CN114335417B - Pre-lithiated negative electrode plate, preparation method thereof and lithium battery - Google Patents

Abstract

The application discloses a pre-lithiated negative electrode plate, a preparation method thereof and a lithium battery, wherein the pre-lithiated negative electrode comprises a negative electrode current collector, an active material layer covered on the surface of the negative electrode current collector, a plurality of modification layers covered on part of the surface of the active material layer, and a lithium-containing layer covered on the residual surface of the active material layer and the surfaces of the modification layers, wherein the modification layers are distributed on the surface of the active material layer at intervals, and the coverage rate is 30-75%. The modification layer/lithium-containing layer interface in the pre-lithiated cathode is used as an artificial electronic path and is responsible for stabilizing the electronic transmission between two phase interfaces in the pre-lithiation process, so that the damage of interface stress fluctuation to the electronic path structure is avoided, the reaction depth of contact pre-lithiation is obviously enhanced, the utilization rate of the lithium-containing layer is improved, the yield of inert lithium formation is reduced, and the capacity retention rate and the cycling stability of the battery are improved.

Description

Prelithiated negative electrode sheet, preparation method thereof and lithium battery

Technical field

The present application relates to the technical field of lithium-ion batteries, and in particular to a pre-lithiated negative electrode sheet, its preparation method and lithium battery.

Background technique

During the first charging process of a lithium-ion battery, a solid electrolyte film (SEI film) will spontaneously form on the surface of the negative electrode, resulting in a partial loss of reversible lithium ion capacity, which in turn manifests as a low first Coulombic efficiency, resulting in a vacancy in the lithium ion inventory of the positive electrode, which Reduced reversible cycle capacity of lithium-ion batteries.

Contact prelithiation is an effective method to increase the first Coulombic efficiency of lithium-ion batteries and improve battery cycle performance. Specifically, a lithium-containing layer is composited on the surface of the negative electrode to trigger a contact prelithiation process of an internal short-circuit electrochemical reaction, thereby storing a certain amount of lithium ions in the negative electrode structure in advance to compensate for the capacity generated during the first cycle of the battery. vacancy.

During the contact prelithiation reaction, the direct contact site between the lithium-containing layer and the negative electrode serves as an electron path to transfer electrons, while the electrolyte adsorbed on the lithium-containing layer/negative electrode contact interface serves as an ion path to transfer lithium ions. role. However, due to the reaction nature of short-circuit electrochemistry, the contact prelithiation process will be accompanied by the growth of a solid electrolyte film on the surface of the negative electrode, and since the electron path carries a large electron density, this causes the electron path structure to be easily damaged by the solid electrolyte. The expansion of the film causes damage, causing the electronic path to be blocked, prompting the contact pre-lithiation reaction to stop prematurely, resulting in low utilization of the lithium-containing layer. At this time, due to the loss of effective electron transfer paths, the lithium-containing layer left on the surface of the negative electrode becomes electronically inert "dead" lithium. Excessive inert lithium not only reduces the utilization rate of the lithium-containing layer, but also hinders the battery operation process. The diffusion and migration of lithium ions in the battery will increase the electrochemical polarization phenomenon, thereby reducing the capacity retention rate and cycle stability of the battery, and may trigger lithium precipitation in the negative electrode.

Contents of the invention

This application provides a pre-lithiated negative electrode sheet, its preparation method and a lithium battery, aiming to solve the problem that the lithium-containing layer cannot be fully utilized due to unstable electronic pathways during the pre-lithiation process, causing it to become inert lithium.

On the one hand, embodiments of the present application provide a pre-lithiated negative electrode sheet, including a negative electrode current collector, an active material layer covering the surface of the negative electrode current collector, a plurality of modification layers covering part of the surface of the active material layer, and an active material layer covering the surface of the active material layer. The lithium-containing layer on the remaining surface of the material layer and the surface of the multiple modified layers. The multiple modified layers are spaced apart on the surface of the active material layer, with a coverage rate of 30 to 75%; the multiple modified layers include lithium-philic metals and lithium-philic metal oxides. and one or more nitrides of lithiophilic metals.

Optionally, the unit area mass of the plurality of modification layers is 0.1 to 5% of the unit area mass of the active material layer.

Optionally, the average area of a single modification layer among the plurality of modification layers is 100 to 1,000,000 nm ² .

Optionally, the lithiophilic metal includes one or more of gold, silver, copper, iron, titanium, aluminum, manganese, tin, cobalt, nickel, chromium, bismuth, vanadium, molybdenum and niobium.

