WO2014129096A1 - リチウムイオン二次電池及びその製造方法 - Google Patents
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- WO2014129096A1 WO2014129096A1 PCT/JP2014/000036 JP2014000036W WO2014129096A1 WO 2014129096 A1 WO2014129096 A1 WO 2014129096A1 JP 2014000036 W JP2014000036 W JP 2014000036W WO 2014129096 A1 WO2014129096 A1 WO 2014129096A1
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
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- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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- H01M2220/00—Batteries for particular applications
- H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E60/10—Energy storage using batteries
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Definitions
- the present invention relates to a lithium ion secondary battery with improved battery capacity and a method for manufacturing the same.
- Lithium ion secondary batteries are widely used as power sources for portable electronic devices.
- a composite oxide such as LiCoO 2 and LiMn 2 O 4 is mainly used as the positive electrode active material of the lithium ion secondary battery, and a graphite-based material is used as the negative electrode active material. Since these materials have small irreversible capacity, the capacity as a battery can be taken out without reducing the capacity of the positive electrode or the negative electrode so much.
- the silicate material has a problem that its irreversible capacity is larger than that of a conventional composite oxide such as LiCoO 2 and LiMn 2 O 4 . Therefore, when a battery is composed of a positive electrode using a silicate material having a large irreversible capacity as a positive electrode active material and a negative electrode using a graphite-based material having a small irreversible capacity as a negative electrode active material, the actual capacity of the negative electrode There is a problem of reduction.
- tin-based materials and silicon-based materials having larger capacities than graphite materials are being conducted as negative electrode active materials.
- the tin-based material and the silicon-based material have a problem that the irreversible capacity is large. Therefore, when a battery is composed of a positive electrode using the above composite oxide having a small irreversible capacity as a positive electrode active material and a negative electrode using a tin-based material or a silicon-based material having a large irreversible capacity as a negative electrode active material, the positive electrode This causes a problem that the actual capacity of the battery is reduced. In order to improve this, it is conceivable to reduce the irreversible capacity by pre-doping lithium into a tin-based or silicon-based material. However, since the pre-doping process increases, it is disadvantageous for battery mass production.
- Patent Document 1 proposes that a metal compound that is electrochemically reduced to a metal by charging is added to the negative electrode, thereby making it possible to maximize the reversible capacity of the positive electrode and the negative electrode and increase the capacity. Has been. However, the number of steps for adding a metal compound to the negative electrode is increased, which is not suitable for battery mass production.
- Patent Document 2 the amount of use of the negative electrode active material is reduced as compared with the prior art based on the knowledge that positive ions other than Li ions are transferred from the positive electrode active material Li 2 MnO 3 to the negative electrode by the initial charge. Accordingly, it has been proposed to reduce the battery weight and size without reducing the battery capacity by setting the actual capacity of the negative electrode smaller than the actual capacity of the positive electrode.
- the inventor has developed a lithium ion secondary battery that can effectively extract the actual capacity of the battery by a method different from Patent Documents 1 and 2.
- the present invention has been made in view of such circumstances, and an object of the present invention is to provide a lithium ion secondary battery that can effectively take out the actual capacity of the battery.
- a lithium ion secondary battery includes a positive electrode including a positive electrode active material composite formed by combining a lithium silicate material and a carbon material, a negative electrode including a negative electrode active material having silicon, and an electrolyte.
- the irreversible capacity of the positive electrode is A and the irreversible capacity of the negative electrode is B, the relationship is 0.8 ⁇ B / A ⁇ 1.2.
- a method for producing a lithium ion secondary battery of the present invention includes a positive electrode including a positive electrode active material composite formed by combining a lithium silicate material and a carbon material, a negative electrode including a negative electrode active material having silicon, an electrolyte,
- a lithium ion secondary battery manufacturing method for manufacturing a lithium ion secondary battery comprising: the lithium silicate material and the carbon material by mechanically milling the lithium silicate material and the carbon material.
- the relationship is 0.8 ⁇ B / A ⁇ 1.2. For this reason, the actual capacity of the battery can be taken out effectively.
- the SEM photograph of sample 5 is shown.
- An SEM photograph of Sample 6 is shown.
- the SEM photograph of the cross section of the sample 4 is shown, and the scale of the upper figure of FIG. 10 and the lower figure is 5 micrometers and 1 micrometer.
- the SEM photograph of the cross section of the sample 6 is shown, and the upper, middle and lower scales of FIG. 11 are 10 ⁇ m, 5 ⁇ m and 1 ⁇ m.
- FIG. It is a figure which shows the charging / discharging curve of the half battery produced using the positive electrode active material of the sample 4.
- FIG. 4 is a graph showing the relationship between the ratio (B / A) of the irreversible capacity B of the negative electrode to the irreversible capacity A of the positive electrodes of the batteries 1 to 3 and the initial discharge capacity retention rate of each battery.
- the lithium ion secondary battery according to the embodiment of the present invention will be described in detail.
- the positive electrode of the lithium ion secondary battery includes a positive electrode active material composite formed by combining a lithium silicate material and a carbon material, and the negative electrode includes a negative electrode active material having silicon.
- the inventor has found that the irreversible capacity can be adjusted in the step of obtaining a positive electrode active material composite by combining a lithium silicate material and a carbon material.
- the irreversible capacity with respect to the reversible capacity of the positive electrode is changed by operating the process of compositing the lithium silicate material and the carbon material.
- the difference between the irreversible capacity of the positive electrode and the irreversible capacity of the negative electrode is set so that the irreversible capacity A of the positive electrode approaches the irreversible capacity B of the negative electrode, and 0.8 ⁇ B / A ⁇ 1.2.
- the capacities of the positive electrode and the negative electrode include an irreversible capacity and a reversible capacity.
- the irreversible capacity refers to the capacity that cannot be discharged among the charge capacity of each electrode, and the irreversible capacity corresponds to the capacity difference between the initial charge capacity of each electrode and the initial discharge capacity of each electrode.
- the reversible capacity refers to the capacity that can be discharged out of the charge capacity of each electrode, and corresponds to the initial discharge capacity of each electrode.
- the combined capacity of the reversible capacity and the irreversible capacity corresponds to the initial charge capacity.
- the initial charge capacity, reversible capacity, and irreversible capacity of the positive electrode and the negative electrode are the capacities detected when the half-cells each including the positive electrode and the negative electrode of the present invention as one electrode are assembled.
- the actual capacity refers to the initial discharge capacity that can be actually taken out when the secondary battery of the present invention including the positive electrode and the negative electrode is assembled.
- the first time refers to the time when voltage is first applied to the positive and negative electrodes to which no voltage is applied.
