secondary battery with non-aqueous electrolyte

Abstract

A secondary battery with a non-aqueous electrolyte comprises: a positive electrode plate (100); a negative electrode plate (200); and a separator (300) arranged between the positive electrode plate (100) and the negative electrode plate (200). The separator (300) includes a porous resin layer (301). The porous resin layer (301) is made of polyolefin with a melting point of 80°C or higher and 135°C or lower. At least one surface (S1) of the positive electrode plate (100) and the negative electrode plate (200) has a surface facing the porous resin layer (301). The surface (S1) forms a contact angle (θ) of 30° or more with a molten droplet of the polyolefin.

Description

[0001] This non-provisional application is based on Japanese patent application no. 2015-175613 filed with the Japan Patent Office on September 7, 2015, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION Area of ​​the invention

[0002] The present invention relates to a secondary battery with a non-aqueous electrolyte. Description of the current state of the art

[0003] WO2008 / 044761 discloses a separator which has a shutdown function and forms a contact angle of 40° or less with an electrolyte solution. SUMMARY OF THE INVENTION

[0004] The separator acts as an insulator, preventing contact between a positive electrode plate and a negative electrode plate while allowing the passage of charge carriers (typically lithium ions). Furthermore, the separator also serves as a fluid-retaining material, holding an electrolyte solution within its internal cavities.

[0005] WO2008 / 044761 discloses a separator with a shutdown function. According to the shutdown function, a separator material melts when the battery temperature rises excessively, for example due to exceptional usage conditions such as overcharging, thereby closing pores within the separator and blocking ion permeation.

[0006] According to the disclosure in WO2008 / 044761, the separator, which has the shutdown function described above, is designed such that the contact angle of the electrolyte solution with the separator surface is set small, so that the electrolyte solution can be easily retained in the separator, thereby improving battery performance.

[0007] However, the following points require further improvement. Specifically, during an overload, the high temperature condition can be maintained even after the separator has performed its shutdown function. In this case, the separator continues to melt, causing the molten separator to penetrate from the surface of the electrode plate (either a positive or a negative electrode plate) into the electrode plate itself. As a result, the separator thickness is reduced, allowing the positive and negative electrode plates to come into contact with each other.

[0008] The present invention was developed in consideration of the problems described above. Specifically, one object of the present invention is to provide a secondary battery with a non-aqueous electrolyte that possesses improved overcharge resistance properties. [1] A secondary battery with a non-aqueous electrolyte comprises: a positive electrode plate; a negative electrode plate; and a separator arranged between the positive and negative electrode plates. The separator includes a porous resin layer. The porous resin layer is made of polyolefin with a melting point of 80°C or more and 135°C or less. At least one of the positive and negative electrode plates has a surface facing the porous resin layer. The surface forms a contact angle of 30° or more with a molten droplet of the polyolefin.

[0009] In the embodiment described above [1], the porous polyolefin resin layer performs a shutdown function. Specifically, the polyolefin melts when the temperature inside the battery reaches 80°C or above, thereby closing pores within the porous resin layer and blocking ion permeation.

[0010] If the high temperature condition is maintained, the molten polyolefin must penetrate one of the electrode plates facing the porous resin layer (at least one from the positive and negative electrode plates). However, in the embodiment described above [1], the electrode plate facing the porous resin layer has a solid surface that is hardly wetted by a polyolefin melt. In other words, the surface of the electrode plate facing the porous resin layer forms a contact angle of 30° or more with a molten polyolefin droplet. In this case, the contact angle is an indicator of the wetting resistance. Thus, the larger the contact angle, the more likely it is that the surface of the electrode plate will repel molten polyolefin.According to the investigation of the present inventors, the contact angle between the molten polyolefin droplet and the surface of the electrode plate is set to 30° or more, so that the molten polyolefin is significantly prevented from penetrating the electrode plate. Consequently, the molten polyolefin is retained between the positive and negative electrode plates, thereby reducing the possibility of the positive and negative electrode plates coming into contact with each other.

[0011] It should be noted that the melting point of polyolefin, which forms a porous resin layer, should be set at 135°C or lower. If the melting point of polyolefin exceeds 135°C, it takes a relatively long time from the start of heat generation in the battery until the cutoff function activates. Consequently, the overcharge resistance properties may deteriorate.

[0012] Furthermore, the melting point of polyolefin is set at 80°C or higher, as temperatures below 80°C fall within the range of battery operating temperatures. In other words, polyolefin with a melting point below 80°C can cause defects, such as shrinkage of the separator pores, even under normal operating conditions. [2] In the secondary battery with non-aqueous electrolyte described above according to [1], the contact angle can be set to 30° or more and 60° or less. From the point of view of suppressing permeation of polyolefin, the contact angle is preferably larger. The upper limit of the contact angle can, for example, be set to 60°. [3] In the case of the secondary battery with non-aqueous electrolyte described above according to [1], it is preferable that the contact angle be 45° or more and 60° or less. This is because an improvement in the overcharge resistance properties can be expected.

[0013] The foregoing and further tasks, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Fig. Figure 1 is a schematic cross-sectional view showing an example of the design of a secondary battery with non-aqueous electrolyte according to the present embodiment.

[0015] Fig. Figure 2 is a schematic diagram showing an example of the design of an electrode arrangement.

[0016] Fig. Figure 3 is a schematic cross-sectional view showing an interface between an electrode plate and a separator.

[0017] Fig. Figure 4 is a schematic cross-sectional view illustrating a method for measuring a contact angle.

[0018] Fig. Figure 5 is a schematic diagram showing an example of the design of a positive electrode plate.

[0019] Fig. Figure 6 is a schematic diagram showing an example of the design of a negative electrode plate.

