Material for lithium secondary battery of high performance

a secondary battery and lithium mixed technology, applied in nickel compounds, cell components, sustainable manufacturing/processing, etc., can solve the problems of low safety, limited practical and mass application of lithium manganese oxide as a power source, and shortcomings of lithium manganese oxide, etc., to achieve high cycle stability, high capacity, and superior thermal stability

Inactive Publication Date: 2007-12-20
LG ENERGY SOLUTION LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0014] As a result of a variety of extensive and intensive studies and experiments and in view of the problems as described above, the inventors of the present invention provide herewith a lithium mixed transition metal oxide, as will be illustrated hereinafter, having a given composition and a specific atomic-level structure, with which it is possible to realize superior thermal stability, and high cycle stability in conjunction with a high capacity, due to impr

Problems solved by technology

Of the aforementioned cathode active materials, LiCoO2 is currently widely used due to superior general properties including excellent cycle characteristics, but suffers from low safety, expensiveness due to finite resources of cobalt as a raw material, and limitations in practical and mass application thereof as a power source for electric vehicles (EVs) and the like.
However, these lithium manganese oxides suffer from shortcomings such as low capacity and poor cycle characteristics.
However, the LiNiO2-based cathode active materials suffer from some limitations in practical application thereof, due to the following problems.
First, LiNiO2-based oxides undergo sharp phase transition of the crystal structure with volumetric changes accompanied by repeated charge/discharge cycling, and thereby may suffer from cracking of particles or formation of voids in grain boundaries.
Consequently, intercalation/deintercalation of lithium ions may be hindered to increase the polarization resistance, thereby resulting in deterioration of the charge/discharge performance.
However, the thus-prepared cathode active material, under the charged state, undergoes structural swelling and destabilization due to the repulsive force between oxygen atoms, and suffers from problems of severe deterioration in cycle characteristics due to repeated charge/discharge cycles.
Further, LiNiO2 particles have an agglomerate secondary particle structure in which primary particles are agglomerated to form secondary particles and consequently a contact area w

Method used

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  • Material for lithium secondary battery of high performance
  • Material for lithium secondary battery of high performance
  • Material for lithium secondary battery of high performance

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0110] A mixed hydroxide of Formula MOOH (M=Ni4 / 15(Mn1 / 2Ni1 / 2)8 / 15Cu0.2) as a mixed transition metal precursor and Li2CO3 were mixed in a stoichiometric ratio (Li:M=1.02:1), and the mixture was sintered in air at various temperatures of 850 (Ex. 1A), 900 (Ex. 1B), 950 (Ex. 1C), and 1,000° C. for 10 hours, to preparing a lithium mixed transition metal oxide. Herein, secondary particles were maintained intact without being collapsed, and the crystal size increased with an increase in the sintering temperature.

[0111] X-ray analysis showed that all samples have a well-layered crystal structure. Further, a unit cell volume did not exhibit a significant change with an increase in the sintering temperature, thus representing that there was no significant oxygen-deficiency and no significant increase of cation mixing, in conjunction with essentially no occurrence of lithium evaporation.

[0112] The crystallographic data for the thus-prepared lithium mixed transition metal oxide are given in...

example 2

[0119] The pH titration was carried out for a sample of the lithium mixed transition metal oxide in accordance with Example 2 prior to exposure to moisture, and samples stored in a wet chamber (90% RH) at 60° C. in air for 17 hours and 3 days, respectively. The results thus obtained are given in FIG. 9. Upon comparing the lithium mixed transition metal oxide of Example 2 (see FIG. 9) with the sample of Comparative Example 3 (see FIG. 8), the sample of Comparative Example 3 (stored for 17 hours) exhibited consumption of about 20 mL of HCl, whereas the sample of Example 2 (stored for 17 hours) exhibited consumption of 10 mL of HCl, thus showing an about two-fold decrease in production of the water-soluble bases. Further, in 3-day-storage samples, the sample of Comparative Example 3 exhibited consumption of about 110 mL of HCl, whereas the sample of Example 2 exhibited consumption of 26 mL of HCl, which corresponds to an about five-fold decrease in production of the water-soluble bases...

example 3

[0121] A mixture of Li2CO3 with mixed hydroxide of Formula MOOH (M=Ni4 / 15(Mn1 / 2Ni1 / 2)8 / 15Co0.2) was introduced into a furnace with an about 20 L chamber and sintered at 920° C. for 10 hours, during which more than 10 m3 of air was pumped into the furnace, thereby preparing about 5 kg of LiNiMO2 in one batch.

[0122] After sintering was complete, a unit cell constant was determined by X-ray analysis, and a unit cell volume was compared with a target value (Sample B of Example 1: 33.921 Å3). ICP analysis showed that a ratio of Li and M is very close to 1.00, and the unit cell volume was within the target range. FIG. 10 shows an SEM image of the thus-prepared cathode active material and FIG. 11 shows results of Rietveld refinement. Referring to these drawings, it was found that the sample exhibits high crystallinity and well-layered structure, a mole fraction of Ni2+ inserted into a reversible lithium layer is 3.97%, and the calculated value and the measured value of the mole fraction o...

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Abstract

Provided is a lithium mixed transition metal oxide having a composition represented by Formula I of LixMyO2 (M, x and y are as defined in the specification) having mixed transition metal oxide layers (“MO layers”) comprising Ni ions and lithium ions, wherein lithium ions intercalate into and deintercalate from the MO layers and a portion of MO layer-derived Ni ions are inserted into intercalation/deintercalation layers of lithium ions (“reversible lithium layers”) thereby resulting in the interconnection between the MO layers. The lithium mixed transition metal oxide of the present invention has a stable layered structure and therefore exhibits improved stability of the crystal structure upon charge/discharge. In addition, a battery comprising such a cathode active material can exhibit a high capacity and a high cycle stability. Further, such a lithium mixed transition metal oxide is substantially free of water-soluble bases, and thereby can provide excellent storage stability, decreased gas evolution and consequently superior high-temperature stability with the feasibility of low-cost mass production.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a Ni-based lithium mixed transition metal oxide and a cathode active material for a secondary battery comprising the same. More specifically, the Ni-based lithium mixed transition metal oxide according to the present invention has a given composition and exhibits intercalation / deintercalation of lithium ions into / from mixed transition metal oxide layers (“MO layers”) and interconnection of MO layers via the insertion of a portion of MO layer-derived Ni ions into intercalation / deintercalation layers (reversible lithium layers) of lithium ions, thereby improving the structural stability of the crystal structure upon charge / discharge to provide an excellent sintering stability. In addition, a battery comprising such a cathode active material can exert a high capacity and a high cycle stability. Further, with substantially no water-soluble bases present, such a lithium mixed transition metal oxide exhibits excellent storage ...

Claims

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Application Information

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IPC IPC(8): H01M4/40C22C24/00H01M4/50H01M4/52H01M4/505H01M4/525H01M10/052H01M10/36
CPCC01P2002/77H01M4/485C01P2004/03C01P2006/40C01P2006/80H01M4/505H01M4/525H01M10/052Y02E60/122C01G45/1228C01G51/50C01G53/50C01P2002/54C01P2002/72C01P2004/84C01P2006/10C01P2006/37H01M4/131C01P2002/88H01M2004/028Y02E60/10Y02P70/50
Inventor PARK, HONG-KYUSHIN, SUN SIKPARK, SIN YOUNGSHIN, HO SUKPAULSEN, JENS M.
Owner LG ENERGY SOLUTION LTD
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