WO2023174301A1 - Inorganic solid-state electrolyte layer of lithium battery, composite negative electrode plate for lithium battery and preparation method therefor, and lithium battery - Google Patents

Abstract

The present invention relates to the field of lithium batteries, and disclosed are an inorganic solid-state electrolyte layer of a lithium battery, a composite negative electrode plate for a lithium battery and a preparation method therefor, and a lithium battery. The inorganic solid-state electrolyte layer of the present invention comprises inorganic solid-state electrolyte particles; the inorganic solid-state electrolyte particles are selected from a lithium-containing material or a mixture of the lithium-containing material and AlPO₄; and the lithium-containing material comprises a compound composed of elements of lithium, hydrogen, aluminum, phosphorus, halogen and oxygen. An inorganic solid-state electrolyte used in the present invention is high in stability and low in cost; moreover, the inorganic solid-state electrolyte itself has a certain ionic electricity-conduction capability, and does not significantly hinder ionic transport capabilities of the surface of a negative electrode plate and in a negative electrode after being coated on the surface of the negative electrode plate to form a composite negative electrode plate; and the thermal stability of the negative electrode plate is improved without affecting electrochemical performance, thus ensuring the safety of the battery.

Description

Lithium battery inorganic solid electrolyte layer and composite negative electrode sheet for lithium battery and preparation method thereof and lithium battery

Cross-references to related applications

This application claims the rights and interests of Chinese patent application 202210247212.4 submitted on March 14, 2022. The content of this application is incorporated herein by reference.

Technical field

The invention relates to the field of lithium batteries, and specifically relates to an inorganic solid electrolyte layer for lithium batteries and a composite negative electrode sheet for lithium batteries, a preparation method thereof and a lithium battery.

Background technique

Lithium-ion batteries have the advantages of high energy density, good cycle performance, long service life, low self-discharge, and no memory effect. They have gradually occupied a larger application market in energy storage, power batteries, and 3C electronics, and have broad application prospects. .

As an important component of lithium-ion batteries, negative electrode materials are one of the main shortcomings that limit battery energy density, rate and other performance. At present, the main anode materials include lithium titanate anode materials, graphite anode materials, hard carbon, soft carbon anode materials, silicon carbon, silicon oxygen, silicon oxygen carbon composite anode materials, pure silicon anode materials, tin oxide and other metal oxide anode materials. . From the perspective of energy storage cost and cycle performance, hard carbon and soft carbon with good cycle performance and low cost have obvious advantages. Considering the cycle performance, volume energy density and rate performance of 3C electrons, graphite anode materials with good cycle performance and rate performance have obvious advantages. Considering the energy density of power batteries and the cruising range of electric vehicles, high-capacity silicon-carbon anode material systems have obvious advantages. Different anode materials have good application prospects in different segments.

Although different anode materials can match different application fields, there are still safety issues when using several anode materials in batteries, among which:

The safety problems of graphite materials are: when the battery is operating at a high charging rate, the battery polarization increases, reaching the lithium ion deposition overpotential, and lithium ions precipitate in the form of lithium dendrites on the surface of the graphite particles. Highly active lithium dendrites react violently with the electrolyte, inducing thermal runaway in the battery, and the heat release increases sharply during the thermal runaway process.

The safety problems of silicon-based materials (such as silicon-oxygen, silicon-carbon, silicon-oxycarbon and pure silicon materials) are: 1) Silicon is pulverized during the circulation process, forming a large number of nanoparticles, and the reaction of silicon particles with high specific surface area Higher activity, increasing the heat release when the battery thermal runaway; 2) Li-Si alloy in the charged state has high reactivity; 3) Due to the continuous volume changes of the silicon material, it is difficult to form a stable SEI film on the surface, which inhibits the thermal runaway of the battery The effect is worse.

At the same time, the safety performance of the battery is related to the interaction between the positive and negative electrodes: the charged positive electrode material releases oxygen in a high-temperature environment and diffuses to the negative electrode side, where a violent oxidation-reduction reaction occurs, releasing a large amount of heat, and ultimately leading to thermal runaway.

The above battery problems are all related to the negative side, resulting in poor battery safety performance. How to effectively solve the safety hazards on the negative electrode side and avoid thermal runaway of batteries has become an urgent problem that domestic and foreign companies need to solve.

At present, the main methods to improve the safety of lithium batteries include: modification of negative electrode materials, electrolyte additives, adding PTC coatings, insulating/flame-retardant coatings, ceramic separator coatings, positive electrode material coatings, etc.

For example, CN113233451A discloses a special method of modifying artificial graphite. The modified artificial graphite has a rich microporous structure. By improving the rate performance of the graphite material, the risk of lithium precipitation in the negative electrode is reduced, and the safety performance of the battery is improved. However, the porous modified artificial graphite prepared by this invention has a complicated process and cannot completely solve the problem of lithium precipitation caused by high rates, and the improvement in safety performance is limited.

CN112952035A discloses a method for preparing a silicon-oxygen material that can improve battery safety performance. By coating graphene on the surface of the silicon-oxygen material, the powdering caused by the volume change of the silicon-oxygen material during the cycle is suppressed to improve battery safety performance. . However, the coating layer will gradually fall off as the cycle progresses, and there are still potential safety hazards during long cycles.

CN104409681A discloses a method for preparing a lithium-ion battery pole piece containing a PTC coating. It discloses a method of coating a current collector with a temperature-sensitive pre-coating layer in advance, and then coating the positive electrode or negative electrode active material. The pre-coating has good electrical conductivity at room temperature. When the temperature rises, the resistance rises sharply, preventing the battery from further heating, thus improving the safety of lithium-ion batteries. However, due to the instantaneous thermal runaway of acupuncture, the coating's mechanism of action often has no time to take effect and cannot effectively improve the safety of acupuncture.

However, the above-mentioned methods such as coating of ceramic separators, using electrolyte additives, constructing PTC coatings, constructing insulating or flame-retardant coatings, etc., on the one hand, will reduce the electrochemical performance of the battery. After using these methods, the overall performance of the battery core will still be reduced. It needs to be optimized; on the other hand, the material preparation process is complicated, or it may also have a certain impact on the electrode or battery core preparation process, and it is not easy to produce on a large scale. Therefore, it is still necessary to find a simple, effective and easy-to-scale production method to improve the safety performance of the battery without affecting the electrical performance of the battery.

Contents of the invention

The purpose of the present invention is to overcome the problem in the prior art that the safety of lithium batteries cannot be ensured while ensuring the electrochemical performance of lithium batteries, and to provide an inorganic solid electrolyte layer for lithium batteries and a composite negative electrode sheet for lithium batteries and a preparation method thereof and lithium batteries. The inorganic solid electrolyte layer formed by the inorganic solid electrolyte particles of the present invention has high stability and low cost, and the inorganic solid electrolyte layer itself has a certain ionic conductivity. When coated on the surface of the negative electrode sheet to form a composite negative electrode sheet, it will not The ion transmission capacity on the surface of the negative electrode piece and in the negative electrode is significantly hindered; without affecting the electrochemical performance, the thermal stability of the negative electrode piece is improved and the safety of the battery is ensured.

