Negative electrode plate and its manufacturing method, secondary battery, battery module, battery pack and power consumption device

Abstract

The present application provides a negative electrode plate for a secondary battery and a manufacturing method thereof, as well as a secondary battery, a battery module, a battery pack and a power consumption device including the negative electrode plate. The composite lithium metal negative electrode plate of the present application includes a current collector and an active material layer coated on at least one surface of the current collector, the active material layer including an active material and a lithium affinity material having a core-shell structure, the core of the lithium affinity material contains the lithium affinity material, and the shell is a carbon material.

Description

[Technical field]

[0001] The present application relates to the technical field of secondary batteries, and in particular to a composite lithium metal negative plate for secondary batteries, a method for manufacturing the negative plate, and a secondary battery, a battery module, a battery pack and a power consuming device including the negative plate. [Background technology]

[0002] In recent years, as the application range of lithium-ion batteries becomes wider and wider, lithium-ion batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As lithium-ion batteries have made rapid development, the requirements for their energy density, cycle performance and safety performance are also increasing.

[0003] In conventional technologies, graphite is generally used as the active material for the negative electrode plate of lithium-ion secondary batteries. However, during charging of conventional lithium-ion secondary batteries, lithium ions are reduced and deposited on the electrode plate, forming lithium dendrites (see Figure 1). The growth of lithium dendrites causes the battery to expand, which destabilizes the electrode-electrolyte interface during battery cycles, leading to poor electrolyte infiltration and destruction of the solid electrolyte interface (SEI) film that has formed, shortening the battery's service life. Lithium dendrites may break through the separator and cause a short circuit inside the lithium-ion battery, which may cause the battery to thermally runaway, resulting in combustion or explosion.

[0004] Therefore, it is necessary to develop a negative plate that can improve the service life and safety performance of lithium-ion batteries by improving the electrode structure, controlling the deposition of lithium ions, and inhibiting the growth of lithium dendrites. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the problems existing in the prior art, the objective of the present application is to provide a composite lithium metal negative plate, which can improve the service life and safety performance of a lithium ion battery using the negative plate, while ensuring the rate performance of the battery and reducing the capacity fade of the battery. [Means for solving the problem]

[0006] In order to achieve the above object, according to a first aspect, the present application provides a composite lithium metal negative electrode plate comprising a current collector and an active material layer coated on at least one surface of the current collector, The active material layer is An active material; and a lithium affinity material having a core-shell structure, The core of the lithium affinity material contains a lithium affinity substance, and the shell is characterized by being a carbon material.

[0007] By increasing the amount of lithium affinity material with a core-shell structure on the surface of the negative plate, the lithium nucleation barrier can be lowered and lithium metal can be oriented to deposit on the lithium affinity material inside the carbon shell. By controlling the position of lithium deposition (inside the carbon shell) and limiting the space for lithium deposition, the growth of lithium dendrites can be significantly suppressed and the expansion of lithium metal during cycling can be reduced. This improves the safety and cycle performance of the battery while achieving extremely high energy density.

[0008] In any embodiment, the weight percentage of the lithium affinity material in the active material layer is between 0.1% and 5%, optionally between 0.3% and 3%.

[0009] This allows one to control the ratio of lithium affinity material in the active material layer to ensure that the energy density of the negative plate is not reduced and that there is sufficient lithium affinity material to induce and control lithium deposition.

[0010] In any embodiment, the lithium affinity material is one or more of an elemental metal, such as Si, Ni, Ga, Sn, In, Ge, Ti, Mo, Pt, Al, Mg, Zn, Ag, Au, Co, Fe, and / or one or more of an oxide, sulfide, fluoride, nitride, chloride, or carbide containing the above metal elements.

[0011] Thus, by selecting a metal and / or its oxide, sulfide, fluoride, nitride, chloride, or carbide having high lithium affinity as the lithium affinity material, it is possible to effectively induce lithium ions to deposit on the surface and prevent the lithium ions from forming lithium dendrites at any position on the negative electrode surface, thereby preventing the lithium dendrites from breaking through the separator and causing a local short circuit, thereby causing a deterioration in the safety performance of the battery.

[0012] In any embodiment, the carbonaceous shell of the lithium-affinitive material has a thickness of between 10 and 70 nm.

[0013] If the thickness of the carbon material shell is too thin, the carbon shell will be easily fractured during cold pressing of the carbon material, and if the thickness is too thick, it will affect the diffusion of lithium ions inside and outside the carbon material shell, and the lithium affinity material in the shell body will be less able to exert its lithium affinity effect.

[0014] In an optional embodiment, the lithium affinitive material has a cavity within the carbonaceous shell.

[0015] This avoids the uncontrolled growth of lithium dendrites on the negative electrode surface by using the internal cavities of the carbon shell material to restrict the lithium deposition space, while at the same time mitigating the expansion problem caused by lithium metal during cycling.

[0016] In an optional embodiment, lithium metal is further contained within the cavity of the lithium-affine material.

[0017] As a result, due to the induction and area restriction effect of the lithium affinity substance in the cavity-containing lithium affinity material, lithium ions undergo a reduction reaction during charging and discharging, and are precipitated and deposited inside the cavities of the lithium affinity material.

[0018] In any embodiment, the active material is selected from one or more of a carbon-based material, a silicone-based material, and a metal oxide.

[0019] By selecting the above-described substances as the active material for the negative electrode plate, it is possible to ensure good lithium ion absorption / release performance and high theoretical capacity of the negative electrode plate, while at the same time forming a stable solid electrolyte interface film (SEI film) on the electrode interface, thereby improving the stability of the negative electrode plate.

[0020] In any embodiment, the carbon-based material is one or more of natural graphite, synthetic graphite, mesocarbon microbeads, hard carbon, soft carbon, and / or The silicone-based material is one or more of silicone carbon, silicon oxide, and / or The metal oxide may be one or more of iron oxide, tin oxide.

[0021] Thus, by selecting the above-mentioned materials as the active material of the negative electrode active material, it is possible to ensure that the performance of the negative electrode plate meets the requirements.

[0022] In an optional embodiment, in addition to the active material layer, there is further included a second active material layer that does not contain a lithium affinity material.

[0023] This allows the addition of a second active material layer that does not contain a lithium affinity material to the outside of the active material layer, which is advantageous for the deposition of lithium metal closer to the current collector and reduces lithium dendrites on the electrode surface.

[0024] According to a second aspect, the present application provides a composite lithium metal negative electrode plate comprising a current collector and an active material layer, further comprising a lithium affinity material layer located between the current collector and the active material layer; the lithium affinity material layer comprises a lithium affinity material having a core-shell structure; The lithium affinity material is characterized in that the core contains a lithium affinity substance and the shell is a carbon material.

[0025] By increasing the amount of lithium affinity material with a core-shell structure between the current collector and the active material layer, the lithium nucleation barrier can be lowered and the lithium metal can be oriented so that it deposits on the lithium affinity material inside the carbon shell, and the deposited lithium metal is closer to the current collector. By controlling the position of lithium deposition (inside the carbon shell) and limiting the space for lithium deposition, the growth of lithium dendrites is greatly suppressed and the expansion of lithium metal during cycling is reduced. This improves the safety and cycle performance of the battery while achieving extremely high energy density.

[0026] In any embodiment, the thickness ratio of the lithium affinity material layer to the active material layer is 0.1 / 100 to 6 / 100, preferably 0.3 / 100 to 5 / 100.

[0027] This allows one to control the thickness ratio of the lithium affinity material layer to the active material layer to ensure that the energy density of the negative plate is not reduced and that there is sufficient lithium affinity material to induce and control lithium deposition.

[0028] In any embodiment, the lithium affinity material is one or more of an elemental metal, such as Si, Ni, Ga, Sn, In, Ge, Ti, Mo, Pt, Al, Mg, Zn, Ag, Au, Co, Fe, and / or one or more of an oxide, sulfide, fluoride, nitride, chloride, or carbide containing the above metal elements.

