Lithium supplement agent and preparation method and application thereof

Abstract

The invention discloses a lithium supplement agent and a preparation method and application thereof. Relates to the technical field of lithium ion battery lithium supplementation agents. The lithium supplement agent comprises the following structure: a lithium-containing matrix; the inner coating layer coats the outer surface of the lithium-containing matrix; the outer coating layer coats the outer surface of the inner coating layer; the inner coating layer comprises the following components: La (1-x) A (1 + x) BO (4-y); and the outer coating layer comprises the following components: MQO (3-z). The positive electrode lithium supplementing agent provided by the invention is a lithium supplementing agent co-coated with two perovskite materials, and the two perovskite materials are lithium and oxygen dual-ion conductors, so that the separation of lithium ions in the lithium supplementing agent can be promoted, and the utilization rate of the lithium supplementing agent is improved while gas production is inhibited.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium supplementation, and in particular to a lithium supplementation agent and a preparation method and application thereof. Background Art

[0002] Lithium-ion battery is an important energy storage device widely used in modern electronic devices and electric vehicles. It consists of four parts: positive electrode, negative electrode, electrolyte and separator. It uses the reciprocating migration of lithium ions between positive and negative electrode materials to achieve the storage and release of electrical energy. The positive electrode usually uses oxides (such as lithium cobalt oxide, nickel cobalt manganese oxide, etc.), the negative electrode uses materials such as graphite or graphene, the electrolyte is a liquid or solid medium that conducts ions, and the separator prevents the positive and negative electrodes from directly contacting each other.

[0003] As a key component of lithium-ion batteries, lithium supplements are commonly composed of compounds such as cobalt oxide and nickel oxide. Its main function is to replenish the structural changes in the positive electrode materials (such as oxides) caused by the flow of lithium ions during the charge and discharge cycle of the battery by releasing and absorbing lithium ions. This process ensures the long-term stable operation and efficient energy storage capabilities of the battery.

[0004] During use, the lithium ions in the lithium supplement molecules are extracted from the positive electrode material during the battery charging process and transferred to the negative electrode material through the electrolyte. During the discharge process, the lithium ions migrate in the opposite direction and are re-embedded into the positive electrode material. This lithium ion exchange between positive and negative electrode materials is the basis for lithium-ion batteries to achieve cyclic charging and discharging.

[0005] However, the application of lithium supplements also faces some challenges, one of which is the problem of gas generation. Under certain working conditions, such as overcharging or high temperature environment, the chemical components in the lithium supplement may react to release gases such as hydrogen and oxygen. The accumulation of these gases may cause the internal pressure of the battery to increase, which may cause the battery to swell, rupture or even safety accidents. In addition, the generated gas may also react with the components in the electrolyte, causing changes in the internal environment of the battery, thereby affecting the long-term stability and cycle life of the battery.

[0006] Based on this, there is an urgent need to develop a safe lithium supplement with low gas production. Summary of the invention

[0007] The object of the present invention is to provide a lithium supplement which is safe, produces little gas, and can improve the cycle performance of a battery.

[0008] A first aspect of the present invention is:

[0009] A lithium supplement is provided.

[0010] A second aspect of the present invention is:

[0011] Provided is a method for preparing a lithium supplement.

[0012] The third aspect of the present invention is:

[0013] Application of the lithium supplement.

[0014] The present invention also provides a battery, comprising the lithium supplement.

[0015] Specifically, the technical solution adopted according to the first aspect of the present invention is:

[0016] A lithium supplement comprises the following structure:

[0017] A lithium-containing matrix;

[0018] An inner coating layer, coating the outer surface of the lithium-containing substrate;

[0019] An outer coating layer, covering the outer surface of the inner coating layer;

[0020] The components of the inner coating layer include: La (1-x) A (1+x) BO (4-y) ;

[0021] The components of the outer coating layer include: MQO (3-z) ;

[0022] Wherein, the A element includes at least one of Sr, Ba and Ca;

[0023] Wherein, the B element includes at least one of Cu, Co and Ni;

[0024] Wherein, the M element includes at least one of La, Sr, Ba and Ca;

[0025] Wherein, Q element is an element with a valence state less than or equal to +3;

[0026] Among them, x, y>0, z≤1.

