CN117012929A

CN117012929A - Composite lithium supplementing material and preparation method and application thereof

Info

Publication number: CN117012929A
Application number: CN202310992966.7A
Authority: CN
Inventors: 林律欢; 万远鑫; 孔令涌; 裴现一男; 谭旗清
Original assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Current assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Priority date: 2023-08-08
Filing date: 2023-08-08
Publication date: 2023-11-07

Abstract

The application discloses a composite lithium supplementing material and a preparation method and application thereof. The composite lithium supplementing material comprises iron lithium supplementing agent particles and a carbon coating layer,the Raman spectrum of the composite lithium supplementing material comprises a first characteristic peak, a second characteristic peak and a third characteristic peak, and the intensity I of the first characteristic peak ₁ Intensity of the second characteristic peak I ₂ Intensity of third characteristic peak I ₃ The following relationships are satisfied: i is not less than 0.80 ₁ /I ₂ ≤1.40、2.00≤I ₁ /I ₃ ≤6.50、1.50≤I ₂ /I ₃ Less than or equal to 6.00. The composite lithium supplementing material has high conductivity and structural stability, has good lithium supplementing effect, and can improve the reversible capacity and the cycle performance of a lithium battery.

Description

Composite lithium supplementing material and preparation method and application thereof

Technical Field

The application belongs to the technical field of battery materials, and particularly relates to a composite lithium supplementing material, and a preparation method and application thereof.

Background

SEI film can be generated in the first charging process of the lithium battery, and a large amount of Li is consumed ⁺ So that Li ⁺ Is greatly reduced in capacity, and Li extracted from the negative electrode during the first discharge ⁺ Much smaller than Li deintercalated from positive electrode upon charging ⁺ Resulting in reduced coulombic efficiency of the lithium battery, directly affecting the cycle life and energy density of the lithium battery. In order to solve the problem, the positive electrode lithium supplementing material is added into the positive electrode material to intercalate and deintercalate irreversible lithium, so that active lithium ions of the positive electrode material consumed for generating the SEI film are reduced, the irreversible capacity content of the lithium battery is reduced, and the energy density and the electrochemical performance of the lithium battery are improved.

However, the existing lithium supplementing materials often have the defects of low conductivity, unstable surface interface, high residual alkalinity and the like. In order to improve the electronic conductivity of the lithium-supplementing material, it is reported that the lithium-supplementing material is designed into a coating structure, for example, a coating layer with electrons is used for coating the particles of the lithium-supplementing material, so as to attempt to improve the performance of the lithium-supplementing material by carrying out surface interface coating modification on the lithium-supplementing material.

However, in the practical application process, the performances of the lithium supplementing materials with the coating structures, such as conductivity, still cannot meet the current application requirements, the residual alkali content is high, and the coating structure is unstable, so that the lithium supplementing effect of the lithium supplementing materials with the coating structures is affected, and the performances of the lithium ion battery, such as energy density, cannot be further improved.

Disclosure of Invention

The application aims to provide a composite lithium supplementing material, a preparation method and application thereof, and aims to solve the technical problem that the conductivity, the coating structure and other performances of the lithium supplementing material with the existing coating structure are difficult to further improve.

In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows:

in a first aspect, an embodiment of the present application provides a composite lithium-supplementing material. The composite lithium supplementing material comprises an iron-based lithium supplementing agent and a carbon material, wherein the carbon material coats iron-based lithium supplementing agent particles, a Raman spectrum of the composite lithium supplementing material comprises a first characteristic peak, a second characteristic peak and a third characteristic peak, and the intensity of the first characteristic peak is recorded as I ₁ The intensity of the second characteristic peak is denoted as I ₂ The intensity of the third characteristic peak is denoted as I ₃ ，I ₁ To I ₃ The following relationship is satisfied:

0.80≤I ₁ /I ₂ ≤1.40、2.00≤I ₁ /I ₃ ≤6.50、1.50≤I ₂ /I ₃ ≤6.00。

the composite lithium supplementing material of the embodiment of the application coats the surface of the iron-based lithium supplementing agent particles by the carbon coating layer, and enables the Raman spectrum of the composite lithium supplementing material of the embodiment of the application to have the I at the same time ₁ To I ₃ The three characteristic peaks of the indicated relation range of the lithium ion battery material provided by the embodiment of the application have high conductivity. The bonding strength between the carbon coating layer and the iron-based lithium supplementing agent particles can be enhanced, the overall structural stability and the surface-interface stability of the composite lithium supplementing material are improved, and meanwhile, the residual alkali content is obviously reduced, so that the lithium supplementing effect of the lithium supplementing material is improved, the internal resistance of a lithium battery is reduced, and the reversible capacity, the cycling stability and other electrochemical performances of the lithium battery are further improved.

In some embodiments, raman shift intervals corresponding to the first, second, and third characteristic peaks are respectively as follows:

the raman shift interval of the first characteristic peak is: 1343-1353cm ^-1 ；

The raman shift interval of the second characteristic peak is: 1580 cm to 1600cm ^-1 ；

The raman shift interval of the third characteristic peak is: 645-655 cm ^-1 。

In some embodiments, the carbon material forms a carbon coating layer having a thickness in the range of 1nm to 1 μm.

In some embodiments, the carbon material comprises at least one of carbon black, hard carbon, soft carbon, graphite, graphene oxide.

In some embodiments, the iron-based lithium supplement has a Dv50 particle size of 1 to 20 μm.

In some embodiments, the iron-based lithium supplement includes Li ₅ FeO ₄ 。

In some embodiments, the carbon coating layer comprises an amorphous carbon layer coating the iron-based lithium-compensating agent and a graphitized carbon layer coating the surface of the amorphous carbon layer; wherein, the thickness ratio of the amorphous carbon layer to the graphitized carbon layer is: 0.2 to 10:1.

in some embodiments, the composite lithium-supplementing material includes at least one of the following (1) to (6):

(1) Specific surface area of 0.1-100 m ² /g；

(2) Tap density of 0.8-2 g/cm ³ ；

(3) Residual alkalinity is more than 0 and less than or equal to 5wt%;

(4) The Dv50 particle size is 1-20 mu m;

(5) Dv99 is 10-50 mu m;

(6) The carbon content accounts for 0.1-20% of the total mass of the composite lithium supplementing material;

(7) The water absorption rate of the composite lithium supplementing material is 0-50 ppm/s in the environment with the standard atmospheric pressure, the temperature of 23-27 ℃ and the relative humidity of 10-50%.

In some embodiments, at 0.05C magnification: the first charge constant current ratio is more than 80%, wherein the constant current section charge specific capacity C1 under the voltage of 2.5-4.3V is more than 450mAh/g, and the total charge specific capacity C2 under the voltage of 4.3V is more than 465mAh/g.

In a second aspect, an embodiment of the present application provides a method for preparing a composite lithium-supplementing material. The preparation method of the composite lithium supplementing material comprises the following steps:

performing first mixing treatment on a carbon source and iron-based lithium supplementing agent particles to obtain a first mixture;

and (3) sintering the mixture to form a carbon coating layer on the surface of the iron-based lithium supplementing agent particles to obtain the composite lithium supplementing material.

The sintering treatment comprises a first sintering treatment and a second sintering treatment after the first sintering treatment, wherein the temperature of the first sintering treatment is 300-700 ℃, and the temperature of the second sintering treatment is higher than that of the first sintering treatment;

or;

performing second mixing treatment on the amorphous carbon precursor and the iron-based lithium supplementing agent particles to obtain a second mixture;

performing third sintering treatment on the second mixture to obtain amorphous carbon coated particles;

carrying out third mixing treatment on the graphitized carbon precursor and the amorphous carbon coated particles to obtain a third mixture;

performing fourth sintering treatment on the third mixture to obtain a composite lithium supplementing material; wherein the temperature of the fourth sintering process is higher than the temperature of the third sintering process.

According to the preparation method of the composite lithium supplementing material, disclosed by the embodiment of the application, the carbon coating layer is directly generated on the surface of the iron-based lithium supplementing agent particles by directly mixing the iron-based lithium supplementing agent particles with the carbon source and then carrying out sintering treatment, so that the core-shell structure composite lithium supplementing material with the carbon coating layer coating the iron-based lithium supplementing agent particles is formed, and the Raman spectrum of the generated composite lithium supplementing material simultaneously has the I ₁ To I ₃ The three characteristic peaks of the indicated relation range of (c) thus allowing the preparation of a composite lithium-supplementing material having high electrical conductivity and structural stability as above.

