Titanium-Enriched Cathode Layer for Battery Stability
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Solution Overview
Problem
Current cathode active materials for lithium ion secondary batteries, particularly lithium nickel composite oxides, face challenges with thermal stability, charge-discharge cycle characteristics, and high power output, especially for applications requiring instant high current, such as hybrid electric vehicles.
Innovation Solution
A cathode active material represented by the formula LitNi1.x.y.zCoxAlyTizO2, where 0.98≤t≤1.10, 0<x≤0.30, 0.03≤y≤0.15, 0.001≤z≤0.03, with a titanium-enriched layer on the surface and/or grain boundary of secondary particles, enhancing lithium ion conductivity and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel composite oxide is used as cathode active material, then battery capacity and energy density are improved, but thermal stability and charge-discharge cycle characteristics deteriorate
Solution Approach 1:
The patent applies local quality by creating a titanium-enriched layer specifically at the surface and grain boundaries of the cathode active material particles. This localized titanium concentration (higher than the bulk composition) provides thermal stability and structural support only where needed at the particle surfaces, while the interior bulk material maintains its high nickel content for maximum capacity. This resolves the contradiction by having different compositions in different regions of the same material.
Solution Approach 2:
The patent creates a composite structure where titanium is incorporated into the lithium nickel composite oxide lattice, forming a multi-element composite material with formula Li[Ni1-x-y-zCoxAlyTiz]O2. The composite nature of this material combines the high capacity characteristics of nickel-rich compositions with the thermal stability of titanium, allowing simultaneous achievement of both improved capacity and reliability.
2Stability of the object's composition
If substitution of nickel with cobalt, manganese, iron, aluminum, or vanadium is performed, then crystal structure stability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent uses local quality by concentrating titanium substitution at specific locations (surface and grain boundaries) rather than uniformly distributing multiple substituent elements throughout the bulk material. This localized approach achieves the necessary crystal structure stability with a simpler manufacturing process, avoiding the complexity of simultaneously controlling multiple substitution elements.
Solution Approach 2:
The patent changes the compositional parameter by incorporating titanium at specific concentration ranges (0.001≤z≤0.03 in the bulk, with higher concentration at surface/grain boundaries). This parameter optimization achieves crystal structure stability without requiring complex multi-element substitutions, simplifying the manufacturing process while maintaining reliability.
3Reliability
If washing process is applied after firing, then thermal stability and capacity are improved, but output characteristics and surface integrity deteriorate
Solution Approach 1:
The patent applies preliminary action by incorporating titanium into the cathode active material composition before the firing process. The titanium is pre-distributed in the precursor materials and incorporated into the crystal structure during firing, eliminating the need for post-firing washing. This preliminary incorporation of titanium provides thermal stability without requiring subsequent washing that would damage the surface and reduce output characteristics.
Solution Approach 2:
The patent extracts the washing step from the manufacturing process by achieving thermal stability through titanium incorporation during firing itself. This eliminates the harmful washing operation that would otherwise be needed to remove impurities, thereby preserving surface integrity and output characteristics while still achieving the desired thermal stability.
4Quantity of substance
If high nickel content is used in cathode active material, then battery energy density is improved, but charge-discharge cycle characteristics and safety deteriorate
Solution Approach 1:
The patent applies local quality by maintaining high nickel content in the bulk material for maximum energy density while concentrating titanium at the surface and grain boundaries to provide structural stability. This spatial differentiation allows the bulk to deliver high capacity while the titanium-enriched regions maintain crystal structure integrity during charge-discharge cycling, resolving the contradiction between energy density and cycle characteristics.
Solution Approach 2:
The patent creates a composite material with formula Li[Ni1-x-y-zCoxAlyTiz]O2 where titanium is incorporated into the lithium nickel composite oxide lattice. This composite structure combines the high capacity characteristics of nickel-rich compositions with the structural stability provided by titanium, enabling simultaneous achievement of high energy density and good charge-discharge cycle characteristics.
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 titanium-enriched layer improves thermal stability, charge/discharge cycle stability, and output characteristics, enabling high-capacity, high-power nonaqueous electrolyte secondary batteries with enhanced safety and durability.
Implementation Method 1
with a titanium-enriched layer on the surface and/or grain boundary of secondary particles, enhancing lithium ion conductivity
Implementation Method 2
heat treating a nickel cobalt aluminum composite hydroxide... heat treating a nickel cobalt aluminum titanium composite hydroxide
Data Source
AI summary
The present invention provides a cathode active material for a nonaqueous electrolyte secondary battery with a high capacity, high stability and excellent output characteristics and a method for producing the same, and a nonaqueous electrolyte secondary battery using the cathode active material.The cathode active material for a nonaqueous electrolyte secondary battery is represented by a general formula: LitNi1-x-y-zCoxAlyTizO2 wherein 0.98≤t≤1.10, 0<x≤0.30, 0.03≤y≤0.15, 0.001≤z≤0.03; and includes a hexagonal lithium-containing composite oxide with a layer structure of secondary particles having primary particles, in which a titanium-enriched layer is formed on a surface of the primary particles and/or a grain boundary between the primary particles. The titanium-enriched layer on the surface of the primary particles and/or a grain boundary between the primary particles serves as a lithium ion conductor, yielding smooth extraction and insertion of lithium ions. Accordingly, the secondary battery with a high capacity, high stability and excellent output characteristics can be produced when a positive electrode is formed with the lithium nickel composite oxide as a cathode active material.