In order to achieve the above object, a first aspect of the present invention provides an inorganic solid electrolyte layer for a lithium battery, the inorganic solid electrolyte layer including inorganic solid electrolyte particles;

The inorganic solid electrolyte particles are selected from lithium-containing materials or a mixture of lithium-containing materials and AlPO ₄ ;

The lithium-containing material includes compounds composed of lithium, hydrogen, aluminum, phosphorus, halogen and oxygen elements.

According to the present invention, preferably, the chemical formula of the lithium-containing material is Li _1+x H _1-x Al(PO ₄ )O _1-y M _2y , where 0≤x<1, 0<y<0.1, and M is Halogen elements,

Preferably, the M is selected from any one of F, Cl, Br and I.

Preferably, the mass ratio of the lithium-containing material to AlPO ₄ is (1-4):1.

More preferably, the lithium-containing material is selected from at least one of LiHAl(PO ₄ )O _1-y M _2y , most preferably from LiHAl(PO ₄ )O _0.96 F _0.08 , LiHAl(PO ₄ )O _0.95 F _0.1 , at least one of LiHAl(PO ₄ )O _0.94 Cl _0.12 and LiHAl(PO ₄ )O _0.94 Br _0.12 .

The crystal form of the aluminum phosphate is selected from at least one of quartz type, tridymite type and cristobalite type.

According to the present invention, preferably, the preparation method of the lithium-containing material is:

Step (1): Weigh the lithium salt, aluminum-containing material, phosphorus-containing material and halogen-containing material correspondingly according to the composition of the lithium-containing material, and perform the first mixing to obtain a mixture (Mixture-1);

Step (2): The mixture (Mixture-1) is subjected to sintering treatment and optionally pulverization treatment to obtain the lithium-containing material.

Preferably, among the lithium salt, aluminum-containing material, phosphorus-containing material and halogen-containing material, the first step is carried out according to a molar ratio of Li, Al, P and halogen of 10-20:10-20:10-20:1. mix.

Preferably, the lithium salt is selected from at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium acetate.

Preferably, the aluminum-containing material is selected from at least one of aluminum oxide, aluminum hydroxide and aluminum sulfate.

Preferably, the phosphorus-containing material is selected from at least one of phosphorus pentoxide, phosphoric acid, phosphate and phosphine.

Preferably, the halogen-containing material is selected from at least one of lithium hexafluorophosphate, hydrogen fluoride and phosphorus fluoride.

Preferably, in step (1), the first mixing adopts stirring and mixing.

Preferably, the first mixing time is 10s-30min.

Preferably, the stirring speed of the stirring mixing is 200-2000 rpm.

Preferably, in step (2), the temperature of the sintering treatment is 300°C-1000°C, and the time is 5-256h; the sintering treatment is performed in an air atmosphere or an inert gas atmosphere.

Preferably, during the crushing process, the semi-finished lithium-containing materials are first poured into the crushing equipment for primary crushing, and then the materials after primary crushing are put into the crushing equipment for crushing, and finally the lithium-containing materials are obtained.

Preferably, during X-ray diffraction of the lithium-containing material prepared in the present invention, the measured 2θ angle has a characteristic diffraction peak at 15-35°.

According to the present invention, preferably, when the inorganic solid electrolyte particles are a mixture of lithium-containing materials and aluminum phosphate, the preparation method of the inorganic solid electrolyte particles is:

The lithium-containing material and aluminum phosphate are mixed for a second time to obtain a mixture (Mixture-2), and then the mixture (Mixture-2) is heat-treated under the protection of an inert gas, and then cooled and pulverized to obtain the mixture. The inorganic solid electrolyte particles are materials that improve battery safety.

Preferably, the inert gas includes at least one of nitrogen, helium and argon.

Preferably, the heat treatment method is to maintain the temperature at 100°C-1000°C for 1-20 hours, and preferably to increase to 100°C-1000°C at a rate of 1-20°C/min.

Preferably, the temperature reduction method is to reduce the temperature to room temperature at a rate of 1-20°C/min.

Preferably, the mixing equipment used for the second mixing is selected from the group consisting of a dual-motion mixer, a three-dimensional mixer, a V-shaped mixer, a single cone double-spiral mixer, a trough ribbon mixer and a horizontal gravity-free mixer. A sort of.

Preferably, the heat treatment equipment is selected from one of a box furnace, a tube furnace, a roller kiln, a push plate kiln and a rotary kiln.

Preferably, crushing equipment is used to finely crush the powder or lump mixed material obtained after heat treatment and cooling; the crushing equipment is selected from the group consisting of jaw crusher, cone crusher, impact crusher, hammer crusher and roller crusher. broken, flat At least one of a jet pulverizer, a fluidized bed jet pulverizer, a circulating jet pulverizer, an impact crusher, an expansion crusher, a ball mill, a high-speed rotating projectile pulverizer, and a high-speed rotating impact pulverizer. kind.

According to the present invention, preferably, the inorganic solid electrolyte layer further includes a binder (Binder-1) and additives;

The mass ratio of the inorganic solid electrolyte particles, binder (binder-1), and additive is 100: (0.3-5): (0.3-5). When the mass ratio meets this range, the solid electrolyte layer can be kept smooth and evenly coated on the surface of the electrode piece, and the coating and the base of the electrode piece are firmly bonded without falling off.

The size of the inorganic solid electrolyte particles is 10 nm-10 μm. When the size of the inorganic solid electrolyte particles meets this range, the coating thickness is no more than 20 μm and can be coated evenly and flatly. The coating has suitable pores to accommodate electrolyte infiltration, and some electrolyte particles can penetrate into the negative electrode piece.

Further, the size of the inorganic solid electrolyte particles is 50 nm-1 μm.

According to the present invention, preferably, the binder (Binder-1) is selected from styrene-butadiene rubber (SBR), polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, sodium carboxymethyl cellulose, methane At least one of hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylhydroxyethylcellulose and hydroxypropylcellulose; preferably styrene-butadiene rubber, sodium carboxymethylcellulose, hydroxypropylmethyl At least one of cellulose, carboxymethylhydroxyethylcellulose and hydroxypropylcellulose.

The present invention has no special restrictions on the parameters of the binder (Binder-1), such as weight average molecular weight, etc., as long as it meets the requirements as a binder.

The additives include dispersants and wetting agents. In the present invention, the mass ratio of the dispersant and the wetting agent is determined according to the usage requirements, and is proportioned according to the conventional dosage. Preferably, the weight ratio of the dispersant to the inorganic solid electrolyte particles is (0.005-0.1):1, and the weight ratio of the wetting agent to the inorganic solid electrolyte particles is (0.001-0.05):1.

According to the present invention, preferably, the dispersant is selected from at least one of sodium polyacrylate, ammonium polyacrylate copolymer, polyvinyl alcohol, polyethylene glycol, polyacrylamide and polyvinylpyrrolidone, preferably polyacrylic acid. At least one of sodium, ammonium polyacrylate copolymer and polyacrylamide.