- the irreversible capacity of the positive electrode is generated when Li ions are released from the positive electrode active material at the first charge, and the released Li ions are not occluded by the positive electrode active material at the next discharge. Further, the irreversible capacity of the negative electrode is caused by the fact that Li ions occluded in the negative electrode active material during the initial charge are not released during the next discharge.
- FIG. 1 is an explanatory diagram showing the relationship between the positive electrode and the negative electrode when the irreversible capacities of the positive electrode and the negative electrode are approximate.
- the irreversible capacity A of the positive electrode and the irreversible capacity B of the negative electrode are approximated to establish a relationship of 0.8 ⁇ B / A ⁇ 1.2. Is done. That is, most of the irreversible capacity of Li ions released from the positive electrode during the first charge is stored in the irreversible capacity of the negative electrode. At the first charge, the irreversible capacity of the positive electrode and the irreversible capacity of the negative electrode are satisfied without excess or deficiency. Therefore, the reversible capacity of both electrodes can be taken out effectively. There is no need to pre-dope Li into the negative electrode.
- the relationship between A and B is preferably 1.0 ⁇ B / A ⁇ 1.2.
- the irreversible capacity A of the positive electrode and the irreversible capacity B of the negative electrode are further approximated, and the reversible capacity of both electrodes can be effectively taken out.
- FIG. 2 is an explanatory diagram showing the relationship between the positive electrode and the negative electrode when the irreversible capacity of the positive electrode is larger than the irreversible capacity of the negative electrode.
- the irreversible capacity of the positive electrode is made larger than the irreversible capacity of the negative electrode, so that B / A is 0.8 or less.
- the irreversible capacity A of the positive electrode is larger than the irreversible capacity B of the negative electrode.
- the difference (AB) between the irreversible capacity of the positive electrode and the irreversible capacity of the negative electrode is not utilized. For this reason, the actual capacity of the negative electrode becomes smaller than the reversible capacity of the negative electrode.
- FIG. 3 is an explanatory diagram showing the relationship between the positive electrode and the negative electrode when the irreversible capacity of the positive electrode is smaller than the irreversible capacity of the negative electrode.
- the irreversible capacity of the positive electrode is made smaller than the irreversible capacity of the negative electrode and B / A is 1.2 or more
- the irreversible capacity A of the positive electrode is smaller than the irreversible capacity B of the negative electrode.
- the difference (BA) between the irreversible capacity of the negative electrode and the irreversible capacity of the positive electrode is not utilized. For this reason, the actual capacity of the positive electrode becomes smaller than the reversible capacity of the positive electrode.
- the relationship is preferably 0.8 ⁇ D / C ⁇ 1.2. Furthermore, a relationship of 1.0 ⁇ D / C ⁇ 1.1 is preferable. In this case, the reversible capacity C of the positive electrode and the reversible capacity D of the negative electrode are approximated.
- the reversible capacity of the positive electrode and the reversible capacity of the negative electrode contribute to the occlusion / release reaction of Li ions without excess or deficiency. For this reason, mutual reversible capacity can be taken out effectively.
- the reversible capacity D of the negative electrode is excessively smaller than the reversible capacity C of the positive electrode.
- a part of the reversible capacity D of the negative electrode cannot be taken out as the actual capacity of the battery, and a part of the negative electrode active material becomes a surplus.
- the reversible capacity C of the positive electrode is excessively smaller than the reversible capacity D of the negative electrode. A part of the reversible capacity C of the positive electrode cannot be taken out as the actual capacity of the battery, and a part of the positive electrode active material may become an excess.
- the positive electrode has a positive electrode active material.
- the positive electrode active material is composed of a positive electrode active material composite formed by combining a lithium silicate material and a carbon material.
- the positive electrode active material composite is preferably formed by combining a lithium silicate material and a carbon material by subjecting the lithium silicate material and the carbon material to mechanical milling.
- the irreversible capacity of the positive electrode active material composite is mainly manipulated.
- the irreversible capacity of the positive electrode active material composite can be adjusted by, for example, the energy given to the lithium silicate-based material and the carbon material during the composite. The greater the energy applied, the smaller the irreversible capacity of the positive electrode, and the smaller the energy, the greater the irreversible capacity of the positive electrode.
- the lithium silicate-based material and the carbon material are mechanically milled to compound the lithium silicate-based material and the carbon material into the positive electrode active material composite, and the irreversible capacity of the positive electrode is defined as A.
- the irreversible capacity of the negative electrode is B, it is preferable that the relationship is 0.8 ⁇ B / A ⁇ 1.2.
- the irreversible capacity of the positive electrode active material composite can be adjusted by changing the processing temperature and / or the mixing ratio of the carbon material during the mechanical milling process.
- the irreversible capacity of the positive electrode decreases, and if the processing speed is decreased, the irreversible capacity of the positive electrode tends to increase.
- Increasing the processing time of the mechanical milling process tends to decrease the irreversible capacity of the positive electrode, and decreasing the processing time tends to increase the irreversible capacity of the positive electrode.
- the irreversible capacity of the positive electrode can be adjusted by the amount of energy given to the lithium silicate material and the carbon material at the time of compounding because of the following reasons.
- the crystal system of the lithium silicate material does not change much, but the ion distribution in the crystal structure changes. Specifically, when the energy is small, each site exists uniquely at each site in the crystal by arranging elements corresponding to each site.
- the amount of the positive electrode active material composite applied to the positive electrode current collector, and the negative electrode of the negative electrode active material A coating amount on the current collector may be set to a predetermined amount. This is because changing the amount of the positive electrode active material composite applied to the positive electrode current collector and the amount of the negative electrode active material applied to the negative electrode current collector may change the irreversible capacity and reversible capacity of the positive electrode.
- the positive electrode active material composite is a composite of a lithium silicate material and a carbon material.
- the lithium silicate-based material mainly serves as an active material.
- the carbon material plays a role as a conductive material and enhances conductivity between silicate materials. By combining both, the charge / discharge characteristics of the positive electrode active material composite can be enhanced.
- the lithium silicate-based material for example, the lithium silicate-based material has a composition formula: Li 2 + ab Ab M 1- ⁇ M ′ ⁇ Si 1 + ⁇ O 4 + c (where A is Na, K, Rb, And at least one element selected from the group consisting of Cs, M is at least one element selected from the group consisting of Fe and Mn, and M ′ is Mg, Ca, Co, Al, Ni, It is at least one element selected from the group consisting of Nb, Ti, Cr, Cu, Zn, Zr, V, Mo and W.
- the subscripts are as follows: 0 ⁇ ⁇ ⁇ 0.2, 0 ⁇ ⁇ ⁇ 0.5, 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.2, 0 ⁇ c ⁇ 0.3).