[0027] According to the embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0028] The positive electrode lithium supplement provided by the present invention is a lithium supplement co-coated with two perovskite materials. The two perovskite materials are dual ion conductors of lithium and oxygen, which can promote the release of lithium ions in the lithium supplement, and improve the utilization rate of the lithium supplement while inhibiting gas production.

[0029] Among them, the components of the inner coating layer include La (1-x) A (1+x) BO (4-y), its perovskite-like structure contains a large number of oxygen vacancies, which can exist in the form of oxygen vacancies or oxygen interstitials, and can greatly absorb the oxygen generated by the lithium supplement during the charging and discharging process;

[0030] Among them, the components of the outer coating layer include MQO (3-z) In its perovskite structure, the oxygen defect form is only oxygen vacancies. While absorbing the oxygen released by the lithium supplement, the oxygen concentration of the outer coating layer increases, forming a stable defect-free perovskite structure MQO 3 , which is more stable than the inner coating layer, thus further inhibiting the continued outward diffusion of oxygen;

[0031] In summary, in the lithium supplement agent of the present invention, the two perovskite coating layers existing simultaneously can be coupled with each other and are both lithium ion conductors, which can improve the use efficiency of the lithium supplement agent.

[0032] According to one embodiment of the present invention, the components of the outer coating layer include: MQO (3-z) , where the ionic radius of the Q element is less than 0.1 nm.

[0033] According to one embodiment of the present invention, La (1-x) A (1+x) BO (4-y) The selection of A and B elements in MQO (3-z) The choice of M and Q elements affects whether the perovskite structure can be formed and the amount of oxygen vacancies, which in turn affects the gas production and electrical properties of the lithium supplement during use.

[0034] According to one embodiment of the present invention, the inner coating layer partially covers (non-uniformly covers) the outer surface of the lithium-containing matrix, so that the coating layer is more tightly combined with the lithium-containing matrix.

[0035] According to one embodiment of the present invention, the outer coating layer densely coats (uniformly coats) the outer surface of the inner coating layer, which can minimize the contact between the lithium supplement of the present invention and the electrolyte and reduce the occurrence of side reactions.

[0036] The inner coating layer uses a simple and mature sintering process to form a perovskite-like La with stronger oxygen storage capacity on the surface of the substrate. (1-x) A (1+x) BO (4-y) ; The outer coating layer is processed by a wet process to form a dense perovskite coating layer MQO on the outermost layer (3-z) , which can minimize the contact between the lithium supplement and the electrolyte and reduce the occurrence of side reactions. At the same time, the two coating layers have similar structures. According to the principle of "like dissolves like", there will be no obvious separation of the coating layers, which will not cause the structural failure and destruction of the coating layers.

[0037] According to one embodiment of the present invention, the mass of the inner coating layer is 0.5%-2.0% of the mass of the lithium supplement agent.

[0038] According to one embodiment of the present invention, in the lithium supplement of the present invention, the inner coating layer is a perovskite-like structure, and the outer coating layer is a perovskite-like structure. The two structures are similar, which will result in an additional rock salt layer on the perovskite-like microstructure, and the rock salt layer has a good coupling effect. Since the inner coating layer components include La (1-x) A (1+x) BO (4-y) The outer coating layer includes MQO (3-z) , therefore, the middle is connected through the rock salt layer (La / A / MO).

[0039] According to one embodiment of the present invention, the components of the lithium-containing matrix include the following materials: LiFeO 4 , Li 2 NiO 2 , Li 6 CoO 4 At least one of .