The present invention has no special restrictions on the parameters of the dispersant, such as weight average molecular weight, etc., as long as it meets the requirements as a dispersant.

The wetting agent is selected from the group consisting of sodium perfluorooctanoate, nonylphenol polyoxyethylene ether, fluoroalkyl methoxy alcohol ether, polyoxyethylene alkylamine, sodium butyl naphthalene sulfonate, sodium arylnaphthalene sulfonate, and At least one of sodium dialkylbenzene sulfonate and sodium alkyl sulfate, preferably at least one of sodium perfluorooctanoate, nonylphenol polyoxyethylene ether and sodium dodecylbenzene sulfonate.

A second aspect of the present invention provides a composite negative electrode sheet for lithium batteries, which includes a current collector and a negative electrode material layer. The composite negative electrode sheet further includes the inorganic solid electrolyte layer provided by the present invention;

The negative electrode material layer is located on the surface of the current collector;

The inorganic solid electrolyte layer is located on the surface of the negative electrode material layer or is located on the surface of the negative electrode material layer and partially or completely penetrates into the negative electrode material layer.

According to the present invention, preferably, the thickness of the inorganic solid electrolyte layer formed in the composite negative electrode sheet is 0 nm-20 μm, preferably 0.1 nm-5 μm. In the present invention, the thickness of the inorganic solid electrolyte layer is the thickness of the inorganic solid electrolyte layer located above the surface of the negative electrode material layer.

A third aspect of the present invention provides a method for preparing the composite negative electrode sheet for lithium batteries provided by the present invention. The preparation method includes:

(1) After stirring and grinding the inorganic solid electrolyte particles and solvent evenly, optionally add additives and binder (Binder-1) and stir thoroughly to prepare the first slurry;

(2) The first slurry is applied to the negative electrode sheet, and then baked (first baking) and rolled (first rolled) to obtain the composite negative electrode sheet.

According to the present invention, preferably, in step (1), the solvent is selected from at least one of water, ethanol, N-methylpyrrolidone (NMP), isopropyl alcohol and acetone.

Preferably, the mass ratio of the inorganic solid electrolyte particles to the solvent is 1: (0.5-99), preferably 1: (1-9).

In step (2), the coating method includes microgravure coating, spray coating and simultaneous coating.

Preferably, the temperature of the first baking is 75-110°C and the time is 1 minute-1 hour; the pressure of the first rolling is 5-100t. When the composite negative electrode sheet is prepared to meet these conditions, a uniform and smooth solid electrolyte coating can be obtained.

In the present invention, the negative electrode sheet can be made of existing conventional materials and prepared by conventional processes. The negative electrode material layer contained in the negative electrode sheet is located on the surface of the current collector. Preferably, the negative electrode material layer includes negative electrode active material particles, a conductive agent, and a binder (Binder-2).

Preferably, the negative active material particles are selected from at least one of carbon materials, lithium-containing oxides, transition metal oxides, sulfides, metal alloys and silicon-containing materials.

Preferably, the carbon material is selected from at least one of graphite, hard carbon and soft carbon.

Preferably, the lithium-containing oxide is selected from Li ₄ Ti ₅ O ₁₂ and/or LiVO ₂ .

Preferably, the transition metal oxide is selected from SnO and/or CoO.

Preferably, the sulfide is MoS ₂ .

Preferably, the metal alloy is tin alloy.

Preferably, the silicon-containing material is selected from at least one of silicon, silicon-oxygen, silicon-carbon and silicon-oxycarbon.

Preferably, the conductive agent is selected from conductive graphite, conductive carbon black, acetylene black, Super P, carbon nanotubes, carbon nanofibers, conductive silver particles, conductive copper particles, conductive aluminum particles, conductive silver fibers, conductive copper fibers and At least one type of conductive aluminum fiber.

Preferably, the binder (Binder-2) is selected from polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), carboxymethyl At least one of sodium cellulose, methylcellulose, hydroxypropylmethylcellulose, carboxymethylhydroxyethylcellulose and hydroxypropylcellulose.

The present invention has no special restrictions on the parameters of the binder (Binder-2), such as weight average molecular weight, etc., as long as it meets the requirements as a binder.

Preferably, based on the total weight of the negative electrode material layer being 100wt%, the content of the negative active material particles is 82-99.8wt%, the content of the conductive agent is 0.1-8wt%, and the binder ( The content of binder-2) is 0.1-10wt%. When the components in the negative electrode material layer meet this ratio, a better balance can be achieved in terms of negative electrode active material loading, negative electrode rate performance, negative electrode cycle performance and negative electrode safety performance.

Preferably, the preparation method of the negative electrode sheet is as follows: uniformly mixing negative active material particles, conductive agent, and binder (Binder-2) to prepare a second slurry; applying the second slurry to the set. on the fluid, and then bake (second baking) and rolling (second rolling) to obtain the negative electrode sheet.

Preferably, the second baking temperature is 50-180°C and the time is 1 minute-1 hour.

Preferably, the second rolling pressure is 5-100t. When the preparation of the negative electrode sheet meets this condition, a uniform and smooth negative electrode active material coating can be obtained.

Preferably, the second slurry further includes Solvent-2.

Preferably, based on the total weight of the second slurry being 100g, the amount of solvent-2 is 20-70g.

A fourth aspect of the present invention provides a lithium battery, which includes the inorganic solid electrolyte layer provided by the present invention or the composite negative electrode sheet for lithium batteries provided by the present invention. Preferably, the lithium battery is a liquid lithium battery, a hybrid solid-liquid lithium battery or a solid-state lithium battery.

The main purpose of the inorganic solid electrolyte layer in the present invention is to modify the negative electrode sheet and use it as a composite negative electrode sheet. Therefore, the liquid electrolyte can be injected into the lithium battery according to the conventional assembly process.

The present invention combines inorganic solid electrolyte particles with optional additives and binders to form an inorganic solid electrolyte layer, which improves the thermal stability of the negative electrode sheet and ensures the safety of the battery without affecting the electrochemical performance. .

The technical principle is as follows: First, inorganic solid electrolyte particles have a certain ion transmission ability. Use them as coating materials on the surface of the negative electrode sheet to reduce the contact area between the negative electrode active material and the electrolyte to improve safety performance and at the same time prevent the polarization of the battery. is too large; secondly, the inorganic solid electrolyte particles themselves have an endothermic effect, which can absorb part of the heat and delay thermal runaway on the negative electrode side of the battery; thirdly, the halogen elements in the lithium-containing materials can participate in the formation of the SEI of the negative electrode, forming Li-X ( If The doping of hydrogen elements in lithium-containing materials changes the polarization properties and surface energy of inorganic solid electrolyte particles, making them compatible with SEI produced by the decomposition of existing electrolytes, and helps to generate more stable SEI, thus improving the efficiency of inorganic electrolyte particles. Interfacial stability of solid electrolyte particles.

