CN115548344A

CN115548344A - Negative plate of battery without negative active material, preparation method thereof and battery

Info

Publication number: CN115548344A
Application number: CN202211295403.4A
Authority: CN
Inventors: 孟庆飞; 张凯凯; 齐宇阳; 施樰; 吴际良; 徐谦; 李江; 张磊; 叶心怡
Original assignee: China Electronic New Energy Wuhan Research Institute Co ltd
Current assignee: China Electronic New Energy Wuhan Research Institute Co ltd
Priority date: 2022-10-21
Filing date: 2022-10-21
Publication date: 2022-12-30

Abstract

The invention provides a negative pole piece of a battery without a negative pole active substance, a preparation method thereof and the battery, wherein a stable lithium (sodium) fluoride SEI can be formed in the charging process through the synergistic effect of a negative pole current collector, nano carbon fluoride and a binder in a protective layer, so that the lithium (sodium) is prevented from directly contacting other components of the battery to generate side reaction, the high-temperature performance of the battery can be improved, and the high-temperature flatulence of the battery is inhibited; and can induce lithium (sodium) to be uniformly deposited, and inhibit the generation of dendrites and dead lithium (sodium), thereby improving the coulombic efficiency and the cycle performance of the battery. The invention does not use negative electrode active material, so that the energy density of the battery can be greatly improved compared with the conventional lithium (sodium) ion battery taking carbon material as the negative electrode active material.

Description

Negative plate of battery without negative active material, preparation method thereof and battery

Technical Field

The invention relates to the technical field of batteries, in particular to a negative plate of a battery without a negative active substance, a preparation method of the negative plate and the battery.

Background

In recent years, a "non-negative electrode active material" battery technology has been developed for lithium ion batteries and sodium ion batteries, and the energy density of the battery is greatly improved by not using a negative electrode active material. The principle of the technology is that lithium in a positive electrode material is deposited on a negative electrode current collector through formation charging. However, since a severe volume expansion occurs during lithium (sodium) deposition and the deposition is not uniform, the following problems are caused:

1) Poor high temperature performance: due to severe volume expansion in the lithium (sodium) deposition process, stable SEI is difficult to form on the surface of the negative electrode, high-activity lithium (sodium) can be directly contacted with other components of the battery to generate side reaction, and particularly at high temperature, severe side reaction can cause battery flatulence to cause battery failure;

2) Poor cycle performance: because lithium (sodium) is deposited unevenly, dendritic crystals and dead lithium (sodium) are easily formed in the charging and discharging processes of the battery, so that the coulomb efficiency of the battery is low, the cycle attenuation is fast, and the internal resistance is increased;

in order to solve the above technical problems, researchers have done a lot of work. Among them, an effective method includes coating a protective layer on a negative electrode current collector and surface-treating the current collector.

According to the prior art, agCl is coated on a current collector, so that generation of dendritic lithium is inhibited, a deposited lithium layer is more uniform, dead lithium is reduced, and reversible capacity and cycle performance of a battery are improved.

However, agCl is expensive, difficult to be used in industrial production, and has poor stability, is easily decomposed by light or heat, and has a limited effect of improving the high-temperature performance of the battery.

Disclosure of Invention

In view of the above, the invention provides a negative electrode plate of a battery without a negative electrode active material, a preparation method thereof and a battery, wherein a complete and stable lithium (sodium) fluoride-rich SEI can be formed in a charging process through the synergistic effect of a negative electrode current collector, nano carbon fluoride and a binder in a protective layer, so that the lithium (sodium) is prevented from directly contacting with other components of the battery to generate side reaction, the high-temperature performance of the battery can be improved, and the high-temperature flatulence of the battery can be inhibited; and can induce lithium (sodium) to be uniformly deposited, and inhibit the generation of dendrites and dead lithium (sodium), thereby improving the coulombic efficiency and the cycle performance of the battery.

The technical scheme of the invention is realized as follows:

in one aspect, the invention provides a negative plate of a battery without negative active material, which comprises a negative current collector and a protective layer attached on the negative current collector, wherein the protective layer comprises nano carbon fluoride and a binder.