- the above composition formula indicates the basic composition of the lithium silicate material.
- a part of Li, A, M, M ′, Si, and O in the above composition formula may be substituted with another element. In the case of substitution with other elements, it is preferably performed within a range that does not adversely affect the capacity.
- Lithium silicate materials having a composition slightly deviating from the above composition formula due to unavoidable loss of Li, A, M, M ′, Si or O and oxidation of the compound are also included.
- lithium silicate-based material examples include Li 2 FeSiO 4 , Li 2 MnSiO 4, Li 2 CoSiO 4 , and Li 2 NiSiO 4 .
- the carbon material is preferably conductive, and for example, acetylene black (AB), ketjen black (KB), carbon material black, carbon material nanotube, graphene, carbon material fiber, graphite, or the like can be used. Among these, acetylene black (AB), ketjen black (KB), and carbon material black are preferable.
- the mass ratio of the carbon material when the positive electrode active material composite is 100% by mass is preferably 1% by mass to 50% by mass, and more preferably 5% by mass to 30% by mass.
- the lithium silicate material and the carbon material are uniformly dispersed, and the electric capacity can be greatly extracted.
- the average particle size of the lithium silicate-based material before applying energy is preferably, for example, 200 nm or more and 5 ⁇ m or less, and the average particle size of the carbon material before applying energy is, for example, 100 nm or more and 5 ⁇ m or less. There should be. In this case, by applying mechanical energy to the lithium silicate-based material and the carbon material, both are combined, and a positive electrode active material composite can be easily obtained.
- Mechanical energy should be given to the lithium silicate material and carbon material by mechanical milling. Thereby, mechanical energy can be uniformly given to the lithium silicate material and the carbon material.
- mechanical milling method ball milling in which mechanical energy is introduced by moving the container by an external force in a state where a hard ball is accommodated in the container together with the sample is preferable.
- the ball milling device any of a planetary type that gives energy to the sample by rotation and revolution and a vibration type that gives energy to the sample by vibration in the horizontal direction or the vertical direction can be adopted.
- the processing speed may be adjusted within a range of, for example, 100 rpm to 1000 rpm.
- the processing time may be adjusted, for example, between 1 minute and 20 hours. Preferably, it is 1 hour or more.
- the irreversible capacity of the positive electrode becomes relatively large, and when it exceeds 700 rpm, the irreversible of the positive electrode The capacity tends to be relatively small.
- the rotation speed of the ball mill is 700 rpm or more, the lithium silicate material and the carbon material are densely combined. At this time, the lithium silicate-based material and the carbon material are mixed and joined to each other in a very small nano-level fine particle state with an average particle size of 100 nm or less.
- the specific surface area of the positive electrode active material composite can be 150 m 2 / g or more, and more preferably 170 m 2 / g or more.
- the positive electrode active material composite can be formed into secondary particles having an average particle diameter of 0.7 ⁇ m or more and 20 ⁇ m or less by joining the lithium silicate material and the carbon material. Furthermore, it is possible to form relatively large secondary particles having a size of 1 ⁇ m to 10 ⁇ m. In this case, fine surface particles are preferably attached to the surface of the positive electrode active material composite.
- the average particle size of the surface particles is preferably 20 nm or more and 100 nm or less, more preferably 30 nm or more and 90 nm or less, and preferably 35 nm or more and 75 nm or less.
- the surface particles may contain, for example, a part of the raw material for the lithium silicate material. Since the positive electrode active material composite has surface particles, the reaction for occluding and releasing lithium ions is promoted.
- the irreversible capacity of the positive electrode becomes relatively small.
- the reversible capacity of the positive electrode is C and the irreversible capacity is A, A / C can be less than 0.1.
- the average particle diameter of each material and each particle is obtained by analyzing a TEM (transmission electron microscope) image of the positive electrode active material complex.
- the maximum value of the distance between the parallel lines of the book) is a value calculated by actual measurement.
- the lithium silicate material and the carbon material are slowly combined. At this time, both are mixed with each other with a relatively large particle size of 100 nm or more.
- the specific surface area of the positive electrode active material composite can be less than 150 m 2 / g.
- Each site exists uniquely by arranging Li at the Li site in the crystal and arranging other elements at sites of other elements (for example, Fe, Mn). Therefore, the irreversible capacity of the positive electrode becomes relatively large. For example, when the initial discharge capacity (reversible capacity) of the positive electrode is C and the irreversible capacity is A, A / C can be 0.1 or more.
- the irreversible capacity becomes relatively small, and the A / C can be less than 0.1.
- the irreversible capacity becomes relatively large, and A / C can be 0.1 or more.
- the initial charge capacity of the positive electrode tends to increase. This is because Li and other elements are mixed between the sites in the crystal structure of the lithium silicate-based material, so that Li can easily move. As the initial charge capacity increases, the reversible capacity and irreversible capacity also increase.
- a lithium silicate material and a carbon material When applying energy, it is preferable to mix a lithium silicate material and a carbon material in an inert gas atmosphere (argon gas, nitrogen gas) or in an air atmosphere.
- an inert gas atmosphere argon gas, nitrogen gas
- the irreversible capacity of the positive electrode can be adjusted by changing the processing conditions of the lithium silicate material and the carbon material.
- heat treatment may be performed on the mixture of the lithium silicate material and the carbon material to which mechanical energy is applied.
- the mixed active material and conductive material are heated at a predetermined temperature.
- the heat treatment temperature is preferably 500 to 800 ° C. If the heat treatment temperature is too low, it is difficult to deposit carbon uniformly around the lithium silicate material, while if the heat treatment temperature is too high, decomposition of the lithium silicate material or lithium deficiency may occur. This is not preferable because the charge / discharge capacity decreases.
- the heat treatment time is usually 1 to 10 hours.
- the heat treatment may be performed in a reducing atmosphere in order to keep the transition metal ions contained in the lithium silicate material divalent.
- a reducing atmosphere in this case, in order to suppress the reduction of the divalent transition metal ion to the metal state, as in the synthesis reaction of the lithium silicate material in the molten salt, the reducing atmosphere is reduced with carbon dioxide.
- a gas mixed gas atmosphere is preferred. The mixing ratio of carbon dioxide and reducing gas may be the same as in the synthesis reaction of the lithium silicate material.
- the negative electrode has a negative electrode active material.
- the negative electrode active material has silicon (Si).
- the irreversible capacity with respect to the reversible capacity of the negative electrode can be adjusted by changing the content of silicon in the negative electrode active material.
- the negative electrode active material may be made of at least one of Si and SiOx (x0).
- Si is made of silicon (Si).