[0020] Fig. Figure 7 is a schematic cross-sectional view showing an example of the electrode plate formed from a granular body.

[0021] Fig. Figure 8 is a schematic conceptual diagram showing an example of the design of a granular particle.

[0022] Fig. Figure 9 is a schematic diagram showing an electrode manufacturing device.

[0023] Fig. Figure 10 is a graph showing the relationship between the contact angle and the voltage achieved in an overload test.

[0024] Fig. Figure 11 is a graph showing the relationship between the melting point of polyolefin, which forms a porous resin layer, and the voltage achieved in the overload test. DESCRIPTION OF PREFERRED EXECUTION FORMS

[0025] An example of an embodiment of the present invention (hereinafter referred to as the “present embodiment”) is described below. However, the present embodiment is not limited to the following description. In the following description, a secondary battery with a non-aqueous electrolyte may simply be referred to as a “battery”. <Sekundärbatterie mit nicht-wässrigem Elektrolyt>

[0026] Fig. Figure 1 is a schematic cross-sectional view showing an example of the design of a secondary battery with a non-aqueous electrolyte according to the present embodiment. A battery 1000 is a prismatic battery, used, for example, in automotive applications. The battery 1000 includes a prismatic battery housing 500 The battery casing 500 For example, it is made of an aluminum (Al) alloy. The battery casing500 It is typically formed from: a prismatic housing body with a base; and a lid.

[0027] The battery casing 500 is connected with a positive connection 501 and a negative terminal 502 The battery housing is equipped with each of the following external connections. 500 It may be equipped with a liquid inlet, a safety valve, a current-disconnect device, and the like. The battery housing 500 takes up an electrode arrangement 800 and an electrolyte solution 900 on. The electrode arrangement 800 is connected to the positive connection 501 and the negative connection 502 connected. The electrolyte solution also penetrates the electrode arrangement. 800 . < <elektrodenanordnung>>

[0028] Fig. Figure 2 is a schematic diagram showing an example of the design of an electrode arrangement. The electrode arrangement 800 is a wound-type electrode arrangement. The electrode arrangement 800 is made from a positive electrode plate 100 , a negative electrode plate 200 and a separator 300 formed, each of which consists of strip-shaped track elements. The electrode arrangement 800 is achieved by stacking the positive electrode plate 100 and the negative electrode plate 200 with the separator in between 300 and winding this stack was formed. After winding the electrode arrangement. 800 It is pressed in such a way that its outer shape is formed in a flat shape.

[0029] Fig. Figure 3 is a schematic cross-sectional view showing an interface between an electrode plate and a separator. As in Fig. As shown in Figure 3, the secondary battery with non-aqueous electrolyte of the present embodiment includes the positive electrode plate. 100 , the negative electrode plate 200 and the one between the positive electrode plate 100 and the negative electrode plate 200 arranged separator 300 .

[0030] The positive electrode plate 100 includes a positive electrode collector 101 and a positive electrode mixture layer 102 , which positive electrode active material particles 1 contains. The surface of the positive electrode plate 100 is from the positive electrode mixture layer 102 formed. The positive electrode mixture layer 102 is a porous layer. This is because the positive electrode mixture layer, which contains a plurality of solid particles (positive electrode active material particles), cannot completely fill the voids between particles.

[0031] The negative electrode plate 200 includes a negative electrode collector 201 and a negative electrode mixture layer 202 , which negative electrode active material particles 2 It contains the negative electrode plate. 200 possesses a layer consisting of the negative electrode mixture 202 formed surface S1. The negative electrode mixture layer 202 It is a porous layer. This is because the negative electrode mixture layer, like a positive electrode mixture layer, contains a plurality of solid particles (negative electrode active material particles).

[0032] The separator 300 includes a first porous resin layer 301 Made of polyolefin with a melting point of 80°C or higher and 135°C or lower. At least one from the positive electrode plate. 100 and the negative electrode plate 200 possesses a surface that resembles the first porous resin layer 301 is turned towards. Fig. Figure 3 shows an exemplary embodiment in which the negative electrode plate 200 possesses a surface S1, which is the first porous resin layer 301 is turned towards. Also in the in Fig. The separator is included in the 3 examples shown. 300 furthermore, a second porous resin layer 302 Made of polyolefin with a melting point above 135°C. The positive electrode plate 100 is the second porous resin layer 302 facing.

[0033] An arrow 10 in Fig. Figure 3 shows the direction in which the molten first porous resin layer flows. 301 penetrates after a shutdown function has occurred in the overload state. As indicated by the arrow 10 As shown, the molten first porous resin layer penetrates 301 (Polyolefin) through an adjacent electrode plate (negative electrode plate) 200 in Fig. 3) This is because the negative electrode mixture layer 202 , which is the surface S1 of the negative electrode plate 200 forms a porous layer. Since in the example in Fig. 3 the second porous resin layer 302 Since it has a relatively higher melting point, it has not yet begun to melt.

[0034] In the present embodiment, the electrode plate (negative electrode plate) has 200 in Fig. 3) a surface S1 which is a porous resin layer (the first porous resin layer) 301 in Fig. 3) made of polyolefin with a melting point of 80°C or more and 135°C or less. This surface S1 of the electrode plate forms a contact angle of 30° or more with a molten droplet of this polyolefin. In the case that the positive and negative electrode plates each have a surface facing this porous resin layer, the surface of each of the positive and negative electrode plates forms a contact angle of 30° or more with a molten droplet of this polyolefin. This does not apply exclusively to the surface facing a porous resin layer (the second porous resin layer). 302 ) and the like, which, for example, has a melting point above 135°C, as is the case with the surface of the in Fig. 3 positive electrode plates shown 100 .