[0040] Specifically, the technical solution adopted according to the second aspect of the present invention is:

[0041] A method for preparing the lithium supplement comprises the following steps:

[0042] S1 solid phase mixed matrix material, salt containing La element, salt containing A element and salt containing B element, and sintered to obtain a semi-finished product containing lithium-containing matrix and inner coating layer;

[0043] S2: mixing the semi-finished product containing the lithium-containing matrix and the inner coating layer, the salt containing the M element and the salt containing the Q element with a solvent, evaporating the solvent and then sintering to obtain the lithium supplement agent.

[0044] According to the embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0045] In the preparation method of the present invention, the inner coating layer is prepared by dry sintering to form an inner coating layer with stronger oxygen storage capacity, and the inner coating layer is non-uniformly coated (partially coated) on the surface of the lithium-containing matrix, so that the inner coating layer and the lithium-containing matrix are more tightly combined; the outer coating layer is prepared by wet sintering to form a dense outer coating layer, and the outer coating layer is uniformly coated (densely coated) on the outermost layer, which can minimize the contact between the lithium supplement agent of the present invention and the electrolyte and reduce the generation of side reactions.

[0046] It should be noted that the present invention adopts the steps of dry sintering first and then wet sintering to form a coating structure with a non-uniform inner layer and a uniform outer layer. Because when the steps of wet sintering first and then dry sintering are adopted, the temperature of the fire coating sintering process is much higher than that of the wet method, which will cause the uniform coating layer prepared previously to be destroyed, and it is impossible to achieve a uniform inner coating layer and a non-uniform outer coating layer, and finally only a structure with non-uniform inner and outer layers will be obtained.

[0047] According to one embodiment of the present invention, in step S1, the sintering temperature is 800-1200°C.

[0048] According to one embodiment of the present invention, in step S1, the sintering temperature is 900-1000°C.

[0049] According to one embodiment of the present invention, in step S1, the sintering time is 5-8 hours.

[0050] According to one embodiment of the present invention, in step S2, the sintering temperature is 400-600°C.

[0051] According to one embodiment of the present invention, in step S2, the sintering time is 6-10 hours.

[0052] According to one embodiment of the present invention, in step S2, the temperature used for evaporating the solvent is 80-100°C.

[0053] According to one embodiment of the present invention, the solvent comprises deionized water.

[0054] Another aspect of the present invention further provides a battery, which includes the lithium supplement agent as described in the embodiment of the first aspect. Since the application adopts all the technical solutions of the lithium supplement agent, it at least has all the beneficial effects brought by the technical solutions of the above embodiments.

[0055] According to one embodiment of the present invention, the positive electrode material of the battery is lithium cobalt oxide, and the mass ratio of the lithium cobalt oxide to the lithium supplement is 98-100:2-3.

[0056] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0058] Figure 1 Schematic diagram of the structure of the lithium supplement in Example 1. DETAILED DESCRIPTION

[0059] In the description of the present invention, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0060] In the description of the present invention, it should be understood that descriptions involving orientation, such as orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the embodiments, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0061] The words "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0062] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0063] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0064] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0065] Example 1

[0066] A lithium supplement, the structural diagram of which is as follows Figure 1 As shown (the schematic diagram mainly illustrates that the inner coating layer is only a partial coating, and the inner coating layer is not necessarily spherical, and the schematic diagram takes a spherical shape as an example), specifically, it includes the following structures:

[0067] Lithium-containing matrix Li 6 CoO 4 ;

[0068] An inner coating layer partially covers the outer surface of the lithium-containing substrate;

[0069] An outer coating layer densely covers the outer surface of the inner coating layer;

[0070] The components of the inner coating layer are: La 0.8 Ba 1.2 CoO 3.9 ;

[0071] The components of the outer coating layer are: LaCoO 3 .

[0072] A method for preparing the lithium supplement comprises the following steps:

[0073] S1 was added with La according to the molar ratio of metal elements La:Ba:Co=0.8:1.2:1 2 O 3 , BaCO 3 ,Co 3 O 4 , and the matrix material Li 6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent;

[0074] S2 is mixed with La(CH 3 COO 3 and Co(CH 3 COO 3 , adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 and Co(CH 3 COO 3 The mass fraction of each is 1% of the mass of the semi-finished product, the water is evaporated with stirring at 100° C., the obtained powder is ground, and sintered at 400° C. in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0075] Example 2

[0076] The difference between Example 2 and Example 1 is that the component of the inner coating layer in Example 2 is La 0.8 Ca 1.2 CoO 3.9 .

