CN113488615A - Over-discharge prevention cathode, preparation method thereof and battery - Google Patents
Over-discharge prevention cathode, preparation method thereof and battery Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides an anti-over-discharge negative electrode, a preparation method thereof and a battery. The anti-overdischarge functional layer comprising the niobium-titanium compound is arranged between the current collector and the negative active material layer, so that the further reduction of the negative potential is buffered, SEI decomposition and dissolution and precipitation of the current collector are avoided, and the anti-overdischarge functional layer has the characteristics of simple structure, simple preparation process, small influence on the battery capacity, good anti-overdischarge effect, high safety and the like.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to an over-discharge prevention negative electrode, a preparation method thereof and a battery.
Background
The lithium ion battery is widely applied to various mobile or fixed energy storage scenes such as new energy automobiles, consumer electronics products, energy storage and the like. Overdischarge is one of the common potential safety hazards of lithium ion batteries. The phenomenon of overdischarge is generally divided into two categories: overruns in use and overruns in storage shelves.
The use of over-discharge mainly has several situations that when the battery is normally discharged at a large rate, due to the inconsistency of polarization inside the battery, although the overall potential of the battery is within a normal operation range, the potential of the negative electrode is locally too high, so that over-discharge can occur. In addition, the battery may be subject to abuse, resulting in over-discharge. The reason for the over-discharge of the storage is that even if the quality control is good, the lithium ion battery inevitably has a slight internal short circuit, the battery is slightly discharged all the time in the process of storing and not using the battery, and after the storage is put for a long time, the self-discharge capacity of the battery exceeds the normal working capacity and is over-discharged.
The consequences of over-discharging can lead to negative pole SEI membrane decomposition and make battery life decay fast on the one hand, and on the other hand, when the battery was over-discharged seriously, when the negative pole potential reached the precipitation potential of negative pole current collector copper, copper metal became copper ion from the current collector and is precipitated inside the battery, and when the battery was charged once more, copper ion reduction was copper metal and arouses the inside short circuit of battery, produced the potential safety hazard.
To prevent overdischarge, there are three main techniques: (1) an over-discharge protection circuit is added outside the battery, and when the voltage of the battery is lower than the operating voltage, the external circuit is cut off, so that the battery can not discharge any more. Such a method may have an effect on the over-discharge of the battery in use, but cannot prevent the over-discharge of the battery when it is stored for a long time. (2) And adding an additive which can generate oxidation reduction reaction under the over-discharge condition into the electrolyte for over-discharge protection. However, this method has two disadvantages, namely that the amount of additive is always limited, and therefore the number of electrons that can be accepted is limited, and therefore the degree of protection against overdischarge is limited, and that redox products often cover the surface of the cell material, which results in irreversible, i.e. only one-time protection, and that these products lead to an increase in the internal resistance of the cell in terms of capacity fade. (3) Lithium titanate is introduced as an overdischarge protection additive.
CN103840130A discloses a lithium battery carbon negative electrode for preventing overdischarge, which is used to solve the problems that the capacity of the existing carbon negative electrode is consumed, the potential is rapidly increased, and further the dissolution of copper in the negative current collector and the precipitation on the surface of the positive electrode occur. The invention comprises a current collector, wherein both sides of the current collector are coated with negative slurry layers subjected to vacuum drying, and the negative slurry layers are formed by mixing a carbon active material, an overdischarge function additive, a conductive agent and a binder; the overdischarge function additive is lithium titanate. The invention ensures that the carbon cathode battery has a part of capacity after the discharge lower limit voltage, thereby avoiding the dissolution and precipitation of the current collector copper caused by over-discharge and improving the storage life and the service life of the battery.
