Secondary batteries

Abstract

To provide a secondary battery configuration that allows lithium ions to move through the electrolyte during charging and discharging, using metals that are commonly used as the positive and negative electrodes. [Solution] A secondary battery that can achieve the above problem by using copper as the positive electrode 1, using one of aluminum, iron, nickel, cobalt, or zinc as the negative electrode 2, or using an alloy of two or three types of aluminum, iron, nickel, cobalt, or zinc, and using an electrolyte containing lithium ions and an organic solvent as the electrolyte.

Description

[Technical Field]

[0001] This invention relates to a secondary battery in which lithium ions move through the electrolyte during charging and discharging, similar to a lithium-ion battery. [Background technology]

[0002] Small, high-capacity lithium-ion rechargeable batteries are used as power sources for portable electronic devices such as laptops and smartphones, but in recent years, from the perspective of global environmental issues and decarbonization, they have also been adopted as storage batteries for renewable energy and as rechargeable batteries for electric vehicles.

[0003] In lithium-ion secondary batteries, lithium cobalt oxide (LiCoO2) is typically used as the positive electrode, as shown in Non-Patent Document 1, and lithium-containing graphite (usually represented by the chemical formula LixC6) is used as the negative electrode.

[0004] During charging and discharging, at the positive electrode, The ionization reaction TIFF2026052235000002.tif1297 occurs, and at the negative electrode, The ionization reaction TIFF2026052235000003.tif1479 has been achieved.

[0005] In typical lithium-ion batteries, an electrolyte solution is used in which an electrolyte such as lithium tetrafluoroborate (LiBF4) and an organic solvent coexist, and lithium ions (Li) appear through the ionization reaction. + ) moves during charging and discharging.

[0006] However, lithium (Li), a rare metal, is expensive compared to metals commonly used as electrodes, such as copper (Cu) and iron (Fe), while its refining process is complicated.

[0007] When considering such economic costs, instead of adopting a configuration containing lithium like a lithium-ion battery as the positive and negative electrodes, a metal commonly adopted in the prior art is adopted, and a configuration in which lithium ions (Li + ) flow in the electrolyte is highly expected and demanded.

[0008] However, a technical configuration corresponding to such a demand has not been proposed so far.

Prior Art Documents

Non-Patent Documents

[0009]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a configuration of a secondary battery that enables lithium ions to move in an electrolyte during charge and discharge, after selecting a metal commonly used as a positive electrode and a negative electrode.

Means for Solving the Problems

[0011] For the purpose of solving the above problems, the basic configuration of the present invention is (1) A secondary battery that uses copper as the positive electrode, any one of aluminum, iron, nickel, cobalt, and zinc as the negative electrode, and an electrolyte and an organic solvent containing lithium ions as the electrolyte. (2) A secondary battery that uses copper as the positive electrode, an alloy of two or three of aluminum, iron, nickel, cobalt, and zinc as the negative electrode, and an electrolyte and an organic solvent containing lithium ions as the electrolyte. It consists of.

Effects of the Invention

[0012] Both basic configurations (1) and (2) employ copper as the positive electrode.

[0013] Therefore, during the charging stage, at the positive electrode, the ionization reaction of Cu→Cu 2+ 2e - is realized, and copper ions (Cu 2+ ) flow in the electrolyte, while performing an ionization reaction as described later. On the other hand, electrons (e - ) move to the negative electrode side through the conductive line between the electrodes.

[0014] Conversely, during the discharging stage, copper ions (Cu 2+ ) realize an ionization reaction in the opposite direction to the above ionization reaction and move to the positive electrode side.

[0015] In an electrolyte containing lithium ions, prior to charging and discharging, lithium ions (Li + ) are contained, and an electrolyte Lix is formed by ionic bonding with a minus ion compound (x - ) and is dissolved in an organic solvent.

[0016] Between the electrolyte Lix and the copper ions (Cu 2+ ) moving in the electrolyte, the following ionization formula holds during charging and discharging (note that the upper arrow indicates the state during the charging stage, and the lower arrow indicates the state during the discharging stage). TIFF2026052235000004.tif1182···(1) The basis for the establishment of the above formula (1) is as follows.