- SiOx is either in its entirety consists of SiO 2, or may contain Si phase in part.
- SiOx has a range of x ⁇ 0.5 ⁇ x ⁇ 1.5, and is preferably composed of a SiO 2 phase and a Si phase.
- the negative electrode active material is composed of at least one of Si and SiOx, and the SiOx powder is represented by the formula: SiOx (0.5 ⁇ x ⁇ 1.5), and is composed of a Si phase and a SiO 2 phase. preferable.
- Silicon (Si) contributes to the battery reaction, and silicon oxide (SiO 2 ) greatly affects the irreversible capacity.
- Li 4 SiO 4 produced in the formula (1) is an irreversible component and is not used in the subsequent reaction. In subsequent charge / discharge cycles, the reaction is repeated alternately between Si and SiLi 4.4 (Electrochemistry, 80 (6), 405-408 (2012)). For this reason, silicon oxide (SiO 2 ) greatly affects the irreversible capacity of the negative electrode. Increasing the ratio of silicon oxide increases the irreversible capacity of the negative electrode, and decreasing the ratio of silicon oxide decreases the irreversible capacity of the negative electrode.
- the ratio (B / D) of the irreversible capacity B to the reversible capacity D of the negative electrode active material may be 0.5 ⁇ B / D ⁇ 0.7.
- the ratio (A / C) of the irreversible capacity A to the reversible capacity C of the positive electrode is also preferably 0.5 ⁇ A / C ⁇ 0.7.
- the average particle diameter of the lithium silicate material of the positive electrode active material composite having this ratio is, for example, 10 nm or more and 10 ⁇ m or less, and the average particle diameter of the carbon material is 10 nm or more and 1 ⁇ m or less.
- the negative electrode active material is synthesized from Si powder, and the average particle size of the lithium silicate material of the positive electrode active material is 10 nm or more and 10 ⁇ m or less, and the average particle size of the carbon material is 10 nm or more and 1 ⁇ m or less. Good.
- the ratio (B / D) of the irreversible capacity B to the reversible capacity D of the negative electrode active material may be 0.3 ⁇ B / D ⁇ 0.5.
- the ratio (A / C) of the irreversible capacity A to the reversible capacity C of the positive electrode is preferably 0.3 ⁇ A / C ⁇ 0.5.
- the average particle diameter of the lithium silicate material of the positive electrode active material composite having this ratio is, for example, 10 nm or more and 20 ⁇ m or less, and the average particle diameter of the carbon material is 10 nm or more and 1 ⁇ m or less.
- the negative electrode active material is synthesized from SiOx powder, the lithium silicate material of the positive electrode active material has an average particle size of 10 nm to 20 ⁇ m, and the carbon material has an average particle size of 10 nm to 1 ⁇ m.
- the amount of the positive electrode active material composite applied to the positive electrode current collector, and the negative electrode current collector of the negative electrode active material may be set to a predetermined amount. This is because changing the amount of the positive electrode active material composite applied to the positive electrode current collector and the amount of the negative electrode active material applied to the negative electrode current collector may change the irreversible capacity and reversible capacity of the negative electrode.
- the positive electrode active material composite is formed by combining a lithium silicate-based material and a carbon material.
- the lithium silicate-based material compounded with the carbon material can be produced by, for example, a molten salt method, a solid phase method, a hydrothermal method, or the like. Especially, it is good to manufacture by the molten salt method.
- the molten salt method is a method of synthesizing a lithium silicate material in a molten salt containing an alkali metal salt.
- the alkali metal salt used in the molten salt method include at least one selected from the group consisting of a lithium salt, a potassium salt, a sodium salt, a rubium salt, and a cesium salt. Of these, lithium salts are desirable.
- a molten salt containing a lithium salt is used, the formation of an impurity phase is small, and a lithium silicate-based material containing excess lithium atoms is likely to be formed.
- the lithium silicate-based material thus obtained becomes a positive electrode material for a lithium ion battery having good cycle characteristics and high capacity.
- the alkali metal salt used in the molten salt method contains at least one of alkali metal chloride, alkali metal carbonate, alkali metal nitrate, and alkali metal hydroxide.
- Alkali metal salts are preferably alkali metal carbonates, and more preferably contain lithium carbonate.
- a carbonate mixture comprising at least one alkali metal carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate and lithium carbonate is preferable.
- the reaction by performing the reaction at a relatively low temperature of 400 to 650 ° C. in the molten salt of the mixture, the growth of crystal grains is suppressed, and the average particle diameter becomes fine particles of 50 nm to 10 ⁇ m. The amount is greatly reduced. As a result, when used as a positive electrode active material for a non-aqueous electrolyte secondary battery, the material has good cycle characteristics and high capacity.
- a molten salt of a carbonate mixture consisting of at least one alkali metal carbonate and lithium carbonate selected from the group consisting of potassium carbonate, sodium carbonate, rubidium carbonate and cesium carbonate it is represented by Li 2 SiO 3.
- the lithium silicate compound may be reacted with a substance containing at least one metal element selected from the group consisting of iron and manganese at 400 to 650 ° C.
- the specific reaction method is not particularly limited.
- the above-described carbonate mixture, lithium silicate compound, and a substance containing a metal element are mixed to form a ball mill. Or the like, and then the carbonate mixture may be melted by heating. Thereby, in molten carbonate, reaction with a lithium silicate compound and the said metal element advances, and a lithium silicate type material can be obtained.
- the mixing ratio of the raw material composed of the lithium silicate compound and the metal element-containing material and the carbonate mixture is not particularly limited, and the amount of the raw material can be uniformly dispersed in the molten salt of the carbonate mixture.
- the total amount of the molten salt raw material is preferably in the range of 20 to 300 parts by mass with respect to 100 parts by mass of the total amount of the carbonate mixture.
- the amount is more preferably in the range of ⁇ 80 parts by mass.
- the above-described reaction is performed in a mixed gas atmosphere containing carbon dioxide and a reducing gas because the metal element stably exists as a divalent ion during the reaction. Under this atmosphere, the metal element can be stably maintained in a divalent state.
- the reducing gas may be 0.01 to 0.5 mol, preferably 0.03 to 0.4 mol, per 1 mol of carbon dioxide.
- the reducing gas for example, hydrogen, carbon monoxide and the like can be used, and hydrogen is particularly preferable.
- the pressure of the mixed gas of carbon dioxide and reducing gas is usually just atmospheric pressure, but it may be under pressure or under reduced pressure.
- the reaction time between the lithium silicate compound and the substance containing the metal element is usually 0.1 hour to 30 hours, preferably 5 hours to 25 hours.
