A negative electrode active material for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery using the same, and a method for manufacturing the negative electrode active material for a non-aqueous electrolyte secondary battery.

Abstract

The disclosed negative electrode active material for a non-aqueous electrolyte secondary battery includes active material particles containing silicon, and a surface layer formed on the surface of the active material particles. The surface layer includes a reaction product obtained as a result of a compound being reacted so as to form a siloxane bond. The compound includes a structure represented by Si-R1-Si. R1 is an atomic group having a chain part that includes, as constituent elements, an alkylene group and at least one substance selected from the group consisting of sulfur atoms, oxygen atoms, and nitrogen atoms. At least one atomic group selected from the group consisting of C1-C6 alkoxy groups and the like is bonded to each of the two Si.

Description

Technical Field

[0001] The present disclosure relates to a negative electrode active material for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery using the same, and a method for manufacturing a negative electrode active material for a non-aqueous electrolyte secondary battery.

Background Art

[0002] Silicon materials such as silicon (Si) and silicon oxides represented by SiOx are known to be able to occlude more lithium ions per unit volume than carbon materials such as graphite, and their application to the negative electrode of lithium ion batteries and the like has been studied. A non-aqueous electrolyte secondary battery using a silicon material as a negative electrode active material has a problem that the charge-discharge efficiency is low compared with the case where graphite is used as the negative electrode active material. Therefore, in order to improve the charge-discharge efficiency, it has been proposed to use lithium silicate as the negative electrode active material.

[0003] Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-160328) discloses "lithium-containing silicon oxide powder represented by the general formula SiLi" x O y "where the ranges of x and y are 0 < x < 1.0 and 0 < y < 1.5, and lithium is fused and a part of it is crystallized."

[0004] Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-150068) discloses "a negative electrode active material for a predetermined non-aqueous electrolyte secondary battery obtained by a production method including a step of surface-treating a silicon-containing substance having a surface moisture content (200 - 300 °C) per unit specific surface area of 0.1 to 20 ppm / (m" 2 " / g) with a silane coupling agent."

[0005] Non-Patent Document 1 reports that by adding a vinyl group-containing silane coupling agent to the electrolyte of a single electrode battery using a Si / C composite, the capacity retention rate in the charge-discharge cycle is improved.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2003-160328 [Patent Document 2] Japanese Patent Publication No. 2014-150068 [Non-patent literature]

[0007] [Non-Patent Document 1] Ionics, 2018, 24, 3691-3698 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] For non-aqueous electrolyte secondary batteries, there is a need to further suppress the decrease in discharge capacity when repeated charge-discharge cycles are performed. In this context, one of the objectives of this disclosure is to provide a negative electrode active material that can constitute a non-aqueous electrolyte secondary battery with a high capacity retention rate during charge-discharge cycles. [Means for solving the problem]

[0009] One aspect of this disclosure relates to a negative electrode active material for a non-aqueous electrolyte secondary battery. The negative electrode active material comprises silicon-containing active material particles and a surface layer formed on the surface of the active material particles, the surface layer comprising a reaction product obtained by a compound reacting to form a siloxane bond, the compound comprising a structure represented as Si-R1-Si, where R1 is an atomic group having a chain portion comprising at least one selected from the group consisting of sulfur atoms, oxygen atoms, and nitrogen atoms and an alkylene group as constituent elements, and one of the two Si contains an alkoxy group, an oxyalkylene group having a carbon number in the range of 1 to 6 -O-(C x1 H 2x1+1 O y1At least one atomic group selected from the group consisting of a group represented by (where x1 is an integer of 2 or more and 6 or less, and y1 is an integer of 1 or more and 3 or less), a chloro group, and a hydroxyl group is bonded, and to the other of the two Si, an alkoxy group having 1 to 6 carbon atoms, an oxyalkylene group containing -O-(C x2 H 2x2+1 O y2 ) (where x2 is an integer of 2 or more and 6 or less, and y2 is an integer of 1 or more and 3 or less), a chloro group, and at least one atomic group selected from the group consisting of a hydroxyl group is bonded.

[0010] Another aspect of the present disclosure relates to a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the negative electrode includes a negative electrode active material according to the present disclosure. This disclosure further relates to the following examples. (Example 1) A negative electrode active material for a non-aqueous electrolyte secondary battery, Silicon-containing active material particles, The active material particles include a surface layer formed on the surface of the active material particles, The surface layer contains reaction products obtained when the compound reacts to form siloxane bonds. The aforementioned compound comprises a structure represented by Si-R1-Si, The aforementioned R1 is an atomic group having a chain-like portion comprising at least one selected from the group consisting of sulfur atoms, oxygen atoms, and nitrogen atoms, and an alkylene group as constituent elements. One of the two Si components contains an alkoxy group and an oxyalkylene group with a carbon number in the range of 1 to 6 -O-(C x1 H 2x1+1 O y1 At least one atomic group selected from the group consisting of a group represented by (x1 is an integer between 2 and 6 and y1 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded, The other of the two Si components contains an alkoxy group and an oxyalkylene group with a carbon number in the range of 1 to 6 -O-(C x2 H 2x2+1 O y2 A negative electrode active material for a non-aqueous electrolyte secondary battery, to which at least one atomic group selected from the group consisting of a group represented by (x2 is an integer between 2 and 6 and y2 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded. (Example 2) The aforementioned compound is a compound represented by formula (1) described later, the negative electrode active material as described in Example 1. (Example 3) The negative electrode active material according to Example 2, wherein in formula (1) above, R2 to R7 are methoxy groups or ethoxy groups. (Example 4) The R1 comprises at least one heteroatom selected from the group consisting of a sulfur atom, an oxygen atom, and a nitrogen atom, and two alkylene groups that constitute the chain portion so as to sandwich the at least one heteroatom. The negative electrode active material according to any one of Examples 1 to 3, wherein the number of carbon atoms in each of the two alkylene groups is independently in the range of 2 to 4. (Example 5) The aforementioned R1 is -(CH 2 ) p S n (CH 2 ) q -(1≦n≦6, 2≦p≦4, 2≦q≦4), -(CH 2 ) p O(CH 2 ) q -(2≦p≦4, 2≦q≦4), -(CH 2 ) p O(CH 2 ) r O(CH 2 ) q -(2≦p≦4, 2≦q≦4, 2≦r≦4), and -(CH 2 ) p NH(CH 2 ) q - A negative electrode active material described in any one of Examples 1 to 3, where n, p, q, and r are natural numbers, and the conditions are either -(2≦p≦4 or 2≦q≦4). (Example 6) The negative electrode active material according to any one of Examples 1 to 5, wherein the surface layer contains conductive carbon. (Example 7) The active material particles are Li x SiO y The negative electrode active material according to any one of Examples 1 to 6, which is a composite particle including a lithium silicate phase represented by (0 < x ≦ 4, 0 < y ≦ 4) and a silicon phase dispersed in the lithium silicate phase. (Example 8) The negative electrode active material according to Example 7, wherein the crystallite size of the silicon phase is in the range of 1 nm to 1000 nm. (Example 9) The negative electrode active material according to any one of Examples 1 to 6, wherein the active material particles include a carbon phase and a silicon phase dispersed in the carbon phase. (Example 10) Including a positive electrode, a negative electrode, and a non-aqueous electrolyte, A non-aqueous electrolyte secondary battery, wherein the negative electrode includes the negative electrode active material according to any one of Examples 1 to 9.

[0011] Another aspect of this disclosure relates to a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery. The method comprises a first step of contacting a compound, or a liquid in which the compound is dissolved, with silicon-containing active material particles, and a second step of reacting the compound so as to form siloxane bonds while the compound or the liquid and the active material particles are in contact, wherein the compound comprises a structure represented as Si-R1-Si, where R1 is an atomic group having a chain portion comprising at least one selected from the group consisting of sulfur atoms, oxygen atoms, and nitrogen atoms, and an alkylene group, and one of the two Sis contains an alkoxy group, an oxyalkylene group having 1 to 6 carbon atoms -O-(C x1 H 2x1+1 O y1 At least one atomic group selected from the group consisting of a group represented by (x1 is an integer between 2 and 6 and y1 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded to the other of the two Si atoms, and the other of the two Si atoms contains an alkoxy group or an oxyalkylene group having 1 to 6 carbon atoms -O-(C x2 H 2x2+1 O y2 At least one atomic group selected from the group consisting of a group represented by (x2 is an integer between 2 and 6 and y2 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded to the atom. [Effects of the Invention]

[0012] According to this disclosure, a negative electrode active material can be obtained that can constitute a non-aqueous electrolyte secondary battery with a high capacity retention rate during charge-discharge cycles. Furthermore, according to this disclosure, a non-aqueous electrolyte secondary battery using said negative electrode active material can be obtained. Novel features of the present invention are described in the appended claims, but the present invention, both in terms of structure and content, and in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in conjunction with the drawings. [Brief explanation of the drawing]

[0013]

Figure 1

Figure 2

[0014] The embodiments relating to this disclosure will be described below with examples, but the embodiments relating to this disclosure are not limited to the examples described below. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits are given as examples for numerical values ​​of specific physical properties or conditions, any combination of the given lower limits and given upper limits can be used as appropriate, as long as the lower limit is not greater than or equal to the upper limit.

