Layered Cathode Material to Suppress Oxygen Release in Li-Ion Batteries
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Solution Overview
Problem
The high activity of lattice oxygen in positive electrode materials during charge-discharge cycling leads to the generation of gaseous oxygen, accelerating electrolyte decomposition, interface impedance, and irreversible phase transitions, which compromises the stability and safety of lithium-ion batteries.
Innovation Solution
A three-layer structured positive electrode material is developed, comprising a core, an oxygen-absorbing layer, and a passivation layer, where the core includes Ni, Li, a metal element M, and a non-metal element Q, the oxygen-absorbing layer is an unsaturated oxide, and the passivation layer contains fluorine, to inhibit gaseous oxygen evolution and enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a layered lithium nickel-cobalt-manganese oxide composite is used as positive electrode material, then high capacity and energy density are achieved, but lattice oxygen evolves to generate gaseous oxygen during charging, causing electrolyte decomposition and increased interface impedance
Solution Approach 1:
An oxygen-absorbing layer containing coating element L (V, Ga, In, Sn, Bi, Ce, Pr, or Sb) is introduced as an intermediary between the core positive electrode material and the electrolyte. This layer absorbs excess lattice oxygen through redox reactions, preventing oxygen evolution into the electrolyte while maintaining lithium ion transport pathways.
Solution Approach 2:
The positive electrode material is designed as a composite structure with a core (lithium nickel-cobalt-manganese oxide) and an outer oxygen-absorbing layer. This composite structure combines the high capacity of the core material with the oxygen-stabilizing properties of the coating layer, achieving both high performance and safety.
2Speed
If lattice oxygen is highly active during charge-discharge cycling, then fast lithium ion diffusion is enabled, but irreversible phase transition and micro-crack formation occur, reducing battery lifespan
Solution Approach 1:
The oxygen-absorbing layer acts as a protective cushion that preemptively absorbs excess oxygen before it can cause harmful effects. By maintaining oxygen balance in advance, the layer prevents micro-crack formation and phase transitions that would otherwise occur during cycling, thereby extending battery lifespan.
Solution Approach 2:
The valence state of coating element L in the oxygen-absorbing layer is dynamically adjusted during charging and discharging. The layer transitions between different oxidation states (e.g., Ce3+/Ce4+, V3+/V4+/V5+), enabling it to absorb or release oxygen as needed to maintain lattice stability while accommodating lithium ion diffusion.
3Temperature
If gaseous oxygen is generated during charging, then high voltage operation is achieved, but electrolyte decomposition accelerates, increasing interface impedance and reducing safety
Solution Approach 1:
The oxygen-absorbing layer converts the potentially harmful excess lattice oxygen into a beneficial oxygen reservoir. By controlling oxygen release through reversible redox reactions of the coating element, the layer prevents uncontrolled oxygen evolution that would decompose the electrolyte, while still enabling high voltage operation.
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 structured material effectively prevents gaseous oxygen generation, improves battery safety and stability by immobilizing oxygen and reducing electrolyte corrosion, thereby enhancing the performance and lifespan of lithium-ion batteries.
Implementation Method 1
a bond energy between the metal element M and element oxygen being greater than a bond energy between transition-metal element and element oxygen, thus the metal element M can immobilize the element oxygen within the core
Implementation Method 2
element boron, element phosphorus and element silicon and element oxygen form a stable polyanion structure, which is more stable, therefore, the non-metal element Q can play a role in immobilizing oxygen atoms
Implementation Method 3
Element fluorine replaces the lattice oxygen, and since a bond energy between element fluorine and the transition-metal element is greater than a bond energy between the transition-metal element and element oxygen, the material is more stable
Implementation Method 4
it undergoes a redox reaction itself, and the valence state of coating element L changes from low to high, which can effectively prevent the lattice oxygen from being oxidized to generate gaseous oxygen
Data Source
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Figure 4
AI summary
The present invention provides a positive electrode material and a preparation method thereof, and a lithium-ion battery. The positive electrode material includes a core, an oxygen-absorbing layer, and a passivation layer in sequence from inside to outside; the core includes an oxide composed of Ni, Li, a metal element M, and a non-metal element Q; the metal element M includes at least one of Mg, Al, Zr, Ca, Ti, Sr, Y, Nb, Mo, W, Ta, or Ce; the non-metal element Q includes at least one of F, B, P, or Si; the oxygen-absorbing layer is an unsaturated oxide including a coating element L; the coating element L includes at least one of V, Ga, In, Sn, Bi, Ce, Pr, or Sb; the passivation layer is a compound including element F. In the present invention, the effect of suppressing evolution of gaseous oxygen can be achieved by the functional design of different layered structures for the positive electrode material.