Through the above technical solutions, the beneficial effects of the present invention are:

The inorganic solid electrolyte particles added to the inorganic solid electrolyte layer of the present invention have low halogen content, are less difficult to synthesize materials, and are not prone to segregation and uneven distribution of halogen elements; and they have a phosphate structure, which is better than existing calcium titanium Mineral structure and garnet structure solid electrolytes, phosphate structure solid electrolyte materials have better stability.

The inorganic solid electrolyte particles added to the inorganic solid electrolyte layer of the present invention mainly contain elements such as lithium aluminum phosphorus oxide compounds, and do not contain Ti or Ge elements that are easily reduced at the negative electrode. The SEI formed on the surface of the negative electrode is more stable. Existing common solid electrolytes such as LAGP (Li _1.5 Al _0.5 Ge _1.5 P ₃ O ₁₂ ), LLZO, LATP and other materials are prone to reduction reactions of metal ions at the negative electrode potential. In the present invention, the metal elements in the particles in the solid electrolyte are It is not easily reduced under low voltage, which improves the stability of the negative electrode.

The halogen element in the inorganic solid electrolyte particles added to the inorganic solid electrolyte layer of the present invention can participate in the formation of the negative electrode SEI, such as forming LiF, which improves the stability of the negative electrode surface SEI; the doping of hydrogen elements changes the polarization of the solid electrolyte material. The properties and surface energy make it compatible with the SEI produced by the decomposition of the existing electrolyte, and helps to generate a more stable SEI; therefore, the interface stability of the solid electrolyte material is improved, and the reaction between the negative electrode and the electrolyte during thermal runaway is suppressed. Thereby improving the safety performance of the battery.

The inorganic solid electrolyte layer of the present invention has the advantages of high stability and low cost, and the method of coating the surface of the negative electrode sheet with the inorganic solid electrolyte is compatible with the existing negative electrode sheet coating process and battery manufacturing process, without changing the process. Suitable for large-scale applications.

The lithium battery assembled based on the composite negative electrode sheet of the present invention can improve the safety characteristics of the battery without affecting the electrochemical performance. The battery can successfully pass the acupuncture test, and other safety performance test results are improved.

Description of the drawings

Figure 1 is a schematic structural diagram of a composite negative electrode sheet prepared according to a specific embodiment of the present invention;

Figure 2 is a schematic structural diagram of a composite negative electrode sheet prepared in another specific embodiment of the present invention;

Figure 3 is an XRD pattern of the lithium-containing material prepared in Preparation Example 1 of the present invention;

Figure 4 is a morphology and F element distribution diagram of the lithium-containing material prepared in Preparation Example 1 of the present invention;

Figure 5 is an XRD pattern of the lithium-containing material prepared in Preparation Example 2 of the present invention;

Figure 6 is an XRD pattern of the lithium-containing material prepared in Preparation Example 3 of the present invention;

Figure 7 is an XRD pattern of the lithium-containing material prepared in Preparation Example 4 of the present invention.

Explanation of reference signs
11 Current collector 21 Negative electrode material layer 31 Inorganic solid electrolyte layer

Detailed ways

The endpoints of ranges and any values disclosed herein are not limited to the precise range or value, but these ranges or values are to be understood to include values approaching such ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges. These values The scope shall be deemed to be specifically disclosed herein.

The present invention will be described in detail below through examples and comparative examples. In the following examples and comparative examples, unless otherwise specified, all are conventional methods; unless otherwise specified, all reagents and materials used can be obtained from commercial sources. The test methods involved in the examples and comparative examples are as follows:

Lithium battery electrochemical performance testing method:

1. Capacity and energy density test

a) Weigh the battery weight and record it;

b) At 23±2°C, the battery is discharged at a constant current of 0.33C until it reaches the discharge termination voltage and left to stand for 1 hour;

c) Charge at a constant current of 0.33C until the charging end voltage is reached, then switch to constant voltage charging until the charging voltage is reached. When the flow rate drops to 0.05C, stop charging and let it sit for 1 hour;

d) The battery is discharged at a constant current of 0.33C until it reaches the discharge termination voltage and stops discharging;

e) Record the discharge capacity (Ah) and discharge energy, divide the discharge energy by the mass, and obtain the energy density (Wh/Kg);

f) Repeat steps c)-e) 5 times. When the range of the three consecutive test results is less than 3%, the test can be terminated early and the average of the last three test results will be taken.

Note: Range refers to the difference between the maximum value and the minimum value of the test result;

2. Cycle performance test

a) At 23℃±2℃, charge at 1C constant current until the charging end voltage is reached, then switch to constant voltage charging until the charging current rate drops to 0.05C, stop charging, and let it stand for 1 hour;

b) The battery is discharged at a constant current of 1C until it reaches the discharge end voltage, stops discharging, records the discharge capacity, and completes a cycle;

c) Repeat steps a and b until the discharge capacity is lower than 80% of the discharge capacity in the first week, and record the total number of battery cycles at this time.

3. Magnification test

a) At 23°C ± 2°C, the battery is charged at 0.1C, 0.2C, 0.33C, 1C, 2C, and 3C rates to the charge end voltage and then discharged with the same rate current to the discharge end voltage. The same rate is cycled 4 times. ;

b) Record the discharge capacity at different rates;

c) Calculate the ratio of 3C discharge capacity to 0.33C discharge capacity, recorded as 3C/0.33C, and evaluate the rate performance.

4. High temperature cycle

a) Charge at 45°C with a constant current of 1C until the charging termination voltage is reached, then switch to constant voltage charging until the charging current rate drops to 0.05C, then stop charging;

b) The battery is left standing at 45°C for 5 hours;

c) Under high temperature conditions of 45°C, the battery is discharged at a constant current of 1C until it reaches the discharge end voltage, stops discharging, and records the discharge capacity, thus completing a cycle;

d) Repeat steps a-c until the discharge capacity is lower than 80% of the discharge capacity in the first week. Record the discharge capacity of the battery and the total number of cycles at this time.

Lithium battery safety performance testing method:

1. Overcharging

a) At 23℃±2℃, charge at 1C constant current until the charging end voltage is reached, then switch to constant voltage charging until the charging current rate drops to 0.05C, stop charging, and let it stand for 1 hour;

b) Continue charging at a constant current of 1C until the battery undergoes thermal runaway, and record the voltage value of the battery when thermal runaway begins.

2. Hot box

a) At 23℃±2℃, charge at 1C constant current until the charging end voltage is reached, then switch to constant voltage charging. Until the charging current rate drops to 0.05C, stop charging and let it sit for 1 hour;

b) Put the battery into the test box. The test box heats up at a temperature rise rate of 5°C/min. When the temperature inside the box reaches 160°C ± 2°C, it is kept at a constant temperature for 1 hour;

The battery passes if it does not smoke, catch fire or explode, otherwise it fails.

3. Fall

a) At 23℃±2℃, charge at 1C constant current until the charging end voltage is reached, then switch to constant voltage charging until the charging current rate drops to 0.05C, stop charging, and let it stand for 1 hour;

b) Drop the body freely onto the concrete slab from a drop height of 1m; drop each side of the soft-packed battery once, and conduct a total of six tests; after six tests, the battery will pass if it does not smoke, catch fire, or explode. Otherwise it will not pass.