The main reasons for poor high-temperature performance and poor tendency to gas expansion of the battery without the negative electrode active material are that complete and stable SEI cannot be generated, and the exposed metal lithium (sodium) has extremely strong reactivity and is very easy to generate side reaction with other components in the battery at high temperature. Therefore, the invention provides a negative plate of a battery without negative active material, which can generate complete and stable lithium (sodium) fluoride-rich SEI through the synergistic effect of a negative current collector, nano carbon fluoride and a binder in a protective layer, wrap metal lithium (sodium) deposited by a negative electrode, and prevent side reaction at high temperature, and has the following characteristics:

(1) The negative plate of the battery without the negative active material consists of a negative current collector and a protective layer attached on the negative current collector, and the protective layer is required to be closely attached on the negative current collector and can not be attached on other components of the battery, such as a diaphragm, a solid electrolyte, a positive plate and a shell. Because, if the protective layer is attached to other components of the battery, a gap must be created between the protective layer and the current collector during the assembly process, resulting in failure to generate a complete and stable SEI, and thus resulting in occurrence of side reactions at high temperatures.

(2) The protective layer is composed of nano carbon fluoride and a binder, and the nano carbon fluoride and the binder must exist at the same time. Because, without the nano carbon fluoride, lithium fluoride (sodium) rich SEI cannot be generated on the surface of the negative electrode; without the binder, the protective layer is prone to cracking and falling off, resulting in failure to generate complete and stable SEI, and further resulting in side reactions at high temperatures.

(3) Nano-sized carbon fluorides must be used and other sizes of carbon fluorides (e.g., micro-sized carbon fluorides) cannot be used. Because micron carbon fluoride particles have larger size, the thickness of a formed protective layer is larger, and larger volume expansion can occur in the charging process, so that the protective layer falls off and cracks, complete and stable SEI cannot be generated, and side reactions at high temperature are caused.

(4) The protective layer may contain a small amount of electrochemically inert material or material that does not expand in volume during charging, but the amount of nano-fluorocarbons cannot be less than 90wt%. If the content of the nano carbon fluoride is low, the nano carbon fluoride particles cannot be continuously and tightly contacted, a large number of defects can be formed on the protective layer, and complete and stable SEI rich in lithium fluoride (sodium) cannot be formed at the defects of the protective layer, so that side reactions at high temperature are caused; if the protective layer contains more substances which expand in a larger volume in the charging process, the protective layer can crack and fall off, so that complete and stable SEI cannot be generated, and side reactions at high temperature can be caused.

(5) The technical scheme of the invention can generate synergistic effect only when the whole body exists, thereby realizing the technical effects of improving the high-temperature performance of the battery and inhibiting the high-temperature flatulence of the battery. If the technical scheme of the invention is split into a plurality of sub-schemes and the sub-schemes are used independently, the synergistic effect cannot be generated, the high-temperature performance of the battery cannot be effectively improved, and the high-temperature flatulence of the battery cannot be effectively inhibited.

In summary, the high temperature performance of the battery is directly related to the morphology of the protective layer. Only an integral and stable protective layer can generate integral and stable SEI rich in lithium fluoride (sodium fluoride), so that the battery has good high-temperature performance; if the protective layer is incomplete and unstable and there are defects or cracks on the protective layer, the generated SEI may have defects or cracks, resulting in poor high temperature performance of the battery.

On the basis of the technical scheme, the mass ratio of the nano carbon fluoride to the binder in the protective layer is preferably (90-99) to (10-1).

Further preferably, the mass ratio of the nano carbon fluoride and the binder in the protective layer is (92-98): 8-2.

On the basis of the technical scheme, preferably, the thickness of the protective layer is 0.5-4 um.

Based on the above technical solution, preferably, the chemical general formula of the nano carbon fluoride is CF _x Wherein x is more than or equal to 0.35 and less than or equal to 1. More preferably, 0.5. Ltoreq. X.ltoreq.0.9.

Further preferably, the nano carbon fluoride is one or a combination of several of nano graphite fluoride, nano hard carbon fluoride, nano soft carbon fluoride, nano active carbon fluoride, carbon fluoride nanotube, fluorinated graphene and fluorinated carbon fiber.

Based on the above technical solution, preferably, the particle diameter D50 of the nano carbon fluoride is 40 to 400nm. More preferably, the particle diameter D50 of the nano carbon fluoride is 40 to 200nm.

On the basis of the above technical solution, preferably, the binder is one or a combination of several of PVDF, PTFE, SBR, CMC, PAA, and LA 133.

On the basis of the above technical solution, preferably, the negative current collector is a metal foil, specifically one of a copper foil, an aluminum foil, a tin foil, a nickel foil, a zinc foil, or an alloy foil with the above metal as a main component.

