Prelithiated Graphite Negative Electrode for Capacity Retention
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Solution Overview
Problem
Conventional lithium secondary batteries face issues with capacity and energy density due to the formation of a passivated coating film on carbon electrodes, leading to lithium ion consumption and degradation of cycle life.
Innovation Solution
A prelithiated negative electrode with high-capacity artificial graphite, having no carbon coating, is developed, where the negative electrode active material layer is prelithiated to 3-5% lithium content, enhancing cycle characteristics and energy density through direct electric contact with a lithium ion-supplying metal sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon electrode is used as a negative electrode in lithium secondary batteries, then the electrode structure is stabilized and reversibility is improved through formation of a passivated coating film, but lithium ions are consumed during coating film formation leading to decreased battery capacity
Solution Approach 1:
The patent applies preliminary action by pre-lithiating the negative electrode before battery assembly. The negative electrode is subjected to a preliminary charging process that introduces lithium ions into the electrode structure in advance, so that when the battery is first charged, the coating film formation does not consume capacity from the battery's operational lithium inventory, thereby preserving battery capacity while still forming the necessary protective coating
Solution Approach 2:
The patent changes the parameter of lithium content in the negative electrode by controlling the preliminary charging conditions (charge capacity, charge rate, number of cycles) to achieve a specific lithium intercalation level (3-5% of total charge capacity). This parameter adjustment ensures sufficient lithium is stored in the negative electrode to compensate for coating film formation losses without causing lithium plating or other adverse effects
2Reliability
If a carbon electrode is used as a negative electrode, then the electrode can be stabilized through coating film formation, but lithium ion consumption occurs during cycling leading to degradation of cycle life
Solution Approach 1:
The preliminary lithiation action prepares the negative electrode in advance by establishing the coating film and stabilizing the electrode structure before the battery enters its operational cycling phase. This preliminary stabilization reduces subsequent degradation during cycling, thereby extending cycle life
Solution Approach 2:
The patent applies beforehand cushioning by pre-introducing lithium ions into the negative electrode to create a buffer that compensates for future lithium consumption during cycling. This cushion of pre-stored lithium protects against capacity loss and maintains electrode stability throughout the battery's operational life, effectively cushioning against degradation
3Quantity of substance
If high-capacity artificial graphite with no carbon coating is used in the negative electrode, then energy density and capacity are increased, but the electrode requires prelithiation to prevent lithium ion consumption and improve cycle characteristics
Solution Approach 1:
The patent applies preliminary action by implementing a controlled preliminary charging process that introduces the exact amount of lithium (3-5% of total charge capacity) needed to compensate for future coating film formation and cycling losses. This preliminary lithiation enables the use of high-capacity uncoated graphite while maintaining good cycle characteristics
Solution Approach 2:
The patent changes multiple parameters including the lithiation level (3-5% intercalation), particle diameter (18 μm or more), and capacity (360 mAh/g or more) of the artificial graphite to optimize both energy density and cycle life. These parameter adjustments allow the electrode to achieve high capacity while the controlled preliminary lithiation prevents the cycle life degradation that would otherwise occur with uncoated high-capacity graphite
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 prelithiated negative electrode improves capacity retention, energy density, and high-temperature storage performance, maintaining 10% higher capacity retention and 5% higher high-temperature storage performance compared to non-prelithiated batteries after 500 cycles.
Implementation Method 1
the content of lithium intercalated to the prelithiated negative electrode active material layer is 3-5% based on the lithium content intercalated when the negative electrode is charged to 100%
Data Source
AI summary
A prelithiated negative electrode, and a secondary battery including a prelithiated electrode, including a negative electrode current collector; and a negative electrode active material layer present on at least one surface of the negative electrode current collector. The negative electrode active material layer includes high-capacity artificial graphite having no carbon coating. The negative electrode active material layer is prelithiated, and the content of lithium intercalated to the prelithiated negative electrode active material layer is 3% to 5% based on the lithium content intercalated when the negative electrode is charged to 100%.