Negative electrode and method for manufacturing a negative electrode

Abstract

To provide a negative electrode body including a negative electrode that is capable of significantly increasing capacity while maintaining excellent battery characteristics and that is also capable of suppressing expansion when a battery is fully charged.SOLUTION: A negative electrode body includes: a negative electrode that includes a negative electrode current collector with a roughened surface, a negative electrode active material layer provided on the negative electrode current collector, and an ion conductive layer provided on a surface of the negative electrode active material layer and having lithium ion conductivity; and a solid electrolyte layer adjacent to the ion conductive layer. The negative electrode active material layer contains negative electrode active material particles including a compound containing lithium, silicon, and oxygen, and the negative electrode active material particles can be represented by SiOx1Liy1 where the value of x1 is more than 0.8 and 1.2 or less, and the value of y1 is 0.5 or more and 3.4 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a negative electrode and a method for manufacturing a negative electrode. [Background technology]

[0002] In recent years, small electronic devices such as mobile terminals have become widespread, and there is a strong demand for further miniaturization, weight reduction, and longer lifespan. In response to these market demands, development is progressing on secondary batteries that are particularly small, lightweight, and capable of achieving high energy density. These secondary batteries are being considered not only for small electronic devices but also for large electronic devices such as automobiles, and for power storage systems such as those found in homes.

[0003] Among these, lithium-ion secondary batteries are particularly promising because they are easy to miniaturize and increase capacity, and they can achieve a higher energy density than lead-acid batteries and nickel-cadmium batteries.

[0004] The lithium-ion secondary battery described above comprises an electrolyte along with a positive electrode, a negative electrode, and a separator, and the negative electrode contains a negative electrode active material that is involved in the charge-discharge reaction.

[0005] While carbon-based active materials are widely used as negative electrode active materials, recent market demands require further improvements in battery capacity. To improve battery capacity, the use of silicon as a negative electrode active material is being considered. This is because the theoretical capacity of silicon (4199 mAh / g) is more than 10 times greater than that of graphite (372 mAh / g), so a significant improvement in battery capacity can be expected. The development of silicon materials as negative electrode active materials is being considered not only for pure silicon but also for compounds such as alloys and oxides. Furthermore, the shape of the active material is being considered from the standard coated type for carbon-based active materials to an integrated type that is directly deposited on the current collector.

[0006] However, when silicon is used as the main raw material for the negative electrode active material, the negative electrode active material expands and contracts during charging and discharging, making it prone to cracking, mainly near the surface of the negative electrode active material. In addition, ionic substances are generated inside the active material, making the negative electrode active material more susceptible to cracking. When the surface of the negative electrode active material cracks, a new surface is created, increasing the reaction area of ​​the active material. At this time, a decomposition reaction of the electrolyte occurs on the new surface, and a film of electrolyte decomposition products is formed on the new surface, thus consuming the electrolyte. As a result, the cycle characteristics tend to deteriorate.

[0007] To date, various studies have been conducted on negative electrode materials and electrode configurations for lithium-ion secondary batteries, primarily using silica as the main material, in order to improve the initial efficiency and cycle characteristics of batteries.

[0008] Specifically, to obtain good cycle characteristics and high safety, silicon and amorphous silicon dioxide are deposited simultaneously using a vapor phase method (see, for example, Patent Document 1). In addition, to obtain high battery capacity and safety, a carbon material (electron conductive material) is provided on the surface of the silicon oxide particles (see, for example, Patent Document 2). Furthermore, in order to improve cycle characteristics and obtain high input / output characteristics, an active material containing silicon and oxygen is prepared, and an active material layer with a high oxygen ratio near the current collector is formed (see, for example, Patent Document 3). In addition, in order to improve cycle characteristics, oxygen is incorporated into the silicon active material, and it is formed so that the average oxygen content is 40 at% or less, and the oxygen content is higher near the current collector (see, for example, Patent Document 4).

[0009] In addition, in order to improve the initial charge-discharge efficiency, a nano-composite containing Si phase, SiO2, and MyO metal oxide is used (see, for example, Patent Document 5). Also, for improving cycle characteristics, SiOx (0.8 ≤ x ≤ 1.5, particle size range = 1 μm to 50 μm) and a carbon material are mixed and fired at high temperature (see, for example, Patent Document 6). Further, for improving cycle characteristics, the molar ratio of oxygen to silicon in the negative electrode active material is set to 0.1 to 1.2, and the active material is controlled within a range where the difference between the maximum value and the minimum value of the molar ratio near the active material and current collector interface is 0.4 or less (see, for example, Patent Document 7). In addition, in order to improve the battery load characteristics, a metal oxide containing lithium is used (see, for example, Patent Document 8). Also, in order to improve cycle characteristics, a hydrophobic layer such as a silane compound is formed on the surface layer of the silicon material (see, for example, Patent Document 9). Further, for improving cycle characteristics, silicon oxide is used, and conductivity is imparted by forming a graphite film on its surface layer (see, for example, Patent Document 10). In Patent Document 10, regarding the shift value obtained from the RAMAN spectrum of the graphite film, broad peaks appear at 1330 cm-1 and 1580 cm-1, and the intensity ratio I1330 / I1580 is 1.5 < I1330 / I1580 < 3. Also, for improving high battery capacity and cycle characteristics, particles having a silicon microcrystalline phase dispersed in silicon dioxide are used (see, for example, Patent Document 11). In addition, in order to improve overcharge and overdischarge characteristics, a silicon oxide in which the atomic ratio of silicon to oxygen is controlled to 1:y (0 < y < 2) is used (see, for example, Patent Document 12).

[0010] The lithium-ion secondary battery using silicon oxide was started to be shipped by Hitachi Maxell in June 2010 for a rectangular secondary battery for smartphones that adopted a nano-silicon composite (see, for example, Non-Patent Document 1). The silicon oxide proposed by Hohl is Si 0+ ~Si 4+It is a composite material and has various oxidation states (see Non-Patent Document 2). Kapaklis has also proposed a disproportionation structure in which silicon oxide separates into Si and SiO2 when a thermal load is applied (see Non-Patent Document 3). Miyachi et al. have focused on Si and SiO2, which contribute to charging and discharging, among the silicon oxides having a disproportionation structure (see Non-Patent Document 4), and Yamada et al. have proposed the following reaction equation between silicon oxide and Li (see Non-Patent Document 5).

[0011] 2SiO(Si+SiO2) + 6.85Li + + 6.85e - → 1.4Li 3.75 Si + 0.4Li4SiO4 + 0.2SiO2

[0012] The above reaction equation shows that the Si and SiO2 that make up silicon oxide react with Li to separate into Li silicide, Li silicate, and some unreacted SiO2.

[0013] The Li silicate produced here is irreversible and, once formed, is considered a stable substance that does not release Li. The volume per unit weight calculated from this reaction equation is close to experimental values ​​and is recognized as a reaction mechanism for silicon oxides. Kim et al. referred to the irreversible component of silicon oxide charging and discharging, Li silicate, as Li4SiO4. 7 Li-MAS-NMR and 29 Identification is performed using Si-MAS-NMR (see Non-Patent Document 6).

[0014] This irreversible capacity is the biggest weakness of silicon oxides, and improvement is needed. Therefore, Kim et al. have used a Li pre-doping method, which involves forming Li silicate in advance, to significantly improve the initial efficiency of the battery and create a negative electrode that can withstand practical use (see Non-Patent Document 7).

[0015] Furthermore, instead of doping the electrodes with Li, a method of treating the powder has also been proposed, and this method has achieved an improvement in irreversible capacity (see Patent Document 13).

[0016] Silicon oxide with improved irreversible capacity can replace carbon material anodes at a high rate, significantly increasing battery capacity. However, increasing the proportion of silicon oxide in the anode increases the risk of ignition in the event of a malfunction in a battery using a liquid electrolyte, thus reducing battery safety.

[0017] Therefore, in order to ensure the safety of batteries, various development efforts are underway to create all-solid-state batteries in which the liquid electrolyte is replaced with a solid electrolyte (see Patent Documents 14-17). [Prior art documents] [Patent Documents]

[0018] [Patent Document 1] Japanese Patent Publication No. 2001-185127 [Patent Document 2] Japanese Patent Publication No. 2002-042806 [Patent Document 3] Japanese Patent Publication No. 2006-164954 [Patent Document 4] Japanese Patent Publication No. 2006-114454 [Patent Document 5] Japanese Patent Publication No. 2009-070825 [Patent Document 6] Japanese Patent Publication No. 2008-282819 [Patent Document 7] Japanese Patent Publication No. 2008-251369 [Patent Document 8] Japanese Patent Publication No. 2008-177346 [Patent Document 9] Japanese Patent Publication No. 2007-234255 [Patent Document 10] Japanese Patent Publication No. 2009-212074 [Patent Document 11] Japanese Patent Publication No. 2009-205950 [Patent Document 12] Japanese Patent Application Publication No. 06-325765 [Patent Document 13] Special Announcement No. 2015-156355 [License 14] Special Announcement No. 11-007942 [License 15] Special Announcement No. 2017-033647 [License 16] Special Announcement No. 2018-142431 [License 17] Special Announcement No. 2022-165490 [License 18] Special Announcement No. 2003-059492 [License 19] Special Announcement No. 2015-220196 [Patent Document 20] Special Announcement No. 2017-068929 [Patent Document 21] Special Announcement No. 2020-068104 [License 22] Special Announcement No. 2020-030919 [License 23] Special Announcement No. 2021-128857 [Non-licensed literature]

[0019] [Non-licensed Document 1] Battery Industry Association Official Paper "Denchi", May 1, 2013, page 10 [Non-licensed Document 2] A. Hohl, T. Wieder, PA van Aken, TE Weirich, G. Denninger, M. Vidal, S. Oswald, C. Deneke, J. Mayer, and H. Fuess: J. Non-Cryst. Solids, 320, (2003), 255. [Non-licensed Document 3] V. Kapaklis, J. Non-Crystalline Solids, 354 (2008) 612. [Non-licensed Document 4] Mariko Miyachi, Hironori Yamamoto, and Hidemasa Kawai, J. Electrochem. Soc. 2007 volume 154, issue 4, A376-A380 [Non-Patent Document 5] M. Yamada, M. Inaba, A. Ueda, K. Matsumoto, T. Iwasaki, T. Ohzuku, J.Electrochem. Soc., 159, A1630 (2012) [Non-Patent Document 6] Taeahn Kim, Sangjin Park, and Seung M. Oh, J. Electrochem. Soc. volume 154, (2007), A1112-A1117. [Non-Patent Document 7] Hye Jin Kim, Sunghun Choi, Seung Jong Lee, Myung Won Seo, Jae Goo Lee, Erhan Deniz, Yong Ju Lee, Eun Kyung Kim, and Jang Wook Choi,. Nano Lett. 2016, 16, 282-288. [Non-Patent Document 8] Sato, Noboru (supervisor), "The Cutting Edge of Automotive Lithium-ion Battery Development," CMC Publishing, November 27, 2020, pp. 96-111. [Overview of the Initiative] [Problems that the invention aims to solve]

[0020] As mentioned above, in recent years, small electronic devices such as mobile terminals have become more high-performance and multi-functional, and the lithium-ion secondary batteries that are their main power source require increased battery capacity. One way to solve this problem is to develop a lithium-ion secondary battery with a negative electrode made primarily of silica material. Furthermore, lithium-ion secondary batteries using silica material are desired to have initial charge-discharge characteristics and cycle characteristics that are close to those of lithium-ion secondary batteries using carbon-based active materials. Therefore, cycle characteristics and initial charge-discharge characteristics have been improved by using silicon oxide modified by insertion and partial desorption of Li as the negative electrode active material. Recently, by mainly using silicon oxide and pre-containing Li to create Li silicate, the irreversible capacity, which is a disadvantage of silicon oxide, has been reduced, and such products have actually begun to be marketed. Batteries have been prototyped by replacing the carbon negative electrode material with Li-SiO-C (Non-Patent Literature 8), which uses Li in silicon oxide, at a high ratio, and a significant increase in capacity has been made, but safety decreases as the amount of silicon oxide added increases.

