JP6004540B2 - Binder-free battery - Google Patents

Description

The present invention relates to binder-free batteries that conductive material and binder are not mixed.

In lithium ion secondary batteries widely used as rechargeable secondary batteries, the positive electrode is made of an active material such as LiCoO ₂ or LiMn ₂ O _4, a conductive material such as acetylene black, polyvinylidene fluoride: PVDF or polytetra A structure in which a binder such as fluoroethylene: PTFE is mixed and attached to a metal electrode is conventionally known. In the positive electrode, an oxidation-reduction reaction at the active material / binder / conductive material interface, ion transport in the binder, and the like occur, and various factors dominate battery characteristics (cycle characteristics, charge / discharge speed, etc.). .

As a technique using a Prussian blue analog as a positive electrode of a secondary battery, techniques described in Non-Patent Documents 1 to 4 below are conventionally known.
Non-Patent Document 1 (N.Imanishi et al./Journal of Power Sources, 79 (1999) 215-219) shows iron cyanide (Fe ₄ [Fe (CN) ₆ ]) in the middle part of the left column on page 216. ) A mixture of Prussian blue analog powder, 20% by weight of acetylene black conductive material and 0.1% by weight of polytetrafluoroethylene binder is used as the negative electrode. Describes a lithium-ion secondary battery using as a positive electrode, using a polyethylene separator and using LiClO ₄ as an electrolyte.

In Non-Patent Document 2 (N.Imanishi et al./Journal of Power Sources, 81-82 (1999) 530-534), from the second row from the bottom of page 531 to the right column, iron which is a Prussian blue analog. Using a complex powder mixed with acetylene black conductive material 20 [wt%] and polytetrafluoroethylene binder 0.1 [wt%] as a negative electrode, using a metallic lithium thin film as a positive electrode, A lithium ion secondary battery using a separator of polyethylene and using LiClO ₄ as an electrolyte is described. Non-Patent Document 2 describes a battery using an Mn-Fe complex, a Co-Fe complex, a Ni-Fe complex, a Cu-Fe complex, or a V-Fe complex as an iron complex.

  Non-Patent Document 3 (M.Okubo et al./The Journal of Physical Chemistry Letters, 2010, 1,2063-2071) contains powdery Prussian blue analogues (PBAs) in the latter part of page 2069. The paste sample describes that 20% by weight of acetylene black (conductive material) is mixed.

  Non-Patent Document 4 (Daisuke Asakura, 6 others, The Physical Society of Japan, 2010 Autumn Meeting, 23pRG-4) describes lithium as a positive material for powdery Mn-Mn-based cyano complexes as Prussian blue analogues. Techniques relating to ion batteries are described. Note that, as in Non-Patent Documents 3 and 4, the powdery Prussian blue analog is prepared by mixing a binder or the like without a method of directly attaching to the electrode.

N. Imanishi and 6 others, “Lithium intercalation behavior into iron cyanide complex as positive electrode of lithium secondary battery”, Journal of the Power Society of Japan ( Journal of Power Sources), 1999, 79, p215-p219 N. Imanishi, et al., 7 “Lithium intercalation behavior of iron cyanometallates”, Journal of Power Sources, 1999, 81-82, p530- p534 M.Okubo and 6 others, “Switching redox active sites by atomization compatible isomerism of Prussian blue analogue (AxMny [Fe (CN) 6] / nH2O (A: K, Rb)): reversible lithium storage Robust frameworks for reversible Li storage (Switching redox-active sites by valence tautomerism in Prussian blue analogues AxMny [Fe (CN) 6] / nH2O (A: K, Rb): robust frameworks for reversible Li storage) ” (The Journal of Physical Chemistry Letters), 2010, 1, p2063-p2071 Daisuke Asakura and 6 others, "Change of electronic state of Prussian blue analogue in K ion desorption process", The Physical Society of Japan, 2010, 23pRG-4

(Problems of conventional technology)
In the technologies described in Non-Patent Documents 1 to 4, it is described that a relatively large charge / discharge capacity (140 mAh / g, etc.) is exhibited, which is about the same as LiCoO ₂ which is a practical positive electrode material. Is realized. However, in the techniques described in Non-Patent Documents 1 to 4, the cycle characteristics, that is, the characteristics of how much the charge / discharge capacity decreases when repeated charge / discharge is performed are several times, and the cycle characteristics are extremely poor. As it is, practical use is difficult.

This invention makes it a technical subject to improve the cycling characteristics of the positive electrode member which uses a Prussian blue analog.
Moreover, this invention makes it the 2nd technical subject to improve the characteristic of the battery which uses a Prussian blue analog.

In order to solve the technical problem, the binder-free battery of the invention according to claim 1,
A positive electrode member in which a conductive material and a binder are not mixed and a thin film containing a Prussian blue type cyano-bridged metal complex as an active material is formed on the surface of the conductive member;
A negative electrode member paired with the positive electrode member;
An electrolyte containing lithium salt and in contact with the positive electrode member and the negative electrode member;
It is provided with.

The invention according to claim 2 is the binder-free battery according to claim 1,
The positive electrode member having the conductive member made of indium tin oxide, and a thin film containing the cyano-bridged metal complex electrolytically deposited on the surface of the conductive member,
It is provided with.