[0015] (Negative electrode active material for non-aqueous electrolyte secondary batteries) The negative electrode active material for a non-aqueous electrolyte secondary battery according to this disclosure comprises silicon-containing active material particles and a surface layer formed on the surface of the active material particles. The negative electrode active material and the surface layer may hereinafter be referred to as "negative electrode active material (N)" and "surface layer (L)," respectively. The surface layer (L) contains reaction products obtained by a predetermined compound reacting to form siloxane bonds. The compound may hereinafter be referred to as "compound (1)." Compound (1) includes a structure represented as Si-R1-Si. R1 is an atomic group having a chain portion comprising at least one selected from the group consisting of sulfur atoms, oxygen atoms, and nitrogen atoms, and an alkylene group as constituent elements. One of the two Si contains an alkoxy group, an oxyalkylene group with a carbon number in the range of 1 to 6 -O-(C x1 H 2x1+1 O y1 At least one atomic group selected from the group consisting of a group represented by (x1 is an integer between 2 and 6 and y1 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded to the other of the two Si atoms, which contains an alkoxy group or an oxyalkylene group with carbon atoms in the range of 1 to 6 -O-(C x2 H2x2+1 O y2 At least one atomic group selected from the group consisting of a group represented by (x2 is an integer between 2 and 6 and y2 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded to the atom.

[0016] The oxyalkylene group is -OC x H 2x It is a group represented by -. It contains an oxyalkylene group -O-(C x1 H 2x1+1 O y1 A group represented by ) and an oxyalkylene group -O-(C x2 H 2x2+1 O y2 In the group represented by ), the oxygen atom of the oxyalkylene group is bonded to Si. Below, the oxyalkylene group containing the oxygen atom bonded to Si is included -O-(C x H 2x+1 O y A group represented by (where x is an integer between 2 and 6, and y is an integer between 1 and 3) is sometimes called an "oxyalkyl group". In all oxyalkyl groups bonded to Si of compound (1), y (e.g., y1, y2, y6 described later) may be 1 or 2. Examples of oxyalkyl groups include -OC x4 H 2x4 -OC x5 H 2x5+1 The base is represented by (x4 is an integer between 1 and 3, and x5 is an integer between 1 and 3), and includes, for example, -OCH2CH2OCH3.

[0017] Compound (1) may also be a compound represented by the following formula (1).

[0018] [ka] [In formula (1), at least one selected from the group consisting of R2, R3, and R4 is independently an alkoxy group or an oxyalkylene group having 1 to 6 carbon atoms -O-(C x1 H 2x1+1O y1 The group is represented by (x1 is an integer between 2 and 6 and y1 is an integer between 1 and 3), a chloro group, or a hydroxyl group. At least one selected from the group consisting of R5, R6, and R7 is independently an alkoxy group or an oxyalkylene group having 1 to 6 carbon atoms -O-(C x2 H 2x2+1 O y2 The group is represented by (x2 is an integer between 2 and 6 and y2 is an integer between 1 and 3), a chloro group, or a hydroxyl group. The remaining R2 to R7 are each independently a hydrocarbon group with 1 to 6 carbon atoms, a hydrogen atom, or C x3 H 2x3+y3+1 N y3 O z3 S w3 The base is represented by (x3 is an integer between 1 and 6, y3 is an integer between 0 and 3, z3 is an integer between 0 and 3, w3 is an integer between 0 and 3, and 1 ≤ y3 + z3 + w3). R2 to R7 may be the same or different.

[0019] Examples of hydrocarbon groups with 1 to 6 carbon atoms include alkyl groups, alkenyl groups, and alkynyl groups, all of which have 1 to 6 carbon atoms. x3 H 2x3+y3+1 N y3 O z3 S w3 The group represented by is not an alkoxy group with 1 to 6 carbon atoms, and is -O-(C x1 H 2x1+1 O y1 The above base is not represented by ). y3, Z3, and w3 may each be an integer between 0 and 2 or an integer between 0 and 1, independently. The sum of y3, z3, and w3 may be in the range of 1 to 3 or in the range of 1 to 2. The sum of y3, z3, and w3 may be 1 or 2, and in one example it is 1. C x3 H 2x3+y3+1 N y3 O z3 S w3 Examples of bases represented by C include x3 H 2x3+1 O y3Groups represented by, alkylamino groups having 1 to 6 carbon atoms, and mercaptoalkyl groups having 1 to 6 carbon atoms are included. C x3 H 2x3+1 O y3 The group represented by is bonded to Si via a carbon atom, for example. C x3 H 2x3+1 O y3 Examples of the group represented by include hydroxyalkyl groups. The rest of R2 to R7 may each independently be a hydrocarbon group having 1 to 6 carbon atoms or a hydrogen atom.

[0020] In compound (1), the alkoxy group having 1 to 6 carbon atoms and the above-described oxyalkylene group are combined and read as "a group containing an alkoxy group bonded to Si or an oxyalkylene group bonded to Si and represented by -O-(C x6 H 2x6+1 O y6 )(where x6 is an integer of 2 or more and 6 or less and y6 is an integer of 0 or more and 3 or less)". Alternatively, the alkoxy group having 1 to 6 carbon atoms and the above-described oxyalkylene group may be combined and read as "a group containing an alkoxy group and having 1 to 6 carbon atoms".

[0021] From another perspective, the surface layer formed on the surface of the active material particles contains reaction products obtained when compound (0) reacts to form siloxane bonds. Compound (0) is a compound containing two silicon atoms to which atomic groups capable of forming siloxane bonds by reaction are bonded, and R1 connecting the two silicon atoms. The number of such atomic groups bonded to one silicon atom is in the range of 1 to 3, preferably 2, and more preferably 3. Examples of atomic groups capable of forming siloxane bonds by reaction include alkoxy groups, hydroxyl groups, chloro groups, and the oxyalkyl groups mentioned above. Hereinafter, alkoxy groups, hydroxyl groups, chloro groups, and the oxyalkyl groups mentioned above, which have 1 to 6 carbon atoms, may be collectively referred to as "atomic group (G)". Reactions in which compounds having alkoxysilyl groups react to form siloxane bonds (e.g., hydrolysis-condensation reactions) are widely known. For R1 in compound (0), the R1 exemplified for compound (1) can be applied. Examples of compound (0) include at least some of the examples for compound (1).

[0022] Compounds (0) and (1) may be commercially available if they are commercially available compounds. Alternatively, if the synthesis method of the compound is known, it may be synthesized using a known synthetic method.

[0023] In a typical example of compound (1), the chain in the linear portion of R1, which connects two silicon atoms, is composed of at least one atom selected from the group consisting of sulfur atoms, oxygen atoms, and nitrogen atoms, and carbon atoms in the alkylene group.

[0024] In the negative electrode active material (N) according to this disclosure, the surface of the active material particles is protected by the reaction products of compound (1). At least a portion of compound (1) forms siloxane bonds with the silicon in the active material particles. Compound (1) links the silyl groups that form siloxane bonds at R1. Therefore, the surface of the active material particles is protected by the two silyl groups forming siloxane bonds with the silicon in the active material particles. Since the reaction products of compound (1) include the R1 portion, they flexibly follow the expansion and contraction of the active material particles during charging and discharging, and the surface protective layer is less likely to be destroyed even if the active material particles repeatedly expand and contract during the charge-discharge cycle. Therefore, according to this disclosure, side reactions with components in the electrolyte on the surface of the active material particles can be suppressed. As a result, according to this disclosure, the capacity retention rate during the charge-discharge cycle can be increased.

[0025] Of R2 to R7, those that are not part of the atomic group (G) described above may independently be the groups described above. Specifically, of R2 to R7, those that are not part of the atomic group (G) described above may independently be a hydrocarbon group with 1 to 6 carbon atoms, a hydrogen atom, or the C group described above. x3 H 2x3+y3+1 N y3 O z3 S w3 It may also be a base represented by .

[0026] Formula (1) preferably satisfies the following conditions (V1) or (V2), and more preferably satisfies the following conditions (V3) or (V4). Formula (1) may also satisfy the following conditions (V5) or (V6). (V1) Each of R2 to R7 contains 4 or fewer carbon atoms. (V2) At least two selected from the group consisting of R2, R3, and R4 are alkoxy groups having 1 to 4 carbon atoms, and at least two selected from the group consisting of R5, R6, and R7 are alkoxy groups having 1 to 4 carbon atoms. Of R2 to R7, those that are not alkoxy groups having 1 to 4 carbon atoms are hydrocarbon groups (alkyl groups, alkenyl groups, alkynyl groups) having 1 to 6 carbon atoms, or hydrogen atoms. (V3)All of R2 to R7 are alkoxy groups having a carbon number in the range of 1 to 4 (for example, in the range of 1 to 3). (V4)All of R2 to R7 are each independently a methoxy group or an ethoxy group. R2 to R7 may be a methoxy group or an ethoxy group. For example, all of R2 to R7 may be a methoxy group, or all of R2 to R7 may be an ethoxy group. (V5)In condition (V2), it satisfies the condition where all descriptions of "having a carbon number in the range of 1 to 4" are replaced with "having a carbon number in the range of 1 to 3". (V6)In condition (V2), it satisfies the condition where all descriptions of "having a carbon number in the range of 1 to 4" are replaced with "having a carbon number of 1 or 2".

[0027] A preferred example of formula (1) satisfies any one of the above conditions (V1) to (V6) and satisfies the following condition (W1). A preferred example of formula (1) satisfies any one of the above conditions (V1) to (V6) and satisfies condition (W2) or (W3). In these cases, formula (1) may further satisfy condition (W4) or (W5). (W1)R1 is an atomic group containing a chain portion composed of at least one selected from the group consisting of a sulfur atom, an oxygen atom, and a nitrogen atom and an alkylene group. (W2)R1 contains a chain portion composed of at least one heteroatom selected from the group consisting of a sulfur atom, an oxygen atom, and a nitrogen atom and two alkylene groups that constitute the chain portion so as to sandwich the at least one heteroatom. The carbon numbers of the two alkylene groups are each independently in the range of 2 to 4. The two alkylene groups may be directly bonded to the heteroatom. (W3)R1 is -(CH2) p S n (CH2) q -(1 ≤ n ≤ 6, 2 ≤ p ≤ 4, 2 ≤ q ≤ 4), -(CH2) p O(CH2) q -(2 ≤ p ≤ 4, 2 ≤ q ≤ 4), -(CH2) p O(CH2) r O(CH2) q-(2≦p≦4, 2≦q≦4, 2≦r≦4), and -(CH2) p NH(CH2) q -(2≦p≦4, 2≦q≦4). In this case, p=q=3, and r=2 or 3. Note that n, p, q, and r are all natural numbers. (W4) In condition (W1) or (W2), the number of atoms constituting the chain portion of the chain is 2 or more, 3 or more, 5 or more, or 6 or more, and 20 or less, 15 or less, or 10 or less. For example, the number of atoms may be in the range of 3 to 20, 3 to 15, or 3 to 10. The lower limit of these ranges may be replaced with 5 or 6. Here, the number of atoms constituting the chain portion of the chain is the number of atoms that make up the chain connecting two silicon atoms. For example, in the case of an alkylene group, only the number of carbon atoms that make up the chain is counted. (W5) In condition (W1), (W2), or (W4), R1 is a straight chain that does not contain branched chains.

