Carbon-Coated Lithium-Rich Iron Composite for Stable Cathode Prelithiation
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Solution Overview
Problem
Existing lithium-supplementing materials for cathodes in lithium-ion batteries suffer from low purity, high residual alkali content, poor stability, and difficulty in large-scale production due to the lack of a passivation layer, leading to inadequate lithium supplementation and electrochemical performance.
Innovation Solution
A lithium-rich iron-based composite material with a molecular formula aLiFeO2·bLi2O·cMxOy, where a, b, and c are moles, and 0≤c/(a+b+c)≤0.02, 1.8≤b/a≤2.1, M is a doping element, and 1≤y/x≤2.5, is prepared by mixing iron, lithium, and doping element sources, followed by sintering and surface coating with carbon to enhance purity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional sol-gel method is used to prepare lithium-supplementing material Li5FeO4, then the material has large capacity, but the surface layer has large residual alkali and poor environmental adaptability, making it difficult to manufacture
Solution Approach 1:
The patent applies preliminary action by pre-coating the lithium ferrite particles with a carbon layer before final sintering. This carbon coating is formed by adding a carbon source and conducting a first sintering treatment at 600-800°C to form a carbon-containing layer, followed by a second sintering treatment. This preliminary carbon coating prevents residual alkali on the surface from reacting with environmental moisture and CO2, thereby improving environmental adaptability and manufacturability while preserving the high lithium capacity of the material.
2Reliability
If carbon source is used for in-situ coating at high temperature in conventional sol-gel process, then the material is isolated from external environment, but the sol-gel reacts with lithium source to form electrochemically inactive lithium carbonate, affecting the proportion of active bodies
Solution Approach 1:
The patent applies parameter changes by optimizing the sintering temperature parameters to resolve the contradiction. The first sintering treatment is conducted at a lower temperature range (600-800°C) which is sufficient to form the carbon-containing layer but below the temperature where significant reaction between sol-gel and lithium source occurs. The second sintering treatment then completes the formation of lithium ferrite. This two-stage temperature parameter control prevents formation of electrochemically inactive lithium carbonate while maintaining material stability through carbon coating.
3Ease of manufacture
If no passivation layer is present on the material interface, then the material can be easily processed, but it reacts with moisture in the environment to form Li2O again, causing low purity and instability
Solution Approach 1:
The patent applies the flexible shell and thin film principle by forming a thin carbon-containing layer on the surface of lithium ferrite particles. This carbon layer acts as a protective passivation shell that prevents the underlying lithium ferrite from reacting with environmental moisture and CO2. The carbon layer is formed in-situ during the sintering process and maintains the ease of processing while providing the necessary protection to prevent reformation of Li2O, thereby ensuring composition stability.
4Quantity of substance
If lithium-rich iron-based material is used to supplement lithium, then the theoretical capacity is high, but the initial coulombic efficiency is very low due to irreversible Li+ consumption by anode
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molar ratio parameters in the molecular formula aLiFeO2·bLi2O·cMxOy, where 1.8≤b/a≤2.1 and 0≤c/(a+b+c)≤0.02. These parameter optimizations ensure the material has sufficient lithium content to supplement the battery while maintaining structural stability. The controlled excess lithium (through the b/a ratio) provides lithium ions to compensate for irreversible consumption at the anode, thereby improving initial coulombic efficiency while maintaining high theoretical capacity.
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 material provides high lithium capacity, improved electrical conductivity, and enhanced stability, resulting in better electrochemical performance and efficient lithium supplementation, with initial coulombic efficiency of 75%-99% and long cycle life.
Implementation Method 1
A carbon source is used for gas-phase coating to isolate the external environment, avoiding lithium ferrite from being in contact with water or carbon dioxide in the air, thus improves the material stability
Implementation Method 2
carrying out a first sintering treatment of the precursor to generate a lithium-rich iron-based material
Data Source
AI summary
The present application discloses a lithium-rich iron-based composite material and a preparation method and application thereof. The lithium-rich iron-based composite material includes a lithium-rich iron-based material having a molecular formula of aLiFeO2·bLi2O·cMxOy, where a, b, and c are numbers of moles, and 0≤c/(a+b+c)≤0.02, 1.8≤b/a≤2.1, M is a doping element, and 1≤y/x≤2.5. The lithium-rich iron-based composite material can provide abundant lithium, and the lithium-rich iron-based material has a high purity and low residual alkali on the surface, which lead to high capacity and good lithium supplementing effect, as well as good stability for storage and processing. The application of the lithium-rich iron-based composite material in a lithium-supplementing additive for cathodes, a cathode material, a cathode and a lithium-ion battery.