The invention according to claim 3 is the binder-free battery according to claim 1,
The conductive member made of a transparent material;
A white separator disposed between the positive electrode member and the negative electrode member to isolate the positive electrode member and the negative electrode member and hold the electrolyte ;
The positive electrode member, the negative electrode member, the case containing the separator inside, and a case having a transparent transparent portion that allows the internal positive electrode member to be visually recognized;
It is provided with.

The invention described in claim 4 is the binder-free battery according to claim 1,
When A is at least one kind of alkali metal, x is a number greater than 0 and less than or equal to 2, y is a number greater than 0 and less than or equal to 1, and z is greater than 0 and less than or equal to 14, the chemical formula A _x Mn [Fe (CN ₆ ] The cyano bridged metal complex represented by _y · z H ₂ O,
It is provided with.

The invention according to claim 5 is the binder-free battery according to claim 1,
The thin film composed of particles having a particle size of 100 nm or less;
It is provided with.

According to the first aspect of the present invention, the cycle characteristics of the positive electrode member using the Prussian blue analog can be improved as compared with the conventional configuration in which the conductive material and the binder are mixed, and the battery characteristics are improved. Can be improved.
According to invention of Claim 2, the Prussian blue analog in which a electrically conductive material and a binder are not mixed by electrolytic deposition can be created.
According to invention of Claim 3, the change of the color of the positive electrode member accompanying charging / discharging can be observed through a transparent part.
According to the invention described in claim 4, a battery having high cycle characteristics and a large capacity can be produced using a Mn—Fe-based cyano-bridged metal complex.
According to the fifth aspect of the present invention, charge / discharge characteristics can be improved as compared with a thin film having a particle size of a micron order of particles constituting the thin film.

1 is an explanatory diagram of a binder-free battery according to a first embodiment of the present invention, FIG. 1A is a perspective view, and FIG. 1B is a cross-sectional view taken along line IB-IB in FIG. 1A. FIG. 2 is an explanatory view of a main part of the positive electrode plate of Example 1. 3 is an explanatory diagram of a transparent portion of the binder-free battery of Example 1, and is a cross-sectional view taken along the line III-III in FIG. 1A. 4 is an explanatory diagram of the experimental results of Experimental Example 1 and Comparative Example 1, FIG. 4A is a graph of the experimental results of Experimental Example 1, and FIG. 4B is a graph of the experimental results of Comparative Example 1. FIG. 5 is an explanatory diagram of the experimental results of Experimental Example 2, in which the horizontal axis represents capacity and the vertical axis represents potential with respect to metallic lithium. FIG. 6 is an explanatory diagram of the experimental results of the charge / discharge characteristics of Experimental Example 3, in which the horizontal axis represents capacity and the vertical axis represents electromotive force. FIG. 7 is an explanatory diagram of the experimental results of the cycle characteristics of Experimental Example 3, in which the horizontal axis represents capacity and the vertical axis represents electromotive force. FIG. 8 is an explanatory diagram of the experimental results of Experimental Example 4, in which the horizontal axis represents capacity and the vertical axis represents electromotive force. FIG. 9 is an explanatory diagram of the experimental results of Experimental Example 5-1, in which the horizontal axis represents the X-ray diffraction angle (2θ) and the vertical axis represents the intensity. FIG. 10 is an explanatory diagram of the experimental results of Experimental Example 5-2, in which the horizontal axis represents the X-ray diffraction angle (2θ) and the vertical axis represents the intensity. FIG. 11 is an explanatory diagram of the relationship between the lattice constant and lithium ion, and is a graph in which the horizontal axis represents the lithium ion concentration and the vertical axis represents the lattice constant. FIG. 12 is an explanatory diagram of a layered rock salt structure of lithium cobalt oxide crystals, which is a conventional positive electrode member. 13 is an explanatory diagram of a crystal structure of the Prussian blue type cyano bridged metal complex of Example 1, FIG. 13A is an explanatory diagram of a charged state, and FIG. 13B is an explanatory diagram of a discharged state. 14A and 14B are explanatory diagrams of Experimental Example 6. FIG. 14A is an SEM image of Experimental Example 6-1, FIG. 14B is an SEM image of Experimental Example 6-2, and FIG. 14C is an SEM image of Experimental Example 6-3. 14D is a SEM image of Experimental Example 6-4, and FIG. 14E is a graph of the particle size distribution of Experimental Example 6 in which the horizontal axis indicates the particle size and the vertical axis indicates the frequency. FIG. 15 is an explanatory diagram of the experimental results of Experimental Example 7, and is a graph in which the horizontal axis represents the number of repetitions and the vertical axis represents the capacity.

Next, examples which are specific examples of embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.
In the following description using the drawings, illustrations other than members necessary for the description are omitted as appropriate for easy understanding.

