Positive Electrode Sheet Border Layer for Lithium Metal Cycle Life
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Solution Overview
Problem
Batteries face challenges in achieving high energy density and long cycle life due to the softness of lithium metal foils, which are easily cut by the edges of positive electrode sheets during charge and discharge, leading to loss of electrical connection and rapid cycle failure, and the growth of lithium dendrites, which can cause short circuits.
Innovation Solution
A positive electrode sheet design with an inactive material layer around the active material layer, using insulating materials like organic and inorganic polymers and particles, ensures the lithium metal foil edge is covered, preventing cutting and dendrite growth, and includes a composite current collector for improved energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium metal foil is used as negative electrode to increase energy density, then energy density is improved, but the soft lithium metal foil is easily cut by positive electrode sheet edges during charge and discharge, causing loss of electrical connection and short cycle life
Solution Approach 1:
The positive electrode sheet is segmented into active material layer and inactive material layer, with the inactive material layer forming a protective border around the active material layer to prevent edge cutting of the lithium metal foil while maintaining the energy density benefits of the lithium metal negative electrode
Solution Approach 2:
The inactive material layer acts as an intermediary protective layer between the positive electrode sheet edge and the lithium metal foil, preventing direct contact and cutting while allowing the battery to maintain high energy density through proper layer configuration
2Ease of manufacture
If positive electrode sheet edge directly contacts lithium metal foil, then manufacturing is simplified, but lithium dendrites grow on the edge causing short circuits
Solution Approach 1:
The positive electrode sheet is divided into active material layer and inactive material layer, creating a physical barrier that prevents dendrite growth while maintaining manufacturing feasibility through a straightforward lamination process
Solution Approach 2:
The harmful edge region is extracted and isolated by the inactive material layer, separating the active material from direct contact with the lithium metal foil edge, thereby preventing dendrite initiation while maintaining ease of manufacture
Data Source
AI summary
A positive electrode sheet, a battery, and an electric apparatus. The positive electrode sheet includes a positive electrode current collector, and an active material layer and an inactive material layer that are disposed on at least one surface of the positive electrode current collector, the inactive material layer being disposed around a periphery of the active material layer, the active material layer including a positive electrode active material, and the active material layer and the inactive material layer being disposed in a same layer.