CN102299365A discloses a lithium ion battery cell for preventing overdischarge and a battery pack containing the same, wherein the negative electrode active material of the battery cell is mainly a first negative electrode active material graphite or lithium titanate, and at least one of a second negative electrode active material hard carbon, soft carbon and silicon carbon alloy with high capacity is added, so as to greatly improve the capacity of the lithium ion battery cell at the end of discharge (i.e. the end of discharge voltage plateau and below). The technical scheme of the invention not only realizes the improvement of the capacity of the single battery, but also avoids the over-discharge of a certain single battery in the battery pack, maximizes the capacity of the battery pack and ensures the safety of the work of the battery pack.
The existing anti-overdischarge cathodes have the problems of complex structure, large influence on battery capacity, low safety and the like, so that the problem that the battery capacity is influenced little under the condition that the anti-overdischarge cathodes are simple in structure and simple in preparation process is solved urgently at present.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide the anti-overdischarge negative electrode, the preparation method thereof and the battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides an anti-overdischarge negative electrode, which comprises a current collector, wherein at least one side surface of the current collector is sequentially laminated with an anti-overdischarge functional layer and a negative electrode active material layer, and the anti-overdischarge functional layer comprises a niobium-titanium compound.
According to the invention, the over-discharge prevention functional layer comprising the niobium-titanium compound is arranged between the current collector and the negative electrode active material layer, so that when the battery is charged for the first time, lithium ions can be embedded into the niobium-titanium compound to form a good conductor, and the performance of the battery is not influenced; when the battery works normally, the niobium-titanium compound does not participate in the charge and discharge of the battery under low potential because the discharge potential of the niobium-titanium compound is higher; when the battery is over-discharged, the negative electrode potential rises to the lithium-intercalated and deintercalated potential of the niobium-titanium compound, the deintercalated lithium ions can provide capacity and buffer further reduction of the negative electrode potential, so that SEI decomposition and dissolution and separation of a current collector (such as a Cu current collector) are avoided, in addition, after the capacity of the niobium-titanium compound is released, the electronic conductivity of an over-discharge prevention functional layer is rapidly reduced to become an insulator, the electronic conduction of the current collector and a negative electrode active material layer is blocked, and the over-discharge problem is effectively prevented.
In a preferred embodiment of the present invention, the niobium-titanium compound comprises TiNb2O7。
The invention is provided with TiNb2O7TiNb as a niobium-titanium compound in the anti-overdischarge functional layer2O7The lithium ion battery is an electronic insulator, and is a good electronic conductor after lithium ions are embedded, the lithium embedding voltage is 1.6V, and the gram capacity is 387 mAh/g; within the normal operating voltage range of the lithium ion battery, the potential of the negative electrode is generally lower than 1V, so when the battery is charged for the first time, lithium ions can be embedded into TiNb2O7Make it a good conductor without affecting the cell performance, and when the cell is in normal operation, TiNb2O7Does not participate in the charging and discharging of the battery. When the battery is over-discharged, the potential of the negative electrode is raised to TiNb2O7At the time of deintercalation of lithium potential of (2), TiNb2O7Can extract lithium ionsSupply capacity, buffer further reduction of the potential of the negative electrode, avoid SEI decomposition and dissolution and precipitation of current collectors, and further overdischarge causes TiNb2O7After the capacity of (2) is released, TiNb2O7The electron conductivity of the anode active material layer is rapidly reduced to become an insulator, and the electron conduction of the anode active material layer and the current collector is blocked, so that the over-discharge is effectively prevented.
As a preferable technical scheme of the invention, TiNb is arranged in the over-discharge prevention functional layer2O7The content of (b) is 50 to 95% by mass, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%.
The invention controls TiNb in the over-discharge prevention functional layer2O7The mass content of the TiNb-based lithium iron oxide can be 50-95%, the over-discharge prevention effect of the over-discharge prevention functional layer can be effectively ensured, the capacity of the battery is not influenced, and if the TiNb-based lithium iron oxide is used as the TiNb-based lithium iron oxide, the TiNb-based lithium iron oxide is used as the TiNb-based lithium iron oxide2O7The mass content of (2) is lower than 50%, the active substance proportion is lower, the quantity of consumed lithium ions is limited, and the over-discharge prevention effect is poor; if TiNb2O7The mass content of the anti-overdischarge functional layer is higher than 95%, the forming effect of the anti-overdischarge functional layer is poor, the active substance occupation ratio is high, the binder occupation ratio is low, and the anti-overdischarge functional layer is easy to fall off in the charging process to influence the anti-overdischarge effect.
