Patent Description:
Batteries are a type of device for utilizing, as electric energy, chemical energy which results from a chemical reaction between a positive active material and negative active material through an electrolyte. Batteries are roughly divided into primary and secondary batteries. The primary battery is, so to speak, a single-use battery that cannot be recharged once it has been discharged, whereas the secondary battery is a type of battery that can be repeatedly charged and discharged. Due to such a nature, the secondary battery is also called the storage battery.

Secondary batteries are used in various applications. For example, they are used as a power source for small-sized consumer appliances, such as a handheld information terminal, mobile electronics, portable music player or digital camera, or as a battery for an electric bicycle, hybrid electric vehicle, or drone. They are also used as a storage battery device to be embedded in a power generator which uses natural energy (renewable energy), such as solar generation or wind-power generation (Patent Literature <NUM> or <NUM>).

The charging of a secondary battery is performed by setting the secondary battery in a charger which is connected, for example, to a commercial AC power supply. The charger has a power conditioner (converter) configured to convert alternating current into direct current. The device converts the alternating current from the commercial AC power supply into direct current, and passes the resulting current between the positive electrode and negative electrode of the secondary battery.

On the other hand, small-sized consumer appliances, electric vehicles and other aforementioned types of products are normally driven by alternating current. Therefore, in order to drive such AC-driven equipment by the direct current released from a secondary battery, it is necessary to convert direct current into alternating current by means of a power conditioner (inverter) or similar device.

In summary, a two-stage power conversion including AC-to-DC power conversion and DC-to-AC power conversion is needed in order to supply AC-driven equipment with electric power if a conventional and common type of secondary battery is used. The power conversion efficiency from DC to AC through an inverter as well as the power conversion efficiency from AC to DC through a converter are each within a range from <NUM> % to <NUM> %. It cannot reach <NUM> %. Accordingly, there is the problem that a power loss associated with the power conversion is present, which lowers the power utilization efficiency.

With respect to this problem, Patent Literature <NUM> discloses a new secondary battery capable of the charging and discharging of the alternating current and alternating power. This secondary battery has three electrodes, i.e. the positive electrode and negative electrode as well as a bipolar electrode located between the positive and negative electrodes, having an intermediate electrode potential between the positive and negative electrodes.

When the secondary battery described in Patent Literature <NUM> is charged or discharged, the battery is alternately switched between the state in which the positive terminal and bipolar terminal are connected to a pair of output ends of a commercial AC power supply or a pair of input ends of a load, and the state in which the negative terminal and bipolar terminal are connected to the pair of output or input ends. Consequently, cations alternately move between the positive and bipolar electrodes as well as between the bipolar and negative electrodes. During the period in which cations are moving between the positive and bipolar electrodes, electrons flow between the positive and bipolar electrodes through an external circuit. During the period in which cations are moving between the bipolar and negative electrode, electrons flow between the bipolar and negative electrodes through an external circuit. Since the direction of the flow of the electrons is inverted for each period, the charging and discharging of the alternating current is possible.

For the previously described charging and discharging operation, it is necessary that the electrons which have come from the positive or negative electrode to the bipolar electrode should subsequently be made to flow toward the negative or positive electrode of the same battery. In other words, the charging and discharging of the alternating current cannot be achieved if the electrons which have come from the positive or negative electrode to the bipolar electrode in one secondary battery are subsequently made to flow to the negative or positive electrode of another secondary battery. This means that two or more secondary batteries having previously described configuration cannot be serially connected for use, which prevents the previously described secondary battery from being used as a high-voltage power source.

The problem to be solved by the present invention is to create a secondary battery which allows for the charging and discharging of the alternating current as well as one which produces high voltage.

The first aspect of the present invention developed for solving the previously described problem is a secondary battery pack including:.

where the third battery includes the following elements, with n being an integer equal to or greater than zero:.

The second aspect of the present invention developed for solving the previously described problem is a secondary battery pack including:.

In the secondary battery pack according to the first or second aspect of the present invention, the third battery having the positive and negative electrodes as well as the bipolar electrodes arranged between the positive and negative electrodes enables the charging and discharging of alternating current. The serial connection of the third electrode to the first battery as well as to the second battery enables the production of high voltage.