[0029] Thus, by selecting a metal and / or its oxide, sulfide, fluoride, nitride, chloride, or carbide having high lithium affinity as the lithium affinity material, it is possible to effectively induce lithium ions to deposit on the surface and prevent the lithium ions from forming lithium dendrites at any position on the negative electrode surface, thereby preventing the lithium dendrites from breaking through the separator and causing a local short circuit, thereby causing a deterioration in the safety performance of the battery.

[0030] In any embodiment, the carbonaceous shell of the lithium-affinitive material has a thickness of between 10 and 70 nm.

[0031] If the thickness of the carbon material shell is too thin, the carbon shell is easily broken during cold pressing of the carbon material, and if the thickness is too thick, it affects the diffusion of lithium ions in and out of the carbon material shell, and the lithium affinity material in the shell body is difficult to exert the lithium affinity effect. In any embodiment, the carbon material shell of the lithium affinity material has a cavity inside.

[0032] This avoids the uncontrolled growth of lithium dendrites on the negative electrode surface by using the internal cavities of the carbon shell material to restrict the lithium deposition space, while at the same time mitigating the expansion problem caused by lithium metal during cycling.

[0033] In an optional embodiment, lithium metal is further contained within the cavity of the lithium-affine material.

[0034] As a result, due to the induction and area restriction effect of the lithium affinity substance in the cavity-containing lithium affinity material, lithium ions undergo a reduction reaction during charging and discharging, and are precipitated and deposited inside the cavities of the lithium affinity material.

[0035] According to a third aspect, the present application provides a method of making a composite lithium metal negative electrode plate, the method comprising: Step S1-1: mixing an active material and a lithium affinity material in a dispersion medium in a predetermined ratio to prepare a slurry A; and Step S1-2 of coating the slurry A obtained in Step S1-1 onto at least one surface of a current collector.

[0036] As a result, the above-described manufacturing method can provide a negative electrode plate having a higher energy density and higher cycle use safety.

[0037] In some embodiments, Step S1-3 of dispersing the active material in a dispersion medium to prepare a slurry B; The method further includes step S1-4 of coating the negative electrode plate obtained in step S1-2 with the slurry B obtained in step S1-3.

[0038] As a result, in the negative electrode plate obtained by the above-described manufacturing method, lithium metal is more likely to accumulate in the direction closer to the current collector, and lithium dendrites on the surface of the electrode plate are reduced.

[0039] According to a fourth aspect, the present application provides a method of making a composite lithium metal negative electrode plate, the method comprising: Step S2-1 of dispersing a lithium affinity material in a dispersion medium to prepare a slurry C; Step S2-2 of dispersing the active material in a dispersion medium to prepare a slurry D; Step S2-3: coating the slurry C obtained in step S2-1 on at least one surface of a current collector to form a lithium affinity material coating; and step S2-4 of coating the slurry D obtained in step S2-2 on the surface of the lithium affinity material coating obtained in step S2-3.

[0040] As a result, the negative electrode plate obtained by the above-described manufacturing method has a higher energy density, and higher safety and cycle performance.

[0041] According to a fifth aspect, the present application provides a secondary battery, the secondary battery comprising: The present invention includes a composite lithium metal negative electrode plate according to the first or second aspect of the present application, or a composite lithium metal negative electrode plate manufactured by the manufacturing method according to the third or fourth aspect of the present application, and a positive electrode plate, an electrolyte, and a separator.

[0042] As described above, the secondary battery of the present application has improved service life and safety performance while at the same time ensuring sufficient mass energy density.

[0043] In any embodiment, the lithium absorption capacity of the negative electrode is N, and the lithium release capacity of the positive electrode is P, and the ratio of the lithium capacities of the negative and positive electrode plates is N / P<1, and optionally 0.3≦N / P≦0.9, which is advantageous for further improving the mass energy density of the secondary battery.

[0044] According to a sixth aspect, the present application provides a battery module including the secondary battery of the fifth aspect of the present application.

[0045] According to a seventh aspect, the present application provides a battery pack including the battery module of the sixth aspect of the present application.

[0046] According to an eighth aspect, the present application provides a power consuming device including the secondary battery according to the fifth aspect of the present application, the battery module according to the sixth aspect of the present application, or the battery pack according to the seventh aspect of the present application.

[0047] In the negative plate of the present application, by adding a core-shell lithiophilic material with a lithiophilic material inside onto the negative plate, the nucleation barrier of lithium can be effectively lowered and the lithium metal can be oriented and induced to deposit on the lithiophilic material inside the shell structure, thereby improving the service life and safety performance of the lithium ion battery while ensuring the mass energy density of the battery. [Brief description of the drawings]

[0048] [Figure 1]FIG. 1 is an illustrative schematic diagram of a negative plate having an active material layer on one surface of a current collector, according to one embodiment of the prior art. [Diagram 2] FIG. 2 is an illustrative schematic diagram of a negative plate having an active material layer on one surface of a current collector according to one embodiment of the present application. [Diagram 3] FIG. 2 is an illustrative schematic diagram of a negative plate having an active material layer and a second active material layer on one surface of a current collector according to one embodiment of the present application. [Figure 4] FIG. 2 is an illustrative schematic diagram of a negative plate having an active material layer and a lithium-affinity material layer on one surface of a current collector according to one embodiment of the present application. [Diagram 5] FIG. 1 is a structural schematic diagram of a lithium affinity material according to an embodiment of the present application. [Figure 6] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Figure 7] FIG. 7 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 6. [Figure 8] FIG. 1 is a schematic diagram of a battery module according to an embodiment of the present application. [Figure 9] FIG. 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 10] FIG. 10 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 9. [Figure 11] 1 is a schematic diagram of a power consuming device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Hereinafter, with reference to the drawings as appropriate, embodiments specifically disclosing a negative electrode plate for a secondary battery and a manufacturing method thereof, a secondary battery, a battery module, a battery pack, and a power consumption device according to the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to allow those skilled in the art to easily understand. Note that the drawings and the following description are provided to allow those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0050] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the extreme values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also envisioned. However, if 1 and 2 are listed as minimum range values, and 3, 4, and 5 are listed as maximum range values, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all envisioned. In this application, unless otherwise specified, a numerical range "a to b" represents a shorthand representation of any combination of real numbers from a to b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed herein, and "0-5" is just a shorthand for combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. Unless otherwise stated, all the embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0051] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0052] Unless otherwise stated, all steps in this application may be performed in sequence or randomly, and preferably in sequence. For example, the method includes steps (a) and (b) to mean that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method may further include step (c) as mentioned above to mean that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0053] Unless otherwise specified, the terms "comprise" and "include" referred to in this application may be open ended or closed ended. For example, the terms "comprise" and "include" may further include or include other ingredients not listed, or may include or include only the ingredients listed.

[0054] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied in the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and A and B are both true (or exist).

[0055] The charging and discharging process of lithium ion batteries in the prior art is an oxidation-reduction reaction on the positive and negative electrode plates of lithium ions, and its essence is the process of lithium ion absorption and release on the positive and negative electrode plates. Therefore, it is required that the negative electrode has an appropriate lithium potential, is not easily structurally changed during oxidation and reduction, and has a small volume change of the negative electrode active material during lithium ion absorption and release, has a stable structure, has good cycle performance, and has a high capacity, so that the battery has a high energy density. However, lithium ions are irreversibly deposited on the surface of the negative electrode to form lithium dendrites, which reduces the effective lithium ion content and reduces the initial coulombic efficiency of the battery, and at the same time, the lithium dendrites are easily broken through the separator, which causes a short circuit and reduces the safety of the battery.

[0056] Therefore, there is a strong demand for a new negative plate structure that can ensure the structural stability of the negative plate during charging and discharging, while at the same time ensuring the rate performance of the battery and reducing the decay of the battery capacity.