In a preferred embodiment of the present invention, the thickness of the anti-overdischarge function layer is 0.1 to 10 μm, for example, 0.1 μm, 0.5 μm, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, 8.0 μm, 9.0 μm or 10.0 μm, preferably 2 to 7 μm.
According to the invention, the thickness of the over-discharge prevention functional layer is controlled to be 0.1-10 μm, the active substance content is high, the over-discharge prevention capability is strong, if the thickness is less than 0.1 μm, the thickness of the over-discharge prevention functional layer is too thin, the active substance is less, and the over-discharge prevention capability is reduced; if the thickness is larger than 10 mu m, the thickness of the over-discharge prevention functional layer is too thick, on one hand, the whole thickness of the battery core is influenced, the energy density of the battery is reduced under the same thickness, and in addition, the active substances are too much, more lithium ions are consumed, and the first efficiency of the battery is reduced.
As a preferred embodiment of the present invention, the anti-overdischarge functional layer further includes a first binder.
Preferably, the first binder comprises one or a combination of at least two of polyimide, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyacrylate, polyvinylidene fluoride, sodium carboxymethyl cellulose, or lithium carboxymethyl cellulose.
As a preferable embodiment of the present invention, the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a second binder.
As a preferred embodiment of the present invention, the negative active material includes one or a combination of at least two of graphite, soft carbon, hard carbon, or mesocarbon microbeads.
Preferably, the conductive agent includes one or a combination of at least two of super P, conductive carbon black, carbon nanotubes, flake graphite, graphene, carbon fibers, or ketjen black.
Preferably, the second binder comprises one or a combination of at least two of polyimide, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyacrylate, polyvinylidene fluoride, sodium carboxymethyl cellulose, or lithium carboxymethyl cellulose.
Preferably, the second binder is the same kind as the first binder.
In a second aspect, the present invention provides a method for preparing an anti-overdischarge negative electrode according to the first aspect, the method comprising:
preparing an anti-over-discharge functional layer comprising a niobium-titanium compound on at least one side surface of the current collector, and preparing a negative active material layer on the surface of the anti-over-discharge functional layer.
As a preferred embodiment of the present invention, the preparation manner of the anti-overdischarge functional layer includes coating.
Preferably, the preparation manner of the anode active material layer includes coating.
Illustratively, the preparation method of the anti-overdischarge negative electrode specifically comprises the following steps:
and mixing the first binder and the niobium-titanium compound, coating the mixture on the surface of a current collector to form an over-discharge prevention functional layer, coating a negative electrode active material comprising a negative electrode active material, a conductive agent and a second binder on the surface of the over-discharge prevention functional layer to form a negative electrode active material layer, and preparing the over-discharge prevention negative electrode.
In a third aspect, the present invention provides a battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode employs the anti-overdischarge negative electrode according to the first aspect.
The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the over-discharge prevention functional layer comprising the niobium-titanium compound is arranged between the current collector and the negative electrode active material layer, so that when the battery is charged for the first time, lithium ions can be embedded into the niobium-titanium compound to form a good conductor, and the performance of the battery is not influenced; when the battery works normally, the niobium-titanium compound does not participate in the charge and discharge of the battery; when the battery is over-discharged, the negative electrode potential rises to the lithium-intercalated and deintercalated potential of the niobium-titanium compound, the deintercalated lithium ions can provide capacity and buffer further reduction of the negative electrode potential, so that SEI decomposition and dissolution and separation of a current collector are avoided, in addition, after the capacity of the niobium-titanium compound is released, the electronic conductivity of an over-discharge prevention functional layer is rapidly reduced to become an insulator, the electronic conduction of the current collector and a negative electrode active material layer is blocked, and the over-discharge problem is effectively prevented.