On the basis of the above technical solution, preferably, the thickness of the negative current collector is 4 to 100um.

In a second aspect, the invention provides a method for preparing a negative electrode sheet of a battery without negative active material, comprising the following steps,

weighing nano carbon fluoride and a binder according to a ratio, respectively adding the nano carbon fluoride and the binder into a solvent, and uniformly stirring and mixing to prepare a slurry;

coating the slurry on a negative current collector, and drying to form a protective layer;

and die cutting the negative current collector coated with the protective layer to manufacture a negative plate.

Specifically, deionized water or NMP may be used as the slurry solvent.

In a third aspect, the present invention provides a battery comprising the negative electrode sheet according to the first aspect of the present invention.

On the basis of the technical scheme, the lithium battery further comprises a positive plate and a shell, wherein the negative plate and the positive plate are arranged oppositely, the shell encapsulates the negative plate and the positive plate, the positive plate is coated with a positive active substance, and the protective layer is fully coated in the area of the negative current collector opposite to the positive active substance.

Specifically, the positive plate is composed of a positive active material, a positive conductive agent, a positive binder and a positive current collector.

The positive active material contains lithium element or (and) sodium element, and during charging, the lithium element or (and) sodium element can be extracted to form lithium ions or (and) sodium ions, and the lithium ions or (and) sodium ions migrate to the negative electrode through the electrolyte and are reduced to metallic lithium or metallic sodium. The kind and components of the positive active material are not limited, and the positive active material can be lithium battery positive active materials such as lithium cobaltate, lithium manganate, lithium iron phosphate, lithium nickel cobalt manganese, lithium nickel cobalt aluminate and the like only by satisfying the above principle; and can also be sodium battery positive electrode active substances, such as sodium nickel manganese oxide, sodium copper manganese oxide, sodium iron phosphate, sodium vanadium phosphate, prussian blue (white) and the like.

The positive electrode conductive agent is one or more of conductive graphite, conductive carbon black, carbon nano tubes, graphene or carbon fibers.

Specifically, if a liquid electrolyte is adopted, the lithium ion battery further comprises an isolation film and electrolyte, wherein the isolation film is arranged between the negative plate and the positive plate, the negative plate, the positive plate and the isolation film are encapsulated by the shell, and the electrolyte is filled in the shell; if solid electrolyte is adopted, the solid electrolyte is arranged between the negative plate and the positive plate 3, and the shell encapsulates the negative plate, the positive plate and the solid electrolyte.

The electrolyte consists of a solvent, lithium salt (sodium salt) and an additive. Further preferably, if the battery is a lithium battery, the electrolyte comprises a lithium salt; or if the battery is a sodium battery, the electrolyte comprises sodium salt.

The shell is an aluminum plastic film.

Compared with the prior art, the negative plate of the battery without the negative active material, the preparation method thereof and the battery have the following beneficial effects:

(1) According to the invention, through the synergistic effect of the negative current collector and the nano carbon fluoride and the binder in the protective layer, the protective layer can be completely and stably existed, so that complete and stable lithium (sodium) fluoride-rich SEI can be formed, the lithium (sodium) is prevented from directly contacting with other components of the battery to generate side reaction, the high-temperature performance of the battery can be improved, and the high-temperature flatulence of the battery can be inhibited;

(2) The protective layer can induce lithium (sodium) to be uniformly deposited, generation of dendritic crystals and dead lithium (sodium) is inhibited, and the coulombic efficiency and the cycle performance of the battery can be effectively improved;

(3) The battery provided by the invention does not use a negative electrode active substance, so that the energy density of the battery can be greatly improved compared with the conventional lithium (sodium) ion battery taking a carbon material and a silicon material as the negative electrode active substance;

(4) The battery provided by the invention does not use active metals such as lithium, sodium and the like, and a drying room or inert gas protection is not needed in the battery assembly process, so that the production cost can be reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic cross-sectional view of a battery according to example 1 of the present invention;

FIG. 2 shows the charge-discharge cycle curves of example 1 and comparative example 1.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

The battery of the embodiment comprises a negative plate consisting of a negative current collector 1 and a protective layer 2, a positive plate 3, an isolating membrane 4, a shell and electrolyte, and the preparation comprises the following steps:

(1) Preparation of negative plate

Per nano graphite fluoride CF _0.53 (D50 is 120 nm) and the binder LA133 are weighed according to the mass ratio of 95. And die-cutting the negative current collector 1 coated with the protective layer 2 to manufacture a negative plate.

