DRX Cathode Active Material With Spinel Phase Switching
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Solution Overview
Problem
Conventional lithium secondary battery cathode active materials face issues such as low rate capability, high cost due to cobalt content, and instability, particularly with lithium manganese oxides and disordered rocksalt structures, which lead to reduced charge and discharge capacities and irreversible voltage drops.
Innovation Solution
A lithium oxide with a disordered rocksalt structure that phase-transforms into a spinel-like structure during charging and back to the disordered rocksalt structure during discharging, incorporating fluorine doping to enhance lithium diffusion and stability, thereby improving electrochemical characteristics and life efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium manganese-based oxide with disordered rocksalt structure is used as cathode active material, then high capacity is achieved, but rate capability is reduced due to low electrical conductivity
Solution Approach 1:
The patent applies parameter changes by doping fluorine into the lithium manganese oxide lattice, which modifies the electrical conductivity parameter. The fluorine doping creates additional charge carriers and improves electron transport, thereby enhancing rate capability while maintaining the high capacity characteristics of the disordered rocksalt structure.
Solution Approach 2:
The patent creates a composite material system by incorporating fluorine-doped lithium manganese oxide with dual-phase structure (disordered rocksalt and spinel phases). This composite approach combines the high capacity of DRX structure with the improved conductivity of spinel phase, resolving the contradiction between capacity and rate capability.
2Quantity of substance
If lithium manganese oxide with disordered rocksalt structure is used, then high capacity is achieved, but irreversible voltage drop occurs during cycling
Solution Approach 1:
The patent employs parameter changes through controlled phase transformation behavior. By adjusting the composition and doping level, the material undergoes reversible phase transformation between disordered rocksalt and spinel structures during charging-discharging cycles, which stabilizes the voltage profile and prevents irreversible voltage drop while maintaining high capacity.
Solution Approach 2:
The patent utilizes dynamic phase transformation as a mechanism to improve voltage stability. The material dynamically transforms between different crystal phases during electrochemical cycling, allowing it to adapt to stress and maintain structural integrity, thereby preventing irreversible voltage degradation.
3Reliability
If cobalt-containing cathode active material is used, then excellent life characteristics and charge efficiency are achieved, but cost increases due to cobalt resource limitations
Solution Approach 1:
The patent replaces expensive cobalt-containing materials with cheaper lithium manganese oxide-based materials. By using abundant manganese and lithium resources instead of scarce cobalt, the patent achieves cost reduction while maintaining acceptable life characteristics through fluorine doping and phase control strategies.
Solution Approach 2:
The patent modifies the compositional parameters of lithium manganese oxide through fluorine doping and stoichiometric control to enhance life characteristics. By adjusting the doping level and phase composition, the material achieves improved cycling stability and charge efficiency comparable to cobalt-based materials, but at lower cost.
4Quantity of substance
If lithium manganese oxide with cation mixing is used, then high discharge capacity is achieved, but synthesis difficulty increases and rate capability deteriorates
Solution Approach 1:
The patent controls the degree of cation mixing as a parameter to optimize both discharge capacity and synthesis ease. By maintaining moderate cation mixing rather than complete mixing, the material achieves high discharge capacity while remaining synthesizable through conventional solid-state reactions, and the fluorine doping further simplifies the synthesis process by stabilizing the structure.
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 phase transformation mechanism enhances lithium secondary battery performance by maintaining high capacity, reducing voltage loss, and improving rate capability and life retention, while also reducing cobalt content for cost-effectiveness.
Implementation Method 1
at least a part of which is phase-transformed from the disordered rocksalt structure into a spinel-like structure when charging
Implementation Method 2
when a cathode and an anode intercalate and deintercalate lithium ions
Implementation Method 3
incorporating fluorine doping to enhance lithium diffusion and stability
Data Source
AI summary
In an embodiment, a cathode active material can include a lithium oxide having a disordered rocksalt (DRX) structure, and the lithium oxide is configured to phase-transform from the DRX structure into a spinel-like structure during charging so as to alleviate and/or prevent rate capability decrease and irreversible voltage drop caused by lithium and manganese existing in excess in the lithium oxide, and a lithium secondary battery embodiment including the same.