Drawings
Fig. 1 is a schematic structural diagram of an anti-overdischarge negative electrode according to an embodiment of the present invention.
Wherein, 1-a negative electrode active material layer; 2-an anti-over-discharge functional layer; and 3, collecting the current.
Detailed Description
It is to be understood that in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be taken as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
It should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "disposed," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The technical solution of the present invention is further explained by the following embodiments.
In one embodiment, the invention provides an anti-overdischarge negative electrode, as shown in fig. 1, comprising a current collector 3, wherein at least one side surface of the current collector 3 is sequentially laminated with an anti-overdischarge functional layer 2 and a negative active material layer 1, and the anti-overdischarge functional layer 2 comprises a niobium-titanium compound. Further, the niobium-titanium compound includes TiNb2O7。
Further, the anti-over-discharge functional layer 2 further comprises a first binder, wherein the first binder comprises polyimide, styrene-butadiene rubber and polyOne or the combination of at least two of acrylic acid, polyacrylonitrile, polyacrylate, polyvinylidene fluoride, sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. Further, TiNb in the anti-overdischarge functional layer 22O7The mass content of (A) is 50-95%. The thickness of the over-discharge prevention functional layer 2 is 0.1-10 mu m.
Further, the anode active material layer 1 includes an anode active material, a conductive agent, and a second binder. The negative active material comprises one or the combination of at least two of graphite, soft carbon, hard carbon or mesocarbon microbeads; the conductive agent comprises one or the combination of at least two of super P, conductive carbon black, carbon nano tubes, crystalline flake graphite, graphene, carbon fibers or Ketjen black; the second binder comprises one or the combination of at least two of polyimide, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyacrylate, polyvinylidene fluoride, sodium carboxymethylcellulose or lithium carboxymethylcellulose. Further, the second binder is the same as the first binder.
The invention also provides a battery, which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the negative electrode adopts the over-discharge prevention negative electrode.
In another embodiment, the present invention provides a method for preparing the above-mentioned anti-overdischarge negative electrode, the method comprising:
coating and preparing an anti-over-discharge functional layer 2 comprising niobium-titanium compound on at least one side surface of a current collector 3, and coating and preparing a negative electrode active material layer 1 on the surface of the anti-over-discharge functional layer 2.
Example 1
The embodiment provides an anti-over-discharge cathode, wherein an anti-over-discharge functional layer 2 and a cathode active material layer 1 are sequentially stacked on one side surface of a current collector 3, and the anti-over-discharge functional layer 2 comprises a first binder and TiNb2O7. TiNb in anti-over-discharge functional layer 22O7The mass content of (A) is 75%. The thickness of the anti-overdischarge functional layer 2 was 5 μm, and the first binder was polyimide.
The negative electrode active material layer 1 includes a negative electrode active material, a conductive agent, and a second binder at a mass ratio of 97:1: 2. The negative active material is graphite; the conductive agent is super P; the second binder is polyimide.
Example 2
The embodiment provides an anti-over-discharge cathode, wherein the surfaces of two sides of a current collector 3 are sequentially stacked with an anti-over-discharge functional layer 2 and a cathode active material layer 1, and the anti-over-discharge functional layer 2 comprises a first binder and TiNb2O7. TiNb in anti-over-discharge functional layer 22O7The mass content of (A) is 50%. The thickness of the anti-overdischarge functional layer 2 was 10 μm.
The anode active material layer 1 is exactly the same as in example 1.
Example 3
The embodiment provides an anti-over-discharge cathode, wherein an anti-over-discharge functional layer 2 and a cathode active material layer 1 are sequentially stacked on one side surface of a current collector 3, and the anti-over-discharge functional layer 2 comprises a first binder and TiNb2O7. TiNb in anti-over-discharge functional layer 22O7The mass content of (a) is 95%. The thickness of the anti-overdischarge functional layer 2 was 0.1 μm.