In some embodiments, the iron-based lithium supplement is prepared according to a method comprising the steps of:

the precursor of the iron-based lithium supplementing agent is sintered for 1 to 9 hours at 100 to 350 ℃ in a protective atmosphere, and then sintered for 2 to 24 hours at 800 to 950 ℃.

In some embodiments, the time of the first sintering process is 2 to 15 hours.

In some embodiments, the second sintering process is performed at a temperature of 600 to 1400 ℃ for a time of 2 to 15 hours.

In some embodiments, the carbon source comprises at least one of a saccharide, a polymeric organic compound, and a conductive carbon.

In some embodiments, the amorphous carbon precursor comprises at least one of glucose, sucrose, fructose, chitosan, lignin, carboxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, phenolic resin, resin.

In some embodiments, the graphitized carbon precursor comprises at least one of needle coke, petroleum coke, pitch, polyphenylene, polyphenylacetylene.

In some embodiments, the temperature of the third sintering process is 300-700 ℃ for 2-15 hours.

In some embodiments, the fourth sintering process is performed at a temperature of 600 to 1400 ℃ for a time of 2 to 15 hours.

In a third aspect, embodiments of the present application provide a lithium-rich cathode material. The lithium-rich positive electrode material comprises a positive electrode material and the composite lithium supplementing material or the composite lithium supplementing material prepared by the preparation method of the composite lithium supplementing material.

The lithium-rich positive electrode material provided by the embodiment of the application contains the composite lithium supplementing material provided by the embodiment of the application. Therefore, in the first charge and discharge process, the composite lithium supplementing material can fully play a role of supplementing lithium, and the reversible capacity of the lithium-rich positive electrode material is improved. And the internal resistance of the lithium-rich positive electrode material is reduced, and the cycling stability of the lithium-rich positive electrode material is improved.

In some embodiments, the raman spectrum of the lithium-rich cathode material includes a fourth characteristic peak, a fifth characteristic peak, and a sixth characteristic peak, the fourth characteristic peak having an intensity denoted as I ₄ The intensity of the fifth characteristic peak is denoted as I ₅ The intensity of the sixth characteristic peak is denoted as I ₆ ，I ₄ To I ₆ The following relationship is satisfied:

0.8≤I ₄ /I ₅ ≤1.4，0.5≤I ₄ /I ₆ less than or equal to 1.0; and/or the number of the groups of groups,

wavelength ranges corresponding to the fourth characteristic peak, the fifth characteristic peak and the sixth characteristic peak are as follows:

the raman shift interval of the fourth characteristic peak is: 945-950 cm ^-1 ；

The raman shift interval of the fifth characteristic peak is: 580-590 cm ^-1 ；

The raman shift interval of the sixth characteristic peak is: 389-394 cm ^-1 。

In some embodiments, the capacity improvement of the lithium-rich cathode material over the cathode material is greater than 1% at the same mass.

In some embodiments, the positive electrode material includes at least one of the following (1) to (4):

(1) The mass ratio of the positive electrode material to the composite lithium supplementing material is 90-99: 1 to 10;

(2) The particle diameter of the Dv50 is 0.1-15 mu m;

(3) Dv99 is 5-50 mu m;

(4) The water absorption rate of the anode material is 0-50 ppm/s in the environment with the standard atmospheric pressure, the temperature of 23-27 ℃ and the relative humidity of 10-50%.

In a fourth aspect, an embodiment of the present application provides a positive electrode. The positive electrode comprises a positive electrode active layer, and the positive electrode active layer comprises the lithium-rich positive electrode material.

The positive electrode active layer of the positive electrode contains the composite lithium supplementing material, so that the embodiment of the application has high first efficiency and good cycle performance, and the contained composite lithium supplementing material can also serve as a conductive agent after lithium removal is completed, so that the internal resistance of the positive electrode is effectively reduced.

In a fifth aspect, an embodiment of the present application provides a secondary battery. The secondary battery of the present application includes the above text application positive electrode.

The battery provided by the embodiment of the application has higher first efficiency and better cycle stability because the battery provided by the embodiment of the application contains the positive electrode.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained by those skilled in the art without the inventive effort.

FIG. 1 is a schematic diagram of a composite lithium-supplementing material according to an embodiment of the present application;

FIG. 2 is a Raman spectrum of the composite lithium-supplementing material in the embodiment A3 of the application;

fig. 3 is a raman spectrum of the lithium-rich cathode material in example B3 of the application.

Reference numerals illustrate:

1-iron-based lithium supplementing agent particles, 2-carbon coating layer.

Detailed Description

In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.

In the present application, the term "and/or" describes an association relationship of an association object, which means that three relationships may exist, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.

In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c," may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.

It should be understood that, in various embodiments of the present application, the sequence number of each process described above does not mean that the execution sequence of some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The weights of the relevant components mentioned in the description of the embodiments of the present application may refer not only to the specific contents of the components, but also to the proportional relationship between the weights of the components, so long as the contents of the relevant components in the description of the embodiments of the present application are scaled up or down within the scope of the disclosure of the embodiments of the present application. Specifically, the mass in the specification of the embodiment of the application can be a mass unit which is known in the chemical industry field such as mu g, mg, g, kg.

The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated for distinguishing between objects such as substances from each other. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the application. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.

In a first aspect, an embodiment of the present application provides a composite lithium-supplementing material. In some embodiments, the composite lithium supplementing material of the present application includes an iron-based lithium supplementing agent and a carbon material. Wherein the carbon material coats the iron-based lithium supplementing agent, and the Raman spectrum of the composite lithium supplementing material comprises a first characteristic peak, a second characteristic peak and a third characteristic peak, and the intensity of the first characteristic peak is recorded as I ₁ The intensity of the second characteristic peak is denoted as I ₂ The intensity of the third characteristic peak is denoted as I ₃ ，I ₁ To I ₃ The following relationship is satisfied:

in the composite lithium supplementing material provided by the embodiment of the application, the iron-based lithium supplementing agent is used as the lithium supplementing agent, so that irreversible lithium ions can be removed at least in the first charge and discharge process. The carbon material can serve as an electron and ion conductivity modifier of the iron-based lithium supplementing agent, and can improve the conductivity of the composite lithium supplementing material. The carbon material coating means that the carbon material is at least bonded to the surface of the iron-based lithium-supplementing agent, for example, a continuous or discontinuous carbon material layer is formed, and the carbon material layer is at least bonded to the surface of the iron-based lithium-supplementing agent.

Therefore, the iron-based lithium supplementing agent contained in the composite lithium supplementing material can provide rich irreversible lithium, and at least can release lithium ions in the first charge and discharge process, so that the iron-based lithium supplementing agent is used as a sacrificial agent in the first charge process to supplement the irreversible lithium ions consumed by forming an SEI film, thereby improving the first efficiency and the reversible capacity of the battery. The carbon material can effectively play a role of a conductive agent, so that the electronic conductivity and the ionic conductivity of the composite lithium supplementing material can be remarkably improved. The composite structure formed by the iron-based lithium supplementing agent and the carbon material ensures that the Raman spectrum of the composite lithium supplementing material in the embodiment of the application simultaneously contains the I ₁ To I ₃ The three characteristic peaks of the indicated relation range of the composite lithium-supplementing material provided by the embodiment of the application have higher electronic and ionic conductivities, the bonding strength between the carbon material and the iron-based lithium-supplementing agent can be enhanced, the overall structural stability and the surface-interface stability of the composite lithium-supplementing material provided by the embodiment of the application are improved, and meanwhile, the residual alkali content is obviously reduced, so that the lithium-supplementing effect and the lithium-supplementing stability of the composite lithium-supplementing material are improved, the internal resistance of a lithium battery is reduced, and the reversible capacity, the cycling stability and other electrochemical performances of the lithium battery are further improved.

In further detection, the Raman spectrum of the composite lithium supplementing material provided by the embodiment of the application has the I ₁ To I ₃ When three characteristic peaks of the indicated relation range are included, the carbon-containing material and the iron-based lithium supplementing agent of the composite lithium supplementing material are good in combination, good in coating integrity and low in residual alkali content, and therefore the processing and storage stability of the composite lithium supplementing material are effectively improved.

Further tests show that when I ₁ /I ₂ If the value is too small, for example, less than 0.8, the content of graphitized structures contained in the composite lithium supplementing material is low, and the conductivity is relatively poor; if I ₁ /I ₂ When the value is too large, if the value is larger than 1.40, poor combination between the carbon material contained in the composite lithium supplementing material and the iron-based lithium supplementing agent can be caused, so that the structural stability is reduced, the isolation effect of the carbon material on the iron-based lithium supplementing agent and the external environment is reduced, the content of residual alkali is increased due to the contact of the iron-based lithium supplementing agent and adverse factors such as environmental water vapor, and the processing and storage performances of the composite lithium supplementing material are reduced. Thus, the present embodiment is achieved by combining I ₁ /I ₂ The control can obviously improve the overall conductivity of the lithium supplementing material and ensure the bonding tight strength between the carbon material and the lithium supplementing agent, thereby effectively improving the structural stability and the lithium supplementing effect of the lithium supplementing material.

