WO2017005077A1

WO2017005077A1 - Electrochemical preparation method for perovskite-type solid electrolyte lithium-lanthanum-titanium oxide compound

Info

Publication number: WO2017005077A1
Application number: PCT/CN2016/085322
Authority: WO
Inventors: 张庆朋; 赵成龙; 李丽; 王瑛; 于文倩; 王超武; 陈建伟
Original assignee: 山东玉皇新能源科技有限公司
Priority date: 2015-07-09
Filing date: 2016-06-08
Publication date: 2017-01-12
Also published as: CN105047989A; CN105047989B

Abstract

An electrochemical preparation method for a perovskite-type solid electrolyte lithium-lanthanum-titanium oxide compound. The electrochemical preparation method comprises: preparing a mixture of lanthanum oxide and titanium dioxide according to the lanthanum-to-titanium ratio; embedding the titanium dioxide into lithium ions by using an electrochemical method; and then annealing the lithium ions to obtain a high-purity LLTO. The preparation method can control the lithium-lanthanum-titanium ratio accurately, thereby resolving the problem of low purity of products due to general volatilization of lithium salt in a solid-phase method at a high temperature. In addition, the raw materials are cheap, the process is simple, and the high-purity lithium-lanthanum-titanium oxide compound can be obtained through two steps of electrochemical and high-temperature treatment.

Description

Electrochemical preparation method of perovskite type solid electrolyte lithium niobium titanium oxide compound

(1) Technical field

The invention relates to the field of lithium ion batteries, in particular to an electrochemical preparation method of a perovskite type solid electrolyte lithium niobium titanium oxide compound.

(2) Background technology

The popularity of new energy vehicles can reduce environmental pollution. Among them, power batteries are the key factor. Power batteries usually use liquid electrolytes, which may cause fire or explosion in the case of abuse, which poses a safety hazard. An all-solid battery using a solid electrolyte does not use a flammable liquid electrolyte, and the safety is greatly improved. At the same time, the all-solid battery has more electric storage and higher output power, but the low ionic conductivity of the solid electrolyte hinders the all-solid battery. Practical.

Among the solid electrolytes, the perovskite structure compound lithium lanthanum titanium oxide Li _3x La _2/3-x TiO ₃ (LLTO) has a room temperature ionic conductivity of up to 10 ^-3 S/cm, which is particularly interesting in close to commercial electrolyte levels. At present, the common methods for synthesizing lithium niobium titanium oxide mainly include solid phase method and sol-gel method, and the solid phase method is simple, but long-time high-temperature calcination leads to high energy consumption, and the purity of the product is caused by the lithium salt being volatilized at a high temperature. Lower, the sol-gel method uses expensive alkoxides and is costly and is only suitable for laboratory research.

(3) Invention content

In order to make up for the deficiencies of the prior art, the present invention provides an electrochemical preparation method of a perovskite type solid electrolyte lithium niobium titanium oxide compound with precise proportional control, high product purity and large-scale production.

The invention is achieved by the following technical solutions:

An electrochemical preparation method of a perovskite solid electrolyte lithium niobium titanium oxide compound, which comprises titanium dioxide and cerium oxide as raw materials, comprising the following steps:

(1) mixing raw materials of titanium dioxide, cerium oxide, a binder and a conductive agent, and then pressing into a tablet;

(2) The sheet pressed in the step (1) is a positive electrode, and the lithium sheet is a negative electrode assembled into a battery, and the amount of electricity required for lithium insertion is calculated according to the mass of the titanium dioxide and the ratio of lithium to titanium, and discharged on the discharge instrument;

(3) After the discharge is completed, the lithium-incorporated positive electrode is taken out, and the lithium niobium titanium oxide compound is obtained by high temperature degradation treatment.

A more preferred embodiment of the invention is:

The titanium dioxide is a nano particle with a particle size of 25 nm; large particles increase the difficulty of lithium ion insertion, may cause uneven lithium intercalation, reduce purity, high cost of small particles, and difficult operation, and 25 nm titanium dioxide particles are currently mature. Commercial materials are the best overall performance.

In the step (1), the binder is polyvinylidene fluoride or polytetrafluoroethylene, and the conductive agent is one or two of acetylene black and Super P.