[0035] The surface S1 of the negative electrode plate 200 forms a contact angle of 30° or more with the molten droplet of polyolefin, which forms the first porous resin layer 301 forms, so that the molten first porous resin layer 301 (molten polyolefin) is prevented from passing through the negative electrode mixture layer 202 to penetrate. This causes polyolefin, which acts as an insulator, to be deposited between the positive electrode plate. 100 and the negative electrode plate 200 held, thus creating contact between the positive electrode plate 100 and the negative electrode plate 200 is suppressed.

[0036] From the perspective of suppressing permeation of molten polyolefin, the contact angle is preferably larger. The contact angle is preferably 45° or more. This is expected to improve the overload resistance properties. The upper limit of the contact angle is not necessarily restricted. The upper limit of the contact angle can, for example, be set at 60°. Later, it will be explained how the positive electrode plate or the negative electrode plate is formed such that it has a surface that is hardly wetted by molten polyolefin. <<Verfahren zum Messen des Berührungswinkels> >

[0037] Fig. Figure 4 is a schematic cross-sectional view illustrating a method for measuring a contact angle. The contact angle is the angle formed between the tangent line of a molten droplet and the surface of the electrode plate, which arises when the molten polyolefin droplet drips onto the surface of the electrode plate. It should be noted that the angle formed in this case is an angle within the molten droplet. Fig. 4 corresponds to the angle (θ) that is formed between a tangent line 20 of the molten drop 3 and the surface S1, a contact angle. The contact angle is calculated using a “θ / 2 method”. In other words, assuming the shape of the molten droplet is part of a sphere, a radius (r) and a height (h) of the surface (surface S1) in contact with the molten droplet are measured, and the contact angle can be calculated using the following equation (i): θ = 2arctan(h / r) (i)

[0038] The contact angle can be measured using a commercially available contact angle gauge. The contact angle gauge could be, for example, a "PG-X" (trade name) manufactured by MATSUBO Corporation, or similar. The contact angle is measured in an environment at a temperature of 150°C. The amount of molten material applied is set to 0.1 g. < <separator>>

[0039] In the present embodiment, a separator is an element arranged between a positive electrode plate and a negative electrode plate.

[0040] The separator includes a porous resin layer. The porous resin layer has a thickness of, for example, about 2 μm to 30 μm, preferably about 2 μm to 20 μm, and more preferably about 2 μm to 15 μm. The porous resin layer is made of polyolefin with a melting point of 80°C or higher and 135°C or lower. The polyolefin can be, for example, polyethylene (PE), polypropylene (PP), and the like. The polyolefin is preferably low-density polyethylene (LDPE), high-density polyethylene (HDPE), and the like.

[0041] From the perspective of improving the response sensitivity to overload, the melting point of the polyolefin is preferably 120°C or less, and more preferably 100°C or less. In this case, the melting point of the resin in this specification represents the uppermost peak temperature of the melting point obtained by differential scanning calorimetry (DSC) in accordance with the procedure defined in "JIS K 7121: 2012 Methods for Testing Transition Temperatures of Plastics".

[0042] The separator can be formed from a single porous resin layer or from multiple porous resin layers. If the separator contains multiple porous resin layers, it can include a porous resin layer with a melting point above, for example, 135°C, provided it contains at least one porous resin layer made of polyolefin with a melting point of 80°C or higher and 135°C or lower. Furthermore, the separator can contain an inorganic porous layer, such as a nonwoven fabric of resin fibers or an inorganic sintered body, provided it contains at least one porous resin layer.

[0043] An embodiment comprising multiple porous resin layers can, for example, be a configuration obtained by stacking a porous PE resin layer and a porous PP resin layer. The separator can include an inorganic filler layer containing inorganic fillers (for example, aluminum oxide particles and the like). Even with an inorganic filler layer, the desired effect of the present embodiment is achieved. The total thickness of the separator is, for example, approximately 2 μm to 50 μm, preferably approximately 2 μm to 20 μm, and more preferably approximately 2 μm to 15 μm.

[0044] The porous resin layer is produced, for example, by the stretch-opening process, the phase separation process, or similar methods. The pore size, porosity, and other properties of the porous resin layer can be adjusted to achieve the desired air permeability of the separator. The Gurley permeability of the separator simply needs to be set to, for example, approximately 100 to 400 s / 100 ml. The Gurley permeability can be measured, for example, using a Gurley permeability tester or similar equipment. The average pore size of the porous resin layer only needs to be, for example, approximately 0.05 μm to 0.5 μm. The average pore size can be measured, for example, by mercury porosimetry or similar methods. < <positivelektrodenplatte>>

[0045] Fig. Figure 5 is a schematic diagram showing an example of the design of the positive electrode plate. The positive electrode plate 100 includes a positive electrode collector 101 and one on the positive electrode collector 101 arranged positive electrode mixture layer 102 The positive electrode mixture layer 102 can be located on one of the main surfaces of the positive electrode collector 101 The positive electrode collector can be arranged on one or both of the main surfaces. For example, the positive electrode collector is an aluminum foil or similar material. The positive electrode collector can have a thickness of, for example, approximately 5 μm to 25 μm. A section of the positive electrode collector 101 , which is from the positive electrode mixture layer 102 Once exposed, it is considered an exposed section. 103 defined. This exposed section 103 is intended to ensure a positive connection 501 and the electrode arrangement 800 to connect (see Fig. 1).

