Square section liquid metal batteries with grid device to suppress instabilities of fluids

Abstract

Square section liquid metal batteries (LMBs) with a grid device to suppress instabilities of fluids. The LMBs include a shell, negative current collector, negative material, metallic nets/plates, grid device, electrolyte, positive material, rectangular holes on partitions of grid device, and positive current collector. The positive material, electrolyte, and negative material are filled in the shell and automatically stratified from bottom to top according to the density from large to small. The negative current collector is linked with negative material, and the positive current collector is linked with positive material. The grid device is composed of partitions which cross each other and pass through the negative material, the electrolyte vertically in sequence, and extend inside the positive material. There are rectangular holes opened on the grid device, and the vertical height of each rectangular hole is larger than the biggest displacement of electrolyte during charging and discharging processes.

Claims

1. Square section liquid metal batteries (LMBs) with a grid device to suppress the instabilities of fluids, comprising: a shell, an electrical current collector of a negative electrode, a negative material, metallic nets or metallic plates, a grid device, an electrolyte, a positive material, rectangular holes, an electrical current collector of a positive electrode; wherein the positive material, the electrolyte and the negative material are filled and stratified in the shell from bottom to top; the positive material and the negative material are liquid metals or alloys; the electrolyte is liquid molten salt; densities of three layers have a sequence of positive material>electrolyte>negative material; the electrical current collector of the negative electrode and the electrical current collector of the positive electrode are linked with the negative material and the positive material respectively from outside of LMBs; the grid device within the shell is composed of partitions crossing each other, and the grid device passes through the negative material and the electrolyte vertically in sequence, and extends to an inside of the positive material; there is no gap between a top end of the grid device and the electrical current collector of the negative electrode to avoid movement of the negative material when an electrical current density changes; a bottom end of the grid device is lower than a maximum displacement of the electrolyte during a charging process, and extends to ⅔-½ of an initial height of the positive material to assure that the instabilities in LMBs are suppressed by the grid device during a whole process of charging/discharging; a core of each partition of the grid device is a metallic net or a metallic plate, and the rectangular holes are opened on the partitions of the grid device; a vertical height of each rectangular hole is larger than the maximum displacement of the electrolyte during charging/discharging to keep two liquid interfaces of LMBs at their own horizontal level respectively, and a distribution of the rectangular holes is to prevent a formation of a single enclosed induced magnetic loop in a whole liquid metal battery or a formation of a medium-sized enclosed induced magnetic field loop through the rectangular holes.

2. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 1, wherein: the partitions are assembled to form a uniform grid in horizontal sections of LMBs; when a pair number of the partitions is greater than one, a special design is introduced for processing and installation; when the pair number of the partitions is even, a structure of the grid device is centrosymmetric and the grid device is mounted by splicing because of a limitation of a distribution of the rectangular holes; when placing the grid device with two pairs of partitions, two-stage splicing grid device is used; when the pair number of partitions is odd, the structure of the grid device is axisymmetric or centrosymmetric and the grid device is mounted by splicing because of the limitation of the distribution of the rectangular holes; when placing the grid device with three pairs of partitions, three-stage splicing grid device is used.

3. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 1, wherein: there is no space between the grid device and side walls of LMBs, the partitions directly touch an inner wall of the shell; the top end of the grid device is directly embedded into the electrical current collector of the negative electrode, or directly contacts with the electrical current collector of the negative electrode; the bottom end of the grid device is lower than the maximum displacement of the electrolyte during the charging process, and extends to ⅔-½ of the initial height of the positive material; a thickness of each partition of the grid device is 1/60- 1/100 of a side width of the shell; a material of the grid device is electrically and magnetically insulated, and is corrosion resistant.

4. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 1, wherein: regulations for the rectangular holes on the partitions comprise: firstly, the rectangular holes are set at special positions on the partitions, right next to inner walls of LMBs or right next to junctions of any two partitions; secondly, no magnetic induction line continually passes through four or more rectangular holes to form an enclosed loop; thirdly, except inside walls of LMBs, there is only one rectangular hole on each side edge of a grid, which is enclosed by the partitions or by the partitions and the inside wall/walls of LMBs; finally, a width of each rectangular hole is not greater than ⅕ of a corresponding width of the side edge of the grid, which is enclosed by the partitions or by the partitions and the inside wall/walls of LMBs and a lower limit of the width of each rectangular hole guarantees smooth flowing through by the liquid metals or the electrolyte.

5. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 3, wherein: regulations for the rectangular holes on the partitions comprise: firstly, the rectangular holes are set at special positions on the partitions, right next to inner walls of LMBs or right next to junctions of any two partitions; secondly, no magnetic induction line continually passes through four or more rectangular holes to form an enclosed loop; thirdly, except inside walls of LMBs, there is only one rectangular hole on each side edge of a grid, which is enclosed by the partitions or by the partitions and the inside wall/walls of LMBs; finally, a width of each rectangular hole is not greater than ⅕ of a corresponding width of the side edge of the grid, which is enclosed by the partitions or by the partitions and the inside wall/walls of LMBs and a lower limit of the width of each rectangular hole is a minimal size that guarantees smooth flowing through by the liquid metals or the electrolyte.

6. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 1, wherein: in the square section LMBs, a top end of each rectangular hole is higher than the maximum displacement of the electrolyte when it moves up during the discharging process; a bottom end of each rectangular hole is lower than the maximum displacement of the electrolyte when it moves down during the charging process, and the bottom end of each rectangular hole extends to ⅔- 7/12 of the initial height of the positive material; when the bottom end of the grid device only extends to the ⅔ of the initial height of the positive material, the bottom end of each rectangular hole and the bottom end of the grid device are at a same horizontal level.

7. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids, according to claim 3 wherein: in the square section LMBs, a top end of each rectangular hole is higher than the maximum displacement of the electrolyte when it moves up during the discharging process; a bottom end of each rectangular hole is lower than the maximum displacement of the electrolyte when it moves down during the charging process, and the bottom end of each rectangular hole extends to ⅔- 7/12 of the initial height of the positive material; when the bottom end of the grid device only extends to ⅔ of the initial height of the positive material, the bottom end of each rectangular hole and the bottom end of the grid device are at a same horizontal level.

8. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 4, wherein: in the square section LMBs, a top end of each rectangular hole is higher than the maximum displacement of the electrolyte when it moves up during the discharging process; a bottom end of each rectangular hole is lower than the maximum displacement of the electrolyte when it moves down during the charging process, and the bottom end of each rectangular hole extends to ⅔- 7/12 of the initial height of the positive material; when the bottom end of the grid device only extends to ⅔ of the initial height of the positive material, the bottom end of each rectangular hole and the bottom end of the grid device are at a same horizontal level.

9. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 1, wherein: a thickness or a height in a vertical direction of the electrolyte is 1/9- 1/40 of a total height of the shell; in a domain where there is the grid device, a fluid flow area occupies at least √{square root over (2)}/2 of a total section area of the LMBs in horizontal sections.

10. The square section liquid metal batteries (LMBs) with the grid device to suppress the instabilities of fluids according to claim 6, wherein: a thickness or a height in a vertical direction of the electrolyte is 1/9- 1/40 of a total height of the shell; in a domain where there is the grid device, a fluid flow area occupies at least √{square root over (2)}/2 of a total section area of the LMBs in horizontal sections.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A is the schematic diagram of discharging process of LMBs.

(2) FIG. 1B is the schematic diagram of charging process of LMBs.

(3) FIG. 2A is the general structural schematic diagram (A-A sectional view) of one LMB when the grid device with one pair of partitions is mounted.

(4) FIG. 2B is the B-B sectional view of FIG. 2A.

(5) FIG. 3A is the structural schematic diagram (A-A sectional view) of the grid device when the gird device with two pairs of partitions is mounted.