[0057] In one embodiment of the present application, the present application provides a composite lithium metal negative electrode plate comprising a current collector and an active material layer coated on at least one surface of the current collector, the active material layer comprising: An active material; and a lithium affinity material having a core-shell structure, The core of the lithium affinity material contains a lithium affinity substance and the shell is a carbon material.

[0058] Although the mechanism is not fully understood, the applicant has found the following after many experiments. As shown in FIG. 2, the present application provides a lithium affinity material (63) in the active material layer (61) to lower the lithium nucleation barrier and induce the lithium metal to deposit on the lithium affinity material (65) inside the carbon shell (64), so that the deposited lithium metal is closer to the current collector. By controlling the position of lithium deposition (inside the carbon shell) and limiting the space of lithium deposition, the growth of lithium dendrites is greatly suppressed and the expansion of lithium metal during cycling is reduced (as shown in FIG. 5). This improves the safety and cycle performance of the battery while achieving an extremely high energy density. Therefore, the provision of the lithium affinity material (63) in the active material layer (61) can reduce the generation of irregular lithium dendrites on the surface of the negative plate. The presence of the lithium affinity material (63) induces lithium to be uniformly dispersed and deposited on the negative plate in the form of lithium metal, thereby improving the energy density of the negative plate, avoiding the local high concentration of lithium metal causing irreversible deposition, improving the cycle performance and service life of the battery, reducing the decay of specific capacity due to cycling, and providing the battery with excellent overcharge and overdischarge resistance. In addition, the reduction of lithium dendrites reduces the damage to the separator and avoids short circuiting of the electrodes, thereby improving the safety performance of the battery.

[0059] The active material layer may include an active material, a lithium affinity material, a conductive agent, an adhesive, and an optional thickener. In the present application, the lithium affinity material in the lithium affinity material may be any material that can lower the nucleation barrier of lithium and induce the deposition of lithium in an oriented manner, as described above, and the type of the lithium affinity material is not specifically limited. Optionally, the lithium affinity material may be in various forms, such as an elemental lithium affinity metal, an oxide, or a sulfide. The types of the conductive agent, adhesive, and optional thickener are not specifically limited, and those skilled in the art may select them according to actual needs. The contents of the active material, the lithium affinity material, the conductive agent, the adhesive, and the optional thickener in the active material layer are not specifically limited, and those skilled in the art may select them according to actual needs.

[0060] In some embodiments, the mass percentage of the lithium affinity material in the active material layer is 0.1%-5%, preferably 0.3%-3%. As is already known, the main function of the lithium affinity material in the lithium affinity material is to induce lithium to deposit on its surface, and if the content of the lithium affinity material is too low, sufficient lithium deposition sites cannot be formed, and a large amount of lithium still deposits on the surface of the active material to form lithium dendrites, and if the content of the lithium affinity material is too high, the lithium ions are easy to react with the lithium affinity material and difficult to release, resulting in the loss of lithium ions and the energy density of the battery is reduced. Therefore, by controlling the ratio of the lithium affinity material in the active material layer, it is possible to ensure that the energy density of the negative plate is not reduced, and at the same time ensure that there is enough lithium affinity material to induce and control lithium deposition.

[0061] In some embodiments, the lithium affinity material is one or more of metal elements such as Si, Ni, Ga, Sn, In, Ge, Ti, Mo, Pt, Al, Mg, Zn, Ag, Au, Co, Fe, and / or one or more of oxides, sulfides, fluorides, nitrides, chlorides, and carbides containing the above metal elements, where the lithium affinity property refers to the lithium affinity defined in the lithium affinity test method described below.

[0062] The lithium-affinity metal element and / or its oxide, sulfide, fluoride, nitride, chloride, and carbide can effectively induce lithium ions to deposit on its surface and prevent the lithium ions from forming lithium dendrites at any position on the negative electrode surface, thereby preventing the lithium dendrites from breaking through the separator and causing a local short circuit, thereby causing a deterioration in the safety performance of the battery.

[0063] In some embodiments, the carbon material shell of the lithium affinity material has a thickness of 10 to 70 nm. By having such a thickness, it is possible to take into consideration the ion transport efficiency, while at the same time having an ideal and appropriate strength, and to prevent the metal particles generated in the carbon shell from leaking out of the carbon shell. If the carbon material shell layer is too thin, the stability of the carbon shell is low, and the collapse of the structure is likely to occur during the production of the electrode plate and the use of the electrode, or the deposited lithium tears / breaks through the carbon shell, destroying the oriented deposition of lithium in the shell layer structure. If the carbon shell is too thick, the ion transport path becomes long, the ion transport efficiency decreases, and the rate performance of the battery is significantly reduced.

[0064] In some embodiments, the carbonaceous shell of the lithium affinity material has a cavity inside, the shell layer structure encloses a certain space for lithium deposition, and the formation of the cavity can provide a good growth space for lithium deposition, while at the same time playing a certain area limiting role for the growth of lithium metal, avoiding the disorderly growth of lithium dendrites on the negative electrode surface, while at the same time reducing the expansion problem caused by lithium metal during cycling, and improving the safety of use of lithium ion batteries.

[0065] In some embodiments, lithium metal is further contained in the cavity of the lithium affinity material. The lithium metal may be derived from the deposition of lithium ions on the surface of the lithium affinity material when contacting with the electrolyte. Regardless of whether or not lithium metal is present in the cavity of the lithium affinity material, the induction of the lithium affinity material and the area restriction effect of the cavity are not affected. In general, due to the induction of the lithium affinity material in the shell layer structure, the lithium ions in the electrolyte are deposited in the form of lithium metal, and there is an equilibrium reaction of dynamic conversion between lithium metal and lithium ions. Furthermore, since the specific capacity of the active material is insufficient to accommodate the absorption and release of sufficient lithium ions, a certain amount of metallic lithium may always exist in the cavity. As is already known, the theoretical gram capacity of lithium metal is extremely high, and the presence of metallic lithium significantly improves the energy density of lithium-ion batteries.

[0066] During charging, lithium ions in excess of the capacity of the active material are precipitated and deposited inside the cavities of the lithium affinity material in the form of lithium metal, and during discharging, the lithium ions converted by this precipitated lithium metal are returned to the electrolyte before the lithium ions accommodated in the active material.

[0067] In some embodiments, the active material is selected from one or more of carbon-based materials, silicone-based materials, and metal oxides. As is known, these materials are all common negative plate materials, and have various advantages such as suitable lithium potential, high structural stability, resistance to deformation during lithium ion absorption and release cycles, high energy density, and ease of forming a stable SEI film on the surface, and are therefore generally selected as the active material of the negative electrode. By selecting the above-mentioned materials as the active material of the negative electrode, it is possible to more easily form a composite lithium metal negative electrode structure in the formed negative electrode and the corresponding secondary battery, and ensure that the stability of the negative plate is higher.

[0068] In some embodiments, the carbon-based material is one or more of natural graphite, synthetic graphite, mesocarbon microbeads, hard carbon, soft carbon, and / or The silicone-based material is one or more of silicone carbon, silicon oxide, and / or The metal oxide may be one or more of iron oxide, tin oxide.

[0069] Thus, by selecting the above-mentioned materials as the active material of the negative electrode active material, it is possible to ensure that the performance of the negative electrode plate meets the requirements.

[0070] In some embodiments, in addition to the active material layer, there is a second active material layer (sometimes called a "single active material layer") that does not contain a lithium affinity material. In order to guide the lithium to deposit closer to the current collector and reduce the possibility of depositing at any position on the active material layer surface, the active material layer containing the lithium affinity material is placed closer to the current collector, which can guide the oriented deposition of lithium and reduce the disorder of lithium deposition.

[0071] According to a second aspect, the present application provides a composite lithium metal negative electrode plate comprising a current collector and an active material layer, further comprising a lithium affinity material layer located between the current collector and the active material layer; the lithium affinity material layer comprises a lithium affinity material having a core-shell structure; The lithium affinity material is characterized in that the core contains a lithium affinity substance and the shell is a carbon material.

