112 is fabricated from a rigid material and is sized and configured to constrain expansion so as to maintain a suitable pressure at all times to limit dendrite growth, as described herein. It is shown that four cell design is a realistic compromise between various aspects, such as pack size/capacity, case strength, size and weight, and charge density specifications. The housing 112 may be constructed of a rectangular tube machined from polymer impregnated fiberglass. Alternatively, segments of carbon fiber square tubing or other materials exhibiting similar strength, lightweight, and stiffness characteristics may be used.

Fig. 3 and 4 are cross-sectional views of the battery pack of the present disclosure, viewed in the directions a-a and B-B, respectively. Battery pack 110 also includes compliant pads 116 positioned between first battery cell 114a and second battery cell 114b and between third battery cell 114c and fourth battery cell 114d, respectively. Compliant pads mean that the pads can evenly distribute cell expansion pressure during charging and push back to the cells during discharging. A cooling pad 118 is also placed between the second cell 114b and the third cell 114c to dissipate heat. In general, the X-Y dimensions of compliant pad 116 may correspond to the dimensions of battery cells 114a-d, while the thickness of compliant pad 116 is determined by the degree of expansion of the battery cells and is optimized between variables of the allowable battery pack volume and stiffness rating of the pad to control the cell area pressure at a desired level, e.g., at or above 50 psi. In one embodiment, the compliant pads may be fabricated from polyurethane sheet having dimensions of approximately 2.8 inches by 1.8 inches and having a thickness of approximately 0.625 inches, and such pads may allow for 20% cell expansion. Examples of suitable polyurethane sheet properties are provided in table 1 below.

The cooling liner 118 may comprise a thin sheet of a metal having a high thermal conductivity, such as copper or aluminum. Heat can be dissipated radiatively, for example by exposing the edges of the cooling pad to ambient conditions or by attaching to a heat sink. Alternatively, the cooling pad 118 may comprise a sheet of material provided with small passages for circulating a cooling fluid therethrough.

As discussed above, the material and thickness of compliant pad 116 is selected to provide a linear and uniform pressure distribution across the surface of each cell 114a-d in this embodiment. It has been found that if the pressure does not remain substantially uniform across the surface of the cell, then "hot spots" with greater dendrite growth can grow, which can lead to premature failure of the cell. To ensure a critical pressure of about 50psi, the internal cavity size of the housing 112 is selected in combination with the uncompressed height of the stack of battery cells, compliant gasket, and cooling gasket such that when the stack of battery cells is placed into the housing 112, the initial compression of the stack to the size of the rigid housing opening imparts the desired critical surface pressure to the stack of battery cells. In other words, the surface pressure of the battery cell stack is a function of the compression to the size of the opening through which the stack is inserted. The internal cavity of the case 112 for the battery pack may thus control the pressure exerted on the surface of the battery cells and inhibit dendrite growth for improved cycle life.

Although the present embodiment shows 6mAh for a 4 cell battery, if more or fewer cells are used, the number of cycle lives may be suitably maintained as long as the pressure applied to each cell of the battery is at least at or above the critical pressure, i.e., 50 psi.

In an alternative embodiment, as shown in fig. 5, battery pack 510 employs five compliant pads 516, each sandwiched between battery cells 514 and/or between battery cells 514 and the inner wall of housing 512. In one embodiment of this alternative embodiment, the compliant pad is approximately 58mm in length and approximately 48mm in width. Each compliant pad 516 has a thickness of approximately 3.175mm (0.125 inches). Similarly, the gasket may be manufactured from a polyurethane sheet material having a smooth surface texture and material properties as indicated above in table 1. The five pad embodiments described herein can provide battery cells having a gravimetric energy density of >350Wh/Kg and a volumetric energy density of >590Wh/L at 30% SoC (state of charge).

A further alternative embodiment of a restraint system employing an elastically expandable mechanism is shown in fig. 6-9. Those skilled in the art will appreciate that the elastic members described below apply an increasing force as they are inflated, however, the change in pressure applied to the surface of the battery cell in this embodiment is substantially less than the change in pressure experienced by the battery cell within the constant volume housing as described above. In the embodiment as shown in fig. 2, the pressure applied to the battery cell by the housing 110 increases as the battery cell expands.