1 is an explanatory diagram of a binder-free battery according to a first embodiment of the present invention, FIG. 1A is a perspective view, and FIG. 1B is a cross-sectional view taken along line IB-IB in FIG. 1A.
Note that, in FIG. 1B, in order to facilitate understanding of the configuration, a part is schematically shown instead of the entire cross section.
In FIG. 1, a binder-free battery 1 according to Example 1 of the present invention has a cylindrical case 2. The case 2 of Example 1 includes a negative electrode portion 3 made of aluminum as an example of a conductive material, and an insulating tube 4 made of an insulating material that covers the outer surface of the negative electrode portion 3. The negative electrode portion 3 includes a cylindrical tube portion 3a, a disk-shaped negative electrode terminal portion 3b supported by the lower end of the tube portion 3a, and a disk-shaped upper plate portion 3c supported by the upper end of the tube portion 3a. And have. A positive electrode support hole 3d as an example of a positive electrode terminal support portion is formed in the central portion of the upper plate portion 3c. A positive electrode terminal portion 7 is supported in the positive electrode support hole 3d through an insulating packing 6.

Inside the case 2 are a plurality of positive plates 11 as an example of a positive electrode member, a plurality of negative plates 12 as an example of a negative member, and a separator 13 disposed between the positive plate 11 and the negative plate 12. And are arranged. In Example 1, the positive electrode plates 11 and the negative electrode plates 12 are alternately arranged in a concentric cylindrical shape, and concentric cylindrical separators 13 are arranged between the positive electrode plates 11 and the negative electrode plate 12. Yes. Each positive electrode plate 11 is electrically connected to the positive electrode terminal portion 7 by a tab 16, and each negative electrode plate 12 is electrically connected to the negative electrode portion 3 by a tab 17. Each separator 13 is connected at its lower end by a disk-shaped plate portion 13a.
Although the negative electrode plate 12 of Example 1 is composed of a metal lithium plate, a conventionally known material such as a carbon-based material can be used.

The separator 13 of Example 1 can use a conventionally known material that can separate the positive electrode plate 11 and the negative electrode plate 12 and can hold lithium and allow lithium ions to pass therethrough. Polyolefin-based materials can be used. In Example 1, the separator 13 having a white surface is used.
In Example 1, as an electrolyte retained in the separator 13, perchlorine was added to a solution in which EC (ethylene carbonate) and DEC (diethyl carbonate) were mixed at a volume ratio of 1: 1 to 1 [mol / l]. While using what dissolved lithium acid (LiClO _4), not limited to this, it is possible to use an electrolyte for conventional batteries.

FIG. 2 is an explanatory view of a main part of the positive electrode plate of Example 1.
In FIG. 2, the positive electrode plate 11 of Example 1 includes a base layer portion 21 as an example of a conductive member and thin film portions 22 formed on both front and back surfaces of the base layer portion 21.
The base layer portion 21 of Example 1 is configured by a transparent electrode of ITO (Indium Tin Oxide).
The thin film portion 22 of Example 1 is made of a thin film containing a conductive material such as acetylene black and a binder such as PTFE and containing a Prussian blue-type cyano-bridged metal complex (Prussian blue analog) as an active material. It is configured. In particular, in Example 1, a complex containing Mn [Fe (CN) ₆ ] ions, which is a so-called Mn—Fe-based complex, is used as an example of a Prussian blue type cyano-bridged metal complex. That is, when A is at least one alkali metal, x is a number greater than 0 and less than or equal to 2, y is a number greater than 0 and less than or equal to 1, and z is a number greater than 0 and less than or equal to 14, the chemical formula A _x Mn [Fe (CN) ₆ ] A cyano bridged metal complex represented by _y · z H ₂ O is used.

In Example 1, the thin film portion 22 is formed on the surface of the ITO substrate that is the base layer portion 21 by electrolytic deposition. Specifically, a 1.0 [mmol / l] solution of K ₃ [Fe (CN) ₆ ] containing [Fe (CN) ₆ ] ³⁻ as an example of a cyano complex ion, and an example of a transition metal ion To a mixed solution of 1.5 [mmol / l] MnCl ₂ containing Mn ²⁺ and 1.0 [mol / l] NaNO ₃ solution containing Na ⁺ , which is an example of an alkali metal ion, Then, the ITO substrate was immersed, and connected to a three-terminal potentiostat so that the ITO substrate became a working electrode, and the thin film portion 22 was electrolytically deposited on the surface of the ITO substrate. In addition, since the potentiostat can employ | adopt the conventionally well-known and commercially available thing, detailed description is abbreviate | omitted.
Such thin film portion 22 of the first embodiment is a film by electrolytic deposition in the was _{Na 1.32 Mn [Fe (CN)} 6] 0.83 · 3.6H 2 O. Hereinafter, in the present specification, this cyano bridged metal complex is abbreviated as “NMF83” using “N” of Na, “M” of Mn, “F” of Fe, and “83” of 0.83. In the case of explaining cyano-bridged metal complexes having different compositions, the same notation is used.

  In Example 1, the thin film portion 22 was formed on the surface of the base layer portion 21 by electrolytic deposition. However, the present invention is not limited to this, and any method such as spin coating or printer technology can be adopted. is there. In addition, when performing electrolytic deposition, as described in Japanese Patent Application No. 2010-0776810 which is an earlier application of the present applicant, an epitaxial stacking technique for depositing a cyano-bridged metal complex in a state where crystal orientations are aligned. It is also possible to form a film by employing the above.