[0077] Specific:

[0078] A lithium supplement comprises the following structure:

[0079] A lithium-containing matrix;

[0080] An inner coating layer non-uniformly covers the outer surface of the lithium-containing substrate;

[0081] An outer coating layer uniformly covers the outer surface of the inner coating layer;

[0082] The components of the inner coating layer are: La 0.8 Ca 1.2 CoO 3.9 ;

[0083] The components of the outer coating layer are: LaCoO 3 .

[0084] A method for preparing the lithium supplement comprises the following steps:

[0085] S1 was mixed with La at a metal element molar ratio of 0.8:1.2:1 2 O 3 , CaCO 3 ,Co 3 O 4 , and the matrix material Li 6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent;

[0086] S2 is mixed with La(CH 3 COO 3 and Co(CH 3 COO 3 , adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 and Co(CH 3 COO 3 The mass fraction of each is 1% of the mass of the semi-finished product, the water is evaporated with stirring at 100° C., the obtained powder is ground, and sintered at 400° C. in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0087] Example 3

[0088] The difference between Example 3 and Example 1 is that the component of the inner coating layer in Example 3 is La 0.8 Sr 1.2 CoO 3.9 .

[0089] Specific:

[0090] A lithium supplement comprises the following structure:

[0091] A lithium-containing matrix;

[0092] An inner coating layer non-uniformly covers the outer surface of the lithium-containing substrate;

[0093] An outer coating layer uniformly covers the outer surface of the inner coating layer;

[0094] The components of the inner coating layer are: La 0.8 Sr 1.2 CoO 3.9 ;

[0095] The components of the outer coating layer are: LaCoO 3 .

[0096] A method for preparing the lithium supplement comprises the following steps:

[0097] S1 was mixed with La at a metal element molar ratio of 0.8:1.2:1 2 O 3 , SrO, Co 3 O 4 , and the matrix material Li 6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent;

[0098] S2 is mixed with La(CH 3 COO 3 and Co(CH 3 COO 3 , adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 and Co(CH 3 COO 3 The mass fraction of each is 1% of the mass of the semi-finished product, the water is evaporated with stirring at 100° C., the obtained powder is ground, and sintered at 400° C. in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0099] Example 4

[0100] The difference between Example 4 and Example 1 is that the components of the inner coating layer in Example 4 are: La 0.8 Ba 1.2 NiO 3.9 .

[0101] Specific:

[0102] A lithium supplement comprises the following structure:

[0103] A lithium-containing matrix;

[0104] An inner coating layer non-uniformly covers the outer surface of the lithium-containing substrate;

[0105] An outer coating layer uniformly covers the outer surface of the inner coating layer;

[0106] The components of the inner coating layer are: La 0.8 Ba 1.2 NiO 3.9 ;

[0107] The components of the outer coating layer are: LaCoO 3 .

[0108] A method for preparing the lithium supplement comprises the following steps:

[0109] S1 was mixed with La at a metal element molar ratio of 0.8:1.2:1 2 O 3 , BaCO 3 , Ni(OH) 3 , and the matrix material Li 6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent;

[0110] S2 is mixed with La(CH 3 COO 3 and Co(CH 3 COO 3 , adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 and Co(CH 3 COO 3 The mass fraction of each is 1% of the mass of the semi-finished product, the water is evaporated with stirring at 100° C., the obtained powder is ground, and sintered at 400° C. in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0111] Example 5

[0112] The difference between Example 5 and Example 1 is that the components of the inner coating layer in Example 5 are: La 0.8 Ba 1.2 CuO 3.9 .

