WO2012097457A1

WO2012097457A1 - Cylindrical shaped ion-exchange battery

Info

Publication number: WO2012097457A1
Application number: PCT/CA2012/050033
Authority: WO
Inventors: Pu Chen
Original assignee: Liu, Hao; YAN, Jing
Priority date: 2011-01-21
Filing date: 2012-01-20
Publication date: 2012-07-26
Also published as: AU2012208933A1

Abstract

A cylindrical shaped rechargeable battery comprises a cathode current collector, a cathode constrained within a cylindrical separator membrane, and a cylindrical anode electrode, each of which are arranged concentrically. Preferably, the cathode comprises lithium and/or sodium intercalation compounds as the cathode active material. The electrolyte comprises a solution, preferably an aqueous solution, containing metal salts. The solvent for the electrolyte may comprise water, ethanol, methanol or a combination thereof. The metal salt of the electrolyte comprises at least one metal ion, which can be reduced and deposited onto the surface of the anode during charging and oxidized and dissolved into the electrolyte during discharging.

Description

PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1 CYLINDRICAL SHAPED ION-EXCHANGE BATTERY CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority under the Paris Convention to US

Application Number 61/434,975, filed January 21 , 201 1 , the entire contents of which are incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention relates to a secondary battery. In particular, the invention relates to an ion exchange secondary battery having a cylindrical configuration. BACKGROUND OF THE INVENTION [0003] Since the invention of lead-acid batteries, the energy storage and conversion industry has entered the "secondary battery times". As known in the art, a "secondary battery", also referred to as a rechargeable battery, is a battery wherein the internal electrochemical reactions are reversible. Various kinds of secondary batteries are applied in different fields depending on their specific requirements. For example, portable electronic devices require a battery with a high energy density as in lithium ion (Li-ion) batteries, electric tools require a high power output as in Li-ion, Ni-MH, and Ni-Cd batteries, and large energy storage applications (such as a UPS), motor start-up batteries, wind power/solar energy storage devices all require batteries with low cost and long service life. [0004] Lead-acid batteries have been occupying the majority of the battery market share, especially among energy storage fields for several decades. But this fact should not conceal many disadvantages of the lead-acid batteries, in particular, the lead pollution problem associated with its manufacture, battery recall and recycle after use, short service life (typically 2 years), and low energy density. It is necessary to find a new battery, which comes with low cost, long service life, environment friendly and good safety characteristics, to replace the present lead-acid batteries. Although the current Li-ion and Ni-MH batteries have better performance than lead-acid batteries in energy density, power density, service life and environment aspects, they still cannot replace the lead-acid batteries mainly because of the cost. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0005] To solve this problem, many researchers turned to aqueous Li-ion battery, hoping to use water based electrolytes in place of organic electrolytes and drastically reduce the cost of Li-ion batteries, and also to solve the safety problem with Li-ion batteries. In 1994, Jeff Dahn et al. presented an aqueous battery with LiMn₂0₄ as the cathode material, vanadium oxide such as V0₂ as the anode material, and a water solution of lithium salts as the electrolyte [LI W., DAHN J.R., WAINWRIGHT D.S., Science, 264 (1994), 1 1 15]. Up to now, all reported aqueous Li-ion batteries used the same principle as the Li-ion battery, based on an embedded type structure on both positive and negative electrodes, such as LiMn₂0₄/V0₂, LiNi_{0 8}iCoo i₉0₂/LiV₃0₈, LiM^O^TiP^, LiMn₂0₄/LiTi₂(P0₄)3, and