[0072] By increasing the amount of lithium affinity material with a core-shell structure between the current collector and the active material layer, the lithium nucleation barrier can be lowered and the lithium metal can be oriented so that it deposits on the lithium affinity material inside the carbon shell, and the deposited lithium metal is closer to the current collector. By controlling the position of lithium deposition (inside the carbon shell) and limiting the space for lithium deposition, the growth of lithium dendrites is greatly suppressed and the expansion of lithium metal during cycling is reduced. This improves the safety and cycle performance of the battery while achieving extremely high energy density.

[0073] The active material layer may include a general active material, a conductive agent, an adhesive, and an optional thickener. The general active material is a commercially available product that does not contain a lithium affinity material. The types of the conductive agent, adhesive, and optional thickener are not specifically limited, and those skilled in the art may select them according to actual needs. The contents of the active material, conductive agent, adhesive, and optional thickener in the active material layer are not specifically limited, and those skilled in the art may select them according to actual needs. Optionally, based on the total weight of the active material layer, the amount of the active material may be 93.0 to 98.0 wt%, the amount of the conductive agent may be 0.3 to 4.0 wt%, the amount of the adhesive may be 0.3 to 2.0 wt%, and the amount of the optional thickener may be 0.1 to 1.0 wt%.

[0074] In some embodiments, the thickness ratio of the lithium affinity material layer to the active material layer is 0.1 / 100 to 6 / 100, preferably 0.3 / 100 to 5 / 100. When the lithium affinity material layer and the active material layer are different materials, the thickness ratio of the lithium affinity material layer to the active material layer can be controlled to control the amount ratio of the lithium affinity material and the active material on the current collector surface, ensuring that the energy density of the negative plate is not reduced and that there is enough lithium affinity material to induce and control lithium deposition.

[0075] In some embodiments, the lithium affinity material is one or more of an elemental metal, such as Si, Ni, Ga, Sn, In, Ge, Ti, Mo, Pt, Al, Mg, Zn, Ag, Au, Co, Fe, and / or one or more of an oxide, sulfide, fluoride, nitride, chloride, or carbide containing the above metal elements.

[0076] Thus, by selecting a metal and / or its oxide, sulfide, fluoride, nitride, chloride, or carbide having high lithium affinity as the lithium affinity material, it is possible to effectively induce lithium ions to deposit on the surface and prevent the lithium ions from forming lithium dendrites at any position on the negative electrode surface, thereby preventing the lithium dendrites from breaking through the separator and causing a local short circuit, thereby causing a deterioration in the safety performance of the battery.

[0077] In some embodiments, the carbon shell of the lithium affinity material has a thickness of 10 to 70 nm. By having such a thickness, it is possible to take into consideration the ion transport efficiency, while at the same time having an ideal and appropriate strength, and to prevent the metal particles generated in the carbon shell from leaking out of the carbon shell. If the shell layer of the lithium affinity material is too thin, the stability of the carbon shell is low, and the collapse of the structure is likely to occur during the production of the electrode plate and the use of the electrode, or the deposited lithium tears / breaks through the carbon shell, destroying the oriented deposition of lithium in the shell layer structure. And when the carbon shell structure is destroyed, the metal deposited inside the carbon shell is released, and there is a risk that the oriented deposition of lithium metal cannot be induced. If the carbon shell is too thick, the ion transport path becomes long, the ion transport efficiency decreases, and the rate performance of the battery is significantly reduced.

[0078] In some embodiments, the carbonaceous shell of the lithium affinity material has a cavity inside. As described above, the shell layer structure encloses a certain space for lithium deposition, and the formation of the cavity can provide a good growth space for lithium deposition, while at the same time playing a certain area limiting role for the growth of lithium metal, avoiding the disorderly growth of lithium dendrites on the negative electrode surface, while at the same time reducing the expansion problem caused by lithium metal during cycling, and improving the safety of use of lithium ion batteries.

[0079] In some embodiments, lithium metal is further contained in the cavity of the lithium affinity material. The lithium metal may be derived from the deposition of lithium ions on the surface of the lithium affinity material when contacting with the electrolyte. Regardless of whether or not lithium metal is present in the cavity of the lithium affinity material, the induction of the lithium affinity material and the area restriction effect of the cavity are not affected. In general, due to the induction of the lithium affinity material in the shell layer structure, the lithium ions in the electrolyte are deposited in the form of lithium metal, and there is an equilibrium reaction of dynamic conversion between lithium metal and lithium ions. Furthermore, since the specific capacity of the active material is insufficient to accommodate the absorption and release of sufficient lithium ions, a certain amount of metallic lithium may always exist in the cavity. As is already known, the theoretical gram capacity of lithium metal is extremely high, and the presence of metallic lithium significantly improves the energy density of lithium-ion batteries.

[0080] During charging, lithium ions in excess of the capacity of the active material are precipitated and deposited inside the cavities of the lithium affinity material in the form of lithium metal, and during discharging, the lithium ions converted by this precipitated lithium metal are returned to the electrolyte before the lithium ions accommodated in the active material.

[0081] The present application further provides a method for producing a composite lithium metal negative electrode plate, the method comprising: Step S1-1: mixing an active material and a lithium affinity material in a dispersion medium in a predetermined ratio to prepare a slurry A; and Step S1-2 of coating the slurry A obtained in Step S1-1 onto at least one surface of a current collector.

[0082] As a result, the above-described manufacturing method can provide a negative electrode plate having a higher energy density and higher cycle use safety.

[0083] In some embodiments, Step S1-3 of dispersing the active material in a dispersion medium to prepare a slurry B; The method further includes step S1-4 of coating the negative electrode plate obtained in step S1-2 with the slurry B obtained in step S1-3.

[0084] As a result, in the negative electrode plate obtained by the above-described manufacturing method, lithium metal is more likely to accumulate in the direction closer to the current collector, and lithium dendrites on the surface of the electrode plate are reduced.

[0085] According to a fourth aspect, the present application provides a method of making a composite lithium metal negative electrode plate, the method comprising: Step S2-1 of dispersing a lithium affinity material in a dispersion medium to prepare a slurry C; Step S2-2 of dispersing the active material in a dispersion medium to prepare a slurry D; Step S2-3: coating the slurry C obtained in step S2-1 on at least one surface of a current collector to form a lithium affinity material coating; and step S2-4 of coating the slurry D obtained in step S2-2 on the surface of the lithium affinity material coating obtained in step S2-3.

[0086] As a result, the negative electrode plate obtained by the above-described manufacturing method has a higher energy density, and higher safety and cycle performance.

[0087] The present application further provides a secondary battery, which includes the negative electrode plate of the present application described above, and further includes a positive electrode plate, an electrolyte, and a separator.

[0088] In the secondary battery of the present application, when the lithium absorption capacity of the negative electrode is N and the lithium release capacity of the positive electrode is P, the lithium capacity ratio of the negative and positive electrode plates is N / P<1, and preferably 0.3≦N / P≦0.9.

[0089] Thus, by controlling the capacity ratio of the active materials to N / P<1, the lithium content that can be accommodated in a unit weight of the negative electrode plate can be effectively increased, which is advantageous for improving the energy density of the entire battery. From the viewpoint of further improving the energy density of the entire battery, N / P≦0.9 is preferable. From the viewpoint of better preventing the generation of dendrites and the loss of lithium ions, 0.3≦N / P is preferable.

[0090] The "lithium absorption capacity of the negative electrode" here refers to the amount of lithium ions that can theoretically be absorbed into the negative electrode active material when the battery is fully charged, and does not include lithium metal deposited on the surface of the negative electrode active material, and lithium induced by the lithium affinity material and deposited in the lithium affinity material in the form of lithium metal. The "lithium release capacity of the positive electrode" refers to the amount of lithium that can theoretically be released from the positive electrode when the battery is fully charged. The "lithium absorption capacity of the negative electrode" and the "lithium release capacity of the positive electrode" can be calculated from the amounts of the positive and negative electrode active materials used.