[0113] Specific:

[0114] A lithium supplement comprises the following structure:

[0115] A lithium-containing matrix;

[0116] An inner coating layer non-uniformly covers the outer surface of the lithium-containing substrate;

[0117] An outer coating layer uniformly covers the outer surface of the inner coating layer;

[0118] The components of the inner coating layer are: La 0.8 Ba 1.2 CuO 3.9 ;

[0119] The components of the outer coating layer are: LaCoO 3 .

[0120] A method for preparing the lithium supplement comprises the following steps:

[0121] S1 was mixed with La at a metal element molar ratio of 0.8:1.2:1 2 O 3 , BaCO 3 , CuO, and matrix material Li 6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent;

[0122] S2 is mixed with La(CH 3 COO 3 and Co(CH 3 COO 3 , adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 and Co(CH 3 COO 3 The mass fraction of each is 1% of the mass of the semi-finished product, the water is evaporated with stirring at 100° C., the obtained powder is ground, and sintered at 400° C. in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0123] Example 6

[0124] The difference between Example 6 and Example 1 is that the composition of the outer coating layer in Example 6 is: LaMgO 2.5 .

[0125] Specific:

[0126] A lithium supplement comprises the following structure:

[0127] A lithium-containing matrix;

[0128] An inner coating layer non-uniformly covers the outer surface of the lithium-containing substrate;

[0129] An outer coating layer uniformly covers the outer surface of the inner coating layer;

[0130] The components of the inner coating layer are: La 0.8 Ba 1.2 CoO 3.9 ;

[0131] The components of the outer coating layer are: LaMgO 2.5 .

[0132] A method for preparing the lithium supplement comprises the following steps:

[0133] S1 was mixed with La at a metal element molar ratio of 0.8:1.2:1 2 O 3 , BaCO 3 ,Co 3 O 4 , and the matrix material Li 6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent;

[0134] S2 is mixed with La(CH 3 COO 3 and Mg(CH3COO)2, adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 The mass fraction of Mg(CH3COO)2 is 1% of the mass of the semi-finished product. The water is evaporated by stirring at 100°C, the obtained powder is ground, and sintered at 400°C in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0135] Example 7

[0136] The difference between Example 7 and Example 1 is that the composition of the outer coating layer in Example 7 is: LaNaO 2 .

[0137] Specific:

[0138] A lithium supplement comprises the following structure:

[0139] A lithium-containing matrix;

[0140] An inner coating layer non-uniformly covers the outer surface of the lithium-containing substrate;

[0141] An outer coating layer uniformly covers the outer surface of the inner coating layer;

[0142] The components of the inner coating layer are: La 0.8 Ba 1.2 CoO 3.9 ;

[0143] The components of the outer coating layer are: LaNaO 2 .

[0144] A method for preparing the lithium supplement comprises the following steps:

[0145] S1 was mixed with La at a metal element molar ratio of 0.8:1.2:1 2 O 3 , BaCO 3 ,Co 3 O 4 , and the matrix material Li 6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent;

[0146] S2 is mixed with La(CH 3 COO 3 and CH 3 COONa, adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 and CH 3 The mass fraction of COONa is 1% of the mass of the semi-finished product. The water is evaporated by stirring at 100° C., the obtained powder is ground, and sintered at 400° C. in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0147] Example 8

[0148] The only difference between Example 8 and Example 1 is that in Example 8, the sintering temperature in step S1 is 1100° C. and the sintering time is 5 h; and the sintering time in step S2 is 600° C. and the sintering time is 8 h.

[0149] The rest is the same as Example 1 and will not be described in detail.

[0150] Example 9

[0151] The only difference between Example 9 and Example 1 is that in Example 9, the mass of the inner coating layer is 0.8% of the mass of the lithium supplement agent.

[0152] The rest is the same as Example 1 and will not be described in detail.

[0153] Example 10

[0154] The difference between Example 10 and Example 1 is that in Example 10, the mass of the inner coating layer is 1% of the mass of the lithium supplement agent.

[0155] The rest is the same as Example 1 and will not be described in detail.