[0046] The thickness of the positive electrode mixture layer is, for example, approximately 20 μm to 100 μm. The positive electrode mixture layer contains positive electrode active material particles and a binder resin. The positive electrode mixture layer contains, for example, approximately 80 wt% to 99 wt% positive electrode active material particles. The positive electrode active material particles are typically particles of a lithium (Li)-containing metal oxide. Li-containing metal oxide can, for example, have a layered rock salt structure, a spinel-type structure, an olivine-type structure, and the like. The Li-containing metal oxide can, for example, be LiCoO₂, LiNiO₂, or one described by the general formula LiNi. a Co b O2 (where a + b = 1, 0 < a < 1 and 0 < b < 1) compound represented, LiMnO2, LiMn2O4, a compound represented by the general formula LiNi a Co b Mn c O2 (where a + b + c = 1, 0 < a < 1, 0 < b < 1 and 0 < c < 1) represented compound (for example LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and the like), LiFePO4 and the like. The average particle diameter of the positive electrode active material particles can, for example, be approximately 1 μm to 20 μm. In this specification, it is assumed that the average particle diameter in this case represents a particle size at 50% of a cumulative value (also referred to as "d50", a "mean diameter", or the like) in the particle size distribution of the volume reference measured by the laser diffraction and scattering method.

[0047] The positive electrode mixture layer contains, for example, approximately 1 wt% to 20 wt% binder resin. Preferably, the binder resin has a melting point higher than that of the polyolefin forming a porous resin layer in the separator. This is intended to increase the contact angle with the molten polyolefin droplet. The binder resin can be, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and the like. Alternatively, the binder resin can be a copolymer of: a monomer such as vinylidene fluoride (VDF) and tetrafluoroethylene (TFE); and other monomers. The monomer that can be copolymerized with VDF or TFE can be, for example, hexafluoropropylene (HFP), ethylene, perfluoroalkyl vinyl ether, and the like. The copolymers can be an alternating copolymer, a statistical copolymer, a graft copolymer, a block copolymer, and the like.The binding resin can be used alone, or two or more types of binding resins can be used in combination.

[0048] The positive electrode mixture layer can contain a conductive material. For example, the positive electrode mixture layer contains approximately 1 wt% to 10 wt% of a conductive material. The conductive material can be, for example, carbon black, such as acetylene black and thermal carbon black. < <negativelektrodenplatte>>

[0049] Fig. Figure 6 is a schematic diagram showing an example of the design of a negative electrode plate. The negative electrode plate 200 includes a negative electrode collector 201 and one on the negative electrode collector 201 arranged negative electrode mixture layer 202 The negative electrode mixture layer 202 can be located on one of the main surfaces of the negative electrode collector 201 The negative electrode collector can be arranged on one or both of the main surfaces. For example, the negative electrode collector is a copper (Cu) foil or similar material. The thickness of the negative electrode collector can be, for example, approximately 5 μm to 25 μm. A section of the negative electrode collector 201 , which is from the negative electrode mixture layer 202 Once exposed, it is considered an exposed section. 203 defined. This exposed section 203 is intended to connect the negative terminal 502 and the electrode arrangement 800 to connect (see Fig. 1).

[0050] The thickness of the negative electrode mixture layer is, for example, approximately 20 μm to 100 μm. This layer contains negative electrode active material particles and a binder resin. The negative electrode mixture layer contains, for example, approximately 80 wt% to 99 wt% negative electrode active material particles. These particles can be carbon-based or alloy-based. Carbon-based negative electrode active material can be, for example, graphite, soft (graphitizable) carbon, hard (difficult to graphitize) carbon, and the like. Alloy-based negative electrode active material can be silicon (Si), silicon dioxide (SiO2), tin (Sn), a tin-copper alloy (SnCu), and the like.

[0051] The negative electrode mixture layer contains, for example, approximately 1 wt% to 10 wt% binder resin. In addition to the binder resin specified as an example in the description of the positive electrode mixture layer, the binder resin can be styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), sodium carboxymethylcellulose (CMC-Na), sodium polyacrylate (PAA-Na), and the like. The binder resin can be used alone, or two or more types of binder resins can be used in combination. < <Ausgestaltung einer Elektrodenplatte, die einen großen Berührungswinkel mit einem geschmolzenen Polyolefintropfen bildet> >

[0052] A conceivable configuration of the electrode plate, which forms a relatively large contact angle with a molten polyolefin droplet, can be one in which, for example, a binder resin is deposited on the surface side of the electrode mixture layer (a positive electrode mixture layer or a negative electrode mixture layer). The surface side used here refers to the side opposite the side on which an electrode collector (a positive electrode collector or a negative electrode collector) is located. A section forming the surface of the electrode mixture layer preferably contains 8 wt% or more and 20 wt% or less binder resin. This allows the contact angle between the molten polyolefin droplet and the surface of the electrode plate to be set to 30° or more.

[0053] Alternatively, an inorganic filler layer can be formed on the surface of the electrode mixture layer, preferably containing 8 wt% or more and 20 wt% or less binder resin, and otherwise an inorganic filler. Even in such an inorganic filler layer, the cavity around the inorganic filler cannot be completely filled. Consequently, this inorganic filler layer results in a porous layer. (Granular body)

[0054] If the aforementioned inorganic filler is located on the surface of the electrode mixture layer, binder resin in the inorganic filler layer can penetrate the electrode mixture layer, thereby degrading the discharge performance. Furthermore, the binder resin content in the electrode mixture layer is relatively high, ranging from 8% to 20% by weight. The binder resin is a resistive component. Therefore, simply maintaining the binder resin content at 8% to 20% by weight can further degrade the discharge performance.

[0055] As an embodiment of the electrode plate capable of forming a relatively large angle while suppressing a deterioration in discharge performance, an electrode mixture layer formed from a granular body is conceivable. A granular body means an accumulation of granular particles. A granular particle is a composite particle obtained by granulating electrode active material particles (positive electrode active material particles or negative electrode active material particles) and a binder resin or the like. According to the investigation of the present inventors, the contact angle formed on the surface of the electrode plate can be efficiently increased while suppressing a deterioration in discharge performance when using the granular body, which is formed in particular by a two-stage granulation process.