The third battery has positive, bipolar and negative electrodes (which may hereinafter be simply called the "electrodes" when no discrimination is made between the positive, bipolar and negative electrodes) arranged in a predetermined order in the electrolyte, with a separator sandwiched between the neighboring electrodes. Being "arranged in order" does not necessarily mean that the electrodes are linearly arranged; it includes various arrangements, such as a U-shaped, V-shaped or zigzag form. It is also possible to prepare each of the positive, negative and bipolar electrodes in the form of a sheet electrode, and to join the electrodes together in a laminated form with a separator sandwiched between the neighboring electrodes.

In any of the previously described secondary battery packs, commercially available secondary batteries may be used as the first and second batteries. In that case, a plurality of secondary battery cells may be connected in series or in parallel and used as the first or second battery. Connecting a plurality of secondary battery cells in series enables the first and second batteries to produce high voltage. Connecting a plurality of secondary battery cells in parallel provides the first and second batteries with a high amount of capacity. Accordingly, a plurality of secondary battery cells connected in series, or those connected in parallel, can be used as the first battery and/or second battery depending on the purpose of use of the secondary battery pack.

Let Ec denote the electrode potential of the positive electrodes of the third battery, Ea denote the electrode potential of the negative electrodes, and Eb denote the electrode potential of the bipolar electrodes ("Biodes"). The three potentials satisfy the relationship expressed as Ec>Eb>Ea. Such a relationship in potential level reflects the capacity of each electrode to give or receive electrons. The active materials for the positive, negative and bipolar electrodes, the material for the current collector, as well as the electrolyte should be selected to satisfy the aforementioned relational expression. As far as the aforementioned relational expression is satisfied, the secondary battery pack according to the first or second aspect of the present invention can be applied in any type of secondary battery, such as a nickel-hydride secondary battery, nickel-cadmium secondary battery, lead-acid secondary battery, lithium ion secondary battery, or sodium ion secondary battery.

The electrode potential of the positive electrodes of the first and second batteries only needs to be higher than the electrode potential Ea of the negative electrodes of the third battery, while it is insignificant whether the electrode potential in question is higher or lower than the electrode potential Ec of the positive electrodes of the third battery. Similarly, the electrode potential of the negative electrodes of the first and second batteries only needs to be lower than the electrode potential Ec of the positive electrodes of the third battery, while it is insignificant whether the electrode potential in question is higher or lower than the electrode potential Ea of the negative electrodes of the third battery.

Examples of the active material for the positive electrodes of the first, second and third batteries include, but not limited to, the compounds represented by the following chemical formulae: LiCoPO<NUM>, LiNiPO<NUM>, LiNiVO<NUM>, LiMn<NUM>/<NUM>Ni<NUM>/<NUM>O<NUM>, LiCoPO<NUM>, LiPtO<NUM>, LiCrMnO<NUM>, LiMn<NUM>O<NUM>, LiMnPO<NUM>, LiNi<NUM>/<NUM>Mn<NUM>/<NUM>Co<NUM>/<NUM>O<NUM>, LiNi<NUM>/<NUM>Mn<NUM>/<NUM>O<NUM>, LiNi<NUM>/<NUM>Co<NUM>/<NUM>O<NUM>, LiCoVO<NUM>, LiCoO<NUM>, LINiO<NUM>, LiFe<NUM>(SO<NUM>)<NUM>, LIFePO<NUM>, Li<NUM>+x(Fe<NUM>/<NUM>Mn<NUM>/<NUM>Ti<NUM>/<NUM>)<NUM>-xO<NUM>, Li<NUM>FeSiO<NUM>, and Li<NUM>MnSiO<NUM>.

Examples of the active material for the negative electrodes of the first, second and third batteries include, but not limited to, the materials represented by the following names: lithium metal, lithium alloy, graphite, graphene (two-dimensional graphite sheet), hard carbon, soft carbon, crystal(line) silicon, amorphous silicon, silica (silicon dioxide), silicene (two-dimensional silicon sheet), tin metal, and tin alloy.

For example, when the secondary battery pack according to the first or second aspect of the present invention is applied in a lithium ion secondary battery, LiFePO<NUM> can be used as the active material of the positive electrodes, a carbon-based material as the active material of the negative electrodes, and Li<NUM>/<NUM>Ti<NUM>/<NUM>O<NUM> as the active material of the bipolar electrodes.

