阅读说明：本技术 一种兼具高安全、高容量的锂电池用正极极片及其制备方法和用途 (High-safety and high-capacity positive pole piece for lithium battery and preparation method and application thereof ) 是由 李文俊 丁秋凤 丁泽鹏 徐航宇 俞会根 于 2020-05-27 设计创作，主要内容包括：本发明涉及一种兼具高安全、高容量的锂电池用正极极片及其制备方法和用途,所述正极极片中掺混有富含锂的化合物,所述富含锂的化合物选自富锂锰基固溶体、富含锂的固态电解质及脱锂态的氧化亚硅中的至少一种,所述富含锂的化合物在电池过充、内短路、外短路、热滥用、针刺、挤压或过热等极端条件下够脱出Li离子,进而填补正极材料中的锂空位,稳定正极材料的晶格结构,改善由其制备得到的电池的安全性,且正极极片可在较高的面容量下保持优异的循环性能。(The invention relates to a high-safety high-capacity positive pole piece for a lithium battery, a preparation method and application thereof, wherein a lithium-rich compound is blended in the positive pole piece, the lithium-rich compound is selected from at least one of a lithium-rich manganese-based solid solution, a lithium-rich solid electrolyte and a lithium-removed state silicon oxide, and the lithium-rich compound can remove Li ions under extreme conditions of battery overcharge, internal short circuit, external short circuit, heat abuse, needling, extrusion or overheating and the like, so that lithium vacancies in a positive pole material are filled, the lattice structure of the positive pole material is stabilized, the safety of the battery prepared from the positive pole material is improved, and the positive pole piece can keep excellent cycle performance under higher surface capacity.)

1. The positive pole piece for the lithium battery is characterized in that a lithium-rich compound is blended in the positive pole piece for the lithium battery, and the lithium-rich compound is selected from at least one of a lithium-rich manganese-based solid solution, a lithium-rich solid electrolyte and a delithiated silicon oxide.

2. The positive electrode sheet for a lithium battery as claimed in claim 1, wherein the lithium-rich compound is capable of extracting lithium ions under extreme conditions of the battery;

preferably, the battery extreme conditions include at least one of battery overcharge, high temperature, needle prick, crush, internal short circuit, external short circuit, heat abuse or overheating;

preferably, the lithium-rich manganese-based solid solution isHas the sub-formula xLi₂MnO₃·(1-x)LiMO₂Wherein x is more than 0 and less than or equal to 1, and M is at least one of Ni, Co or Mn.

3. The positive electrode sheet for lithium battery as claimed in claim 1 or 2, wherein the lithium-rich solid electrolyte is selected from Li₇La₃Zr₂O₁₂And a material obtained by doping other elements, wherein the doping element is at least one of La, Nb, Sb, Ga, Te, W, Al, Sn, Ca, Ti, Hf and Ta.

4. The positive electrode sheet for lithium battery as claimed in any one of claims 1 to 3, wherein the delithiated silicon oxide has a molecular formula of Li_xSiO_yWherein x is selected from 1.4-2.1, and y is selected from 0.9-1.1.

5. The positive electrode sheet for a lithium battery as claimed in any one of claims 1 to 4, wherein the particle diameter of the lithium-rich compound is 0.1 to 10 μm, preferably 0.5 to 2 μm, when D50 is D50.

6. The positive electrode sheet for a lithium battery according to any one of claims 1 to 5, wherein the mass percentage of the lithium-rich compound is 0.1 to 20%, preferably 1 to 5%, based on 100% of the sum of the mass of the positive electrode active material and the mass of the lithium-rich compound in the positive electrode sheet for a lithium battery.

7. The positive electrode sheet for lithium battery as claimed in any one of claims 1 to 6, wherein the surface capacity of the positive electrode sheet for lithium battery is not less than 4mAh/cm³；

Preferably, the positive active material in the positive electrode plate for the lithium battery is LiNi_xCo_1-x-yM_yO₂Wherein x is more than or equal to 0.8, y is less than or equal to 0.2, and M is selected from any one or the combination of at least two of Mn, Al and Mg.