(6) FIG. 3B is the B-B sectional view of FIG. 3A.

(7) FIG. 4A is the structural schematic diagram (A-A sectional view) of the grid device when the gird device with three pairs of partitions is mounted.

(8) FIG. 4B is the B-B sectional view of FIG. 4A.

(9) FIG. 5A shows the 3D shape of the electrolyte layer when the applied voltage is 64V without grid device.

(10) FIG. 5B shows the 2D shape of the electrolyte layer on a XOZ (y=0) plane when the applied voltage is 64V without grid device.

(11) FIG. 5C shows the 2D shape of the electrolyte layer on a YOZ (x=0) plane when the applied voltage is 64V without grid device.

(12) FIG. 5D shows the 3D shape of the electrolyte layer when the applied voltage is 65V without grid device.

(13) FIG. 5E shows the 2D shape of the electrolyte layer on a XOZ (y=0) plane when the applied voltage is 65V without grid device.

(14) FIG. 5F shows the 2D shape of the electrolyte layer on a YOZ (x=0) plane when the applied voltage is 65V without grid device.

(15) FIGS. 6A-6C show the streamlines on a YOZ (x=0) plane within the LMB without grid device, AE=64V, BE=65V, CE=70V.

(16) FIG. 7A shows the 3D shape of the electrolyte layer when the applied voltage is 140V with grid device comprising three pairs of partitions.

(17) FIG. 7B shows the 2D shape of the electrolyte layer on a XOZ (y=12.5) plane when the applied voltage is 140V with grid device comprising three pairs of partitions.

(18) FIG. 7C shows the 2D shape of the electrolyte layer on a YOZ (x=12.5) plane when the applied voltage is 140V with grid device comprising three pairs of partitions.

(19) FIG. 7D shows the 3D shape of the electrolyte layer when the applied voltage is 142.5V with grid device comprising three pairs of partitions.

(20) FIG. 7E shows the 2D shape of the electrolyte layer on a XOZ (y=12.5) plane when the applied voltage is 142.5V with grid device comprising three pairs of partitions.

(21) FIG. 7F shows the 2D shape of the electrolyte layer on a YOZ (x=12.5) plane when the applied voltage is 142.5V with grid device comprising three pairs of partitions.

(22) FIGS. 8A-8B show the streamlines on a YOZ plane within the LMB with grid device comprising three pairs of partitions, (a) E=140V, (b) E=142.5V.

(23) FIG. 9 depicts the critical voltage profile against pair numbers of partitions of grid device when LMBs work stably.

(24) In FIGS. 2A-2B: the shell 1, the electrical current collector of the negative electrode 2, the negative material 3, the metallic nets or the metallic plates 4, the grid device 5, the electrolyte 6, the positive material 7, the rectangular holes 8 on partitions, the electrical current collector of the positive electrode 9.

(25) In captions of FIGS. 6A-6C and 8A-8B, E is the imposed electrical voltage in the numerical simulations.

DETAILED DESCRIPTION

(26) The following are the detailed description of present invention associated with drawings.

