JP6699473B2 - All-solid-state battery system and manufacturing method thereof - Google Patents

Description

  The present invention relates to an all solid state battery system and a method for manufacturing the same.

  At present, among various types of batteries, lithium ion batteries are drawing attention because of their high energy density. Among them, all-solid-state batteries in which the electrolytic solution is replaced with a solid electrolyte have been particularly attracting attention. This is because unlike the secondary battery that uses an electrolytic solution, the all-solid-state battery does not use an electrolytic solution, so that decomposition of the electrolytic solution due to overcharge does not occur, and high cycle characteristics and energy density are achieved. Because it has. Examples of the negative electrode active material generally used in lithium ion batteries include carbon-based negative electrode active materials such as graphite, soft carbon, and hard carbon. In recent years, an alloy-based negative electrode active material having a larger capacity has been studied in place of the carbon-based negative electrode active material. Examples include silicon, tin, germanium, aluminum and the like. Among them, silicon particles have attracted particular attention because of their particularly large capacity.

  It is known that the battery using the alloy-based negative electrode active material as the negative electrode active material has lower cycle characteristics than the battery using the carbon-based negative electrode active material or the like as the negative electrode active material. The cause is that the alloy-based negative electrode active material particles expand and contract with charging and discharging, so that the alloy-based negative electrode active material particles are crushed, and the alloy-based negative electrode active material particles and other negative electrode active material layer materials It can be mentioned that the internal resistance of the all-solid-state battery increases due to the formation of voids between them.

  In Patent Document 1, in an all-solid-state battery using silicon particles as an alloy-based negative electrode active material, the volume change of silicon particles due to charge/discharge is adjusted to crush the silicon particles and the silicon particles and other negative electrode active material layers. The voids formed between the material and the material are reduced, thereby suppressing an increase in internal resistance of the all-solid-state battery.

  Further, in Patent Document 2, an all-solid-state battery using silicon particles as an alloy-based negative electrode active material is initially charged and discharged only once at an initial time, and is charged for a long time at a voltage lower than usual, thereby forming silicon particles. It discloses a method of activating to improve the utilization rate, and to bond the interface between the silicon particles and the other negative electrode active material layer material well.

JP, 2014-0886218, A Japanese Patent Laid-Open No. 2014-041783

  An all-solid-state battery using alloy-based negative electrode active material particles as the negative-electrode active material has alloy-based negative electrode active material particles crushed by the expansion and contraction of the alloy-based negative electrode active material particles during charging/discharging. Since a void is generated between the active material particles and the other negative electrode active material layer material, there is a problem that cycle characteristics are low.

  Therefore, there is a demand for a method of solving the above problems and improving the cycle characteristics of an all-solid-state battery using alloy-based negative electrode active material particles as the negative electrode active material. As a specific method, as in Patent Document 1, for example, when silicon particles are used as the alloy-based negative electrode active material particles, the volume change amount of the silicon particles is adjusted to reduce resistance and cycle characteristics. It is possible to improve.

  However, even when the volume change amount is adjusted as in Patent Document 1, the cycle characteristics are deteriorated. This suggests not only the crushing of the silicon particles due to the expansion and contraction of the silicon particles, but also the possibility that some kind of chemical deterioration is progressing.

  Therefore, a technique for further improving cycle characteristics is required.

  That is, the main object of the present invention is to provide an all-solid-state battery system with improved cycle characteristics and a method for manufacturing the same.

1. An all-solid-state battery system having a positive electrode active material layer, a solid electrolyte layer, and an all-solid-state battery having a negative electrode active material layer, and a control device for controlling charge/discharge voltage during use of the all-solid-state battery, An all-solid-state battery having alloy-type negative electrode active material particles in the negative-electrode active material layer, the amorphization rate of the alloy-type negative electrode active material particles being 27.8 to 82.8%, and satisfying the following conditions. system:
0.32≦Z/W≦0.60
Z: Controlled discharge capacity (mAh) of all solid state battery
W: theoretical capacity (mAh/g) of alloy-based negative electrode active material particles×total weight (g) of alloy-based negative electrode active material particles×amorphization rate (%).
2. The all-solid-state battery system according to 1 above, wherein the alloy-based negative electrode active material particles are silicon particles.
3. 3. The all-solid-state battery system according to 1 or 2 above, wherein the positive electrode active material layer has a positive electrode active material covered with a protective coating which is a lithium-containing metal oxide.
4. 4. The all-solid-state battery system according to 3 above, wherein the lithium-containing metal oxide of the protective coating is lithium niobate.
5. The all-solid-state battery system according to any one of 1 to 4 above, wherein the control device controls the charge/discharge voltage within a range of 2.50 V or more and 4.40 V or less.
6. A method for manufacturing an all-solid-state battery system having an all-solid-state battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and a control device that controls a charge/discharge voltage when the all-solid-state battery is used. Then, a stacking step of stacking the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer having the alloy-based negative electrode active material particles, and charging the all-solid-state battery to an initial charging voltage higher than the charge/discharge voltage. A method for manufacturing an all-solid-state battery system having an initial charging step.
7. 7. The method according to 6 above, wherein the alloy-based negative electrode active material particles are silicon particles.
8. 8. The method according to 6 or 7 above, wherein the charge/discharge voltage is in the range of 2.50 V or more and 4.40 V or less, and the initial charging voltage is higher than 4.45 V and 5.00 V or less in the initial charging step.
9. 9. The method according to any one of 6 to 8 above, wherein the positive electrode active material layer has a positive electrode active material coated with a protective coating that is a lithium-containing metal oxide.
10. 10. The method according to 9 above, wherein the lithium-containing metal oxide of the protective coating is lithium niobate.
11. The method according to 9 or 10, wherein the initial charging step is performed so as to satisfy the following conditions: (Change rate (dQ/dV) of charge amount (Q) with respect to voltage (V) at upper limit charging voltage in initial charging step) /(Average value of change rate (dQ/dV) of charge amount (Q) with respect to voltage (V) when charge voltage is 4.00 V or more and 4.40 V or less)>1.3

  According to the present invention, it is possible to provide an all-solid-state battery system with improved cycle characteristics and a method for manufacturing the same.

FIG. 1 illustrates an example of the all-solid-state battery system of the present invention. FIG. 2 illustrates an example of the all-solid-state battery used in the all-solid-state battery system of the present invention. FIG. 3 illustrates an example of the all-solid-state battery used in the all-solid-state battery system of the present invention. FIG. 4 shows an example of the all-solid-state battery used in the all-solid-state battery system of the present invention. FIG. 5 is a diagram explaining the operation principle of the manufacturing method of the present invention. FIG. 6 is a graph showing the relationship between the amorphization rate and the initial charge amount.

  Hereinafter, embodiments of the present invention will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be carried out within the scope of the gist of the present invention.

<<All-solid-state battery system of the present invention>>
The all-solid-state battery system of the present invention includes an all-solid-state battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and a control device for controlling the charge/discharge voltage when the all-solid-state battery is used. An all-solid-state battery system having the alloy-based negative electrode active material particles in the negative electrode active material layer, wherein the alloy-based negative electrode active material particles have an amorphization rate of 27.8 to 82.8%, and Meet the following conditions:
0.32≦Z/W≦0.60
Z: Controlled discharge capacity (mAh) of all solid state battery
W: theoretical capacity (mAh/g) of alloy-based negative electrode active material particles×total weight (g) of alloy-based negative electrode active material particles×amorphization rate (%).