3 is an explanatory diagram of a transparent portion of the binder-free battery of Example 1, and is a cross-sectional view taken along the line III-III in FIG. 1A.
In FIG. 1A and FIG. 3, the case 2 of Example 1 is formed with a remaining amount display window 26 as an example of a transparent portion. The remaining amount display window 26 is formed so as to penetrate the insulating tube 4, the cylindrical portion 3 a of the negative electrode portion 3, and the outermost separator 13, and each of the penetrating portions has PET: polyethylene as an example of a transparent material. A terephthalate film is supported. Therefore, the outermost positive electrode plate 11 is configured to be visible from the outside through the transparent window 26. In addition, the positive electrode plate 11 of Example 1 was brown when charged (the remaining amount was 100%) and transparent when discharged (the remaining amount was 0%).

(Operation of Example 1)
In the binder-free battery 1 of Example 1 having the above-described configuration, the movement of lithium ions and electrons between the negative electrode plate 12 and the positive electrode plate 11 composed of a cyano bridged metal complex in which a conductive material and a binder are not mixed. Along with this, charging and discharging are performed.
The chemical reaction in the positive electrode and the negative electrode during charging is as follows.
_{^{(Cathode) Li 2 Mn II [Fe II}} (CN) 6] → LiMn II [Fe III (CN) 6] + Li + + e -
^{→ Mn III [Fe III (CN} ) 6] + 2Li + + 2e -
(Negative electrode) Li ^{+ +} e ^- → Li

At this time, the remaining amount display window 26 is formed in the binder-free battery 1 of Example 1, and the positive electrode plate 11 disposed in front of the white separator 13 is visible from the outside. And in the positive electrode plate 11 of Example 1, since NMF83 turns brown when charging is completed and becomes transparent when discharged, brown is visually recognized through the remaining amount display window 26 when there is a remaining amount of battery. The When the remaining amount of the battery runs out, the NMF 83 of the thin film portion 22 becomes transparent and the ITO of the base layer portion 21 is also transparent, so that the white color of the separator 13 on the back side is visually recognized.
In the prior art, when a conductive material such as acetylene black or a binder is mixed, the color of the positive electrode plate 11 becomes black of acetylene black, etc., and almost no color change can be confirmed. Needed to be equipped with a remaining amount indicator. When the remaining amount indicator is provided, it is necessary to supply electric power from the battery 1, and there is a problem that power consumption occurs.
On the other hand, in the binder-free battery 1 of Example 1, the presence or absence of the remaining amount can be visually recognized only by checking the color change of the cyano-bridged metal complex itself in which the conductive material and the binder are not mixed in the remaining amount display window 26. It is possible to easily check whether there is a remaining amount while eliminating power consumption.

(Experimental example)
Next, an experiment for confirming the effect of Example 1 was performed.
(Experimental example 1)
In the experiment, NMF83 formed on the surface of the ITO substrate by the electrolytic deposition method of Example 1 was immersed in an EC: DEC electrolyte in which 1 mol / l of lithium perchlorate was dissolved, and charging / discharging was performed. Repeated 10 times. One charge / discharge time was about 2 hours (0.5 C) for both charging and discharging.
(Comparative Example 1)
In Comparative Example 1, the NMF83 thin film obtained in Experimental Example 1 was peeled to form a powder, and a mixture of carbon black as a conductive material and PTFE as a binder was applied to a stainless steel mesh in the same manner as a conventional electrode. Then, a positive electrode was prepared, and the experiment was conducted in the same manner as in Experimental Example 1.
FIG. 4 shows the experimental results.

4 is an explanatory diagram of the experimental results of Experimental Example 1 and Comparative Example 1, FIG. 4A is a graph of the experimental results of Experimental Example 1, and FIG. 4B is a graph of the experimental results of Comparative Example 1.
In the graph of FIG. 4, the horizontal axis represents capacity and the vertical axis represents voltage.
In FIG. 4A, in Experimental Example 1, it was confirmed that the capacity decreased during the first to second charging, but thereafter, the capacity hardly decreased for both the 10th charging and discharging.
On the other hand, in FIG. 4B, it was confirmed that in Comparative Example 1, the capacity gradually decreased when charging and discharging were repeated.

  Therefore, in the binder-free battery 1 of Example 1, the capacity, which is a characteristic of the battery at the time of charging / discharging, is less likely to decrease compared to the conventional case where no conductive material, binder, or the like is added. Can be created. In particular, in the binder-free battery 1 of Example 1 using a thin-film cyano-bridged metal complex, repeated charge / discharge characteristics can be greatly improved as compared with the conventional technique using a powdery cyano-bridged metal complex. . In addition, the binder-free battery 1 of Example 1 can be realized with a low-cost cyano-bridged metal complex as compared with a conventional positive electrode using rare elements such as Li and Co, and the cost is greatly reduced. Is possible.