When I ₁ /I ₃ And I ₂ /I ₃ Too small a value, e.g. I ₁ /I ₃ ＜2，I ₂ /I ₃ When the content of the carbon material in the composite lithium supplementing material is less than 1.5, the coating integrity of the carbon material on the iron-based lithium supplementing agent is low, the isolation effect of the carbon material on the iron-based lithium supplementing agent and the external environment is reduced, and the residual alkali content is increased due to the contact of the iron-based lithium supplementing agent with adverse factors such as environmental water vapor, so that the processing and storage performances of the composite lithium supplementing material are reduced; if I ₁ /I ₃ And I ₂ /I ₃ Excessive values, e.g. I ₁ /I ₃ ＞6.50，I ₂ /I ₃ When the content of the carbon material is more than 6.00, the content of the carbon material is too high, the mass ratio of the iron-based lithium supplementing agent in the composite lithium supplementing material is reduced, the lithium supplementing capacity is reduced, and meanwhile, the combination property of the carbon layer and the iron-based lithium supplementing agent is reduced. Thus, the present embodiment is achieved by combining I ₁ /I ₃ And I ₂ /I ₃ Controlled on top ofIn the range, the coating and environmental isolation effects of the carbonaceous material of the composite lithium supplementing material on the iron-based lithium supplementing agent can be effectively ensured, and the lithium supplementing capacity is improved.

Therefore, the Raman spectrum of the composite lithium supplementing material contains I corresponding to the three characteristic peaks ₁ To I ₃ In the above relation range, the electronic and ionic conductivity of the composite lithium-supplementing material is better, and the overall structure and the surface interface are more stable, which is more beneficial to the stable lithium supplementation of the composite lithium-supplementing material. And the residual alkali content is lower.

Based on the above I ₁ To I ₃ In the raman spectrum of the composite lithium-supplementing material according to the embodiment of the present application, the raman shift interval of the first characteristic peak is: 1343-1353 cm ^-1 Specifically 1345cm ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The raman shift interval of the second characteristic peak is: 1580 cm to 1600cm ^-1 In particular 1590cm ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The raman shift interval of the third characteristic peak is: 645-655 cm ^-1 Specifically, 650cm ^-1 。

Based on three characteristic peaks included in the raman spectrum of the composite lithium-supplementing material of each of the above embodiments, the iron-based lithium-supplementing agent of each of the above embodiments includes at least one of the following features (1) to (2):

(1) The iron-based lithium supplementing agent has a particle morphology, and the Dv50 particle diameter of the particles is 1 to 20 μm, and further may be 5 to 15 μm, and in an exemplary embodiment, the Dv50 particle diameter may be in a typical but non-limiting particle diameter range of 1 to 5 μm, 5 to 10 μm, 10 to 15 μm, 15 to 20 μm, and the like. The particle diameter in this range can be adjusted together with the carbon material to adjust the particle diameter of the composite lithium supplementing material.

(2) The iron-based lithium supplementing agent comprises Li ₅ FeO ₄ . The iron-based lithium supplementing agent and the carbon material of the materials can play a role in synergism, so that the composite lithium supplementing material provided by the embodiment of the application has the Raman spectrum with three characteristic peaks, has high electronic and ionic conductivities on the basis of high-efficiency lithium supplementing effect, and is stable in structure.

Based on the three characteristic peaks included in the raman spectrum of the composite lithium-supplementing material according to the above embodiments, the composite structure formed by coating the iron-based lithium-supplementing agent with the carbon material included in the composite lithium-supplementing material according to the above embodiments, that is, the composite structure formed by forming a continuous or discontinuous carbon material layer by combining the iron-based lithium-supplementing agent with at least the surface of the iron-based lithium-supplementing agent may include at least the following structures:

in one embodiment, as shown in fig. 1, the carbon material forms a carbon coating layer 2, the iron-based lithium-supplementing agent is iron-based lithium-supplementing agent particles 1, and the carbon coating layer 2 coats the surfaces of the iron-based lithium-supplementing agent particles 1. The carbon coating layer 2 may be a continuous coating layer or may be discontinuous, such as a carbon coating layer formed by a plurality of islands.

In another embodiment, the carbon material forms carbon particles and bonds to the particle surfaces of the iron-based lithium supplement. Wherein, the carbon particles can be isolated from each other, or at least part of adjacent two carbon particles can be combined with each other.

In yet another embodiment, the carbon material may be diffused into the surface layer of the particles of the iron-based lithium-compensating agent to form the transition layer, in addition to forming the carbon coating layer or coating the carbon particles on the surface of the particles of the iron-based lithium-compensating agent.

The existence of the carbon-containing material in the composite lithium-supplementing material in the above embodiments can obviously improve the conductivity of the composite lithium-supplementing material and reduce the residual alkali content, and further researches show that the content of the carbon material can have relatively obvious influence on the conductivity, the residual alkali content, the structure and other performances of the composite lithium-supplementing material. For example, the content of the carbon material in the composite lithium supplementing material is regulated, so that the composite lithium supplementing material has the first to third characteristic peaks, the conductivity and structure of the composite lithium supplementing material and the stability of a surface interface can be obviously improved, and the content of residual alkali can be obviously reduced.

Therefore, no matter which mode the carbon material is coated with the iron-based lithium supplementing agent, the carbon material and the iron-based lithium supplementing agent can play a role in synergy, so that the composite lithium supplementing material provided by the embodiment of the application has the Raman spectrum with three characteristic peaks, and has high electronic and ionic conductivity, stable structure and low residual alkali content on the basis of high-efficiency lithium supplementing effect.

Wherein, in further embodiments, when the carbon material forms a continuous or discontinuous carbon coating, the carbon coating may have a thickness ranging from 1nm to 1 μm, and further may have a thickness ranging from 10 to 400nm, and in exemplary embodiments, the carbon coating may have a thickness ranging from 1 to 10nm, 10 to 50nm, 50 to 100nm, 100 to 200nm, 200 to 300nm, 300 to 400nm, 400 to 500nm, 500 to 600nm, 600 to 700nm, 700 to 800nm, 800 to 900nm, 900 to 1 μm, and the like, typically but not limited thereto; the carbon coating layer with the thickness and the iron-based lithium supplementing agent particles can also adjust the particle size of the composite lithium supplementing material according to the embodiment of the application on the basis of endowing the composite lithium supplementing material with the Raman spectrum containing three characteristic peaks, such as controlling the Dv50 particle size below to be 1-20 mu m.

In further embodiments, the carbon content of the composite lithium-supplementing material in each of the above embodiments may be controlled to be 0.1 to 20%, and further may be 1 to 10%, and in examples, may be a typical but non-limiting content such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

In further embodiments, the carbon material may include at least one of carbon black (cracked carbon), soft carbon, hard carbon, graphite, graphene oxide.

In some embodiments, when the carbon material forms a carbon coating, the carbon coating comprises an amorphous carbon layer and a graphitized carbon layer, and the amorphous carbon layer coats the iron-based lithium-compensating agent, and the graphitized carbon layer coats the surface of the amorphous carbon layer. The thickness ratio of the amorphous carbon layer to the graphitized carbon layer is (0.2 to 10): 1 in the embodiment based on the composite carbon coating layer containing the amorphous carbon layer and the graphitized carbon layer, and further may be (1 to 10): 1, and in the exemplary embodiment, may be a typical but non-limiting ratio or a range between any two ratios of 0.2:1, 0.5:1, 1:1, 3:1, 5:1, 8:1, 10:1, etc.

In the composite carbon coating layer, the amorphous carbon layer refers to transition state carbon, and refers to carbon materials with low graphitization crystallization degree and approximate amorphous state (or no fixed shape and periodic structural rule), such as carbon black and the likeAnd (3) forming a carbon layer. The graphitized carbon layer refers to a carbon layer formed of a carbon material having a layered structure, and the layer structure of graphitized carbon is similar to graphite. The carbon coating layer is arranged as the composite carbon coating layer, which is provided with the I corresponding to the three characteristic peaks when the composite lithium supplementing material is endowed with ₁ To I ₃ And in the above relation range, the electronic and ionic conductivity of the composite lithium-supplementing material can be improved, and the overall structure and the surface interface are more stable, so that the composite lithium-supplementing material is more beneficial to stably supplementing lithium.