When such a secondary battery pack is charged, one of the two output terminals of an AC power source is selectively connected to either the positive terminal of the first battery or the negative terminal of the second battery, while the other output terminal is connected to the bipolar terminal of the third battery. When the former output terminal of the AC power source is connected to the positive terminal of the first battery, electrons flow from the positive terminal of the first battery toward the bipolar terminal (bipolar electrode) of the third battery through an external circuit, causing the oxidization of the active material of the positive electrode in the first battery. The resulting cations (positive ions, Li+) move toward the negative electrode, to be eventually reduced to C<NUM>Li. Meanwhile, the active material of the positive electrode in the third battery undergoes oxidization, and the resulting cations move toward the bipolar electrode.

The former output terminal of the AC power source is subsequently connected to the negative terminal of the second battery. Then, electrons flow from the bipolar terminal of the third battery toward the negative terminal of the second battery through the external circuit, and cations move from the bipolar electrode toward the negative electrode in the third battery, to be eventually reduced to C<NUM>Li. Meanwhile, the active material of the positive electrode in the second battery undergoes oxidization, and the resulting cations (positive ions, Li+) move toward the negative electrode, to be eventually reduced to C<NUM>Li.

The chemical reactions which respectively occur at the electrodes in the first, second and third batteries in the charging process are expressed by the following formulae (<NUM>) and (<NUM>):.

Thus, the secondary battery pack according to the first or second aspect of the present invention is charged through the two-stage chemical reactions. The flow of the electrons occurs in the opposite direction in each stage. Accordingly, the battery pack can be charged with the alternating current by alternately connecting the bipolar terminal of the third battery to either the positive terminal of the first battery or the negative terminal of the second battery according to the direction of the alternating current taken from the AC power supply.

In the discharging process, the chemical reactions at the electrodes in the first, second and third batteries occur in the direction opposite to the charging process. Initially, the active material of the negative electrode in the second battery undergoes oxidization. The resulting cations (positive ions, Li+) move toward the positive electrode, to be eventually reduced to LiFePO<NUM>. Meanwhile, the active material of the negative electrode in the third battery undergoes oxidization, and the resulting cations (positive ions, Li+) move toward the bipolar electrode. During this process, electrons flow from the negative terminal of the second battery toward the bipolar electrode of the third battery through the external circuit. Subsequently, the cations move from the bipolar electrode toward the positive electrode in the positive electrode, to be eventually reduced to LiFePO<NUM>. Meanwhile, the active material of the negative electrode in the first battery undergoes oxidization, and the resulting cations (positive ions, Li+) move toward the positive electrode, to be eventually reduced to LiFePO<NUM>. During this process, electrons flow from the bipolar terminal of the third battery toward the positive terminal of the first battery through the external circuit. Accordingly, alternating current can be released by switching the electrode to be connected to the bipolar electrode between the negative terminal of the second battery and the positive terminal of the first battery at appropriate timings.

The secondary battery pack according to the first or second aspect of the present invention does not only allow for the charging and discharging of the alternating current but can also be modified to allow for the charging and discharging of the direct current by providing a switching circuit at each of the positive and negative sides of a direct-current battery and operating the switching circuits in such a manner as to switch the battery pack at appropriate timings between the state in which the positive terminal of the first battery and the bipolar terminal of the third battery are respectively connected to the positive electrode and the negative electrode of the direct-current battery, and the state in which the bipolar terminal of the third battery and the negative terminal of the second battery are respectively connected to the positive electrode and the negative electrode of the direct-current battery.

The previously described secondary battery packs can be charged and discharged by the following device.

That is to say, a charger configured to charge one of the previously described secondary battery packs includes:.

A discharger configured to discharge one of the previously described secondary battery packs includes:.

As for the switching means, for example, a bipolar transistor can be used.

Yet another aspect of the present invention is a secondary battery module including:.

In the secondary battery pack according to the present invention, the third battery having the positive, negative and bipolar electrodes enables the charging of the AC power from an AC power supply without the help of a power conditioner, as well as the discharging of the AC power without the help of a power conditioner. Furthermore, the serial connection of the first battery and the second battery, which are common types of secondary batteries, to the third battery enables the secondary battery pack to produce high voltage.

Embodiments of the secondary battery according to the present invention are hereinafter described.