[0021] To address this decrease in safety, it has been reported that high safety can be achieved by using a solid electrolyte (Patent Documents 18-20). However, when using a graphite anode, the capacity increase seen with silicon oxides cannot be expected. With lithium anodes and silicon-based compound anodes, even if Coulomb efficiency can be improved, the reduction in cycle characteristics due to conduction path breakage caused by volume expansion remains a problem (Patent Document 21). Suppressing volume expansion using silicon-based anodes also results in a decrease in energy density due to the presence of void layers and the mixing of solid electrolytes into the anode (Patent Documents 22, 23).

[0022] The present invention has been made in view of the above-mentioned problems, and aims to provide a negative electrode body having a negative electrode that can significantly increase capacity while maintaining excellent battery characteristics and can suppress swelling when fully charged, and a method for manufacturing such a negative electrode body. [Means for solving the problem]

[0023] In order to solve the above problems, the present invention provides a negative electrode body having a negative electrode current collector with a roughened surface, a negative electrode active material layer provided on the negative electrode current collector, and an ion conduction layer having lithium ion conductivity on the surface of the negative electrode active material layer, and having a solid electrolyte layer adjacent to the ion conduction layer. The negative electrode active material layer contains negative electrode active material particles having a compound containing lithium, silicon, and oxygen. The negative electrode active material particles can be represented by SiO x1 Li y1 and it is characterized in that the value of x1 exceeds 0.8 and is 1.2 or less, and the value of y1 is 0.5 or more and 3.4 or less, thereby providing a negative electrode body.

[0024] Such a negative electrode body has a negative electrode active material layer containing negative electrode active material particles having a compound of lithium, silicon, and oxygen, so that the battery capacity can be improved. Further, the negative electrode body of the present invention can directly support the negative electrode active material layer on the roughened surface of the negative electrode current collector without using a binder, a conductive assistant, etc., can reduce the region not involved in charge and discharge in the electrode, and can also reduce extra voids, so that the energy density of the electrode can be greatly improved. Further, the negative electrode body of the present invention has a layer (ion conduction layer) having lithium ion conductivity on the surface (the outermost surface) of the negative electrode active material layer, and the adjacent ion conduction layer and solid electrolyte layer improve the ion conductivity between the solid electrolyte and the negative electrode active material compared to the conventional negative electrode active material layer using silicon powder or silicon-based compound powder, and the battery characteristics can be improved. Furthermore, the negative electrode body of the present invention can be a negative electrode body capable of suppressing expansion during full charge. Furthermore, the negative electrode body of the present invention can represent the composition formula of the negative electrode active material particles by SiO x1 Li y1 and by having the value of x1 exceed 0.8 and be 1.2 or less, and the value of y1 be 0.5 or more and 3.4 or less, excellent battery characteristics can be maintained. In the description of the present invention, an integrated body of a negative electrode and a solid electrolyte is referred to as a negative electrode body.

[0025] In this case, the negative electrode active material layer has a multilayer structure consisting of two or more layers, and the negative electrode active material layer forms secondary particles, which are aggregates of the primary particles, when the negative electrode active material particles are defined as primary particles, and the secondary particles are separated in the in-plane direction, and the thickness T1 of the negative electrode active material layer before charging and the thickness T2 when fully charged can be such that T2 / T1 ≤ 1.4.

[0026] Thus, the negative electrode body of the present invention may have a multilayer structure, and the negative electrode active material particles may form secondary particles. A negative electrode active material layer having a multilayer structure consisting of two or more layers can mitigate the expansion and contraction of the negative electrode active material layer. Therefore, the negative electrode body of the present invention can suppress changes in thickness before and after charging. If the thickness T1 of the negative electrode active material layer before charging and the thickness T2 when fully charged are in a relationship of T2 / T1 ≤ 1.4, then the expansion and contraction of the active material during charging and discharging is suppressed, the electronic contacts are less likely to break, and excellent battery characteristics can be maintained.

[0027] Furthermore, it is preferable that the negative electrode active material layer having a multilayer structure has at least one interlayer lithium ion conductive layer having lithium ion conductivity between each of the layers constituting the multilayer structure.

[0028] With such a negative electrode, ionic conductivity is improved and resistance between the negative electrode active material layers can be reduced, thus improving battery performance.

[0029] Furthermore, it is preferable that the negative electrode active material layer contains at least one of Li4SiO4, Li2Si2O5, Li2SiO3, and Li6Si2O7.

[0030] Having at least one of these Li silicates allows for a stable state during charging and discharging, resulting in excellent cycle characteristics.

[0031] Furthermore, it is preferable that the lithium ion conductive ion conductive layer consists of at least one of Li carbonate, Li phosphate, Li fluoride, Al carbonate, Al phosphate, Al fluoride, a compound having a silyl group, and a carbonized compound containing a polycyclic aromatic hydrocarbon.

[0032] By creating such an ion-conducting layer, reactions with moisture and oxygen can be suppressed, reducing material degradation, making it easier to introduce lithium and maintain excellent battery characteristics.

[0033] Furthermore, it is preferable that the secondary particles of the negative electrode active material layer consist of an average of four or more primary particles.

[0034] Such a negative electrode can more effectively prevent electrode breakdown due to charging and discharging, and maintain a stable negative electrode active material layer.

[0035] Furthermore, in the negative electrode of the present invention, the solid electrolyte layer may be made of a sulfide-based solid electrolyte.

[0036] While sulfide-based solid electrolytes may generate heat through a reaction with lithium released from silicon-based active materials, the negative electrode of the present invention has an ion-conducting layer on its surface, which can suppress this reaction. This allows for the design of a safe battery that generates less heat while maintaining high ion conductivity.

[0037] In this case, the sulfide-based solid electrolyte may contain at least one of lithium, indium, sulfur, and phosphorus.

[0038] Furthermore, the sulfide-based solid electrolyte may have at least one of Li2S, P2S5, SiS2, LiI, LiBr, P2O5, Li3PO4, and GeS2.

[0039] In the negative electrode of the present invention, the above-mentioned sulfide-based solid electrolyte can be suitably used.

[0040] In the negative electrode body of the present invention, the solid electrolyte layer can be made of an oxide-based solid electrolyte.

[0041] Since the oxide-based solid electrolyte is stable and easy to handle in air, a safe battery can be designed.

[0042] At this time, the oxide-based solid electrolyte can have a perovskite structure.

[0043] At this time, the oxide-based solid electrolyte can contain at least one of lanthanum, lithium, magnesium, tungsten, niobium, and titanium.

[0044] In addition, the oxide-based solid electrolyte has a composition formula of A x2 BO3 (0 < x2 < 1), and at least one of La and Li is included in the element A, and at least one of Mg, W, Nb, and Ti is included in the element B.

[0045] In addition, the oxide-based solid electrolyte can have a NASICON-type phosphate compound.

[0046] In this case, the solid electrolyte having the NASICON-type phosphate compound can contain at least one of lithium, aluminum, germanium, zirconium, titanium, and calcium.

[0047] In addition, the NASICON-type phosphate compound is represented by Li (1+x3) M1 (x3) M2 (2-x3) (PO4)3, the element M1 contains at least one selected from the group consisting of Al, Y, Ga, and In, the element M2 contains at least one selected from the group consisting of Ti, Ge, and Zr, and x3 is 0 ≦ x3 ≦ 2.

[0048] Furthermore, the oxide-based solid electrolyte may have a garnet-type crystal structure.

[0049] Furthermore, the solid electrolyte having the garnet-type crystal structure may contain at least one of lithium, lanthanum, calcium, zirconium, bismuth, aluminum, cerium, gallium, boron, and oxygen.

[0050] Furthermore, the solid electrolyte having the garnet-type crystal structure is Li (7-3x4+y4-z4) M x4 La (3-y4) A' (y4) Zr (2-z4) T (z4) O 12 (It can be assumed that element M is one or more of Al and Ga, element A' is one of Ca and Sr, and T is one of Nb and Ta, satisfying 0 ≤ x 4 ≤ 0.18, 0 ≤ y 4 ≤ 0.18, and 0 ≤ z 4 ≤ 1.5.)

[0051] In the negative electrode of the present invention, the above-mentioned oxide-based solid electrolyte can be suitably used.

[0052] Furthermore, the present invention provides a method for manufacturing a negative electrode, comprising the steps of: winding the negative electrode current collector onto a can roll having curvature; vapor phase growth of a multilayer film containing silicon and / or silicon monoxide consisting of two or more layers while the negative electrode current collector is running on the can roll; blowing an oxygen-containing gas onto the film containing silicon and / or silicon monoxide to form a multilayer layer containing silicon dioxide on top of each layer; inserting and deinserting lithium into the multilayer layer to form the negative electrode active material layer; forming the ion conductive layer having lithium ion conductivity on the surface of the negative electrode active material layer; and forming the solid electrolyte layer adjacent to the ion conductive layer.

[0053] The negative electrode manufacturing method of the present invention makes it possible to manufacture a negative electrode that can significantly increase capacity while maintaining battery characteristics.

[0054] In this case, it is preferable to include the steps of forming the multilayer structure in which each layer contains silicon oxide containing silicon dioxide, and in the vapor phase growth step, vapor phase growth of a negative electrode active material layer containing silicon oxide on the negative electrode current collector, immersing the negative electrode active material layer containing silicon oxide in a lithium-containing solution, and modifying the silicon oxide by electrochemical means to produce a compound containing lithium, silicon and oxygen, and to form the ion conductive layer.