[0028] The more alkoxy groups contained in formula (1), the easier it is for a three-dimensional network to be formed by the reaction of compounds (1) with each other. Part of this network bonds with silicon present on the surface of the negative electrode active material particles. Even when a three-dimensional network is formed, the presence of R1 regions in the network suggests that the formed network has high flexibility. It is believed that a higher effect can be obtained by forming a highly flexible three-dimensional network.

[0029] If R1 contains at least one heteroatom selected from the group consisting of sulfur, oxygen, and nitrogen atoms, it is thought that the ionic coordinating ability of the heteroatom causes lithium ions to dissociate from the lithium salt in the electrolyte as carrier ions, thereby promoting lithium ion conduction in the surface layer. This is thought to reduce the inhibition of lithium ion transfer between the active material and electrolyte during charging and discharging by the surface layer.

[0030] If R1 contains a nitrogen atom, R1 may also contain an amide bond. If formula (1) satisfies condition (W1), the compound (1) represented by formula (1) may be a sulfide, an ether, or an amine.

[0031] The mass of the reaction product of compound (1) contained in the surface layer may be in the range of 0.001% to 10% (for example, 0.05% to 1%) of the mass of the active material particles. This percentage may be analyzed by ICP analysis or other methods.

[0032] The reaction product may have a chemical structure in which the Si in the Si-R1-Si structure is bonded to the Si in the active material particles by siloxane bonds. That is, the surface layer (L) may contain a chemical structure (reaction product of compound (1)) in which the Si in multiple Si-R1-Si structures is bonded to the Si in the active material particles by siloxane bonds. The reaction product may have a structure in which the Si in multiple Si-R1-Si structures is bonded to each other and to the Si in the active material particles by siloxane bonds. That is, the surface layer (L) may contain a chemical structure (reaction product of compound (1)) in which the Si in multiple Si-R1-Si structures is bonded to each other and to the Si in the active material particles by siloxane bonds.

[0033] (The chain portion of R1 contains sulfur (1)) In compound (1) (for example, the compound represented by formula (1)), the chain portion R1 may contain sulfur. For example, compound (1) may be a bis(alkoxysilylalkyl) sulfide. An example of compound (1) in which the chain portion R1 contains sulfur is described below. R1 is C t1 H 2t1 S zThe sulfide group is represented by , where t1 and z are integers of 1 or more. At least one of R2 to R4 is selected from the group consisting of alkoxy groups having 1 to 6 carbon atoms, the alkyloxy groups, hydroxyl groups, and chloro groups mentioned above. At least one of R5 to R7 is selected from the group consisting of alkoxy groups having 1 to 6 carbon atoms, the alkyloxy groups, hydroxyl groups, and chloro groups mentioned above. The remaining R2 to R7 may each be independently one of the groups mentioned above. Specifically, of R2 to R7, those that are not atomic groups (G) mentioned above may each be independently one of a hydrocarbon group having 1 to 6 carbon atoms, a hydrogen atom, or the above formula C x3 H 2x3+y3+1 N y3 O z3 S w3 It may also be a base represented by .

[0034] The atomic groups (G) contained in R2-R4 and R5-R7 can form XO-Si-R1 bonds with the surface of the silicon-containing material, and the surface of the silicon-containing material can be covered with a Si-R1-Si structure having stable siloxane bonds at both ends. In other words, the surface of the silicon-containing material can be covered with a coating containing a bissilyl sulfide structure (a coating formed by the reaction products of compound (1), which may be referred to as the "SSS coating" below).

[0035] In equation (1), C t1 H 2t1 S z The sulfide group (R1) represented by R11-S z It may have a structure represented by -R12. Here, R11 and R12 are each independently alkylene groups having 1 or more carbon atoms. Such R1 has excellent flexibility and S z The structure provides significant electron shielding, which is thought to be a major factor in suppressing side reactions.

[0036] The more carbon atoms R11 and R12 have, the better the flexibility, making reversible deformation of the SSS coating easier. However, if the number of carbon atoms in R11 and R12 is excessively high, the alkylene chain becomes too long, reducing the density of the SSS coating and diminishing its effect in suppressing side reactions. Therefore, it is desirable for the number of carbon atoms in R11 and R12 to be between 1 and 6, and more preferably between 2 and 4. Bis(alkoxysilylalkyl) sulfide is bis(alkoxysilylC 1-6 It is preferable that it be an alkyl sulfide, and bis(alkoxysilyl C 2-4 It may also be an alkyl sulfide.

[0037] Also, S which constitutes R1 z The more consecutive sulfur atoms a group has, the better its flexibility, thus facilitating the reversible deformation of the SSS coating. However, if the number of sulfur atoms becomes excessively high, the density of the SSS coating decreases, and S z The group itself may produce side reactions. Therefore, S z The number of sulfur atoms in the group should preferably be 1 to 6, and more preferably 2 to 4. That is, bis(alkoxysilylalkyl) sulfide is bis(alkoxysilylC 1-6 Alkyl)S 1-6 It is preferable that it be a sulfide, bis(alkoxysilyl C 2-4 Alkyl)S 2-4 It may also be a sulfide.

[0038] Since R2 to R7 have been explained above, we will omit any redundant explanations. From the viewpoint of increasing reactivity with the surface of materials containing silicon, the number of carbon atoms in the alkoxy group may be in the range of 1 to 3, and the number of carbon atoms in the oxyalkyl group may be in the range of 2 to 3.

[0039] The remaining R2-R7 may be the groups described above. Specifically, of R2-R7, those that are not the atomic group (G) described above may each be, independently, a hydrocarbon group with 1-6 carbon atoms, a hydrogen atom, or the C group described above. x3 H 2x3+y3+1 N y3 O z3 Sw3 The group may be represented by . From the viewpoint of minimizing steric hindrance during the reaction, it may have 1 to 3 carbon atoms. R2 to R4 are independent of each other, and all of R2 to R4 may have the same number of carbon atoms, all of them may have different numbers of carbon atoms, or two of R2 to R4 may have the same number of carbon atoms. Similarly, R5 to R7 are independent of each other, and all of R5 to R7 may have the same number of carbon atoms, all of them may have different numbers of carbon atoms, or two of R5 to R7 may have the same number of carbon atoms.

[0040] The two alkoxysilyl groups linked to R1 (R2R3R4Si-, or R5R6R7Si-) may be the same or different. However, in order to enhance the structural symmetry of the SSS coating and create a more stable structure, the two alkoxysilyl groups linked to R1 may have the same structure.

[0041] Bis(trialkoxysilyl C) 1-6 Alkyl)S 1-6 Among sulfides, at least one selected from the group consisting of bis(triethoxysilylpropyl)sulfide, bis(triethoxysilylpropyl)disulfide, bis(triethoxysilylpropyl)trisulfide, and bis(triethoxysilylpropyl)tetrasulfide is readily available. Bis(triethoxysilylpropyl)tetrasulfide (TESPT, also known as bis[3-(triethoxysilyl)propyl]tetrasulfide) is shown below. These may be commercially available or synthesized by known methods.

[0042] [ka]

[0043] (1) A compound in which the chain portion of R1 contains nitrogen. In compound (1) (for example, the compound represented by formula (1)), the chain portion of R1 may contain nitrogen. For example, compound (1) may be a bis(alkoxysilylalkyl)amine. In the case where the chain portion of R1 contains nitrogen, compound (1) is described in the above description relating to compound (1) in which the chain portion of R1 contains sulfur, S z The compounds may also be those in which the group is replaced with a secondary amino group (-NH-) or a tertiary amino group. In the case of a tertiary amino group, examples of side chains bonded to the nitrogen atom include alkyl groups and alkoxysilylalkyl groups. An example of bis(alkoxysilylalkyl)amines is shown below. These may be commercially available or synthesized by known methods.

[0044] [ka]

[0045] The amino group constituting R1 may have a structure represented as R11-N-R12. Here, R11 and R12 are each independently alkylene groups having one or more carbon atoms. Such a R1 is thought to have excellent flexibility, high electron shielding properties, and a greater effect in suppressing side reactions.

[0046] The more carbon atoms an amino group has, the more flexible it becomes, thus facilitating the reversible deformation of the film formed by the reaction product of compound (1). However, if the number of carbon atoms in the amino group is excessively large, R1 becomes too long, reducing the density of the film and diminishing its effect in suppressing side reactions. Therefore, it is desirable for the alkylene group to have 1 to 6 carbon atoms, and 2 to 4 carbon atoms is more desirable. For example, bis(alkoxysilylalkyl)amine is bis(alkoxysilylC 1-6 It is preferable that it be an alkylamine, and bis(alkoxysilyl C 2-4 Alkylamines may also be used.

