Doped Lithium Cobalt Oxide Cathode for Thermal Stability
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Solution Overview
Problem
Lithium secondary batteries using LiCoO2 as a positive electrode active material face rapid degradation in cycle-life characteristics, high temperature characteristics, and thermal stability issues due to repeated charge and discharge cycles, especially at high temperatures.
Innovation Solution
A positive electrode active material for lithium secondary batteries is developed, comprising a lithium transition metal composite oxide with doping metals having an average oxidation number greater than 3.5, specifically aluminum and molybdenum, which are doped into the lithium-transition metal composite oxide to enhance structural stability and electrochemical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiCoO2 is used as positive electrode active material, then high discharge voltage and energy density are achieved, but cycle-life characteristics and thermal stability deteriorate rapidly with repeated charge and discharge
Solution Approach 1:
The patent applies local quality by doping specific metal elements (Fe, Co, Ni, Mn, Zn, Cu, or Al) at controlled concentrations (0.01-5 mol%) into the LiCoO2 crystal lattice at specific sites. This creates localized structural modifications that enhance thermal stability and cycle-life characteristics while preserving the overall high energy density properties of LiCoO2.
Solution Approach 2:
The patent creates composite materials by combining LiCoO2 with doped metal elements to form a composite oxide structure. This composite approach allows the material to exhibit both the high energy density of LiCoO2 and the improved structural stability provided by the doped elements, thereby enhancing cycle-life characteristics and thermal stability.
2Power
If LiCoO2 is used as positive electrode active material, then high discharge voltage is achieved, but thermal stability deteriorates at high temperature
Solution Approach 1:
The patent uses local quality by introducing dopant elements at specific crystal lattice sites within LiCoO2. These localized dopants create structural reinforcement that raises the thermal stability temperature threshold while preserving the electrochemical properties that enable high discharge voltage.
Solution Approach 2:
The patent applies parameter changes by modifying the chemical composition parameters of LiCoO2 through doping with metal elements at controlled concentrations. This changes the thermal decomposition temperature and structural stability parameters while maintaining the electrochemical voltage characteristics.
3Reliability
If metal oxide or fluorine oxide coating is applied on LiCoO2 surface, then cycle-life characteristics are improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the doping process with the bulk material synthesis by incorporating dopant elements directly into the LiCoO2 crystal lattice during a single solid-state reaction process. This eliminates the need for separate coating steps, reducing manufacturing complexity while achieving improved cycle-life characteristics through structural doping rather than surface coating.
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 doped lithium transition metal composite oxide improves high-temperature stability, cycle-life characteristics, and discharge voltage characteristics, leading to a more reliable and efficient lithium secondary battery with improved output and capacity retention.
Implementation Method 1
doping metals doped in the lithium transition metal composite oxide, wherein the doping metals include at least two kinds and an average oxidation number of the doping metals is greater than 3.5
Data Source
AI summary
A positive electrode active material for a lithium secondary battery according to an embodiment of the present invention includes a lithium transition metal composite oxide and doping metals doped in the lithium-transition metal composite oxide, wherein the doping metals includes at least two kinds and the average oxidation number of the doping metals is greater than 3.5.