  In this equation, the control discharge capacity Z of the all-solid-state battery is the discharge capacity in the voltage range actually controlled by the control device in the all-solid-state battery system at the time of completion as a product.

  In other words, in this formula, the controlled discharge capacity Z of the all-solid-state battery is substantially the same as that of the completed all-solid-state battery when the first all-charge, that is, the first normal use, due to the discharge in the voltage range controlled by the controller. It represents the amount of lithium that can be released during charge and discharge.

  In this formula, the theoretical capacity (mAh/g) of the alloy-based negative electrode active material particles means the electron amount n (mol) and the Faraday constant F (C/mol) when the alloy-based negative electrode active material particles store the maximum amount of lithium. ) And the molecular weight M (g/mol), it is a value calculated using the formula of nF/M.

  In other words, the theoretical capacity W of the alloy-based negative electrode active material particles substantially represents the total amount of lithium that can be theoretically accepted by the amorphized portion of the alloy-based negative electrode active material particles.

  Therefore, this formula is substantially the same as the theoretical amount of lithium that is stored in the negative electrode active material layer after charging the battery and that can be released by discharge as amorphized in the alloy-based negative electrode active material particles. It is shown to be less than the total amount of lithium that can be accepted and within a certain range.

  When the value of Z/W is less than 0.32, the energy density is reduced and the performance as a battery is reduced. On the other hand, when the Z/W value is more than 0.60, the alloy-type negative electrode active material particles are crystallized by expansion/contraction of the amorphized portion of the alloy-type negative electrode active material particles when the all-solid battery is charged/discharged. It is considered that the alloy-based negative electrode active material particles are easily broken by the stress because the ratio of the alloy-based negative electrode active material particles becomes large.

  The lower limit of Z/W may be 0.33 or more, 0.35 or more, 0.37 or more, 0.40 or more, 0.42 or more, or 0.45 or more, and the upper limit is 0. It may be 58 or less, 0.55 or less, 0.53 or less, 0.50 or less, or 0.48 or less.

  The all-solid-state battery of the present invention can realize high cycle characteristics by satisfying such conditions. FIG. 1 illustrates an example of the all-solid-state battery system of the present invention. The all-solid-state battery system of the present invention includes an all-solid-state battery (6) and a control device (100) that controls a charge/discharge voltage when the all-solid-state battery is used.

  Although not limited by theory, it is considered that the improvement of the cycle characteristics of the all-solid-state battery system of the present invention occurs as follows.

  When the lithium ion secondary battery using the alloy-based negative electrode active material particles as the negative electrode active material is initially charged, the lithium ions released from the positive electrode active material react with the alloy-based negative electrode active material particles, and the alloy-based negative electrode An alloy of the active material and lithium is produced. In this reaction, the crystalline structure of the alloy-based negative electrode active material particles is destroyed, and the alloy-based negative electrode active material that has reacted with lithium becomes amorphous. When discharging is further performed from this state, the alloy of the alloy-based negative electrode active material and lithium returns to the alloy-based negative electrode active material by releasing lithium as lithium ions, but this alloy-based negative electrode active material The amorphized part does not return to the crystalline structure before the initial charging, but maintains the amorphized structure as it is. Then, in the subsequent charging, this amorphous portion mainly reacts with lithium ions to form an alloy of the alloy-based negative electrode active material and lithium.

  When an all-solid battery using alloy-based negative electrode active material particles as the negative electrode active material is initially charged, this amorphization reaction occurs not in the entire alloy-based negative electrode active material particles but in only a part of the alloy-based negative electrode active material particles, and The portion of does not react with lithium and remains crystalline.

  In conventional all-solid-state batteries, since the alloy-based negative electrode active material particles have few amorphized parts, the amorphous part and lithium react preferentially during charging and discharging, resulting in local expansion and contraction in the amorphized part. Occurs. Therefore, the volume expansion/contraction ratio of the amorphized portion becomes large. Therefore, by repeating charging and discharging, a part of the alloy-based negative electrode active material particles repeatedly expands and contracts, and reacts with lithium ions in the alloy-based negative electrode active material particles to become an alloy, and does not react with the lithium ions. The alloy-based negative electrode active material particles are crushed due to stress or the like generated between the alloy-based negative electrode active material particles and the non-reactive portion.

  On the other hand, in this case, by increasing the number of amorphized portions, it is possible to prevent local reaction of lithium and reduce the amount of reaction with lithium at each portion of the amorphized portions. The volume expansion coefficient of the converted portion can be reduced. This reduces the stress applied to the alloy-based negative electrode active material particles, suppresses crushing of the alloy-based negative electrode active material particles, and improves the cycle characteristics of the all-solid battery. It is also presumed that the progress of chemical deterioration may be suppressed by the change in the volume expansion coefficient of the amorphized portion.

  The amorphization rate of the alloy-based negative electrode active material particles is 27.8 to 82.8%.

  It is considered that the cycle characteristics of the all-solid-state battery are improved when a part of the alloy-based negative electrode active material particles is crystalline rather than when the entire alloy-based negative electrode active material particles are made amorphous. It is considered that this is because the crystalline portion in the alloy-based negative electrode active material particles serves as a core to stabilize the structure of the entire particle.

<Cathode active material layer>
The positive electrode active material layer in the present invention has a positive electrode active material, and optionally a binder, a conductive additive, and a solid electrolyte.

The positive electrode active material is not particularly limited as long as it is a material used as a positive electrode active material material of a lithium secondary battery. For example, lithium cobalt oxide, lithium nickel oxide, nickel cobalt lithium manganate, lithium manganate, different element substitution Li-Mn spinel, lithium titanate, or LiMPO ₄ (M is one selected from Fe, Mn, Co, and Ni) Examples of the lithium metal phosphate having the composition represented by the above) or a combination thereof.

  The positive electrode active material may be covered with a protective coating which is a lithium-containing metal oxide having lithium as a component. This can prevent the positive electrode active material from reacting with the solid electrolyte to form an oxide film, and prevent deterioration of the positive electrode active material.

The lithium-containing metal oxide is not particularly limited as long as it has lithium ion conductivity and can maintain the form of the coating layer that does not flow even when contacted with the positive electrode active material or the solid electrolyte. For example, lithium niobate (LiNbO _3), lithium titanate _{(Li 4 Ti 5 O 12)} , or lithium phosphate _(Li 3 PO ₄₎ or the like can be used.

As the solid electrolyte, a sulfide solid electrolyte used as a solid electrolyte of an all-solid battery can be used. For _{example, Li 2 S-SiS 2,} LiI-Li 2 S-SiS 2, LiI-Li 2 S-P 2 S 5, LiI-Li 3 PO 4 -P 2 S 5, Li 2 S-P 2 S 5 , etc. Is mentioned.

  The binder is not particularly limited, but a polymer resin such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide (PA), polyamideimide (PAI), butadiene rubber (BR). , Styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), styrene-ethylene-butylene-styrene block copolymer (SEBS), carboxymethyl cellulose (CMC), and the like, or a combination thereof.

  Examples of the conductive additive include carbon materials such as VGCF, acetylene black, Ketjen black, carbon nanotube (CNT), and carbon nanofiber (CNF), and metals such as nickel, aluminum, and SUS, or a combination thereof. be able to.