<FIG> is a schematic configuration diagram of a secondary battery pack according to the first embodiment of the present invention. The secondary battery pack <NUM> includes a case <NUM> as well as a first battery <NUM>, second battery <NUM> and third battery <NUM> contained in the case <NUM>. The first battery <NUM> includes two secondary battery cells <NUM> and <NUM>. The second battery <NUM> also includes two secondary battery cells <NUM> and <NUM>, while the third battery <NUM> includes one secondary battery cell <NUM>. The five secondary battery cells <NUM>-<NUM> each include a closed container <NUM> as well as a plurality of electrodes <NUM>, separators <NUM> and an electrolyte <NUM> which are contained in the closed container <NUM>. The closed container <NUM> is provided with external terminals <NUM> electrically connected through connection members <NUM> to the electrodes <NUM> contained in the closed container <NUM>.

The case <NUM> includes, for example, a metallic case body <NUM> having an upper opening sealed with a metallic cover <NUM>. The cover <NUM> has a positive terminal <NUM> and a negative terminal <NUM>, while the case body <NUM> has a bipolar terminal <NUM> on its bottom side.

The two secondary battery cells <NUM> and <NUM> forming the first battery <NUM>, as well as the two secondary battery cells <NUM> and <NUM> forming the second battery <NUM>, each have two electrodes <NUM>, i.e. a positive electrode (cathode) "C" and a negative electrode (anode) "A" arranged within the closed container <NUM>. The secondary battery cell <NUM> forming the third battery <NUM> has three electrodes <NUM> arranged within the closed container <NUM>. The three electrodes <NUM> include a positive electrode "C" a negative electrode "A" as well as a bipolar electrode (Biode) "B" located between the positive electrode C and the negative electrode A.

The first battery <NUM> is formed by the secondary battery cells <NUM> and <NUM> connected in series. The external terminal <NUM> of the negative electrode A of the secondary battery cell <NUM> is electrically connected to that of the positive electrode C of the secondary battery cell <NUM> by a connection line <NUM>. The external terminal <NUM> of the positive electrode C of the secondary battery cell <NUM> is electrically connected to the positive terminal <NUM> by a connection line <NUM>. In the present embodiment, the external terminal <NUM> of the positive electrode C of the secondary battery cell <NUM> and the external terminal <NUM> of the negative electrode A of the secondary battery cell <NUM> correspond to the positive terminal and the negative terminal of the first battery <NUM>, respectively.

The second battery <NUM> is formed by the secondary battery cells <NUM> and <NUM> connected in series. The external terminal <NUM> of the negative electrode A of the secondary battery cell <NUM> is electrically connected to that of the positive electrode C of the secondary battery cell <NUM> by a connection line <NUM>. The external terminal <NUM> of the negative electrode A of the secondary battery cell <NUM> is electrically connected to the negative terminal <NUM> by a connection line <NUM>. In the present embodiment, the external terminal <NUM> of the positive electrode C of the secondary battery cell <NUM> and the external terminal <NUM> of the negative electrode A of the secondary battery cell <NUM> correspond to the positive terminal and the negative terminal of the second battery <NUM>, respectively.

The third battery <NUM> is serially connected to each of the first and second batteries <NUM> and <NUM>. Specifically, the external terminal <NUM> of the negative electrode A of the secondary battery cell <NUM> is electrically connected to that of the positive electrode C of the secondary battery cell <NUM> by a connection line <NUM>, while the external terminal <NUM> of the positive electrode C of the secondary battery cell <NUM> is electrically connected to that of the negative electrode A of the secondary battery cell <NUM> by a connection line <NUM>. The external terminal of the bipolar electrode B of the secondary battery cell <NUM> is electrically connected to the bipolar terminal <NUM> by a connection line <NUM>. In the present embodiment, the external terminals <NUM> connected to the positive electrode C, negative electrode A and bipolar electrode B correspond to the positive terminal, negative terminal and bipolar terminal of the third battery <NUM>, respectively. The connection members <NUM> which connect the positive electrode C, negative electrode A and bipolar electrode B to the corresponding external terminals <NUM> respectively correspond to the positive-electrode connection member, negative-electrode connection member and bipolar-electrode connection member. The connection lines <NUM> and <NUM> respectively correspond to the first connector and the second connector.

The electrodes <NUM> (positive electrodes C, bipolar electrode B and negative electrodes A) each include a current collector and an active-material layer formed on the surface of the current collector. The active-material layer is made of an active material and an adhesive for adhering the active material to the current collector. As for the active materials contained in the positive electrode C and the negative electrode A, active materials commonly used for the positive and negative electrodes in secondary batteries can be used. The active material contained in the active-material layer of the bipolar electrode B is not limited to any specific material and may be any material which gives the bipolar electrode B an electrode potential between the electrode potential of the positive electrode C and that of the negative electrode A.