[0056] Fig. Figure 7 is a schematic cross-sectional view showing an example of the electrode plate formed from a granular body. Fig. Figure 7 shows an example of a positive electrode plate. Of course, a negative electrode plate can also be formed from a granular material. The positive electrode plate 100 includes a positive electrode collector 101 and one on the positive electrode collector 101 arranged positive electrode mixture layer 102 The positive electrode mixture layer 102 contains a plurality of granular particles 50 .

[0057] The granular particle 50 It possesses a so-called core-shell structure. Specifically, the granular particle has 50 a core-shell structure that includes a first granular section 51 as a core and a second granular section 52 as a shell. The second granular section 52 forms the surface S1 of the positive electrode plate 100 .

[0058] The first granular section 51 and the second granular section 52 They contain positive electrode active material particles or a binding resin. For the sake of simplicity, it shows Fig. 7. No positive electrode active material particles and no binding resin. The second granular section 52 preferably contains 8 wt% or more and 20 wt% or less binding resin. The first granular section 51 contains less of a binding resin than the second granular section 52 The first granular section 51 For example, it contains approximately 1 wt% to 4 wt% binding resin (typically about 2 wt%).

[0059] According to the embodiment described above, the binder resin content on the surface of the electrode plate is locally increased, thus efficiently increasing the contact angle while suppressing a deterioration in discharge performance. Preferably, the ratio of the thickness of the second granular section to the thickness of the electrode mixture layer is set to, for example, approximately 1% to 30%. It should be noted that this ratio represents the percentage of the value obtained by dividing the thickness of the second granular section by the thickness of the electrode mixture layer. (Method for manufacturing a granular body and an electrode plate)

[0060] A method for manufacturing a granular body and a method for manufacturing an electrode plate using the granular body are then described below. 1. Method for manufacturing a granular body

[0061] A granular body can be manufactured using a conventional granulation device. Examples of granulation methods include shake granulation, tumbling granulation, fluidized bed granulation, and the like. Fig. Figure 8 is a schematic conceptual diagram showing an example of the design of a granular particle. In the present embodiment, an accumulation of in Fig. 8 granular particles shown 50 , that is, a granular body, preferably produced by a two-stage granulation process. 1-1. Primary granulation process

[0062] First, primary granular particles are manufactured, which serve as the first granular section. 51 (Core) are to be used. Primary granular particles can be produced by granulating electrode active material particles, a binder resin, a solvent, and the like, which are introduced into a granulation vessel of the granulation device in a prescribed proportion. The particle size of the primary granular particle can, for example, be approximately 0.1 mm to 5 mm. Since the granular particles are stretched thinly to form an electrode mixture layer, the particle size of each granular particle is closely matched to the desired thickness of the electrode mixture layer. 1-2. Secondary granulation process

[0063] Then a granular particle is formed. 50 (a secondary granular particle) with a first granular section 51 (core) and a second granular section adhering to it 52 (Crust). Granular particles can be produced by granulating primary granular particles, electrode active material particles, a binding resin, a solvent, and the like, which are introduced in a prescribed proportion into a granulation vessel of the granulation device. The electrode active material particles and the binding resin introduced at this stage serve to form a second granular section (crust). The binding resin content in the second granular section is set higher than the binding resin content in the first granular section.

[0064] This can allow the in Fig. 8 granular particles shown 50 The particle size of the granular particle can be, for example, approximately 0.1 mm to 5 mm. In the present embodiment, the second granular section only needs to adhere to the first granular section, but does not need to completely cover the first granular section. 2. Method for manufacturing an electrode plate

[0065] A method for manufacturing an electrode plate using the granular body is then described below. Fig. Figure 9 is a schematic diagram showing an example of the design of an electrode manufacturing device. An electrode manufacturing device 90 includes a feeding device 95 and three rollers (one A-roller) 91 , a B-roller 92 and a C-roller 93 The curved arrow shown on each roller indicates the direction of rotation of each roller.

[0066] The granular body is fed to the feeding device. 95 fed. The feeding device 95 leads to a gap between the A-roller 91 and the B-roller 92 granular body 60 to. The roller 91 is subjected to a prescribed force. The granular body is placed in the gap between the A-roller. 91 and the B-roller 92 The material is compacted and formed into a flat shape. The application weight (mass per unit area) of the granular body formed into a flat shape can be adjusted by the gap between the rollers.

[0067] Then the granular body, which is formed in a planar shape, is 61 arranged on an electrode collector. Fig. Figure 9 shows the positive electrode collector 101 as an electrode collector. As in Fig. Figure 9 shows the positive electrode collector. 101 on the C-roller 93 transported and the gap between the B-roller 92 and the C-roller 93 supplied. After the granular body 61 through the gap between the A-roller 91 and the B-roller 92 and once he gets out of it, he will be on the B-roller 92 transported and the gap between the B-roller 92 and the C-roller 93 supplied.

[0068] In the gap between the B-roller 92 and the C-roller 93 The granular body 61 against the positive electrode collector 101 pressed. Then the granular body is... 61 from the B-roller 92 separated and with the positive electrode collector 101 The granular body is connected by pressure. In other words, it is transferred to the positive electrode collector. In this way, the granular body is arranged in a planar form on the electrode collector.

[0069] After the granular body has been arranged on the electrode body, a drying process can be carried out to allow the solvent remaining in the granular body to evaporate. The drying process is carried out, for example, in a hot-air drying oven (not shown), which is located on a C-roller. 93 the route is planned. Furthermore, the electrode collector, which has a granular body arranged on one of its surfaces, is again connected to the C-roller. 93 supplied so that the granular body can also be arranged on both surfaces of the electrode collector.