[0047] (1) Compound in which the chain portion of R1 contains an amide bond Compound (1) in which the chain portion of R1 has an amide bond is, in the above description relating to compound (1) in which the chain portion of R1 contains sulfur, z The compound may also be one in which the group is replaced with an amide group.

[0048] (Compound (1) in which the chain portion of R1 contains an ether bond) In compound (1) (for example, the compound represented by formula (1)), the chain portion of R1 may include an ether bond. In that case, compound (1) may be a compound obtained by replacing R1 with an atomic group containing an ether bond, as described above for compound (1) in which the chain portion of R1 contains sulfur.

[0049] If R1 of compound (1) contains an ether bond, then in formula (1), R1 is R11-(O-R12) n The structure may be represented as -O-R13. Here, R11, R12, and R13 are each independently alkylene groups having 1 or more carbon atoms, and n is an integer of 0 or more. Such R1 has excellent flexibility, and the oxygen bonding R11 and R12, and the oxygen bonding R12 and R13, coordinate to the cation, which can promote the movement of cations into and out of the silicon-containing material. This is thought to increase the cation conductivity and further suppress the decrease in capacity retention. Note that when n is 2 or more, the multiple R12s in the (O-R12) unit may all be the same alkylene group, or they may include alkylene groups with different numbers of carbon atoms.

[0050] The more carbon atoms R11 and R13 have, the better the flexibility, making it easier to reversibly deform the film formed by the reaction product of compound (1). However, if the number of carbon atoms in R11 and R13 is excessively high, the alkylene chain becomes too long, reducing the density of the film and diminishing its effect in suppressing side reactions. Therefore, it is desirable for the number of carbon atoms in R11 and R13 to be between 1 and 6, and more preferably between 2 and 4 carbon atoms. Bis(alkoxysilylalkyl) ethers are bis(alkoxysilylC 1-6 It is preferable that it be an alkyl ether, and bis(alkoxysilyl C2-4 It may also be an alkyl ether.

[0051] Furthermore, the -O- groups constituting R1 enhance cation conductivity and contribute to improved capacity retention. However, if the number of -O- groups becomes excessively large, the density of the coating decreases, so it is desirable that the number of -O- groups be between 1 and 5, with 1 to 3 being more desirable. In other words, the number n of (O-R12) units contained in the above R1 is preferably between 0 and 4, with 0 to 2 being more desirable.

[0052] On the other hand, the number of carbon atoms in R12 is preferably 4 or less, and more preferably between 2 and 4, from the viewpoint of promoting cation transfer between adjacent oxygen atoms.

[0053] R1 may be -C3H6-O-C3H6- or -C2H4-O-C2H4-O-C3H6-. R2 to R7 may each be a methoxy group.

[0054] A specific example of a desirable alkoxysilyl compound is, for example, the bis(alkoxysilylalkyl) ether shown in the following formula.

[0055] [ka]

[0056] [ka]

[0057] The surface layer (L) of the negative electrode active material (N) may contain conductive carbon. In this case, it is preferable that formula (1) satisfies the above conditions (V2) or (V5). Silicon-containing active materials tend to experience capacity degradation during charge-discharge cycles due to their low conductivity. By placing conductive carbon on the surface of the active material, capacity degradation during charge-discharge cycles can be suppressed. However, simply placing conductive carbon on the surface is insufficient, as the expansion and contraction of the active material during charge-discharge cycles reduces the adhesion between the active material and the conductive carbon, leading to a decrease in conductivity between them. In contrast, by including the reaction products of compound (1) and conductive carbon in the surface layer (L), the charge-discharge efficiency of the silicon-containing negative electrode active material can be significantly improved. This may be because the network formed by the reaction products of compound (1) maintains the adhesion between the active material and the conductive carbon.

[0058] Examples of conductive carbons include amorphous carbon, graphite, easily graphitizable carbon (soft carbon), and difficult-to-graphitize carbon (hard carbon). Among these, amorphous carbon is preferred because it easily forms a thin conductive layer covering the surface of composite particles. Examples of amorphous carbons include carbon black, calcined pitch, coke, and activated carbon. Examples of graphites include natural graphite, artificial graphite, and graphitized mesophase carbon.

[0059] (active material particles) The active material particles contain silicon (element silicon). Materials containing silicon are sometimes treated as a type of alloying material. Here, alloying materials refer to materials containing elements that can form alloys with lithium. Elements that can form alloys with lithium include silicon and tin, with silicon (Si) being particularly promising. There are no limitations on the method of manufacturing the active material particles. The active material particles may be manufactured by known methods, or commercially available particles may be used.

[0060] The silicon-containing material may be a silicon alloy, a silicon compound, or a composite material. Among these, a composite material containing a lithium-ion conductive phase and silicon particles dispersed in the lithium-ion conductive phase is promising. As the lithium-ion conductive phase, for example, a silicon oxide phase, a silicate phase, or a carbon phase can be used. The silicon oxide phase is a material with a relatively high irreversible capacity. On the other hand, the silicate phase is preferred because it has a low irreversible capacity.

[0061] The main component of the silicon oxide phase (e.g., 95-100% by mass) may be silicon dioxide. The overall composition of the composite material containing the silicon oxide phase and silicon particles dispersed therein is SiO2. x It can be expressed as follows. SiOx has a structure in which silicon nanoparticles are dispersed in amorphous SiO2. The oxygen content ratio x to silicon is, for example, 0.5 ≤ x < 2.0, and more preferably 0.8 ≤ x ≤ 1.5.

[0062] The silicate phase may contain, for example, at least one element selected from the group consisting of Group 1 and Group 2 elements of the long-period periodic table. Examples of Group 1 and Group 2 elements of the long-period periodic table include lithium (Li), potassium (K), sodium (Na), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Other elements that may be included include aluminum (Al), boron (B), lanthanum (La), phosphorus (P), zirconium (Zr), and titanium (Ti). Among these, a lithium-containing silicate phase (hereinafter also referred to as the lithium silicate phase) is preferred because it has a small irreversible capacity and high initial charge-discharge efficiency.

[0063] The lithium silicate phase may be an oxide phase containing lithium (Li), silicon (Si), and oxygen (O), and may also contain other elements. The atomic ratio of O to Si in the lithium silicate phase: O / Si is, for example, greater than 2 and less than 4. Preferably, O / Si is greater than 2 and less than 3. The atomic ratio of Li to Si in the lithium silicate phase: Li / Si is, for example, greater than 0 and less than 4. The lithium silicate phase has the formula: Li 2z SiO 2+z (0 < z < 2). z preferably satisfies the relationship 0 < z < 1, and more preferably z = 1 / 2. Examples of elements other than Li, Si, and O that may be included in the lithium silicate phase include iron (Fe), chromium (Cr), nickel (Ni), manganese (Mn), copper (Cu), molybdenum (Mo), zinc (Zn), aluminum (Al), and the like.

[0064] The carbon phase may be composed of, for example, poorly crystalline amorphous carbon (i.e., amorphous carbon). The amorphous carbon may be, for example, hard carbon, soft carbon, or the like.

[0065] Each of the active material particles (N) and the negative electrode binder layer may contain, in addition to a material containing a silicon element, a material that electrochemically intercalates and deintercalates lithium ions, lithium metal, a lithium alloy, and the like. As the material that electrochemically intercalates and deintercalates lithium ions, a carbon material is preferable. Examples of the carbon material include graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), and the like. Among them, graphite, which is excellent in charge-discharge stability and has a small irreversible capacity, is preferable.

[0066] [[ID=1"6]]The active material particles are Li x SiO yIt may be a composite particle including a lithium silicate phase represented by (0 < x ≦ 4, 0 < y ≦ 4) and a silicon phase dispersed in the lithium silicate phase. Here, x and y are independent of x and y regarding the compound (1). Such a composite particle may be manufactured, for example, by the method described in the examples or by a known method. The crystallite size of the silicon phase may be in the range of 1 nm to 1000 nm (for example, in the range of 200 nm to 500 nm).

[0067] The crystallite size of the silicon phase is calculated by the Scherrer equation from the half-width of the diffraction peak attributed to the (111) plane of the silicon phase (elemental Si) in the X-ray diffraction pattern.

[0068] The active material particles may be composite particles including a carbon phase and a silicon phase dispersed in the carbon phase. The carbon phase may be composed of, for example, amorphous carbon (that is, non-crystalline carbon). The amorphous carbon may be, for example, hard carbon, soft carbon, or others. Amorphous carbon (non-crystalline carbon) generally refers to a carbon material in which the average interplanar spacing d002 of the (002) plane measured by the X-ray diffraction method exceeds 0.34 nm.

[0069] (Method for manufacturing the negative electrode active material (N)) The manufacturing method according to the present disclosure is a method for manufacturing the negative electrode active material (N) for a non-aqueous electrolyte secondary battery according to the present disclosure. However, the negative electrode active material (N) may be manufactured by a method other than the method described below. Since the matters described for the negative electrode active material (N) can be applied to the following manufacturing method, duplicate explanations may be omitted. The matters described for the following manufacturing method may also be applied to the negative electrode active material according to the present disclosure.

[0070] This manufacturing method includes a first step and a second step, which are included in this order. The first and second steps are performed under conditions where the compound (1) forms a siloxane bond. The first and second steps may be performed under the same conditions as those for hydrolysis and condensation so that a known silane coupling agent containing an alkoxysilyl group forms a siloxane bond.

[0071] (First step) The first step is to bring compound (1), or a liquid in which compound (1) is dissolved, into contact with silicon-containing active material particles. This liquid may be referred to as "liquid (S)" below. The first step may also be to disperse the silicon-containing active material particles in compound (1) or liquid (S). Alternatively, the first step may be to coat the surface of the silicon-containing active material particles with compound (1) or liquid (S).

