Phosphate-Coated Ni-Rich Cathode Material for Crack Stability
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Solution Overview
Problem
Existing Ni-based cathode active materials for lithium secondary batteries suffer from microcracks during long-term charge/discharge processes, leading to side reactions with the electrolyte, reduced stability, and limited high-energy density capabilities.
Innovation Solution
A cathode active material is developed with a core composed of a compound represented by Formula 1, Li1−xNaxM1αM21−αO2, where M is Zr or W, and a coating layer containing a phosphorus-containing compound, such as Li3PO4, to stabilize unstable Ni ions and enhance structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni-based cathode active material is synthesized by co-precipitation method to achieve high reversible capacity, then cost is reduced and capacity is improved, but microcracks are generated during long-term charge/discharge process leading to electrolyte depletion and stability deterioration
Solution Approach 1:
The patent applies preliminary action by synthesizing the cathode active material as single particles with controlled crystal structure before battery assembly, preventing microcrack formation during subsequent charge/discharge cycles. The single-particle morphology and stabilized crystal structure are prepared in advance to avoid degradation issues that would otherwise occur during battery operation.
Solution Approach 2:
The patent employs parameter changes by modifying the synthesis conditions and composition parameters to achieve single-particle morphology instead of secondary particles. Specific compositional parameters (Ni content, doping elements) and synthesis parameters (temperature, time, pH control) are optimized to produce monodisperse single particles with stable crystal structures that resist microcrack formation while maintaining high reversible capacity.
2Use of energy by moving object
If electrode density is increased to achieve high energy density, then energy density is improved, but secondary particles collapse causing electrolyte depletion and rapid initial life decrease
Solution Approach 1:
The patent applies preliminary action by pre-forming single-particle cathode materials with optimized density and structural integrity before battery assembly. This preliminary structuring prevents particle collapse during high-density electrode fabrication and subsequent battery operation, maintaining both high energy density and extended initial life.
Solution Approach 2:
The patent employs composite materials by incorporating doping elements into the Ni-based cathode structure to create a composite material system. This composite approach enhances the mechanical strength and structural stability of the single particles, enabling them to withstand the stresses of high electrode density fabrication without collapsing, thereby maintaining both energy density and initial life performance.
3Use of energy by moving object
If monocrystalline Ni-based cathode active material is used to prevent particle collapse, then energy density is improved, but structural and thermal instability occurs due to unstable Ni3+ and Ni4+ ions
Solution Approach 1:
The patent employs parameter changes by adjusting the oxidation state parameters of nickel ions through compositional modification and synthesis condition optimization. By controlling the ratio of Ni3+ to Ni4+ ions through doping and synthesis parameters, the patent stabilizes the monocrystalline structure while maintaining high energy density capabilities.
Solution Approach 2:
The patent applies composite materials by introducing stabilizing elements into the monocrystalline Ni-based structure. These dopant elements form a composite material system that provides structural stabilization to the monocrystal, reducing the instability caused by Ni3+ and Ni4+ ions while preserving the high energy density benefits of the monocrystalline form.
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 proposed cathode active material achieves improved high-energy density and extended lifespan characteristics by stabilizing Ni ions and reducing side reactions with the electrolyte, thereby enhancing the overall performance of lithium secondary batteries.
Implementation Method 1
a coating layer including a phosphorus-containing compound disposed on a surface of the core
Data Source
AI summary
A cathode active material includesa core having a compound represented by Formula 2-2 or 2-3, as follows:Li1−x″Nax″Zrβ″Wγ″Ni1−β″Coy″Alz″O2, and (Formula 2-3)Li1−x′″Nax′″Zrβ′″Wγ′″Ni1−β′″−γ′″−y′″Coy′″O2; (Formula 2-3)wherein in Formula 2-2,0<x″≤0.01, 0<β″≤0.005, 0<γ″≤0.005, 0<y″≤0.2, and 0<z″≤0.1, andwherein in Formula 2-3,0<x′″≤0.01, 0<β′″≤0.005, 0<γ′″<0.005, and 0<y′″<0.2; anda coating layer having a phosphorus-containing compound disposed on the surface of the core, wherein the phosphorus-containing compound comprises a compound represented by Formula 3, as follows:LiaPbOc, (Formula 3)in Formula 3, 0<a≤3, 0<b≤1, and 0<c≤4.