Lithium Rich Cathode Cycling Protocol for Capacity Retention
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Solution Overview
Problem
Lithium ion batteries with high capacity lithium rich metal oxide cathodes experience performance degradation over multiple cycles, leading to reduced capacity and voltage stability, which is undesirable for applications requiring long-term reliability, such as electric vehicles.
Innovation Solution
The development of lithium ion batteries with a lithium rich metal oxide composition that involves cycling protocols including initial activation charges above 4.45V, followed by cycling within specific voltage windows to stabilize the positive electrode active material, reducing irreversible capacity loss and maintaining high capacity and voltage stability over thousands of cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium rich metal oxide cathode materials are used to increase battery capacity, then energy density is improved, but cycling stability deteriorates with increased cycle number
Solution Approach 1:
The patent applies preliminary action by performing an initial activation charge above 4.45V before normal cycling. This preliminary high-voltage charge transforms the cathode material structure in advance, creating a stabilized phase that resists degradation during subsequent cycling. The activation step prepares the material to achieve both high capacity retention and voltage stability over thousands of cycles.
2Quantity of substance
If high charge voltages above 4.45V are applied to maximize capacity utilization, then initial capacity is improved, but irreversible capacity loss increases
Solution Approach 1:
The patent uses preliminary action by applying a high voltage charge above 4.45V only during the initial activation step, not during normal cycling. This one-time preliminary action extracts maximum lithium to achieve high initial capacity, while subsequent cycling occurs at lower voltages that prevent further irreversible loss. The harmful high-voltage stress is applied beforehand rather than continuously.
Solution Approach 2:
The patent implements periodic action by alternating between high-voltage activation (initial step only) and lower-voltage normal cycling. The charging protocol periodically cycles between charge and discharge at moderate voltages, avoiding continuous exposure to high voltages that would cause irreversible degradation. This periodic moderate cycling maintains capacity while enabling long-term stability.
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 approach results in lithium ion batteries that retain at least 80% of their initial capacity and average voltage after 2000 cycles, offering exceptional cycling stability and extended battery life suitable for high-energy applications like electric vehicles.
Implementation Method 1
a negative electrode comprising a lithium intercalation/alloying composition
Implementation Method 2
Rechargeable lithium ion batteries... are desirable as power sources
Implementation Method 3
a non-aqueous electrolyte comprising lithium ions
Data Source
AI summary
Lithium ion batteries can be activated and then cycled to exploit a moderate fraction of the discharge cycling capacity such that the discharge capacity and average discharge voltage stay within initial values for thousands of cycles. The superior cycling performance has been achieved at relatively high discharge rates and for practical battery formats. Lithium ion battery performance can also be achieved with superior cycling performance with partially activated batteries such that good discharge capacities can be exploited for many thousands of cycles before the discharge capacity and average discharge voltage drops more than 20% from initial values. The positive electrode active material can be a lithium rich metal oxide. The activation of the battery can comprise phase changes of the active materials. As described herein, the phase changes can be manipulated to exploit a reasonable fraction of the available high capacity of the material while providing outstanding cycling stability.