The content and the type of the carbon material in the composite lithium supplementing material are selected and controlled, so that a synergistic effect can be achieved between the carbon material and the iron-based lithium supplementing agent, the composite lithium supplementing material provided by the embodiment of the application has the Raman spectrum with three characteristic peaks, the electronic conductivity and the ionic conductivity of the composite lithium supplementing material can be improved, the stability of the structure and the surface interface is further improved, and the residual alkali content is further reduced. Meanwhile, the content of the carbon material is controlled, so that the carbon material can form a continuous coating layer as far as possible to effectively protect the iron-based lithium supplementing agent, and the lithium supplementing effect and the processing performance of the composite lithium supplementing material are further improved.

Based on the iron-based lithium-supplementing agent and the carbon material contained in the above-described respective embodiment composite lithium-supplementing material, the above-described respective embodiment composite lithium-supplementing material includes at least one of the following features (1) to (6):

(1) Specific surface area of 0.1-100 m ² The ratio of the total amount of the components per gram is 0.5 to 50m ² In the example, the ratio of the ratio to the ratio of the total weight of the catalyst to the total weight of the catalyst is 0.1 to 0.5m ² /g、0.5～1m ² /g、1～10m ² /g、10～20m ² /g、20～30m ² /g、30～40m ² /g、40～50m ² /g、50～60m ² /g、60～70m ² /g、70～80m ² /g、80～90m ² /g、90～100m ² Typical but non-limiting specific surface area ranges such as/g;

(2) The tap density is 0.8-2.0 g/cm ³ Further, the concentration may be 1.0 to 1.5g/cm ³ In the example, the ratio may be 0.8-1 g/cm ³ 、1～1.2g/cm ³ 、1.2～1.5g/cm ³ 、1.5～1.8g/cm ³ 、1.8～2g/cm ³ Typical but non-limiting tap density ranges;

(3) The residual alkalinity is greater than 0, less than or equal to 5wt%, further less than or equal to 2wt%, and in exemplary embodiments may be in the typical but non-limiting tap density range of 0.1 to 0.5wt%, 0.5 to 1wt%, 1 to 1.5wt%, 1.5 to 2wt%, 2 to 2.5wt%, 2.5 to 3wt%, 3 to 3.5wt%, 3.5 to 4wt%, 4 to 4.5wt%, 4.5 to 5wt%, etc.;

(4) The Dv50 particle size is 1 to 20 μm, further 5 to 15 μm, and in the exemplary case, typical but non-limiting particle size ranges of 1 to 5 μm, 5 to 10 μm, 10 to 15 μm, 15 to 20 μm, etc. are possible;

(5) Dv99 is 10 to 50 μm, and further may be 15 to 40 μm, and in the exemplary case, may be a typical but non-limiting particle size range of 10 to 15 μm, 15 to 20 μm, 20 to 25 μm, 25 to 30 μm, 30 to 35 μm, 35 to 40 μm, 40 to 45 μm, 45 to 50 μm, etc.;

(6) The carbon content is 0.1-20% of the total mass of the composite lithium supplementing material, further 1-10%, in the example, 0.1-0.5%, 0.5-1%, 1-2%, 2-3%, 3-4%, 4-5%, 5-6%, 6-7%, 7-8%, 8-9%, 10-11%, 11-12%, 12-13%, 14-15%, 15-16%, 16-17%, 17-18%, 18-19%, 19-20% and the like, and typical but non-limiting content ranges;

The composite lithium supplementing material of each embodiment has the specific raman spectrum, and can effectively improve the conductivity of the composite lithium supplementing material by further controlling the content of carbon in the range, so that the carbon material has a protective effect on the iron-based lithium supplementing agent, the iron-based lithium supplementing agent can be effectively isolated from water, gas and the like in the environment, the lithium supplementing effect, the processing performance and the storage performance of the iron-based lithium supplementing agent are improved, and the relatively low water absorption is realized. The particle size in the range enables the composite lithium supplementing material to have the tap density range, so that the density of the active material layer can be improved together with the positive electrode material, and the energy density of the pole piece can be improved.

As checked, the above examples composite lithium supplementing material was at 0.05C at magnification: the first charge constant current ratio is more than 80%, wherein the constant current section charge specific capacity C1 under the voltage of 2.5-4.3V is more than 450mAh/g, and the total charge specific capacity C2 under the voltage of 4.3V is more than 465mAh/g.

In a second aspect, the embodiment of the application also provides a preparation method of the composite lithium supplementing material. In one embodiment, the method for preparing the composite lithium supplementing material comprises the following steps:

S10: performing first mixing treatment on a carbon source and iron-based lithium supplementing agent particles to obtain a first mixture;

s20: and sintering the mixture to make the carbon source generate a carbon material and coat the surface of the iron-based lithium supplementing agent particles to obtain the composite lithium supplementing material.

The carbon source in step S10 is a precursor for forming the carbon material contained in the composite lithium-supplementing material of the above-mentioned application example, and the mixing treatment is performed so that the carbon source is coated on the surface of the iron-based lithium-supplementing agent particles as much as possible, thereby forming a carbon source coating layer. The iron-based lithium supplementing agent particles are iron-based lithium supplementing agents contained in the composite lithium supplementing material of the embodiment of the application, and in the embodiment, the iron-based lithium supplementing agent can be in a particle shape, such as particles with a Dv50 particle size of 1-20 mu m. The carbon source generating carbon material in step S20 is a carbon material contained in the composite lithium supplementing material according to the above-described embodiment of the present application, and in an embodiment, the carbon material may be a carbon coating layer or carbon particles. The sintering process in step S20 includes a first sintering process and a second sintering process after the first sintering process, and the temperature of the first sintering process is 300 to 700 ℃, and the temperature of the second sintering process is higher than the temperature of the first sintering process.

The preparation method of the composite lithium supplementing material of the embodiment of the application comprises the steps of coating the carbon material of the iron-based lithium supplementing agent, controlling conditions such as sintering treatment and the like, so that the prepared composite lithium supplementing material has a specific Raman spectrum of the composite lithium supplementing material of the embodiment of the application, wherein the specific Raman spectrum comprises a first characteristic peak, a second characteristic peak and a third characteristic peak, and the intensity of the first characteristic peak is recorded as I ₁ The intensity of the second characteristic peak is denoted as I ₂ The intensity of the third characteristic peak is denoted as I ₃ The I is ₁ To I ₃ The following relationship is satisfied: i is not less than 0.80 ₁ /I ₂ ≤1.40、2.00≤I ₁ /I ₃ ≤6.50、1.50≤I ₂ /I ₃ Less than or equal to 6.00. Therefore, the prepared composite lithium supplementing material has good electronic and ionic conductivity, and the carbon material and the iron-based lithium supplementing agent have strong binding force, structural stability and low residual alkali content. In addition, the preparation method has controllable conditions, and the prepared composite lithium supplementing material has stable performance and is suitable for industrial mass production and application.

In the embodiment, the iron-based lithium supplementing agent in the step S10 is prepared according to the following steps:

the precursor of the iron-based lithium supplementing agent is subjected to a first-stage sintering treatment for 1 to 9 hours at 100 to 350 ℃ and then a second-stage sintering treatment for 2 to 24 hours at 800 to 950 ℃ in a protective atmosphere.

The preparation method of the iron-based lithium supplementing agent is controlled, so that the prepared iron-based lithium supplementing agent has the characteristics of the iron-based lithium supplementing agent contained in the composite lithium supplementing material, and acts with the carbon material formed in the step S10, so that the prepared composite lithium supplementing material has the specific Raman spectrum.

Wherein the precursor of the iron-based lithium supplementing agent can be specifically determined according to the material of the iron-based lithium supplementing agent, such as when the iron-based lithium supplementing agent is Li ₅ FeO ₄ Etc. Wherein, the iron source contained in the iron-based lithium supplementing agent precursor can comprise at least one of oxide, hydroxide, carbonate, nitrate, sulfate and acetate. The lithium source may include one or more of lithium hydroxide, lithium oxide, lithium carbonate, lithium sulfate, lithium oxalate. The protective atmosphere is at least one of nitrogen, argon, helium and neon.

In the embodiment, the mixing ratio of the carbon source and the iron-based lithium-compensating agent during the mixing treatment should ensure that the thickness of the carbon coating layer generated in step S20 satisfies the carbon content range of the above composite lithium-compensating material, for example, carbon accounts for 0.1-20% of the total mass of the composite lithium-compensating agent. If the carbon material is produced, the thickness of the carbon coating layer is 1 nm-1 mu m.