Optionally, the lithium-containing layer includes metallic lithium, lithium silicon alloy, lithium magnesium alloy, lithium copper alloy, lithium silver alloy, lithium beryllium alloy, lithium zinc alloy, lithium cadmium alloy, lithium aluminum alloy, lithium gold alloy and lithium boron alloy one or more of them.

On the other hand, embodiments of the present application provide a method for preparing the above-mentioned pre-lithiated negative electrode sheet, including the following steps:

(1) Preparing a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector, and an active material layer covering the surface of the negative electrode current collector;

(2) Deposit a plurality of modification layers at intervals on the surface of the lithium ion battery negative electrode, so that part of the surface of the active material layer covers the plurality of modification layers to obtain a lithium ion battery negative electrode sheet;

(3) Deposit a lithium-containing layer on the surface of the lithium-ion battery negative electrode sheet, so that the remaining surface of the active material layer and the surfaces of the plurality of modified layers are covered with a lithium-containing layer to obtain a lithium-loaded negative electrode sheet. ;

(4) Place the lithium-carrying negative electrode sheet in the electrolyte to complete the contact prelithiation reaction and obtain the prelithiated negative electrode sheet. Optionally, the surface of the lithium ion battery negative electrode is covered with a lithium-containing layer.

Optionally, in step (2), the method for depositing multiple modified layers at intervals on the surface of the negative electrode of the lithium ion battery includes one or more of magnetron sputtering, vacuum evaporation, scraping, spraying and chemical vapor deposition. combination of species.

Optionally, in step (3), the method of depositing a lithium-containing layer on the surface of the lithium-ion battery negative electrode sheet includes one or a combination of vacuum evaporation, mechanical rolling, scraping and spraying.

Optionally, after step (3), the lithium-carrying negative electrode sheet is also subjected to a rolling pressing process, and the pressure range of the rolling pressing process is 20-50 MPa.

In another aspect, embodiments of the present application provide a lithium battery, including a positive electrode sheet, a separator, an electrolyte, and the above-mentioned prelithiated negative electrode sheet.

The prelithiated negative electrode sheet provided by this application includes a plurality of modification layers covering part of the surface of the active material layer, and a lithium-containing layer covering the remaining surface of the active material layer and the surface of the plurality of modification layers, wherein the plurality of modification layers include One or more of lithium metal, oxides of the lithiophilic metal, and nitrides of the lithiophilic metal. The above-mentioned multi-layer structure of the prelithiated negative electrode sheet forms three interfaces, namely: active material layer/modified layer interface, modified layer/lithium-containing layer interface, and active material layer/lithium-containing layer interface. Among them, the active material layer/modified layer interface and the modified layer/lithium-containing layer interface serve as artificial electron pathways, responsible for stabilizing the electron transmission between the two phase interfaces during the prelithiation process; while the active material layer/lithium-containing layer interface serves as The ion pathway is responsible for the diffusion and migration of ions in the two-phase structure during the prelithiation process.

The above-mentioned artificial electron path can effectively avoid the formation of lithium dendrite morphology during the pre-lithiation reaction, thereby increasing the effective contact sites between the lithium-containing layer and the negative electrode and promoting the reaction rate of contact pre-lithiation. At the same time, suppressing the lithium dendrite morphology, that is, reducing the area of the lithium-containing layer exposed to the electrolyte, is beneficial to reducing side reactions and improving the utilization rate of the lithium-containing layer.

The above-mentioned artificial electron path effectively stabilizes the electron conductivity between the lithium-containing layer/anode interface during the pre-lithiation reaction, and avoids the impact of interface stress fluctuations on electrons caused by the growth of the solid electrolyte film, the dissolution of the lithium-containing layer, and the lithiation of the anode. The destruction of the via structure significantly enhances the reaction depth of contact prelithiation, improves the utilization rate of the lithium-containing layer, reduces the yield of inert lithium formation, and improves the capacity retention rate and cycle stability of the battery. At the same time, the artificial electronic path can avoid spontaneous chemical reactions of the lithium-loaded anode in a dry environment, thereby further improving the physical and chemical stability of the lithium-containing layer during the non-prelithiation process.

Description of the drawings

The features, advantages and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.