(27) The most important innovations of present invention lie in that: the capacity of LMBs is directly related to the structure design and the shape of horizontal section. For instance, the capacity of fine-high type LMBs are larger than that of plate type LMBs for cylindrical LMBs with the same volume. All substances within LMBs are liquid and automatically stratify into three layers due to gravity: the top, the middle, and the bottom layers are the negative electrode 3, the electrolyte 6, and the positive electrode 7, correspondingly. This special strategy of design makes LMBs have the characteristics of simple structures, easily assembling, low cost and long life. However, these typical LMBs have their inherent disadvantages, like, LMBs can only work in stationary environment; the electrolyte 6 will move up and down during charging/discharging processes, and this may cause sloshing instability of interfaces due to surface tension and electro-magnetic force, and further lead to short circuit; since the viscosities (especially the positive material 7 has higher viscosity) and the wettability (relative to solid) of fluids are different, the liquid metals may stick on to the inner walls of LMBs when the electrolyte moves up and down, and further result in short circuit; within the charging/discharging cycles, the solid intermetallic compounds may appear on the interface between the electrolyte 6 and the positive material 7, and the compounds may also stick on the inner walls or even arch, then result in short circuit; usually LMBs work at an environment of high temperature (>250° C.), and the electrolyte will produce lots of Joule heat, therefore the Rayleigh-Bénard convection may happen due to temperature differences; there is a big difference between cross-sectional area of external cable and interface between electrical current collector (thinner) and liquid electrode, this will produce non-uniform distribution of electrical current density in liquid metal, resultantly leads to electro-vortex flow and further short circuit; when the charging/discharging current intensity is greater than the critical one (usually up to thousands of amperes or even more, depending on the volume, the materials, and the thickness of the electrolyte), there exists Tayler instability (also called sausage instability) which is a kind of kink-type instability. Tayler instability, which can also lead to short circuit, are one kind of the main and inherent instabilities in LMBs. In order to overcome these disadvantages of LMBs, a completely new structure, i.e., the grid device is designed in the present invention. There is no space between the grid device 5 and the negative electrical current collector 2, or the grid device 5 is directly embedded into the collector. This design can uniform the electrical current in the negative liquid electrode 3 and further suppress electro-vortex flow in this domain. On the other hand, the grid device 5 doesn't extend to the positive current collector 9, whilst due to the thickness of partitions, the current density near the positive electric current collector 9 within the positive liquid metal 7 is inhomogeneous. This will improve the appearing of electro-vortex flow in the positive material 7, further inhibit or slow the formation of the solid intermetallic compounds. The rectangular holes 8 in vertical direction on partitions can always assure each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms locates at the same horizontal level when LMBs work normally. For avoiding short circuit due to adhesion of fluid on partitions, the top end of the rectangular holes 8 should be higher than the location where the electrolyte 6 can reach during discharging process of LMBs, while the bottom end of the rectangular holes 8 should be lower than the location where the electrolyte 6 can reach during charging process, and extend to ⅔- 7/12 of initial height of the positive material 7. The lower limit of the rectangular holes' 8 width should be the minimal size that can assure the electrolyte 6 and liquid metals can smoothly flow through the rectangular holes (e.g., 4 mm), but the width shouldn't be greater than ⅕ of the corresponding width of that side edge of grid, which is enclosed by partitions or by partitions and inside wall/walls of LMBs. Besides, a special design is necessary for convenience of manufacturing and assembling when the pair number of partitions is larger than one. When the pair number is even, the structure of the grid device should be centrosymmetric and the grid device should be mounted by splicing because of the limitation of the rectangular holes distribution, e.g., for two pairs of partitions, two-stage splicing is used as shown in FIG. 3. While, when the pair number is odd, the structure of the grid device can be axisymmetric or centrosymmetric and the grid device should also be mounted by splicing because of the limitation of the rectangular holes 8 distribution, e.g., for three pairs of partitions, three-stage splicing is used as shown in FIG. 4.

