Lithium-Excess High-Nickel Cathode Material for Stable Cycle Life
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Solution Overview
Problem
High-nickel based layered positive electrode active materials for lithium secondary batteries face challenges in stability and capacity due to instability of Ni(III) and cation mixing, which affects electrochemical characteristics and cycle-life, especially with small changes in lithium content during synthesis.
Innovation Solution
A lithium excess high nickel-based positive electrode active material with a specific chemical composition (Li1+a(NibM11-b)1-aO2) and manufacturing method involving a molar ratio of 1:1.03 to 1:1.3 of a nickel-based metal hydroxide precursor and lithium raw material, heat-treated between 680° C. to 780° C., to achieve a stable structure with excess lithium and high nickel content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-nickel based layered positive electrode active materials are used to achieve high capacity, then energy density is improved, but stability deteriorates due to Ni(III) instability and cation mixing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the lithium content parameter (Li1+a where a=0.01-0.06) and synthesis temperature (680-780°C) to achieve a stable high-nickel material structure. By adjusting these parameters, the material maintains high nickel content for energy density while achieving structural stability through excess lithium that prevents cation mixing and Ni(III) instability.
Solution Approach 2:
The patent creates a composite material system with excess lithium (Li1+a) incorporated into the high-nickel layered structure. This composite approach where lithium serves dual roles as both charge carrier and structural stabilizer resolves the contradiction between high nickel content for energy density and structural stability, as the excess lithium prevents cation mixing and stabilizes the layered structure.
2Reliability
If lithium content is increased to stabilize the structure and reduce cation mixing, then stability is improved, but manufacturing precision deteriorates due to difficulty in controlling small changes in lithium content
Solution Approach 1:
The patent applies preliminary action by pre-calculating and preparing the exact molar ratio of lithium raw material to precursor (1:1.03 to 1:1.3) before synthesis. This advance preparation ensures that the correct amount of excess lithium is incorporated from the start, preventing cation mixing and stabilizing the structure while avoiding the need for difficult post-synthesis adjustments.
Solution Approach 2:
The patent simplifies the manufacturing precision challenge by changing the control parameter from precise lithium content (a=0.01-0.06) to a broader, easier-to-control molar ratio range (1:1.03 to 1:1.3) and temperature range (680-780°C). This parameter transformation makes the synthesis process more robust and less sensitive to small variations.
3Duration of action of stationary object
If excess lithium is incorporated to achieve Li1+a structure with high stability, then cycle-life is improved, but productivity deteriorates due to complex synthesis process
Solution Approach 1:
The patent improves synthesis efficiency by changing the temperature parameter to a broader optimal range (680-780°C) rather than a single precise value, and by defining a clear molar ratio range (1:1.03 to 1:1.3). These parameter specifications make the synthesis process more robust and easier to execute consistently, improving productivity while maintaining the Li1+a structure for high cycle-life.
4Use of energy by moving object
If high-nickel content is maintained for high energy density, then capacity is improved, but electrochemical characteristics worsen due to Ni(III) instability
Solution Approach 1:
The patent creates a composite material system where excess lithium (Li1+a) is incorporated into the high-nickel layered structure. This composite approach stabilizes the high-nickel material by preventing Ni(III) instability and cation mixing, allowing the material to maintain high capacity while achieving stable electrochemical characteristics through the dual role of excess lithium as both charge carrier and structural stabilizer.
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 price competitiveness, stability, high energy density, and extended cycle-life, minimizing impurities like Li2CO3 and Li2O, and reducing cation mixing, thereby enhancing battery performance.
Implementation Method 1
positive electrode active material for lithium secondary battery
Implementation Method 2
a molar content of lithium present in the structure of the positive electrode active material, measured through neutron diffraction analysis
Implementation Method 3
heating them in the temperature range of 680° C. to 780° C.
Data Source
AI summary
It is related to a positive electrode active material for lithium secondary battery, comprising: a compound represented by Chemical Formula 1, wherein a molar content of lithium present in the structure of the positive electrode active material, measured through neutron diffraction analysis, is 1.01 to 1.15 for 1 mole of the positive electrode active material, a method of preparing it, and a lithium secondary battery including the same.Li1+a(NibM11-b)1-aO2 [Chemical Formula 1]In the Chemical Formula 1, 0<a<0.2, 0.8<b<1, M1 is at least one element selected from Co, Mn, Al, Mg, Ca, Ti, V, Cr, Zr, Nb, Mo, and W.