[0072] Compound (1) is the compound described above and is represented by formula (1). The active material particles are the active material particles described above. Liquid (S) can be prepared by dissolving compound (1) in a solvent. Note that before the second step, some of compound (1) may have reacted to form siloxane bonds. The solvent may include lower alcohols (e.g., ethanol), water, and acids. Examples of acids include hydrochloric acid.

[0073] The content of the reaction product of compound (1) in the negative electrode active material (N) can be varied by changing the concentration of compound (1) in the liquid (S). The concentration of compound (1) in the liquid (S) may be in the range of 0.0001 to 10 moles / liter (for example, in the range of 0.001 to 0.1 moles / liter). The mass of compound (1) per 1 g of active material particles dispersed in the liquid (S) may be in the range of 0.0001 to 1 g (for example, in the range of 0.001 to 0.1 g).

[0074] (Second step) The second step is to react compound (1) with active material particles in contact with compound (1) or liquid (S) to form siloxane bonds. The second step may be carried out, for example, by raising the temperature of the liquid (S) and active material particles to a predetermined temperature and maintaining it for a predetermined time. If the active material particles are dispersed in the liquid (S), the liquid (S) may be stirred in the second step. The predetermined temperature may be in the range of 10 to 200°C (for example, in the range of 40 to 100°C). The predetermined time may be in the range of 1 to 120 hours (for example, in the range of 12 to 72 hours).

[0075] The second step yields the negative electrode active material (N). The negative electrode active material (N) obtained in the second step may be washed and / or dried as needed.

[0076] The manufacturing method according to this disclosure may include step (a) of placing conductive carbon on the surface of the active material particles before the first step, between the first and second steps, or after the second step. By performing step (a), a surface layer (L) containing the reaction product of compound (1) and conductive carbon can be formed.

[0077] Step (a) may be carried out by heat treatment of a mixture of active material particles and conductive carbon. As raw materials for conductive carbon, for example, coal pitch or coal tar pitch, petroleum pitch, phenolic resin, etc. may be used. The heat treatment may be carried out by heating at a temperature of 450 to 1000°C for 1 to 10 hours, for example. The conductive carbon described above can be used as the conductive carbon. Alternatively, in step (a), a conductive carbon layer may be formed by reacting a hydrocarbon gas on the surface of the composite particles using a gas-phase method such as CVD. As hydrocarbon gas, acetylene, methane, etc. may be used. According to these methods, a conductive layer into which the reaction product of compound (1) can permeate can be formed.

[0078] (Negative electrode for non-aqueous electrolyte secondary batteries) This disclosure provides a negative electrode for a non-aqueous electrolyte secondary battery. The negative electrode comprises a negative electrode active material (N) according to this disclosure.

[0079] (Nonaqueous electrolyte secondary battery) The non-aqueous electrolyte secondary battery according to this disclosure includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The negative electrode includes a negative electrode active material (N). There are no particular limitations on the components other than the negative electrode, and known components used in non-aqueous electrolyte secondary batteries may be applied. There are no particular limitations on the configuration of the negative electrode except that it includes a negative electrode active material (N). For components of the negative electrode other than the negative electrode active material (N), known components for negative electrodes of non-aqueous electrolyte secondary batteries may be applied. An example of a negative electrode according to this disclosure includes a negative electrode current collector and a negative electrode mixture layer disposed on the surface of the negative electrode current collector. There are no limitations on the manufacturing method of the non-aqueous electrolyte secondary battery according to this disclosure except for the use of a negative electrode active material (N), and it may be manufactured by known methods.

[0080] An example of the configuration of a non-aqueous electrolyte secondary battery relating to this disclosure is described below. However, the configuration of a non-aqueous electrolyte secondary battery is not limited to the following configuration, except for the use of a negative electrode active material (N).

[0081] (Negative electrode) The negative electrode includes, for example, a negative electrode current collector and a negative electrode mixture layer formed on the surface of the negative electrode current collector. The negative electrode mixture layer contains a negative electrode active material (N) as an essential component and may also contain optional components such as binders, conductive materials, and thickeners. In addition to the negative electrode active material (N), the negative electrode mixture layer may also contain other active materials for the negative electrode. Known materials can be used for the optional components such as binders, conductive materials, and thickeners.

[0082] The negative electrode mixture layer can be formed, for example, by dispersing a negative electrode slurry containing a negative electrode active material (N) and a predetermined optional component in a dispersion medium, applying it to the surface of the negative electrode current collector, and drying it. The dried coating may be rolled if necessary. The negative electrode mixture layer may be formed on one surface of the negative electrode current collector, or on both surfaces.

[0083] For the negative electrode current collector, a metal sheet or metal foil is used, for example. Examples of materials for the negative electrode current collector include stainless steel, nickel, nickel alloys, copper, and copper alloys.

[0084] (positive electrode) The positive electrode includes, for example, a positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector. The positive electrode mixture layer contains a positive electrode active material as an essential component and may also contain optional components such as a binder, a conductive material, and a thickening agent. Known materials can be used for the optional components such as the binder, conductive material, and thickening agent.

[0085] The positive electrode mixture layer can be formed, for example, by dispersing a positive electrode slurry containing a positive electrode active material and a predetermined optional component in a dispersion medium, applying it to the surface of the positive electrode current collector, and drying it. The dried coating may be rolled if necessary. The positive electrode mixture layer may be formed on one surface of the positive electrode current collector, or on both surfaces.

[0086] For example, a lithium-containing composite oxide can be used as the positive electrode active material. a CoO2, Li a KiO2, Li a MnO2, Li a Co b Ni 1-b O2, Li a Co b Me 1-b O c Li a Ni 1-b Me b O c Li a Mn2O4, Li a Mn 2-b Me b Examples include O4, LiMePO4, and Li2MePO4F (where Me is at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B). Here, a = 0 to 1.2, b = 0 to 0.9, and c = 2.0 to 2.3. Note that the value of a, which indicates the molar ratio of lithium, increases or decreases with charging and discharging.

[0087] Among them, Li a Ni b Me 1-b O2 (Me is at least one selected from the group consisting of Mn, Co, and Al, 0 < a ≤ 1.2, and 0.3 ≤ b ≤ 1.) represented lithium nickel composite oxide is preferred. From the viewpoint of increasing the capacity, it is more preferable to satisfy 0.85 ≤ b < 1. From the viewpoint of the stability of the crystal structure, Li containing Co and Al as Me a Ni b Co c Al d O2 (0 < a ≤ 1.2, 0.85 ≤ b < 1, 0 < c < 0.15, 0 < d ≤ 0.1, b + c + d = 1) is even more preferred.

[0088] The positive electrode active material (especially the lithium-containing composite oxide) usually has the form of secondary particles in which primary particles are aggregated. The average particle diameter of the positive electrode active material may be, for example, 2 μm or more and 20 μm or less. Here, the average particle diameter refers to the median diameter at which the cumulative volume in the volume-based particle size distribution is 50%. The volume-based particle size distribution can be measured by a laser diffraction type particle size distribution measuring device. [[ID=2"1]]

[0089] For the positive electrode current collector, for example, a metal sheet or a metal foil is used. Examples of the material of the positive electrode current collector include stainless steel, aluminum, aluminum alloy, titanium, and the like.

[0090] Examples of the conductive material used in the positive electrode binder layer and the negative electrode binder layer include carbon materials such as carbon black (CB), acetylene black (AB), ketjen black (KB), carbon nanotube (CNT), and graphite. These may be used alone or in combination of two or more.

[0091] Examples of binders used in the positive electrode mixture layer and the negative electrode mixture layer include fluororesins (polytetrafluoroethylene, polyvinylidene fluoride, etc.), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. These may be used individually or in combination of two or more types.

[0092] (Separator) Non-aqueous electrolyte secondary batteries typically include a separator placed between the positive and negative electrodes. The separator has high ion permeability and possesses moderate mechanical strength and insulating properties. Microporous membranes, woven fabrics, nonwoven fabrics, etc., can be used as separators. Examples of separator materials include polyolefins (polypropylene, polyethylene, etc.).

[0093] (Non-aqueous electrolytes) A non-aqueous electrolyte (or non-aqueous electrolyte solution) comprises a non-aqueous solvent and a salt (solute) dissolved in the non-aqueous solvent. The salt (solute) is an electrolyte salt that undergoes ion dissociation in the non-aqueous solvent. When a non-aqueous electrolyte is used in a lithium-ion secondary battery, the salt contains at least a lithium salt. The non-aqueous electrolyte may also contain additives other than the non-aqueous solvent and salt. For example, the non-aqueous electrolyte may contain compound (1) and / or the reaction products of compound (1).

[0094] Examples of non-aqueous solvents include cyclic carbonate esters, linear carbonate esters, cyclic carboxylic acid esters, and linear carboxylic acid esters. Examples of cyclic carbonate esters include propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC). Examples of linear carbonate esters include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone (GVL). Examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP). Non-aqueous solvents may be used individually or in combination of two or more.

[0095] In particular, linear carboxylic acid esters are suitable for preparing low-viscosity non-aqueous electrolytes. Therefore, the non-aqueous electrolyte may contain 1% or more by mass of linear carboxylic acid esters and up to 90% by mass of linear carboxylic acid esters. Among linear carboxylic acid esters, methyl acetate has particularly low viscosity. Therefore, 90% or more by mass of the linear carboxylic acid ester may be methyl acetate.

[0096] Other non-aqueous solvents include cyclic ethers, linear ethers, nitriles such as acetonitrile, and amides such as dimethylformamide.

[0097] Examples of cyclic ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, and crown ethers.

[0098] Examples of linear ethers include 1,2-dimethoxyethane, dimethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methylphenyl ether, ethylphenyl ether, butylphenyl ether, pentylphenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and the like.

[0099] These solvents may be fluorinated solvents in which some of the hydrogen atoms are replaced by fluorine atoms. Fluoroethylene carbonate (FEC) may be used as the fluorinated solvent.

