Clad Positive Electrode Material for Stable High-Energy Li-Ion Cathodes
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Solution Overview
Problem
Lithium-ion batteries face challenges in increasing energy density due to limitations in the proportion of active materials, and issues with initial coulombic efficiency and cycling capacity retention, primarily caused by surface reactions and material expansion during charging and discharging, which affect electrochemical performance.
Innovation Solution
A modified positive electrode material is developed, comprising an inner core coated with a cladding layer of polymer electrolyte and ferroelectric ceramic material, which reduces side reactions, inhibits material expansion, and enhances ionic conductivity, thereby improving structural stability and rate performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the content of active materials is increased to improve energy density, then the energy density of lithium-ion batteries is improved, but the proportion of active materials becomes difficult to increase further due to bottlenecks
Solution Approach 1:
A solid electrolyte film layer is cladded on the surface of the positive electrode material particles. This thin film protective layer prevents further reaction between the electrolyte solution and electrode material during cycling, reducing capacity loss while maintaining high active material content. The film acts as a barrier that protects the active material without significantly increasing the overall volume.
Solution Approach 2:
The patent uses composite positive electrode materials (such as LiNi0.8Co0.1Mn0.1O2, LiNi0.9Co0.05Mn0.05O2, or LiNi0.95Co0.01Mn0.04Al0.02O2) combined with solid electrolyte film coating. The composite structure allows the active material to maintain high capacity while the solid electrolyte film provides protection, enabling higher energy density without compromising stability.
2Reliability
If a solid electrolyte film layer is cladded on the electrode material surface to improve initial coulombic efficiency, then the initial coulombic efficiency is improved, but the material expansion and cracking during cycling affects capacity retention
Solution Approach 1:
The solid electrolyte film is formed on the surface of the positive electrode material before battery assembly and cycling. This preliminary coating prevents direct contact between the electrolyte solution and electrode material during the first charging-discharging process, avoiding lithium ion loss and improving initial coulombic efficiency. The film is already in place to prevent harmful reactions before they can occur.
Solution Approach 2:
The solid electrolyte film acts as a cushioning layer that accommodates the expansion and contraction of the active material during cycling. This pre-formed protective layer prevents cracks from forming in the electrode material structure, maintaining structural integrity and capacity retention over multiple cycles. The film absorbs mechanical stress that would otherwise damage the active material.
3Productivity
If the positive electrode material expands and shrinks during cycling, then lithium ions are inserted and extracted, but cracks form causing electrolyte solution to pass through and react further, affecting impedance and capacity retention
Solution Approach 1:
The solid electrolyte film serves as a flexible protective shell that covers the positive electrode material particles. This film allows lithium ions to pass through during charging and discharging while preventing the electrolyte solution from contacting and reacting with the active material. The film maintains structural stability by preventing crack formation and propagation during volume changes.
Solution Approach 2:
The solid electrolyte film acts as an intermediary layer between the active material and the electrolyte solution. It mediates the interaction by allowing necessary lithium ion transport while blocking harmful reactions. The film protects the active material from direct exposure to the electrolyte solution, preventing further degradation reactions that would increase impedance and reduce capacity retention.
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 modified positive electrode material achieves better structural stability, rate performance, and cycling performance by forming a protective film that reduces surface reactions and material expansion, leading to improved energy density and capacity retention.
Implementation Method 1
the polymer electrolyte body forms a film-like cladding layer on the outer layer of the positive electrode material particles
Implementation Method 2
the composite cladding layer including the polymer electrolyte and the ferroelectric ceramic material has high ionic conductivity, which provides more channels for ion transport
Implementation Method 3
the flexible cladding layer formed by the polymer electrolyte body can inhibit the shrinkage and expansion of the positive electrode material during charging and discharging to a certain extent, thereby reducing cracking/chalking of the positive electrode material
Data Source
AI summary
A modified positive electrode material includes an inner core and a cladding layer. The inner core is a positive electrode material, and the cladding layer includes a polymer electrolyte body and a ferroelectric ceramic material dispersed in the polymer electrolyte body.