4. Impact of heavy objects

a) At 23℃±2℃, charge at 1C constant current until the charging end voltage is reached, then switch to constant voltage charging until the charging current rate drops to 0.05C, stop charging, and let it stand for 1 hour;

b) Place the battery on the surface of the platform, place a metal rod with a diameter of 15.8mm±0.2mm horizontally on the upper surface of the geometric center of the battery, and use a weight with a mass of 9.1kg±0.1kg to fall freely from a height of 610mm±25mm. Impact the battery surface with a metal rod and observe for 6 hours. If the battery does not smoke, fire or explode, it will pass, otherwise it will not pass.

5. Acupuncture

a) At 23℃±2℃, charge at 1C constant current until the charging end voltage is reached, then switch to constant voltage charging until the charging current rate drops to 0.05C, stop charging, and let it stand for 1 hour;

b) Use a φ8mm high-temperature steel needle (the cone angle of the needle tip is 45°, the surface of the needle is smooth, free of rust, oxide layer and oil stain), and penetrate it from the direction perpendicular to the battery plate at a speed of 25mm/s. The position is the geometric center of the stabbed surface, and the steel needle stays in the battery;

c) Observe for 1 hour; if the battery does not smoke, fire or explode, it will pass, otherwise it will not pass.

Preparation Example 1

The preparation method of lithium-containing material LiHAl(PO ₄ )O _0.95 F _0.1 is as follows:

Step (1): Stir and mix the lithium salt lithium hydroxide, the aluminum-containing material aluminum hydroxide, the phosphorus-containing material phosphoric acid and the halogen-containing material hydrogen fluoride according to the composition of the lithium-containing material. The molar ratio of Li, Al, P, and halogen is 10:10:10:1, the mixing time is 10min, the stirring rate is 500rpm; a mixture is obtained;

Step (2): Sintering the mixture, the sintering temperature is 1000°C, the sintering time is 5 hours; the sintering atmosphere is air atmosphere, to obtain the semi-finished lithium-containing material, and then first pour the semi-finished lithium-containing material into the crushing equipment. Primary crushing treatment, and then the materials after primary crushing treatment are put into the crushing equipment for crushing. After the crushing process, lithium-containing materials with an average particle size of 3 μm are obtained.

The lithium-containing material prepared by the above method includes hydrogen, aluminum, phosphorus, halogen and oxygen elements, and the chemical formula is LiHAl(PO ₄ )O _0.95 F _0.1 ; during X-ray diffraction of the lithium-containing material, the measured 2θ angle is in the range of 15- There is a characteristic diffraction peak at 35°, and the corresponding XRD is shown in Figure 3; the F element of this lithium-containing material is evenly distributed on the particles without segregation. The corresponding morphology and F element distribution test results are shown in Figure 4.

Preparation Example 2

The preparation method of lithium-containing material LiHAl(PO ₄ )O _0.96 F _0.08 is as follows:

Step (1): Stir and mix the lithium salt lithium carbonate, the aluminum-containing material alumina, the phosphorus-containing material phosphorus pentoxide and the halogen-containing material hydrogen fluoride according to the composition of the lithium-containing material. The molar ratio of Li, Al, P, and halogen is The ratio is 12.5:12.5:12.5:1, the mixing time is 30min, and the stirring rate is 200rpm; a mixture is obtained;

Step (2): Sintering the mixture at a temperature of 300°C and a sintering time of 200 hours; the sintering atmosphere is a nitrogen atmosphere to obtain a semi-finished lithium-containing material, and then first pour the semi-finished lithium-containing material into the crushing equipment. Primary crushing treatment, and then the materials after the primary crushing treatment are put into the crushing equipment for crushing. After the crushing process, lithium-containing materials with a particle size of 5 μm are obtained.

The lithium-containing material prepared by the above method includes hydrogen, aluminum, phosphorus, halogen and oxygen elements, and the chemical formula is LiHAl(PO ₄ )O _0.96 F _0.08 ; during X-ray diffraction of the lithium-containing material, the measured 2θ angle is 15 There is a characteristic diffraction peak at -35°, and the corresponding XRD is shown in Figure 5.

Preparation Example 3

The preparation method of lithium-containing material LiHAl(PO ₄ )O _0.94 Cl _0.12 is as follows:

Step (1): Stir and mix the lithium salt lithium acetate, the aluminum-containing material aluminum hydroxide, the phosphorus-containing material phosphine and the halogen-containing material phosphorus chloride according to the composition of the lithium-containing material, where Li, Al, P, halogen The molar ratio is 16.6:16.6:16.6:1, the mixing time is 1min, and the stirring rate is 1800rpm; a mixture is obtained;

Step (2): Sintering the mixture at a temperature of 500°C and a sintering time of 100 hours; the sintering atmosphere is a nitrogen atmosphere to obtain a semi-finished lithium-containing material, and then first pour the semi-finished lithium-containing material into the crushing equipment. Primary crushing treatment, and then the materials after primary crushing treatment are put into the crushing equipment for crushing. After the crushing process, lithium-containing materials with a particle size of 10 μm are obtained.

The lithium-containing material prepared by the above method includes hydrogen, aluminum, phosphorus, halogen and oxygen elements, and the chemical formula is LiHAl(PO ₄ )O _0.94 Cl _0.12 ; during X-ray diffraction of the lithium-containing material, the measured 2θ angle is at 15 There is a characteristic diffraction peak at -35°, and the corresponding XRD is shown in Figure 6.

Preparation Example 4

The preparation method of lithium-containing material LiHAl(PO ₄ )O _0.94 Br _0.12 is as follows:

Step (1): Stir and mix the lithium salt lithium acetate, the aluminum-containing material aluminum hydroxide, the phosphorus-containing material phosphine and the halogen-containing material phosphorus bromide according to the composition of the lithium-containing material, where Li, Al, P, halogen The molar ratio is 16.6:16.6:16.6:1, the mixing time is 10min, and the stirring rate is 1000rpm; a mixture is obtained;

Step (2): Sintering the mixture at a temperature of 800°C and a sintering time of 50 hours; the sintering atmosphere is a nitrogen atmosphere to obtain a semi-finished lithium-containing material, and then first pour the semi-finished lithium-containing material into the crushing equipment. Carry out primary crushing treatment, and then put the materials after primary crushing treatment into the crushing equipment for crushing. After the crushing process, lithium-containing materials with a particle size of 20 μm are obtained.

The lithium-containing material prepared by the above method includes hydrogen, aluminum, phosphorus, halogen and oxygen elements, and the chemical formula is LiHAl(PO ₄ )O _0.94 Br _0.12 ; during X-ray diffraction of the lithium-containing material, the measured 2θ angle is 15 There is a characteristic diffraction peak at -35°, and the corresponding XRD is shown in Figure 7.