8. The method for producing a positive electrode sheet for a lithium battery as claimed in any one of claims 1 to 7, wherein the method comprises: premixing a positive active material and a lithium-rich compound to obtain premixed powder;

mixing the premixed powder, the glue solution and the conductive agent to obtain anode slurry;

coating the positive electrode slurry on a current collector, and drying, cold pressing and flaking to obtain the positive electrode piece for the lithium battery;

preferably, the premixed powder, the glue solution and the conductive agent are mixed in a manner that the glue solution is added into the premixed powder, and then the conductive agent is added to obtain the anode slurry.

9. A battery comprising the positive electrode sheet for a lithium battery according to any one of claims 1 to 7;

preferably, the battery further comprises a negative electrode pole piece, wherein the negative active material in the negative electrode pole piece is selected from silicon monoxide and/or silicon carbon;

preferably, the negative electrode plate comprises a negative electrode active material, a conductive agent, a thickening agent and a binder;

preferably, the battery further comprises a separator.

10. The battery of claim 9, wherein the separator is selected from the group consisting of ceramic barrier coated separators;

preferably, the separator has a thickness of 10 to 40 μm and a porosity of 20 to 60%.

Technical Field

The invention belongs to the field of battery materials, and relates to a high-safety high-capacity positive pole piece for a lithium battery, and a preparation method and application thereof.

Background

Under the social environment that the current energy crisis and environmental problems are more and more prominent, new energy automobiles have gradually become the mainstream trend of the automobile industry development. The new energy automobile is put into use, the dependence on fossil fuels such as petroleum can be reduced, and the emission of greenhouse gases and standard pollutants can be effectively reduced. As is well known, lithium ion batteries have been widely used in portable electronic products in recent years, and have begun to develop towards power batteries and medium and large batteries, which not only provides great challenges for cycle period, service life and manufacturing cost of lithium ion batteries, but also provides higher requirements for safety of lithium ion batteries.

CN107768647A discloses a high safe cladding type high-nickel ternary positive pole piece, including the positive pole layer that high-nickel ternary positive pole material formed, and the cladding in the surface of positive pole layer, the cladding is prepared by the raw materials that include following mass percent: 1-95% of inorganic flame retardant, 1-95% of inorganic phase change material and 1-20% of high-heat-conductivity inorganic material; the inorganic flame retardant is selected from one or more of aluminum hydroxide, magnesium hydroxide, ammonium polyphosphate, antimony oxide, zinc borate and molybdenum-containing inorganic compounds, and the inorganic phase-change material is selected from AlCl₃、LiNO₃、NaNO₃、KNO₃And NaNO₂One or more ofOne or more compounds or compounds and molten salt compounds, wherein the high-thermal-conductivity inorganic material is selected from one or more of graphite, graphene, carbon nano tubes and aluminum nitride; the high-nickel ternary positive electrode material is selected from lithium nickel cobalt manganese oxide and/or lithium nickel cobalt aluminate; this scheme does not fundamentally avoid the stability of the nickelic material in the high oxidation state.

Therefore, the development of the positive pole piece for the lithium battery, which has high safety and high capacity under the conditions of pole end conditions such as overcharge, high temperature, needling, extrusion, internal short circuit, external short circuit, heat abuse or overheating, is still significant.

Disclosure of Invention

The invention aims to provide a positive pole piece for a lithium battery with high safety and high capacity, a preparation method and application thereof, the positive pole piece for the lithium battery is blended with a lithium-rich compound, the lithium-rich compound is selected from at least one of a lithium-rich manganese-based solid solution, a lithium-rich solid electrolyte and a delithiated silicon oxide, the lithium-rich compound can remove Li ions under extreme conditions of battery overcharge, high temperature, needling, extrusion, internal short circuit, external short circuit, heat abuse or overheating and the like, fills up lithium vacancies in the anode material, reduces the oxidation state of the anode under the extreme condition state, stabilizes the lattice structure of the anode material, improves the safety of the battery prepared by the lithium-rich compound, and the positive pole piece for the lithium battery can keep excellent cycle performance under higher surface capacity, so that the battery obtains high safety performance on the basis of keeping higher specific energy and good cycle life.