- the target lithium silicate-based material can be obtained by removing the alkali metal carbonate used as the flux.
- the alkali metal carbonate may be dissolved and removed by washing the product using a solvent capable of dissolving the alkali metal carbonate.
- a solvent capable of dissolving the alkali metal carbonate for example, although water can be used as the solvent, it is preferable to use a nonaqueous solvent such as alcohol or acetone in order to prevent oxidation of the transition metal contained in the lithium silicate material.
- acetic anhydride and acetic acid in a mass ratio of 2: 1 to 1: 1.
- this mixed solvent when acetic acid reacts with the alkali metal carbonate to produce water, acetic anhydride takes in the water and produces acetic acid. Therefore, it is possible to suppress the separation of water.
- acetic anhydride and acetic acid are used, first, acetic anhydride is mixed with the product, ground with a mortar or the like to make particles fine, and then acetic anhydride is added in a state where acetic anhydride is intimately mixed with the particles. It is preferable. According to this method, since the water produced by the reaction of acetic acid and alkali metal carbonate reacts quickly with acetic anhydride, the chance of the product and water coming into contact with each other can be reduced. Can be suppressed.
- the negative electrode active material may contain SiOx powder.
- a raw material powder containing silicon monoxide may be used as a raw material for the SiOx powder.
- silicon monoxide in the raw material powder is disproportionated into two phases of SiO 2 phase and Si phase.
- silicon monoxide SiOn: n is 0.5 ⁇ n ⁇ 1.5
- SiO 2 phase and Si phase silicon monoxide
- the silicon oxide powder obtained by disproportionation includes a SiO 2 phase and a Si phase.
- Disproportionation of silicon monoxide in the raw powder proceeds by applying energy to the raw powder.
- energy for example, a method of heating or milling the raw material powder can be mentioned.
- a raw material powder containing amorphous silicon monoxide powder is subjected to heat treatment at 800 to 1200 ° C. for 1 to 5 hours in an inert atmosphere such as vacuum or in an inert gas.
- a silicon oxide powder containing two phases of an amorphous SiO 2 phase and a crystalline Si phase is obtained.
- the raw material powder When milling the raw material powder, a part of the mechanical energy of the milling contributes to chemical atomic diffusion at the solid phase interface of the raw material powder, and generates an oxide phase and a silicon phase.
- the raw material powder may be mixed using a V-type mixer, a ball mill, an attritor, a jet mill, a vibration mill, a high energy ball mill or the like in an inert gas atmosphere such as vacuum or argon gas. Further heat treatment may be performed after milling to further promote disproportionation of silicon monoxide.
- a lithium ion secondary battery includes a positive electrode having a positive electrode active material composite, a negative electrode having a negative electrode active material, an electrolyte, and, if necessary, a separator.
- the positive electrode is preferably composed of the positive electrode active material composite and a current collector.
- the positive electrode can have the same structure as a normal positive electrode for a nonaqueous electrolyte secondary battery.
- a positive electrode can be produced by adding a conductive additive and / or a binder as necessary to the above positive electrode active material composite, making it into a paste with a solvent, and applying it to a current collector.
- a conductive assistant acetylene black (AB), ketjen black (KB), vapor grown carbon fiber (Vapor Carbon Carbon Fiber: VGCF), or the like can be used.
- VGCF vapor grown carbon fiber
- binder polyvinylidene fluoride (Polyvinylidene Fluoride: PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), or the like can be used.
- the amount of the conductive aid used is not particularly limited, but can be 5 to 20 parts by mass with respect to 100 parts by mass of the positive electrode active material composite, for example.
- the amount of the binder used is not particularly limited, but can be, for example, 5 to 20 parts by mass with respect to 100 parts by mass of the positive electrode active material composite.
- a method of kneading a mixture of the positive electrode active material composite, the conductive aid and the binder described above with a mortar or a press to form a film, and then crimping this to a current collector with a press Can also produce a positive electrode.
- the current collector is not particularly limited, and materials conventionally used as positive electrodes for nonaqueous electrolyte secondary batteries, such as aluminum foil, aluminum mesh, stainless steel mesh, copper foil, and copper mesh, can be used. . Furthermore, a carbon nonwoven fabric, a carbon woven fabric, etc. can be used as a collector.
- the shape, thickness and the like of the positive electrode are not particularly limited.
- the positive electrode is preferably compressed to 10 to 200 ⁇ m, more preferably 20 to 100 ⁇ m, by compressing after filling with the active material. . Therefore, the filling amount of the active material may be appropriately determined so as to have the above-described thickness after compression according to the type and structure of the current collector to be used.
- the negative electrode has at least a negative electrode active material.
- the negative electrode includes a negative electrode active material and a current collector.
- the negative electrode active material may be applied to the surface of the current collector by forming a negative electrode material together with a binder or / and a conductive auxiliary, if necessary, and pasting with a solvent. Copper foil or copper mesh is used as the current collector.
- the binder and the conductive additive the same materials as those of the positive electrode can be used.
- a lithium salt such as lithium perchlorate, LiPF 6 , LiBF 4 , LiCF 3 SO 3 or the like in a known non-aqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, dimethyl carbonate, etc.
- a solution dissolved at a concentration of 7 mol / L may be used, and other known battery components may be used.
- the separator is preferably made of, for example, a microporous film or non-woven fabric made of polyolefin such as polypropylene, polyethylene, or a copolymer of propylene and ethylene.
- the lithium ion secondary battery can be mounted on, for example, a vehicle, a personal computer, a portable communication device, or the like.
- the positive electrode active materials of Samples 1 to 7 were manufactured by the following method.
- Example 1 A mixture of 0.03 mol of iron (purity 99.9%, manufactured by High Purity Chemical Co., Ltd.) and 0.03 mol of lithium silicate-based material Li 2 SiO 3 (purity 99.5%, manufactured by Kishida Chemical Co., Ltd.) Acetone (20 ml) was added to the mixture, and mixed with a zirconia ball mill at 500 rpm for 60 minutes and dried. This was mixed with the carbonate mixture.
- the carbonate mixture consists of lithium carbonate (Kishida Chemical Co., Ltd., purity 99.9%), sodium carbonate (Kishida Chemical Co., Ltd., purity 99.5%), and potassium carbonate (Kishida Chemical Co., Ltd., purity 99.3%).
- Li 2 FeSiO 4 belonging to the space group P2 1 / n was confirmed.
- the average particle size of Li 2 FeSiO 4 was 0.5 ⁇ m.
- the obtained Li 2 FeSiO 4 was used as Sample 1.