In the step (1), the molar ratio of cerium oxide to titanium oxide is 2/3-x:2, wherein 0.06 ≤ x ≤ 1/6; and lithium lanthanum titanium oxide Li _3x La _2/3-x TiO ₃ has various kinds. Different ratios of compounds, the molar ratio of niobium and titanium are determined according to the ratio of the final product; the binder ensures the strength of the tablet, but too much will affect the conductivity of the tablet and increase the cost, too little to bond The effect, the mass fraction of 5-20% is the best ratio. The conductive agent ensures the conductivity of the tablet during the discharge process, but too much will affect the difficulty of the tablet and increase the cost. Too little effect is not obvious, and the mass fraction of 5-20% is the optimal ratio.

In the step (1), the mixing method of the raw materials is a ball milling method or a grinding method.

In the step (2), the battery is a button battery.

In the step (2), the discharge capacity is a quantity required for lithium intercalation calculated from the mass of titanium dioxide and the ratio of lithium to titanium, and the molar ratio of lithium to titanium in the lithium niobium titanium oxide compound Li _3x La _2/3-x TiO ₃ is 3x:1. The calculation formula for the amount of electricity required to embed a certain amount of titanium dioxide into the corresponding amount of lithium is:

Where m is the number of grams of titanium dioxide and M is the molecular weight of titanium dioxide. At this point, the amount of lithium intercalation of titanium dioxide is exactly 3x.

In step (2), the discharge instrument is a battery tester or an electrochemical workstation. Under the condition that the range is satisfied, the low-range battery tester is selected as much as possible, and the discharge current is controlled below 0.1 C to ensure that lithium ions can be uniformly embedded in the titanium dioxide. .

In the step (3), the high temperature annealing is divided into two stages of calcination and sintering, and the pre-firing can ensure the removal of the binder, the conductive agent and other impurities in the material and the gas generated by the decomposition. Higher temperature sintering ensures adequate reaction to form a grain-controlled lithium niobium titanate compound.

The invention can accurately control the ratio of lithium antimony and titanium, and solves the problem that the solid phase method long lithium salt volatilizes at a high temperature to cause low purity of the product, and the raw material is cheap, the process is simple, and the electrochemical and high temperature treatment can be carried out in two steps. A high purity lithium lanthanum titanium oxide compound is obtained.

(4) Description of the drawings

The invention will now be further described with reference to the accompanying drawings.

1 is an XRD pattern of Li _0.33 La _0.557 TiO ₃ prepared in Example 1 of the present invention;

2 is an XRD chart of Li _0.485 La _0.505 TiO ₃ prepared in Example 2 of the present invention.

(5) Specific implementation methods

The invention is further described in detail below by way of specific examples, but these examples are only intended to be illustrative, and not to limit the scope of the invention.

Example 1:

0.7987 g of titanium dioxide, 0.9068 g of cerium oxide, 0.2132 g of PVDF and 0.2132 g of acetylene black were weighed, thoroughly mixed in a mortar for half an hour, and 0.2 g of the mixture was placed in a mold and pressed at 20 MPa for 1 minute to form a tablet. The positive electrode is pressed, the CR2032 button battery case is selected, the battery is assembled in the order of the negative electrode case, the spring piece, the gasket, the lithium piece, the separator, the positive electrode and the positive electrode case, and 5 drops of lithium ion battery electrolyte are added dropwise, and the sealing machine is sealed with a sealing machine. Prepare button batteries. The prepared button battery was placed on a battery tester and discharged at a constant current of 0.05 C to a capacity of 8.30 mAh. The tablet after lithium insertion was taken out, calcined at 800 ° C for 5 hours in a muffle furnace, and sintered again at 1000 ° C for 10 hours to obtain Li _0.33 La _0.557 TiO ₃ .

Example 2:

0.7987 g of titanium dioxide, 0.8226 g of cerium oxide, 0.2027 g of PVDF and 0.2027 g of Super P were weighed, thoroughly mixed in a mortar for half an hour, and 0.2 g of the mixture was placed in a mold and pressed at 20 MPa for 1 minute to form a tablet. The positive electrode is pressed, the CR2032 button battery case is selected, the battery is assembled in the order of the negative electrode case, the spring piece, the gasket, the lithium piece, the separator, the positive electrode and the positive electrode case, and 5 drops of lithium ion battery electrolyte are added dropwise, and the sealing machine is sealed with a sealing machine. Prepare button batteries. The prepared button battery was placed on a battery tester and discharged at a constant current of 0.05 C to a capacity of 12.83 mAh. The tablet after lithium insertion was taken out, calcined at 800 ° C for 5 hours in a muffle furnace, and sintered again at 1000 ° C for 10 hours to obtain Li _0.485 La _0.505 TiO ₃ .