The high safety refers to that the lithium-rich compound which can remove lithium ions under extreme conditions of overcharge, high temperature, needling, extrusion, internal short circuit, external short circuit, heat abuse or overheating and the like is contained in the positive electrode piece for the lithium battery, so that the safety of the battery prepared from the compound is remarkably improved, the battery can pass needling detection and 190 ℃ hot box experiment, and fire and explosion are avoided in the process.

The high capacity refers to the surface capacity of the positive pole piece for the lithium battery, which can reach 4mAh/cm²The above.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a positive electrode plate for a lithium battery, in which a lithium-rich compound is blended, and the lithium-rich compound is selected from at least one of a lithium-rich manganese-based solid solution, a lithium-rich solid electrolyte, and a delithiated silicon oxide.

The lithium-rich compound provided by the invention can remove Li ions under extreme conditions of battery overcharge, high temperature, needling, extrusion, internal short circuit, external short circuit, thermal abuse or overheating and the like, so that lithium vacancies in the anode material are filled, the lattice structure of the anode material is stabilized, the safety of the battery prepared from the anode material is improved, and the anode plate for the lithium battery can keep excellent cycle performance under higher surface capacity.

The traditional high-nickel ternary positive pole piece has strong oxidizability under an extreme condition state, and transition metal is dissolved out to cause instability of a material structure and oxygen evolution of a positive pole material, so that the material structure and the positive pole material can generate side reaction with electrolyte, a large amount of heat is released, thermal runaway is easily caused, and a safety problem is caused.

The positive pole piece is blended with the lithium-rich compound, and the lithium-rich compound can stabilize the lithium content in the positive pole, improve the overall thermal stability of the positive pole and further improve the safety performance of the battery under an extreme condition state.

Preferably, the lithium-rich compound is capable of extracting lithium ions under extreme conditions of the battery.

Preferably, the battery extreme condition includes at least one of battery overcharge, high temperature, needle punching, pressing, internal short circuit, external short circuit, thermal abuse, or overheating.

Preferably, the molecular formula of the lithium-rich manganese-based solid solution is xLi₂MnO₃·(1-x)LiMO₂Wherein, 0 < x.ltoreq.1, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, etc., preferably 0.9 to 1.0, and M is selected from at least one of Ni, Co or Mn.

Here, the lithium-rich manganese-based solid solution as a lithium-rich compound is different from the conventional positive electrode materialWhich is two-phase (Li)₂MnO₃And LiNi_xCo_yMn_1-x-yO₂) A solid solution of (2).

Preferably, the lithium-rich solid electrolyte is selected from Li₇La₃Zr₂O₁₂And a solid electrolyte obtained after doping, wherein the doping element is at least one of La, Nb, Sb, Ga, Te, W, Al, Sn, Ca, Ti, Hf and Ta.

Preferably, the delithiated silica has the formula Li_xSiO_yWherein x is selected from 1.4-2.1, such as 1.5, 1.6, 1.7, 1.8, 1.9 or 2, etc., and y is selected from 0.9-1.1, such as 0.92, 0.95, 0.98, 1, 1.02 or 1.08, etc.

The molecular formula of the delithiated silicon oxide is that x is selected from 1.4-2.1, y is selected from 0.9-1.1, and the composition is adopted, so that the delithiated silicon oxide is beneficial to timely removing lithium ions of a battery in extreme states such as overcharge, high temperature, needling, extrusion, internal short circuit, external short circuit, thermal abuse or overheating, further the balance of the lithium ions in the positive electrode is maintained, the thermal stability of the positive electrode is improved, and further the delithiated silicon oxide has high safety in extreme condition states.

Preferably, the particle size of the lithium rich compound is 0.1-10 μm, e.g. 0.5, 1, 2, 3, 4, 5, 6, 7, 8 or 9 μm, etc., with D50, preferably 0.5-2 μm, preferably D50.