Figure 1 is a schematic structural diagram of the pre-lithiated negative electrode sheet of the present application;

Figure 2 is an atomic force microscope image of the surface after depositing a modification layer on the negative electrode of a lithium ion battery in Example 1 of the present application;

Figure 3 is a scanning electron microscope image of the surface after depositing a modification layer on the negative electrode of a lithium ion battery in Example 1 of the present application;

Figure 4 is a scanning electron microscope image of the lithium-loaded negative electrode sheet in Example 1 of the present application after contact with the prelithiation reaction;

Figure 5 is a graph showing the electrical performance results of the lithium batteries disclosed in Examples 1 to 10 and Comparative Example 1 of the present application.

In the attached picture:

10-prelithiated negative electrode sheet; 11-lithium ion battery negative electrode; 12-modification layer; 13-lithium-containing layer; 20-electrolyte.

Detailed ways

In order to make the purpose, technical solutions and beneficial technical effects of the present invention clearer, the present invention will be further described in detail below with reference to examples. It should be understood that the embodiments described in this specification are only for explaining the present invention and are not intended to limit the present invention.

For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range. In addition, although not explicitly stated, every point or individual value between the endpoints of a range is included in the range. Thus, each point or single value may serve as a lower or upper limit on its own in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.

In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" are inclusive of the original number, and the "multiple" in "one or more" means two or more, and "a The "multiple" in "or more" means two or more.

The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The following description illustrates exemplary embodiments in more detail. At various points throughout this application, guidance is provided through a series of examples, which may be used in various combinations. In various embodiments, the enumerations are merely representative groups and should not be construed as exhaustive.

During the contact prelithiation process of the negative electrode of lithium-ion batteries, the electronic path structure between the negative electrode/lithium-containing layer is a key factor affecting the prelithiation effect and the utilization rate of the lithium-containing layer. Therefore, interface modification methods can be used to stabilize the electronic pathway structure to improve the traditional contact prelithiation behavior, increase the reaction depth of prelithiation, improve the utilization of the lithium-containing layer, and reduce the formation and production of inert lithium. In order to better utilize the high specific capacity advantages of high-capacity anodes, further promote the application of high-capacity anodes in commercial lithium-ion batteries, and improve the environmental value and price advantages of contact prelithiation technology, a new method for lithium-ion batteries was developed. It is very important and urgent to apply the interface modification method of negative electrode contact prelithiation to lithium-ion batteries.

Prelithiated negative electrode sheet

An embodiment of the first aspect of the present application provides a pre-lithiated negative electrode sheet, which includes a negative electrode current collector, an active material layer covering the surface of the negative electrode current collector, and a plurality of modification layers (artificial electron path layers) covering part of the surface of the active material layer. , and a lithium-containing layer covering the remaining surface of the active material layer and the surface of multiple modification layers. The multiple modification layers are spaced apart on the surface of the active material layer, with a coverage rate of 30 to 75%; the multiple modification layers include lithium-philic metals, One or more of lithium metal oxides and lithiophilic metal nitrides.

According to embodiments of the present application, the structure of the above-mentioned prelithiated negative electrode sheet includes three two-phase interfaces, namely: active material layer/modified layer interface, modified layer/lithium-containing layer interface, and active material layer/lithium-containing layer Interface, the unit area proportions of the above three two-phase interfaces are 30-75%, 30-75%, and 25-70% respectively.

Among them, the active material layer/modified layer interface and the modified layer/lithium-containing layer interface serve as artificial electron pathways, responsible for stabilizing the electron transmission between the two phase interfaces during the prelithiation process; while the active material layer/lithium-containing layer interface serves as The ion pathway is responsible for the diffusion and migration of ions in the two-phase structure during the prelithiation process.

Due to the chemical potential energy difference at the active material layer/lithium-containing layer contact interface, the lithium-containing layer will dissolve (even if no electrolyte is added), thus forming a pore structure to accommodate the electrolyte, which further serves as an ion channel to transmit lithium ions. effect.

The above-mentioned artificial electron path can effectively avoid the formation of lithium dendrite morphology during the pre-lithiation reaction, thereby increasing the effective contact sites between the lithium-containing layer and the negative electrode and promoting the reaction rate of contact pre-lithiation. At the same time, suppressing the lithium dendrite morphology, that is, reducing the area of the lithium-containing layer exposed to the electrolyte, is beneficial to reducing side reactions and improving the utilization rate of the lithium-containing layer.

The above-mentioned artificial electron path effectively stabilizes the electron conductivity between the lithium-containing layer/anode interface during the pre-lithiation reaction, and avoids the impact of interface stress fluctuations on electrons caused by the growth of the solid electrolyte film, the dissolution of the lithium-containing layer, and the lithiation of the anode. The destruction of the via structure significantly enhances the reaction depth of contact prelithiation, improves the utilization rate of the lithium-containing layer, reduces the yield of inert lithium formation, and improves the capacity retention rate and cycle stability of the battery. At the same time, the artificial electronic path can avoid spontaneous chemical reactions of the lithium-bearing anode in a dry environment, thereby further improving the physical and chemical stability of the lithium-containing layer during the non-prelithiation process.