[0017] The electrolytic energy of copper, that is, the energy required to release electrons and ionize itself, and the energy corresponding to an index capable of realizing ionic bonding is 7.726 eV, while the electrolytic energy of lithium is 5.390 eV.

[0018] In such a case, the copper ions (Cu 2+ ) formed during the charging stage are lithium ions (Li +(x - ) vs. lithium ions (Li + ) is in a situation where ionic bonding is more easily achieved than with lithium ions (Li + ) rejects negative ion compounds (x - It is possible to bond with ), and in fact, as shown in equation (1) above, Cux2 is formed by ionic bonding.

[0019] Therefore, during the charging phase, negative ion compounds (x - Lithium ions (Li) that have broken away from the ionic bond state with ) + ) is copper ion (Cu 2+ This results in the movement to the negative electrode side instead.

[0020] Lithium ion (Li) is charged by + When lithium reaches the negative electrode, any of the metals constituting the negative electrode—aluminum, iron, nickel, cobalt, or zinc—can form an alloy with lithium through solid solution.

[0021] That is, if each metal is represented as Y, and the relative abundance of lithium in the alloy to each of the aforementioned metals is n, then at the negative electrode, nLi + +Y+ne - →Li n This is due to the establishment of an alloy bonding reaction called Y.

[0022] During the discharge phase, the Li at the negative electrode is caused by the potential difference formed through the electrolyte during charging. n Y→nLi + +Y+ne - This alloy decomposition reaction occurs, and lithium ions (Li + ) moves to the positive electrode side via the organic solvent.

[0023] In response to the aforementioned movement, electrons (e - ) moves from the negative electrode to the positive electrode via the conductive line.

[0024] The electrolyte Cux2 formed by charging returns to the state on the left side of equation (1) during the discharge phase, and copper ions (Cu) formed by this return 2+ ) moves to the positive electrode side, and Cu 2+ +2e - →Cu electrons (e - ) bond with copper ions (Cu 2+ ) becomes the metal that makes up the positive electrode.

[0025] copper ions (Cu 2+ The negative ion compound (x) is released from its bond with ) - ) is lithium ion (Li + This ultimately boils down to recombining with it.

[0026] Thus, in the basic configurations (1) and (2), lithium ions (Li) are used, similar to lithium-ion batteries. + By having the electrons move through the electrolyte, efficient charging and discharging can be achieved, while by selecting metals commonly used for the positive and negative electrodes, a secondary battery that is cheaper than a lithium-ion battery can be realized.

[0027] Lithium ions (Li) are formed before charging and discharging occur and are present in the electrolyte. + In the electrolyte LiX2, which is the source of the formation of ), in reality, in an organic solvent, According to the equilibrium equation TIFF2026052235000005.tif1142, lithium ions (Li + ) and negative ion compounds (x - A state of equilibrium has been achieved in which ) and are partially ionized.

[0028] Similarly, in the electrolyte Cux2 formed by charging, in an organic solvent, An equilibrium state has been achieved according to the equilibrium equation TIFF2026052235000006.tif1351. [Brief explanation of the drawing]

[0029] [Figure 1]This is a schematic diagram showing the configuration of the secondary battery in the basic configurations (1) and (2). [Figure 2] This is a schematic diagram showing the typical configuration of a lithium-ion battery. [Figure 3(a)] This graph shows the relationship between time and voltage, indicating the charging and discharging states, and illustrates the case where aluminum is used as the negative electrode. [Figure 3(b)] This graph shows the relationship between time and voltage, indicating the charging and discharging states, and illustrates the case where iron is used as the negative electrode. [Figure 3(c)] This graph shows the relationship between time and voltage, indicating the charging and discharging states, and illustrates the case where nickel is used as the negative electrode. [Figure 3(d)] This graph shows the relationship between time and voltage, indicating the charging and discharging states, and illustrates the case where cobalt is used as the negative electrode. [Figure 3(e)] This graph shows the relationship between time and voltage, indicating the charging and discharging states, and illustrates the case where zinc is used as the negative electrode. [Figure 4(a)] This graph shows the cycle characteristics based on the relationship between the number of charge / discharge cycles (i.e., the cycle number) and the discharge current capacity, which is expressed in units of mA × time. [Figure 4(b)] This graph shows the relationship between the cycle number and the average discharge voltage. [Figure 4(c)] This graph shows the relationship between current capacity (mA × time), which is the current value at 20 cycles, and voltage (V) at the charging and discharging stages. [Figure 5] This is a schematic diagram showing an embodiment in which a Solid Electrolyte Interphase (SEI coating) is placed between the negative electrode and the separator. [Figure 6] This is a cross-sectional view showing an embodiment in which a magnesium coating is formed on the negative electrode. [Modes for carrying out the invention]