[0055] With this method of manufacturing negative electrodes, lithium can be inserted using an electrochemical process, making it possible to more reliably produce negative electrodes that can significantly increase capacity while maintaining battery characteristics. [Effects of the Invention]

[0056] As described above, when the negative electrode of the present invention is used as a component of a secondary battery, it can achieve high initial efficiency, high capacity, and high cycle characteristics. Furthermore, the method for manufacturing the negative electrode of the present invention makes it possible to manufacture a negative electrode that has good cycle characteristics and, when used as a negative electrode in a secondary battery, has high capacity and good initial charge / discharge characteristics. [Brief explanation of the drawing]

[0057] [Figure 1] This is a schematic cross-sectional view showing an example of the configuration of the negative electrode body of the present invention. [Figure 2] This is a schematic exploded view showing an example configuration of a lithium-ion secondary battery including the negative electrode of the present invention. [Figure 3] This is an SEM image of the surface of the negative electrode active material layer of an example of the negative electrode body of the present invention. [Modes for carrying out the invention]

[0058] As mentioned above, one method being considered to increase the battery capacity of lithium-ion secondary batteries is to use a negative electrode made primarily of silicon oxide. It is desirable that lithium-ion secondary batteries using silicon oxide have initial charge-discharge characteristics close to those of lithium-ion secondary batteries using carbon-based active materials. Furthermore, while a significant increase in capacity can be expected by using Li-doped SiO2, which can improve initial charge-discharge characteristics, further capacity improvements are required when considering applications such as automotive use.

[0059] Therefore, the inventors diligently conducted research to obtain a negative electrode that, when used as the negative electrode of a secondary battery, can improve initial charge-discharge characteristics while obtaining high cycle characteristics and increasing battery capacity, leading to the present invention.

[0060] That is, one aspect of the present invention is a negative electrode having a surface roughened negative electrode current collector, a negative electrode active material layer provided on the negative electrode current collector, and an ion conducting layer having lithium ion conductivity on the surface of the negative electrode active material layer, and having a solid electrolyte layer adjacent to the ion conducting layer, wherein the negative electrode active material layer includes negative electrode active material particles having a compound containing lithium, silicon and oxygen, and the negative electrode active material particles are SiO x1 Li y1 The negative electrode body can be expressed as follows, and is characterized in that the value of x1 is greater than 0.8 and less than or equal to 1.2, and the value of y1 is between 0.5 and 3.4. Thus, the negative electrode body of the present invention has a negative electrode and a solid electrolyte layer.

[0061] Another aspect of the present invention is a method for manufacturing a negative electrode, the method comprising the steps of: winding the negative electrode current collector onto a can roll having curvature; vapor phase growth of a multilayer film containing silicon and / or silicon monoxide consisting of two or more layers while the negative electrode current collector is running on the can roll; blowing an oxygen-containing gas onto the film containing silicon and / or silicon monoxide to form a multilayer layer containing silicon dioxide on top of each layer; inserting and deinserting lithium into the multilayer layer to form the negative electrode active material layer; forming an ion conductive layer having lithium ion conductivity on the surface of the negative electrode active material layer; and forming the solid electrolyte layer adjacent to the ion conductive layer.

[0062] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0063] <Negative electrode> First, the configuration of the negative electrode of the present invention will be described with reference to the drawings.

[0064] Figure 1 shows a schematic cross-sectional view of an example of the negative electrode body of the present invention. As shown in Figure 1, the negative electrode body 10 has a configuration comprising a negative electrode current collector 11 and a negative electrode active material layer 12 provided on the surface 11a of the negative electrode current collector 11. This negative electrode active material layer 12 may be provided on both surfaces 11a of the negative electrode current collector 11, or on only one surface 11a, as shown in Figure 1. Furthermore, the negative electrode body 10 comprises an ion conductive layer 14 having lithium ion conductivity on the surface of the negative electrode active material layer 12. That is, the structure of the negative electrode comprises a negative electrode current collector 11, a negative electrode active material layer 12, and an ion conductive layer 14. The negative electrode body 10 further has a solid electrolyte layer 16 adjacent to the ion conductive layer 14.

[0065] The surface 11a of the negative electrode current collector 11 is a roughened surface. That is, the negative electrode active material layer 12 is provided on the roughened surface 11a of the negative electrode current collector 11.

[0066] The negative electrode current collector 11 and the negative electrode active material layer 12 will be described below.

[0067] [Negative electrode current collector] The negative electrode current collector 11 is made of a material that has excellent conductivity and high mechanical strength. Examples of conductive materials that can be used for the negative electrode current collector 11 include copper (Cu) and nickel (Ni). It is preferable that this conductive material does not form intermetallic compounds with lithium (Li).

[0068] The negative electrode current collector 11 preferably contains carbon (C) and sulfur (S) in addition to the main element. This is because it improves the physical strength of the negative electrode current collector. In particular, if the active material layer expands during charging, the presence of the above elements in the current collector has the effect of suppressing electrode deformation, including the current collector. The content of the above elements is not particularly limited, but it is preferable that each be at least 100 ppm by mass. This is because a higher deformation suppression effect can be obtained. Such deformation suppression effect can further improve cycle characteristics.

[0069] Furthermore, the surface 11a of the negative electrode current collector 11 needs to be roughened, and preferably, the ten-point average roughness Rz of the surface should be between 1.5 μm and 5.0 μm. If the negative electrode body 10 includes a negative electrode current collector 11 having such a desirable average roughness Rz of surface 11a, not only can the negative electrode active material layer 12 be supported more stably, but the density of negative electrode active material particles in the negative electrode active material layer 12 can be made appropriate, and as a result, better battery characteristics can be observed. The roughened negative electrode current collector 11 is, for example, a metal foil that has been electrolytically treated, embossed, or chemically etched.

[0070] [Negative electrode active material layer] The negative electrode active material layer 12 of the negative electrode body 10 of the present invention contains negative electrode active material particles having a compound (silicon compound particles) containing lithium, silicon, and oxygen. That is, it has silicon compound particles containing lithium and oxygen and is provided on the negative electrode current collector 11. The negative electrode body 10 can be said to have a structure in which the negative electrode active material particles are directly supported on the roughened surface 11a of the negative electrode current collector 11 as part of its structure.

[0071] The negative electrode body 10 of the present invention contains negative electrode active material particles, which are silicon compound particles, and can therefore improve battery capacity. Furthermore, unlike conventional electrodes, the negative electrode body 10 of the present invention allows the negative electrode active material layer 12 to be directly supported on the roughened surface 11a of the negative electrode current collector 11 without using a binder or conductive additive. This reduces the area of ​​the electrode that does not participate in charging and discharging, and also reduces excess voids, thereby significantly improving the energy density of the electrode.

[0072] Thus, by using a negative electrode body 10 having a densely supported negative electrode active material layer 12, it becomes possible to increase the energy density of the battery in a way that is not possible with powder electrodes, for example.

[0073] Furthermore, in the negative electrode active material layer 12, negative electrode active material particles having compounds containing lithium, silicon, and oxygen can exist adjacent to each other. On the surface of the negative electrode active material layer 12, an ion conductive layer 14 having lithium ion conductivity is formed as described above, and it is preferable that the ion conductive layer 14 consists of at least one of Li carbonate, Li phosphate, Li fluoride, Al carbonate, Al phosphate, Al fluoride, compounds having a silyl group, and carbonides containing polycyclic aromatic hydrocarbons. As carbonides, examples include carbonides whose main component is an aromatic compound, but it is particularly preferable that the carbonide's main component is a polycyclic aromatic hydrocarbon. The film forming the ion conductive layer 14 acts as a protective layer, protecting the interface between the negative electrode active material layer 12 and the solid electrolyte layer 16. Due to the presence of such a film, the negative electrode 10 of the present invention can exhibit excellent cycle characteristics.

[0074] Examples of silyl groups in the above-mentioned compounds include silyl groups having organic groups such as alkyl groups. In this case, silyl groups having organic groups with 1 to 5 carbon atoms are preferred. More preferably, silyl groups having alkyl groups with 1 to 5 carbon atoms are preferred. In this case, the alkyl group is preferably a methyl group, ethyl group, propyl group, isopropyl group, butyl group, tert-butyl group, or isobutyl group. Examples of such silyl groups having alkyl groups include trialkylsilyl groups such as trimethylsilyl group and triethylsilyl group. In this case, the three alkyl groups may be the same as above, or they may be different. The organic group with 1 to 5 carbon atoms may contain an unsaturated bond. Furthermore, the alkyl group may contain a fluorine atom.

[0075] Furthermore, in the negative electrode body 10 of the present invention, the negative electrode active material particles are SiO x1 Li y1 It can be expressed as such, where the value of x1 is greater than 0.8 and less than or equal to 1.2, and the value of y1 is between 0.5 and 3.4. If x1 is greater than 0.8, the oxygen ratio is higher than that of elemental silicon, resulting in good cycle characteristics. It is more preferable that x1 be 0.9 or higher. It is also preferable that x1 be 1.2 or lower, as this prevents the resistance of the silicon oxide from becoming too high. Among these, SiO x1 Li y1 A value of x1 closer to 1 is preferable, because it allows for high cycle performance. Note that the silicon compound composition in this invention does not necessarily mean 100% purity and may contain trace amounts of impurity elements. If the value of y1 is 0.5 or higher, the irreversible components of SiO generated during the initial charge and discharge can be fixed in advance, significantly improving the energy density of the electrode. If the value of y1 is 3.4 or lower, the negative electrode active material particles become stable with respect to oxygen and moisture, allowing for the construction of a higher-capacity battery.

[0076] In other words, the negative electrode 10 of the present invention makes it possible to significantly increase the capacity while maintaining the battery characteristics.

[0077] On the other hand, if the value of x1 is 0.8 or less, the capacitance will increase, but Si 0+ The surface area that reacts with the electrolyte increases, worsening the cycle performance. Also, if the value of x1 exceeds 1.2, it becomes a load substance, which also degrades battery performance. It is desirable for the value of x1 to be as close to 1 as possible.

[0078] In the present invention, it is preferable that the negative electrode body 10 has a multilayer structure in which the negative electrode active material layer 12 consists of two or more layers. A negative electrode body 10 having a multilayer structure of the negative electrode active material layer 12 is more preferable because it can mitigate the expansion and contraction of the negative electrode active material layer 12, thereby improving the capacity retention rate.

[0079] Furthermore, as will be described later, when manufacturing the negative electrode body 10 of the present invention, Li is introduced into the negative electrode active material layer 12. To introduce Li more smoothly, it is preferable to make the negative electrode active material layer 12 a multilayer structure consisting of two or more layers at the time of formation. A negative electrode active material layer 12 having a multilayer structure consisting of two or more layers can achieve smooth insertion of Li while suppressing the decomposition of the electrolyte.

[0080] When the negative electrode active material layer 12 has a multilayer structure, it is preferable that each layer of the multilayer structure has a layer on its surface made of a high number of silicon compounds containing at least one of lithium and oxygen. Having a layer made of silicon compounds on the surface mitigates the expansion and contraction of the negative electrode active material layer 12 due to charging and discharging, and a stable negative electrode active material layer 12 can be maintained.