EXAMPLES

Example 1

(28) Square section LMBs with a grid device to suppress the instabilities of fluids, the embodiments of LMBs comprise, a shell 1, an electrical current collector of negative electrode 2, a negative material 3, metallic nets or metallic plates 4, a grid device 5, an electrolyte 6, a positive material 7, rectangular holes 8 on partitions, an electrical current collector of positive electrode 9. The mentioned positive material 7, electrolyte 6 and negative material 3 are filled in the shell 1 and automatically stratified from bottom to top. The positive material 7 and the negative material 3 are liquid metals or alloys, the electrolyte 6 is liquid molten salt with high temperature. The densities sequence of the three-layer liquids within LMBs is as follow, positive material 7>electrolyte 6>negative material 3. Two electrical current collectors 2 and 9 are linked with the negative material 3 and the positive material 7 respectively from outside of LMBs. The grid device 5 within the shell 1 is composed of partitions crossing each other, and the grid device 5 passes through the negative material 3, the electrolyte 6 vertically in sequence, and extends to inside of the positive material 7. There is no gap between the top end of the grid device 5 and the negative electrical current collector 2, so that the grid device 5 can avoid promoting movement of the negative material 3 when electrical current density changes. The bottom end of the grid device 5 is lower than the maximum displacement of the electrolyte 6 during charging process, but it doesn't extend to the positive current collector 9 to assure that the grid device 5 can always suppress instabilities in LMBs during the whole charging/discharging cycles. The core of the partitions of the grid device 5 has to be the metallic nets or the metallic plates 4, and the rectangular holes 8 are made on the partitions of the gird device 5. The vertical height of the rectangular holes 8 is larger than the maximum displacement of the electrolyte 6 during charging/discharging process. The lower limit of the rectangular holes' 8 width should be the minimal size that can assure the electrolyte and liquid metals can smoothly flow through the rectangular holes 8 (e.g., 4 mm), but the width shouldn't be greater than ⅕ of the corresponding width of that side edge of grid, which is enclosed by partitions or by partitions and inside wall/walls of LMBs, to keep each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms at the same horizontal level in each child zone separated by partitions. This design can also prevent the formation of a big single enclosed induced magnetic loop in the whole LMB or the formation of a medium-sized enclosed induced magnetic field loop through some rectangular holes.

(29) In example 1, the grid device 5 in LMBs comprises one pair of partitions, as shown in FIG. 2B. The partitions are mounted crossing each other perpendicularly. In this case, we say the grid device 5 comprises one pair of partitions.

(30) The method of setting up the rectangular holes 8 in this case is: for one pair of partitions, the rectangular holes 8 should be made as shown in FIG. 2B. The rectangular holes 8 are just made at the location where two partitions are crossing because the induced magnetic field is weakest at the symmetric center of the LMBs. These rectangular holes 8 can guarantee each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms at the same horizontal level in each child zone separated by partitions. Besides, the vertical height of the rectangular holes 8 should be larger than the maximum displacement of the electrolyte 6 during charging/discharging process to prevent short circuit due to liquid metals sticking on partitions, and the rectangular holes' 8 width need be large enough to assure the electrolyte 6, the liquid metals 3 and 7 can smoothly flow through the rectangular holes 8 (e.g., 4 mm), but the width shouldn't be greater than ⅕ of the corresponding width of that side edge of grid, which is enclosed by partitions or by partitions and inside wall/walls of LMBs.

Example 2

(31) The most structures are the same as in example 1 except that the grid device 5 in LMBs comprises two pairs of partitions, as shown in FIG. 3B. In example 2, partitions 1I and 1II are coplanar, 2I and 2II are coplanar (one pair is composed of partitions 1, 1I and 1II; the other pair is composed of 2, 2I and 2II). This time, we say the grid device 5 comprises two pairs of partitions.

(32) The method of setting up the rectangular holes 8 in this case is: FIG. 3B depicts the detail assembling of the rectangular holes 8 when the pair number of partitions increases to two. In order to guarantee each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms at the same horizontal level in each child zone separated by partitions, and also to prevent the formation of a big single enclosed induced magnetic field loop in the whole LMB or the formation of a medium-sized enclosed induced magnetic field loop through some rectangular holes (ideally, the enclosed induced magnetic field loop should only be formed within each separated grid), the rectangular holes 8 should be set at special positions on partitions, right next to the inner walls of LMBs or right next to the junctions of any two partitions. In this way, no magnetic induction line continually passes through four or more rectangular holes to form an enclosed loop. Finally, there is only one rectangular hole on each side edge (except the inside walls of LMBs) of grid, which is enclosed by partitions or by partitions and inside wall/walls of LMBs. For convenience of manufacturing, the grid device 5 is designed center-symmetrically and manufactured in the method of two-stage splicing.