[0030] As shown in Figure 1, the basic configuration (1) is a secondary battery in which copper is used as the positive electrode, aluminum, iron, nickel, cobalt, or zinc is used as the negative electrode, and an electrolyte containing lithium ions and an organic solvent are used as the electrolyte solution.

[0031] Similarly, as shown in Figure 1, the basic configuration (2) is a secondary battery that uses copper as the positive electrode, two or three alloys from aluminum, iron, nickel, cobalt, and zinc as the negative electrode, and an electrolyte containing lithium ions and an organic solvent as the electrolyte solution.

[0032] As is clear from the comparison between Figure 1 and Figure 2, the basic configurations (1) and (2) can achieve a simpler configuration compared to lithium-ion batteries.

[0033] The effects of the basic configurations (1) and (2) have already been explained in the section on effects, but we will now explain them in more detail in relation to specific embodiments.

[0034] Typical examples of LiX forming the electrolytic solute in the basic configurations (1) and (2) of the electrolytic solution include: LIPF6 (Lithium Hexafluorophosphate) LiBF4 (Lithium Tetrafluoroborate) LiClO4 (Lithium Perchlorate) LiFSI (Lithium Bis(Fluorosulfonyl)imide) LiTFSI (Lithium Bis(Trifluoromethanesulfonyl)imide) One could list these:

[0035] In the basic configurations (1) and (2), the use of organic solvents that coexist with the electrolytic solute is considered essential.

[0036] Typical examples of the aforementioned organic solvents include: PC (Propylene Carbonate) EC (Ethylene Carbonate) DMC (Dimethyl Carbonate) DME (Dimethoxyethane) SL (Sulfolane) AST (Asset Liton) GEO5X (Dioxysolane) DRAH (Tetratroplan) BURT (Rammer Petit L'Olactan) One could list these:

[0037] In the basic configurations (1) and (2), as shown in Figure 5, embodiments can be adopted that feature a porous separator capable of absorbing electrolytes placed between the positive electrode and the negative electrode, and a Solid Electrolyte Interphase, i.e., an SEI film, which promotes the permeation of lithium ions, placed between the separator and the negative electrode.

[0038] In the above embodiment, the ion-bonded compound CuX2 purified by charging is absorbed by the porous separator, while the SEI film present on the negative electrode side is absorbed by lithium ions (Li + ) allows permeation to prevent the ionic bond compound CuX2 from approaching the negative electrode, and efficiently utilizes the Li alloy. n It is possible to form Y.

[0039] In the basic configurations (1) and (2), an embodiment can be adopted in which a magnesium coating is formed on the negative electrode, as shown in Figure 6. Furthermore, the magnesium coating can be easily formed by electroplating the metal used for negative electrode formation.

[0040] The chemical properties of lithium are very similar to those of magnesium.

[0041] Therefore, when a magnesium coating is formed on the negative electrode, an alloy can be formed during charging by the easy solid solution of lithium and magnesium.

[0042] Furthermore, while the standard electrode potential of lithium is -3.05V, the standard electrode potential of magnesium is -2.36V, therefore, lithium ions (Li + As long as ionized magnesium (Mg) is in a state where it easily moves to the positive electrode side during discharge, 2+ Before the lithium ions (Li) move from the negative electrode side to the positive electrode side + ) has moved to the positive electrode side, and magnesium ions (Mg 2+ This prevents the movement of ) to the positive electrode.

