WO2015126285A1 - Anode material for lithium-ion battery and method for the production thereof - Google Patents

Abstract

The invention relates to chemical technology and is used for producing anode materials for lithium-ion autonomous energy systems (batteries for hybrid transportation, electric vehicles, energy storage buffer systems etc.). The proposed material, LiCrTiO₄, is a Cr-substituted derivative of lithium-titanium spinel, Li₄Ti₅O₁₂. The production method thereof includes mixing lithium salt (Li₂CO₃), titanium oxide (IV) (TiO₂) and chromium oxide (III) (Cr₂O₃) in a stoichiometric ratio in the presence of a gelling agent (starch). The particles of the mixture are ground in a ball mill in an acetone medium, and subsequently thermally treated at a temperature of 800-850ºC. The invention allows for producing an anode material having high indicators of specific capacity and reversibility of cycling.

Description

 ANODE MATERIAL FOR LITHIUM-IONIC

 BATTERY AND METHOD FOR PRODUCING IT

The invention relates to chemical technology and is used to produce anode materials for lithium-ion autonomous energy (batteries for hybrid vehicles, electric vehicles, energy storage buffer systems, etc.).

Significant progress in lithium-ion battery technology (LIA) has made autonomous power supplies of this type the most energy-intensive among rechargeable electrochemical systems. The traditional anode material in such batteries is graphite, capable of reversibly introducing lithium [1], and the cathode is lithiated cobalt oxide (lithium-cobalt oxide) LiCo0 ₂ [2]. Despite the fact that LIA systems “carbon - lithium-cobalt oxide” currently occupy a significant part of the market for power supplies for portable electronics, their use for powering transport and energy is impossible due to such inherent disadvantages as fire hazard at high temperatures, capacity degradation at high potentials, temperatures and cycling rates, short service life (500 cycles).

 The solution to the problem of creating reliable, safe, but at the same time powerful and energy-intensive batteries for transport and energy is impossible without the creation of fundamentally new active electrode materials. The traditional way to improve the anode materials is to create high-capacity lithium-accumulating compounds with high lithium activity and electrode potential close to the potential of metallic lithium.

Known anode materials based on lithium alloys with silicon [3]. The theoretical capacity of the richest lithium silicon compound (Li ₂₂ Si ₅ ) reaches 4200 mAh / g calculated on pure silicon or 2011 mA'h / g calculated on the Li ₂₂ Sis compound. The main obstacle to the stable operation of the lithium-silicon intercalation electrode is the large volumetric changes that occur during lithium incorporation / extraction cycles. These changes reach 310% of the initial volume of silicon and are the cause of the mechanical instability of the material.

Known anode materials based on lithium alloys with tin [4]. Being in the same subgroup of the periodic system with silicon, tin forms similar crystalline structures and compounds similar in stoichiometry. It also fuses with lithium to form Li ₂₂ Sns. However, tin has a larger with silicon, the unit cell volume, in connection with which it suffers less from volume changes. A disadvantage of the proposed solutions is that tin is four times heavier than silicon, and the specific capacity of Li intercalated Sn5 ₂₂ as many times lower than - 990 mAh / g vs. 4200 mAh / g of Li in ₂₂ Si5.

The possibilities of increasing the specific capacity of carbon-graphite materials have now been exhausted and correspond to the most abundant lithium compound 1lC _b (372 mAh / g). A promising solution to the problem of the limited capacity of lithiated carbon is the use of lithiated Si – C, Sn – C, or Si – Sn – C composites [5]. The disadvantage of this solution is the high activity of lithium in the above materials, which determines their insufficient safety.

Promising anode materials LIA is a group of compounds with moderate capacitance values, in which lithium activity and, accordingly, electrode potential have an intermediate value between traditional anode and cathode materials. A typical example is lithium titanium spinel, or lithium titanate, Li ^ i ^ On [6]. This material has a theoretical capacity of 175 mAh / g and a charge-discharge curve plateau potential of -1, 55 V. This potential is much higher than the recovery potentials of most organic solvents, therefore, solid-state electrolyte films with high resistance are not formed, and lithium metal is released on the anode is practically eliminated. Another advantage of L D ^ Op compared with silicon and tin compounds is small volume changes (less than 0.2%) during lithiation and delitration, which guarantees stability during long-term cycling. In addition to all of the above, the material has high conductive properties for lithium ions: the specific conductivity is 5.8 · 10 ^" Ohm ^" -cm ^" even at room temperature [7]. The most significant drawback of Li ₄ Ti ₅ 0i ₂ is its low electronic conductivity (about 10 ^"13 Ohm ^{" 1-} cm ^"1 ) [8].