In an embodiment, the carbon source may include at least one of a saccharide, a high molecular organic matter, an inorganic carbon material, and in an embodiment, the saccharide may include at least one of glucose, sucrose, fructose, and the like. As an example, the polymer organic matter may include at least one of phenolic resin, polytetrafluoroethylene, and the like. In an embodiment, the inorganic carbon material may include at least one of hard carbon, graphite, graphene oxide, and the like.

The protective atmosphere in the above-described method for producing an iron-based lithium-compensating agent may be a gas that is chemically stable or does not participate in the reaction of the precursor of the iron-based lithium-compensating agent, and in the example, the protective atmosphere may be a protective atmosphere formed by including nitrogen or an inert gas or the like.

In an embodiment, when the temperature of the first sintering treatment in step S20 is 300 to 700 ℃, the sintering treatment time may be 2 to 15 hours, and may further be 2 to 10 hours. In other embodiments, the temperature of the second sintering process may be 600 to 1400 ℃, and further may be 700 to 1200 ℃; the time may be 2 to 15 hours, and may be further 2 to 10 hours. By controlling the temperature, time and the like of the sintering treatment in the step S20, the carbon source can be effectively carbonized to form the carbon material, and the carbon material can be controlled, for example, the generated carbon material has amorphous carbon close to the surface of the iron-based lithium supplement agent particles and forms an amorphous carbon coating layer, and the carbon material far away from the surface of the iron-based lithium supplement agent particles is graphitized carbon and forms a graphitized carbon coating layer, so that the raman spectrum stability, electrochemical, ionic and electronic conductivities and structural stability of the composite lithium supplement material are improved, and the residual alkali content is reduced.

In another embodiment, the method for preparing the composite lithium supplementing material includes the following steps:

s30: performing second mixing treatment on the amorphous carbon precursor and the iron-based lithium supplementing agent particles to obtain a second mixture;

s40: performing third sintering treatment on the second mixture to obtain amorphous carbon coated particles;

s50: carrying out third mixing treatment on the graphitized carbon precursor and the amorphous carbon coated particles to obtain a third mixture;

s60: and performing fourth sintering treatment on the third mixture to obtain the composite lithium supplementing material.

Wherein the amorphous carbon precursor in step S30 and the graphitized carbon precursor in step S50 together constitute the precursor of the carbon material contained in the composite lithium-supplementing material of the above-described embodiment. In the step S30, the amorphous carbon precursor is coated on the surface of the iron-based lithium supplementing agent particles as much as possible through the second mixing treatment, and an amorphous carbon coating layer is generated through the third sintering treatment in the step S40; in step S50, the graphitized carbon precursor is subjected to a third mixing treatment, so that the graphitized carbon precursor is coated on the surface of the amorphous carbon coating layer contained in the amorphous carbon coating layer particles as much as possible, and the graphitized carbon coating layer is generated through a fourth sintering treatment in step S60. The amorphous carbon coating layer and the graphitized carbon coating layer together form a carbon material contained in the composite lithium supplementing material according to the above-described embodiment of the present application, and in an embodiment, the carbon material may be a carbon coating layer or carbon particles. Wherein the temperature of the fourth sintering treatment is higher than the temperature of the third sintering treatment. The iron-based lithium supplementing agent particles are iron-based lithium supplementing agents contained in the composite lithium supplementing material of the embodiment of the application.

According to the preparation method of the composite lithium supplementing material, the iron-based lithium supplementing agent is coated with the amorphous carbon and graphitized carbon material, so that the prepared composite lithium supplementing material has the specific Raman spectrum of the composite lithium supplementing material in the embodiment of the application, for example, the composite lithium supplementing material comprises a first characteristic peak, a second characteristic peak and a third characteristic peak, and the intensity of the first characteristic peak is recorded as I ₁ The intensity of the second characteristic peak is denoted as I ₂ The intensity of the third characteristic peak is denoted as I ₃ The I is ₁ To I ₃ The following relationship is satisfied: i is not less than 0.80 ₁ /I ₂ ≤1.40、2.00≤I ₁ /I ₃ ≤6.50、1.50≤I ₂ /I ₃ Less than or equal to 6.00. Therefore, the prepared composite lithium supplementing material has good electronic and ionic conductivity, and the carbon material and the iron-based lithium supplementing agent have strong binding force, structural stability and low residual alkali content. In addition, the preparation method has controllable conditions, and the prepared composite lithium supplementing materialStable performance and is suitable for industrialized mass production and application.

In some embodiments, the mixing ratio of the amorphous carbon precursor and the iron-based lithium-compensating agent particles in the step S30 should ensure that the total mass of the graphitized carbon coating layer (i.e., the total mass of the amorphous carbon coating layer and the graphitized carbon coating layer) generated in the step S60 should satisfy the content range of carbon contained in the above composite lithium-compensating material, for example, carbon accounts for 0.1 to 20% of the total mass of the composite lithium-compensating agent, for example, the amorphous carbon coating layer and the graphitized carbon coating layer have a carbon coating layer thickness of 1nm to 1 μm.

In some embodiments, the iron-based lithium-supplementing agent particles in step S30 may be prepared according to the above preparation method of the iron-based lithium-supplementing agent particles.

In some embodiments, the amorphous carbon precursor in step S30 includes at least one of glucose, sucrose, fructose, chitosan, lignin, carboxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, phenolic resin, resin. After the third sintering process in step S40, the amorphous carbon precursor can effectively produce an amorphous carbon material.

In some embodiments, the temperature of the third sintering process in step S40 may be 300 to 700 ℃ for 2 to 15 hours. The third sintering process is effective to react the amorphous carbon precursor to produce an amorphous carbon material. Of course, this third sintering treatment should be performed in a protective atmosphere, as described above.

In some embodiments, the graphitized carbon precursor in step S50 comprises at least one of needle coke, petroleum coke, pitch, polyphenylene, polyphenylacetylene. The graphitized carbon precursor can effectively generate graphitized carbon material after the fourth sintering process in step S60.

In some embodiments, the temperature of the fourth sintering process in step S60 may be 600 to 1400 ℃, alternatively 600 to 1200 ℃, for 2 to 15 hours. The fourth sintering treatment can effectively carry out fourth sintering treatment on the graphitized carbon precursor to generate graphitized carbon materials. Of course, the fourth sintering treatment should be performed in a protective atmosphere, as described above.

In a third aspect, the embodiment of the application also provides a lithium-rich cathode material. The lithium-rich positive electrode material provided by the embodiment of the application comprises a positive electrode material and a composite lithium supplementing material. The composite lithium supplementing material is the composite lithium supplementing material of the embodiment of the application.

Therefore, in the charge and discharge process, particularly in the first charge and discharge process, the lithium-rich cathode material provided by the embodiment of the application can effectively remove lithium ions, and realize lithium supplementation, so that the reversible capacity of the lithium-rich cathode material is relatively improved. The composite lithium supplementing material can also play a role of a conductive agent, so that the internal resistance of the lithium-rich positive electrode material is effectively reduced, and the cycle performance of the lithium-rich positive electrode material is good.

In an embodiment, the positive electrode material contained in the lithium-rich positive electrode material includes at least one of the following features (1) to (4):

(1) The mass ratio of the positive electrode material to the composite lithium supplementing material is 90-99: 1 to 10, and further 92 to 98:2 to 8, in the example, may be 90: 10. 91: 9. 92: 8. 93: 7. 94: 6. 95: 5. 96: 4. 97: 3. 98: 2. 99:1, etc. typical but non-limiting mixing ratios. The proportion in the range can improve the reversible capacity of the lithium-rich positive electrode material under the effect of effectively playing the role of lithium supplementation of the composite lithium supplementing material.

(2) The Dv50 particle size may be in the range of 0.1 to 15. Mu.m, and further may be in the range of 0.5 to 10. Mu.m, and in the exemplary case, may be in the typical but non-limiting particle size range of 0.1 to 0.5. Mu.m, 0.5 to 1. Mu.m, 5 to 10. Mu.m, 10 to 15. Mu.m, etc.

(3) Dv99 is 5 to 50. Mu.m, more preferably 10 to 30. Mu.m, and in the exemplary embodiment, it may be in the typical but non-limiting particle size range of 5 to 10. Mu.m, 10 to 15. Mu.m, 15 to 20. Mu.m, 20 to 25. Mu.m, 25 to 30. Mu.m, 30 to 35. Mu.m, 35 to 40. Mu.m, 40 to 45. Mu.m, 45 to 50. Mu.m, etc.

