CN102522535B - Lithium ion battery cathode material and preparation method thereof - Google Patents

Abstract

A lithium ion battery negative electrode material and a preparation method thereof. The lithium ion battery negative electrode material is a lithium titanate with a controllable valence state, which can be expressed by the chemical formula: Li ₄ Ti(IV) _5-x Ti(III) _x O _{(12- x/2)} , where 0<x<5; IV and III are the valence states of Ti respectively. The controllable valence state lithium titanate structure is a spinel structure, the appearance is blue, and it has good conductivity. The intrinsic conductivity is 10 ^-3 -10 ^-8 S/cm, and its lithium intercalation potential is less than 1.55V (vs Li /Li ⁺ ). The preparation method includes: 1) uniform mixing of raw materials; 2) solid phase reaction; 3) pretreatment; 4) solid phase sintering. The lithium ion battery prepared by the negative electrode material of the invention has the characteristics of high voltage, excellent rate charge and discharge performance, high energy density and the like.

Description

Lithium-ion battery negative electrode material and preparation method thereof

【Technical field】

The invention relates to the technical field of new energy materials, in particular to a lithium ion battery negative electrode material and a preparation method thereof.

【Background technique】

With the increasingly severe energy crisis, it is imminent to adjust the energy structure. On the one hand, people meet the ever-increasing demand by developing new energy sources, and on the other hand, they choose to make rational use of renewable energy sources. In the process of developing and utilizing renewable energy, electric energy storage technology plays an important role. In order to solve the balance problem of power system in power production and consumption and to meet the needs of wind power, photovoltaic power generation and other highly volatile new energy power grid integration, large-scale energy storage power stations are ready to come out. At present, the chemical power sources that can be used in the field of energy storage mainly include lead-acid batteries, sodium-sulfur batteries, flow batteries and lithium-ion batteries. Among them, lead-acid batteries have stable performance, but their lifespan is too short and their energy density is too low; sodium-sulfur batteries must ensure an operating temperature of 300°C; and flow batteries have too low an energy density. Lithium-ion batteries have become the focus of research because of their excellent comprehensive performance. At the same time, lithium-ion batteries have become the most potential power source for electric vehicles and hybrid vehicles due to their high energy density. After the on-board lithium-ion battery market appeared in 2009, the application of lithium-ion batteries in electric vehicles has become a trend, and major countries have spent huge sums of money to support them. For China, it is regarded as a "curve overtaking" in the automobile industry hope. The development of electric vehicles will bring far-reaching opportunities to the lithium-ion battery industry. In the near future, the power battery market for lithium-ion batteries will surpass its existing market in consumer electronics products.

Lithium titanate is used as the negative electrode material of lithium ion battery, which can avoid the formation of solid electrolyte film and lithium dendrite on the surface of carbon negative electrode material and the specific capacity decay caused by volume change during the cycle of lithium ion battery. The above characteristics of lithium titanate ensure the extremely high safety performance and cycle life of lithium titanate lithium ion batteries. In addition, lithium ions in lithium titanate have a three-dimensional network diffusion channel, and its chemical diffusion coefficient is about 2×10 ^-8 cm ² /s, which is almost an order of magnitude higher than that of graphite, which is suitable for fast charging and discharging. Therefore, lithium-ion batteries using lithium titanate as the negative electrode material are expected to be applied in large-scale energy storage power stations and vehicle power batteries.

Although lithium titanate has very significant advantages in lithium-ion power batteries and large-scale energy storage batteries, some problems in lithium titanate have seriously hindered its commercial application process: 1) The conductivity of lithium titanate is low , because of its intrinsic conductivity of 10 ^-9 S/cm, it presents the characteristics of an insulator. When a large current is charged and discharged, the enriched electrons will conversely limit the insertion and extraction of lithium ions through the polarization effect, which will deteriorate the electrochemical performance of the material. 2) The high lithium-deintercalation potential of lithium titanate brings the low voltage of the battery (1.55V vs Li ⁺ /Li), and the lithium-ion battery voltage prepared with conventional positive electrode materials such as lithium cobaltate and lithium manganate is only about 2.2 V ~ 2.5V, which is about 1.5V lower than that of lithium-ion batteries that use graphite as the negative electrode material. Therefore, how to improve the conductivity of lithium titanate and reduce its potential for lithium deintercalation and lithium intercalation has become an important issue for improving the performance of lithium titanate.

【Content of invention】

The present invention aims to solve the above problems and provide a lithium ion battery negative electrode material with high voltage, good safety, good rate charge and discharge performance and higher energy density.