According to the embodiments of the present application, when the coverage rate of the multiple modification layers on the surface of the active material layer is less than 30%, there are too few artificial electron paths, too few electron transmission paths, and the improvement of prelithiation is not obvious; multiple modification layers When the coverage rate of the surface of the active material layer is higher than 75%, the degree of electrolyte infiltration in the contact interface is reduced, causing adverse reactions, resulting in reduced utilization of the lithium-containing layer, first Coulombic efficiency, and reversible capacity.

According to embodiments of the present application, the modification layer includes one or more of lithium-philic metals, lithium-philic metal oxides, and lithium-philic metal nitrides. The modification layer includes the above substances to ensure that they are deposited on the surface of the active material layer. It can form a stable interface layer with the active material layer; at the same time, it also ensures that the lithium-containing layer can form a stable interface layer with it after it is deposited on its surface.

In embodiments of the present application, the lithiophilic metal includes one or more of gold, silver, copper, iron, titanium, aluminum, manganese, tin, cobalt, nickel, chromium, bismuth, vanadium, molybdenum and niobium.

In the embodiments of the present application, the unit area mass of the multiple modification layers is 0.1 to 5% of the unit area mass of the active material layer. The calculation method is: unit area mass of the multiple modification layers/unit area mass of the active material layer. .

According to the embodiments of the present application, when the mass per unit area of multiple modification layers is less than 0.1%, the improvement in prelithiation is not obvious; when the mass per unit area of multiple modification layers is higher than 5%, the actual energy density of the battery is reduced. .

In the embodiment of the present application, the average area of a single modification layer among the plurality of modification layers is 100 to 1,000,000 nm ² . When the average area of a single modification layer is less than 100nm ² , a stable electronic path structure is missing. Severe interface fluctuations during the prelithiation process will cause the structure of the electronic path to collapse, and the improvement of prelithiation is not obvious. When the average area of a single modification layer is greater than ^1,000,000 nm, the ion path density between the contact interface between the content layer and the negative electrode layer is low, resulting in obstruction of lithium ion diffusion, which is not conducive to the pre-lithiation reaction.

In embodiments of the present application, the lithium-containing layer includes metallic lithium, lithium silicon alloy, lithium magnesium alloy, lithium copper alloy, lithium silver alloy, lithium beryllium alloy, lithium zinc alloy, lithium cadmium alloy, lithium aluminum alloy, lithium gold alloy and one or more of lithium boron alloys.

The lithium-containing layer material has a lower electrochemical potential than the negative active layer, and is one of the necessary conditions for triggering the contact prelithiation reaction. In addition, the theoretical unit mass capacity of the lithium-containing layer material is higher than the theoretical unit mass capacity of the negative electrode active layer material, thereby achieving an effective prelithiation effect.

During the lithiation reaction, due to the potential difference between the lithium-containing layer and the negative electrode layer, the lithium-containing layer undergoes an oxidation reaction, while the negative electrode layer undergoes a reduction reaction. During this period, the lithium-containing layer is oxidized to give lithium ions and electrons. The electrons flow to the negative electrode layer through the electron path, and the lithium ions flow to the negative electrode layer through the electrolyte (ion path), and after contact with the electrons and the negative electrode layer, a lithiation reaction of the negative electrode occurs. .

Preparation method of prelithiated negative electrode sheet

A second embodiment of the present application provides a method for preparing the above-mentioned pre-lithiated negative electrode sheet, including the following steps:

(1) Preparing a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector, and an active material layer covering the surface of the negative electrode current collector;

(2) Deposit a plurality of modification layers at intervals on the surface of the lithium ion battery negative electrode, so that part of the surface of the active material layer covers the plurality of modification layers to obtain a lithium ion battery negative electrode sheet;

(3) Deposit a lithium-containing layer on the surface of the lithium-ion battery negative electrode sheet, so that the remaining surface of the active material layer and the surfaces of the plurality of modified layers are covered with a lithium-containing layer to obtain a lithium-loaded negative electrode sheet. ;

(4) Place the lithium-carrying negative electrode sheet in the electrolyte to complete the contact prelithiation reaction and obtain the prelithiated negative electrode sheet. Optionally, the surface of the lithium ion battery negative electrode is covered with a lithium-containing layer.