Turning to fig. 6, 7, and 8, the battery pack 610 includes a plurality of battery cells 614, twelve in the illustrated embodiment, constrained between a pair of end plates 622. One or more resilient members 624 surround the stack of battery cells 614 and the end plates 622 to apply a continuous restraining force. The elastic member 624 may store energy and continuously maintain a compressive force between the pair of end plates 622 when the battery is being charged (expanded). The resilient member 624 is selected to exert a force on the end plate 622 that produces a critical surface pressure of about 50psi, as explained previously. In one embodiment, the resilient member 624 may have a rectangular cross-sectional shape with a K (spring constant) over time of 5.43 lbs/inch (approximately 5.16N/mm). The inner perimeter of the resilient member is approximately 4 inches (101.6mm) in one embodiment, having a flat length of approximately 2 inches (50.8 mm); the width is approximately 0.5 inches (12.7mm) and the thickness is approximately 0.125 inches (3.175 mm). The battery cell stack constructed as in the present embodiment may expand by about 20% due to the plating and re-plating of the negative electrode during the charge cycle. In another embodiment, the resilient member may have an inner diameter of about 1.25 inches and an outer diameter of about 1.5 inches.

To maintain substantially uniform surface pressure on the cell faces during expansion and contraction, the end plates 622 are each provided with four collars 626, two on each side in the length direction. Each collar 626 is provided with a hole to receive a guide member 628 inserted therein. The guide members 628 may slide into the holes of the collar 626 and achieve a clearance fit therebetween. This can restrict expansion in the width direction and apply evenly distributed pressure on both side portions of the battery pack 610. The length of the collar 626 is sized to sufficiently resist binding or excessive friction with the guide member 628 if an eccentric load is experienced during expansion or contraction of the battery cell stack. For example, in one embodiment, the guide member 628 is constructed of a composite epoxy structure having a tensile strength of 600kpsi, and an elastic modulus of 34 Mpsi. In this embodiment, the guide member may be about 3.70 inches (94mm) in length and weigh about 1.2 grams.

Fig. 9 illustrates a perspective view of an assembly process of the battery pack 610. At step I, a plurality of cells 614 are initially assembled together in a jig 632 using an adhesive pad 629 placed therebetween (step II). A variety of suitable adhesive materials may be used as the adhesive pad, such as double-sided acrylic foam tape. Clamp 632 includes a cavity member 634 and a back plate 636, clamp 632 defining a cavity therein. The stack of cells 614 is received within the cavity. After the cells are assembled together, the clamp 632 is removed. At step II, the stack of battery cells 614 held together by the adhesive pads 629 is inserted into the space defined by the end plates 622 and the guide members 628. At step III, the resilient member 624 is placed around the stack of battery cells 614, the assembly of end plates 622 and guide members 628. Then, the assembly of the battery pack is completed.

Fig. 10 shows an apparatus for testing the surface pressure of a battery cell. To test the effect of surface pressure on dendrite growth and cycle life, the cell was placed in a test apparatus. A uniform pressure may be applied and measured over multiple discharge/charge cycles. The testing apparatus 140 as schematically depicted herein includes a top plate 142, a bottom plate 144, and a middle plate 146, which are rigidly held together at the corners by threaded fasteners 148. To ensure assembly of the test apparatus 140, four nuts 150 are also used. One segment of each threaded fastener 148 is lubricated to prevent friction. Each fastener 148 passes through a bushing in the plate to prevent eccentric loading of the fastener. The fastener 148 is used in conjunction with a washer 152 and a top nut 154 to ensure assembly of the test equipment during testing. A force sensor 156 (e.g., a load sensor) is sandwiched between the middle plate 146 and the bottom plate 144. The battery cell 114 to be tested is placed between the top plate 142 and the middle plate 146. A torque wrench is used to provide precise tightening torque on each top nut 154 to provide uniform pressure on the surface of the battery cell 114. In one illustrative embodiment, the uniform surface pressure is set to 50psi by applying a torque of 6lb-f to each top nut 154. The force sensor 156 allows the initial pressure to be accurately set and then monitored for changes throughout the cycle. The pressure exerted on the battery cell 114 is calculated from the force sensor output and the surface area of the battery cell 114.