[0043] The following explanation will be based on each graph. A rectangular copper plate measuring 50 mm x 70 mm x 0.1 mm thick was used as the positive electrode 1, a rectangular iron, nickel, cobalt, or aluminum plate measuring 50 mm x 70 mm x 0.1 mm thick was used as the negative electrode 2, LiBF4 (lithium tetrafluoroate) was used as the electrolyte, a sulfolane-based electrolyte was used as the organic solvent, and glass filter paper was used as the separator.

[0044] The cells were assembled according to the above dimensions, and a 0.1mm thick aluminum laminate film was used as an outer casing, creating a vacuum-sealed secondary battery.

[0045] A charge-discharge cycle test was conducted by repeatedly charging under conditions of 20mA current and 3.7V termination voltage, and discharging under conditions of 10mA current and 3.3V termination voltage, under an ambient temperature of 25℃.

[0046] The results of the aforementioned charge-discharge cycle tests are shown in Figures 3(a), 3(b), 3(c), 3(d), and 3(e) for cases where aluminum, iron, nickel, cobalt, and zinc were used as the negative electrode active material, respectively, by their respective charge-discharge curves.

[0047] In the discharge curves shown in Figures 3(a), (b), (c), (d), and (e), a voltage value indicating a plateau, i.e., a voltage value indicating a relatively stable state, was observed around 3.4V.

[0048] The decay ratios of the discharge curves in Figures 3(a), (b), (c), (d), and (e) compared to the charge curves can be seen to be comparable to those of lithium batteries. Furthermore, since the defendant employs two or three types of alloys in basic configuration (1), there is no doubt that the same charge-discharge characteristics as in the case of Figure 3(a) can be achieved in basic configuration (2).

[0049] As is clear from the graphs in Figures 4(a) and 4(b), the negative electrodes made of iron, nickel, cobalt, and zinc exhibit roughly similar voltage and current characteristics in relation to discharge. In contrast, the aluminum negative electrode exhibits better current characteristics than the four aforementioned negative electrodes, but slightly inferior voltage characteristics.

[0050] As is clear from Figure 4(c), it was found that a considerably high discharge can be achieved when the charging voltage in the 20-cycle stage is set to be approximately the same for any of the metals constituting the negative electrode.

[0051] As is clear from the graphs in Figures 3(a), (b), (c), (d), and (e), and the graphs in Figures 4(a), (b), and (c), in basic configurations (1) and (2), it is quite possible to apply a charging voltage of 3.5V or higher with a capacity of at least 600mAh, and as a result, a discharge voltage of at least approximately 3.2V can be secured. [Industrial applicability]

[0052] The secondary battery of the present invention relating to the basic configurations (1) and (2) has lower manufacturing costs and a simpler configuration compared to lithium-ion batteries, while achieving performance comparable to lithium-ion batteries in terms of charge and discharge characteristics.

[0053] Therefore, the secondary battery according to the present invention can be used in a wide range of industrial fields similar to lithium-ion batteries. [Explanation of Symbols]

[0054] 1 positive electrode 2 negative electrode 20 Magnesium coating 3 Separators 4 Solid Electrolyte Interphase (SEI membrane) 40 Cathode Active Material in Lithium-ion Batteries 50 Negative electrode active material in lithium-ion batteries 60 Positive electrode current collector in lithium-ion batteries 70 Negative electrode current collector in lithium-ion batteries

Claims

1. A secondary battery that uses copper as the positive electrode, aluminum, iron, nickel, cobalt, or zinc as the negative electrode, and an electrolyte containing lithium ions and an organic solvent as the electrolyte solution.

2. A secondary battery that uses copper as the positive electrode, two or three alloys from aluminum, iron, nickel, cobalt, and zinc as the negative electrode, and an electrolyte containing lithium ions and an organic solvent as the electrolyte solution.

3. A secondary battery according to either claim 1 or 2, characterized in that a porous separator capable of absorbing an electrolyte is placed between the positive electrode and the negative electrode, and a solid electrolyte interface that promotes the permeation of lithium ions is placed between the separator and the negative electrode.

4. A secondary battery according to either claim 1 or 2, characterized in that a magnesium coating is formed on the negative electrode.

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