[0091] When the lithium capacity ratio N / P of the positive and negative plates is 1, all of the lithium released from the positive active material can theoretically be absorbed into the negative active material. However, in practice, some of the lithium is precipitated on the surface of the active material, so in the prior art, N / P is generally greater than 1 in order to utilize more of the capacity of the negative active material.

[0092] The present invention can effectively prevent the precipitation of dendrites by inducing lithium to deposit in the lithium affinity material in the form of metal, regardless of the value of N / P. However, the effect of the present invention is particularly remarkable when N / P<1.

[0093] It should also be noted that even if N / P<1, metallic lithium can still be deposited on the surface of the anode active material. However, the deposited metallic lithium will mainly reside inside the lithium affinity material until the cavities in the lithium affinity material are filled. Even if N / P>1, metallic lithium can still be deposited on the lithium affinity material, and not all of it will be absorbed into the anode active material.

[0094] The present application further provides a battery module including the secondary battery of the present application described above.

[0095] The present application further provides a battery pack including the battery module of the present application described above.

[0096] The present application further provides a power consuming device including the secondary battery of the present application described above, the battery module of the present application described above, or the battery pack of the present application described above.

[0097] In the negative plate of the present application, by adding a core-shell lithiophilic material with a lithiophilic material inside onto the negative plate, the nucleation barrier of lithium can be effectively lowered and the lithium metal can be oriented and induced to deposit on the lithiophilic material inside the shell structure, thereby improving the service life and safety performance of the lithium ion battery while ensuring the mass energy density of the battery.

[0098] The method for synthesizing the lithium affinity material as a carbon shell structure is not particularly limited, and examples thereof include coating the outside of the lithium affinity material with a carbon source, and then carbonizing the carbon source by a common method such as an arc discharge method, a hydrothermal method, chemical vapor deposition, or high-temperature pyrolysis.

[0099] As the carbon source, for example, a water-soluble carbon source such as glucose or yellow dextrin may be used.

[0100] Preferably, the lithium affinity material is synthesized by one-step hydrothermal method using a carbon source and a lithium affinity material under the action of a surfactant (e.g., sodium dodecylsulfonate). At this time, the size of the lithium affinity material can be controlled by adjusting the amount of the surfactant. Alternatively, the metal-organic framework compound (MOF) can be directly carbonized.

[0101] The carbonization reaction may be carried out by heating at 160° C. to 180° C. for 1 to 3 hours.

[0102] MOF is a coordination polymer formed by self-assembly of polydentate organic ligands containing oxygen, nitrogen, etc. and transition metal ions. It has characteristics such as being porous and having a large specific surface area. The MOF used in the present invention is not particularly limited, and examples thereof include MOFs synthesized by a solvent method, a liquid phase diffusion method, a sol-gel method, a stirring synthesis method, a solid phase synthesis method, a microwave method, an ultrasonic method, an ion heat method, and the like.

[0103] The polydentate organic ligand may be any substance commonly used as a polydentate organic ligand, and is not particularly limited as long as it can be carbonized. For example, polyols, polyacids, polyamines, and mixtures thereof may be used.

[0104] As the transition metal ion, any transition metal ion can be used without limitation as long as the effect of the present invention is not impaired, and includes a substance with an affinity for lithium.

[0105] The carbon shell formed by the organic polymer is characterized by easy production and low cost, which is advantageous for reducing the cost of the battery.The carbon shell formed by the MOF is characterized by high lithium ion permeability and high mechanical strength, which is advantageous for improving the charge / discharge rate of the battery and for maintaining the structure of the carbon shell of the lithium affinity material, and is advantageous for inducing uniform deposition of lithium because it contains transition metals uniformly.

[0106] The secondary battery, battery module, battery pack and power consuming device of the present application will be described below with appropriate reference to the drawings.

[0107] In one embodiment of the present application, a secondary battery is provided.

[0108] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During charging and discharging of the battery, active ions shuttle between the positive electrode plate and the negative electrode plate to absorb and release. The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. The separator is installed between the positive electrode plate and the negative electrode plate, and mainly functions to prevent short circuit between the positive and negative electrodes, while allowing ions to pass through.

[0109] [Positive plate] The positive electrode plate may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in a thickness direction of the positive electrode current collector, and the positive electrode active material layer is disposed on either one or both of the two facing surfaces of the positive electrode current collector.

[0110] The positive electrode current collector may be a metal foil sheet or a composite current collector. For example, an aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0111] The positive electrode active material layer includes a positive electrode active material. The positive electrode active material includes, but is not limited to, lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, lithium manganese spinel oxide, lithium nickel manganese spinel oxide, lithium titanate, etc. The positive electrode active material may be one or more of these.

[0112] The positive electrode active material layer may further include an adhesive. The type of adhesive is not specifically limited, and those skilled in the art may select it according to actual needs. For example, the adhesive may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0113] The positive electrode active material layer may further include a conductive agent. The type of the conductive agent is not specifically limited, and a person skilled in the art may select the conductive agent according to actual needs. For example, the conductive agent used in the positive electrode active material layer may be selected from one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0114] The positive electrode plate may be manufactured based on a method known in the art. For example, a positive electrode active material, a conductive agent, and an adhesive are dispersed in a solvent (e.g., N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry, and the positive electrode slurry is coated on a positive electrode current collector, followed by drying, cold pressing, and other processes to obtain a positive electrode plate.

[0115] [Negative plate] The negative electrode plate in the secondary battery of the present application uses the negative electrode plate for secondary batteries described above, which includes a current collector and a coating containing a lithium affinity material disposed on at least one surface of the current collector, and it has various structural arrangement forms. For example, the lithium affinity material containing the lithium affinity material and the negative active material are thoroughly mixed and then disposed on at least one surface of the current collector to form a single-layer active material layer, or the lithium affinity material containing the lithium affinity material and the negative active material are thoroughly mixed and then disposed on at least one surface of the current collector to form a first active material layer, and an active material not containing a lithium affinity material is disposed on the surface of the first active material layer to form a two-layer active material layer, or the lithium affinity material containing only the lithium affinity material is disposed on at least one surface of the current collector to form a lithium affinity material layer, and an active material not containing a lithium affinity material is disposed on the surface of the lithium affinity material layer.

[0116] When an active material layer containing a lithium affinity material is formed on one surface of the current collector, the current collector and active material layer of the negative electrode plate may have a structure as exemplarily shown in Figure 2, Figure 3, or Figure 4. When active material layers are formed on both surfaces of the current collector, the two active material layers of the negative electrode plate may have a symmetrical structure.

[0117] The negative electrode current collector may be a metal foil sheet or a composite current collector. For example, a copper foil may be used as the metal foil sheet. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymeric material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0118] The negative electrode active material may be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one of carbon-based materials such as artificial graphite, natural graphite, soft carbon, and hard carbon, silicone-based materials, tin-based materials, and lithium titanate. The silicone-based material may be selected from at least one of silicone alone, silicone oxide, silicone carbon composite, silicone nitrogen composite, and silicone alloy. The tin-based material may be selected from at least one of tin alone, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery may be used. These negative electrode active materials may be used alone or in combination of two or more.

[0119] Both the lithium affinity material layer and the active material layer (with or without the lithium affinity material) in the negative electrode active material layer may contain other auxiliary agents such as adhesives, conductive agents, and optional thickeners.

[0120] The conductive agents used in the active material layer and the lithium affinity material layer may be the same or different, and can be selected by those skilled in the art according to needs. For example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0121] The adhesives used for the active material layer and the lithium affinity material layer may be the same or different, and can be selected by those skilled in the art according to needs. For example, the adhesive may be selected from one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0122] The other auxiliary agents used in the active material layer and the lithium affinity material layer may be the same or different, and can be selected by those skilled in the art according to need. For example, the auxiliary agent optionally includes a thickener, such as sodium carboxymethylcellulose (CMC-Na).