[0070] The granular body arranged on the electrode collector serves as an electrode mixture layer. A compression process can then be carried out to adjust the thickness and density of this layer. This compression process is performed, for example, using a roller rolling machine.

[0071] Finally, the entire product is cut to a prescribed size, for example using a cutting machine or similar equipment, resulting in, for example, a product that is Fig. 5 positive electrode plate shown 100 is completed.

[0072] The design of the electrode plate, which forms a large contact angle with the molten polyolefin droplet, was described above. The properties of the design described above are summarized below. [4] The surface of the electrode plate facing the porous resin layer is formed from a porous layer containing 8 wt% or more and 20 wt% or less binder resin.

[0073] The porous layer can be an inorganic filler layer arranged on the surface of the electrode mixture layer. The porous layer can be an electrode mixture layer (a positive electrode mixture layer or a negative electrode mixture layer) containing electrode active material particles (positive electrode active material particles or negative electrode active material particles). [5] The electrode mixture layer contains a plurality of granular particles. A granular particle has a core-shell structure, comprising the first granular section as a core and the second granular section as a shell. The first granular section and the second granular section contain electrode active material particles and a binder resin, respectively. The second granular section contains 8 wt% or more and 20 wt% or less binder resin. The first granular section has a lower binder resin content than the second granular section. The second granular section forms a surface of the electrode plate facing the porous resin layer. <<Elektrolytlösung> >

[0074] An electrolyte solution is a liquid electrolyte obtained by dissolving lithium (Li) salt as a carrier electrolyte in an aprotic solvent. Examples of aprotic solvents include cyclic carbonates, such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and γ-butyrolactone (γBL); and chain carbonates, such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). Two or more types of such aprotic solvents can be combined to obtain a mixed solvent. In the mixed solvent, the volume ratio between cyclic carbonates and chain carbonates can be adjusted, for example, such that cyclic carbonates:chain carbonates = approximately 1:9 to 5:5. Such a range of volume ratios can achieve an excellent balance between electrical conductivity and electrochemical stability.

[0075] Examples of lithium salts include LiPF6, LiBF4, LiClO4, LiAsF6, Li[(FSO2)2N] (abbreviated as "LiFSI"), Li[(CF3SO2)2N] (abbreviated as "LiTFSI"), Li[CF3SO3], and the like. The electrolyte solution may contain two or more types of lithium salts. The lithium salt concentration is, for example, approximately 0.5 mol / L (mol / liter) to 2.0 mol / L (typically about 0.8 mol / L to 1.2 mol / L).

[0076] The electrolyte solution may contain an additive in addition to the components described above. Examples of additives include lithium salts containing an oxalate complex as an anion, such as Li[(C2O4)2B] (abbreviated as "LiBOB"), Li[(C2O4)BF2], Li[(C2O4)2PF2]; vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), propane sultone (PS), Li[PO2F2], cyclohexylbenzene (CHB), biphenyl (BP), and the like.

[0077] In the present embodiment, a gel electrolyte or a solid electrolyte can also be used instead of an electrolyte solution (liquid electrolyte).

[0078] The present embodiment has been described above with exemplary reference to a prismatic battery. It should be noted that the present embodiment is not limited to such a prismatic battery. The present embodiment is applicable to a cylindrical battery, a laminate-type battery, and the like. The electrode arrangement is also not limited to a wound type. The electrode arrangement can also be of a laminate type (also referred to as a "stack type"). The present embodiment is suitable for automotive applications where overcharge resistance is of great importance. [Examples]

[0079] The present embodiment is described below with reference to examples. It should be noted that the present embodiment is not limited to these examples. <Fertigung einer Sekundärbatterie mit nicht-wässrigem Elektrolyt>

[0080] As described above, various secondary batteries with non-aqueous electrolyte were manufactured, and their overcharge resistance properties were assessed. <<Nr. 1> >1. Manufacturing a positive electrode plate

[0081] The following materials have been prepared. Positive electrode active material particles: lithium-containing layered nickel-manganese-cobalt composite oxide Conductive material: Acetylene carbon black Binding resin: PVDF Positive electrode collector: Al foil (thickness = 20 μm) Solvent: NMP. 1-1. Primary granulation

[0082] Positive electrode active material particles, a conductive material, and a binding resin were placed in a granulation vessel of the granulation device to establish a mass ratio of positive electrode active material particles to conductive material to binding resin = 90:8:2. A small amount of solvent was then added, and primary granulation was carried out. This resulted in an accumulation of primary granular particles, which served as the first granular section. 1-2. Secondary granulation

[0083] The primary granular particles obtained as described above, along with positive electrode active material particles, conductive materials, and a binder resin (consisting of the second granular section), were placed in a granulation vessel of the granulation apparatus. A small amount of solvent was added, and secondary granulation was carried out. The positive electrode active material particles, conductive materials, and binder resin (consisting of the second granular section) were mixed in a mass ratio of 84:8:8. As described above, a granular body was obtained as an accumulation of granular particles. This granular body comprises granular particles, each with a core-shell structure, containing the first granular section as a core and the second granular section as a shell. 1-3. Manufacturing an electrode plate