Fig. 11 illustrates an exemplary battery cell 114 as used in embodiments disclosed herein, such as the battery core packs 110 and 610. Fig. 11 illustrates only some basic functional components of the battery cell 114. A realistic example of a battery cell will typically be embodied using a wound or stacked configuration, including other components not shown in fig. 11 for ease of illustration, such as electrical terminals, seals, heat strike layers, and/or vents, among others. In the illustrated embodiment, the battery cell 114 includes spaced apart positive and negative electrodes 208, 204 and a pair of corresponding respective current collectors 203, 205. A dielectric membrane 212 is located between the positive and negative electrodes 208, 204 to electrically separate the positive and negative electrodes but allow lithium ions, ions of the electrolyte 216, and ions of the redox shuttle additive 218 to flow therethrough. The membrane may be porous. The separator 212 and/or one, the other, or both of the positive electrode 208 and the negative electrode 204 may also be impregnated with an electrolyte 216 and an additive 218. Cell 114 includes a container 220 that houses current collectors 203, 205, positive electrode 208, negative electrode 204, separator 212, and electrolyte 216.

The positive and negative electrodes 208, 204 may include a variety of different structures and materials that are compatible with the lithium metal ions and the electrolyte 216. Each of current collectors 203, 205 may be made of any suitable conductive material, such as copper or aluminum, or any combination thereof. The diaphragm 212 may be fabricated from any suitable porous dielectric material, such as a porous polymer, among others.

The positive electrode 208 may be formed from a variety of materials, such as a material of the general formula LixMyOz, where M is a transition metal such as Co, Mn, Ni, V, Fe, or Cr, and x, y, z are selected to meet valence requirements. In one or more embodiments, the positive electrode is selected from the group consisting of LiCoO₂、Li(Ni_1/3Mn_1/3Co_1/3)O₂、Li(Ni_0.8Co_0.15Al_0.05)O₂、LiMn₂O₄、Li(Mn_1.5Ni_0.5)₂O₄Or their lithium-rich formsA layered or spinel oxide material of the group (a). In one or more embodiments, the positive electrode material is LiCoO₂(charged to 4.4V versus Li metal), NCA or NCM (622, 811) (charged to 4.30V versus Li metal).

The anode 204 may be a thin lithium metal anode having a thickness in the range of 10 μm-100 μm or 20 μm-80 μm or 40 μm-60 μm in the discharged state. Although fig. 11 schematically illustrates that the anode 204 is adjacent to the current collector 203, a sheet or film of an anode material such as lithium metal may be disposed on both side portions of the current collector. In another embodiment, the cell 114 may have a non-negative design, where the cell simply includes a negative current collector 203 and a positive electrode 208. Lithium ions are deposited on the negative electrode current collector 203 during initial cell charging to form a lithium negative electrode 204. Further information regarding exemplary materials and configurations of the battery cells 114 may be found in PCT publication No. WO 2017/214276 entitled "High energy density, High power density, High capacity, and room temperature capacity" and free-free rechargeable batteries, "which is incorporated herein by reference in its entirety.

Redox shuttle additive 218 can be any of a variety of redox shuttle additives known in the art, for example, 2, 5-di-tert-butyl-1, 4-bis (2-methoxyethoxy) benzene (DBBB), 2, 5-di-tert-butyl-1, 4-bis (methoxy) benzene (DDB), 2, 5-di-tert-butyl-1, 4-bis (2,2, 2-trifluoroethoxy) benzene (DBDFB), 2, 5-di-tert-butyl-1, 4-bis (2,2,3, 3-tetrafluoropropoxy) benzene (DBTFP), 2, 5-di-tert-butyl-1, 4-bis (4,4, 3,2, 2-hexafluorobutoxy) benzene (DBHFB), 2, 7-diacetylthianthrene, 2, 7-dibromothianthrene, 2, 7-diisobutylthiane, 2-acetylthianthrene, 2, 5-difluoro-1, 4-dimethoxybenzene (DFDB), 2- (pentafluorophenyl) -tetrafluoro-1, 3, 2-benzodioxole, Li2B12F12, tetraethyl-2, 5-di-tert-butyl-1, 4-benzenediphosphonic acid (TEDBPDP), 1, 4-bis [ bis (1-methylethyl) phosphinyl group]-2, 5-dimethoxybenzene (BPDB), 1, 4-bis [ bis (1-methyl) phosphinyl group]-2, 5-difluoro-3, 6-dimethoxybenzene (BPDFDB), pentafluorophenyl-tetrafluorobenzyl-1, 2-dioxoborane (PFPTFBDB), ferrocene and derivatives thereof, phenothiazine derivatives, N-dialkyl-dihydrophenazine, thiobenzophenones, benzophenones,2,2,6, 6-tetramethylpiperidine oxide (TEMPO), Li₂B₁₂H_12-xF_x(x ═ 9 and 12).

