CN103280567B - A kind of surface electroless metal plating modified Li4Ti5O12 and its preparation method - Google Patents

Abstract

The invention discloses a kind of surface chemical metal plating and modify Li₄Ti₅O₁₂And preparation method thereof, surface chemical metal plating modifies Li₄Ti₅O₁₂Preparation method be by Li₄Ti₅O₁₂The powder abundant moistening in a small amount of activating solution surface, is subsequently adding appropriate chemical plating fluid, mix homogeneously, is placed in the reaction of thermostat water bath magnetic agitation, after question response a period of time, filters, washing, and vacuum drying i.e. obtains the Li that surface chemical metal plating is modified₄Ti₅O₁₂.The present invention uses chemical plating method to make plating solution and Li₄Ti₅O₁₂It is fully contacted reaction, and at Li₄Ti₅O₁₂Surface forms the coating of careful light, has prepared the Li of high conductivity₄Ti₅O₁₂/ M (M=Ni, Cu) composite, gained composite has high rate charge-discharge performance and excellent cycle performance.The method of the invention is simple and easy to do, has good industrial applications prospect.

Description

A kind of surface electroless metal plating modified Li4Ti5O12 and its preparation method

technical field

The invention belongs to the field of battery materials, and in particular relates to a surface chemically plated metal-modified Li ₄ Ti ₅ O ₁₂ and a preparation method thereof.

Background technique

Environmental problems and energy crisis have become increasingly prominent and have attracted the attention of countries all over the world. The development of electric vehicles (EV) can reduce gasoline consumption and vehicle exhaust emissions. Lithium-ion batteries have high energy density and capacity density, and are considered to be the most promising power batteries. Compared with metal lithium, the safety performance of batteries using various carbon materials as negative electrodes has indeed been greatly improved. However, after lithium intercalation, the potential of the carbon negative electrode is very close to that of metal lithium. During overcharging, it is easy to precipitate active metal lithium on the surface of the carbon electrode. It reacts with the electrolyte to produce a flammable gas mixture, which affects the safety performance of the battery. At the same time, in the process of repeated intercalation and deintercalation of lithium ions, the matrix of the carbon electrode is prone to expansion, which in turn affects the cycle life of the secondary battery system.

Spinel-type lithium titanate (Li ₄ Ti ₅ O ₁₂ ) has obvious advantages as the anode material of lithium-ion batteries: the material has a long cycle life and good cycle stability; the discharge platform is high and flat, and it is not easy to generate lithium dendrites, which is safe Good performance; it is a zero-strain electrode material, and the volume change of the material is small during the intercalation and extraction of lithium ions; it has a high chemical diffusion coefficient (2×10 ^-8 cm ² /s), and can achieve high rate Charge and discharge, etc. At the same time, Li ₄ Ti ₅ O ₁₂ also has the characteristics of anti-overcharge and good thermal stability. Therefore, this material has great commercial value and application prospect as an anode material for power lithium-ion batteries.

However, the electronic conductivity of Li ₄ Ti ₅ O ₁₂ itself is low (about 10 ^-13 S/cm), and its specific capacity decays rapidly when working in a high-rate environment. Therefore, in order to realize the commercial application of Li ₄ Ti ₅ O ₁₂ high-rate performance materials in power lithium-ion batteries, improving the high-rate performance of Li ₄ Ti ₅ O ₁₂ is the key. At present, introducing a phase with high electronic conductivity to the surface of Li ₄ Ti ₅ O ₁₂ , coating or dispersing it on the particle surface to enhance the electronic conductivity between the main phase particles and improve the conductivity of the material is an effective way to improve the rate performance of the material. method. Although carbon coating and preparation of metal and metal oxide composite materials can improve the electrical conductivity and high-current charge and discharge performance, it is difficult to dope or coat the surface of Li ₄ Ti ₅ O ₁₂ material uniformly and firmly, resulting in poor performance. Stable, compared with metal oxide metal, the conductivity of metal is relatively better, but the conductivity of simple Ag is more expensive. Inert gas protection and other processes are added to the carbon coating preparation process, which increases the complexity of process control and production costs. And the present invention uses electroless metal plating to modify the conductivity of the material, which can make the Li ₄ Ti ₅ O ₁₂ powder completely and fully contact with the plating solution to react, forming a fine and bright nickel coating or copper coating, and Li ₄ Ti ₅ O ₁₂ powder The combination is tighter and firmer, which is an effective way to improve the rate performance of materials.