The purpose of the present invention is also to provide a preparation method of the lithium ion battery negative electrode material.

In order to achieve the above object, the present invention provides a lithium ion battery negative electrode material, the lithium ion battery negative electrode material is lithium titanate with a controllable valence state, and its chemical formula is: Li ₄ Ti(IV) _5-x Ti(III) _x O _(12-x/2) , wherein, 0<x<5; IV and III are the valence states of Ti respectively, and the negative electrode material structure of the lithium ion battery is a spinel structure.

The intrinsic conductivity of the negative electrode material of the lithium ion battery is 10 ^-3 -10 ^-8 S/cm.

The lithium intercalation potential of the negative electrode material of the lithium ion battery is lower than the lithium intercalation potential of the stoichiometric lithium titanate Li ₄ Ti ₅ O ₁₂ .

The lithium intercalation potential of the negative pole material of the lithium ion battery is 1.50-1.55V.

The reversible specific capacity of the negative electrode material of the lithium ion battery is 120mAh/g-170mAh/g, and can realize charge and discharge at a rate of 1-20C.

The appearance color of the negative electrode material of the lithium ion battery is blue.

The present invention also provides a preparation method for the negative electrode material of the lithium ion battery, the method comprising the steps of:

a, Lithium source and titanium source are mixed uniformly by lithium, titanium molar ratio Li:Ti=0.80～0.84:1;

b. Heat the mixture of lithium source and titanium source to 600-1000°C at a heating rate of 1-50°C/min in a high-temperature furnace, keep the temperature constant for 3-72 hours, and cool down to room temperature with the furnace to obtain stoichiometric titanic acid Lithium pure phase;

c. The pure phase of lithium titanate is firstly added with additives with a weight percentage of 0.5-10% and a solvent with a weight percentage of 100-900%, and mixed by ball milling through stirring mill or ultrafine milling, and drying by heating evaporation drying method and vacuum heating method or spray drying method, the additive is one or more of glucose, sucrose, starch, polyvinyl alcohol, phenolic resin, epoxy resin and furfural resin, and the solvent is deionized water, ethanol or acetone ;

d. Put the dried material into a high-temperature furnace, raise the temperature to 600-900°C at a rate of 1-50°C/min under an inert protective gas, and keep the temperature constant for 2-30 hours. After fully reacting, cool to room temperature to obtain Lithium titanate in controlled valence state.

The lithium source is lithium carbonate, lithium hydroxide or lithium nitrate, and the titanium source is anatase, rutile, amorphous or brookite titanium dioxide.

Preferably, in step b, the mixture of lithium source and titanium source is heated to 700-850°C in a high-temperature furnace at a heating rate of 5-20°C/min, kept at a constant temperature for 12-48 hours, and cooled to room temperature with the furnace to obtain chemical Lithium titanate pure phase in stoichiometric ratio; in step d, put the dried material into a high-temperature furnace, raise the temperature to 600-750°C at a rate of 5-20°C/min under an inert protective gas, and keep the temperature constant for 6-24 hours, After fully reacting, it is cooled to room temperature to obtain lithium titanate with a controllable valence state.

Preferably, in step c, the pure phase of lithium titanate is first added with an additive with a weight percentage of 1 to 7.5 and a solvent with a weight percentage of 200 to 300, and is ball-milled and mixed by stirring mill or ultrafine mill, and dried by heating and evaporating. , vacuum heating drying method or spray drying method for drying, the additive is one or more of glucose, sucrose, starch, polyvinyl alcohol, phenolic resin, epoxy resin and furfural resin, and the solvent is deionized water , ethanol or acetone.

The contribution of the present invention is that it provides a negative electrode material of a lithium ion battery with a new structure. During the charge and discharge process of the negative electrode material, its charge and discharge curve is compared with the charge and discharge curve of stoichiometric lithium titanate, and its potential shifts to a lower potential; at the same time, the controllable valence lithium titanate has better conductivity, Even without the addition of a conductive agent, it can meet the charge and discharge capacity of the practical application level. The lithium ion battery assembled with the negative electrode material of the invention has the characteristics of high voltage, good safety, good rate charge and discharge performance, higher energy density and the like.

【Description of drawings】

Fig. 1 is a comparison photo of the lithium titanate with controllable valence state (in blue) prepared in Example 1 and Example 2 of the present invention and the stoichiometric ratio of lithium titanate (in white) prepared in Comparative Example 1.