<Solid electrolyte layer>
For the solid electrolyte layer, the electrolyte described in the positive electrode active material layer can be used. The thickness of the solid electrolyte layer may be, for example, 0.1 μm or more and 300 μm or less, and particularly 0.1 μm or more and 100 μm or less.

<Negative electrode active material layer>
The negative electrode active material layer has a negative electrode active material, and optionally a conductive additive, a binder, and a solid electrolyte.

  Alloy negative electrode active material particles are used as the negative electrode active material. Here, in the present invention, the alloy-based negative electrode active material is a metal-based negative electrode active material that reacts with lithium in a battery reaction to form an amorphous alloy. The alloy-based negative electrode active material particles are not particularly limited, and examples thereof include silicon particles, tin particles, germanium particles, aluminum particles, and combinations thereof. The primary particle diameter (median diameter) of the alloy-based negative electrode active material particles is preferably 10 μm or less, 7 μm or less, 5 μm or less, or 3 μm or less. Here, the primary particle diameter (median diameter) of the alloy-based negative electrode active material particles was measured using a laser diffraction/scattering particle size distribution measuring device LA-920 (manufactured by Horiba Ltd.).

  Part of the particles of the alloy-based negative electrode active material particles included in the all-solid-state battery used in the all-solid-state battery system of the present invention is made amorphous. Amorphization of the alloy-based negative electrode active material particles can be performed, for example, by initial charge/discharge performed after assembling the all-solid-state battery.

  The amorphization rate of the alloy-based negative electrode active material particles is 27.8 to 82.8%. The amorphization ratio may be 30% or more, 35% or more, 40% or more, or 50% or more, and 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, or 55%. May be: Here, the amorphization ratio refers to a ratio of an amorphized portion to the entire alloy-based negative electrode active material particles.

  This amorphization rate is, for example, TEM measurement at a position apart from the solid electrolyte layer by 5 μm to 15 μm in the negative electrode active material layer after charging the all-solid-state battery by applying a specified voltage and discharging to 2.5 V. At least 4 particles or more of the alloy-based negative electrode active material particles present in the visual field of 10 μm×10 μm measured by (the alloy-based negative electrode active material particles need only be partially contained, and the entire image does not necessarily have to be visible). It can be calculated as the ratio of the area of the amorphized portion of the alloy-based negative electrode active material particles to the area of the alloy-based negative electrode active material particles confirmed from the BF image.

  As the conductive additive, the binder, and the solid electrolyte, those described for the positive electrode active material layer can be used.

<Control device>
The control device used in the all-solid-state battery system of the present invention controls the charge/discharge voltage when the all-solid-state battery is used. The control device is not particularly limited as long as it is a device capable of controlling the charge/discharge voltage. The control device, for example, at the time of discharging the all-solid-state battery, determines whether the voltage of the all-solid-state battery has reached a certain voltage, a function to terminate the discharge when it reaches a certain voltage, and the all-solid-state battery During charging, it may have a function of determining whether the voltage of the all-solid-state battery has reached a certain voltage and ending the charging when the voltage of the all-solid-state battery has reached a certain voltage.

  It is preferable that the control device controls the voltage when the all-solid-state battery is used within the range of 2.50 V or more and 4.40 V or less. This is because when discharged to a voltage lower than 2.50 V or charged to a voltage higher than 4.40 V, the positive electrode active material or the negative electrode active material may deteriorate and the battery performance may decrease. The controlled discharge voltage range may be 2.60 V or higher, 2.70 V or higher, 2.90 V or higher, 3.00 V or higher, 3.10 V or higher, or 3.20 V or higher, and 4.30 V or lower. 4.20V or less, 4.10V or less, 4.00V or less, 3.90V or less, 3.80V or less, 3.70V or less, 3.60V or less, 3.50V or less, 3.40V or less, or 3.30V May be:

<Configuration example of all-solid-state battery used in the all-solid-state battery system of the present invention>
Specific examples of the structure of the all-solid battery (6) used in the all-solid battery system of the present invention include a positive electrode current collector (1), a positive electrode active material layer (2), a solid electrolyte layer (3), and a negative electrode active material. A configuration having the material layer (4) and the negative electrode current collector (5) in this order can be mentioned (see FIG. 2 ).

  Further, as shown in FIG. 3, the all-solid-state battery (7) used in the all-solid-state battery system of the present invention has a negative electrode current collector (5) as a center and a negative electrode active material layer (4) and a solid electrolyte on both sides thereof. The structure may include the layer (3), the positive electrode active material layer (2), and the positive electrode current collector (1).

  In addition, as shown in FIG. 4, the all-solid-state battery (8) used in the all-solid-state battery system of the present invention has a positive electrode current collector (1) as a center, and a positive electrode active material layer (2) and a solid electrolyte on both sides thereof. The structure may include the layer (3), the negative electrode active material layer (4), and the negative electrode current collector (5).

  2 to 4 are not intended to limit the configuration of the all-solid-state battery used in the all-solid-state battery system of the present invention.

<<Method for Manufacturing All-Solid-State Battery System of the Present Invention>>
The method for manufacturing the all-solid-state battery system of the present invention includes a stacking step of stacking a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer having alloy-based negative electrode active material particles as a negative electrode active material, and a stacking step. It is a method that has an initial charging step of later charging to a charging voltage higher than the charging/discharging voltage when using the battery.

  Although not limited by the principle, the operating principle of the present invention is considered as follows.

  Part of the alloy-based negative electrode active material particles reacts with lithium by charging to become an alloy. Then, the alloyed portion remains amorphized even after lithium ions are released by the discharge.

  By performing the initial charging at a voltage higher than the usage range of the battery as a product, more lithium ions move to the negative electrode side than in the case of being used as a product and can react with the alloy-based negative electrode active material particles. This makes it possible to increase the amorphous portion of the alloy-based negative electrode active material particles over the lithium ion releasing capacity of the positive electrode active material in normal use, and to increase the lithium ion receiving capacity of the negative electrode.

  Further, since the present inventor causes more lithium ions to react with the alloy-based negative electrode active material particles during initial charging, the positive electrode active material is covered with a protective coating which is a lithium-containing metal oxide such as lithium niobate. It was found that one can be used.

  The lithium-containing metal oxide used for such a protective coating emits lithium ions at a voltage higher than the normal operating range of batteries. Therefore, by charging the battery at a voltage higher than the normal operating range of the battery, more lithium ions than the positive electrode active material can release can be released to the negative electrode side. As a result, a larger amount of the alloy-based negative electrode active material particles can be reacted with lithium ions to further increase the amorphization rate of the alloy-based negative electrode active material particles.

  When the battery is charged and discharged at a voltage higher than the normal operating range of the battery, the positive electrode active material deteriorates, and the ability of the positive electrode active material to store and release lithium ions decreases. However, since the amorphization rate of the alloy-based negative electrode active material particles can be further increased, the cycle characteristics of the battery as a whole are improved.

<Lamination process>
The laminating step is a step of laminating the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer having the alloy-based negative electrode active material particles as the negative electrode active material. The positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the alloy-based negative electrode active material particles used in the laminating step are the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer used in the all-solid-state battery of the present invention. , And the same as the alloy-based negative electrode active material particles can be used. Further, all or part of the positive electrode active material contained in the positive electrode active material layer can be covered with a protective coating of a lithium-containing metal oxide containing lithium as a component. The lithium-containing metal oxide is not particularly limited, but examples thereof include lithium niobate.