[0123] According to the manufacturing method of the present application, a lithium affinity material containing a lithium affinity material and a negative electrode active material may be thoroughly mixed and then disposed on at least one surface of a current collector to obtain a single-layer active material layer containing a lithium affinity material and an active material; a lithium affinity material containing a lithium affinity material and a negative electrode active material may be thoroughly mixed and then disposed on at least one surface of a current collector to form a first active material layer, and an active material not containing a lithium affinity material may be disposed on the surface of the first active material layer to form a second active material layer to obtain a composite coating structure; or a lithium affinity material containing only a lithium affinity material may be disposed on at least one surface of a current collector to form a lithium affinity material layer, and an active material not containing a lithium affinity material may be disposed on the surface of the lithium affinity material layer to similarly obtain a composite coating structure including a lithium affinity material layer and an active material layer.

[0124] For example, the active material, the lithium affinity material, the conductive agent, the adhesive and optional other auxiliary agents may be dispersed in a solvent (e.g., deionized water) to form a uniform slurry, which is then coated on at least one surface of a negative electrode current collector by a common coating process and then dried to obtain a first active material layer. Optionally, the active material, the conductive agent, the adhesive and optional other auxiliary agents may be dispersed in a solvent (e.g., deionized water) to form a uniform slurry, which is then coated on the surface of the first active material layer by a common coating process and then dried to obtain a second active material layer. Then, the obtained composite coating structure including the current collector, the lithium affinity material and the active material is cold pressed under cold pressing conditions to obtain a negative electrode plate.

[0125] [Electrolyte] The electrolyte serves to conduct ions between the positive and negative plates. The present application does not specifically limit the type of electrolyte, which can be selected according to need. For example, the electrolyte may be liquid, gel, or all solid.

[0126] In some embodiments, the electrolyte employs an electrolytic solution, the electrolytic solution including an electrolyte salt and a solvent.

[0127] By way of example, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0128] By way of example, the solvent may be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), and ethyl methyl sulfone (EMS) and diethyl sulfone (ESE).

[0129] In some embodiments, the electrolyte optionally further includes additives. For example, the electrolyte may include an anode film-forming additive, a cathode film-forming additive, an additive for improving the overcharge performance of the battery, an additive for improving the high temperature performance of the battery, an additive for improving the low temperature performance of the battery, etc.

[0130] [Separator] The separator separates the positive and negative plates to prevent short circuits inside the battery, while allowing active ions to pass through the separator and move between the positive and negative electrodes. In the secondary battery of the present application, there is no particular limitation on the type of separator, and any known separator with a porous structure having good chemical stability and mechanical stability may be selected.

[0131] In some embodiments, the material of the separator may be selected from one or more of a glass fiber film, a nonwoven film, a polyethylene (PE) film, a polypropylene (PP) film, a polyvinylidene fluoride film, and a multi-layer composite film containing one or more of them. The separator may be a single-layer separator or a multi-layer composite separator, and there is no particular limitation. When the separator is a multi-layer composite separator, the materials of each layer may be the same or different, and there is no particular limitation.

[0132] In some embodiments, the positive plate, the negative plate and the separator may be fabricated into an electrode assembly by a winding process or a stacking process.

[0133] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and electrolyte described above.

[0134] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0135] The present application is not particularly limited to the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, FIG. 6 shows a secondary battery 5 with a rectangular structure as an example.

[0136] In some embodiments, referring to FIG. 7, the exterior body may include a case 51 and a top cover assembly 53. Here, the case 51 may include a bottom plate and a side plate connected on the bottom plate, and the bottom plate and the side plate surround the bottom plate to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be provided to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and can be selected by those skilled in the art according to actual specific needs.

[0137] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, with the specific number being selectable by one skilled in the art based on the application and capacity of the battery module.

[0138] 8 shows an example of a battery module 4. In the battery module 4, the secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the secondary batteries 5 may be fixed with fasteners.

[0139] Optionally, the battery module 4 may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0140] In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be selected by one skilled in the art based on the application and capacity of the battery pack.

[0141] 9 and 10 show an example of a battery pack 1. The battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is provided to cover the lower housing 3 to form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box according to any manner.

[0142] The present application further provides a power consuming device, which includes a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0143] As the power consuming device, a secondary battery, a battery module, or a battery pack can be selected according to the demands of the usage.

[0144] 11 is an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be adopted to meet the power consuming device's demand for high power and high energy density of secondary batteries.

[0145] Another example of the power consuming device may be a mobile phone, a tablet computer, a notebook computer, etc. The power consuming device is generally required to be lightweight and may employ a secondary battery as a power source.

[0146] Working Example The following describes the examples of the present application. The examples described below are illustrative and are only for interpreting the present application, and should not be understood as limitations on the present application. If no specific techniques or conditions are specified in the examples, they will be performed according to the techniques or conditions described in the technical literature or the product instructions. For reagents or instruments used, those without the manufacturer's name are all common products that can be purchased commercially.

[0147] Fabrication of Lithophilic Materials The lithium affinity material or its salt used in each example was added to an aqueous solution containing glucose and sodium dodecyl sulfonate, the dispersion was thoroughly homogenized, and then a lithium affinity material having a complete carbon shell was synthesized by a one-step hydrothermal method, whereby the amount of glucose was adjusted to make the carbon shell of the lithium affinity material reach the required thickness, and the amount of sodium dodecyl sulfonate was adjusted to make the carbon shell of the lithium affinity material reach the required size.

[0148] In addition, a carbon shell material not containing the lithium affinity material in the comparative example was synthesized by a one-step hydrothermal method using only an aqueous solution containing glucose and sodium dodecylsulfonate.

[0149] Negative plate manufacturing 1. Preparation of a negative electrode plate containing a mixed active material monolayer The total amount of the active material and the lithium affinity material, the conductive agent carbon black, the adhesive styrene butadiene rubber (SBR), and the thickener sodium carboxymethylcellulose (CMC) were added to deionized water in a mass ratio of 97.2:0.3:1.25:1.25, and the mixture was thoroughly stirred for 0.5 to 6 hours to prepare a slurry (solid content 10%) for forming a negative electrode coating by uniformly mixing. The slurry was uniformly applied onto the copper foil of the current collector by a general process, and then dried at a temperature of 100°C to form a mixed active material layer with a thickness of 80 μm on the current collector.

[0150] 2. Manufacturing a negative electrode plate including a composite layer of a single active material layer and a mixed active material layer The total amount of the active material and the lithium affinity material, the conductive agent carbon black, the adhesive styrene butadiene rubber (SBR), and the thickener sodium carboxymethylcellulose (CMC) were added to deionized water in a mass ratio of 97.2:0.3:1.25:1.25, and stirred thoroughly for 0.5 to 6 hours to prepare a slurry (solid content 50%) for forming a negative electrode coating by uniformly mixing. The slurry was uniformly applied onto the copper foil of the current collector by a general process, and then dried at a temperature of 100°C to form a mixed active material layer with a thickness of 80 μm on the current collector.

[0151] Next, the active material, carbon black as a conductive agent, styrene butadiene rubber (SBR) as an adhesive, and sodium carboxymethylcellulose (CMC) as a thickener were added to deionized water in a mass ratio of 96.7:0.8:1.25:1.25, and thoroughly stirred. The mixture was mixed and stirred for 0.5 to 6 hours to prepare a slurry (solid content 50%) for forming a negative electrode coating by uniformly mixing the slurry on the surface of the formed mixed active material layer by a general process, and then dried at a temperature of 100°C to form a composite coating having a single active material layer with a thickness of 40 μm and a mixed active material layer with a thickness of 40 μm on the current collector.

