Positive Electrode Composition for Li-Ion Capacity Loss Control
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Solution Overview
Problem
Lithium-ion batteries suffer from irreversible capacity loss and reduced energy density due to the formation of a solid electrolyte interface (SEI) film during the first charge and discharge cycle, leading to shorter cycle life, especially under high-temperature conditions.
Innovation Solution
The use of a positive electrode plate with a lithium cobalt composite oxide and lithium manganese composite oxide with a layered crystal structure, characterized by specific Raman spectrum peaks, enhances cycling performance and structural stability, allowing for slow release of active lithium and reducing SEI film damage, thereby prolonging high-temperature cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-ion battery uses conventional positive electrode materials, then initial charge specific capacity is achieved, but irreversible capacity loss occurs due to SEI film formation, reducing energy density and cycle life
Solution Approach 1:
The patent applies preliminary action by pre-intercalating active lithium into the lithium manganese composite oxide during the initial charge process. This preliminary storage of lithium serves as a reservoir that can be slowly released during subsequent cycling to replenish lithium consumed by SEI film formation and degradation, thereby compensating for irreversible capacity loss and extending battery cycle life
Solution Approach 2:
The patent utilizes parameter changes by controlling the Raman spectrum characteristics (peak intensity ratio IA1/IB1 between 1.4-36) to indicate optimal structural stability of the lithium manganese composite oxide. This structural parameter control ensures the material can effectively store and release lithium while maintaining stability during cycling, directly addressing the capacity loss problem
2Quantity of substance
If lithium manganese composite oxide with layered crystal structure is used, then high initial charge specific capacity is achieved, but low initial coulombic efficiency occurs due to excessive active lithium consumption
Solution Approach 1:
The patent controls the Raman spectrum parameters (peak intensity ratio IA1/IB1) to indicate optimal structural stability of the lithium manganese composite oxide. By adjusting compositional parameters (Li content, Mn content, doping elements) to achieve the target Raman characteristics, the material structure is optimized to reduce excessive lithium consumption while maintaining high charge capacity, thus improving initial coulombic efficiency
Solution Approach 2:
The patent employs composite materials by combining lithium cobalt composite oxide with lithium manganese composite oxide in specific ratios. This composite structure leverages the high coulombic efficiency of lithium cobalt oxide while utilizing the high charge capacity of lithium manganese oxide, achieving a balance between capacity and efficiency
3Quantity of substance
If high voltage range lithium intercalation is performed during initial discharge, then active lithium is stored in lithium manganese composite oxide, but structural damage may occur during subsequent high-temperature cycling
Solution Approach 1:
The patent uses Raman spectrum parameters (peak intensity ratio IA1/IB1 and peak positions) as indicators of structural stability. By controlling compositional parameters (Li content, Mn content, doping elements like Ni, Co, Al, Ti) to achieve optimal Raman characteristics, the material maintains structural stability even after high-voltage lithium intercalation during initial discharge, preventing structural damage during high-temperature cycling
Solution Approach 2:
The patent applies beforehand cushioning by optimizing the material composition and structure in advance to withstand the stress of high-voltage lithium intercalation and subsequent high-temperature cycling. The pre-designed structural stability (indicated by Raman characteristics) acts as a cushion against potential structural damage during 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
This configuration significantly improves the energy density and extends the high-temperature cycle life of lithium-ion batteries by maintaining structural stability and providing sufficient lithium sources for SEI film regeneration, outperforming batteries without this specific material combination.
Implementation Method 1
a Raman spectrum of the positive electrode active material layer has a characteristic peak A1 within a range of 580 cm−1 to 640 cm−1 and a characteristic peak B1 within a range of 420 cm−1 to 520 cm−1. The characteristic peak B1 is a characteristic vibration peak of a Li—O—Li bond in a lithium manganese composite oxide with a layered crystal structure, and the characteristic peak A1 is a characteristic vibration peak of a metal-O bond in a lithium cobalt composite oxide and lithium manganese composite oxide with a layered crystal structure.
Implementation Method 2
during the initial discharge of the electrochemical apparatus, part of active lithium is intercalated back to a high voltage range of the lithium manganese composite oxide with the layered crystal structure, and in a subsequent cycling process, as the active lithium continues to be consumed, a positive electrode potential synchronously rises. At this time, the active lithium intercalated back to the high voltage range of the lithium manganese composite oxide with the layered crystal structure is released slowly.
Data Source
AI summary
An electrochemical apparatus, including a positive electrode plate, where the positive electrode plate includes a positive electrode active material layer, and in a fully charged state of the electrochemical apparatus, a Raman spectrum of the positive electrode active material layer has a characteristic peak A1 within a range of 580 cm−1 to 640 cm−1 and a characteristic peak B1 within a range of 420 cm−1 to 520 cm−1. The electrochemical apparatus of this application has high energy density and good cycling performance.