Layered Cathode Active Material for Reversible Phase Transition
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Solution Overview
Problem
Existing cathode active materials in lithium secondary batteries face irreversible structural changes during charging and discharging, limiting their high theoretical capacity and lifespan due to the formation of thermodynamically stable spinel crystal structures.
Innovation Solution
A cathode active material with a two-dimensional layered crystal structure and a thermodynamically metastable three-dimensional crystal structure, incorporating crystal water and a dopant, allows for reversible phase transitions between these structures, maintaining structural integrity and enhancing capacity and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a layered crystal structure is used to achieve high theoretical capacity, then the capacity is improved, but the structural stability deteriorates due to irreversible phase transition to spinel structure
Solution Approach 1:
The patent applies parameter changes by controlling the oxidation state of manganese to +3.5 through specific synthesis conditions and doping strategies. This parameter adjustment stabilizes the layered crystal structure during charging/discharging cycles, preventing the irreversible phase transition to spinel structure while maintaining high capacity. The controlled oxidation state serves as a key parameter that resolves the contradiction between capacity and structural stability.
Solution Approach 2:
The patent employs composite material strategies by creating a cathode active material that combines layered manganese oxide with specific dopants (such as Ni, Co, Zn) in controlled amounts. This composite structure leverages the high capacity of the layered structure while the dopant elements provide structural stabilization, preventing Jahn-Teller distortion and phase transitions. The composite approach allows simultaneous achievement of high capacity and structural stability.
2Quantity of substance
If the cathode material undergoes structural change during charging/discharging, then the capacity can be increased, but the lifespan deteriorates due to irreversible phase transition
Solution Approach 1:
The patent applies dynamics by enabling reversible phase transitions between different crystal structures during charging and discharging cycles. The material dynamically adapts its structure during operation, transitioning between layered and spinel phases in a controlled, reversible manner. This dynamic behavior allows the material to accommodate structural changes without permanent degradation, thereby extending lifespan while maintaining high capacity utilization.
Solution Approach 2:
The patent utilizes parameter changes by controlling the oxidation state of manganese and the composition ratios of dopant elements to enable reversible structural transitions. By adjusting these parameters within specific ranges, the material can undergo controlled phase changes during charging/discharging that are reversible, preventing irreversible degradation and extending battery lifespan while maintaining high capacity.
3Quantity of substance
If high voltage charging is applied to increase capacity utilization, then the capacity is improved, but the structural integrity worsens due to formation of thermodynamically stable spinel structure
Solution Approach 1:
The patent applies preliminary action by pre-doping the cathode material with stabilizing elements (such as Ni, Co, Zn) before the charging process. This preliminary structural modification creates a more stable framework that can withstand high voltage charging conditions. The pre-established dopant structure prevents Jahn-Teller distortion and stabilizes the layered phase during high voltage operation, enabling high capacity utilization without structural degradation.
Solution Approach 2:
The patent employs beforehand cushioning by introducing dopant elements that act as structural buffers before high voltage charging occurs. These dopants (Ni, Co, Zn) provide structural cushioning that absorbs the stress of high voltage charging, preventing the formation of thermodynamically stable but capacity-limiting spinel structures. The cushioning effect allows the material to withstand high voltage conditions while maintaining structural integrity and layered phase stability.
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 material achieves reversible structural changes during charging and discharging, maintaining high capacity and lifespan characteristics, approaching the theoretical capacity of layered structure-based materials.
Implementation Method 1
a dopant is doped between the two or more unit layers
Implementation Method 2
reversible phase transition of the layered structure to a spinel crystal structure
Implementation Method 3
as some manganese in the manganese-based metal oxide forming the layered structure is chemically bonded to oxygen in the crystal water
Implementation Method 4
Batteries are devices that stores electrical energy in a form of chemical energy
Data Source
AI summary
The inventive concept discloses a cathode active material containing crystal water and a manganese-based metal oxide.