Example 3

(33) The most structures are the same as in example 1 except that the grid device 5 in LMBs comprises three pairs of partitions as shown in FIG. 4B. In example 3, partitions 1I, 1II and 1III are coplanar; 2I, 2II and 2III are coplanar; 3I, 3II and 3III are coplanar (the first pair is composed of partitions 1, 1I, 1II and 1III; the second pair is composed of 2, 2I, 2II and 2III; the third pair is composed of 3, 3I, 3II and 3III). This time, we say the grid device 5 comprises three pairs of partitions.

(34) The method of setting up the rectangular holes 8 in this case is: FIG. 4B depicts the detail assembling of the rectangular holes 8 when the pair number of partitions increases to three. Similarly, in order to guarantee each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms at the same horizontal level in each child zone separated by partitions, and also to prevent the formation of a big single enclosed induced magnetic field loop in the whole LMB or the formation of a medium-sized enclosed induced magnetic field loop through some rectangular holes (ideally, the enclosed magnetic field loop should only be formed within each separated grid), the rectangular holes 8 should be set at special positions on partitions, right next to the inner walls of LMBs or right next to the junctions of any two partitions. In this way, no magnetic induction line continually passes through four or more rectangular holes to form an enclosed loop. Finally, there is only one rectangular hole on each side edge (except the inside walls of LMBs) of grid, which is enclosed by partitions or by partitions and inside wall/walls of LMBs. For convenience of manufacturing, the grid device 5 is designed in the method of three-stage splicing, and the whole grid device is axis-symmetrically or center-symmetrically.

Example 4

(35) In order to verify the effectiveness of this proposed new grid device for suppressing multi-instabilities in LMBs, some numerical experiments are conducted in example 4. The physical model for numerical simulations is obtained by simplifying the real physical problems. The magnetic permeability of the negative material 3, the electrolyte 6 and the positive material 7 are the same and assumed as the vacuum magnetic permeability μ.sub.0; the thickness of all partitions is neglected; the chemical reactions within LMB are also ignored. The detailed description of physical model is as follow:

(36) 1. The scales of a square section LMB have the values of 100 mm×100 mm×450 mm in X×Y×Z dimensions (square section in horizontal XOY plane and vertical height in Z). Three liquid layers are Li|LiCl—KCl|Pb—Bi (Table 1 lists the properties).

(37) 2. There is no space between the side edges of the grid device 5 and the inner walls of the LMB. The top end of the grid device 5 extends to ¼ (the initial point is on the interface between the negative material 3 and the electrolyte 6) of initial height of the negative material 3, and the bottom end extends to ¾ (the initial point is on the interface between the positive material 7 and the positive electrical current collector 9) of initial height of the positive material 7 (the thickness of partitions is zero and all chemical reactions are ignored, these lead to the difference of partitions' thickness from above content). The material of the grid device 5 is electrically and magnetically insulated, and corrosion resistance.

(38) 3. In numerical simulations, each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms can be set to at the same horizontal level in each child zone separated by partitions easily, therefore, those rectangular holes 8 on partitions are not needed. In actual operation of LMBs, the materials are added into LMBs in solid state, and then they are heated to liquid state. So these rectangular holes 8 are necessary in real working.

(39) 4. The thickness in vertical direction of the electrolyte 6 is 1/9 of effective height of the LMB's shell.

(40) 5. The material of the shell 1 is electrically insulated, high temperature resistance and corrosion resistance.

(41) 6. The thickness of partitions of the grid device 5 is zero, but the material is set to be electrically and magnetically insulated, and corrosion resistant.

(42) Numerical simulations are performed for above LMB with and without the grid device 5. The results indicate that, the present newly invented structures can drastically improve the critical charging/discharging electrical current/electrical voltage, and can effectively suppress multi-instabilities in LMBs. In the following, two cases are adopted, i.e., one case without the grid device 5, the other case with the grid device 5 comprising three pairs of partitions, to illustrate the effectiveness of present invention.