<Initial charging process>
In the initial charging step, the lithium ions released from the positive electrode active material are reacted with the particles of the alloy-based negative electrode active material to promote amorphization of the alloy-based negative electrode active material.

  The initial charging voltage in the initial charging step is higher than the charging/discharging voltage controlled in the manufactured all-solid-state battery system. For example, when manufacturing an all-solid-state battery system in which the charge/discharge voltage is planned to be controlled within the range of 2.50 V or more and 4.40 V or less, the initial charge voltage is a value greater than 4.45 V and less than 5.00 V. Can be selected.

  Further, it is preferable to charge the battery so as to satisfy the following conditions.

  (Change rate (dQ/dV) of charge amount (Q) with respect to voltage (V) at charge voltage)/(charge amount (Q) with respect to voltage (V) when charge voltage is 4.00 V or more and 4.40 V or less) Change rate (average value of dQ/dV))>1.3.

  Note that (rate of change of charge amount (Q) with respect to voltage (V) at charge voltage (dQ/dV))/(charge amount with respect to voltage (V) when the charge voltage is 4.00 V or more and 4.40 V or less ( The average rate of change (dQ/dV) of Q) is 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more. , Or 2.1 or higher.

  The above equation will be described with reference to FIG. When the all-solid-state battery is charged within the range of charge/discharge voltage controlled by the control device, lithium ions are mainly released from the positive electrode active material, and the charge amount (Q) increases as the voltage (V) increases. (Range (10) in FIG. 5). When the charging voltage of the all-solid-state battery is further increased, lithium ions are released from the protective coating of the lithium-containing metal oxide at a constant voltage, so that the total amount of lithium ions moving from the positive electrode side to the negative electrode side is increased. The rate of change (dQ/dV) of the charge amount (Q) with respect to the voltage (V) increases ((range 20) in FIG. 5).

  In order to further improve the cycle characteristics of the all-solid-state battery, a method of exchanging the positive electrode active material layer after the initial charging step can be used. This method includes, for example, a positive electrode active material layer, a solid electrolyte layer, and a laminate having a negative electrode active material layer having alloy negative electrode active material particles as a negative electrode active material after the initial charging step. Alternatively, the positive electrode active material layer and the solid electrolyte layer are removed, and the newly prepared positive electrode active material layer or the positive electrode active material layer and the solid electrolyte layer are used as a negative electrode active material having alloy negative electrode active material particles as a negative electrode active material. This can be done by stacking layers.

  By adding this step, the positive electrode active material layer deteriorated due to the initial charging step can be replaced with a new positive electrode active material layer to further improve the battery performance. Further, since it is premised that the positive electrode active material layer is replaced, it is possible to charge and discharge at a high voltage without considering deterioration of the positive electrode active material layer in the initial charging step.

  In addition, when performing the method of replacing the positive electrode active material layer after the initial charging step, the releasable lithium content of the positive electrode active material layer before replacement is higher than the releasable lithium content of the positive electrode active material layer after replacement. The larger is also preferable.

  When the lithium ion content that can be released by the positive electrode active material layer before replacement is higher than the lithium content that can be released by the positive electrode active material layer after replacement, the voltage in the initial charging step is controlled by the control device. It does not have to be higher than the range of controlled charge/discharge voltage. This is because when the charging voltage is the same, the amount of lithium ions released by the positive electrode active material layer increases as the lithium content that can be released by the positive electrode active material layer increases.

  With such a configuration, in the initial charging step, more lithium ions than the lithium ions that can be released by the positive electrode active material layer after replacement can be supplied to the negative electrode active material layer. The amorphization ratio of the particles can be increased.

<<Examples 1 to 3 and Comparative Examples 1 to 5>>
As described below, all-solid-state batteries of Examples 1 to 3 and Comparative Examples 1 to 5 were produced and the battery performance was evaluated.

<Example 1>
The all-solid-state battery of Example 1 was prepared and the battery performance was evaluated as follows.

1. Preparation of all-solid-state battery (1) Preparation of positive electrode active material layer Positive electrode active material coated with butyl butyrate as a dispersion medium, 5 wt% butyl butyrate solution containing polyvinylidene fluoride as a binder, and lithium niobate as a protective coating. LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as a substance, Li ₂ S-P ₂ S ₅ based glass ceramic as a solid electrolyte, and VGCF (vapor grown carbon fiber) as a conduction aid, In addition to the polypropylene container, the mixture was stirred for 30 seconds with an ultrasonic dispersion device (SMT, product name UH-50). Then, the polypropylene container was shaken with a shaker (Shibata Scientific Co., Ltd., product name TTM-1) for 3 minutes and further stirred with an ultrasonic dispersion device for 30 seconds to prepare a paste for a positive electrode active material layer. ..

  The positive electrode active material layer paste is applied to an aluminum foil as a positive electrode current collector by a doctor blade method using an applicator, and then dried on a hot plate heated to 100° C. for 30 minutes, A positive electrode active material layer was produced.

(2) Preparation of Negative Electrode Active Material Layer Butyl butyrate as a dispersion medium, a 5 wt% butyl butyrate solution in which polyvinylidene fluoride is dissolved as a binder, silicon particles (manufactured by High Purity Chemical Co.) as a negative electrode active material, and Li as a solid electrolyte. _{2 S-P 2} S ₅ based glass ceramics, and VGCF (vapor grown carbon fiber) as a conductive additive, in addition to the polypropylene container, and stirred for 30 seconds with an ultrasonic dispersing device. Then, the polypropylene container was shaken with a shaker for 30 minutes to prepare a negative electrode active material layer paste.

  The negative electrode active material layer paste is applied to a copper foil as a negative electrode current collector by a doctor blade method using an applicator, and then dried on a hot plate heated to 100° C. for 30 minutes, A negative electrode active material layer was produced.

(3) heptane as making the dispersion medium of the solid electrolyte layer, 5 wt% heptane solution of butadiene rubber as a binder, and Li 2 _{S-P 2} S ₅ based glass ceramics containing lithium iodide as a solid electrolyte , A container made of polypropylene, and stirred for 30 seconds with an ultrasonic dispersion device. Then, the polypropylene container was shaken with a shaker for 30 minutes to prepare a solid electrolyte layer paste.

  The solid electrolyte layer paste is applied to an aluminum foil as a base by a blade method using an applicator, and then dried on a hot plate heated to 100° C. for 30 minutes to prepare a solid electrolyte layer. did.

(4) Laminating/Pressing Step A solid electrolyte layer is laminated on the positive electrode active material layer so that the solid electrolyte layer is in contact with the positive electrode active material layer, and pressed at 1 ton/cm ² , and an aluminum foil as a base of the solid electrolyte layer. Was peeled off to prepare a laminate of the solid electrolyte layer and the positive electrode active material layer.

Then, a negative electrode active material layer was overlaid on the solid electrolyte layer side of this laminate and pressed at 6 ton/cm ² to complete a battery. The prepared cell was restrained with a restraining pressure of 2 N·m using a restraining jig and put in a desiccator for evaluation.