- the mixture was subjected to a ball milling treatment under the following predetermined conditions in an air atmosphere using a mechanical milling device (French Japan Co., Ltd., planetary ball mill P-7). This step was performed by putting ⁇ 4 mm zirconia balls (50 g) and a mixture (300 mg) in a ball mill grinding container made of zirconia and having a volume of 45 cc.
- Sample 3 was an active material composite obtained when the rotation speed of the ball mill was 200 rpm and the rotation time was 5 hours.
- Sample 4 was an active material composite obtained when the rotation speed of the ball mill was 450 rpm and the rotation time was 5 hours.
- Sample 5 was an active material composite obtained when the rotation speed of the ball mill was 700 rpm and the rotation time was 5 hours.
- Sample 6 was an active material composite obtained when the rotation speed of the ball mill was 800 rpm and the rotation time was 5 hours.
- Sample 7 was an active material composite obtained when the rotation speed of the ball mill was 800 rpm and the rotation time was 2 hours.
- Each sample 3-7 was heat-treated.
- lithium silicate-based particles having an average particle size of 1000 nm (particulate white portions) and carbon particles having an average particle size of 100 nm (fluffy light gray portions) were mixed. .
- Each particle had the same shape and size before mixing and was not agglomerated.
- the lithium silicate-based particles and the carbon particles were smaller than the particle size before mixing and were combined.
- the lithium silicate-based particles and the carbon particles were mixed as they were primary particles, and no secondary particles were formed.
- the specific surface area of this composite was 59.3 m 2 / g.
- lithium silicate-based particles (gray portion) and carbon particles (black portion) were mixed in a larger size than sample 1.
- the average particle size of the lithium silicate-based particles was 500 nm, and the average particle size of the carbon particles was 100 nm.
- Lithium silicate particles and carbon particles aggregated slowly to form a composite.
- the average particle diameter of the composite was about 1 ⁇ m, which was smaller than the secondary particles of Sample 1, and had a cavity inside.
- the sizes of the lithium silicate-based particles and the carbon particles varied, and the lithium silicate-based particles and the carbon particles were dispersed unevenly.
- the specific surface area of the composite was 106 m 2 / g.
- lithium silicate particles and carbon particles were gradually aggregated to form a composite. Cavities remained in the composite, both of which varied in size. For this reason, it cannot be said that the lithium silicate-based particles and the carbon particles are bonded to each other in a finely dispersed state.
- the specific surface area of the composite was 130.7 m 2 / g.
- Sample 6 as shown in FIG. 9, relatively large large particles having a major axis of about 20 ⁇ m and fine particles having a particle size of about 1 to 4 ⁇ m were mixed.
- a large number of fine particles were uniformly dispersed inside the large particles. That is, the large particles are those in which fine primary particles are combined into secondary particles.
- this composite showed a high value of 171.7 m 2 / g.
- the active material composite had a core part and a surface layer covering the surface of the core part.
- lithium silicate particles having an average particle diameter of 10 to 30 nm made of Li 2 FeSiO 4 were uniformly dispersed in a matrix made of carbon.
- the surface layer had a thickness of about 1 ⁇ m and was composed of a CO rich layer.
- a positive electrode active material of Sample 7, acetylene black (AB) as a conductive additive, and polyvinylidene fluoride (PVDF) as a binder were mixed, and a solvent was added to obtain a paste-like positive electrode material.
- the solvent was N-methylpyrrolidone (NMP).
- NMP N-methylpyrrolidone
- the mass ratio of the positive electrode active material, AB, and PVDF in the positive electrode material was 90: 5: 5.
- a positive electrode material was pressure-bonded to an aluminum current collector to produce an electrode, and vacuum-dried at 140 ° C. for 3 hours was used as the positive electrode.
- a half cell was constructed using this electrode and lithium metal as a counter electrode.
- the details of the half-cell were the same as the half-cell constructed using the above sample.
- a charge / discharge test was conducted on this half-cell.
- the test conditions were a voltage range of 4.8 to 1.5 V, a current density of 0.05 C rate, and 30 ° C.
- the measured initial charge capacity and initial discharge capacity are shown in Table 2.
- a negative electrode was produced.
- a commercially available SiO powder was put in a ball mill and milled at 450 rpm for 20 hours in an Ar atmosphere, and then heat-treated at 900 ° C. for 2 hours in an inert gas atmosphere. Thereby, SiO powder was disproportionated and disproportionated SiOx powder was obtained.
- XRD X-ray diffraction
- Disproportionated SiOx powder, a conductive additive, and polyimide (PI) as a binder were mixed, and a solvent was added to obtain a slurry mixture.
- Acetylene black (AB) was used as the conductive assistant.
- the solvent was NMP.
- the mass ratio of the disproportionated SiOx powder, the conductive auxiliary agent, and the binder was in percentage, and the disproportionated SiOx powder / conductive auxiliary agent / binder was 80/2/18.
- the slurry-like mixture was formed into a film on one side of a copper foil as a current collector using a doctor blade. After film formation, the film was pressed at a predetermined pressure, heated (200 ° C., 2 hours), and allowed to cool. As a result, a negative electrode in which a negative electrode material (negative electrode active material layer) was fixed on the current collector surface was produced.
- a half cell was constructed using this electrode and lithium metal as a counter electrode.
- the details of the half-cell were the same as the half-cell constructed using the above sample.
- a charge / discharge test was conducted on this half-cell.
- the test conditions were voltage range 0-1.0V, current density 0.1C rate, 30 ° C.
- the measured initial charge capacity and initial discharge capacity are shown in Table 2.
- a lithium ion secondary battery was assembled using a positive electrode having a positive electrode active material composite made of Sample 7 and a negative electrode having a negative electrode active material made of SiOx powder.
- a polypropylene film (Celgard 2400, manufactured by Celgard) was used as a separator.
- the charge / discharge test was performed on this lithium ion secondary battery.
- the test conditions were a voltage range of 4.79-0.8 V, a current density of 0.05 C rate, and 30 ° C.
- the measured initial discharge capacity (actual capacity) and initial discharge capacity retention rate are shown in Table 2.
- the initial discharge capacity maintenance ratio is a value indicating the ratio (E / C) of the initial discharge capacity E of the battery to the initial discharge capacity C of the positive electrode as a percentage.
- the ratio (B / A) of the irreversible capacity B of the negative electrode to the irreversible capacity A of the positive electrode is 2.08, and the initial discharge capacity (reversible capacity) of the negative electrode with respect to the initial discharge capacity (reversible capacity) C of the positive electrode.
- the ratio of capacity) D (D / C) was 0.76, and the initial discharge capacity retention rate of the battery was 42%. It was found that 58% of the initial discharge capacity C of the positive electrode could not be taken out.
- the positive electrode of the battery 2 is the same as the positive electrode of the battery 1.