The particle size of the lithium-rich compound is limited to be 0.1-10 mu m, which is beneficial to the lithium ion removal of the compound under the extreme condition of the battery, and the lithium content in the positive electrode is maintained, thus achieving the effect of high safety; when the particle size is less than 0.1 μm, the interface resistance is increased, which affects the ion transmission in the positive electrode sheet, and when the particle size is more than 10 μm, the effect of isolating the positive electrode active particles is not obvious, thereby improving the safety performance of the battery.

Preferably, the mass percentage of the lithium-rich compound is 0.1-20%, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, 7%, 9%, 10%, 12%, 14%, 16%, 18%, etc., preferably 1-5%, based on 100% of the sum of the mass of the positive electrode active material and the mass of the lithium-rich compound in the positive electrode sheet for a lithium battery.

The blending amount of the lithium-rich compound is in the range, so that the lithium content in the positive electrode of the battery can be maintained under an extreme condition state, and the effect of high safety is achieved; when the mass percentage content of the lithium-rich compound is less than or equal to 0.1 percent, the quantity of the provided Li is limited, and the effect of improving the safety performance of the high-energy battery is not obvious; when the mass percentage of the lithium-rich compound is more than or equal to 20%, the energy density of the battery is reduced by the low percentage of the positive electrode active material.

Preferably, the surface capacity of the positive pole piece for the lithium battery is more than or equal to 4mAh/cm³E.g. 5mAh/cm³、6mAh/cm³、7mAh/cm³、8mAh/cm³、9mAh/cm³Or 10mAh/cm³And the like.

The positive pole piece is doped with the lithium-rich compound, so that the cycle performance of the positive pole piece under high surface capacity can be obviously improved.

Preferably, the positive active material in the positive electrode plate for the lithium battery is LiNi_xCo_1-x-yM_yO₂Wherein x is 0.8, such as 0.8, 0.83, 0.85, 0.88 or 0.90, etc., y is 0.2, such as 0.05, 0.08, 0.1, 0.13, 0.15, 0.18 or 0.2, etc., and M is selected from any one or a combination of at least two of Mn, Al or Mg, illustratively including combinations of Mn and Al, Mg and Mn, Al and Mg, etc.

In a second aspect, the present invention provides a method for preparing a positive electrode plate for a lithium battery according to the first aspect, wherein the method comprises: premixing a positive active material and a lithium-rich compound to obtain premixed powder;

mixing the premixed powder, the glue solution and the conductive agent to obtain anode slurry;

and coating the positive electrode slurry on a current collector, and drying, cold pressing and flaking to obtain the positive electrode piece for the lithium battery.

Preferably, the premixed powder, the glue solution and the conductive agent are mixed in a manner that the glue solution is added into the premixed powder, and then the conductive agent is added to obtain the anode slurry.

In a third aspect, the invention provides a battery comprising the positive electrode plate for the lithium battery of the first aspect.

Preferably, the battery further comprises a negative electrode pole piece, and the negative active material in the negative electrode pole piece is selected from silicon monoxide and/or silicon carbon.

Preferably, the negative electrode plate comprises a negative active material, a conductive agent, a thickening agent and a binder.

Preferably, the battery further comprises a separator.

Preferably, the membrane is selected from ceramic barrier coated membranes.

Preferably, the separator has a thickness of 10-40 μm, such as 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, or the like, and a porosity of 20-60%, such as 25%, 30%, 35%, 40%, 45%, 50%, 55%, or the like.

Preferably, the battery further comprises an electrolyte, wherein the electrolyte comprises a lithium salt, a solvent and a film-forming additive.

Preferably, the lithium salt is selected from LiPF₆、LiBF₄Or LiClO₄Any one or a combination of at least two of the above, the combination illustratively comprising LiPF₆And LiBF₄Combination of (2) and LiClO₄And LiPF₆Combinations of (5) or LiBF₄And LiClO₄Combinations of (a), (b), and the like.

Preferably, the solvent is at least one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate and fluoroethylene carbonate.