Fig. 2 is an XRD spectrum of lithium titanate with controllable valence state prepared in Example 1 of the present invention.

Fig. 3 is the XPS spectrum of the controllable valence state lithium titanate (Blue LTO in the figure) prepared in Example 1 of the present invention and the stoichiometric lithium titanate (White LTO in the figure) prepared in Comparative Example 1.

Fig. 4 is the controllable valence lithium titanate (Blue LTO in the figure) prepared by Example 1 of the present invention and the lithium titanate (White LTO in the figure) of the stoichiometric ratio prepared in Comparative Example 1 without adding a conductive agent The charge and discharge curves of the coin half-cell assembled under the condition of 0.2C and 1C rate current.

Fig. 5 is the controllable valence state lithium titanate (Blue LTO in the figure) prepared by Example 1 of the present invention and the lithium titanate (White LTO in the figure) of the stoichiometric ratio prepared in Comparative Example 1 under the condition of adding a conductive agent The charging and discharging curves of the button half-cells assembled below under 0.2C and 1C rate currents.

Figure 6 is the assembly of the lithium titanate with controllable valence state (a in the figure) prepared in Example 1 of the present invention and the stoichiometric ratio of lithium titanate (b in the figure) prepared in Comparative Example 1 under the condition of adding a conductive agent High-rate charge-discharge curves of the fabricated coin half-cell.

【Detailed ways】

The following examples are further explanations and illustrations of the present invention, and do not constitute any limitation to the present invention.

In order to test the electrochemical performance of the lithium ion battery negative electrode material provided by the present invention, the lithium ion battery negative electrode material in the present invention can control the valence lithium titanate (LTO) and binder polyvinylidene fluoride (PVDF), conductive Agent Super P-Li (SP) and solvent N-methylpyrrolidone (NMP) were mixed according to the mass ratio of LTO:PVDF:SP:NMP=80:10:10:80 or 90:10:0:80 to prepare slurry The material was coated on the surface of aluminum foil to make a negative electrode, and a metal lithium sheet was used as a counter electrode to prepare a button-type half-cell for testing. Charge and discharge voltage range 0.8V ~ 2.5V.

Example 1

The lithium source and the titanium source are weighed according to the lithium-titanium molar ratio Li:Ti=0.80:1. The lithium source in the present embodiment is lithium carbonate, gets 14.78 parts of lithium carbonates. The titanium source is anatase-type titanium dioxide, and 39.94 parts of anatase-type titanium dioxide are taken. Mix the weighed lithium source and titanium source. Put the mixed lithium source and titanium source in a high-temperature furnace with air at a rate of 1°C/min to 700°C for sintering. After constant temperature for 48 hours, it was cooled to room temperature with the furnace. The product obtained by sintering is lithium titanate with spinel structure stoichiometric ratio.

Additives and solvents are then added to the material obtained after sintering. The additive in this embodiment is glucose, and glucose accounts for 5% (mass percentage, the same below) of the sintered material. In this embodiment, the solvent is deionized water, and deionized water is added to make the solid content 20%. The additive can partially reduce the tetravalent titanium in the sintered material to trivalent titanium in the second sintering.

Add the above mixed solution into the ultrafine mill, ball mill for 10 hours, and carry out thorough mixing and reaction. The time of ball milling can also be changed as needed, as long as the substances in the mixture are fully mixed and ground to a certain size. Ball milling can fully control the grain size of subsequent products, so that the lithium ion battery negative electrode material of the present invention has excellent rate charge and discharge performance.

The above materials are then dried. The drying method may be heating evaporation drying method, vacuum heating drying method or spray drying method and the like. In this example, it is spray drying.

The obtained material was raised to 600°C at a rate of 10°C/min in a high-temperature furnace filled with high-purity argon gas, and then subjected to secondary sintering. After the temperature was kept constant for 6 hours, it was cooled to room temperature with the furnace. The material obtained after cooling to room temperature is the lithium ion battery negative electrode material of the present invention. The negative electrode material is lithium titanate with a controllable valence state. The specific product is shown in the container a in Figure 1. The appearance of the lithium ion battery negative electrode material is blue. color. After testing, the controllable valence lithium titanate of the lithium-ion battery negative electrode material can be expressed by the following chemical formula:

Li ₄ Ti(IV) _5-x Ti(III) _x O _(12-x/2)

Wherein, 0<x<5; IV and III are the valence states of Ti respectively.