The traditional way to increase the conductive properties of Li ₄ Ti ₅ 0 | ₂ is the solution according to the patent [9], which consists in creating a matrix of electrically conductive material (most often carbon graphite) and the distribution of particles of electroactive material in the volume of this matrix. The disadvantage of this method is that when it is used, there is an increase in electrical conductivity at the boundary of the crystals of the active substance, while the value of internal electrical conductivity

remains virtually unchanged.

A promising way to increase the electrical conductivity of Li ₄ Ti ₅ 0i ₂ is the doping of lithium titanate with various modifying 3-elements. In the patent [10], adopted as a prototype, it is proposed to use as an active electrode material LIA substance composition LiCrTi0 ₄ . The electron conductivity in the LiCrTi0 ₄ compound rises to values of the order of 10 ^"6 Ohm ^ cm ^{" 1} [11]. The presence of chromium ions reduces the charge transfer resistance inside the particles of the active material, thereby increasing its specific power. This technical solution involves the synthesis of the active material in the presence of a reducing agent, the role of which is carbon formed as a result of combustion and decomposition of the organic precursor contained in the initial charge. The disadvantage of this solution is a slight decrease in the reversible electric capacitance caused by the presence of chromium ions.

 An effective way to increase the utilization of the active material and increase the delivered electric capacity is to further reduce the resistance to charge transfer between the particles of the active substance due to the use of nanostructured materials with particles of a sufficiently small size. Colloidal methods are known [12], which make it possible to obtain active material with smaller particles, however, they are complex, expensive, and therefore unsuitable for constructing a technological process based on them, and therefore are used in practice only in laboratory conditions. More technologically advanced are methods with mechanochemical homogenization of precursors [13]. The proposed technical solution to a certain extent combines these two types of methods: a mixture of precursors is processed mechanochemically, but a gelling agent is introduced into its composition, which forms a viscous medium during heat treatment. This medium, on the one hand, promotes the formation of small particles, and on the other hand, is a precursor to the conductive carbon matrix.

The present invention is to develop a method for producing a powdered dispersed anode material with a spinel structure and a carbon coating with improved electrochemical parameters for use in LIA.

 The technical result is to increase the specific capacity and reversibility, charge-discharge current and stability during cycling.

Said technical result is achieved by the method for producing the anode material LiCrTiC C with a spinel structure and carbon coated lithium-ion battery power comprises mixing lithium Li ₂ C0 _3, titanium oxide (IV) T ₂ and a chromium oxide (III) Cr ₂ 0 ₃ in a stoichiometric ratio, as well as a certain amount of a carbon precursor, grinding particles of the mixture in a ball mill and subsequent heat treatment, according to the solution as a carbon precursor starch (С ₆ Ню0 ₅ ) _{p is used} , grinding is carried out in acetone, and heat treatment is carried out at a temperature of 800 - 850 ° С.

 The proposed technology for producing anode materials is simple and low cost due to the use of low temperatures and inexpensive synthesis precursors.

In FIG. Figure 1 shows the charge – discharge curves for LiCrTi0 ₄ / C obtained at a cyclic current of 0.1 C in the range of potentials of 1.0–2.5 V relative to metallic lithium. The inventive electrode material excels in its characteristics the best world samples.

The inventive electrode material with structure type spinel, carbon coating, and the general formula LiCrTiCVC prepared by a method comprising the following steps: grinding in a mill-activator (e.g., ASC-2) a mixture of precursor 1 l ₂ cos, Ti0 _2, Cr ₂ 0z taken in stoichiometric ratio and starch (C ₆ Hio0 ₅₎ n. Grinding is carried out in acetone to obtain particles with a size of not more than 10 microns. After grinding, the mixture is annealed in the temperature range 800 ° C - 850 ° C for 3 to 10 hours to obtain the anode material LIA composition LiCrTiCVC. The specified temperature range is sufficient for the entry of the ingredients into the solid-phase interaction.