LiCo0₂/LiV₃0₈. A further example of such batteries is provided in US Patent Number 7, 189,475. However, all these batteries have a low energy density and poor cycle life, because of the decomposition of the intercalation anode materials during charging and discharging in the aqueous solution (i.e. water). [0006] A need exists for an improved aqueous secondary battery that can replace current lead-acid batteries. SUMMARY OF THE INVENTION [0007] Accordingly to one aspect, the invention provides a generally cylindrical rechargeable battery consisting of a cathode electrode, an anode electrode and an electrolyte, wherein the components of the battery are coaxially arranged. [0008] In one aspect, the invention provides a rechargeable battery having a generally cylindrical structure, the battery comprising: [0009] - a cathode current collector; [0010] - a generally cylindrical cathode arranged coaxially around the current collector, the cathode being constrained by a separator membrane provided on an outer surface of the cathode; [0011] - a generally cylindrical anode arranged coaxially around the separator membrane; [0012] - an electrolyte comprising a solution of at least one metal salt, wherein the metal is capable of being reduced and deposited onto the surface of the anode during PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1 charging of the battery and oxidized and dissolved into the electrolyte during discharging of the battery. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The features of the invention will become more apparent in the following detailed description in which reference is made to the appended drawings wherein: [0014] Figure 1 shows a schematic view of a battery unit according to an aspect of the invention. [0015] Figure 2 shows a schematic of a cathode electrode according to one aspect of the invention. [0016] Figure 3 is a schematic front elevation of a battery according to one aspect of the invention, comprising a number of the battery units of Figure 1 . [0017] Figure 4 shows the charge and discharge curve of the battery of Example 1 . [0018] Figure 5 shows the cyclability curve of the battery in Example 1 . [0019] Figure 6 shows a schematic view of a battery according to one aspect of the invention, comprising a single battery unit of Figure 1 . [0020] Figure 7 is a schematic side elevation of the battery of Figure 3. [0021] Figure 8 is a schematic cross sectional plan view of the battery of Figure 3. DETAILED DESCRIPTION OF THE INVENTION [0022] The terms "comprise", "comprises", "comprised" or "comprising" may be used in the present description. As used herein (including the specification and/or the claims), these terms are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not as precluding the presence of one or more other feature, integer, step, component or a group thereof as would be apparent to persons having ordinary skill in the relevant art. [0023] In one aspect, the present invention relates to a structure design of a novel secondary battery, based on the principle of ion-exchange in the electrolyte. Such battery is referred to herein as an Ion-Exchange Battery (IEB). PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0024] In one aspect of the present invention, as illustrated in the accompanying figures, there is provided a cylindrically shaped rechargeable battery unit 100 having a typical structure as shown in Figure 1 . Such cylindrical structures for battery units are known in the art. The battery unit 100 consists of a positive electrode or cathode 103, in association with a cathode current collector 101 , a negative electrode or anode 201 and an electrolyte. The cathode 103 is constrained by a separator or "bag" 104, or similar known device, and upper and lower cathode locating rings 102. The anode is similarly constrained by upper and lower anode locating rings 202. [0025] In a preferred embodiment of the invention, the cathode active material of the cathode comprises lithium (Li) and/or sodium (Na) intercalation cathode materials, which are described further below. [0026] The lithium ion intercalation compounds may comprise layered structure compounds, spinel structure compounds or olivine structure compounds. The layered structure compounds may be represented by the compositional formula Li_1+xM_yM'_zM"_c0₂₊n, where each of M, M', M" represents an element selected from Ni, Mn, Co, Mg, Ti, Cr, V, Zn, Zr, Si, Al, and where x, y, z, c, n individually satisfy the following relationships: 0< x <0.5, 0< y <1 , 0< z <1 , 0 <c <1 , and -0.2< n <0.2. The spinel structure compounds may be represented by the compositional formula Li_{1 +x}Mn_yM_zO_k, where M is at least one element selected from Na, Li, Co, Mg, Ti, Cr, V, Zn, Zr, Si, Al, and where x, y, z, k individually satisfy the following relationships: 0< x <0.5, 1 < y <2.5, 0< z <0.5, and 3< k <6. The olivine structure compounds may be represented by the compositional formula Li_xM₁._yM'_y(XO₄)n, where: M is an element selected from Fe, Mn, V, Co; M' is at least one element selected from Mg, Ti, Cr, V, Al, Co; X' is selected from S, P and Si; and, x, y and n individually satisfy the following relationships: 0< x <2, 0< y <0.6, 1 < n <1 .5. [0027] According to one embodiment, the invention comprises a LiMn₂0₄/Zn battery with LiMn₂0₄ as the cathode active material, tin plated copper film/foil as the anode, and 5 mol/L ZnCI₂ as the electrolyte. In such example, during charging, Li⁺ ions deintercalate from the spinel crystal lattice of LiMn₂0₄, while trivalent manganese is oxidized to tetravalent manganese with an accompanying electron output. In this example of the invention, LiMn₂0₄ turns to Li-|._x Mn₂0₄ and Zn^{2 +} ions in the electrolyte are reduced to a metallic state and are deposited on the anode surface. When the battery is charging (as shown in Figure 2), the reaction at the cathode is LiMn₂0₄-xe^~→ Li⁺ + Li-|._xMn₂0₄, and the reaction at the anode is Zn^{2 +} + xe^~→ (x / 2) Zn. The discharging process reverses these reactions. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0028] In the current lithium battery industry, almost all cathode materials are doped, coated, or modified by various methods. For example, LiMn₂0₄ is no longer able to represent the general formula of a "lithium manganese oxide" that is widely used. Strictly, the general formula of the material should be according to the general formula of the spinel structure compound that the present invention involves. However, doping, coating and other modifications cause the chemical formula of the material to be more complex, so the formula LiMn₂0₄ should include the cathode materials of a variety of modifications, and be consistent with the general formula of the spinel structure compounds, as described in the present invention. The chemical formula of LiFeP0₄, and other materials described herein, will be understood to include the materials of a variety of modifications and to be consistent with the general formulae of layered structure, spinel structure or olivine structure compounds. [0029] In one aspect of the invention, the cathode active material comprises a material that can reversibly intercalate-deintercalate. Such compounds include those that are able to intercalate-deintercalate lithium, sodium and other ions. When the cathode