(Experimental example 2)
In Experimental Example 2, in the same manner as in Example 1, a thin film of Prussian blue type cyano-bridged metal complex was formed on the surface of the ITO substrate by electrolytic deposition. When the prepared thin film is subjected to ICP-AES analysis and CNH organic analysis (analysis to determine the weight ratio of C, N, H by burning the sample into gas), Na _1.24 Mn [Fe (CN) ₆ ] _0.81 3.0H ₂ O (NMF81). The obtained thin film was colorless and transparent, and the film thickness was 1 [μm]. Next, the lithium ion was immersed in an EC: DEC electrolyte in which 1 mol / l of lithium perchlorate was dissolved, and charge / discharge was performed to replace sodium ions with lithium ions. In this way, a thin film of lithium compound (Li _1.24 Mn [Fe (CN) ₆ ] _0.81 · 3.0H ₂ O (LMF81)) was obtained.
The lithium compound thin film thus prepared was immersed in an EC: DEC electrolyte in which 1 mol / l of lithium perchlorate was dissolved, and charge / discharge characteristics were measured using Li metal as a negative electrode. The experimental results are shown in FIG.

FIG. 5 is an explanatory diagram of the experimental results of Experimental Example 2, in which the horizontal axis represents capacity and the vertical axis represents potential with respect to metallic lithium.
In Experimental Example 2, the charge / discharge rate was 0.5 C, and the upper and lower limits of the voltage were 4.2 [V] and 2 [V]. Further, the capacity of the thin film electrode was 110 [mAh / g], which was almost the same as the theoretical capacity of 115 [mAh / g] and also showed high cycle characteristics. In addition, when an endurance test was performed 100 times at a charge / discharge rate of 0.5 C, the charged amount showed a high value of 87% of the initial value.
The charging curve shows two plateaus (stagnation state) at 3.4 [V] and 3.9 [V]. These plateaus correspond to the oxidation of [Fe (CN) ₆ ] ^{4− and} the oxidation of Mn ²⁺ , respectively. On the other hand, the discharge curve shows three plateaus at 3.9 [V], 3.6 [V], and 3.4 [V]. The first and second plateaus are considered to correspond to the reduction of Mn ³⁺ , and the third plateau corresponds to the reduction of [Fe (CN) ₆ ] ³⁻ . Thus, the positive electrode of Example 1 exhibits an electromotive force of 3.5 [V] to 3.9 [V] with respect to lithium metal (cathode).

(Experimental example 3)
In Experimental Example 3, using the same LMF81 as in Experimental Example 2, experiments related to charge / discharge characteristics (C rate), capacity, and electromotive force were performed. In the experiment, the same thin film of LMF81 as in Experimental Example 2 was used as a positive electrode, lithium metal was used as a negative electrode, and discharge rates were 1C, 10C, 30C, and 100C, and charge / discharge characteristics were evaluated. In the case where the discharge rate is 100 C, the cycle characteristics were also tested. The experimental results are shown in FIGS.

FIG. 6 is an explanatory diagram of the experimental results of the charge / discharge characteristics of Experimental Example 3, in which the horizontal axis represents capacity and the vertical axis represents electromotive force.
FIG. 7 is an explanatory diagram of the experimental results of the cycle characteristics of Experimental Example 3, in which the horizontal axis represents capacity and the vertical axis represents electromotive force.
As can be seen from the experimental results in FIG. 6, the capacity and the electromotive force decrease as the discharge rate increases. However, even at a high rate of 100C, the capacity can be secured about 70% of 1C and the electromotive force of 3V class It was confirmed that can be secured. In FIG. 7, even at a high rate of 100 C, even when charging / discharging is performed 10 cycles (repeated 10 times), almost the same charging / discharging characteristics as in the case of 1 cycle are obtained. It was confirmed that there was little deterioration and high cycle characteristics were obtained.

(Experimental example 4)
In Experimental Example 4, an experiment was conducted on the relationship between the thickness of the Prussian blue-type cyano-bridged metal complex and the discharge rate. In Experimental Example 3, when preparing a thin film by the electrolytic deposition method, the positive electrode plate with the adjusted film thickness was prepared by adjusting the electrolytic deposition time, and while changing the charge / discharge rate, Experimental Example 2, The relationship between capacity and voltage was measured in the same manner as in FIG.
(Experimental example 4-1)
In Experimental Example 4-1, a thin film of LMF81 having a thickness of 16.0 [μm] was used. Experiments were performed at charge / discharge rates of 0.1C, 1C, 4C, 20C, and 60C.
(Experimental example 4-2)
In Experimental Example 4-2, a thin film of LMF81 having a film thickness of 3.9 [μm] was used. Experiments were conducted at charge / discharge rates of 0.1C, 4C, 15C, 63C, and 189C.
(Experimental example 4-3)
In Experimental Example 4-3, a thin film of LMF81 having a thickness of 0.05 [μm] = 50 [nm] was used. Experiments were performed at charge / discharge rates of 2C, 71C, and 740C.
The experimental results are shown in FIG.

FIG. 8 is an explanatory diagram of the experimental results of Experimental Example 4, in which the horizontal axis represents capacity and the vertical axis represents electromotive force.
In FIG. 8, as can be seen from Experimental Examples 4-1 to 4-3, it was confirmed that the thinner the film thickness, the easier it is to secure the capacity and electromotive force even when the charge / discharge rate is high. In particular, by setting the film thickness to the order of 0.01 μm (10 nm order) as in Experimental Example 4-3, compared to Experimental Example 4-1 on the order of 10 μm and Experimental Example 4-2 on the order of 1 μm. It was confirmed that the discharge rate (C rate) increased by two orders and the C rate increased dramatically as the film thickness decreased. Accordingly, it is expected to realize a battery capable of high-speed charge / discharge (high power density) exceeding 1000 C and having a large capacity (high energy density), and a battery that can be used in an electric vehicle or the like is also expected.