(43) TABLE-US-00001 TABLE 1 Properties of LMB (Li∥LiCl—KCl∥Pb—Bi) at 500° C. properties Electrical Kinematic conductivity(σ) Permeability(μ) Density(ρ) viscosity(ν) [kg.sup.−1 .Math. m.sup.−3 .Math. [kg .Math. m .Math. Material [kg .Math. m.sup.−3] [m.sup.2 .Math. s.sup.−1] s.sup.3 .Math. A.sup.2] s.sup.−2.Math. A.sup.−2] Negative  484.7 6.64 × 10.sup.−7  3.0 × 10.sup.6 4π × 10.sup.−7 material Electrolyte 1597.9 1.38 × 10.sup.−6 187.1 4π × 10.sup.−7 Positive 1.0065 × 10.sup.4 1.29 × 10.sup.−7 7.81 × 10.sup.5 4π × 10.sup.−7 material

(44) The above Table 1 gives the physical properties of liquid metals and the electrolyte. The imposed voltage is for getting charging/discharging current intensity of LMBs. The 3D and 2D shapes for stable and unstable states of the electrolyte are illustrated comparatively in FIG. 5 ((A)-(F)) without the grid device 5. As shown in plots 5(a)-5(c), there is not fluctuation in the electrolyte layer when the imposed voltage is E=64V and each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms has the same horizontal level in each child zone separated by partitions, which implies the LMB works stably. However, if the imposed voltage is increased to E=6517, the electrolyte loses its original shape and becomes spray like as shown in plots (D)-(F) of FIG. 5. This will lead to direct contact of liquid metals A and B, and result in short circuit. Simultaneously, the temperature in the LMB will rise immediately and create risk. The streamlines on a YOZ (x=0) plane corresponding to FIG. 5A and FIG. 5D are shown in FIG. 6A and FIG. 6B respectively. From FIG. 6A, the fluid flows are limited within their own layers, and there are only a pair of clearly opposite direction vortexes in metals A and B separately, whilst, there are two pairs of vortexes within the electrolyte. FIG. 6A implies the vorticity conservation in each liquid layer. However in FIG. 6B, the vortexes whether in metal A or B, their left parts have broken through the interfaces and some electrolyte moves to metal A or B. When the imposed voltage is increased to E=70V, three liquid layers are mutual blending as shown in FIG. 6C, and many big and small irregular vortexes appear. Similarly, the 3D and 2D shapes for stable and unstable states of the electrolyte are illustrated comparatively in FIG. 7 ((A)-(F)) but with the grid device 5 comprising three pairs of partitions. As shown in plots (A)-(C) of FIG. 7, the electrolyte keeps its original shape when the imposed voltage is less or equal to the critical value (E=140V) and each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms has the same horizontal level in each child zone separated by partitions, which implies the LMB works stably. However, if the imposed voltage is increased to E=142.517 (slightly larger than the critical value), the electrolyte 6 cannot keep its original shape, and becomes spray like, as shown in plots (D)-(F) of FIG. 7. This will lead to direct contact of liquid metals A and B, and result in short circuit. Simultaneously, the temperature in the LMB will rise immediately and create risk. The streamlines on a YOZ (x=12.5 mm) plane corresponding to FIG. 7A and FIG. 7D are shown in FIG. 8A and FIG. 8B, respectively. From FIG. 8A, the fluid flows are limited within their own layers, and there are only one pair of opposite direction vortexes in metals A and B separately, whilst, there is no vortex within the electrolyte 6. FIG. 8A implies the vorticity conservation in each liquid layer. However, in FIG. 8B, the three layers are completely mutual blending, and there are many big and small irregular vortexes, which imply the onset of short circuit. More numerical simulations are conducted to test the effectiveness of the grid device 5. By increasing the imposed voltage gradually for finding out the turning point from stable state to unstable state of the LMB, the critical voltages corresponding to the increased pair numbers (0, 1, 3 and 7) of partitions of the grid device 5 are found as shown in FIG. 9. It clearly shows that, when the pair number of partitions of the grid device 5 is more than one, the critical voltage rises in a linear way with the increases of pair number of partitions of the grid device 5. In other words, the critical charging/discharging current/potential of those LMBs with the grid device 5 can be obviously improved with the increasing pair number of partitions, which further illustrates that the grid device 5 can drastically improve the stability of LMBs. In other words, for LMBs with the same parameters, the grid device 5 can obviously improve the efficiency of LMBs.