active material is a lithium ion intercalation-deintercalation compound, it can preferably be selected from, for example, LiMn₂0₄, LiFeP0₄, LiCo0₂, LiM_xP0₄, LiM_xSiO_y (where M is a metal with a variable valence, x) and other compounds. When the cathode active material is a sodium ion intercalation-deintercalation compounds, it can be, for example, NaVP0₄F. [0030] During charging, Li and/or Na ions inside the cathode material deintercalate into the electrolyte, and during discharging, Li/Na ions in the electrolyte intercalate into the cathode. [0031] Figure 2 shows a schematic of the cathode in isolation, which shows the cathode current collector 101 and the cathode electrode locating rings 102. As shown in Figure 2, the cathode locating rings 102 also serve to locate the position of the cathode current collector 101 . The cathode active material 103 is shown constrained by the cathode electrode bag 104. [0032] Figures 3, 7 and 8 schematically show a battery 400 wherein a plurality of battery units 100 as described above are included. The battery units are contained in a case or shell 301 . The case 301 may be formed of metal and/or plastic or any other material as would be apparent to persons skilled in the art. A cover 302 is also provided to seal the contents of the case 301 and to separate the contents of the case from exposure to the environment. In a preferred embodiment, a pressure relief or limiting valve 303 is provided to limit the pressure within the battery 400. As shown, the various battery units 100 are PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1 electrically connected. Specifically, the cathode current collectors 101 are connected to form a cathode external circuit 105, while the anodes are connected to form an anode external circuit 205. [0033] Figure 6 illustrates a cylindrical battery 200 comprising one of the battery units 100 of Figure 1 . As shown, the battery 200 comprises a cylindrical case or shell 301 , which is open at one end. The battery 200 further comprises an insulative cover 304 provided on the top of the shell 301 in order to seal the opening. As shown in Figure 6, a conductor 206 is electrically connected to the anode 201 . The cathode current collector 101 and the conductor 206 extend through the cover 302 so as to enable same to be electrically connected to an external circuit (similar to that shown in Figure 3). As also shown, caps 306 are provided over the exposed ends of the cathode current collectors 101 protruding through the cover 302. Such caps 306 serve to prevent damage or corrosion etc. to the collectors 101 . For example, when the cathode current collector 101 is made of a porous material, such as graphite, the electrolyte in the battery can penetrate through the opening in the cover 302 and leak out of the battery. The caps 306 serve to cover the cathode current collectors 101 and prevent such penetration of electrolyte. Preferably, the caps 306 should completely wrap the part of the cathode current collectors 101 that extend outside of the cover 302. Meanwhile, the caps 306 also preferably connect to the external circuit wires using welding, bolt connection or riveted connection, etc. The caps 306 may be formed of a material selected from impermeable graphite, conductive plastics, lead, tin, tin alloys, etc. Various other materials for the caps 306 will be known to persons skilled in the art. [0034] The battery 200 shown in Figure 6 is also preferably provided with a pressure relief valve 303 similar to that described above with respect to Figure 3. [0035] The electrolyte according to one aspect of the invention comprises a solution, preferably an aqueous solution, of metal salts. The solvent may comprise water, ethanol, methanol or mixtures thereof. The metal salts comprise at least one sort of metal ion, which can be reduced and deposited onto the surface of the anode 201 during charging, and oxidized and dissolved into the electrolyte during discharging. [0036] Referring again to Figure 1 , it is noted that, in a preferred embodiment, the cathode current collector 101 , the cathode material 103. the cathode electrode bag 104, and the anode electrode 201 are arranged in an overlapping, generally concentric cylinder structure. According to one aspect, the cathode electrode bag 104 and the anode electrode 201 may be separated by a distance of 1 to 15 mm. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0037] The cathode current collector 101 is contained in the cathode electrode bag 104, and the cathode active material 103 and conductive agent fill in the gap between the cathode current collector 101 and the cathode electrode bag 104. [0038] In one aspect, the length of the cathode current collector 101 , the bag 104 and the anode electrode 201 are between 50-4000 mm. In one aspect, the diameter of the cathode current collector 101 is 6-50 mm, the diameter of the bag 104 is 12-240 mm, and the diameter of the anode electrode 201 is 20-320 mm. In a preferred aspect, the lengths of the cathode current collector 101 , the bag 104 and the anode electrode 201 are between 100-4000 mm, the diameter of the cathode current collector 101 is 10-50 mm, the diameter of the bag 104 is 15-200 mm, and the diameter of the anode electrode 201 is 20-240 mm. In another preferred aspect, the current collector 101 comprises a generally cylindrical "stick" shape, having a diameter between 6-50 mm and a length between 50-4000 mm. [0039] In one aspect, the cathode current collector 101 comprises a material such as a stainless steel mesh or foil, graphite, or carbon fiber. Various other known materials may be used for the current collector. The thickness of the collector 101 is preferably between 0.01 mm and 50 mm. [0040] The anode electrode 201 preferably has a thickness between 0.001 mm and 5 mm, and may be formed of a material such as carbon based materials, stainless steel and metals electroplated or coated by one of C, Sn, In, Ag, Pb, Co, and Zn. [0041] The cathode bag 104 functions as an electrical separator between the cathode 103 and anode 201. The bag 104 may therefore be referred to as a "separator" as known in the art. The bag 104 may comprise a porous membrane. In one embodiment, the membrane has pore sizes between 0.01 and 1000 microns and a porosity of 20 - 95%. [0042] In one aspect, the electrolyte of the present ion-exchange battery contains at least one sort of metal ion chosen from: Zn, Ni, Fe, Cr, Cu and Mn and combinations thereof. In operation of the battery of the invention, the metal ion of the electrolyte is reduced and deposited onto the surface of the anode during the charging phase. During the discharge phase, the above reaction/process is reversed. That is, during discharge, the metal deposited on the surface of the anode is oxidized and returned to its ionic state in the electrolyte solution. The solvent of the electrolyte is preferably water or an aqueous solution. For example, the solvent may comprise water, ethanol, methanol, or any mixture thereof. In one aspect, the concentration of the metal dissolved in the solvent may be 0.5-15 mol/L. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0043] According to one embodiment of the invention, the electrolyte comprises an aqueous solution comprising LiCI, Li₂S0₄, LiN0₃, ZnCI₂, ZnS0₄, Zn(N0₃)₂ or any