Fig. 2 is the XRD spectrum of lithium titanate with controllable valence state prepared in the above example for the negative electrode material of lithium ion battery, which is in good agreement with the standard spectrum of spinel lithium titanate with stoichiometric ratio, and still maintains the spinel structure.

Fig. 3 is the XPS spectrum of lithium titanate of controllable valence state of lithium ion battery negative electrode material prepared in the above-mentioned examples, compared with the lithium titanate of the product stoichiometric ratio prepared in comparative example 1 provided by the present invention, its Ti2p The binding energy is shifted from 458.6 eV to 458.3 eV for tetravalent titanium Ti(IV), resulting in trivalent titanium Ti(III). After verification, due to the presence of a certain amount of trivalent titanium, the controllable valence lithium titanate of the lithium ion battery negative electrode material of the present invention has higher conductivity than the traditional stoichiometric lithium titanate. The intrinsic electrical conductivity is about 10 ^-6 S/cm, which is three orders of magnitude higher than the intrinsic electrical conductivity of stoichiometric lithium titanate 10 ^-9 S/cm.

Fig. 4 and Fig. 5 show the relative charge and discharge curves of half cells made of lithium titanate in a controllable valence state of the lithium ion battery negative electrode material of the present invention. Wherein Fig. 4 is the charge-discharge curve of the half-cell when no conductive agent is added, and its 0.2C and 1C reversible specific capacities are 144mAh/g and 120mAh/g respectively; The reversible specific capacities of lithium titanate under the same conditions are 106mAh/g and 62mAh/g respectively, indicating that the lithium titanate with controllable valence state of the present invention has excellent conductivity, and can be charged and discharged even without adding a conductive agent. Figure 5 is the charge-discharge curve of the half-cell when adding conductive agent, its 0.2C and 1C lithium intercalation platforms are about 1.539V (<1.55V) and 1.504V respectively; Lithium titanate, the lithium intercalation platforms under the same conditions are about 1.554V and 1.511V respectively. It shows that the lithium intercalation potential of the controllable valence state lithium titanate of the lithium ion battery negative electrode material of the present invention shifts to a low potential, which can increase the voltage of the prepared battery.

Fig. 6 shows the high-rate charge-discharge curve of the button half-cell made of the controllable valence state lithium titanate of lithium ion battery negative electrode material of the present invention, and the reversible specific capacity under 10C, 20C, 30C rate is respectively 149mAh /g, 132mAh/g, 112mAh/g. And the lithium titanate of the stoichiometric ratio prepared by the comparative example 1 provided by the present invention has a reversible specific capacity of 141mAh/g and 115mAh/g respectively at 10C and 20C, indicating that the valence state can be controlled by the lithium ion battery negative electrode material of the present invention. The lithium intercalation battery of lithium titanate has better high rate charge and discharge performance.

Example 2

The lithium source and the titanium source were weighed according to the molar ratio of lithium to titanium Li:Ti=0.84:1. The lithium source in the present embodiment is lithium carbonate, gets 15.52 parts of lithium carbonates. The titanium source is rutile-type titanium dioxide, and 39.94 parts of rutile-type titanium dioxide are taken. Mix the weighed lithium source and titanium source in a dry mixing device for 2 hours. The mixed lithium source and titanium source were placed in a high-temperature furnace ventilated with air and raised to 900° C. at a rate of 10° C./minute for sintering. After constant temperature for 12 hours, cool to room temperature with the furnace.

Then add a certain amount of sucrose as an additive and deionized water as a solvent to the material obtained after sintering. Among them, sucrose accounts for 0.5% of the material obtained by sintering, and ionized water is added to make the solid content 20%, so as to obtain a proportioned mixed liquid. The above mixed solution was added into an ultrafine mill, and after ball milling for 2 hours, it was spray-dried.

Raise the obtained material to 700°C at a heating rate of 5°C/min in a high-temperature furnace with high-purity argon, perform secondary sintering, and keep the temperature constant for 6 hours, then cool to room temperature with the furnace, and the obtained material is the present invention. The lithium-ion battery negative electrode material, the specific product is shown in the container b in Figure 1, and the lithium-ion battery negative electrode material is blue.

The negative electrode material product of the lithium ion battery is made into a button half battery. When conductive agent is added, its 0.2C and 1C reversible specific capacities are 165mAh/g and 140mAh/g respectively, and the lithium intercalation platform is about 1.539V and 1.504V respectively; when no conductive agent is added, its 0.2C and 1C reversible specific capacities are respectively 140mAh /g and 118mAh/g, the lithium intercalation platform is about 1.534V and 1.501V respectively.

