Sodium-Containing Oxide Cathode for Reversible High-Voltage Phase Change
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Solution Overview
Problem
Existing positive electrode materials undergo severe irreversible phase transitions at high charge cut-off voltages, leading to unstable structures, capacity fading, and poor cycling performance.
Innovation Solution
A sodium-containing oxide material with a chemical formula of LixNa1-xCo1-zMzO2 is developed, where the angle range of a first characteristic peak at an initial voltage is less than that of a second characteristic peak at a cut-off voltage, allowing for more efficient lithium ion release and improved structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge cut-off voltage is increased to achieve higher capacity, then the battery capacity is improved, but the positive electrode material undergoes severe irreversible phase transition leading to structural instability and capacity fading
Solution Approach 1:
The patent modifies the chemical composition parameters of the positive electrode material by introducing doping elements (Ni, Mn, Al) and coating layers (Li2SiO3, Li3PO4, Li2SiOxNy) to stabilize the crystal structure. This allows the material to maintain structural integrity at higher charge cut-off voltages (4.45V or higher), enabling higher capacity while preventing irreversible phase transitions that would otherwise cause structural collapse and capacity fading
Solution Approach 2:
The patent creates a composite structure by combining the base positive electrode material (such as LiCoO2) with doping elements and coating layers. The doping elements substitute into the crystal lattice to reinforce structural stability, while the coating layers form a protective barrier that prevents harmful phase transitions. This composite approach enables the material to achieve higher capacity at elevated voltages while maintaining reliability through multiple protective mechanisms working together
2Reliability
If doping and coating are applied to suppress phase transitions, then structural stability is improved, but capacity loss occurs
Solution Approach 1:
The patent applies doping elements at specific lattice positions and uses thin coating layers only on the surface of the positive electrode particles. The doping concentration is precisely controlled (e.g., Ni0.02Co0.98O2 where only 2% of Co is replaced), and the coating layer thickness is optimized to be sufficiently thin to allow Li ion diffusion while providing protective effects. This localized approach ensures structural stability is enhanced without excessive capacity loss from material removal or blocked ion transport pathways
3Quantity of substance
If the charge cut-off voltage exceeds 4.5V, then higher capacity is achieved, but irreversible phase transition from 03 phase to H1-3 phase occurs causing severe crystal structure contraction
Solution Approach 1:
The patent applies doping elements and coating layers to the positive electrode material before charging at high voltages. The doping elements (such as Ni, Mn, Al) are pre-introduced into the crystal lattice to strengthen it against the stresses of high-voltage charging. The coating layers (such as Li2SiO3, Li3PO4) are applied in advance to form a protective barrier that prevents harmful interactions between the material and electrolyte at high voltages. This preliminary protection enables the material to withstand charge cut-off voltages of 4.5V or higher without undergoing irreversible phase transitions to H1-3 or O1 phases that would cause severe crystal structure contraction and particle destruction
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 sodium-containing oxide material achieves higher capacity, improved rate performance, and enhanced cycling stability by maintaining reversible phase transitions and structural integrity during charge and discharge processes.
Implementation Method 1
the sodium-containing oxide can release more lithium ions at a same voltage, thereby improving a capacity of the positive electrode material, and improving rate performance and cycling performance of the positive electrode material
Implementation Method 2
During a phase transition process of the sodium-containing oxide from the initial voltage to the cut-off voltage, the first characteristic peak and the second characteristic peak are formed
Data Source
AI summary
Disclosed are a positive electrode material, a preparation method of a positive electrode material, a positive electrode plate, and a battery. The positive electrode material includes a sodium-containing oxide, an angle range of a first characteristic peak of the sodium-containing oxide is less than an angle range of a second characteristic peak, the first characteristic peak is a characteristic peak of the sodium-containing oxide at an initial voltage, the second characteristic peak is a characteristic peak of the sodium-containing oxide at a cut-off voltage, and a chemical formula of the sodium-containing oxide is LixNa1-xCo1-z MzO2. M includes a metal element or a non-metal element, 0.7<x<1, and 0.001<z<0.03.