[0156] Embodiment 11

[0157] The difference between Example 11 and Example 1 is that in Example 11, the mass of the inner coating layer is 2% of the mass of the lithium supplement agent.

[0158] The rest is the same as Example 1 and will not be described in detail.

[0159] Comparative Example 1

[0160] The difference between Comparative Example 1 and Example 1 is that the lithium supplement agent in Comparative Example 1 is not coated, and only the lithium matrix Li 6 CoO 4 , without coating.

[0161] Comparative Example 2

[0162] The difference between Comparative Example 2 and Example 1 is that only step S1 is performed, and step S2 is not performed, so that the lithium supplement agent of Comparative Example 2 only contains the lithium-containing matrix and the inner coating layer.

[0163] Comparative Example 3

[0164] The difference between Comparative Example 3 and Example 1 is that only step S2 is performed, and step S1 is not performed, so that the lithium supplement agent of Comparative Example 3 only contains a lithium-containing matrix and an outer coating layer.

[0165] Comparative Example 4

[0166] The difference between Comparative Example 4 and Example 1 is that in step S1 of Comparative Example 4, La 2 O 3 , WO 3 and Co 3 O 4 The inner coating layer is prepared by: La:W:Co = 0.8:1.2:1 2 O 3 , WO 3 and Co 3 O 4 , and the matrix material Li6 CoO 4 Solid phase mixing is performed, and sintering is performed at 900° C. for 8 hours in an air atmosphere to obtain a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein the mass of the inner coating layer is 0.5% of the mass of the lithium supplement agent.

[0167] Comparative Example 5

[0168] The difference between Comparative Example 5 and Example 1 is that in step S2 of Comparative Example 5, La(CH 3 COO 3 and Zr(CH 3 COO 4 The outer coating layer is prepared by mixing La(CH 3 COO 3 and Zr(CH 3 COO 4 , adding a semi-finished product containing a lithium-containing matrix and an inner coating layer, wherein La(CH 3 COO 3 and Zr(CH 3 COO 4 The mass fraction of each is 1% of the mass of the semi-finished product, the water is evaporated with stirring at 100° C., the obtained powder is ground, and sintered at 400° C. in an air atmosphere for 6 hours to obtain the lithium supplement agent.

[0169] Performance Test:

[0170] The lithium supplement agents of Examples 1-11 and Comparative Examples 1-5 were mixed with the positive electrode lithium cobalt oxide material in a certain mass ratio, and soft-pack batteries were prepared through processes such as homogenization, coating, rolling, sheeting, winding and liquid injection.

[0171] Among them, the soft pack battery includes a positive electrode sheet, a negative electrode sheet and an electrolyte, and the preparation method is as follows:

[0172] 1) Preparation of positive electrode sheet: The positive electrode lithium cobalt oxide, the above-mentioned lithium supplement, the conductive agent Super-P, and the binder PVDF are mixed evenly in a mass ratio of 96:2:1:1 to form a positive electrode slurry, and the slurry is coated on an aluminum foil, dried at 85°C and rolled; then the strips are cut and the tabs are welded to form positive electrode sheets. The positive electrode sheets need to be weighed separately for subsequent testing and calculation of gram capacity;

[0173] 2) Preparation of negative electrode sheet: Graphite, conductive agent Super-P, thickener sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96:2:1:1 to form a slurry, which is coated on the current collector copper foil and dried at 85°C. The slurry is then rolled, stripped, and the pole ears are welded to form a negative electrode sheet.

[0174] 3) Preparation of electrolyte: Lithium hexafluorophosphate (LiPF 6 ) was dissolved in a mixed solvent consisting of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) (the mass ratio of the three was 1:2:1) to obtain LiPF 6 The concentration of the electrolyte is 1 mol / L.