Contents of the invention

In order to solve the problem of low rate discharge specific capacity and cycle stability of Li ₄ Ti ₅ O ₁₂ in the prior art, improve the performance of Li ₄ Ti ₅ O ₁₂ rate charge and discharge, the object of the present invention is to provide a surface electroless plating Metal-modified Li ₄ Ti ₅ O ₁₂ , that is, a Li ₄ Ti ₅ O ₁₂ /M composite material. The Li ₄ Ti ₅ O ₁₂ /M composite material is coated with a metal material on the surface, so the high-rate performance of Li ₄ Ti ₅ O ₁₂ is improved.

Another object of the present invention is to provide a method for preparing Li ₄ Ti ₅ O ₁₂ modified by electroless metal plating on the surface. The present invention deposits metal Ni or metal Cu on the surface of Li ₄ Ti ₅ O ₁₂ powder through oxidation-reduction reaction. This method can make Li ₄ Ti ₅ O ₁₂ powder fully contact with the plating solution and react to form fine and bright nickel Plating layer or copper plating layer, tightly combined with Li ₄ Ti ₅ O ₁₂ powder.

The above-mentioned purpose of the present invention is achieved through the following technical solutions:

A surface electroless metal plating modification of Li ₄ Ti ₅ O ₁₂ , that is, metal M is plated on the surface of Li ₄ Ti ₅ O ₁₂ , and the metal M is Ni or Cu.

A method for preparing Li ₄ Ti ₅ O ₁₂ modified by electroless metal plating on the surface as described above, comprising the following steps: fully wet the surface of Li ₄ Ti ₅ O ₁₂ powder with an activation solution, then add the electroless plating solution, and react after mixing After 5-20 minutes, filter, wash, and vacuum-dry to obtain Li ₄ Ti ₅ O ₁₂ modified by electroless metal plating on the surface, that is, Li ₄ Ti ₅ O ₁₂ /M composite material.

Preferably, M in the Li ₄ Ti ₅ O ₁₂ /M composite material is Ni or Cu.

Preferably, the reaction time after mixing is 10 minutes.

Reaction time is an important factor affecting the content of the metal-plated layer on the surface. The content of the metal-plated layer on the surface of Li ₄ Ti ₅ O ₁₂ should not be too high. Too high will reduce the specific capacity of the entire electrode material, which in turn will affect its performance in lithium-ion batteries. Applications. If the content of the coating metal is too low, the conductivity of Li ₄ Ti ₅ O ₁₂ will not be improved. Through creative work, the present invention finds that the content of the metal-plated layer on the surface of Li ₄ Ti ₅ O ₁₂ is just right after about 10 minutes of reaction, which can significantly improve the electrical conductivity of the Li ₄ Ti ₅ O ₁₂ material without affecting the performance of the entire electrode material. Specific capacity.

Specifically, the activation solution is a nickel-plating activation solution or a copper-plating activation solution; preferably, the nickel-plating activation solution is a Pd catalytic solution, and the copper _- plating activation solution is an AgNO solution.

Specifically, the preparation of the pd activation solution is as follows: 0.5ml HNO ₃ is added to 50ml 0.1mol sodium dodecylsulfonate solution, the pH of the solution is about 1~1.5, and then 0.24mmol palladium acetate (Pd(OAc ) ₂ ) Stir continuously at room temperature to dissolve. After 5 minutes, the solution turns orange. Stir continuously and slowly add 0.5ml of 10% hydrazine water to the above solution, and the solution turns dark brown.

Preferably, the copper plating activation solution is a 0.1mol/ _L AgNO standard solution.

Specifically, the electroless plating solution is a nickel plating solution or a copper plating solution, and the electroless plating solution contains a main salt and a reducing agent.

Preferably, the main salt of the nickel plating solution is one of nickel sulfate, nickel chloride, nickel acetate, nickel sulfamate or nickel hypophosphite, and the reducing agent is hypophosphite, sodium borohydride, borane or Hydrazine.

Preferably, the main salt of the copper plating solution is one of copper sulfate, copper chloride, basic copper carbonate, copper tartrate or copper acetate, and the reducing agent can be selected from formaldehyde, sodium hypophosphite, sodium borohydride, dimethyl One of aminoborane (DMAB) or hydrazine.

Preferably, the main salt concentration of the electroless plating solution is 20-40g/L.

Preferably, the reaction temperature after mixing is 80-90°C for nickel plating and 25-35°C for copper plating.