[0152] 3. Manufacturing a negative electrode plate including a composite layer of a single active material layer and a single lithium affinity material layer The lithium affinity material, the adhesive styrene butadiene rubber (SBR), the thickener sodium carboxymethylcellulose (CMC), and the lithium affinity material were added to deionized water in a mass ratio of 1:0.5:0.5, and thoroughly stirred for 0.5-6 hours to prepare a slurry (solid content 10%) for forming a negative electrode coating by uniformly mixing the slurry. The slurry was uniformly applied onto the copper foil of the current collector by a general process, and then dried at a temperature of 100°C to form a single lithium affinity material layer with a thickness of 0.3 μm on the current collector.

[0153] Next, the active material, carbon black as a conductive agent, styrene butadiene rubber (SBR) as an adhesive, and sodium carboxymethylcellulose (CMC) as a thickener were added to deionized water in a mass ratio of 96.7:0.8:1.25:1.25, and thoroughly stirred. The mixture was stirred for 0.5-6 hours to prepare a slurry (solid content 50%) for forming a negative electrode coating. The slurry was uniformly applied onto the surface of the single lithium affinity material layer formed by a general process, and then dried at a temperature of 100°C to form a composite coating having a single lithium affinity material layer with a thickness of 0.5 μm and a single active material layer with a thickness of 80 μm on the current collector.

[0154] The electrode plate formed as above, in which the active material and the lithium affinity material were coated on the current collector, was cold pressed and then slit to obtain a negative electrode plate.

[0155] Battery manufacturing In the examples of this application, the cells were manufactured in the following manner.

[0156] (1) Manufacturing of positive electrodes Positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive are mixed in a mass ratio of 97:1:2, added to the solvent N-methylpyrrolidone (NMP), and then thoroughly stirred for 0.5-6 h to homogeneously mix and prepare a positive electrode slurry (solid content 65%). The positive electrode slurry is prepared by a general process with a concentration of 0.2-200 mg / mm 2 The mixture was uniformly applied onto an aluminum foil current collector in a coating amount of 100 to 130° C., dried at a temperature of 100 to 130° C., cold pressed, and then slit to obtain a positive electrode plate.

[0157] (2) Manufacturing of electrolyte In a glove box with an argon atmosphere (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) were mixed uniformly in a volume ratio of 1:1:1, and 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent (molar concentration 1mol / L), followed by stirring uniformly to obtain an electrolyte for lithium-ion batteries.

[0158] (3) Battery manufacturing The positive electrode plate obtained by the above steps, a polyethylene film as a separator, and a negative electrode plate were stacked in the above order, with the active material layer on the negative electrode plate facing the separator, and then wound to obtain a bare cell, a tab was welded onto the bare cell, the bare cell was inserted into an aluminum case, the assembled cell was baked at 100°C to remove moisture, and an electrolyte was injected to obtain an uncharged battery, which was then left to stand, hot and cold pressed, chemically formed, shaped, and capacity tested, before obtaining a lithium ion battery.

[0159] When manufacturing the battery, the amount of the negative electrode active material in the negative plate and the amount of the positive electrode active material in the positive plate were appropriately adjusted to adjust the lithium capacity ratio of the negative and positive plates in the battery.

[0160] Performance Testing (1) How to calculate the ratio of lithium capacity of negative and positive plates The lithium absorption capacity (N) of the negative electrode and the lithium release capacity (P) of the positive electrode were calculated based on the amount of the positive and negative electrode active materials used, and N was divided by P to calculate the lithium capacity ratio N / P of the corresponding negative and positive electrode plates of the battery. N = negative electrode charging gram capacity × negative electrode surface density × negative electrode active material ratio P = Positive electrode charging gram capacity × Positive electrode surface density × Positive electrode active material ratio (2) Test method for thickness of carbon shell of lithium affinity material The samples were prepared using a hydrothermal synthesis method. After the surface of the samples was cut and polished, the samples were observed using an electron microscope to measure the thickness of the carbon shell in the field of view. Five points were measured for each carbon shell, and a total of 30 carbon shells were tested, and the average value was taken as the carbon shell thickness.

[0161] (3) Test method for cycle capacity retention At 45°C, the battery is charged at a constant current of 1 / 3C to 4.25V, then charged at a constant voltage of 4.25V until the current is 0.05C, left for 5min, and discharged at 1 / 3C to 2.8V. The obtained capacity is recorded as the initial capacity C0. Then, the battery is cycled under the same conditions as above, and the discharge capacity C of the battery after the nth cycle is recorded as the initial capacity C0. n Record the cycle capacity retention rate P of the battery after each cycle. n of Calculated based on the following formula: P n =(C n / C0)×100% P n The cycle life was defined as n when the resistance dropped to less than 80%.

[0162] (4) Testing methods for the lithium affinity of materials The lithiophilicity of the materials was tested by constructing a three-electrode electrochemical cell. The material to be tested was the working electrode, and Li 0.5 FePO4 was used as the reference electrode and lithium metal as the counter electrode. 2 ) to deposit metallic lithium on the working electrode, and Li metal (Li / Li + ) is the ordinate and capacitance is the abscissa.

[0163] When the capacity is improved, the voltage drops once and then levels off, and during this process, if there is no inflection point on the curve or the absolute value of the voltage corresponding to the inflection point is ≦0.03V, the material to be tested has lithium affinity. If there is an inflection point and the absolute value of the voltage corresponding to the inflection point is >0.03V, the material does not have lithium affinity.

[0164] Example 1 Ag is selected as the lithium affinity material, and the lithium affinity material is obtained by the above-mentioned lithium affinity material manufacturing method, where the carbon shell thickness is 35 nm, and commercially available artificial graphite is used as the active material, where the lithium capacity ratio of the negative and positive electrode plates is 0.5, and the mass ratio of the lithium affinity material in the active material layer is 0.5%. Based on the above-mentioned manufacturing method of the negative electrode plate containing the mixed active material layer monolayer, a coating structure containing the mixed active material layer monolayer is formed on two surfaces of the current collector. The negative electrode plate of Example 1 is obtained by drying at 100°C, cold pressing, and then slitting.

[0165] According to the method described above, a lithium ion battery was manufactured using the negative electrode plate of Example 1. The energy density and cycle life of the lithium ion battery manufactured in Example 1 were measured according to the test method described above, and the results are shown in Table 1.

[0166] Examples 2 to 10 and Comparative Examples 1 to 4 Variables such as the lithium affinity material, the shell layer thickness of the lithium affinity material, the mass ratio of the lithium affinity material in the active material layer, the active material, and the lithium capacity ratio of the negative and positive electrode plates were changed as shown in Table 1. Other than that, the secondary batteries of Examples 2 to 10 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1. The results of the battery energy density and cycle life of the obtained secondary batteries are also shown in Table 1. In Comparative Examples 1 and 2, no lithium affinity material was added. In Comparative Example 3, only a carbon shell material that does not contain a lithium affinity material was added. In Comparative Example 4, particles obtained by immobilizing Ag on silicon dioxide in the prior art were used instead of the lithium affinity material.

[0167] [Table 1]

[0168] As can be seen from the results in Table 1, the battery of the present invention can obtain high energy density and sufficient cycle life at the same time by using a lithium affinity material. It should be noted that the energy density of Comparative Examples 1 and 4 is low. Comparative Examples 2 and 3 have high energy density, but cannot induce lithium precipitation, so many dendrites are generated and the cycle life is short.

[0169] Examples 11 to 21 Artificial graphite was used as the negative electrode active material, Ag@C having a cavity therein was used as the lithium affinity material, and variables such as the carbon shell thickness of the lithium affinity material, the mass ratio of the lithium affinity material in the active material layer, and the lithium capacity ratio N / P of the negative and positive electrode plates were changed as shown in Table 2. Other than that, the secondary batteries of Examples 11 to 21 were produced in the same manner as in Example 1. The results of the battery energy density and cycle life of the obtained secondary batteries are also shown in Table 2.