[0175] 4) Preparation of soft-pack batteries: The positive electrode sheet, separator and negative electrode sheet are wound into a battery cell, with the separator located between the positive electrode sheet and the negative electrode sheet. The positive electrode is lead out by spot welding with an aluminum tab, and the negative electrode is lead out by spot welding with a nickel tab. The battery cell is then placed in an aluminum-plastic packaging bag, and the above-mentioned electrolyte is injected. After packaging, formation, capacity division, aging and other processes, a soft-pack battery is made.

[0176] The soft pack battery was tested as follows, and the test results are shown in Table 1:

[0177] 1) Test the gas production of the battery during the first charge and discharge;

[0178] Gas production test: Use Archimedes displacement method to test the volume change of battery cells to get the amount of gas. The volume change is measured by a dedicated sensor to measure the tension of the battery cell sample in water in real time, which is further converted into the battery cell volume, thereby obtaining the gas production.

[0179] Calculation formula:

[0180] ρ 水 V 电芯 +F 拉 =m 电芯 g;

[0181] V 产气量 =V 电芯 -V 0 .

[0182] Among them, ρ 水 represents the density of water, g is the acceleration due to gravity, V 电芯 is the volume of the cell after gas generation, F 拉 is the tension sensor reading, m 电芯 is the cell mass, V 产气量 is the gas production value obtained by the test, V 0 is the volume of the battery cell in its initial state.

[0183] 2) Discharge capacity and first coulombic efficiency: Place the battery in the test cabinet, charge at 0.2C constant current to 4.53V, and then charge at constant voltage to a cut-off current of 0.05C; after standing for 10 minutes, discharge at 0.2C to 3.0V, record the discharge capacity and coulombic efficiency, and calculate the material capacity per gram based on the discharge capacity and the weight of the positive electrode, C 克容 =C disch / m活性物质 ;

[0184] m 活性物质 =(m 极片 -m 铝箔 )*96%.

[0185] Among them C 克容 Indicates the gram capacity of the material, C disch Indicates the discharge capacity of the battery cell, m 活性物质 Indicates the mass of positive electrode active material, m 极片 Indicates the weight of the pole piece, m 铝箔 Indicates the weight of the current collector aluminum foil in the corresponding electrode, 96% of which is the proportion of active material in the coating.

[0186] 3) 45℃, 300cls cycle performance: Place the battery cell in a 45℃ incubator, charge at 1.0C constant current to 4.53V, then charge at constant voltage to a cutoff current of 0.05C, let it stand for 10min, and then discharge at 1.0C constant current to 3.0V. Repeat the above charge and discharge steps 300 times to test the material cycle performance.

[0187] The test results are shown in Table 1.

[0188] Table 1

[0189]

[0190] Examples 1 to 3 respectively use different inner coating layer compositions, wherein Example 1 is La 0.8 Ba 1.2 CoO 3.9 , Example 2 is La 0.8 Ca 1.2 CoO 3.9 , Example 3 is La 0.8 Sr 1.2 CoO 3.9 The discharge capacity of the soft-pack battery prepared by the lithium supplement agent of Examples 1 to 3 is more than 6 mAh / g higher than that of the comparative example, and the first coulombic efficiency and cycle performance are also greatly improved.

[0191] Compared with Examples 1 to 3, Examples 4 to 5 use different components of the inner coating layer, wherein Example 4 is La 0.8 Ba 1.2 NiO 3.9 , Example 5 is La 0.8 Ba 1.2 CuO 3.9 Although a coating layer containing oxygen vacancies can be formed, the structural stability is slightly worse than that of Examples 1 to 3.

[0192] Compared with Example 1, Examples 6 and 7 use different outer coating layer components, wherein Example 6 is LaMgO 2.5 , Example 7 is LaNaO 2 Since these two materials are not stable as outer coatings, the lithium supplement agent does not form a mechanism where the stability of the outer coating is greater than that of the inner coating. This means that although the inner coating has sufficient oxygen vacancies to absorb the oxygen generated by the lithium supplement agent during the charge and discharge process, the outer coating cannot effectively inhibit the diffusion of oxygen outward. Therefore, although the discharge capacity, first efficiency, and cycle of Examples 6 to 7 are still significantly improved compared with the comparative example, they are slightly worse than those of Examples 1 to 3.