2. Battery Performance Evaluation The prepared all-solid-state battery of Example 1 was subjected to constant current-constant voltage charging (termination current 1/100C) up to 4.55V at a 10-hour rate (1/10C) as initial charging, and then initial discharge. As constant current-constant voltage discharge up to 2.50 V. Then, constant current-constant voltage charging (stop current 1/100C) to 4.40 V, constant current-constant voltage discharging to 2.50 V, discharge of all-solid-state battery of Example 1 before endurance test. The capacity was measured.

  Then, as a durability test, a cycle of charging to 4.17V at 0.5 hour rate (2C) and then discharging to 3.17V was repeated 300 times. After the endurance test, constant current-constant voltage charge (stop current 1/100C) to 4.40 V, and constant current-constant voltage discharge to 2.50 V, after the endurance test of the all-solid-state battery of Example 1. Discharge capacity was measured.

  The discharge capacity after the durability test/the discharge capacity before the durability test was calculated to calculate the capacity retention rate of the all-solid-state battery of Example 1.

<Examples 2 and 3 and Comparative Examples 1 to 3>
By the same method as in Example 1, all-solid-state batteries of Examples 2 and 3 and Comparative Examples 1 to 3 were produced. After that, the initial charging voltage was 4.70V for Example 2, 5.00V for Example 3, 4.45V for Comparative Example 1, 4.40V for Comparative Example 2, and 3.60V for Comparative Example 3. Except for this, the battery performance of the all-solid-state batteries of Examples 2 and 3 and Comparative Examples 1 to 3 was evaluated by the same method as in Example 1.

<Comparative Examples 4 and 5>
In the production of the negative electrode active material layer, the thickness of the negative electrode active material layer produced by the doctor blade method was about twice the thickness of the negative electrode active material layer in Example 1 in Comparative Example 4 and Comparative Example. The all-solid-state batteries of Comparative Examples 4 and 5 were produced by the same method as in Example 1 except that the ratio was set to about 0.5 times per 5. After that, in Comparative Examples 4 and 5, the battery performance of the all-solid-state batteries of Comparative Examples 4 and 5 was evaluated by the same method as in Example 1 except that the initial charging voltage was set to 4.45V.

<Measurement result>
The manufacturing conditions, battery configurations, and measurement results of the all-solid-state batteries of Examples 1 to 3 and Comparative Examples 1 to 5 are shown in Table 1 below.

1. Description of Table 1 In Table 1, "Si weight" is the weight of silicon particles as a negative electrode active material contained in the all-solid-state battery.

  Further, the "amorphization rate" is a ratio of an amorphized portion to the entire silicon particles. The “amorphization rate” is calculated by 0.031דinitial charge amount” for simplicity (see <<Relationship between initial charge capacity and amorphization rate>> below).

  In addition, "amorphous capacity (W)" represents the capacity of an amorphized portion of silicon particles. "Amorphous capacity (W)" is "amorphous capacity (W)" = ("Si weight" (mg) x 1000) x "amorphization rate" (%) x 4200 (mAh/g) (theoretical capacity of silicon particles ) Was calculated.

  The "controlled discharge capacity (Z)" was obtained by calculating the value of the discharge capacity before the durability test as the discharge capacity in the voltage range actually controlled by the control device in the all-solid-state battery system at the time of completion as a product. ..

  Further, "Z/W" is a value obtained by dividing "control discharge capacity (Z)" by "amorphous capacity (W)".

  The “capacity maintenance ratio” is a value calculated by setting the result of the durability test of the all-solid-state battery of Comparative Example 1 as 100%.

2. Consideration In the all-solid-state batteries of Examples 1 to 3, the "amorphization rate" was 27.8%, 34.1%, and 36.2%, respectively, and "Z/W" was It was 0.53, 0.54, and 0.52. Therefore, all of the solid-state batteries of Examples 1 to 3 satisfy the amorphization rate of 27.8 to 82.8% and 0.32≦Z/W≦0.60. There is.

  In the all-solid-state batteries of Examples 1 to 3, the “capacity retention ratio” was 108%, 104%, and 109%, respectively.

  In the all-solid-state batteries of Comparative Examples 1 to 4, the "amorphization rate" was 26.6%, 23.9%, 5.8%, and 13.3%, respectively, and "Z/W". Were 0.66, 0.68, 2.85, and 0.64, respectively. Therefore, in all the all-solid-state batteries of Comparative Examples 1 to 4, the amorphization rate is 27.8 to 82.8%, and 0.32≦Z/W≦0.60. Also did not meet.

  In the all-solid-state batteries of Comparative Examples 1 to 4, the “capacity retention rate” is 100%, 99%, 96%, and 97%, respectively, and in the all-solid-state batteries of Comparative Examples 2 to 4, Example 1 to The “capacity maintenance ratio” was smaller than that of the all-solid-state battery of No. 3.

  The all-solid-state battery of Comparative Example 5 had an “amorphization rate” of 43.9% and a “Z/W” of 0.67. Therefore, the all-solid-state battery of Comparative Example 5 satisfied the amorphization rate of 27.8 to 82.8%, but did not satisfy 0.32≦Z/W≦0.60.

  The all-solid-state battery of Comparative Example 5 had a “capacity maintenance ratio” of 97%, and the “capacity maintenance ratio” was smaller than that of the all-solid-state batteries of Examples 1 to 3.

  From the above, the all-solid-state battery having an amorphization rate of 27.8 to 82.8% and 0.32≦Z/W≦0.60 has an amorphization rate of 27.8 to. It can be said that the “capacity maintenance ratio” is larger than that of the all-solid-state battery that does not satisfy 82.8% and 0.32≦Z/W≦0.60.

  This is because the all-solid-state batteries of Examples 1 to 3 have smaller “Z/W” than Comparative Example 1, so that the expansion/contraction ratio of the amorphized portion with respect to the entire silicon particles is smaller than that of Comparative Example 1. It shows that crushing of silicon particles due to repeated charging and discharging is less likely to occur.

  On the other hand, in the all-solid-state batteries of Comparative Examples 1 to 5, since the amorphized portion of the silicon particles is not sufficiently large, the proportion of expansion and contraction due to reaction with lithium ions becomes large, and the charge and discharge of 300 cycles are performed. It shows that the "capacity retention rate" was lowered because the silicon particles were crushed by the stress generated in the silicon particles during the operation. In particular, in Comparative Example 3, “Z/W” was the largest in Examples 1 to 3 and Comparative Examples 1 to 5, and conversely, the “capacity maintenance ratio” was the lowest at 96%. This indicates that in Comparative Example 3, the expansion/contraction ratio of the amorphized portion with respect to the entire silicon particles was large due to charging/discharging, and the silicon particles were crushed more than other Examples and Comparative Examples. ing.

  From this, it can be said that the cycle characteristics of the all-solid-state battery can be further improved by charging to a higher initial charging voltage.

<<Examples 4 to 7 and Comparative Examples 6 and 7>>
As described below, the all-solid-state batteries of Examples 4 to 7 and Comparative Examples 6 and 7 were produced and the battery performance was evaluated.

<Method for manufacturing all-solid-state battery and evaluating battery performance>
By the same method as in Example 1, all-solid-state batteries of Examples 4 to 7 and Comparative Examples 6 and 7 were produced. Then, with respect to Example 4, the battery performance of the all-solid-state battery was evaluated in the same manner as in the method of Example 1. The initial charging voltages of the all-solid-state batteries of Examples 5 to 7 and Comparative Examples 6 and 7 were 4.60 V for Example 5, 4.65 V for Example 6, 4.70 V for Example 7, and Comparative Example 6. The battery performance of the all-solid-state batteries of Examples 5 to 7 and Comparative Examples 6 and 7 was evaluated by the same method as in Example 1 except that the voltage was set to 4.40 and 4.45 V for Comparative Example 7.

