Dual-Layer Positive Electrode Balancing Battery Safety and Energy Density
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Solution Overview
Problem
Lithium-ion batteries face safety issues due to thermal runaway caused by internal short-circuits, which compromises their safety performance while attempting to maintain high energy density, leading to concerns such as mobile phone explosions.
Innovation Solution
A positive electrode structure for lithium-ion batteries incorporating a first active material layer with compounds like lithium nickel cobalt manganese oxide, coated with metal oxides, and a second active material layer, enhancing thermal stability by increasing the DSC peak temperature and reducing heat release, thereby improving safety performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If safety measures are added to prevent thermal runaway, then safety performance is improved, but energy density deteriorates
Solution Approach 1:
The positive electrode is divided into two distinct active material layers: a first layer containing safety-oriented materials (LixNiaCobM1cN1-a-b-cO2-d or LiyM2eFe1-ePO4-f) and a second layer containing high-energy-density materials (lithium cobalt oxide). This segmentation allows each layer to perform its specialized function independently, resolving the contradiction between safety and energy density.
Solution Approach 2:
Different regions of the positive electrode are assigned different material compositions tailored to specific functions. The first active material layer uses materials with high thermal stability and low heat release characteristics for safety, while the second layer uses high-capacity materials for energy density. This local differentiation enables simultaneous optimization of both safety and energy storage.
2Quantity of substance
If high-capacity active materials are used to increase energy density, then energy density is improved, but thermal stability deteriorates
Solution Approach 1:
The positive electrode active materials are segmented into two layers with distinct thermal properties. The second layer contains high-capacity lithium cobalt oxide for energy density, while the first layer contains thermally stable materials to provide overall thermal stability to the electrode assembly, preventing the high-capacity material from causing thermal runaway.
Solution Approach 2:
The positive electrode uses a composite structure combining two types of active materials with complementary properties. The first layer materials (LixNiaCobM1cN1-a-b-cO2-d or LiyM2eFe1-ePO4-f) provide thermal stability, while the second layer material (lithium cobalt oxide) provides high energy density. Together they form a composite electrode that achieves both thermal stability and high energy density.
Data Source
AI summary
The present application provides a positive electrode and a lithium-ion battery. The positive electrode comprises a current collector; a first active material layer comprising a first active material; and a second active material layer; wherein the first active material layer is arranged between the current collector and the second active material layer, the first active material layer comprises a first active material, and the first active material is at least one selected from a group consisting of a modified lithium transition metal oxide positive electrode material and a modified lithium iron phosphate. The positive electrode of the present application helps to improve the thermal stability of the lithium-ion battery, and the improvement of the thermal stability may reduce the proportion of the thermal runaway when the lithium-ion battery is internally short-circuited so that the safety performance of the lithium-ion battery is improved.