Further technical features and alternative embodiments of the present disclosure are outlined in this and the following paragraphs. In one embodiment, the battery core pack includes a plurality of battery cells forming a battery cell stack, wherein each battery cell includes at least one planar negative electrode and at least one planar positive electrode, wherein material is stripped from the negative electrode during cell discharge and re-plated on the negative electrode during cell charge. The restraint structure at least partially surrounds the battery cell stack, wherein the restraint structure imparts a substantially uniform minimum cell face pressure of at least about 50psi to the battery cell stack.

The battery cell may be designed to maintain a discharge capacity greater than 2.5Ah for at least 100 charge/discharge cycles. In one embodiment, such a battery core pack may include at least four battery cells having a core pack energy density of at least about 590Wh/L at 30% SoC (state of charge). In another embodiment, the battery cell may include a lithium metal battery cell.

In a further embodiment, the restraint structure may include a rigid housing into which the cell stack is placed, having a pre-loaded cell face pressure of at least about 50psi, wherein the rigid housing has a stiffness sufficient to at least substantially maintain a minimum cell face pressure over a plurality of charge and discharge cycles of the cell stack. In an alternative embodiment, the battery core pack within the restraining structure may include at least two compliant pads, wherein each compliant pad is disposed between two different battery cells. The compliant pad may include a polyurethane sheet material having a shore hardness of between about 40-90 and a shore elasticity of between about 22-40%.

In another alternative embodiment, the battery core pack may further include a cooling gasket disposed between two of the battery cells. The cooling liner may comprise a cooling insert having a thickness of at least about 150 W.m^-1·K^-1A metal of thermal conductivity of (1).

In yet another embodiment, the restraining structure for a battery core pack may include first and second end plates on opposite ends of a battery cell stack, at least one elastic member surrounding the battery cell stack and the end plates to impart a minimum cell face pressure to the battery cell stack, and a guide bar extending between the end plates to restrain movement of the battery cell stack due to expansion and contraction during charge and discharge cycles to a single degree of freedom substantially perpendicular to the cell faces. The sliding collar may be disposed on the end plate, with the guide bar configured to be slidingly received in the sliding collar at each end.

In certain embodiments, four guide bars and eight sliding collars are provided, wherein each sliding collar is disposed on an end plate approximately adjacent to a corner of the end plate and wherein the guide bars and sliding collars cooperate to allow expansion and contraction of the battery cell stack in a direction substantially perpendicular to the face of the battery cell while limiting twisting, skewing, or flexing of the battery cell stack to maintain substantially uniform minimum pressure on the face of the battery cell.

Further alternative embodiments using a resilient member may include a plurality of resilient members each having a spring constant of at least approximately 5.43 lbs/inch. There may be twelve cells in the cell stack. There may also be an adhesive layer between each battery cell.

Embodiments disclosed herein may include battery cells, including lithium metal battery cells, lithium ion battery cells, and magnesium metal battery cells.

In yet another alternative embodiment, the battery core pack may include a plurality of battery cells forming a battery cell stack, wherein each battery cell includes at least one planar negative electrode and at least one planar positive electrode, wherein material is stripped from the negative electrode during discharge of the battery cell and re-plated on the negative electrode during charge of the battery cell. The rigid housing contains a cell face minimum pressure containing cell stack using a preload of at least about 50psi, wherein the rigid housing has a stiffness sufficient to maintain a minimum cell face pressure through multiple charge and discharge cycles of the cell stack, and at least two compliant pads, each disposed between two different cells. Such an embodiment may include a cell stack of four cells. Alternatively, a cooling gasket formed of a high-conductivity material may be disposed between the centers of two battery cells of a battery cell stack. In another alternative, five compliant pads are provided, one between the cells of each pair and one between each end cell of the stack of cells and the rigid housing.