For example, the active-material layer of the positive electrode C should preferably contain an active material whose electrode potential changes within a range from <NUM> V (vs. Li/Li+) to <NUM> V (vs. Li/Li+), while the active-material layer of the negative electrode A should preferably contain an active material whose electrode potential changes within a range from <NUM> V (vs. Li/Li+) to <NUM> V (vs. Li/Li+). The active-material layer of the bipolar electrode B should preferably contain an active material whose electrode potential changes within a range from <NUM> V (vs. Li/Li+) to <NUM> V (vs. Li/Li+).

As for the electrolyte <NUM>, an appropriate kind of electrolyte compatible with the active materials of the electrodes may be used. It may be an aqueous or non-aqueous electrolyte. It may be an electrolytic solution, polyelectrolyte gel or solid polyelectrolyte.

An operation principle of the secondary battery pack <NUM> is hereinafter described with reference to <FIG> and <FIG>. <FIG> and <FIG> show the movement of cations in the charging process under the condition that the negative electrodes A in the secondary battery cells <NUM>-<NUM> are made of a carbon-based material, the positive electrodes C are made of LiFePO<NUM>, and the bipolar electrode B is made of Li<NUM>/<NUM>Ti<NUM>/<NUM>O<NUM>.

The description is initially concerned with the charging operation for the secondary battery pack <NUM>. A charger <NUM> for the secondary battery pack <NUM> includes a pair of input lines <NUM> and <NUM>, a single-pole double-throw switching circuit <NUM> connected to an end of the input line <NUM>, two branch lines <NUM> and <NUM> connected to the switching circuit <NUM>, as well as a controller <NUM> configured to control the operation of the switching circuit <NUM>. The switching circuit <NUM> switches between the state in which the input line <NUM> is connected to one branch line <NUM> (first state) and the state in which the input line <NUM> is connected to the other branch line <NUM> (second state). The switching circuit <NUM> corresponds to the switching means in the present invention. Various kinds of elements are available for this circuit, such as a bipolar transistor or relay.

When the secondary battery pack <NUM> is charged, the secondary battery pack <NUM> is set in the charger <NUM>. The positive and negative terminals <NUM> and <NUM> of the secondary battery pack <NUM> are thereby connected to the branch lines <NUM> and <NUM> of the charger <NUM>, respectively, while the bipolar terminal <NUM> is connected to the input line <NUM>. Meanwhile, the input lines <NUM> and <NUM> of the charger <NUM> are connected to a pair of output ends of an AC power supply <NUM>. In such a charging circuit, when the electrons flow through the input lines <NUM> and <NUM> in the direction as indicated by the arrows in <FIG>, the controller <NUM> switches the switching circuit <NUM> to the first state in which the input line <NUM> is connected to the branch line <NUM>. In this state, cations (positive ions, Li+) move from the positive electrode C toward the negative electrode A across the electrolyte <NUM> in each of the secondary battery cells <NUM> and <NUM>, while cations (positive ions, Li+) move from the positive electrode C toward the bipolar electrode B across the electrolyte <NUM> in the secondary battery cell <NUM>.

When the electrons flow through the input lines <NUM> and <NUM> in the direction as indicated by the arrows in <FIG>, the controller <NUM> switches the switching circuit <NUM> to the second state in which the input line <NUM> is connected to the branch line <NUM>. In this state, cations move from the bipolar electrode B toward the negative electrode A across the electrolyte <NUM> in the secondary battery cell <NUM>, while cations move from the positive electrode C toward the negative electrode A across the electrolyte <NUM> in each of the secondary battery cells <NUM> and <NUM>. As a result, C<NUM>Li deposits on the negative electrode A.

Thus, the secondary battery pack <NUM> is charged by the two-stage chemical reactions. Accordingly, the charging can be continued by switching the switching circuit <NUM> to the first connection state or the second connection state every time the direction of the alternating current from the AC power supply <NUM> changes its direction.