[0081] Furthermore, when the negative electrode active material layer 12 is defined as primary particles, it forms secondary particles which are aggregates of the primary particles, and it is preferable that these secondary particles are separated in the in-plane direction.

[0082] In the method for manufacturing the negative electrode 10 of the present invention, described later, the negative electrode active material particles grow in the vapor phase due to the roughened areas on the surface 11a of the negative electrode current collector 11. If these are defined as primary particles, it is preferable that they form secondary particles, which are aggregates of these primary particles. This can be controlled by changing the roughened state of the surface 11a of the negative electrode current collector 11. For example, if the roughening interval is wide, the secondary particle group becomes smaller. On the other hand, if the roughening interval is narrow and the primary particles are too densely packed, it becomes difficult to generate secondary particles during charging and discharging.

[0083] It is desirable that these secondary particles have a separated morphology in the in-plane direction. By performing charging and discharging in this state, a stable negative electrode active material layer 12 can be maintained.

[0084] With this configuration, the negative electrode 10 of the present invention can suppress changes in the thickness of the negative electrode active material layer 12 due to charging and discharging. In particular, the thickness T1 of the negative electrode active material layer 12 before charging and the thickness T2 when fully charged can be made such that T2 / T1 ≤ 1.4. With this configuration, expansion at full charge can be suppressed to a state close to that of graphite.

[0085] Furthermore, in the negative electrode body 10 of the present invention, it is preferable that the number of primary particles forming secondary particles of the negative electrode active material particles in the negative electrode active material layer 12 is, on average, four or more. If this number is four or more, the surface area of ​​the negative electrode active material layer becomes appropriate, and material degradation due to battery charging and discharging can be suppressed. In other words, if this number is four or more, stable battery characteristics can be exhibited while suppressing material degradation. The average number of primary particles in the secondary particles can be measured by observation with a scanning electron microscope. Figure 3 shows a surface SEM image of the negative electrode active material layer 12 constituting the negative electrode body 10 of the present invention.

[0086] Furthermore, it is preferable that the negative electrode active material layer 12 has at least one of Li4SiO4, Li2Si2O5, Li2SiO3, and Li6Si2O7. In addition to Li2SiO3, Li silicates such as Li4SiO4 and Li6Si2O7 are relatively more stable than other Li compounds, so silicon-based active materials containing these Li compounds can obtain more stable battery characteristics. These Li compounds can be obtained by selectively changing a portion of the SiO2 component generated inside the silicon compound to the Li compound and modifying the silicon compound.

[0087] Furthermore, in the negative electrode body 10 of the present invention, if the negative electrode active material layer 12 has a multilayer structure, it is preferable that at least one of the layers constituting the multilayer has an ion conductive layer (interlayer lithium ion conductive layer) that conducts lithium ions. In this way, the presence of an ion conductive layer (interlayer lithium ion conductive layer) between the layers of the multilayer structure makes it easier for lithium to move between the layers, thereby improving the battery characteristics.

[0088] [Solid electrolyte layer] The solid electrolyte layer 16 shown in Figure 1 is adjacent to the ion-conducting layer 14 located on the outermost surface of the negative electrode active material.

[0089] The solid electrolyte constituting the solid electrolyte layer 16 is preferably one of either a sulfide-based solid electrolyte or an oxide-based solid electrolyte.

[0090] [Sulfide solid electrolyte] First, let's explain the case where the solid electrolyte layer 16 is made of a sulfide-based solid electrolyte. Known sulfide-based solid electrolytes can be used as the sulfide-based solid electrolyte. Sulfide-based solid electrolytes may react with lithium released from silicon-based active materials and generate heat, but the negative electrode of the present invention has an ion-conducting layer on its surface, which can suppress this reaction, making it possible to design a safe battery that does not generate much heat while maintaining high ion conductivity.

[0091] The sulfide-based solid electrolyte can have at least one of lithium, indium, sulfur, and phosphorus. Further, the sulfide-based solid electrolyte can have at least one of Li2S, P2S5, SiS2, LiI, LiBr, P2O5, Li3PO4, and GeS2. Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5-GeS2, etc.

[0092] [Oxide-based solid electrolyte] Next, the case where the solid electrolyte layer 16 is made of an oxide-based solid electrolyte will be described. Since the oxide-based solid electrolyte is stable in air and easy to handle, a safe battery can be designed.

[0093] [Compound having a perovskite structure] The oxide-based solid electrolyte that can be used in the present invention can have a perovskite structure. The compound having a perovskite structure has a composition formula represented by the general formula A X2 BO3 (where 0 < X2 < 1 is satisfied). In this compound having a perovskite structure, at least one of La and Li is included in element A, and at least one of Mg, W, Nb, and Ti is included in element B. By including Li in element A, Li ion conductivity can be imparted. Further, it is preferable to include Mg and W as element B. This perovskite-type ion-conductive oxide (solid electrolyte) has a basic composition formula (Li 3a ,La 2 / 3-a )(Mg b ,W 1-b)It may be represented by O3 (where 0 < a ≤ 1 / 3 and 0.4 ≤ b ≤ 0.6 are satisfied). At this time, the substitution amount a of Li is preferably 0.04 or more, more preferably in the range of 0.05 or more and 0.30 or less, and even more preferably in the range of 0.07 or more and 0.22 or less. In such a range, it is preferable because the Li ion conductivity can be further increased. Also, the blending amount b of Mg is preferably in the range of 0.48 or more and 0.52 or less, and it is more preferable that Mg and W are closer to an equal amount, and more preferably 0.5. This perovskite-type ion-conductive oxide has a basic composition formula (Li3a,La 2 / 3-a )(Mg 1 / 2 ,W 1 / 2 )O3 (where a is 1 / 6, 1 / 4, 1 / 3), and those represented by this are more preferable. Although the structure of the basic composition formula (La 2 / 3 )(Mg 1 / 2 ,W 1 / 2 )O3 was shown, the perovskite-type ion-conductive oxide of the present disclosure has a structure in which a part of La is substituted with Li.

[0094] [Phosphate compound having a NASICON-type crystal structure] The oxide-based solid electrolyte that can be used in the present invention can have a NASICON-type phosphate compound. The phosphate compound having a NASICON-type crystal structure is not particularly limited as long as it is a NASICON-type phosphate compound. For example, it can have at least one of lithium, aluminum, germanium, zirconium, titanium, and calcium. Also, this NASICON-type phosphate compound is preferably a NASICON-type phosphate compound represented by the general formula (1) Li 1+x3 M1 x3 M2 2-x3 (PO4)3 (in formula (1), M1 is at least one selected from the group consisting of Al, Y, Ga, and In, M2 is at least one selected from the group consisting of Ti, Ge, and Zr, and x3 is 0 ≤ x3 ≤ 2).

[0095] The metal M1 is preferably at least one selected from the group consisting of Al, Y, and Ga, with Al being more preferred. Furthermore, the metal M2 is preferably at least one selected from the group consisting of Ge and Ti, with Ge being more preferred. That is, the general formula (2) Li 1+x3 Al x3 Ge 2-x3 A nasicone-type phosphate compound (LAGP) represented by (PO4)3 (where 0 ≤ x3 ≤ 2 in formula (2)) is preferred. This is because, among nasicone-type phosphate compounds, the compound represented by the above formula (2) has high ionic conductivity.

[0096] Furthermore, the range of x3 is preferably 0.1 ≤ x3 ≤ 1.9, and more preferably 0.3 ≤ x3 ≤ 0.7. In particular, the solid electrolyte material is Li in the above formula. 1.5 Al 0.5 Ge 1.5 (PO4)3 is preferred.

[0097] [Compounds with a garnet-type crystal structure] The oxide-based solid electrolyte that can be used in the present invention can be a solid electrolyte having a garnet-type crystal structure. The solid electrolyte having a garnet-type crystal structure preferably contains at least one of lithium, lanthanum, calcium, zirconium, bismuth, aluminum, cerium, gallium, boron, and oxygen. The compound having a garnet-type crystal structure is Li (7-3x4+y4-z4) M x4 La (3-y4) A' (y4) Zr (2-z4) T (z4) O 12 (It is preferable that element M is one or more of Al and Ga, element A' is one of Ca and Sr, T is one of Nb and Ta, and that 0≦x4≦0.18, 0≦y4≦0.18, and 0≦z4≦1.5 are satisfied.) In particular, a solid electrolyte having a garnet-type crystal structure has the composition formula: Li 7-3x4+α La3Zr2Al x4 O 12-y4The compound having a garnet-type crystal structure is represented by the formula Li3BO3 (wherein 0≦x4<2, 1.1<(7-3x4+α) / (7-3x4)≦1.5 and 0.3≦y4≦2.0). When a compound having a garnet-type crystal structure has the above composition, it becomes cubic at room temperature, and thus has the effect of having high ionic conductivity at room temperature. Furthermore, the compound having a garnet-type crystal structure according to the embodiment of the present invention has the composition formula: Li 7-3x4+α La3Zr2Al x4 O 12-y4 In Li3BO3, the stoichiometric ratio of Li is "Li 7-3x4 It has an excess of Li by "α" compared to "", resulting in a Li excess. Also, in the above formula, 0≦x4<1 is also acceptable. Furthermore, for "y4", which represents the molar ratio of Li3BO3, 0.3≦y4≦1.5 is also acceptable.

[0098] [Method for manufacturing negative electrodes] Preferably, the method for manufacturing a negative electrode of the present invention includes the steps of: winding the negative electrode current collector onto a curved can roll; vapor phase growth of a multilayer film containing silicon and / or silicon monoxide consisting of two or more layers while the negative electrode current collector is running on the can roll; blowing an oxygen-containing gas onto the film containing silicon and / or silicon monoxide to form a multilayer layer containing silicon dioxide on top of each layer; inserting and deinserting lithium into the multilayer layer to form the negative electrode active material layer; forming an ion conductive layer having lithium ion conductivity on the surface of the negative electrode active material layer; and forming the solid electrolyte layer adjacent to the ion conductive layer. With such a method for manufacturing a negative electrode of the present invention, it is possible to manufacture a negative electrode that can significantly increase capacity while maintaining battery characteristics.

[0099] In this case, it is preferable to include the steps of forming the multilayer structure in which each layer contains silicon oxide containing silicon dioxide, in the step of forming the multilayer structure in which the layers contain silicon oxide containing silicon dioxide, in the vapor phase growth step, vapor phase growth of a negative electrode active material layer containing silicon oxide on the negative electrode current collector, immersing the negative electrode active material layer containing silicon oxide in a lithium-containing solution, and modifying the silicon oxide by electrochemical means to produce a compound containing lithium, silicon and oxygen, and to form the ion conductive layer. With such a method for manufacturing a negative electrode, lithium can be inserted by electrochemical means, so a negative electrode that can significantly increase capacity while maintaining battery characteristics can be manufactured more reliably.