<Measurement result>
Table 2 below shows the manufacturing conditions, battery configurations, and measurement results of the all-solid-state batteries of Examples 4 to 7 and Comparative Examples 6 and 7.

1. Description of Table 2 In Table 2, “β” is the rate of change (dQ/dV) of the capacity (Q) with respect to the voltage (V) at the upper limit charging voltage in the initial charging step, and “α” is the charging voltage. It is the average value of the rate of change (dQ/dV) of the capacity (Q) with respect to the voltage (V) when the voltage is 4.0 V or more and 4.4 V or less.

  The "amorphization rate" in Table 2 was calculated by the same method as the "amorphization rate" in Table 1.

  Therefore, “β/α” is (rate of change in capacity (Q) with respect to voltage (V) at the upper limit charging voltage in the initial charging step (dQ/dV))/(charging voltage is 4.0 V or more and 4.4 V or less) It is the average value of the rate of change (dQ/dV) of the capacity (Q) with respect to the voltage (V) at a given time.

  In Table 2, "amorphous capacity" represents the capacity of the amorphous portion of the silicon particles.

  In Table 2, the "capacity maintenance rate" is a value calculated by setting the result of the durability test of the all-solid-state battery of Comparative Example 7 as 100%. Further, “resistance” is the internal resistance of the all-solid-state battery, but is a value calculated with the internal resistance of the all-solid-state battery of Comparative Example 7 as 100%.

2. Discussion In the methods of Examples 4 to 6, all-solid-state batteries were manufactured such that β/α was set to be 1.91, 2.18, and 1.65, respectively. Therefore, the methods of Examples 4 to 6 satisfy β/α>1.3.

  The all-solid-state batteries manufactured by the methods of Examples 4 to 6 had “amorphous capacities” of 3.40 mAh, 3.37 mAh, and 3.62 mAh, respectively, and were manufactured by the methods of Comparative Examples 6 and 7. The amorphous capacity was larger than that of the all-solid-state battery. In addition, the all-solid-state batteries manufactured by the methods of Examples 4 to 6 have “capacity maintenance ratios” of 108%, 108%, and 106%, respectively, and all of them are “capacity maintenance of Comparative Examples 6 and 7. Was greater than the "rate". The "resistance" was 94%, 93%, and 96%, respectively, which were smaller than the "resistance" of Comparative Examples 6 and 7.

  This means that by performing initial charging so that β/α is greater than 1.3, an all-solid-state battery with a large amorphous capacity can be produced, and the “capacity maintenance ratio” of the produced all-solid-state battery. , And “resistance” are improved.

  On the other hand, in the methods of Comparative Examples 6 and 7, all-solid-state batteries were manufactured such that β/α was 1.10 and 1.27, respectively. Therefore, the methods of Comparative Examples 6 and 7 do not satisfy β/α>1.3.

  The all-solid-state batteries manufactured by the methods of Comparative Examples 6 and 7 had the “capacity maintenance ratios” of 96% and 100%, respectively. Moreover, "resistance" was 101% and 100%, respectively.

  Further, in the method of Example 7, an all-solid-state battery was manufactured such that β/α was 0.69.

  The all-solid-state battery manufactured by the method of Example 7 had a “capacity maintenance ratio” of 106%. The “resistance” was 99%.

  In the method of Example 7, the initial charging was performed up to 4.70 V, and β/α was smaller than 1.3, although the initial charging voltage was higher than those of the methods of Examples 4 to 6. It is a value. This is because lithium ions were released from lithium niobate as the charging voltage increased, but before the charging voltage reached 4.70V, most of the lithium ions that lithium niobate could release were released. It is considered that the lithium ions moving from the positive electrode side to the negative electrode side decreased.

  In addition, the all-solid-state battery of Example 7 has a larger “capacity maintenance ratio” and a smaller “resistance” than those of Comparative Examples 6 and 7. On the other hand, the all-solid-state battery of Example 7 has a larger “resistance” than those of Examples 4-6. It is considered that this is because the deterioration of the protective coating of lithium niobate is large. Therefore, it is not necessary to simply increase the initial charge voltage, but the initial charge/discharge is controlled so that β/α becomes larger than 1.3, thereby increasing the “capacity maintenance ratio” and the “resistance”. Can be made smaller.

  From this, it can be said that the cycle characteristics of the all-solid-state battery can be improved by controlling the initial charge/discharge so that β/α becomes larger than 1.3.

<Reference Examples 1 to 6>
In order to show the relationship between the value of β/α and the protective coating of the positive electrode active material with the lithium-containing metal oxide, the following all-solid-state batteries of Reference Examples 1 to 6 were prepared and the battery performance was evaluated. ..

1. Reference Examples 1-3
All solid state batteries of Reference Examples 1 to 3 were produced in the same manner as in Example 4 except that the negative electrode active material was replaced with natural graphite carbon.

  Examples except that the initial charging voltage was set to 4.45 V for Reference Example 1, 4.55 V for Reference Example 2, and 4.70 V for Reference Example 3 for the prepared all-solid-state batteries of Reference Examples 1 to 3. In the same manner as in 4, initial charging was performed on the all solid state batteries of Reference Examples 1 to 3 and β/α was measured.

2. Reference Examples 4-6
Example 4 except that the positive electrode active material was replaced with LiNi _1/3 Co _1/3 Mn _1/3 O ₂ which was not coated with lithium niobate, and the negative electrode active material was replaced with natural graphite-based carbon. Similarly, the all-solid-state batteries of Reference Examples 4 to 6 were produced.

  Examples except that the initial charging voltage was 4.45 V for Reference Example 4, 4.55 V for Reference Example 5, and 4.70 V for Reference Example 6 for the prepared all-solid-state batteries of Reference Examples 4 to 6. In the same manner as in 4, initial charging was performed on the all solid state batteries of Reference Examples 4 to 6 and β/α was measured.

3. Measurement Results Experimental conditions and measurement results of the all-solid-state batteries of Reference Examples 1 to 6 are shown in Table 3 below.

1. Description of Table 3 In Table 3, “β/α” is as described in the description of Table 2.

2. Discussion As shown in Table 3, in Reference Examples 1 to 3, β/α were 1.19, 1.77, and 1.52, respectively, and were larger than 1, while Reference Examples 4 to 6 were used. , Β/α were 0.93, 0.90, and 0.53, respectively, and were smaller than 1. This indicates that the value of β/α can be increased by including lithium niobate in the positive electrode active material layer. That is, by including lithium niobate in the positive electrode active material layer, more lithium ions can be supplied to the negative electrode active material at high voltage.

<<Examples 8 to 11>>
As described below, the all-solid-state batteries of Examples 8 to 11 were produced and the battery performance was evaluated.