combination thereof. In one aspect, the electrolyte comprises a solution containing 1 mol/L LiCI, or Li₂S0₄, LiN0₃, and 4 mol/L ZnCI₂, or ZnS0₄, or Zn(N0₃)₂. [0044] To accelerate the rate of ion exchange, additional Li or Na salts may be added to the electrolyte. In such case, these salts may be added to any desired concentration, such as 1 -15 mol/L. [0045] In one aspect of the invention, there is provides a battery pack 400 as illustrated in Figures 3, 7 and 8, which consists of a plurality of electrically connected cylindrical ion- exchange batteries 100. [0046] As described herein, the present invention comprises new battery system, wherein the cathode active material comprises ion intercalation/deintercalation compounds. The electrochemical reversibility of the cathode relies on the intercalation (during charging of the battery) and deintercalation (during discharging of the battery) of ions to/from the cathode active material. The electrochemical reversibility of the anode relies on a metal ion being reduced (during charging of the battery) and oxidized (during discharging of the battery) on the surface of the anode. [0047] In a preferred embodiment, the electrolyte of the invention contains both the deintercalated ions of the cathode active material and the ion that deposits/dissolves to/from the anode surface. [0048] As discussed above, the cathode of the invention comprises at least a cathode current collector, one or more cathode active materials, one or more binders, and one or more conductive agents. The cathode current collector preferably comprises a composite material that may use carbon based conductive materials. Different carbon or carbon composite materials have different electrical properties. For example, graphite and conductive carbon fibre are both good electronic conductors, and also have excellent structural strength. As such, these materials can be used as a cathode current collector in the present invention. In addition, by mixing the conductive carbon black and a binder, such as PVDF (polyvinylidene fluoride), polyethylene, polypropylene, uniformly and heat treating, the conductive material can be made with both good electronic conductivity and flexibility. Such a conductive material is found to have suitable properties for use as a cathode collector for the invention. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0049] In a preferred embodiment, the cathode active material are mixed with the cathode conductive agent and binder uniformly, and are then coated onto the current collector. To obtain a desired energy density, the current collector should not be too thick; the preferred range of the thickness is between 0.01 mm - 5 mm. To facilitate the mobility of ions in the cathode active material, the coating of the cathode active material should not be thick, and the preferred range of such thickness is between 0.1 mm - 10 mm. As mentioned above, a cathode structure according to the invention is shown in Figure 2. [0050] The anode structure consists mainly of an anode sheet that is provided as a cylindrical structure. In principle, any material that has good conductivity and sufficient chemical stability can be used as the anode. In general, the anode does not participate in the electrochemical reaction of the battery, and only serves as a substrate for depositing the metal ions in the electrolyte once reduced. For example, Al, Fe, Ni, Cu, Ag, Cd, W, Au, Pb, Sn, stainless steel and graphite, and combinations of same, can be used for making an anode according to the invention. Considering conductive resistance, structural strength and weight, the preferred thickness of the anode should be between 0.005 - 1 mm. [0051] To protect the anode, improve the overpotential of hydrogen evolution on the surface of the anode, and enhance the current efficiency of the anode, the anode surface is preferably covered with a layer of metal or metal oxide by a process such as plating, coating, etc. The material for the plating or coating is selected from at least one of Sn, Ag, Pb, Co, Zn, and their oxide powders. The thickness of the plating or coating is preferably between 0 - 0.1 mm. [0052] The cathode of the battery is preferably porous, made of powder, and has a high- current discharge capability. But the anode, which comprises a sheet or foil of carbon or of the aforementioned metals, is flat, and its specific area may be limited. For example, if the surface of the anode is porous, the specific area will be high and, as such, the anode would have better electrochemical properties and a higher current discharge capability. [0053] The present inventor has found that using metal foam as the anode substrate, and further plating suitable material thereon, can improve the discharge performance of the anode. For example, an anode comprised of a nickel foam material with silver plated thereon was found to have better discharge performance than nickel foam itself. [0054] The electrolyte of the invention preferably includes at least one kind of metal ion that proceeds with reduction-oxidation reactions on the surface of the anode during charge and discharge, respectively. For example, with LiMn₂0₄ as the cathode active material, the PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1 electrolyte preferably contains Zn²⁺ ions, and the zinc salt may be chosen from the sulfate or chloride. In such case, the preferred concentration of Zn²⁺ in the electrolyte is about 4 - 6 mol/L. [0055] The cathode, anode, separator membrane (i.e. "bag") and electrolyte can be placed in a special container, such as discussed above and as shown in the appended figures. As will be understood, the cathode and anode need to be connected to an external circuit, to provide an electron conducting channel. [0056] The aforementioned cathode and anode form the two main components of a battery unit according to the invention. To increase battery capacity, a plurality of such battery units can be connected in parallel in order to form a battery system. As shown in Figure 3, the cathodes and the anodes of such system are connected to the external circuit. [0057] In one embodiment of the invention, as illustrated in Figure 3, the current collectors 31 1 of the cathodes extend externally of the case or shell 301 and run across the battery cover 302 to connect with external circuit 105. It will be understood that the apertures in the cover 302 through with the current collectors 31 1 extend are preferably sealed in a suitable manner. In the illustrated embodiment, the conductors 206, electrically connected to the anodes 201 , also extend through the cover 302 and run across same to connect with the external circuit 205. [0058] As shown for example in Figure 6, and as discussed above, the portions of the cathode current collectors 101 extending through the battery cover 302 are preferably sealed with a protective cover or cap 101 that has good electrical conductivity and is chemically stable. The role of the protective cap 101 is to prevent water in the electrolyte of the battery from evaporating out through the opening through which the cathode current collectors extend. In the result, the caps 101 aid in preventing the corrosion of the external circuit wires and the cathode current collectors. The preferred materials of the protective caps 101 are impermeable graphite, conductive plastics, lead alloy, etc. Various materials having the aforementioned properties will be apparent to persons skilled in the art. [0059] In one aspect of the present invention, where the cathode active material is an ion intercalation-deintercalation compound and the anode material is a metal, the cathode comprises a "bag electrode". That is, as described above, the cathode comprises a cylindrical structure that is constrained by a separator membrane or "bag". Using locating ring 102, the relative positions of the cathode current collector 101 and the electrode bag 104 are fixed, thereby forming a concentric cylinder structure. The cylindrical gap or space PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1 between the current collector 101 and the bag 104 is then filled with a mixture comprising the cathode active material, a conductive agent, a binder and other known components that may be used for cathodes. [0060] The cylindrical anode 201 is provided around the cathode and is positioned with one or more locating rings 202 to separate the anode from the cathode. In one aspect, the distance between the anode and cathode is determined by the size of the locating rings 202. [0061] One embodiment of a cylindrical cathode-anode system, as mentioned above, comprises a battery unit 100. In another aspect of the invention, a number of battery units 100 can be combined to form a battery with enhanced capacity by electrically connecting such units in parallel. The battery units 100 and the electrolyte are placed into a battery case or shell 301 , which may be made of a metal and/or plastic material. [0062] As will be understood by persons skilled in the art, all features described herein can be replaced by features that can provide the same, equal or similar purposes.