[0100] The negative electrode of the present invention can be manufactured using the method described above. However, the method for manufacturing the negative electrode of the present invention is not limited to the method described herein.

[0101] The following describes a specific example of a method for manufacturing the negative electrode body of the present invention, but the method for manufacturing the negative electrode body of the present invention is not limited to the example described below.

[0102] First, a multilayer film containing silicon and / or silicon monoxide, consisting of two or more layers, is fabricated. Here, the multilayer film containing silicon and / or silicon monoxide is grown in the vapor phase on a negative electrode current collector. The silicon-containing film may contain silicon particles. The silicon-containing film may contain silicon monoxide particles, which are silicon compounds (silicon oxides) containing oxygen. Therefore, a multilayer film containing silicon and / or silicon monoxide, consisting of two or more layers, may contain silicon-containing particles.

[0103] This multilayer film containing silicon and / or silicon monoxide can be formed by depositing, for example, a silicon vapor stream or silicon oxide gas onto a surface-roughened negative electrode current collector, for example, a roughened foil (e.g., roughened copper foil) having a surface ten-point average roughness Rz of 1.5 μm or more and 5.0 μm or less (e.g., 2.5 μm). In the method for manufacturing the negative electrode of the present invention, the negative electrode current collector is wound onto a can roll having curvature. The curvature (R) of the can roll is, for example, 4 m -1 More than 20m -1 The following is preferable.

[0104] Examples of methods for forming a multilayer film containing silicon and / or silicon monoxide are as follows:

[0105] A silicon monoxide film can be formed, for example, by the following procedure. First, a raw material that generates silicon oxide gas is heated under reduced pressure at a temperature of 1100°C or higher to generate silicon oxide gas. At this time, a mixture of metallic silicon powder and silicon dioxide powder can be used as the raw material. Considering the presence of surface oxygen in the metallic silicon powder and trace amounts of oxygen in the reactor, it is desirable that the molar ratio of the mixture be in the range of 0.9 < metallic silicon powder / silicon dioxide powder < 1.2.

[0106] Furthermore, silicon oxide can also be formed by vapor deposition using metallic silicon and introducing oxygen gas into the deposited silicon; however, in this case, valency control is not possible, resulting in a composite material in which silicon is separated into a zero-valence state and a tetra-valence compound state. Similarly, it is possible to introduce a reducing gas (hydrogen) into silicon dioxide gas, but it is difficult to introduce sufficient hydrogen into vapor that is close to the speed of sound. Consequently, in the method for manufacturing the negative electrode of the present invention, it is preferable to use metallic silicon and silicon dioxide powder as raw materials for the silicon monoxide film.

[0107] The silicon oxide gas generated as described above is deposited on the roughened surface of the negative electrode current collector, forming primary particles with a columnar structure.

[0108] Furthermore, silicon films can be formed, for example, by vapor deposition using metallic silicon.

[0109] During the deposition of silicon films and / or silicon monoxide films, the structure of primary particles can be altered by changing the surface roughening structure of the negative electrode current collector.

[0110] The heat of solidification during deposition, as well as the radiant heat from the heated section, promotes the crystallization of the negative electrode active material layer. Therefore, in the negative electrode manufacturing method of the present invention, the negative electrode current collector is run on a curved can roll, allowing for vapor phase growth while reducing the heat load and preventing Si crystallization.

[0111] In particular, unlike silicon, silicon oxide is sublimable, allowing for early deposition, and there is no concern about radiant heat from molten silicon, which is a problem with silicon films. Therefore, it can be said that silicon oxide is suitable for forming active materials by vapor deposition.

[0112] In the negative electrode manufacturing method of the present invention, since a negative electrode current collector is moved on a curved can roll while multilayer deposition (for example, reciprocating multilayer deposition) is performed, a portion of the surface of each layer is deposited at an angle, creating voids.

[0113] Vapor deposition can also be performed on both roughened surfaces of the negative electrode current collector. For example, vapor deposition can be performed on one roughened surface of the negative electrode current collector, and then the negative electrode current collector can be flipped over and vapor deposition can be performed on the other roughened surface of the negative electrode current collector.

[0114] A film containing silicon and / or silicon monoxide formed as described above is then blown with an oxygen-containing gas to form a multilayer structure containing silicon dioxide on top of each layer.

[0115] The oxygen-containing gas is not particularly limited as long as it contains oxygen, but for example, it could be oxygen-containing nitrogen gas.

[0116] By blowing in an oxygen-containing gas, oxygen enters the voids at the top of each layer, allowing oxygen to be introduced into each layer. Furthermore, this allows at least a portion of the silicon and / or silicon monoxide at the top of each layer to be converted to silicon dioxide. In other words, by blowing in an oxygen-containing gas, a multilayer structure can be formed in which each layer contains silicon oxides, including silicon dioxide.

[0117] Next, Li is doped (inserted) into the multilayer structure containing silicon dioxide on top of each layer prepared as described above. This results in a negative electrode active material layer containing negative electrode active material particles that include silicon oxide particles into which lithium has been inserted. In other words, the silicon oxide particles are modified, and Li compounds are formed inside the silicon oxide particles.

[0118] [Reformation by electrochemical method] In electrochemical modification, lithium can be inserted by first immersing a negative electrode active material layer containing silicon oxide particles as the anode and lithium metal cathode in a liquid non-aqueous electrolyte (electrolyte), and then supplying an electric current. This electrolyte contains an electrolyte salt dissolved in a solvent and may also contain other materials such as additives.

[0119] For example, a non-aqueous solvent can be used as the solvent. Examples of non-aqueous solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, 1,2-dimethoxyethane, or tetrahydrofuran. Among these, it is desirable to use at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or ethylmethyl carbonate, as this will yield better properties. Furthermore, in this case, combining a high-viscosity solvent such as ethylene carbonate or propylene carbonate with a low-viscosity solvent such as dimethyl carbonate, ethylmethyl carbonate, or diethyl carbonate will yield even more advantageous properties, as this improves the dissociation and ion mobility of the electrolyte salt.

[0120] In particular, it is desirable that the solvent contains at least one of the following: a halogenated chain carbonate ester or a halogenated cyclic carbonate ester. This allows for the formation of a stable film on the surface of the negative electrode active material during charging and discharging, especially during charging. Here, a halogenated chain carbonate ester is a chain carbonate ester having halogen as a constituent element (at least one hydrogen atom is substituted by halogen). A halogenated cyclic carbonate ester is a cyclic carbonate ester having halogen as a constituent element (i.e., at least one hydrogen atom is substituted by halogen).

[0121] While there are no particular limitations on the type of halogen, fluorine is preferred because it forms a better quality film than other halogens. Furthermore, a higher number of halogens is desirable because it results in a more stable film and reduces the decomposition reaction of the electrolyte.

[0122] Examples of halogenated chain carbonate esters include fluoromethylmethyl carbonate and difluoromethylmethyl carbonate. Examples of halogenated cyclic carbonate esters include 4-fluoro-1,3-dioxolan-2-one and 4,5-difluoro-1,3-dioxolan-2-one.

[0123] It is preferable that the solvent additive contains an unsaturated carbon-bonded cyclic carbonate ester. This is because a stable film is formed on the surface of the negative electrode active material layer during charging and discharging, which can suppress the decomposition reaction of the electrolyte. Examples of unsaturated carbon-bonded cyclic carbonate esters include vinylene carbonate or vinylethylene carbonate.

[0124] Furthermore, it is preferable to include a sultone (cyclic sulfonic acid ester) as a solvent additive, as this improves the chemical stability of the battery. Examples of sultones include propanesultone and propenesultone.

[0125] Furthermore, the solvent preferably contains an acid anhydride, as this improves the chemical stability of the electrolyte. Examples of acid anhydrides include propanedisulfonic acid anhydride.

[0126] The electrolyte salt may contain one or more light metal salts, such as lithium salts. Examples of lithium salts include lithium hexafluoride phosphate (LiPF6) and lithium tetrafluoroborate (LiBF4).

[0127] The electrolyte salt content is preferably 0.5 mol / kg to 2.5 mol / kg relative to the solvent, because this allows for high ionic conductivity.

[0128] After lithium insertion, lithium can be desorbed by supplying current to the negative electrode active material layer containing silicon oxide particles, which acts as the cathode and the lithium metal anode. At this time, the state of the packed film (composite compound) can be controlled by adjusting the solvent temperature, the type and concentration of the polyphenylene compound or polycyclic aromatic compound included in the solvent, and the concentration of the polycyclic aromatic compound complexed with Li. The resulting silicon active material particles may also be heat-treated by inert gasification. Heat treatment can stabilize the Li compound.

[0129] The resulting complex compounds may contain multiple types of compounds.

[0130] [Formation of a lithium-ion conductive coating] A lithium ion conductive coating (ion-conducting layer) is formed on the negative electrode active material layer obtained by electrochemical modification. By blowing carbon dioxide onto the negative electrode active material layer, a lithium carbonate coating can be formed on the surface and between the layers. Alternatively, a coating can be formed by adding aluminum phosphate to the electrolyte during lithium insertion and removal. By not removing the electrolyte salt after lithium insertion and removal, a coating consisting of Li3PO4, LiF, and Li2CO3 can be formed on the surface.

[0131] Compounds containing silyl groups are preferably formed by alkylsilazane treatment. In this way, the treatment occurs on the material surface, allowing for the efficient formation of a layer containing compounds containing silyl groups. More specifically, for example, a layer containing compounds containing silyl groups can be formed by the following procedure. Note that OH groups are present on the surface of the negative electrode active material layer, and it is thought that these OH groups react with the decomposition products of the alkylsilazane, introducing trialkylsilyl groups to the surface of silicon compound particles and carbon material.

[0132] First, dehydrated toluene, a negative electrode active material equivalent to one-quarter of the mass of the dehydrated toluene, and HMDS (hexamethyldisilazane) equivalent to 3% by mass of the negative electrode active material are placed in a container and left to stand for 1 hour. After that, the negative electrode active material layer is dried to form a coating of a compound having a silyl group.

[0133] Carbonized materials whose main component is an aromatic compound (polycyclic aromatic hydrocarbon) are preferably formed by coal tar and pitch treatment. Specifically, a coating can be formed by applying coal tar or pitch to the negative electrode active material layer and then heat-treating it. The coal tar or pitch decomposes under heat to form a carbonized material that is an aromatic compound (polycyclic aromatic hydrocarbon), and this forms a coating on the negative electrode active material layer. The thermal decomposition temperature is not particularly limited.

[0134] [Formation of the solid electrolyte layer] After forming the ion-conducting layer, a solid electrolyte layer adjacent to the ion-conducting layer is formed. This process can be carried out by placing the solid electrolyte layer adjacent to the ion-conducting layer and then applying pressure.

[0135] As described above, the negative electrode body of the present invention can be manufactured.

[0136] <Lithium-ion rechargeable battery> The negative electrode of the present invention can be used in all-solid-state batteries, such as lithium-ion secondary batteries.