(2) Preparation of positive plate

The positive electrode active material 30 adopts lithium cobaltate, the positive electrode conductive agent adopts SP, the positive electrode binder adopts PVDF, and the positive electrode current collector adopts aluminum foil. The mass ratio of the positive electrode active material 30, the positive electrode conductive agent, and the positive electrode binder is 97. And preparing the positive active material 30, the positive conductive agent and the positive binder into slurry, coating the slurry on a positive current collector, and drying, rolling and die-cutting the slurry to prepare the positive plate 3.

(3) Battery preparation

And (2) adopting a soft-package laminated structure, alternately stacking the negative plate, the isolating film 4 and the positive plate 3 to prepare an electrode group, then welding a tab, packaging by using an aluminum-plastic film shell, injecting electrolyte (the volume ratio of each component of an electrolyte solvent is EC: DMC: DEC = 1.

Example 2

(1) Preparation of negative plate

Per nano fluorinated hard carbon CF _0.35 Weighing materials according to the mass ratio of (D50 is 40 nm) to the binder LA133 of 99, adding the materials into deionized water, uniformly stirring and mixing to prepare slurry, coating the slurry on a negative current collector 1 (8 um thick copper foil), and drying to form a protective layer 2, wherein the thickness of the protective layer 2 is 0.5um. And die-cutting the negative current collector 2 coated with the protective layer 2 to manufacture a negative plate.

(2) Positive plate and battery preparation

A positive electrode sheet 3 and a battery were prepared in the same manner as in example 1.

Example 3

(1) Preparation of negative plate

Weighing the materials according to the mass ratio of the nano fluorinated activated carbon CF (D50 is 400 nm) to the binder LA133 being 90. And die-cutting the negative current collector 2 coated with the protective layer 2 to manufacture a negative plate.

(2) Positive plate and battery preparation

Example 4

(1) Preparation of negative plate

Per nanometer graphite fluoride CF _0.61 (D50 is 200 nm) and the binder LA133, PAA in a mass ratio of 94Foil) and dried to form the protective layer 2, the thickness of the protective layer 2 being 2um. And die cutting the negative current collector 2 coated with the protective layer 2 to manufacture a negative plate.

(2) Preparation of positive plate

The positive electrode active material 30 is sodium nickel iron manganese (NaNi) _0.33 Fe _0.33 Mn _0.33 O ₂ ) The positive electrode conductive agent adopts SP, the positive electrode binder adopts PVDF, and the positive electrode current collector adopts aluminum foil. The mass ratio of the positive electrode active material 30, the positive electrode conductive agent, and the positive electrode binder is 95. And preparing the positive active material 30, the positive conductive agent and the positive binder into slurry, coating the slurry on a positive current collector, and drying, rolling and die-cutting the slurry to prepare the positive plate 3.

(3) Battery preparation

A battery was produced by the same method as in example 1, except that the electrolyte used was composed of a solvent, sodium hexafluorophosphate having a concentration of 1mol/L, and FEC having a mass ratio of 2% as an additive, in which the volume ratio of the components of the solvent was EC: DMC: DEC = 1.

Example 5

(1) Preparation of negative plate

A negative electrode sheet was prepared by the method of example 4.

(2) Preparation of positive plate

The positive electrode sheet 3 was prepared by the method of example 4 except that the positive electrode active material 30 was changed to sodium vanadium phosphate.

(3) Battery preparation

A battery was prepared using the method of example 4.

Example 6

(1) Preparation of negative plate

Per nanometer graphite fluoride CF _0.61 (D50 is 100 nm) and a binder LA133, PAA, the mass ratio of which is 94. And die-cutting the negative current collector 2 coated with the protective layer 2 to manufacture a negative plate.

(2) Preparation of positive plate

The positive electrode sheet 3 was prepared in the same manner as in example 1.

(3) Battery preparation

Adopts a soft package laminated structure, and comprises a negative plate and a solid electrolyte (Li) ₇ La ₃ Zr ₂ O ₁₂ ) The positive electrode plates 3 are alternately stacked to form an electrode group, then a tab is welded, the electrode group is packaged by an aluminum plastic film shell, electrolyte (the volume ratio of each component of an electrolyte solvent is EC: DMC: DEC = 1.

