Lithium Battery Cathode Material Crystallite Ratio Optimization
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Solution Overview
Problem
Conventional lithium-containing composite metal oxides used in lithium secondary batteries have limitations in discharge capacity, necessitating the development of a more effective positive electrode active material.
Innovation Solution
A positive electrode active material with an α-NaFeO2 type crystal structure, represented by Li[Lix(NiaCobMncMd)1-x]O2, is developed, featuring specific crystallite size ratios, BET specific surface area, and metal element compositions to enhance discharge capacity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional lithium-containing composite metal oxides are used as positive electrode active materials, then the battery structure is simple and manufacturing is easy, but the discharge capacity is insufficient
Solution Approach 1:
The invention changes the crystal structure parameters by adopting an α-NaFeO2 type structure with specific crystallite size ratios (α/β ≥ 1.60), where α represents crystallite size in the direction perpendicular to the 104 plane and β represents crystallite size in the direction perpendicular to the 003 plane. This parameter optimization enables higher discharge capacity while maintaining structural stability.
Solution Approach 2:
The invention uses composite metal oxides with the general formula Li1.00Ni0.33Co0.34Mn0.33O2, combining multiple transition metals (Ni, Co, Mn) in specific ratios within an α-NaFeO2 structure. This composite approach leverages the beneficial properties of each metal to achieve enhanced discharge capacity and cycle performance.
2Quantity of substance
If the crystallite size is increased to improve discharge capacity, then the battery performance improves, but the surface area to volume ratio decreases affecting reaction efficiency
Solution Approach 1:
The invention optimizes the crystallite size parameters by controlling the ratio α/β ≥ 1.60, where α and β represent crystallite dimensions in different crystallographic directions. This anisotropic crystallite growth maintains sufficient surface area for electrochemical reactions while developing the bulk capacity needed for high discharge performance.
Data Source
AI summary
A positive electrode active material for a lithium secondary battery, including secondary particles formed by aggregation of primary particles capable of being doped and undoped with lithium ions, said positive electrode active material having: an α-NaFeO2 type crystal structure represented by formula: Li[Lix(NiaCobMncMd)1-x]O2 (I), wherein 0≤x≤0.1, 0.7<a<1, 0<b<0.2, 0≤c<0.2, 0<d<0.1, a+b+c+d=1, and M is at least one metal element selected from the group consisting of Fe, Cr, Ti, Mg, Al, Zr, Ca, Sc, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In and Sn; and a crystallite size α/crystallite size β ratio (α/β) of 1.60 to 2.40, wherein the crystallite size α is within a peak region of 2θ=18.7±1° and the crystallite size β is within a peak region of 2θ=44.4±1°, each determined by a powder X-ray diffraction measurement using Cu-Kα radiation.