The particle size range is combined with the particle size of the composite lithium supplementing material disclosed by the embodiment of the application, so that the compaction density of the lithium-rich positive electrode material can be improved.

(4) The water absorption rate of the anode material is 0-50 ppm/s in the environment with the standard atmospheric pressure, the temperature of 23-27 ℃ and the relative humidity of 10-50%. The lithium-rich positive electrode material has low water absorption, good processing and storage performances and stable electrochemical performance.

According to detection, on the basis that the quality of the lithium-rich positive electrode material is the same as that of the positive electrode material, the capacity improvement rate of the lithium-rich positive electrode material is higher than 1% compared with the positive electrode material. The capacity increase rate represents a ratio of a difference of a capacity Q1 of the lithium-rich positive electrode material minus a capacity Q2 of the positive electrode material to the capacity Q2 of the positive electrode material, specifically, a capacity increase rate= (Q1-Q2)/Q2×100%.

In an embodiment, the positive electrode material may include at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium nickel manganate, NCM ternary material, and the like.

When the positive electrode material is lithium iron phosphate, the Raman spectrum of the lithium-rich positive electrode material formed by compounding the lithium iron phosphate and the composite lithium-supplementing material in the embodiment of the application comprises a fourth characteristic peak, a fifth characteristic peak and a sixth characteristic peak, wherein the intensity of the fourth characteristic peak is recorded as I ₄ The intensity of the fifth characteristic peak is denoted as I ₅ The intensity of the sixth characteristic peak is denoted as I ₆ ，I ₄ To I ₆ The following relationship is satisfied:

0.8≤I ₄ /I ₅ ≤1.4，0.5≤I ₄ /I ₆ ≤1.0；

further tests show that when I ₄ /I ₅ When the value is too small, if the value is smaller than 0.8, the mass ratio of the composite lithium supplementing material in the lithium-rich positive electrode material is low, the synergistic effect with the positive electrode material cannot be exerted, and the lithium supplementing effect is poor; if I ₄ /I ₅ If the value is too large, if the value is larger than 1.4, the mass ratio of the positive electrode material in the lithium-rich positive electrode material is low, and the reversible capacity of the lithium-rich positive electrode is reduced. Thus, the present embodiment is achieved by combining I ₄ /I ₅ In the above range, the synergistic effect of the composite lithium supplementing material and the positive electrode material can be enhanced, the good lithium supplementing effect is ensured, and the relatively high reversible capacity is maintained, so that the enrichment is effectively improved The lithium positive electrode material has reversible capacity, cycling stability and other electrochemical properties.

If I ₄ /I ₆ When the value is too small, if the value is smaller than 0.5, the mass ratio of the composite lithium supplementing material in the lithium-rich positive electrode material is low, the synergistic effect with the positive electrode material cannot be exerted, and the lithium supplementing effect is poor; if I ₄ /I ₆ If the value is too large, if the value is larger than 1.0, the mass ratio of the positive electrode material in the lithium-rich positive electrode material is low, and the reversible capacity of the lithium-rich positive electrode is reduced. Thus, the present embodiment is achieved by combining I ₄ /I ₆ Preferably, in the above range, the synergistic effect of the composite lithium-supplementing material and the positive electrode material can be enhanced, a good lithium supplementing effect is ensured, and relatively high reversible capacity can be maintained, so that the electrochemical performances such as reversible capacity, cycling stability and the like of the lithium-rich positive electrode material are effectively improved.

Based on the above I ₄ To I ₆ In the Raman spectrum of the lithium-rich cathode material of the embodiment of the application, the Raman shift interval of the fourth characteristic peak is 945 cm to 950cm ^-1 In particular 948cm ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The Raman shift interval of the fifth characteristic peak is 580-590 cm ^-1 In particular at 583cm ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The Raman shift interval of the sixth characteristic peak is 389-394 cm ^-1 In particular 391cm ^-1 . When the Raman spectrum of the lithium iron phosphate is measured independently, the lithium iron phosphate does not have the fourth characteristic peak, and the fifth characteristic peak and the sixth characteristic peak exist, so that the synergistic effect of the composite lithium supplementing material and the lithium iron phosphate in the embodiment of the application is proved, and the improvement of the electrochemical performance is facilitated.

In a fourth aspect, an embodiment of the present application further provides a positive electrode. In some embodiments, the positive electrode of the present application comprises a current collector and a positive electrode active layer bonded to at least one surface of the current collector, wherein the positive electrode active layer comprises the lithium-rich positive electrode material of the present application.

In an embodiment, the positive electrode active layer further includes a binder and further includes a conductive agent, wherein the binder may be a commonly used electrode binder such as one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivatives. In embodiments of the present application, the conductive agent may be a conventional conductive agent, such as graphite, carbon black, acetylene black, graphene, carbon fiber, C ₆₀ And one or more of carbon nanotubes. Since positive electrode lithium is generally used at present, the embodiment of the application can be a positive electrode, and the electrode active layer contained in the positive electrode is a positive electrode active layer.

In a fifth aspect, embodiments of the present application further provide a battery. The battery provided by the embodiment of the application comprises necessary components such as a positive plate, a negative plate and the like, and also comprises other necessary or auxiliary components. Wherein, the positive plate is the positive electrode of the embodiment of the application.

Because the battery provided by the embodiment of the application contains the composite lithium supplementing material provided by the embodiment of the application, the battery provided by the embodiment of the application has high energy density and good cycle performance based on the effect of the composite lithium supplementing material provided by the embodiment of the application.

In an embodiment, the battery of the embodiment of the application may include a battery cell, a battery module, a battery pack, or the like. The battery cell is a battery which comprises a battery shell and a bare cell assembled by the positive plate, the negative plate and other necessary components, wherein the battery shell is encapsulated in the battery shell. The battery module is assembled by a plurality of lithium ion battery cells. The battery pack is assembled from battery modules.

The battery monomer, the battery module or the battery pack all contain the composite lithium supplementing material according to the embodiment of the application. Therefore, the battery cell, the battery module or the battery pack has high energy density and good cycle performance.

In order that the above implementation details and operation of the present application may be clearly understood by those skilled in the art, and that the advanced performance of the composite lithium supplementing material, the preparation method and the application of the embodiment of the present application are significantly embodied, the above technical solution is exemplified by a plurality of embodiments below.

1. Composite lithium supplementing material and preparation method thereof are as follows:

example A1

The embodiment provides a composite lithium supplementing material and a preparation method thereof. The composite lithium supplementing material comprises Li ₅ FeO ₄ Nucleus and coating the Li ₅ FeO ₄ Carbon coating of the core.

The preparation method of the embodiment comprises the following steps:

step S1: uniformly mixing ferric hydroxide and lithium hydroxide according to the mol ratio of 1:5, and sintering to obtain Li ₅ FeO ₄ Particles;

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles with glucose according to the mass ratio of = 100:1, sintering for 4 hours at 450 ℃ and then sintering for 6 hours at 650 ℃ in nitrogen atmosphere, and obtaining the composite lithium supplementing material.

Example A2

The preparation method of the embodiment comprises the following steps:

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles with phenolic resin according to the mass ratio of 100:5, sintering for 5 hours at 500 ℃ and then sintering for 8 hours at 850 ℃ in nitrogen atmosphere, and obtaining the composite lithium supplementing material.

Example A3

The preparation method of the embodiment comprises the following steps:

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles with glucose according to the mass ratio of = 100:3, sintering for 6 hours at 550 ℃ and then sintering for 4 hours at 900 ℃ in nitrogen atmosphere, and obtaining the composite lithium supplementing material.

Example A4

The preparation method of the embodiment comprises the following steps:

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles and asphalt according to the mass ratio of 100:1, sintering for 10 hours at 600 ℃ and then sintering for 5 hours at 750 ℃ in nitrogen atmosphere, and obtaining the composite lithium supplementing material.

Example A5

The preparation method of the embodiment comprises the following steps:

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles and polyaniline according to the mass ratio of 100:15, sintering for 8 hours at 500 ℃ and then sintering for 15 hours at 650 ℃ in nitrogen atmosphere to obtainTo the composite lithium supplementing material.