Example 7

(1) Preparation of negative plate

Per nano graphite fluoride CF _0.5 (D50 is 100 nm) and a binder LA133, PAA, in a mass ratio of 94. And die-cutting the negative current collector 2 coated with the protective layer 2 to manufacture a negative plate.

(2) Positive plate and battery preparation

A positive electrode sheet 3 and a battery were produced in the same manner as in example 6.

Example 8

(1) Preparation of negative plate

Per nanometer graphite fluoride CF _0.9 (D50 is 120 nm) and a binder LA133, PAA, the mass ratio of which is 94. And die-cutting the negative current collector 2 coated with the protective layer 2 to manufacture a negative plate.

(2) Positive plate and battery preparation

Comparative example 1

(1) Preparation of cathode plate

And die-cutting the 8um thick copper foil without the protective layer to manufacture the negative plate.

(2) Positive plate and battery preparation

A positive electrode sheet and a battery were prepared in the same manner as in example 1.

Comparative example 2

(1) Preparation of cathode plate

The negative electrode sheet was prepared in the same manner as in comparative example 1.

(2) Positive plate and battery preparation

A positive electrode sheet and a battery were prepared in the same manner as in example 6.

The technical scheme of example 6 of the present invention is decomposed into the following three sub-schemes, and a negative active material free battery is prepared by comparative examples 3 to 5:

sub-scheme A: a protective layer was prepared as in example 6, but the protective layer was not coated on the current collector, but on the solid electrolyte (comparative example 3);

sub-scheme B: a negative electrode sheet was prepared in the same manner as in example 6, except that a binder was not used (comparative example 4);

sub-scheme C: a negative electrode sheet was prepared by the method of example 6, but nano carbon fluoride was not used (comparative example 5); comparative example 3

(1) Preparation of negative plate

(2) Solid electrolyte modification

Per nanometer graphite fluoride CF _0.61 (D50 is 100 nm), a binder LA133 and PTFE are weighed according to the mass ratio of 94 to 4, the materials are added into deionized water, the mixture is stirred and mixed uniformly to prepare slurry, and the slurry is coated on a solid electrolyte (Li ₇ La ₃ Zr ₂ O ₁₂ ) And (3) drying.

(3) Positive plate and battery preparation

Comparative example 4

(1) Preparation of negative plate

Per nano graphite fluoride CF _0.61 (D50 is 100 n)m) adding the mixture into deionized water, stirring and mixing uniformly to prepare slurry, coating the slurry on a current collector 8um thick copper foil, and drying to form a dressing layer, wherein the thickness of the dressing layer is 2um. And die-cutting the current collector coated with the coating layer to prepare the negative plate.

(2) Positive plate and battery preparation

Comparative example 5

(1) Preparation of cathode plate

The negative electrode sheet was prepared in the same manner as in example 6 except that micro graphite fluoride CF was used _0.61 (D50 is 5 um), and the thickness of the protective layer is 12um.

(2) Positive plate and battery preparation

Comparative example 6

(1) Preparation of cathode plate

According to nanometer silicon and nanometer graphite fluoride CF _0.9 Weighing the materials according to the mass ratio of (D50 is 120 nm), the binder LA133 and the conductive agent SP is 70. And die cutting the current collector coated with the coating to manufacture the negative plate.

(2) Positive plate and battery preparation

Comparative example 7

(1) Preparation of negative plate

The negative active material adopts graphite, the conductive agent adopts SP, the binder adopts LA133, and the current collector adopts copper foil. The mass ratio of the negative electrode active material to the conductive agent to the binder is 95. Preparing a slurry from a negative active material, a conductive agent and a binder, coating the slurry on a current collector, and drying, rolling and die-cutting the coated current collector to obtain a negative plate.

(2) Positive plate and battery preparation

Testing of

The charge and discharge method comprises the following steps: the charge current of examples 1 to 3 and comparative example 1 was 0.5C, the charge cut-off voltage was 4.2V, the discharge current was 0.5C, and the discharge cut-off voltage was 2.75V; examples 4, 5 and the charge current was 0.5C, the charge cut-off voltage was 4V, the discharge current was 0.5C, and the discharge cut-off voltage was 1.5V; the charge current of examples 6 to 8 and comparative examples 2 to 5 was 0.1C, the charge cut-off voltage was 4.2V, the discharge current was 0.1C, and the discharge cut-off voltage was 2.75V.