Example 3

The lithium source and the titanium source are weighed according to the lithium-titanium molar ratio Li:Ti=0.82:1. The lithium source in this embodiment is lithium hydroxide, and 11.05 parts of lithium hydroxide are taken. The titanium source is rutile-type titanium dioxide, and 39.94 parts of rutile-type titanium dioxide are taken. Mix the weighed lithium source and titanium source in a dry mixing device for 2 hours.

The mixed lithium source and titanium source were placed in a high-temperature furnace ventilated with air and raised to 750° C. at a rate of 5° C./min for sintering. After 24 hours at constant temperature, it was cooled to room temperature with the furnace.

Then add a certain amount of epoxy resin as an additive and alcohol as a solvent to the material obtained after sintering. Epoxy resin accounts for 10% of the material obtained by sintering, and alcohol is added to make the solid content 33%, so as to obtain a proportioned mixed solution.

The above mixed solution was added into the stirring mill, and after ball milling for 4 hours, it was heated and dried under vacuum.

Raise the obtained material to 700°C at a heating rate of 5°C/min in a high-temperature furnace with high-purity argon, perform secondary sintering, and keep the temperature constant for 12 hours, then cool to room temperature with the furnace, and the obtained material is the present invention. Lithium-ion battery negative electrode material, the lithium-ion battery negative electrode material is blue.

The negative electrode material product of the lithium ion battery is made into a button half battery. When conductive agent is added, its 0.2C and 1C reversible specific capacities are 165mAh/g and 166mAh/g respectively, and the lithium intercalation platform is about 1.538V and 1.508V respectively; when no conductive agent is added, its 0.2C and 1C reversible specific capacities are 150mAh respectively /g and 130mAh/g, the lithium intercalation platform is about 1.534V and 1.504V respectively.

Example 4

The lithium source and the titanium source are weighed according to the lithium-titanium molar ratio Li:Ti=0.82:1. The lithium source in this embodiment is lithium hydroxide, 11.05 parts of lithium hydroxide is taken, the titanium source is rutile titanium dioxide, and 39.94 parts of rutile titanium dioxide are taken. Mix the weighed lithium source and titanium source in a dry mixing device for 2 hours. The mixed lithium source and titanium source were placed in a high-temperature furnace ventilated with air and raised to 800° C. at a rate of 5° C./min for sintering. After 24 hours at constant temperature, it was cooled to room temperature with the furnace. Then, a certain amount of polyethylene resin as an additive and acetone as a solvent are added to the material obtained after sintering. Epoxy resin accounts for 3% of the material obtained by sintering, and acetone is added to make the solid content 33%, so as to obtain a proportioned mixed solution. The above mixed solution was added into the stirring mill, and after ball milling for 4 hours, it was heated and evaporated to dryness.

Raise the obtained material to 600°C at a heating rate of 5°C/min in a high-purity nitrogen furnace, perform secondary sintering, keep the temperature for 24 hours, and cool to room temperature with the furnace. The obtained material is the Lithium-ion battery negative electrode material, the lithium-ion battery negative electrode material is blue.

The negative electrode material product of the lithium ion battery is made into a button half battery. When conductive agent is added, its 0.2C and 1C reversible specific capacities are 165mAh/g and 160mAh/g respectively, and the lithium intercalation platform is about 1.539V and 1.507V respectively; when no conductive agent is added, its 0.2C and 1C reversible specific capacities are 155mAh respectively /g and 140mAh/g, the lithium intercalation platform is about 1.533V and 1.503V respectively.

Comparative Example 1

The lithium source and the titanium source are weighed according to the lithium-titanium molar ratio Li:Ti=0.80:1. The lithium source in the present embodiment is lithium carbonate, gets 15.15 parts of lithium carbonates. The titanium source is 39.94 parts of anatase titanium dioxide. Mix the weighed lithium source and titanium source in a dry mixing device for 2 hours. The mixed lithium source and titanium source were placed in a high-temperature furnace ventilated with air and raised to 750° C. at a rate of 10° C./min for sintering. After 24 hours at constant temperature, it was cooled to room temperature with the furnace.