(Experimental example 5)
In Experimental Example 5, an experiment was performed to confirm whether or not a structural phase transition of the thin film occurred when charging / discharging in a lithium battery cell. In the experiment, whether or not a structural phase transition was exhibited with respect to ingress and desorption (increase or decrease in lithium) of lithium ions was performed. In the experiment, charging and discharging were performed in a lithium battery cell having a lithium metal cathode, the battery was disassembled in a glove box, the powder was sealed in a capillary, and synchrotron radiation X-rays (wavelength: 0.4990 [Å]) were emitted. The powder diffraction experiment was conducted using the same.

(Experimental example 5-1)
In Experimental Example 5-1, NMF83 similar to Experimental Example 1 was replaced with Lithium ion in the same manner as in Experimental Example 2, but LMF83 (Li _x Mn [Fe (CN) ₆ ] _0.83 · 3.5H ₂ O) Was used as the positive electrode plate. The number x of lithium ions was measured when x = 1.3, 0.9, 0.7, 0.4, and 0.1.
(Experimental example 5-2)
In Experimental Example 5-2, LMF81 similar to that in Experimental Example 2 (Li _x Mn [Fe (CN) ₆ ] _0.81 · 3.0H ₂ O) was used as the positive electrode plate. The number (concentration) x of lithium ions was measured when x = 1.24 and 0.52.
The diffraction pattern which is an experimental result is shown in FIGS.

FIG. 9 is an explanatory diagram of the experimental results of Experimental Example 5-1, in which the horizontal axis represents the X-ray diffraction angle (2θ) and the vertical axis represents the intensity.
FIG. 10 is an explanatory diagram of the experimental results of Experimental Example 5-2, in which the horizontal axis represents the X-ray diffraction angle (2θ) and the vertical axis represents the intensity.
9 and 10, the same diffraction pattern can be obtained even when lithium enters and desorbs. That is, the Prussian blue type cyano-bridged metal complex has a structural phase transition even when charged and discharged. It was confirmed that it does not cause. Moreover, when the obtained diffraction pattern was subjected to Rietveld analysis, it was a face-centered cubic lattice model.
Further, FIG. 11 shows a graph obtained by plotting the lattice constant as a function of lithium ions from the obtained results.

FIG. 11 is an explanatory diagram of the relationship between the lattice constant and lithium ion, and is a graph in which the horizontal axis represents the lithium ion concentration and the vertical axis represents the lattice constant.
In FIG. 11, the lattice constant decreases when x is near 0, but the lattice constant is substantially constant in other lithium ion concentration regions.

FIG. 12 is an explanatory diagram of a layered rock salt structure of lithium cobalt oxide crystals, which is a conventional positive electrode member.
Lithium cobalt oxide (LiCoO ₂ ) widely used as a positive electrode material for conventional lithium ion batteries has a lattice of CoO ₂ in which cobalt ions 01 and oxygen 02 are bonded as shown in FIG. The lithium ions 03 are located between CoO ₂ layers that are strongly covalently bonded. Therefore, in the conventional lithium cobaltate positive electrode material, when lithium ions are extracted during charging, a very complicated and intense structural phase transition is exhibited, and finally, CdI ₂ type CoO ₂ is generated, There has been a problem of adversely affecting battery characteristics (cycle characteristics and charge / discharge characteristics).
In addition, spinel-structured LiMn ₂ O ₄ used as a positive electrode material for lithium ion batteries is positioned so as to play a role of three-dimensionally connecting lithium ions to MnO ₆ octahedrons. However, when the lithium ion concentration is low with the extraction of lithium ions, γ-MnO ₂ is generated and structural phase transition is induced, which has a problem of adversely affecting battery characteristics.

Furthermore, in LiFePO ₄ having an olivine structure used as a positive electrode material for lithium ion batteries, it is located in a one-dimensional gap created by the PO ₄ tetrahedron and the FeO ₆ octahedron. However, when lithium ions are extracted, the PO ₄ tetrahedron and the FeO ₆ octahedron skeleton are maintained, and FePO ₄ is generated. For this reason, there has been a problem in that the reaction proceeds in a two-phase coexistence state of “LiFePO ₄ ” and “FePO ₄ ” with charge and discharge, and the battery characteristics are adversely affected. In addition, this material system is extremely low in electron conductivity because of the extrinsic electron system, and is considered to be difficult to charge and discharge at a high rate because it is a two-phase coexistence system. Although the rate has been improved by coating the surface of LiFePO ₄ with a carbon-based electronic conductive material, the problem of the two-phase coexistence system has not been solved, and an extra effort of coating is required. It was.