(1) High temperature Performance test

The negative electrode active material-free batteries prepared in examples 1 to 8 and comparative examples 1 to 6 were subjected to a discharge and charge test at normal temperature, then stored in a 55 ℃ high-temperature box for 30 days, and discharged at 55 ℃ to test the discharge capacity and gas generation volume of the batteries, and the results are shown in table 1.

TABLE 1 high temperature Performance test data sheet

In comparative examples 1 and 2, since the metal foil without the protective layer was used as the negative electrode, the surface of the negative electrode was difficult to form a stable and complete SEI due to severe volume expansion of the negative electrode during charging, and at high temperature, the electrolyte and lithium in the SEI cracks generated side reactions, resulting in active lithium being consumed, severe swelling of the battery, and a significant decrease in discharge capacity.

The comparative example 3 is different from the example 6 in that a protective layer is coated on a solid electrolyte, and although the protective layer is provided, the protective layer is not attached to a current collector, so that a synergistic effect cannot be generated, a negative electrode cannot be effectively protected, and at a high temperature, the electrolyte can generate a side reaction with lithium at an SEI crack, so that active lithium is consumed, the battery is severely inflated, and the discharge capacity is greatly reduced.

The comparative example 4 is different from the example 6 in that a protective layer does not adopt a binder, which results in poor strength of the protective layer and poor adhesion on a current collector, so that a synergistic effect cannot be generated, the protective layer is cracked due to severe volume expansion of a negative electrode during charging, and an electrolyte can generate a side reaction with lithium at an SEI crack at a high temperature, so that active lithium is consumed, the battery is severely inflated, and the discharge capacity is greatly reduced.

The difference between the comparative example 5 and the example 6 is that micron-sized carbon fluoride is adopted, the micron-sized carbon fluoride can generate larger volume expansion in the charging process to cause the cracking of a protective layer, and the electrolyte can generate side reaction with lithium at an SEI crack under high temperature to cause the consumption of active lithium, the gas expansion of the battery and the great reduction of the discharge capacity.

The comparative example 6 is different from the example 1 in that a large amount of nano silicon and SP are additionally added, so that the content of nano carbon fluoride in the coating is low (about 55%), nano carbon fluoride particles cannot be continuously and closely contacted, and a large amount of defects can be formed on the protective layer; in addition, the nano silicon can generate larger volume expansion in the charging process, and silicon particles can be cracked, so that a protective layer is cracked, and a large number of defects and cracks exist on the generated SEI. At high temperature, the electrolyte can generate side reaction with lithium at SEI defects and cracks, so that active lithium is consumed, the battery is inflated, and the discharge capacity is greatly reduced.

In embodiments 1 to 8, with the negative electrode plate of the battery without the negative electrode active material of the present invention, the negative electrode current collector, the nano carbon fluoride and the binder in the protective layer can generate a synergistic effect, so that the protective layer can exist completely and stably, and a complete and stable lithium (sodium) fluoride-rich SEI can be further formed, thereby preventing the lithium (sodium) from directly contacting with the electrolyte to generate a side reaction, inhibiting the high temperature flatulence of the battery, and greatly improving the high temperature capacity retention rate of the battery.

Based on comparative example 2, the effect of example 6 and comparative examples 3 to 5 on improving the high-temperature performance of the battery was evaluated (see table 2). Wherein, the improvement effect of the embodiment 6 on the high-temperature storage capacity retention rate is as high as 60.7 percent, while the average improvement effect of the comparative examples 3 to 5 is only about 13.9 percent and is far lower than that of the embodiment 6; and the sum of the effects of comparative examples 3 to 5 is 41.6%, which is still much lower than that of example 6. The inhibiting effect of the example 6 on high-temperature storage gas generation is as high as 5.6mL, while the average inhibiting effect of the comparative examples 3-5 is only about 1.1mL and is far lower than that of the example 6; and the sum of the effects of comparative examples 3 to 5 was 3.3mL, which is still much lower than example 6. The technical effect of the invention (example 6) is better than the sum of the respective effects of the three sub-schemes (comparative examples 3-5) split by the scheme of the invention, and the synergistic effect of the components of the negative plate of the battery without the negative active material objectively exists.

TABLE 2 data sheet

(2) Cycle performance test

The negative electrode active material-less batteries prepared in examples 1 to 6 and comparative examples 1 to 5 were subjected to 50-cycle charge and discharge tests, and the results are shown in table 3 and fig. 1.

