Layered Positive Electrode Material for Crack-Resistant Li-Ion Capacity
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Solution Overview
Problem
Li2NiO2 has poor reversibility for Li ion absorption and release, leading to reduced discharge capacity in non-aqueous electrolyte secondary batteries, and existing techniques do not adequately address this irreversibility.
Innovation Solution
A positive electrode active material comprising a first lithium-metal composite oxide with a specific formula and structure, including a layer structure with Li coordinated at a tetrahedral site of oxygen, and a second lithium-metal composite oxide with larger particle sizes to improve packing density and discharge capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Li2NiO2 is contained in the positive electrode to supply sufficient Li ions during charging, then the battery capacity reduction is suppressed, but the discharge capacity is actually reduced due to poor reversibility of Li ion absorption and release
Solution Approach 1:
The patent changes the particle size parameter of Li2NiO2 from fine particles to coarse particles with a specific size range (5-15 μm). This parameter change improves reversibility of Li ion absorption and release, thereby improving discharge capacity while maintaining sufficient Li ion supply during charging.
Solution Approach 2:
The patent creates a composite positive electrode material combining Li2NiO2 coarse particles with other lithium-metal composite oxides. This composite structure leverages the advantages of different materials: Li2NiO2 provides sufficient Li ion supply capacity, while the other materials contribute to reversible Li ion absorption and release, achieving both high battery capacity maintenance and high discharge capacity.
2Quantity of substance
If Li2NiO2 is used in the positive electrode, then Li ion supply capacity is improved, but particle cracking occurs leading to reduced capacity maintenance
Solution Approach 1:
The patent changes the particle size parameter of Li2NiO2 to a coarse particle range (5-15 μm). This parameter change reduces particle cracking during charging and discharging cycles, thereby improving capacity maintenance while maintaining sufficient Li ion supply capacity.
Solution Approach 2:
The patent performs preliminary action by controlling the particle size of Li2NiO2 before electrode fabrication. By pre-establishing the optimal particle size range, the material is prepared to withstand expansion and contraction during Li ion insertion and extraction, preventing crack formation and maintaining structural integrity throughout battery cycling.
3Speed
If fine particles are used to increase surface area for Li ion reaction, then reaction speed is improved, but particle cracking increases reducing discharge capacity
Solution Approach 1:
The patent changes the particle size parameter from fine particles to coarse particles (5-15 μm). This parameter change reduces particle cracking while maintaining adequate Li ion reaction speed through optimized surface area and internal structure of the coarse particles.
Solution Approach 2:
The patent utilizes the spherical morphology of the Li2NiO2 particles. The spherical shape with optimized size provides uniform stress distribution during Li ion insertion and extraction, reducing crack initiation and propagation. The curvature of the spherical particles helps accommodate volume changes during cycling, maintaining structural integrity and discharge capacity.
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 enhances the discharge capacity of non-aqueous electrolyte secondary batteries by suppressing particle cracking and improving capacity maintenance during charging and discharging.
Implementation Method 1
the first lithium-metal composite oxide has a layer structure, has a Li element coordinated at a tetrahedral site of oxygen
Implementation Method 2
non-aqueous electrolyte secondary batteries are widely in use in which the battery is charged and discharged by moving Li ions or the like between a positive electrode and a negative electrode
Data Source
AI summary
This positive electrode active material contains a first lithium metal composite oxide which is represented by general formula xLiyM1O2-(1−x)LizM1O2 (wherein 0≤x≤1, 1.5≤y≤2.5, 0.9≤z≤1.5, and M1 represents one or more elements that are selected from the group consisting of transition metals, Al, Si, Sn, Ge, Sb, Bi, Mg, Ca and Sr); the first lithium metal composite oxide has a layered structure, while comprising Li element that is coordinated to the position of the oxygen tetrahedron; and the particle diameters of the primary particles are from 0.5 μm to 15 μm.