[0137] Next, we will describe an example of an all-solid-state battery that can use the negative electrode of the present invention.

[0138] The structure of a lithium secondary battery is not particularly limited, but for example, the structure shown in Figure 2 can be cited. Figure 2 is an explanatory diagram showing an example of the structure of an all-solid-state lithium secondary battery 20. This all-solid-state lithium secondary battery has the solid electrolyte layer 16 described above, a positive electrode active material layer 21 formed on one side of the solid electrolyte layer 16 and containing a positive electrode active material that intercepts and releases lithium, and a negative electrode active material layer 12 formed on the other side of the solid electrolyte layer 16 and containing a negative electrode active material that intercepts and releases lithium. A positive electrode current collector 22 is formed on the surface of the positive electrode active material layer 21, and a negative electrode current collector 11 is formed on the surface of the negative electrode active material layer 12. The solid electrolyte layer 16 and the negative electrode active material layer 12 may be a composite negative electrode 10. [Examples]

[0139] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0140] (Comparative Example 1) To establish a standard for the examples, the following particulate coated active material was first prepared.

[0141] (Fabrication of the negative electrode structure) A coated active material was prepared using a particle composite device (NOB-MINI, manufactured by Hosokawa Micron Corporation). First, a total of 30 g of negative electrode active material (Li-doped SiO powder coated with carbon (denoted as "Li-SiO-C")), sulfide solid electrolyte (10LiI-15LiBr-75 (0.75Li2S-0.25P2S5), average particle size 0.5 μm), and conductive additive (spherical carbon, specific surface area 93 m2 / g) were added to the processing container of the device in the proportions shown in Table 1 below. Next, the gap between the rotating blades of the compression shear rotor and the inner wall of the processing container was set to 1 mm, the pressure to 100 Pa, the blade peripheral speed to 26.4 m / s, and the processing time to 12.5 minutes, and a compression shear treatment was performed to obtain the coated active material.

[0142] Li-SiO-C was prepared using the following procedure. First, silicon and silicon dioxide were mixed as raw materials, vaporized at 1300°C, deposited on a deposition substrate, and rapidly cooled to produce SiO blocks. These SiO blocks were pulverized to a median diameter of 7 μm, and then Li doped using a redox method. After doping, the Li silicate was heat-treated to stabilize it, and samples were prepared.

[0143] The obtained active material, sulfide solid electrolyte (10LiI-15LiBr-75 (0.75Li2S-0.25P2S5), average particle size 0.5 μm), conductive additive (VGCF), and binder (PVdF) were prepared. These were weighed in a weight ratio of negative electrode active material:sulfide solid electrolyte:conductive additive:binder = 53:41:4:2 and mixed with dispersion medium (heptane). The resulting mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation) to obtain a negative electrode slurry.

[0144] The obtained negative electrode slurry was coated onto the negative electrode current collector (copper foil) and dried at 100°C for 30 minutes. Then, 1 cm 2 By punching out the material to the specified size, a negative electrode structure having a negative electrode layer and a negative electrode current collector was obtained. Inner diameter cross-sectional area 1 cm 2 A sulfide solid electrolyte (10LiI-15LiBr-75(0.75Li2S-0.25P2S5), average particle size 0.5μm) is placed in a cylindrical plastic container, and the volume is increased to 4 ton / cm². 2 A solid electrolyte layer (15 μm thick) was obtained by pressing. The obtained solid electrolyte layer and the negative electrode structure were arranged at 4 ton / cm². 2 It was pressed. The thickness of the negative electrode layer was 46 μm.

[0145] (Fabrication of positive electrode structure) Cathode active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3A positive electrode slurry was obtained by dispersing the resulting mixture using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). The mixture consisted of O2, a sulfide solid electrolyte (10LiI-15LiBr-75 (0.75Li2S-0.25P2S5), with an average particle size of 0.5 μm), a conductive additive (VGCF), and a binder (PVdF). These were weighed in a weight ratio of positive electrode active material:sulfide solid electrolyte:conductive additive:binder = 85:13:1:1 and mixed with a dispersion medium (heptane). The resulting mixture was dispersed using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation).

[0146] The obtained positive electrode slurry was coated onto the positive electrode current collector (aluminum foil) and dried at 100°C for 30 minutes. Then, 1 cm 2 By punching out the material to the specified size, a positive electrode structure having a positive electrode layer and a positive electrode current collector was obtained. The thickness of the positive electrode layer was 50 μm.

[0147] (Preparation of evaluation batteries) A positive electrode structure and a negative electrode structure are arranged, with a load capacity of 4 tons / cm². 2 The material was then pressed. After that, stainless steel rods were inserted into the positive and negative electrodes, respectively, and restrained at 5 MPa to obtain an all-solid-state battery (evaluation battery).

[0148] (Comparative Example 2) The electrode in Comparative Example 2 was fabricated using the following procedure. A surface-roughened copper foil with a ten-point average surface roughness (roughness) Rz of 2.5 μm was used as the negative electrode current collector.

[0149] [Fabrication of the negative electrode active material layer] Gravel-like metallic silicon was placed in a carbon crucible, and under vacuum, the silicon was melted and vaporized using an electron gun. Using a mobile device, surface-roughened copper foil (which would serve as the negative electrode current collector) was placed on a roll, and five layers of silicon film were formed on the surface-roughened copper foil while the roll was moving.

[0150] [Insertion and detachment of lithium] A non-aqueous solvent was prepared by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC). An electrolyte (non-aqueous electrolyte) was then prepared by dissolving an electrolyte salt (lithium hexafluoride phosphate: LiPF6) in this non-aqueous solvent. In this case, the solvent composition was set to a volume ratio of EC:DMC = 30:70, and the electrolyte salt content was 1 mol / kg relative to the solvent. The resulting negative electrode active material layer was modified using this electrolyte by electrochemical method, inserting and deinserting lithium into silicon compound particles. Lithium insertion was completed when the potential difference between the anode and cathode became zero. Lithium deinsertion was completed when the potential difference between the anode and cathode became 1.2V. After lithium deinsertion was complete, the resulting negative electrode active material layer was washed with a dimethyl carbonate non-aqueous solvent to remove the electrolyte salt.

[0151] [Formation of surface film (ion-conducting layer)] By blowing carbon dioxide onto the negative electrode active material layer obtained by electrochemical modification, a lithium carbonate coating (ion-conducting layer) was formed on the surface and between layers (between each layer of the multilayer structure).

[0152] The obtained negative electrode structure and solid electrolyte layer are placed adjacent to each other, and the pressure is 4 ton / cm³. 2 The negative electrode was obtained by pressing it.

[0153] (Comparative Example 3) In Comparative Example 3, metallic silicon and silicon dioxide were placed in a carbon crucible, and 10 -2 In a vacuum atmosphere of Pa, steam was extracted by heating at 1200°C. The steam was directly supported on a roughened copper foil, as in Comparative Example 2, and five layers of film were deposited.

[0154] In Comparative Example 3, the roughened copper foil, the negative electrode active material layer containing silicon oxide provided on the roughened copper foil, and the solid electrolyte layer were arranged adjacent to each other in this manner, at a rate of 4 ton / cm². 2 The negative electrode was obtained by pressing it.

[0155] (Comparative Examples 4 and 5 and Example 1) In Comparative Examples 4 and 5, and Example 1, the negative electrode was fabricated in the same manner as in Comparative Example 2, except that water vapor was introduced into the silicon vapor stream during film formation to forcibly oxidize the material.

[0156] (Example 2) In Example 2, lithium was inserted and removed from a roughened copper foil obtained in the same manner as in Comparative Example 3, and a negative electrode active material layer containing silicon oxide was provided on this roughened copper foil. A surface coating (ion-conducting layer) was then formed on the foil, and the resulting negative electrode structure and solid electrolyte layer were placed adjacent to each other, with a load capacity of 4 ton / cm². 2 The negative electrode was obtained by pressing it.

[0157] (Comparative Example 6) In Comparative Example 6, the negative electrode was fabricated in the same manner as in Example 2, except that a surface coating (ion-conducting layer) was not formed.

[0158] (Examples 3 and 4 and Comparative Example 7) In Examples 3 and 4 and Comparative Example 7, the SiO2 of the negative electrode active material particles was used. x1 Li y1 The negative electrode was fabricated in the same manner as in Example 2, except that the film deposition rate was adjusted so that the value of x1 was as shown in Table 1, and hydrogen or oxygen was blown into the steam as needed during film deposition.

[0159] (Examples 5 and 6) In Examples 5 and 6, the negative electrode bodies were fabricated in the same manner as in Example 2, except that the deposition rate was controlled to deposit 1 layer and 20 layers, respectively, of the negative electrode active material layer.

[0160] (Example 7) In Example 7, the negative electrode was fabricated in the same manner as in Example 2, except that the surface roughness Rz of the copper foil was set to 0.5.

[0161] (Examples 8-10) In Examples 8-10, each negative electrode was fabricated in the same manner as in Example 2, except that the thickness before battery charging (T1) and the thickness when fully charged (T2) were adjusted by changing the depth of charge during lithium insertion. The depth of charge was defined as 0% before charging and 100% when the Li insertion amount reached zero potential difference between the anode and cathode.

[0162] (Examples 11-14) Example 11 was prepared in the same manner as in Example 2, except that aluminum phosphate was added to the electrolyte during lithium insertion and deinsertion, and carbon dioxide was not blown onto it. Example 12 was prepared in the same manner as in Example 2, except that the electrolyte salts were not removed after lithium insertion and deinsertion, and the negative electrode active material layer had a coating (ion-conducting layer) on its surface consisting of Li3PO4, LiF, and Li2CO3. Example 13 was prepared in the same manner as in Example 2, except that the negative electrode active material layer obtained after lithium insertion and deinsertion was subjected to alkylsilazane treatment. Example 14 was prepared in the same manner as in Example 2, except that the negative electrode active material layer obtained after lithium insertion and deinsertion was washed with a dimethyl carbonate non-aqueous solvent containing 3 vol% tar to remove electrolyte salts, and then heat-treated.

[0163] (Example 15) In Example 15, a negative electrode was prepared in the same manner as in Example 2, except that carbon dioxide, which was sprayed onto the negative electrode active material layer obtained by electrochemical modification, was mixed with Ar and diluted to a concentration of 1.0 vol%, thereby forming a lithium carbonate coating (ion-conducting layer) only on the surface.

[0164] (Examples 16-18) Examples 16 to 18 were fabricated in the same manner as in Example 2, except that the average number of primary particles in the secondary particles was adjusted by setting the surface roughness Rz of the surface roughened copper foil to 1.0, 1.5, and 2.5, respectively.