Example 1

Preparation of negative electrode sheet:

(1) Thoroughly stir, grind and mix the lithium-containing material LiHAl(PO ₄ )O _0.95 F _0.1 (inorganic solid electrolyte particles without aluminum phosphate) and the solvent (deionized water) prepared in Preparation Example 1. After grinding, The average particle size of lithium material is 300nm; based on the mass ratio of lithium-containing material LiHAl(PO ₄ )O _0.95 F _0.1 , binder (SBR), dispersant (sodium polyacrylate), wetting agent (sodium perfluorooctanoate), and solvent Add binder, dispersant and wetting agent in a ratio of 100:3:1.5:0.5:400 and mix evenly to prepare the first slurry;

(2) Mix the negative active material graphite particles, conductive agent Super P, binder (SBR), binder (CMC) and solvent deionized water evenly according to the mass ratio of 96:2:1.2:0.8:110 to prepare The second slurry; apply the second slurry onto the current collector copper foil using a scraper, bake at 110 degrees for 5 minutes, and roll with a pressure of 50t to obtain a negative electrode sheet that does not contain an inorganic solid electrolyte layer;

(3) Spray the first slurry on the prepared negative electrode sheet without the inorganic solid electrolyte layer, bake it at 100°C for 10 minutes to form the inorganic solid electrolyte layer, roll it for 50t and roll it up to obtain the negative electrode sheet.

The negative electrode sheet prepared by the above method includes a current collector 11, a negative electrode material layer 21 and an inorganic solid electrolyte layer 31; the negative electrode material layer 21 is located on the surface of the current collector 1; the inorganic solid electrolyte layer 31 is located on the surface of the negative electrode material layer 21. The structure is as follows: As shown in Figure 1.

The thickness of the negative electrode material layer contained in the prepared negative electrode sheet is 100 μm, and the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 2 μm.

Preparation of positive electrode sheet:

S1: Mix the positive active material particles lithium iron phosphate, the conductive agent Super P, the conductive agent CNT and the binder PVDF evenly to obtain a slurry;

S2: Coat the above slurry on the current collector aluminum foil, bake, roll and die-cut to obtain a positive electrode sheet. Vacuum dry the positive electrode sheet at 120°C for 24 hours to obtain a positive electrode sheet for lithium batteries.

Among them, when preparing the above-mentioned cathode sheet for lithium batteries, based on the weight of the cathode material layer being 100wt%, the amount of cathode active material particles is 95.8wt%; the amount of conductive agent SP is 1wt%; and the amount of conductive agent CNT is 0.2 wt%; the amount of binder is 3wt%.

Preparation of lithium battery:

The negative electrode sheet prepared by the above method follows the structure of the negative electrode, separator, and positive electrode, and together with the prepared lithium iron phosphate positive electrode sheet and separator, it is laminated, tab welded, packaged with aluminum plastic film, and electrolyte (in the form of EC, EMC and DMC As the solvent and using lithium hexafluorophosphate as the lithium salt), top and side sealing, forming two seals and dividing the volume, it is assembled into a battery soft package. The lithium battery prepared above is subjected to electrochemical performance test and safety performance test. The electrochemical performance test results See Table 1, and the safety performance test results are shown in Table 2.

Example 2

The negative electrode sheet was prepared according to the method of Example 1, except that in step (1), the lithium-containing material LiHAl(PO ₄ )O _0.96 F _0.08 prepared according to the method of Preparation Example 2 was selected as the inorganic solid electrolyte particles. Lithium-containing compounds The average particle size is 287nm, and it is prepared with a mass ratio of lithium-containing material LiHAl(PO ₄ )O _0.96 F _0.08 , binder, dispersant, wetting agent and solvent of 100:3:1.5:0.5:400. In the first slurry, graphite is selected as the negative active material of the lithium battery to prepare the negative electrode sheet. Then, the prepared negative electrode sheet and the positive electrode sheet using lithium cobalt oxide as the positive electrode active material are assembled into a soft-pack lithium battery.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; the negative electrode material layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer penetrates into the negative electrode material layer , the thickness of the negative electrode material layer is 100 μm; the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 2 μm, and a small amount of inorganic solid electrolyte particles penetrate into the negative electrode material layer. The structural diagram is shown in Figure 2.

Example 3

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that a mixture of the lithium-containing material LiHAl(PO ₄ )O _0.95 F _0.1 and AlPO ₄ (mass ratio 1:1) was used as the inorganic solid electrolyte particles. After grinding The average particle size of the inorganic solid electrolyte particles is 300 nm, and a negative electrode sheet is prepared. LFP is selected as the cathode active material of lithium battery. Lithium batteries are then produced.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; the negative electrode material layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer partially penetrates into the negative electrode material layer , the thickness of the negative electrode material layer is 100 μm; the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 2.2 μm.

Among them, the preparation method of using a mixture of LiHAl(PO ₄ )O _0.95 F _0.1 and AlPO ₄ (mass ratio 1:1) as inorganic solid electrolyte particles is as follows:

Aluminum phosphate (quartz type) with a particle size of 30 μm and the lithium-containing material LiHAl(PO ₄ )O _0.95 F _0.1 prepared in Preparation Example 1 were mixed evenly in a V-type mixer at a mass ratio of 1:1, and then mixed The material is heated to 600°C at a rate of 2°C/min and kept for 10 hours under the protection of a nitrogen atmosphere in a tube furnace, and then cooled to room temperature at a rate of 10°C/min. Then, the heat-treated material is first crushed into small pieces by a cone crusher, and then crushed into 4.5 μm-sized powder by a flat jet pulverizer to obtain a mixture of LiHAl(PO ₄ )O _0.95 F _0.1 and AlPO ₄ .

Example 4

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that NCM811 was selected as the positive electrode active material of the lithium battery.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; the negative electrode material layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer partially penetrates into the negative electrode Among the material layers, the thickness of the negative electrode material layer is 100 μm; the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 2.1 μm.

Example 5

The negative electrode sheet and lithium battery were prepared according to the method of Example 1. The difference is that in step (1), a mixture of the lithium-containing material LiHAl(PO ₄ )O _0.94 Cl _0.12 and AlPO ₄ (mass ratio 2:1) was selected as the inorganic Solid electrolyte particles. The average particle diameter of the ground inorganic solid electrolyte particles is 310 nm. phenol polyoxyethylene ether) and solvent (remove The mass ratio of ionized water) is 100:3:2:3:400 to prepare the first slurry. SiOC 450 was selected as the negative active material of lithium batteries to prepare negative electrode sheets. Then, a lithium battery was prepared with a positive electrode sheet using NCM811 as the positive active material.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; the negative electrode material layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer partially penetrates into the negative electrode material layer , the thickness of the negative electrode material layer is 100 μm; the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 1.9 μm.