In the embodiment of the present application, in step (2), the method of depositing multiple modified layers at intervals on the surface of the negative electrode of the lithium ion battery includes magnetron sputtering, vacuum evaporation, scraping, spraying and chemical vapor deposition. One or a combination of several.

According to embodiments of the present application, by controlling the parameters of the physical deposition process in step (2), multiple modification layers can be deposited on the surface of the negative electrode of the lithium ion battery. The multiple modification layers are spaced apart and have a coverage rate of 30 to 75%.

By controlling the parameters of the physical deposition process in step (2), the unit area mass of the multiple modification layers can also be 0.1 to 5% of the unit area mass of the active material layer.

By controlling the parameters of the physical deposition process in step (2), the average area of a single modification layer among the plurality of modification layers can also be made to be 100 to 1,000,000 nm ² .

In the embodiment of the present application, in step (3), the method for depositing a lithium-containing layer on the surface of the lithium-ion battery negative electrode sheet includes one or a combination of vacuum evaporation, mechanical rolling, scraping and spraying. .

As shown in Figure 1, according to the embodiment of the present application, controlling the parameters of the physical deposition process in step (3) can enable the lithium-containing layer to fill the surface that is not covered with the modification layer and evenly cover the negative electrode of the lithium ion battery. surface of the piece.

In the embodiment of the present application, after step (3), the lithium-loaded negative electrode sheet is also subjected to a rolling pressing process, and the pressure range of the rolling pressing process is 20-50 MPa.

According to embodiments of the present application, the structure of the lithium-loaded negative electrode after the above-mentioned pressure roller pressing process remains stable during the storage, transportation, packaging, and other processes of the lithium-loaded negative electrode.

lithium battery

A third embodiment of the present application provides a lithium battery, including a positive electrode sheet, a separator, an electrolyte, and the above-mentioned prelithiated negative electrode sheet.

The above-mentioned pre-lithiated negative electrode sheets include not only silicon negative electrode sheets, but also lithium battery negative electrode sheets with other active materials such as graphite, hard carbon, and soft carbon.

Lithium batteries containing the above-mentioned pre-lithiated negative electrode sheets not only have higher first Coulomb efficiency, but also higher capacity retention and cycle stability. It can be used in rechargeable batteries for portable electronic products, power tools, electric vehicles, etc.

Example

Example 1

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use magnetron sputtering technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metallic silver. The unit area mass of the artificial electron path layer is 0.1% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 2500 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 20 MPa to obtain a lithium-loaded negative electrode sheet. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 50%, 50%, and 50% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing.

The test results show that after magnetron sputtering treatment, the atomic force microscope photo shows that nano-sized metallic silver particles are formed on the surface of the negative electrode (Figure 2). The scanning electron microscope shows that the nano-silver particles are evenly dispersed in the active particles of the negative electrode. upper surface (Fig. 3). Among them, the raised metallic silver particles serve as artificial electron pathways, while the exposed active particle surface of the negative electrode serves as an ion pathway during the prelithiation reaction. As shown in Figure 5, the half-cell test shows that (the counter electrode is a metallic lithium sheet), the utilization rate of the lithium-containing layer is 85.4%, and there is no obvious inert lithium formation on the surface of the negative electrode (Figure 4). Full-cell testing showed (the counter electrode was lithium iron phosphate) that the first coulombic efficiency of the pre-lithiated battery was 98.1%, the reversible capacity was 141mAh/g, and the capacity retention rate after 300 cycles was 95.4% (Figure 5).

Example 2

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use magnetron sputtering technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metallic silver. The unit area mass of the artificial electron path layer is 0.5% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 100 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 30 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 30%, 70%, and 30% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows (the counter electrode is a metallic lithium sheet) that the utilization rate of the lithium-containing layer is 90.2%, and the full-cell test shows (the counter electrode is lithium iron phosphate) that the first Coulombic efficiency of the prelithiated battery is 97.5%, the reversible capacity is 139mAh/g, and the capacity retention rate after 300 cycles is 96.3%.

Example 3

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use magnetron sputtering technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metallic copper. The unit area mass of the artificial electron path layer is 0.1% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 900 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer on the surface of the negative electrode described in step (2), which is a lithium-silicon alloy, and perform a rolling process at a pressure of 40 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 45%, 55%, and 45% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows (the counter electrode is a metallic lithium sheet) that the utilization rate of the lithium-containing layer is 88.2%. The full-cell test shows (the counter electrode is lithium iron phosphate) that the first Coulombic efficiency of the pre-lithium battery is 98.5%, the reversible capacity is 145mAh/g, and the capacity retention rate after 300 cycles is 93.7%.