<Example 8>
1. Method of manufacturing provisional all-solid-state lithium secondary battery (1) Preparation of positive electrode active material layer for supplying lithium Butyl butyrate as a dispersion medium, a 5 wt% butyl butyrate solution in which polyvinylidene fluoride as a binder is dissolved, and a positive electrode active material LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , Li ₂ S—P ₂ S ₅ glass ceramic containing lithium iodide as a solid electrolyte, and VGCF (gas phase method carbon fiber) as a conduction aid. ) Was added to a polypropylene container, and the mixture was stirred with an ultrasonic dispersion device (manufactured by SMT, product name UH-50) for 30 seconds. Then, the polypropylene container was shaken with a shaker (Shibata Scientific Co., Ltd., product name TTM-1) for 3 minutes, and further stirred with an ultrasonic dispersing device for 30 seconds to prepare a paste for a positive electrode active material layer.

  The positive electrode active material layer paste was applied to an aluminum foil as a positive electrode current collector by a blade method using an applicator, and then dried on a hot plate heated to 100° C. for 30 minutes to collect the positive electrode current. A positive electrode active material layer for supplying lithium was formed on the electric body.

(2) Preparation of Negative Electrode Active Material Layer Butyl butyrate as a dispersion medium, a 5 wt% butyl butyrate solution in which polyvinylidene fluoride is dissolved as a binder, silicon particles as a negative electrode active material, and Li containing lithium iodide as a solid electrolyte. _{2 S-P 2} S ₅ based glass ceramics, and VGCF (vapor grown carbon fiber) as a conductive additive, in addition to the polypropylene container, and stirred for 30 seconds with an ultrasonic dispersing device. Then, the polypropylene container was shaken for 30 minutes with a shaker to prepare a negative electrode active material layer paste.

  The negative electrode active material layer paste was applied to a copper foil as a negative electrode current collector by a blade method using an applicator, and then dried on a hot plate heated to 100° C. for 30 minutes to obtain a negative electrode current collector. A negative electrode active material layer was formed on the electric body.

(3) heptane as making the dispersion medium of the solid electrolyte layer, 5 wt% heptane solution of butadiene rubber as a binder, and Li 2 _{S-P 2} S ₅ based glass ceramics containing lithium iodide as a solid electrolyte , A container made of polypropylene, and stirred for 30 seconds with an ultrasonic dispersion device. Then, the polypropylene container was shaken with a shaker for 30 minutes to prepare a solid electrolyte layer paste.

The prepared solid electrolyte layer paste was applied to an aluminum foil by a doctor blade method, and then dried on a hot plate heated to 100° C. for 30 minutes to prepare a solid electrolyte layer. By pressing the positive electrode active material layer for supplying lithium, the deactivated lithium-free negative electrode active material layer and the solid electrolyte layer, respectively, at 6 ton/cm ² , and peeling the Al foil on the solid electrolyte layer side, A laminate of a positive electrode active material layer for supplying lithium and a solid electrolyte layer, and a laminate of a deactivated lithium-free negative electrode active material layer and a solid electrolyte layer were produced.

(4) Preparation of provisional all-solid-state lithium secondary battery A laminated body of a positive electrode active material layer for supplying lithium and a solid electrolyte layer was formed into a laminated body of a negative electrode active material layer and a solid electrolyte layer with a punching jig having a diameter of 12.5 mm. Punching was performed with a jig having a diameter of 13.0 mm. Both were laminated so that their respective solid electrolyte layers were in contact with each other, and were constrained with a constraining pressure of 2 N/m using a constraining jig to obtain a temporary all-solid-state lithium secondary battery.

2. Charging and Discharging Temporary All-solid-state Lithium Secondary Battery A temporary all-solid-state lithium secondary battery was put in a desiccator and subjected to constant current-constant voltage charging at 4.5 C to 4.55 V (end current 0.01 C). Then, the battery was discharged to 2.50 V with constant current-constant voltage. As a result, lithium was supplied to the negative electrode active material layer.

3. After disassembling and reassembling the battery, the provisional all-solid lithium secondary battery was unconstrained, and the laminate of the positive electrode active material layer for supplying lithium and the solid electrolyte layer, the deactivated lithium-free negative electrode active material layer, and the solid electrolyte layer were It was disassembled into a laminate. The laminated body of the negative electrode active material layer and the solid electrolyte layer was used as the first laminated body. In addition, the lithium content of the positive electrode active material layer for supplying lithium used in the provisional all-solid-state lithium secondary battery was set to be 1.5 times the lithium content of the positive electrode active material layer of the newly manufactured laminate. Except for the above, a new laminated body was produced by the same manufacturing method as that of the laminated body of the positive electrode active material layer and the solid electrolyte layer described above. The new laminated body was punched with a punching jig having a diameter of 12.5 mm to obtain a second laminated body.

The solid electrolyte layer for joining produced by the following method was laminated on the first laminate so that the solid electrolyte layer of the first laminate and the solid electrolyte layer for joining were in contact with each other, and 1.0 ton/cm ² Then, the aluminum foil as a base was peeled off. Then, the second laminate was laminated so that the solid electrolyte layer of the second laminate and the solid electrolyte layer for bonding were in contact with each other, and pressed at 6 ton/cm ² , to obtain the all-solid lithium secondary material of Example 8. A battery was produced.

4. Preparation of solid electrolyte layer for bonding A heptane as a dispersion medium, a 5 wt% heptane solution in which butadiene rubber was dissolved as a binder, and Li ₂ S-P ₂ S ₅ based glass ceramic containing lithium iodide as a solid electrolyte were prepared. In addition to the polypropylene container, the mixture was stirred for 30 seconds with an ultrasonic dispersion device. Then, the polypropylene container was shaken with a shaker for 30 minutes to prepare a solid electrolyte layer paste for bonding.

  The solid electrolyte paste for bonding is applied to an aluminum foil as a substrate by a doctor blade method, and then dried on a hot plate heated to 100°C for 30 minutes to form a solid electrolyte layer for bonding on the substrate. Then, it was punched with a jig having a diameter of 13.0 mm.

5. Initial charging/discharging The completed all-solid-state lithium secondary battery of Example 8 was put in a desiccator, and constant current-constant voltage charging was performed at 0.05 C to 4.55 V (stop current 0.01 C). Then, the battery was discharged at a constant current-constant voltage to 2.50 V and the discharge capacity was measured.

6. Initial measurement of capacity retention rate After completion of charging and discharging, the all-solid-state lithium secondary battery of Example 8 was charged to 4.40 V by constant current-constant voltage charging, and discharged to 2.50 V by constant current-constant voltage discharging. , Its discharge capacity was measured (first discharge capacity). Then, the process of charging to 4.17V at a 0.5 hour rate (2C) and then discharging to 3.17V was repeated 300 cycles. After 300 cycles, the all-solid-state lithium secondary battery of Example 8 was charged to 4.40 V by constant current-constant voltage charging and discharged to 2.50 V by constant current-constant voltage discharging, and its discharge capacity was measured. (Second discharge capacity). The second discharge capacity/first discharge capacity was calculated and the capacity retention rate was measured.

<Examples 9 and 10>
The lithium content of the positive electrode active material layer used in the provisional all-solid-state lithium secondary battery was 1.50 times in Example 9 and 1 in Example 10 with respect to the lithium content of the positive electrode active material layer of the newly manufactured laminate. An all-solid-state lithium secondary battery was produced in the same manner as in Example 8 except that the power was set to 0.01 times.

  Initial charge and discharge were performed on the all-solid-state lithium secondary batteries of Examples 9 and 10 in the same manner as in Example 8 to measure the discharge capacity. Further, the capacity retention ratios of the all-solid-state lithium secondary batteries of Examples 9 and 10 were measured in the same manner as in Example 8.