Example A6

The embodiment provides a composite lithium supplementing material and a preparation method thereof. The composite lithium supplementing material comprises Li ₅ FeO ₄ Nucleus and coating the Li ₅ FeO ₄ A composite carbon coating layer of the core body, wherein the composite carbon coating layer comprises an amorphous carbon coating layer and a graphitized carbon coating layer coating the amorphous carbon coating layer, and the amorphous carbon coating layer coats Li ₅ FeO ₄ A nucleus. The thickness ratio of amorphous carbon coating layer to graphitized carbon coating layer was 2:1.

the preparation method of the embodiment comprises the following steps:

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles with glucose amorphous carbon source according to the mass ratio of 100:3, and sintering at 600 ℃ for 5 hours in nitrogen atmosphere to obtain particles of an amorphous carbon coating layer;

step S3: mixing the particles of the amorphous carbon coating layer obtained in the step S2 with a petroleum coke graphitized carbon source according to the mass ratio of = 100:2, and sintering at 1000 ℃ for 4 hours in a nitrogen atmosphere to obtain the composite lithium supplementing material of the graphitized carbon coating layer coated with the amorphous carbon coating layer.

Example A7

The embodiment provides a composite lithium supplementing material and a preparation method thereof. The composite lithium supplementing material comprises Li ₅ FeO ₄ Nucleus and coating the Li ₅ FeO ₄ A composite carbon coating layer of the core body, wherein the composite carbon coating layer comprises an amorphous carbon coating layer and a graphitized carbon coating layer coating the amorphous carbon coating layer, and the amorphous carbon coating layer coats Li ₅ FeO ₄ A nucleus. The thickness ratio of amorphous carbon coating layer to graphitized carbon coating layer was 5:1.

the preparation method of the embodiment comprises the following steps:

step S1: iron hydroxide and lithium hydroxide are mixed according to the mole ratio = Mixing uniformly in a ratio of 1:5, and sintering to obtain Li ₅ FeO ₄ Particles;

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles with a phenolic resin amorphous carbon source according to the mass ratio of = 100:6, and sintering at 500 ℃ for 8 hours in a nitrogen atmosphere to obtain particles of an amorphous carbon coating layer;

step S3: mixing the particles of the amorphous carbon coating layer obtained in the step S2 with an asphalt graphitized carbon source according to the mass ratio of = 100:1, and sintering at 1000 ℃ for 4 hours in a nitrogen atmosphere to obtain the composite lithium supplementing material of the graphitized carbon coating layer coated with the amorphous carbon coating layer.

Comparative example A1

The comparative example provides a lithium supplementing material and a preparation method thereof. The composite lithium supplementing material comprises Li ₅ FeO ₄ Nucleus and coating the Li ₅ FeO ₄ Carbon coating of the core. The preparation method of the comparative example comprises the following steps:

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles with polyethylene glycol according to the mass ratio of 100:1, and sintering at 700 ℃ for 10 hours in nitrogen atmosphere to obtain the composite lithium supplementing material.

Comparative example A2

The comparative example provides a lithium supplementing material and a preparation method thereof. The composite lithium supplementing material comprises Li ₅ FeO ₄ Nucleus and coating the Li ₅ FeO ₄ Carbon coating of the core.

The preparation method of the comparative example comprises the following steps:

step S2: li obtained in step S1 ₅ FeO ₄ Mixing the particles and needle coke in a mass ratio of 100:25, and cooling to 900 ℃ in a nitrogen atmosphereSintering for 10 hours to obtain the composite lithium supplementing material.

The composite lithium-supplementing materials provided in the above examples were subjected to the relevant performance tests in the following table 1, respectively, and the measured results are shown in the following table 1.

The Raman test method comprises the following steps: wavenumber range of Raman spectrum from 100 to 3500cm ^-1 The area of the surface sweep is 9 mu m by 9 mu m, the number of points of each line of the surface sweep is 30, the number of lines of the surface sweep is 30, each sampling point is integrated for 20 times, and the integration time is 20 seconds. The raman diagram of the composite lithium-supplementing material provided in example A3 is shown in fig. 2.

The specific surface area detection method comprises the following steps: the specific surface area of the composite positive electrode material was measured by referring to the GB/T19587-2004 gas adsorption BET method.

The tap density detection method comprises the following steps: the measurement was performed according to the measurement method specified in GB/T5162.

Dv50 particle size detection method: the measurement was carried out by using a device Markov 3000 with reference to GB/T19077-2016/ISO 13320:2009 particle size distribution laser diffraction method.

The carbon content detection method comprises the following steps: the measurement was performed according to the measurement method specified in GB/T20123.

The method for detecting the thickness of the carbon coating layer comprises the following steps: TEM was used for photographing and measurement.

TABLE 1

2. Lithium-rich cathode material and lithium battery examples:

examples B1 to B11 and comparative examples B1 to B5

Examples B1 to B11 and comparative examples B1 to B5 provide a lithium-rich cathode material and a lithium battery, respectively.

Among them, each of examples B1 to B11 and comparative examples B1 to B5 contains a positive electrode material and a composite lithium supplementing material mixed with the positive electrode material. The composite lithium-supplementing material in example B1 is the composite lithium-supplementing material in example A1, the composite lithium-supplementing material in example B2 is the composite lithium-supplementing material in example A2, and so on, the composite lithium-supplementing material in example B7 is the composite lithium-supplementing material in example A7, and the lithium-supplementing material in comparative example B1 is the lithium-supplementing material in comparative example A1. The lithium supplementing material contained in comparative example B2 was the lithium supplementing material in comparative example A2. The positive electrode material in the embodiment B8 is lithium manganese iron phosphate, and the composite lithium supplementing material in the embodiment A1 is the composite lithium supplementing material; the positive electrode material in the embodiment B9 is NCM ternary, and the composite lithium supplementing material in the embodiment A1 is the composite lithium supplementing material; the positive electrode materials in the embodiment B10 and the embodiment B11 are lithium iron phosphate, and the composite lithium supplementing materials in the embodiment A1 are the composite lithium supplementing materials; the positive electrode material contained in comparative example B3 was lithium iron phosphate, and no lithium supplementing agent was contained; the positive electrode material contained in comparative example B4 is lithium iron manganese phosphate, and no lithium supplementing agent is contained; the positive electrode material contained in comparative example B5 was NCM ternary, and contained no lithium supplementing agent.

The positive electrode materials and the composite ratio with the composite lithium-supplementing material contained in examples B1 to B11 are shown in table 2 below.

Raman detection was performed on the lithium-rich cathode materials provided in examples B1 to B11, respectively, wherein the raman diagram of the lithium-rich cathode material provided in example B3 is shown in fig. 3.

The lithium batteries provided in each of examples B1 to B11 and comparative examples B1 to B5 were as follows:

1) Preparation of a positive plate: the lithium-rich cathode materials provided in examples B1 to B11 and comparative examples B1 to B2 and the cathode materials provided in comparative examples B3 to B5 were uniformly mixed with SP (conductive carbon black), PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) in a mass ratio of 95:3:2:100, respectively, using a closed mixer for 2 hours, to obtain cathode slurries, respectively; and uniformly coating the prepared positive electrode slurry on an aluminum foil, drying at 130 ℃, rolling and cutting to obtain positive electrode plates respectively.

2) Preparing a negative plate: stirring graphite, SP, SBR (styrene butadiene rubber), CMC (sodium carboxymethylcellulose) and deionized water for 2 hours by a closed stirrer according to the mass ratio of 95:2:2:1:100, and uniformly mixing to obtain negative electrode slurry; and uniformly coating the prepared negative electrode slurry on a copper foil, vacuum drying at 100 ℃, rolling and cutting to obtain the negative electrode plate.

3) Electrolyte solution: liPF at 1.0mol/L ₆ The solution is used as electrolyte, and the solvent of the electrolyte is a mixed solution of Ethylene Carbonate (EC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC) in a volume ratio of 1:1:1;

4) A diaphragm: a PP separator;

5) And (3) battery assembly: the positive electrode sheet and the negative electrode sheet were assembled into a full battery in a glove box, and lithium batteries of examples B1 to B5 and comparative examples B1 to B2 were obtained in this order, respectively. Wherein the lithium battery provided in example B1 contains the lithium-rich cathode material provided in example B1, the lithium battery provided in example B2 contains the lithium-rich cathode material provided in example B1, and so on, and the lithium battery provided in comparative example B1 contains the lithium-rich cathode material provided in comparative example B1.

The above lithium ion batteries were respectively subjected to the following related performance tests in table 2, and the related performance test methods were as follows:

capacity retention test: after the formation of the battery is completed, the battery is charged at 1C (off current 0.025C) at normal temperature of 25 ℃, and the battery is discharged at 1C and circulated for 600 circles. Capacity retention after 500 cycles formula = charge specific capacity for 500 cycles/charge specific capacity for first cycle 100%.