Example 3:

Weigh 7.987g of titanium dioxide, 9.068g of cerium oxide, 0.9475g of PVDF and 0.9475g of Super P, put into a 100ml ball mill tank, the ball to material ratio is 3:1, grind for 2 hours and mix well, take 0.2g of the mixture into the mold, 20MPa Press for 1 minute under pressure to form a tablet. The positive electrode is pressed, and the CR2032 button battery case is selected. The battery is assembled in the order of a negative electrode case, spring piece, gasket, lithium piece, separator, positive electrode and positive electrode case, and 5 drops of lithium ion battery electrolyte are added dropwise, and the sealing machine is used. Sealing to prepare button batteries. The prepared button battery was placed on a battery tester and discharged at a constant current of 0.05 C to a capacity of 9.33 mAh. The tablet after lithium insertion was taken out, calcined at 550 ° C for 5 hours in a muffle furnace, and sintered again at 1200 ° C for 10 hours to obtain Li _0.33 La _0.557 TiO ₃ .

Claims

An electrochemical preparation method of a perovskite solid electrolyte lithium niobium titanium oxide compound, which comprises titanium dioxide and cerium oxide as raw materials, and is characterized in that the method comprises the following steps: (1) preparing raw materials of titanium dioxide, cerium oxide, binder and conductive The agent is uniformly mixed and pressed into a sheet; (2) the sheet pressed in the step (1) is used as a positive electrode, and the lithium sheet is assembled into a battery as a negative electrode, and the amount of lithium required for lithium insertion is calculated according to the mass of the titanium dioxide and the ratio of lithium to titanium. (1) After the discharge is completed, the lithium-incorporated positive electrode is taken out, and the lithium niobium titanium oxide compound is obtained by high temperature degradation treatment.
The method for electrochemically preparing a perovskite-type solid electrolyte lithium niobium titanate according to claim 1, wherein the titanium dioxide is a nanoparticle having a particle size of 25 nm.
The method for electrochemically preparing a perovskite-type solid electrolyte lithium niobium titanate according to claim 1, wherein in the step (1), the binder is polyvinylidene fluoride or polytetrafluoroethylene, and a conductive agent It is one or two of acetylene black and Super P.
The method for electrochemically preparing a perovskite-type solid electrolyte lithium niobium titanate according to claim 1, wherein in the step (1), the molar ratio of cerium oxide to titanium oxide is 2/3-x:2, Wherein, 0.06≤x≤1/6; the binder is 5-20% of the total mass of the raw material, and the conductive agent is 5-20% of the total mass of the raw material.
The method for electrochemically preparing a perovskite-type solid electrolyte lithium niobium titanate according to claim 1, wherein in the step (1), the method of mixing the raw materials is a ball milling method or a grinding method.
The method for electrochemically preparing a perovskite solid electrolyte lithium niobium titanate according to claim 1, wherein in the step (2), the battery is a button battery.
The method for electrochemically preparing a perovskite-type solid electrolyte lithium niobium titanate according to claim 1, wherein in the step (2), the discharge capacity is lithium intercalation calculated according to the mass of the titanium dioxide and the ratio of lithium to titanium. The required amount of electricity, lithium-titanium-titanium oxide Li 3x La 2/3-x TiO 3 molar ratio of lithium to titanium is 3x: 1, the calculation formula for the amount of electricity required for a certain amount of titanium dioxide to embed the corresponding amount of lithium is:

Where m is the number of grams of titanium dioxide and M is the molecular weight of titanium dioxide. At this point, the amount of lithium intercalation of titanium dioxide is exactly 3x.
The method for electrochemically preparing a perovskite solid electrolyte lithium niobium titanate according to claim 1, wherein in the step (2), the discharge instrument is a battery tester or an electrochemical workstation, and the discharge current is controlled at 0.1. Below C.
The electrochemical preparation method of the perovskite solid electrolyte lithium niobium titanate according to claim 1 The method is characterized in that in the step (3), the high temperature annealing is divided into two stages of pre-firing and sintering.