Preferably, the film forming additive is selected from VC and/or PS.

Compared with the prior art, the invention has the following beneficial effects:

(1) the lithium battery positive pole piece is blended with a compound rich in lithium ions and capable of releasing lithium ions under extreme use conditions, the battery assembled with the positive pole piece can release the Li ions under the extreme conditions of overcharge, overheating and the like of the battery, lithium vacancies in the positive pole material are filled, the lattice structure of the positive pole material is stabilized, the safety of the battery prepared from the positive pole piece is improved, the lithium balance in the positive pole is maintained, the overall thermal stability of the positive pole is further improved, and the safety of the battery under the extreme conditions is improved;

(2) the lithium battery positive pole piece is doped with a lithium-rich compound, so that the cycle performance of the positive pole piece under high surface capacity can be improved.

Drawings

FIG. 1 is a test curve of the cycling performance at high face capacity for 15Ah cell energy density up to 300Wh/Kg for comparative and examples 1, 3, 5.

FIG. 2 is a high energy needling test chart of a high nickel ternary positive electrode material used in a comparative example and a lithium-rich solid electrolyte Li blended in a high nickel ternary positive electrode plate of example 3₇La₃Zr₂O₁₂The high energy battery of (1).

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Comparative example

In the comparative example, the positive pole piece is not mixed with a lithium-rich compound; the positive active material in the positive pole piece is LiNi_0.83Co_0.12Mn_0.05O₂(Ni83), PVDF as a binder, and CNT as a conductive agent; the mass ratio of the positive active substance to the binder to the conductive agent is 95:2:3, and the preparation method of the positive pole piece comprises the following steps:

and uniformly mixing the glue solution and Ni83, adding a conductive agent to prepare anode slurry, coating the anode slurry on an aluminum foil to obtain an anode piece with the surface capacity of 5.4mAh/cm3, drying, and performing cold pressing and sheet making to obtain the anode piece.

Assembling, welding, testing hi-pot, packaging and baking the well-designed and matched negative plate (active material is SiC) and a ceramic diaphragm with the thickness of 15 mu m and the porosity of 50 percent, and injecting lithium salt LiPF₆The solvent is ethylene carbonate, dimethyl carbonate and fluoroethylene carbonateEster mixed solvent and electrolyte with additive VC; after the liquid is injected, the processes of packaging, formation and capacity grading are carried out to prepare the battery;

example 1

In the embodiment, the positive pole piece is doped with a lithium-rich manganese-based solid solution, and the lithium-rich manganese-based solid solution is 0.5Li₂MnO₃·0.5LiMn_0.54Ni_0.13Co_0.13O₂The mass ratio of the positive electrode active material to the lithium-rich compound is 94: 6; the particle size of the lithium rich compound is 500 nm; the positive active substance in the positive pole piece is Ni83, the binder is PVDF, and the conductive agent is CNT; the preparation method comprises the following steps:

premixing the positive active material and the lithium-rich compound nano-particles for 1h in advance, revolving at 40r/min, and dispersing at a rotating speed of 500r/min to obtain premixed powder;

adding glue solution into the premixed material according to the mass ratio of the premixed powder to the binder to the conductive agent of 95:2:3, uniformly mixing, and adding the conductive agent to prepare anode slurry; and then coating the aluminum foil with the surface capacity of 5.4mAh/cm3, drying, and then carrying out cold pressing and flaking to prepare the positive pole piece.

Assembling, welding, testing hi-pot, packaging and baking the well-designed and matched negative plate (active material is SiC) and a ceramic diaphragm with the thickness of 15 mu m and the porosity of 50 percent, and injecting lithium salt LiPF₆The solvent is a mixed solvent of ethylene carbonate, dimethyl carbonate and fluoroethylene carbonate, and the additive is electrolyte of VC; after the liquid is injected, the processes of packaging, formation and capacity grading are carried out to prepare the battery;

example 2

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich manganese-based solid solution was 90: 10; lithium-rich manganese-based solid solution of 0.37Li₂MnO₃·0.63LiNi_0.13Co_0.13Mn_0.54O₂The particle diameter of the lithium-rich manganese-based solid solution was 2 μm, and other parameters and conditions were exactly the same as those in example 1.