[0165] (Example 19) In Example 19, the solid electrolyte adjacent to the ion-conducting layer on the outermost surface of the negative electrode active material is a compound having a perovskite structure, Li 0.5La 0.5 Mg 0.5 W 0.5 A negative electrode body was produced in the same manner as in Example 2, except that it was changed to 0.5 W

[0166] [Preparation of Compound with Perovskite Structure] The basic composition formula is Li 0.5 La 0.5 Mg 0.5 W 0.5 Li2CO3 (manufactured by high purity chemicals), La(OH)3 (manufactured by high purity chemicals), MgO (manufactured by high purity chemicals), and WO3 (manufactured by high purity chemicals) were weighed so as to become 0.5

[0167] (Example 20) In Example 20, a negative electrode body was produced in the same manner as in Example 2, except that the solid electrolyte adjacent to the ion conduction layer on the outermost surface of the negative electrode active material was changed to Li3In2(PO4)3, which is a NASICON-type phosphate compound.

[0168] [Preparation of NASICON-Type Phosphate Compound] Using In as the In-containing active material and glassy Li 1.5 Al 0.5 Ge 1.5 (PO4)3 (LAGP) as the amorphous phosphate compound, an intermediate in which In and LAGP are in contact with each other was prepared. Next, the intermediate was fired at a predetermined temperature to react In and LAGP, and a sintered body for a battery containing an active material material having a crystal phase of Li3In2(PO4)3 was obtained.

[0169] (Example 21) In Example 21, the solid electrolyte adjacent to the ion conduction layer on the outermost surface of the negative electrode active material was changed to Li 6.8 (La 2.95 Ca 0.05 )(Zr 1.75 Nb 0.25 )O 12 (LLZ-CN), and the negative electrode body was fabricated in the same manner as in Example 2, except for this change.

[0170] [Fabrication of a Compound with a Garnet-Type Crystal Structure] As starting materials, LiOH(H2O), La(OH)3, Ca(OH)2, ZrO2, and Nb2O5 were used. The starting materials were weighed to a stoichiometric ratio, mixed, and pulverized. The mixing and pulverization were carried out using zirconia balls in ethanol by a planetary ball mill (300 rpm) for 1 hour. Thereafter, calcination (700 °C, 48 h) was performed. After the calcination, LiOH(H2O) was added in excess so as to be 10 at% with respect to Li in the composition for the purpose of compensating for Li deficiency in sintering. Thereafter, mixing and pulverization were carried out again under the same conditions. Thereafter, calcination (700 °C, 10 h) was performed again. The powder that had undergone the above calcination twice was identified for the crystal phase by XRD, and it was confirmed that there was no remaining unreacted raw material. Thereafter, Li and H exchange was carried out by immersing this LLZ-CN powder in water. The immersion conditions were such that Li and H exchange was carried out by allowing it to stand at room temperature (near 25 °C) for 30 minutes at a ratio of 50 mg of water to 4 g of LLZ-CN. When the composition after the Li and H exchange was analyzed under these conditions, (Li 5.6 ,H 1.2 )(La 2.95 ,Ca 0.05 )(Zr 1.75 ,Nb 0.25 )O 12The result was (LLZ-HCN). Here, the amount of H was identified as follows. First, the powder after H substitution was subjected to TG·DTA-MASS measurement, and the temperature range in which H2O (molecular weight 18) evaporates from the sample was determined by MASS measurement, and the weight loss in that temperature range was quantified by Tg. From the mass and molecular weight of LLZ-CN and the mass and molecular weight of the evaporated water, the atomic weight of the amount of H contained in LLZ-HCN was calculated.

[0171] [Evaluation of discharge capacity and cycle characteristics] The fabricated evaluation battery was subjected to a discharge termination potential of 2.0V (vs.Li / Li) in a constant temperature bath at 25°C. + ), charge end potential 4.8V (vs.Li / Li + CC charge and discharge cycles were repeated at a current density of 0.1C. The discharge capacity after the first cycle was used as the baseline (100%), and the retention rate (%) of the discharge capacity after 100 cycles was calculated.

[0172] [Table 1] [Table 2]

[0173] [result] Tables 1 and 2 above show the capacity retention rate and discharge capacity up to 100 cycles.

[0174] As is clear from Tables 1 and 2, the negative electrodes of Examples 1 to 21 all maintained a capacity retention rate of 80% after 100 cycles while also achieving battery characteristics with a discharge capacity of 240 mAh / g.

[0175] On the other hand, the negative electrode of Comparative Example 1, which was made using powdered Li-SiO, had a lower discharge capacity than the negative electrodes of Examples 1 to 20. This is thought to be because the negative electrode of Comparative Example 1 used powder instead of vapor deposition, resulting in the presence of a binder that does not participate in charging and discharging, and also due to the presence of many extra voids.

[0176] Furthermore, the negative electrode of Comparative Example 2 exhibited significantly inferior cycle characteristics compared to Examples 1-21.

[0177] Comparative Example 3 showed significantly lower cycle characteristics and discharge capacity compared to Examples 1-21. This is thought to be due to the absence of lithium insertion in the silicon oxide.

[0178] Since silicon dioxide is produced from silicon and silicon dioxide, it is difficult to increase or decrease the amount of oxygen. In fact, SiO x1 Li y1 Silicon oxide with x1 of 0.7 (Comparative Example 4) could not have its valency controlled, resulting in a significant amount of silicon remaining in the material.

[0179] To achieve even lower oxygen levels, it is necessary not only to introduce hydrogen into the steam and actively reduce it, but also to significantly reduce the film deposition rate.

[0180] The negative electrode material of Comparative Examples 4 and 5 is SiO x1 Li y1 When x1 was set to 0.7 and 0.8, the discharge capacity became lower than that of the negative electrodes in Examples 1 and 2. This is because the negative electrodes of Comparative Examples 4 and 5 contained SiO x1 Li y1 It is believed that the problem was caused by setting x1 to 0.7 and 0.8, which resulted in an excessively large surface area for zero-valent Si to react with the electrolyte, causing the conductive path to break during discharge.

[0181] On the other hand, when increasing the amount of oxygen, the film deposition rate was also reduced, and oxygen was blown directly into the steam stream for molding. However, when the amount of oxygen increased, it became difficult to prepare the silicon oxide film.

[0182] The negative electrode material of Comparative Example 7 is SiO x1 Li y1 When x1 was set to 1.3, the discharge capacity became lower than that of the negative electrodes in Examples 1-4. This is because in the negative electrode of Comparative Example 7, SiO x1 Li y1The problem is likely due to the excessive amount of load material resulting from setting x1 to 1.3. Since increasing x tends to decrease the discharge capacity, it is preferable to keep x1 at 1.2 or less.

[0183] In Comparative Example 6, the discharge capacity of the negative electrode body decreased as a result of eliminating the ion-conducting layer on the outermost surface of the negative electrode active material layer. This is thought to be because, in the negative electrode body of Comparative Example 6, the absence of the ion-conducting layer on the outermost surface of the negative electrode active material layer increased the interfacial resistance with the solid electrolyte.

[0184] The negative electrodes of Examples 1-4, compared to Comparative Examples 4 and 5, are composed of SiO x1 Li y1 By setting x1 to 0.9-1.2, the irreversible component of the negative electrode can be suppressed, improving both the initial efficiency and cycle characteristics.

[0185] In Example 5, the discharge capacity is improved because the interlayer resistance is reduced due to the negative electrode active material layer being a single layer film, but the capacity retention rate decreases because it becomes more difficult to mitigate the expansion and contraction during charging and discharging. A multilayer negative electrode body, such as in Examples 2 and 6, is more preferable because the expansion and contraction of the negative electrode active material layer in the negative electrode body can be mitigated, thus improving the capacity retention rate.

[0186] Compared to Example 2, Example 7 does not form secondary particles, and its structure makes it difficult to mitigate the expansion and contraction of the negative electrode active material layer in the negative electrode body, which is thought to have resulted in a decrease in the capacity retention rate. It is preferable for secondary particles to be formed as in Example 2.

[0187] Examples 8-10 are examples aimed at finding the optimal point for the thickness of the negative electrode active material before charging (T1) and the thickness after charging to full capacity (T2).

[0188] A smaller T2 / T1 value is thought to reduce expansion and contraction during charging and discharging, thereby improving capacity retention.

[0189] The presence of a coating (ion-conducting layer) as shown in Examples 3, 11-14 on the outermost surface of the negative electrode active material layer is thought to suppress reactions with moisture and oxygen, thereby reducing material degradation and maintaining excellent battery characteristics. Therefore, having such a coating (ion-conducting layer) is preferable.

[0190] The anode body of Example 15 exhibits a reduced discharge capacity compared to Example 3 due to the absence of an ion-conducting layer between the layers of the anode active material. Therefore, it is considered that anode bodies with an ion-conducting layer between the layers of the anode active material, as in Example 3, have improved ion conductivity and can maintain superior battery characteristics. Thus, it is preferable to have an ion-conducting layer between the layers of the anode active material.

[0191] Examples 16-18 are examples aimed at exploring the optimal number of primary particles in secondary particles. It is believed that a large number of primary particles in secondary particles can alleviate the stress of expansion during charging and discharging, thereby improving the capacity retention rate.

[0192] Examples 19-21 are examples intended to explore the types of solid electrolytes adjacent to the ion-conducting layer. The negative electrode active materials of Examples 19-21 can exhibit excellent battery characteristics when combined with any solid electrolyte as a negative electrode.

[0193] This specification includes the following embodiments: [1]: A negative electrode current collector with a roughened surface, A negative electrode active material layer provided on the negative electrode current collector, An ion conductive layer having lithium ion conductivity is provided on the surface of the negative electrode active material layer. A negative electrode having a negative electrode containing and having a solid electrolyte layer adjacent to the ion conducting layer, The negative electrode active material layer comprises negative electrode active material particles having a compound containing lithium, silicon, and oxygen, wherein the negative electrode active material particles are SiO x1 Li y1 A negative electrode body characterized by being expressible as such, where the value of x1 is greater than 0.8 and less than or equal to 1.2, and the value of y1 is between 0.5 and 3.4. [2]: The negative electrode active material layer has a multilayer structure consisting of two or more layers, The negative electrode active material layer, when the negative electrode active material particles are defined as primary particles, forms secondary particles which are aggregates of the primary particles. These secondary particles have a separated form in the in-plane direction. The negative electrode body described in [1] above, wherein the thickness T1 of the negative electrode active material layer before charging and the thickness T2 when fully charged are in a relationship of T2 / T1 ≤ 1.4. [3]: The anode body according to [2], wherein the anode active material layer having a multilayer structure has at least one interlayer lithium ion conductive layer having lithium ion conductivity between each layer constituting the multilayer. [4]: The negative electrode body according to any of the above [1] to [3], wherein the negative electrode active material layer contains at least one of Li4SiO4, Li2Si2O5, Li2SiO3, and Li6Si2O7. [5]: The negative electrode according to any of the above [1] to [4], wherein the lithium-ion conductive ion conducting layer consists of at least one of Li carbonate, Li phosphate, Li fluoride, Al carbonate, Al phosphate, Al fluoride, compounds having a silyl group, and carbonides containing polycyclic aromatic hydrocarbons. [6]: The negative electrode body of any of the above [2] to [5], wherein the secondary particles of the negative electrode active material layer consist of an average of four or more primary particles. [7]: The negative electrode body of any of the above [1] to [6], wherein the solid electrolyte layer is made of a sulfide-based solid electrolyte. [8]: The anode body of [7], wherein the sulfide-based solid electrolyte has at least one of lithium, indium, sulfur, and phosphorus. [9]: The anode according to [7] or [8] above, wherein the sulfide-based solid electrolyte has at least one of Li2S, P2S5, SiS2, LiI, LiBr, P2O5, Li3PO4 and GeS2.