[0084] Granular particles were found in Fig. The material was fed into the electrode manufacturing device shown in section 9, and a granular body was arranged in a planar form on the positive electrode collector as described above. The entire product obtained in this way was cut to a prescribed size, thereby producing a Fig. 5 positive electrode plate shown 100 was obtained. In the positive electrode plate 100 The second granular section, which contains 8 wt% binding resin, forms a surface of the positive electrode mixture layer. 102 (the surface area of ​​the positive electrode plate). The mass per unit area of ​​the positive electrode mixture layer. 102 was set to 15 mg / cm² 2 set. The dimensions of each in Fig. The 5 components shown were fixed as described below. Width of the positive electrode mixture layer 102 (W102) = 110 mm Width of the exposed section 103 (W103) = 20 mm. 2. Manufacturing a negative electrode plate

[0085] The following materials have been prepared. Negative electrode active material particles: Natural graphite particles Binding resin: PVDF Negative electrode collector: Cu foil (thickness = 10 μm) Solvent: NMP. 2-1. Primary granulation

[0086] Negative electrode active material particles and a binding resin were introduced into a granulation vessel of the granulation device, achieving a mass ratio of negative electrode active material particles to binding resin of 98:2. A small amount of solvent was then added, and primary granulation was carried out. This resulted in an accumulation of primary granular particles, which served as the first granular section. 2-2. Secondary granulation

[0087] The primary granular particles obtained as described above, along with negative electrode active material particles and a binder resin (consisting of the second granular section), were placed in a granulation vessel of the granulation device. A small amount of solvent was added, and the second granulation was then carried out. The negative electrode active material particles and the binder resin (consisting of the second granular section) were mixed in a mass ratio of 92:8. This resulted in a granular body consisting of an aggregate of granular particles. This granular body comprises granular particles, each with a core-shell structure, incorporating the first granular section as a core and the second granular section as a shell. 2-3. Manufacturing an electrode plate

[0088] Granular particles were found in Fig. The material was fed into the electrode manufacturing device shown in section 9, and a granular body was arranged in a planar form on the negative electrode collector as described above. The entire product obtained as described above was cut to a prescribed size, thereby producing a Fig. 6 negative electrode plate shown 200 was obtained. In the negative electrode plate 200 The second granular section, which contains 8 wt% binding resin, forms a surface of the negative electrode mixture layer. 202 (the surface of the negative electrode plate). The mass per unit area of ​​the negative electrode mixture layer 202 was set to 15 mg / cm² 2 fixed. The dimensions of each in Fig. The 6 components shown were adjusted as indicated below. Width of the negative electrode mixture layer 202 (W202) = 115 mm Width of the exposed section 203 (W203) = 20 mm. 3. Manufacturing an electrode arrangement

[0089] A separator with a width of 120 mm and a thickness of 10 μm was prepared. The separator is formed from a single porous resin layer. The porous resin layer is made of PE (polyolefin) with a melting point of 135°C.

[0090] A winding device was used to stack a positive electrode plate and a negative electrode plate with an intermediate separator, which were then wound. This resulted in a wound body formed in an elliptical shape. This wound body was then pressed into a flat shape using a flat plate press. This resulted in a Fig. 2 Electrode arrangement shown 800 manufactured. 4. Assembly

[0091] A prismatic battery case (75 mm long, 120 mm wide, 15 mm deep, and 1 mm thick) was prepared. As in Fig. As shown in section 1, the exposed section was 103 and the positive connection 501 connected, the exposed section 203 and the negative terminal 502 were connected and the electrode arrangement 800 was inserted into the battery casing 500 enclosed. 5. Supply of a solution

[0092] EC, EMC, and DEC were mixed to achieve a volume ratio of EC:EMC:DEC = 3:5:2, thus preparing a mixed solvent. LiPF6 was then dissolved in this mixed solvent to adjust the concentration to 1 M (1 mol / L), thus preparing an electrolyte solution. The electrolyte solution was poured through a liquid inlet port of the battery casing, and this port was then sealed. 6. Initial charging / discharging

[0093] In an environment at a temperature of 25°C, the following charge and discharge cycle was performed to verify the initial capacity (discharge capacity at the second cycle). The unit "C" used herein represents the current required to fully discharge the battery's nominal capacity in 1 hour. Furthermore, "CC" represents a constant current scheme, "CV" a constant voltage scheme, and "CC-CV" a constant current-constant voltage scheme. (First cycle) CC charging: CC current = 1 C, final voltage 4.2 V Rest: 5 minutes CC discharge: CC current = 1 C, final voltage 3.0 V Rest: 5 minutes. (Second cycle) CC-CV charging: CC current = 1 C, CV voltage = 4.1 V, final current = 0.01 C CC-CV discharge: CC current = 1 C, CV voltage = 3.0 V, final current = 0.01 C.

[0094] As described above, a secondary battery with non-aqueous electrolyte (nominal capacity = 5 Ah) was manufactured according to No. 1. <<Nr. 2 bis Nr. 14> >

[0095] As shown in Table 1, various separators were prepared which were made from polyolefin (PE) with different melting points and formed a porous resin layer.

[0096] Furthermore, different positive and negative electrode plates were manufactured, while the mass ratio of the binder resin was changed during secondary granulation, so that these positive and negative electrode plates differed in the content of binder resin on each surface of the electrode plates (the second granular section), as shown in Table 1.

[0097] Several batteries were manufactured exactly like No. 1, except that the above features were combined as shown in Table 1. In Table 1, Nos. 1 to 8 are examples, and Nos. 9 to 14 are comparison examples. 7. Assessment 7-1. Measurement of the contact angle

[0098] As described above, each contact angle between the molten PE droplet forming each porous resin layer and each surface of the positive and negative electrode plates used for each battery was measured. The results are shown in Table 1. 7-2. Overload attempt

[0099] The battery's overcharge resistance characteristics were assessed through an overcharge test. The test conditions were as follows: First, in an environment at a temperature of 25°C, the battery's state of charge (SOC) was set to 100% using constant current (CC) to constant voltage (CV) charging (CC current = 1 C, CV voltage = 4.1 V, and final current = 0.01 V).