Example 3

This example is different from example 1 in that the positive electrodeThe mass ratio of the active material to the lithium-rich solid electrolyte was 99.5:0.5, the particle size of the lithium-rich solid electrolyte was 200nm, and the lithium-rich solid electrolyte was Li₇La₃Zr₂O₁₂Other parameters and conditions were exactly the same as in example 1.

Example 4

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich solid electrolyte was 92:8, and the particle diameter of the lithium-rich solid electrolyte was 2 μm; the lithium-rich solid electrolyte is Li_6.75La₃Zr_1.75Ta_0.25O₁₂Other parameters and conditions were exactly the same as in example 1.

Example 5

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich delithiated compound was 99.5:0.5, the particle size of the lithium-rich delithiated compound was 200nm, and the lithium-rich delithiated compound was Li_1.4SiO_0.9Other parameters and conditions were exactly the same as in example 1.

Example 6

This example is different from example 1 in that the positive electrode active material is LiNi_0.8Co_0.1Al_0.1O₂The lithium-rich delithiated compound is Li_2.1SiO, wherein the mass ratio of the positive electrode active material to the lithium-rich lithium-removing compound is 95:5, and the particle size of the lithium-rich lithium-removing compound is 1 mu m; other parameters and conditions were exactly the same as in example 1.

Example 7

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich solid electrolyte was 94: 6; the particle size of the lithium-rich solid electrolyte is 500 nm; the lithium-rich solid electrolyte is Li₇La₃Zr₂O₁₂Other parameters and conditions were exactly the same as in example 1.

Example 8

This example differs from example 1 in that the positive electrode active material and the lithium-rich delithiated stateThe mass ratio of the compounds is 94: 6; the particle size of the lithium-rich delithiated compound is 500 nm; the lithium-rich delithiated compound being Li_1.4SiO_0.9(ii) a Other parameters and conditions were exactly the same as in example 1.

Example 9

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich manganese-based solid solution is 94: 6; the particle diameter of the lithium-rich manganese-based solid solution is 10 mu m; the lithium-rich manganese-based solid solution is 0.5Li₂MnO₃·0.5LiMn_0.54Ni_0.13Co_0.13O₂(ii) a Other parameters and conditions were exactly the same as in example 1.

Example 10

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich manganese-based solid solution is 94: 6; the particle size of the lithium-rich manganese-based solid solution is 100 nm; the lithium-rich manganese-based solid solution is 0.5Li₂MnO₃·0.5LiMn_0.54Ni_0.13Co_0.13O₂(ii) a Other parameters and conditions were exactly the same as in example 1.

Example 11

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich manganese-based solid solution was 99: 1; the particle size of the lithium-rich manganese-based solid solution is 500 nm; the lithium-rich manganese-based solid solution is 0.5Li₂MnO₃·0.5LiMn_0.54Ni_0.13Co_0.13O₂(ii) a Other parameters and conditions were exactly the same as in example 1.

Example 12

This example differs from example 1 in that the mass ratio of the positive electrode active material to the lithium-rich manganese-based solid solution was 95: 5; the particle size of the lithium-rich manganese-based solid solution is 500 nm; the lithium-rich manganese-based solid solution is 0.5Li₂MnO₃·0.5LiMn_0.54Ni_0.13Co_0.13O₂(ii) a Other parameters and conditions were exactly the same as in example 1.

Example 13

This example is different from example 1 in thatThe mass ratio of the pole active material to the lithium-rich delithiated compound is 80: 20; the particle size of the lithium-rich delithiated compound is 500 nm; the lithium-rich delithiated compound being Li_1.6SiO_1.1Other parameters and conditions were exactly the same as in example 1.

Example 14

The difference between this example and example 5 is that the mass ratio of the positive electrode active material to the lithium-rich delithiated compound was 99.5:0.5, the particle size of the lithium-rich delithiated compound was 200nm, and the lithium-rich delithiated compound was Li_2.1SiO, the other parameters and conditions were exactly the same as in example 5.