[0193] Compared with Example 1, Example 8 adjusts the sintering temperature, and the effects of the inner and outer coating layers are not as good as those of Example 1. The effect of partial coating of the inner coating layer and dense coating of the outer coating layer is not strictly achieved. However, compared with the comparative example, its discharge capacity per gram, first efficiency and cycle are significantly improved.

[0194] Examples 9 to 11 adjusted the content of the coating material. As the coating amount increased, the coating layer thickness increased, and oxygen vacancies increased, which was somewhat helpful for gas production. However, since the coating layer was inactive, there was a slight loss in gram capacity and first efficiency, and the cycle performance was slightly improved.

[0195] In Comparative Examples 1 to 5, Comparative Example 1 was not coated; Comparative Example 2 did not contain an outer coating layer, resulting in no improvement in stability, but a significant decrease in gas production; Comparative Example 3 did not contain an inner coating layer, resulting in insufficient oxygen vacancies to absorb the oxygen generated by the lithium supplement during the charge and discharge process, and no significant improvement in gas production, but due to its dense coating layer, the cycle performance was improved; Comparative Example 4 used a metal salt of La 2 O 3 , WO 3 and Co 3 O 4 , it is difficult to form a perovskite-like structure, so the gas production of the material has no significant improvement, but due to the existence of the outer coating layer, the cycle performance is significantly improved; the metal salt used in comparative example 5 is La(CH 3 COO 3 and Zr(CH 3 COO 4 , which is not conducive to the formation of oxygen vacancies. Only the inner layer can store oxygen. The gas production of the material is slightly improved, but due to its dense coating, the cycle performance is improved.

[0196] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A lithium supplement, characterized in that: Includes the following structures: A lithium-containing matrix; An inner coating layer, coating the outer surface of the lithium-containing substrate; An outer coating layer, covering the outer surface of the inner coating layer; The components of the inner coating layer include: La (1-x) A (1+x) BO (4-y) ; The components of the outer coating layer include: MQO (3-z) ; wherein A includes at least one of Sr, Ba and Ca; Wherein, B includes at least one of Cu, Co and Ni; wherein M includes at least one of La, Sr, Ba and Ca; Wherein, Q element is an element with a valence state less than or equal to +3; Among them, x>0, y>0, z≤1.

2. A lithium supplement according to claim 1, characterized in that: The inner coating layer partially covers the outer surface of the lithium-containing substrate.

3. A lithium supplement according to claim 1, characterized in that: The outer coating layer densely covers the outer surface of the inner coating layer.

4. A lithium supplement according to claim 1, characterized in that: The mass of the inner coating layer is 0.5%-2.0% of the mass of the lithium supplement agent, and the mass of the outer coating layer is 0.5%-3.0% of the mass of the lithium supplement agent.

5. A lithium supplement according to claim 1, characterized in that: The lithium-containing matrix includes at least one of LiFeO4, Li2NiO2, and Li6CoO4.

6. A method for preparing the lithium supplement according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1 solid phase mixed matrix material, salt containing La element, salt containing A element and salt containing B element, and sintered to obtain a semi-finished product containing lithium-containing matrix and inner coating layer; S2: mixing the semi-finished product containing the lithium-containing matrix and the inner coating layer, the salt containing the M element and the salt containing the Q element with a solvent, evaporating the solvent and then sintering to obtain the lithium supplement agent.

7. The method according to claim 6, characterized in that: In step S1, the sintering temperature is 800-1200°C and the sintering time is 5-8h.

8. The method according to claim 6, characterized in that: In step S2, the sintering temperature is 400-600°C and the sintering time is 6-10 hours.

9. A battery, characterized in that: The invention comprises the lithium supplement according to any one of claims 1 to 5.

10. The battery according to claim 9, characterized in that: The positive electrode material of the battery is lithium cobalt oxide, and the mass ratio of the lithium cobalt oxide to the lithium supplement agent is 98-100:2-3.

Images