13 is an explanatory diagram of a crystal structure of the Prussian blue type cyano bridged metal complex of Example 1, FIG. 13A is an explanatory diagram of a charged state, and FIG. 13B is an explanatory diagram of a discharged state.
In FIG. 13, in the Prussian blue type cyano bridged metal complex of Example 1, two transition metals of iron 31 and manganese 32 are bridged to the cyano group 33 to form a three-dimensional polymer structure. This polymer structure is a structure having many gaps, and the lithium ions 34 can occupy voids. Therefore, lithium ions can pass, conduct, and move three-dimensionally in the six directions of front, rear, left, and right and up and down through the gap.
Therefore, in the positive electrode plate 11 of Example 1, Mn [Fe (CN) ₆ is different from the conventional material in which a structural phase transition occurs or a two-phase coexistence state occurs when lithium ions are extracted. The crystal structure is solid, it is difficult for structural phase transitions and two-phase coexistence to occur, and it can be expected that there is little adverse effect on battery characteristics structurally, which can also be considered from experimental results. In particular, in Example 1 in which lithium ion can move three-dimensionally compared to one-dimensional LiFePO ₄ or two-dimensional LiCoO ₂ in the electric path of ions, lithium can move at high speed, that is, the charge / discharge rate is improved. I can expect.

  In particular, the Prussian blue-type cyano-bridged metal complex of Example 1 is formed on an ITO substrate, and is in electrical contact with the substrate as compared with a conventional configuration in which a powdery complex is solidified with a binder or the like. Has improved. Therefore, compared with the structure described in the nonpatent literatures 1-4, the capacity | capacitance has improved to near the theoretical value and the charge / discharge rate has also improved.

(Experimental example 6)
In Experimental Example 6, an experiment related to the particle size of the particles constituting the thin film was performed. In Experimental Example 6, the surface of the thin film used in Experimental Example 4 was observed using a scanning electron microscope (SEM), the particle size distribution was measured from the surface image, and the average particle size was calculated. . That is, in Experimental Examples 6-1, 6-2, and 6-3, the average particle diameter was measured for the thin films used in Experimental Examples 4-1, 4-2, and 4-3, respectively. In Experimental Example 6-4, the average particle size was also measured for the LMF81 thin film having a thickness of 0.55 [μm].
The experimental results are shown in FIG.

14A and 14B are explanatory diagrams of Experimental Example 6. FIG. 14A is an SEM image of Experimental Example 6-1, FIG. 14B is an SEM image of Experimental Example 6-2, and FIG. 14C is an SEM image of Experimental Example 6-3. 14D is a SEM image of Experimental Example 6-4, and FIG. 14E is a graph of the particle size distribution of Experimental Example 6 in which the horizontal axis indicates the particle size and the vertical axis indicates the frequency.
In FIG. 14, in Experimental Example 6-1, the average particle diameter was 7 [μm], and the error was ± 2 [μm]. In Experimental Example 6-2, the average particle size is 1.1 ± 4 [μm], in Experimental Example 6-3 is 0.3 ± 1 [μm], and in Experimental Example 6-4 is 0.7 ± 2 [μm]. μm].
Therefore, it was confirmed from Experimental Example 4 that by reducing the thickness of the thin film to the nano order, the charge / discharge rate can be improved by two orders or more compared to the case of the micron order. This is because when the thin film is thick to the micron order, the crystal grains are large and lithium needs to move over a long distance. However, when the thin film is thin to the nano order, the crystal grains become small and the lithium is reduced. It is considered that the moving distance is shortened and the charge / discharge rate is improved. From the results of Experimental Examples 4 and 6, the charge / discharge rate is improved as the particle size is reduced. In particular, from the results of Experimental Examples 4-3 and 6-3, the grain size of the crystal grains is on the order of 100 nm or less. It was confirmed that the charge / discharge rate was remarkably improved. Therefore, from the results of Experimental Examples 4 and 6, the rate can be improved by reducing the crystal grains even in a thick film.

(Experimental example 7)
In Experimental Example 7, an experiment related to repetition characteristics was performed. In the experiment, the same NMF83 as in Experimental Example 1 was used, and the capacity when charging / discharging was performed at a constant current density of 56 [mA / g] was measured. The measurement was repeated 1 to 100 times of charge and discharge, and the change in capacity at that time was observed. The experimental results are shown in FIG.

FIG. 15 is an explanatory diagram of the experimental results of Experimental Example 7, and is a graph in which the horizontal axis represents the number of repetitions and the vertical axis represents the capacity.
In FIG. 15, the electrode using the NMF83 thin film does not decrease in electric capacity even after 100 repetitions, and has a capacity of 87% with respect to the initial value of the capacity even after 100 repetitions. confirmed. Therefore, it was confirmed that the repetition characteristics were sufficiently high.

(Example of change)
As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the said Example, A various change is performed within the range of the summary of this invention described in the claim. It is possible. Modification examples (H01) to (H08) of the present invention are exemplified below.
(H01) Although the cylindrical configuration is exemplified as the shape of the binder-free battery in the above embodiment, it is not limited to this, and any shape such as a button shape or a square shape can be used. Therefore, it is not limited to the shape of the concentric cylindrical electrode plate, but can be a disc shape or a square flat plate shape according to the shape of the battery. Further, the number of the negative electrode plate, the positive electrode plate, and the separator, that is, the number of stacked layers is not limited to the number illustrated in the embodiment, and may be an arbitrary number depending on the capacity or the like.