Testing the batteries assembled by the positive pole pieces obtained in the comparative example 1 and the examples 1 to 14;

1. and (3) cycle testing: under high surface capacity, the energy density of the 15Ah battery of the comparative example 1 and the examples 1, 3 and 5 reaches 300Wh/Kg, the cycle performance test is carried out, the percentage of the battery discharge capacity is more than 80 percent, and the test is continued, otherwise, the test is stopped; the test results are shown in fig. 1; as can be seen from fig. 1 above: the percentage of the 1C cycle 1000 cycle discharge capacity of the high-surface capacity battery is more than 80 percent, and the lithium-rich compound is added into the positive plate, thereby improving the cycle performance of the battery.

2. And (3) needle punching test: the energy density of the 15Ah battery is more than or equal to 300Wh/Kg, and the test condition isThe speed of the needle is 25-80 mm/s; vertically piercing a battery core body, keeping the needle in the battery for 1h, and recording that the battery passes through the situation of no fire or explosion, otherwise, failing;

TABLE 1

As can be seen from the above table 1, the energy density of the battery with the positive electrode added with the lithium-rich compound is more than 300Wh/Kg, the surface temperature after needling can not change obviously, and when the addition amount is 20%, the energy density of the battery is reduced obviously; while cells that did not add a lithium-rich compound failed the pin puncture test;

3. and (3) thermal shock test: the energy density of the 15Ah battery is more than or equal to 300Wh/Kg, and the battery is heated for 2 hours at 190 ℃; heating to 190 ℃ at a heating rate of 5 ℃/min, keeping the temperature for 2h, and observing for 1 h; "not on fire, not exploding" is recorded as pass, otherwise fails; the test results are shown in table 2;

TABLE 2

As can be seen from the above table 2, the energy density of the battery with the lithium-rich compound added to the positive electrode is more than 300Wh/Kg, and the energy density of the battery can be obviously reduced through thermal shock at 190 ℃ for 2h, when the addition amount is 20%; without the addition of a lithium rich compound cell, failed the 190 ℃ thermal shock test.

According to the invention, the lithium-rich compound is mixed in the high-nickel ternary positive plate, so that the safety performance of the high-energy density battery is obviously improved. The energy density of the batteries of the comparative example and the examples 1, 3 and 5 reaches 300Wh/Kg, the batteries of the examples 1, 3 and 5 added with different lithium-rich compounds can pass needle punching, and the temperature change of the surfaces of the batteries is not obvious; the battery is subjected to thermal shock of heat preservation for 2 hours at 190 ℃, and mainly because a lithium-rich compound can remove Li ions under the extreme condition, so that lithium vacancies in the anode material are filled, and the lattice structure of the anode material is stabilized, so that the lithium content in the anode is stabilized, the oxidation state of the anode under the extreme condition state is reduced, and the safety of the battery prepared by the battery under the extreme condition state is improved;

comparative examples 9, 10 and 1 show that the addition of different particle sizes affects the safety performance of the battery, the particle size of the positive electrode blend is too small or too large to achieve a good effect of improving the safety, the particle size of the lithium-rich compound is too small, the interface resistance is increased, and the ion transmission is blocked; the particle size is too large, the effect of isolating the anode is not obvious, and the safety is not obviously improved;

comparative examples 5 and 13 show the effect of adding the lithium-rich compound in the amount of the positive electrode active material particles on the safety performance of the battery, the improvement of the safety performance is not significant when the amount of the lithium-rich compound added is too small, the improvement of the safety performance when the amount of the lithium-rich compound added is too large, the energy density of the battery is reduced due to the reduction of the active material particles in the positive electrode sheet, and the energy density of the battery of example 13 is reduced to 294 Wh/Kg.

It can be seen from comparison of examples 1, 7 and 8 that the lithium-rich solid electrolyte has better safety performance when blended in the same amount, and the highest temperature of the battery surface is the lowest during the needling test.

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.