Then add deionized water as a solvent to the material obtained after sintering, and add ionized water to make the solid content 33%, to obtain a proportioned mixed solution. The above mixed solution was added into an ultrafine mill, and after ball milling for 10 hours, it was spray-dried. Raise the obtained material to 600°C at a rate of 5°C/min in a high-temperature furnace with high-purity argon, and perform secondary sintering. After constant temperature for 6 hours, cool to room temperature with the furnace to obtain the stoichiometric ratio. Lithium titanate, the specific product is shown in the c container in Figure 1, the negative electrode material of the lithium ion battery is white, and its intrinsic electrical conductivity is about 10 _-9 S/cm.

The negative electrode material product of the lithium ion battery is made into a button half battery. When the conductive agent is added, its 0.2C and 1C reversible specific capacities are 162mAh/g and 155mAh/g respectively, and the lithium intercalation platform is about 1.554V and 1.511V respectively; when no conductive agent is added, the 0.2C and 1C reversible specific capacities are respectively It is 106mAh/g and 62mAh/g, and the lithium intercalation platform is about 1.547V and 1.511V respectively. It shows that for white lithium titanate, due to poor conductivity, if no conductive agent is added, its charge and discharge performance will be greatly deteriorated. The reversible specific capacities are 141mAh/g and 115mAh/g at 10C and 20C, respectively.

Claims (4)

1. a lithium ion battery negative material, is characterized in that, this lithium ion battery negative material is controlled valence state lithium titanate, and its chemical formula is: Li ₄ti (IV) _5-xti (III) _xo _(12-x/2), wherein, 0 < x < 5; IV, III are respectively the valence state of Ti, and this lithium ion battery negative material structure is spinel structure, and the intrinsic conductivity of described lithium ion battery negative material is 10 ^-3～10 ^-8s/cm, embedding lithium current potential is lower than the lithium titanate Li of stoichiometric proportion ₄ti ₅o ₁₂embedding lithium current potential, and embedding lithium current potential is 1.50～1.55V, reversible specific capacity is 120mAh/g～170mAh/g, can realize 1～20C rate charge-discharge, its appearance color of described lithium ion battery negative material is blue;

Described lithium ion battery negative material is prepared by a method comprising the following steps:

A, He Tai source, lithium source is mixed by lithium, titanium mol ratio Li:Ti=0.80～0.84:1;

B, the mixture in Yu Tai source, lithium source is warming up to 600～1000 DEG C with the programming rate of 1～50 DEG C/min in high temperature furnace, constant temperature 3～72 hours, cools to room temperature with the furnace, obtains the lithium titanate pure phase of stoichiometric proportion;

C, lithium titanate pure phase is first added to percentage by weight is the solvent that 0.5～10 additive and percentage by weight are 100%～900%, grind or Ultrafine Grinding carries out ball milling mixing by stirring, and be dried by heating evaporation seasoning, vacuum and heating drying method or spray drying process, described additive is one or more in glucose, sucrose, starch, polyvinyl alcohol, phenolic resins, epoxy resin and furfural resin, and described solvent is deionized water, ethanol or acetone;

D, will be dried after material put into high temperature furnace, under inert protective gas, be warming up to 600～900 DEG C with the programming rate of 1～50 DEG C/min, constant temperature 2～30 hours, after abundant reaction, is cooled to room temperature, obtains controlled valence state lithium titanate.

2. material as claimed in claim 1, the feature of preparing the method that this material adopts is also, and described lithium source is lithium carbonate, lithium hydroxide or lithium nitrate, and titanium source is the titanium dioxide of anatase, rutile, amorphous or brookite type.

3. material as claimed in claim 1, the feature of preparing the method that this material adopts is also, in step (b), the mixture in Yu Tai source, lithium source is warming up to 700～850 DEG C with the programming rate of 5～20 DEG C/min in high temperature furnace, constant temperature 12～48 hours, cool to room temperature with the furnace, obtain the lithium titanate pure phase of stoichiometric proportion; In step (d), after being dried, material is put into high temperature furnace, under inert protective gas, is warming up to 600～750 DEG C with the programming rate of 5～20 DEG C/min, and constant temperature 6～24 hours, after abundant reaction, is cooled to room temperature, obtains controlled valence state lithium titanate.

4. material as claimed in claim 1, the feature of preparing the method that this material adopts is also, in step (c), it is the solvent that 1～7.5 additive and percentage by weight are 200%～300% that lithium titanate pure phase is first added to percentage by weight, grind or Ultrafine Grinding carries out ball milling mixing by stirring, and by heating evaporation seasoning, vacuum and heating drying method or spray drying process are dried, described additive is glucose, sucrose, starch, polyvinyl alcohol, phenolic resins, one or more in epoxy resin and furfural resin, described solvent is deionized water, ethanol or acetone.