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

Compared with carbon coating and traditional metal surface modification, this method can make Li ₄ Ti ₅ O ₁₂ powder fully contact with the plating solution to undergo redox reaction, forming a fine and bright coating uniformly, more tightly combined with Li ₄ Ti ₅ O ₁₂ powder, and strong corrosion resistance, which can greatly improve the electronic conductivity of the material and effectively improve the high rate charge and discharge performance of the material. The coating metal introduced in the invention is Ni and Cu, has good electrical conductivity, low price, wide source of raw materials, and the chemical plating process of the metal is very mature, and the operation process is simple and suitable for industrialized production. The composite material obtained by this method, 1C charge and discharge, the first reversible specific capacity is 152~163mAh/g, 3C charge and discharge, the first reversible specific capacity is 145~154 mAh/g, the capacity retention rate of the material after 50 cycles during discharge Higher than 95%, suitable for the field of electric vehicles and energy storage equipment.

Description of drawings

Fig. 1. Flow chart of Li ₄ Ti ₅ O ₁₂ /M composite preparation process.

Fig. 2. The scanning electron micrograph of Li ₄ Ti ₅ O ₁₂ /Ni prepared in Example 1.

Fig. 3. The charge-discharge curve of Li ₄ Ti ₅ O ₁₂ /Ni prepared in Example 1.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following examples of the present invention are preferred embodiments of the present invention, but the examples do not limit the present invention in any form.

Example 1

Preparation of pd activation solution: add 0.5ml HNO ₃ to 50ml 0.1mol sodium dodecylsulfonate solution, the pH of the solution is about 1~1.5, then add 0.24mmol palladium acetate (Pd(OAc) ₂ ), at room temperature Stir continuously to make it dissolve. After 5 minutes, the solution turns orange. Stir continuously and slowly add 0.5ml of 10% hydrazine water to the above solution, and the solution turns dark brown.

Preparation of nickel plating solution: Accurately weigh 25% of the main salt nickel sulfate, after it is completely dissolved in deionized water, add complexing agent sodium citrate 30g, sodium pyrophosphate 10g, triethanolamine 10~15ml/L, and then reduce Add 25g of sodium hypophosphite, and finally add 30g of ammonium chloride, adjust the pH to about 9, and prepare a total solution of 1L.

Accurately weigh 5g of Li ₄ Ti ₅ O ₁₂ powder, drop 2~3ml of Pd activation solution to fully wet the surface of Li ₄ Ti ₅ O ₁₂ powder, then pour about 500ml of electroless plating solution, in which the solubility of nickel sulfate is 25g/ L, after mixing evenly, place it at 80°C for 10 minutes with magnetic stirring, then filter, wash, and vacuum dry to obtain the Li ₄ Ti ₅ O ₁₂ /Ni composite material.

With the lithium sheet as the negative electrode, in a glove box full of hydrogen, a button battery is made, and within the voltage range of 0.8V ~ 2.5V, the Li ₄ Ti ₅ O ₁₂ /Ni composite electrode material prepared by the method of Example 1, The morphology is shown in Figure 2. The Li ₄ Ti ₅ O ₁₂ /Ni composite electrode material 1C charge and discharge, the first reversible specific capacity is 158mAh/g, 3C charge and discharge, the first reversible specific capacity is 153mAh/g, the material after 50 cycles of 1C charge and discharge The capacity retention is higher than 95 %; as shown in Figure 3.

Example 2

The preparation of pd activation solution: with embodiment 1.

The preparation of nickel plating solution: with embodiment 1.

Accurately weigh 5g of Li ₄ Ti ₅ O ₁₂ powder, drop 2~3ml of Pd activation solution to fully wet the surface of Li ₄ Ti ₅ O ₁₂ powder, then pour about 500ml of electroless plating solution, in which the solubility of nickel sulfate is 30g/ L, after mixing evenly, place it at 80°C for 10 minutes with magnetic stirring, then filter, wash, and vacuum dry to obtain the Li ₄ Ti ₅ O ₁₂ /Ni composite material.

With the lithium sheet as the negative electrode, in a glove box full of hydrogen, a button battery is made, and within the voltage range of 0.8V ~ 2.5V, the Li ₄ Ti ₅ O ₁₂ /Ni composite electrode material prepared by the method of Example 2, 1C charge and discharge, the first reversible specific capacity is 156mAh/g, 3C charge and discharge, the first reversible specific capacity is 149mAh/g, and the capacity retention rate of the material after 50 cycles during 1C charge and discharge is higher than 95%.

