Li2NiO2 Cathode Additive for Silicon Anode Capacity Retention
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Solution Overview
Problem
Lithium secondary batteries using non-carbon-based anode materials face challenges in maintaining capacity retention ratios during initial cycles, with existing solutions either reducing battery capacity or leading to inefficiencies due to excessive carbon-based materials.
Innovation Solution
Incorporating Li2NiO2 as a cathode active material, supplemented by other lithium-containing transition metal oxides, to provide sufficient lithium and improve capacity retention, along with a carbon-based anode material and a non-aqueous electrolyte solution, to enhance cycling stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-carbon-based anode materials (e.g., silicon oxide) are used to improve capacity, then battery capacity increases, but capacity retention ratio decreases during initial cycles due to irreversible lithium ion intercalation
Solution Approach 1:
The cathode is designed with excess lithium content (lithium-rich composition with Li2NiO2 as main component) before battery operation begins. This preliminary lithium excess compensates for the irreversible lithium loss that occurs during initial charging cycles, ensuring sufficient lithium remains for subsequent reversible cycling and maintaining high capacity retention ratio.
Solution Approach 2:
The invention changes the lithium content parameter in the cathode material, using a lithium-rich composition (Li2NiO2 with lithium content exceeding stoichiometric requirements) to balance the lithium budget. This parameter change allows the system to accommodate irreversible lithium loss while maintaining operational capacity.
2Reliability
If carbon-based anode materials are used to improve capacity retention, then capacity retention ratio improves, but battery energy density decreases due to low anode material density
Solution Approach 1:
Instead of modifying the anode to improve lithium retention, the invention inverts the approach by modifying the cathode composition to provide excess lithium. This allows the use of high-capacity non-carbon anodes while maintaining capacity retention through cathode design rather than anode design.
3Power
If graphite anode is used to achieve high discharge voltage, then discharge voltage increases, but safety risk increases due to adverse reactions with organic electrolyte at high voltage
Solution Approach 1:
The invention introduces a lithium-rich cathode composition as an intermediary system that provides a lithium buffer. This intermediary lithium reservoir prevents direct high-voltage stress and adverse reactions between the anode and organic electrolyte, mediating the interaction and reducing safety risks while maintaining high discharge voltage capability.
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 lithium secondary battery achieves a capacity retention ratio of 90% or more after 50 cycles, maintaining performance and safety without deteriorating cycle characteristics.
Implementation Method 1
a cathode made of lithium-containing oxides... capable of intercalating or disintercalating lithium ions
Implementation Method 2
a non-aqueous electrolyte solution obtained by dissolving a suitable amount of lithium salt in a mixed organic solvent
Data Source
Figure 1
AI summary
The present disclosure refers to a lithium secondary battery comprising Li2NiO2 in a cathode active material so as to improve the phenomenon that the capacity retention ratio decreases at initial cycles when using an anode active material selected from the group consisting of Si, SiC, SiOx (0 < x < 2), Sn, SnO2, Sb, Ge and a mixture thereof The lithium secondary battery according to the present disclosure can substantially improve the decrease of a capacity retention ratio during initial cycles.