Therefore, unless otherwise stated, the features disclosed herein are only the general features of equal or similar examples. [0063] As will be understood by persons skilled in the art after having reviewed the present description, the main advantages offered by the present invention include one or more of: 1) desirable qualitative characteristics such a battery providing good

electrochemical performance, environmental safety, and/or low-cost; 2) a battery having a simple structure, which facilitates manufacturing time/cost and provides high reliability; and 3) a battery that can be widely used, including replacing the current lead-acid batteries. With respect to structure, the battery of the invention comprises a concentrically arranged structure comprising a cylindrical cathode (constrained in a "bag"), a cylindrical anode that "wraps" around the cathode. [0064] Without being limited to any theory, when the battery of the invention is charging, the lithium or sodium ions deintercalate from the cathode active material, accompanied by oxidation of the valency varying metal in the active material and releasing electrons. The electrons flow through the external circuit to reach the anode of the battery; meanwhile metal ions in the electrolyte (at least one sort of metal ion among the elements of Zn, Ni, Fe, Cr, Cu and Mn) are reduced to metallic state and are deposited onto the anode surface. The discharging process is the reverse of the charging process. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0065] Again, without limiting the invention in any way, the principle of the battery of the invention is: when charging, the cathode active material reacts, where Li (HOST)- e^"→ Li ⁺ + (HOST), and the anode presents M^x+ + xe^~→ M. Li (HOST) is a lithium ion intercalation compound; M is a metal; M^x+ is the ionic state of M. If the cathode active material is a sodium ion intercalation compound, the cathode active material reacts with Na (HOST)-e^"→ Na ⁺ + (HOST), and the anode presents M^{x +} + xe^~→ M when charging. [0066] Examples [0067] Aspects of the present invention are described below by means of various illustrative examples. The examples contained herein are not intended to limit the invention in any way but to illustrate same in more detail. It should be understood that the