<Example 11>
A solid electrolyte layer for bonding produced in the same manner as in the method of Example 8 was inserted and laminated between the laminate of the positive electrode active material layer and the solid electrolyte layer and the laminate of the negative electrode active material layer and the solid electrolyte layer. An all-solid lithium secondary battery of Example 11 was obtained in the same manner as the all-solid lithium secondary battery of Example 8 except for the above. Initial charge and discharge were performed on the all-solid-state lithium secondary battery of Example 11 in the same manner as in Example 8 to measure the discharge capacity. Further, the capacity retention ratio was measured for the all-solid-state lithium secondary battery of Example 11 in the same manner as in Example 8.

<Measurement result>
Table 4 shows manufacturing conditions, battery configurations, and measurement results of the all-solid-state batteries of Examples 8 to 11.

1. Description of Table 4 In Table 4, "presence or absence of disassembly/reconstruction" indicates the presence or absence of the step of disassembling the all-solid-state battery and replacing the positive electrode active material layer (the above-mentioned "disassembly/reconstruction of battery"). There is.

  In Table 4, "A" is the capacity of the positive electrode active material layer for supplying lithium, and substantially represents the releasable lithium content of the positive electrode active material layer for supplying lithium. Further, “B” is the capacity of the positive electrode active material layer, and substantially represents the releasable lithium content of the positive electrode active material layer. Therefore, “A/B” is a value obtained by dividing the capacity of the positive electrode active material layer for supplying lithium by the capacity of the positive electrode active material layer. It should be noted that in Example 11, since the above-described “Battery disassembly/reconstruction” was not performed, no numerical value is described.

  The “amorphization ratio” and “Z/W” are as described in the description of Table 1. In Table 4, specific numerical values of "Z" and "W" are omitted for simplicity.

  The “capacity maintenance ratio” is a value calculated by setting the result of the durability test of the all-solid-state battery of Example 11 as 100%. Moreover, "resistance" is an internal resistance of the all-solid-state battery, and is a value calculated with the internal resistance of the all-solid-state battery of Example 11 as 100%.

2. Consideration The "resistance" of the all-solid-state lithium secondary battery of Example 10 is 96%, which is smaller than the "resistance" of the all-solid-state lithium secondary battery of Example 11. On the other hand, the “capacity maintenance ratio” of the all-solid-state lithium secondary battery of Example 10 is 132%, which is larger than the “capacity maintenance ratio” of the all-solid-state lithium secondary battery of Example 11.

  In the all-solid-state lithium secondary battery of Example 10, the releasable lithium content of the positive electrode active material layer for supplying lithium was “A” and the releasable lithium content of the positive electrode active material layer was “B”. The ratio is 1.01, and although there is no large difference, the resistance and capacity retention ratios are significantly improved compared to the case of Example 11. This is an all-solid-state lithium secondary battery with reduced resistance and improved capacity retention rate by replacing the positive-electrode active material layer deteriorated by charging the all-solid-state lithium secondary battery with a new positive-electrode active material layer. It shows that it can be manufactured. Further, comparing Examples 8 to 10, it can be said that the “resistance” decreases and the “capacity retention ratio” improves as the value of “A/B” increases.

  From this, it can be said that the cycle characteristics of the all-solid-state battery can be further improved by replacing the positive electrode active material layer deteriorated due to the initial charging step with a new positive electrode active material layer.

<<Relationship between initial charge and amorphization rate>>
The amorphization ratio is measured by TEM measurement at a position 5 μm to 15 μm away from the solid electrolyte layer in the negative electrode active material layer after charging the all-solid-state battery by applying a specified voltage and discharging to 2.50 V. For silicon particles of at least 4 particles or more existing in a visual field of 10 μm×10 μm (the silicon particles only have to be partially contained, it is not necessary to see the whole image), the silicon confirmed from the BF image. It can be calculated as the ratio of the area of the amorphized portion of the silicon particles to the area of the particles. The correlation between the value of the amorphization ratio obtained by this calculation and the value of the initial charge amount was examined for the all-solid-state batteries of Example 1, Comparative Example 1 and Comparative Example 2.

  Table 5 shows the relationship between the initial charge amount and the amorphization rate of the all-solid-state batteries of Example 1, Comparative Example 1, and Comparative Example 2.

From the values of “initial charge amount” and “amorphization rate” of Example 1, Comparative Example 1 and Comparative Example 2, as shown in FIG. 5, “amorphization rate (%)=0.031×initial charge” It was confirmed that the relationship of “amount (mAh 2 /g 2 )” was satisfied.

1 Positive Electrode Current Collector 2 Positive Electrode Active Material Layer 3 Solid Electrolyte Layer 4 Negative Electrode Active Material Layer 5 Negative Electrode Current Collector 6-8 All Solid State Battery

Claims (11)

An all-solid-state battery system having an all-solid-state battery having a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and a control device for controlling a charge/discharge voltage during use of the all-solid-state battery. ,
Having the alloy-based negative electrode active material particles in the negative electrode active material layer,
An all-solid-state battery system in which the amorphization rate of the alloy-based negative electrode active material particles is 27.8 to 82.8% and the following conditions are satisfied:
0.32≦Z/W≦0.60
Z: Controlled discharge capacity (mAh) of the all-solid-state battery
W: theoretical capacity (mAh/g) of alloy-based negative electrode active material particles x total weight (g) of the alloy-based negative electrode active material particles x amorphization rate (%).   The all-solid-state battery system according to claim 1, wherein the alloy-based negative electrode active material particles are silicon particles.   The all-solid-state battery system according to claim 1 or 2, wherein the positive electrode active material layer has a positive electrode active material covered with a protective coating which is a lithium-containing metal oxide.   The all-solid-state battery system of claim 3, wherein the lithium-containing metal oxide of the protective coating is lithium niobate.   The all-solid-state battery system according to claim 1, wherein the control device controls the charge/discharge voltage within a range of 2.50 V or more and 4.40 V or less.   Method for manufacturing all-solid-state battery system having all-solid-state battery having positive electrode active material layer, solid electrolyte layer, and negative-electrode active material layer, and control device for controlling charge/discharge voltage when using the all-solid-state battery That is, the positive electrode active material layer, the solid electrolyte layer, and a stacking step of stacking the negative electrode active material layer having alloy-based negative electrode active material particles, and the initial charging voltage higher than the charging and discharging voltage. A method for manufacturing an all-solid-state battery system having an initial charging step of charging the all-solid-state battery.   The method according to claim 6, wherein the alloy-based negative electrode active material particles are silicon particles.   8. The charging/discharging voltage is in the range of 2.50 V or more and 4.40 V or less, and in the initial charging step, the initial charging voltage is higher than 4.45 V and 5.00 V or lower. Method.   9. The method according to any one of claims 6 to 8, wherein the positive electrode active material layer has a positive electrode active material coated with a protective coating that is a lithium-containing metal oxide.   10. The method of claim 9, wherein the lithium-containing metal oxide of the protective coating is lithium niobate. The method according to claim 9 or 10, wherein the initial charging step is performed so as to satisfy the following conditions:
(Change rate (dQ/dV) of charge amount (Q) with respect to voltage (V) at upper limit charging voltage in initial charging step)/(with respect to voltage (V) when charging voltage is 4.00 V or more and 4.40 V or less) Change rate (dQ/dV) average value of charge amount (Q))>1.3.

Images