Among them, the preparation method of using a mixture of lithium-containing materials LiHAl(PO ₄ )O _0.94 Cl _0.12 and AlPO ₄ (mass ratio 2:1) as inorganic solid electrolyte particles is as follows:

Aluminum phosphate (cristobalite type) with a particle size of 3 μm and the lithium-containing material LiHAl(PO ₄ )O _0.94 Cl _0.12 prepared in Preparation Example 3 were mixed evenly in a trough ribbon mixer at a mass ratio of 1:2, and then The mixed materials were heated to 500°C in a rotary kiln under the protection of nitrogen atmosphere at 6°C/min and kept for 15 hours, and then cooled to room temperature at 8°C/min. The heat-treated material is then crushed into small pieces by a roller crusher, and then crushed into 3 μm-sized powder by a fluidized bed jet pulverizer to obtain inorganic solid electrolyte particles.

Example 6

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that in step (1), a mixture of lithium-containing materials LiHAl(PO ₄ )O _0.94 Br _0.12 and AlPO ₄ (mass ratio 4:1) was used as the inorganic Solid electrolyte particles, the average particle size of the ground inorganic solid electrolyte particles is 300nm. Micron silicon is selected as the negative active material of the lithium battery to prepare a negative electrode sheet, and is assembled with a positive electrode sheet using lithium iron phosphate as the positive active material to prepare a lithium battery.

Among them, the preparation method of using a mixture of lithium-containing materials LiHAl(PO ₄ )O _0.94 Br _0.12 and AlPO ₄ (mass ratio 4:1) as inorganic solid electrolyte particles is as follows:

Aluminum phosphate (cristobalite type) with a particle size of 5 μm and the lithium-containing material LiHAl(PO ₄ )O _0.94 Br _0.12 prepared in Preparation Example 4 were mixed evenly in a trough ribbon mixer at a mass ratio of 1:4, and then Place the mixed materials in a rotary kiln under the protection of nitrogen atmosphere, raise the temperature to 1000°C at 15°C/min and keep it for 1 hour, and then cool down to room temperature at 1°C/min. The heat-treated material is then crushed into small pieces by a roller crusher, and then crushed into 10 μm-sized powder by a fluidized bed jet pulverizer to obtain inorganic solid electrolyte particles.

Example 7

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the average particle size of the ground inorganic solid electrolyte particles was 1 μm. Then the negative electrode sheet and lithium battery are prepared.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; the negative electrode material layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer partially penetrates into the negative electrode material layer , the thickness of the negative electrode material layer is 100 μm; the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 2.1 μm.

Example 8

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the average particle size of the ground inorganic solid electrolyte particles was 100 nm. Then the negative electrode sheet and lithium battery are prepared.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; negative electrode material The layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer partially penetrates into the negative electrode material layer. The thickness of the negative electrode material layer is 100 μm; the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 2.1 μm.

Example 9

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the average particle size of the ground inorganic solid electrolyte particles was 50 nm. Then the negative electrode sheet and lithium battery are prepared.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; the negative electrode material layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer penetrates into the negative electrode material layer , the thickness of the negative electrode material layer is 100 μm, and the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 100 nm.

Example 10

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the average particle size of the ground inorganic solid electrolyte particles was 305 nm. Then the negative electrode sheet and lithium battery are prepared.

The negative electrode sheet prepared by the above method includes a current collector, a negative electrode material layer and an inorganic solid electrolyte layer; the negative electrode material layer is located on the surface of the current collector; the inorganic solid electrolyte layer is located on the surface of the negative electrode material layer, and a small amount of the inorganic solid electrolyte layer partially penetrates into the negative electrode material layer , the thickness of the negative electrode material layer is 100 μm; the thickness of the inorganic solid electrolyte layer above the negative electrode material layer is 5 μm.

Example 11

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the mass ratio of the lithium-containing material LiHAl(PO ₄ )O _0.95 F _0.1 , binder, dispersant, wetting agent, and solvent was 100:0.3. :0.15:0.15:400 ratio to prepare the first slurry. Then the negative electrode sheet and lithium battery are prepared.

Example 12

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the mass ratio of the lithium-containing material LiHAl(PO ₄ )O _0.95 F _0.1 , binder, dispersant, wetting agent, and solvent was 100:5. :2.5:2.5:400 ratio to prepare the first slurry. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 1

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the negative electrode sheet did not contain an inorganic solid electrolyte layer. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 2

The negative electrode sheet and lithium battery were prepared according to the method of Example 2, except that the negative electrode sheet did not contain an inorganic solid electrolyte layer. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 3

The negative electrode sheet and lithium battery were prepared according to the method of Example 4, except that the negative electrode sheet did not contain an inorganic solid electrolyte layer. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 4

The negative electrode sheet and lithium battery were prepared according to the method of Example 5. The difference is that the negative electrode sheet does not contain inorganic solid electrolyte. qualitative layer. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 5

The negative electrode sheet and lithium battery were prepared according to the method of Example 6, except that the negative electrode sheet did not contain an inorganic solid electrolyte layer. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 6

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that alumina was used instead of the inorganic solid electrolyte particles LiHAl(PO ₄ )O _0.95 F _0.1 . Then the negative electrode sheet and lithium battery are prepared.

Comparative example 7

The negative electrode sheet and lithium battery were prepared according to the method of Example 2, except that LATP (Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ ) was used instead of the inorganic solid electrolyte particles LiHAl (PO ₄ )O _0.96 F _0.08 . Then the negative electrode sheet and lithium battery are prepared.

Comparative example 8

The negative electrode sheet and lithium battery were prepared according to the method of Example 4, except that LLTO (La _0.57 Li _0.29 TiO ₃ ) was used instead of the inorganic solid electrolyte particles LiHAl (PO ₄ )O _0.95 F _0.1 . Then the negative electrode sheet and lithium battery are prepared.

Comparative example 9

The negative electrode sheet and lithium battery were prepared according to the method of Example 5, except that LLZO (Li ₇ La ₃ Zr ₂ O ₁₂ ) was used instead of the inorganic solid electrolyte particles of Example 5. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 10

The negative electrode sheet and lithium battery were prepared according to the method of Example 5, except that 15 wt% F-doped LLZO was used instead of the inorganic solid electrolyte particles of Example 5. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 11

The negative electrode sheet and lithium battery were prepared according to the method of Example 6, except that LiOF ₃ was used instead of the inorganic solid electrolyte particles of Example 6. Then the negative electrode sheet and lithium battery are prepared.

Comparative example 12

The negative electrode sheet and lithium battery were prepared according to the method of Example 1, except that the inorganic solid electrolyte particles were AlPO ₄ . Then the negative electrode sheet and lithium battery are prepared.

test case

The electrochemical performance and safety performance of the lithium batteries prepared in each embodiment and comparative example were measured respectively. The specific electrochemical performance test results of the lithium batteries prepared in each embodiment and comparative example are shown in Table 1, and the safety performance test results are shown in Table 2.