In still further embodiments, the battery core pack may include a plurality of battery cells forming a battery cell stack, each battery cell including at least one planar negative electrode and at least one planar positive electrode, wherein material is stripped from the negative electrode during discharge of the battery cell and re-plated on the negative electrode during charge of the battery cell. The first and second end plates are disposed on opposite ends of the battery cell stack. A plurality of elastic members surrounding the battery cell stack and the end plates impart a substantially uniform minimum cell face pressure of at least about 50psi to the battery cell stack. At least four substantially rigid guide rods extend between the end plates, and a sliding collar disposed on the end plates approximately adjacent each corner of each end plate slidingly receives the guide rods. The sliding collar and guide bar are configured and dimensioned to limit movement of the battery cell stack during charge and discharge cycles due to expansion and contraction to a single degree of freedom substantially perpendicular to the face of the battery cell. In a further alternative, the battery core pack may include five elastic members having a minimum spring constant of approximately 5.43 lbs/inch and may include an adhesive layer between each battery cell of the battery cell stack. Such a configuration may have twelve cells in a stack of cells.

In another aspect of the disclosure, a method of controlling dendrite growth on a negative electrode of a metal or metal-ion battery cell is described. The battery cell in the present method may include at least one planar negative electrode and at least one planar positive electrode, wherein material is stripped from the negative electrode during discharge of the battery cell and re-plated on the negative electrode during charge of the battery cell. A method of limiting dendrite growth in such a battery cell may include assembling a plurality of battery cells into a battery cell stack and applying and maintaining a uniform minimum cell face pressure of at least about 50psi across the battery cells of the battery cell stack. In one alternative, a method of controlling dendrite growth in a battery cell may include applying and maintaining a minimum cell face pressure at an orientation at least substantially perpendicular to a cell face.

In a further alternative embodiment for controlling dendrite growth, applying and maintaining a minimum cell face pressure may include positioning a compliant gasket in a cell stack between at least two pairs of cells, preloading the cell stack with the minimum cell face pressure, and placing the cell stack within a rigid housing while maintaining the minimum cell face pressure. In such embodiments, the rigid housing is configured and dimensioned to have a stiffness sufficient to maintain a minimum cell face pressure through multiple charge and discharge cycles of the cell stack.

In a further alternative embodiment for controlling dendrite growth, applying and maintaining a minimum cell face pressure may include placing the stack of cells between two substantially rigid end plates, placing a plurality of elastic members around the stack of cells and the end plates, wherein the elastic members are configured and dimensioned to have a minimum spring constant selected to apply the minimum cell face pressure to the stack of cells in an initial unexpanded state. In such embodiments, a further step of limiting skewing or twisting of the end plates relative to each other and the battery cell stack may be included.

The foregoing has been a detailed description of illustrative embodiments of the present disclosure. It is noted that, in the specification and the appended claims, conjunctive language, such as used in the phrases "at least one of X, Y and Z" and "one or more of X, Y and Z," unless specifically stated or indicated otherwise, should be taken to mean that each item in the conjunctive list can be present in any number that excludes every other item in the list or in any number in combination with any or all of the other items in the conjunctive list, each of which can also be present in any number. Applying this general rule, the conjunct phrases in the above examples where the conjunct list consists of X, Y and Z should each encompass: one or more of X; one or more of Y; one or more of Z; one or more of X and one or more of Y; one or more of Y and one or more of Z; one or more of X and one or more of Z; and one or more of X, one or more of Y, and one or more of Z.

Various modifications and additions can be made without departing from the spirit and scope of the disclosure. The features of each of the various embodiments described above may be combined with the features of the other described embodiments as appropriate to provide various combinations of features in the associated new embodiments. Furthermore, while a number of separate embodiments have been described above, what has been described herein is merely illustrative of the application of the principles of the disclosure. Additionally, while particular methods herein may be illustrated and/or described as occurring in a particular order, the order is highly variable within the general knowledge to achieve aspects of the disclosure. Accordingly, this description is intended by way of example only, and not to otherwise limit the scope of the present disclosure.

Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. Those skilled in the art will appreciate that various changes, omissions and additions may be made to the specifically disclosed matter herein without departing from the spirit and scope of the present disclosure.