- the negative electrode of the battery 2 is the same as the negative electrode of the battery 1 except that chicory (Si) powder is used instead of the non-uniformized SiOx particles of the battery 1.
- a charge / discharge test was conducted on the half battery using the positive electrode of the battery 2, the half battery using the negative electrode, and the battery 2 in the same manner as the battery 1, and the results are shown in Table 2.
- the ratio (B / A) of the irreversible capacity B of the negative electrode to the irreversible capacity A of the positive electrode is 1.16, and the initial discharge capacity (reversible capacity) of the negative electrode with respect to the initial discharge capacity (reversible capacity) C of the positive electrode.
- the ratio of capacity) D (D / C) was 1.05, and the initial discharge capacity retention rate of the battery was 72%. It was found that 28% of the initial discharge capacity C of the positive electrode could not be taken out.
- the positive electrode and negative electrode of the battery 3 have the same components as the positive electrode and negative electrode of the battery 2, but both are different from the battery 2 in that the amount applied to the current collector is reduced.
- a charge / discharge test was conducted on the half battery using the positive electrode of the battery 2, the half battery using the negative electrode, and the battery 2 in the same manner as the battery 1, and the results are shown in Table 2.
- the ratio (B / A) of the irreversible capacity B of the negative electrode to the irreversible capacity A of the positive electrode is 0.73, and the initial discharge capacity (reversible capacity) of the negative electrode with respect to the initial discharge capacity (reversible capacity) C of the positive electrode.
- the ratio (D / C) of capacity) D was 0.66, and the initial discharge capacity retention rate of the battery was 64%. It was found that nearly 40% of the initial discharge capacity C of the positive electrode could not be taken out.
- FIG. 17 shows the relationship between the ratio (B / A) of the irreversible capacity B of the negative electrode to the irreversible capacity A of the positive electrode of each battery and the initial discharge capacity maintenance rate of each battery. The closer the B / A is to 1, the higher the initial discharge capacity and the initial discharge capacity retention rate.
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Abstract
Description
正極は、正極活物質を有する。正極活物質は、リチウムシリケート系材料と炭素材料とを複合化させてなる正極活物質複合体からなる。正極活物質複合体は、リチウムシリケート系材料と炭素材料とにメカニカルミリング処理を行うことでリチウムシリケート系材料と炭素材料とを複合化させてなることが好ましい。
負極は、負極活物質を有する。負極活物質は、シリコン(Si)を有する。負極活物質中のシリコンの含有量を変化させることで、負極の可逆容量に対する不可逆容量を調整することができる。例えば、負極活物質は、Si及びSiOx(x0)の少なくとも一種からなるとよい。
式(1)で生成したLi4SiO4は、不可逆成分であり、その後の反応には使われない。その後の充放電サイクルではSiとSiLi4.4の間で反応が交互に繰り返される(Electrochemistry, 80(6),405-408(2012))。このため、シリコン酸化物(SiO2)は、負極の不可逆容量に大きく影響している。シリコン酸化物の比率を大きくすると、負極の不可逆容量が大きくなり、シリコン酸化物の比率を小さくすると、負極の不可逆容量が小さくなる。
正極活物質複合体は、リチウムシリケート系材料と炭素材料とを複合化させてなる。炭素材料と複合化されるリチウムシリケート系材料は、例えば、溶融塩法、固相法、水熱法などにより製造することができる。中でも、溶融塩法で製造するとよい。
負極活物質には、SiOx粉末が含まれる場合がある。このSiOx粉末の製造にあたっては、SiOx粉末の原料として、一酸化珪素を含む原料粉末を用いるとよい。この場合、原料粉末中の一酸化珪素を、SiO2相とSi相との二相に不均化する。一酸化珪素の不均化では、SiとOとの原子比が概ね1:1の均質な固体である一酸化珪素(SiOn:nは0.5≦n≦1.5)が固体内部の反応により、SiO2相とSi相との二相に分離する。不均化により得られる酸化珪素粉末は、SiO2相とSi相とを含む。
リチウムイオン二次電池は、正極活物質複合体を有する正極と、負極活物質を有する負極と、電解質と、必要に応じてセパレータとを備えている。
以下の方法により、試料1~7の正極活物質を製造した。
鉄(高純度化学株式会社製、純度99.9%)0.03モルと、リチウムシリケート系材料Li2SiO3(キシダ化学株式会社製、純度99.5%)0.03モルと、の混合物にアセトン20mlを加えてジルコニア製ボールミルにて500rpmで60分混合し、乾燥した。これを炭酸塩混合物と混合した。炭酸塩混合物は、炭酸リチウム(キシダ化学株式会社製、純度99.9%)、炭酸ナトリウム(キシダ化学株式会社製、純度99.5%)、及び炭酸カリウム(キシダ化学株式会社製、純度99.5%)を、0.435モル:0.315モル:0.25モルのモル比で混合した。混合割合は、鉄とリチウムシリケート系材料との合計量を100質量部に対して、炭酸塩混合物90質量部とした。
Li2FeSiO4と、炭素材料としてのアセチレンブラック(AB、平均粒径0.3μm)とを、Li2FeSiO4:AB=5:4の質量比で混合した。混合物を、手で乳鉢を用いて30分間混合した。混合物に熱処理を行った。熱処理条件は、700℃、2時間、CO2/H2=100/3ccm雰囲気とした。これらの複合体のXRDパターンは、合成直後のLi2FeSiO4と一致することを確認した。これを試料2とした。