The anode active material layer 1 is exactly the same as in example 1.
Example 4
This example provides an anti-overdischarge anode, which differs from example 1 in that TiNb is present in the anti-overdischarge functional layer 22O7The mass content of (A) was 40%, and the remaining structural parameters and composition were exactly the same as in example 1.
Example 5
This example provides an anti-overdischarge anode, which differs from example 1 in that TiNb is present in the anti-overdischarge functional layer 22O7The mass content of (A) was 98%, and the remaining structural parameters and composition were exactly the same as in example 1.
Example 6
This example provides an anti-overdischarge anode, which is different from example 1 in that the thickness of the anti-overdischarge functional layer 2 is 0.05 μm, and the remaining structural parameters and composition are exactly the same as those of example 1.
Example 7
This example provides an anti-overdischarge anode, which is different from example 1 in that the thickness of the anti-overdischarge functional layer 2 is 12 μm, and the remaining structural parameters and composition are exactly the same as those of example 1.
Comparative example 1
This comparative example provides an anti-overdischarge anode, which is different from example 1 in that the anti-overdischarge functional layer 2 is not provided and the remaining structural parameters and composition are completely the same as those of example 1.
Comparative example 2
This comparative example provides an anti-overdischarge anode, which is different from example 1 in that TiNb is contained in the anti-overdischarge functional layer 22O7Replacement by Li4Ti5O12The remaining structural parameters and compositions are exactly the same as in example 1.
The anti-overdischarge cathodes in the above examples and comparative examples were prepared as pouch batteries, and the preparation method of the batteries included: the positive electrode includes an active material NCM, a binder, a conductive agent, the negative electrode is the overdischarge-preventing negative electrode of the above examples and comparative examples, and the electrolyte is an EC/DEC/EMC solution containing a lithium salt.
And (3) carrying out performance test on the prepared battery, wherein the performance test method comprises the following steps: fully charging the battery at room temperature (25 ℃) with current of 1/3 ℃; after full charge, discharge was performed at a current of 1C (i.e., 31A).
The test results are shown in table 1.
TABLE 1
| Over-discharge prevention capability | |
| Example 1 | 180％SOC |
| Example 2 | 165％SOC |
| Example 3 | 157％SOC |
| Example 4 | 152％SOC |
| Example 5 | 175％SOC |
| Example 6 | 153％SOC |
| Example 7 | 178％SOC |
| Comparative example 1 | 141％SOC |
| Comparative example 2 | 148％SOC |
As can be seen from the above table:
(1) example 1 is superior to examples 4 and 5 in the anti-overdischarge capacity of example 1 compared with examples 4 and 5, and it can be seen that the invention controls TiNb in the anti-overdischarge functional layer 22O7The mass content of (2) is 50-95%, the over-discharge prevention effect of the over-discharge prevention functional layer 2 can be effectively ensured, the capacity of the battery is not influenced, and if the TiNb is adopted, the TiNb is not added2O7The mass content of (2) is lower than 50%, the active substance proportion is lower, the quantity of consumed lithium ions is limited, and the over-discharge prevention effect is poor; if TiNb2O7If the mass content of (2) is more than 95%, the molding effect of the over-discharge prevention functional layer 2 is poor, the ratio of active substances is high, and adhesion existsThe ratio of the agent is low, the anti-overdischarge functional layer 2 is easy to fall off in the charging process, the anti-overdischarge effect and the cycle performance are influenced, and the cycle effect in the embodiment 5 is poor.