Example 4

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use vacuum evaporation technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metallic aluminum. The unit area mass of the artificial electron path layer is 1.0% of the mass of the active material per unit area of the negative electrode. More than The average area of a single modification layer among the modification layers is 900nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 25 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 45%, 55%, and 45% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows (the counter electrode is a metallic lithium sheet) that the utilization rate of the lithium-containing layer is 84.7%. The full-cell test shows (the counter electrode is lithium iron phosphate) that the first Coulombic efficiency of the pre-lithium battery is The reversible capacity is 136mAh/g, and the capacity retention rate after 300 cycles is 93.8%.

Example 5

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use spraying technology to load an artificial electron path layer on the surface of the negative electrode described in step (1). The material is manganese oxide. The unit area mass of the artificial electron path layer is 2.5% of the mass of the active material per unit area of the negative electrode. Multiple modifications The average area of a single modified layer in the layer is 40000 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 30 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 75%, 25%, and 75% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows (the counter electrode is a metallic lithium sheet) that the utilization rate of the lithium-containing layer is 81.3%, and the full-cell test shows (the counter electrode is lithium iron phosphate) that the first Coulombic efficiency of the prelithium battery is The reversible capacity is 131mAh/g, and the capacity retention rate after 300 cycles is 91.2%.

Example 6

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use spraying technology to load an artificial electron path layer on the surface of the negative electrode described in step (1). The material is nickel oxide. The mass per unit area of the artificial electron path layer is 1.4% of the mass of the active material per unit area of the negative electrode. Multiple modifications The average area of a single modified layer in the layer is 40000 nm ² .

(3) Use mechanical rolling technology to laminate the lithium-containing layer on the surface of the negative electrode described in step (2), which is a lithium-silver alloy, and perform rolling processing at a pressure of 50 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 67%, 33%, and 67% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows (the counter electrode is a metallic lithium sheet) that the utilization rate of the lithium-containing layer is 87.8%, and the full-cell test shows (the counter electrode is lithium iron phosphate) that the first Coulombic efficiency of the pre-lithium battery is The reversible capacity is 132mAh/g, and the capacity retention rate after 300 cycles is 97.6%.

Example 7

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Deposit an artificial electron path layer on the surface of the negative electrode in step (1) by magnetron sputtering. The material is molybdenum nitride. The unit area mass of the artificial electron path layer is 5.0% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 360000 nm ² .

(3) Use mechanical rolling technology to attach the lithium-containing layer, which is metallic lithium, to the surface of the negative electrode described in step (2), and perform rolling processing at a pressure of 50 MPa. The unit area proportions of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 70%, 30%, and 70% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows (the counter electrode is a metallic lithium sheet) that the utilization rate of the lithium-containing layer is 87.3%. The full-cell test shows (the counter electrode is lithium iron phosphate) that the first Coulombic efficiency of the pre-lithium battery is The reversible capacity is 134mAh/g, and the capacity retention rate after 300 cycles is 97.1%.

Example 8

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Deposit an artificial electron path layer on the surface of the negative electrode in step (1) by magnetron sputtering. The material is metallic silver. The mass per unit area of the artificial electron path layer is 5.0% of the mass of the active material per unit area of the negative electrode. More The average area of a single modification layer among the modification layers is 2500nm ² .

(3) Use mechanical rolling technology to laminate the lithium-containing layer on the surface of the negative electrode described in step (2), which is metallic lithium, and perform rolling processing at a pressure of 40 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 55%, 45%, and 55% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows that (the counter electrode is a metallic lithium sheet), the utilization rate of the lithium-containing layer is 85.2%, and the full-cell test shows that (the counter electrode is lithium iron phosphate), the first Coulombic efficiency of the prelithiated battery is The reversible capacity is 140mAh/g, and the capacity retention rate after 300 cycles is 95.8%.

Example 9

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Apply an artificial electron path layer on the surface of the negative electrode described in step (1) using scraping technology. The material is iron oxide. The mass per unit area of the artificial electron path layer is 0.5% of the mass of the active material per unit area of the negative electrode. More than The average area of a single modification layer among the modification layers is 100 nm ² .