experiments in the following examples, unless otherwise indicated, are in accordance with conditions as would be known to persons skilled in the art or the conditions recommended by manufacturers. Unless indicated otherwise, all percentages, ratios, proportions referred to in the examples are calculated by weight. [0068] Example 1 [0069] A battery unit was formed. The cathode current collector was a cylindrical graphite rod with a diameter of 10 mm and length of 150 mm. The cathode electrode bag was a bottom sealed hollow cylinder with a diameter of 12 mm and height of 120 mm, and was made by bonding non-woven membranes together. As shown in Figure 2, the cathode current collector was fixed at the centre of the electrode bag with an upper and lower holding or locating ring. The cathode active material comprising LiMn₂0₄ and conductive carbon black were mixed uniformly in a ratio of 80:20, and then the mixture was filled into the gap between the current collector and the electrode bag. The amount of the cathode active material in the bag was about 7 g. [0070] The anode substrate was a copper foil with a thickness of 0.1 mm, the surface of which was plated with tin, with a plating thickness of about 50 μηι. As shown in Figure 1 , the anode comprised a bottomless hollow cylinder with a diameter of 16 mm. The battery separator was a non-woven membrane with a thickness of 0.1 mm. Locating rings were provided between the cylindrical anode and the cathode bag to ensure a certain distance and maintain their relative positions. The cathode bag and the anode constitute parts of a battery unit. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0071] The battery unit was placed into a cylindrical battery case having a diameter of 18 mm. The cathode current collector was extended through the cover of the battery case, and was connected to an external circuit. A copper wire with a diameter of 1 mm was led out from the anode by welding, and this wire was passed through the battery cover to connect to the external circuit. [0072] The electrolyte of the battery comprised a water solution containing 3 mol/L LiCI and 4 mol/L ZnS0₄. An amount of 17 ml of the electrolyte was injected into the battery case, and left to stand still for 24 hours, after which the testing of the electrochemical properties was started. [0073] The capacity of the battery was 700 mAh (calculated by 100 mAh/g as the specific capacity of the cathode active material LiMn₂0₄), the charge-discharge testing procedure was as follows: charge with constant current 700 mA to 2.35V, then discharge with constant current to 1 .5 V, and then cycle the above two steps. The first charge and discharge curve is shown in Figure 4. [0074] The battery exhibited excellent charge and discharge reversibility, and the charge and discharge columbic efficiency was 97%. No significant capacity decay was obvious after the first 100 charge and discharge cycles, which illustrates excellent cycling