TABLE 3 Cyclic Performance test data sheet

In comparative examples 1 and 2, because the metal foil without the protective layer is used as the negative electrode, dendritic crystals and dead lithium (sodium) are easily formed in the charging and discharging processes, and active lithium (sodium) is rapidly consumed, the coulombic efficiency of the battery is low, the cycle performance is poor, and the capacity retention rate is lower than 5% after 50 weeks of cycle.

The fluorocarbon coatings of comparative examples 3-5 can induce uniform deposition of lithium, inhibit the generation of dendrites and dead lithium, and greatly improve the first efficiency and the cycle capacity retention rate of the battery.

In examples 1 to 6, when the negative electrode plate of the battery without the negative electrode active material is adopted, the protective layer can induce lithium (sodium) to be uniformly deposited, generation of dendrite and dead lithium (sodium) is inhibited, and the first efficiency and the cycle capacity retention rate of the battery are greatly improved.

(3) Energy density test

The batteries of example 1 and comparative example 7 were weighed and then discharged at a discharge current of 0.5C and a discharge cut-off voltage of 2.75V, and the discharge energy of the batteries was measured to calculate the energy density of the batteries. The data are shown in table 4.

TABLE 4 energy Density data sheet

The comparison shows that the energy density of example 1 is 28% higher than that of comparative example 7, which indicates that the energy density of the battery without the negative electrode active material provided by the invention is greatly higher than that of the conventional lithium ion battery. Because the capacity of the test battery is small, the weight ratio of structural components such as a shell, a lug and the like is high, and the energy density advantage of the battery without the negative active material is not completely reflected. Through calculation, if the battery capacity reaches 10Ah, the energy density of the battery without the negative electrode active material can be higher than that of the conventional lithium ion by more than 40%.

In conclusion, the invention can greatly improve the high-temperature performance of the battery without the negative active material, inhibit the high-temperature flatulence of the battery and improve the coulombic efficiency and the cycle performance of the battery.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.

Claims

1. A negative plate of a battery without negative active material comprises a negative current collector (1) and a protective layer (2) attached on the negative current collector, and is characterized in that: the protective layer (2) comprises nano carbon fluoride and a binder.

2. The negative electrode sheet for a battery having no negative active material as claimed in claim 1, wherein: the mass ratio of the nano carbon fluoride to the adhesive in the protective layer (2) is (90-99) to (10-1), and the thickness of the protective layer (2) is 0.5-4 um.

3. The negative electrode sheet for a battery having no negative active material as claimed in claim 1, wherein: the chemical general formula of the nano carbon fluoride is CF _x Wherein x is more than or equal to 0.35 and less than or equal to 1.

4. The negative electrode sheet for a battery having no negative active material as claimed in claim 3, wherein: the nano carbon fluoride is one or the combination of several of nano graphite fluoride, nano hard carbon fluoride, nano soft carbon fluoride, nano active carbon fluoride, carbon fluoride nano tube, fluorinated graphene and fluorinated carbon fiber.

5. The negative electrode sheet for a battery having no negative active material as claimed in claim 1, wherein: the grain diameter D50 of the nano carbon fluoride is 40-400 nm.

6. The protective layer of claim 1, wherein: the binder is one or a combination of several of PVDF, PTFE, SBR, CMC, PAA and LA 133.

7. The method for preparing a negative electrode sheet for a battery having no negative electrode active material according to claim 1, wherein: comprises the following steps of (a) preparing a solution,

weighing nano carbon fluoride and a binder according to a proportion, respectively adding the nano carbon fluoride and the binder into a solvent, and uniformly stirring and mixing to prepare slurry;

coating the slurry on a negative current collector (1), and drying to form a protective layer (2);

and die cutting the negative current collector (1) coated with the protective layer (2) to manufacture a negative plate.

8. A battery, characterized by: comprising the negative electrode sheet according to any one of claims 1 to 6.

9. The battery of claim 8, wherein: still include positive plate (3) and casing, negative pole piece and positive plate (3) set up relatively, and the casing encapsulates negative pole piece and positive plate (3), coating anodal active material (30) on positive plate (3), the region that negative current collector (1) is just to anodal active material (30) is scribbled to protective layer (2).

10. The battery of claim 9, wherein: the battery is a lithium battery or a sodium battery.