 For the manufacture of the active material from the obtained material for negative LIA electrodes, mechanical mixing of the active material LiCrTiCVC, a binder (polyvinylidene difluoride, PVdF) and an electrically conductive additive (acetylene black) in a ratio of 80:10:10 is carried out, followed by additional homogenization of the mixture by ultrasonic dispersion.

 An example of a specific implementation.

To obtain the LiCrTiCVC composite, initial precursors are taken in the indicated or proportional to the indicated amounts: L1 ₂ CO ₃ - 2.719 g, TU ₂ - 5.879 g, Cr ₂ 0 ₃ - 5.593 g, starch (С _b НюС ^) ,, - 7.360 g. the components are mixed in an AGO-2 ball mill activator in acetone taken in an amount of 35 ml for 20 minutes, followed by heat treatment in argon at 800 ° C for 8 hours. The specific discharge capacity of the anode material is 143 mA'h / g, and charging 145 mAh / g on the first cycle at a current of 0.1 C. Thus, the invention allows you to achieve Oka specific capacity and reversibility with cycling (FIG. 1).

PUBLICATIONS TAKEN INTO ACCOUNT WHEN DRAWING IN THE APPLICATION U.S. Patent 4,668,595 of May 26, 1987. Secondary chemical current source.

US Patent 4,302,518 of November 24, 1981. An electrochemical cell with new fast ionic conductors.

U.S. Patent N ° 3,969,139 of July 13, 1976. A lithium electrode and an electric energy storage device based thereon.

US Patent Ns 3,506,490 dated April 14, 1970. A solid electrolyte current source with a lithium or lithium alloy anode.

US Patent N ° 5,587,256 of December 24, 1996. Carbon interstitial compounds and their use as anodes in rechargeable chemical current sources.

US Patent Ne 5,545,468 of August 13, 1996. Rechargeable lithium current source and anode manufacturing technology for it.

Porotnikov, N.V. Synthesis and study of the electrical conductivity of complex oxides in the Li ₂ 0 - ZnO - Ti0 _{2 system} / N.V. Porotnikov, N.G. Chaban, K.I. Petrov // Izvestiya AN SSSR. Norg. materials. - 1982. - T. 18, Jfe 6. - S. 1066 - 1067.

Chen, S. N. Studies of Mg-Substituted Li ₄ - _x Mg _x Ti ₅ 0i2 Spinel Electrodes (0 <x <1) for Lithium Batteries / C. H. Chen, JT Vaughey, AN Jansen, DW Dees, AJ ahaian , T. Goacher and MM Thackeray // J. Electrochem. Soc. - 2001. - Vol. 148, Issue 1. - P. A 102 - A104.

Canadian Patent Ne 2,327,370 Al dated June 5, 2002. A new method for producing pure Li ₄ Ti ₅ 0i ₂ H3 ternary mixture TiX-LiY-carbon: the effect of carbon on the synthesis and conductivity of the electrode.

US patent N ° 6,706,445 B2 of March 16, 2004. Synthesis of lithium transition metal titanates for lithium current sources.

Feng, XY Lithium Chromium Oxide Modified Spinel LiCrTi0 ₄ with Improved Electrochemical Properties / XY Feng, C. Shen, N. Ding, C. H. Chen // J. Mater. Chem. - 2012. - Vol. 22. - P. 20861-20865.

US patent jN ° 7,547,490 B2 of June 16, 2009. Lithium titanium spinel Li ₄ Ti ₅ 0i ₂ with improved characteristics for use as an electrode material. US patent Ne 7,879,493 B2 of February 1, 201 1 g. Alkali metal titanates and methods for their synthesis.

Claims

 CLAIM

A method for producing an anode material with a spinel structure for lithium-ion autonomous energy, comprising mixing a lithium salt of LiGCO3, titanium oxide (IV) T ₂ and chromium oxide (III) Cr ₂ 0 ₃ in a stoichiometric ratio, as well as a carbon precursor, grinding particles of the mixture in a ball mill, and subsequent heat treatment, characterized in that the carbon precursor is used as starch (C ₆ Nyu05) _n, grinding is carried out in acetone, and the heat treatment temperature is in the range 800 - 850 ° C.