Table 1


Note: ¹ - Room temperature is 23℃±2℃; 80% retention rate
² - Room temperature is 23℃±2℃; 80% retention rate
³ -80% retention rate

It can be seen from the results in Table 1 that when the battery system is the same and the battery capacity is similar, such as Example 1 and Example 3, Example 7, Example 8, Example 9, Example 10, Example 11, and Example 12 , Comparative Example 1; Example 2 and Comparative Example 2; Example 4 and Comparative Example 3; Example 5 and Comparative Example 4; Example 6 and Comparative Example 5. When the type, particle size, inorganic solid electrolyte coating thickness, and first slurry formula of the inorganic solid electrolyte particles are within the preferred range, changing the type of inorganic solid electrolyte particles, the particle size of the inorganic solid electrolyte particles, the thickness of the inorganic solid electrolyte coating, and the first slurry formula are within the preferred range. The slurry formulation did not have a significant impact on battery performance.

Table 2

It can be seen from the results in Table 2 that there are several groups of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 4 and Comparative Example 3, Example 5 and Comparative Example 4, and Example 6 and Comparative Example 5. Data comparison shows that the negative electrode sheet containing solid electrolyte coating prepared by using the inorganic solid electrolyte particles of the present invention can improve the safety performance of the battery in hot box, heavy impact, drop, needle puncture and overcharge. Comparison between Example 1 and Comparative Example 6 shows that the inorganic solid electrolyte coating of the present invention has better safety performance than the conventional alumina ceramic coating. The comparison between Example 2 and Comparative Example 7, Example 4 and Comparative Example 8, and Example 5 and Comparative Example 9 shows that the inorganic solid electrolyte coating of the present invention has better safety performance than the conventional inorganic solid electrolyte coating. promote. A comparison between Example 5 and Comparative Example 10 shows that the inorganic oxide solid electrolyte containing a small amount of halogen in the present invention has better safety performance than the conventional inorganic oxide solid electrolyte doped with halogen. A comparison between Example 6 and Comparative Example 11 shows that the inorganic oxide solid electrolyte of the present invention has better safety performance than the inorganic oxide solid electrolyte with high F content. Comparing Example 1 with Example 3, and Example 5 with Example 6 compared with Comparative Example 4 and Comparative Example 5 respectively, the safety performance is improved to a greater extent, indicating that when the inorganic oxide solid electrolyte of the present invention is used and contains aluminum phosphate, The improvement effect on safety performance is more obvious. Comparing Example 1, Comparative Example 1 and Comparative Example 12 shows that only adding lithium phosphate or aluminum phosphate to the negative electrode sheet cannot achieve the effect of improving battery safety performance. Example 7, Example 8, Example 9 and Example 10 illustrate that when the particle size and addition amount are within the preferred range, safety performance can be effectively improved. Example 11 and Example 12 illustrate that when the first slurry formula is within the preferred range, the battery safety performance can still be effectively improved after adjusting the first slurry formula.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, many simple modifications can be made to the technical solution of the present invention, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the disclosed content of the present invention. All belong to the protection scope of the present invention.

Claims (10)

1. An inorganic solid electrolyte layer for lithium batteries, characterized by:

   The inorganic solid electrolyte layer includes inorganic solid electrolyte particles;

   The inorganic solid electrolyte particles are selected from lithium-containing materials or a mixture of lithium-containing materials and AlPO ₄ ;

   The lithium-containing material includes compounds composed of lithium, hydrogen, aluminum, phosphorus, halogen and oxygen elements.
2. The inorganic solid electrolyte layer of lithium battery according to claim 1, characterized in that:

   The chemical formula of the lithium-containing material is Li _1+x H _1-x Al(PO ₄ )O _1-y M _2y , where 0≤x<1, 0<y<0.1, M is a halogen element,

   Preferably, the M is selected from any one of F, Cl, Br and I;

   Preferably, the mass ratio of the lithium-containing material and AlPO ₄ is (1-4):1;

   More preferably, the lithium-containing material is selected from at least one of LiHAl(PO ₄ )O _1-y M _2y , most preferably from LiHAl(PO ₄ )O _0.96 F _0.08 , LiHAl(PO ₄ )O _0.95 F _0.1 , at least one of LiHAl(PO ₄ )O _0.94 Cl _0.12 and LiHAl(PO ₄ )O _0.94 Br _0.12 ;

   The crystal form of the aluminum phosphate is selected from at least one of quartz type, tridymite type and cristobalite type.
3. The inorganic solid electrolyte layer of lithium battery according to claim 1 or 2, characterized in that:

   The inorganic solid electrolyte layer also includes binders and additives;

   The weight ratio of the inorganic solid electrolyte particles, binder and additive is 100: (0.3-5): (0.3-5);

   The size of the inorganic solid electrolyte particles is 10 nm-10 μm, preferably 50 nm-1 μm.
4. The inorganic solid electrolyte layer of lithium battery according to any one of claims 1-3, characterized in that:

   The binder is selected from styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, sodium carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, carboxymethylhydroxyethyl At least one of hydroxypropyl cellulose and hydroxypropyl cellulose;

   The additives include dispersants and wetting agents.
5. The lithium battery inorganic solid electrolyte layer according to any one of claims 1-4, characterized in that:

   The dispersant is selected from at least one of sodium polyacrylate, ammonium polyacrylate copolymer, polyvinyl alcohol, polyethylene glycol, polyacrylamide and polyvinylpyrrolidone;

   The wetting agent is selected from the group consisting of sodium perfluorooctanoate, nonylphenol polyoxyethylene ether, fluoroalkyl methoxy alcohol ether, polyoxyethylene alkylamine, sodium butyl naphthalene sulfonate, sodium arylnaphthalene sulfonate, and At least one of sodium dialkyl benzene sulfonate and sodium alkyl sulfate.
6. A composite negative electrode sheet for lithium batteries, which includes a current collector and a negative electrode material layer, and is characterized by:

   The composite negative electrode sheet further includes the inorganic solid electrolyte layer according to any one of claims 1-5;

   The negative electrode material layer is located on the surface of the current collector;

   The inorganic solid electrolyte layer is located on the surface of the negative electrode material layer or is located on the surface of the negative electrode material layer and partially or completely penetrates into the negative electrode material layer.
7. The composite negative electrode sheet for lithium batteries according to claim 6, characterized in that:

   The thickness of the inorganic solid electrolyte layer formed in the composite negative electrode sheet is 0 nm-20 μm, preferably 0.1 nm-5 μm.
8. A method for preparing a composite negative electrode sheet for lithium batteries according to claim 6 or 7, characterized in that: The preparation method includes:

   (1) After stirring and grinding the inorganic solid electrolyte particles and solvent evenly, optionally adding additives and binders and stirring thoroughly to prepare the first slurry;

   (2) Take the first slurry and apply it on the negative electrode sheet, and then bake and roll it to obtain the composite negative electrode sheet.
9. The preparation method according to claim 8, characterized in that:

   In step (1), the solvent is selected from at least one of water, ethanol, N-methylpyrrolidone, isopropyl alcohol and acetone;

   In step (2), the coating method includes microgravure coating, spray coating and simultaneous coating.
10. A lithium battery, characterized in that: the lithium battery includes the inorganic solid electrolyte layer according to any one of claims 1 to 5 or the composite negative electrode sheet for lithium batteries according to claim 6 or 7, preferably, the The lithium battery is a liquid lithium battery, a hybrid solid-liquid lithium battery or a solid-state lithium battery.