LixV2O5 Additive for Lithium Battery Initial Discharge Efficiency
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Solution Overview
Problem
Rechargeable lithium batteries face issues with irreversible capacity and initial discharge efficiency due to the reactivity of lithium-based negative active materials with moisture and oxygen, leading to safety concerns and reduced energy density.
Innovation Solution
A positive electrode for rechargeable lithium batteries is developed, incorporating a current collector with a positive active material layer that includes LixV2O5 or its composite with metal oxides, where 1<x<4, and optionally substituted with elements like Al, Mg, or Ti, along with an additive that has a lower lithium oxidation potential than the positive active material, enhancing initial charge and discharge efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-based negative active materials are used to achieve high energy density, then capacity density is improved, but irreversible capacity increases and initial discharge efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by incorporating a lithium-containing compound into the positive electrode before battery operation. This pre-added lithium source compensates for the lithium that will be irreversibly consumed during initial charging, ensuring that sufficient lithium is available for subsequent discharge cycles and maintaining high initial discharge efficiency while preserving the high capacity density benefits of lithium-based negative active materials.
Solution Approach 2:
The patent utilizes parameter changes by controlling the amount of lithium-containing compound added to the positive electrode (0.1-10 mmol relative to negative electrode capacity) and adjusting its composition (lithium metal, lithium oxide, lithium hydroxide, or lithium carbonate). This parameter optimization allows compensation for irreversible capacity loss while maintaining overall battery performance and energy density.
2Reliability
If lithium-containing compounds are added to positive electrode to compensate irreversible capacity, then initial discharge efficiency is improved, but positive electrode potential increases
Solution Approach 1:
The patent controls the potential increase by precisely adjusting the amount of lithium-containing compound (0.1-10 mmol) and selecting appropriate lithium compounds with different electrochemical properties. This parameter optimization ensures that the positive electrode potential remains within a safe range (below 4.3V vs. Li/Li+) while still providing sufficient lithium compensation for irreversible capacity loss.
Solution Approach 2:
The lithium-containing compound acts as an intermediary that mediates between the high capacity density requirements and the potential control requirements. It provides the necessary lithium compensation without directly participating in the main charge-discharge reactions at high potentials, thus protecting the positive electrode from excessive potential while maintaining discharge efficiency.
3Quantity of substance
If negative electrode uses materials highly reactive with moisture and oxygen to achieve higher capacity, then energy density is improved, but manufacturing safety deteriorates
Solution Approach 1:
The patent extracts the lithium compensation function from the negative electrode system and relocates it to the positive electrode through the addition of lithium-containing compounds. This separation allows the negative electrode to maintain its high-capacity lithium-reactive materials (such as silicon, tin, or hard carbon) while the positive electrode handles the lithium management, thereby preserving energy density benefits while improving manufacturing safety by reducing the need for highly reactive materials in the negative electrode.
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 solution effectively compensates for irreversible capacity, improves initial charge and discharge efficiency, and enhances the cycle-life characteristics of rechargeable lithium batteries by stabilizing the lithium structure and preventing impurity formation, thus maintaining energy density and safety.
Implementation Method 1
the additive including LixV2O5 where 1<x<4... the additive having a lower lithium oxidation potential than the lithium oxidation potential (Li/Li+) of the positive active material
Implementation Method 2
the positive active material layer including a positive active material and an additive including LixV2O5... the additive having a lower lithium oxidation potential than the lithium oxidation potential (Li/Li+) of the positive active material
Implementation Method 3
lithium-transition element composite oxides being capable of intercalating lithium, such as LiCoO2, LiMn2O4, LiNi1−xCoxO2
Data Source
AI summary
Disclosed are a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same, and the positive electrode includes a current collector; and a positive active material layer including an additive which is LixV2O5 (1<x<4) or a composite of LixV2O5 (1<x<4) and metal oxide, and a positive active material, and being disposed on the current collector.