[0100] A constant voltage charge was performed at 8 V. If the battery did not emit smoke, the voltage was increased by 1 V, and a constant voltage charge was performed at 9 V. Similarly, the test was continued, with the voltage simultaneously increased by 1 V, until the battery emitted smoke. In this test, the charging voltage was increased up to 40 V. The test results are shown in Table 1. The "achieved voltage" in Table 1 represents the charging voltage at the point at which the battery emitted smoke. In this test, the overcharge resistance properties are more excellent the higher the "achieved voltage". <Ergebnisse und Betrachtungen> <<Nr. 1 bis Nr. 14> >

[0101] Regarding a battery that meets the condition that the surface of the electrode plate facing a porous resin layer forms a contact angle of 30° or more with a molten polyolefin droplet, Table 1 shows that this battery achieves a higher voltage and has better overcharge resistance properties than a battery that does not meet the aforementioned conditions. The contact angle tends to be larger when the concentration of binder resin on the surface of the electrode plate (mixed layer) is higher. <<Nr. 1 bis Nr. 3 und Nr. 9> >

[0102] Fig. Figure 10 is a graph showing the relationship between the contact angle and the achieved voltage. Fig. Figure 10 shows a representation of the results obtained in Nos. 1 to 3 and No. 9 in Table 1.

[0103] Fig. Figure 10 shows that the achieved voltage is noticeably improved when the contact angle is increased by 20° to 30°. In this experiment, an electrode plate was fabricated that formed a contact angle of 60°. Therefore, the upper limit of the contact angle can, for example, be 60°. Fig. Figure 10 shows that the overload resistance properties are particularly excellent when the contact angle falls within a range of 45° or more and 60° or less. <<Nr. 1, Nr. 10 und Nr. 11> >

[0104] According to Table 1, Nos. 10 and 11 each exhibit a relatively low achieved voltage. In this experiment, a surface of both the positive and negative electrode plates faces the porous resin layer. For No. 10, the contact angle at the surface of the positive electrode plate is less than 30°. For No. 11, the contact angle at the surface of the negative electrode plate is also less than 30°. In other words, these batteries each contain an electrode plate surface that forms a contact angle of less than 30° with the molten polyolefin droplet, even though this surface faces the porous resin layer. In this case, it is assumed that even if one of the electrode plates can suppress polyolefin permeation, polyolefin will permeate through the other electrode plate, resulting in the achieved voltage not being increased.

[0105] Therefore, at least the electrode facing a porous resin layer on both the positive and negative electrode plates must have a surface that forms a contact angle of 30° or more with the molten polyolefin droplet (see, for example, No. 1). In other words, if both the positive and negative electrode plates face the porous resin layer, then each of these positive and negative electrode plates must have a surface that forms a contact angle of 30° or more with the molten polyolefin droplet. <<Nr. 1, Nr. 6 bis Nr. 8 und Nr. 13> >

[0106] Fig. Figure 11 is a graph showing the relationship between the melting point of polyolefin and the achieved stress. Fig. Figure 11 shows a representation of the results obtained in Nos. 1, 6 to 8 and 13 in Table 1. If according to Fig. 11. As the melting point increases from 135°C to 140°C, the dielectric strength deteriorates significantly. It is assumed that when the melting point exceeds 135°C, the response of the porous resin layer to heat generation from the battery during the early overcharge phase (i.e., shutdown) is delayed, thus worsening the overcharge resistance properties. According to Fig. 11 It is assumed that the melting point of polyolefin is preferably 80°C or more and 120°C or less, and more preferably 80°C or more and 100°C or less. <<Nr. 9, Nr. 12 und Nr. 14> >

[0107] In configurations where the contact angle at the electrode plate surface is less than 30°, the overload resistance properties tend to worsen when the melting point of polyolefin is lowered. This is assumed to be because, in configurations where molten polyolefin is more likely to penetrate the electrode plate, the polyolefin is also more likely to melt, thus increasing the amount of polyolefin permeating.

[0108] Although the embodiments of the present invention have been described above, it should be understood that the embodiments disclosed herein are in every respect illustrative and not limiting. The scope of protection of the present invention is defined by the wording of the claims and is intended to include any modifications that are equivalent in meaning and scope to the wording of the claims. QUOTES INCLUDED IN THE DESCRIPTION

[0109] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0110] JP 2015-175613

[0001] WO 2008 / 044761 [0003, 0005, 0006] Cited non-patent literature

[0111] JIS K 7121: 2012 Test methods for transition temperatures of plastics

[0041] < / negativelektrodenplatte> < / positivelektrodenplatte> < / separator> < / elektrodenanordnung>

Claims

[1] Secondary battery with non-aqueous electrolyte, comprising: a positive electrode plate ( 100 ); a negative electrode plate ( 200 ); and one between the positive electrode plate ( 100 ) and the negative electrode plate ( 200 ) arranged separator ( 300 ), where the separator ( 300 ) a porous resin layer ( 301 ) contains, the porous resin layer ( 301 ) is made from polyolefin with a melting point of 80°C or more and 135°C or less, where at least one is from the positive electrode plate ( 100 ) and the negative electrode plate ( 200 ) has a surface (S1) which corresponds to the porous resin layer ( 301 ) is turned towards, and wherein the surface (S1) forms a contact angle (θ) of 30° or more with a molten droplet of the polyolefin. [2] Secondary battery with non-aqueous electrolyte according to claim 1, wherein the contact angle (θ) is 30° or more and 60° or less. [3] Secondary battery with non-aqueous electrolyte according to claim 2, wherein the contact angle (θ) is 45° or more and 60° or less.