A discharging operation for the secondary battery pack <NUM> is hereinafter described with reference to <FIG> and <FIG>. A discharger <NUM> for the secondary battery pack <NUM> includes a pair of output lines <NUM> and <NUM>, a single-pole double-throw switching circuit <NUM> connected to an end of the output line <NUM>, two branch lines <NUM> and <NUM> connected to the switching circuit <NUM>, as well as a controller <NUM> configured to control the operation of the switching circuit <NUM>. The switching circuit <NUM> switches between the state in which the output line <NUM> is connected to one branch line <NUM> (third state) and the state in which the output line <NUM> is connected to the other branch line <NUM> (fourth state).

When the secondary battery pack <NUM> is discharged, the secondary battery pack <NUM> is set in the discharger <NUM>. The positive and negative terminals <NUM> and <NUM> of the secondary battery pack <NUM> are thereby connected to the branch lines <NUM> and <NUM> of the discharger <NUM>, respectively, while the bipolar terminal <NUM> is connected to the output line <NUM>. Meanwhile, the output lines <NUM> and <NUM> of the discharger <NUM> are connected to a pair of input ends of a load <NUM>. In such a discharging circuit, the controller <NUM> switches the switching circuit <NUM> to the fourth state in which the output line <NUM> is connected to the branch <NUM> (see <FIG>). Then, the active material on the negative electrode A is dissolved in each of the secondary battery cells <NUM> and <NUM>. The resulting cations (positive ions, Li+) move toward the positive electrode C across the electrolyte <NUM>. Meanwhile, the active material on the negative electrode A in the secondary battery cell <NUM> is dissolved, and the resulting cations (positive ions, Li+) move toward the bipolar electrode B across the electrolyte <NUM>. During this process, electrons flow from the negative electrode A of the secondary battery cell <NUM> toward the bipolar electrode B of the secondary battery cell <NUM> through the external circuit (output lines <NUM> and <NUM>).

The controller <NUM> subsequently switches the switching circuit <NUM> to the third state in which the output line <NUM> is connected to the branch line <NUM> (see <FIG>). Then, cations move from the bipolar electrode B toward the positive electrode C across the electrode <NUM> in the secondary battery cell <NUM>, and eventually deposit in the form of LiFePO<NUM>. Meanwhile, the active material on the negative electrode A is dissolved in each of the secondary battery cells <NUM> and <NUM>. The resulting cations (positive ions, Li+) move toward the positive electrode C across the electrolyte <NUM>. During this process, electrons flow from the bipolar electrode B of the secondary battery cell <NUM> toward the positive electrode C of the secondary battery cell <NUM> through the external circuit (output lines <NUM> and <NUM>). Accordingly, alternating current can be released by operating the switching circuit <NUM> so that the electrode to be connected to the bipolar electrode B of the secondary battery cell <NUM> is alternately changed between the negative electrode A of the secondary battery cell <NUM> and the positive electrode C of the secondary battery cell <NUM> at an appropriate timing (e.g. according to the frequency of the load <NUM>).

As can be understood from the comparison of <FIG> and <FIG> with <FIG> and <FIG>, the relationship of the input lines <NUM>, <NUM>, switching circuit <NUM> and secondary battery pack <NUM> in the charging process is basically the same as that of the output lines <NUM>, <NUM>, switching circuit <NUM> and secondary battery pack <NUM> in the discharging process. Accordingly, it is possible to make the charger <NUM> or discharger <NUM> be a charging-and-discharger having both the charging and discharging functions by appropriately controlling the timing to switch the switching circuit.

In the secondary battery pack <NUM> having the previously described configuration, the voltage value of the entire secondary battery pack <NUM> is determined by the voltage difference between the positive electrode C and the negative electrode A in the secondary battery cells <NUM>-<NUM>, voltage difference between the positive electrode C and the bipolar electrode B in the secondary battery cell <NUM>, as well as voltage difference between the bipolar electrode B and the negative electrode A in the secondary battery cell <NUM>. <FIG> shows an example of the voltage values in the case where the positive electrodes C made of the same electrode material and the negative electrodes A made of the same electrode material are used in all secondary battery cells <NUM>-<NUM>. On the other hand, <FIG> show an example of the voltage values in the case where the negative electrode of the secondary battery cell <NUM> and that of the secondary battery cell <NUM> are each made of the same electrode material as the bipolar electrode B of the secondary battery cell <NUM>. Those examples demonstrate that secondary battery packs <NUM> with various voltage values can be obtained by appropriately selecting the electrode materials.