(2) Compared with the embodiments 6 and 7, the over-discharge prevention capability of the embodiment 1 is superior to that of the embodiments 6 and 7, so that the over-discharge prevention capability is reduced by controlling the thickness of the over-discharge prevention functional layer 2 to be 0.1-10 microns, the content of active substances is high, and the over-discharge prevention capability is strong, and if the thickness is less than 0.1 micron, the thickness of the over-discharge prevention functional layer 2 is too thin and the active substances are few; if the thickness is greater than 10 μm, the thickness of the over-discharge prevention functional layer 2 is too thick, which affects the overall thickness of the battery cell, reduces the energy density of the battery with the same thickness, consumes more lithium ions due to too much active material, reduces the first efficiency of the battery, and affects the cycle performance of the battery due to too thick thickness, thus the cycle performance of example 7 is poor.
(3) Example 1 compared with comparative examples 1 and 2, the anti-overdischarge capacity of example 1 is superior to that of comparative examples 1 and 2, and thus it can be seen that, according to the present invention, by providing the anti-overdischarge functional layer 2 including the niobium-titanium compound between the current collector 3 and the anode active material layer 1, lithium ions can be inserted into the niobium-titanium compound to form a good conductor when the battery is first charged, without affecting the performance of the battery; when the battery works normally, the niobium-titanium compound does not participate in the charge and discharge of the battery; when the battery is overdischarged, the negative electrode potential rises to the lithium intercalation and deintercalation potential of the niobium-titanium compound, the deintercalated lithium ions can provide capacity and buffer further reduction of the negative electrode potential, so that SEI decomposition and dissolution and separation of the current collector 3 are avoided, in addition, after the capacity of the niobium-titanium compound is released, the electronic conductivity of the overdischarge prevention functional layer 2 is rapidly reduced to become an insulator, the electronic conduction of the current collector 3 and the negative electrode active material layer 1 is blocked, and the overdischarge problem is effectively prevented.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. The utility model provides an prevent putting negative pole which characterized in that, prevent putting the negative pole including the mass flow body, at least one side surface of the mass flow body stacks gradually and is provided with prevents putting functional layer and negative pole active material layer, prevent putting the functional layer including niobium titanium compound.
2. The anti-overdischarge anode of claim 1, wherein the niobium-titanium compound comprises TiNb2O7。
3. The anti-overdischarge anode according to claim 2, wherein TiNb in the anti-overdischarge functional layer2O7The mass content of (A) is 50-95%.
4. An overdischarge-prevention negative electrode according to any of claims 1 to 3, wherein the thickness of the overdischarge-prevention functional layer is 0.1 to 10 μm, preferably 2 to 7 μm.
5. The anti-overdischarge anode according to any one of claims 1 to 4, wherein the anti-overdischarge functional layer further comprises a first binder;
preferably, the first binder comprises one or a combination of at least two of polyimide, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyacrylate, polyvinylidene fluoride, sodium carboxymethyl cellulose, or lithium carboxymethyl cellulose.
6. The anti-overdischarge anode according to any one of claims 1 to 5, wherein the anode active material layer comprises an anode active material, a conductive agent, and a second binder.
7. The anti-overdischarge anode according to claim 6, wherein the anode active material comprises one or a combination of at least two of graphite, soft carbon, hard carbon or mesocarbon microbeads;
preferably, the conductive agent comprises one or a combination of at least two of super P, conductive carbon black, carbon nanotubes, crystalline flake graphite, graphene, carbon fibers or Ketjen black;
preferably, the second binder comprises one or a combination of at least two of polyimide, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, polyacrylate, polyvinylidene fluoride, sodium carboxymethyl cellulose or lithium carboxymethyl cellulose;
preferably, the second binder is the same kind as the first binder.
8. A method for preparing an overdischarge-preventing negative electrode according to any one of claims 1 to 7, characterized in that the method comprises:
preparing an anti-over-discharge functional layer comprising a niobium-titanium compound on at least one side surface of the current collector, and preparing a negative active material layer on the surface of the anti-over-discharge functional layer.
9. The production method according to claim 8, wherein the anti-overdischarge functional layer is produced by coating;
preferably, the preparation manner of the anode active material layer includes coating.
10. A battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode comprises the anti-overdischarge negative electrode according to any one of claims 1 to 7.
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