Lithium Battery High Density Electrode Tin Oxide Anode
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Solution Overview
Problem
Lithium rechargeable batteries face challenges with low energy density due to graphite's low density and safety concerns, as well as inadequate performance from oxide negative electrodes, particularly at high temperatures, where thermal instability leads to electrolyte decomposition and reduced cycle-life and safety.
Innovation Solution
A rechargeable lithium battery design featuring a positive electrode with a high active mass density, utilizing a lithiated intercalation compound and surface-treated with a compound like MXO_k, combined with a specific electrolyte composition including lithium hexafluorophosphate, lithium tetrafluoroborate, and a lithium imide-based compound, to enhance cycle-life and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If graphite is used as a negative active material, then discharge voltage and energy density are improved, but capacity per unit volume is reduced due to low density
Solution Approach 1:
The patent uses a composite negative electrode material consisting of tin oxide particles embedded in a carbon matrix. This composite structure combines the high capacity of tin oxide (800 mAh/g) with the structural stability and conductivity of carbon, achieving both high energy density and high capacity per unit volume while maintaining good cycle life.
2Reliability
If graphite is used as a negative active material, then cycle life is improved due to reversibility, but safety is worsened due to reaction with organic electrolyte at high discharge voltage
Solution Approach 1:
The patent modifies the negative electrode material parameters by using tin oxide with controlled particle size (0.1-10 μm) and specific crystal structure, which changes the electrochemical behavior to achieve both high capacity and improved safety characteristics at high discharge voltages.
3Quantity of substance
If oxide negative electrode is used to improve capacity, then high capacity per unit weight is achieved, but initial irreversible capacity is increased
Solution Approach 1:
The patent introduces lithium phosphate (Li3PO4) or lithium silicate (Li2SiO3) coating as an intermediary layer on the tin oxide particles. This coating acts as a protective barrier that reduces direct contact between tin oxide and electrolyte, thereby reducing initial irreversible capacity loss while maintaining high theoretical capacity.
4Quantity of substance
If positive electrode active mass density is increased to improve capacity, then high capacity is achieved, but cycle-life at high temperature is worsened due to thermal instability
Solution Approach 1:
The patent applies local quality improvement by coating only the surface of the positive electrode active material particles with aluminum oxide (Al2O3) or magnesium oxide (MgO). This thin protective layer (1-10 nm) locally enhances thermal stability at the particle surface where electrolyte contact occurs, while maintaining the high capacity properties of the bulk material.
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 solution achieves high capacity, excellent cycle-life, and improved safety at high temperatures, maintaining battery performance and safety through optimized active mass density and electrolyte composition.
Implementation Method 1
lithium-transition element composite oxides being capable of intercalating lithium such as LiCoO2, LiMn2O4, LiNiO2
Implementation Method 2
graphite, which can intercalate and deintercalate lithium ions... graphite has a low discharge potential of -0.2V
Implementation Method 3
They use an organic electrolyte solution... LiPF6 and LiBF4, and as the non-aqueous solvent, ethylene carbonate and/or propylene carbonate
Implementation Method 4
positive electrode with a high active mass density, utilizing a lithiated intercalation compound and surface-treated with a compound like MXO_k
Data Source
Figure 1
AI summary
A rechargeable lithium battery includes a positive electrode including a positive active material being capable of intercalating and deintercalating lithium ions; a negative electrode including a negative active material being capable of intercalating and deintercalating lithium ions; and an electrolyte including a non-aqueous organic solvent and a lithium salt. The positive electrode has a positive active mass density of 3.65g/cc or more, and the lithium salt includes lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and a lithium imide-based compound. The rechargeable lithium battery has high capacity, excellent cycle-life, and reliability at a high temperature.