LVPF Cathode Pre-Lithiation for First-Cycle Lithium Loss

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Solution Overview

Problem

Lithium-ion batteries face significant first cycle active lithium losses due to solid electrolyte interphase (SEI) formation, leading to reduced energy density and capacity fade over time, with existing pre-lithiation methods posing safety risks and stability issues.

Innovation Solution

The use of lithium vanadium fluorophosphate (LVPF) as a cathode active material with a specific pre-lithiated chemistry, adjusting the degree of pre-lithiation by selecting the value of x in the formula Li1+xV1−yMyPO4Fz to compensate for expected lithium losses, ensuring safe and controlled lithium release during initial charging and subsequent cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If metallic lithium powder is used for pre-lithiation, then lithium loss is compensated and energy density is improved, but safety risks increase due to reactivity and flammability

Engineering Contradiction:

Improveactive lithium lossVSAvoidsafety

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent uses lithium vanadium fluorophosphate (LVPF) as an intermediary material in the cathode that indirectly provides lithium compensation. Instead of directly adding reactive metallic lithium to the anode, the LVPF releases lithium ions during initial charging cycles, which then compensate for SEI formation losses. This mediator approach eliminates safety hazards while achieving the same functional goal of compensating lithium loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the normally harmful effect of lithium loss during initial cycles into a beneficial pre-lithiation effect. By designing the cathode with LVPF that releases lithium during the first charge, the harmful lithium consumption by SEI formation is transformed into a controlled lithium release mechanism that compensates for losses without the dangers of metallic lithium handling.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Loss of energy

If metallic lithium powder is used for pre-lithiation, then lithium loss is compensated, but stability decreases due to reaction with oxygen and moisture

Engineering Contradiction:

Improveactive lithium lossVSAvoidstability

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

LVPF serves as a stable intermediary that releases lithium ions in a controlled manner during initial charging. Unlike metallic lithium powder that reacts uncontrollably with oxygen and moisture, the LVPF structure provides stable lithium release through electrochemical reactions, ensuring long-term compositional stability while achieving lithium compensation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the chemical form of lithium from reactive metallic powder to a stable compound form within LVPF. This parameter change from metal to compound state fundamentally improves stability while maintaining the ability to release lithium ions when needed, eliminating reactions with oxygen and moisture.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If active lithium is added to compensate for first cycle loss, then energy density improves, but device complexity increases due to additional processing requirements

Engineering Contradiction:

Improveactive lithium lossVSAvoidprocessing complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent merges the pre-lithiation function with the existing cathode structure by incorporating LVPF into the cathode material composition. Instead of adding separate pre-lithiation components or modifying anode processing, the lithium compensation capability is integrated directly into the cathode, simplifying the overall device architecture and processing requirements.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The LVPF compound serves multiple functions: it acts as a cathode active material for energy storage and simultaneously provides pre-lithiation capability by releasing lithium during initial charging. This multi-functionality eliminates the need for separate pre-lithiation components or processes, reducing device complexity while achieving lithium loss compensation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

This approach effectively compensates for lithium losses, maintaining high reversible capacity and energy density, improving cycling efficiency and stability while avoiding safety hazards associated with traditional pre-lithiation methods.

Implementation Method 1

an active material is a material which participates in the electrochemical reactions to produce electrical energy when the secondary cell is discharging

Methodology Applied

Scientific EffectElectrochemical reaction: Redox Reactions

Data Source

PatentUS11831001B2Pre-lithiation method and pre-lithiated lithium-ion secondary battery

Publication Date: 2023.11.28 SAFT AMERICA INC

AI summary

Pre-lithiation methods using lithium vanadium fluorophosphate (e.g., LiVPO4F and its derivatives) (“LVPF”) as a cathode active material in a lithium-ion secondary battery. The pre-lithiation methods include compensating for an expected loss of active lithium by selecting LVPF having a specific pre-lithiated chemistry (or a blend of LVPF selected to have a specific pre-lithiated chemistry) and selecting a total amount of the pre-lithiated LVPF. The pre-lithiation methods may include initially charging the lithium-ion secondary battery at the lower of the two charge/discharge plateaus of LVPF to release active lithium.