The test results are shown in table 2 below:

TABLE 2

In the batteries provided in examples B1 to B11 containing the composite lithium-supplementing material in examples A1 to A7 of the present application, respectively, in which the capacity retention after 500 cycles of each battery was 89% or more, the capacity retention after 500 cycles of the battery in examples B1 to B9 was 94% or more, the first-cycle charge specific capacity of the battery in examples B1 to B11 was also significantly higher than that of the comparative examples B1 to B5 of the same positive electrode material, and the first-cycle charge specific capacity of the battery in specific examples B1 to B7 was significantly higher than that of comparative example B3 without adding the lithium-supplementing material, in combination with tables 1 and 2; the first-charge specific capacity of the battery in example B8 was significantly higher than that of comparative example B4, in which no lithium supplementing material was added; the first-charge specific capacity of the battery in example B9 was significantly higher than that of comparative example B5, in which no lithium supplementing material was added.

Comparing examples B10 and B11 with examples B1 to B7, the three characteristic peak ratios of the lithium-rich cathode material have an effect on the electrochemical performance of the lithium-rich cathode material, as in example B10, I ₄ /I ₅ =1.39 is close to I of the lithium-rich cathode material of the embodiment of the application ₄ /I ₅ The end of range, 1.40, reduced reversible capacity and capacity retention of the battery relative to examples B1 to B7; example B11I ₄ /I ₅ =0.80 is close to I of the lithium-rich cathode material of the embodiment of the application ₄ /I ₅ End of range, I ₄ /I ₆ I=0.55 close to the lithium-rich cathode material of the example of the application ₄ /I ₅ The range end value of 0.55 also decreased the reversible capacity and capacity retention of the battery relative to examples B1 to B7.

Comparing examples B1 to B11 with comparative examples B1 and B2, the composite lithium-supplementing material used in comparative examples B1 and B2 does not satisfy the Raman spectrum of 0.80.ltoreq.I ₁ /I ₂ ≤1.40、2.00≤I ₁ /I ₃ ≤6.50、1.50≤I ₂ /I ₃ And 6.00, resulting in significantly lower initial charge specific capacity and capacity retention of the batteries in comparative examples B1 and B2. As the first-charge specific capacity and capacity retention rate of the battery in comparative example B1 were significantly lower than those of example B1, and the first-charge specific capacity and capacity retention rate of the battery in comparative example B2 were significantly lower than those of example B2.

Therefore, the bonding strength of the carbon layer and the lithium supplementing core of the composite lithium supplementing material is high, the overall structural stability, the surface interface stability and the processing performance of the composite lithium supplementing material are improved, the good lithium supplementing performance is exerted, and the first-cycle charging specific capacity and the capacity retention rate are improved.

The results show that the composite lithium supplementing material provided by the embodiment of the application has high electronic conductivity, can enhance the bonding strength between the carbon material and the iron-based lithium supplementing agent particles, improves the overall structural stability and the surface interface stability of the composite lithium supplementing material, and simultaneously obviously reduces the residual alkali content, thereby improving the lithium supplementing effect of the lithium supplementing material, reducing the internal resistance of a lithium battery, and further improving the reversible capacity, the cycling stability and other electrochemical properties of the lithium battery.

The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the application.

Claims

1. The composite lithium supplementing material is characterized in that: comprises an iron-based lithium supplementing agent and a carbon material, wherein the carbon material coats the iron-based lithium supplementing agent, the Raman spectrum of the composite lithium supplementing material comprises a first characteristic peak, a second characteristic peak and a third characteristic peak, and the intensity of the first characteristic peak is recorded as I ₁ The intensity of the second characteristic peak is recorded as I ₂ The intensity of the third characteristic peak is recorded as I ₃ The I is ₁ To I ₃ The following relationship is satisfied:

2. The composite lithium-supplementing material of claim 1, wherein: the raman shift intervals corresponding to the first characteristic peak, the second characteristic peak and the third characteristic peak are respectively as follows:

the raman shift interval of the first characteristic peak is: 1343-1353 cm ^-1 ；

3. The composite lithium-supplementing material according to any one of claims 1 to 2, wherein: the carbon material forms a carbon coating layer, and the thickness of the carbon coating layer ranges from 1nm to 1 mu m; and/or

The carbon material comprises at least one of carbon black, hard carbon, soft carbon, graphite and graphene oxide; and/or

The Dv50 particle size of the iron-based lithium supplementing agent is 1-20 mu m; and/or

The iron-based lithium supplementing agent comprises Li ₅ FeO ₄ 。

4. The composite lithium-supplementing material of claim 3, wherein: the carbon coating layer comprises an amorphous carbon layer and a graphitized carbon layer, the amorphous carbon layer coats the iron-based lithium supplementing agent, and the graphitized carbon layer coats the surface of the amorphous carbon layer; wherein the thickness ratio of the amorphous carbon layer to the graphitized carbon layer is (0.2 to 10): 1.

5. the composite lithium supplementing material according to any one of claims 1 to 2 and 4, wherein: the composite lithium supplementing material includes at least one of the following (1) to (6):

(1) Specific surface area of 0.1-100 m ² /g；

(2) Tap density of 0.8-2 g/cm ³ ；

(3) Residual alkalinity is more than 0 and less than or equal to 5wt%;

(4) The Dv50 particle size is 1-20 mu m;

(5) Dv99 is 10-50 mu m;

6. The composite lithium supplementing material according to any one of claims 1 to 2 and 4, wherein: at 0.05C magnification: the first charge constant current ratio is more than 80%, wherein the constant current section charge specific capacity C1 under the voltage of 2.5-4.3V is more than 450mAh/g, and the total charge specific capacity C2 under the voltage of 4.3V is more than 465mAh/g.

7. The preparation method of the composite lithium supplementing material is characterized by comprising the following steps of:

sintering the mixture to form a carbon coating layer on the surface of the iron-based lithium supplementing agent particles to obtain a composite lithium supplementing material;

Or alternatively, the first and second heat exchangers may be,

performing fourth sintering treatment on the third mixture to obtain a composite lithium supplementing material; wherein the temperature of the fourth sintering treatment is higher than the temperature of the third sintering treatment.

8. The method of manufacturing according to claim 7, wherein: the iron-based lithium supplementing agent is prepared by the following steps:

sintering the precursor of the iron-based lithium supplementing agent for 1-9 hours at 100-350 ℃ in a protective atmosphere, and then sintering at 800-950 ℃ for 2-24 hours;

and/or

The first sintering treatment is carried out for 2 to 15 hours at the temperature of 300 to 700 ℃; and/or

The temperature of the second sintering treatment is 600-1400 ℃ and the time is 2-15 h; and/or

The carbon source comprises at least one of saccharides, high molecular organic matters and conductive carbon; and/or

The amorphous carbon precursor comprises at least one of glucose, sucrose, fructose, chitosan, lignin, carboxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, phenolic resin and resin; and/or

The graphitized carbon precursor comprises at least one of needle coke, petroleum coke, asphalt, polyphenylene and polyphenylacetylene; and/or

The temperature of the third sintering treatment is 300-700 ℃ and the time is 2-15 h; and/or

The temperature of the fourth sintering treatment is 600-1400 ℃ and the time is 2-15 h.

9. A lithium-rich positive electrode material is characterized in that: comprising a positive electrode material and the composite lithium supplementing material according to any one of claims 1 to 6 or the composite lithium supplementing material prepared by the preparation method according to any one of claims 7 to 8.

10. The lithium-rich cathode material according to claim 9, characterized in that: the Raman spectrum of the lithium-rich positive electrode material comprises a fourth characteristic peak, a fifth characteristic peak and a sixth characteristic peak, and the intensity of the fourth characteristic peak is recorded as I ₄ The intensity of the fifth characteristic peak is denoted as I ₅ The intensity of the sixth characteristic peak is denoted as I ₆ The I is ₄ To I ₆ The following relationship is satisfied:

wavelength intervals corresponding to the fourth characteristic peak, the fifth characteristic peak and the sixth characteristic peak are respectively as follows:

11. The lithium-rich cathode material according to claim 9 or 10, characterized in that: under the same mass, the capacity improvement rate of the lithium-rich positive electrode material is more than 1% compared with that of the positive electrode material;

and/or

The positive electrode material includes at least one of the following (1) to (4):

(2) The particle diameter of the Dv50 is 0.1-15 mu m;

(3) Dv99 is 5-50 mu m;

(4) The water absorption rate of the positive electrode material is 0-50 ppm/s in the environment with the standard atmospheric pressure, the temperature of 23-27 ℃ and the relative humidity of 10-50%.

12. A positive electrode comprising a positive electrode active layer, characterized in that: the positive electrode active layer comprises the lithium-rich positive electrode material according to any one of claims 9 to 11.

13. A secondary battery characterized in that: comprising the positive electrode of claim 12.