[0100] Examples of lithium salts include lithium salts of chlorine-containing acids (LiClO4, LiAlCl4, LiB 10 Cl 10 Lithium salts of fluorine-containing acids (such as LiPF6, LiPF2O2, LiBF4, LiSbF6, LiAsF6, LiCF3SO3, LiCF3CO2, etc.), lithium salts of fluorine-containing acid imides (such as LiN(FSO2)2, LiN(CF3SO2)2, LiN(CF3SO2)(C4F9SO2), LiN(C2F5SO2)2, etc.), lithium halides (such as LiCl, LiBr, LiI, etc.) can be used. Lithium salts may be used individually or in combination of two or more types.

[0101] The lithium salt concentration in the non-aqueous electrolyte may be 0.5 mol / liter or more and 2 mol / liter or less, or 1 mol / liter or more and 1.5 mol / liter or less. By controlling the lithium salt concentration within the above range, a non-aqueous electrolyte with excellent ionic conductivity and low viscosity can be obtained.

[0102] Examples of additives include 1,3-propanesaltone, methylbenzenesulfonate, cyclohexylbenzene, biphenyl, diphenyl ether, and fluorobenzene.

[0103] An example of a non-aqueous electrolyte secondary battery includes an outer casing, an electrode group housed within the casing, and a non-aqueous electrolyte. The electrode group may be a wound electrode group formed by winding a positive electrode and a negative electrode with a separator in between. Alternatively, other forms of electrode groups may be used instead of the wound electrode group. For example, the electrode group may be a stacked electrode group formed by stacking a positive electrode and a negative electrode with a separator in between. The non-aqueous electrolyte secondary battery may take any form, such as cylindrical, prismatic, coin-type, button-type, or sheet-type (laminated).

[0104] A non-aqueous electrolyte secondary battery according to one embodiment of the present invention will be described below with reference to Figures 1 and 2. Figure 1 is a partially cutaway plan view schematically showing an example of the structure of a non-aqueous electrolyte secondary battery. Figure 2 is a cross-sectional view taken along the line X-X' in Figure 1.

[0105] As shown in Figures 1 and 2, the non-aqueous electrolyte secondary battery 100 is a sheet-type battery and comprises an electrode plate group 4 and an outer case 5 that houses the electrode plate group 4.

[0106] The electrode plate group 4 has a structure in which the positive electrode 10, separator 30, and negative electrode 20 are stacked in this order, with the positive electrode 10 and negative electrode 20 facing each other via the separator 30. This forms the electrode plate group 4. The electrode plate group 4 is impregnated with a non-aqueous electrolyte (not shown).

[0107] The positive electrode 10 includes a positive electrode active material layer 1a and a positive electrode current collector 1b. The positive electrode active material layer 1a is formed on the surface of the positive electrode current collector 1b.

[0108] The negative electrode 20 includes a negative electrode mixture layer 2a and a negative electrode current collector 2b. The negative electrode mixture layer 2a is formed on the surface of the negative electrode current collector 2b. The negative electrode mixture layer 2a contains the negative electrode active material (N) according to this disclosure.

[0109] A positive electrode tab lead 1c is connected to the positive electrode current collector 1b, and a negative electrode tab lead 2c is connected to the negative electrode current collector 2b. Both the positive electrode tab lead 1c and the negative electrode tab lead 2c extend outside the outer casing 5.

[0110] The positive electrode tab lead 1c and the outer casing 5, and the negative electrode tab lead 2c and the outer casing 5 are insulated by insulating tab films 6, respectively.

[0111] (An example of a synthesis method for compound (1) in which the chain portion of R1 contains oxygen) An example of compound (1) in which the chain portion of R1 contains oxygen may be synthesized by the following method. First, 1.0 g of allyl ether, 40.0 mL of dichloroethane (C2H4Cl2), 3.7 g of trimethoxysilane (HSi(OMe)3), and 0.1 g of cyclooctadiene iridium chloride dimer ([Ir(COD)Cl]2) were added to a dry four-necked container (100 mL) and stirred to allow the reaction shown in the following formula to proceed. The mixture was heated and stirred from room temperature to 50°C until the allyl ether, the starting material, was gone. After confirming that the starting material had disappeared, heating and stirring were stopped. Next, the dichloroethane (solvent) was removed from the reaction mixture using an evaporator to obtain brown oil K1 (4.0 g), which is a crude product containing alkoxysilyl compound A.

[0112] [ka]

[0113] Next, 5.0 g of allyl ether, 200 mL of dichloroethane (C2H4Cl2), 18.6 g of trimethoxysilane (HSi(OMe)3), and 0.68 g of cyclooctadiene iridium chloride dimer ([Ir(COD)Cl]2) were added to a dried eggplant-shaped container (500 mL), and the mixture was heated and stirred from room temperature to 50 °C. After confirming that the starting materials had disappeared, heating and stirring were stopped. Next, dichloroethane (solvent) was removed from the reaction mixture using a vacuum pump. Brown oil K1 was added to the crude mixture after distillation, and distillation purification was carried out at an oil bath temperature of 190 °C and a vacuum of 0.1-0.01 mmHg using a distillation purification apparatus connected to a flask, T-tube, thermometer, condenser, vacuum pump, and pressure gauge to obtain brown oil K2 (9.3 g) containing alkoxysilyl compound A.

[0114] Furthermore, 5.0 g of allyl ether, 200 mL of dichloroethane (C2H4Cl2), 18.6 g of trimethoxysilane (HSi(OMe)3), and 0.5 g of cyclooctadiene iridium chloride dimer ([Ir(COD)Cl]2) were added to a dried eggplant-shaped container (500 mL), and the mixture was heated and stirred from room temperature to 50 °C. After confirming that the starting materials had disappeared, heating and stirring were stopped. Next, dichloroethane (solvent) was removed from the reaction mixture using a vacuum pump. Brown oil K2 was added to the crude mixture after distillation, and distillation purification was performed again at an oil bath temperature of 190 °C and a vacuum of 0.1-0.01 mmHg to obtain a colorless oil compound K3 (13.3 g, 38.8 mol, yield 34.6%) containing alkoxysilyl compound A. 1 Purity was confirmed by 1H-NMR and gas chromatography (GC).

[0115] (Another example of a method for synthesizing compound (1) in which the chain portion of R1 contains oxygen) At room temperature, ethylene glycol monovinyl ether (5.0 g, 1.0 eq.), super-dehydrated dimethylformamide (DMF) (50 mL), and allyl bromide (7.55 g, 1.1 eq.) were added to a 200 mL reactor. To this solution, NaH (2.27 g, 1.0 eq.) was slowly added in several portions over 20 minutes while stirring to obtain a white suspension. The white suspension was stirred at room temperature for 16 hours to allow the reaction shown in the following formula to proceed. After stirring, water was added to quench the reaction and a reaction solution containing compound B was obtained.

[0116] [ka]

[0117] The reaction mixture was placed in a separatory funnel, 30 mL of diethyl ether was added and stirred, and the organic phase was extracted. This process was repeated three times. The extracted organic phases were combined and placed back into the separatory funnel, 100 mL of water was added and stirred, and the aqueous phase was drained. This process was repeated three times. Subsequently, 100 mL of saturated saline solution was added and stirred, and the aqueous phase was drained. Then, 20 g of anhydrous sodium sulfate was added to the remaining organic phase and stirred to remove the water, and the anhydrous sodium sulfate was removed by filtration. After that, the diethyl ether was removed under atmospheric pressure at a bath temperature of 50°C, and the residue was purified by distillation using a distillation purification apparatus connected to a flask, T-tube, thermometer, condenser, vacuum pump, and pressure gauge (vacuum: 20 mmHg, oil bath temperature: 70°C, vapor temperature: 50°C) to obtain a colorless liquid Y1 containing compound B.

[0118] Next, compound B (1.0 g, 1.0 eq.), 30 mL of super-dehydrated dichloromethane, and cyclooctadiene iridium chloride dimer ([Ir(COD)Cl]2) (52 g, 0.01 eq.) were added to a 50 mL reactor to obtain an orange solution. Trimethoxysilane (HSi(OMe)3) (3.0 mL, 3.0 eq.) was slowly added dropwise to the orange solution over 15 minutes while stirring. The solution was stirred at room temperature for 2 hours to allow the reaction shown in the following formula to proceed, yielding solution Y2 containing alkoxysilyl compound C.

[0119] [ka]

[0120] Furthermore, at room temperature, compound B (5.0 g, 1.0 eq.), 125 mL of super-dehydrated dichloromethane, and 0.26 g of cyclooctadiene iridium chloride dimer ([Ir(COD)Cl]2) were added to a 50 mL reactor to obtain an orange solution. Trimethoxysilane (HSi(OMe)3) (14.9 mL, 3.0 eq.) was slowly added dropwise to the orange solution over 15 minutes while stirring. After stirring the solution at room temperature for 2 hours, solution Y2 was added to the stirred solution. A distillation purification apparatus was attached to the reactor, and dichloromethane was removed at a bath temperature of 50°C, and volatile components were further removed under reduced pressure of 20 mmHg / 70°C. The residue was purified by distillation (vacuum: 0.1-0.3 mmHg, oil bath temperature: 180-195°C, vapor temperature: 139-142°C) to obtain compound C (10.4 g, 27.9 mol, yield 59.6%), which was a light brown solution. [Examples]

[0121] The present disclosure will be described below in detail based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0122] <Battery (A1-1)> [Fabrication of negative electrode active material] Lithium carbonate (Li2CO3) and silicon dioxide (SiO2) were mixed in a molar ratio of Li2CO3:SiO2 = 34:66, and the mixture was heated in an inert gas atmosphere at 1500°C for 5 hours to dissolve and obtain a melt. The melt was passed through a metal roller to form a flake-like solid, and this solid was heat-treated at 750°C for 5 hours to obtain a lithium silicate composite oxide existing as a mixed phase of amorphous and crystalline material. The obtained lithium silicate composite oxide was pulverized to an average particle size of 10 μm.

