Protective Conductive Layer for Lithium Ion Battery Positive Electrode
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Solution Overview
Problem
Lithium ion secondary battery positive electrode active material particles react with moisture and carbon dioxide, leading to the generation of lithium hydroxide and lithium carbonate, which increases IV resistance and hinders lithium ion insertion and removal, causing higher resistance in batteries.
Innovation Solution
A positive electrode plate with a protective conductive layer containing a conductive material and a binding agent is applied over the active material layer, preventing direct contact with moisture and carbon dioxide, and optionally including a moisture absorbent to further reduce moisture exposure, thereby reducing lithium hydroxide and carbonate generation and maintaining crystal structure integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If positive electrode active material particles are exposed to atmosphere during handling, then lithium hydroxide and lithium carbonate are generated on particle surfaces, but IV resistance increases and battery performance deteriorates
Solution Approach 1:
A protective conductive layer is introduced as an intermediary between the positive electrode active material particles and the atmosphere. This layer contains conductive material particles and binding agent, preventing direct contact between moisture/carbon dioxide and the active material while maintaining electrical conductivity for lithium ion insertion and removal.
Solution Approach 2:
The protective conductive layer forms a thin film structure over the active material layer. This film is thin enough to allow lithium ion diffusion and electron conduction while being sufficiently continuous to block harmful atmospheric reactions. The layer includes conductive material particles dispersed in a binding agent matrix.
2Reliability
If a protective layer is added over the active material layer, then protection from moisture and carbon dioxide is improved, but device complexity increases
Solution Approach 1:
The protective conductive layer performs multiple functions simultaneously: (1) protects active material from atmospheric reaction, (2) provides electrical conductivity for charge transfer, (3) facilitates lithium ion insertion and removal, and (4) maintains structural integrity. This multi-functionality avoids the need for separate protective and conductive layers.
Solution Approach 2:
The protective conductive layer is formed as a composite material consisting of conductive material particles (such as acetylene black, ketjen black, or graphite) dispersed in a binding agent matrix. This composite structure provides both protective barrier properties and electrical conductivity.
3Reliability
If conductive material is included in the protective layer, then conductivity in thickness direction is improved, but manufacturing complexity increases
Solution Approach 1:
The protective layer formation and conductive material application are merged into a single coating process. The conductive material particles are mixed with the binding agent to form a slurry or paste, which is then applied in one step to create both the protective barrier and conductive pathway simultaneously.
Solution Approach 2:
The coating process parameters (such as slurry composition, coating thickness, drying temperature) are optimized to achieve the desired balance between protection and conductivity. The conductive material particle size, shape, and concentration are controlled to ensure adequate conductivity while maintaining ease of application.
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 implementation of a protective conductive layer reduces IV resistance in lithium ion secondary batteries by minimizing the reaction of positive electrode active material particles with moisture and carbon dioxide, enhancing conductivity and maintaining battery performance.
Implementation Method 1
a protective conductive layer that does not include the positive electrode active material particles and includes a conductive material and a binding agent on the active material layer
Implementation Method 2
since the conductive material is included in the protective conductive layer, compared to a positive electrode plate in which the conductive material is not included in the protective conductive layer, the conductivity of the positive electrode plate in the thickness direction can be improved
Data Source
AI summary
A positive electrode plate of a lithium ion secondary battery includes a current collector foil, an active material layer including positive electrode active material particles containing lithium oxide on the current collector foil, and a protective conductive layer that does not include the positive electrode active material particles and includes a conductive material and a binding agent on the active material layer.