[10] : The solid electrolyte layer is any of the negative electrodes described in [1] to [6] above, wherein the solid electrolyte layer is made of an oxide-based solid electrolyte.

[11] : The oxide-based solid electrolyte is the negative electrode body of the above

[10] having a perovskite structure.

[12] : The oxide-based solid electrolyte is the negative electrode body of the above

[10] or

[11] having at least one of lanthanum, lithium, magnesium, tungsten, niobium, and titanium.

[13] : The oxide-based solid electrolyte has a composition formula of A x2 BO3 (0 < x2 < 1), the element A includes La and Li, and the element B includes Mg, W, Nb, and Ti. It is the negative electrode body of any one of the above

[10] to

[12] .

[14] : The oxide-based solid electrolyte is the negative electrode body of the above

[10] having a NASICON-type phosphate compound.

[15] : The solid electrolyte having the NASICON-type phosphate compound is the negative electrode body of the above

[14] having at least one of lithium, aluminum, germanium, zirconium, titanium, and calcium.

[16] : The NASICON-type phosphate compound is Li (1+x3) M1 (x3) M2 (2-x3) (PO4)3, the element M1 includes at least one selected from the group consisting of Al, Y, Ga, and In, the element M2 includes at least one selected from the group consisting of Ti, Ge, and Zr, and x3 is 0 ≦ x3 ≦ 2. It is the negative electrode body of the above

[14] or

[15] .

[17] : The oxide-based solid electrolyte is the negative electrode body of the above

[10] having a garnet-type crystal structure.

[18] : The solid electrolyte having the garnet-type crystal structure is the negative electrode body of the above

[17] having at least one of lithium, lanthanum, calcium, zirconium, bismuth, aluminum, cerium, gallium, boron, and oxygen.

[19] : The solid electrolyte having the garnet-type crystal structure is Li (7-3x4+y4-z4) M x4 La (3-y4) A’ (y4) Zr (2-z4) T (z4) O 12The negative electrode body of the above

[17] or

[18] , wherein (element M is one or more of Al and Ga, element A' is one of Ca and Sr, T is one of Nb and Ta, and satisfies 0 ≤ x 4 ≤ 0.18, 0 ≤ y 4 ≤ 0.18, and 0 ≤ z 4 ≤ 1.5).

[20] : A method for manufacturing a negative electrode, which is one of the negative electrodes described in [1] to

[19] above, A step of winding the negative electrode current collector onto a can roll having curvature, A vapor phase growth step is performed in which a film containing silicon and / or silicon monoxide, having a multilayer structure consisting of two or more layers, is vapor-grown on the negative electrode current collector while the negative electrode current collector is being moved on the can roll. A step of blowing an oxygen-containing gas onto the film containing silicon and / or silicon monoxide to form a multilayer structure with silicon dioxide on top of each layer, The process involves inserting and de-inserting lithium into the multilayer structure to form the negative electrode active material layer, A step of forming an ion conductive layer having lithium ion conductivity on the surface of the negative electrode active material layer, A step of forming the ion conductive layer adjacent to the solid electrolyte layer. A method for manufacturing a negative electrode, characterized by including the following:

[21] : In the step of forming the multilayer structure, the multilayer structure is formed in which each layer contains silicon oxide containing silicon dioxide, In the vapor phase growth step, a negative electrode active material layer containing silicon oxide is grown on the negative electrode current collector using vapor phase growth. The process involves immersing the negative electrode active material layer containing silicon oxide in a lithium-containing solution and modifying the silicon oxide by an electrochemical method to generate a compound containing lithium, silicon, and oxygen, and forming the ion-conducting layer. A method for manufacturing the negative electrode described above

[20] , including the above.

[0194] Note that the present invention is not limited to the above-described embodiments. The above embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Description of Reference Numerals

[0195] 10... Negative electrode body, 11... Negative electrode current collector, 11a... Surface of the negative electrode current collector 12... Negative electrode active material layer 14... Ion conduction layer 16... Solid electrolyte 20... Lithium-ion secondary battery 21... Positive electrode material layer, 22... Positive electrode current collector

Claims

1. A negative electrode current collector with a roughened surface, A negative electrode active material layer provided on the negative electrode current collector, An ion conductive layer having lithium ion conductivity is provided on the surface of the negative electrode active material layer. A negative electrode having a negative electrode containing and having a solid electrolyte layer adjacent to the ion conducting layer, The ten-point average roughness Rz of the surface of the negative electrode current collector is 1.5 μm or more and 5.0 μm or less. The negative electrode active material layer comprises negative electrode active material particles having a compound containing lithium, silicon, and oxygen, and the negative electrode active material particles are SiO ｘ１ Li ｙ１ It can be expressed as follows, where the value of x1 is greater than 0.8 and less than or equal to 1.2, and the value of y1 is greater than or equal to 0.5 and less than or equal to 3.

4. The negative electrode active material layer has a multilayer structure consisting of two or more layers. The negative electrode active material layer, when the negative electrode active material particles are defined as primary particles, forms secondary particles which are aggregates of the primary particles. These secondary particles have a form that is separated in the in-plane direction. The negative electrode is characterized in that the thickness T1 of the negative electrode active material layer before charging and the thickness T2 when fully charged are in a relationship of T2 / T1 ≤ 1.

4.

2. The negative electrode according to claim 1, characterized in that the negative electrode active material layer having a multilayer structure has at least one interlayer lithium ion conductive layer having lithium ion conductivity between each of the layers constituting the multilayer structure.

3. The negative electrode active material layer contains Li ４ SiO ４ , Li ２ Si ２ O ５ , Li ２ SiO ３ and Li ６ Si ２ O ７ The negative electrode body according to claim 1, characterized in that it contains at least any one of them.

4. The negative electrode according to claim 1, characterized in that the lithium ion conductive ion conductive layer comprises at least one of Li carbonate, Li phosphate, Li fluoride, Al carbonate, Al phosphate, Al fluoride, a compound having a silyl group, and a carbonide containing a polycyclic aromatic hydrocarbon.

5. The negative electrode body according to claim 1, characterized in that the secondary particles of the negative electrode active material layer consist of an average of four or more primary particles.

6. The negative electrode according to claim 1, characterized in that the solid electrolyte layer is made of a sulfide-based solid electrolyte.

7. The negative electrode according to claim 6, characterized in that the sulfide-based solid electrolyte has at least one of lithium, indium, sulfur, and phosphorus.

8. The sulfide-based solid electrolyte is Li ２ S, P ２ S ５ SiS ２ , LiI, LiBr, P ２ O ５ Li ３ PO ４ and GeS ２ The negative electrode body according to claim 6, characterized in that it has at least one of the following.

9. The negative electrode according to claim 1, characterized in that the solid electrolyte layer is made of an oxide-based solid electrolyte.

10. The negative electrode according to claim 9, characterized in that the oxide-based solid electrolyte has a perovskite structure.

11. The negative electrode according to claim 9, characterized in that the oxide-based solid electrolyte has at least one of lanthanum, lithium, magnesium, tungsten, niobium, and titanium.

12. The oxide-based solid electrolyte has compositional formula A ｘ２ BO ３ The negative electrode according to claim 9, characterized in that it is represented by (0 < x² < 1), element A contains at least one of La and Li, and element B contains at least one of Mg, W, Nb, and Ti.

13. The negative electrode according to claim 9, characterized in that the oxide-based solid electrolyte has a nasicone-type phosphate compound.

14. The negative electrode according to claim 13, characterized in that the solid electrolyte having the NASCON-type phosphate compound has at least one of lithium, aluminum, germanium, zirconium, titanium, and calcium.

15. The aforementioned nasicone-type phosphate compound is Li （１＋ｘ３） M1 （ｘ３） M2 （２－ｘ３） (PO ４ ) ３ The negative electrode body according to claim 13, characterized in that it is represented as such, the element M1 includes at least one selected from the group consisting of Al, Y, Ga, and In, the element M2 includes at least one selected from the group consisting of Ti, Ge, and Zr, and x3 is 0 ≤ x3 ≤ 2.

16. The negative electrode according to claim 9, characterized in that the oxide-based solid electrolyte has a garnet-type crystal structure.

17. The negative electrode according to claim 16, characterized in that the solid electrolyte having the garnet-type crystal structure contains at least one of lithium, lanthanum, calcium, zirconium, bismuth, aluminum, cerium, gallium, boron, and oxygen.

18. The solid electrolyte having the garnet-type crystal structure is Li （７－３ｘ４＋ｙ４－ｚ４） M ｘ４ La （３－ｙ４） A' （（ｙ４） Zr （２－ｚ４） T （ｚ４） O １２ The negative electrode body according to claim 16, characterized in that (element M is one or more of Al and Ga, element A' is one of Ca and Sr, T is one of Nb and Ta, and satisfies 0 ≤ x 4 ≤ 0.18, 0 ≤ y 4 ≤ 0.18, and 0 ≤ z 4 ≤ 1.5).

19. A method for manufacturing a negative electrode according to any one of claims 1 to 18, A step of winding the negative electrode current collector onto a can roll having curvature, A vapor phase growth step is performed in which a film containing silicon and / or silicon monoxide, having a multilayer structure consisting of two or more layers, is vapor-grown on the negative electrode current collector while the negative electrode current collector is being moved on the can roll. A step of blowing an oxygen-containing gas onto the film containing silicon and / or silicon monoxide to form a multilayer structure with silicon dioxide on top of each layer, The process involves inserting and de-inserting lithium into the multilayer structure to form the negative electrode active material layer, A step of forming an ion conductive layer having lithium ion conductivity on the surface of the negative electrode active material layer, A step of forming the ion conductive layer adjacent to the solid electrolyte layer. A method for manufacturing a negative electrode, characterized by including the following:

20. In the step of forming the multilayer structure, the multilayer structure is formed in which each layer contains silicon oxide containing silicon dioxide, In the vapor phase growth step, a negative electrode active material layer containing silicon oxide is grown on the negative electrode current collector using vapor phase growth. The process involves immersing the negative electrode active material layer containing silicon oxide in a lithium-containing solution and modifying the silicon oxide by an electrochemical method to generate a compound containing lithium, silicon, and oxygen, and forming the ion-conducting layer. A method for manufacturing a negative electrode according to claim 19, characterized by including the following:

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