Lithium Mixed Transition Metal Oxide Cathode Stabilization
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Solution Overview
Problem
Lithium nickel oxide-based cathode active materials for secondary batteries face issues such as crystal structure instability, gas evolution, poor chemical resistance, and high production costs due to impurities and structural changes during charge/discharge cycles, limiting their practical application in high-capacity and high-temperature environments.
Innovation Solution
A lithium mixed transition metal oxide with a specific composition and structure, where Ni ions are inserted into reversible lithium layers, stabilizing the crystal structure and reducing impurities, allowing for high-capacity and high-cycle stability, while being produced without water-soluble bases and at lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiNiO2-based oxide is used as cathode active material, then high discharge capacity and low cost are achieved, but crystal structure instability and poor cycle characteristics occur due to phase transition and volumetric changes
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core maintains high nickel content (LiNi1-x-yMxO2) for high capacity while the outer shell has modified composition with additional elements (LiNi1-a-bMn a Co b O2) for structural stability. This spatial differentiation of material properties resolves the contradiction between high discharge capacity and crystal structure stability.
Solution Approach 2:
The invention uses composite materials by combining nickel-rich lithium oxide core with a stabilizing shell layer containing nickel, manganese, and cobalt. This composite structure allows the inner core to provide high capacity while the outer shell provides structural stability during charge-discharge cycles, preventing phase transitions and volumetric changes.
2Stability of the object's composition
If excess Li source is added and heat treatment is performed, then crystal structure formation is improved, but water-soluble bases (Li2CO3, LiOH) remain as impurities causing gas evolution
Solution Approach 1:
The patent applies the taking out principle by selectively removing water-soluble base impurities (Li2CO3, LiOH) through acid washing treatment using dilute nitric acid or hydrochloric acid. This extraction process eliminates the harmful impurities that cause gas evolution while preserving the desired crystal structure of the cathode material.
Solution Approach 2:
The invention converts the harmful effect of water-soluble bases into a benefit by using controlled acid washing. The acid treatment selectively dissolves the unwanted Li2CO3 and LiOH impurities while leaving the stable crystal structure intact, thereby transforming a harmful impurity problem into a controlled purification process that enhances battery performance.
3Quantity of substance
If LiNiO2 is charged to 4.3 V, then high discharge capacity is achieved, but structural swelling and destabilization occur due to repulsive force between oxygen atoms
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the inner core maintains high nickel content (LiNi1-x-yMxO2) for high capacity while the outer shell has modified composition with additional elements (LiNi1-a-bMn a Co b O2) for structural stability. This spatial differentiation of material properties resolves the contradiction between high discharge capacity and crystal structure stability.
Solution Approach 2:
The invention applies beforehand cushioning by pre-forming a stabilizing shell layer around the high-capacity core before battery operation. This shell acts as a protective cushion that prevents structural swelling and destabilization during high-voltage charging, accommodating the repulsive forces between oxygen atoms before they can cause damage.
4Productivity
If LiNiO2 particles have agglomerate secondary particle structure, then contact area with electrolyte increases, but CO2 gas evolution and battery swelling are severe
Solution Approach 1:
The patent applies the taking out principle by selectively removing water-soluble base impurities (Li2CO3, LiOH) through acid washing treatment using dilute nitric acid or hydrochloric acid. This extraction process eliminates the harmful impurities that cause gas evolution while preserving the desired crystal structure of the cathode material.
Solution Approach 2:
The invention applies local quality by creating a core-shell structure where the inner core maintains high nickel content (LiNi1-x-yMxO2) for high capacity while the outer shell has modified composition with additional elements (LiNi1-a-bMn a Co b O2) for structural stability. This spatial differentiation of material properties resolves the contradiction between high discharge capacity and crystal structure stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides superior thermal and cycle stability, reduced gas evolution, and cost-effective mass production, enhancing the safety and performance of lithium nickel-based batteries.
Implementation Method 1
exhibits intercalation/deintercalation of lithium ions into/from mixed transition metal oxide layers (MO layers) and interconnection of MO layers via the insertion of some MO layer-derived Ni ions into intercalation/deintercalation layers (reversible lithium layers) of lithium ions
Implementation Method 2
exhibits intercalation/deintercalation of lithium ions into/from mixed transition metal oxide layers (MO layers)
Data Source
Figure 1~2
Figure 3~4
Figure 5A~6B
AI summary
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), wherein lithium ions intercalate into and deintercalate from mixed transition metal oxide layers ("MO layers") and some of the 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.