Positive Electrode Active Material Doping Control for Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high-capacity, long-life, and thermal stability due to limitations in the composition and structure of positive active materials, particularly with excessive content of additive metals which deteriorate charge/discharge characteristics.
Innovation Solution
A positive active material comprising lithium, an additive metal, and nickel, cobalt, or aluminum, with a controlled crystal structure and doping concentration of the additive metal less than 2 mol%, is fabricated using a method involving a base and additive aqueous solutions in a reactor, adjusting pH and firing temperature to optimize crystal structure and reduce fluorine permeation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of additive metal is increased to improve capacity, then the capacity increases, but the charge/discharge characteristics deteriorate
Solution Approach 1:
The patent optimizes the additive metal content by controlling the doping concentration parameter to be less than 2 mol%, which resolves the contradiction by finding the optimal parameter value that maintains both capacity and charge/discharge characteristics
Solution Approach 2:
The patent creates a core-shell structure where the surface region has different composition characteristics from the central region, with the surface having higher additive metal content to improve charge/discharge characteristics while the core maintains high capacity
2Stability of the object's composition
If the firing temperature is increased to improve crystal structure, then the crystal structure improves, but the energy consumption increases
Solution Approach 1:
The patent optimizes the firing temperature parameter to a specific range (700-900°C) that achieves the desired crystal structure (cubic and/or trigonal/rhombohedral) while minimizing energy consumption, resolving the contradiction between structure quality and energy use
3Duration of action of moving object
If the additive metal content is increased to improve capacity retention, then the capacity retention improves, but the thermal stability deteriorates
Solution Approach 1:
The patent controls the additive metal doping concentration to be less than 2 mol%, which optimizes the balance between capacity retention and thermal stability by preventing excessive additive metal content that would cause thermal instability while maintaining sufficient content for capacity retention
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 charge/discharge efficiency, capacity retention, and thermal stability of lithium secondary batteries by maintaining the additive metal content below 2 mol%, improving mechanical strength and reducing residual lithium, while maintaining the structural integrity of the battery.
Implementation Method 1
a positive active material in which a metal oxide including lithium and at least one of nickel, cobalt, manganese, or aluminum is doped with the additive metal
Implementation Method 2
fabricate a positive active material precursor in which a metal hydroxide including at least one of nickel, cobalt, manganese, or aluminum is doped with the additive metal
Implementation Method 3
firing the positive active material precursor and lithium salt to fabricate a positive active material
Data Source
AI summary
A positive active material is provided. The positive active material may include lithium, an additive metal, and at least one of nickel, cobalt, manganese, or aluminum. The additive metal may include an element different from nickel, cobalt, manganese, and aluminum. An average content of the additive metal may be less than 2 mol %.