<FIG> is a schematic configuration diagram of a secondary battery pack 1A according to the second embodiment of the present invention. In <FIG>, the outer shape of the secondary battery pack 1A is shown by the long dashed short dashed line. The portions which are identical or correspond to those of the secondary battery pack <NUM> according to the first embodiment are denoted by the same reference signs. A difference of this secondary battery pack 1A from the secondary battery pack <NUM> exists in the configuration of the third battery 4A. Specifically, the third battery 4A is formed by a secondary battery cell 16A having five electrodes <NUM> arranged within the closed container <NUM>. The five electrodes include two negative electrodes A at both extremities, one positive electrode C located between the two negative electrodes A, and two bipolar electrodes B respectively located in the two spaces formed between the two negative electrodes A and the positive electrode C.

The two negative electrodes A are electrically connected to each other by a connection line <NUM>. This connection line <NUM> is electrically connected to the positive electrode C of the secondary battery cell <NUM> by a connection line <NUM>. The two bipolar electrodes B are electrically connected to each other by a connection line <NUM>. This connection line <NUM> is electrically connected to the bipolar terminal <NUM> by a connection line <NUM>.

The secondary battery pack 1A having the previously described configuration also allows for the charge and discharge of alternating current, as with the secondary battery pack <NUM>.

<FIG> shows one embodiment of the secondary battery module according to the present invention. This secondary battery module <NUM> includes a case <NUM> having a pair of terminals <NUM> and <NUM>, a secondary battery pack <NUM> contained in the case <NUM>, a switching circuit <NUM> functioning as the switching means, and a controller <NUM> configured to control the switching circuit <NUM>. The secondary battery pack <NUM> has almost the same configuration as the previously described secondary battery pack <NUM> according to the first embodiment. Therefore, the portions which are identical or correspond to those of the secondary battery pack <NUM> are denoted by the same reference signs, and detailed descriptions of the secondary battery pack <NUM> will be omitted.

The terminal <NUM> of the secondary battery module <NUM> is connected to the switching circuit <NUM> by a first input/output line <NUM>. The terminal <NUM> of the secondary battery module <NUM> is connected to the bipolar terminal <NUM> of the secondary battery pack <NUM> by a second input/output line <NUM>. One of the two contacts of the switching circuit <NUM> is connected to the positive terminal <NUM> of the secondary battery pack <NUM> by a first line <NUM>, while the other contact is connected to the negative terminal <NUM> by a second line <NUM>.

In the secondary battery module <NUM>, when the pair of terminals <NUM> and <NUM> are connected to a pair of output ends of an AC power supply, a charging circuit for the secondary battery pack <NUM> is formed, and the secondary battery pack <NUM> is thereby charged. The direction of the flow of the electrons and the timing to switch the switching circuit <NUM> in this charging process are the same as in the charging operation performed by the charger <NUM> when the secondary battery pack <NUM> according to the first embodiment is set in the charger <NUM>.

When the pair of terminals <NUM> and <NUM> of the secondary battery module <NUM> are connected to a pair of input ends of a load, a discharging circuit for the secondary battery pack <NUM> is formed, and alternating current is supplied from the secondary battery pack <NUM> to the load. The direction of the flow of the electrons and the timing to switch the switching circuit <NUM> in this discharging process are the same as in the charging operation performed by the discharger <NUM> in which when the secondary battery pack <NUM> according to the first embodiment is set in the discharger <NUM>.

<FIG> is an embodiment of a high-voltage generator using a secondary battery pack according to the present invention. This high-voltage generator <NUM> includes a secondary battery pack <NUM>, a switching unit <NUM>, and a high-voltage generation unit <NUM> including a multistage rectification capacitor circuit. The secondary battery pack <NUM> has the same configuration as the secondary battery pack <NUM> according to the first embodiment. Therefore, the portions which are identical or correspond to those of the secondary battery pack <NUM> are denoted by the same reference signs, and detailed descriptions of the secondary battery pack <NUM> will be omitted.

The switching unit <NUM> includes a single-pole double-throw switching circuit <NUM> and a controller <NUM> configured to control the operation of the switching circuit <NUM>. The two contacts of the switching circuit <NUM> are respectively connected to the positive terminal <NUM> and the negative terminal <NUM> of the secondary battery pack <NUM> in a removable manner.