また、Li2FeSiO4とABとを、Li2FeSiO4:AB=5:4の質量比で混合した。混合物に、メカニカルミリング装置(フリッチュ・ジャパン株式会社製、遊星型ボールミルP-7)を用いて、大気雰囲気下において下記の所定の条件でボールミリング処理を行った。本工程は、ジルコニア製で容積45ccのボールミル用粉砕容器に、φ4mmジルコニア製ボール(50g)および混合物(300mg)を入れて行った。
試料1~6について、SEM(走査型電子顕微鏡)で撮影した。試料1、試料2、試料3、試料4、試料5、試料6のSEM写真を、順に、図4、図5、図6、図7、図8、図9に示した。試料4、6の断面をSEMで撮影し、それぞれ図10、図11に示した。
以下に示すように、試料3~7の正極活物質を用いて半電池を作製し、充放電試験を行った。
このコイン電池について、30℃にて充放電試験を行った。試験条件は、0.05mA/cm2にて電圧1.5~4.5V(初回充電のみ4.8Vで10時間定電圧充電)とした。試料3、4、5、6、7の各正極活物質を用いて作製した半電池の充放電曲線を、図12、図13、図14、図15、図16に示した。また、各半電池の初回充電容量、初回放電容量、不可逆容量、初回放電容量(可逆容量)に対する不可逆容量の比を表1に示した。
電池1~3に示す3種類のリチウムイオン二次電池を作製し、実容量を測定した。
試料7の正極活物質と、導電助剤としてのアセチレンブラック(AB)と、結着剤としてのポリフッ化ビニリデン(PVDF)とを混合し、溶媒を加えてペースト状の正極材料を得た。溶剤はN-メチルピロリドン(NMP)であった。正極材料での正極活物質、AB、PVDFの質量比は90:5:5とした。正極材料をアルミニウム製の集電体に圧着して電極を製作し、140℃で3時間真空乾燥したものを正極とした。
電池2の正極は、電池1の正極と同様である。電池2の負極は、電池1の不均一化SiOx粒子の代わりに、シコリン(Si)粉末を用いた点を除いて、電池1の負極と同様である。電池2の正極を用いた半電池、負極を用いた半電池、及び上記電池2について、電池1と同様に充放電試験を行い、その結果を表2に示した。
電池3の正極、負極は、電池2の正極、負極と成分は同じであるが、いずれも集電体への塗布量を減少させた点が、電池2と相違する。電池2の正極を用いた半電池、負極を用いた半電池、及び上記電池2について、電池1と同様に充放電試験を行い、その結果を表2に示した。
Claims (11)
- リチウムシリケート系材料と炭素材料とを複合化させてなる正極活物質複合体を含む正極と、シリコンを有する負極活物質を含む負極と、電解質とを有するリチウムイオン二次電池であって、
前記正極の不可逆容量をAとし、前記負極の不可逆容量をBとしたとき、0.8<B/A<1.2の関係であることを特徴とするリチウムイオン二次電池。 - 前記正極の可逆容量をCとし、前記負極の可逆容量をDとしたとき、0.8<D/C<1.2の関係である請求項1記載のリチウムイオン二次電池。
- 前記正極活物質複合体は、前記リチウムシリケート系材料と前記炭素材料とにメカニカルミリング処理を行うことで前記リチウムシリケート系材料と前記炭素材料とを複合化させてなる請求項1または2に記載のリチウムイオン二次電池。
- 前記メカニカルミリング処理の処理速度及び処理時間の少なくとも一方により、前記正極の不可逆容量を調整してなる請求項3記載のリチウムイオン二次電池。
- 前記リチウムシリケート系材料は、組成式:Li2+a-bAbM1-βM’βSi1+αO4+c(式中、Aは、Na、K、Rb、及びCsからなる群から選ばれた少なくとも一種の元素であり、Mは、Fe及びMnからなる群から選ばれた少なくとも一種の元素であり、M’は、Mg、Ca、Co、Al、Ni、Nb、Ti、Cr、Cu、Zn、Zr、V、Mo及びWからなる群から選ばれた少なくとも一種の元素である。各添字は次のとおりである。0≦α≦0.2、0≦β≦0.5、0≦a<1,0≦b<0.2,0<c<0.3)で表される請求項1~4のいずれか1項に記載のリチウムイオン二次電池。
- 前記正極活物質複合体の質量を100質量%としたときに、前記炭素材料の含有量は1質量%以上50質量%以下である請求項1~5のいずれか1項に記載のリチウムイオン二次電池。
- 前記負極活物質は、Si及びSiOxの少なくとも一種からなり、
前記SiOxは、全体組成が式:SiOx(0.5≦x≦1.5)であらわされ、Si相とSiO2相とからなる請求項1~6のいずれか1項に記載のリチウムイオン二次電池。 - 前記負極活物質は、Siの粉末から合成され、前記正極活物質の前記リチウムシリケート系材料の平均粒径は、10nm以上10μm以下であり、前記炭素材料の平均粒径は、10nm以上1μm以下である請求項1~7のいずれか1項に記載のリチウムイオン二次電池。
- 前記負極活物質は、SiOxの粉末から合成され、前記正極活物質の前記リチウムシリケート系材料の平均粒径は、10nm以上20μm以下であり、前記炭素材料の平均粒径は、10nm以上1μm以下である請求項1~8のいずれか1項に記載のリチウムイオン二次電池。
- リチウムシリケート系材料と炭素材料とを複合化させてなる正極活物質複合体を含む正極と、シリコンを有する負極活物質を含む負極と、電解質とを有するリチウムイオン二次電池を製造するリチウムイオン二次電池の製造方法であって、
前記リチウムシリケート系材料と前記炭素材料とにメカニカルミリング処理を行うことで、前記リチウムシリケート系材料と前記炭素材料とを複合化させて前記正極活物質複合体とするとともに、前記正極の不可逆容量をAとし、前記負極の不可逆容量をBとしたとき、0.8<B/A<1.2の関係とすることを特徴とするリチウムイオン二次電池の製造方法。 - 前記メカニカルミリング処理の処理速度及び処理時間の少なくとも一方により、前記正極の不可逆容量を調整してなる請求項10記載のリチウムイオン二次電池の製造方法。
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US14/769,750 US9590237B2 (en) | 2013-02-25 | 2014-01-08 | Lithium-ion secondary battery and method for producing the same |
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US9728786B2 (en) * | 2015-12-21 | 2017-08-08 | Nissan North America, Inc. | Electrode having active material encased in conductive net |
US11984604B2 (en) * | 2017-11-29 | 2024-05-14 | Panasonic Intellectual Property Management Co., Ltd. | Lithium ion battery |
CN111357140B (zh) * | 2017-12-28 | 2023-11-14 | 松下知识产权经营株式会社 | 非水电解质二次电池用负极活性物质 |
CN108568615B (zh) * | 2018-04-26 | 2020-08-11 | 天能集团(河南)能源科技有限公司 | 一种铅酸蓄电池用高导电性水性助焊剂及其制备方法 |
US10938063B2 (en) | 2019-01-31 | 2021-03-02 | University Of Maryland, College Park | Lithium silicate compounds as Li super-ionic conductor, solid electrolyte and coating layer for lithium metal battery and lithium-ion battery |
EP3863105B1 (en) * | 2019-03-12 | 2024-06-12 | LG Energy Solution, Ltd. | Secondary battery |
US20220255061A1 (en) * | 2019-08-01 | 2022-08-11 | Gs Yuasa International Ltd. | Nonaqueous electrolyte energy storage device, method for manufacturing the same, and energy storage apparatus |
CN110993923B (zh) * | 2019-12-26 | 2021-11-23 | 湖北亿纬动力有限公司 | 一种碳包覆辅助的钠钛双掺杂硅酸铁锂正极材料及其制备方法和用途 |
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