performance of the battery. The cycle performance of the battery is shown in Figure 5. [0075] The charging process of the battery normally produces a small amount of gas (due to water decomposing to hydrogen and oxygen), and a part of such gas, that is generated on the electrode, arrives the opposite electrode by diffusion and is converted back to water (which may involve redox reactions on the electrode surface). Thus, pressure relief valves were set up on the battery cover to prevent the pressure inside the battery shell from increasing too much. The cell structure was similar to that shown in Figure 6. [0076] Example 2 [0077] A battery was made according to Example 1 . However, in this case, tin plated nickel foam was used as the anode instead of the tin plated copper foil. Nickel foam as a skeleton provides more specific area than a metal plate/foil, and tin plating provides a better interface for the electrodepositing of Zn. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

[0078] Example 3 [0079] A battery was made according to Example 1 . However, in this case, LiFeP0₄ was used as the cathode active material instead of LiMn₂0₄. The average discharge voltage of this battery was 1 .3 V (charge and discharge with 1 C rate). [0080] Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the purpose and scope of the invention as outlined in the claims appended hereto. Any examples provided herein are included solely for the purpose of illustrating the invention and are not intended to limit the invention in any way. Any drawings provided herein are solely for the purpose of illustrating various aspects of the invention and are not intended to be drawn to scale or to limit the invention in any way. The disclosures of all prior art recited herein are incorporated herein by reference in their entirety.