(H02) In the above examples, the cyano bridged metal complex is not limited to the configuration exemplified in the experimental example, and A is at least one alkali metal, M and M ′ are at least transition metals, depending on the production method and application. When x is a number greater than 0 and less than or equal to 2, y is a number greater than 0 and less than or equal to 1, and z is a number greater than 0 and less than or equal to 14, the chemical formula A _x M [M ′ (CN) ₆ ] _y · Cyano-bridged metal complexes represented by z H ₂ O can be used. Examples of the alkali metal of A include Li, Na, K, Rb, and Cs. Examples of the M transition metal include Fe, Mn, Ni, Co, Cr, V, Cu, and Zn. Examples of the transition metal of M ′ include Fe, Cr, V, Mn, and Ti. X, y and z represent the ratio (mole) of alkali metal A, M ′ (CN) ₆ and crystal water H ₂ O to 1 mol of transition metal M, respectively. Depending on the structure, x can take values from 0 to 2, y from 0 to 1, and z from 0 to 14. In the specification and claims of the present application, the “complex of different composition” refers to a complex in which at least one of the alkali metal A, the transition metal M, M ′ and the number x, y is different.
Therefore, as shown in the experimental examples, it is not limited to the cheapest and large capacity Mn-Fe-based cyano-bridged metal complexes, but other cyano-bridged metal complexes such as Cu-Fe and Mn-Mn Alternatively, Ni-Fe-based, Co-Fe-based, etc. cyano-bridged metal complexes can also be used depending on the capacity required for the battery.

(H03) In the above embodiment, the configuration in which a cyano-bridged metal complex is formed on a transparent ITO substrate is exemplified, but the present invention is not limited to this, and the surface of an opaque substrate, for example, a conductor such as platinum, gold, or aluminum It is possible to form a film.
(H04) In the above-described embodiment, the remaining amount display window 26 is illustrated as being formed in a part of the case 2, but is not limited thereto, and the entire case 2 may be transparent. It is.

(H05) In the above embodiments, the display of the remaining amount is exemplified based on the color change. However, the present invention is not limited to this, and the characters are displayed by arranging the cyano-bridged metal complexes using a printing technique or the like. Is also possible. For example, using a cyano-bridged metal complex that develops color when charged and becomes transparent when discharged, displays “remaining” when charging, and the display disappears (becomes transparent) when discharged, or becomes transparent when charged It is also possible to use a cyano-bridged metal complex that is colored at the time of discharge and the display disappears at the time of charging, and “please charge” is displayed at the time of discharging. Moreover, it is also possible to combine these. Furthermore, it is possible to arrange the three primary colors so that the color changes according to the state of charge and discharge, or to display characters in color.

(H06) In the above-described embodiment, it is also possible to use in combination with a power generation element such as a so-called solar cell, such as charging the generated electricity with the binder-free battery 1 or supplying electric power to an electronic device.
(H07) In the above-described embodiment, the configuration in which the thin film portion 22 is formed on both surfaces of the base layer portion 21 is exemplified, but the present invention is not limited to this, and a configuration in which the thin film portion 22 is formed only on one surface is also possible.
(H08) In the above embodiment, it is desirable to use a nano-order thin film with small crystal grains in order to improve the charge / discharge rate. However, the present invention is not limited to this, and it is possible to increase the thickness while reducing the crystal grains. Thus, it can be expected to improve the capacity while improving the charge / discharge rate.

In the battery using the cyano bridged metal complex of the present invention described above, since the cyano bridged metal complex can be thinned, for example, a card-embedded thin film battery or electrical appliance (e.g., electric motor) embedded in an IC card or the like. It can be suitably applied to a toothbrush, a mobile phone, a notebook computer, or the like.
In addition, the positive electrode member and the negative electrode member of the present invention can be multilayered to increase the capacity, and can be expected to be applied to batteries such as electric vehicles.

1 ... Binder-free battery,
2 ... Case,
11 ... positive electrode member,
12 ... negative electrode member,
13 ... Separator,
21: Conductive member,
22 ... thin film,
26: Transparent portion.

Claims (5)

A positive electrode member in which a conductive material and a binder are not mixed and a thin film containing a Prussian blue type cyano-bridged metal complex as an active material is formed on the surface of the conductive member;
A negative electrode member paired with the positive electrode member;
An electrolyte containing lithium salt and in contact with the positive electrode member and the negative electrode member;
A binder-free battery comprising: The positive electrode member having the conductive member made of indium tin oxide, and a thin film containing the cyano-bridged metal complex electrolytically deposited on the surface of the conductive member,
The binder-free battery according to claim 1, comprising: The conductive member made of a transparent material;
A white separator disposed between the positive electrode member and the negative electrode member to isolate the positive electrode member and the negative electrode member and hold the electrolyte ;
The positive electrode member, the negative electrode member, the case containing the separator inside, and a case having a transparent transparent portion that allows the internal positive electrode member to be visually recognized;
The binder-free battery according to claim 1, comprising: When A is at least one kind of alkali metal, x is a number greater than 0 and less than or equal to 2, y is a number greater than 0 and less than or equal to 1, and z is greater than 0 and less than or equal to 14, the chemical formula A _x Mn [Fe (CN ₆ ] The cyano bridged metal complex represented by _y · zH ₂ O,
The binder-free battery according to claim 1, comprising: The thin film composed of particles having a particle size of 100 nm or less;
The binder-free battery according to claim 1, comprising: