Lithium Nickel Complex Oxide Electrode for High Capacity Batteries
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Solution Overview
Problem
Lithium nickel complex oxides in lithium ion secondary batteries face challenges with high irreversible capacity, low initial charge/discharge efficiency, and inferior rate characteristics, which hinder their performance in high-capacity and high-output applications, especially in large-scale batteries for electric vehicles.
Innovation Solution
A hexagonal lithium nickel complex oxide with a specific composition and crystal structure, represented by the formula LixNi1−y−zCoyMzO2, is developed, where the lithium occupancy rate is at least 98.7% and the crystallite diameter is between 50 to 300 nm, achieved through optimal calcination conditions and control of compositional ratios, enhancing crystal structure perfection and reducing irreversible capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel complex oxide is used as positive electrode active material to achieve high capacity, then the theoretical capacity is high, but the irreversible capacity is high and initial charge/discharge efficiency is low
Solution Approach 1:
The patent applies parameter changes by precisely controlling the lithium occupancy rate (≥98.7%) and crystallite diameter (50-300 nm) of the lithium nickel complex oxide. By optimizing these physical and chemical parameters, the material achieves both high theoretical capacity and low irreversible capacity, resolving the contradiction between capacity quantity and energy loss.
2Quantity of substance
If lithium nickel complex oxide is used to achieve high capacity, then the energy density is improved, but the rate characteristic is poor
Solution Approach 1:
The patent applies local quality by creating a specific crystallite size distribution (50-300 nm) within the lithium nickel complex oxide structure. This localized structural optimization ensures that regions with appropriate crystallite sizes are present to facilitate fast ion transport, thereby improving rate characteristics while maintaining high overall capacity.
3Reliability
If lithium cobalt complex oxide is used as positive electrode active material to achieve high voltage and high energy density, then the battery performance is excellent, but the cost is high due to expensive cobalt compounds
Solution Approach 1:
The patent applies this principle by substituting expensive cobalt with cheaper nickel as the primary metal in the complex oxide structure. While nickel has some drawbacks, the patent overcomes these through precise structural control (lithium occupancy ≥98.7%, crystallite diameter 50-300 nm), achieving acceptable performance at lower cost, effectively using a cheaper material to replace the expensive one.
4Object-affected harmful factors
If lithium manganese complex oxide is used as positive electrode active material to reduce cost and improve safety, then the thermal stability is excellent, but the theoretical capacity is only about one-half that of lithium cobalt complex oxide
Solution Approach 1:
The patent applies composite materials by creating a lithium nickel complex oxide with specific structural characteristics (high lithium occupancy, controlled crystallite size) that combines the advantages of different materials. The resulting material achieves both high capacity and improved safety characteristics, effectively creating a composite-like performance through controlled composition and structure.
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 results in a positive electrode active material with high capacity, low irreversible capacity, and excellent initial charge/discharge efficiency, suitable for both small portable devices and high-output applications like electric vehicles, with improved thermal stability and safety.
Implementation Method 1
Materials capable of the extraction insertion of lithium are used for the positive electrode and negative electrode materials of lithium ion secondary batteries
Implementation Method 2
a calcination step of calcining the obtained lithium mixture at a temperature of 720 to 830° C. in an oxygen atmosphere thereby obtaining a lithium nickel complex oxide
Data Source
AI summary
A positive electrode active material is provided that has a high capacity, a low irreversible capacity, an excellent initial charge/discharge efficiency, and excellent rate characteristics. This positive electrode active material comprises a hexagonal lithium nickel complex oxide having a layer structure and represented by the general formula LixNi1−y−zCoyMzO2 (0.98≤x≤1.04, 0.25≤y≤0.40, 0≤z≤0.07, and M is at least one element selected from Al, Ti, Mn, Ga, Mg, and Nb), wherein a lithium occupancy rate in a lithium main layer as obtained by Rietveld analysis from the x-ray diffraction pattern is at least 98.7%, and a crystallite diameter as calculated from the peak for the (003) plane in x-ray diffraction is 50 to 300 nm.