Claims

PCT Application Docket No.: 79350/00007 Doc. No: 22193779.1WE CLAIM:

1. A rechargeable battery having a generally cylindrical structure, the battery comprising:

- a cathode current collector;

- a generally cylindrical cathode arranged coaxially around the current collector, the cathode being constrained by a separator membrane provided on an outer surface of the cathode;

- a generally cylindrical anode arranged coaxially around the separator membrane;

- an electrolyte comprising a solution of at least one metal salt, wherein the metal is capable of being reduced and deposited onto the surface of the anode during charging of the battery and oxidized and dissolved into the electrolyte during discharging of the battery.

2. The rechargeable battery according to claim 1 , wherein the cathode active material comprises a lithium intercalation compound, a sodium intercalation compound or mixtures thereof.

3. The rechargeable battery according to claim 1 or 2, wherein the electrolyte contains at least one metal ion selected from the group comprising Zn, Ni, Fe, Cr, Cu and Mn.

4. The rechargeable battery according to claim 3, wherein the concentration of the metal ion is 0.5-15 mol/L.

5. The rechargeable battery according to claim 3, wherein the electrolyte comprises an aqueous solution.

6. The rechargeable battery according to claim 5, wherein the electrolyte comprises a solution of water, ethanol, methanol or a combination thereof.

7. The rechargeable battery according to claim 1 , wherein the battery further comprises a cylindrical shell and an insulative cover.

8. The rechargeable battery according to claim 7, wherein the cathode current collector and the anode include electrical terminals extending through the insulative cover, and wherein said terminals are adapted for connection to one or more respective external circuits. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

9. The rechargeable battery according to claim 8, wherein the battery further comprises a pressure relief valve to limit the pressure inside the battery.

10. The rechargeable battery according to claim 1 , wherein the coaxially arranged separator membrane and the anode electrode are separated by a distance of between 1-15 mm.

1 1. The rechargeable battery according to claim 1 , wherein the coxially

12. The rechargeable battery according to claim 2, wherein said lithium ion intercalation compound comprises a layer structure compound, a spinel structure compound or an olivine structure compound.

13 The rechargeable battery according to claim 12, wherein said layer structure compound is represented by the formula Li_1+xM_yM'_zM"_c0₂₊n, where:

- M, M', and M" are selected from Ni, Mn, Co, Mg, Ti, Cr, V, Zn, Zr, Si, Al; and,

- x, y, z, c, and n satisfy the relationship 0<x<0.5, 0<y<1 , 0<z<1 , 0<c<1 , and - 0.2<n<0.2.

14. The rechargeable battery according to claim 12, wherein said spinel structure compound is represented by the formula Li_1+xMn_yM_zO_k, where:

- M is selected from Na, Li, Co, Mg, Ti, Cr, V, Zn, Zr, Si, and Al; and,

- x, y, z, and k satisfy the relationship 0<x<0.5, 1 <y<2.5, 0<z<0.5, and 3<k<6.

15. The rechargeable battery according to claim 12, wherein said olivine structure compound is represented by the formula Li_xM₁._yM'_y(XO₄)n, where:

- M is selected from Fe, Mn, V, and Co;

- M' is selected from Mg, Ti, Cr, V, Al, and Co;

- X' is selected from S, P and Si; and,

- x, y, and n satisfy the relationship 0<x<2, 0<y<0.6, and 1 <n<1.5.

16. The rechargeable battery according to claim 2, wherein the sodium ion intercalation compound comprises NaVP0₄F. PCT Application

Docket No.: 79350/00007 Doc. No: 22193779.1

17. The rechargeable battery according to any one of claims 1 to 16, wherein the anode comprises: a carbon-based material; stainless steel; metals electroplated or coated by at least one of C, Sn, In, Ag, Pb, Co, and Zn; or, combinations thereof.

18. The rechargeable battery according to claim 17, wherein the thickness of the anode is between 0.005-1 mm.

19. A battery system comprising a plurality of rechargeable batteries according to any one of claims 1 to 18, wherein said batteries are electrically connected in parallel.