The high-voltage generator <NUM> includes a Cockcroft-Walton (CW) circuit having a plurality of serially connected diodes D<NUM> to Dn and capacitors C<NUM> to Cn forming a multistage circuit. The CW circuit has a pair of input terminals <NUM> and <NUM>, to which the switching circuit <NUM> of the switching unit <NUM> and the bipolar terminal <NUM> of the secondary battery pack <NUM> are respectively connected. The connection between the input terminal <NUM> of the CW circuit and the bipolar terminal <NUM> of the secondary battery pack <NUM> is removable. The pair of output terminals <NUM> and <NUM> of the CW circuit serve as the output terminals of the high-voltage generator <NUM>.

When a pair of input terminals of a load (not shown) is connected to the output terminals <NUM> and <NUM> of the high-voltage generator <NUM>, the controller <NUM> operates the switching circuit <NUM> so that the circuit is alternately switched between the first state indicated by the solid line in <FIG> (i.e. the state in which the CW circuit is connected between the positive terminal <NUM> and the bipolar terminal <NUM>) and the second state indicated by the dashed line (i.e. the state in which the CW circuit is connected between the negative terminal <NUM> and the bipolar terminal <NUM>). As a result, AC power is supplied from the secondary battery pack <NUM> to the high-voltage generation unit <NUM>, which produces a high-voltage DC-power output to the load connected to the output terminals <NUM> and <NUM> of the CW circuit. It is possible to configure the controller <NUM> so that it disconnects the two contacts from both the positive terminal <NUM> and the negative terminal <NUM> upon detecting that all capacitors of the CW circuit have been fully charged.

When the amount of charges stored in the secondary battery pack <NUM> has been decreased to a certain level, the secondary battery pack <NUM> can be removed from the high-voltage generator <NUM> and set in a charger. For example, the previously described charger <NUM> (see <FIG>) can be used for this purpose. The operation for charging the secondary battery pack <NUM> is the same as the charging operation for the secondary battery pack <NUM> using the charger <NUM>, and therefore, will not be described in this embodiment.

The previously described embodiments are mere examples and can be appropriately changed or modified along with the gist of the present invention.

In the first to fourth embodiments, the plurality of electrodes included in the third battery in the secondary battery pack are horizontally arranged in a row (see <FIG> and <FIG>). If there are a considerable number of electrodes, those electrodes may be arranged in a V-shaped, U-shaped or zigzag form. <FIG> shows an example in which <NUM> electrodes are arranged in a zigzag form. Such an arrangement makes the positive electrodes C be closer to each other, the bipolar electrodes B be closer to each other, and the negative electrodes C be closer to each other in the third battery, thereby reducing the connection distance between the positive electrodes C, between the bipolar electrodes B as well as between the negative electrodes A.

In the first to fourth embodiments, the five secondary battery cells <NUM>-<NUM> forming the secondary battery pack are horizontally arranged in a row. Those secondary battery cells <NUM>-<NUM> may be arranged in any way as long as their electrical connection is the same.

In the first to fourth embodiments, a plurality of secondary battery cells is connected in series to construct the first and second batteries. It is also possible that one or both first and second batteries include a plurality of secondary battery cells connected in parallel.

In the first embodiment, the secondary battery pack <NUM> is separated from the charger <NUM> or discharger <NUM>. The secondary battery pack <NUM> and a charging-and-discharging circuit may be contained in one case to form a secondary battery module.

Claim 1:
A secondary battery pack comprising:
a first battery and a second battery each of which includes a positive terminal and a negative terminal;
a third battery including a positive terminal, a negative terminal and a bipolar terminal;
a first connector configured to electrically connect the negative terminal of the first battery and the positive terminal of the third battery; and
a second connector configured to electrically connect the positive terminal of the second battery and the negative terminal of the third battery,
where the third battery includes the following elements, with n being an integer equal to or greater than zero:
(n+<NUM>) positive electrodes and (n+<NUM>) negative electrodes alternately arranged;
(2n+<NUM>) bipolar electrodes individually located in spaces between the positive electrodes and the negative electrodes neighboring each other;
an electrolyte;
a positive-electrode connection member configured to electrically connect the positive terminal of the third battery and the (n+<NUM>) positive electrodes;
a negative-electrode connection member configured to electrically connect the negative terminal and the (n+<NUM>) negative electrodes; and
a bipolar-electrode connection member configured to electrically connect the bipolar terminal and each of the (2n+<NUM>) bipolar electrodes.