(3) Apply a lithium-containing layer, which is a lithium-silver alloy, on the surface of the negative electrode described in step (2) by using scraper coating technology, and perform a rolling process with a pressure of 30 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 30%, 70%, and 30% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows that (the counter electrode is a metallic lithium sheet), the utilization rate of the lithium-containing layer is 82.1%, and the full-cell test shows that (the counter electrode is lithium iron phosphate), the first Coulombic efficiency of the prelithium battery is The reversible capacity is 135mAh/g, and the capacity retention rate after 300 cycles is 92.8%.

Example 10

This embodiment provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use magnetron sputtering technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metal molybdenum. The unit area mass of the artificial electron path layer is 3.0% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 10000 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 40 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 55%, 45%, and 55% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows that (the counter electrode is a metallic lithium sheet), the utilization rate of the lithium-containing layer is 81.6%, and the full-cell test shows that (the counter electrode is lithium iron phosphate), the first Coulombic efficiency of the prelithium battery is 92.5%, the reversible capacity is 133mAh/g, and the capacity retention rate after 300 cycles is 90.9%.

Comparative ratio

Comparative example 1

This comparative example provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (1), and perform a rolling process at a pressure of 20 MPa.

(3) Wet the lithium-carrying negative electrode described in step (2) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. As shown in Figure 3, the half-cell test shows (the counter electrode is a metallic lithium sheet) that the utilization rate of the lithium-containing layer is 64.5%. The full-cell test shows (the counter electrode is lithium iron phosphate) that the first Coulombic efficiency of the prelithium battery is 79.9%, and the capacity retention rate after 300 cycles is 81.4%.

Comparative example 2

This comparative example provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use magnetron sputtering technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metal molybdenum. The unit area mass of the artificial electron path layer is 10.0% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 90000 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 30 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 65%, 35%, and 65% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. The half-cell test showed (the counter electrode was metallic lithium sheet) that the utilization rate of the lithium-containing layer was 83.2%, and the full-cell test showed (the counter electrode was lithium iron phosphate) that the first Coulombic efficiency of the pre-lithiated battery was 89.5%, and the reversible capacity was 115mAh/g, indicating that excessive electronic path content causes the actual unit mass capacity of the battery to decrease.

Comparative example 3

This comparative example provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use magnetron sputtering technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metallic silver. The unit area mass of the artificial electron path layer is 5.0% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 4,000,000 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 30 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 100%, 0%, and 100% respectively, that is, the artificial electron path layer Completely cover the upper surface of the negative electrode.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. The half-cell test showed (the counter electrode was metallic lithium sheet) that the utilization rate of the lithium-containing layer was 54.3%, and the full-cell test showed (the counter electrode was lithium iron phosphate) that the first Coulombic efficiency of the prelithiated battery was 76.8%, and the reversible capacity was 109mAh/g.

Comparative example 4

This comparative example provides a prelithiated negative electrode sheet, its preparation method and a lithium battery, including the following steps:

(1) Make a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector and an active material layer covering the surface of the negative electrode current collector.

(2) Use magnetron sputtering technology to deposit an artificial electron path layer on the surface of the negative electrode described in step (1). The material is metallic silver. The unit area mass of the artificial electron path layer is 0.1% of the mass of the active material per unit area of the negative electrode. The average area of a single modification layer among the plurality of modification layers is 16 nm ² .

(3) Use vacuum evaporation technology to deposit a lithium-containing layer, which is metallic lithium, on the surface of the negative electrode described in step (2), and perform a rolling process at a pressure of 30 MPa. The unit area ratios of the negative electrode/artificial electron path interface, the negative electrode/lithium-containing layer interface, and the artificial electron path/lithium-containing layer interface in the obtained lithium-loaded anode structure are 15%, 85%, and 15% respectively.

(4) Wet the lithium-carrying negative electrode described in step (3) into the electrolyte to complete the contact prelithiation reaction, and assemble it into a battery for testing. The half-cell test showed (the counter electrode was metallic lithium sheet) that the utilization rate of the lithium-containing layer was 67.1%, and the full-cell test showed (the counter electrode was lithium iron phosphate) that the first Coulombic efficiency of the prelithiated battery was 75.4% and the cycle was 300 The capacity retention rate after the second operation was 83.8%.

The prelithiated negative electrode sheet in Comparative Example 1 does not include a modification layer, and the lithium-containing layer utilization rate, first Coulombic efficiency, and cycle stability of the lithium battery are lower than those of the lithium battery in the embodiment.

In Comparative Example 2, the unit area mass of the modified layer of the prelithiated negative electrode sheet is 10.0% of the unit area active material mass of the negative electrode. The results show that excessive electron path content causes the actual unit mass capacity of the battery to decrease.