[0123] Next, in an inert gas atmosphere, Si particles (3N, average particle size 10 μm) and the above-mentioned lithium silicate composite oxide were mixed in a mass ratio of Si particles:lithium silicate composite oxide = 58:42, and the mixture was packed into a 500 mL pot (made of SUS (stainless steel)) of a planetary ball mill (Fritsch, P-5). Twenty-four SUS balls (diameter 20 mm) were placed in the pot, the lid was closed, and the mixture was ground at 200 rpm for 50 hours to obtain a powder. Subsequently, the obtained powder was removed in an inert gas atmosphere and heat-treated at 800 °C for 4 hours in an inert gas atmosphere to obtain a sintered body of Si-containing lithium silicate composite oxide. In other words, composite particles containing a lithium silicate phase and a silicon phase dispersed in the lithium silicate phase were produced by the above process.

[0124] Subsequently, the sintered body was crushed and passed through a 40 μm mesh. The particles that passed through the mesh were then mixed with coal pitch (JFE Chemical Corporation, MCP250) to obtain a mixture. Next, the mixture was heat-treated at 800°C for 5 hours in an inert gas atmosphere to coat the particle surface with conductive carbon and form a conductive layer. The amount of conductive layer coating was 5% by mass relative to the total mass of the Si-containing lithium silicate composite oxide particles and the conductive layer. Subsequently, active material particles with an average particle size of 5 μm and a conductive layer were obtained using a sieve. The active material particles and the conductive layer formed on their surface may be collectively referred to as "active material particles (a0)" below.

[0125] [Analysis of active material particles] TEM observation of the cross-section of the active material particle (a0) revealed that the average particle size of the Si particles (Si phase) was less than 50 nm. SEM observation of the particle cross-section of the active material particle (a0) confirmed that a large number of Si particles (Si phase) were almost uniformly dispersed within the silicate phase.

[0126] The XRD pattern of the active material particle (a0) showed peaks originating from Si and Li2Si2O5. No peaks originating from SiO2 around 2θ=25° were observed. Si-NMR measurements of the active material particle (a0) showed that the SiO2 content was below the detection limit.

[0127] [Coating treatment of negative electrode active material 1-1] A solution with a pH of approximately 4.5 (hereinafter sometimes referred to as the "mother liquor") was prepared by mixing 342 mL of ethanol, 10 mL of pure water, and 326 μL of hydrochloric acid (concentration: 37% by mass). Bis[3-(triethoxysilyl)propyl]tetrasulfide (commercial product, hereinafter sometimes referred to as "P1") was added to the mother liquor to a concentration of 0.5% by mass and mixed to prepare the P1 solution. Next, 22 g of active material particles (a0) were mixed into the P1 solution to form a suspension, which was stirred at 50°C for 24 hours using a stirring bar. This reacted P1 to form siloxane bonds.

[0128] Next, the suspension was filtered by suction using a polytetrafluoroethylene (PTFE) membrane filter, and rinsed with 500 mL of ethanol, followed by 500 mL of pure water. The recovered particles were vacuum-dried at 100°C for 24 hours to obtain the negative electrode active material (a1-1). A cross-section of this negative electrode active material (a1-1) was observed using a TEM-EDX apparatus (JEOL Ltd., JEM-F200). As a result, it was confirmed that a surface layer was formed on the Si-containing lithium silicate composite oxide particles. The surface layer was found to contain a conductive layer (a layer of conductive carbon) and a substance derived from P1 (including reaction products of P1) impregnated into the conductive layer.

[0129] [Coating treatment of negative electrode active material 1-2] A P1 aqueous solution was prepared by adding 0.77% by mass of P1 to 17 mL of pure water and mixing. A paste was obtained by mixing 31 g of active material particles (a0) with the P1 aqueous solution. Next, the paste was vacuum-dried at 100°C for 24 hours. This reacted P1 to form siloxane bonds, yielding a powdered negative electrode active material (a1-2).

[0130] Observation of the cross-section of the negative electrode active material (a1-2) using a TEM-EDX instrument (JEOL Ltd., JEM-F200) confirmed that a surface layer was formed on Si-containing lithium silicate composite oxide particles. The surface layer was found to contain a conductive layer (a layer of conductive carbon) and a substance derived from P1 (including reaction products of P1) that had permeated the conductive layer.

[0131] [Coating treatment of negative electrode active material 2-1] A solution with a pH of approximately 4.5 (hereinafter referred to as "mother liquor") was prepared by mixing 342 mL of ethanol, 10 mL of pure water, and 326 μL of hydrochloric acid (concentration: 37% by mass). 0.5% by mass of compound C was added to the mother liquor and mixed to prepare a solution of compound C. Next, 22 g of active material particles (a0) were mixed with the compound C solution to form a suspension, which was stirred at 50°C for 24 hours using a stirring bar. The suspension was then filtered by suction using a PTFE membrane filter and rinsed with 500 mL of ethanol, followed by 500 mL of pure water. The recovered particles were vacuum-dried at 100°C for 24 hours to obtain the negative electrode active material (a2-1). A cross-section of this negative electrode active material (a2-1) was observed using a TEM-EDX apparatus (JEOL Ltd., JEM-F200). The results confirmed the formation of a surface layer on the Si-containing lithium silicate composite oxide particles. We confirmed that the surface layer contains a conductive layer (a layer of conductive carbon) and a substance derived from compound C (including reaction products of compound C) that has permeated the conductive layer.

[0132] [Coating treatment of negative electrode active material 2-2] A compound C aqueous solution was prepared by adding 0.6% by mass of compound C to 17 mL of pure water and mixing. 31 g of active material particles (a0) and the compound C aqueous solution were mixed to obtain a paste. Next, the paste was vacuum-dried at 100°C for 24 hours to obtain powdered negative electrode active material (a2-2). A cross-section of this negative electrode active material (a2-2) was observed using a TEM-EDX apparatus (JEOL Ltd., JEM-F200). As a result, it was confirmed that a surface layer was formed on the Si-containing lithium silicate composite oxide particles. The surface layer was found to contain a conductive layer (a layer of conductive carbon) and a substance derived from compound C (including reaction products of compound C) impregnated into the conductive layer.

[0133] [Fabrication of the negative electrode] A mixture of active materials containing negative electrode active material (a1-1) and graphite in a mass ratio of negative electrode active material (a1-1):graphite = 5:95 was mixed with sodium salt of carboxymethylcellulose (CMC-Na) and styrene-butadiene rubber (SBR) in a mass ratio of active material mixture:CMC-Na:SBR = 97.5:1.0:1.5, and water was added to obtain a mixture. This mixture was stirred using a mixer (Primix, TK Hibiscus Mix) to prepare a negative electrode slurry. Next, the negative electrode slurry was applied to both sides of a copper foil (negative electrode current collector), the coating was dried, and then rolled to create a surface on both sides of the copper foil with a density of 1.6 g / cm³. 3 A negative electrode was obtained in which a negative electrode mixture layer was formed.

[0134] [Fabrication of the positive electrode] Lithium cobalt oxide, acetylene black (HS100, manufactured by Denki Kagaku Kogyo Co., Ltd.), and polyvinylidene fluoride (PVdF) were mixed in a mass ratio of lithium cobalt oxide:acetylene black:PVdF = 98.7:0.7:0.6. N-methyl-2-pyrrolidone (NMP) was added to the mixture as a dispersion medium, and then the mixture was stirred using a mixer (TK Hibiscus Mix, manufactured by Primix Co., Ltd.) to prepare a positive electrode slurry. Next, the positive electrode slurry was applied to both sides of an aluminum foil (positive electrode current collector), the coating was dried, and then rolled with a rolling mill to create a positive electrode slurry with a density of 3.6 g / cm³ on both sides of the positive electrode current collector. 3A positive electrode was fabricated with a positive electrode mixture layer formed thereon.

[0135] [Preparation of non-aqueous electrolyte solution] A non-aqueous electrolyte was prepared by adding 1.3 mol / liter of lithium hexafluoride phosphate (LiPF6) to a mixed solvent prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of EC:EMC:DMC = 4:1:15.

[0136] [Fabrication of non-aqueous electrolyte secondary batteries] Tabs were attached to each of the electrodes mentioned above. Next, a wound electrode group was fabricated by spirally winding the positive and negative electrodes with a separator between them. At this time, the electrode plates were wound so that the tabs were located on the outermost part. The resulting electrode group was inserted into an enclosure made of aluminum laminate sheet measuring 62 mm in height and 35 mm in width, and vacuum-dried at 105°C for 2 hours. Next, the non-aqueous electrolyte was injected into the enclosure, and the opening of the enclosure was sealed. In this way, a battery (A1-1), which is a non-aqueous electrolyte secondary battery, was fabricated. The design capacity of this battery was 360 mAh.

[0137] <Battery (A1-2)> Battery (A1-2) was fabricated under the same conditions as battery (A1-1), except that negative electrode active material (a1-2) was used instead of negative electrode active material (a1-1).

[0138] <Battery (A2-1)> Battery (A2-1) was fabricated under the same conditions as battery (A1-1), except that negative electrode active material (a2-1) was used instead of negative electrode active material (a1-1).

[0139] <Battery (A2-2)> Battery (A2-2) was fabricated under the same conditions as battery (A1-1), except that negative electrode active material (a2-2) was used instead of negative electrode active material (a1-1). <Battery B> Comparative example battery B was fabricated under the same conditions as battery (A1-1), except that active material particles (a0) were used instead of the negative electrode active material (a1-1).