Example 3

The preparation of pd activation solution: with embodiment 1.

The preparation of nickel plating solution: with embodiment 1.

Accurately weigh 5g of Li ₄ Ti ₅ O ₁₂ powder, drop 2~3ml of Pd activation solution to fully wet the surface of Li ₄ Ti ₅ O ₁₂ powder, then pour about 500ml of electroless plating solution, in which the solubility of nickel sulfate is 25g/ L, after mixing evenly, place it at 80°C for 15 minutes with magnetic stirring, then filter, wash, and dry in vacuum to obtain the Li ₄ Ti ₅ O ₁₂ /Ni composite material.

With the lithium sheet as the negative electrode, in a glove box full of hydrogen, a button battery is made, and within the voltage range of 0.8V~2.5V, the Li ₄ Ti ₅ O ₁₂ /Ni composite electrode material prepared according to the method of Example 3, 1C charge and discharge, the first reversible specific capacity is 152mAh/g, 3C charge and discharge, the first reversible specific capacity is 145mAh/g, and the capacity retention rate of the material after 50 cycles during 1C charge and discharge is higher than 95%.

Example 4

Configuration of AgNO ₃ activation solution: 0.1mol/L AgNO ₃ standard solution.

Preparation of copper plating solution: Accurately weigh 25g of copper sulfate, after it is completely dissolved in deionized water, add 40g of complexing agent disodium edetate, 25ml of 2,2'-bipyridyl, 15ml of reducing agent formaldehyde, Adjust the pH to about 12.5, and prepare a total solution of 1 L. standard solution

Accurately weigh 5g of Li ₄ Ti ₅ O ₁₂ powder, drop 2~3ml of AgNO ₃ activation solution to fully wet the surface of Li ₄ Ti ₅ O ₁₂ powder, and then pour about 500ml of copper plating solution, in which the solubility of copper sulfate is 25g/L, mixed evenly, placed at 35°C for 15min with magnetic stirring, then filtered, washed, and vacuum dried to obtain the Li ₄ Ti ₅ O ₁₂ /Cu composite material.

With the lithium sheet as the negative electrode, in a glove box full of hydrogen, make a button battery, in the voltage range of 0.8V ~ 2.5V, the Li ₄ Ti ₅ O ₁₂ /Cu composite electrode material prepared according to the method of Example 4, 1C charge and discharge, the first reversible specific capacity is 163mAh/g, 3C charge and discharge, the first reversible specific capacity is 154mAh/g, and the capacity retention rate of the material after 50 cycles during 1C charge and discharge is higher than 95%.

Claims (6)

1. A preparation method for surface electroless metal plating modification Li ₄ Ti ₅ O ₁₂ , characterized in that it comprises the steps of: Li ₄ Ti ₅ O ₁₂ powder is fully wetted with an activation solution surface, then adds an electroless plating solution, mixes After uniform reaction for 5 to 20 minutes, filter, wash, and vacuum dry to obtain surface chemically plated metal-modified Li ₄ Ti ₅ O ₁₂ , that is, Li ₄ Ti ₅ O ₁₂ /M composite material; the Li ₄ Ti ₅ O ₁₂ /M M in the composite material is Ni or Cu; the reaction temperature after mixing is 80-90°C for nickel plating, and 25-35°C for copper plating; the electroless plating solution is a nickel plating solution or a copper plating solution; the electroless plating The solution contains the main salt and reducing agent. 2. The preparation method according to claim 1, characterized in that, the reaction time after the mixing is 10 minutes. 3. preparation method according to claim 1, is characterized in that, described activation solution is nickel plating activation solution or copper plating activation solution; Nickel plating activation solution is Pd activation solution, and copper plating activation solution is _AgNO solution. 4. preparation method according to claim 1, is characterized in that, the main salt of described nickel plating solution is the one in nickel sulfate, nickel chloride, nickel acetate, nickel sulfamate or nickel hypophosphite, and reducing agent is Hypophosphite, Sodium Borohydride, Borane, or Hydrazine. 5. according to the described preparation method of claim 1, it is characterized in that, the main salt of described copper plating liquid is the one in copper sulfate, copper chloride, basic copper carbonate, copper tartrate or copper acetate, and reducing agent is selected formaldehyde for use , sodium hypophosphite, sodium borohydride, dimethylaminoborane or hydrazine. 6. preparation method according to claim 1, is characterized in that, the concentration of the main salt of described electroless plating solution is 20～40g/L.