Olivine Composite Cathode Material for High-Voltage Battery Performance
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Solution Overview
Problem
Existing lithium secondary batteries face challenges with safety due to the use of flammable organic solvents in electrolytes, and phosphate cathode materials with an olivine structure have low electron conductivity and voltage, limiting their performance.
Innovation Solution
A composite cathode active material with an olivine structure, represented by Formula Lix(Co1-wM1w)yPO4, is developed, where M1 includes elements like Sc, Ti, V, Cr, Cu, or Zn, and optionally Fe or Ni, with specific ranges for x, y, and w, to enhance high-voltage characteristics and reduce charge/discharge overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phosphate cathode material with an olivine structure is used, then the battery safety is improved (no flammable organic solvent), but the voltage and electron conductivity are low
Solution Approach 1:
The patent changes the chemical composition parameters of the cathode material by incorporating multiple transition metals (Mn, Ni, Co) in specific ratios defined by parameters x, y, and z where x+y+z=1. This compositional parameter optimization enables the material to achieve both high voltage (>3.4V) and good electron conductivity while maintaining the safe olivine structure
Solution Approach 2:
The patent creates a composite cathode material with general formula Li1+a-bMn1-x-yTixM2yPO4 where M2 is Ni or Co, combining multiple metallic elements within the olivine structure. This composite approach synergistically improves electron conductivity and voltage characteristics while preserving the inherent safety of the phosphate olivine framework
2Quantity of substance
If the unit-cell volume is increased to improve discharge capacity, then the energy density is improved, but the high-rate characteristics deteriorate
Solution Approach 1:
The patent optimizes the unit-cell volume parameter to a specific range of 283-284.6 ų through precise control of compositional parameters (x, y, z ratios of Mn, Ni/Co, and Ti). This parameter optimization achieves a balance where the unit cell is large enough to provide high discharge capacity but not so large that it degrades high-rate charge/discharge characteristics
3Power
If transition metals are doped to improve electron conductivity, then the voltage characteristics are improved, but the structural stability may deteriorate
Solution Approach 1:
The patent carefully controls the doping levels of transition metals through optimized compositional parameters where the sum x+y+z=1. Specifically, Ti doping is limited to controlled amounts while Ni or Co are incorporated at optimized ratios. This parameter control enhances electron conductivity and voltage while preventing excessive lattice distortion that would compromise structural stability
Solution Approach 2:
The patent creates a multi-element composite structure Li1+a-bMn1-x-yTixM2yPO4 where Mn provides structural framework stability, Ti enhances electron conductivity, and Ni/Co improve voltage characteristics. The synergistic composite design ensures that each element compensates for potential weaknesses, maintaining overall structural stability while achieving superior electrochemical performance
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 composite cathode active material achieves improved high-voltage characteristics, reduced charge/discharge overvoltage, and enhanced discharge capacity, leading to improved lifespan, high-rate characteristics, and energy density in secondary batteries.
Implementation Method 1
heat-treating the precursor mixture to form a composite cathode active material represented by Formula 1 and having an olivine structure
Data Source
AI summary
A cathode including a cathode current collector; and a cathode active material layer on a surface of the cathode current collector, the cathode active material layer comprising a cathode active material represented by any one of Formula 1, 8, 9, or 10-1 as described herein, and having an olivine structure, wherein a unit-cell volume of the composite cathode active material is in a range of about 283 Å3 to about 284.6 Å3. A secondary battery including the cathode; an anode; and an electrolyte disposed between the cathode and the anode.