[0170] [Table 2]

[0171] As can be seen from the results in Table 2, the smaller the capacity ratio N / P, the higher the energy density of the battery, and the larger the capacity ratio, the better the cycle life. The lithium ion battery manufactured by adding the lithium affinity material of the present invention to the negative electrode plate shows good energy density and cycle life.

[0172] Example 22 Ag is selected as the lithium affinity material, and the lithium affinity material is obtained by the above-mentioned lithium affinity material manufacturing method, in which the carbon shell thickness is 35 nm, and commercially available artificial graphite is used as the active material, in which the lithium capacity ratio of the negative and positive electrode plates is 0.5, and in the mixed active material layer, the mass ratio of the lithium affinity material in the active material layer is 0.5%. Based on the above-mentioned manufacturing method of the negative electrode plate including the composite layer of the single active material layer and the mixed active material layer, a composite layer coating structure of the mixed active material layer with a thickness of 40 μm and the single active material layer with a thickness of 40 μm is formed on two surfaces of the current collector. The negative electrode plate of Example 22 is obtained by drying at 100 ° C, cold pressing, and then slitting.

[0173] According to the method described above, a lithium ion battery was manufactured using the negative electrode plate of Example 22. According to the test method described above, the energy density and cycle life of the lithium ion battery manufactured in Example 22 were measured, and the result was a lithium ion battery with an energy density of 365Wh / kg and a cycle life of 420 times.

[0174] Example 23 The lithium affinity material used was Ag@C, where the carbon shell was 35 nm thick, and the active material used was commercially available artificial graphite. Based on the above-described method for manufacturing a negative plate containing a composite layer of a single active material layer and a single lithium affinity material layer, a composite layer coating structure of a single lithium affinity material layer with a thickness of 0.5 μm and a single active material layer with a thickness of 80 μm was formed on two surfaces of a current collector. The negative plate was dried at 100° C., cold pressed, and then slit to obtain the negative plate of Example 23.

[0175] According to the method described above, a lithium ion battery was manufactured using the negative electrode plate of Example 23. According to the test method described above, the energy density and cycle life of the lithium ion battery manufactured in Example 23 were measured, and the result was a lithium ion battery with an energy density of 370Wh / kg and a cycle life of 680 times.

[0176] Examples 24 to 28 The thickness of the single lithium affinity material layer in the inner layer and the thickness of the single active material layer in the outer layer were changed as shown in Table 3, and otherwise the secondary batteries of Examples 24 to 28 were produced in the same manner as in Example 23.

[0177] The results of the battery energy density and cycle life of the obtained secondary battery are also shown in Table 3.

[0178] [Table 3]

[0179] As can be seen from the results in Table 3, the energy density and cycle life of a lithium-ion battery can be significantly improved by using a negative electrode plate in which a lithium affinity material layer is placed between a layer containing only active material and a current collector.

[0180] It should be noted that the present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is an example, and any embodiment having substantially the same configuration as the technical idea and the same effect within the scope of the technical proposal of the present application is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiment and other forms constructed by combining some of the components in the embodiment are also included in the scope of the present application, within the scope of the purpose of the present application. [Explanation of symbols]

[0181] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 top cover assembly, 6 negative electrode plate, 60 current collector, 61 active material layer, 62 lithium affinity material layer, 63 lithium affinity material, 64 carbon shell, 65 lithium affinity material, 66 second active material layer, 67 lithium metal deposition, 68 cavity

Claims

1. A composite lithium metal negative electrode plate comprising a current collector and an active material layer coated on at least one surface of the current collector, The active material layer is An active material; a lithium affinity material having a core-shell structure, the core of the lithium affinity material contains a lithium affinity substance, and the shell is a carbon material; A composite lithium metal negative electrode plate, further comprising a second active material layer outside the active material layer, the second active material layer not containing the lithium affinity material.

2. 2. The negative electrode plate according to claim 1, wherein the mass percentage of the lithium affinity material in the active material layer is 0.1% to 5%.

3. 3. The negative electrode plate according to claim 1, wherein the lithium affinity material is one or more of a metal element such as Si, Ni, Ga, Sn, In, Ge, Ti, Mo, Pt, Al, Mg, Zn, Ag, Au, Co, or Fe, and / or one or more of an oxide, sulfide, fluoride, nitride, chloride, or carbide containing the metal element.

4. 3. The negative electrode plate according to claim 1, wherein the carbonaceous shell of the lithium affinity material has a thickness of 10 to 70 nm.

5. 3. The negative electrode plate according to claim 1, wherein the carbonaceous shell of the lithium affinity material has a cavity therein.

6. 6. The negative electrode plate of claim 5, further comprising lithium metal contained within the cavities of the lithium affinity material.

7. 3. The negative electrode plate according to claim 1, wherein the active material is selected from one or more of a carbon-based material, a silicon-based material, and a metal oxide.

8. the carbon-based material is one or more of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon; and / or the silicon-based material is one or more of silicon carbon, silicon oxide, and / or 8. The negative electrode plate according to claim 7, wherein the metal oxide is one or more of iron oxide and tin oxide.

9. A composite lithium metal negative electrode plate including a current collector and an active material layer, further comprising a lithium affinity material layer located between the current collector and the active material layer; the lithium affinity material layer includes a lithium affinity material having a core-shell structure, the core of the lithium affinity material contains a lithium affinity substance, and the shell is a carbon material; The composite lithium metal negative electrode plate is characterized in that the active material layer does not contain the lithium affinity material.

10. 10. The negative electrode plate according to claim 9, wherein the thickness ratio of the lithium affinity material layer to the active material layer is 0.1 / 100 to 6 / 100.

11. The negative electrode plate according to claim 9 or 10, characterized in that the lithium affinity material is one or more of simple metals such as Si, Ni, Ga, Sn, In, Ge, Ti, Mo, Pt, Al, Mg, Zn, Ag, Au, Co, and Fe, and / or one or more of oxides, sulfides, fluorides, nitrides, chlorides, and carbides containing the above metal elements.

12. The negative electrode plate according to claim 9 or 10, wherein the carbonaceous shell of the lithium affinity material has a thickness of 10 to 70 nm.

13. 11. The negative electrode plate according to claim 9, wherein the carbonaceous shell of the lithium affinity material has a cavity therein.

14. 14. The negative plate of claim 13, further comprising lithium metal contained within the cavities of the lithophilic material.

15. The method for producing a negative electrode plate according to claim 1 or 2, Step S1-1: mixing an active material and a lithium affinity material in a dispersion medium at a predetermined ratio to prepare a slurry A; and Step S1-2 of coating the slurry A obtained in Step S1-1 onto at least one surface of a current collector.

16. Step S1-3 of dispersing the active material in a dispersion medium to prepare a slurry B; The method for producing a negative electrode plate according to claim 15, further comprising step S1-4 of coating the negative electrode plate obtained in step S1-2 with the slurry B obtained in step S1-3.

17. Step S2-1: dispersing a lithium affinity material in a dispersion medium to prepare a slurry C; Step S2-2 of dispersing the active material in a dispersion medium to prepare a slurry D; Step S2-3: coating the slurry C obtained in step S2-1 onto at least one surface of a current collector to form a lithium affinity material coating; The method for producing a negative electrode plate according to claim 9 or 10, further comprising: a step S2-4 of coating the slurry D obtained in step S2-2 on the surface of the lithium affinity material coating obtained in step S2-3.

18. A secondary battery comprising the negative electrode plate according to claim 1, a positive electrode plate, an electrolyte, and a separator.

19. If the lithium absorption capacity of the negative electrode is N and the lithium desorption capacity of the positive electrode is P, then 19. The secondary battery according to claim 18, wherein the ratio of lithium capacities of the negative and positive plates is N / P<1.

20. A battery module comprising the secondary battery according to claim 18.

21. A battery pack comprising the battery module according to claim 20.

22. A power consuming device comprising at least one selected from the group consisting of the secondary battery according to claim 18, the battery module according to claim 20, and the battery pack according to claim 21.

Images