In Comparative Example 3, the coverage rate of the multiple modified layers of the prelithiated negative electrode sheet on the surface of the active material layer is 100% (that is, the active material layer/modified layer interface accounts for 100% of the unit area, and the modified layer/lithium-containing layer interface accounts for 100%. Ratio of 100%, active material layer/lithium-containing layer interface accounted for 0%), the results show that after the modification layer completely covers the active material layer, the utilization rate of the lithium-containing layer, the first Coulombic efficiency and the cycle stability of the battery decrease.

In Comparative Example 4, the coverage rate of the multiple modified layers of the prelithiated negative electrode sheet on the surface of the active material layer is 15% (the average area of a single modified layer is 16 nm ² ). The results show that there are serious interface structure fluctuations during the prelithiation process. It is easy to cause the collapse of the modification layer structure, prompting the early termination of the pre-lithiation process. At the same time, the lower coverage area of the modified layer results in a lower electron path density, so the prelithiation rate is slower, which overall reflects an unsatisfactory prelithiation process.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person familiar with the technical field can easily think of various equivalent methods within the technical scope disclosed in the present application. Modification or replacement, these modifications or replacements shall be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims (7)

1. A prelithiated negative electrode sheet, characterized in that it includes a negative electrode current collector, an active material layer covering the surface of the negative electrode current collector, a plurality of modification layers covering part of the surface of the active material layer, and a the remaining surface of the active material layer and the lithium-containing layer on the surface of the plurality of modified layers, The plurality of modification layers are spaced apart on the surface of the active material layer, with a coverage rate of 30 to 75%; the plurality of modification layers include lithium-philic metals, oxides of the lithium-philic metals and oxides of the lithium-philic metals. One or more types of nitrides; The unit area mass of the plurality of modification layers is 0.1~5% of the unit area mass of the active material layer; The average area of a single modification layer among the plurality of modification layers is 100~1000000nm ² ; The lithium-containing layer includes metal lithium, lithium silicon alloy, lithium magnesium alloy, lithium copper alloy, lithium silver alloy, lithium beryllium alloy, lithium zinc alloy, lithium cadmium alloy, lithium aluminum alloy, lithium gold alloy and lithium boron alloy. one or more. 2. The prelithiated negative electrode sheet according to claim 1, wherein the lithiophilic metal includes gold, silver, copper, iron, titanium, aluminum, manganese, tin, cobalt, nickel, chromium, bismuth, and vanadium. , one or more of molybdenum and niobium. 3. A method for preparing the prelithiated negative electrode sheet according to any one of claims 1 to 2, characterized in that it includes the following steps: (1) Preparing a lithium-ion battery negative electrode, wherein the lithium-ion battery negative electrode includes a negative electrode current collector, and an active material layer covering the surface of the negative electrode current collector; (2) Deposit a plurality of modification layers at intervals on the surface of the lithium ion battery negative electrode, so that part of the surface of the active material layer covers the plurality of modification layers to obtain a lithium ion battery negative electrode sheet; (3) Deposit a lithium-containing layer on the surface of the lithium-ion battery negative electrode sheet, so that the remaining surface of the active material layer and the surfaces of the plurality of modified layers are covered with a lithium-containing layer to obtain a lithium-loaded negative electrode sheet. ; (4) Place the lithium-carrying negative electrode sheet in the electrolyte to complete the contact pre-lithiation reaction to obtain the pre-lithiated negative electrode sheet. 4. The method for preparing a pre-lithiated negative electrode sheet according to claim 3, characterized in that in step (2), the method of depositing a plurality of modification layers at intervals on the surface of the negative electrode of the lithium ion battery includes magnetron sputtering, One or a combination of vacuum evaporation, blade coating, spray coating and chemical vapor deposition. 5. The method for preparing a pre-lithiated negative electrode sheet according to claim 3, wherein in step (3), the method for depositing a lithium-containing layer on the surface of the lithium-ion battery negative electrode sheet includes vacuum evaporation, mechanical One or a combination of rolling, scraping and spraying. 6. The method for preparing the pre-lithiated negative electrode sheet according to claim 3, characterized in that after step (3), it also includes rolling the lithium-loaded negative electrode sheet, and the pressure range of the roller pressing process is is 20-50Mpa. 7. A lithium battery, characterized by comprising a positive electrode sheet, a separator, an electrolyte, and the prelithiated negative electrode sheet according to any one of claims 1 to 2.