Pre-doped Coated Negative Electrode Active Material for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries exhibit high irreversible capacity due to lithium ions occluded in the negative electrode during charging that are not released during discharging, and electrolyte decomposition during pre-charging, which complicates the production process.
Innovation Solution
A coated negative electrode active material is developed by coating a portion of the surface with a coating agent and doping it with lithium or lithium ions, eliminating the need for a degassing step and reducing the burden on the positive electrode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-charging is performed to compensate irreversible capacity, then the irreversible capacity is reduced, but electrolyte decomposition occurs and gas is generated requiring a degassing step
Solution Approach 1:
The negative electrode active material is pre-doped with lithium or lithium ions before battery assembly, so that the irreversible capacity compensation occurs during manufacturing rather than during a separate pre-charging step. This eliminates the need for post-assembly degassing operations while achieving the same capacity compensation effect.
Solution Approach 2:
The harmful gas-generating step (electrolyte decomposition during pre-charging) is extracted and eliminated from the production process. Instead, the necessary lithium insertion is achieved through a different method (direct doping during manufacturing) that does not produce harmful byproducts.
2Ease of manufacture
If conventional negative electrode active material is used, then the battery can be manufactured simply, but high irreversible capacity occurs during first charging and discharging
Solution Approach 1:
The negative electrode active material is pre-doped with lithium or lithium ions during the manufacturing process, before the battery is assembled and put into service. This preliminary lithium insertion compensates for the irreversible capacity that would otherwise occur during the first charge-discharge cycle, improving reliability without complicating manufacturing.
Solution Approach 2:
The lithium content of the negative electrode active material is adjusted by controlling the doping conditions (temperature, time, lithium source amount). By changing these parameters, the material is pre-loaded with the specific amount of lithium needed to compensate for irreversible capacity while maintaining manufacturing simplicity.
3Speed
If the surface of negative electrode active material is coated with coating agent, then charge-discharge rate is improved, but additional manufacturing steps are required
Solution Approach 1:
The coating process and lithium doping process are merged into a single manufacturing step. The coating agent serves as the lithium source, so that coating and doping occur simultaneously rather than as separate sequential steps, improving charge-discharge rate without proportionally increasing manufacturing complexity.
Solution Approach 2:
The coating agent performs multiple functions: it coats the surface of the negative electrode active material to improve charge-discharge kinetics, and simultaneously serves as the lithium source for doping. This multi-functionality reduces the need for additional separate processing steps.
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 coated negative electrode active material reduces irreversible capacity, minimizes electrolyte decomposition, and improves charge-discharge rates, simplifying the production process and reducing the amount of expensive positive electrode material required.
Implementation Method 1
at least a portion of the surface of a negative electrode active material for lithium ion batteries is coated with a coating agent
Implementation Method 2
the coated negative electrode active material is doped with at least one of lithium and lithium ions
Implementation Method 3
lithium ions are extracted from the positive electrode active material and are occluded in the negative electrode active material
Data Source
AI summary
An object of the present invention is to provide a negative electrode active material capable of reducing the irreversible capacity of a lithium ion battery. The present invention provides a coated negative electrode active material for lithium ion batteries wherein at least a portion of the surface of a particulate negative electrode active material for lithium ion batteries is coated with a coating agent and the coated negative electrode active material is doped with at least one of lithium and lithium ions.