[0140] (Charge / Discharge Cycle Characteristics) The above non-aqueous electrolyte secondary battery underwent a total of 400 charge-discharge cycles at a temperature of 25°C. Each charge-discharge cycle consisted of four sets of 100 charge-discharge cycles. Each set of charge-discharge cycles was performed by first performing one charge-discharge cycle under charge-discharge condition 1, then one charge-discharge cycle under charge-discharge condition 2, and finally repeating 98 charge-discharge cycles under charge-discharge condition 3.

[0141] [Charge / discharge condition 1] Constant current charging was performed at a constant current of 0.3C (1C is the current value that discharges the design capacity in one hour) until the battery voltage reached 4.2V, and then constant voltage charging was performed at a constant voltage of 4.2V until the current value was 0.02C. After a 20-minute pause, constant current discharge was performed at a constant current of 0.05C until the battery voltage reached 2.5V, followed by a 20-minute pause. [Charge / discharge condition 2] Constant current charging was performed at a constant current of 0.05C until the battery voltage reached 4.2V, and then constant voltage charging was performed at a constant voltage of 4.2V until the current value was 0.02C. After a 20-minute pause, constant current discharge was performed at a constant current of 0.5C until the battery voltage reached 2.5V, followed by a 20-minute pause. Subsequently, constant current discharge was performed at a constant current of 0.2C until the battery voltage reached 2.5V, followed by a 20-minute pause. [Charge / discharge condition 3] Constant current charging was performed at a constant current of 0.5C until the battery voltage reached 4.2V, and then constant voltage charging was performed at a constant voltage of 4.2V until the current value was 0.05C. After a 20-minute pause, constant current discharge was performed at a constant current of 0.7C until the battery voltage reached 2.5V, followed by a 20-minute pause.

[0142] [Capacity retention rate after 400 cycles] The discharge capacity at the 3rd cycle and the discharge capacity at the 400th cycle were measured under the above charge-discharge conditions, and the capacity retention rate after 400 cycles was calculated using the following formula. The results are shown in Table 1.

[0143] Capacity retention rate after 400 cycles (%) = (Discharge capacity at 400 cycles / Discharge capacity at 3 cycles) × 100

[0144] [Table 1]

[0145] Battery B is a comparative example battery, while the others are batteries according to this disclosure. Batteries A1-1 to A2-2 according to this disclosure were able to suppress the decrease in capacity retention rate associated with charge-discharge cycles compared with comparative example battery B. In batteries A1-1 to A2-2, the surface of the negative electrode active material (a1-1) to (a2-2) is protected by the reaction product of compound (1). Therefore, it is thought that the reaction (side reaction) between Si and the electrolyte is suppressed, and the decrease in capacity retention rate is suppressed. [Industrial applicability]

[0146] This disclosure can be used for negative electrode active materials for non-aqueous electrolyte secondary batteries, and for non-aqueous electrolytes using the same. Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention. [Explanation of Symbols]

[0147] 1a: Positive electrode mixture layer, 1b: Positive electrode current collector, 1c: Positive electrode tab lead, 2a: Negative electrode mixture layer, 2b: Negative electrode current collector, 2c: Negative electrode tab lead, 4: Electrode plate group, 5: Outer case, 6: Insulating tab film, 10: Positive electrode, 20: Negative electrode, 30: Separator, 100: Non-aqueous electrolyte secondary battery

Claims

1. A negative electrode active material for a non-aqueous electrolyte secondary battery, Silicon-containing active material particles, The active material particles include a surface layer formed on the surface of the active material particles, The surface layer contains reaction products obtained when the compound reacts to form siloxane bonds. The aforementioned compound comprises a structure represented by Si-R1-Si, The aforementioned R1 is one of the following: -(CH2) p S n (CH2) q - (1≦n≦6, 2≦p≦4, 2≦q≦4), -(CH2) p O(CH2) q - (2≦p≦4, 2≦q≦4), -(CH2) p O(CH2) r O(CH2) q - (2≦p≦4, 2≦q≦4, 2≦r≦4), and -(CH2) p NH(CH2) q - (2≦p≦4, 2≦q≦4) (where n, p, q, and r are each natural numbers). One of the two Si atoms contains an alkoxy group or an oxyalkylene group having 1 to 6 carbon atoms -O-(C ｘ１ H ２ｘ１＋１ O ｙ１ At least one atomic group selected from the group consisting of a group represented by (x1 is an integer between 2 and 6 and y1 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded, The other of the two Si components contains an alkoxy group and an oxyalkylene group having 1 to 6 carbon atoms -O-(C ｘ２ H ２ｘ２＋１ O ｙ２ A negative electrode active material for a non-aqueous electrolyte secondary battery, to which at least one atomic group selected from the group consisting of a group represented by (x2 is an integer between 2 and 6 and y2 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded.

2. The negative electrode active material according to claim 1, wherein the compound is a compound represented by the following formula (1). 【Chemistry 1】 In formula (1), at least one selected from the group consisting of R2, R3, and R4 is each independently an alkoxy group having 1 to 6 carbon atoms, an oxyalkylene group containing -O-(C ｘ１ H ２ｘ１＋１ O ｙ１ ), a group represented by ) (x1 is an integer of 2 or more and 6 or less, y1 is an integer of 1 or more and 3 or less), a chloro group, or a hydroxyl group. At least one selected from the group consisting of R5, R6, and R7 is each independently an alkoxy group having 1 to 6 carbon atoms, an oxyalkylene group containing -O-(C ｘ２ H ２ｘ２＋１ O ｙ２ ), a group represented by ) (x2 is an integer of 2 or more and 6 or less, y2 is an integer of 1 or more and 3 or less), a chloro group, or a hydroxyl group. The remainder of R2 to R7 are each independently a hydrocarbon group having 1 to 6 carbon atoms, a hydrogen atom, or a group represented by C ｘ３ H ２ｘ３＋ｙ３＋１ N ｙ３ O ｚ３ S ｗ３ (x3 is an integer of 1 or more and 6 or less, y3 is an integer of 0 or more and 3 or less, z3 is an integer of 0 or more and 3 or less, w3 is an integer of 0 or more and 3 or less, and 1 ≤ y3 + z3 + w3). R2 to R7 may be the same or different.]

3. The negative electrode active material according to claim 2, wherein in formula (1), R2 to R7 are methoxy groups or ethoxy groups.

4. The negative electrode active material according to claim 1, wherein the surface layer contains conductive carbon.

5. The active material particles are Li ｘ SiO ｙ The negative electrode active material according to claim 1, which is a composite particle comprising a lithium silicate phase represented by (0 < x ≤ 4, 0 < y ≤ 4) and a silicon phase dispersed in the lithium silicate phase.

6. The negative electrode active material according to claim 5, wherein the crystallite size of the silicon phase is in the range of 1 nm to 1000 nm.

7. The negative electrode active material according to claim 1, wherein the active material particles include a carbon phase and a silicon phase dispersed within the carbon phase.

8. It includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. A non-aqueous electrolyte secondary battery comprising the negative electrode active material described in any one of claims 1 to 7.

9. A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, A first step involves bringing a compound, or a liquid in which the compound is dissolved, into contact with silicon-containing active material particles. The process includes a second step of reacting the compound so as to form siloxane bonds while the compound or the liquid is in contact with the active material particles, The aforementioned compound comprises a structure represented by Si-R1-Si, The aforementioned R1 is one of the following: -(CH2) p S n (CH2) q - (1≦n≦6, 2≦p≦4, 2≦q≦4), -(CH2) p O(CH2) q - (2≦p≦4, 2≦q≦4), -(CH2) p O(CH2) r O(CH2) q - (2≦p≦4, 2≦q≦4, 2≦r≦4), and -(CH2) p NH(CH2) q - (2≦p≦4, 2≦q≦4) (where n, p, q, and r are each natural numbers). One of the two Si atoms contains an alkoxy group or an oxyalkylene group having 1 to 6 carbon atoms -O-(C ｘ１ H ２ｘ１＋１ O ｙ１ At least one atomic group selected from the group consisting of a group represented by (x1 is an integer between 2 and 6 and y1 is an integer between 1 and 3), a chloro group, and a hydroxyl group is bonded, The other of the two Si components contains an alkoxy group and an oxyalkylene group having 1 to 6 carbon atoms -O-(C ｘ２ H ２ｘ２＋１ O ｙ２ ) represented by a base (x² is 2 or more and 6 or less A method for producing a negative electrode active material, wherein at least one atomic group selected from the group consisting of a chloro group and a hydroxyl group (where y2 is an integer between 1 and 3) is bonded to the negative electrode active material.

10. The manufacturing method according to claim 9, wherein the compound is a compound represented by the following formula (1). 【Chemistry 2】 [In formula (1), at least one selected from the group consisting of R2, R3, and R4 is independently an alkoxy group or an oxyalkylene group having 1 to 6 carbon atoms -O-(C ｘ１ H ２ｘ１＋１ O ｙ１ The group is represented by (x1 is an integer between 2 and 6 and y1 is an integer between 1 and 3), a chloro group, or a hydroxyl group. At least one selected from the group consisting of R5, R6, and R7 is independently an alkoxy group or an oxyalkylene group having 1 to 6 carbon atoms -O-(C ｘ２ H ２ｘ２＋１ O ｙ２ The group is represented by (x2 is an integer between 2 and 6 and y2 is an integer between 1 and 3), a chloro group, or a hydroxyl group. The remaining R2 to R7 are each independently a hydrocarbon group with 1 to 6 carbon atoms, a hydrogen atom, or C ｘ３ H ２ｘ３＋ｙ３＋１ N ｙ３ O ｚ３ S ｗ３ The base is represented by (x³ is an integer between 1 and 6, y³ is an integer between 0 and 3, z³ is an integer between 0 and 3, w³ is an integer between 0 and 3, and 1 ≤ y³ + z³ + w³). R² to Rₙ can be the same or different.

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