(45) From numerical simulations, the more pair of partitions in the grid device 5, the more obvious effect of the grid device 5 on suppressing multi-instabilities in LMBs, (as shown in FIG. 9, the critical voltage of the LMB with the grid device 5 comprising seven pairs of partitions rises almost 5 times of that without the grid device 5). While, the assembling of the grid device 5 in LMBs will occupy some available room, then the total amount of liquid metals A and B, and of the electrolyte will decrease when the whole volume of a LMB is fixed. Moreover, the total capacities of LMBs depend on the amount of liquid metals A and B disregarding instabilities. In this view, there is a conflict between the pair number of partitions and the total capacities of LMBs, so, it doesn't say, the more pairs of the partitions, the better. In principle, in the domain where there is the grid device 5, after subtracting the gross area of the grid device 5, the fluid flow area should occupy at least √{square root over (2)}/2 of the total section area of LMB in horizontal sections. Finally, how many pairs of partitions should be inserted, it depends on many factors, such as, the size of LMB, the thickness of partition, the materials of liquid metals A and B, and the electrolyte, the thickness of the electrolyte layer, etc.

(46) The introduction of the rectangular holes 8 on partitions is to assure that, each interface (one is between the negative material 3 and the electrolyte 6, the other is between the electrolyte 6 and the positive material 7) of two terms has the same horizontal level in each child zone separated by partitions, and the rectangular holes 8 cannot against the main targets of the grid device 5 (to change the distributions of flow and induced magnetic fields within LMBs). Thus the rectangular holes 8 should only be set at special positions on partitions, right next to the inner walls of LMBs or right next to the junctions of any two partitions. In this way, no magnetic induction line continually passes through four or more rectangular holes to form an enclosed loop. There is only one rectangular hole on each side edge (except the inside walls of LMBs) of grid, which is enclosed by partitions or by partitions and inside wall/walls of LMBs. The lower limit of the rectangular holes' 8 width should be the minimal size that can assure the electrolyte and liquid metals can smoothly flow through the rectangular holes 8 (e.g., 4 mm), but the width shouldn't be greater than ⅕ of the corresponding width of that side edge of grid, which is enclosed by partitions or by partitions and inside wall/walls of LMBs.

(47) The height of the rectangular holes 8 in the vertical direction should be greater than the maximum displacement of the electrolyte 6 during charging/discharging process. Because there is no gap between the top end of the grid device 5 and the negative electrical current collector 2 or the top end of the grid device 5 is directly embedded in the negative electrical current collector 2, the top end of the rectangular holes 8 can be just higher than the maximum displacement of the electrolyte 6 when it moves up during discharging process, the bottom end of the rectangular holes 8 should be lower than the maximum displacement of the electrolyte 6 when it moves down during charging process, and the bottom end of the rectangular holes 8 will extend to the ⅔- 7/12 of initial height of the positive material 7 (When the bottom end of the grid device 5 only extends to the ⅔ of initial height of the positive material 7, the bottom end of the rectangular holes 8 and the bottom end of the grid device 5 will be at the same horizontal level).

(48) The present invention concerned with the grid device 5 is mainly used for fine-high type (smaller horizontal section area but higher) square section LMBs. The thickness of the electrolyte layer 6 may be chosen as 1/9- 1/40 of the height of the shell 1. Under the premise of stably operation, it is prioritized to choose thinner electrolyte layer to reduce the electrical energy waste.